7 DEVELOPMENT PLANNING & MODEL WATER QUALITY MANAGEMENT PLAN (WQMP)

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1 7 DEVELOPMENT PLANNING & MODEL WATER QUALITY MANAGEMENT PLAN (WQMP) 7.1 INTRODUCTION The Development Planning and Model Water Quality Management Plan (WQMP) Section of the City s LIP has been developed from the 2007 Orange County Drainage Area Management Plan (DAMP) to address post-construction surface runoff from all new development and redevelopment projects in the City. The Draft DAMP is available at: ( This Section describes the required Hydro modification, Low Impact Development (LID), Treatment Control and Source Control requirements for all new and re-development projects occurring within the City. This Section contains the City s Model Water Quality Management Plan and associated tools for implementation, including a hydro modification Best Management Practice (BMP) sizing tool and a WQMP template to assist applicants in meeting the requirements. These documents and tools are part of the Development Project Guidance, as referenced in the City s Storm Water/Surface Runoff Water Quality Protection Code (Water Quality Ordinance), and may be amended from time to time to meet the requirements of Order No.R This Section of the LIP provides a program to 1) reduce development project discharges of storm water pollutants from the Municipal Separate Storm Sewer System (MS4) to the Maximum Extent Practicable (MEP); 2) prevent development project discharges from the MS4 from causing or contributing to a violation of water quality standards; 3) prevent illicit discharges into the MS4; and 4) manage increases in runoff discharge rates and durations from development projects that are likely to cause increased erosion of stream beds and banks, silt pollutant generation, or other impacts to beneficial uses and stream habitat due to increased erosive force, in accordance with Directive F.1 of the Order. City of Dana Point Local Implementation Plan 7-1 Revised February 2011

2 7.2 GENERAL PLAN The City s General Plan was evaluated and revised to provide effective water quality and watershed protection principles and policies that direct land-use decisions and require implementation of consistent water quality protection measures for all development and redevelopment projects. The policies are located predominantly in the Land Use and Conservation/Open Space Elements. The City s General Plan can be found at: ENVIRONMENTAL REVIEW PROCESS The City evaluates water quality impacts and identifies appropriate measures to avoid, minimize and mitigate those impacts for development projects through the California Environmental Quality Act (CEQA) process. 7.4 REQUIREMENTS FOR ALL NEW DEVELOPMENT AND REDEVELOPMENT PROJECTS All new development and redevelopment projects must implement Low Impact Development (LID) and Source Control Best Management Practices (BMPs), as applicable and feasible. The project proponent must submit plans that demonstrate implementation of LID and Source Control BMPs, as applicable, to the City for review and approval during the planning process and prior to project approval. Project proponents are also required to submit proof of mechanisms under which assure long-term maintenance of all structural BMPs. Figure 7.1 provides a simplified schematic of the new development and redevelopment planning process. Development shall mean New Development or Redevelopment projects involving land disturbing activities, or structural development, including construction or installation of a building or structure, and/or the creation of Impervious Surface Areas. New Development shall mean all public and private Development (whether residential single family, multi-unit or planned unit development,- industrial, commercial, retail and/or other non-residential construction projects), involving grading for future construction, for which either a discretionary land use approval, a grading permit, a building permit or a Non-Residential Plumbing Permit is required. Redevelopment shall mean the proposed creation, addition, and/or replacement of impervious surface area on an already developed site. Examples include the expansion of a building footprint, road widening, the addition to or replacement of a structure, and creation or addition of impervious surface areas. Replacement of impervious surface areas includes any activity that is not part of a routine maintenance activity where impervious material(s) are removed, exposing underlying soil during construction. Redevelopment does not include trenching and resurfacing associated with utility work; resurfacing existing roadways; new sidewalk construction, pedestrian ramps, or bike lane on existing roads; and routine replacement of damaged pavement, such as pothole repair. City of Dana Point Local Implementation Plan 7-2 Revised February 2011

