Loading...
HomeMy WebLinkAboutCC ORD 2008-2307 Adopt Urban Stormwater Mitigation Plan (SUSMP) REPEALING ORDINANCE NO. 2002-2213ORDINANCE NO. 2008 — 2307 AN ORDINANCE OF THE CITY COUNCIL OF THE CITY OF NATIONAL CITY ADOPTING THE STANDARD URBAN STORMWATER MITIGATION PLAN (SUSMP), AND REPEALING ORDINANCE NO. 2002-2213 WHEREAS, the San Diego Regional Water Quality Control Board issued the National Pollutant Discharge Elimination System (NPDES) permit No. CAS0108758, Order No. R9-2007-001, requiring changes to the City's Standard Urban Stormwater Mitigation Plan (SUSMP). NOW, THEREFORE, the City Council of the City Of National City does hereby ordain as follows: Section 1. Introduction of the Standard Urban Stormwater Mitigation Plan (SUSMP). The City Council of the City of National City introduces the Standard Urban Stormwater Mitigation Plan (SUSMP) attached hereto as Appendix "A", hereafter abbreviated as "SUSMP", as the City of National City's program for management of stormwater runoff. A cop of Appendix "A" shall be kept on file in the Office of the City Engineer. Section 2. Implementation and administration. All City departments, under the direction of the City Manager, shall implement, administer and enforce the provisions of the SUSMP, and shall modify their administrative procedure for permit issuance and plan approval accordingly, In case of conflict between a provision of the Municipal Code and the SUSMP, the SUSMP, shall take precedence, unless the City Manager determines that compliance is impossible, impractical or is not in the public's best interest. In this event, the City Manager shall immediately advise the City Council and recommend appropriate measures for resolution. Section 3. Department review. To the extent not already provided for, City department directors under the direction of the City Manager will review and propose amendments to the Municipal Code that are or may become necessary for the further implementation of the SUSMP. Section 4. Criminal and administrative enforcement. The mandatory provisions and prohibitions of the SUSMP shall be enforceable as misdemeanors pursuant to Section 1.20.010 of the National City Municipal Code, and administrative penalties may be imposed in accordance with Chapters 1.44 or 1.48 of the National City Municipal Code, as appropriate. Section 5. Repeal of previous ordinance. Ordinance No. 2002-2213 is hereby repealed. -- Signature Page to Follow -- Ordinance No. 2008-2307 1 SUSMP Ordinance Ordinance No. 2008 — Page 2 PASSED and ADOPTED this 19th day of February, 200 Ron orrison, Mayor ATTEST: Miclbael R. Dalla, sCity Clerk APPROVED AS TO FORM: George H. Eiser, II City Attorney Ordinance No. 2008-2307 2 SUSMP Ordinance Passed and adopted by the Council of the City of National City, Califomia, on February 19, 2008, by the following vote, to -wit: Ayes: Councilmembers Morrison, Natividad, Parra, Ungab. Nays: None. Absent: Councilmember Zarate. Abstain: None. AUTHENTICATED BY: By: RON MORRISON Mayor of the City of National City, California /� CI k of the City of at ional City, California Deputy I HEREBY CERTIFY that the foregoing ordinance was not finally adopted until seven calendar days had elapsed between the day of its introduction and the day of its final passage, to wit, on February 5, 2008, and on February 19, 2008. I FURTHER CERTIFY THAT said ordinance was read in full prior to its final passage or that the reading of said ordinance in full was dispensed with by a vote of not less than a majority of the members elected to the Council and that there was available for the consideration of each member of the Council and the public prior to the day of its passage a written or printed copy of said ordinance. I FURTHER CERTIFY that the above and foregoing is a full, true and correct copy of ORDINANCE NO. 2008-2307 of the City Council of the City of National City, passed and adopted by the Council of said City on February 19, 2008. By: City Clerk of the City of National City, California Deputy The City of National City STANDARD URBAN STORM WATER MITIGATION PLAN Adopted February 19, 2008 APPENDIX A TABLE OF CONTENTS I. BACKGROUND 1 II. SUMMARY 1 III. DEFINITIONS 2 IV. CONFLICTS WITI-I LOCAL PRACTICES OR MUNICIPAL PERMIT 7 V. IMPLEMENTATION PROCESS 7 VI. STORM WATER BMP SELECTION PROCEDURE 8 1. Identify Pollutants & Conditions of Concern 11 a. Identify Pollutants from the Project Area • 13 b. Identify Pollutants of Concern in Receiving Waters 14 c. Identify Conditions of Concern in Receiving Waters 14 2. Establish Storm Water BMPs 17 a. Site Design BMPs 21 b. Source Control BMPs 24 c. Treatment Control BMPs 28 3. Provide Proof of Ongoing BMP Maintenance 32 4. Waiver Of Structural Treatment BMP Requirements 34 VII. RESOURCES & REFERENCES 35 Appendix A: Example Best Management Practices 35 Appendix B: Suggested Resources 39 Appendix C: City of San Diego LEAD Pilot Study Proposal 42 List of Figures Figure 1: Storm Water BMP Selection Procedure 10 List of Tables Table 1: Anticipated and Potential Pollutants Generated by Land Use Type 13 Table 2: Standard Storm Water BMP Selection Matrix 19 Table 3: Enhanced Storm Water BMP Selection Matrix 20 Table 4. Pollutants and Associated Particle Sizes 21 The municipal storm water National Pollutant Discharge Elimination System (NPDES) permit (Order No. R9-2007-0001, NPDES No. CASOI08758, hereinafter referred to as "Municipal Permit") issued to San Diego County, the Port of San Diego, San Diego County Regional Airport Authority, and 18 cities (Copermittees) by the San Diego Regional Water Quality Control Board (Regional Board) on January 24, 2007, requires the development and implementation of a program addressing urban runoff -pollution issues in development planning for puhlic and private projects. The requirement to implement a program for development planning is based on federal and state statutes including: Section 402 (p) of the Clean Water Act, Section 6217 of the Coastal Zone Act Reauthorization Amendments of 1990 ("CLARA"), and the California Water Code. The Clean Water Act amendments of 1987 established a framework for regulating urban runoff discharges from municipal, industrial, and construction activities under the NPDES program. The Municipal Permit requires the implementation of a Jurisdictional Urban Runoff Management Program (URMP). The primary objectives of the Jurisdictional URMP requirements are to: 1. Ensure that discharges from municipal urban runoff conveyance systems do not cause or contribute to a violation of water quality standards; 2. Effectively prohibit non -stone water discharges in urban runoff; and 3. Reduce the discharge of pollutants from urban runoff conveyance systems to the Maximum Extent Practicable (MEP statutory standard). The Model Standard Urban Storm Water Mitigation Plan (SUSMP) was collectively developed by the Copennittees to address post -construction urban runoff pollution from new development and redevelopment projects that fall under "priority project" categories. The goal of the Model SUSMP is to develop and implement practicable policies to ensure to the maximum extent practicable that development does not increase pollutant loads from a project site and considers urban runoff flow rates, velocities, and durations. This goal may be achieved through site - specific controls and/or drainage area -based or shared structural treatment controls. The Model SUSMP identifies appropriate Best Management Practices (BMPs) for certain designated project types to achieve this goal. The City of National City's (City) SUSMP has been reviewed and approved by the City Council in a puhlic process. C:a.unvu aW Stump, omvwkV nnl Sni Ile Temporary lien. F3atOLKSISCSlfl ix SC 2 19 US.FmL+Un Pagel The City will approve SUSMP project plan(s) as part of the development plan approval process for discretionary projects, and prior to issuing permits for ministerial projects. To allow flexibility in meeting SUSMP design standards, structural treatment control BMPs may he located on or off -site, used singly or in combination, or shared by multiple developments, provided certain conditions arc met. All new development and significant redevelopment projects that fall into one of the following "Priority Project" categories are subject to these SUSMP requirements, subject to the lawful prior approval provisions of the Municipal Permit. In the instance where a project feature, such as a parking lot, falls into a Priority Project category, the entire project footprint is subject to these SUSMP requirements. These "Priority Project Categories" are: ❑ Residential development of 10 units or more ❑ Commercial development greater than one acre ❑ Industrial development greater than one acrc u Automotive repair shops ❑ Restaurants u Hillside development greater than 5,000 square feet o Projects discharging to receiving waters within environmentally sensitive areas o Parking Lots > 5,000 square fect of impervious surface or with > 15 parking spaces and potentially exposed to urban runoff ❑ Streets, roads, highways, and freeways which would create a new paved surface that is 5,000 square feet or greater of impervious surface. o Retail gasoline outlets 5,000 square feet or more or with a projected Average Daily Traffic (ADT) of 100 or more vehicles per day Limited Exclusion: Trenching and resurfacing work associated with utility projects are not considered priority projects such as resurfacing and reconfiguring surface parking lots and existing roadways, new sidewalk construction, pedestrian ramps, or hike lane on existing roads, and routine replacement of damage pavement, such as pothole repair. Parking lots, buildings and other structures associated with utility projects are subject to SUSMP requirements if one or more of the criteria for the above categories are met. u "Attached Residential Development," means any development that provides residential units that share an interior/exterior wall. This category includes, but is not limited to: dormitories, condominiums and apartments. ❑ "Automotive Repair Shop" means a facility that is categorized in any one of the following Standard Industrial Classification (SIC) codes: 5013, 5014, 5541, 7532-7534, or 7536- 7539. Page 2 ❑ "Commercial Development" means any development on private land that is not exclusively industrial or residential uses. The category includes, but is not limited to: mini -malls and other business complexes, shopping malls, hotels, office buildings, public warehouses, hospitals, laboratories and other medical facilities, educational institutions, recreational facilities, plant nurseries, car wash facilities, and other light industrial complexes. ❑ "Commercial Development greater than one acre" means any commercial development that results in the disturbance of one acre or more of land. ❑ "Detached Residential Development," means any development that provides freestanding residential units. This category includes, but is not limited to: detached homes, such as single-family homes and detached condominiums. ❑ "Directly Connected hnpervious Area (DCIA)" means the area covered by a building, impermeable pavement, and/or other impervious surfaces, which drains directly into the storm drain without first flowing across permeable vegetated land area (e.g., lawns). ❑ "Enviromnentally Sensitive Areas" means areas that include, but arc not limited to, all Clean Water Act 303(d) impaired water bodies ("303[d) water bodies"); areas designated as an "Area of Special Biological Significance" (ASBS) by the State Water Resources Control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments); watcr bodies designated as having a RARE beneficial use by the State Water Resources Control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments), or areas designated as preserves or their equivalent under the Multiple Species Conservation Program (MSCP) within the Cities and County of San Diego. The limits of Areas of Special Biological Significance are those defined in the Water Quality Control Plan for the San Diego Basin (1994 and amendments). Environmentally sensitive area is defined for the purposes of implementing SUSMP requirements, and does not replace or supplement other environmental resource -based terms, such as "Environmentally Sensitive Lands," employed by Copermittees in their land development review processes. As appropriate, National City will distinguish between environmentally sensitive area and other similar terms in its SIJSMP. ❑ "Hillside" means lands that have a natural gradient of 25 percent (4 feet of horizontal distance for every 1 foot of vertical distance) or greater and a minimum elevation differential of 50 feet, or a natural gradient of 200 percent (1 foot of horizontal distance for every 2 feet of vertical distance) or greater and a minimum elevation differential of 10 feet. ❑ "Hillside development greater than 5,000 square feet" means any development that would create more than 5,000 square feet of impervious surfaces in hillsides with known erosive soil conditions. ❑ "Hydromodification" means the change in the natural hydrologic processes and runoff characteristics (i.c. interception, infiltration, overland flow, interflow and groundwater flow) caused by urbanization or other land use changes that result in increased stream Page 3 flows and changes in sediment transport. In addition, alternation of stream and river channels, installation of dams and water impoundments, and excessive streambank and shoreline erosion are also considered hydromodification, due to their disruption of natural watershed hydrologic processes. ❑ "Industrial development greater than one acre" means development of industrial facilities that results in the disturbance of over one acre of land. Industrial facilities include those defined at 40 CFR 122.26(6)(14), including those subject to the General Industrial Permit or other individual NPDES permit, operating and closed landfills, facilities subject to SARA Title III, and hazardous waste treatment, disposal, storage and recovery facilities. Examples of industrial facilities includes manufacturing plants, food processing plants, metal working facilities, printing plants, and fleet storage areas (bus, truck, etc.). o "Infiltration" means the downward entry of water into the surface of the soil. o "Integrated Management Practice (IMP)" means a facility (BMP) that provides small- scale treatment, retention, or detention and is integrated into site layout, landscaping, and drainage design. ❑ "Low Impact Development (LID)" means a storm water management and land development strategy that emphasizes conservation and the use of on -site natural features integrated with engineered, small-scale hydrologic controls to more closely reflect pre - development hydrologic features. ❑ "Maximum Extent Practicable (MEP)" means the technology -based standard established by Congress in the Clean Water Act 402(p)(3)(B)(iii) that municipal dischargers of urban runoff must meet. MEP generally emphasizes pollution prevention and source control BMPs primarily (as the first line of defense) in combination with treatment methods serving as a backup (additional lines of defense). ❑ "Natural drainage" means a natural swale or topographic depression which gathers and/or conveys runoff to a permanent or intermittent watercourse or waterbody. ❑ "New Development" means land disturbing activities; surface grading for structural development, including construction or installation of a building or structure, the creation of impervious surfaces; and land subdivision. ❑ "Parking Lot" means land area or facility for the temporary parking or storage of