Camarillo City Council
May 13, 2026

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concentrations, storage and application of fertilizers, and discharges of nutrientrich sediments. Most of the nutrient TMDLs in Attachment H require that dischargers comply with waste load allocations by meeting the translated numeric action levels or numeric effluent limitations, while one TMDL relies on RUSLE2 modeling. The compliance cost impact for implementation of the nutrient TMDLs is expected to be medium to high since additional BMPs (filter media BMPs for phosphorus and advanced BMPs for nitrogen) and monitoring may be required for controlling the specific nutrient concentrations from construction sites.

The RUSLE2 modeling used to demonstrate compliance with the San Diego Creek and Newport Bay Nutrients TMDL in Region 8 is estimated to add $750 to $1,500 in costs, per project.

If non-visible pollutant monitoring is required, Responsible Dischargers in some watersheds located in Regions 3, 4 and 8 (Central Coast, Los Angeles Basin and Santa Ana), as specified in Attachment H, shall conduct analyses for the TMDL-specific pollutant(s) such as total nitrogen, ammonia, nitrates, nitrites, phosphorous, and orthophosphates. The estimated additional cost of the TMDL monitoring would be approximately $200-$400 for sampling and $200-$400 for analysis and SMARTS data entry, per sampled discharge location per event.

The May 2021 draft of the Construction Stormwater General Permit, issued for public comments, proposed translations of nitrogen-based nutrient waste load allocations into numeric effluent limitations. The translation of the nitrogenbased nutrient waste load allocations was revised to numeric action levels in this General Permit per the following explanation that numeric action levels are consistent with the assumptions and requirements of the waste load allocations.

All applicable TMDLs with nitrogen-based nutrient waste load allocations discuss low flow as the critical condition for the receiving water impairment.

Unlike general urban runoff that occurs year-round, construction stormwater discharges only occur as a result of precipitation events; discharges from construction sites do not typically occur during low flow receiving water conditions. A numeric action level is a more appropriate limitation to implement a TMDL primarily concerned with dry weather discharges. Further, each TMDL discusses municipal wastewater treatment plants as a principal source of nutrient loading. Although stormwater is identified as a potential source, the TMDL did not calculate a source-specific waste load allocation and instead used the water quality objective as the waste load allocation for nutrients.

Although the TMDLs sets the compliance location at the point of discharge, because of how the waste load allocation was calculated, the waste load allocations are similar to TMDLs where the compliance point is set at the receiving water. As set forth in Section I.D.3, this General Permit translated

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concentration-based waste load allocations to be met in receiving waters into numeric action levels.

The State Water Board has very few nitrogen-based nutrient sampling results from construction stormwater because the previous permit did not require sampling for nutrients. However, nutrient data is available from required monitoring in the Industrial Stormwater General Permit. An analysis of all stormwater data from implementation of the Industrial Stormwater General Permit from 2015 – 2021 shows that of collected nutrients samples, approximately 95 percent of nitrate-plus-nitrite samples (as nitrogen), and 92 percent of ammonia samples had concentration results were lower than numeric action levels listed in this General Permit. The average sampling results, 0.68 mg/L for nitrate-plus-nitrite and 2.16 mg/L for ammonia, were below the numeric action levels in the Industrial Stormwater General Permit.

Both observed average sampling results are a fraction of the action levels in this General Permit. The sampling results available through the implementation of the statewide Industrial Stormwater General Permit include stormwater discharge data from industrial facilities, such as fertilizer manufacturers, with significant potential sources of nutrients. In contrast, sources of nutrients from construction sites are generally limited to existing legacy concentrations in the sediment from past land uses that involved application of fertilizers, pesticides, and herbicides, and storage facilities that store the chemicals. Accordingly, it is generally expected that construction stormwater discharges will not exceed the waste load allocations and numeric action levels are appropriate.

Numeric action levels are consistent with the TMDLs and protective of water quality. All dischargers are required to implement sediment control BMPs and eliminate or minimize site erosion. If the Discharger exceeds the numeric action level, as set forth in Attachment H, Section I.D.3.e, the discharger must report and respond to a numeric action level exceedances. As described in Attachment D and E, Section III.G, when there is an exceedance of a numeric action level, dischargers must determine the source of the pollutant, implement corrective actions to reduce or prevent further exceedances and implement iterative corrective actions until the discharge is in compliance with the action level. Within 14 calendar days of an exceedance, a QSD and QSP must perform on-site visual inspections and the QSP must document any areas of concern (Order, Section V.C.3 & V.D.4). For example, if the construction activities include the application or storage of fertilizers, pesticides, and herbicides, exposure of those products to stormwater must be prevented or minimized. Corrective actions may also include implementing BMPs that eliminate stormwater discharges, BMPs with filter media, or other sediment control BMPs. The Regional Water Boards may require additional monitoring, reporting, and BMP requirements upon obtaining site-specific information about an exceedance to a numeric action level (Attachment H, Section I.D.3.f). The

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State Water Board expects that dischargers can feasibly comply with the nitrogen numeric action levels in this General Permit without the need to implement more advanced BMPs, which as discussed below are not typically possible to install at construction sites.

The most effective BMPs for removal of nitrogen-based nutrients through denitrification, biofiltration, or bioretention are advanced structural treatment BMPs that are used at permanent sites, not temporary construction sites.

Denitrification, the process by which nitrates are reduced to gaseous nitrogen by facultative microbes under anaerobic conditions, is often employed at wastewater treatment plants with numeric effluent limitations for ammonia and/or nitrates. Biofiltration BMPs capture and treat stormwater runoff using conditioned soil beds for planting vegetation and establishing microbial communities to filter out pollutants. Denitrifying treatment and bioretention BMPs requires the retention of all the construction site’s stormwater. Sites would need adequate space to accommodate the proper sizing and design of such treatment BMPs to effectively remove nutrients. Construction sites often have limited available area, and the larger the site, the more area is needed for treatment BMPs. Construction of permanent BMPs is not typically compatible with construction stormwater management, as site conditions are inherently transient during the term of the construction, and the nutrient removal BMPs would only be needed during land disturbance activities.

Biofiltration basins require established vegetation to efficiently remove nutrients. The vegetation in a biofiltration basin typically needs, at minimum, several growing seasons, (at minimum several months under ideal weather and soil conditions, up through several years under non-supportive growing conditions), for the vegetation to establish itself and provide effective treatment for nutrient removal. Most construction projects are active for a short duration with insufficient time to establish a vegetative biofiltration process that effectively removes nutrients. Although biofiltration is a commonly used postconstruction BMP, its utility during construction is limited due to the inability to move biofiltration BMPs; additionally, biofiltration BMPs are designed specifically to treat a defined stormwater discharge quality under specific site conditions. Biofiltration BMPs are expensive, generally costing tens-ofthousands of dollars in addition to the cost of retention of the site’s stormwater.

Due to the time period needed to design and establish effective treatment, the long-term nature of treatment implementation, and the relative cost, biofiltration BMPs are not well-suited for construction sites that are temporary in nature.

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e. Sediment 20
Excess sediment delivery to stream channels can be a pollutant and is associated with several natural processes as well as anthropogenic sources.

Sediment can transport other pollutants that attach to it, including nutrients, trace metals, and organic compounds. Sediment is the primary component of turbidity, the most common sediment water quality analytical parameter used in this General Permit. Anthropogenic construction sources include, but are not limited to, track in and out from earth moving equipment, unpaved access roadrelated erosion (e.g., construction and maintenance of paved and unpaved roadways), dust, and soil/earth disturbing activities. All Responsible Dischargers are required to comply with the existing requirements of this General Permit, including the turbidity numeric action levels, associated exceedance actions, and the sediment TMDLs incorporated into this General Permit. However, many of the sediment TMDLs will also require additional RUSLE2 modeling to demonstrate compliance with the assigned waste load allocations. Responsible Dischargers for the Los Peñasquitos Lagoon Sediment TMDL are required to submit an estimate of the representative flow rate from their construction site for one precipitation event, each reporting period. Although imposing these additional requirements is expected to result in a low to medium cost impact for Dischargers, they were considered a more cost-effective approach than other means of complying with the TMDL such as TMDL-specific monitoring.

The cost of a runoff flow rate assessment varies by methodology and the method is often determined by the availability of input data. A relatively simple equation such as the Rational Method would require an hour or less for a QSD to calculate. The more complex and accurate National Resources Conservation Service method may require a site visit or extensive internet research and take two to six hours to complete. This translates to a cost range of $100 to $600, based on an average billable rate of $100 per hour for QSDs.

In addition to the regular numeric action level sediment monitoring required by the permit, Responsible Dischargers in some watersheds located in Region 1, as specified in Attachment H, shall conduct RUSLE2 to demonstrate compliance with the waste load allocations. The estimated additional cost of the RUSLE2 calculation requirement will add $750 to $1,500 to each project in these Regions.
20 California Stormwater Quality Association (CASQA) Construction BMP Handbook, p. 1-7.

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f. Temperature21
This General Permit includes seven temperature TMDLs, all of which are located in the North Coast Regional Water Quality Control Board’s jurisdiction.

The removal of riparian vegetation from road building and urbanization construction are amongst the sources observed to increase Northern California stream temperatures, which can negatively impact juvenile salmonids.

Excessive sediment input also raises stream temperature by widening stream channels, filling pools, and eliminating riparian vegetation during flood events.

Responsible Dischargers are required to comply with the requirements of this General Permit in order to achieve the applicable waste load allocations in the North Coast Temperature Implementation Policy. Compliance with these TMDLs is not expected to result in additional costs.
g. Metals and Toxics22
Metals (e.g., aluminum, cadmium, chromium, copper, lead, mercury, nickel, and zinc) and selenium can be found in construction stormwater discharges and are potentially toxic to aquatic life. Many of the equipment and materials used in the built environment (e.g., pipes, rebar, conductors, galvanized metal, paint, vehicles, preserved wood, tires, and vehicle brakes) contain metals, which enter stormwater as the surfaces corrode, decay, dissolve, flake, leach, or rust.

Toxic, synthetic organic compounds (e.g., adhesives, cleaners, herbicides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), pesticides, sealants, solvents) may be found in low concentrations but can still be toxic to aquatic life. Sources of synthetic organic compounds at construction sites include, but are not limited to, exposure of the compounds to stormwater during use and/or storage, improper disposal, and accidental release into storm drains or off-site.

The primary transport mechanism for metals and toxics is the mobilization and discharge of fine sediment through stormwater. Metals and organic compounds have an affinity for other organic substances and will partition from water and sorb to sediment. For this reason, it was appropriate to translate mass-based waste load allocations into requiring additional RUSLE2 modeling to estimate sediment delivery from a construction site into a watershed. Using RUSLE2 to 21 United States Environmental Protection Agency Region IX, Final Upper Main Eel River and Tributaries (including Tomki Creek, Outlet Creek and Lake Pillsbury) Total Maximum Daily Loads for Temperature and Sediment (December 29, 2004) <https://www.waterboards.ca.gov/northcoast/water_issues/programs/tmdls/eel_river_u pper_main/pdf/uer-tmdl-final-12-28.pdf> [as of May 20, 2021] 22 CASQA Construction BMP Handbook, p. 1-7.

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demonstrate compliance with the waste load allocations avoids cost impacts associated with monitoring for toxic and metal pollutants.

However, a number of the metal and toxics TMDLs are assigned concentrationbased waste load allocations, which were translated into numeric action levels or numeric effluent limitations. Many dischargers are not currently implementing BMPs designed to minimize concentrations for metals and toxics, but many Responsible Dischargers will need to implement BMPs designed to comply with the TMDL requirements. The compliance cost impact for the metal and toxics TMDL implementation is expected to be similar to that for normal sediment removal unless site-specific advanced BMPs and additional monitoring are required to comply with the requirements of these TMDLs. In the latter case, more advanced systems such as bioretention ponds, active treatment systems, or membrane filtration structures will likely have costs in the tens of thousands of dollars.

If non-visible pollutant monitoring is required, Responsible Dischargers in some watersheds located in Regions 4, 8 and 9 (Los Angeles Basin, Santa Ana, San Diego), as specified in Attachment H, would have to conduct TMDL analyses for metals and toxics listed for the individual watersheds. These pollutants may include copper, lead, zinc, mercury, nickel, cadmium, chromium and selenium, and toxics in the form of organochlorine pesticides, polychlorinated biphenyls (PCB), and polycyclic aromatic hydrocarbons (PAH). The estimated additional cost of this TMDL monitoring would be approximately $200-$400 for sampling and $525-$750 for analysis and SMARTS data entry, per sampling location per event. For the Los Angeles Area Lakes TMDL, the waste load allocations for organochlorine pesticides and PCBs are below the analytical reporting limits.

Additionally, the Los Angeles and Long Beach Harbor Waters TMDL waste load allocations for total copper, lead, and zinc are analytically detectible, but limited data from construction site stormwater sampling indicates that compliance with these waste load allocations would be extremely difficult. As further detailed below, because organochlorine pesticides, PCBs, copper, lead, and zinc all bind to sediment and sediment is a common pollutant in stormwater from construction sites that can be managed effectively with BMPs, compliance with these two TMDLs is implemented through a soil screening investigation and, if applicable, a total suspended solids (TSS) numeric effluent limitation detailed in Attachment H, Section I.G.5.

The soil screening investigation is used to determine the presence of the applicable metals, organochlorine pesticides, or PCBs by comparing the concentration of pollutants in the soil to the analytical reporting limit for each substance. The analytical reporting limit is the lowest concentration at which an analyte can be measured in a sample and its concentration can be reported with a reasonable degree of accuracy and precision.

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If the analytical reporting limit for any of the TMDL-specific pollutants is exceeded in any soil sample obtained for the soil screening investigation, the Responsible Discharger will be required to sample for TSS as a proxy for the identified TMDL pollutants if the non-visible sampling requirements are triggered. The numeric effluent limitation for TSS is 100 mg/L, and any exceedances require corrective actions detailed in Attachment D, Section III.G and Attachment E, Section III.G.

The value of 100 mg/L TSS is derived from several lines of evidence, including a study where the probability curve between organochlorine pesticides and TSS was modeled to determine that 100 mg/L TSS is protective of water quality when the criteria for 4,4 DDE was 0.00059 mg/L which is equal to the waste load allocation concentrations for chlordane and 4,4 DDT listed in the Los Angeles Area Lakes TMDL. Additionally, a 2018 study found that 100 mg/L TSS correlated with the boundary between particulate and dissolved phase metals in multiple watersheds when the Kd (distribution coefficient) for the metal is 10,000 L/kg.
23 I.G.6. Stormwater BMP Selection
a. This General Permit provides dischargers flexibility in selecting the site-specific BMPs necessary to achieve compliance. This flexibility is also provided to Responsible Dischargers in selecting, installing, and maintaining the appropriate BMPs for site-specific situations to meet applicable TMDL requirements, including BMP combinations of:
i. Non-structural BMPs (such as good housekeeping and staff training); ii. Structural source control BMPs (physical, structural, or mechanical devices or BMPs intended to prevent pollutants from entering stormwater) such as erosion control practices, maintenance of stormwater facilities (e.g., cleaning out sediment traps), construction of roofs over storage and working areas, and direction of equipment wash water and similar discharges to the sanitary sewer or other end-use systems; and/or
iii. Structural treatment BMPs which include flow or volume-based treatment BMPs. Structural source control and treatment BMPs usually include a capital investment but are cost-effective compared to removing pollutants 23 Nasrabadi T, Ruegner H, Schwientek M, Bennett J, Fazel Valipour S, Grathwohl P (2018) “Bulk metal concentrations versus total suspended solids in rivers: Timeinvariant & catchment-specific relationships.” Washington Department of Ecology (2004) “A Total Maximum Daily Load Evaluation for Chlorinated Pesticides and PCBs in the Walla Walla River.” Angela Gorgogline, Fabián A. Bomberdelli, Bruno J. L. Pitton, Lorence R. Oki, Darren L. Haver and Thomas M. Young (2018), “Role of Sediments in Insecticide Runoff from Urban Surfaces: Analysis and Modeling.”

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after they have entered stormwater and been discharged into a receiving water body.
b. Stormwater BMP categories for the TMDL pollutant types above are, in general, physical, chemical, hydraulic, and biological. Selection of appropriate site BMPs must be determined based on site-specific factors. No single BMP can achieve the required pollutant reductions for every given situation or pollutant, and each BMP approach has pros and cons. The Responsible Discharger should consider the cost-benefit24 when selecting stormwater BMPs. Some factors include, but are not limited to, upfront-cost, maintenance-cost, pollutant removal efficiency per area/treatment unit, local permitting, site hydrology and geology, safety, space, staffing, and monitoring needs for implementing the BMP(s).

There are many ways to calculate the upfront and maintenance cost of BMPs that consider, for example, BMP sizing, the annual cost for maintenance and/or the annual maintenance hours required.25
Table 1 – University of New Hampshire Stormwater Center26 Select BMP Maintenance Costs and Hours
BMP Maintenance Cost (per
year)
Annual Maintenance
Hours
Bioretention $1,890.00 20.7
Chamber System Not Assessed Not Assessed
Detention Pond $2,380.00 24.0
Gravel Wetland $2,138.00 21.7
Porous Asphalt $1,080.00 6.0
Pervious Concrete $1,080.00 6.0
Retention Pond $3,060.00 28.0
Sand Filter $2,807.00 28.5
I.G.7. Stormwater BMP Categories
24 State of Hawaii Department of Transportation Highways Division. Stormwater Permanent Best Management Practices Manual, page 7-2 Table 1. (February 2007). <http://hidot.hawaii.gov/wp-content/uploads/2015/05/Appx-E.1-Permanent-BMPManual-Feb-2007.pdf>. [as of May 20, 2021]. (State of Hawaii BMP Manual) 25 U.S. EPA. Methodology for developing cost estimates for Opti-Tool Memorandum (February 20, 2016), page 8.
<https://www3.epa.gov/region1/npdes/stormwater/tools/green-infrastructurestormwater-bmp-cost-estimation.pdf>. [as of April 28, 2022]. (U.S. EPA BMP Cost Estimation Memorandum)
26 U.S. EPA BMP Cost Estimation Memorandum, University of New Hampshire Stormwater Center (UNHSC) Select BMP Maintenance Costs and Hours, page 8.

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The following categories generally describe currently available types of stormwater BMPs, their expected effectiveness for the TMDL pollutant categories, and some general cost comparisons. The cost comparisons for 6.a-b are based on:
· Staff experience in administering this General Permit for the non-structural and structural source control BMPs;
· The CASQA Industrial and Commercial BMP Handbook for appropriateness of minimum BMPs to control pollutants;
· The CASQA Construction Handbook for appropriateness of minimum BMPs to control pollutants;27 and
· The California Department of Transportation (Caltrans) Construction Site BMP Manual.28
The cost for non-structural controls, which includes good housekeeping, preventative maintenance, spill and leak prevention and response, erosion and sediment controls, employee training programs, and quality assurance and record keeping, is lower than the costs for other BMPs. For example, these costs consist of staff time for training or conducting routine minimum BMP activities and minimal costs for certain materials such as spill kits or for materials for retaining records.

Costs for source control BMPs were estimated generally as being low, medium, or high, dependent on a variety of factors.

The cost comparisons and information in Table 2 for 6.a-i are based on general conclusions from research conducted by the California Stormwater Quality Association, U.S. EPA, U.S. Department of Transportation, State of Hawaii Department of Transportation Highways Division, State of Minnesota Pollution Control Agency, and the Water Environment and Reuse Foundation. State Water Board staff reviewed these sources on:
· The selection of BMPs for general categories of pollutants and performance of pollutant removal;
· The provided upfront costs for a BMP category from a range of low, medium, and high; and
· The provided maintenance costs for a BMP category from a range of low, medium, and high.
27 CASQA Construction BMP Handbook, 2015.
28 California Department of Transportation (Caltrans), Construction Site BMP Manual (May 2017). <https://dot.ca.gov/-/media/dotmedia/programs/construction/documents/environmental-compliance/csbmp-may2017-final.pdf> [as of May 20, 2021]

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More specific information on methodology and estimates is available from these sources, which are cited below.
a. Non-Structural BMPs, which include, but are not limited to, site sweeping, staff training and education, dumpster and waste management, routine portable toilet maintenance and cleaning, and proper handling and spill response for construction materials.29 These BMPs can significantly reduce pollutant concentrations in all categories (4.a-g) and can range from low to medium upfront costs depending on the staffing and size of size. In general, operation and maintenance costs are low.
b. Source control BMPs, which include minimizing or eliminating exposure of a pollutant source, can significantly reduce pollutant concentrations in all categories (4.a-g). Upfront costs can range from low (e.g., moving materials or activities indoors or under cover) to high (if, for example, the site must move or build extra covered areas/structures). In general, the operation and maintenance costs are low for exposure minimization and elimination BMPs. c. Bioretention BMPs30 are soil and plant-based filtration structures that reduce runoff velocity and remove pollutants over time through a variety of processes.

Bioretention can significantly reduce pollutant concentrations for categories (4.a), (4.d), (4.e), (4.f), and (4.g) (varies for dissolved metals).31 Usually, costs are medium to high32 per area treated and are tied to proper sizing and design, with low to medium maintenance requirements and cost.33 29 U.S. Department of Transportation (DOT), Federal Highway Administration.

Stormwater Best Management Practices in an Ultra-Urban Setting: Selection and Monitoring. Section 6.5 Table 57. Relative Rankings of Cost Elements and Effective Life of BMP Options.
<https://www.environment.fhwa.dot.gov/Env_topics/water/ultraurban_bmp_rpt/uubmp 6p4.aspx> [as of April 28, 2022]. (U.S. DOT BMP Selection and Monitoring) 30 California Stormwater Association (CASQA), Industrial and Commercial Best Management Practice Online Handbook September 2014, TC-32. <https://www.casqa.org/sites/default/files/casqa-handbookindustrial/full_handbook_2014.pdf> [as of May 20, 2021] (CASQA Industrial and Commercial BMP Handbook)
31 Water Environment and Reuse Foundation (WERF). International Stormwater BMP Database 2020 Summary Statistics Final Report,
<https://www.waterrf.org/system/files/resource/2020-11/DRPT-4968_0.pdf> [as of April 28, 2022]. (International Stormwater BMP Database). 32 State of Hawaii BMP Manual, page 7-2 Table 1.
33 U.S. DOT BMP Selection and Monitoring, section 6.5 Table 57; State of Hawaii BMP Manual, page 7-2 Table 1; U.S. EPA BMP Cost Estimation Memorandum, page 8.

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d. Media or Treatment Filtration BMPs34 include either active or passive processes. In passive processes, water flows through treatment media or surface by gravity. In active processes, stormwater flows through media via a pump or similar mechanized system. The media are usually a custom or proprietary blend from the manufacturer and/or vendor (e.g., flocculants, coagulants, carbon, sand, organics). Active systems are chambered and may include pretreatment features to enhance the treatment process. Media filtration can significantly reduce pollutant concentrations categories (4.a), (4.e), and (4.g)35 depending on the specific treatment media. The costs vary significantly depending on the pollutant(s) intended for treatment, the size of the system, and the system design. Upfront costs are generally medium to high per area treated with medium to high maintenance requirements and cost.36 e. Retention BMPs (sediment basin, retention wet pond or extended detention wet pond)37 are constructed basins that have a permanent pool of water most of the year which settle out pollutants and can use plant life to biologically remove pollutants. Retention can significantly reduce pollutant concentrations for all categories but (4.c) and effectiveness for category (4.g) varies depending on the metal and whether the metal is dissolved.38 The upfront and maintenance requirements and costs are tied to proper sizing and design of the system and vary from medium to low.39
f. Detention BMPs (Dry extended detention ponds, dry ponds, extended detention basins, detention ponds, extended detention ponds)40 are basins with designed outlets to achieve a required stormwater draw down time (e.g., 24, 48, or 72 hours). The basins are designed to detain stormwater runoff for some minimum time (e.g., 48 hours) allowing particles and associated pollutants to settle. These basins have a temporary wet pool dependent on the infiltration rate of the subsoil. Detention can significantly reduce pollutant concentrations 34 CASQA Industrial and Commercial BMP Handbook, TC-40 Media Filter. 35 CASQA Industrial and Commercial BMP Handbook, TC-40 Media Filter. 36 State of Hawaii BMP Manual, page 7-2 Table 1; U.S. DOT BMP Selection and Monitoring, section 6.5 Table 57; U.S. EPA BMP Cost Estimation Memorandum, page

8. 37 CASQA Industrial and Commercial BMP Handbook, TC-20 Wet Pond. 38 WERF International Stormwater BMP Database 2016 Summary Report. 39 State of Hawaii BMP Manual, page 7-2 Table 1; U.S. DOT BMP Selection and Monitoring, section 6.5 Table 57; U.S. EPA BMP Cost Estimation Memorandum, page

8. 40 CASQA Industrial and Commercial BMP Handbook, TC-22 Extended Detention Basins.

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for all categories except for (4.c) and (4.g), though detention’s effectiveness for metals is variable depending on the metal and whether the metal is dissolved.41 The upfront and maintenance requirements and costs are tied to proper sizing and design of the system and vary from medium to low.42 g. Wetland BMPs (constructed wetlands)43 are constructed basins with a permanent pool of water for most of the year and are shallower with more vegetation than wet ponds. Stormwater is stored in the shallow pools of vegetation. Pollutant removal is achieved through microbial transformation, plant uptake, settling, and adsorption. Pretreatment is suggested to reduce the needed annual maintenance by reducing the amount of sediment and other solids entering the BMP. Wetlands can significantly reduce pollutant concentrations for all categories except for (4.b) and (4.c).44 The upfront costs are medium to high, and the operation and maintenance costs and requirements are medium.45
h. Infiltration BMPs (volume reduction)46 are trenches or basins which store stormwater in the void space between the media (e.g., rock, stones, soil media) and infiltrates/exfiltrates through the bottom and sides into the ground.

Infiltration reduces stormwater discharge volume and pollutant loadings to surface waters and can recharge groundwater aquifers or be used for other appropriate purposes and provide cost-savings by offsetting the use of potable water (e.g., cooling towers and equipment cleaning water). Pretreatment is necessary to limit the amount of gross pollutants, oil & grease, and sediment to the system to ensure the system functions properly. Infiltration can significantly reduce pollutant concentrations for all categories, however, in all cases fate and transport of pollutants to groundwater should be evaluated for impacts to drinking water beneficial uses (e.g., salts, solvents). The upfront and 41 WERF International Stormwater BMP Database 2016 Summary Report. 42 State of Hawaii BMP Manual, page 7-2 Table 1; U.S. DOT BMP Selection and Monitoring, section 6.5 Table 57; U.S. EPA BMP Cost Estimation Memorandum, page

8. 43 CASQA Industrial and Commercial BMP Handbook, TC-21 Constructed Wetlands. 44 WERF International Stormwater BMP Database 2016 Summary Report. 45 State of Hawaii BMP Manual, page 7-2 Table 1; U.S. DOT BMP Selection and Monitoring, section 6.5 Table 57; U.S. EPA BMP Cost Estimation Memorandum, page

8. 46 CASQA Industrial and Commercial BMP Handbook, TC-10 Infiltration Trench and TC11 Infiltration Basin.

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maintenance costs and requirements are tied to proper sizing and design of the system and are medium.47
Table 2 – Effective BMP Examples for TMDL Pollutant Categories48 Best
Management
Practice
Bacteria
(4.a)
Chloride
and
Salts
(4.b)49
Diazinon
(4.c)
Nutrients
(4.d)
Sediment
(4.e)
Temperature
(4.f)
Toxics
and
Metals
(4.g)50
NonStructural
and
Exposure
Minimization

X X X X X X X
Bioretention
Devices

X X X X X
Media or
Treatment
Filtration
X X X
Retention
Basins/
Ponds

X X X X X X
Detention
Basins/
Ponds

X X X X X
Constructed
Wetlands

X X X X X
Infiltration
or Volume
Reduction

X X X X X X
47 State of Hawaii BMP Manual, page 7-2 Table 1; U.S. DOT BMP Selection and Monitoring, section 6.5 Table 57; U.S. EPA BMP Cost Estimation Memorandum, page

8. 48 WERF International Stormwater BMP Database 2016 Summary Report. Also see Table 2 footnotes 47 and 48.
49 Not evaluated in the WERF International Stormwater BMP Database 2017 Summary and is based upon guidance from the Minnesota 2015 Industrial Stormwater BMP Handbook.
50 From CASQA TC-10 and TC-11 not evaluated in the WERF International Stormwater BMP Database 2017 Summary.