3 7.4.1 Low Impact Development Requirements The primary goal of LID is to preserve a site s predevelopment hydrology. The effects of changes to runoff patterns and pollutant loading caused by land use modifications can be reduced through the use of structural and non-structural techniques that store, infiltrate, evaporate, and detain runoff. LID site design elements include a wide range of potential features that can be implemented to reduce the volume of storm water runoff generated on a project site as well as improve the quality of runoff that leaves the site. LID site design is predominantly preventative in nature as it consists of elements that reduce the amount of runoff and other impacts before, or immediately after, they occur. Examples of preventative aspects of LID site design include reduction of impervious area, preservation of drainage courses and restoration of impacted soils. LID site design should be considered in the earliest phases of a project. The following Low Impact Development (LID) Best Management Practices (BMPs), must be implemented on all development projects, where applicable and feasible, as determined by the Director of Public Works, to maximize infiltration, provide retention, and slow runoff: Conserve natural areas, including existing trees, other vegetation and soils. Construct streets, sidewalks and parking lot aisles to the minimum widths necessary, provided that public safety is not compromised. Minimize the impervious footprint of the project. Minimize soil compaction in landscaped areas. Minimize disturbances in natural drainages, for example, natural swales, topographic depressions, etc. Disconnect impervious surfaces through distributed pervious areas by draining rooftops into adjacent landscaping, using vegetated swales in lieu of underground piping, incorporating sheet flow over vegetated areas, incorporating low flow infiltration, etc.; Create buffer zones for natural water bodies, where feasible and if buffer zones are not feasible, implement other buffer, such as trees, access restrictions, etc.; Address infiltration and groundwater protection, as applicable. See Infiltration and Groundwater Protection in Section 7.7.7; and Any other LID BMPs deemed necessary, as directed by the Public Works Director. More detailed information on LID BMPs is provided in Section City of Dana Point Local Implementation Plan 7-3 Revised February 2011

4 7.4.2 Source Control BMP Requirements The following Source Control BMPs are required for all development projects, as determined by the Director of Public Works, to reduce storm water pollutants of concern in runoff: Prevent illicit discharges into the MS4. Prevent irrigation runoff. Stencil, sign or otherwise mark, with approval from City, the storm drain system with no dumping messages. Properly design outdoor material storage areas, when applicable to project. Properly design outdoor work areas, when applicable to project. Properly design trash storage areas, when applicable to project. Street and parking lot sweeping at a minimum frequency of monthly. Landscape with native or low water species, where feasible. Any other source control BMPs deemed necessary, as directed by the Public Works Director. 7.5 PRIORITY DEVELOPMENT PROJECTS (PDPs) CRITERIA Projects that are identified as Priority Development Projects (PDPs) per the criteria below in Table 7.1 will be required to prepare a Project Water Quality Management Plan, based upon the City s Model WQMP (see Section 7.6 below), including applicable hydro modification and LID requirements. Table 7.1: Priority Development Projects (PDPs) 1. New development projects that create 10,000 square feet or more of impervious surface (collectively over the entire project site), including commercial, industrial, residential, mixed-use, and public projects on private or public land within the City. 2. All redevelopment projects that create, add or replace at least 5,000 or more square feet of impervious surface on an already developed site, and the existing development or redevelopment project falls under another Priority Project category below. If the redevelopment results in the addition or replacement of less than 50% of the existing impervious area on-site and the existing development was not subject to WQMP requirement, the numeric sizing criteria discussed below only applies to the addition or replacement area. If the addition or replacement accounts for 50% or more of the existing impervious area, the WQMP requirements apply to the entire development. 3. Parking lots of 5,000 square feet or more or with 15 parking spaces or more and potentially exposed to runoff. Parking lot shall mean land area or a facility for the temporary parking or storage of motor vehicles used personally, for business or for commerce. 4. New streets, roads, highways, and freeways. This category includes any paved surface that is 5,000 square feet or greater used for the transportation of automobiles, trucks, motorcycles, and other vehicles. This does not include existing street repair and rehabilitation. 5. Hillside development greater than 5,000 square feet. Hillside development: shall mean any development which is located in an area with known erosive soil conditions or where the natural slope is twenty-five percent or greater. City of Dana Point Local Implementation Plan 7-4 Revised February 2011

