and volume to contain all liquid and concrete waste generated by washout operations. The length and width of a facility may be increased, at the Contractor’s expense, upon approval from the RE.
■ Straw bales, wood stakes, and sandbag materials shall conform to the provisions in SC-9, “Temporary Straw Bale Barrier.”
■ Plastic lining material shall be a minimum of 10-mil polyethylene sheeting and shall be free of holes, tears, or other defects that compromise the impermeability of the material. Liner seams shall be installed in accordance with manufacturers’ recommendations. ■ Portable delineators shall conform to the provisions in Standard Specifications Section 12 3.04 – “Portable Delineators.” The delineator bases shall be cemented to the pavement in the same manner as provided for cementing pavement markers to pavement. Portable delineators shall be applied only to a clean, dry surface.
Temporary Concrete Washout Facility Type “Below Grade”
■ Temporary concrete washout facility type “Below Grade” shall be constructed as shown on page 6, with a recommended minimum length and width of 10 feet. The quantity and volume shall be sufficient to contain all liquid and concrete waste generated by washout operations. The length and width of a facility may be increased, at the Contractor’s expense, upon approval of the RE.
Lath and flagging shall be commercial type.
■ Plastic lining material shall be a minimum of 10-mil polyethylene sheeting and shall be free of holes, tears, or other defects that compromise the impermeability of the material. Liner seams shall be installed in accordance with manufacturers’ recommendations. ■ The soil base shall be prepared free of rocks or other debris that may cause tears or holes in the plastic lining material.
■ Temporary washout facilities shall implement BMPs to prevent run-on and runoff from the facility.
Concrete Waste Management WM-8
Caltrans Stormwater Quality Handbooks Section 8
Construction Site BMP Manual Concrete Waste Management WM-8 March 2024 4 of 5
Removal of Temporary Concrete Washout Facilities
■ When temporary concrete washout facilities are no longer required for the work, as determined by the RE, the hardened concrete shall be removed and disposed. Disposal of PCC dried residues, slurries, or liquid waste shall be disposed outside the highway right-of-way in conformance with provisions of Standard Specifications Section 14-10. Materials used to construct temporary concrete washout facilities shall become the property of the Contractor, shall be removed from the work site, and be disposed outside the highway right-of-way. ■ Holes, depressions, or other ground disturbance caused by the removal of the temporary concrete washout facilities shall be backfilled and repaired in conformance with the provisions in Standard Specifications Section 5 –“Control of Work.”
Maintenance and Inspection
■ Inspect concrete waste management areas before, during, and after rainfall events, and at least weekly during other times.
■ The WPC manager shall monitor concrete working tasks, such as saw cutting, coring, grinding and grooving daily to ensure proper methods are employed or as directed by the RE. ■ Temporary concrete washout facilities shall be maintained to provide adequate holding capacity with a minimum freeboard of 4 inches for above-grade facilities and 12 inches for below-grade facilities.
■ Maintaining temporary concrete washout facilities shall include removing and disposing hardened concrete and returning the facilities to a functional condition. ■ Hardened concrete materials shall be removed and disposed in conformance with the provisions in Standard Specifications Section 13-4 and 14-10. ■ Existing facilities must be cleaned, or new facilities must be constructed and ready for use, once the washout is 75% full.
■ Temporary concrete washout facilities shall be inspected for damage (e.g., tears in polyethylene liner, missing sandbags, etc.).
■ Inspection and maintenance of these areas must be properly documented and ensure no potential for discharges from these areas occur as part of the non-visible monitoring requirements.
SWPPP or WPCP
Concrete waste management must be discussed in Section 600.2.2 of the SWPPP or Section
30.3.2 of the WPCP.
Concrete Waste Management WM-8
Caltrans Stormwater Quality Handbooks Section 8
Construction Site BMP Manual Concrete Waste Management WM-8 March 2024 5 of 5
WM-9
Caltrans Stormwater Quality Handbooks Section 8
Construction Site BMP Manual Sanitary and Septic Waste Management WM-9 March 2024 1 of 2
Sanitary and Septic Waste Management
Standard Symbol
Definition and Purpose
Procedures and practices to minimize or eliminate the discharge of construction site sanitary and septic waste materials to the storm drain system or to receiving waters.
Appropriate Application
Sanitary/septic waste management practices are implemented on all construction sites that use temporary or portable sanitary and septic waste systems.
Limitations
None identified.
Standards and Specifications
Education
■ Educate employees, subcontractors, and suppliers on sanitary and septic waste storage and disposal procedures.
■ Educate employees, subcontractors, and suppliers of potential dangers to humans and the environment from sanitary/septic wastes.
■ Instruct employees, subcontractors, and suppliers in identification of sanitary/septic waste. ■ Hold regular meetings to discuss and reinforce disposal procedures (incorporate into regular safety meetings and tailgates).
■ Establish a continuing education program to indoctrinate new employees.
Sanitary and Septic Waste Management WM-9
Caltrans Stormwater Quality Handbooks Section 8
Construction Site BMP Manual Sanitary and Septic Waste Management WM-9 March 2024 2 of 2
Storage and Disposal Procedures
■ Temporary sanitary facilities shall be located away from drainage facilities, receiving waters, and traffic circulation.
■ When subjected to high winds or risk for overtopping, temporary systems must be properly secured.
■ Wastewater shall not be discharged or buried within the highway right of way. ■ Sanitary facilities require secondary containment to prevent discharges of pollutants to the stormwater drainage system or receiving water.
■ Sanitary and septic systems that discharge directly into sanitary sewer systems, where permissible, shall comply with the local health agency, city, county, and sewer district requirements.
■ If using an on-site disposal system, such as a septic system, comply with local health agency requirements.
■ Properly connect temporary sanitary facilities that discharge to the sanitary sewer system to avoid illicit discharges.
■ Ensure that sanitary and septic facilities are maintained in good working order by a licensed service.
■ Use only reputable, licensed sanitary/septic waste haulers.
Maintenance and Inspection
■ Inspect on-site sanitary and septic waste storage and disposal procedures at least weekly, prior to a forecasted rain event, daily during extended rain events, and post storm events. ■ Locations for portable sanitary systems must be shown on the WPCDs and reflect current site conditions.
SWPPP or WPCP
Sanitary and Septic Waste Management must be discussed in Section 600.2.2 of the SWPPP or Section 30.3.2 of the WPCP.
WM-10
Caltrans Stormwater Quality Handbooks Section 8
Construction Site BMP Manual Liquid Waste Management WM-10 March 2024 1 of 4
Liquid Waste Management
Standard Symbol
Definition and Purpose
Procedures and practices to prevent discharge of pollutants to the storm drain system or to receiving waters as a result of the creation, collection, and disposal of non-hazardous liquid wastes.
Appropriate Applications
Liquid waste management is applicable to construction projects that generate any of the following non-hazardous by-products, residuals, or wastes:
■ Drilling slurries and drilling fluids
■ Grease-free and oil-free wastewater and rinse water
■ Dredgings
■ Other non-storm water liquid discharges not permitted by separate permits Limitations
■ Disposal of some liquid wastes may be subject to specific laws and regulations, or to requirements of other permits secured for the construction project (e.g., NPDES permits, Army Corps permits, Coastal Commission permits, etc.).
■ Does not apply to dewatering operations (see NS-2, “Dewatering”), solid waste management (see WM-5, “Solid Waste Management”), hazardous wastes (see WM-6, “Hazardous Waste Management”), or concrete slurry residue (see WM-8, “Concrete Waste Management”).
Liquid Waste Management WM-10
Caltrans Stormwater Quality Handbooks Section 8
Construction Site BMP Manual Liquid Waste Management WM-10 March 2024 2 of 4
■ Does not apply to non-stormwater discharges permitted by any NPDES permit held by the pertinent Caltrans District unless the discharge is determined by Caltrans to be a source of pollutants. Typical permitted non-stormwater discharges can include water-line flushing, landscape irrigation, diverted stream flows, rising ground waters, uncontaminated pumped ground water, discharges from potable water sources, foundation drains, irrigation water, springs, water from crawl space pumps, footing drains, lawn watering, flows from riparian habitats and wetlands, and discharges or flows from emergency firefighting activities. See SWMP for a complete list of permitted non-stormwater discharges.
Standards and Specification
General Practices
■ Must comply with Standard Specifications Section 13-4.03B – “Spill Prevention and Control.” ■ Instruct employees and subcontractors on how to safely differentiate between non-hazardous liquid waste and potential or known hazardous liquid waste. ■ Instruct employees, subcontractors, and suppliers that it is unacceptable for any liquid waste to enter any storm drainage structure, waterway, or receiving water. ■ Educate employees and subcontractors on liquid-waste-generating activities, and liquid waste storage and disposal procedures.
■ Hold regular meetings to discuss and reinforce disposal procedures (incorporate into regular safety meetings and tailgates).
■ Verify which non-stormwater discharges are permitted by the Caltrans NPDES permit; different regions might have different requirements not outlined in this permit. Some listed discharges may be prohibited if Caltrans determines the discharge to be a source of pollutants. ■ Apply the NS-8, “Vehicle and Equipment Cleaning” BMP for managing wash water and rinse water from vehicle and equipment cleaning operations.
Containing Liquid Wastes
■ Drilling residue and drilling fluids shall not be allowed to enter storm drains and receiving waters and shall be disposed outside the highway right of way in conformance with the provisions in the Standard Specifications.
■ If an appropriate location is available, as determined by the Resident Engineer, drilling residue and drilling fluids that are exempt under California Code of Regulations (CCR) Title 23 §2511(g) may be dried by infiltration and evaporation in a containment facility constructed in conformance with the provisions concerning the temporary concrete washout facilities detailed in WM-08, “Concrete Waste Management.”
■ Liquid wastes generated as part of an operational procedure, such as water-laden dredged material and drilling mud, shall be contained and not allowed to flow into drainage channels or receiving waters prior to treatment.
■ Contain liquid wastes in a controlled area, such as a holding pit, sediment basin, roll-off bin, or portable tank.
■ Containment devices must be structurally sound and leak free.
Liquid Waste Management WM-10
Caltrans Stormwater Quality Handbooks Section 8
Construction Site BMP Manual Liquid Waste Management WM-10 March 2024 3 of 4
■ Containment devices must be of sufficient quantity or volume to completely contain the liquid wastes generated.
■ Take precautions to avoid spills or accidental releases of contained liquid wastes. Apply the education measures and spill response procedures outlined in WM-4, “Spill Prevention and Control.”
■ Do not locate containment areas or devices where accidental release of the contained liquid can threaten health or safety, or discharge to water bodies, channels, or storm drains.