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I.H. Rationale
I.H.1. General Permit Approach
A General Permit for construction activities over one acre is an appropriate permitting approach for the following reasons:
a. A General Permit is an efficient method to establish the essential regulatory requirements for a broad range of construction activities under differing site conditions;
b. A General Permit is the most efficient method to handle the large number of construction stormwater permit applications;
c. A General Permit application process for coverage is far less onerous than that for individual permit and hence more cost effective;
d. A General Permit is consistent with U.S. EPA's four-tier permitting strategy, the purpose of which is to use the flexibility provided by the Clean Water Act in designing a workable and efficient permitting system; and e. A General Permit is designed to provide coverage for a group of related facilities or operations of a specific industry type or group of industries. It is appropriate when the discharge characteristics are sufficiently similar, and a standard set of permit requirements can effectively provide environmental protection and comply with water quality standards for discharges. In most cases, the general permit will provide sufficient and appropriate management requirements to protect the quality of receiving waters from discharges of stormwater from construction sites.

There may be instances where a General Permit is not appropriate for a specific construction project. A Regional Water Board may require any discharger otherwise covered under this General Permit to apply for and obtain an individual permit or apply for coverage under a more specific General Permit. The Regional Water Board must determine that this General Permit does not provide adequate assurance that water quality will be protected, or that there is a site-specific reason why an individual permit should be required.

There may be other permits or requirements in addition to this General Permit. For example, the discharger may also need a streambed alteration agreement from the California Department of Fish and Wildlife, a Water Quality Certification (CWA § 401) as administered by the State and Regional Water Boards, CWA § 404 permit administered by the U.S. Army Corp. of Engineers, and/or a permit for low threat or de minimis discharges. Contact the appropriate Regional Water Board(s) to determine if other permits are required for the construction activity.

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I.H.2. Antidegradation Findings
Federal regulations at 40 Code of Federal Regulations § 131.12 require that state water quality standards include an antidegradation policy consistent with federal requirements. The State Water Board established California’s antidegradation policy in State Water Board Resolution No. 68-16 (“Statement of Policy with Respect to Maintaining High Quality of Waters in California”). Where the federal antidegradation policy is applicable, the State Water Board has interpreted Resolution No. 68-16 to incorporate the federal antidegradation policy.51 The permitted discharge must be consistent with the antidegradation provision of 40 Code of Federal Regulations § 131.12 and State Water Board Resolution No. 68-

16. The State Water Board finds that the permitted discharges authorized by this general NPDES permit are consistent with the antidegradation provisions of 40 Code of Federal Regulations § 131.12 and State Water Board Resolution No. 68- 16, as set forth herein.

In the context of this general NPDES permit, compliance with the federal antidegradation policy requires consideration of the following. First, the State Water Board must ensure that “existing instream uses and the level of water quality necessary to protect the existing uses” are maintained and protected.52 Second, if the baseline quality of a waterbody for a given constituent “exceeds levels necessary to support propagation of fish, shellfish, and wildlife and recreation in and on the water,53 that quality shall be maintained and protected” through the requirements of this general NPDES permit unless the State Water Board makes findings that: (1) any lowering of the water quality is “necessary to accommodate important economic or social development in the area in which the waters are located”; (2) “water quality adequate to protect existing uses fully” is assured; and (3) “the highest statutory and regulatory requirements for all new and existing point sources and all cost-effective and reasonable best management practices for nonpoint source control” are achieved.54 Before allowing any lowering of high quality water, the Board must conduct an analysis of alternatives that evaluates practicable alternatives that would prevent or lessen the degradation associated with the discharges permitted. In the context of 40 Code of Federal 51 State Water Board Order WQ 86-17 (Fay), pages 16-19. 52 State Water Board, Administrative Procedures Update, Antidegradation Policy Implementation for NPDES Permitting, 90-004 (APU 90-004), page 4. 40 Code of Federal Regulations § 131.12(a)(1). This provision has been interpreted to mean that, “[i]f baseline water quality is equal to or less than the quality as defined by the water quality objective, water quality shall be maintained or improved to a level that achieves the objectives.”
53 This discussion refers to such waters as “high quality waters.” 54 40 Code of Federal Regulations § 131.12(a)(2).

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Regulations § 131.12(a)(2)(ii), practicable means “technologically possible, able to be put into practice, and economically viable.”55
The permit must also comply with any requirements of State Water Board Resolution No. 68-16 beyond those imposed through incorporation of the federal antidegradation policy.56 Resolution No. 68-16 requires that high quality waters be maintained unless degradation is justified based on findings that any lowering of water quality is “consistent with the maximum benefit to the people of the State” and “will not unreasonably affect present and anticipated beneficial use of such water and will not result in water quality less than that prescribed in the policies” and further that the discharge is subject to “waste discharge requirements which will result in the best practicable treatment or control of the discharge.”57 The baseline quality considered in making the appropriate findings is the best quality of the water since 1968, the year of adoption of Resolution No. 68-16, or a lower level if that lower level was allowed through a permitting or other regulatory action, such as establishing a water quality objective, that was consistent with the federal and state antidegradation policies.58 The following analysis assumes, without deciding, that the baseline for antidegradation analysis is 1968.59

55 40 Code of Federal Regulations § 131.3(n).
56 State Water Board Order No WQ 86-17 (Fay), page 23, Finding No. 11 57 State Water Board Orders WQ 81-5 (City of Lompoc), WQ 82-5 (Chino Basin Municipal Water District), WQ 90-6 (Environmental Resources Protection Council).

State Water Board Resolution 68-16, Resolve 2. Best practicable treatment or control is not defined in Resolution 68-16; however, the State Water Board has evaluated what level of treatment or control is technically achievable using “best efforts.” Questions and Answers, State Water Board Resolution 68-16, (Feb. 16, 1995), pp. 5-

6. The State Water Board states: “To evaluate the best practicable treatment or control method, the discharger should compare the proposed method to existing proven technology; evaluate performance data, e.g., through treatability studies; compare alternative methods of treatment or control; and/or consider the method currently used by the discharger or similarly situated dischargers...The costs of the treatment or control should also be considered....”
58 State Water Board APU 90-004, page.4. The baseline for application of the federal antidegradation policy is 1975, which is the date used in 40 Code of Federal Regulations § 131.3(e) to define existing uses of a waterbody. For state antidegradation requirements, see also Asociacion de Gente Unida por el Agua (AGUA) v. Central Valley Water Board (2012) 210 Cal.App.4th 1255,1270. The baseline for the application of the state antidegradation policy is generally the highest water quality achieved since 1968, the year the policy was adopted. 59 State Water Board Resolution 68-16, Resolve 1. The baseline may be later than 1968 for two reasons. First, the appropriate baseline is determined by the date on which a

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a. The Board Is Not Required to Make Waterbody by Waterbody and Pollutant by Pollutant Antidegradation Findings
The State Water Board finds that it is not required to conduct a waterbody by waterbody and pollutant by pollutant antidegradation analysis for this permit.

The State Water Board makes this finding for two reasons. First, the Administrative Procedures Update, Antidegradation Policy Implementation for NPDES Permitting, 90-004 (APU 90-004), which specifies a waterbody by waterbody and pollutant by pollutant analysis for some permitting actions, does not address permitting for diffuse stormwater discharges. Second, APU 90-004 itself indicates that a waterbody by waterbody and pollutant by pollutant analysis is only required when conducting a “complete” antidegradation analysis; a complete analysis, in turn, is not required where any “reduction in water quality is temporally limited and would not result in any long-term deleterious effects on water quality.”60 As detailed below in the section regarding waters that do not meet water quality objectives and in Alternative 1, a complete analysis is not required. The discussion below elaborates on these two reasons.

APU 90-004 is a State Water Board internal guidance document establishing methods for implementing the federal and state antidegradation policies in NPDES permits. APU 90-004 suggests that an antidegradation analysis requires a pollutant by pollutant and waterbody by waterbody analysis in certain contexts, specifically where the discharge at issue is a discrete discharge from a singular facility, such as discharges from publicly owned treatment works.

However, APU 90-004 has limited value when considering antidegradation in the context of diffuse stormwater discharges from tens of thousands of future construction projects of a wide variety distributed throughout the entire state over the life of the permit, each with the potential for discharging multiple policy establishing the level of water quality to protect was effective.

State Water Board APU 90-004, page 2. The various water quality control plans and State Policies for Water Quality Control have been adopted and amended many times since the 1970’s to include new or revised water quality objectives. Second, a permitting action with appropriate antidegradation findings allowing degradation may establish a new baseline consistent with the level of water quality achieved under that permit. The State Water Board has regulated construction stormwater discharges in the past through general permits issued in 1999 and 2009. APU 90-004 acknowledges that no antidegradation analysis is required where the water board has no expectation that water quality will be reduced by the permitting action; here, if the water quality achieved under the prior general permits had been used as the baseline, arguably, no antidegradation analysis would have been required. Nevertheless, for ease of analysis, 1968 is used herein as the baseline.
60 State Water Board APU 90-004, page 2.

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pollutants, to a wide variety of waterbodies statewide.61 This interpretation is sensible, if not necessary, for this general NPDES permit, given the short-term nature of construction projects and the fact that, as of the date of adoption of this permit, the type and location of the construction projects that will be regulated by this General Permit is unknown. Therefore, only a generalized antidegradation analysis can, and must, be conducted for the discharges authorized by this general NPDES permit.

In addition, reliable data on the baseline water quality since 1968 is not available for all pollutants for all surface waters of the state that might receive discharges authorized by this General Permit. The State Water Board did not begin conducting statewide assessments of water quality until 1973. That first assessment was based only on very limited sampling for only five water quality parameters on portions of 23 water bodies. Over the course of the next five decades, those assessments have gradually become more comprehensive and thorough, culminating with the State Water Board’s most recent 2020-2022 Integrated Report, which assessed the waterbodies for three of the nine Regional Water Quality Control Boards. However, even though a large amount of ambient water quality data is now collected and evaluated for these biennial assessments, the integrated reports are focused on assessing whether the waterbodies are supporting beneficial uses. The assessments are not intended to provide information about whether the waterbodies are of a higher quality than necessary to support their beneficial uses.62 As a result, this analysis assumes that some of the waterbodies that will receive stormwater discharges from some of the construction sites are high quality waters with respect to at least some pollutants that might be in the authorized discharges. Due to the wide variety and unknown identity of the large number of potential waterbodies that might receive authorized discharges from construction projects under this permit and the lack of specific, reliable data regarding each potential receiving waterbody, the analysis of waterbodies that might be affected by this general NPDES permit must also be done at a generalized level.

The State Water Board additionally finds that, even if APU 90-004 applies to the issuance of this permit, it requires at most a “simple” antidegradation analysis. APU 90-004 contemplates that a “simple” antidegradation analysis is 61 State Water Board Order WQ 2018-0002, page 77. Reaches a similar conclusion for agricultural discharges. This is even more so for the discharges authorized by this Order, because, unlike discharges from agricultural lands, there is much more uncertainty as to the location of the future construction projects and the temporal nature of discharges of stormwater from construction sites. 62 Regional Water Quality Control Boards Biennial Assessments. <https://www.waterboards.ca.gov/water_issues/programs/water_quality_assessment> [as of July 19, 2022]

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appropriate under specified circumstances. In particular, as stated above, APU 90-004 states that a simple antidegradation analysis is allowed when the “[Water] Board determines the reduction in water quality is temporally limited and will not result in any long-term deleterious effects on water quality; e.g., will cease after a storm event is over.”63
APU 90-004 does not provide guidance on the scope and content of a simple antidegradation analysis. Nor does it define the terms “temporally limited” or “long term.” Those terms must therefore be interpreted in the context of the types of discharges being permitted and with deference to the best professional judgment of the State Water Board. Construction stormwater discharges fit within the example provided by the APU and are temporal and inherently shortterm. Therefore, any degradation would be temporally limited and would not result in long-term deleterious effects on water quality. In addition, the permit continues the requirements of the previous permits or imposes equivalent or more protective requirements such that, in at least at a generalized level, the water quality established under the prior permits is expected to be maintained and improved.

The State Water Board determines that the findings made below meet the requirements of a simple antidegradation analysis and are also consistent with an antidegradation analysis done at a generalized level, as appropriate for this permit. With these findings, based on the information available to it and using its best professional judgment, the State Water Board concludes that the discharge will not be adverse to the intent and purpose of the State and federal antidegradation policies. Regardless of APU 90-004’s application, however, the below analysis is consistent with the generalized antidegradation analysis appropriate for this general NPDES permit and complies with both the federal antidegradation regulations, and with the State antidegradation policy. b. The State Water Board Makes the Following Antidegradation Findings The discharges permitted in the permit are consistent with the antidegradation provisions of 40 Code of Federal Regulations § 131.12 and Resolution No. 68-

16. The State Water Board’s conclusion that the terms and conditions of the permit are consistent with the antidegradation policies is based on the following analysis.

First, for waterbodies that meet, but do not exceed, the water quality objective for a particular pollutant, no antidegradation findings are required. For these waterbody and pollutant combinations, compliance with the General Permit’s requirements ensures that all construction stormwater discharges authorized by 63 State Water Board APU 90-004, p. 2

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this permit do not interfere with the maintenance and protection of existing beneficial uses and water quality objectives.
i. Waterbodies that do not meet water quality objectives (waterbodies that are not high quality)
Because coverage under this General Permit is available statewide, this General Permit authorizes discharges to at least some surface waters that are not meeting water quality objectives. Some of these waterbodies are listed on the State Water Board’s section 303(d) list of impaired waters, some of which have applicable TMDLs developed by the Regional Water Boards or U.S. EPA.64 Some receiving waters are not meeting water quality objectives for multiple pollutants. Under both federal and state antidegradation policies, these receiving waters are not considered “high quality” waters for these pollutants. For receiving waters that are not high quality waters, the federal antidegradation policy requires that regulatory actions ensure that existing instream uses and the level of water quality necessary to protect the existing uses are maintained and protected. (40 Code of Federal Regulations § 131.12(a)(1).)65 The General Permit ensures that existing instream (beneficial) uses and the level of water quality necessary to protect the existing uses are maintained and protected through requirements that discharges authorized by this General Permit do not cause or contribute to exceedances of water quality objectives in the receiving water and to restore impaired waterbodies by requiring compliance with TMDL-specific requirements as set forth in Attachment H and compliance with receiving water limitations set forth in the General Permit, Section IV.D. These provisions are collectively designed to ensure that discharges authorized by this General Permit do not cause any further degradation of impaired waterbodies and do not interfere with the improvement of the quality of such waters to a level protective of existing uses over a time schedule that is as short as possible.

The antidegradation policies do not explicitly or implicitly override the authority and discretion the Clean Water Act and the Water Code grant to the State Water Board as to how it structures a permit to ensure water 64 Impaired waters, or waters that are not high quality, are not confined to those listed only on the 303(d) List. There are several reasons for this, including but not limited to that some of the 303(d) Lists do not reflect current data. In addition, sometimes the State lacks sufficient data to add a waterbody to the 303(d) List. Accordingly, the 303(d) List itself does not reflect all waterbodies that are impaired. 65 By its terms, State Water Board Resolution No. 68-16 does not separately apply to waters that are not high quality, except by incorporating the federal antidegradation policy as discussed above.

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quality necessary to protect beneficial uses. The law does not require immediate restoration of impaired waterbodies nor does it require an immediate prohibition of discharges that contribute to an exceedance in the waterbody. Rather, federal regulations at 40 Code of Federal Regulations § 122.47 allow NPDES permits to have compliance schedules. Similarly, Water Code § 13263, subdivision (c), authorizes the Regional Water Boards to include a time schedule for achieving water quality objectives in waste discharge requirements. Consistent with Water Code § 13242, TMDL implementation plans, as incorporated into the water quality control plans, include a time schedule for actions to be taken. When issuing waste discharge requirements, Water Code § 13263 requires Regional Boards to implement any relevant water quality control plans that have been adopted.

Certainly, water quality objectives must be achieved; but the law, as cited above, recognizes and allows for the fact that it can take time to restore or achieve the objectives. In this regard, some impaired waterbodies may fail to improve or, rarely, continue to degrade, for a period of time before showing improvement. This period of time may be as long as multiple years.

This is not contrary to the authorities for compliance schedules stated above and is not contrary to the antidegradation policies.
ii. High quality waterbodies
Some of the waterbodies within the area covered by this General Permit may be high quality waters for certain pollutants. Some of these waterbodies may be currently high quality as compared to currently applicable objectives. Others of these waterbodies may be currently impaired but may be classified as high quality waters because they were historically high quality for certain pollutants.

Although compliance with the General Permit will generally not result in degradation in high quality waters, compliance with the General Permit does not guarantee that there could never be any degradation in any high quality waters from a specific construction project. Therefore, the State Water Board makes the following findings to comply with antidegradation requirements for any discharges authorized by this General Permit to high quality waters.

For high quality waterbodies, the State Water Board finds as follows:

First, to determine whether the discharge is necessary, the State Water Board must determine whether there are any cost-effective alternatives available that eliminate or reduce the reduction in water quality. For a general, statewide permit, the appropriate inquiry is whether there are costeffective alternatives to the regulatory framework in the General Permit, not whether there is a cost-effective alternative to an individual project eligible for enrollment under the General Permit. The State Water Board has

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determined that construction stormwater discharges are appropriately regulated under a general permit rather than individual NPDES permits.

There are typically approximately 10,000 ongoing construction projects with stormwater discharges authorized under this General Permit (or its predecessor general permits) at any given time, according to the State Water Board’s SMARTS database. These projects typically last from one to three years, at which point coverage under this General Permit is terminated and discharges are no longer authorized. Employing the large number of additional staff necessary to review and issue such a high volume of individual stormwater permits would not be efficient use of resources, would necessitate very large increases in permit fees under Water Code § 13260, subdivision (d)(1)(B) to pay for the additional staff, and would likely result in economic disruption due to delays in permitting construction projects. As further explained in Fact Sheet, Section I.H.1, a General Permit is the appropriate mechanism to regulate a large number of similar discharges while still protecting water quality.

Practicable Alternatives: The State Water Board has evaluated a range of practicable alternatives that would prevent or lessen any degradation associated with permitted construction stormwater discharges to high quality waters. These alternatives are discussed below.

Alternative 1 – The first alternative is the approach that the General Permit takes. The General Permit requires dischargers, with the assistance of qualified stormwater professionals, to:
1) Determine the risk the construction project poses on the receiving water, based on how much sediment is anticipated to be discharged offsite and whether the receiving water is impaired for sediment or supports COLD, SPAWN, and MIGRATORY beneficial uses. Higher risk projects must comply with additional permit requirements, including sampling and monitoring, and additional BMPs.
2) Assess conditions at the construction site that could impact stormwater quality such as sources of pollutants that could be transported offsite by stormwater runoff.
3) Develop a site-specific Stormwater Pollution Prevention Plan to include information needed to demonstrate compliance with all requirements of the permit and to ensure water quality is protected (Fact Sheet, Section I.V.). This includes identification and implementation of a suite of best management practices tailored to the construction project and the conditions at the site to minimize or eliminate the stormwater discharges, or the pollutants in the stormwater discharges, or both, in compliance with BCT/BAT/BPT standards.

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4) Visually inspect the construction site to verify implementation of best management practices is in accordance with the Stormwater Pollution Prevention Plan.
5) Monitor stormwater discharges for pH and turbidity during each day of a qualifying precipitation event and compare sample results to numeric action levels to verify that implementation of the best management practices is protective of water quality.
6) Monitor stormwater discharges for TMDL-specific pollutants, if applicable, and compare to a TMDL-related numeric action level or numeric effluent limitation to verify that the discharge complies with the TMDL-based waste load allocations. TMDL monitoring requirements apply if the site is in a TMDL watershed with waste load allocations translated into numeric action levels or numeric effluent limitations; has sources of the TMDL-specific pollutant(s) onsite; and there is a failure to implement best management practices, a container spill or leak, or a best management practices breach, failure, or malfunction. 7) Take corrective actions such as repairing or implementing additional best management practices, if visual inspections and discharge monitoring indicate a deficiency.
8) Submit sampling and annual reports regarding implementation of this General Permit.

All discharges authorized by this General Permit must comply with receiving water limitations that require that discharges 1) do not adversely affect human health or the environment, 2) do not contain pollutants in quantities that threaten to cause pollution or public nuisance, 3) do not contain pollutants that cause or contribute to an exceedance of any applicable water quality objectives or standards contained within an applicable water quality control plan, and 4) comply with the applicable TMDL implementation requirements of this General Permit (Order, Section IV.D). Furthermore, the Regional Water Boards retain the authority to impose any additional sitespecific requirements where necessary to prevent degradation and to protect water quality standards.

Under this General Permit, there are disincentives to discharging such that dischargers already seek to minimize or eliminate their stormwater discharges where possible. The General Permit promotes efforts to maximize the capture of stormwater from construction sites through retention basins, infiltration galleries, and other controls that reduce the amount of stormwater that is discharged from the site. If there are no discharges, the General Permit’s sampling requirements and any otherwise applicable numeric action levels or numeric effluent limitations are not

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applicable to that discharger and the discharger would not risk an enforcement action for any potential discharge-related General Permit violations. Accordingly, dischargers have an incentive to schedule their work during dry weather or to retain stormwater whenever possible. Collectively, these requirements generally prevent degradation, and where that is not possible, minimize degradation and the duration of any degradation. This alternative does not, however, guarantee that no construction site will ever have authorized stormwater discharges that may result in temporary, limited degradation.

Alternative 2 – The second alternative would be more stringent permit requirements in watersheds with high quality waters. Different approaches for more stringent requirements could include a construction prohibition, a prohibition of discharges, a requirement that active treatment be used for all pollutants in all stormwater discharges, or numeric effluent limitations for all pollutants in all stormwater discharges.

The State Water Board finds that more stringent requirements are not currently possible for any of these approaches for the following reasons:
· Construction prohibition: Such a prohibition would exceed the State Water Board’s authority to regulate discharges of waste to waters of the state from discharges. The State Water Board does not have the authority to directly regulate land use. (Wat. Code, §§ 13260, 13263.) Such a prohibition is also not possible because many construction projects are essential and cannot be relocated (e.g., repair of existing roads and utilities).
· Prohibition on discharges: By eliminating all stormwater discharges, pollutants from stormwater would not reach high quality receiving waters during wet weather and therefore could not cause any degradation. As wet weather will always occur, this approach would require all construction sites to retain all stormwater through retention basins, infiltration galleries, and other controls that would prevent stormwater from reaching surface waters through infiltration, evaporation, or storage and reuse. The complete retention to eliminate any possibility of discharge is not typically technologically or economically feasible in many locations. Although retention, detention, and run-on BMPs are frequently implemented as part of the SWPPP, these BMPs are typically designed only to reduce stormwater discharges or the likelihood thereof, not to completely eliminate discharges. Retention that eliminates the possibility of discharges to any surface waters would require much larger sizing than a retention or detention BMP used to reduce discharges because it would need to be sized to capture even extreme weather

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events.66 U.S. EPA estimated that the base cost, which does not include costs of acquiring the land,67 annual maintenance costs, design, geotechnical testing, legal fees, land costs, and other unexpected or additional costs such as fees for disposing of contaminated excavated soils, for a retention and detention basins is $0.50-$1.00 per cubic foot.68 The estimate of typical costs reflects 15,000 – 150,000 cubic feet of storage. Thus, a retention basin for a 50-acre residential site would have the base cost of $100,000. But this base cost only represents the typical implementation of stormwater BMPs, which only provide for detention or partial retention. A retention basin for a 50-acre residential site that eliminated the possibility of discharge would need to be much larger and therefore is more costly. Most California counties require stormwater basins to be designed to a 2-year, 24-hour storm intensity at minimum.

Assuming a typical bare soil runoff coefficient of 0.35 (Type C soil), a 2- year, 24-hour storm (2.27 inches of rainfall) at a 50-acre site in Orange County, for example, would produce a total of approximately 3.31 acrefeet of runoff per day. Adding a normal Factor of Safety for detention structures of 2.0, 5,770 cubic feet of water would need to be retained per acre, or 288,400 cubic feet for the entire parcel. An ‘atmospheric river’ type storm that lasted three days at this intensity would require at least six times this amount of storage, as the runoff coefficient would increase each day. The costs would vary significantly depending on land costs (e.g., urban versus rural area) and slope. Complete retention of all stormwater would not be technologically feasible at all construction sites. 66 For example, in October 2021, there were historic Category 5 atmospheric rivers throughout California.
67 The cost of acquiring land can be substantial.

E.g. Working Paper 19-01: The Price of Residential Land for Counties, ZIP codes, and Census Tracts in the United States.,
<https://www.fhfa.gov/PolicyProgramsResearch/Research/Pages/wp1901.aspx> [as of July 19, 2022]. For example, in Los Angeles County, residential land costs were estimated at $1-3 million per acre. Id.

See also, Southern California Coastal Water Research Project. Concept Development: Design Storm for Water Quality in the Los Angeles Region, Technical Report 520. October 1, 2007, page 7.
<https://ftp.sccwrp.org/pub/download/DOCUMENTS/TechnicalReports/520_designSto rm.pdf> [as of July 19, 2022].
68 U.S. EPA Urban Storm Water BMP Preliminary Data Summary - 1999, page 6-3. <https://www.epa.gov/sites/default/files/2015-11/documents/urban-stormwaterbmps_preliminary-study_1999.pdf> [as of July 19, 2022]. Other costs could include, for example, filling, regrading, and vegetating the retention pond after the construction project has concluded.

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Certain sediment types are poorly suited for infiltration (e.g., clay soils infiltrate poorly). Construction sites are inherently dynamic, but retention basins cannot move. Stormwater may have different discharge points during different phases of construction, and a retention basin could not be moved to accommodate the changing points. In urban areas with infill development, there is not sufficient space for such large retention basins. In some cases, such large basins could also implicate vector control or public safety issues.69 In other areas where the groundwater table is high, it may not be possible to design an effective retention basin without hitting the groundwater table and potentially causing groundwater quality problems.

Even if complete retention were technologically possible, the costs associated with constructing effective complete retention structures are not generally economically feasible for most construction projects.70 Expensive, structural BMPs are generally not economically feasible to implement on construction sites, which are temporary in nature, in part because the useful life of the investment is short-term and difficult to recoup. Requiring implementation of substantially more expensive controls may render projects that are beneficial to the people of the state economically infeasible. For example, government-funded road projects often operate on fixed budgets where increased costs on one construction project leaves less money to complete other projects.71 Similarly, restoration projects are frequently funded by grants. Increased construction costs would render less money available for additional restoration projects. Increased construction 69 Southern California Coastal Water Research Project. Concept Development: Design Storm for Water Quality in the Los Angeles Region, Technical Report 520. October 1, 2007, page 7.
<https://ftp.sccwrp.org/pub/download/DOCUMENTS/TechnicalReports/520_designSto rm.pdf> [as of July 19, 2022]. Notes the potential trade-offs between water quality and ensuring public safety, including protecting property from flood damage and maintaining passable roadways.
70 Southern California Coastal Water Research Project. Concept Development: Design Storm for Water Quality in the Los Angeles Region, Technical Report 520. October 1, 2007, p. 14.
<https://ftp.sccwrp.org/pub/download/DOCUMENTS/TechnicalReports/520_designSto rm.pdf> [as of July 19, 2022]. Provides an example. Discusses the feasibility of BMP implementation costs in the Ballona Creek watershed and highlighting the difference between new or redevelopment versus retrofit.
71 Overview of Transportation Funding (2015).
<https://lao.ca.gov/handouts/transportation/2015/Transportation-Funding-022315.pdf> [as of July 19, 2022]. For example, general obligation bonds can help pay for transportation projects and are for a set amount.

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costs might also deter affordable housing projects, which operate on thin margins and frequently depend on government subsidies.72

Determining a range of costs for complete retention of stormwater is complex due to the wide variety of conditions. Costs vary widely across construction projects throughout California due to precipitation, size, soil types, topography, and other location-specific factors such as labor costs.

