14.13.030 Findings.
The city of San Dimas (hereinafter referred to as “city City”) finds the following that:
A. Waterbodies, roadways, structures, and other property within and downstream of the city City are at times subject to flooding.
B. Land development alters the hydrologic response of watersheds, resulting in increased stormwater runoff rates and volumes, increased flooding, increased stream channel erosion, increased sediment transport and deposition, and increased nonpoint source pollutant loading to the receiving waterbodies and the beaches.
C. Stormwater runoff produced by land development contributes to increased quantities of water-borne pollutants.
1. Increases of stormwater runoff, soil erosion, and non-point source pollution have occurred as a result of land development, and have impacted the water resources of the San Gabriel River Watershed.
2. Increased stormwater runoff rates and volumes and the sediments and pollutants associated with stormwater runoff from future development projects within the city City will, absent proper regulation and control, adversely affect the city City's waterbodies and water resources, and those of downstream municipalities.
3. Stormwater runoff, soil erosion, and non-point source pollution can be controlled and minimized by the regulation of stormwater runoff from development.
4. Adopting the standards, criteria, and procedures contained in this chapter and implementing the same will address many of the deleterious effects of stormwater runoff. (Ord. 1231 § 1, 2014)
14.13.040 Construction of language Definitions.
For purposes of this chapter, the following rules of construction apply any term used in this chapter shall be defined as the term in the Los Angeles Regional Phase I Municipal Storm Water Permit, Order No. R4-2021-0105 (Permit), and any amendments revisions or reissuance thereof. Terms not specifically defined in this chapter shall have the meaning customarily assigned to them. The following words and phrases shall have the following meanings when used in this chapter:
85th Percentile, 24-Hour Storm Event is a statistical design storm defined through a
hydrologic analysis of long-term rainfall records for a particular geographic area. At the most basic level, the design storm represents the 85th percentile, 24-hour rainfall depth (typically measured in inches of rain) among all 24-hour rainfall depths evaluated in the historical record. Analyses that define this storm event often express the 85th percentile, 24-hour storm event as an “isohyetal” or “isopluvial” map with contour lines connecting areas with the same 85th percentile 24-hour rainfall depth. In some situations (e.g., in storm hydrographs), the temporal distribution of rainfall during the 85th percentile, 24-hour storm event may be assumed.
Act or Clean Water Act (CWA) means the Federal Water Pollution Control Act, also known as the Clean Water Act as amended 33 U.S.C. 1251, et seq.
Applicant means any person proposing or implementing the development of land.
Areas of Special Biological Significance (ASBS) as defined in the Water Quality Control Plan for Ocean Waters of California (California Ocean Plan), ASBS are all those areas designated by the State Water Board as ocean areas requiring protection of species or biological communities to the extent that maintenance of natural water quality is assured. All Areas of Special Biological Significance are also classifies as a subset of State Water Quality Protections Areas. ASBS are also referred to as State Water Quality Protection Areas – Areas of Special Biological Significance (SWQPAASBS).
Automotive Service Facility means a facility that is categorized in any one of the following Standard Industrial Classification (SIC) and North American Industry Classification System (NACIS) codes (5013, 5014, 5511, 5541, 7532 -7534and 7536- 7539).
Best Management Practice (BMP) means practices or physical devices or systems designed to prevent or reduce pollutant loading from stormwater or non-stormwater discharges to receiving waters.
Biofiltration means a LID BMP that reduces stormwater pollutant discharges by intercepting rainfall on vegetative canopy, and through incidental infiltration and/or evapotranspiration, and filtration. Incidental infiltration is an important factor in achieving the required pollutant load reduction. Therefore, the term “biofiltration” as used in achieving the required pollutant load reduction. Therefore, the term “biofiltration” as used is defined to include only systems designed to facilitate incidental or achieve the equivalent pollutant reduction as biofiltration BMPs with an underdrain. Biofiltration BMPs include bioretention systems with an underdrain and bioswales.
Bioretention means a LIP BMP that reduces stormwater runoff by intercepting rainfall on vegetative canopy, and through evapotranspiration and infiltration. The bioretention system typically includes a minimum 2-foot top layer of a specified soil
and compost mixture underlain by a gravel-filled temporary storage pit dug into the insitu soil. As defined in the Permit, a bioretention BMP may be designed with an overflow drain, but may not include an underdrain. When a bioretention BMP is designed or constructed with an underdrain, it is regulated by the Permit as biofiltration.
City means the City of San Dimas.