5 6. Impervious surface of 2,500 square feet or more located within, directly adjacent to (within 200 feet), or discharging directly 1 to an Environmentally Sensitive Area; or a project with an increase in impervious area by10% or more of its naturally occurring condition located within, directly adjacent to (within 200 feet), or discharging directly to an Environmentally Sensitive Area. 7. Restaurants where the land area of development or redevelopment is 5,000 square feet or more including parking area. Restaurants shall mean facilities that sell prepared foods and drinks for consumption, including stationary lunch counters and refreshment stands selling prepared foods and drinks for immediate consumption (SIC code 5812). Restaurants where land development is less than 5,000 square feet shall meet all WQMP requirements except for LID BMP retention, treatment control BMP, and hydro-modification requirements. 8. Automotive repair shops. This applies to facilities that are categorized in any one of the following Standard Industrial Classification (SIC) codes: 5013, 5014, 5541, , and Retail Gasoline Outlets (RGOs). This category includes RGOs that meet the following criteria: (a) 5,000 square feet or more, or (b) a projected Average Daily Traffic (ADT) of 100 or more vehicles per day. 10. Beginning December 16, 2012: All pollutant-generating development or redevelopment projects that result in the disturbance of one acre or more of land. 1 Discharging directly to means outflow from a drainage conveyance system that is composed entirely of flows from the subject development project, and not commingled with flows from adjacent lands. Where a new Development project feature, such as a parking lot, falls into a PDP Project Category, the entire project is a PDP. PDP categories may be amended as necessary, as reflected in the most current version of the City s Model WQMP. WQMP and hydro modification requirements apply to all priority projects or phases of priority project which have not yet begun grading or construction activities at the time any updated Project WQMP or hydro modification requirement commences, unless a lawful prior approval of the project exists, whereby requiring an updated Project WQMP or hydro modification is not required Public Agency Priority Development Projects (PDPs) New Development and Redevelopment requirements apply to Public Agency projects that meet the definitions in the Priority Project Categories described in Table 7.1 above. In general, the same WQMP overall requirements described herein apply to public agency projects as well as private development projects. However, there are unique issues associated with certain Public Agency Projects that are either specifically recognized in the Permits, or for which particular approaches can be considered. New streets, roads, highways and freeways of 5,000 square feet or more of paved surface shall incorporate United States Environmental Protection Agency (USEPA) guidance, Managing Wet Weather with Green Infrastructure: Green Streets in a manner consistent with the maximum extent practicable standard or alternative criteria. In the case of below ground utility projects, such as storm drains, sewers, and water lines, it is assumed that these projects would be in a similar category as projects which maintain original line and grade at the surface and therefore would not qualify as a Priority Development Project. By the same token, street rehabilitation projects, such as repaving, City of Dana Point Local Implementation Plan 7-5 Revised February 2011

6 replacement of curb and gutter, driveways, sidewalks and other street improvements to restore original line and grade do not qualify as PDPs. The City may elect to develop a separate Master Project WQMP for streets, roads and highways projects based upon the requirements outlined in this document. A Master Project WQMP document would need to list all of the qualifying streets, roads and highways projects anticipated to occur within the Permittee s jurisdiction and the proposed methods of compliance with this Model WQMP. 7.6 MODEL WATER QUALITY MANAGEMENT PLAN (WQMP) The City s Model Water Quality Management Plan (WQMP) also referred to as the Standard Storm Water Mitigation Plan (SSMP) in the RWQCB NPDES Order, has been developed to guide project applicants in meeting the new development and redevelopment requirements for PDPs, including applicable hydro modification and LID requirements. The goal of the Model WQMP is to provide a framework for developing a Project WQMP that minimizes the effects of urbanization on site hydrology, urban runoff flow rates or velocities and pollutant loads. This goal may be achieved through practicable and enforceable site-specific project-based controls, or a combination of project-based and regional or watershed-based controls. The process will first involve preparing a Preliminary Project WQMP to incorporate Low Impact Development (LID) and, where necessary, hydro modification control BMPs, at the earliest conceptual planning stages of a project for early review. A Preliminary Project WQMP is required to be submitted with the project entitlement application package. An application is deemed incomplete without an adequate preliminary WQMP. Applicants are encouraged to use the City s WQMP template (Exhibit 7.1) to complete the project s Preliminary WQMP and Final WQMP. The Preliminary Project WQMP must include all structural site design, structural source control, low impact development, treatment and hydro modification BMPs that were selected for the project accompanied by detailed project-specific sizing calculations. Final details of non-structural source control BMPs and operation and maintenance details are not required to be included with the Preliminary Project WQMP, but will be required as part of the Final Project WQMP. Owner certification is required for both the Preliminary and Final WQMP submittals. All final plans must show all the structural and any applicable non-structural source control BMPs per the approved Final WQMP. The process to develop a Preliminary WQMP and Final WQMP is described in Section 7.7 below. The term Model Water Quality Management Plan refers to the general water quality requirements for PDPs. The term Project Water Quality Management Plan refers to the WQMP that is developed to a specific project. The word Project may be omitted when referring to the project specific WQMP in this document, thus WQMP and Project WQMP may be used interchangeably. City of Dana Point Local Implementation Plan 7-6 Revised February 2011