Two examples of costs to complete full retention of stormwater on a site with 16 acres of disturbed soil area (mean CGP size), based solely on the difference in precipitation, are as follows:

On a 16-acre project in the rainy North Coast region, a 2 year, 24-hour storm (2.93 inches of rainfall) would require a 148,900 cubic foot capacity detention basin, equivalent to a 29,780 square foot excavation at five feet in depth, including the required one foot of freeboard. A typical cost of $10/cubic yard for excavation73 is approximately $55,150, not including offhaul of spoils, if required. In addition, the basin would require engineered backfill if any roadways or buildings were subsequently constructed at the site, increasing the costs by $415,000 for import backfill and compaction (at $75/cubic yard).74 This scenario would therefore have a total cost of at least $470,150, since there would be additional costs for engineering design and final grading.

On a 16-acre project in an arid southern California region, the 2-year, 24- hour storm (1.72 inches of rainfall) for a similar level of retention would require an 87,400 cubic foot capacity detention basin at an excavation-only cost of $32,375. Using the same assumptions as above, engineered backfill would increase the total costs to at least $275,150.

The above examples show excavation and backfill costs only for a one-day design storm, and would add $3,000–$5,000 to the cost of each house in a typical residential development, depending on location (based on six houses/acre). However, an ‘atmospheric river’ storm lasting three days at the same intensity would require far more retention capacity, as the runoff coefficient would increase each day. In the northern part of the state, such a storm would necessitate an 893,400 cubic foot (33,100 cubic yard) basin, covering four acres at a four-foot depth and one foot of freeboard. The costs 72 Affordable Housing and Sustainable Communities Program. <https://www.hcd.ca.gov/affordable-housing-and-sustainable-communities> [as of July 19, 2022]. Provides an example.
73 Caltrans project 01-476604, Mendocino County, Item 044. <http://website.dot.ca.gov/hq/construc/estdet/01-476604-025.txt> [as of July 19, 2022] 74 Caltrans project 01-262004, Mendocino County, Item 072. <http://website.dot.ca.gov/hq/construc/estdet/01-262004-064.txt> [as of July 19, 2022]

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for excavation and engineered backfill would amount to $2.8 million.

Complete retention of stormwater for all construction sites regulated by this General Permit would be cost prohibitive.
· Active treatment: This approach would be to require the use of active treatment of all construction stormwater prior to discharge in areas with high quality waters. This approach may not be feasible because generally speaking, this permit may not specify the design location, type of construction, or particular manner in which compliance may be achieved with a requirement. (Wat. Code, § 13360.) In addition, active treatment is highly effective at treating water for TSS and turbidity, but generally does not remove pollutants that do not sorb to sediment, such as dissolved phase metals and hydrocarbon compounds. In order for this approach to be successful in guaranteeing no degradation of high quality waters, it would be necessary for active treatment to reliably treat all pollutants to levels that are equal to, or better than, the actual levels of each pollutant in each waterbody. Such limitations could only be established if the high quality waterbody and existing levels of each pollutant for which that water was high quality were known. As explained above, this data does not exist on a statewide basis. In addition, active treatment of all stormwater would likely be cost-prohibitive for some construction sites, because the cost of active treatment is directly related to the volume of stormwater that must be treated. For example, costs for a one-time use of active treatment systems ranges from $10,029 for 1.9 acres to $96,674 for 145 acres.75 However, current information obtained from staff conversations with an active treatment system vendor in the Sacramento area indicates that installed systems typically range from $70,000-$80,000 for a 200 gallon per minute seasonal system to $700,000 for a 2,000 gallon per minute seasonal system such as may be required to accommodate 3-inch storm events on a 16-acre site. Finally, based on staff conversations with the same active treatment system vendor and staff’s limited market search for additional active treatment vendors, active treatment systems are not evenly distributed throughout the state and there are currently an insufficient number of systems available to deploy to all construction sites during regional precipitation events.
75 U.S. EPA, Development Document for Final Effluent Guidelines and Standards for the Construction & Development Category (Nov. 2009) page. 9-35. <https://www.epa.gov/sites/default/files/2015-
06/documents/construction_development_dd_2009_chapters_1-11.pdf> [as of July 19, 2022]

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· Establishment of numeric effluent limitations for discharges to high quality waters: In order to prevent any degradation of any high quality water under this approach, the General Permit would have to implement water quality-based numeric effluent limitations that are equal to, or lower than, the actual ambient levels of each pollutant in each waterbody. Such limitations could only be established if the high quality waterbody and existing levels of each pollutant for which that water was high quality were known. As explained above, this data does not exist on a statewide basis. Even if the data did exist, it would not be possible to determine whether the methods to achieve compliance with the numeric effluent limitations would be technically or economically feasible at most or all construction sites. Further, because such numeric effluent limitations would necessarily be waterbody and pollutant specific, administration of such limitations would not be feasible under the General Permit structure.

Alternative 3 – Given the uncertainties about the locations of, and data limitations about, high quality waters, a third alternative would be to mandate specific requirements that would apply to all construction projects statewide. These statewide requirements could include more numeric effluent limitations, more stringent numeric action levels, or requiring the installation of specific BMPs, like active treatment.
· Require on-site stormwater retention for a compliance storm:

Because a prohibition on all discharges is not feasible as discussed above, one approach would be to require controls that eliminated discharges in most storms. For example, dischargers could be required to retain all runoff from the 95th percentile, 24-hour storm volume or the 85th percentile, 24-hour storm volume.76 Requiring all construction sites to install retention basins designed to retain all stormwater from large “compliance storms,” rather than complete retention from storms of all sizes, would encounter similar technological and economic difficulties as those identified above, just at a somewhat lesser scale. Considerations would have to include engineering design cost, available space for both the basin and excavation spoils stockpiles, avoidance of underground utility installations, schedule delays caused by constructing, using, backfilling and regrading the basin, off-haul of spoils and import of 76 Southern California Coastal Water Research Project. Concept Development: Design Storm for Water Quality in the Los Angeles Region, Technical Report 520, October 1, 2007, page 12.
<https://ftp.sccwrp.org/pub/download/DOCUMENTS/TechnicalReports/520_designSto rm.pdf> [as of July 19, 2022]. For example, a BMP sized to capture 90% instead of 80% of decadal runoff volume would require a BMP nearly triple the size.

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engineered fill, if required, disposition of accumulated stormwater or allowance for evaporation, vector control, and safety barriers. Further, there is no guarantee that the discharges from storms larger than the selected compliance storm would not cause degradation of high quality waters.
· Establishment of numeric technology based effluent limitations statewide: Even assuming that there might be a treatment technology that, if utilized, could guarantee no degradation of high quality waters, the State Water Board does not have the data that would be necessary to impose effluent limitation that would be derived from the use of that technology. In previous litigation, the superior court determined that the State Water Board did not have sufficient BMP performance data to impose technology based numeric effluent limitations for pH and turbidity for Risk Level 3 sites. Absent the development of this needed additional data, the Board would not be able to support the implementation of numeric technology based effluent limitations to prevent any possibility of degradation.77
· Active treatment: This option would suffer from the same problems identified for active treatment described under alternative 2, above.

Consistent with the Blue Ribbon Panel’s findings, active treatment is not feasible for all sites: “The active treatment systems have generally been employed on sites five acres or larger. While the systems are technically 77 California Building Industry Association v. State Water Resources Control Board, Sacramento Superior Court Case No. 34-20009-80000338-CU-WM-GDS.

Effluent Limitations Guidelines and Standards for the Construction and Development Point Source Category, 79 Federal Register 12661-01 (March 06,2014). The U.S.

EPA provides an explanation for not including a previous numeric effluent limitation for turbidity in its Effluent Limitation Guidelines for construction stormwater: “At this time, EPA is concerned that a numeric limitation may create a disincentive to green infrastructure techniques for managing stormwater. For example, meeting a numeric standard may require installation of a sediment basin or other impoundment on certain sites, which may be a disincentive to installing distributed stormwater controls. Also, EPA recognizes that additional data collection would likely be necessary in order to inform any establishment of numeric discharge standards and monitoring requirements in the future. At such time that EPA decides on a path forward with respect to numeric discharge standards and monitoring requirements, EPA will take appropriate actions to notify interested stakeholders. EPA encourages interested parties to continue submitting data and information to EPA with respect to numeric discharge standards at construction sites.”

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feasible for sites of any size, including sites or drainages as small as an acre or less, the cost may be prohibitive.”78
· Use of other, specific BMPs: Alternative 1 already requires the use of minimum BMPs such as non-structural BMPs (e.g., maintenance, good housekeeping, staff training/education, proper handling, spill response, project planning/scheduling) and source control BMPs (e.g., site design and planning, irrigation). This alternative approach would be to specify that certain additional BMPs would need to be used at all sites. This approach may not be feasible because generally speaking, as discussed above, this General Permit may not specify the design location, type of construction, or particular manner in which compliance may be had with a requirement. (Wat. Code, § 13360.) In addition, the efficacy of any structural BMPs are both site specific and pollutant specific, such that there are not universally beneficial BMPs that should be mandatory on all sites.

One of the first basic steps in creating a stormwater management plan is to assess site and watershed conditions. Site and watershed conditions include information such as geographic features or landmarks, drainage patterns, and general topography. Next, a plan should evaluate pollutants of concern and other additional benefits that BMPs can provide. Accordingly, the selection of appropriate BMPs is a highly site-specific inquiry. Because of the complexity of appropriate BMP selection, the permit requires a qualified stormwater professional to identify the appropriate site-specific BMPs and prepare the SWPPP. The General Permit imposes substantial education and training requirements for qualified stormwater professionals to ensure that the selection of site-specific BMPs is appropriate. (See General Permit, Sections V.C. – V.I.)
For example, bioretention basins are very effective for multiple pollutants, but are not feasible at many construction sites, as discussed in further detail in Fact Sheet, Section I.G.5.d. Media filters are another BMP that may be effective at removing multiple pollutants, but are already typically recommended by qualified stormwater professionals under Alternative 1.

Accordingly, requiring the universal use of specific structural BMPs for antidegradation purposes is not a feasible alternative because requiring specific BMPs may not be effective at reducing pollution and may not be technically feasible or cost effective depending on site characteristics. 78 The Feasibility of Numeric Effluent Limits Applicable to Discharges of Storm Water Associated with Municipal, Industrial, and Construction Activities, page 16.

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iii. Economic and Social Development Considerations and Consistency with Maximum Benefit to the People of the State
The State Water Board adopts the approach set forth in Alternative 1 for the General Permit. This alternative may allow limited and temporal degradation of high quality waters by construction stormwater discharges, but this alternative does require all construction stormwater discharges to not cause or contribute to exceedances of water quality objectives or interfere with the maintenance and protection of beneficial uses for high quality waters in all cases. Two of the approaches described under Alternative 2 would guarantee no degradation of high quality waters (i.e., construction prohibition and prohibition on discharges), but all of the approaches described under Alternative 2 are infeasible for the reasons described above and would hamper important social and economic development. The approaches described under Alternative 3 would not guarantee no degradation of high quality waters from authorized discharges, and are either technically or economically infeasible, or contrary to the framework of a general permit in which the methods for reducing or eliminating pollutants in stormwater discharges are developed by a stormwater professional and tailored to each individual construction site, or both.

The limited and temporal degradation of high quality waters that could occur under this General Permit is necessary to accommodate important economic or social development in the area and is consistent with the maximum benefit to the people of the state. Construction activities support important economic and social development. Construction is a large, vital industry in California, adding an estimated $240 billion in value in 2017 and a major source of employment.79 The U.S. Bureau of Labor Statistics estimates that there are 968,760 construction laborers in California.80 Construction projects include critical infrastructure (e.g., broadband 79 U. S. Census Bureau. Construction (NAICS Sector 23), (2017). <https://www.census.gov/data/tables/2017/econ/economic-census/naics-sector23.html> [as of July 19, 2022].

Legislative Analyst’s Office. CalFacts 2018. Construction is one of the major sectors for California’s 17 million jobs. <https://lao.ca.gov/reports/2018/3905/calfacts2018.pdf> [as of July 19, 2022]. 80 U. S. Bureau of Labor Statistics. Occupation Employment and Wage Statistics, 47- 2061 Construction Laborers (May 2021).
<https://www.bls.gov/oes/current/oes472061.htm> [as of July 19, 2022].

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internet,81 roads,82 utility lines), public safety (e.g., flood control,83 system hardening84), restoration,85 housing,86 and commercial development. As noted by many commenters on the draft versions of this General Permit, California is facing a housing shortage.

Where there is a public utility, increased construction costs could be passed on by increased fees to utility users or road users. Higher construction costs could affect whether a housing project remains affordable.

Importantly, under Alternative 1, notwithstanding the possibility of limited and temporal degradation from some authorized stormwater discharges, the State Water Board finds that authorized stormwater discharges will not cause or contribute to exceedances of water quality objectives in high quality waters, and therefore will not cause pollution or conditions of nuisance or otherwise adversely affect beneficial uses of the receiving waterbodies. Because all beneficial uses will be maintained and protected, there will be only very minor impacts to water quality resulting from any degradation that does occur, so any resulting harm to the public interest associated with any degradation will also be very minor and speculative 81 State of California Executive Department. Executive Order N-73-20 (August 14, 2020). <https://www.gov.ca.gov/wp-content/uploads/2020/08/8.14.20-EO-N-73-20.pdf> [as of July 19, 2022].
82 State Highway Operation and Protection Program. Ten-Year Project Book, Fiscal Years 2021/22-2030/31. <https://dot.ca.gov/-/media/dot-media/programs/assetmanagement/documents/2022-q2-book-combined-a11y.pdf> [as of July 19, 2022]. 83 California Department of Water Resources. Small Communities Flood Risk Reduction. <https://water.ca.gov/Work-With-Us/Grants-And-Loans/Small-Communities-FloodRisk-Reduction> [July 19, 2022]. 84 E.g., Governor Newsom Signs Historic Legislation to Boost California’s Housing Supply and Fight the Housing Crisis (September 16, 2021). <https://www.nytimes.com/2021/07/21/business/energy-environment/pgeunderground-powerlines-wildfires.html> [as of July 19, 2022]. In response to wildfires, utility companies aim to put power lines underground.
85 Southern California Wetlands Recovery Project. Work Plan 2020. <https://scwrp.org/wp-content/uploads/2020/04/Work-Plan-Report-2020.pdf> [as of July 19, 2022].
86 Office of the Governor. Governor Newsom Signs Historic Legislation to Boost California’s Housing Supply and Fight the Housing Crisis (September 16, 2021). <https://www.gov.ca.gov/2021/09/16/governor-newsom-signs-historic-legislation-toboost-californias-housing-supply-and-fight-the-housing-crisis/> [as of July 19, 2022]. In 2021, Governor Newsom signed bipartisan legislation to expand housing production in California.

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because all high quality waters will still fully support all beneficial uses.

Therefore, it is not necessary to analyze the harm to the public interest associated with the authorized stormwater discharges, especially in a generalized and simple antidegradation analysis.
iv. Requirement for Highest Statutory and Regulatory Requirements and Best Practicable Treatment and Control
The permit requires the highest statutory and regulatory requirements and requires that the dischargers meet best practicable treatment or control and, as described more fully above, requires the following:
· Implementation of BAT/BCT/BPT, including compliance with U.S. EPA’s effluent limitation guidelines for the construction and development category as the level of pollutant abatement that is the best available technology economically achievable;
· Compliance with receiving water limitations;
· Enhanced requirements on non-stormwater discharges;
· TMDL-specific requirements that are consistent with the waste load allocations established by TMDLs that identify construction stormwater as a source; and
· Reservation of authority for the Regional Water Boards to retain the ability to impose additional sampling and monitoring requirements or coverage under an individual NPDES permit if necessary. v. Public Participation:

Numerous public participation opportunities have been provided during the development of this permit. In addition to the minimum public participation requirements required by the federal regulations governing NPDES permits and Water Code § 13167, State Water Board staff has met informally with stakeholders, held staff workshops, and accepted comments on an administrative draft of the permit.

I.I. Regional Water Board Authorities
Because this General Permit will be issued to thousands of construction sites across the State, the Regional Water Boards retain discretionary authority over certain issues that may arise from the discharges in their respective regions. This General Permit does not grant the Regional Water Boards any authority they do not otherwise have; rather, it merely emphasizes that the Regional Water Boards can take specific actions related to this General Permit. For example, the Regional Water Boards will be enforcing this General Permit and may need to adjust some requirements for a discharger based on the discharger’s compliance history.

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I.J. Construction Activities Covered
I.J.1. General Activities Covered
Construction activity phases (demolition and pre-development site preparation, grading and land development, streets and utilities, vertical construction, and final landscaping and site stabilization) can impact a construction site’s runoff sediment supply, pollutant loading, and transport characteristics. These modifications can occur both during and after the construction phase and, without proper controls, such as the requirements set forth in this General Permit, could result in significant degradation of the established water body beneficial uses in California. The primary stormwater pollutant at construction sites is excess sediment. Excess sediment can cloud the water and reduce the amount of sunlight reaching aquatic plants, clog fish gills, smother aquatic habitat and spawning areas, and impede navigation in our waterways. Sediment also transports other pollutants such as nutrients, metals, oils, and greases, and pesticides. In addition to sediment, other pollutants that are commonly associated with construction activities include, but are not limited to, pollutants from cement, stucco, paints, cleaning materials, general debris, chemicals associated with historical structures mobilized through demolition, historical contamination chemicals in soil mobilized by construction disturbance, and other construction related products easily transported by stormwater runoff. Dischargers can reduce and avoid the effects of these pollutants on water quality through better construction site design and use of best management practices (BMPs).
a. In accordance with the Ninth Circuit Court of Appeals’ decision in Natural Resource Defense Council v. U.S. EPA (9th Cir. 2008) 526 F.3d 591, and subsequent denial of the U.S. EPA’s petition for reconsideration in November 2008, oil and gas construction activities discharging stormwater contaminated only with sediment are no longer exempt from the NPDES program; b. Site geotechnical investigation work requires special precaution when backfilling bore holes so that aquifers are adequately protected from surface contamination;
c. Disturbances related to geotechnical or other site investigation work is a construction activity requiring permit coverage;
d. Construction activities that disturb 1 or more acres of soil associated with the construction of new fire prevention methods (e.g., fire barriers, fire breaks, and fire prevention areas) require permit coverage;
e. Stormwater discharges from dredge spoil placement that occur outside of U.S.

Army Corps of Engineers jurisdiction (upland sites) and that disturb one or more acres of land surface from construction activity are covered by this General Permit. Construction projects that include in-water work that require a

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Clean Water Act 404 permit should contact the Regional Board to determine whether a Clean Water Act 401 Certification is necessary; and f. Concrete mixing for the purpose of construction, in which all mixing activities occur solely within a specific project site, may do so under this General Permit.

The project site boundary are those as defined in the project’s site-specific SWPPP.

I.J.2. Linear Underground and Overhead Projects subject to this General Permit a. Underground and overhead facilities typically constructed as linear underground and overhead projects include, but are not limited to, any conveyance, pipe, or pipeline for the transportation of any gaseous, liquid (including water, wastewater for domestic municipal services), liquescent, or slurry substance; any cable line or wire for the transmission of electrical energy; any cable line or wire for communications (e.g., telephone, telegraph, radio, or television messages); and associated ancillary facilities. Construction activities associated with linear underground and overhead projects include, but are not limited to, those activities necessary for the installation of underground and overhead linear facilities (e.g., conduits, substructures, pipelines, towers, poles, cables, wires, connectors, switching, regulating and transforming equipment and associated ancillary facilities) and include, but are not limited to, underground utility mark-out, potholing, concrete and asphalt cutting and removal, trenching, excavation, boring and drilling, access road and pole/tower pad and cable/wire pull station, substation construction, substructure installation, construction of tower footings and/or foundations, pole and tower installations, pipeline installations, welding, concrete and/or pavement repair or replacement, and stockpile/borrow locations.
b. Water Quality Order 2003-0007-DWQ regulated construction activities associated with small linear underground and overhead projects that resulted in land disturbances greater than one acre, but less than five acres. These projects were considered non-traditional construction projects. Attachment E of this Order now regulates all construction activities from linear underground and overhead projects resulting in land disturbances greater than one acre. c. All disturbances to the ground must be accounted for and considered additive.

The following formula attempts to account for all disturbances from the construction activity, not just the trenching activity itself:

Total Disturbed Area = Wt*Lt + Ap + Db*Nb + Wr*Lr
Where:
· Wt is the width of the disturbance, including trench width, plus the immediate access width;
· Lt is the length of the trench or project pipe;

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· Ap is the area where project-related activity occurs (i.e., equipment and material storage, staging, and preparation areas not on paved surfaces, ancillary facility areas);
· Db is the bore hole diameter multiplied by the immediate access width; · Nb is the number of bore holes;
· Wr is the new road construction width; and
· Lr is the length of the new road.

This formula illustrates how to account for all disturbances to the ground resulting from the construction activity. Although dischargers are not required to use this exact formula, they must include all disturbances to the ground in their total calculation.
d. The visual inspection requirements set forth in Monitoring and Reporting Requirements in Attachment E are applicable to all linear underground and overhead projects regardless of type.
e. This General Permit’s visual inspection requirements apply to linear underground and overhead project Type 1 projects in both populated (developed or paved) and rural (undeveloped or unpaved) settings. In a populated environment, daily closure requirements for an open excavation may be an important element of a SWPPP for stormwater protection and safety plans because open excavations present a safety hazard to both pedestrians and traffic. However, uncovered excavations in rural settings do not pose as significant a threat to safety. Likewise, it makes sense for linear underground and overhead project Type 1 projects in developed settings to return disturbed land back to pre-construction conditions daily, because of incidental nonstormwater discharges in an urban environment and the associated potential for runoff from paved, impermeable surfaces. However, projects in rural settings, are less likely to have impervious surfaces and non-stormwater discharges and may not present the same threat to water quality.

I.J.3. Demolition
a. When a construction project involves demolition or renovation, construction and demolition debris is created. Construction and demolition debris can consist of three types of wastes:
i. Inert or non-hazardous waste;
ii. Hazardous waste as regulated by the United States Environmental Protection Agency under the Resource Conservation and Recovery Act (RCRA); and
iii. Items that contain hazardous components that might be regulated by the state.

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b. This General Permit requires best management practices (BMPs) to reduce the exposure of hazardous materials found in older structures from mobilizing in stormwater. Common hazardous materials related to demolition can be found on the U.S. EPA’s website87 and include but are not limited to:
i. Asbestos-Containing Materials
State of California Department of Industrial Relations Cal/OSHA has adopted regulations regarding asbestos exposure California Code of Regulations, Title 8, § 1529.
ii. Mercury Containing Devices
Many structures utilize devices that contain mercury. Mercury is persistent and toxic to human health and the environment. Mercury containing devices such as thermostats fluorescent lamps shall be isolated, removed and taken to an appropriate disposal facility.
iii. Lead-Based Paint
Older structures have a high likelihood of containing lead-based interior and exterior lead-based paint. During the demolition process the lead-based paint can be mobilized and behave like dust. The lead-based paint can be inhaled by workers on the demolition site and tracked off-site causing hazardous exposure to lead to the community. Therefore, it is important to minimize exposure by implementing lead-safe practices during demolition activities.
iv. Polychlorinated Biphenyls (PCBs) in Caulk
PCBs have been identified in caulk in many older structures. Protective BMPs and OSHA approved Personal Protective Equipment shall be utilized to prevent the exposure of PCBs to workers and the surrounding environment during and after demolition.

In order to be in compliant with all PCB TMDLs, Mercury TMDLs and statewide policies, dischargers are required to schedule demolition at times of the year with a low probability of a precipitation event, cover demolished material when activity stops for the day or prior to precipitation, or have a certified individual examine the structure for hazardous materials and mitigate the hazard with a method that prevents the material from discharging off-site.
87 U.S. EPA, Harmful Materials and Residential Demolition, <https://www.epa.gov/largescale-residential-demolition/harmful-materials-and-residential-demolition> [as of May 20, 2021]

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Because of the production ban of PCBs in 1979, this General Permit has requirements for demolition of buildings built prior to January 1, 1980.88 I.J.4. Common Plan of Development or Sale
U.S. EPA regulations include the term “common plan of development or sale” to ensure that acreage within a common project does not artificially escape this General Permit’s requirements because construction activities are phased, split among smaller parcels, or completed by different owners or developers. The State Water Board is required to exercise its regulatory discretion in providing a common-sense interpretation of the term as it applies to construction projects and permit coverage. An overbroad interpretation of the term would render meaningless the clear “one acre” federal permitting threshold and would potentially trigger permitting of almost any construction activity that occurs within an area that had previously received area-wide utility or road improvements.

The 2008 U.S. EPA NPDES General Permit for Discharges from Construction Activity (2008 Construction General Permit) provided further clarification on the common plan of development or sale regarding non-contiguous construction activities. Where discrete construction projects within a larger common plan of development or sale are located at least 1/4 mile apart and the area between the projects is not being disturbed, each individual project can be treated as a separate plan of development or sale provided any interconnecting road, pipeline, or utility project that is part of the same “common plan” is not concurrently being disturbed.

For example, oil and gas well pads separated by 1/4 mile could be treated as separate projects. However, if the same two well pads and an interconnecting access road were all under construction at the same time, they would generally be considered as part of a single “common plan” for permitting purposes. If a utility company was constructing new trunk lines off an existing transmission line to serve separate residential subdivisions located more than 1/4 mile apart, the two trunk line projects could be considered separate projects.

Construction projects generally receive grading and/or building permits (Local Permits) from local authorities prior to initiating construction activity. These Local Permits spell out the scope of the project, the parcels involved, the type of construction approved, etc. Referring to the Local Permit helps define “common plan of development or sale.” In cases such as tract home development, a Local Permit will include all phases of the construction project including rough grading, utility and road installation, and vertical construction. All construction activities approved in the Local Permit are part of the common plan and must remain under the General Permit until construction is completed. For custom home construction, 88 Geosyntec Consultants for the Bay Area Stormwater Management Association.

Integrated Monitoring Report Part B: PCB and Mercury Loads Avoided and Reduced via Stormwater (IMR). 2013.

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Local Permits typically only approve vertical construction as the rough grading, utilities, and road improvements were already independently completed under the previous Local Permit. In the case of a custom home site, the homeowner must submit plans and obtain a distinct and separate Local Permit from the local authority in order to proceed. General Permit coverage for an individual homeowner building a custom home on a private lot of less than one acre is not required. Similarly, the installation of a swimming pool, deck, or landscaping that disturbs less than one acre that was not part of any previous Local Permit are not required to obtain General Permit coverage.

The following are several examples of construction activity of less than one acre that would require permit coverage:
a. A landowner receives a building permit(s) to build tract homes on a 100-acre site split into 200 one-third acre parcels, (the remaining acreage consists of streets and parkways) which are sold to individual homeowners as they are completed. The landowner completes and sells all the parcels except for two.

Although the remaining two parcels combined are less than one acre, the landowner must continue permit coverage for the two parcels. b. One of the parcels discussed above is sold to another owner who intends to complete the construction as already approved in the local permit. The new landowner must electronically certify and submit Permit Registration Documents to complete the construction even if the new landowner is required to obtain a separate Local Permit.
c. The landowner in (1) above purchases 50 additional one half-acre parcels adjacent to the original 200-acre project. The landowner seeks a Local Permit (or amendment to existing local permit) to build on 20 parcels while leaving the remaining 30 parcels for future development. The landowner must amend Permit Registration Documents to include the 20 parcels 14 days prior to commencement of construction activity on those parcels.

I.K. Construction Activities Not Covered
I.K.1. Traditional and Linear Construction Activities Not Covered Construction activities not covered by this General Permit are listed in the Order Section II.B and Section II.D.

I.K.2. Notice of Non-Applicability
Reliance on approved jurisdictional determinations is not allowed in the General Permit for a number of reasons. First, approved jurisdictional determinations delineate the scope of waters of the United States. They do not determine whether an activity results in a discharge to a water of the United States. Second, the scope of waters of the United States is subject to changes based on change of regulations or judicial decisions. Approved jurisdictional determinations are valid

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for a discrete number of years, and they may not be up-to-date with respect to implementing the current regulations if there is an intervening change during the duration of the validity of the approved jurisdictional determination. Finally, it is likely that the approved jurisdictional determination was requested by another party and in another context, such as the discharge of dredged or fill material. As such, the findings may not be easily extrapolated.