Clean Water Act (CWA) means the Federal Water Pollution Control Act enacted in 1972, by Public Law 92-500, and amended by the Water Quality Act of 1987. The Clean Water Act prohibits the discharge of pollutants to Waters of the United States unless the discharge is in accordance with an NPDES permit.
Commercial Malls means any development on private land comprised of one or more buildings forming a complex of stores which sells various merchandise, with interconnecting walkways enabling visitors to easily walk from store-to-store, along with parking area(s). A commercial mall includes but is not limited to mini-malls, strip malls, other retail complexes, and enclosed shopping malls or shopping centers.
Construction Activity means any construction or demolition activity, clearing, grading, grubbing, or excavation or any other activity that result in land disturbance.
Construction does not include emergency construction activities required to immediately protect the public health and safety of routine maintenance activities required to maintain the integrity of structures by performing minor repair and restoration work, maintain the original line and grade, hydraulic capacity, or original purposes of the facility.
Design Engineer means the registered professional engineer responsible for the design of the stormwater management plan.
Development means construction, rehabilitation, redevelopment, or reconstruction of any public or private residential project (whether single-family, multi-unit, or planned unit development); industrial, commercial, retail, and other non-residential projects, including public agency projects; or mass grading for future construction. It does not include routine maintenance to maintain original line and grade, hydraulic capacity, or original purpose of facility, nor does it include emergency construction activities required to immediately protect public health and safety.
Directly Adjacent means situated within 200 feet of the contiguous zone required for the continued maintenance, function, and structural stability of the environmentally sensitive area.
Effective Impervious Area (EIA) is the portion of the surface area that is hydrologically connected to a drainage system via a hardened conveyance or impervious surface without any intervening pervious area to mitigate the runoff volume.
Emergency Situation means any incident, whether natural, technological, or humancaused, that requires responsive action to protect life or property (as defined by the Federal Emergency Management Agency). The responsive action should implement measures, to the fullest extent possible, to reduce the threat to water quality.
Flow-through BMPs means modular, vault type “high flow biotreatment” devices contained within an impervious vault with an underdrain or designed with an impervious liner and an underdrain.
General Construction Activities Storm Water Permit (GCASP) means the general NPDES permit adopted by the State Board which authorizes the discharge of stormwater from construction activities under certain conditions.
Green Roof means a LID BMP using planter boxes and vegetation to intercept rainfall on the roof surface. Rainfall is intercepted by vegetation leaves and through evapotranspiration. Green roofs may be designed as either a bioretention BMP or as a biofiltration BMP. To receive credit as a bioretention BMP, the green roof system planting medium shall be of sufficient depth to provide capacity within the pore space volume to contain the design storm depth and may not be designed or constructed with an underdrain.
Hydrologic Unit Code (HUC) is standardized watershed classification system in which each hydrologic unit is identified by a unique hydrologic unit code (HUC). The HUC may consist of an eight (8) to twelve (12) digit number. The 8-digit HUC identifies an area based on four levels of classification: region, sub-region, hydrologic basin, and hydrologic sub-basin. The Watershed Boundary Dataset includes the 12-digit HUC delineation, which further divides each hydrologic unit into watersheds and subwatersheds based on scientific information and not administrative boundaries.
Hydromodification means the alteration away from a natural state of stream flows or the beds or banks of rivers, streams, or creeks, including ephemeral washes, which results in hydrogeomorphic changes.
Impervious Surface means any man-made or modified surface that prevents or significantly reduces the entry of water into the underlying soil, resulting in runoff from the surface in greater quantities and/or at an increased rate, when compared to natural conditions prior to development. Examples of places that commonly exhibit impervious surfaces include parking lots, driveways, roadways, storage areas, and rooftops. The imperviousness of these areas commonly results from paving, compacted gravel, compacted earth, and oiled earth.
Industrial Park means land development that is set aside for industrial development.
Industrial parks are usually located close to transport facilities, especially where more than one transport modalities coincide: highways, railroads, airports, and navigable rivers. It includes office parks, which have offices and light industry.
Infiltration BMP means a LID BMP that reduces stormwater runoff by capturing and infiltrating the runoff into in-situ soils or amended on-site soils. Examples of infiltration BMPs include infiltration basins, dry wells, and pervious pavement.
LID means Low Impact Development. LID consists of building and landscape features designed to retain or filter stormwater runoff.
Maintenance Agreement means a binding agreement that sets forth the terms, measures, and conditions for the maintenance of post-construction BMP requirements, with exception of simple LID BMP’s implemented on single family residences.
Natural Drainage System means a drainage system that has not been improved (e.g., channelized or armored). The clearing or dredging of a natural drainage system does not cause the system to be classified as modified as defined in Hydromodification.