motor vehicles used personally, or for business or commerce. ❑ "Projects Discharging to Receiving Waters within Environmentally Sensitive Areas" means all development and significant redevelopment that would create 2,500 square feet of impervious surfaces or increase the area of imperviousness of a project site to 10% or more of its naturally occurring condition, and is located within or directly adjacent to (where any portion of the project footprint is located within 200 feet of the environmentally sensitive area) an environmentally sensitive area (where discharges from the development or redevelopment will enter receiving waters within the environmentally Page 4 sensitive area) or discharges to a receiving water within an environmentally sensitive area without mixing with flows from adjacent lands (where the project footprint is located more than 200 feet from the environmentally sensitive area). ❑ "Project Footprint" means the limits of all grading and ground disturbance, including landscaping, associated with a project. u "Receiving Waters" means swface bodies of water, which directly or indirectly receive discharges from urban runoff conveyance systems, including naturally occurring wetlands, streams (perennial, intermittent, and ephemeral [exhibiting bed, bank, and ordinary high water mark]), creeks, rivers, reservoirs, lakes, lagoons, estuaries, harbors, bays and the Pacific Ocean. National City will determine the definition for wetlands and the limits thereof for the purposes of this definition as protective as the United States Environmental Protection Agency. Constructed wetlands are not considered wetlands under this definition, unless the wetlands were constructed as mitigation for habitat loss. Other constructed BMPs are not considered receiving waters under this definition, unless the BMP was originally constructed in receiving waters. Construction of treatment control BMPs in "Receiving Waters" is prohibited and therefore may not he used to satisfy SUSMP requirements. ❑ "Residential Development" means any development on private land that provides living accommodations for one or more persons. This category includes, but is not limited to: single-family homes, multi -family homes, condominiums, and apartments. u "Residential Development of 10 units or more" means any development that provides 10 or more residential units. Residential units can be attached or detached. ❑ "Restaurant" means a stand-alone facility that sells prepared foods and drinks for consumption, including stationary lunch counters and refreshment stands selling prepared foods and drinks for immediate consumption (SIC code 5812), where the land area for development is greater than 5,000 square feet. Restaurants where land development is less than 5,000 square feet shall meet all SUSMP requirements except for structural treatment BMP and numeric sizing criteria.requirement and hydmmodification requirement. ❑ "Sediment" means soils or other surficial materials eroded and then transported or deposited by the action of wind, water, ice, or gravity. Sediments can increase turbidity, clog fish gills, reduce spawning habitat, lower young aquatic organism survival rates, smother bottom dwelling organisms, and suppress aquatic vegetation growth. ❑ "Significant Redevelopment" means development that would create or add or replace at least 5,000 square feet of impervious surfaces on an already developed site that falls under one or more priority development project categories. Where redevelopment results in an increase of less than 50 percent of the impervious surfaces of a previously existing development, and the existing development was not subject to SIJSMP requirements, the numberic sizing criteria identified in Section 2, Step 8 apply only to the addition, and not Page 5 the entire development. When redevelopment results in an increase of more than 50 percent of the impervious surfaces of a previously existing development, the numeric sizing criteria applies to the entire development. Significant redevelopment includes, but is not limited to: the expansion of a building footprint; addition to or replacement of a structure; replacement of an impervious surface that is not part of a routine maintenance activity; and land disturbing activities related with structural or impervious surfaces. Replacement of impervious surfaces includes any activity that is not part of a routine maintenance activity where impervious material(s) are removed, exposing underlying soil during construction. Significant redevelopment does not include trenching and resurfacing associated with utility work, resurfacing and reconfiguring surface parking lots, new sidewalk, pedestrian ramps or bike lane construction on existing roads, and replacement of damaged pavement. ❑ "Site Design BMP" known as a significant part of Low impact Development (LID), means any project design feature that reduces the amount of impervious surfaces, disconnects impervious surfaces, reduces creation or severity of potential pollutant sources and/or reduces the alteration of the project site's natural flow regime. Redevelopment projects that are undertaken to remove pollutant sources (such as existing surface parking Tots and other impervious surfaces) or to reduce the need for new roads and other impervious surfaces (as compared to conventional or low -density new development) by incorporating higher densities and/or mixed land uses into the project design, are also considered site design BMPs. ❑ "Source Control BMP (both structural and non-structural)" means land use or site planning practices, or structures that aim to prevent urban runoff pollution by reducing the potential for contamination at the source of pollution. Source control BMPs minimize the contact between pollutants and urban runoff. Examples include roof structures over trash or material storage areas, and berms around fuel dispensing areas. ❑ "Storm Water Best Management Practice (BMP)" means any schedules of activities, prohibitions of practices, general good house keeping practices, pollution prevention and educational practices, maintenance procedures, structural treatment BMPs, and other management practices to prevent or reduce to the maximum extent practicable the discharge of pollutants directly or indirectly to receiving waters. Stonn Water 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. This SIJSMP groups storm water BMPs into the following categories: site design; source control; and treatment control (pollutant removal). ❑ "Storm Water Conveyance System" means private and public drainage facilities by which stonn water may be conveyed to Receiving Waters, such as: natural drainages, roads, streets, constructed channels, aqueducts, storm drains, pipes, street gutters, or catch basins. ❑ "Streets, Roads, I lighways, and Freeways" means any project that is not part of a routine maintenance activity, and would create a new paved surface that is 5,000 square feet or Page 6 greater used for the transportation of automobiles, trucks, motorcycles and other vehicles. For the purposes of SUSMP requirements, Streets, Roads, Highways and Freeways do not include trenching and resurfacing associated with utility work; applying asphalt overlay to existing pavement; new sidewalk, pedestrian ramps, or bike lane construction on existing roads; and replacement of damaged pavement. u "Treatment Control (Structural) BMP" means any engineered system designed and constructed to remove pollutants from urban runoff. Pollutant removal is achieved by simple gravity settling of particulate pollutants, filtration, biological uptake, media adsorption or any other physical, biological, or chemical process. Where requirements of the local SI.JSMP conflict with established local codes, (c.g., specific language of signage used on storm drain stenciling), National City may continue the local practice and modify the SUSMP to he consistent with the code, except that to the extent that the standards in the SUSMP arc more stringent than those under local codes, such more stringent standards shall apply. This SUSMP is based on the Municipal Permit as it was in force in January 2007, except as that Municipal Permit was directed to be revised by the State Water Resources Control Board. If as a result of court action any part of the Municipal Permit is invalidated, stayed, or required to be revised by a final judgment, National City's SUSMP and local ordinances may be appropriate. National City has identified the department(s) responsible for ensuring SIJSMP requirements are implemented in its Jurisdictional URMP, and the roles and responsibilities each department possesses. At a minimum, for discretionary projects, SUSMP requirements shall be incorporated into the project design and shown on the plans prior to decision -maker approval of discretionary permits. For projects requiring only ministerial permits, SUSMP requirements shall he incorporated into the project design and shown on the plans prior to the issuance of any ministerial permits. National City's departments carrying out public projects that are not required to obtain permits shall be responsible for ensuring SUSMP requirements are incorporated into the project design and shown on the plans prior to bidding for construction contracts, or equivalent. For public projects SUSMP requirements must be incorporated into the project design and shown on the plans before allowing the project to commence. Page 7 Section VI provides a procedure for identifying a project's pollutants and conditions of concern, and addressing these through site design, source control, and treatment control storm water BMPs. All priority projects shall implement one or a combination of storm water BMPs, including, 1) LII) and site design RMPs, 2) source control BMPs and, 3) structural treatment BMPs after the pollutants and conditions of concern have been identified. Storm water BMPs, from those listed in Appendix A: "Approved Storm Water Best Management Practices", shall be considered and implemented where determined applicable and feasible by National City. Additional information on BMPs is included in the notes to Table 3 and in the references in Appendix B. The storm water BMPs shall adhere to the requirements in Section VI of this Model SUSMP, and shall be correctly designed so as to remove pollutants to the maximum extent. practicable. A flow chart summarizing the storm water I3MI' selection procedure is provided in Figure 1. Site Design Storm Water Treatment Credits National City agrees it may develop and submit for Regional Roard review and approval a Site Design Storm Water Treatment Credits program that allows reductions in the volume or flow of storm water that must he captured or treated on a project in return for the inclusion of specified project design features in the project, and further agree that any such submittal shall be deemed to be a part of this Model SUSMP jointly submitted to the Regional Board for review and approval. Any such model program shall specify the conditions under which project proponents can be credited for the use of site design features and low impact development techniques that can reduce the volume of storm water runoff, preserve natural areas, and minimize the pollutant loads generated and potentially discharged from the site. Provided, however that if a method for determining site design credits is developed on a time schedule that will permit further National City review prior to submission to the Regional Board, that proposal shall first be submitted to the Copermittees and if agreed to by the Copermittees will be submitted to the Regional Board as a single regional model. Any Copennittee may adopt and implement a Storm Water Credit Program consistent with this model approved by the Regional Board. Altemative Methods for Achieving Treatment Requirements National City may implement the Local Equivalent Area Drainage (LEAD) Method, as proposed by the City of San Diego in its May 16, 2002 letter (Appendix C), for meeting the BMP requirements in Section VI.2.c, Step 8, "Design to Treatment Control BMP Standards." The alternative method must minimally meet the following criteria: • The alternative treatment area shall be located within the proximity of the project; • The altcmative treatment area shall discharge to the same receiving water as the project; • The alternative treatment area shall be equivalent or greater than the project footprint; • The alternative treatment area shall have an equivalent or greater impervious surface area than the project; Page 8 • The alternative treatment area shall have an equivalent or greater pollutant Toad than the project; • Site Design and Source Control BMPs (Section VI.2.a & b) shall he required in the project design; • Alternative treatments shall be limited to redevelopment and/or infill projects. National City may implement the alternative LEAD method for no more than three pilot projects within its jurisdiction during this permit cycle. For each project where an alternative method is implemented, the effectiveness of the alternative method shall he monitored and reported on to the Regional Board by the end of the permit -cycle. Page 9 r Figure 1. Storm Water BMP Selection Procedure Flow Chart 1. Identify Pollutants from proposed project (Section VI.1.a) • 2. Identify Pollutants & Conditions of Concern in Receiving Waters (Section VI.1.b) NO YES Would the Project Generate Pollutants or Conditions of Concern? Page 10 Project required to Implement: • • • Site Design • Source Control BMPs • BMPs for Individual Categories • Standard Treatment Control BMPs (Table 2) OR • Site Design • Source Control BMPs • BMPs for Individual Categories • Enhanced Treatment Control BMPs (Table 3) 1. IDENTIFY POLLUTANTS & CONDITIONS OF CONCERN Priority project proponents shall use this guidance to identify pollutants and conditions of concern, for which they need to mitigate or protect against. Once identified, appropriate control measures for these pollutants and conditions are specified in Section VI.2, "Establish Storm Water BMPs." Standard control measures are required based on pollutants commonly associated with the proposed project type (see Table 2, "Standard Storm Water BMP Selection Matrix"). Priority projects required to implement structural treatment control BMPs using the standard BMP selection procedure should use Table 3, "Enhanced Treatment Control BMP Selection Matrix," to aid in selecting the structural treatment BMP(s) from Appendix A that would have the greatest pollutant removal efficiency for projects. Enhanced control measures are required for projects anticipated to generate pollutants that are also identified as pollutants of concern in the project's downstream receiving water(s) (see Table 3). National City will incorporate the requirements listed in Sections VI.1.a-c in the procedure for identifying pollutants and conditions of concern in its SUSMP. For private priority projects, National City shall require the information to be provided with the project application prior to being deemed complete. For public priority projects, National City shall approve the information prior to bidding for construction contracts. General Categories of Water Pollution Urban runoff from a developed site has the potential to contribute pollutants, including oil and grease, suspended solids, metals, gasoline, pesticides, and pathogens to the storm water conveyance system and receiving waters. For the purposes of identifying pollutants of concern and associated storm water BMPs, pollutants are grouped in nine general categories as follows: 1. Sediments - Sediments are soils or other surficial materials eroded and then transported or deposited by the action of wind, water, ice, or gravity. Sediments can increase turbidity, clog fish gills, reduce spawning habitat, lower young aquatic organisms survival rates, smother bottom dwelling organisms, and suppress aquatic vegetation growth. 