In 1998, the California Water Code was amended to require entities who are requested by the State Water Board to obtain General Permit coverage, but that have a valid reason to not obtain General Permit coverage, to submit a Notice of Non-Applicability (NONA). (Cal Wat. Code, § 13399.30, subd. (a)(2)).

The State Water Board considered allowing Entities to review United States Army Corp of Engineer approved jurisdictional determinations to evaluate, without a California licensed professional geologist, whether their facility location is within a basin and/or other physical location that is not hydrologically connected to waters of the United States. The State Water Board believes that this process can be difficult in some cases. In addition, there may be areas of the state that are not hydrologically connected to waters of the United States for which there is not a corresponding United States Army Corps of Engineer approved Jurisdictional Determination. Therefore, all “No Discharge” Technical Reports must be signed (wet signature and license number) by a California licensed professional engineer or geologist. In addition, the discharger must obtain a concurrence letter from the Regional Water Board that has jurisdiction over the site location.

I.K.3. Small Construction Erosivity Waiver
The U.S. EPA’s Stormwater Phase II Final Rule provides the option for a Small Construction Rainfall Erosivity waiver. This waiver applies to construction sites between 1 and 5 acres and allows permitting authorities to waive those sites that do not have adverse water quality impacts.

Projects that do not qualify for the Small Construction Rainfall Erosivity waiver include:
a. Projects that are part of a larger common plan of development disturbing more than 5 acres; and/or
b. Projects with construction lasting one year or greater.

Dischargers eligible for the Small Construction Erosivity waiver are exempt from coverage for this General Permit. The discharger must certify and submit to the State Water Board that small construction activity will occur only when the rainfall erosivity factor (“R” factor in the Revised Universal Soil Loss Equation) is less than 5 to obtain the waiver. The period of construction activity begins when the WDID number is issued and ends when the disturbed areas of the project meet the final stabilization conditions in Order Section III.H. The R value is calculated from the construction start date through all phases of construction (initial land disturbance

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through final stabilization). Small projects that are part of a larger plan of development (less than 5 combined acres of disturbance) use the earliest start date associated with the plan of development and their estimated time of meeting the final stabilization requirements.

Projects that qualify for the small construction erosivity waiver are not subject to the post-construction standards of this General Permit, but may be subject to existing permitted Phase I or Phase II municipal separate storm sewer system (MS4) post-construction requirements.

A waiver eligibility condition requires the operator to periodically inspect and properly maintain the area until the criteria for final stabilization defined in this General Permit is met. If use of this interim stabilization eligibility condition is relied upon to qualify for the waiver, a signature on the waiver with a certification statement constitutes acceptance of and commitment to complete the final stabilization process. The discharger must apply for a waiver in SMARTS prior to commencing construction activities.

U.S. EPA funded a cooperative agreement with Texas A&M University to develop an online rainfall erosivity calculator. Dischargers can access the calculator from the U.S. EPA’s website.89 Use of the calculator allows the discharger to determine potential eligibility for the rainfall erosivity waiver. It may also be useful in determining the time periods during which construction activity could be waived from General Permit coverage.

I.L. Obtaining and Modifying General Permit Coverage
This General Permit states the Legally Responsible Person (LRP) or a person legally authorized to sign and certify on behalf of the LRP is responsible for obtaining General Permit coverage. The LRP must electronically submit90 Permit Registration Documents prior to commencement of construction activities in the Stormwater Multiple Application Report Tracking System (SMARTS). Permit Registration Documents consist of:
· A Notice of Intent;
· A Risk Assessment;
· Post-Construction Calculations (when applicable);
· A Site Map;
· A SWPPP; and
89 U.S. EPA, Rainfall Erosivity Factor Calculator for Small Construction Sites, <https://lew.epa.gov/> [as of May 20, 2021]
90 Each signatory (LRP or DAR) must have an electronic authorization form on file with the State Water Board for each organization they represent in SMARTS.

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· The application fee.

A Waste Discharge Identification number (WDID) will automatically be emailed to the LRP once these components have been submitted and are deemed complete.

Failure to obtain coverage under this General Permit for stormwater discharges to waters of the United States is a violation of the Clean Water Act and the California Water Code.

The LRP is typically the person who possesses the title of the land, easement, or leasehold interest of the estate upon which the construction activities will occur for the regulated site. The LRP for linear underground and overhead projects is typically the person authorized to make management decisions of the utility company, municipality, or other public or private company or agency that owns or operates the linear underground and overhead project.

The Duly Authorized Representative is a person who has legal authority to sign, certify, and electronically submit Permit Registration Documents and Notices of Termination on behalf of the Legally Responsible Person.

It is expected that as the stormwater program develops, the Regional Water Boards may issue general or individual permits containing more specific provisions. If this occurs, this General Permit no longer regulates those dischargers obtaining coverage under those general or individual permits.

Any information provided to the Regional Water Board shall comply with the Homeland Security Act and any other federal law that concerns security in the United States; any information that does not comply should not be submitted.

Annual Reports must be submitted by projects that are enrolled under this General Permit for more than 90 days in a reporting period. The Annual Reports shall be submitted electronically in SMARTS. Annual Reports are due to the State Water Board by September 1st of each year with a July 1st through June 30th reporting period.

The application requirements clearly identify the responsible parties, locations, and scope of operations of dischargers covered by this General Permit and documents the discharger’s knowledge of the General Permit’s requirements. Regional Water Boards will enter their inspection and enforcement data into SMARTS.

Coverage under this General Permit remains in effect until a Notice of Termination is submitted in SMARTS and approved by the applicable Regional Water Board where the project is located. The discharger is responsible for any missed or outstanding invoices if the Regional Water Board denies the Notice of Termination. For outstanding invoices, a complete Notice of Termination must be received by the Regional Water Board 90 days from the original invoice date in order to cancel the invoice. The invoice is deemed valid and payable if a complete Notice of Termination is received after 90 days.

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This General Permit allows a discharger to terminate portions of a construction project if those portions have been sold to another owner. This General Permit is not transferable, so the new owner has the responsibility to obtain coverage, update the Stormwater Pollution Prevention Plan (SWPPP), and comply with General Permit requirements. The seller must notify the new owner about their responsibilities concerning this General Permit and must notify the State Water Board by submitting the new owner's name, address, and phone number on the Change of Information form for the termination to be processed. The seller must also disclose the state of construction, if construction activity is ongoing, or if the post-construction requirements are completed. The new owner for ongoing construction activity after the change of ownership is not exempt from this General Permit’s SWPPP requirements and must submit new Permit Registration Documents within 30 days of the date of change of ownership. The new owner is expected to review and update the existing SWPPP to ensure it is appropriate for the construction activity being undertaken.91
The Legally Responsible Person is always ultimately responsible for project compliance. This individual must certify the Permit Registration Documents and will be the recipient of any Notices of Violations or Administrative Civil Liabilities (fines) for the project.

The current annual fees are included in the Water Code fee schedule92 and are based on total disturbed area (acres) of the construction project. Projects continuing from the previous permit into this General Permit will pay the annual fees based on their current billing cycle.

Consistent with the 2022 U.S. EPA NPDES General Permit for Discharges from Construction Activity, this General Permit requires the discharger to post a sign or other General Permit coverage notice at a location viewable and legible by the public from a safe, publicly accessible location. This General Permit requires the posting of the project’s unique WDID number, waiver identification number, and site and project contact information. If posting in a publicly accessible location is not possible, the discharger must make the site-specific WDID readily available upon request. 91 The SWPPP must be amended, or a new SWPPP developed by the discharger’s QSD if not already in compliance with this General Permit’s SWPPP requirements in the Order for Linear Underground and Overhead Projects.
92 State Water Resources Control Board, NPDES Storm Water Fees, <https://waterboards.ca.gov/resources/fees/water_quality/#stormwater> [as of May 20, 2021]

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I.M. Notice of Termination Final Stabilization
This General Permit is consistent with the 2022 U.S. EPA NPDES General Permit for Discharges from Construction Activity which requires the following for Notice of Termination final stabilization:

I.M.1. Establish uniform, perennial cover of vegetation93 (i.e., evenly distributed, without large bare areas) to provide 70 percent or more of the cover that is provided by permanent vegetation in local undisturbed areas; and/or I.M.2. Implement permanent non-vegetative stabilization measures to provide effective cover of any areas of exposed soil.

I.M.3. Exceptions:
a. Arid, semi-arid, and drought-stricken areas. Final stabilization is met if the area has been seeded or planted to establish vegetation that provides 70 percent or more of the cover that is provided by permanent vegetation in local undisturbed areas within three years and, to the extent necessary to prevent erosion on the seeded or planted area, non-vegetative erosion controls have been applied that provide cover for at least three years without active maintenance. b. Disturbed areas on agricultural land that are restored to their preconstruction agricultural use.
c. Areas that need to remain disturbed (e.g., racetracks, animal corrals, baseball diamonds, etc.). In limited circumstances, stabilization may not be required if the intended function of a specific area of the site necessitates that it remains disturbed, and only the minimum area needed remains disturbed (e.g., dirt access roads, utility pole pads, areas being used for storage of vehicles, equipment, materials).

I.N. Discharge Prohibitions
This General Permit authorizes the discharge of stormwater to surface waters from construction activities that result in the disturbance of one or more acres of land, provided that the discharger satisfies all General Permit conditions. This General Permit prohibits the discharge of pollutants other than stormwater and nonstormwater discharges authorized by this General Permit or another NPDES permit.

This General Permit also prohibits all discharges which contain a hazardous substance in excess of reportable quantities established in 40 Code of Federal Regulations §§ 117.3 and 302.4, unless a separate NPDES permit has been issued to regulate those discharges. In addition, this General Permit incorporates discharge prohibitions contained in water quality control plans, as implemented by the nine 93 Applications of products where stabilization is dependent on vegetative growth (e.g., hydroseed) does not meet final stabilization criteria if vegetative growth is not achieved.

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Regional Water Boards. Discharges to Areas of Special Biological Significance (ASBS) are prohibited unless covered by an exception that the State Water Board has approved.

Non-stormwater discharges include a wide variety of sources, including improper dumping, spills, or leakage from storage tanks or transfer areas. Non-stormwater discharges may contribute significant pollutant loads to receiving waters. Measures to control spills, leakage, and dumping, and to prevent illicit connections during construction must be addressed through structural as well as non-structural BMPs.

The State Water Board recognizes, however, that certain non-stormwater discharges may be necessary for the completion of construction projects. Authorized non-stormwater discharges may include those from de-chlorinated potable water sources such as: fire hydrant flushing, irrigation of vegetative erosion control measures, pipe flushing and testing, water to control dust, uncontaminated ground water dewatering, and other discharges not subject to a separate general NPDES permit adopted by a region. Therefore, this General Permit authorizes such discharges provided they meet the following conditions:

These authorized non-stormwater discharges must:

1. Comply with BMPs as described in the SWPPP;

2. Filter or treat, using appropriate technology, all dewatering discharges from sedimentation basins;

3. Meet the numeric action levels for pH and turbidity; and

4. Not cause or contribute to a violation of water quality standards.

Additionally, authorized non-stormwater discharges must not be used to clean up failed or inadequate construction or post-construction BMPs designed to keep materials on-site. This General Permit prohibits the discharge of stormwater that causes or threatens to cause pollution or nuisance. Dewatering is also discussed in Section I.B.3.b.iii above.

I.O. Technology and Water Quality Based Effluent Limitations for All Types of Discharges
I.O.1. Technology-Based Effluent Limitations
NPDES permits for stormwater discharges associated with construction activity must meet all applicable provisions of §§ 301 and 402 of the Clean Water Act.

These provisions require controls of pollutant discharges that utilize best available technology economically achievable (BAT) for toxic pollutants and nonconventional pollutants and best conventional pollutant control technology (BCT) for conventional pollutants. Additionally, these provisions require controls of pollutant discharges to reduce pollutants and any more stringent controls necessary to meet water quality standards. The U.S. EPA has already established such limitations, known as effluent limitation guidelines, for some industrial

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categories. The State Water Board implemented the effluent limitation guidelines and standards for the construction and development point source category into this General Permit as discussed in Section I.B.3 above. In instances where there are no effluent limitation guidelines, the permit writer is to use best professional judgment to establish discharger requirements using BAT and BCT technology.

This General Permit contains narrative effluent limitations, technology-based numeric effluent limitations for active treatment systems and BMP-based, narrative, and numeric water quality-based effluent limitations for Total Maximum Daily Loads (TMDL) waste load allocation implementation.

The previous permit, as originally adopted by the State Water Board on September 2, 2009, contained numeric effluent limitations for pH (within the range of 6.0 and

9.0 pH units) and turbidity (500 Nephelometric Turbidity Units (NTU)) that applied only to Risk Level 3 and linear underground and overhead project Type 3 construction sites. The California Building Industry Association, the Building Industry Legal Defense Foundation, and the California Business Properties Association (petitioners) challenged the previous permit in California Building Industry Association et al. v. State Water Resources Control Board. The Superior Court ruled in favor of the State Water Board on almost all of the issues the petitioners raised, but the Superior Court invalidated the numeric effluent limitations for pH and turbidity for Risk Level 3 and linear underground and overhead project Type 3 sites because it determined that the State Water Board did not have sufficient BMP performance data to support those numeric effluent limitations. As a result of the Superior Court’s writ of mandamus, the numeric effluent limitations for pH and turbidity were removed from the previous permit, except for active treatment systems. In addition, the previous permit required Risk Level 3 and linear underground and overhead project Type 3 dischargers with discharges directly to surface waters to conduct receiving water monitoring if directed by Water Boards whenever their effluent exceeds specified receiving water monitoring triggers. The receiving water monitoring triggers were established at the same levels as the previous numeric effluent limitations (effluent pH outside the range of 6.0 and 9.0 pH units or turbidity exceeding 500 NTU). In restoring the receiving water monitoring requirements, the State Water Board determined that it was appropriate to require receiving water monitoring at the request of the Water Boards for these types of sites with discharges directly to surface waters that exceeded the receiving water monitoring triggers under any precipitation event scenarios because these sites represent the highest threat to receiving water quality.

This General Permit includes receiving water monitoring requirements for Risk Level 3 and linear underground and overhead project Type 3 with discharges directly to surface water. An exceedance of a receiving water monitoring trigger is not a violation of this General Permit.

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BAT and BCT technologies include passive systems such as conventional runoff and sediment control and treatment systems such as coagulation or flocculation using sand filtration, when appropriate. Such technologies allow for effective treatment of soil particles less 0.02 mm (medium silt) in diameter. This General Permit requires the discharger to install structural controls, as necessary, such as erosion and sediment controls that meet BAT and BCT to achieve compliance with water quality standards. These effluent limitations constitute compliance with the requirements of the Clean Water Act.

Because this General Permit is an NPDES permit, there is no legal requirement to address the factors set forth in Water Code §§ 13241 and 13263, unless the permit is more stringent than what federal law requires. (See City of Burbank v. State Water Resources Control Bd. (2005) 35 Cal.4th 613, 618, 627.) None of the requirements in this General Permit are more stringent than the minimum federal requirements, which include technology-based requirements achieving BAT and BCT and strict compliance with water quality standards. The inclusion of numeric effluent limitations in the permit for active treatment systems does not cause this General Permit to be more stringent than current federal law. Numeric effluent limitations and best management practices are simply two different methods of achieving the same federal requirement: strict compliance with state water quality standards. Federal law authorizes both narrative and numeric effluent limitations to meet state water quality standards. The use of numeric effluent limitations to achieve compliance with water quality standards is not a more stringent requirement than the use of BMPs. (State Water Board Order No. WQ 2006-0012 (Boeing).) Accordingly, the State Water Board does not need to take into account the factors in Water Code §§ 13241 and 13263.

The State Water Board has concluded that the establishment of BAT and BCT will not create or aggravate other environmental problems through increases in air pollution, solid waste generation, or energy consumption. While there may be a slight increase in non-water quality impacts due to the implementation of additional monitoring or the construction of additional BMPs, these impacts will be negligible in comparison with the construction activities taking place on-site and would be justified by the water quality benefits associated with compliance. a. pH Receiving Water Monitoring Trigger
The minimum standard control methods for pH in runoff requires the use of preventive measures such as avoiding concrete pours during rainy weather, covering concrete and directing flow away from fresh concrete if a pour occurs during rain, covering scrap drywall and stucco materials when stored outside and potentially exposed to rain, and other housekeeping measures to control potential contaminants. If necessary, pH-impaired stormwater from construction sites can be treated in a filter, settling pond, or basin, with additional natural or chemical treatment required to meet pH limits set forth in this General Permit.

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The basin or pond acts as a collection point and holds stormwater for a sufficient period for the contaminants to be settled out, either naturally or artificially, and allows any additional treatment to take place. The State Water Board considers these techniques to be equivalent to BCT. The State Water Board used best professional judgement in determining the pH concentration discharge limitations.

The chosen trigger was established by calculating three standard deviations above and below the mean pH of runoff from highway construction sites94 in California. Proper implementation of BMPs should result in discharges that are within the range of 6.0 to 9.0 pH units.
b. Turbidity Receiving Water Monitoring Trigger
The turbidity receiving water monitoring trigger of 500 NTU is a performancebased trigger and was developed using three different analyses aimed at finding the appropriate threshold to set the performance-based limit to ensure environmental protection, effluent quality, and cost-effectiveness. The analyses fell into three, main types: (1) an ecoregion-specific dataset developed by Simon et. al. (2004); (2) Statewide Regional Water Quality Control Board enforcement data; and (3) published, peer-reviewed studies and reports on insitu performance of best management practices in terms of erosion and sediment control on active construction sites.

A 1:3 relationship between turbidity (expressed as NTU) and suspended sediment concentration (expressed as mg/L) is assumed based on a review of suspended sediment and turbidity data from three gauges used in the USGS National Water Quality Assessment Program:

USGS 11074000 SANTA ANA R BL PRADO DAM CA
USGS 11447650 SACRAMENTO R A FREEPORT CA
USGS 11303500 SAN JOAQUIN R NR VERNALIS CA
The receiving water monitoring trigger represents staff determination that the trigger value is the most practicable based on available data. The turbidity receiving water monitoring trigger represents a bridge between the narrative effluent limitations and receiving water limitations. State Water Board staff analyzed construction site discharge information (monitoring data, estimates) and receiving water monitoring information to support this receiving water monitoring trigger.
94 California Department of Transportation, Caltrans Construction Sites Runoff Characterization Study (September 2002) <https://dot.ca.gov/-/media/dotmedia/programs/environmental-analysis/documents/env/ctsw-rt-03-065-a11y.pdf> [as of May 20, 2021]

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Compliance with this value does not necessarily represent compliance with either the narrative effluent limitations (as enforced through the BAT and BCT standard) or the receiving water limitations since the turbidity receiving water monitoring trigger represents an appropriate threshold level expected at a site.

In the San Diego region, some inland surface waters have a receiving water objective for turbidity equal to 20 NTU. A discharge up to, but not exceeding, the turbidity receiving water monitoring trigger of 500 NTU may still cause or contribute to the exceedance of the 20 NTU standard. Most of the waters of the State are protected by turbidity objectives based on background conditions.

Table 3 – Regional Water Board Basin Plans, Water Quality Objectives for Turbidity
Regional Water
Board WQ Objective Background/Natural Turbidity
Maximum
Increase
1 Based on background All levels 20 percent
2 Based on background > 50 NTU 10 percent
3 Based on background
0-50 JTU
50-100 JTU
> 100 JTU
20 percent
10 JTU
10 percent
4 Based on background 0-50 NTU
> 50 NTU
20 percent
10 percent
5 Based on background
0-5 NTU
5-50 NTU
50-100 NTU
> 100 NTU
1 NTU
20 percent
10 NTU
10 percent
6 Based on background All levels 10 percent
7 Based on background N/A N/A
8 Based on background
0-50 NTU
50-100 NTU
> 100 NTU
20 percent
10 NTU
10 percent
9 Inland Surface Waters,
20 NTU
All others, based on
background
0-50 NTU
50-100 NTU
> 100 NTU
20 percent
10 NTU
10 percent
Table 4 shows the suspended sediment concentrations at the 1.5-year flow recurrence interval for the 12 ecoregions in California from Simon et. al (2004).

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Table 4 – Results of Ecoregion Analysis
Ecoregion Percent of California Land
Area
Median Suspended Sediment
Concentration (mg/L)
1 9.1 874
4 0.2 120
5 8.8 35.6
6 20.7 1530
7 7.7 122
8 3.0 47.4
9 9.4 284
13 5.2 143
14 21.7 5150
78 8.1 581
80 2.4 199
81 3.7 503
The area-weighted average for the suspended sediment concentration is 1633 mg/L.

If a 1:3 relationship between turbidity and suspended sediment is assumed, the median turbidity is 544 NTU.

The following Table 5 is composed of turbidity readings measured in NTUs from administrative civil liability actions for construction sites from 2003 - 2009.

This data was derived from the complete listing of construction-related administrative civil liabilities (ACLs) for the six-year period. All administrative civil liabilities were reviewed and those that included turbidimeter readings at the point of stormwater discharge were selected for this dataset.

Table 5 – Administrative Civil Liabilities (ACL) Sampling Data taken by Regional Water Board Staff
WDID# Region Discharger Turbidity (NTU)
5S34C331884 5S Bradshaw Interceptor Section
6B 1800
5S05C325110 5S Bridalwood Subdivision 1670
5S48C336297 5S Cheyenne at Browns Valley 1629
5R32C314271 5R Grizzly Ranch Construction 1400
6A090406008 6T El Dorado County Department
of Transportation, Angora Creek 97.4
5S03C346861 5S TML Development, LLC 1600
6A31C325917 6T Northstar Village See Subdata Set

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Table 6 – Subdata Set Turbidity for Point of Stormwater Runoff Discharge at Northstar Village
Date Turbidity (NTU) Location
10/5/2006 900 Middle Martis Creek
11/2/2006 190 Middle Martis Creek
01/04/2007 36 West Fork, West Martis Creek
02/08/2007 180 Middle Martis Creek
02/09/2007 130 Middle Martis Creek
02/09/2007 290 Middle Martis Creek
02/09/2007 100 West Fork, West Martis Creek
02/10/2007 28 Middle Martis Creek
02/10/2007 23 Middle Martis Creek
02/10/2007 32 Middle Martis Creek
02/10/2007 12 Middle Martis Creek
02/10/2007 60 West Fork, West Martis Creek
02/10/2007 34 West Fork, West Martis Creek
A 95 percent confidence interval for mean turbidity in an administrative civil liability order was constructed. The data set used was a small sample size, so the 500 NTU (the value derived as the receiving water monitoring trigger for this General Permit) needed to be verified as a possible population mean. In this case, the population refers to a hypothetical population of turbidity measurements of which our sample of 20 represents. A t-distribution was assumed due to the small sample size:

Mean: 512.23 NTU
Standard Deviation: 686.85
Margin of Error: 31.45
Confide Interval: 190.78 NTU (Low), 833.68 NTU (High)
Based on a constructed 95 percent confidence interval, an administrative civil liability order turbidity measurement will be between 190.78 – 833.68 NTU. 500 NTU falls within this range. Using the same data set, a small-sample hypothesis test was also performed to test if the administrative civil liability turbidity data set contains enough information to cast doubt on choosing a 500 NTU as a mean. 500 NTU was again chosen due to its proposed use as an acceptable value. The test was carried out using a 95 percent confidence interval. Results indicated that the administrative civil liability turbidity data set does not contain significant sample evidence to reject the claim of 500 NTU as an acceptable mean for the administrative civil liability turbidity population.

There are few published, peer-reviewed studies and reports on in-situ performance of best management practices in terms of erosion and sediment control on active construction sites. The most often cited study is a report titled,

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“Improving the Cost Effectiveness of Highway Construction Site Erosion and Pollution Control”95. The primary author, Dr. Horner states the following in a comment letter to the State Water Board summarizing this report:
“The most effective erosion control product was wood fiber mulch applied at two different rates along with a bonding agent and grass seed in sufficient time before the tests to achieve germination. Plots treated in this way reduced influent turbidity by more than 97 percent and discharged effluent exhibiting mean and maximum turbidity values of 21 and 73 NTU, respectively. Some other mulch and blanket materials performed nearly as well. These tests demonstrated the control ability of widely available BMPs over a very broad range of erosion potential.”
Other technologies studied in this report produced effluent quality at or near 100 NTU. It is the best professional judgement of the State Water Board staff that erosion control is preferred and that technology performance in a controlled study showing effluent quality directly leaving a BMP is always easier and cheaper to control than effluent being discharged from the project (edge of property, etc.).

To summarize, the analysis showed that: (1) results of the Simon et. al dataset reveals turbidity values in background receiving water in California’s ecoregions range from 16 NTU to 1716 NTU (with a mean of 544 NTU); (2) based on a constructed 95 percent confidence interval, construction sites will be subject to administrative civil liability (ACL) when their turbidity measurement falls between 190.78 – 833.68 NTU; and (3) sites with highly controlled discharges employing and maintaining good erosion control practices can discharge effluent from the BMP with turbidity values less than 100 NTU. State Water Board staff has determined, using its best professional judgement, that it is most cost effective to set the receiving water monitoring trigger for turbidity at 500 NTU.

I.O.2. Determining Compliance with Effluent Standards
a. Numeric Action Levels
This General Permit contains technology based numeric action levels for pH and turbidity, and requirements for effluent monitoring at all Risk Level 2 and 3, and linear underground and overhead project Type 2 and 3 sites. The numeric action levels are: a pH numeric action level of 6.5 to 8.5, and a turbidity numeric action level of 250 Nephelometric Turbidity Units (NTUs). Additionally, this General Permit sets a turbidity numeric action level for receiving water 95 Horner, Guedry, and Kortenhof, Improving the Cost Effectiveness of Highway Construction Site Erosion and Pollution Control (1990)
<https://wsdot.wa.gov/research/reports/fullreports/200.1.pdf> [as of April 28, 2022]

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monitoring of 500 NTU. Numeric action levels are essentially numeric benchmark values for certain parameters that, if exceeded in effluent sampling, trigger the discharger to take actions.

The primary purpose of numeric action levels is to assist dischargers in evaluating the effectiveness of their on-site measures. Construction sites need to employ many different systems that must work together to achieve compliance with the permit's requirements. The numeric action levels chosen should indicate whether the systems are working as intended. This General Permit requires dischargers with numeric action level exceedances to implement additional, alternative, or improved BMPs and revise their SWPPPs accordingly to either prevent pollutants in stormwater and authorized nonstormwater discharges from being discharged, or to substantially reduce the pollutants to levels consistently below the numeric action levels. An exceedance of a numeric action level does not constitute a violation of this General Permit, however, failure to implement any applicable requirement of this General Permit, or additional BMPs or improved BMPs to adequately prevent future numeric action level exceedances, and/or not reporting any numeric action level exceedance through SMARTS is a violation of this General Permit. Dischargers are required to electronically self-report any discharges that exceed numeric action levels or numeric effluent limitations. Multiple exceedances of a numeric action level or failure to report numeric action level exceedances through SMARTS can be cause for the discharger to implement an active treatment system.

Another purpose of numeric action levels is to provide information regarding construction activities and water quality impacts. This data will provide the Water Boards and the rest of the stormwater community with more information about levels and types of pollutants present in runoff and how effective the dischargers’ BMPs are at reducing pollutants in effluent. The State Water Board also hopes to learn more about the linkage between effluent and receiving water quality. In addition, these requirements will provide information on the mechanisms needed to establish compliance monitoring programs at construction sites in future permit deliberations.
i. pH
The chosen limits were established by calculating one standard deviation above and below the mean pH of runoff from highway construction sites in California. Proper implementation of BMPs should result in discharges that are within the range of 6.5 to 8.5 pH units.

The Caltrans study included 33 highway construction sites throughout California over a period of four years, which included 120 storm events. All of these sites had BMPs in place that would be generally implemented at all types of construction sites in California.