New Development means land disturbing activities; structural development, including construction or installation of a building or structure, creation of impervious surfaces; and land subdivision.
Parking Lot means land area or facility for the parking or storage of motor vehicles used for businesses, commerce, industry, or personal use, with a lot size of 5,000 square feet or more of surface area.
Plan means written narratives, specifications, drawings, sketches, written standards, operating procedures, or any combination of these which contain information pursuant to this Order.
Planning Priority Projects means development projects subject to Permittee conditioning and approval for the design and implementation of post-construction controls to mitigate stormwater pollution, prior to completion of the project(s).
Rainfall Harvest and Use means a LID BMP system designed to capture runoff, typically from a roof but can also include runoff capture from elsewhere within the site, and to provide for temporary storage until the harvested water can be used for irrigation or non-potable uses. The harvested water may also be used for potable water uses if the system includes disinfection treatment and is approved for such use by the local building department.
Receiving Water means “water of the United States” into which waste and/or pollutants are or may be discharged.
Redevelopment includes but is not limited to the following: the expansion of a building footprint; addition or replacement of a structure; replacement of impervious surface area that is not part of a routine maintenance activity; and land disturbing activities related to structural or impervious surfaces. It does not include routine maintenance
to maintain original line and grade, hydraulic capacity, or original purpose of facility, nor does it include emergency construction activities required to immediately protect public health and safety.
Restaurant Establishments primarily engaged in the retail sale of prepared food and drinks for on-premise or immediate consumption. Caterers and industrial and institutional food service establishments are also included in this industry (SIC Code 5812).
Retail Gasoline Outlet means any facility engaged in selling gasoline and lubricating oils – SIC 5541 and NAICS 447110 and 447190.
Retention means a holding system for stormwater, either natural or man-made, which does not have an outlet to adjoining watercourses or wetlands and in which water is removed through infiltration and/or evaporation processes.
Routine MaintenanceRoutine maintenance Projects include, but are not limited to projects conducted to the following:
1. Maintain the original line and grade, hydraulic capacity, or original purpose of the facility.
2. Perform as needed the restoration work to preserve the original design grade, integrity, and hydraulic capacity of flood control facilities.
3. Includes road shoulder work, re-grading dirt or gravel roadways and shoulders and performing ditch cleanouts.
4. Upgrade existing lines* and facilities to comply with applicable codes, standards, and regulations regardless if such projects result in increased capacity.
5. Repair leaks.
6. Routine maintenance does not include construction of new** lines or facilities resulting from compliance with applicable codes, standards, and regulations. * Update existing lines includes replacing existing lines with new materials or pipes. ** New lines are those that are not associated with existing facilities and are not part of a project to update or replace existing lines.
Runoff means any runoff including stormwater and non-stormwater from a drainage area that reaches a receiving water body.
Significant Ecological Area (SEA) means an area that is determined to possess an example of biotic resources that cumulatively represent biological diversity for the purpose of protecting biotic diversity as part of the Los Angeles County General Plan.
Single-family hillside home means, one acre or greater property located in an area with known erosive soil conditions, where the development contemplates grading on any natural slope that is 25% or greater and where grading, contemplates cut or fill slopes.
Site means land or water area where any “facility or activity” is physically located or conducted, including adjacent land used in connection with the facility or activity.
Source Control BMP means any schedules of activities, prohibitions of practices, maintenance procedures, managerial practices, or operational practices that aim to prevent stormwater pollution by reducing the potential for contamination at the source of pollution.
Storm Drain System means any facilities or any part of those facilities, including streets, gutters, conduits, natural or artificial drains, channels, and watercourses that are used for the purpose of collecting, storing, transporting, or disposing of stormwater and are located within the City of San Dimas.
Storm Water or Stormwater means water that originates from atmospheric moisture (rain or snow) and that falls onto land, water, or other surfaces. Without any change in its meaning, this term may be spelled or written as one word or two separate words.
Stormwater Quality Design Volume (SWQDv) means the runoff from a. The 0.75-inch, 24-hour rain event; or
b. The 85th percentile, 24-hour rain event as determined from the Los Angeles County 85th percentile precipitation isohytal map, whichever is greater.
Stormwater Runoff means that part of precipitation (rainfall or snowmelt) which travels across a surface to the storm drain system or receiving waters.
SUSMP means the Los Angeles Countywide Standard Urban Stormwater Mitigation Plan.
The SUSMP was required as part of the previous Municipal NPDES Permit (Order No. 01- 182, NPDES No. CAS004001) and required plans that designate best management practices (BMPs) that must be used in specified categories of development projects.