7 7.7 PRELIMINARY AND FINAL PROJECT WATER QUALITY MANAGEMENT PLAN (WQMP) PREPARATION Several steps are involved in completing a Preliminary and Final Project WQMP. Figure 7.1 is an overview of the Project WQMP development process, including the major implementation and decision steps that must be followed to successfully complete a Project WQMP, after determining that the project is a PDP. Each of the steps, bulleted below, will be described in detail in subsequent sub-sections. Project Description and Site Assessment; Determine Pollutants of Concern; Address Hydro modification/hydrologic Conditions of Concern - Select & size hydro modification control BMPs, (if necessary); Address Low Impact Development (LID) BMPs - Select and size site design elements and LID BMPs, as appropriate; Address Treatment Control BMPs - Select and size Treatment BMPs if LID and Hydro modification BMPs do not achieve required performance criteria; Select and size structural source control BMPs, as applicable; Prepare and submit Preliminary WQMP for approval; Implement applicable non-structural source control BMPs; Determine BMP maintenance requirements and identify mechanism for long-term maintenance and implementation of WQMP; and Prepare and submit for approval, Final WQMP and finalize plans showing LID, Treatment and other applicable BMPs. It is imperative for the project proponent to take a holistic approach when addressing the hydro modification and LID BMPs as they are directly related and will impact the design and selection of each other. The City has prepared a Project WQMP Template, see Exhibit 7.1 to assist the applicant in preparing a project-specific WQMP, available at Other resources are also provided on the same webpage. The sections that follow describe necessary elements of a Project WQMP. Figure 7.1 provides a simplified schematic of the new development and redevelopment planning process. LID, Hydro modification Control and Treatment BMPs design and sizing calculations must be prepared, signed and sealed by a California registered Civil Engineer. City of Dana Point Local Implementation Plan 7-7 Revised February 2011

8 Figure 7.1: New Development & Redevelopment Process Is the Project A Priority Project? Yes Conduct Site Assessment Identify Pollutants of Concern Is the Project Subject to Hydromodification Requirements? No No Yes Assess Project & Implement Applicable LID BMPs Implement Applicable Source Control BMPs Identify Mechanism for Long-Term Maintenance & Implementation Select & Size LID BMPs Select & Size Treatment & Applicable Structural Source Control BMPs Prepare & Submit Preliminary WQMP Implement Applicable Non- Structural Source Control BMPs Determine Maintenance Requirements & Identify Mechanism for Long-Term Implementation Prepare & Submit Final WQMP and finalize Plans with BMPs Select & Size BMPs per Hydromodification BMP Sizing Tool Select & Size LID and Treatment BMPs, if necessary, and Applicable Structural Source Control BMPs Prepare & Submit Preliminary WQMP Implement Applicable Non- Structural Source Control BMPs Determine Maintenance Requirements & Identify Mechanism for Long-Term Implementation Prepare & Submit Final WQMP and finalize Plans with BMPs City of Dana Point Local Implementation Plan 7-8 Revised February 2011

9 7.7.1 Project Description & Site Assessment Project Description & Site Assessment involves compiling the following: Detailed description of project, existing use, proposed use, type of development, zoning, project components, etc. Location, site address, site size, APN, GIS coordinates, etc. Existing and proposed percent of impervious surface coverage Watershed name, applicable 303(d) Listed waterbodies, TMDL Info, ESAs, etc. Site characteristics, including description offsite drainage and how it ties with drainage of surrounding property. Reference the Project WQMP s Plot Plan showing drainage flow arrows and how drainage ties to drainage of surrounding property. Project Location Map Determine Pollutants of Concern Surface runoff from a developed site has the potential to contribute pollutants, including suspended solids/sediment, nutrients, metals, microbial pathogens, oil and grease, toxic organic compounds, and trash and debris from the municipal storm drain system to tributary receiving waters. Pollutants of concern associated with new development and redevelopment projects are a function of both receiving water issues and pollutants that can be found in runoff from developed land uses Receiving Water Pollutants of Concern For the purposes of identifying receiving water pollutants of concern and selecting appropriate Treatment Control BMPs for projects, pollutants are grouped in seven general categories: Suspended Solids / Sediment Suspended solids / sediment consist of soils or other surficial materials that are eroded and then transported or deposited by the action of wind, water, or gravity. Excessive sedimentation can increase turbidity, clog fish gills, reduce spawning habitat, lower young aquatic organisms survival rates, smother bottom dwelling organisms, and suppress aquatic vegetation growth. The largest source of suspended solids / sediment is typically erosion from disturbed soils. Nutrients This category includes the macro-nutrients nitrogen and phosphorus. They commonly exist in the form of mineral salts dissolved or suspended in water and as particulate organic matter transported by storm water. Excessive discharge of nutrients to water bodies and streams can cause eutrophication, including excessive aquatic algae and plant growth, loss of dissolved oxygen, release of toxins in sediment, and significant swings in hydrogen ion concentration (ph). Primary sources of nutrients in urban runoff are fertilizers, trash and debris, and eroded soils. Urban areas with improperly managed landscapes can be substantial sources. City of Dana Point Local Implementation Plan 7-9 Revised February 2011