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The Surface Water Ambient Monitoring Program (SWAMP) has a Guidance Compendium for Watershed Monitoring and Assessment. Sections 3.1.4 and 3.1.5 of this Compendium contain guidance for pH and turbidity sampling.96
ii. Turbidity
The State Water Board’s staff used their best professional judgement to develop a numeric action level that can be used as a learning tool to help dischargers improve their site controls, and to provide meaningful information on the effectiveness of stormwater controls. A statewide turbidity numeric action level has been set at 250 NTU.

The Surface Water Ambient Monitoring Program (SWAMP) has a Guidance Compendium for Watershed Monitoring and Assessment. Sections 3.1.4 and 3.1.5 of this Compendium contain guidance for pH and turbidity sampling.

I.O.3. Receiving Water Limitations
Construction activities that cause or contribute to an exceedance of water quality objectives or standards must be addressed. The dynamic nature of construction activity gives the discharger the ability to quickly identify and monitor the source of the exceedances. This is because when stormwater mobilizes sediment, it provides visual cues of erosion, where corrective actions should take place, and how effective they are once implemented.

This General Permit requires that stormwater, dewatering, and authorized nonstormwater discharges eliminate the discharge of pollutants that cause or contribute to an exceedance of any applicable water quality objectives or standards. The sampling and analysis monitoring requirements in this General Permit will help determine whether BMPs installed and maintained are preventing pollutants in discharges from the construction site that may cause or contribute to an exceedance of water quality objectives or standards.

Water quality objectives or standards consist of designated beneficial uses of surface waters and the adoption of ambient criteria necessary to protect those uses. The ambient criteria are termed “water quality objectives” when adopted by the Water Boards. There is a risk that stormwater runoff from construction sites containing pollutants could enter surface waters and cause or contribute to an exceedance of water quality standards. For that reason, dischargers should be aware of the applicable water quality standards in their receiving waters. The best method to ensure compliance with receiving water limitations is to implement 96 A SWAMP Field Methods Course training CD is also available for the public at <www.waterboards.ca.gov/water_issues/programs/swamp/cdrom.html> or please contact [email protected] to request a copy. [as of May 20, 2021]

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BMPs that prevent pollutants from contacting stormwater or leaving the construction site in runoff.

California water quality standards are published in the Basin Plans adopted by each Regional Water Board, the California Toxics Rule (CTR), the National Toxics Rule (NTR), and Statewide Water Board Plans, for example, the California Ocean Plan.

Dischargers can determine the applicable water quality standards by contacting Regional Water Board staff or by consulting one of the following sources. The actual Basin Plans that contain the water quality standards can be viewed at the website of the appropriate Regional Water Board97, the State Water Board site for statewide plans,
98 or the U.S. EPA regulations for the NTR and CTR (40 Code of Federal Regulations §§ 131.36-38). Basin Plans and statewide plans are also available by mail from the appropriate Regional Water Board or the State Water Board. The U.S. EPA regulations are available on their website.99 I.O.4. Water Quality Based Effluent Limitations for Construction Stormwater: TMDLs and Waste Load Allocations
This General Permit implements Clean Water Act § 303(d) impaired water body(ies) with Regional Water Board or U.S. EPA adopted TMDLs identifying sources regulated by this General Permit. The TMDLs in Attachment H include the specific waste load allocation for this activity and source. Dischargers are required to comply with any applicable TMDL requirements in this General Permit (see Attachment H and Section I.W of this Fact Sheet for additional TMDL applicability information).

Responsible Dischargers that are assigned TMDL-related numeric action levels or numeric effluent limitations are required to collect samples in accordance with the non-visible sampling requirements in Attachments D and E and compare all analytical results to the applicable numeric action levels or numeric effluent limitations specified in Attachment H of this General Permit.

I.P. Training Qualifications and Requirements
To ensure that the preparation, implementation, and oversight of the SWPPP is sufficient for effective pollution prevention, the Qualified SWPPP Developer and 97 State Water Resources Control Board, RWQCB Directory, <https://www.waterboards.ca.gov/about_us/contact_us/rwqcbs_directory.html> [as of May 20, 2021]
98 State Water Resources Control Board, Plans and Policies, <https://www.waterboards.ca.gov/plans_policies/> [as of May 20, 2021] 99 U.S. EPA Website <https://www.epa.gov/> [as of May 20, 2021]

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Qualified SWPPP Practitioner are responsible for creating, revising, overseeing, and implementing the SWPPP.

I.Q. Sampling, Monitoring, Reporting, and Record Keeping for Linear Underground and Overhead Projects and Traditional Construction Monitoring Requirements I.Q.1. Introduction
This General Permit requires visual monitoring at all sites and effluent water quality monitoring at all Risk Level 2 and 3 and linear underground and overhead project Type 2 and 3 sites (also some Type 1 and Risk Level 1 sites). Receiving water monitoring may be required by the Regional Water Board at some Risk Level 3 and Type 3 sites as described below. All sites are required to submit the sampling results, inspection records, and Annual Reports specified in this General Permit, which contain specific documentation collected over the reporting period.

I.Q.2. Visual
Visual inspections of stormwater discharges, dewatering discharges, authorized non-stormwater discharges, and unauthorized non-stormwater discharges are required for all sites subject to this General Permit. This General Permit requires dischargers to implement corrective actions at the site to address deficiencies identified during the visual monitoring.

All dischargers are required to conduct visual inspections as described in General Permit Attachment’s D or E. This General Permit requires the discharger to visually-inspect a site for indications of pollutants in stormwater runoff, erosion, failed BMPs, and improper BMP installation. Each discharge location and drainage area require an inspection for the presence of (or indications such as erosion, pollutant mobilization, or other potential threat to human health and the environment) unauthorized and authorized non-stormwater discharges and their sources. Dischargers must conduct pre, during, and post-precipitation event inspections to: (1) identify adequacy of BMP design, implementation, and effectiveness, (2) identify any necessary additional BMPs, and (3) revise the SWPPP on-site and in SMARTS accordingly. Dischargers must maintain on-site records of all visual observations, personnel performing the observations, observation dates, weather conditions, locations observed, and corrective actions taken in response to the observations.

This General Permit requires visual monitoring for precipitation events which result in the discharge of water from the site. Sites are encouraged to use size catch basins to retain the first flush of a precipitation event, which is consistent with BAT and BCT. The size of a precipitation event cannot be predicted so an adequate trigger for a pre-precipitation event visual inspection is 50 percent or greater probability of producing precipitation based on the National Weather Service Forecast Office of the National Oceanic and Atmospheric Administration (NOAA).

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General Permit Attachments D and E list the minimum criteria for an inspection checklist. Dischargers may develop their own inspection forms or may use a Water Board-developed form if one is available.

Some visual inspections may be delegated by the QSP to an individual that has received training as described in the discharger’s site personnel roles and responsibilities in this General Permit.

I.Q.3. Non-Visible Pollutant Monitoring
This General Permit requires that all dischargers develop a sampling and analysis strategy for monitoring pollutants that are not visually detectable in stormwater.

Some monitoring may be delegated by the QSP to an individual that has received training as described in the discharger’s site personnel roles and responsibilities in this General Permit. Monitoring for non-visible pollutants is required at any site when the exposure of construction materials occurs and where a potential discharge can cause or contribute to an exceedance of a water quality objective or standard. Pollutants found in materials used in large quantities at construction sites throughout California and exposed throughout the rainy season, such as cement, fly ash, and other recycled materials or by-products of combustion are a significant concern for construction discharges. The water quality standards that apply to these materials will depend on their composition. Some of the more common stormwater pollutants from construction activity are not CTR pollutants. Examples of construction non-visible pollutants100 include, but are not limited to, bacteria and viruses, fertilizers or nutrients, herbicides, greases; lubricants; oils, metals, synthetic chemicals, and pesticides.
a. Bacteria and Viruses
Bacteria and viruses are common stormwater contaminants. Construction site sources include, but are not limited to, animal excrement, waste management, and sanitary facilities. High levels of indicator bacteria in stormwater have led to the closure of beaches, lakes, and rivers to contact recreation such as swimming.
b. Fertilizers and Nutrients
Fertilizers and nutrients are common stormwater contaminants. Construction site sources include, but are not limited to, landscape fertilization, these nutrients can result in excessive vegetation or algae growth in natural water systems or be toxic to aquatic life, resulting in impaired beneficial uses. 100 Section P.1.b adapted from the CASQA Construction BMP Handbook, p. 1-6, 1-7, 1-

10.

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c. Herbicides and Pesticides
Herbicides and pesticides (including fungicides, rodenticides, and insecticides) have been detected repeatedly in stormwater at levels toxic to certain organisms, even when pesticides have been applied in accordance with label instructions. The washing of construction equipment used for noxious weed removal can also spread invasive species101. Construction site sources include, but are not limited to, noxious weed and vegetation management, pest control, and vector control.
d. Greases, Lubricants, Oils
Greases, lubricants, and oils include a wide array of hydrocarbon compounds and other synthetic materials, some of which are toxic to aquatic organisms at low concentrations. Construction site sources include, but are not limited to, equipment spills and leaks from delivery; storage; use, equipment and vehicle drive train; suspension; hydraulic system cleaning and maintenance, material storage, on-site staff parking areas, paving operations, and waste disposal. e. Metals
Metals including, but not limited to, cadmium, copper, chromium, iron, lead, nickel, and zinc are commonly found in stormwater and are of concern because some are toxic to aquatic organisms, can bioaccumulate (accumulate to toxic levels in aquatic animals such as fish), and have the potential to contaminate drinking water supplies. Construction site sources, include but are not limited to, naturally occurring metals associated with earth disturbance, gravel materials, construction materials, equipment maintenance, equipment fluids, paving operations, and welding and fabrication activities. f. Synthetic Chemicals
Synthetic chemicals may be found in stormwater and can be toxic in low concentrations. Construction site sources include, but are not limited to, batteries, construction materials, chemical fire suppression, chemical storage, equipment and vehicle fueling (also related to Section I.Q.3.d above), paving operations, and waste management.

Many of the above sources can result in construction stormwater discharges containing pollutants. For example, high pH can result from improperly maintained treatment systems, cement and gypsum, and wash waters. Salts can also be found 101 Center for Environmental Excellence by AASHTO, Chapter 4 Construction Practices for Environmental Stewardship 4.11 Vegetation Management in Construction (2019) <https://www.epa.gov/sites/default/files/2015-11/documents/25-25-4-_fr.pdf> [as of April 28, 2022]

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in construction site materials, including but not limited to, fertilizers and nutrients, herbicides and pesticides, soil treatments, and surfactants.

Some of these constituents are subject to Statewide Policy, water quality control plans, or Attachment H’s TMDL Water Quality Based Effluent Limitations.

Dischargers are encouraged to discuss these standards with Water Board staff and other stormwater quality professionals.

The most effective way to reduce or minimize the non-visible sampling and analysis requirements is to reduce and manage exposure of construction materials, activities, and equipment to precipitation and/or stormwater runoff.

Materials or activities that are not exposed do not have the potential to enter stormwater runoff, and therefore receiving water sampling is not required.

Preventing contact between stormwater and construction materials, equipment, or materials or preventing the runoff are the most important BMPs at any construction site.

Preventing or eliminating the exposure of pollutants at construction sites is not always possible. Some materials and activities, such as soil amendments or earth moving equipment, are designed to be used in a manner that will result in exposure to stormwater. In these cases, it is important to make sure that these materials and activities are applied and operated according to the manufacturer’s instructions and at a time when pollutants are less likely to be washed away. Other construction materials can be exposed when storage, waste disposal, or the application of the material is done in a manner not protective of water quality.

Representative sampling is required for these situations, unless there is capture and containment of all stormwater that has been exposed. In cases where construction materials may be exposed to stormwater, but the stormwater is contained and is not allowed to run off the site, sampling will only be required when inspections show that the containment failed or is breached, resulting in potential exposure or discharge to receiving waters.

This General Permit requires the discharger to conduct a pollutant source assessment to develop a list of potential pollutants based on a review of site or project potential sources, which will include construction activities, equipment materials, soil amendments, soil treatments, and historic contamination at the site.

The discharger must review existing environmental and real estate documentation to determine the potential pollutants that could be present on the construction site as a result of past land use activities.

Possible reference materials for previously existing pollution and past land uses:
i. Environmental Assessments;
ii. Initial Studies;
iii. Phase 1 Assessments prepared for property transfers;

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iv. Environmental Impact Reports or Environmental Impact Statements prepared under the requirements of the National Environmental Policy Act or the California Environmental Quality Act; and
v. Available soil chemical analysis results.

I.Q.4. Effluent Monitoring
Consistent with 40 Code of Federal Regulations, § 122.44, all linear underground and overhead project Type 2 and 3 and Risk Level 2 and 3 dischargers (also some Type 1 and Risk Level 1 sites) must perform sampling and analysis of effluent discharges to characterize discharges associated with construction activity from the entire area disturbed by the project. Dischargers must collect samples of stored or contained stormwater that is discharged during or subsequent to a precipitation event. Some monitoring may be delegated by the QSP to an individual that has received training as described in the discharger’s site personnel roles and responsibilities in this General Permit.

This General Permit requires stormwater runoff sampling for pH and turbidity for all Risk Level 2, linear underground and overhead project Type 2, Risk Level 3, and linear underground and overhead project Type 3 sites. Sampling is required at all locations where stormwater, dewatering, and/or authorized non-stormwater associated with construction activity is discharged off-site or enters any on-site waters of the United States (e.g., a creek running through a site). Dischargers are required to identify all sampling locations in the SWPPP and site map and sampling is only required when a discharge occurs. Attachments D and E of this General Permit require specific sampling requirements and non-sampling justifications.

This General Permit contains sampling, analysis, and monitoring requirements for pH and turbidity. Sampling of non-visible pollutants identified in the pollutant source assessment is required when the materials or chemicals have the potential to cause or contribute to an exceedance of a water quality standard (e.g., BMP breach, failure, malfunction, or leak or spill observed during a visual inspection).

This General Permit requires that all dischargers maintain a paper or electronic copy of all required records for three years from the date generated or date submitted, whichever is later. These records shall be available at the site until a Notice of Termination is approved by the Regional Water Board. Linear underground and overhead project documents may be retained in a crew member’s vehicle and made available upon request.
a. Traditional Construction Monitoring Requirements
A summary of the monitoring and reporting requirements is found in Table 7 and 8 below. Dischargers are also required to report and retain records in accordance with this General Permit’s Order and Attachment D requirements.

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Table 7 – Required Monitoring Elements for Risk Levels
Risk Level Visual Non-Visible
Pollutants Effluent Receiving Water
Risk Level 1 Required As needed Where
applicable Not required
Risk Level 2 Required As needed pH, turbidity Not required Risk Level 3 Required As needed pH, turbidity
For discharges directly
to surface waters if:
1) pH or turbidity
Receiving Water
Monitoring Trigger
exceeded; and
2) upon Regional Water
Board direction
Table 8 – Stormwater Effluent Monitoring Requirements by Risk Level Level Frequency Effluent Monitoring
Risk Level 1
When non-visible pollutants, identified in the
SWPPP or otherwise known to be on site,
may be discharged due to failure to
implement BMPs, a container spill or leak, or
a BMP breach, failure, or malfunction.

Applicable non-visible
pollutant parameters
Risk Level 2
and 3
When non-visible pollutants, identified in the
SWPPP or otherwise known to be on site,
may be discharged due to failure to
implement BMPs, a container spill or leak, or
a BMP breach, failure, or malfunction.

Applicable non-visible
pollutant parameters
Risk Level 2
and 3
One sample per discharge location per day
of a precipitation event characterizing
discharges associated with construction
activity from the entire project disturbed area.
pH, turbidity, and
applicable non-visible
pollutant parameters
b. Linear Construction Monitoring and Sampling Requirements Attachment E establishes minimum monitoring and reporting requirements for all linear underground and overhead projects and the specific monitoring requirements depending on project complexity and risk to water quality. The monitoring requirements for Type 1 linear underground and overhead project are less than Type 2 and 3 projects because Type 1 projects have a lower potential to impact water quality.

This General Permit requires the discharger to prepare a monitoring program prior to the start of construction and immediately implement the program at the start of construction for linear underground and overhead projects. The monitoring program must be implemented at the appropriate level to protect water quality at all times throughout the life of the project. Dischargers are also

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required to report and retain records in accordance with this General Permit’s Order and Attachment E requirements.

Table 9 – Require Monitoring Elements for Linear Underground and Overhead Project Types
Risk Level Visual Non-Visible
Pollutants Effluent Receiving Water
Type 1 Required As needed Where applicable Not required Type 2 Required As needed pH, turbidity Not required
Type 3 Required As needed pH, turbidity
For discharges
directly to receiving
waters if:
1) pH or turbidity
Receiving Water
Monitoring
Trigger exceed;
and
2) upon Regional
Water Board
direction.
i. Type 1 Linear Underground and Overhead Project Monitoring Requirements This General Permit requires a discharger to conduct daily visual inspections of Type 1 linear underground and overhead projects during site operating hours while construction activities are occurring. Inspections are to be conducted by qualified personnel and can be conducted in conjunction with other daily activities. Inspections are conducted to ensure the BMPs are adequate, maintained, and in place at the end of the construction day.

The required SWPPP revisions (when appropriate) should be based on the results of the daily inspections and reported so the site General Permit implementation is currently reflected. Inspections can be discontinued in non-active construction areas where soil disturbing activities have been completed and final stabilization has been achieved (e.g., trench has been paved, substructures have been installed, and successful final vegetative cover or other stabilization criteria have been met).

A discharger implementing a monitoring program for Type 1 linear underground and overhead projects is required to implement temporary and permanent stabilization BMPs after active construction is completed.

Inspection activities are required until adequate permanent stabilization has been established and will continue in areas where re-vegetation is chosen until minimum vegetative coverage has been established. The required photograph requirements taken during site inspections are for verification of requirements and are submitted through SMARTS.

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This General Permit also includes the minimum criteria required for an inspection checklist. Dischargers may develop their own inspection forms or may contact the Water Board for an inspection form, if one is available. ii. Type 2 and 3 Linear Underground and Overhead Project Monitoring Requirements
This General Permit requires the discharger to conduct daily visual inspections of Type 2 and 3 linear underground and overhead projects during site operating hours when construction activities are occurring.

Inspections are to be conducted by qualified personnel and can be in conjunction with other daily activities.

All Type 2 and 3 linear underground and overhead project dischargers are required to conduct inspections by qualified personnel of the construction site during site operating hours prior to all anticipated precipitation events, during, and after actual precipitation events. The discharger is required to conduct inspections during site operating hours for each 24-hour period during extended precipitation events. Inspections can be discontinued in non-active construction areas where soil disturbing activities have been completed and final stabilization has been achieved (e.g., trench has been paved, substructures installed, and successful vegetative cover or other stabilization criteria have been met).

The goals of these inspections are: (1) to identify areas contributing to a stormwater discharge; (2) to evaluate whether measures to reduce pollutant loadings identified in the SWPPP are adequate, properly installed, and functioning in accordance with the terms of this General Permit; and (3) to determine if additional control practices or corrective maintenance activities are needed. Equipment, materials, and workers must be available for rapid response to failures and emergencies. All corrective BMP maintenance is to be performed as soon as possible, depending upon worker safety.

All dischargers are required to develop and implement a monitoring program for inspecting Type 2 and 3 linear underground and overhead projects that require temporary and permanent stabilization BMPs after active construction is completed. The inspections will be conducted to ensure the BMPs are adequate and maintained and will continue until adequate permanent stabilization has been established in areas where revegetation is chosen until minimum vegetative coverage has been established.

This General Permit also requires a log of inspections conducted before, during, and after the precipitation event(s) be maintained in the SWPPP.

The log will provide the date and time of the inspection and who conducted the inspection. Photographs must be taken during site inspections and submitted through SMARTS.

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This General Permit’s Attachment E lists minimum criteria required for an inspection checklist. Dischargers may develop their own inspection forms or may contact the Water Board for an inspection form, if one is available. iii. Sampling Requirements for all Linear Underground and Overhead Project Types
Linear underground and overhead projects are subject to sampling and analysis requirements for visible pollutants (i.e., sedimentation/siltation, turbidity, pH) and for non-visible pollutants.
1) Sampling for non-visible pollutants is required for Type 1, 2, and 3 linear underground and overhead projects.

Non-visible pollutant monitoring is required for pollutants associated with construction sites and activities that (1) are not visually detectable in stormwater discharges, (2) are known or should be known to occur on the construction site, and (3) could cause or contribute to an exceedance of water quality standard or objectives in the site’s receiving waters.

Sample collection for non-visible pollutants are required only: (1) during a precipitation event when pollutants associated with construction activities may be discharged with stormwater runoff in the event of a BMP breach, failure, malfunction, leak or spill, (2) identified in the discharge and is from construction activities and/or materials, and (3) when the discharger has failed to adequately clean the area of material and pollutants. Failure to implement appropriate BMPs will trigger the same sampling requirements as those required in (1) above, or when the discharger has failed to implement appropriate BMPs prior to the next precipitation event.

It is not anticipated that all linear underground and overhead projects will be required to collect samples for pollutants not visually detected in runoff due to the nature and character of the construction site and activities as previously described in this Fact Sheet. Most linear underground and overhead projects are constructed in urban areas with public access (e.g., existing roadways, road shoulders, parking areas, etc.). This raises a concern regarding the potential contribution of pollutants from vehicle use and/or from normal activities of the public (e.g., vehicle washing, landscape fertilization, pest spraying, etc.) in runoff from the project site. Since the dischargers are not necessarily the landowners of the project area and are not able to control the presence of these pollutants in the stormwater that runs through their projects, it is not the intent of this General Permit to require dischargers to sample for these pollutants unless they are generated specifically from the linear underground and overhead project materials and/or activities. This General Permit does not require the discharger to sample for these

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types of pollutants except where the discharger has on-site materials or activities containing or specifically generating these pollutants and when the conditions described above occur.
2) Regional Water Board-Required Additional Monitoring Requirements The Regional Water Board can require, in writing, additional monitoring requirements in this General Permit under Clean Water Act authority and specific authorities listed in this General Permit’s Order and Attachment E. Additional monitoring requirements include, but are not limited to, requirements specified in an enforcement order, additional sampling parameters, frequency, methods, practices, and/or reporting (for stormwater, dewatering, and/or non-stormwater) based upon sitespecific analysis. 3) Receiving Water Monitoring
This General Permit protects the receiving water’s beneficial uses from construction site pollutants. Risk Level 3 and linear underground and overhead project Type 3 site discharges subject to the receiving water monitoring triggers with: (1) receiving water monitoring trigger exceedances defined in this General Permit, (2) discharges are directly into receiving waters, and (3) the discharger is directed to monitor by the Water Boards are required to monitor the upstream and downstream receiving water(s) for turbidity and pH (if applicable). These requirements were modified to make it clear that they do not apply to discharges to an MS4 that later discharges into a surface water.

Table 10 – Receiving Water Monitoring Requirements
Level or Type Receiving Water Monitoring Triggers
Risk Level 1 and Linear
Underground and Overhead
Project Type 1
Not applicable/required
Risk Level 2 and Linear
Underground and Overhead
Project Type 2
Not applicable/required
Risk Level 3 and Linear
Underground and Overhead
Project Type 3
For discharges directly to surface waters if:
1) pH or turbidity Receiving Water Monitoring Trigger
exceeded; and
2) upon Regional Water Board direction.

I.Q.5. Reporting Requirements
a. Reporting Numeric Effluent Limitation Violations (Water Quality Based Corrective Actions or Numeric Effluent Limitation Violation Report) All discharges subject to TMDL-specific numeric effluent limitations requirements must electronically submit all precipitation event sampling results

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to the Water Boards through SMARTS no later than 10 days after receiving the field analysis results or analytical laboratory results. The purpose of the electronic certification and submittal of the Water Quality Based Corrective Actions or Numeric Effluent Limitation Violation Report is to: (1) allow public access to General Permit-required reporting, (2) document the discharger’s compliance actions, and (3) notify the Water Boards of the exceedance so that they can determine whether any follow-up (e.g., inspection, enforcement) is necessary to bring the site into compliance.

Responsible Dischargers with a water quality exceedance are in violation of this General Permit and must additionally submit the Water Quality Based Corrective Actions or Numeric Effluent Limitation Violation Report containing:
· The analytical method(s), reporting unit(s), and method detection limit(s) of each analytical parameter (analytical results that are less than the method detection limit are to be reported as "less than the method detection limit or <MDL");
· The date, place, and time of sampling;
· Any visual observation (inspections);
· Any measurements, including precipitation; and
· A description of the current BMPs associated with the effluent sample that exceeded the numeric effluent limitation and any proposed corrective actions taken.
b. Reporting Numeric Action Level Exceedances (Numeric Action Level Exceedance Report)
All Risk Level 2 and 3 and linear underground and overhead project Type 2 and 3 dischargers must electronically submit all precipitation event sampling results for the pH and turbidity numeric action levels, through SMARTS, no later than 10 days after the conclusion of the precipitation event. All Risk Level 2 and 3 and linear underground and overhead project Type 2 and 3 dischargers must electronically submit all precipitation event sampling results for TMDL-related numeric action levels, through SMARTS, no later than 10 days after receiving the analytical laboratory results. In the event that any effluent sample exceeds an applicable numeric action level, a Regional Water Board or its delegate may request (in writing) that the Risk Level 2 or 3 and linear underground and overhead project Type 2 or 3 dischargers submit and certify a Numeric Action Level Exceedance Report, through SMARTS, within 30 days of receiving the written request.

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In the event that an applicable pH, turbidity or TMDL-specific numeric action level has been exceeded, the required reporting contains:
· The analytical method(s), reporting unit(s), and method detection limit(s) of each analytical parameter (analytical results that are less than the method detection limit are to be reported as "less than the method detection limit or <MDL");
· The date, place, and time of sampling;
· Any visual observation (inspections);
· Any measurements, including precipitation; and
· A description of the current BMPs associated with the effluent sample that exceeded the numeric action level and any proposed corrective actions taken.
c. Analytical Sample Reporting
All dischargers are required to certify and submit analytical monitoring results in SMARTS using the monitoring ad hoc report (a separate ad hoc monitoring report is needed for each precipitation event). Electronically certified and submitted sampling and analysis results are required to include an upload of the original laboratory reports and chain of custody forms. d. Annual Report
All dischargers must prepare and electronically certify and submit an Annual Report no later than September 1st of each year using SMARTS including the specified information described in this General Permit’s Order and any additional necessary site compliance information such as a summary of all corrective actions taken during the reporting period, or the identification of any compliance activities or corrective actions that were not implemented.

I.Q.6. Record Keeping
According to 40 Code of Federal Regulations §§ 122.21(p) and 122.41(j), the discharger is required to retain paper or electronic copies of all records required by this General Permit for a period of at least three years from the date generated or the date submitted to the Water Boards. A discharger must retain records for a period beyond three years if directed by Regional Water Board.

I.R. Risk Determination
A site Risk Level calculation is the estimated potential for sediment transport and risk to the receiving water. This General Permit contains calculation requirements to determine a project’s Risk Level 1, 2 and 3, or a linear underground and overhead projects Type 1, 2, and 3 as described below. Construction industry-accepted sediment erosion models and Water Boards-provided or site-specific receiving water

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risk models are used to determine pre-construction project and post-construction project risks for all the project’s construction phases.

I.R.1. Traditional Construction Projects
a. Overall Risk Determination
There are two major requirements related to site planning and risk determination in this General Permit. The project’s overall risk is broken up into two elements: (1) project sediment risk (the relative amount of sediment that can be discharged, given the project and location details) and (2) receiving water risk (the risk sediment discharges pose to the receiving waters). i. Project Sediment Risk:

The Revised Universal Soil Loss Equation (RUSLE) is used to calculate watershed sediment risk. The RUSLE was originally developed to calculate sheet and rill erosion rate in tons/acre/project duration. It is consistent with the original intent of the RUSLE to not introduce a project size threshold to develop risk categories expressed on tons/project duration.

The Regional Board has the authority to question any aspect of the sediment risk calculation, including the R factor used in determining Watershed Sediment Risk. The RUSLE2 computer program can also be used to calculate the R factor and in many cases yields more accurate values than those generated from the EPA Erosivity Calculator.