Treatment Control BMP means any engineered system designed to remove pollutants by simple gravity settling of particulate pollutants, filtration, biological uptake, media absorption or any other physical, biological, or chemical process.
A. Terms not specifically defined in this chapter shall have the meaning customarily assigned to them.
B. Considering that stormwater management in many cases requires sophisticated engineering design and improvements, some of the terms of this chapter are complex in nature. Effort has been made to simplify terns to the extent the subject
matter permits. (Ord. 1231 § 1, 2014)
14.13.050 development Development and redevelopment Redevelopment project Project provisions Provisions applicability Applicability
These procedures and standards set forth in this chapter and the BMP design information found in the apply to Priority Development Projects that fall under the City’s planning and building authority for which specific requirements, including the implementation of structural BMPs meeting the performance requirements of the Los Angeles County Regional Phase I Municipal Storm Water Permit Order No, R4 2012-0175 2021-0105 (Order) and any all amendment, revisions, or reissuance thereof. The standards set forth in Order provide minimum standards to be complied with by developers and in no way limit the authority of the city City of San Dimas to adopt or publish and/or enforce higher standards as a condition of approval of developments.
A A. New Development Projects Priority Development Projects include the following:
Development projects subject to city conditioning and approval for the design and implementation of post construction controls to mitigate stormwater pollution prior to completion of the project(s) include:
1. New Development Projects within any of the following categories or meeting the following criteria:
a. All development projects equal to one acre or greater of disturbed area and adding more than ten thousand (10,000) square feet of impervious surface area (collectively over the entire project site).
b. Industrial parks ten thousand (10,000) square feet or more of surface area. c. Commercial malls ten thousand (10,000) square feet or more of surface area.
2. Redevelopment projects that create and/or replace five thousand (5,000) square feet or more of impervious surface (collectively over the entire project site) on any of the following:
a. Existing site of ten thousand (10,000) square feet or more impervious surface area;
b. Industrial parks ten thousand (10,000) square feet or more impervious surface area; or
c. Commercial malls ten thousand (10,000) square feet or more impervious surface area.
3. New development and redevelopment projects that create and/or replace five thousand (5,000) square feet or more impervious surface (collectively) over the entire project site) and support one or more of the following uses:
a. Restaurants
b. Parking lots
c. Automotive service facilities (standard industrial classifications
[SIC] 5013, 5014, 5511, 7532-7534, and 7536-7539)
e. Retail gasoline outlets five thousand feet or more or surface area f. Restaurants five thousand square feet or more of surface area.
Parking lots five thousand square feet or more of impervious surface area, or with twenty five or more parking spaces.
4. New development and redevelopment projects that create and/or replace twenty-five (2,500_ square feet or more of impervious area that are likely to impact a sensitive biological species or habitat; and are located or directly adjacent to an Area of Special Biological Significance or Sensitive Ecological Area (SEA) such as San Dimas Canyon/San Antonio Wash.
5. Street and road construction of ten thousand (10,000) square feet or more of impervious surface area shall follow the city City of San Dimas green Green streets Streets policy Policy to the maximum extent practicable. Street and road construction applies to streets, roads, highways, and freeway projects, and also applies to streets within larger projects.
Automotive services facilities (as referenced by standard industrial classifications in the Los Angeles County Municipal Storm Water Permit Order No. R4-2012-0175, and any amendment, revision, or reissuance thereof) five thousand square feet or more of surface area.
6. Redevelopment projects in subject categories that meeting the redevelopment thresholds identified in subsection B (Redevelopment Projects) of this section that result in the alteration to more than fifty percent (50%) of impervious surfaces of a previously existing development, shall address the entire project.
7. Redevelopment projects meeting the redevelopment thresholds that result in the alteration to less than fifty percent (50%) of impervious surfaces of a previously existing development, only the alteration must be mitigated, not the entire project site.
8. Single-Family Hillside Homes. During the construction of a single-family hillside home, the following measures shall be considered to the maximum extent practicable:
a. Conserve natural areas.
b. Protect slopes and channels.
c. Provide storm drain system stenciling and signage.
d. Divert roof runoff to vegetated areas before discharge unless the diversion would result in slope instability.
e. Direct surface flow to vegetated areas before discharge unless the diversion would result in slope instability.
B. Redevelopment Projects. Redevelopment projects subject to conditioning and approval requirements outlined in this chapter for the design and implementation of post-construction controls to mitigate stormwater pollution prior to completion of the project(s) include the following:
1. Land disturbing activity that results in the creation or addition or replacement of five thousand square feet or more of impervious surface area on an already developed site.