Capturing Liquid Wastes
■ Capture all liquid wastes running off a surface, which has the potential to affect the storm drainage system, such as wash water and rinse water from cleaning walls or pavement. ■ Do not allow liquid wastes to flow or discharge uncontrolled. Use temporary dikes or berms to intercept flows and direct them to a containment area or device for capture. ■ If the liquid waste is sediment laden, use a sediment trap (see SC-3, “Sediment Trap/Curb Cutback”) for capturing and treating the liquid waste stream, or capture in a containment device and allow sediment to settle.
Disposing of Liquid Wastes
■ Typical method is to dewater the contained liquid waste using procedures such as described in NS-2, “Dewatering Operations” and SC-2, “Sediment/Desilting Basin.” Dispose resulting solids per WM-5, “Solid Waste Management.”
■ Method of disposal for some liquid wastes may be prescribed in water quality reports, NPDES permits, Environmental Impact Reports, 401 Water Quality Certifications or 404 permits, local agency discharge permits, etc., and may be defined elsewhere in the special provisions. ■ Liquid wastes, such as from dredged material, may require testing and certification, whether it is hazardous or not, before a disposal method can be determined. ■ For disposal of hazardous waste, see WM-6, “Hazardous Waste Management.” ■ If necessary, further treat liquid wastes prior to disposal. Treatment may include, though is not limited to, sedimentation, filtration, and chemical neutralization.
Maintenance and Inspection
■ Spot-check employees and subcontractors at least monthly throughout the job to ensure appropriate practices are being employed. At a minimum, liquid waste containment areas must be inspected before, during, and after rain events. Findings must be properly documented, and any deficiencies timely corrected.
■ Remove deposited solids in containment areas and capturing devices as needed, and at the completion of the task. Dispose any solids as described in WM-5, “Solid Waste Management.” ■ Inspect containment areas and capturing devices frequently for damage and repair as needed. ■ Improper storage, containment, or disposal might trigger sampling requirements per section 1000 of the SWPPP.
■ Locations for liquid waste management must be shown on the WPCDs and reflect current site conditions.
Liquid Waste Management WM-10
Caltrans Stormwater Quality Handbooks Section 8
Construction Site BMP Manual Liquid Waste Management WM-10 March 2024 4 of 4
SWPPP or WPCP
Liquid Waste Management must be discussed in Section 600.2.2 of the SWPPP or Section 30.3.2 of the WPCP.
9-1
Section 9
TMDL Implementation
Requirements
9.1 Introduction
A TMDL, or total maximum daily load, is a regulatory term used by the SWRCB to establish water quality management regulations. TMDLs serve as regulatory instruments that establish the upper allowable limit of a pollutant that a water body within a watershed can receive while still maintaining compliance with water quality standards. The 2022 CGP introduces new provisions related to TMDL monitoring and reporting. These TMDL implementation criteria are applicable to projects that meet two conditions:
1) they discharge into a water body or watershed for which the EPA has established a TMDL, and
2) they possess on-site sources of the specific TMDL pollutant, as determined through a pollutant source assessment.
Construction projects within a TMDL watershed can be subject to the following requirements (depending on watershed, applicability can be one or all of the following):
1) non-visible pollutant sampling
2) RUSLE2 modeling
3) Representative flow rate of discharge (Peñasquitos Lagoon TMDL) 4) QSP Training (Bacteria TMDL)
5) TMDL-related NAL/NELs
6) Soil screening (post-2032)
9.2 Waste Load Allocations
Some TMDL watersheds have assigned waste load allocations (WLAs) as listed in Attachment H of the CGP. The following Water Board regions have WLAs for the listed TMDLs:
• Region 1 (North Coast Regional Water Quality Control Board) – Sediment TMDLs • Region 4 (Los Angeles Regional Water Quality Control Board) – Metals and Toxics TMDLs • Region 8 (Santa Ana Regional Water Quality Control Board) – Metals and Toxics TMDLs, Nutrients TMDLs
Under Attachment H of the CGP, RUSLE2 modeling is required to demonstrate compliance with these TMDL WLAs. This is because the primary transport mechanism for most Caltrans TMDLs is the mobilization and discharge of sediment.
The need for sampling TMDL pollutants arises when there is a risk of pollutant discharge due to:
• The failure to implement BMPs or
• a spill or leak from a container, or a.
• a BMP breach, malfunction, or failure.
Construction Site Best Management Practices (BMP) Manual Section 9 9-2
The SWPPP Template Section 300 includes the specifics for the pollutant source assessment; Section 1000 deals with sampling for non-visible (including TMDLs).
9.2.1 Additional TMDL Requirements
In addition to meeting the general requirements of the CGP, a Responsible Discharger that is assigned a mass-based WLA of zero shall install erosion and sediment controls that will result in predicted erosion rates that are as protective as pre-construction conditions (e.g., undisturbed vegetation for the area). The calculated RUSLE2 soil loss and sediment delivery rates for the selected BMPs and controls shall be equal to, or less than, the soil loss and sediment delivery rates for pre-construction conditions during each phase of the construction project.
Section 1900 of the SWPPP Template addresses RUSLE2 modeling with respect to TMDLs. 10-1
Section 10
Post-construction Treatment BMPs
10.1 Regulatory Environment
The Caltrans Permit under section 402 of the CWA, and Section 401 Water Quality Certifications and 404 (through the Army Corps of Engineers) requires implementation of permanent stormwater treatment best management practices (TBMP) for projects within Caltrans right-of-way to capture pollutants from roadway runoff.
Caltrans projects during the initial Project Initiation Documentation (PID) phase undergo an assessment to determine TBMP applicability. The assessment is refined during the Plans, Specification and Estimate phase; treatment BMP plans, specifications and estimates for TBMPs are then incorporated into the project. This process is described in the Project Planning and Design Guide (PPDG).
10.2 List of Approved TBMPs
TBMPs are permanent measures to improve stormwater quality after construction is completed, though there are instances when construction might use the footprint area or the TBMP as well. The TBMPs listed in Table 10-1 are Caltrans-approved. TBMPs are selected and developed to best meet water quality objectives using a prioritization process described in the PPDG.
Table 10-1. Approved TBMPs
TBMP Name
Biofiltration Systems
Design Pollution Prevention Infiltration Areas
Infiltration Devices
Detention Devices
Traction Sand Traps
Dry Weather Flow Diversion
Full-capture Trash Devices
Media Filters
Multi-chamber Treatment Train
Wet Basins
Bioretention
Open Graded Friction Course
Porous Pavement (Non-Highway Facilities Only)
Construction Site Best Management Practices (BMP) Manual Section 10 10-2
10.3 Construction Implementation Checklist
TBMPs must be implemented in accordance with the contract plans in order to fulfill permit obligations. The following checklist should be used by construction staff as general guidelines for TBMP inspections:
Layout (before starting excavation)
• Square footage of the facility meets or exceeds minimum shown in approved plans. • Site grading and grade breaks are consistent with the boundaries of the contributing drainage areas shown in the approved plans.
• Facility inlet elevation is low enough to receive drainage from the entire contributing drainage area.
• Locations and elevations of overland flow or piping from impervious areas to the facility have been laid out and any conflicts resolved.;
• Facility rim elevation is laid out to be level all the way around, or elevations are consistent with a detailed cross-section.;
• Locations for vaults, utility boxes, and light standards have been identified so they will not conflict with the facility.; and
• Facility is protected as needed from construction-phase (sediment-laden) runoff.
Excavation (prior to backfilling or pipe installation)
• No work in heavy precipitation.
• Excavation conducted with materials and techniques to minimize soil compaction within the TBMP footprint if TBMP is not hardscape-based.
• Slopes or side walls protect against sloughing of native soils into the facility. • Vertical moisture barrier, if specified, has been added to protect adjacent pavement or structures. • Native soils at bottom of excavation are protected from compaction attributable to construction equipment and are ripped or loosened to promote infiltration, if specified. • No groundwater seepage or standing water encountered.
Overflow or Surface Connection to Storm Drainage (prior to backfilling with any materials) • Overflow is at specified elevation.
• No knockouts or side inlets are in overflow riser.
• Overflow location selected to minimize surface flow velocity (near, but offset from, inlet recommended).
• When specified, overflow is connected to storm drain via appropriately sized piping.
Materials
• Source is listed on tags as specified.
• Dimensions match specification
• Delivery amounts and dates are recorded.
• Sieve analysis from quarry and general appearance of subbase, base, bedding, jointing aggregates, aggregate topsoil, and soil components conforms to specifications. • Geotextile and geomembrane matches specification (if applicable).
Drain Rock/Underdrain
• Aggregate/rock is installed as specified.
Construction Site Best Management Practices (BMP) Manual Section 10 10-3
• Aggregate/rock is smoothed to a level top elevation; depth and top elevation are as shown in plans.
• Slopes or side walls protect against sloughing of native soils into the facility. • No filter fabric is installed between the subdrain and soil mix layers, unless specified. • Size, perforations, locations, slope, and outfalls meet specifications and drawings.
Backfilling with Biofiltration Soil, Aggregate Topsoil or other Specialized Treatment Media • Imported aggregate, aggregate topsoil, biofiltration soil, or other media matches specification. • Soil is placed in lifts not exceeding 12 inches and is spread evenly.; • Media is not compacted during installation but may be thoroughly wetted to encourage consolidation.
• Mix is smoothed to a level top elevation. Depth of mix and top elevation are as shown in plans, accounting for depth of mulch to follow and required reservoir depth. • Biofiltration soil or other non-structural media is not placed within the Clear Recovery Zone unless shown in the plans.
Planting
• Plants are installed consistent with approved planting plan. • Any trees and large shrubs are staked securely.
• No fertilizer is added unless specified.
• No native soil or clayey material is imported into the facility with plantings. • 1-inch to 2-inch mulch may be applied following planting to avoid floating. • Final elevation of soil mix is maintained following planting. • Curb openings are free of obstructions.
Final Inspection
• Contributing Drainage Area(s) are free of construction sediment, and landscaped areas are stabilized.
• Inlets are installed to ensure entry of runoff from adjoining pavement, have sufficient reveal (drop from the adjoining pavement to the top of the mulch or soil mix), and are not blocked. • Rock or other energy dissipation at piped or surface inlets is adequate. • Temporary flow diversions are removed.
• Overflow outlets are configured to allow the facility to flood and fill to near rim before overflow. • Plantings are healthy and becoming established.
• Irrigation is operable (if applicable).
• Facility drains. No surface ponding is evident.
• Accumulated construction debris, trash, and/or sediment is removed from the facility. • Permanent signage is installed and is visible to site users and maintenance personnel (typically referred to as TBMP Paddles).
Caltrans Division of Environmental Analysis has created TBMP certification forms. These certification forms are required at various phases of project development, such as Ready To List, Construction Contract Acceptance, and Project Closeout. This is in addition to the Division of Maintenance transfer of TBMPs where the MTCE-0023 form is completed and certified by Construction and Maintenance.