2. Nutrients - Nutrients are inorganic substances, such as nitrogen and phosphorus. They commonly exist in the form of mineral salts that are either dissolved or suspended in water. Primary sources of nutrients in urban runoff are fertilizers and eroded soils. Excessive discharge of nutrients to water bodies and streams can cause excessive aquatic algae and plant growth. Such excessive production, referred to as cultural eutrophication, may lead to excessive decay of organic matter in the water body, loss of oxygen in the water, release of toxins in sediment, and the eventual death of aquatic organisms. 3. Metals Metals are raw material components in non-metal products such as fuels, adhesives, paints, and other coatings. Primary source of metal pollution in storm water are typically commercially available metals and metal products. Metals of concern include cadmium, chromium, copper, lead, mercury, and zinc. Lead and chromium have been used as corrosion inhibitors in primer coatings and cooling tower systems. At low concentrations naturally occurring in soil, metals are not toxic. However, at higher C:\Uwimnr. m1 tinlmps..n,, ,,M1 4 St, 1..I $T1a19NX/to. Fik,(ll K LSl ISP.0 kw NC • 2 19I auu.L to Pagell concentrations, certain metals can be toxic to aquatic life. Humans can be impacted from contaminated groundwater resources, and hioaccumulation of metals in fish and shellfish. Environmental concerns, regarding the potential for release of metals to the environment, have already led to restricted metal usage in certain applications. 4. Organic Compounds — Organic compounds are carbon -based. Commercially available or naturally occurring organic compounds are found in pesticides, solvents, and hydrocarbons. Organic compounds can, at certain concentrations, indirectly or directly constitute a hazard to life or health. When rinsing off objects, toxic levels of solvents and cleaning compounds can be discharged to storm drains. Dirt, grease, and grime retained in the cleaning fluid or rinse water may also adsorb levels of organic compounds that arc harmful or hazardous to aquatic life. 5. Trash & Debris — Trash (such as paper, plastic, polystyrene packing foam, and aluminum materials) and biodegradable organic matter (such as leaves, grass cuttings, and food waste) are general waste products on the landscape. The presence of trash & debris may have a significant impact on the recreational value of a water body and aquatic habitat. Excess organic matter can create a high biochemical oxygen demand in a stream and thereby lower its water quality. Also, in areas where stagnant water exists, the presence of excess organic matter can promote septic conditions resulting in the growth of undesirable organisms and the release of odorous and hazardous compounds such as hydrogen sulfide. 6. Oxygen -Demanding Substances — This category includes biodegradable organic material as well as chemicals that react with dissolved oxygen in water to form other compounds. Proteins, carbohydrates, and fats are examples of biodegradable organic compounds. Compounds such as ammonia and hydrogen sulfide are examples of oxygen -demanding compounds. The oxygen demand of a substance can lead to depletion of dissolved oxygen in a water body and possibly the development of septic conditions. 7. Oil and Grease - Oil and grease are characterized as high -molecular weight organic compounds. Primary sources of oil and grease are petroleum hydrocarbon products, motor products from leaking vehicles, esters, oils, fats, waxes, and high molecular -weight fatty acids. Introduction of these pollutants to the water bodies are very possible due to the wide uses and applications of some of these products in municipal, residential, commercial, industrial, and construction areas. Elevated oil and grease content can decrease the aesthetic value of the water body, as well as the water quality. 8. Bacteria and Viruses - Bacteria and viruses are ubiquitous micro-organisms that thrive under certain environmental conditions. Their proliferation is typically caused by the transport of animal or human fecal wastes from the watershed. Water containing excessive bacteria and viruses can alter the aquatic habitat and create a harmful environment for humans and aquatic life. Also, the decomposition of excess organic waste causes increased growth of undesirable organisms in the water. 9. Pesticides - Pesticides (including herbicides) are chemical compounds commonly used to control nuisance growth or prevalence of organisms. Excessive application of a pesticide may result in runoff containing toxic levels of its active component. Page 12 a. Identify Pollutants from the Project Area Using Table 1, identify pollutants that arc anticipated to be generated from the proposed priority project categories. Pollutants associated with any hazardous material sites that have been remediated or arc not threatened by the proposed project are not considered a pollutant of concern. Table 1. Anticipated and Potential Pollutants Generated by Land Use Type. Priority Project Categories Detached Residential _ Development Attached Residential Development Commercial Development > One Acre Industrial development > One Acre Automotive Repair Shops Restaurants Sediments X X Nutrients p(n Heavy Metals X X General Pollutant Categories Organic Compounds Trash Debris Oxygen Demanding Substances p(n X X p(5) X Oil & Grease X X X X X Bacteria & Viruses X p p(t) X Pesticides X X p(5) I lillsidc Development >5,000 tt7 X X X X X X Parking lots Retail Gasoline Outlets Streets, Ilighways & X p(i) X Freeways X — anticipated P = potential (I) A potential pollutant if landscaping exists on -site. (2) A potential pollutant if the project includes uncovered parking areAs. (3) A potential pollutant if land use involves food or animal waste products. (4) Including petroleum hydrocarbons. (5) Including solvents. pun p(I) X X p0) X P(5) X Page 13 b. Identify Pollutants of Concern in Receiving Waters Pollutants generated by the proposed priority project that exhibits one or more of the following characteristics arc considered primary pollutants of concern: • Current loadings or historical deposits of the pollutant are impairing the beneficial uses of a receiving water; ■ Elevated levels of the pollutant are found in water or sediments of a receiving water and/or have the potential to be toxic or to bioaccumulate in organisms therein; and • Inputs of the pollutant are at a level high enough to be considered potentially toxic. To identify pollutants of concern in receiving waters, each priority project shall, at a minimum, do the following: 1. For each of the proposed projects discharge points, identify the receiving water(s) that each discharge point proposes to discharge to, including hydrologic unit basin numbcr(s), as identified in the most recent version of the Water Quality Control Plan for the San Diego Basin', prepared by the San Diego Regional Water Quality Control Board. 2. Identify any receiving waters, into which the developed area would discharge to, listed on the most recent list of Clean Water Act Section 303(d) impaired water bodies'. List any and all pollutants for which the receiving waters are impaired. 3. Compare the list of pollutants for which the receiving waters arc impaired with the pollutants anticipated to be generated by the project (as identified in Table 1). Any pollutants identified by Table 1, which are also causing unpairmcnt of receiving waters, shall he considered primary pollutants of concern. For projects where no primary pollutants of concern exist, those pollutants identified through the use of Table 1 shall he considered secondary pollutants of concern. c. Identify Conditions of Concern in Receiving Waters Common impacts to the hydrologic regime resulting from development typically include increased runoff volume and velocity; reduced infiltration; increased flow frequency, duration, and peaks; faster time to reach peak flow; and water quality degradation. These changes have the potential to permanently impact downstream channels and habitat integrity. A change to a priority project site's hydrologic regime would be considered a condition of concern if the change would impact downstream channels and habitat integrity. 1. http://www.swrcb.ca.gov/—rwgcb9/Programs/Planning_and_Services/SD Basin/sd_basin.html 2. http://www.swrcb.ca.gov/tmd1/303d_lists.html, San Diego is in Region 9 Page 14 Because of these potential impacts, municipal staff may require that the following steps be followed for Priority Projects which, in their judgment, may impact the hydrologic regime: 1. Evaluate the project's conditions of concern in a drainage study report prepared by a registered civil engineer in the Statc of California, with experience in fluvial geomorphology and water resources management. The report shall consider the project area's location (from the larger watershed perspective), topography, soil and vegetation conditions, percent impervious area, natural and infrastructure drainage features, , wet season groundwater depth, and any other relevant hydrologic and environmental factors to be protected specific to the project area's watershed. 2. As part of the drainage study, a qualified, licensed professional shall provide a report on proposed infiltration techniques (trenches, basins, dry wells, permeable pavements with underground reservoir for infiltration) regarding any potential adverse gcotechnical concerns. Geotcchnical conditions such as slope stability, expansive soils, compressible soils, seepage, groundwater depth, and loss of foundation or pavement subgrade strength should be addressed, and mitigation measures should he provided. 3. As part of the drainage study, the civil engineer shall conduct a field reconnaissance to observe and report on downstream conditions, including undercutting erosion, slope stability, vegetative stress (due to flooding, erosion, water quality degradation, or loss of water supplies) and the area's susceptibility to erosion or habitat alteration as a result of an altered flow regime. 4. The drainage study shall compute rainfall runoff characteristics from the project area including, at a minimum, runoff volume, time of concentration, and retention volume. These characteristics shall he developed for the two-year and 10-year frequency, Type I storm, of six -hour or 24-hour duration (whichever is the closer approximation of the site's time of concentration), during critical hydrologic conditions for soil and vegetative cover'. The drainage study shall report the project's conditions of concern based on the hydrologic and downstream conditions discussed above. Where downstream conditions of concern have been identified, the drainage study shall establish that pre -project hydrologic conditions affecting downstream conditions of concern would be maintained by the proposed project, satisfactory to National City, by incorporating the site design, source control, and treatment control requirements identified in Section VI.2. Priority Development Projects that disturb 50 acres or more are subject to the City's Interim Hydromodification Criteria (IHC). The ll-IC was developed regionally and was modified from the Contra Costa Hydromodification Plan. Iwo compliance options are provided — curve - matching based on continuous simulation modeling, and implementation of LID. "1'he curve - matching approach as described below is currently available for use by Priority Development Projects within the City's jurisdiction. The range of flows to be managed under the curve- 3. Design storms can be found at httpJ/www.wrcc.dri.edulpcpnfreq.html. The Copermittees may calculate the storm events using local rain data. In addition, isopluvial maps contained in the County of San Diego Hydrology Manual may be used to extrapolate rainfall data to areas where insufficient data exists. If isopluvial maps are selected, Copermittees shall describe their method for using isopluvial maps in their Jurisdictional SUSMP. Page 15 matching option is expressed as a percentage of the 5-year peak flow (Q5) based on the understanding that dominant discharge for southern California streams is in the vicinity of Q5. The LID implementation option may become available later if design and sizing procedures are created and approved regionally during the course of developing the final Hydromodification Plan. If LID design guidance is not approved during the period that the IBC are in place, the curve -matching standard is the default compliance standard. 1. Curve -matching based on continuous simulation modeling: Estimated post -project runoff durations and peak flows do not exceed pre -project durations and peak flows. The project proponent must use a continuous simulation hydrologic computer model such as t1SEPA's llydrograph Simulation Program —Fortran (IISPF) to simulate pre - project and post -project runoff, including the effect of proposed Integrated Management Practices (TMPs), detention basins, or other storm water management facilities. To use this method, the project proponent shall compare the pre -project and post -project model output for a rainfall record of at least 30 years, and shall show the following criteria are met: a. For flow rates from 20% of the pre -project 5-year runoff event (0.2Q5) to the pre -project 10-year runoff event (Q10), the post -project discharge rates and durations shall not deviate above the pre -project rates and durations by more than 10% over more than 10% of the length of the flow duration curve. h. For flow rates from 0.2Q5 to Q5, the post -project peak flows shall not exceed pre -project peak flows. For flow rates from Q5 to Q10, post -project peak flows may exceed pre -project flows by up to 10% for a 1-year frequency interval. For example, post -project flows could exceed pre -project flows by up to 10% for the interval from Q9 to Q I0 or from Q5.5 to Q6.5, but not from Q8 to Q10. (Note that the 0.2Q5 end of the range may be modified). 2. Implementation of LID 1MPs. The project proponent may implement LID IMPS to manage hydrograph modification impacts, using design procedures, criteria, and sizing factors (ratios of 'JD IMP volume or area to tributary area) as specified by the City of National City once standard design procedures, criteria, and sizing factors are accepted by the City. The LID IMP designs and sizing factors shall be determined using continuous simulation of' runoff from a long-term rainfall record. Priority Development Projects disturbing 50 acres of more are exempt from the above INC when: 1. The project would discharge into channels that are concrete -lined or significantly hardened (e.g., with rip -rap, sackcrete, etc.) downstream to their outfall in bays or the ocean; 2. The project would discharge into underground storm drains discharging directly to bays or the ocean; or 3. The project would discharge to a channel where the watershed areas below the project's discharge points are highly impervious (e.g. >70%)." Page 16 4. The applicant conducts an assessment incorporating sediment transport modeling across the range of gcomorphically-significant flows that demonstrates to the permitting agencies satisfaction that the project flows and sediment reductions will not detrimentally affect the receiving water. 