2. 1. Redevelopment projects that result in an alteration to more than fifty percent (50%) of impervious surfaces of an existing development which had not been not subject to post-construction stormwater quality control requirements at the time of the previous development shall be required to mitigate the entire project site.
2. Redevelopment projects that result in an alteration to more than fifty percent (50%) of impervious surfaces of an existing development which had not been not subject to postconstruction stormwater quality control requirements at the time of the previous development shall be required to mitigate the entire project site.
4. 3. Redevelopment does not include routine maintenance activities that are conducted to maintain original line and grade, hydraulic capacity, original purpose of facility or emergency redevelopment activity required to protect public health and safety. Impervious surface replacement, such as the reconstruction of parking lots and roadways, which does not disturb additional area and maintains the original grade and alignment, is not considered a routine maintenance activity. Redevelopment does not include the repaving of exiting roads to maintain original line and grade.
4. Existing single-family dwelling and accessory structures are exempt from the redevelopment requirements unless such projects create, add, or replace ten thousand square feet of impervious area. (Ord. 1231 §, 2014)
14.13.060 Project performance Performance criteria Criteria.
All development projects that fit the project critiera listed in Section 14.13.050 of this chapter shall control pollutants, pollutant loads, and runoff volume by retaining the stormwater quality design (SWQDv) on-site through the following:
1. A. Minimizing the impervious surface area On-site infiltration, bioretention bioretention and/or rainfall harvest and use; and
1.
2. B. Controlling runoff from impervious surfaces through infiltration, bioretention and/or rainfall harvest and use. Ord. 1231 § 1, 2014) If subpart A above is infeasible, on-site biofiltration, offsite groundwater replenishment and/or off-site retrofit; or
2. 3. C. If subpart B above is infeasible, on-site treatment is required, where all the above options are infeasible.
14.13.070 Alternative compliance Compliance for technical Techincal infeasiblity Infeasiblity.
To demonstrate technical infeasibility, the project applicant shall demonstrate to the city City engineer Engineer that the project cannot reliably retain one hundred percent of the SWQDv on-site, even with the maximum application of green roofs and rainwater harvest and use, and that compliance with the application post-construction requirements would be technically infeasible. This shall be demonstrated by submitting a site-specific hydrologic and/or design analysis conducted and endorsed by a registered professional engineer, geologist, architect, and/or landscape architect and shall be subject to review and approval by the city City engineer Engineer.
When evaluating the potential on-site retention, each applicant shall consider the maximum potential for evapotranspiration from green roofs and rainfall harvest and use.
A. 1.- If partial or complete on-site retention is technically infeasible, the project applicant shall considered the following Alternative alternative compliance measures include the following:
1. A. On-Site Biofiltration. Biofiltration systems shall meet the design specifications provided in Attachment H of the Los Angeles County Municipal Storm Water Permit Order No. R4-2012-0175 LID Manual (2014 and its, and any amendment, revisions), or reissuance thereof equivalent LID manual. If using biofiltration due to demonstrated technical infeasibility, then the new project must biofiltrate 1.5 times the portion of the SWQDv that is not reliably retained on-site, as calculated by Equation 1 below:
Equation 1:
Bv = 1.5 x [SWQDv - Rv]
Where:
Bv = biofiltration volume.
SWQDv = the stormwater runoff from a 0.75 inch, twenty-four-hour storm or the eighty-fifth percentile storm, whichever is greater.
Rv = volume reliably retained on-site.
Biofiltration systems discharging to a receiving water that is included on the Clean Water Act section 303(d) list of water quality impairments due to nitrogen compounds, shall be designed and maintained to achieve enhanced nitrogen removal capacity.
B. Off-Site Infiltration. Use An applicant may use infiltration or bioretention BMPs to intercept a volume of stormwater runoff equal to the SWQDv, less the volume of stormwater runoff reliably retained on-site, at an approved off-site project located within the same subwatershed (HUC-12) as the Priority Development Project, and shall provide pollutant reduction (i.e., treatment) of stormwater runoff from the project site. The required off-site mitigation volume shall be calculated by Equation 2 below:
Equation 2:
Mv = 1.0 x [SWQDv - Rv]
Where:
Mv = mitigation volume.
SWQDv = runoff from the 0.75-inch, twenty-four-hour storm event or the eightyfifth percentile storm, whichever is greater.
Rv = the volume of stormwater runoff reliably retained on-site.