Construction Site Best Management Practices (BMP) Manual Section 10 10-4
10.4 TBMP Maintenance Indicators
Maintenance indicators are provided below for each type of TBMP. While these indicators are typically applied to established TBMPs after construction is complete and maintenance has begun, their presence prior to construction completion may indicate a problem that needs to be remedied before the TBMP is transfer to the Division of Maintenance. The Contractor can use TBMP areas during the construction phase so long as the areas are either restored or not allowed to erode, accumulate sediment, or modify the proposed soil type, drainage, or infiltration capacity.
Biofiltration Systems
• No evidence of significant channeling, erosion, seeps, or ponding • The Average vegetation height does not exceed 12 inches, no emergence of trees, or woody vegetation
• There is more than 70 percent background coverage of vegetation in swale invert and swale side slope
• No debris/trash is present
• Sediment is not at or near vegetation height, there is no channeling of flow within swale and energy dissipaters, no inhibited flow due to change in slope • No evidence of burrows, holes, or mounds
• Water has not accumulated in spreader ditch and/or collector ditch for more than 72 hours • No evidence of inlet structures, outlet structures, side slopes, or other features being hindered by debris or being damaged; no evidence of, significant erosion, fence damage, graffiti, vandalism, etc.
Design Pollution Prevention Infiltration Areas
• Drain time does not exceed 96 hours after end of rain event • No debris/trash is present
• No evidence of erosion
• No evidence of burrows, holes, or mounds
• Sediment depth does not exceed marker on staff gage; no sediment interferes with gravity drainage
• No evidence of inlet structures, outlet structures, side slopes, or other features being hindered by debris or being damaged; no evidence of, significant erosion, fence damage, graffiti, vandalism, etc.
Infiltration Devices
• No standing surface water for more than 72 hours
• No standing water for more than 96 hours
• No debris/trash is present
• No visible sediment
• No evidence of inlet structures, outlet structures, filter fabric, or other features hindered by debris or being damaged
• No emerging trees or woody vegetation, graffiti or vandalism, fence damage, etc.
Construction Site Best Management Practices (BMP) Manual Section 10 10-5
Detention Devices
• No emerging trees or woody vegetation
• No debris/trash is present
• No evidence of erosion
• No standing water for more than 96 hours
• Sediment depth does not exceed marker on staff gage (average 18 inches) • No evidence of burrows, holes, or mounds
• No evidence of inlet structures, outlet structures, side slopes, or other features being hindered by debris or being damaged; no significant erosion, graffiti or vandalism, fence damage, etc. • Average plant height is greater than 12 inches
Traction Sand Traps
• Sediment volume does not exceed design capacity
• Inlet/outlet structural integrity is not compromised; no evidence of damaged structures, graffiti or vandalism, etc.
• No standing water in structure 72 hours after any storm.
Full Capture Trash Devices
• No evidence of inlet structures, outlet structures, or other features being hindered by debris or being damaged. Check for graffiti or vandalism.
• No presence of gross solids (trash and debris)
• No standing water in structure 72 hours after any storm • No standing water for more than 96 hours (vector monitoring and abatement may be done through agreement with the local vector control authority) • Screens are in working order and are not clogged, damaged, or loose, and open/ close properly.
Media Filters
• Drain time does not exceed 72 hours (in the filter chamber for Delaware Sand Filter) • No standing water for more than 96 hours
• Sediment depth does not exceed marker on staff gage in sedimentation basin; no sediment interferes with gravity drainage in standpipe and/or orifice plate (for Austin Sand Filter) • No debris/trash present
• No evidence of burrows, holes, mounds
• No water accumulation in any structure or other location within the filter • No evidence of inlet structures, outlet structures, filter fabric, or other features being hindered by debris or being damaged; no signs of emerging vegetation, graffiti or vandalism, fence damage, etc.
• No valve leakage (for Delaware Sand Filter)
Bioretention
• Drain time does not exceed 96 hours after end of rain event • No debris/trash present
• No signs of erosion
• No evidence of burrows, holes, or mounds
Construction Site Best Management Practices (BMP) Manual Section 10 10-6
• Sediment depth does not exceed marker; sediment does not interfere with gravity drainage in standpipe and/or orifice plate,
• No evidence of inlet structures, outlet structures, filter fabric, or other features being hindered by debris or damaged; no emerging vegetation, graffiti or vandalism, fence damage, etc. • No underdrain sediment accumulation and/or broken caps or corrosion of pumps (if present).
Open Graded Friction Coarse
• Check for cracking, raveling, delamination, clogging, and other failure of the overlay.
Porous Pavement
• Paving surface is draining properly after storm,
• No evidence of surface deterioration, including cracking, raveling, delamination, and other failures.
Construction Site Best Management Practices (BMP) Manual A
Appendix A:
Definition of Terms
A-1
Appendix A
Definition of Terms
Active Areas. An area where soil-disturbing activities have occurred at least once within 14 days.
Areas of Construction. All areas subject to land surface disturbance activities related to the project, including, but not limited to, project staging areas, immediate access areas, and storage areas.
Active Treatment System (ATS). A treatment system that employs chemical coagulation, chemical flocculation, or electrocoagulation to help reduce turbidity caused by fine suspended sediment.
Air Deposition. Airborne particulates from construction activities.
Best Available Technology Economically Achievable (BAT). As defined by USEPA, BAT is a technology-based standard established by the CWA as the most appropriate means available on a national basis for controlling the direct discharge of toxic and non-conventional pollutants to navigable waters. The BAT effluent limitations guidelines, in general, represent the best existing performance of treatment technologies that are economically achievable within an industrial point source category or subcategory.
Best Conventional Pollutant Control Technology (BCT). As defined by USEPA, BCT is a technologybased standard for the discharge from existing industrial point sources of conventional pollutants, including biochemical oxygen demand, total suspended sediment, fecal coliform, pH, oil and grease.
Best Management Practice (BMP). BMPs are scheduling of activities, prohibitions of practices, maintenance procedures, and other management practices to prevent or reduce the discharge of pollutants. BMPs also include treatment requirements, operating procedures, and practices to control site runoff, spillage or leaks, sludge or waste disposal, or drainage from raw material storage.
Caltrans Permit. The Caltrans Statewide National Pollution Discharge Elimination System (NPDES) Permit for discharges from Caltrans properties, facilities, and activities (Order No. 2022-0033-DWQ, NPDES No. CAS000003), issued by the SWRCB.
Construction Activity. Includes clearing, grading, or excavation and Contractor activities that result in soil disturbance.
Construction Site. The area involved in a construction project as a whole.
Construction Site BMPs. Temporary control practices (BMPs) that are required only temporarily to address a short-term stormwater contamination threat as a result of construction activities. For example, silt fences are located near the base of newly graded slopes that have a substantial area of exposed soil. During rainfall, the silt fences capture sediment from slope erosion.
Contractor. Party responsible for carrying out the contract per plans and specifications. The Standard Specifications and contract special provisions contain stormwater protection requirements the Contractor must address.
Contractor-Support Facilities. Contractor-support facilities include staging areas, storage yards for equipment and materials, mobile operations, batch plants for Portland cement concrete and hot mix asphalt, crushing plants for rock and aggregate, and other facilities installed for Contractor convenience such as haul roads.
Debris. Litter, rubble, discarded refuse, and remains of destroyed inorganic anthropogenic waste.
Construction Site Best Management Practices (BMP) Manual A-2
Direct Discharge. Surface runoff that directly enters the surface water body without first flowing through a municipal separate storm sewer system (MS4).
Discharge. Any release, spill, leak, pump, flow, escape, dumping, or disposal of any liquid, semi-solid, or solid substance.
Disturbed Soil Area (DSA). Area of exposed, erodible soil, including stockpiles, that are within the construction limits and that result from construction activities.
Drainage Area. The area of land that drains water, sediment, pollutants, and dissolved materials to a common outlet.
Effluent. Any discharge of water by a discharger either to the receiving water or beyond the property boundary controlled by the discharger.
Environmental Protection Agency (EPA). Agency that issues the regulations to control pollutants in stormwater runoff discharges (e.g., CWA and NPDES permit requirements).
Erosion. The process by which soil particles are detached and transported by the actions of wind, water, or gravity.
Erosion Control BMPs. Vegetation, such as grasses and wildflowers, and other materials, such as straw, fiber, stabilizing emulsion, protective blankets, etc., placed to stabilize areas of disturbed soils, reduce loss of soil due to the action of water or wind, and prevent water pollution.
Exempt Construction Activities. Activities exempt from the CGP, including routine maintenance to maintain original line and grade, hydraulic capacity, or original purpose of the facility, and emergency construction activities required to protect public health and safety. Local permits may not exempt these activities.
Existing vegetation. Any vegetated area that has not already been cleared and grubbed.
Expenditure Authorization. A Caltrans expenditure authorization (EA) is a unique identifier assigned to transportation projects that are financed with federal and/or state funds.
Final Stabilization. Indicates all soil-disturbing activities at each individual parcel within the site have been completed in a manner consistent with the requirements in this General Permit.
Forecasted Storm Event. A storm that produces or is forecasted to produce at least 0.10 inches of precipitation within a 24-hour period.
General Permit. The Construction General Permit for Stormwater Discharges Associated with Construction Activity (Order No. 2022-0057-DWQ, NPDES Permit CAS000002) issued by the SWRCB.
Good Housekeeping. A common practice related to the storage, use, or cleanup of materials performed in a manner that minimizes the discharge of pollutants.
Good Housekeeping BMPs. BMPs designed to reduce or eliminate the addition of pollutants to construction site runoff through analysis of pollutant sources, implementation of proper handling/disposal practices, employee education, and other actions. The grading (part of the Grading and Land Development Phase) includes reconfiguring the topography and slope, including alluvium removals; canyon cleanouts; rock undercuts; keyway excavations; landform grading; and stockpiling of select material for capping operations.
Illegal Connection. Discarding or disposal within the Caltrans right-of-way, properties, or facilities, either intentionally or unintentionally, of trash or other wastes in non-designated areas that may contribute to stormwater pollution.
Illegal Dumping. An engineered conveyance that is connected to an MS4 without authorization by local, state, or federal statutes, ordinances, codes, or regulations.
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Illicit Discharge. Any discharge to an MS4 that is prohibited under local, state, or federal statutes, ordinances, codes, or regulations. It includes all non-stormwater discharges except conditionally exempt non-stormwater discharges.
Inactive Construction Area. Any active construction area at which construction activities are expected to be discontinued for 14 days or longer.
Indirect Discharge. Surface runoff that enters the surface water body through an MS4 stormwater conveyance system or unlisted tributary before reaching the surface water.