2. ESTABLISH STORM WATER BMI's Site design BMPs reduce the need for source and/or treatment control BMPs, and source control BMI's may reduce the amount of treatment control RMPs needed. Throughout all the following sections, all priority projects shall consider, and incorporate and implement where expressly required by the Permit and if not so required where determined applicable and feasible by National City, storm water IIMPs into the project design, in the following progression: • Site Design BMPs • Source Control BMPs • Treatment Control BMPs At a minimum, priority projects must implement Lfl) site design BMPs and source control RMPs, and must also implement treatment control RMPs unless a waiver is granted based on the infeasibility of all treatment control BMPs. LID BMPs must meet minimum requirements in municipal permit section D.1.d.(4). BMPs must also achieve certain performance standards set out in the municipal permit section D.1.d.(5) and (6). Selection of BMPs from the menus included in this SUSMP, using the rules set out in this SUSMP, must fulfill these requirements. In addition, runoff treated by LID and site design or source control BMPs, such as rooftop runoff treated in landscaping, may be useful in reducing the quantity of runoff required to be treated in Section VI.2.c, "Treatment Control BMPs." To select a structural treatment BMP using the Treatment Control BMP Selection Matrix, each priority project shall compare the list of pollutants for which the downstream receiving waters are impaired (if any), with the pollutants anticipated to be generated by the project (as identified in Table 1). Any pollutants identified by Table I which also cause a Clean Water Act section 303(d) impairment of the receiving waters of the project shall be considered primary pollutants of concern. Priority projects that are anticipated to generate a primary pollutant of concern shall meet all applicable requirements in Section VI.2, and shall select a singe or combination of storm water BMPs from Table 3 that are effective for pollutant removal of the particular primary pollutant(s) of concern. Alternatively, a project proponent may elect to implement a combination of LID BMPs that either disperse and infiltrate, or direct to biorctcntion facilities, the flows from all impervious areas on -site. These BMPs are presumed to provide maximum extent practicable treatment for all pollutants of concern; therefore no further documentation of the treatment BMP selection process is required. Page 17 Priority projects that are not anticipated to generate a pollutant for which the receiving water is Clean Water Act Section 303(d) impaired shall meet applicable standard requirements in Section VI.2, and shall select a single or combination of stomm water BMPs from Table 3 which are effective for pollutants removal of the identified secondary pollutants of concern, consistent with the "maximum extent practicable" standard defined in Attachment C of the Municipal Permit. Where a site generates both primary and secondary pollutants of concern, primary pollutants of concern receive priority of BMP selection. For such sites, selected BMPs must only maximize pollutants removal for the primary pollutants of concern. Where a site generates only secondary pollutants of concern selected BMPs shall target the secondary pollutants of concern to be the most significant for the project. Selected BMPs must be effective for the widest range of pollutants of concern with the maximum extent practicable standard defined in Attachment C of the municipal Permit. Treatment control BMPs with a high or medium pollutant removal efficiency for the project's most significant pollutant of concern shall be selected. Treatment control BMPs with a low removal efficiency ranking shall only he approved by the Copermittee when a feasibility analysis has been conducted which exhibits that implementation of treatment control BMPs with a high or medium removal efficiency ranking are infeasible. Treatment control BMPs shall not be constructed within a receiving water. Alternative storm water BMPs not identified in Table 3 may he approved at the discretion of National City, provided the altcmative BMP is as effective in removal of pollutants of concern as other feasible BMPs listed in Table 3. Page 18 Table 2. Standard Storm Water BMP Selecdon Matrix. Priority Project Category Site Design BMW Source Control RAIPs/21 Requ rements Applicable to Individual Priority Project Cutegoriesf4t en C. . Maintenance Hays Detached Residential Development R R Attached Residential Development R R ry 0 3 v A — o o .. R Commercial Development > One Acre Industrial Development > One Acre R R Automotive Repair Shop Restaurants Hillside Development >5,000 ft2 Parking Lots Streets, Ilighways & Freeways Retail Gasoline Outlets R R R R R R R K K It K R R R R k R R R R R R(t) R R R — Required; select BMPs as required from the applicable steps in Section VL2a & b, or equivalent in Appendix A. (I) Refer to Section V I.2.a. (2) Refer to Section VI.2.1i. (3) Priority project categories must apply specific storm water BMP requirements, where applicable. Projects are subject to the requirements of all priority project categories that apply. (4) Applies if the paved arca totals>5 000 square feet or with > I S parking spaces and is potentially exposed to mbar runot% Cnitx.utmoo ad Sdiuy4urmmkInul SOI ile.\Ta,nnry In.rto 19n'.q KSlSUSMP I .r NC • 2 1918 andub dnc Page 19 Table 3. Treatment Control BMP Selection Matrix. Trash Racks & Hydro -dynamic Devices Pollutants of Concern Bioretention Facilities (LID) Settling Basins (Dry Ponds) Wet Ponds and Wetlands Infiltration Facilities or Practices (LID) Media Filters High rate biofilters High -rate media Iiltm Coarse Sediment and Trash Ili high High High high High High High Pollutants that tend to associate with fine particles during treatment high High High High High Medium Medium Low Pollutants that tend to be dissolved following treatment Medium I Low Medium High tow Low Low Iuw ..._ Notes on Treatment Control BMP Categories All rankings are relative. Ranking of all facilities assumes proper sizing, design, and periodic maintenance. Following are general descriptions of each category. • Bioretention Facilities (infiltration planters, flow -through planters, bioretention areas, and bioretention swales). Facilities are designed to capture runoff and infiltrate slowly through soil media which also supports vegetation. Bioretention facilities, except for flow -through planters, effectively promote infiltration into native soils. In clay soils, facilities may capture excess treated runoff in an underdrain piped to the municipal storm drain system. Typical criteria: an infiltration surface arca at least 4% of tributary impervious urea, 6-inch average depth of top reservoir, 18-inch soil layer, 12-inch to 18- inch gravel subsurface storage layer. • Settling 13asins and Wetlands (extended detention basins, "wet" basins, decorative or recreational lakes or water features also used for storm water treatment, constructed wetlands). Facilities are designed to capture a minimum water quality volume of 80% of total runoff and detain for a minimum of 48 hours. Somc wetland designs have proven effective in removing nutrients, but performance varies. • Infiltration Facilities or Practices (infiltration basins, infiltration trenches, dry wells, dispersal of runoff to landscape, pervious pavements). These facilities and landscape designs capture, retain, and infiltrate a minimum of 80% of runoff into the ground. Infiltration facilities are generally only feasible in permeable (Hydrologic Soil Group A or B) soils. Volume and area of infiltration facilities depends on soil permeability and safety factor used. Typical criteria: Infiltration facilities should have pretreatment to remove silt to prolong life of the facility. A 10-foot vertical separation from average seasonal groundwater depth is required. Dispersal to landscape may he accomplished in any soil type and generally requires a maximum 2:1 ratio irnpervious:pervious and concave topography to ensure the first I inch of rainfall is retained. Page 20 • Media Filters (sand filters). Filters designed to treat runoff produced by a rainfall of 0.2 inches per hour (or 2 :.I 85th percentile hourly rainfall intensity) by slow infiltration through sand or other media. Typical criteria: Surface loading rate not to exceed 5 inches/hour. Entire surface of the sand must be accessible for maintenance. • High Rate Biofilters (tree wells, typically proprietary). Biofilters with specially designed media to rapidly filter runoff while removing some pollutants. Filterra® (proprietary version) recommends surface loading rates of up to 100 inches/hour. • High -rate Media Filters (typically proprietary). Vaults with replaceable cartridge filters filled with inorganic media. Notes on Pollutants of Concern: In Table 3, Pollutants of Concern are grouped as gross pollutants, pollutants that tend to associate with fine particles, and pollutants that remain dissolved. Table 4. Pollutants and Associated Particle Sizes Pollutants that tend to associate with fine particles during treatment X X X Pollutant Sediment Nutrients Heavy Metals Organic Compounds Trash & Debris Oxygen Demanding Bacteria Oil & Crease Pesticides Coarse Sediment and Trash X X Pollutants That tend to be dissolved following treatment X X a. Low Impact Development (LID) and Site Design BMPs Priority project., shall be designed so as to minimize, directly connected impervious surfaces and to promote infiltration using LID techniques. Priority projects shall, to the maximum extent practicable, minimize the introduction of pollutants and conditions of concern that may result in significant impacts, generated from site runoff to the storm water conveyance system. Priority Projects shall also control post -development peak storm water runoff discharge rates and velocities to maintain or reduce pre -development downstream erosion and protect stream habitat. Although not mandatory, priority projects can address these objectives through the creation of a hydrologically functional project design that attempts to mimic the natural hydrologic regime. Many of these techniques are outlined and reviewed in the County of San Diego's LID Handbook and Appendices. Mimicking a site's natural hydrologic regime can.be pursued by: • Reducing imperviousness, conserving natural resources and areas, maintaining and using natural drainage courses in the storm water conveyance system, and minimizing clearing and grading. Page 21 • Providing runoff storage measures dispersed uniformly throughout a site's landscape with the use of bioretention facilities and detention, retention, and infiltration practices. These design principles offer an innovative approach to urban storm water management, one that does not rely on the conventional end -of -pipe or in -the -pipe structural methods but instead uniformly or strategically integrates storm water controls throughout the urban landscape. Useful resources for applying these principles, referenced in the appendix, include the County of San Diego's LID Handbook (2007), Start at the Source (1999), and Low -Impact Development Design Strategies (1999) ), the City of Portland's Stormwater Manual (2004), and the Contra Costa Clean Water Program's Stormwater C.3 Guidebook (2006).. Step 1: Objective: Maintain Pre -Development Rainfall Runoff Characteristics Priority projects shall control post -development peak storm water runoff discharge rates and velocities to maintain or reduce pre -development development downstream erosion. In addition, projects should control runoff discharge volumes and durations to the maximum extent practicable using the site design, source control, and treatment control requirements identified in Section V1.2. Design Concept 1: Minimize Project's Impervious Footprint & Conserve Natural Areas The following site design options shall be considered and shall be incorporated and implemented where determined applicable and feasible by National City, during the site planning and approval process, consistent with applicable General Plan policies and other development regulations. 1. Minimize and disconnect impervious surfaces. This can be achieved in various ways, including, but not limited to increasing building density (number of stories above or below ground) and developing land use regulations seeking to limit impervious surfaces. Decreasing the project's footprint can substantially reduce the project's impacts to water quality and hydrologic conditions. Page 22 2. Conserve natural areas, soils, and vegetation where feasible. Concentrating or clustering development on the least environmentally sensitive portions of a site while leaving the remaining land in a natural, undisturbed condition can achieve this. The following list provides a guideline for determining the least sensitive portions of the site, in order of increasing sensitivity. Jurisdictions should also refer to their Multiple Species Conservation Plans or other biological regulations, as appropriate. a. Areas devoid of vegetation, including previously graded areas and agricultural fields. b. Areas of non-native vegetation, disturbed habitats and eucalyptus woodlands. c. Areas of chamise or mixed chaparral, and non-native grasslands. d. Areas containing coastal scrub communities. e. All other upland conununities. f. Occupied habitat of sensitive species and all wetlands (as both are defined by National City). g. All areas necessary to maintain the viability of wildlife corridors. Within each of the previous categories, areas containing hillsides (as defined in this SUSMP) should be considered more sensitive than the same category without hillsides. 3. Construct walkways, trails, patios, overflow parking lots and alleys and other low -traffic areas with permeable surfaces, such as pervious concrete, permeable asphalt, unit pavers and granular materials. 4. Construct streets, sidewalks and parking lot aisles to the minimum widths necessary, provided that public safety and a walkable environment for pedestrians are not compromised. 5. Maximize canopy interception and water conservation by preserving existing native trees and shrubs, and planting additional native or drought tolerant trees and large shrubs. 6. Minimize the use of impervious surfaces, such as decorative concrete, in the landscape design. 7. Ilse natural drainage systems to the maximum extent practicable. R. Minimize soil compaction 9. Other site design options, which arc comparable, and equally effective. Page 23 r Design Concept 2: Minimize Directly Connected Impervious Areas (DCIAs) Priority projects shall consider, and incorporate and implement the following design characteristics, where determined applicable and feasible: 1. Where landscaping is proposed, drain rooftops into adjacent landscaping prior to discharging to the storm drain. 2. Where landscaping is proposed, drain impervious sidewalks, walkways, trails, and patios into adjacent landscaping. 3. Other design characteristics that is comparable and equally effective. Step 2: Protect Slopes and Channels Project plans shall include storm water BMPs to decrease the potential for erosion of slopes and/or channels, consistent with local codes and ordinances and with the approval of all agencies with jurisdiction, e.g., the U.S. Army Corps of Engineers, the San Diego Regional Water Quality Control Board, and the California Department of Fish and Game. The following design principles shall be considered, and incorporated and implemented where determined applicahlc and feasible by National City: 1. Minimize disturbances to Natural Drainages 2. Convey runoff safely from the tops of slopes. 