C. Onsite Flow-based BMPs. If onsite biofiltration and off-site alternative compliance measures are not technically feasible, the applicant may request authorization by the City Engineer to allow the use of onsite flow-based BMPs. The applicant shall document why none of the other alternative compliance measures are feasible. Approval will only be granted to areas where other alternative compliance measures are not feasible due to significant technical issues. If approved the Flowbased treatment control BMPs must be sized and designed to do the following:
1. Filter or treat either:
a. The maximum flow rate of runoff produced from a rainfall intensity if 0.2 inch of rainfall per hour, for each hour of a storm event; or
b. The maximum flow rate of runoff produced by the 85th percentile hourly rainfall intensity (for each hour of a storm event), as determined from the local historical rainfall record, multiplied by a factor of two;
2. Be certified for Enhanced Treatment under the Washington State Department of Ecology’s TAPE Program; or an appropriate future BMP certification developed by the State of California.
D. Off-Site Project-Retrofit Existing Development. Use infiltration, bioretention, rainfall harvest and use and/or biofiltration BMPs to retrofit an existing development, with similar land uses as the new development or land uses associated with comparable or higher stormwater runoff event mean concentrations (EMCs) than the new development. The retrofit plan shall be designed and constructed as described in the Los Angeles County Municipal Regional Storm Water Permit Order No. R4-2012 2021 -0175 0105, and any amendments, revisions, or reissuance thereof.
E. Other alternative Groundwater Replenishment. Regional projects to replenish regional groundwater supplies at an off-site location, provided the groundwater supply has a designed beneficial use, in accordance with – compliance performance requirements standards are detailed in the Los Angeles County Municipal Regional Storm Water Permit Order No. R4 2012 2021- 0175 0105, and any amendments, revisions, or reissuance thereof.
2. Projects approved for off-site mitigation or ground water replenishment shall also provide treatment of stormwater runoff from the project site. Project applicant shall design and implement post-construction stormwater BMPs and control measures to reduce pollutant loading as necessary to ensure that the controls implemented on the site are designed so that stormwater discharges do not cause or contribute to exceedances of receiving water standards.
Applicants and/or designers may select any combination of stormwater BMPs which meet the performance standards provided in this section and identified in the Los Angeles County Municipal Storm Water Permit Order No. R4-2012-0175 and any amendment, revision, or reissuance thereof. (Ord. 1231 § 1, 2014)
14.13.080 Hydromodification Management Requirements.
Planning Priority Projects located within natural drainage systems shall implement hydrological control measures to prevent accelerated downstream erosion and protect stream habitat.
A. Natural drainage systems that are subject to the hydromodification assessments and control include all drainages that have not been modified using engineering controls or drainages that are tributary to a natural drainage
system. Examples of engineering modifications to drainage include channelization, armoring with concrete, and application of rip-rap.
B. At the City’s discretion the following New Development and Redevelopment projects may be exempted from implementation of hydromodification controls where it has been documented that adverse hydromodification effects to Natural Drainage Systems are unlikely:
1. Projects consisting of replacement, maintenance, or repair of an existing flood control facility, storm drain, or transportation network.
2. Redevelopment Projects in the urban core that do not increase the effective impervious area or decrease the infiltration capacity of previous areas compared to pre-project conditions.
3. Projects that have any increased discharge directly via a storm drain to a sump, lake, into a waterway that has a 100-year peak flow (Q100) of 25,000 cubic feet per second or more, or other receiving water that is not susceptible to hydromodification impacts.
4. Projects that discharge directly or via a storm drain into concrete or otherwise engineered channels which in turn, discharge into a receiving water that is not susceptible to hydromodification impacts.
5. LID BMPs implemented on single-family homes are sufficient to comply with the hydromodification criteria.
C. Projects disturbing an area less than or equal to 1 acre shall implement the applicable LID performance standards in subchapters 14.13.060 and/or
14.13.070.
D. Projects disturbing an area greater than 1 acre, but less than 50 acres will be presumed to meet pre-development hydrology if one of the following demonstrations are made:
The project is designed to retain on-site the runoff of the 95th percentile 24-hour storm; or
1. The runoff flow rate, volume, velocity, and duration of the postdevelopment condition does not exceed the pre-development condition for the 2-year, 24-hour storm event; or
2. The Erosion Potential (Ep) in the receiving water is approximately 1. Ep shall be determined in accordance with the NPDES permit.
E. Projects disturbing 50 acres or more will be presumed to meet predevelopment hydrology based on the successful demonstration of one of the following conditions:
1. The project site infiltrates on-site runoff from a 2-year, 24-hour storm event; or
2. The runoff flow rate, volume, velocity, and duration for the postdevelopment condition does not exceed the pre-development condition for the 2-year, 24-hour storm event.