Middle-Mile Broadband Network. Middle-Mile Broadband Network (MMBN) is a collection of anticipated linear underground/overhead projects initiated by Governor’s Executive Order N-73-20. It is regulated under Section III.B.4 of the CGP. MMBN is a statewide program, and all projects will share one common waste discharge identification number. See MMBN Guidance.
National Pollutant Discharge Elimination System (NPDES) Permit. A permit issued pursuant to the CWA that requires control of pollutant discharges from stormwater to Waters of the United States.
Non-Stormwater Discharges. Discharges that do not originate from forecasted storm events. They can include, but are not limited to, discharges of process water, air conditioner condensate, noncontact cooling water, vehicle wash water, sanitary wastes, concrete washout water, paint wash water, irrigation water, or pipe testing water.
Non-visible Pollutants. Pollutants associated with a specific site or activity that can have a negative impact on water quality but cannot be seen though observation (e.g., chlorine). Such pollutants being discharged are not authorized.
Notice of Non-applicability. Construction projects that exceed 1 acre of DSA and are not hydrologically connected to Waters of the United States. NONA projects must be certified in SMARTS and a Technical Report must be submitted, see PPDG Section 1.4.4. pH. Unit universally used to express the intensity of the acid or alkaline condition of a water sample.
The pH of natural waters tends to range between 6 and 9, with neutral being 7. Extremes of pH can have deleterious effects on aquatic systems.
Pollution. The man-made or man-induced alteration of the chemical, physical, biological, and radiological integrity of water. An alteration of water quality by waste to a degree that unreasonably affects either the waters for beneficial uses or facilities that serve these beneficial uses.
Post-Construction BMPs. Structural and non-structural controls that detain, retain, or filter the release of pollutants to receiving waters after final stabilization is attained.
Qualified SWPPP Developer (QSD). Individual who is authorized to develop and revise SWPPPs.
Qualified SWPPP Practitioner (QSP). Individual assigned responsibility for non-stormwater and stormwater visual observations, sampling and analysis, and responsibility to ensure full compliance with the permit and implementation of all elements of the SWPPP, including the preparation of the annual compliance evaluation and the elimination of all unauthorized discharges.
Receiving Waters. All surface water bodies within the permit area.
Regional Water Quality Control Board (RWQCB). California agencies that implement and enforce CWA Section 402(p) NPDES permit requirements, and are issuers and administrators of these permits as delegated by EPA. There are nine regional boards working with the SWRCB.
Resident Engineer (RE). The Caltrans representative charged with construction contracts administration, acceptability of material furnished and work performed. The RE has “contractual authority” to direct the Contractor and impose sanctions if the Contractor fails to take prompt and appropriate action to correct deficiencies. The following contractual sanctions can be imposed by the RE: (a) withholding payments (or portions of payments), (b) suspending work, (c) bringing in a Construction Site Best Management Practices (BMP) Manual A-4
separate Contractor to complete work items (the Contractor is billed for such costs), (d) assessing liquidated damages, including passing along fines for permit violations, (e) initiating construction contract cancellation.
Routine Maintenance. Activities intended to maintain the original line and grade, hydraulic capacity, or original purpose of a facility.
Runoff Control BMPs. Measures used to divert run-on from off site and runoff within the site.
Runoff Effect. The effect that a particular soil stabilization product has on the production of stormwater runoff. Runoff from an area protected by a particular product may be compared to the amount of runoff measured for bare soil.
Run-on. Discharges that originate off site and flow onto the property of a separate project site.
Sediment. Solid particulate matter, both mineral and organic, that is in suspension, is being transported, or has been moved from its site of origin by air, water, gravity, or ice and has come to rest on the earth's surface either above or below sea level.
Sedimentation. Process of depositing suspended matter carried by water, wastewater, or other liquids, by gravity. It is usually accomplished by reducing the velocity of the liquid below the point at which it can transport the suspended material.
Sediment Control BMPs. Practices that trap soil particles after they have been eroded by rain, flowing water, or wind. They include practices that intercept and slow or detain the flow of stormwater to allow sediment to settle and be trapped (e.g., silt fence, sediment basin, fiber rolls, etc.).
Sheet Flow. Flow of water that occurs overland in areas where there are no defined channels, which allows the water to spread out over a large area at a uniform depth.
Soil Amendment. Any material that is added to the soil to change its chemical properties, engineering properties, or erosion resistance that could become mobilized by stormwater.
State Water Resources Control Board (SWRCB). California agency that implements and enforces CWA Section 402(p) NPDES permit requirements, is issuer and administrator of these permits as delegated by EPA. Works with the nine Regional Water Quality Control Boards.
Storm Drain System. Streets, gutters, inlets, conduits, natural or artificial drains, channels and watercourses, or other facilities that are owned, operated, maintained, and used for collecting, storing, transporting, or disposing of stormwater.
Stormwater. Rainfall runoff, snow melt runoff, and surface runoff and drainage. It excludes infiltration and runoff from agricultural land.
Stormwater Pollution Prevention Plan (SWPPP). A plan required by the CGP or the LTCGP that includes site map(s), an identification of construction/contractor activities that could cause pollutants in the stormwater, and a description of measures or practices to control these pollutants.
It must be prepared and authorized before construction begins. A SWPPP prepared in accordance with the special provisions and the Handbooks will satisfy Standard Specifications Section 13 – “Water Pollution Control.”
Temporary Construction Site BMPs. Construction Site BMPs that are required only temporarily to address a short-term stormwater contamination threat. For example, silt fences are located near the base of newly graded slopes that have a substantial area of exposed soil. Then, during rainfall, the silt fences filter and collect sediment from runoff flowing off the slope.
Water Pollution Control Manager (WPC Manager). The person responsible for the implementation of the SWPPPP or WPCP, whichever is applicable for the project. The WPC Manager must be a QSP Construction Site Best Management Practices (BMP) Manual A-5
whenever the project requires a WPCP. The WPC Manager must be a QSD whenever the project requires a SWPPP.
Water Pollution Control Program (WPCP). A plan that identifies water quality management practices to be implemented on all construction projects that do not require preparation of a SWPPP. For Caltrans projects disturbing more than 1 acre, a SWPPP satisfies the requirement for a WPCP.
Waters of the United States. Generally, refers to surface waters, as defined by the federal environmental water quality objectives in the California Water Code as limits or levels of water quality constituents or characteristics established for the reasonable protection of beneficial uses of water or the prevention of nuisance within a specific area.
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Appendix B:
Selection of Temporary Soil Stabilization Controls
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Appendix B
Selection of Temporary Soil
Stabilization Controls
Temporary Soil Stabilization BMPs (SS BMPs) are designed to eliminate or reduce the erosion of disturbed soil areas and to reduce the transport of sediment and pollutants by stormwater during construction. SS BMPs are used to bind soil particles together, or coat the disturbed soil surface area, thereby protecting the disturbed soil area from the erosive forces of water and wind.
Section 3 of this Manual provides guidance on the selection, limitations, installation, and maintenance for approved SS BMPs. This appendix provides additional details for Field Staff and Contractors on relevant factors to consider for selecting appropriate products for project specific construction sites/areas.
Caltrans has approved six types of SS BMPs (Standard Specifications Section 13-5) listed below.
These BMPs are to be applied to disturbed soil areas to eliminate or reduce erosion and the potential transport and discharge of sediment and other pollutants from Caltrans right-of-way. The SS BMPs listed as sub bullets are acceptable alternatives because they have the same general function. For example, when a project requires the use of Mulch (SS-3) both Temporary Hydraulic Mulch or Temporary Bonded Fiber Matrix Hydraulic Mulch can be used to meet the requirement. • Mulch (SS-3)
− Temporary Hydraulic Mulch
− Temporary Bonded Fiber Matrix Hydraulic Mulch
• Temporary Hydroseed (SS-4)
• Soil Binders (SS-5)
− Temporary Cementitious Binder Hydraulic Mulch
− Temporary Soil Binder
• Temporary Tacked Straw (SS-6)
− Temporary Tacked Straw
• Temporary Rolled Erosion Control Products (SS-7)
− Temporary Erosion Control Blanket
− Erosion Control Blanket
− Temporary Covers
• Temporary Wood Mulch (SS-8)
− Temporary Mulch
Subsection B.1 includes general factors that should be considered when the SS BMPs listed above may be selected. Subsection B.2 includes a flowchart and tables that will guide the user through the site evaluation to optimize the selection of SS BMPs for the specific construction area. Subsection B.3 includes some general description of sediment control BMPs, as they should be used in conjunction with SS BMPs to optimize BMP coverage and comply with Permit requirements.
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B.1 – General factors to consider for maximizing usage of Temporary Soil Stabilization BMPs
Understanding the characteristics of a construction site/area, including how it will impact stormwater and how stormwater will impact it, is important for SS BMP planning and selection. The following characteristics must be considered before selecting a SS BMP(s). • Preparing soil to optimize SS BMP effectiveness
− The proper application of SS BMPs can be improved by ensuring that the area(s) that will receive SS BMPs have adequate soil preparation, whether it is track walking the slope, imprinting, or using soil amendments, or to ensure long-term vegetation sustainability having seed testing done prior to seeding the area. These techniques, in conjunction with the selection of correct SS BMP, can prevent sediment-laden discharges, reduce the need for continuous maintenance, and increase establishment of permanent vegetative cover. • Proper Timing for application of SS BMPs
− Consider the timing of construction as it relates to the seasonal distribution of erosive rainfall and the climate regime that the construction site/area is located in. Large areas of California are located in a Mediterranean climate regime where summers are hot and dry and winters are cool and rainy. Simply timing the application of stabilization measures prior to the beginning of the rainy season in late fall makes a significant difference in erosion and sediment delivery rates. Construction during a period of high erosive potential requires a much shorter bare soil period and will influence the choice of sediment controls. Those sediment controls that provide instant protection will be preferred over those requiring germination and establishment of vegetation.
• Determining the Specific Soil Erosivity Potential
− A proper evaluation of the soil erosive potential and sediment delivery rates for the project specific construction site/area during the planned construction period is crucial to preventing both multiple applications of SS BMPs and sediment-laden discharges. Caltrans has a variety of tools available, from their refined RUSLE, which conform to Caltrans construction sites and is more user friendly, to the Caltrans Landscape Architecture Toolbox which can be accessed via
http://www.dot.ca.gov/hq/LandArch/16_la_design/guidance/roadside_safety_tb/index.htm The RUSLE assessment and the Landscape Toolbox can be used to evaluate soil conditions, erosivity potential, and proposed soil stabilization concepts for any construction sites/areas, even those that are less than an acre in size, and not subject to CGP or LTCGP.