3. Vegetate slopes with native or drought tolerant vegetation. 4. Control and treat flows in landscaping and/or other controls prior to reaching existing natural drainage systems. 5. Stabilize permanent channel crossings. 6. Install energy dissipaters, such as riprap, at the outlets of new storm drains, culverts, conduits, or channels that enter unlined channels in accordance with applicable specifications to minimize erosion. Energy dissipaters shall be installed in such a way as to minimize impacts to receiving waters. 7. Other design principles, which are comparable and equally effective. b. Source Control BMPs Step 3: Provide Storm Drain System Stenciling and Siinatte Storm drain stencils are highly visible source control messages, typically placed directly adjacent to storm drain inlets. The stencils contain a brief statement that prohibits the dumping of improper materials into the urban runoff conveyance system. Graphical icons, either illustrating anti -dumping symbols or images of receiving water fauna, are effective supplements to the anti- dumping message. Priority projects shall include the following requirements in the project design, where determined applicable and feasible by National City. Page 24 1. Provide stenciling or labeling of all storm drain inlets and catch basins within the project area with prohibitive language (such as: "NO DUMPING — I LIVE DOWNSTREAM") and/or graphical icons to discourage illegal dumping. 2. Post signs and prohibitive language and/or graphical icons, which prohibit illegal dumping at public access points along channels and creeks within the project area. 3. Maintain legibility of stencils and signs. Step 4: Design Outdoor Material Storage Areas to Reduce Pollution Introduction Improper storage of materials outdoors may increase the potential for toxic compounds, oil and grease, heavy metals, nutrients, suspended solids, and other pollutants to enter the urban runoff conveyance system. Where the priority project plans include outdoor areas for storage of hazardous materials that may contribute pollutants to the urban nmoff conveyance system, the following storm water BMPs arc required: Hazardous materials with the potential to contaminate urban runoff shall either be: (I) • placed in an enclosure such as, but not limited to, a cabinet, shed, or similar structure that prevents contact with runoff or spillage to the storm water conveyance system; or (2) protected by secondary containment structures such as berms, dikes, or curbs. The storage area shall he paved and sufficiently impervious to contain leaks and spills. The storage area shall have a roof or awning to minimize direct precipitation within the secondary containment area. Step 5: Design Trash Storage Areas to Reduce Pollution Introduction All trash container areas shall meet the following requirements (limited exclusion: detached residential homes): I. The area shall be paved with an impervious surface, designed not to allow nin-on from adjoining areas, screened or walled to prevent off -site transport of trash; or, 2. Attached lids shall he mounted on all trash containers that exclude rain, or a roof or awning be installed to minimize direct precipitation. Step 6:Use Efficient Irrigation Systems & Landscape Design Priority projects shall design the timing and methods of application of irrigation watcr to minimize the nmoff of excess irrigation water into the storm water conveyance system (with the limited exclusion of detached residential homes.) In compliance with the Water Conservation in Landscaping Act, the following methods to reduce excessive irrigation runoff shall he considered, and shall he incorporated and implemented where determined applicable and feasible by National City: Page 25 ``Formatted: Bullets and Numbering 1. Employment of rain shutoff devices to prevent irrigation after precipitation. 2. Design of irrigation systems to each landscape area's specific water requirements. 3. Use of flow reducers or shutoff valves triggered by a pressure drop to control water loss in the event of broken sprinkler heads or lines. 4. Employment of other comparable, equally effective, methods to reduce irrigation water runoff. Step 7: Incorporate Requirements Applicable to Individual Priority Proiect Categories Where identified in Table 2, the following requirements shall be incorporated into applicable priority projects during the storm water BMP selection and design process. Projects shall adhere to each of the individual priority project category requirements that apply to the project (e.g., a restaurant with more than 15 parking spaces would be required to incorporate the requirements for" g. Equipment Wash Areas" and "h. Parking Areas" into the project design). a. Private Roads The design of private roadway drainage shall use at least one of the following (for further guidance, see Start at the Source [19991): 1. Rural swale system: street sheet flows to vegetated swale or gravel shoulder, curbs at street comers, culverts under driveways and street crossings; 2. Urban curb/swale system: street slopes to curb, periodic swale inlets drain to vegetated swale/biofilter; 3. Dual drainage system: First tlush captured in street catch basins and discharged to adjacent vegetated swale or gravel shoulder, high flows connect directly to storm water conveyance system. 4. Other methods, which are comparable and equally effective within the project may be used. b. Residential Driveways & Guest Parking The design of driveways and private residential parking areas shall incorporate at least one of the following features: 1. Design driveways with shared access, flared (single lane at street) or wheelstrips (paving only under tires); or, draining into landscaping prior to discharging to the storm water conveyance system. 2. Pave temporary or guest parking on private residential lots with a permeable surface; or he, designed to drain into landscaping prior to discharging to the storm water conveyance system. 3. Other features which are comparable and equally effective. Page 26 c. Dock Areas Loading/unloading dock areas shall include or observe the following: 1. Loading dock areas shall be covered or drainage designed to preclude urban run-on and runoff. 2. Direct connections to storm drains from depressed loading docks (truck wells) shall be prohibited. 3. Other features may be used which are comparable and equally effective. d. Maintenance Bays Maintenance bays shall include and observe the following: 1. Repair/maintenance bays shall be installed indoors; or, be designed to preclude urban run- on and runoff. 2. The repair/maintenance bay drainage system shall be designed to capture all wash water, leaks and spills. Drains shall be connected to a sump for collection and disposal. Direct connection of the repair/maintenance bays to the storm drain system shall be prohibited. if required by National City, an Industrial Waste Discharge Permit shall be obtained by the business. OR 3. Other features which are comparable and equally effective may be used. e. Vehicle Wash Areas Priority projects that include areas for washing/steam cleaning of vehicles shall consider, and shall incorporate and implement where determined applicable and feasible by National City, the following. 1. Be self-contained; or covered with a roof or overhang; 2. Be equipped with a clarifier or other pretreatment facility; 3. I3e properly connected to a sanitary sewer. 4. Consider other features which are comparable and equally effective for design and use. f Outdoor Processing Areas Outdoor process equipment operations, such as rock grinding or crushing, painting or coating, grinding or sanding, degreasing or parts cleaning, landfills, waste piles, and wastewater and solid waste treatment and disposal, and other operations determined to be a potential threat to the water quality by National City shall adhere and observe the following requirements: Page 27 1. Areas that would be the most significant source of pollutants are to be covered or enclosed; or, slope the area toward a dead-end sump; or be discharged to the sanitary sewer system following appropriate treatment in accordance with conditions established by the applicable sewer agency. 2. Grade or berm the area to prevent run-on from surrounding areas. 3. Storm drains shall not be installed in areas of equipment repair. 4. Other features, which are comparable or equally effective, may be used. g. Equipment Wash Areas Outdoor equipment/accessory washing and steam cleaning activities at priority projects shall use or observe at least one of the following: 1. Be self-containcd, or be covered with a roof or overhang; 2. Be equipped with a clarifier, grease trap or other pretreatment facility, as appropriate; 3. Be properly connected to a sanitary sewer. 4. Use other features, which are comparable or equally effective. h. Parking Areas To minimize the offsite transport of pollutants from parking areas, the following design concepts shall he considered, and shall he incorporated and implemented where determined applicable and feasible by National City: I. Where landscaping is proposed in parking areas, landscape areas are to be incorporated into the drainage design. 2. Construct overflow parking (parking stalls provided in excess of National City's minimum parking requirements) with permeable paving. 3. IJsc other design concepts, which are comparable and equally effective. Roadways Priority roadway projects shall select treatment control BMPs following the enhanced treatment control selection procedure identified in Section V1.2. "Establish Storm Water BMPs." j. Fueling Areas Page 2t Fuel dispensing areas shall contain the following: 1. Use an overhanging roof structure or canopy. The cover's minimum dimensions must be equal to or greater than the area within the grade break. The cover must not drain onto the fuel dispensing area and the downspouts must be routed to prevent drainage across the fueling area. The fueling area shall drain to the project's treatment control BMP(s) prior to discharging to the storm water conveyance system. 2. Be paved with Portland cement concrete (or equivalent smooth impervious surface). The use of asphalt concrete shall be prohibited. 3. An appropriate slope to prevent ponding shall be provided, and must be separated from the rest of the site by a grade break that prevents run-on of urban runoff. 4. At a minimum, the concrete fuel dispensing area shall extend 6.5 feet (2.0 meters) from the comer of each fuel dispenser, or the length at which the hose and nozzle assembly may be operated plus 1 foot (0.3 meter), whichever is less. k. Hillside Landscaping Hillside areas, as defined in this SUSMI', that are disturbed by project development shall be landscaped with deep-rooted, drought tolerant plant species selected for erosion control, satisfactory to National City. a. Treatment Control BMPs Minimizing a development's detrimental effects on water quality can be most effectively achieved through the use of a combination of site design, source and treatment control storm water BMPs. Priority projects shall he designed to remove pollutants of concern from the storm water conveyance system to the maximum extent practicable through the incorporation and implementation of treatment control BMPs. In meeting the requirements in this section, priority projects shall implement a single or combination of stone water BMPs that will remove anticipated pollutants of concern, as identified by the procedure in Section VI.I, in site runoff to the maximum extent practicable. Treatment control BMPs with a high or medium pollutant removal efficiency for the project's most significant pollutant of concern shall be selected. Treatment control BMPs with a low removal efficiency ranking shall only be approved by the City when a feasibility analysis has been conducted which exhibits that implementation of treatment control 13MPs with a high or medium removal efficiency ranking are infeasible. "Treatment control BMPs must be implemented unless a waiver is granted to the project by National City based on the infeasibility of any treatment control BMP. Step 8: Desien to Treatment Control BMP Standards All priority projects shall he designed, constructed and shall implement structural treatment control BMPs that meet the design standards of this section, unless specifically exempted by the limited exclusions listed at the end of Step R. Structural treatment control BMPs required by this section shall be operational prior to the use of any dependent development, and shall he located Page 29 and designed in accordance with the requirements in Step 8 and Step 9. National City may choose to eliminate one or more of the numeric volume or flow sizing methods listed below. Volume 1. Volume -based BMPs shall be designed to mitigate (infiltrate, filter, or treat) either: i. The volume of runoff produced from a 24-hour 85th percentile storm event, as determined from the local historical rainfall record (0.6 inch approximate average for the San Diego County area)4; or ii. The volume of runoff produced by the 85th percentile 24-hour runoff event, determined as the maximized capture urban runoff volume for the area, from the formula recommended in Urban Runoff -Quality Management, WEFManual of Practice No. 23/ ASCE Manual of Practice No. 87, (1998); or iii. The volume of annual runoff based on unit basin storage volume, to achieve 90 percent or more volume treatment by the method re ommended in California Stormwater Rest Management Practices Handbook—Industrial/Commercial, (1993), or iv. The volume of runoff, as determined from the local historical rainfall record, that achieves approximately the same reduction in pollutant loads and flows as achieved by mitigation of the 85th percentile 24-hour runoff event,5 OR Flow 2. Flow -based 13MPs shall be designed to mitigate (infiltrate, filter, or treat) either: i. The maximum flow rate of runoff produced from a rainfall intensity of 0.2 inch of rainfall per hour for each hour of a storm event; or ii. The maximum flow rate of runoff produced by the 85th percentile hourly rainfall intensity, as determined from the local historical rainfall record, multiplied by a factor of two; or 4. This volume is not a single volume to be applied to all of San Diego County. The size of the 85'" percentile storm event is different for various parts of the County. Nationals City has calculated the 851' percentile storm event using local rain data. In addition, isopluvial maps contained in the County of San Diego Hydrology Manual may be used to extrapolate rainfall data to areas where insufficient data exists. If isopluvial maps are selected, Copemiittees shall describe their method for using isopluvial maps In their Jurisdictional SUSMP. 5. Under this volume criterion, hourly rainfall data may be used to calculate the 85'" percentile storm event, where each storm event is identified by its separation from other stoma events by at least six hours of no rain. If hourly rainfall data is selected, National City shall describe the method using hourly rainfall data in its Jurisdictional SUSMP. !'age 30 iii. The maximum flow rate of runoff, as determined from the local historical rainfall record, that achieves approximately the same reduction in pollutant Toads and flows as achieved by mitigation of the 85`h percentile hourly rainfall intensity multiplied by a factor of two. Limited Exclusions: I. Proposed restaurants, where the land area for development or redevelopment is less than 5,0011 square feet, are excluded from the numerical sizing criteria requirements listed in Section V1.2.c, Step 8. 