Project Sediment Risk is determined by multiplying the R, K, and LS factors from the Revised Universal Soil Loss Equation (RUSLE) to obtain an estimate of project-related bare ground soil loss expressed in tons/acre. The RUSLE equation is as follows:

A = (R)(K)(LS)(C)(P)
Where:

A is the rate of sheet and rill erosion
R is the rainfall-runoff erosivity factor
K is the soil erodibility factor
LS is the length-slope factor
C is the cover factor (erosion controls)
P is the management operations and support practices (sediment controls)
The C and P factors are given values of 1.0 to simulate bare ground conditions.

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There is a map option102 and a manual calculation option for determining soil loss. For the map option, the R factor for the project is calculated using the online calculator.103 To determine soil loss in tons per acre, the discharger multiplies the R factor times the value for K times LS.

For the manual calculation option, the R factor for the project is calculated using the online calculator. The K and LS factors are determined using Attachment D.1.

Soil loss of less than 15 tons/acre is considered low sediment risk.

Soil loss between 15 and 75 tons/acre is medium sediment risk.

Soil loss over 75 tons/acre is considered high sediment risk.

The soil loss values and risk categories were obtained from mean and standard deviation RKLS values from the U.S. EPA EMAP program. High risk is the mean RKLS value plus two standard deviations. Low risk is the mean RKLS value minus two standard deviations
ii. Receiving Water Risk:

Receiving water risk is based on whether a project drains to a water body or watershed that is sediment-sensitive. A sediment-sensitive water body or watershed is either:
· On the most recent 303(d) list for water bodies impaired for sediment; or · Has the beneficial uses of COLD, SPAWN, and MIGRATORY.

A project that meets at least one of the two criteria has a high receiving water risk. A list of sediment-sensitive water bodies is posted on the State Water Board’s website104 and included in Attachment D.1. An interactive map of 303(d) listed water bodies in California is available on the State Board’s website.105
102 The guidance Geographic Information System Risk maps will be provided electronically on the State Water Board’s website prior to the effective date of this General Permit.
103 U.S. EPA, Rainfall Erosivity Factor Calculator for Small Construction Sites, <https://lew.epa.gov/> [as of May 20, 2021]
104 State Water Board, Surface Water Quality Assessment Webpage, <https://www.waterboards.ca.gov/water_issues/programs/water_quality_assessment/ #impaired> [as of May 20, 2021]
105 State Water Board, 303(d) Integrated Report
<https://www.waterboards.ca.gov/water_issues/programs/water_quality_assessment/ 2020_2022_integrated_report.html> [as of June 21, 2022]

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b. Effluent Standards
All dischargers are subject to the narrative effluent limitations specified in the General Permit. The narrative effluent limitations require stormwater discharges associated with construction activity to meet all applicable provisions of §§ 301 and 402 of the Clean Water Act. These provisions require controls of pollutant discharges that utilize BAT and BCT to reduce pollutants and any more stringent controls necessary to meet water quality standards.

Risk Level 2 dischargers that pose a medium risk to water quality are subject to numeric action levels for pH and turbidity, which were established based on best professional judgement. Risk Level 3 dischargers that pose a high risk to water quality are subject to numeric action levels for pH and turbidity, which were established based on best professional judgement.
c. Effluent Monitoring
Effluent monitoring is required for Risk Level 2 and 3 and linear underground and overhead project Type 2 and 3 project sites as described in the Order, Attachments D and E. Effluent monitoring results must be certified and submitted electronically through SMARTS.
d. Good Housekeeping
Proper handling and management of construction materials can help minimize threats to water quality. The discharger must consider good housekeeping measures for construction materials, waste management, vehicle storage and maintenance, landscape materials, and potential pollutant sources. Examples include conducting an inventory of products used, implementing proper storage and containment, and properly cleaning all leaks from equipment and vehicles. e. Non-Stormwater Management
This General Permit’s Order defines the specific authorized non-stormwater discharges allowed and necessary prohibitions on other non-stormwater discharges. Non-stormwater discharges directly connected to receiving waters or the storm drain system have the potential to negatively impact water quality.

The discharger must implement measures to control all non-stormwater discharges (e.g., properly washing vehicles or equipment in contained areas, cleaning streets, and minimizing irrigation runoff) during construction, and construction-associated dewatering activities. This General Permit includes specific construction site dewatering provisions designed to eliminate or reduce pollutant impacts on receiving waters from these activities. f. Erosion Control
The best way to minimize the risk associated with erosion and sedimentation during construction is to disturb as little of the land surface as possible by fitting the development to the terrain. Little grading is necessary and erosion potential

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is lower when development is tailored to natural land contours. Other effective erosion control measures include preserving existing vegetation where feasible, limiting disturbance, timing disturbances around reduced precipitation conditions, and stabilizing and re-vegetating disturbed areas as soon as possible after grading or construction activities. Particular attention must be paid to large, mass-graded sites where the potential for soil exposure to the erosive effects of rainfall, snow melt, and wind is great and where there is potential for significant sediment discharge from the site to surface waters.

Temporary soil stabilization can be the single most important factor in reducing construction site erosion. The discharger is required to consider measures such as: covering disturbed areas with mulch, temporary seeding and vegetation, soil stabilizers, non-toxic binders, fiber rolls or blankets, and permanent seeding. These erosion control measures are only examples of what should be considered and do not preclude the use of new or innovative approaches currently available or being developed. Erosion control BMPs should be the primary means of preventing stormwater contamination, and sediment control techniques should be used to capture any soil that becomes eroded.106 Areas that convey stormwater run-off are required to be appropriately armored against in channel erosion. A California licensed professional engineer may need to provide system design and/or calculations to control the erosion in the conveyance of stormwater (drainage channels).
g. Establishing Vegetation
Planting a site may be necessary during the construction phase to establish vegetation prior to termination of the project. Planted vegetation should match surrounding pre-existing native vegetation. It is expected that local climatic conditions, timing, soil types, soil compaction, topography, and nutrients need to be evaluated to ensure seed germination and plant establishment. The employment of healthy soil107 principles may provide additional guidance on vegetative establishment in dry conditions (e.g., in arid and semi-arid climates dischargers should apply seed prior to the application of mulch). Dischargers may consider the advantages and limitations for each project area in regard to seed planting method (direct drilling, broadcasting, and/or hydraulic applications).
106 U.S. EPA, Developing Your Stormwater Pollution Prevention Plan: A Guide for Construction Sites (May 2007),
<https://www3.epa.gov/npdes/pubs/sw_swppp_guide.pdf> [as of May 20, 2021] 107 California Department of Food and Agriculture, Healthy Soils Program Website <https://www.cdfa.ca.gov/oefi/healthysoils/> [as of May 20, 2021]

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h. Sediment Control
Sediment control BMPs should be the secondary means of preventing polluted stormwater discharges. Sediment control techniques recover some of the soil that becomes eroded when erosion control techniques are ineffective. This General Permit requires dischargers to consider perimeter control measures such as installing silt fences or placing straw wattles below slopes. These sediment control measures are only examples of what should be considered and should not preclude new or innovative approaches currently available or being developed.

Additional requirements for the effective implementation of erosion and sediment controls year-round are imposed on Risk Level and Type 2 and 3 dischargers because these sites pose a higher risk to water quality. This General Permit authorizes the Regional Water Boards to require Risk Level 3 and linear underground and overhead project Type 3 dischargers to implement additional site-specific sediment control requirements when the implementation of other erosion or sediment controls are found to be inadequately protecting the receiving waters.

This General Permit requires the use of wildlife friendly BMPs that minimize wildlife entrapment and sets a prohibition on the discharge of trash and debris.

Wildlife entrapment can be minimized by providing the means for wildlife to escape dig sites that are deeper than one meter and storing materials, like netting and tubing, in locations that are inaccessible to wildlife. Dischargers should use biodegradable wattles containing no plastic that can remain on a site when possible. Wattles containing plastic netting (including plastic specified as photo-degradable) become “trash” in the environment and/or a trap for wildlife. These are also considered “construction materials and waste” and must be disposed of properly per this General Permit.
i. Run-on and Runoff Control
Inappropriate management of run-on and runoff can result in excessive physical and chemical impacts to receiving waters from sediment and increased flows. The discharger is required to manage all run-on and runoff from a project site. Examples include installing berms and other temporary runon and runoff diversions. Dischargers are responsible for commingled run-on (onto the site or within the site) from areas not related to the site’s construction activities and the pollutants contained in the commingled discharge. j. Snow and Ice melt
Construction sites that are affected by snow and ice conditions shall use BMPs to avoid sedimentation migration and erosion from occurring.

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k. Inspection, Maintenance, and Repair
All measures must be periodically inspected, maintained, and repaired to ensure that receiving water quality is protected. Frequent inspections coupled with thorough documentation and timely repair is necessary to ensure that all measures are functioning as intended.

I.R.2. Linear Underground and Overhead Projects
a. Linear Underground and Overhead Risk Determination
Linear underground and overhead projects vary in complexity and water quality concerns based on project type. This General Permit has varying application requirements based on the project’s risk to water quality. Factors that lead to the characterization of the project include location, sediment risk, and receiving water risk.

Linear projects are separated into project types based on the location and complexity of a project area or project segment/section area. Linear underground and overhead projects have been categorized into three project types as follows:
i. Type 1 linear projects are those construction projects where:
1) 70 percent or more of the construction activity occurs on a paved surface and where areas disturbed during construction will be returned to preconstruction conditions or equivalent protection established at the end of the construction activities for the day; or
2) Greater than 30 percent of construction activities occur within the nonpaved shoulders or land immediately adjacent to paved surfaces, or where construction occurs on unpaved improved roads, including their shoulders or land immediately adjacent to them where:
a) Areas disturbed during construction will be returned to preconstruction conditions or equivalent protection established at the end of the construction activities for the day to minimize the potential for erosion and sediment deposition; and
b) Areas where established vegetation was disturbed during construction will be stabilized and re-vegetated by the end of project.

When required, adequate temporary stabilization BMPs will be installed and maintained until vegetation is established to meet minimum cover final stabilization requirements established in this General Permit.

Type 1 linear underground and overhead projects typically do not have a high potential to impact stormwater quality because: (1) these construction activities are not typically conducted during precipitation events, (2) these

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projects are normally constructed over a short period of time108, minimizing the duration that pollutants could potentially be exposed to precipitation, and (3) disturbed soils such as those from trench excavation are required to be hauled away, backfilled into the trench, and/or covered (e.g., metal plates, pavement, plastic covers over spoil piles) at the end of the site operating hours for the construction day.

Type 1 linear underground and overhead projects are determined during the risk assessment found in Attachment E.1 to be 1) low sediment risk and low receiving water risk; 2) low sediment risk and medium receiving water risk; and 3) medium sediment risk and low receiving water risk.

This General Permit requires the discharger to ensure a SWPPP is developed by a Qualified SWPPP Developer for these construction activities that is specific to linear underground and overhead project type, location, and characteristics.
ii. Type 2 Linear Underground and Overhead Projects
Type 2 linear underground and overhead projects are determined to have a combination of High, Medium, and Low project sediment risk along with High, Medium, and Low receiving water risk. Type 2 linear underground and overhead projects are typically constructed over a short period of time like Type 1 projects, however, Type 2 projects have a higher potential to impact water quality because they:
1) Typically occur outside urban or developed areas;
2) Have larger areas of soil disturbance that are not closed or restored at the end of the day;
3) May have on-site stockpiles of soil, spoil, and other materials; 4) Cross or occur in close proximity to a wide variety of sensitive resources that may include, but are not limited to, steep topography and/or water bodies; and
5) Have larger areas of disturbed soils that may be exposed for a longer time interval before final stabilization, cleanup, and/or reclamation occurs.

This General Permit requires the discharger to ensure a SWPPP is developed by a Qualified SWPPP Developer and is implemented these sitespecific construction activities for the project type, location, and characteristics.
108 Short period of time refers to a project duration of weeks to months, but typically less than one year in duration.

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iii. Type 3 Linear Underground and Overhead Projects
Type 3 linear underground and overhead projects are determined to have a combination of High and Medium project sediment risk along with High and Medium receiving water risk. Similar to Type 2 projects, Type 3 projects have a higher potential to impact water quality because they:
1) Typically occur outside urban and developed areas;
2) Have larger areas of soil disturbance that are not closed or restored at the end of the day;
3) May have on-site stockpiles of soil, spoil, and other materials; 4) Cross or occur in close proximity to a wide variety of sensitive resources that may include, but are not limited to, steep topography and/or water bodies; and
5) Have larger areas of disturbed soils that may be exposed for a longer time interval before final stabilization, cleanup, and/or reclamation occurs.

This General Permit requires the discharger to ensure a SWPPP is developed by a Qualified SWPPP Developer and is implemented these sitespecific construction activities for the project type, location, and characteristics.
b. Programmatic Permitting for Linear Underground and Overhead Projects i. Regional Programmatic Permit Coverage:

Regionwide programmatic permit coverage allows a linear underground and overhead project discharger to submit one Notice of Intent for multiple noncontiguous linear underground and overhead projects, if the projects: 1) are located within one Regional Water Board office boundary, 2) are a group of projects of similar scopes with common construction activities, and 3) have the same Legally Responsible Person. Thus, a linear underground and overhead project discharger may be issued a single waste discharge identification number (WDID) for each group of projects (e.g., electrical transmission, gas line transmission, wildfire prevention, etc.) that meet the above criteria.

A linear underground and overhead project discharger opting to obtain regional programmatic permit coverage must submit a common SWPPP with its application that addresses all the construction activities and pollutant sources relevant to the project scope. The linear underground and overhead project discharger must also submit a Linear Construction Activity Notification in SMARTS for each individual project with site-specific information per Attachment E.2, allowing the Regional Water Board to

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enforce individual projects per the requirements in this Order. Each project will share a WDID and will be assigned a WDID extension to identify and track the individual projects. Each individual project is terminated separately through a Linear Construction Termination Notification in SMARTS, pending Regional Water Board staff approval.

Regionwide programmatic permitting was requested by utility stakeholders to improve administrative efficiency related to construction stormwater permitting, in part by training contractors on a common SWPPP that can be implemented on a site-specific basis.
ii. Statewide Programmatic Permit Coverage for Mandated Installation of Broadband Utilities:

Statewide programmatic permit coverage allows a linear underground and overhead project discharger responsible in deploying construction activities to comply with sections 7 – 13 of the Governor’s Executive Order N-73-20, or amendments thereto, to submit one Notice of Intent for multiple noncontiguous linear broadband underground and overhead projects, if the projects:
· Are located throughout two or more Regional Water Board boundaries, · Are a group of projects for broadband utility installation outside of a construction project otherwise regulated by this General Order, and · Have the same Legally Responsible Person.

The discharger will be issued a single waste discharge identification number (WDID) for each group of projects that meet the above criteria.

A linear underground and overhead project discharger opting to obtain statewide programmatic permit coverage must submit:
· A common SWPPP with its application that addresses all the construction activities and pollutant sources relevant to the project scope, and
· Project-specific additional pollution prevention measures to the common SWPPP, as applicable,
A Linear Construction Activity Notification in SMARTS for each individual project with site-specific and project-specific information per Attachment E.2.

Each individual project will share a common WDID and will be assigned a unique WDID extension corresponding to the Regional Water Board

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jurisdiction and the project risk level. The unique project-specific extension number will allow the corresponding Regional Water Board to enforce individual projects per the requirements in this Order specific to the project risk level. Each individual project is terminated separately through the Linear Construction Termination Notification process in SMARTS, and the Notice of Termination process of this General Permit.

Statewide programmatic permitting was requested by the California Department of Transportation, the statewide agency primarily responsible for the construction activity that fully deploys Governor’s Executive Order N-73-20, or amendments thereto, by July 2026. To improve internal project efficiencies to comply with the executive order by July 2026, the Department has reduced its standard design-to-construction procedures from several months to two-tothree weeks. The permit enrollment administrative efficiency provided by statewide programmatic permitting will allow the Department, and other linear project dischargers deploying the executive order, to obtain permit coverage for individual projects, compatible with shortened design-to construction timelines, without submitting repetitive application information for similar projects within different regions.
c. Linear Underground and Overhead Project Effluent Standards All linear underground and overhead projects are subject to the narrative effluent limitations specified in the General Permit. Type 2 and Type 3 projects are subject to technology-based numeric action levels for pH and turbidity. d. Linear Underground and Overhead Project Good Housekeeping Improper use and handling of construction materials could potentially cause a threat to water quality. All linear underground and overhead project dischargers must comply with a minimum set of Good Housekeeping measures specified in Attachment E of this General Permit to ensure proper construction material site management.
e. Linear Underground and Overhead Project Non-Stormwater Management All linear underground and overhead project dischargers must comply with the Non-Stormwater Management measures specified in Attachment E and Order of this General Permit in order to ensure control of all non-stormwater discharges during construction.
f. Linear Underground and Overhead Project Erosion Control This General Permit requires all linear underground and overhead projects dischargers to implement effective wind erosion control measures, and soil cover for inactive areas. Type 3 linear underground and overhead projects

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posing a higher risk to water quality are additionally required to ensure the postconstruction soil loss is equivalent to or less than the pre-construction levels. g. Linear Underground and Overhead Project Sediment Control All linear underground and overhead project dischargers must comply with the general Sediment Control measures specified in Attachment E or this General Permit in order to ensure control and containment of all sediment discharges.

Additional requirements for sediment controls are imposed on Type 2 and 3 linear underground and overhead projects due to their higher risk to water quality.
h. Linear Underground and Overhead Projects Run-on and Runoff Control Discharges originating outside of a project’s perimeter and flowing onto the property can adversely affect the quantity and quality of discharges originating from a project site. All linear underground and overhead projects must comply with the run-on and runoff control measures specified in Attachment E of this General Permit in order to ensure proper management of run-on and runoff.

Due to the lower risk of impacting water quality, Type 1 linear underground and overhead projects are not required to implement run-on and runoff controls unless deemed necessary by the discharger. Examples include installing berms and other temporary run-on and runoff diversions. Dischargers are responsible for commingled run-on (onto the site or within the site) from areas not related to the site’s construction activities and the pollutants contained in the commingled discharge.
i. Linear Underground and Overhead Projects Inspection, Maintenance, and Repair
Proper inspection, maintenance, and repair activities are important to ensure the effectiveness of on-site measures to protect receiving water quality. All linear underground and overhead project dischargers are required to comply with the inspection, maintenance, and repair requirements specified in Attachment E of this General Permit in order to ensure that these activities are adequately performed.

I.S. Active Treatment System109 Requirements
I.S.1. General
The requirements in Attachment F only apply when an active treatment system is implemented on a project site. An active treatment system is defined in this General Permit as “a controlled treatment system that employs chemical 109 An active treatment system is a treatment system that employs chemical coagulation, chemical flocculation, or electrocoagulation in order to reduce turbidity caused by fine suspended sediment.

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coagulation, chemical flocculation, or electrocoagulation to aid in the reduction of turbidity caused by fine suspended sediment.”
The active treatment system is designed to treat and reduce the turbidity level of construction stormwater discharges to meet water quality standards and the requirements of this General Permit at the flowrate required in the Active Treatment System Plans. The specified active treatment system flowrate is designed to dewater the basin within 10 hours. Typical equipment and materials may include pumps, manifolds, flocculants, filter bags, sand media filters, and other items designed to remove suspended materials from construction stormwater. The discharger is required to ensure the operators of the active treatment system are adequately trained and the appropriate professional designed the Active Treatment System Plan.

Bonded-fiber matrices, hydromulches, spray tackifiers, and other land-applied products used to stabilize soil are not considered active treatment nor passive treatment, but rather a form of erosion control.

The use of an active treatment system may be necessary when: (1) traditional erosion and sediment controls do not effectively control accelerated erosion at the construction site, (2) the construction site stormwater discharges may cause or contribute to an exceedance of a water quality standard, and/or (3) site constraints (e.g., very steep or long slope lengths,110 clay, highly erosive soils) inhibit the ability to construct a correctly sized sediment basin.

The active treatment system industry in California started in the mid-1990s and is relatively young, however many developers use these systems to treat stormwater discharges from their construction sites. The active treatment system requirements in this General Permit are based on those in place for small wastewater treatment systems, active treatment system regulations from the Central Valley Regional Water Quality Control Board (September 2005 memorandum “2005/2006 Rainy Season – Monitoring Requirements for Stormwater Treatment Systems that Utilize Chemical Additives to Enhance Sedimentation”), the State of Washington’s Department of Ecology Construction Stormwater Program, and recent advances in technology and knowledge of coagulant performance and aquatic safety.

The effective design of an active treatment system requires a detailed survey and analysis of site conditions. Properly planned and implemented active treatment system provide high-quality discharges and prevent significant impacts to surface water quality, even under extreme environmental conditions. 110 Pitt, R., S. Clark, and D. Lake. 2006. Construction Site Erosion and Sediment Controls: Planning, Design, and Performance. DEStech Publications. Lancaster, PA. 370pp.

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These systems can be very effective in reducing the sediment in stormwater runoff, but the systems that use additives or polymers to enhance sedimentation also pose a potential risk to water quality (e.g., inadequate training, operational failure, equipment failure, additive or polymer release). The State Water Board is concerned about the potential acute and chronic impacts that the polymers and other chemical additives may have on fish and aquatic organisms if released in sufficient quantities or concentrations. The literature and anecdotal evidence of polymer releases causing aquatic toxicity in California supports this concern.111 For example, cationic polymers have been shown to bind with the negatively charged gills of fish, resulting in mechanical suffocation.112 This General Permit establishes residual polymer monitoring and toxicity testing requirements due to the potential toxicity impacts associated with the release of additives or polymers into receiving waters from construction sites utilizing an active treatment system.

The primary treatment process in an active treatment system is coagulation and flocculation. Active treatment system operate on the principle that the added coagulant is bound to suspended sediment, forming floc, which is gravitationally settled in tanks or a basin, or removed by sand filters. A typical installation utilizes an injection pump upstream from the clarifier tank, basin, or sand filters, which is electronically metered to both flow rate and suspended solids level of the influent, assuring a constant dose. The coagulant mixes and reacts with the influent, forming a dense floc. The floc may be removed by gravitational setting in a clarifier tank or basin, or by filtration. Water from the clarifier tank, basin, or sand filters may be routed through cartridge(s) and/or bag filters for final polishing. Vendorspecific systems use various methods of dose control, sediment and floc removal, filtration, etc., that are detailed in project-specific documentation. The particular coagulant and/or flocculant used for a given project is determined based on the site water chemistry because the coagulants are specific in their reactions with various types of sediments. Appropriate selection of dosage must be carefully matched to the characteristics of each site. This General Permit prohibits the operation of an active treatment system or the batch storage to cause an uncontrolled release of chemicals used during the flocculation, coagulation, and/or filtration process for suspended sediment particles because these chemicals can negatively affect the beneficial uses of receiving waters and/or degrade water quality (e.g., acute and chronic toxicity).

Active treatment system are operated in two differing modes, batch or flowthrough. Batch treatment can be defined as Pump-Treat-Hold-Test-Release. In 111 RomØen, K., B. Thu, and Ø. Evensen. 2002. Immersion delivery of plasmid DNA II. A study of the potentials of chitosan-based delivery system in rainbow trout (Onchorhynchus mykiss) fry. Journal of Controlled Release 85: 215-225. 112 Bullock, G., V. Blazer, S. Tsukuda, and S. Summerfelt. 2000. Toxicity of acidified chitosan for cultured rainbow trout (Oncorhynchus mykiss). Aquaculture 185:273-280.

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batch treatment, water is held in a basin or tank, and is not discharged until treatment is complete. Batch treatment involves holding or recirculating the treated water in a holding basin or tank(s) until treatment is complete or the basin or storage tank(s) is full. In flow-through treatment, water is pumped into the active treatment system directly from the runoff collection system or stormwater holding pond, where it is treated and filtered as it flows through the system and is then directly discharged. “Flow-through treatment” is also referred to as “continuous treatment.”
I.S.2. Active Treatment System Effluent Standards
This General Permit requires discharges of stormwater associated with construction activity that undergo active treatment to comply with special operational and effluent limitations to ensure that these discharges do not adversely affect the beneficial uses of the receiving waters or cause degradation of their water quality and establishes numeric effluent limitations for discharges from construction sites that utilize an active treatment system. An exceedance of the active treatment system numeric effluent limitation constitutes a General Permit violation. These systems lend themselves to technology-based numeric effluent limitations for turbidity and pH because of their known reliable treatment. Advanced systems have been in use in some form since the mid-1990s. An active treatment system is considered reliable, can consistently produce a discharge of less than 10 NTU, and has been used successfully at many sites in several states since 1995 to reduce turbidity to very low levels.

This General Permit contains “compliance storm (precipitation) event” exceptions from the technology-based numeric effluent limitations for active treatment system discharges. The rationale is that technology-based requirements are developed assuming a certain design storm (precipitation) event. The industry-standard active treatment system design storm is 10-year, 24-hour (as stated in Attachment F of this General Permit), so the compliance precipitation event has been established as the 10-year, 24-hour event as well to provide consistency.

I.T. Passive Treatment Requirements
The U.S. EPA’s 2022 NPDES General Permit for Stormwater Discharges from Construction Activities113 requires the regulation of any chemically enhanced stormwater treatment. Chemically enhanced treatments are split into two categories:
active treatment systems and passive treatment technologies (passive treatment including chemical and products). More information regarding active treatment systems can be found in the Section I.S above.
113 U.S. EPA, 2022 NPDES General Permit for Discharges from Construction Activities (January 11, 2017), <https://www.epa.gov/npdes/2022-construction-general-permitcgp#2022cgp>

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Passive treatment chemicals and products bind fine soil particles together through chemical ionic processes allowing heavy particles to settle out of solution without a fully mechanical or engineered system. Passive treatment technologies in the construction industry typically use coagulants and flocculants such as polyacrylamides (PAMs).

Construction site operators and dischargers regularly use passive treatment to reduce the turbidity levels in construction stormwater runoff. The construction industry uses passive treatment technologies because these products are a costeffective method of reducing turbidity for compliance with turbidity numeric action levels in this General Permit, especially compared to active treatment systems.

Examples of chemically enhanced BMPs used to meet General Permit turbidity numeric action levels are blocks, wattles, or water-applied products.

Many other industries use passive treatment chemicals in water purification, food production, and other industrial applications to reduce the turbidity and concentration of other pollutants in the discharge.

The types of flocculants and coagulants that can be included in passive treatment for this General Permit are non-ionic and anionic flocculants and coagulants. Cationic flocculants and coagulants can be used in an active treatment system and are regulated in Attachment F. Research on applicable chemical information indicates that many commonly used flocculants are toxic or contain toxic components, and when discharged to surface water have the potential to impact aquatic life and other beneficial uses.

Many types of passive treatment chemicals are toxic to fish and other aquatic organisms. Cationic PAM-based flocculants are acutely toxic to aquatic species in small quantities and are neurotoxins. Other flocculant products such as anionic PAM-based flocculants are chronically toxic to aquatic species in large quantities.

The California Stormwater Quality Association developed past guidance114 on PAMs used in passive treatment technologies and included specific limitations to the use of soil binders containing PAMs:
1) Do not use PAMs on a slope that flows into a waterbody without passing through a sediment trap, sediment basin, or other sediment controls (e.g., wattles, silt fences, gravel bags);
2) The specific PAM copolymer formulation must be anionic. Cationic PAMs should not be used in any application because of known aquatic toxicity problems. Only the highest drinking water grade PAM certified for compliance with ANSI/NSF Standard 60 for drinking water treatment, should be used for soil applications; 114 CASQA Construction BMP Handbook, 2015.

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3) PAMs designated for erosion and sediment control should be “water soluble” or “linear” or “non-cross linked”; and
4) PAMs should not be used as a stand-alone BMP to protect against water-based erosion. When combined with mulch, its effectiveness increases dramatically.

Additionally, a low-turbidity discharge from a passive treatment chemical application site does not always correspond to low levels of solids in the discharge and/or an improvement in water quality downstream because:
1) Turbidity monitoring solely measures small size solids suspended in the water; turbidity monitoring does not measure particle size, weight, or bed load of sediment from flocculated solids leaving a site; and
2) Passive treatment chemicals discharged either by aerial deposition or through stormwater runoff contributes similar toxicity threats to aquatic life.