B.2 Site Evaluation
The following flowchart and tables are an abridged and modified summary of the Guidance for Temporary Soil Stabilization (July 2003) and it is intended to be used to determine the most appropriate SS BMP to be deployed. All steps shown in Figure B-1 must be completed.
Step 1 – Start.
The Construction Field Staff or Contractor should use Figure B-1, the guidance provided in this section, and the tables that follow to determine the best option to stabilize the project specific construction site/area.
Continue to the next step.
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Figure B-1. Consideration of Temporary SS BMPs
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Step 2-Assess the flow conditions for the area that will receive the SS BMP. • Sheet Flow
• Channelized Flow
• Run-on Flow
• Run-off Flow
As velocities increase, the options for SS BMPs decrease. Areas that will receive direct run-on or runoff must be hydraulically evaluated to ensure there will be no additional sediment deposition. It is recommended to use a combination of SS BMPs and Temporary Sediment Control BMPs (SC BMPs) to control impacts due to run-on or run-off.
There are specific inspection requirements in the CGP or the LTCGP that must be complied with and documented by the QSP or QSD as noted in the flowchart.
Continue to the next step.
Step 3-Assess the Slope Inclination and Slope Length of area that will receive the SS BMP. • Less than 1:4 (V:H)
• Greater than 1:2 (V:H)
The slope length is measured or calculated along the continuous inclined surface. A discrete slope can be measured between the following criteria:
• From the top of the slope to the toe of the slope (if there are no benches1) • From the top of the slope to the bench directly below within the slope. • From a bench within the slope to the bench directly below within the slope. • The lowest bench within the slope to the toe of the slope.
Continue to the next step.
Step 4-Assess the soil properties and erodibility for the area that will receive the SS BMP.
Soil properties relate to available soil moisture, available soil nutrients for plant growth, and depth and presence of rock fragments that hinder temporary and permanent seeding establishment. When choosing temporary measures on various soils, the larger concern is the erosion potential (erodibility) of the soil.
Soil erosion rates can be predicted by RUSLE2 on construction sites/areas. RUSLE2 uses USDA Soil Survey data which contains the soil erodibility or K factor for all mineral soils. RUSLE2 requires a K factor to run so in cases where the soil has been disturbed or when no soil K factors range from 0.01 to 0.64. The higher the k the higher the potential erosion rate.
Table B.2-1 provides the soil properties in relation to the Unified Soil Classification and USDA Texture.
1 A bench is a drainage feature or a Temporary Sediment Control BMP that intercepts surface flow and conveys the resulting concentrated flow away from the slope.
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Continue to the next step.
Step 5-What is the total surface area that will receive the SS BMP? Surface area is the amount of disturbed soil area on the construction site/area that will require protection from erosion with various SS BMPs. Surface area categories are grouped in the following way:
• Small: 1 acre or less
• Large: 1 acre or more
In order to maximize effectiveness, the field staff must ensure that the surface area to be stabilized is adequate for the stabilization crew to complete their application prior to onset of rain, and can be accessed as discussed in steps below
Continue to the next step.
Step 6-What is the Predominant Climate Atmospheric Condition on the day the soil stabilization will be installed?
Atmospheric conditions on the day of installation can limit the type of BMP that can be applied to the disturbed soil area because some SS BMPs are not effective in extreme weather conditions such as snow or heat. Other BMPs may require drying times and should not be applied to slopes while it is raining. Climate variations are caused primarily by distance from the coast and elevation. When selecting SS BMPs consider the temperature ranges, frequency and intensity of rainfall, wind, and humidity.
Continue to the next step.
Step 7- Any issues with Accessibility of Equipment?
The accessibility of equipment refers to whether a road or pad capable of supporting equipment for applying SS BMPs is within range of the disturbed soil area. If the construction site/area does not have vehicular access, only SS BMPs applied manually are applicable.
Continue to the next step.
Step 8-Where is the site discharging to, any 303(d) Listed Water Bodies? Within the Clean Water Act regulations, Section 303(d) listed water bodies that are impaired by various pollutants and are designated for developing Total Maximum Daily Loads (TMDLs). If a construction site drains into a Section 303(d) listed water body, understanding and meeting the required TMDL is essential for compliance.
It is essential to understand site run-off dynamics and control needs. The limitations of the SS BMPs, with respect to their potential water quality impacts, must be clearly understood. Proper selection and installation of SS BMPs can facilitate compliance by eliminating pollutants that discharge into Section 303(d) listed water bodies.
Continue to the next step.
Step 9- What is the duration of need?
The timeframe for which SS BMPs are needed will depend on the construction schedule and has a direct correlation to the longevity of the temporary SS BMP selected. Longevity ranges are typically:
• Less than 3 months
• Between 3 and 12 months
• Greater than 12 months
− Stop.
Construction site/area characteristics applicable to the SS BMPs are provided in Table B.2.2 while the timing and cost associated with the SS BMPs are provided in Table B.2.3.
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B.3 Additional BMPs Used with SS BMPs
SS BMPs are more effective when used in conjunction with Temporary Sediment Control BMPs (SC BMPs) and other SS BMPs. To properly stabilize slopes and remove sediment from stormwater, other conditions must be addressed such as, directing and/or slowing concentrated flow, reducing slope lengths, and capturing sediment entrained in stormwater. Therefore, it is required that SS BMPs and SC BMPs are used in conjunction to comply with the General Construction Permit rules regarding erosion and sediment control.
Slope inclination and slope length are the most important factors affecting the installation of combined stabilizations BMPs and SC BMPs, as these factors have the largest potential impact on erosion rates. A combined increase in slope inclination and slope length will require an increase in the use of SS BMPs and SC BMPs.
To limit the erosive effects of stormwater flow the slope lengths shall be broken up with SC BMPs such as fiber rolls or gravel bags as follows:
• If the slope inclination is 1:4 (V:H) or flatter, break up the slope length with sediment control BMPs at intervals no greater than 20 feet.
• If the slope length is between 1:4 (V:H) and 1:2 (V:H), break up the slope length with sediment control BMPs at intervals no greater than 15 feet.
• If the slope inclination is 1:2 (V:H) or greater, break up the slope length with sediment control BMPs at intervals no greater than 10 feet.
Listed below are the SC BMPs applied to compliment the SS BMPs that cover or bind the soil of the disturbed soil areas (Standard Specifications 13-6 and 13-10). The information below also includes a brief explanation of their purpose and applications. Refer Section 4 of this Manual for details regarding the Limitations, Standards and Specifications, and design of SC BMPs. SC BMPs are implemented on a project-by-project basis and with other SS BMPs. • Temporary Earthen Berm
• Temporary Silt Fences
• Temporary Reinforced Silt Fences
• Temporary Large Sediment Barrier
• Temporary Check Dams
• Temporary Fiber Rolls
• Temporary Gravel Bag Berms
• Compost Socks
• Flexible Sediment Barriers
• Temporary Straw Bale Barrier
• Temporary Drainage Inlet Protection
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Appendix C:
Active Treatment Systems
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Appendix C
Active Treatment Systems
C.1 INTRODUCTION
Temporary Active Treatment Systems (ATS) apply conventional water treatment technologies, in use for over a century, to stormwater quality. Neither the CGP nor the LTCGP requires the use of an ATS, but for waters and sites where the reliability of the stormwater quality is of concern, these systems may be used. The information provided here is guidance only and the contractor must ensure the ATS Treatment Plan and its implementation complies with Attachment F of the CGP.
C.1.1 Overview
An ATS may be considered for a project under the following conditions:
• When necessary to meet water quality standards (WQS) of the receiving water. • When necessary to meet the effluent limits of the CGP or LTCGP for turbidity and pH in stormwater.
Under the CGP and the LTCGP, an ATS is recommended for use at high risk work sites, including:
• Where space limits installation of properly-sized containment and detention facilities, such as a sediment trap (see SC-3 “Sediment Trap”) or sediment/desilting basin (see SC-2 “Sediment/Desilting Basin”).
• Where clay and/or highly erosive soils are present.
• Where the site has very steep slopes
• Where project work necessitates on-going and large amounts of disturbed soil area during the rainy season
• Where the project site is highly susceptible to stormwater run-on resulting in erosion and sediment-laden run-off.
An ATS uses a coagulant for the treatment of water with a sedimentation basin (or basins) for facilitating turbidity reduction. In addition, pH adjustment plus bag/cartridge/sand filters may be included. The exact configuration and sizing of the ATS will depend on the anticipated quantity and quality of the water to be treated, the amount of time needed for treatment, and receiving water requirements.
Coagulation can be used to destabilize suspended particles and remove them from suspension, which forms a byproduct referred to as floc or flocculant. There are many different coagulants for use; a coagulant may use different chemical properties and may be suited for different types of water conditions to be treated. Potential chemical residual (i.e., coagulant residual) in the treated effluent must be monitored and managed to attain applicable effluent limits prior to discharge.
An ATS is recommended to remove particles below 0.02 mm and may be warranted for locations that must meet strict turbidity requirements. Some receiving waters may be listed for other parameters of concern for which an ATS might be recommended; however, not all pollutants can be treated with readily available ATS technology.
An ATS does not eliminate the need to implement appropriate soil stabilization and sediment control BMPs.
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C.1.2 CGP and LTCGP
An ATS, as covered by the CGP or the LTCGP, is used for the treatment of stormwater discharges generated from precipitation that falls on or runs through the construction area during a rain event.
Other water generated from construction operations is considered non-stormwater.
In some cases, ATS designers may wish to include non-stormwater treatment as an aspect of, or supplement to, the ATS system. When doing so, any non-stormwater comingled with stormwater may both alter the performance values of the selected coagulant and place different or additional demands upon the other selected ATS components. These modifications of the system will need to be evaluated and if necessary, coverage under a supplemental NPDES Permit in addition to the CGP or LTCGP, may be required.
C.1.3 General Requirements
The following general requirements are applicable to projects that utilize an ATS:
1. Standard Specification Section 13-8 includes provisions for treating and discharging uncontaminated groundwater and accumulated stormwater from excavations or other areas with a temporary ATS.
2. Submit an ATS Plan to the RE within 20 days of contract approval. The ATS Plan must comply with Standard Specification Section 13-8.01C(2). At least 14 days prior to the planned operation of the ATS, the ATS Plan is required to be submitted electronically to the SWRCB and applicable RWQCB.
Each element of the ATS Plan including but not limited to O&M Manual, Monitoring, Sampling & Reporting Plan including QA/QC, Health & Safety Plan, and Spill Prevention Plan must be assessed and evaluated to ensure compliance and functionality with the CGP or LTCGP operational requirements.