2. Where significant redevelopment results in an increase of less than 50 percent of the impervious surfaces of a previously existing development, and the existing development was not subject to SUSMP requirements, the numeric sizing criteria discussed in Section VI.2.c, Step 8 shall apply only to the addition, and not to the entire development. Step 9: Locate BMPs Near Pollutant Sources Structural treatment control storm water 13MPs should be implemented close to pollutant sources to minimize costs and maximize pollutant removal prior to runoff entering receiving waters. Such BMPs may be located on- or off -site, be used singly or in combination, or be shared by multiple new developments, pursuant to the following requirements: I. All structural treatment control BMPs shall he so located as to infiltrate, filter, and/or treat the required runoff volume or flow prior to its discharge to any receiving water body supporting beneficial uses; 2. Multiple post -construction structural treatment control BMPs for a single priority development project shall collectively be designed to comply with the design standards of Step 8; 3. Shared storm water BMPs shall be operational prior to the use of any dependent development or phase of development. The shared BMPs shall only be required to treat the dependent developments or phases of development that are in use; 4. Interim storm water BMPs that provide equivalent or greater treatment than is required by Section 3.a may he implemented by a dependent development until each shared BMP is operational. If interim BMPs are selected, the BMPs shall remain in use until permanent BMPs arc operational. Step 10: Restrictions on Use of Infiltration BMPs Three factors significantly influence the potential for urban runoff to contaminate ground water. They are: (i) pollutant mobility; (ii) pollutant abundance in urban runoff, and, (iii); soluble fraction of pollutant. The risk of contamination of groundwater may be reduced by pretreatment of urban runoff. A discussion of limitations and guidance for infiltration practices is contained in Potential Groundwater Contamination from Intentional and Non -Intentional Stormwater btfltration, Report No. EPA/600/R-94/051, USEPA (1994). Page 31 To protect groundwater quality, National City shall apply restrictions to the use of any BMPs that are designed to primarily function as infiltration devices (such as infiltration trenches and infiltration basins). As additional ground water basin data is obtained, National City may develop additional restrictions on the use of any BMPs that allow incidental infiltration. At a minimum, the use of structural treatment BMPs designed to primarily function as infiltration devices shall meet or observe the following conditions6: 1. Urban runoff from commercial developments shall undergo pretreatment to remove both physical and chemical contaminants, such as sedimentation or filtration, prior to infiltration. 2. All dry weather flows shall he diverted from infiltration devices except for those non - storm water discharges authorized pursuant to 40 CFR 122.26(d)(2)(iv)(B)(1): diverted stream flows, rising ground waters, uncontaminated ground water infiltration [as defined at 40 CFR 35.2005(20)] to storm water conveyance systems, uncontaminated pumped ground water, foundation drains, springs, water from crawl space pumps, footing drains, air conditioning condensation, flow from riparian habitats and wetlands, water line flushing, landscape irrigation, discharges from potable water sources other than water main breaks, irrigation water, individual residential car washing, and dechlorinated swimming pool discharges. 3. Pollution prevention and source control RMPs shall be implemented at a level appropriate to protect groundwater quality at sites where infiltration structural treatment BMPs are to be used. 4. The vertical distance from the base of any infiltration structural treatment BMP to the seasonal high groundwater mark shall be at least 10 feet or as determined on an individual, site -specific basis by the Copermittee. Where groundwater does not support beneficial uses, this vertical distance criterion may he reduced, provided groundwater quality is maintained. 5. The soil through which infiltration is to occur shall have physical and chemical characteristics (such as appropriate cation exchange capacity, organic content, clay content, and infiltration rate) that are adequate for proper infiltration durations and treatment of urban runoff for the protection of groundwater beneficial uses. 6. Infiltration structural treatment BMPs shall not be used for areas of industrial or light industrial activity; areas subject to high vehicular traffic (25,000 or greater average daily traffic on main roadway or 15,000 or more average daily traffic on any intersecting roadway); automotive repair shops; car washes; fleet storage areas (bus, truck, etc.); nurseries; and other high threat to water quality land uses and activities as designated by National City in its SUSMP. 7. The horizontal distance between the base of any infiltration structural BMP and any water supply wells shall be 100 feet or as determined on an individual, site -specific basis by National City. Where infiltration I3MPs are authorized, their performance shall be evaluated for impacts on 6. These conditions do not apply to structural treatment BMPs which allow incidental infiltration and are not designed to primarily function as infiltration devices (such as grassy swales. detention basins, vegetated buffer strips, constructed wetlands, etc.) Page 32 groundwater quality. In developing the Jurisdictional SIJSMP, National City shall develop additional restrictions on the use of treatment control BMPs that arc designed to primarily function as infiltration devices. National City shall consider the Section D.1.g. permit requirements to control the contribution of pollutants from one portion of the watershed to another portion of the watershed through interagency agreements among the Copennittees. In those instances where National City determines that implementation of proposed infiltration BMPs within their jurisdiction has a potential impact to groundwater quality in another jurisdiction, National City will require a notification to by those proposing such use, in addition to requiring the above protection measures. 3. PROVIDE PROOF OF ONGOING STORM WATER BMP MAINTENANCE National City shall not consider structural BMPs "effective," and therefore shall not accept storm water BMPs as meeting the MEP standard, unless a mechanism is in place that will ensure ongoing long-term maintenance of all structural BMPs. This mechanism may he provided by National City or be required by the project proponent. As part of project review, if a project proponent is required to include interim or permanent structural BMPs in project plans. National City shall require that the applicant to provide verification of maintenance requirements through such means as may be appropriate, at the discretion of National City, including, but not limited to covenants, legal agreements, maintenance agreements, and/or conditional use permits. Maintenance Mechanisms 1. Public entity maintenance: National City may approve a public or acceptable quasi - public entity (e.g., the County Flood Control District, or annex to an existing assessment district, an existing utility district, a state or federal resource agency, or a conservation conservancy) to assume responsibility for maintenance, repair and replacement of the I3MP. I Jnless acceptable to National City, public entity maintenance agreements shall ensure estimated costs are front -funded or reliably guaranteed, (e.g., through a trust fund, assessment district fees, bond, letter of credit or similar means). In addition, National City may seek protection from liability by appropriate releases and indemnities. National City shall have the authority to approve storm water BMPs proposed for transfer to any other public entity within its jurisdiction before installation. National City shall be involved in the negotiation of maintenance requirements with any other public entities accepting maintenance responsibilities within their respective jurisdictions; and in negotiations with the resource agencies responsible for issuing permits for the construction and/or maintenance of the facilities. National City must he identified as a third party beneficiary empowered to enforce any such maintenance agreement within their respective jurisdictions. 2. Project proponent agreement to maintain storm water BMPs: National City may enter into a contract with the project proponent obliging the project proponent to maintain, repair and replace the storm water BMP as necessary into perpetuity. Security or performance bonds may be required. Page 33 3. Assessment districts: National City may approve an Assessrent District or other funding mechanism created by the project proponent to provide funds for storm water BMP maintenance, repair and replacement on an ongoing basis. Any agreement with such a District shall be subject to thc Public Entity Maintenance Provisions above. 4. Lease provisions: In those cases where National City holds title to the land in question, and the land is being leased to another party for private or public use, National City may assure storm water BMP maintenance, repair and replacement through conditions in the lease. 5. Conditional use permits: For discretionary projects only, National City may assure maintenance of storm water HMI's through the inclusion of maintenance conditions in the conditional use permit. Security may or performance bond may be required. 6. Alternative mechanisms: National City may accept alternative maintenance mechanisms if such mechanisms are as protective those listed above. Verification Mechanisms For discretionary projects, National City -approved methods of storm water BMP maintenance shall be incorporated into the project's permit, and shall he consistent with permits issued by resource agencies before approval of discretionary permits. For projects requiring only ministerial permits, National City approved method of storm water BMP maintenance shall he incorporated into the permit conditions before the issuance of any ministerial permits. In all instances, the project proponent shall provide proof of execution of National City approved method of maintenance repair and replacement before the issuance of construction approvals. Public projects that arc not required to obtain National City permits shall be required and be responsible for ensuring that National City approved methods of storm water BMP maintenance, repair and replacement is executed prior to the commencement of construction. For all properties, the verification mechanism will include the project proponent's signed statement, as part of thc project application, accepting and guaranteeing responsibility for all structural BMP maintenance, repair and replacement, until a National City approved entity agrees to assume responsibility for structural BMP maintenance, repair and replacement. Maintenance Requirements I. Operation & Maintenance (O&119) Plan: National City shall ensure that a copy of an Operation & Maintenance (O&M) plan, prepared by the project proponent satisfactory to National City, is attached to the approved maintenance agreement, which describes the designated responsible party to manage the storm water BMP(s), employee's training program and duties, operating schedule, maintenance frequency, routine service schedule, specific maintenance activities, copies of resource agency permits, and any other necessary activities. At a minimum, maintenance agreements shall require the inspection and servicing of all structural BMPs on an annual basis. 'the project proponent or National City approved maintenance entity shall complete and maintain O&M forms to document all maintenance requirements. Parties responsible for the O&M plan shall retain records for at least 5 years. These documents shall be made available to National City for inspection upon request at any time. Page 34 2. Access Easement/Agreement: As part of the maintenance mechanism selected above, National City shall require an executed access easement that is binding on the land throughout the life of the project, or until such time that the storm water BMP requiring access is replaced. 4. WAIVER OF STRUCTURAL TREATMENT BMP REQUIREMENTS National City may provide for a project to be waived from the requirement of implementing structural treatment BMPs (Section VL2.c, "Design to Treatment Control BMP Standards") if infeasibility can he established. National City shall only grant a waiver of infeasibility when all available structural treatment BMPs have been considered and rejected as infeasible. National City shall notify the Regional Board within 5 days of each waiver issued and shall include the name of the person granting each waiver. Waivers may only be granted from structural treatment BMP and structural treatment BMP sizing requirements. Priority development projects, whether or not granted a waiver may not cause or contribute to an exceedance of water quality objectives. Pollutants in runoff from projects granted a waiver must still he reduced to the maximum extent practicable. National City will implement a waiver program or at its option also develop a SUSMP waiver impact fee program to require project proponents who have received waivers to transfer the savings in cost, or a proportionate share thereof, as determined by the Copermittee, to a storm water mitigation fund. National City shall notify the RWQCB ifa SUSMP waiver impact fee program is developed pursuant to this model SUSMP. SUSMP waiver impact fee program set out in jurisdictional SI.JSMP submissions, or in supplemental submissions if multiple Copermittecs establish a joint mitigation fund program for that watershed may be substituted. The Jointly Developed by San Diego Copermitees SUSMP does not preclude National City from imposing any other fees or charges on development projects that are permitted by law, or from managing or expending the monies received from such non-SUSMP programs in any other manner authorized by law. Page 35 APPENDIX A STORM WATER BEST MANAGEMENT PRACTICES The following are a list of BMPs to minimize the introduction of pollutants of concern that may result in significant impacts to receiving waters. Other RMPs approved by National City as being equally or more effective in pollutant reduction than comparable BMPs identified below are acecptahle. See Appendix B: Suggested Resources for additional sources of information. All BMPs must comply with local zoning and building codes and other applicable regulations. Site Design BMPs Minimizing Impervious Areas u Reduce sidewalk widths u incorporate landscaped buffer areas between sidewalks and streets. ❑ Design residential streets for the minimum required pavement widths ❑ Minimize the number of residential street cul-de-sacs and incorporate landscaped areas within cul-de-sac centers with curb -cuts or equivalent and equally effective methods to reduce their impervious cover. ❑ Use open space development that incorporates smaller lot sizes u Increase building density while decreasing the building footprint ❑ Reduce overall lot imperviousness by promoting alternative driveway surfaces and shared driveways that connect two or more homes together ❑ Reduce overall imperviousness associated with parking lots by providing compact car spaces, minimizing stall