This General Permit regulates the use of passive treatment in Attachment G, however, specific technology-based and/or water quality-based numeric effluent limitations have not been implemented in this General Permit for passive treatment chemicals because there is currently no consistent and proven data to determine the level of toxicity and water quality impacts that negatively outweighs the economic benefit associated with the use of passive treatment technologies.

I.U. Post-Construction Requirements
I.U.1. General
Past practices for new and redevelopment construction activities have resulted in modified natural watershed and stream processes. This is caused by altering the terrain, modifying the vegetation and soil characteristics, introducing impervious surfaces such as pavement and buildings, increasing drainage density through pipes and channels, and altering the condition of stream channels through straightening, deepening, and armoring. These changes result in a drainage system where sediment transport capacity is increased, and sediment supply is decreased. A receiving channel’s response is dependent on dominant channel materials and its stage of adjustment. Construction activity can lead to impairment of beneficial uses in two main ways:
a. Stormwater discharges occurring during the actual construction process can negatively affect the chemical, biological, and physical properties of downstream receiving waters. The most likely pollutant is sediment due to the disturbance of the landscape, however pH and other non-visible pollutants are also of great concern; and
b. The finished project may result in significant modification of the site’s long-term response to precipitation after most construction activities are completed at a construction site. New development and redevelopment projects have almost

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always resulted in permanent post-construction water quality impacts because more precipitation ends up as runoff and less precipitation is intercepted, evaporated, and infiltrated.

An effective stormwater management strategy must address the full suite of precipitation events (water quality, channel protection, overbank flood protection, extreme flood protection) (Figure 1).

Figure 1 – Suite of Precipitation Events
The post-construction stormwater performance standards in this General Permit specifically address water quality and channel protection events. Overbank flood protection and extreme flood protection events are traditionally dealt with in local drainage and flood protection ordinances. However, measures in this General Permit to address water quality and channel protection also reduce overbank and extreme flooding impacts. This General Permit aims to match post-construction runoff to pre-construction runoff for the 85th percentile, 24-hour storm event, which reduces the risk of impact to the receiving water’s channel morphology and provides some water quality protection.

Projects are exempt from the post-construction requirements in this General Permit if located within an area subject to post-construction standards of an active Phase I or II MS4 permit with approved post-construction requirements or if they are linear underground and overhead projects.

I.U.2. Water Quality
This General Permit requires dischargers to replicate the pre-project runoff water balance (defined as the amount of rainfall that ends up as runoff) for the smallest storms up to the 85th percentile storm event, or the smallest storm event that generates runoff, whichever is larger. Contemporary stormwater management

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generally routes these flows directly to the drainage system, increasing pollutant loads and potentially causing adverse effects on receiving waters. These smaller water quality events happen much more frequently than larger events and generate much higher pollutant loads on an annual basis. There are other adverse hydrological impacts that result from not designing according to the site’s preconstruction water balance. In Maryland, Klein115 noted that baseflow decreases as the extent of urbanization increases. Ferguson and Suckling116 noted a similar relation in watersheds in Georgia. On Long Island, Spinello and Simmons117 noted substantial decreases in base flow in intensely urbanized watersheds.

This General Permit emphasizes runoff reduction through on-site stormwater reuse, interception, evapotranspiration, and infiltration through non-structural controls and conservation design measures (e.g., downspout disconnection, soil quality preservation/enhancement, interceptor trees). Employing these measures close to the source of runoff generation is the easiest and most cost-effective way to comply with the pre-construction water balance standard. Using low-tech runoff reduction techniques close to the source is consistent with a number of recommendations in the literature.118 In many cases, BMPs implemented close to the source of runoff generation cost less than end-of the pipe measures.119 Dischargers are given the option of using the SMARTS Post-Construction Calculator to calculate the required runoff volume or a watershed process-based, continuous simulation model such as the EPA’s Stormwater Management Model (SWMM) or Hydrologic Simulation Program Fortran. Such methods used by the 115 Klein 1979 as cited in Delaware Department of Natural Resources (DDNR). 2004.

Green Technology: The Delaware Urban Runoff Management Approach. Dover, DE, p. 117.
116 Ferguson and Suckling 1990 as cited Delaware Department of Natural Resources (DDNR). 2004. Green Technology: The Delaware Urban Runoff Management Approach. Dover, DE, p. 117.
117 Center for Watershed Protection (CWP). 2000. The Practice of Watershed Protection: Techniques for protecting our nation’s streams, lakes, rivers, and estuaries. Ellicott City, MD, p. 741.
118 Bay Area Stormwater Management Agencies Association (BASMAA). 1997. Start at the Source: Residential Site Planning and Design Guidance Manual for Stormwater Quality Protection. Palo Alto, CA;
McCuen, R.H. 2003 Smart Growth: hydrologic perspective. Journal of Professional Issues in Engineering Education and Practice. Vol (129), p. 151-154; Moglen, G.E. and S. Kim.2007. Impervious imperviousness-are threshold-based policies a good idea? Journal of the American Planning Association, Vol 73 No.2. p. 161-171.
119 Delaware Department of Natural Resources (DDNR). 2004. Green technology: The Delaware Urban Runoff Management Approach. Dover, DE, p. 117.

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discharger will be reviewed by the Regional Water Board upon Notice of Termination application.

I.U.3. Channel Protection
A basic understanding of fluvial geomorphic concepts is necessary to address channel protection. A dominant paradigm in fluvial geomorphology holds that streams adjust their channel dimensions (width and depth) in response to longterm changes in sediment supply and bank full discharge (1.5 to 2-year recurrence interval). The bank full stage corresponds to the discharge at which channel maintenance is the most effective (the discharge at which the moving sediment, forming or removing bars, forming or changing bends and meanders, and generally doing work that results in the average morphologic characteristics of channels).120 Lane (1955 as cited in Rosgen 1996121) showed the generalized relationship between sediment load, sediment size, stream discharge, and stream slope (Figure 2). A change in any one of these variables sets up a series of mutual adjustments in the companion variables with a resulting direct change in the physical characteristics of the stream channel.

Figure 2 – Schematic of the Lane Relationship122
Stream slope multiplied by stream discharge (the right side of the scale) is essentially an approximation of stream power, a unifying concept in fluvial 120 Dunne, T and L.B. Leopold. 1978. Water in Environmental Planning. San Francisco W.H. Freeman and Company.
121 Rosgen. D.L. 1996. Applied River Morphology. Pagosa Springs. Wildland Hydrology. 122 After Lane (1955) as cited in Rosgen (1996).

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geomorphology (Bledsoe 1999). Urbanization generally increases stream power and affects the resisting forces in a channel (sediment load and sediment size represented on the left side of the scale).

Sediment loads can increase from 2 to 40,000 times over pre-construction levels during construction.123 Most of this sediment is delivered to stream channels during large, episodic rain events.124 This increased sediment load leads to an initial aggradation phase where stream depths may decrease as sediment fills the channel, leading to a decrease in channel capacity and increase in flooding and overbank deposition. A degradation phase initiates after construction is completed.

Schumm et. al (1984) developed a channel evolution model that describes the series of adjustments from initial downcutting, to widening, to establishing new floodplains at lower elevations (Figure 3).

Figure 3 – Channel Changes Associated with Urbanization125 Channel incision (Stage II) and widening (Stages III and to a lesser degree, Stage IV) are due to a number of fundamental changes on the landscape. Connected impervious areas and compaction of pervious surfaces increase the frequency and 123 Goldman S.J., K. Jackson, and T.A. Bursztynsky. 1986. Erosion and Sediment Control Handbook. McGraw Hill. San Francisco.
124 Wolman 1967 as cited in Paul, M.P. and J.L. Meyer. 2001. Streams in the Urban Landscape. Annu. Rev. Ecol. Syst. 32, p. 333-365.
125 After incised Channel Evolution Sequence in Schumm et. al 1984.

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volume of bank full discharges.126 Increased drainage density (miles of stream length per square mile of watershed) also negatively impacts receiving stream channels.127 Increased drainage density and hydraulic efficiency leads to an increase in the frequency and volume of bank full discharges because the time of concentration is shortened. Flows from engineered pipes and channels are also often “sediment starved” and seek to replenish their sediment supply from the channel.

Encroachment of stream channels can also lead to an increase in stream slope, which leads to an increase in stream power. In addition, watershed sediment loads and sediment size (with size generally represented as the median bed and bank particle size, or d50) decrease during urbanization.128 This means that even if preand post-development stream power is the same, more erosion will occur in the post-development stage because the smaller particles are less resistant (provided they are non-cohesive).

As shown in Stages II and III, the channel deepens and widens to accommodate the increased stream power129 and decrease in sediment load and sediment size.

Channels may actually narrow as entrained sediment from incision is deposited laterally in the channel. After incised channels begin to migrate laterally (Stage III), bank erosion begins, which leads to general channel widening.130 At this point, a majority of the sediment that leaves a drainage area comes from within the channel, as opposed to the background and construction related hillslope 126 Booth, D.B. and C.R. Jackson. 1997. Urbanization of Aquatic Systems: Degradation Thresholds, Stormwater Detection, and the Limits of Mitigation. Journal of the American Water Resources Association Vol. 33, No. 5, p. 1077-1089. 127 May, C.W. 1998. Cumulative effects of urbanization on small streams in the Puget Sound Lowland ecoregion. Conference proceedings from Puget Sound Research ’98 held March 12, 13 1998 in Seattle, WA;
Santa Clara Valley Urban Runoff Pollution Prevention Program. 2002.

Hydromodification Management Plan Literature Review, p. 80. 128 Finkenbine, J.K., D.S. Atwater, and D.S. Mavinic. 2000. Stream health after urbanization. J. Am. Water Resour. Assoc. 36, p. 1149-60; Pizzuto. J.E. W.S. Hession, and M. McBride. 2000. Comparing gravel-bed rivers in paired urban rural catchments of southeastern Pennsylvania. Geology 28, p. 79-82. 129 Hammer 1973 as cited in Delaware Department of Natural Resources (DDNR). 2004.

Green Technology: The Delaware Urban Runoff Management Approach. Dover, DE, p.117;
Booth, D.B. 1990. Stream Channel Incision Following Drainage Basin Urbanization.

Water Resour. Bull. 26, p. 407-417.
130 Trimble, S.W. 1997. Contribution of Stream Channel Erosion to Sediment Yield from an Urbanizing Watershed. Science: Vol. 278 (21), p. 1442-1444.

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contribution. Stage IV is characterized by more aggradation and localized bank instability. Stage V represents a new quasi-equilibrium channel morphology in balance with the new flow and sediment supply regime. In other words, stream power is in balance with sediment load and sediment size.

The magnitude of the channel morphology changes discussed above varies along a stream network as well as with the age of development, slope, geology (sandbedded channels may cycle through the evolution sequence in a matter of decades whereas clay-dominated channels may take much longer), watershed sediment load and size, type of urbanization, and land use history. It is also dependent on a channel’s stage in the channel evolution sequence when urbanization occurs.

Management strategies must take into account a channel’s stage of adjustment and account for future changes in the evolution of channel form (Stein and Zaleski 2005).131
Traditional structural water quality BMPs (e.g., detention basins and other devices used to store volumes of runoff) unless they are highly engineered to provide adequate flow duration control, do not adequately protect receiving waters from accelerated channel bed and bank erosion, do not address post-development increases in runoff volume, and do not mitigate the decline in benthic macroinvertebrate communities in the receiving waters,
132 and suggest that
structural BMPs are not as effective in protecting aquatic communities as a continuous riparian buffer of native vegetation. This is supported by the findings of Zucker and White,133 where instream biological metrics were correlated with the extent of forested buffers.

This General Permit requires dischargers to maintain pre-development drainage densities and times of concentration in order to protect channels and encourages dischargers to implement setbacks to reduce channel slope and velocity changes that can lead to aquatic habitat degradation.

There are a number of other approaches for modeling fluvial systems, including statistical and physical models and simpler stream power models.134 The use of 131 Stein, E.S. and S. Zaleski. 2005. Managing runoff to protect natural stream: the latest developments on investigation and management of hydromodification in California.

Southern California Coastal Water Research Project Technical Report 475, p. 26. 132 Horner, R.R. 2006. Investigation of the Feasibility and Benefits of Low-Impact Site Design Practices (LID) for the San Diego Region.
133 Delaware Department of Natural Resources (DDNR). 2004. Green Technology: The Delaware Urban Runoff Management Approach. Dover, DE, p. 117. 134 Finlayson, D.P. and D.R. Montgomery. 2003. Modeling large-scale fluvial erosion in geographic information systems. Geomorphology (53), p.147-164.

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these models in California is described in Stein and Zaleski (2005).135 Rather than require a specific one-size-fits-all modeling method in this permit, the State Water Board intends to develop a stream power and channel evolution model-based framework to assess channels and develop a hierarchy of suitable analysis methods and management strategies. In time, this framework may become a State Water Board water quality control policy.

I.U.4. General Permit Linkage to Overbank and Extreme Flood Protection Site design BMPs (e.g., rooftop and impervious disconnection, vegetated swales, setbacks and buffers) filter and settle out pollutants and provide for more infiltration than is possible for traditional centralized structural BMPs placed at the site’s lowest point. They provide source control for runoff and lead to a reduction in pollutant loads. When implemented, they also help reduce the magnitude and volume of larger, less frequent storm events (e.g., 10-yr, 24-hour storm and larger), thereby reducing the need for expensive flood control infrastructure. Non-structural BMPs can also be a landscape amenity, instead of a large, isolated structure requiring substantial area for ancillary access, buffering, screening, and maintenance facilities. The multiple benefits of using non-structural benefits will be critically important as the state’s population increases and imposes strains upon our existing water resources.

Maintaining predevelopment drainage densities and times of concentration will help reduce post-development peak flows and volumes in areas not covered under a municipal permit. The most effective way to preserve drainage areas and maximize time of concentration is to implement landform grading, incorporate site design BMPs and implement distributed structural BMPs (e.g., bioretention cells, rain gardens, rain cisterns).

This General Permit requires dischargers to maximize sheet flow and use an “open” drainage system (e.g., swales, ditches, vegetated channels) for concentrated flows to meet the drainage density requirement. Sheet flow areas, swales, ditches, and vegetated channels are not considered streams for the purpose of calculating drainage density.

This General Permit requires dischargers to use recommended methods in the applicable local hydraulic design or flood control manual to meet the time of concentration requirements. The discharger is required to use the time of concentration calculation method contained in the Natural Resources Conservation Service’s Technical Release 55: Urban Hydrology for Small Watersheds if a recommended method does not exist.
135 Stein, E.S. and S. Zaleski. 2005. Managing runoff to protect natural stream: the latest developments on investigation and management of hydromodification in California.

Southern California Coastal Water Research Project Technical Report 475, p. 26.

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Dischargers with active General Permit coverage are required to use the postconstruction calculator in SMARTS or the approved post-construction standards of an applicable Phase I or Phase II Municipal Separate Storm Sewer System (MS4) NPDES permit to report compliance with this General Permit post-construction requirements.

This General Permit requires the discharger to utilize the post-construction calculator in SMARTS if: (1) a construction project (other than a linear and underground and overhead project that is not subject to this General Permit’s postconstruction requirements) was or is approved by the local municipality prior to the municipality having post-construction standards adopted pursuant to a Phase I or Phase II MS4 permit or (2) the project was not subject to the post-construction standards of a Phase I or Phase II entity.

I.V. Stormwater Pollution Prevention Plans (SWPPPs)
U.S. EPA’s Construction General Permit requires that qualified personnel conduct inspections and defines qualified personnel as “a person knowledgeable in the principles and practice of erosion and sediment controls who possesses the skills to assess conditions at the construction site that could impact stormwater quality and to assess the effectiveness of any sediment and erosion control measures selected to control the quality of stormwater discharges from the construction activity.”136 U.S.

EPA also suggests that qualified personnel prepare SWPPPs and points to numerous states that require certified professionals to be on construction sites at all times.

This General Permit requires that all SWPPPs be site-specific and are written, amended, and certified by a Qualified SWPPP Developer and includes the information needed to demonstrate compliance with all requirements of this General Permit to ensure that water quality is being protected. SWPPP development and updates are required to be based on actual site conditions and maintain continued compliance with requirements of this General Permit. This General Permit also requires the current SWPPP be kept on-site, made available for review, and uploaded through SMARTS.

Although the QSD can change over the life of a project, a QSD, representing the discharger, is expected to make necessary corrections and amendments to the original SWPPP throughout the life of the project to ensure the site’s compliance plan with this General Permit is documented and current. Similarly, a QSP, representing the discharger, must also oversee the implementation of the sitespecific BMPs described in the corresponding site-specific SWPPP. 136 U.S. EPA, Developing Your Stormwater Pollution Prevention Plan (May 2017), <https://www3.epa.gov/npdes/pubs/sw_swppp_guide.pdf> [as of May 20, 2021]

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The local municipality cannot enforce General Permit requirements; this is done by the Regional Water Board inspectors. The local municipality is typically responsible for ensuring compliance with local stormwater ordinance which prohibits sediment and other pollutants from entering the MS4, and with a local grading ordinance that typically requires an erosion and sediment control plan (typically a sheet in the construction plan set) for projects with a grading permit. The local municipality may have a condition in their MS4 stormwater permit requiring the agency to check that certain items are included in the SWPPP. This does not constitute approval of the SWPPP, and the review is typically conducted prior to issuing a grading permit.

The previous versions of the General Permit required development and implementation of a SWPPP as the primary compliance mechanism. The SWPPP has three major objectives: (1) to help identify the sources of sediment and other pollutants that affect the quality of stormwater discharges, (2) to describe and ensure the implementation of site-specific BMPs to reduce or eliminate sediment and other pollutants in stormwater and non-stormwater discharges, and (3) to convey a plan to restore erosion protection and site hydrology post-construction. The SWPPP must include site-specific BMPs that address source control, pollutant control, and treatment control.

This General Permit shifts some of the previous measures into specific General Permit requirements, each individually enforceable as a General Permit term. This General Permit emphasizes the use of appropriately selected, correctly installed, and maintained site-specific BMPs. This approach provides the flexibility necessary to establish BMPs that can effectively control sources of pollutants during changing construction activities. These specific requirements also improve both the clarity and the enforceability of the General Permit so that the dischargers understand, and the Water Boards and public can determine whether the discharges comply with this General Permit’s requirements.

The SWPPP must be implemented at the appropriate level to protect water quality at all times throughout all of the construction project phases. The SWPPP must remain on the site during construction activities, commencing with the initial mobilization and ending with the termination of coverage under the General Permit. Linear underground and overhead project dischargers are required to make the SWPPP available at the construction site during site operating hours while construction is occurring and shall be made available upon request by a State, Federal, or Municipal inspector. A site-specific SWPPP may be kept in electronic format. All maps and figures must be printed, hard copy, full size, and available on the construction site. Current copies of the BMPs and maps and drawings will be left with the field crew and the original SWPPP shall be made available via a request by radio or telephone when the original SWPPP is retained by a crewmember in a construction vehicle and is not currently at the construction site. The SWPPP shall be available from the SWPPP contact listed in the Permit Registration Documents until stabilization is achieved even when construction activities are complete.

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A SWPPP must be appropriate for the type and complexity of a project and will be developed and implemented to address site-specific conditions. Some projects may have similarities or complexities, yet each project is unique in its progressive state that requires specific description and selection of BMPs needed to address all possible generated pollutants.

I.W. Total Maximum Daily Loads (TMDLs)
I.W.1. Introduction
Total Maximum Daily Loads (TMDLs) are regulatory tools that provide the maximum amount of a pollutant from potential sources in the watershed that a water body can receive while attaining water quality standards. A TMDL is defined as the sum of the allowable loads of a single pollutant from all contributing point sources (waste load allocations) and non-point sources (load allocations), plus the contribution from background sources. (40 Code of Federal Regulations § 130.2, subd. (i).) Discharges covered by this General Permit are considered to be point source discharges, and therefore must comply with effluent limitations that are “consistent with the assumptions and requirements of any available waste load allocation for the discharge prepared by the State and approved by EPA pursuant to 40 Code of Federal Regulations section 130.7.” (40 Code of Federal Regulations § 122.44, subd. (d)(1)(vii).) In addition, Water Code § 13263, subdivision (a), requires that waste discharge requirements implement relevant water quality control plans. Many TMDLs in existing water quality control plans include both waste load allocation and implementation requirements. Attachment H of this General Permit lists the watersheds with U.S. EPA-approved and U.S. EPAestablished TMDLs that include TMDL requirements for dischargers covered by this General Permit.

TMDLs are adopted through a separate U.S. EPA and Regional Water Board public process. The previous permit included a list of potentially applicable TMDLs, and this list has been refined in this General Permit through consultation with the Regional Water Boards.

I.W.2. General Permit Implementation Requirements
Water Board staff evaluated and developed the following information in the development of the Attachment H implementation requirements:
· TMDL-specific requirements including implementation timelines, additional monitoring and reporting requirements, compliance determination language regarding compliance with numeric action levels, applicable TMDL-specific effluent limitations, and reporting requirements consistent with the applicable TMDL(s);

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· Information regarding this General Permit’s TMDL-specific requirements, timelines, and deliverables consistent with the assumptions and requirements of applicable waste load allocation(s) to implement the TMDL(s); · Information regarding the implementation of BMPs (as applicable) to comply with applicable waste load allocations;
· Concentration-based monitoring requirements and information regarding the required determination of compliance for numeric effluent limitations through concentration-based compliance monitoring, corresponding calculation methodology, and reporting; and
· Compliance deadlines, based on TMDL implementation schedules, were set for Responsible Dischargers to comply with the TMDL-specific requirements on, and after, the provided date. TMDLs that lacked or surpassed the implementation schedules prior to this issuance of this General Permit were assigned compliance deadlines set for the effective date of this General Permit.

I.W.3. TMDL Evaluation Steps
The State Water Board used the following process to evaluate and translate each TMDL in Attachment H:
· Step 1: Determined whether the TMDL applies to construction stormwater discharges and authorized non-stormwater discharges regulated by this General Permit (discharges regulated by this General Permit); · Step 2: Identified the specific TMDL requirements that are applicable to discharges regulated by this General Permit;
· Step 3: Translated the TMDL requirements into TMDL-specific General Permit requirements, numeric action levels, or numeric effluent limitations; · Step 4: Determined a compliance schedule that corresponds with the compliance date of the TMDL;
· Step 5: Developed monitoring and reporting requirements to determine compliance with waste load allocations;
· Step 6: Identified the existing General Permit requirements applicable to each constituent identified in the TMDLs, and evaluated if additional TMDL-specific requirements were required to implement the TMDL for discharges regulated by this General Permit; and
· Step 7: Provided explanation regarding how the State Water Board translated each TMDL into specific requirements.

I.W.4. Applicability
Responsible Dischargers are: (1) dischargers with Notice of Intent coverage under this General Permit who discharge stormwater associated with construction

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activities and authorized-non-stormwater discharges, (2) either directly or through a municipal separate storm sewer system (MS4) to impaired water bodies identified in a U.S. EPA approved TMDL with an assigned waste load allocation to construction stormwater sources listed in Attachment H, and (3) have identified one or more TMDL-pollutants in the site’s construction stormwater discharges.

Responsible Dischargers must comply with applicable TMDL-specific General Permit requirements in Attachment H and all other applicable provisions of this General Permit.

Each TMDL-specific permit requirement listed in Attachment H (Table H-2 for TMDL-specific General Permit Requirements) provides the specific translation and required actions for Responsible Dischargers as discussed below. Table H-2 includes the specific watershed, water body, or water bodies and additional tributaries to ensure Responsible Dischargers know which Table H-2 TMDL requirement applies depending on the receiving water body(ies) of the site.

This General Permit’s pH and turbidity numeric action levels continue to apply in addition to the TMDL-specific requirements in Table H-2. The measurement of compliance with the TMDL-specific requirements, whether TMDL-related numeric action levels or numeric effluent limits, is defined in the Glossary (Attachment B).

Stormwater discharges are intermittent in nature and many of the Attachment H TMDL waste load allocations are translated to numeric action levels or numeric effluent limitations for protection against acute impacts to beneficial uses in the receiving waters.

The following are examples to assist Responsible Dischargers in determining which water bodies are subject to the TMDLs in Table H-2:
· Watershed example: If the “Impaired Water Body/Watershed” column states “Napa River Watershed,” the TMDL and its requirements are applicable to dischargers discharging directly or through an MS4 into water bodies within the Napa River Watershed.
· River and tributaries (Watershed) example: If the “Impaired Water Body/ Watershed” column states “Los Angeles River and Tributaries,” this TMDL and its requirements are applicable to the dischargers discharging directly or through an MS4 into the Los Angeles River watershed.
· Lagoon example: If the “Impaired Water Body/ Watershed” column states “Colorado Lagoon,” this TMDL and its requirements are applicable to dischargers discharging directly or through an MS4 into the Colorado Lagoon.

TMDL-specific General Permit requirements do not apply to dischargers with a waiver or dischargers that meet the Notice of Non-Applicability (NONA) criteria.

There are currently few environmental laboratory accredited program (ELAP)- accredited laboratories capable of analyzing the following compounds (e.g.,

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chlordane, dieldrin, total PCBs, total DDTs, 4,4-DDT, PAHs) to the low concentrations for some of the numeric action levels or numeric effluent limitations in Attachment H. Attachment H, Section I.G.5 provides a modified compliance protocol for Responsible Dischargers for the Los Angeles Area Lakes TMDL that are required to comply with TMDL-related numeric effluent limitations for Chlordane, Dieldrin, DDT, and PCBs. It is the expectation that the Water Boards will provide guidance and alternative methods for a Responsible Discharger to demonstrate compliance, if the Responsible Discharger has provided the Water Boards adequate information demonstrating that:
· It is infeasible to analyze a translated waste load allocation using an ELAPaccredited laboratory; · The sample results would invalidate federally-required sufficiently sensitive methods; or
· No method in 40 Code of Federal Regulations Part 136 can detect and quantify the amount specified for the construction stormwater.

I.W.5. General Permit Summary
The following requirements, applicable to dischargers enrolled under this General Permit, were considered in determining the necessity of additional TMDL-specific permit implementation for applicable to Responsible Dischargers:
· Storm Water Pollution Prevention Plan (SWPPP): This General Permit requires dischargers to identify construction materials handled at the site and describe all potential sources of pollutants that could be discharged from their site and describe the BMPs that will be implemented to control their discharges. This General Permit requires Responsible Dischargers to revise their SWPPP whenever a significant change in monitoring or sampling occurs. · Non-Stormwater Discharges (NSWDs): The only NSWDs authorized by this General Permit are described in the Order, and the discharge is prohibited unless regulated by a separate NPDES permit.
· Visual Observations: Dischargers are required to conduct pre, during, and post precipitation event site visual inspections which include: 1) monitoring of authorized NSWDs, 2) identification and elimination of unauthorized NSWDs, 3) identification of potential construction pollutant sources, and 4) necessary BMP maintenance and implementation.
· Sampling and Analysis: Dischargers must sample for all construction pollutants (with the potential to discharge to a waters of the United States) identified in their SWPPP in accordance with this General Permit. Dischargers are required to collect and analyze stormwater samples from construction site discharge locations over the reporting period in accordance with the requirements of this General Permit. When this previous permit’s requirements were not sufficient to

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implement the TMDL, additional monitoring and sampling requirements are set forth in Attachment H’s TMDL Compliance Table (Table H-2).

I.W.6. TMDL-Specific Requirements
Attachment H, Table H-2 contains TMDL-specific requirements for each TMDL with sources from discharges regulated by this General Permit. This Fact Sheet discusses TMDLs by pollutant since many of the TMDLs with the same pollutants are translated in the same manner. Table H-2 is organized by Regional Water Board jurisdiction and watershed, allowing the Responsible Dischargers to easily identify their applicable requirements.
a. Bacteria TMDLs
Nine Indicator Bacteria TMDLs (eight established by the Los Angeles Regional Water Quality Control Board and one by the U.S. EPA) apply to construction stormwater dischargers. Each TMDL addresses bacterial pollutants by establishing bacteria water quality objectives for one or more of the following Indicator Bacteria: Enterococcus, Escherichia coli (E. Coli), Fecal Coliform, and Total Coliform. These pollutants are referred to as Indicator Bacteria for the purpose of Attachment H and this Fact Sheet.

The water quality objectives for Indicator Bacteria are specific to fresh and marine waters and designated beneficial uses such as water contact recreation (REC-1), limited water contact recreation (LREC-1), and water non-contact recreation (REC-2).