3. The design, installation, operation, and monitoring of the temporary ATS and monitoring of the treated effluent must comply with Attachment F of NPDES General Permit for Stormwater Discharges Associated with Construction and Land Disturbance Activities (Order No. 2022-0057- DWQ, NPDES No. CAS000002).
4. For a project within the Lake Tahoe Hydrologic Unit, the design, installation, operation, and monitoring of the temporary ATS and monitoring of the treated effluent must comply with Attachment E of the NPDES General Permit for General Waste Discharge Requirements and National Pollutant Discharge Elimination System Permit for Storm Water Discharges Associated with Construction Activity in the Lake Tahoe Hydrologic Unit, counties of Alpine, El Dorado, and Placer, (Order No. R6T-2016-0010, and NPDES No. CAG616002).
5. For a project within the Lake Tahoe Hydrologic Unit, the discharger must perform toxicity testing that complies with Standard Specification Section 13-8.01D(2) if operating a temporary ATS in batch-treatment mode.
6. Training must be provided to each operator of the ATS. The lead person must have the qualifications listed in A.3 of Attachment F.
7. The ATS must be designed for the site conditions and anticipated flow rate and must include (1) a treatment system, (2) a collection and conveyance system, and (3) a discharge method and location.
8. The ATS must be capable of capturing and treating within a 72-hour period a volume equal to the runoff from a 10-year, 24-hour rain event using a watershed coefficient of 1.0.
9. The control system must default to recirculation or shutoff during a power failure or catastrophic event.
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10. The control system must control the amount of the coagulant to prevent overdosing. The coagulant must be mixed rapidly into the water to insure proper dispersion.
11. Pumps and piping must comply with Standard Specification Section 74-2.
12. Discharges may be made into a sanitary sewer system however; the effluent discharge must comply with the publicly-owned treatment works (POTW) requirements and must meet all criteria as set forth in any issued Batch Discharge Permit. The POTW Batch Discharge Permit should be secured as part of the ATS planning process to ensure access and feasibility of discharging expected water quantities. This option is frequently utilized for short term or low volume discharges. The Department does not pay for obtaining the municipal batch discharge permit or for discharging the water.
13. Submit documentation for the delivery and removal of ATS components.
14. If observations and measurements confirm that a residual chemical or water quality standard is exceeded, submit the notice of discharge within 24 hours after exceeding the limits per the requirements of the CGP or the LTCGP.
15. Water discharged from a temporary ATS must comply with the Numeric Effluent Limits (NEL) for discharge effluents and the receiving waters.
16. If an NEL is exceeded, notify the RE and submit a Numeric Effluent Limitation Violation Report- ATS Discharge (DOT CEM-2063SW1) within 6 hours. For a project in the Lake Tahoe Hydrologic Unit, the Numeric Effluent Limitation Violation Report- Lake Tahoe Hydrologic Unit – Lake Tahoe Hydrologic Unit (CEM-2063T2) must be submitted within 2 hours. The analytical results less than the method detection limits must be reported as less than the method detection limits. In compliance with the CGP or LTCGP, electronic filing of the exceedance report to the SWRCB and RWQCB shall occur within 24 hours of either obtaining the results or identifying the exceedance.
17. Calibrate the flow meter and devices for taking water quality measurements under the manufacturer's instructions as outlined in the ATS Plan.
18. Monitoring equipment must be interfaced with the control system of the ATS to provide shutoff or recirculation whenever effluent readings do not comply with the turbidity and pH limits.
19. Monitoring equipment for the ATS must record data at least once every 15 minutes and cumulative flow data daily. The recording system must have the capacity to record a minimum of 7 days of continuous data.
C.2 ATS SELECTION CRITERIA
In general, ATS selection is driven by the available area, and the soil type of the site. Each of these will drive the selection of an ATS that would reliably meet the requirements of the CGP or the LTCGP.
C.2.1 Risk Level
Generally, projects designated as Risk Level 1 under the CGP should implement typical Construction Site BMPs. Project designated as Risk Level 2 or 3 under the CGP should use the following factors to determine whether traditional BMPs are sufficient or an ATS is appropriate for use. The following factors should also be used for projects subject to the LTCGP.
C.2.2 Potential Storage Area and Peak Stormwater Flow
Project sites with enough potential storage area to detain the estimated quantity of stormwater from a rain event and allow sediment to settle out of suspension by gravity may be able to avoid using an ATS. 1 This form can be found at: http://www.dot.ca.gov/hq/construc/forms/DOT CEM-2063SW.pdf 2 This form can be found at: http://forms.dot.ca.gov/v2Forms/servlet/FormRenderer?frmid=CEM2063T Construction Site BMP Manual
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These areas can be used for storage of water with enough detention (dwell) time to settle significant quantities of particles prior to discharge. The minimum detention time can be determined by dividing the available storage by the peak flow expected from a 5 year-24-hour storm. If the minimum detention time of a sedimentation basin can meet the minimum compliance requirements for sedimentation, an ATS is generally not required for turbidity removal. Other considerations that may influence minimum detention time and should be evaluated include, but are not limited to:
• The time required to treat stormwater from successive rain events. • The quantity of stormwater that may run-on into the project. • Conditions caused by on-going construction activities.
The above listed conditions are examples that may trigger the need for an ATS.
Determine the area available for potential stormwater storage (Ap). This can include assigned stormwater treatment locations, existing storage areas, or space outside of the construction footprint which is available for use. Often, these areas will necessitate an engineered design and construction specific to the location used, plus a management understanding of detention time commitment and the need to use this dedicated space exclusively for stormwater detention and treatment.
C.2.3 Soil Type
The minimum detention time required for a construction site will depend on the predominant soil type.
Fine soils, such as clay, will remain suspended for much longer times than coarser soils, such as sand.
To determine the initial minimum detention time required, the composition of the soil within the construction site must be determined. Anticipating and estimating for changing soil conditions from construction activities that affect and change the soil dynamics (e.g., mixing of soil types, compaction, cut/fill areas) may complicate this calculation. Repetitive rain events will also affect the evaluation.
C.2.4 Settling Velocity and Required Settling Area
A calculation of the maximum area for potential treatment must be made. Initially calculate the peak stormwater flow from the site based upon disturbed soil area and the rainfall intensity from a 5 year – 24-hour rain event using the Rational Equation (though this peak flow does not need to be the design flow of a potential ATS). Next, determine the predominant soil type within the construction area.
Conservative estimates will use the minimum particle diameter of each soil type (sand, silt, or clay) in conjunction with Stokes Law to determine the settling velocity of the sediment.
Other methods or models may be substituted for Stokes Law if more information is readily available for project soils. Dividing the peak stormwater flow by the settling velocity will determine the minimum area required (Ar) for settling without active treatment. Note that these calculations should take into consideration the changing soil conditions and dynamics based on the phase and stage of the project, scope of soil work being performed, and other issues related to scheduled soil work.
C.2.5 Determine Appropriate Device
Comparing the minimum area required (Ar) to the potential area available (Ap) will determine whether an ATS may be necessary. If the area available is significantly larger (>20 percent) than the area required, evaluate BMPs based upon site characteristics. If the area required is significantly larger than the area available (>20 percent), then an ATS must be considered. If the design can be refined, such as increasing potential storage area or improving the accuracy of the settling velocity calculation, re-evaluate the site. If no other options are available, an ATS is recommended.
The CGP contains direction for implementation of ATS. Risk level 2 projects do not have NELs for pH and turbidity, unless an ATS is used. Therefore, careful evaluation is necessary before selection; check with the District/Regional Design Stormwater Coordinator.
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C.3 FACTORS AFFECTING PRELIMINARY DESIGN
C.3.1 Pollution Prevention/Sediment Mitigation
Actions to reduce the quantity of sediment in stormwater directed to storage should be implemented in the work area regardless of the decision to use an ATS. With an ATS these measures can lead to more efficient treatment and operational cost savings. Closing off or stabilizing unused portions of the site will reduce the quantity of stormwater that could be impacted by construction activities. Focused consideration should be given to evaluating and installing run-on control and bypass controls means to reduce and minimize the amount of stormwater that would require treatment. Minimizing sheet flow and concentrated flows from up-slope areas and/or drainages coming into the project is critical to reducing not only the quantity of water requiring treatment but also the causative effects of scouring or transport of sediment in run-on water.
To prevent significant sediment loading to an ATS all applicable Construction Site BMPs, especially those that provide erosion and sediment control at the source and within conveyances, should be implemented. If stormwater run-on cannot be prevented from entering the project, installation of lined drainage ditches, bypass piping, or other means, should be considered to direct flows away from disturbed soil areas and steep slopes. This can minimize treatment requirements for run-on. The use of plastic cover is often a significant and beneficial implementation control to prevent direct contact of stormwater with disturbed soil. With plastic cover, the clean run-off can be re-routed, preventing it from entering the ATS collection system. Sampling might be required for run-on to show the turbidity concentrations coming into the project.
To minimize stormwater treatment, evaluate and design for the temporary redirection and bypass of roadway runoff to prevent contact with project disturbed soil areas when feasible. If project plans call for the abandonment or removal of existing storm drain conveyances, outfalls, inlets, or lined drainages consider scheduling the work after the rainy season. Considering staging and phasing of project work, evaluate adjustments to the schedule to minimize the removal of existing constructed storm drain systems until the next dry season approaches.
C.3.2 Collection System/Discharge Piping
Collection piping is required to convey the water generated onsite to the treatment system (i.e., the ATS and its component systems). The size and quantity of piping will be determined by the layout and terrain of the disturbed construction area. It may be necessary to include pumps to move large quantities of water across the site. It is also possible for the site to implement multiple ATS systems. Discharge piping and pumps are required to convey treated effluent to the appropriate discharge location. Proper sizing is required to prevent flow backup or sedimentation within the pipe. Some considerations when designing for and installing collection systems include the following:
• Can the stormwater draining toward the ATS collection system be directed through a lined drainage ditch or conveyance piping by which scour will not create additional sediment? • Can the stormwater draining toward the ATS collection system be filtered by perimeter barriers such as filter lined drainage rock, silt fence, gravel bag check dams, etc., before entering the conveyance? • Can the conveyance sump (where the pumps are placed) be designed large enough to ensure enough area to handle the run-on water?
• Can the conveyance sumps be designed and situated to prevent direct intake of silt, sediment, or soils? Can filters, screens, or protective barriers be installed that surround the sumps and/or pumps to minimize the up-take of transported heavier fines, particulates or floating materials, vegetative detritus, etc.?
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• Can the conveyance pump be so situated by which it can be easily accessed or withdrawn for maintenance or replaced if needed?
• Can the pumps and conveyance piping and/or hose leading to the ATS system from the conveyance sump-pumps be designed to maximize speed of conveyance thereby preventing the sump-pump locations from flooding during peak runoff?