dimensions, incorporating efficient parking lanes, and using pervious materials in spillover parking areas increase Rainfall Infiltration ❑ Use permeable materials for private sidewalks, driveways, parking lots, and interior roadway surfaces (examples: hybrid lots, parking groves, permeable overflow parking, etc.) ❑ Use curb -cuts or equivalent and equally effective methods that convey runoff into swales, landscaping, and natural areas prior to entering the MS4 u Direct rooftop nmoff to pervious areas such as yards, open channels, or vegetated areas, and avoid routing rooftop nmoff to the roadway or the urban runoff conveyance system ❑ Pitch driveways and parking areas toward yards and vegetated areas prior to draining into the MS4. Conserve and utilize natural soils and/or use amended soils to encourage light inf iltrationlpercolation ❑ Minimize disturbances to natural drainages Page 36 ❑ Minimize soil compaction in planned green space (landscaped areas, lawns, etc.) and re - till soils when compacted by grading/construction equipment Maximize Rainfall Interception ❑ Maximizing canopy interception and water conservation by preserving existing native trees and shrubs, and planting additional native or drought tolerant trees and large shrubs. ❑ Cisterns / Rain barrels ❑ Foundation landscaping Minimize Directly Connected Impervious Areas (DCIAs) u Draining rooftops into adjacent landscaping prior to discharging to the storm drain u Use curb -cuts or equivalent and equally effective methods that allow parking lots to drain into landscape areas co -designed as hiofiltration areas and/or swales prior to draining into the MS4 ❑ Draining roads, sidewalks, and impervious trails into adjacent landscaping Slope and Channel Protection ❑ Use of natural drainage systems to the maximum extent practicable ❑ Stabilized permanent channel crossings ❑ Planting native or drought tolerant vegetation on slopes ❑ Energy dissipaters, such as riprap, at the outlets of new storm drains, culverts, conduits, or channels that enter unlined channels Maximize Rainfall Interception ❑ Cisterns ❑ Foundation planting Increase Rainfall Infiltration o Dry wells Source Control BMPs ❑ Storm drain system stenciling and signage ❑ Outdoor material and trash storage area designed to reduce or control rainfall runoff ❑ Efficient irrigation system Page 37 Treatment Control BMPs Biofilters ❑ Bioretention Swale (detains and infiltrates water through soil) ❑ Storm water Planter Box (open -bottomed) ❑ Storm water Flow -Through Planter (sealed bottom) ❑ Vegetated filter strip ❑ Bioretention area u Vegetated Roofs / Modules / Walls Detention Basins o Extended/dry detention basin with grass/vegetated lining ❑ Extended/dry detention basin with impervious lining Infiltration Facilities ❑ Infiltration basin ❑ Infiltration trench ❑ Dry well Permeable Paving o Gravel ❑ Permeable asphalt ❑ Pervious concrete u Unit pavers, ungrouted, set on sand or gravel o Subsurface Reservoir Bed Wet Ponds and Wetlands ❑ Wct pond (permanent pool) ❑ Constructed wetland Drainage Inserts u Oil/Water separator • Catch basin insert ❑ Storm drain inserts ❑ Catch basin screens I'age 38 Filtration Systems u Media filtration u Sand filtration Hydrodynamic Separation Systems ❑ Swirl Concentrator ❑ Cyclone Separator Trash Racks and Screens Page 39 APPENDIX B _ r 4 }`4.:`� rYr. `7 ti} d e r. r uC "� ,e�...t�S '{xr'�'.c'L f '. .3.L l'i-,a� i S•l xF' yy�' a-}i. }�yj FL.� t 4y�)•.Fp,. .e:- ' A.M i'. . The County of San Diego Low Impact Development Handbook; Stormwater Management Strategies . (2007). Presents guidance for LID stormwater planning and management techniques. Fact Sheets on LID BMPs are provided in the Appendices. The County of San Diego The Department of Planning and Land Use 5201 Ruffin Road, Suite B San Diego, CA 92123 Irttp://www,scicounly ca.gov/dplu/LlD PR html www.sdcounty.ca.gov/ciplu/ Better Site Design: A Handbookjor Changing Development Rules in Your Community (1998) Presents guidance for different model development alternatives. Center for Watershed Protection 8391 Main Street Ellicott City, MD 21043 410-461-8323 www.cwp.org California Urban runoff Best Management Practices Handbooks (2003) for Construction Activity, Municipal, and Industrial/Commercial Presents a description of a large variety of Structural 13MPs, Treatment Control, BMPs and Source Control BMPs Los Angelis County Department of Public Works Cashiers Office 900 S. Fremont Avenue Alhambra, CA 91803 626-458-6959 www.cabmphandhooks.org Caltrans Urban runoff Quality Handbook: Planning and Design Staff Guide (Best Management Practices Handbooks (1998) Presents guidance for design of urban runoff BMPs California Department of Transportation P.O. Box 942874 Sacramento, CA 94274-0001 916-653-2975 Bioretention Manual (updated 2002) Presents guidance for designing, building, and maintaining hioretention facilities. Prince George's County Watershed Protection Branch 9400 Peppercorn Place, Suite 600 Landover, MD 20785 http://wynv.co.pg.md.us/Ciovernment/Agencylndex/DER /ESD/Bioretention/bioretention.asp Contra Costa Clean Water Program 255 Glacier Drive Martinez, CA 94553 www.cccleanwater.ore/construction/nd.php Contra Costa Clean Water Program Stormwater C.3 Guidebook Includes an integrated design approach to meet California Stonnwater NPDES treatment and hydrograph modification management requirements using Low Impact Development site design techniques and facilities. Design of Stormwater Filtering Systems (1996) by Richard A. Claytor and Thomas R. Schuler Presents detailed engineering guidance on ten different urban runoff -filtering systems. Center for Watershed Protection 8391 Main Street Ellicott City, MD 21043 410-461-8323 Development Planning Jo,- Stonnwater Management, A Manual for the Standard Urban .Stnnnwater Mitigation Plan (SUSMP), (May 2000) Los Angeles County Department of Public Works http://dow.co.la.ca.us/e rid/ or Idtp://www.888cleanLA.com Page 40 Florida Development Manual: A Guide 10 Sound Land and Water Management (1988) Prtsents detailed guidance for designing BMPs Florida Department of the Environment 2600 Blairstone Road, Mail Station 3570 Tallahassee, FL 32399 850-921-9472 Guidance Specifying Management Measures for Sources of Nonpoint Pollution in Coastal Waters (1993) Report No. FPA--840-B-92-002. Provides an overview of, planning and design considerations, programmatic and regulatory aspects, maintenance considerations, and costs. National Technical Information Service U.S. Department of Conanercc Springfield, VA 22161 800-553-6847 Guide for BMP Selection in Urban Developed Areas (2001) ASCE Envir. and Water Res. Inst. 1801 Alexander Bell Dr. Reston, VA 20191-4400 ' (800) 548-2723 Low -Impact Development Design Strategies - An Integrated Design Approach (June 1999) Prince George's County, Maryland Department of Environmental Resource Programs and Planning Division 9400 Peppercorn Place Largo, Maryland 20774 http: //www. co. p£. tnd. us/Goverronent/DF.R/PPD/pgcouni y/lidmain.htm Maryland Stormwater Design Manual (1999) Presents guidance for designing urban runoff BMPs Maryland Department of the Environment 2500 Braening Highway Baltimore, MD 21224 410-631-3000 National Stormwater Best Management Practices (BMP) Database, Version 1.0 Provides data on performance and evaluation of urban nmoff BMPs American Society of Civil Engineers 1801 Alexander Bell Drive Reston, VA 20191 703-296-6000 National Stormwater .Best Management Practices Database (2001) Urban Water Resources Research Council of ASCE Wright Water Engineers, Inc. (303)480-1700 Operation, Maintenance and Management of Stormwater Management (1997) Provides a thorough look at storm water practices including, planning and design considerations, programmatic and regulatory aspects, maintenance considerations, and costs. Watershed Management Institute, Inc. 410 White Oak Drive Crawfordville, FL 32327 850-926-5310 Portland Stormwater Management Manual (2004) Includes design illustrations and criteria fur bioretenlion facilities. Enviromnental Services 1120 SW 5th Ave., Rm. 1000 Portland, OR 97204 503-823-7740 lm t pl/www. portl andonl ine.com/bes/index.c fm?c--3 5122 & Potential Groundwater Contamination from Intentional and Non -Intentional Stormwater Infiltration Report No. EPA/600/12-94/051, USF.PA (1994). Page 41 Preliminary Data Summary of Urban runoff Best Management Practices (August /999) EPA-821-R-99-012 http://www epa.g¢v/ost/stormwater/ Reference Guide for Stormwater Rest Management Practices (July 2000) City ofl.os Angeles Urban runoff Management Division 650 South Spring Street, 7th Floor Los Angeles, California 90014 hrtp: //wow, laci(v. org/san/,lwrytt/ Second Nature: Adapting L 4 's Landscape for Sustainable Living (1999) by Tree People Detailed discussion of BMP designs presented to conserve water, improve water quality, and achieve flood protection. Tree People 12601 Mullholland Drive Beverly llills, CA 90210 (818) 623-4848 Fax (818) 753-4625 Start at the Source (1999) Detailed discussion of permeable pavements and alternative driveway designs presented. Bay Area Stormwater Management Agencies Association 2101 Webster Street Suite 500 Oakland, CA 510-286-1255 www.hasmaa.org Stormwater Management in Washington State (1999) Vols. 1-5 Presents detailexl guidance on BMP design for new development and construction. Department of Printing State of Washington Department of Ecology P.O. Box 798 Olympia, WA 98507-0798 360-407-7529 Stormwater, Grading and Drainage Control Code, Seattle Municipal Code Section 22.800-22.808. and Director's Rules, Volumes 1-4. (Ordinance 119965, effective July 5, 2000) City of Seattle Department of Design, Construction & Land Ilse 700 5i° Avenue, Suite 1900 Seattle, WA 98104-5070 (206) 684-8880 hap://www.ci.seattle.wa.us4ch(codes/sgdecodehtm Texas Nonpoint Source Book Online Module (1998)www.txnosbook.org 'texas Statewide Urban runoff Quality Task Force North Central Texas Couneil.of Governments 616 Six Flags Drive Arlington, TX 76005 817-695-9150 Presents BMP design and guidance infonnation on-line The Practice of Watershed Protection by Thomas R. Shchuler and !leather K. Holland Center for Watershed Pmtection 8391 Main Street Fllicott City, MD 21043 410-461-8323 www.cwp..rg Urban Storm Drainage, Criteria Manual - Volume 3, Rest Management Practices (1999) Presents guidance for designing BMPs Urban Drainage and Flood Control District 2480 West 26th Avenue, Suite 156-13 Denver, CO 80211 303-455-6277 Page 42 APPENDIX C City of San Diego Localized Equivalent Area Drainage Method Pilot Study Proposal Introduction The San Diego National Pollutant Discharge Elimination System Municipal Sturm Water Permit (Municipal Permit) contains requirements for certain new development and redevelopment projects to comply with Standard Urban Storm Water Mitigation Plans (SIJSMPs). SUSMPs include requirements to implement pollutant source controls, to incorporate site design features, and to infiltrate or treat using structural control measures a portion of the storm water runoff to be generated by the new development or redevelopment project. The City of San Diego's Storm Water Pollution Prevention Program (Storm Water Program) developed, through collaboration with the Regional Water Quality Control Board (Regional Board), the development industry, and environmental organizations, a process designed to provide more efficient, integrated storm water treatment, resulting in water quality improvements more quickly. This process is Called the Localized Equivalent Arca Drainage method or "LEAD" method. Fundamental to the LEAD method is the protection of receiving water quality and support of designated beneficial uses through implementation of structural treatment control measures, also known as Best Management Practices (BMPs), to the maximum extent practicable. The LEAD method provides numerous benefits: • Promotes an integrated, watershed -based storm water treatment by treating runoff from entire sub -drainages once. • Protects receiving water quality and supports designated beneficial uscs through implementation of structural BMPs to the maximum extent practicable. • Provides for accelerated benefits to receiving waters through implementation of structural BMPs in advance of new development or redevelopment projects. • Provides the flexibility required for projects being implemented in developed areas of the City where existing infrastructure limits opportunities for efficient BMP implementation. • Provides increased and more cost-effective opportunities for I3MPs to reside in the public dotnain where BMP operation and maintenance can be assured. ▪ Promotes efficient and integrated implementation of regional solutions in lieu of end -of - pipe solutions. II. LEAD Method — Overview Key aspects for consideration of the LEAD method include the following: • 'the LEAD method is applicable to infill development and redevelopment projects located within existing developed areas. Page 43 • The LEAD method is applicable when implementation of BMPs to treat the runoff from an entire watershed or drainage area that would not otherwise require treatment is more feasible, practical, or beneficial to receiving waters than implementation of BMPs to treat the runoff from an individual project's footprint. • The LEAD method drainage area must be treated prior to discharging to a receiving water supporting beneficial uses. • All development and redevelopment projects subject to regulation under the SUSMP and which are qualified for the LEAD method must continue to address pollutants and conditions of concern at the project site through site design and source control: only the treatment control BMI' requirements would be met at the altemative LEAD watershed. All development and redevelopment projects subject to regulation under the SUSMP are required to assess the pollutants and conditions of concern associated with the proposed project, and to address these pollutants and conditions through site design, source control, and treatment control IIMPs. When the LEAD method is elected, estimates of pollutant load reductions obtained by treating the runoff from the project footprint in accordance with the SUSMP are made to quantify the reduction goal for the project. Then, an alterative treatment area is identified where an equivalent or greater pollutant load reduction can he obtained. The alternative trcatment areas must meet the following requirements: • Located within the proximity of the project. • Discharge to the same receiving water as the project. • Provide for equivalent or greater pollutant load reduction than at the project site. • Located in a drainage basin where no other requirement for treatment exists and treat the entire flow from the drainage basin. • BMPs must be implemented and operational before the project is complete. • Treat runoff from an area equivalent or greater than the project footprint. • Treat runoff from an equivalent or greater impervious area than the project. In all cases, the pollutant load reductions obtainable at the alternative LEAD method treatment area must be greater than that obtained at the project site. 111. LEAD Method Pilot Study The City of San Diego proposes to conduct a pilot study to test the LEAD method and to determine the ability ofthe LEAD method to promote and to achieve the pollution control objectives of the Municipal Permit. The City of San Diego's Storm Water Pollution Prevention Program is proposed as the pilot study lead agency and will be responsible for carrying out all elements of the study. Key attributes of the pilot study include the following: Page 44 • Eligible projects would he limited