These conditions must be substantiated by hydrologic modeling.
14.13.080090 Plan review Review procedures Procedures.
All stormwater plans shall be subject to review and approval by the city City engineer Engineer.
A. If the proposed plan is not sufficient as originally submitted, the City Engineer, or designee, will notify the applicant in writing, setting forth the reasons for withholding and will state the changes necessary to obtain approval.
B. If staff determines that all of the required information has not been received, the applicant may request that the matter be tabled to allow for the submittal of the required information.
C. If all of the required information has been received, staff shall approve, approve with conditions, or recommend denial of the stormwater plan, including waiver submissions. Recommendations for action on the stormwater plan can be part of the recommendation for action on the site plan or subdivision plat.
D. If the plan is approved, the cityCitywill require the following:
1. The applicant shall provide copies of all necessary state, federal, or local permits relating to stormwater management to the city City.
2. A satisfactory maintenance covenant agreement that assures long-term maintenance of all drainage improvements shall be submitted as part of the final plan. The maintenance covenant shall include a listing of the BMPs and their location; an operation and maintenance plan; monitoring plan (where required); and required maintenance frequency verification of ongoing maintenance provisions for LID BMPs. The property owner shall be required to document proper maintenance and operations and maintain such records for a period of two years. Maintenance agreements and records shall be provided upon request to the city City inspector at any time for compliance verification. Failure to do so will result in enforcement actions per the city City code. The approved covenant shall be recorded with the Los Angeles County
recorder prior to issuance of occupancy.
3. A satisfactory maintenance covenant shall at a minimum include the developer's signed statement accepting responsibility for maintenance until the responsibility is legally transferred, and either:
a. A signed statement from the public entity assuming responsibility for BMP maintenance; or
b. Written conditions in the sales or lease agreement, which require the property owner or tenant to assume responsibility for BMP maintenance and conduct a maintenance inspection at least once a year; or c. Written text in project covenants, conditions, and restrictions (CCRs) for residential properties assigning BMP maintenance responsibilities to the homeowners homeowners’ association; or
d. The applicant shall post cash or a letter of credit in an amount not less than one hundred percent of the cost of the stormwater facilities. This deposit shall be held for two years after the date of completion of construction and final inspection of the stormwater facilities, until accepted by the city City. The percentage cost for cash or letter of credit may be reduced to ten percent for projects longer than two years.
4. This deposit shall be returned to the applicant (in the case of cash) or allowed to expire (in the case of a letter of credit), as provided above, provided all stormwater facilities are clean, unobstructed, and in good working order, as determined by the city City engineer Engineer.
5. Reproducible mylars and electronic files (in AutoCAD format) of the asbuilt storm drains and stormwater BMPs shall be submitted by the applicant or his/her engineer to the city City along with the final plan, or upon completion of system construction. The mylars are to be of quality material and three mils in thickness. Complete development agreements (including deed restrictions) must be submitted for the c i t y C i t y ’ s review and approval prior to recording. (Ord. 1231 § 1, 2014)
14.13.090 100 Plan review Review fees Fees.
Fees and escrow account payments shall be sufficient to cover administrative and technical review costs anticipated to be incurred by the city City of San Dimas including the costs of on-site inspections, as set forth by resolution of the city City council. (Ord. 1231 § 1, 2014)
14.13.100 110 Maintenance agreement Agreement.
A. Purpose of Maintenance Agreement. The purpose of the maintenance agreement is to provide the means and assurance that maintenance of stormwater BMPs shall be undertaken. As a condition for issuing a certificate of occupancy for a new development or redevelopment project, the applicant, facility operator(s), and/or owner(s), as appropriate, shall construct and/or employ all stormwater control BMPs identified in the approved LID Plan; and submit a signed certification statement that the project site and all BMPs will be employed and maintained in compliance with the City’s LID ordinance and other applicable regulatory requirements until the responsibility for such maintenance is legally transferred to another party.
B. Maintenance Agreement Required. A maintenance agreement shall be submitted to the city City for review by the city City engineer Engineer and/or designee and, if necessary, city City attorney. The designers may select any combination of stormwater BMPs which meet the performance standards provided this selection and identified in the Los Angeles County Municipal Storm Water Permit Order No. R4-2012-0175 Order and any amendment, revision, or reissuance thereof. A formal maintenance and inspection plan shall be included in the maintenance agreement.