C.3.3 Storage/Pre-Sedimentation
If it is necessary to store large quantities of water onsite during significant rain events, locations such as swales, basins, and other areas conducive for storage may be used to retain water prior to treatment.
These locations provide an additional benefit of settling out some sediment before treatment with an ATS. Design of these storage locations should be in accordance with criteria for those BMPs.
Systems with a high sediment loading may necessitate pretreatment. Pretreatment typically consists of a pre-sedimentation basin such as a weir tank for the removal of easily settleable sediment loads.
Pretreatment can improve coagulant usage and effectiveness, as well as reduce the quantity of flocculant sludge, thus minimizing costs. Systems with pre-sedimentation and storage can be sized to smaller peak flows as large storms can be stored and treated over longer durations. The trade-off will depend on both the amount of storage and design capacity of the system. Additional considerations related to storage and pre-sedimentation may include:
• Can existing long term excavations, or existing curbed and/or walled in areas be used for temporary storage?
• Can a retention basin be constructed and excavated deep enough (or have above ground walls constructed) to minimize the footprint of the required area needed for holding the estimated maximum quantity of collected stormwater prior to conveyance to the ATS? Are there natural, pre-existing areas in the construction work area where stormwater can be collected for holding prior to conveyance? Can the holding areas be lined to minimize the up-take of resident loose sediment or soils?
C.3.4 Treatment Components
Different components may be used within the ATS. These components interact with each other and need to be considered individually and as an integrated treatment system. Recirculation piping will be necessary to meet turbidity and pH discharge requirements. Table C-1 and C-2 summarize many of the components available for integration into a temporary ATS and associated materials.
Figure C-1. Potential Treatment Schematic
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Table C-1. Potential ATS Components
Component Use
Coagulant Dosing Equipment Chemical for forming floc and removing turbidity pH Adjustment Dosing Equipment Chemical for adjusting pH within proper range Sedimentation Tank (or Basin) Gravity particulate removal and sludge removal/collection Bag/Cartridge/Media Filters Filters for particle removal C.3.4.1 Coagulation and Flocculation
Different coagulants are available for use within an ATS system. The choice of a coagulant is an important consideration to achieve turbidity removal requirements. The anticipated water quality of the site based on existing soil/sediment conditions and scheduled contractor work will define which coagulants may be effective at forming floc and improving water quality. Coagulant dosing rates and usage will vary depending on the water quality, flow volumes, and coagulant selection. If evaluation and assessment of the performance values and parameters of a coagulant in relationship to the known and expected project conditions is required to achieve treated effluent quality values.
Some coagulants that have been used on past projects include Chitosan, Ferric Chloride, and Alum. Use of other coagulants/polymers may be more difficult for the RWQCB to approve due to uncertainties about potential effects on water quality. Regardless of the coagulant choice, monitoring of residual chemical in the discharge would likely be required.
Equipment such as a chemical feed pump, a rapid mixer (static or mechanical), and sufficient sedimentation will be necessary to properly dose any coagulant. A streaming current detector should be used to monitor and adjust coagulant dose.
A Coagulant-Handling Work Plan is required as part of the ATS Plan and should be prepared for any coagulant used to ensure protection from potentially toxic effects on both human and wildlife due to exposure from high concentrations of residue coagulant. At a minimum, the Coagulant-Handling Plan should include coagulant storage, monitoring, and disposal during the lifespan of the ATS.
When operating the ATS in a Batch Treatment Mode, the CGP requires acute toxicity testing and has specific criteria for testing methodology, laboratory analysis, and quality assurance. All toxicity testing data performed during ATS operation is required to be electronically uploaded to the State Water Boards Storm Water Multi-application and Reporting Tracking System (SMARTS).
Table C-2. Potential ATS Chemicals
Class of Chemical Chemical Advantages Disadvantages
Approximate
Cost
pH Decrease Hydrochloric Acid (HCl) Low Dose Safety Concerns pH Decrease Sulfuric Acid (H2SO4) Low Dose Safety Concerns pH Decrease Carbon Dioxide (CO2) Inert, Self-Buffering Mechanically Intensive, Requires Diffuser/Basin
pH Increase Sodium Hydroxide (NaOH) Low Dose Safety Concerns Coagulant Alum Lower Cost Drops pH, Can Require High Dose Coagulant Ferric (Chloride/Sulfate) Lower Cost Drops pH, Can Require High Dose Coagulant Chitosan Low Dose May Not Work Well for Certain Soils $2,500 per Tote Construction Site BMP Manual
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C.3.4.2 pH Adjustment
For certain systems, pH adjustment may be necessary to maintain receiving water integrity. Certain site conditions may adversely affect pH and certain coagulant choices can alter pH and should be considered. There are multiple methods for pH adjustment depending on the water quality of the site and each method has inherent strengths and weaknesses dependent upon the condition under which it is used. Each option considered for use should be evaluated for its potential affect upon other aspects and components of the treatment system, both from a physical and chemical perspective. The nature of pH adjustment can not only be highly corrosive to the ATS equipment, but may also present a heightened risk to occupational health of the ATS operator or maintenance technician.
Carbon Dioxide (CO2) can be used to lower the pH. CO2 gas is bubbled through water forming carbonic acid (H2CO3) and thereby reducing pH. Carbon dioxide is mechanically more intensive, but the gas is much safer to store onsite. The CO2 system requires a bubble diffuser and a separate basin for proper implementation.
Strong acids and bases may also be used; dosing generally occurs alongside coagulant addition. Dosing rates will vary depending on water quality, receiving water quality, and acid/base selection. Strong acids/bases have safety concerns associated with storage and dosing. In addition, acid/base selection is important to prevent possible interactions with other treatment components. Strong acids (e.g., hydrochloric acid, sulfuric acid) and bases (e.g., sodium hydroxide) would provide rapid pH response for most waters; an advantage to all the acids and bases listed in the table below is that the corresponding counter-ions (e.g., sulfate, chloride, sodium) are not expected to react with constituents in the treatment system. In contrast, some acids (e.g., citric acid) introduce counter ions (citrate) that can have undesirable side-effects, such as promoting bacterial growth or inhibiting floc formation.
Table C-3. Suggested pH Adjustment Chemicals
Acids Bases
Carbon Dioxide (CO2) – Bubble Carbon Dioxide will form carbonic acid and drop pH Sodium Hydroxide (NaOH) Sulfuric Acid (H2SO4) – strong acid Sodium Hydroxide (NaOH) Hydrochloric Acid (HCl) Sodium Hydroxide (NaOH)
C.3.4.3 Sedimentation Tanks
Sedimentation tanks are required to settle floc formed from coagulation. Sedimentation tanks must provide sufficient area and retention time to allow adequate settling of solids. Sedimentation tanks as opposed to weir tanks are recommended for use with high sediment loads. Weir tanks may be used for systems that have minimal influent sediment loading. Higher sediment loads will quickly fill weir tanks and would require sludge removal at higher frequencies compared to sedimentation tanks. Calculating accurate coagulant dosing rates based on site conditions should allow more accurate estimates of sedimentation tank(s) loading of settled floc and therefore lead to selection of the right size tanks. It is important to provide sufficient area for the settling of solids because accumulated floc increases treatment times and therefore reduces the amount of water that can be treated during rain events. In some cases, it may be more desirable to over-estimate the required area.
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Figure C-2. Sedimentation Tank
C.3.4.4 Bag/Cartridge/Media Filter
Bag, cartridge, or media filters provide additional particle removal prior to discharge. Bag and cartridge filters pass water through mesh filters reducing particle sizes to a predetermined size. Media filters use sand or other granular media to remove particles. Bag and cartridge filters are removed, changed out and discarded. Media filters use treated water to backwash the filter and remove particles.
It may be necessary to reduce turbidity to approximately 25 NTU or below prior to filtration to prevent excessive buildup on the filter. For bag and cartridge filters, higher turbidity levels passed to the filters will cause increased frequency of change-out and likely increase operational costs. For sand filters, more frequent backwashing will be required which will cause greater work, more chemical usage, and more clean water for backwashing. When backwashing is required the on-going affect upon the treatment process must be calculated into the required treatment rate. When backwashing occurs, less influent is treated in that time.
Figure C-3. Bag/Cartridge Filters
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C.3.4.5 Power Sources
An uninterruptible power supply and standby electric generator is recommended for any ATS system.
Storms can routinely interrupt power supply systems; thus, it is necessary to provide a backup in such circumstances. An audible or observable alarm should be an aspect of the ATS design to notify personnel in the event of a power outage. Consequences from a non-operable ATS during a critical time may lead to project site flooding and potentially to a discharge with exceedances.
C.3.4.6 SCADA Monitoring Equipment
Supervisory Control and Data Acquisition (SCADA) systems are standard technology used to monitor and control all monitoring and mechanical systems within an ATS. These systems can record and store all relevant data to the project. Remote operation of an ATS is possible through SCADA systems, but connection stability must be maintained to ensure proper operation.
ATS effluent discharges should meet the requirements of the CGP or LTCGP. Monitoring equipment must be installed. These include, but are not limited to, turbidimeter, pH meters, and flow meters. These meters must be calibrated as recommended by the manufacturer or regulator. The frequency of calibration and a documented process to retrieve and verify data should be specified to the contractor and may be required by the RWQCB. In addition, some water quality analysis will need to be conducted by outside labs for analysis such as total suspended solids (TSS), settleable solids (SS), or residual chemicals. Validate and maintain the sensors in the in-line ATS system that communicate values to the SCADA system regularly. If these sensors are not functioning properly, the SCADA data may be of limited value. Note: the CGP requires that all field recorded monitoring data including but not limited to turbidity, pH, residual chemical, flow rate, and volume be electronically uploaded every 30 days minimum to the State Water Board.
C.4 ACTIVE TREATMENT SYSTEM SIZING
The size of the treatment system will be dependent on the acreage of the active disturbed soil area. The system is required to be sized such that the runoff from a 10-year 24-hour rain event would be captured and treated within 72 hours. Storms that are greater than the design event may cause the ATS to exceed the CGP restrictions. In these circumstances, the RWQCB will still expect the contractor to make efforts for meeting the CGP or other requirements.
C.4.1 Construction Area
The area of the basin will be defined by the contributing drainage area of the disturbed construction site.
The contributing drainage areas will be defined by the designer depending on the orientation of the construction site. For long or flat construction sites, it may be necessary to subdivide the site and set up separate ATS locations. The conveyance systems required to funnel stormwater to a central ATS location may be prohibitive for certain site orientations.
If multiple receiving waters are present in the site, each receiving water basin may require a separate ATS to maintain watershed integrity. For some receiving waters, BMPs may be sufficient to meet turbidity goals.