10 Metals Certain metals can be toxic to aquatic life if concentrations become high enough to stress natural processes. Metals of concern include cadmium, chromium, copper, lead, mercury, nickel and zinc. Lead and chromium have been used as corrosion inhibitors in primer coatings and are also raw material components in non-metal products such as fuels, adhesives, paints, and other coatings. Copper and zinc are typically associated with building materials, including galvanized metal and ornamental copper, and automotive products, including tires and brake pads. Humans can be impacted from contaminated groundwater resources, and bioaccumulation 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. The primary source of metals in urban storm water is typically commercially available metal products and automobiles. Microbial Pathogens (Bacteria and Viruses) Bacteria and viruses are ubiquitous microorganisms that thrive under a range of environmental conditions. Water containing excessive pathogenic bacteria and viruses can create a harmful environment for humans and aquatic life. The source of pathogenic bacteria and viruses is typically the transport of animal or human fecal wastes from the watershed, but pathogenic organisms do occur in the natural environment. Non-pathogenic bacteria (fecal coliform and E. Coli) that can be more routinely detected and quantified are used as indicator organisms to suggest the potential presence of pathogens. Pesticides - Pesticides are chemicals regulated by the State Department of Pesticide Regulation, commonly used around our homes and gardens. Pesticides are not only a threat to aquatic life, but they can also affect the quality of our drinking water. All pesticides are toxic at some level, but each varies in their toxicity to humans and other animals. Organophosphates, including diazinon and chlorpyrifos, are insecticides that contain phosphorus; they are nerve poisons and act by inhibiting important enzymes in the nervous system in animals. Pyrethroids are another class of insecticides that are not as toxic to humans and other mammals, but are quite toxic to fish and invertebrates. Both the organophosphates and pyrethroids pose serious threats to aquatic invertebrates in California waterways. Pyrethroids are found in common residential insecticides, such as products for ant control, home lawn, garden and landscape care, as well as in structural pest control products. Common pyrethroid active ingredients in home use products include bifenthrin, cypermethrin, permethrin, and cyfluthrin. Pyrethroids mimic the mode of action of the plant-derived pesticide pyrethrin, but are much more toxic and persistent in the environment. They attach to soil particles and are washed into waterways on sediment. Organophosphate pesticides containing diazinon and chlorpyrifos were widely used in the 1990s but were withdrawn from the market for home use in the early 2000s because of risks to children. These materials are highly soluble in water and have been found in California creeks at levels toxic to aquatic invertebrates. The U.S. EPA's Office of Pesticide Programs summary sheets explain why these pesticides are no longer available to urban users. City of Dana Point Local Implementation Plan 7-10 Revised February 2011