to areas located within existing developed areas of the City of San Diego. Projects would be limited to urbanized areas to ensure potential LEAD watersheds would not drain into receiving waters supporting beneficial uses prior to treatment at the LEAD method BMP location. • Eligible projects will he limited to projects permitted by the City of San Diego to ensure adequate oversight by the City of San Diego. • A LEAD method pilot study annual report will he submitted to the Regional Board each year of the study. The annual report will include a summary of progress of the pilot study over the previous year, changes proposed for the next year, and lists of projects where the method was applied, including a discussion of the results for each project. The annual report will keep the Regional Board apprised of the progress and results of the pilot study. The remainder of this pilot study proposal describes a proposed methodology that would be used to develop a project under the LEAD method. The document also presents a proposed methodology for completing the details of the methodology through collaboration between the City, the Regional Board, the development industry, and environmental organizations. IV. LEAD Methodology The general methodology for developing a project under the LEAD method is described in this section and illustrated in Figure 1. Step 1 — Determine Project Pollutant Reduction Treatment Goal la — Identify Pollutants and Conditions of Concern Using the process identified in the Final Model SUSMP and repeated in the City's Local SUSMP, determine whether the project would generate pollutants and/or conditions of concern. This step includes: • Identify proposed project type or category and anticipated and potential pollutants generated (SUSMP Section VLi.a). Identify pollutants of concern in the receiving waters to which the project would discharge (StISMP Section V1.1 h and c). Identify those constituents that arc potentially generated from the project or land use type and are pollutants of concern in the receiving waters. These arc the pollutants of concern for this project. If project would discharge to receiving water that does not have specific listed pollutants of concern, select representative pollutants for the project category as shown in Table I of the SUSMP. Determine if project qualifies for the LEAD method. For a project to qualify for the LEAD method, it must meet all of the following criteria: • The LEAD method is applicable to infill development and redevelopment projects located within existing developed areas of the City of San Diego where acceptable potential LEAD sub -drainages arc located in the project's immediate vicinity. Page 45 • The LEAD method is applicable when implementation of BMPs to treat the runoff from an entire watershed or drainage area that would not otherwise require treatment is more feasible, practical, or beneficial to receiving waters than implementation of BMPs to treat the runoff from an individual project's footprint. • The LEAD method is limited to projects within and permitted by the City of San Diego. • The project must propose adequate site design and source controls in the original project design. lb — Estimate Project Site Pollutant Loading Estimate the pollutant loading for the developed qualifying project hased on proposed site land use, characterization data, and water quality design volume. This includes: • Delineate project drainage area into land use types. • Determine the water quality design volume for each land use type based on drainage areas, impervious factors, runoff coefficient, and the methods prescribed in the SUSMP. • Determine representative pollutant event mean concentration for each pollutant of concern and land use type using Table A (to be developed). Calculate Average Pollutant Loading = Event Mean Concentration x Water Quality Design Volume (repeat for each pollutant of concern). 1 c — Determine Candidate Treatment Control BMPs for Project Using the process identified in the SUSMP, and the pollutants of concern identified in Step 1 a, select appropriate BMPs from either Table 2 - Standard Storm Water BMP Selection Matrix, or Table 3 Enhanced Treatment Control BMP Selection Matrix. The 13MP selection should take into account both the pollutants of concern and site factors. Id — Determine Pollutant Reductions Calculate thc pollutant load reduction resulting from thc selected BMPs for each of the pollutants for which pollutant loadings were determined under Step lb. This includes: • Determine the average percentage pollutant reduction for the BMPs using Table B (to be developed). • Apply the pollutant load percent reduction to the average pollutant load estimate developed under Step 1b to determine the average load reduction with BMI's. This average load reduction is the minimum pollutant reduction treatment goal for an alternative LEAD method treatment area. Page 46 Step 2 — Evaluate LEAD Method Treatment Area 2a — Determine LEAD Project Characteristics Locations for candidate LEAD method BMPs will be identified in master drainage plans and will drain to the same receiving water as the qualifying project(s). Once the LEAD method treatment area is selected from the master drainage plan, key characteristics of the LEAD method treatment area watershed/sub-watershed must be determined. 'this includes: • Existing land use(s) and area(s) and impervious factor. • Drainage area. • Rainfall characteristics. 2b — Determine Water Quality Design Volume Estimate the water quality design volume for the LEAD method treatment area using the methods prescribed in the SUSMP. This includes: • Delineate project drainage arca into land use types. • Determine the water quality design volume for each land use type based on drainage areas, impervious factors, runoff coefficient, and the methods prescribed in the SUSMP. 2c — Determine Loading for LEAD Method Treatment Area Pollutants of Concern Determine representative pollutant event mean concentration for each pollutant of concert) and land use type using Table A (to he developed). Calculate Average Pollutant Loading = Event Mean Concentration x Water Quality Design Volume (repeat for each pollutant of concern). This calculation must he made for the potential LEAD method treatment area for the same pollutants of concern identified in Step la for the project site. 2d — Determine Candidate Treatment Control BMPs for LEAD Method Treatment Area LF.AI) method treatment area BMPs will he identified in master drainage plans. The BMPs identified in the master drainage plans will take into account the pollutants of concern identified in Step la, and will have been selected from either Table 2 - Standard Storm Water BMP Selection Matrix, or Table 3 — Enhanced Treatment Control BMP Selection Matrix. 2e — Determine Pollutant Reductions Calculate the pollutant load reduction resulting from the selected LEAD method treatment area BMPs fur each of the pollutants for which average pollutant loadings were determined under Step 2c. 'I his includes: • Determine the average percentage pollutant reduction for the BMPs using Table R (to be developed). Page 47 • Apply the pollutant load percent reduction to the average pollutant load estimate developed under Step 2c to determine the average load reduction with the BMPs for each of the pollutants. 2f — Compare LEAD Method Treatment Area with Qualifying Protect Requirements Compare the pollutant load reduction for the LEAD method treatment area with the pollutant reduction treatment goal for the qualifying project determined under Step 1 d: • If LEAD method Treatment Area Pollutants of Concern Load < Project Pollutants of Concern Load, repeat process with another LEAD site. • If LEAD method Treatment Area Pollutants of Concern Load = Project Pollutants of Concern I.oad, LEAD method Treatment Area is acceptable Implement BMPs at LEAD method treatment area. • 1f LEAD method Treatment Area Pollutants of Concern Load = Project Pollutants of Concern Load, LEAD method Treatment Arca is acceptable — Implement BMPs at LEAD method treatment area. While the comparison must be made for all pollutants of concern, there will typically he one pollutant of concern that will govern the comparison for any given combination of qualifying and LEAD project characteristics. V. LEAD Method Pilot Study Evaluation Fundamental to the LEAD method pilot study is the annual evaluation of the program. The City of San Diego proposes to develop the monitoring and evaluation methodology with San Diego BayKeeper, the American Public Works Association, and technical experts. The methodology would include a descriptive, qualitative component to evaluate indirect measures, which would minimally include the factors listed below. If funding becomes available, the evaluation methodology would include monitoring ofthc LEAD watershed and a similar watershed with treatment of an individual project site. As lead agency responsible for carrying out the pilot study, the City of San Diego's Storm Water Pollution Prevention Program will report the results of the program evaluation in an annual report to the Regional Board. The annual program report will include the following elements: • Listing and description of project(s) to date where the LEAD method was applied. The listing will include the name and location of cach project site and associated LEAD method treatment area. 'Die description will include for each project site and associated LEAD method treatment area: identification of receiving waters; identification of pollutants and conditions of concern; a tabulation of post -project land use; a tabulation of pollutant loading estimates for each pollutant of concern, both without and with BMPs; a listing of the maintenance requirements and evaluation of how effectively the requirements have been fitlfilled; and a listing of site design, source control, and stnictural treatment control BMPs implemented at the project site or LEAD method treatment area. Page 48 • Listing and description of projects currently in the planning stage that arc being evaluated for application of the LEAD method during the next I2-month period, where these are known at the time the annual report is submitted. • Proposed changes in the LEAD method to be implemented during the next 12-month period. The primary criterion for evaluating the effectiveness of the LEAD method will he to compare thc loading of pollutants of concern that are removed at LEAD method treatment areas compared to pollutants of concern that would have been removed at the project site. A secondary criterion for evaluating the effectiveness of the LEAD method will be to compare the timing of HMI's implemented under the LEAD method with the timing under which BMPs might have been implemented outside the program. In general, the LEAD method will be considered to he effective when, 1) pollutant of concern loadings removed as a result of application of the LEAD method exceed loadings that would have been removed at thc project site, and 2) BMPs are implemented in advance of the timing that would have been required without the LEAD method. Additional criteria for evaluating the effectiveness of the LEAD method will he developed as part of the pilot study and will be discussed in the first annual report. VI. LEAD Method Issues to be Further Developed This LEAD method pilot study proposal provides a detailed framework for discussion between thc City, the Regional Board, the development industry, and environmental organizations toward creating an acceptable LEAD method program. In addition to reaching agreement on the overall framework, several key issues will require significant additional development during the initial implementation of the pilot study. Several specific topics include: • Establishing land use or project category based event mean concentrations. • Establishing BMP performance standards for common BMP types. • Determining how to compare a LEAD method treatment area with a qualifying project when one or both projects propose a flow -based BMP methodology. Each of these is briefly discussed further. Establishing Event Mean Concentrations for Calculating Pollutant Loads In order to calculate pollutant loads, typical event mean concentrations for the potential pollutants of concern must be established for land uses and/or project categories to populate a table such as the suggested Table A. • For a number of the common land uses, sufficient land -use based monitoring has been conducted within San Diego County and throughout Southern California (e.g., data compiled by the Southern California Coastal Watershed Research Project) that a set of reasonable values for use in equivalent calculations can he established for a number of the potential pollutants of concern. This is true for such pollutants as total suspended Page 49 sediment, nutrients, heavy metals, oxygen demanding substances (e.g., biological oxygen demand or carbonaceous oxygen demand), oil and grease, and certain indicator hacteria. o Data on other organic compounds is by and large below detection limits and it would be difficult to establish meaningful factors, so it is recommended that this not be included in an analysis. o Data on pesticides is highly variable and often non -detectable and would be difficult to estahlish meaningful values. Data on trash is just now beginning to be compiled and will be highly variahle. It is assumed that both a qualifying project and a LEAD method treatment area would incorporate trash/debris removal as part of the overall plan, and therefore calculating trash loads is also not recommended. Establishing BMP Performance In order to calculate pollutant loads, removal performance data for the potential pollutants of concern must be established for BMP categories to populate a table such as the suggested Table B. • Sufficient data has been published for both operating BMPs and pilot plant research from a number of sources throughout the country that a set of reasonable values for use in equivalent calculations can be established for a number of the potential pollutants of concern. This is true for such pollutants as total suspended sediment, nutrients, heavy metals, oxygen demanding substances (e.g., biological oxygen demand and carbonaceous oxygen demand), oil and grease and to a lesser extent certain indicator bacteria. • BMP performance data for removal of other organic compounds suggests performance is by and large below detection limits and it would be difficult to estahlish meaningful factors, so it is recommended that this not be included in an analysis. • BMP performance data for the removal of low levels of pesticides is generally not available. • Data on trash removal through BMPs is just now beginning to be compiled and will be highly variable. It is assumed that both a qualifying project and a LEAD method treatment area would incorporate trash/debris removal as part of the overall plan, and therefore calculating trash loads is also not recommended. Comparing Flow -Based BMPs Ifa flow -based BMP approach (e.g. vegetated swales, biotilters, hydrodynamic separator) is proposed for either the qualifying project or the LEAD method treatment area, a direct calculation of volume of runoff treated and pollutant load reduced is substantially more complex than for volume - based BMPs (e.g., detention, retention). Methods can be established by evaluating hydrologic data and to develop an approximate relationship between maximum flow treatment capacity and estimated volume treated or continuous simulation models such as the Storage Treatment Overflow Model could he run for each site. Page 50