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C.4.1.1 Flowrate
Peak flowrate can be calculated for each area by the Rational Formula:
Q = C x I x A (Eqn. 1)
Q = Peak Runoff Rate, Cubic Feet per Second
C = Dimensionless Runoff Coefficient (use 1.0)
I = Rainfall intensity, Inches per Hour (10-year, 24-hour) A = Basin Area, Acres
The rainfall intensity will vary by project location.
Per the Standard Specification Section 13-8, the designer shall use a runoff coefficient value of 1.0.
Basin area is the total contributing drainage area to the BMP or ATS.
C.4.1.2 Sedimentation Residence Time
Hydraulic Retention Time should be between 2 and 4 hours to allow sufficient floc settlement to meet turbidity requirements.
HRT = V/Q (Eqn. 2)
HRT = Hydraulic Retention Time, Hours
V = Volume of Sedimentation Basin, Gallons
Q = Flowrate, Gallons per Hour
C.5 MAINTENANCE AND INSPECTION
The ATS requires regular maintenance to ensure it is properly functioning and to prevent leaks. Repair or replace any component of the dewatering equipment that is not functioning properly or as required by the operations and maintenance outlined in the ATS Plan. The detail in the ATS Plan should be of significant nature to clarify most aspects of ATS function and servicing. Each piece of equipment to be used in the ATS needs to be fully described including its purpose and its inter-relationship to the other equipment. Inclusion of manufacturer specification sheets in the ATS Plan is of high value and should be considered. Descriptions of how to assess the ATS components for performance values is instrumental in trouble-shooting deficient operation. A section within the ATS Plan on maintenance scenarios and trouble-shooting examples for commonly known conditions or operational failures is highly recommended. Trouble-shooting questions could include the following:
• Is increased time required because the holding tank is reduced in capacity due to accumulated floc? • Is increased time required because not enough coagulant is being dosed which could be caused by a degraded sensor?
The inclusion of set procedural steps for bringing on-line each piece of equipment of the ATS system and determinants of how to balance the system is invaluable when attempting to maximize operation or solve a functional problem. These aspects of an ATS Plan, if not considered in the planning stage and left out of the ATS Plan, could lead to failures of the system and on-going repeat deficiencies.
Remove sediment from the storage or treatment cells as necessary to ensure the cells maintain their required water storage and treatment capability. Sediments removed from the uncontaminated areas during maintenance of the treatment system may be dried, distributed uniformly, and stabilized at a location within the project limits where authorized. Generally accumulated floc from treatment, and any associated captured sediment in the system, is disposed of at a landfill permitted to receive such a waste stream.
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If observations and measurements determine that the water quality limits are exceeded, immediately stop the discharge, notify the ATS designer, and start corrective measures to change, repair, or replace the equipment and procedures used to treat the water. If a situation occurs in which the operational perimeters of the ATS are exceeded or the criteria for allowed discharges values are compromised, the information must be retained for recordkeeping and reporting purposes. All corrective actions taken including time periods of non-compliance, and/or time periods to institute corrective actions, should be recorded. Record the quantity of discharge that may have been non-compliant. All test reports and records may be included in the report to the RWQCB. If a piece of equipment failed, broke, or an operation process was not followed this information should be noted to allow assessment of reasons for failure and corrective measures to be implemented to prevent a reoccurrence.
After the designer inspects and authorizes your corrective measures, resume treatment and discharge activities under the startup-phase sampling requirements before resuming regular-phase sampling.
Ensure that all required recordkeeping and reporting is completed including submittal of Monthly Monitoring Reports and Exceedance Reports, if applicable.
While the ATS is in operation, at a minimum the following must be monitored:
• Influent and effluent turbidity and pH
• Residual chemical
• Effluent flow rate and volume
If treatment is on-going with dosing and injection of chemicals, the retention of recordkeeping data of the monitored pH and turbidity values is critical for the time periods and is required by the CGP.
Uploading and saving of the data regularly as an aspect of the SCADA system, with on-going back-up and downloading to retain the monitored information, is recommended. Use of a standard time-period to backup data, such as every 72 hours, is recommended. The ability to perform both assessment and determination of compliance with instantaneous maximum discharge limitations, in addition to daily 24-hour averaging for turbidity values, is only feasible if the monitoring data is captured and available for evaluation.
Field ATS operator visual monitoring of the system readouts is standard operating procedure with physical documentation on daily logs that validate the data read-outs. The retention of data for on-going pH monitoring and discharge is an aspect of the CGP compliance process of recordkeeping. Without this data, the ability to validate adherence to Permit criteria is limited and not easily defensible with the RWQCB.
If the ATS discharges treated effluent, prepare a daily inspection report including monitoring information and submit within 24 hours, or as required. The ATS Plan should describe the information to include in the reports. Prepare a template form to clarify the required report information in advance. Adjust the template accordingly to accommodate changing conditions, when required. The daily inspection report will at a minimum include:
• Discharge volumes
• Water quality monitoring records
• Quantities (generally in gallons) of dosed coagulants in addition to pH chemical adjustment additives • Significant repair or maintenance performed on the ATS including but not limited to clean-out of tanks or treatment vessels, maintenance or replacement of sensors or electronic monitoring equipment or components, replacement of pipes, pumps, injection devices, etc. It is important to document the process of ATS upkeep to demonstrate due diligence in maximizing the system’s operation effectiveness and efficiency. This will be important if the system has an accidental upset, failure, or improper discharge.
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• Discharge point information that includes:
− Date and time
− Weather conditions, including wind direction and velocity − A notation describing if a rain event has been continuous is recommended. If the on-site rain gauge is accessible for measurement, including this information can assist in illustrating the demand for the ATS. NOAA weather report data can validate that the rain event exceeds the design capacity of the ATS therefore clarifying maximization of discharge limitations. − Presence or absence of water fowl or aquatic wildlife − Color and clarity of the effluent discharge
− Erosion or ponding downstream of the discharge point
− This is applicable if not discharging to a storm drain inlet or piped outfall − Photographs labeled with the time, date, and location C.6 OTHER ATS CONSIDERATIONS
If an ATS will be utilized on a project site for multiple rainy seasons, there are critical elements to both maintaining the ATS and sustaining its operational lifetime including:
• Ensure the ATS designer is experienced in treatment processes and regulatory requirements, and that the assigned operator(s) of the system are required to have demonstrated experience, knowledge, and skills in ATS operation, maintenance, field testing, data recordkeeping, and reporting. • Selection during planning of equipment and materials that will withstand weather and environmental degradation. For example, choose piping that is UV resistant and sufficiently flexible to withstand some movement, and choose the proper tank such as double lined or walled to minimize breakthrough and leaking.
• Design the ATS layout to minimize movement and or relocation during the lifetime of the project to minimize potential for breakage, misalignment, or disruption of functional operations. This extends to the pre-planning and construction of appropriate collection and conveyance systems based on the staging and phasing of the project. If a substantially sized collection basin is required to hold the stormwater prior to treatment, then the location must be determined beforehand. Commit space for ATS usage during the lifetime of the system and include space to allow access for maintenance and repair.
• If a substantial number of collection sump/pumps will be required to convey the stormwater from multiple locations throughout the project, then the locations, conveyance piping, and drainage ditches must be depicted on plans and must account for scheduled construction work to prevent conflict of alignment. This consideration is to prevent damage to collection apparatus and to ensure stoppage of non-compliant stormwater discharges during critical periods of forecasted rain. • If a complex ATS is required, ensure that the ATS Plan is critically evaluated for all operational components including engineering, field work, and administrative controls. Securing all requisite water quality data relative to the anticipated treatment scope and planning will be instrumental to the ATS selection and successful operation. Resourcing available technical information from CASQA, or leading industry providers of such systems, will be helpful. • Dependent upon the project location, site receiving water bodies, discharge locations, and outfalls storm drain systems may not be allowed to receive the ATS treated effluent. Occasionally a point of discharge will be found to be infeasible due to a sensitive receiving water body, local ecological system, or tidally influenced drainage. In this case, a different discharge option must be explored to allow ATS treated effluent disposal.
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• Supplemental and extended piping and pumping layouts may be required to convey the effluent to an acceptable location or to facilitate a discharge to a POTW, when feasible. During the planning phase, the discharge limitations and the local conditions must be evaluated. Early confirmation that selected discharge options are acceptable is desirable.
C.7 TREATMENT CONSIDERATIONS FOR NON-STORMWATER AND GROUNDWATER Most often construction projects require the management and treatment of stormwater. At times, construction projects may be required to consider management and treatment of groundwater and other non-stormwater due to the complexity and scheduling of different types of work. General site factors to consider in determining the most appropriate management or treatment strategy for the project site include but are not limited to project duration, location, size, affected waterbodies or sources, differing drainages and discharge points (natural and manmade), and pertinent historical and environmental protection considerations. A determination of whether water treatment (of any type) should be done together or as a separate treatment process must be made. These issues must be assessed and understood to achieve a successful treatment plan.
Project excavation work or ground disturbing activities may necessitate managing and treating groundwater in addition to managing construction impacted stormwater runoff. Previous fuel leaks, VOC spills, past chemical discharges, or introduction of hazardous contaminants during the construction phase will likely need management and treatment consideration.
A dual use stormwater/non-stormwater treatment system, if feasible, may be designed to treat and discharge the different water sources. Alternatively, separate treatment systems may be designed. When determining which system is most appropriate, consider first the maximum quantity of stormwater verse the maximum quantity of non-stormwater (e.g., groundwater, co-mingled surface water) that must be managed or treated. Consider the complexity of the treatment science that must be applied to achieve permit discharge requirements and to meet receiving water criteria. Consider also available space on the project site. Is there enough room to accommodate the temporary holding and storage of separate water sources during the treatment process? Can the system be designed to work in tandem to treat both water sources at the same time based on different treatment requirements? Is there a demand for separate treatment trains?
Coverage under different NPDES Permits for specific water sources often dictate the approach and desired outcome of treatment including but not limited to sampling, analysis, monitoring, recordkeeping, and reporting. The differing water management and treatment needs may be combined however insightful planning is critical. For example, the treatment of brackish groundwater from structure dewatering verse extracted groundwater polluted by petroleum products is different when compared to each other and when compared to the CGP and/or LTCGP. While the treatment process will be different, the goal of treatment is the same, to achieve an acceptable discharge water quality.
On occasion a project specific NPDES Permit may be issued to address project conditions that require additional water treatment considerations. In most instances, when multiple water sources require management and treatment during project work, a comprehensive evaluation of treatment options will be required. The evaluation should focus on project needs to better understand if a single treatment system designed to operate in an alternative manner would work, or perhaps a dual treatment system designed to achieve separate water quality objectives may be most appropriate for the project. These example considerations are not exhaustive and professional expertise in the decision-making process of water treatment system choice and design is recommended.