C. Maintenance Agreement Provisions.
1. The maintenance agreement shall include a plan for routine, emergency, and long-term maintenance of all stormwater BMPs, with a detailed annual estimated budget for the initial two years, and a clear statement that only future maintenance activities in accordance with the maintenance agreement plan shall be permitted without the necessity of securing new permits. Written notice of the intent to proceed with maintenance shall be provided by the party responsible for maintenance to the city City of San Dimas at least fourteen (14) days in advance of commencing work.
2. The maintenance agreement shall be binding on all subsequent owners of land served by the stormwater BMPs. A copy of the operation and maintenance plan shall be kept on-site for periodic review by the City’s inspectors.
3. If it has been found by the city City, following notice and an opportunity to be heard by the property owner, that there has been a material failure or refusal to undertake maintenance as required under this chapter and/or as required in the approved maintenance agreement as required hereunder, the city City shall abate such violations, as a public nuisance, pursuant to the procedures set forth
in Chapter 8.16 of the San Dimas Municipal Code.
4. A fully executed "maintenance covenant for permanent BMPs requirements" shall be recorded with the Los Angeles County registrar/recorder and submitted to the public works department prior to the certificate of occupancy. Covenant documents shall be required to include an exhibit that details the installed treatment control devices as well as any site design or source control best management practices (BMPs) for post construction. The information to be provided on this exhibit shall include, but not be limited to the following:
• 8 ½" x 11" exhibits with record property owner information. • Types of BMPs (i.e., site design, source control and/or treatment control) to ensure modifications to the site are not conducted without the property owner being aware of the ramifications to BMP implementation. • Clear depiction of location of BMPs, especially those located below ground. • A matrix depicting the types of BMPs, frequency of inspection, type of maintenance required, and if proprietary BMPs, the company information to perform the necessary maintenance.
• Agreement to retain documentation of proper maintenance for a period of two years.
• Understanding that documentation of proper maintenance must be presented to the city City upon request. (Ord. 1231 § 1, 2014)
5 . The owners of the land served by the stormwater BMPs shall certify annually that all BMPs identified in the approved LID Plan have been inspected and maintained in accordance with the approved BMP maintenance plan. This certification shall be submitted to the City Engineer by September 30th annually.
6. The City of San Dimas shall inspect new development/redevelopment projects once every two (2) years after the date of project completion, to assess operational conditions for LID and hydromodification control BMP repair, replacement, and/or re-vegetation.
14.13.110 120 Enforcement.
Any person violating any provision of this chapter shall be responsible for a municipal civil infraction and subject to the city City’s enforcement policy as set forth in the provisions of Title 1 and/or Chapter 8.16 of the San Dimas Municipal Code. (Ord. 1231 § 1, 2014)
14.13.120 130 Stop work Work order Order.
Where there is work in progress that causes or constitutes, in whole or in part, a violation of any provision of this chapter, the city City is authorized to issue a stop work order so as to prevent further or continuing violations or adverse effects. All persons to whom the stop work order is directed, or who are involved in any way with the work or matter described in the stop work order shall fully and promptly comply therewith. The city City may also undertake or cause to be undertaken, any necessary or advisable protective measures so as to prevent violations of this chapter or to avoid or reduce the effects of noncompliance herewith. The cost of any such protective measures shall be the responsibility of the owner of the property upon which the work is being done and the responsibility of any person carrying out or participating in the work. (Ord. 1231 § 1, 2014)
14.13.130 140 Failure to comply Ccompletion.
In addition to any other remedies, should any property owner fail to comply with the provisions of this chapter, the city City may, after the giving of reasonable notice and opportunity for compliance, have the necessary work done, and the owner shall be obligated to promptly reimburse the city City for all costs of such work. (Ord. 1231 § 1, 2014)
14.13.140 150 Emergency measures Measures.
When emergency measures are necessary to moderate a nuisance, to protect public safety, health and welfare, and/or to prevent loss of life, injury or damage to property, the city City is authorized to carry out or arrange for all such emergency measures. Property owners shall be responsible for the cost of such measures made necessary as a result of a violation of this chapter, and shall promptly reimburse the city City for all of such costs. (Ord. 1231 § 1, 2014)
14.13.150 160 Cost recovery Recovery for damage Damage to storm Storm drain Drain system System.
A discharger shall be liable for all costs incurred by the city City as the result of causing a discharge that produces a deposit or obstruction, or causes damage to, or impairs a storm drain, or violates any of the provisions of this chapter. Costs include, but are not limited to, those penalties levied by the Environmental Protection Agency or Los Angeles Regional Water Quality Control Board for violation of an NPDES permit, attorney fees, and other
costs and expenses. (Ord. 1231 § 1, 2014)
Contact:
City Clerk: 909-394-6216
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