Recreating in waters exceeding indicator bacteria water quality objectives has long been associated with adverse human health effects. Specifically, local and national epidemiological studies demonstrate that there is a causal relationship between adverse health effects and recreational water quality, as measured by bacterial indicator densities.137
The Indicator Bacteria TMDLs and their beneficial uses are summarized below:
· Ballona Creek, Ballona Estuary, and Sepulveda Channel Bacteria TMDL138:

Fresh Waters (LREC-1, REC-1, REC-2) and Marine Waters (REC-1) 137 Ballona Creek, Estuary, and Tributary Bacteria TMDL, p. 2. 138 Los Angeles Regional Water Board, Ballona Creek, Estuary, and Tributary Bacteria TMDL (June 7, 2012),
<https://www.waterboards.ca.gov/losangeles/water_issues/programs/tmdl/docs/R12- 008_RB_BPA.pdf> [as of May 20, 2021]

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· Harbor Beaches of Ventura County Bacteria TMDL139: Marine Waters (REC1) · Long Beach City Beaches and Los Angeles River Estuary Bacteria TMDL140: Marine Waters (REC-1)
· Los Angeles Harbor Bacteria TMDL141: Marine Waters (REC-1) · Los Angeles River Bacteria TMDL142: Fresh Waters (LREC-1) · Malibu Creek Bacteria TMDL143: Fresh Waters (REC-1) and Marine Waters (REC-1)
· Marina del Rey Bacteria TMDL144: Marine Waters (REC-1) 139 Los Angeles Regional Water Quality Control Board, Harbor Beaches of Ventura County (Kiddie Beach and Hobie Beach) Bacteria TMDL (November 1, 2007), <https://www.waterboards.ca.gov/losangeles/water_issues/programs/tmdl/docs/2007- 017_RB_BPA.pdf> [as of May 20, 2021]
140 United States Environmental Protection Agency IX, Long Beach City Beaches and Los Angeles River Estuary Total Maximum Daily Loads for Indicator Bacteria (March 26, 2012),
<https://www.waterboards.ca.gov/losangeles/water_issues/programs/tmdl/Established /Longbeach/finalTMDLs-LongBeachCityBeaches-LARiverEstuaryBacteria.pdf> [as of April 28, 2022]
141 Los Angeles Regional Water Quality Control Board, Los Angeles Harbor Bacteria TMDL (Inner Cabrillo Beach Main Ship Channel) (July 1, 2004), <https://www.waterboards.ca.gov/losangeles/water_issues/programs/tmdl/docs/2004- 011_RB_BPA.pdf> [as of May 20, 2021] (Los Angeles Harbor Bacteria TMDL) 142 Los Angeles Regional Water Quality Control Board, Los Angeles River Watershed Bacteria TMDL (July 9, 2010),
<https://www.waterboards.ca.gov/losangeles/water_issues/programs/tmdl/docs/R10- 007_RB_BPA1.pdf> [as of May 20, 2021] (Los Angeles Bacteria TMDL) 143 Los Angeles Regional Water Quality Control Board, Malibu Creek and Lagoon Bacteria TMDL (June 7, 2012),
<https://www.waterboards.ca.gov/losangeles/water_issues/programs/tmdl/docs/R12- 009_RB_BPA.pdf> [as of May 20, 2021] (Malibu Creek Bacteria TMDL) 144 Los Angeles Regional Water Quality Control Board, Marina del Rey Harbor Mother’s Beach and Back Basins Bacteria TMDL (August 7, 2003),
<https://www.waterboards.ca.gov/losangeles/water_issues/programs/tmdl/docs/2003- 012_RB_BPA.pdf> [as of May 20, 2021] (Marina del Rey Bacterial TMDL)

ORDER WQ 2022-0057-DWQ
NPDES No. CAS000002
FACT SHEET FS-128
· Santa Clara River Bacteria TMDL145: Fresh Waters (REC-1) and Marine Waters (REC-1)
· Santa Monica Bay Beaches Bacterial TMDL146: Marine Waters (REC-1) The bacteria water quality objectives applicable to the beneficial uses associated with these water bodies are listed in Table 11 below.

Table 11 – Los Angeles Regional Water Quality Control Board Bacteria Water Quality Objectives
Beneficial
Uses E. Coli Total Coliform
Fecal
Coliform Enterococcus Total Coliform*
Fresh Waters
REC-1
235/100 ml
Fresh Waters
LREC-1
576/100 ml
Fresh Waters
REC-2
4,000/100
ml
Marine Waters
REC-1
10,000/100
ml
400/100
ml 104/100 ml 1,000/100 ml
* If the fecal-to-total coliform ratio is greater than 0.1 · Source Analysis
The primary sources of elevated indicator bacteria densities include dryweather urban runoff and stormwater conveyed to the impaired waters.

Although construction stormwater dischargers are not expected to be significant sources of indicator bacteria, they are considered Responsible Dischargers for these TMDLs.
· Waste Load Allocation Translation
The Indicator Bacteria TMDLs assign the waste load allocations in two different ways:
i. The TMDLs for the: (1) Harbor Beaches of Ventura County, (2) Santa Clara River, (3) Long Beach City Beaches, and (4) Los Angeles River 145 Los Angeles Regional Water Quality Control Board, Santa Clara River Estuary and Reaches 3, 5, 6, and 7 Indicator Bacteria TMDL (July 8, 2010), <https://www.waterboards.ca.gov/losangeles/water_issues/programs/tmdl/docs/R10- 006_RB_BPA.pdf> [as of May 20, 2021] (Santa Clara River Bacteria TMDL) 146 Los Angeles Regional Water Quality Control Board, Santa Monica Bay Beaches Bacteria TMDL (July 2, 2014),
<https://www.waterboards.ca.gov/losangeles/water_issues/programs/tmdl/docs/R12- 007_RB_BPA1.pdf>

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assigns a waste load allocation of zero (0) allowable exceedance days of the Bacteria WQOs, listed in Table 11 above.
ii. The TMDLs for the: (1) Ballona Creek, Ballona Estuary, and Sepulveda Channel, (2) Malibu Creek, Lagoon, and adjacent beach, (3) Marina del Rey Harbor, Mother’s Beach, and Back Basins, (4) Los Angeles Harbor (including Inner Cabrillo Beach and Main Ship Channel), and (5) Santa Monica Bay Beaches assign waste load allocations to construction stormwater dischargers equal to the Bacteria WQOs.

The two waste load allocation definitions were translated similarly and require Responsible Dischargers to “meet and not exceed” the bacteria water quality objectives listed in Table 11. Responsible Dischargers will be required to implement minimum BMPs in order to comply with the translated waste load allocations because construction stormwater dischargers are not expected to be significant sources of indicator bacteria. This General Permit requires all dischargers to perform a pollutant source assessment and implement specific BMPs to prevent or eliminate any exceedance of water quality objectives contained within applicable TMDLs, including those for indicator bacteria. Therefore, compliance with this General Permit is consistent with the requirements and assumptions of the TMDL and sufficient to achieve compliance with the waste load allocation. · Compliance Actions and Schedule
Responsible Dischargers with an applicable TMDL for Indicator Bacteria listed in Attachment H shall comply with the requirements of this General Permit.

Responsible Dischargers that identify on-site sources of indicator bacteria in the required pollutant source assessment are to implement BMPs specific to preventing or controlling stormwater exposure to indicator bacteria. The minimum bacteria source control BMPs include QSP-conducted training of site staff, sanitary septic waste management, and routine housekeeping of identified bacteria sources. Structural BMPs such as retention, infiltration, or diversion of stormwater reduce bacteria loading to receiving waters.

Responsible Dischargers that implement a suite of minimum BMPs to control stormwater exposure to source of indicator bacteria are expected to meet the assigned waste load allocation. If a BMP is observed failing, the Responsible Discharger is to evaluate the BMPs being used and identify and implement a strategy in the site’s SWPPP to prevent potential exceedances of the waste load allocations in the future. The Regional Water Board may assign additional monitoring, reporting, and BMP requirements upon obtaining site-specific information about exceedances of the waste load allocation.

ORDER WQ 2022-0057-DWQ
NPDES No. CAS000002
FACT SHEET FS-130
Compliance with Indicator Bacteria TMDLs shall be achieved by the effective date of this General Permit, as shown in Table H-2 in Attachment H.
b. Chloride and Salts TMDLs
Three TMDLs for chloride and other salts (Calleguas Creek, Santa Clara River Reach 3, and Upper Santa Clara River) apply to construction stormwater dischargers. Elevated levels of chloride and salts can impair a water body’s beneficial uses associated with agricultural uses for irrigation of salt-sensitive crops and groundwater recharge to provide drinking water. i. Calleguas Creek Watershed Salts TMDL147
The Los Angeles Regional Water Quality Control Board adopted the TMDL for Boron, Chloride, Sulfate, and TDS (salts) on October 4, 2007, to protect and restore water quality in the Calleguas Creek watershed by controlling the loading and accumulation of salts.
· Source Analysis
Sources of salts in the watershed include water supply, water softeners that discharge to publicly treatment works (POTWS), POTW treatment chemicals, atmospheric deposition, pesticides and fertilizers, and indoor water use (e.g., chemicals, cleansers, food, etc.).148 The salts are then transported through POTW discharges and runoff to surface water, shallow groundwater, or accumulate on the watershed within soils.

Construction stormwater permittees are considered Responsible Dischargers for this TMDL.
· Waste Load Allocation Translation
The Calleguas Creek Watershed Salts TMDL assigns interim and final waste load allocations during dry-weather conditions, when instream flow rates are below the 86th percentile flow and there has been no measurable precipitation in the previous 24 hours.149 Both the interim and final dry-weather waste load allocations, shown in Table 12 and Table 13 below, apply in the receiving water at the base of each subwatershed.
147 Los Angeles Regional Water Board, Calleguas Creek Watershed Salts TMDL (October 4, 2007),
<https://www.waterboards.ca.gov/losangeles/water_issues/programs/tmdl/docs/2007- 016_RB_BPA.pdf> [as of May 20, 2021]
148 Calleguas Creek Watershed Salts TMDL, p.3.
149 Calleguas Creek Watershed Salts TMDL, p. 7-8.

ORDER WQ 2022-0057-DWQ
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FACT SHEET FS-131
Table 12 – Calleguas Creek Interim Dry-Weather Waste Load Allocations Pollutant Interim Limit
(mg/L)
Boron Total 1.3
Chloride Total 230
Sulfate Total 1289
TDS Total 1720
Table 13 – Calleguas Creek Final Dry-Weather Waste Load Allocations Receiving
Water
Critical
Condition
Flow Rate
(mgd)
Chloride
Allocation
(lb/day)
TDS
Allocation
(lb/day)
Sulfate
Allocation
(lb/day)
Boron
Allocation
(lb/day)
Simi 1.39 1,738 9,849 2,897 12
Las Posas 0.13 157 887 261 N/A
Conejo 1.26 1,576 8,931 2,627 N/A
Camarillo 0.06 72 406 119 N/A
Pleasant
Valley
(Calleguas)

0.12 150 850 250 N/A
Pleasant
Valley
(Revolon)

0.25 314 1,778 523 2
Discharges that occur during dry-weather conditions are referred to as non-stormwater discharges (NSWDs) and are only authorized by this General Permit if dischargers meet the conditions of Order, Section IV.A to control the discharge of pollutants off-site. Section IV.B of this General Permit’s Order prohibits all NSWDs not authorized under Section IV.A; therefore, all unauthorized NSWDs must be eliminated or have regulatory coverage under a separate NPDES permit. Authorized NSWDs, as defined in this General Permit, are authorized because these discharges are assumed to not commingle with stormwater associated with construction activity. The Los Angeles Regional Water Quality Control Board may impose additional requirements on NSWDs if deemed necessary per a site-specific analysis.

Wet-weather discharges are not assigned waste load allocations as flows transport a larger amount of salts at low concentrations for most construction stormwater dischargers, therefore meeting water quality objectives during wet weather.
· Compliance Actions and Schedule
Compliance with this General Permit’s requirements is consistent with the assumptions and requirements of the Calleguas Creek Salts TMDL

ORDER WQ 2022-0057-DWQ
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FACT SHEET FS-132
and is sufficient to achieve the assigned salts waste load allocations. If a BMP is observed failing, the Responsible Discharger shall evaluate the BMPs being used and identify and implement a strategy in the site’s SWPPP to prevent potential exceedances of the waste load allocations in the future. Responsible Dischargers that perform pollutant assessments and implement BMPs specific to preventing or controlling stormwater exposure with salts are expected to meet the assigned waste load allocations. The Regional Water Board may assign additional monitoring, reporting, and BMP requirements upon obtaining sitespecific information about exceedances of the waste load allocations.

The Calleguas Creek Watershed Salts TMDL’s final compliance deadline is December 2, 2023. Therefore, the interim waste load allocations are applied to Responsible Dischargers upon the effective date of this General Permit.
ii. Santa Clara River Chloride Reach 3 TMDL150
The U.S. EPA adopted the Santa Clara River Chloride Reach 3 TMDL on June 18, 2003, to address the chloride impairment of Santa Clara River, Reach 3. Exceedances of chloride water quality standards in the Santa Clara River can impair the water’s use as agricultural irrigation supply.

The U.S. EPA’s analysis of available flow and loading data concluded that exceedances of the chloride water quality objectives are most likely to occur during low-flow conditions. Therefore, setting the TMDL and associated allocations at levels sufficient to implement the objectives during low-flow conditions will also result in attainment of the objectives during higher flow conditions.151
· Source Analysis
The Santa Clara River Chloride Reach 3 TMDL identifies two major point sources (the Fillmore and Santa Paula Water Reclamation Plants) as well as a number of minor point sources, including runoff from construction sites. Construction stormwater permittees are therefore considered Responsible Dischargers for this TMDL. Sources of salts in the watershed include water supply, water softeners that discharge to 150 United States Environmental Protection Agency IX, Total Maximum Daily Load for Chloride in the Santa Clara River, Reach 3 (June 18, 2003) <https://www.waterboards.ca.gov/losangeles/water_issues/programs/tmdl/Established /Santa%20Clara%20River%20Reach%203%20Chloride%20TMDL/final%20SCR%20 R3%20Cl%20TMDL.pdf> [as of May 20, 2021] (Santa Clara River Chloride Reach 3 TMDL)
151 Santa Clara River Chloride Reach 3 TMDL, p. 14.

ORDER WQ 2022-0057-DWQ
NPDES No. CAS000002
FACT SHEET FS-133
publicly treatment works (POTWS), POTW treatment chemicals, atmospheric deposition, pesticides and fertilizers, and indoor water use (e.g., chemicals, cleansers, food, etc.).152 The salts are then transported through POTW discharges and runoff to surface water, shallow groundwater, or accumulate on the watershed within soils. · Waste Load Allocation Translation
The Santa Clara River Chloride Reach 3 TMDL assigns a concentrationbased chloride waste load allocation of 80 mg/L to Responsible Dischargers at the construction site’s discharge locations(s) for dryweather discharges into Santa Clara River Reach 3.

Discharges that occur during dry-weather conditions are referred to as non-stormwater discharges (NSWDs) and are only authorized by this General Permit if dischargers meet the conditions of Order, Section IV.A to control the discharge of pollutants off the site. Order, Section IV.B prohibits all NSWDs not authorized under Section IV.A; therefore, all unauthorized NSWDs must be eliminated or have regulatory coverage under a separate NPDES permit. Authorized NSWDs, as defined in this General Permit, are authorized because these discharges are assumed to not commingle with stormwater associated with construction activities.

The Los Angeles Regional Water Quality Control Board may impose additional requirements on NSWDs if deemed necessary per a sitespecific analysis. · Compliance Actions and Schedule
Compliance with this General Permit’s requirements is consistent with the assumptions and requirements of the Santa Clara River Chloride Reach 3 TMDL and is consistent with the assigned chloride waste load allocation. If a BMP is observed failing, the Responsible Discharger shall evaluate the BMPs being used and identify and implement a strategy in the site’s SWPPP to prevent potential exceedances of the waste load allocation in the future. Responsible Dischargers that perform pollutant assessments and implement BMPs specific to preventing or controlling stormwater exposure with salts are expected to meet the assigned waste load allocation. The Regional Water Board may assign additional monitoring, reporting, and BMP requirements upon obtaining sitespecific information about exceedances of the waste load allocation.

The Santa Clara River Chloride Reach 3 TMDL does not have an implementation plan, nor compliance deadline, as it was established by the U.S. EPA rather than the Los Angeles Regional Water Quality 152 Santa Clara River Chloride Reach 3 TMDL, p. 11-12.

ORDER WQ 2022-0057-DWQ
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FACT SHEET FS-134
Control Board. Therefore, the discharger shall meet the assigned waste load allocation by the effective date of this General Permit. iii. Upper Santa Clara River Chloride TMDL153
The Los Angeles Regional Water Quality Control Board adopted the Revision of the Upper Santa Clara River Chloride TMDL on October 9, 2014, to address elevated chloride concentrations causing exceedances of water quality objectives for Reaches 5 and 6 of the Santa Clara River.

Chloride-impaired water bodies that are used for agricultural irrigation supply can negatively impact the growth of salt-sensitive crops. · Source Analysis
The primary sources of chloride into Reaches 5 and 6 of the river are discharges from the Saugus and Valencia Water Reclamation Plants, contributing roughly 70 percent of the load.154 Other NPDES dischargers, including those covered under this General Permit, are considered minor contributors of chloride to the Upper Santa Clara River. Therefore, construction stormwater dischargers are considered Responsible Dischargers for this TMDL.
· Waste Load Allocation Translation
The Responsible Dischargers have been assigned a waste load allocation of 100 mg/L as 3-month rolling average. Compliance with the 3-month rolling average is currently beyond the scope of the monitoring and sampling requirements of this General Permit. A requirement to calculate a 3-month rolling average would put an undue burden on the Responsible Dischargers. Therefore, the rolling average limit will be translated into a numeric action level of 100 mg/L, to be met at the construction discharge location(s), as shown in Table 14 below.

Translating the 3-month rolling average limit into a numeric action level with the same concentration ensures that the limit is stringent enough to achieve the surface water quality objectives.

Table 14 – Upper Santa Clara River Chloride Waste Load Allocation Translation Pollutant 3-Month Rolling Average (mg/L) Numeric Action Level (mg/L)
Chloride 100 100
153 Los Angeles Regional Water Quality Control Board, Upper Santa Clara River Chloride TMDL (October 9, 2014),
<https://www.waterboards.ca.gov/losangeles/water_issues/programs/tmdl/docs/R14- 010_RB_BPA.pdf> [as of March 7, 2019]
154 Upper Santa Clara River Chloride TMDL, p. 4.

ORDER WQ 2022-0057-DWQ
NPDES No. CAS000002
FACT SHEET FS-135
Responsible Dischargers that perform the required pollutant source assessment and implement BMPs specific to preventing or controlling stormwater exposure to chloride, as is required in this General Permit, are expected to meet the translated numeric action level. Therefore, compliance with this General Permit’s requirements is consistent with the assumptions and requirements of the Upper Santa Clara River Chloride TMDL and is sufficient to achieve the assigned waste load allocation.
· Compliance Actions and Schedule
Responsible Dischargers shall comply with the requirements of this General Permit. Responsible Dischargers that identify on-site sources of chloride through the required pollutant source assessment shall compare all non-visible sampling and analytical results to the chloride numeric action level. If an exceedance or failure of a BMP is observed, the Responsible Discharger shall evaluate the BMPs implemented and identify a strategy in the site’s SWPPP to prevent potential exceedances of the numeric action level in the future. The Regional Water Board may assign additional monitoring, reporting, and BMP requirements upon obtaining site-specific information about exceedances of the numeric action level.

The Upper Santa Clara River Chloride TMDL assigns the waste load allocation to Responsible Dischargers upon the effective date of the TMDL. Because the TMDL did not specify a final compliance deadline for construction stormwater dischargers, the numeric action level is applicable upon the effective date of this General Permit. c. Diazinon TMDLs
One TMDL for diazinon applies to construction stormwater dischargers.

Diazinon is an organophosphate pesticide that does not sorb to sediment but is instead mobilized through soils by dissolving in water. Discharges of stormwater containing diazinon, can cause exceedances of water quality objectives for toxicity in aquatic life in inland surface and estuarine waters.

Diazinon was once used in both agricultural and urban settings but has since been banned for non-agricultural uses by the California Department of Pesticide Regulation.

ORDER WQ 2022-0057-DWQ
NPDES No. CAS000002
FACT SHEET FS-136
i. Chollas Creek Diazinon TMDL155
The San Diego Regional Water Quality Control Board adopted the Chollas Creek Diazinon TMDL on August 14, 2002, to address the impairment of the Chollas Creek Watershed due to diazinon.
· Source Analysis
The Chollas Creek Diazinon TMDL identifies urban stormwater flows as a significant source of diazinon and lists the Construction General Permit as a means of regulating discharges of diazinon.156 Therefore, construction stormwater dischargers covered by this General Permit are considered Responsible Dischargers. However, the TMDL did not include a separate waste load allocation assigned to construction stormwater discharges.
· Compliance Actions and Schedule
Compliance with this General Permit is consistent with the requirements and assumptions of this TMDL’s waste load allocation(s). No additional requirements are incorporated into this General Permit to implement the Chollas Creek Diazinon TMDL. The Regional Water Board may assign additional monitoring, reporting, and BMP requirements upon obtaining site-specific information about any exceedances of the waste load allocations.
d. Nutrients TMDLs
Seven Nutrient TMDLs apply to construction stormwater discharges and incorporate waste load allocations for one or more of the following pollutants:
nitrogen compounds (e.g., ammonia, nitrate, nitrite) and phosphorous (e.g., orthophosphates). Excessive nutrient loading to water bodies and watersheds can cause eutrophic effects that negatively impact beneficial uses related to recreation, wildlife, and drinking water supply.
155 San Diego Regional Water Quality Control Board, Chollas Creek Diazinon Total Maximum Daily Load (August 14, 2002)
<https://www.waterboards.ca.gov/sandiego/water_issues/programs/tmdls/chollascreek diazinon.html> [as of May 20, 2021]. (Chollas Creek Diazinon TMDL) 156 Chollas Creek Diazinon TMDL, p. 2 and 7.

ORDER WQ 2022-0057-DWQ
NPDES No. CAS000002
FACT SHEET FS-137
i. Pajaro River Basin Nutrients TMDL157
The Central Coast Regional Water Quality Control Board adopted the Pajaro River Basin Nutrients TMDL on July 30, 2015, to address the discharges of nitrogen compounds and orthophosphate within the Pajaro River Basin. These exceedances of nutrient and nutrient-related water quality objectives can have negative impacts on beneficial uses such as municipal and domestic drinking water supply (MUN, GWR) and a range of aquatic habitats uses (WILD, COLD, WARM, MIGR, SPWN, BIOL, RARE).158
· Source Analysis
Industrial and construction NPDES-permitted stormwater discharges were determined to be potential sources of ammonia, nitrate, and orthophosphate loading to receiving waters in the Pajaro River Basin. · Waste Load Allocation Translation
This Pajaro River Basin Nutrients TMDL assigns waste load allocations as concentration-based, single sample limits to construction stormwater dischargers for ammonia, nitrate, total nitrogen, and orthophosphate, to be met in the receiving waters. Therefore, dischargers covered under this General Permit are considered Responsible Dischargers for this TMDL, if they identify sources of these pollutants on their site through the required pollutant source assessment. The waste load allocation for un-ionized ammonia is applied to all streams within the Pajaro River Basin, while waste load allocations for nitrate, total nitrogen, and orthophosphate are specific to individual water bodies in the basin. The waste load allocations are translated from single sample limits to numeric action levels, as shown in Tables 15 through 24 below.

Table 15 – All Streams in Pajaro River Basin – Un-Ionized Ammonia Waste Load Allocation Translation
Pollutant Waste Load Allocation
Single Sample Limit (mg/L)
Numeric Action Level
(mg/L)
Un-ionized Ammonia 0.025 0.025
157 Central Coast Regional Water Quality Control Board, Total Maximum Daily Loads for Nitrogen Compounds and Orthophosphate in Streams of the Pajaro River Basin (July 30, 2015),
<https://www.waterboards.ca.gov/centralcoast/water_issues/programs/tmdl/docs/pajar o/nutrients/basin_plan_amend.pdf> [as of April 29, 2022] (Pajaro River Basin Nutrients TMDL)
158 Pajaro River Basin Nutrients TMDL, p. 1.

ORDER WQ 2022-0057-DWQ
NPDES No. CAS000002
FACT SHEET FS-138
Table 16 – All Streams in Pajaro River Basin (with MUN Beneficial Uses) Waste Load Allocation Translation
Pollutant Waste Load Allocation
Single Sample Limit (mg/L)
Numeric Action Level
(mg/L)
Nitrate-N 10 10
Table 17 – Pajaro River (All Reaches) and Pajaro River Estuary Waste Load Allocation Translation
Pollutant Waste Load Allocation
Single Sample Limit (mg/L)
Numeric Action Level
(mg/L)
Dry-Weather Nitrate-N 3.9 3.9
Dry-Weather
Orthophosphate-P

0.14 0.14
Wet-Weather Nitrate-N 8.0 8.0
Wet-Weather
Orthophosphate-P

0.3 0.3
Table 18 – Corralitos Creek and Salsipuedes Creek (All Reaches) Waste Load Allocation Translation
Pollutant Waste Load Allocation
Single Sample Limit (mg/L)
Numeric Action Level
(mg/L)
Dry-Weather Nitrate-N 1.8 1.8
Dry-Weather
Orthophosphate-P

0.14 0.14
Wet-Weather Nitrate-N 8.0 8.0
Wet-Weather
Orthophosphate-P

0.3 0.3
Table 19 – Beach Road Ditch and McGowan Ditch Waste Load Allocation Translation
Pollutant Waste Load Allocation
Single Sample Limit (mg/L)
Numeric Action Level
(mg/L)
Dry-Weather Nitrate-N 3.3 3.3
Dry-Weather
Orthophosphate-P

0.14 0.14
Wet-Weather Nitrate-N 8.0 8.0
Wet-Weather
Orthophosphate-P

0.3 0.3

ORDER WQ 2022-0057-DWQ
NPDES No. CAS000002
FACT SHEET FS-139
Table 20 – Llagas Creek (Downstream of Cheseboro Reservoir), Carnadero Creek, Uvas Creek, and Furlong Creek (All Reaches) Waste Load Allocation Translation
Pollutant Waste Load Allocation
Single Sample Limit (mg/L)
Numeric Action Level
(mg/L)
Dry-Weather Nitrate-N 1.8 1.8
Dry-Weather
Orthophosphate-P

0.05 0.05
Wet-Weather Nitrate-N 8.0 8.0
Wet-Weather
Orthophosphate-P

0.3 0.3
Table 21 – San Juan Creek and West Branch of San Juan Creek (All Reaches) Waste Load Allocation Translation
Pollutant Waste Load Allocation
Single Sample Limit (mg/L)
Numeric Action Level
(mg/L)
Dry-Weather Nitrate-N 3.3 3.3
Dry-Weather
Orthophosphate-P

0.12 0.12
Wet-Weather Nitrate-N 8.0 8.0
Wet-Weather
Orthophosphate-P

0.3 0.3
Table 22 – Tequisquita Slough Waste Load Allocation Translation Pollutant Waste Load Allocation
Single Sample Limit (mg/L)
Numeric Action Level
(mg/L)
Dry-Weather Nitrate-N 2.2 2.2
Dry-Weather
Orthophosphate-P

0.12 0.12
Wet-Weather Nitrate-N 8.0 8.0
Wet-Weather
Orthophosphate-P

0.3 0.3
Table 23 – Watsonville Slough, Harkins Slough, Gallighan Slough, and Struve Slough (All Reaches) Waste Load Allocation Translations Pollutant Waste Load Allocation
Single Sample Limit (mg/L)
Numeric Action Level
(mg/L)
Dry-Weather Total
Nitrogen-N

2.1 2.1
Dry-Weather
Orthophosphate-P

0.14 0.14
Wet-Weather Total
Nitrogen-N

8.0 8.0
Wet-Weather
Orthophosphate-P

0.3 0.3