11 Oil and Grease Oil and grease are characterized as high-molecular weight organic compounds. Elevated oil and grease content can decrease the aesthetic value of the water body, as well as the water quality. Introduction of these pollutants to water bodies may occur due to the wide use and application of these products in municipal, residential, commercial, industrial, and construction areas. Primary sources of oil and grease include leakage, spills, cleaning and sloughing associated with vehicle and equipment engines and suspensions, leaking and breaks in hydraulic systems, restaurants, and waste oil disposal. Toxic Organic Compounds Organic compounds (pesticides, solvents, hydrocarbons) at toxic concentrations constitute a hazard to humans and aquatic organisms. Stormwater coming into contact with organic compounds can transport excessive levels of organics to receiving waters. Dirt, grease, and grime retained in cleaning fluid or rinse water may also adsorb levels of organic compounds that are harmful or hazardous to aquatic life. Sources of organic compounds include landscape maintenance areas, vehicle maintenance areas, waste handling areas, and potentially other urban areas. Trash and Debris Trash (such as paper, plastic, and various waste materials) are general waste products that can typically be found throughout the urban landscape. Debris includes waste products of natural origin which are not naturally discharged to water bodies (such as landscaping waste, woody debris, etc.) The presence of trash and debris may have a significant impact on the recreational value of a water body and upon the health of aquatic habitat Expected Pollutants from Project Components Using Table 7.2 below, identify pollutants that are anticipated to be generated, or have a potential to be generated from the proposed project s land use categories. Site-specific conditions shall also be considered for potential pollutant sources, such as legacy pesticides or nutrients in site soils as a result of past agricultural practices or hazardous materials in site soils from industrial uses. Hazardous materials that have been remediated and do not pose a current or future threat to storm water quality are not considered a pollutant of concern. Compare the list of pollutants for which the receiving waters are impaired or for which TMDLs have been adopted (as identified in Table 7.3) with the pollutants anticipated to be generated by the land uses included in the project. Primary Pollutants of Concern are any pollutants anticipated to be generated by the project using Table 7.2 that have also been identified as causing impairment of project receiving waters in Table 7.3. Other pollutants of concern are those pollutants anticipated to be generated by the project using Table 7.2 that have not been identified as causing impairment. Further information on pollutants of concern may also be available from the environmental impact assessment for the project (e.g., project-specific pollutant evaluations in California Environmental Quality Act (CEQA) Environmental Impact Reports). City of Dana Point Local Implementation Plan 7-11 Revised February 2011

12 Table 7.2 Expected and Potential Pollutants Generated by Land Use Type Priority Project Categories and/or Project Features Heavy Metals Nutrients Pesticides General Pollutant Categories Toxic Organic Compounds Suspended Solids/ Sediments Trash & Debris Oil & Grease Bacteria/Virus/ Pathogens Detached Residential Development Attached Residential Development Commercial/ Industrial Development N E E N E E E E N E E N E E E (2) E E (4) E (1) E (1) E (2) E E E E (3) Automotive Repair Shops E N N E N E E N Restaurants & Food Service Establishments E (2) E (1) E (1) N E (1) (2) E E E Retail Gasoline Outlets E N N E N E E N Hillside Development N E E N E E E E Parking Lots E E (1) E (1) E E E E N Streets, Highways & Freeways E E (1) E (1) E E E E N E = expected to be of concern N = not expected to be of concern (1) A potential pollutant if landscaping or open area exist on-site, otherwise not expected. (2) A potential pollutant if the project includes uncovered parking areas, otherwise not expected. (3) A potential pollutant if land use involves food or animal waste products, otherwise not expected. (4) Expected if outdoor storage or metal roofs, otherwise not expected. City of Dana Point Local Implementation Plan 7-12 Revised December 2010

13 Table 7.3 Summary of the 2006 & (d) Listed Water Bodies and Associated Pollutants of Concern for Dana Point Pollutant Water Body Watershed Bacteria Indicators/ Pathogens Metals Nutrients Pesticides Toxicity Trash Salinity/TDS/ Chlorides Turbidity Dana Point Harbor K X Pacific Ocean Shoreline, Dana Point HSA K X Pacific Ocean Shoreline, Lower San Juan HSA L X Cu, Zn X San Juan Creek (Lower one Mile, including mouth) L X 1 The (d) List of Impaired Water bodies will be confirmed upon approval by the EPA Hydro modification/hydrologic Conditions of Concern Hydro modification is the alteration of natural flow characteristics and sediment supply, which can result from new development and significant redevelopment projects without appropriate preventative controls. Common impacts to the hydrologic regime resulting from development include increased runoff volume and velocity; reduced infiltration; increased flow frequency, duration, and peaks; and faster time to reach peak flow. Under certain circumstances, new development and significant redevelopment could also result in the reduction in the amount of sediment supplied to the channel for transport. If the sediment supplied to the channel is reduced such that in-stream flows are transporting sediment faster than it can be replenished, then erosion of the channel s bed and bank may occur. These changes have the potential to permanently impact downstream channels and habitat integrity. A change to a Priority Project site s hydrologic characteristics would be considered a condition of concern if the change would have a significant impact on downstream natural channels and habitat integrity. In determining whether an impact is significant, the cumulative effects on the watershed must be considered. The first step to determine whether or not hydro modification requirements apply is based on the Proposed Project s location and point of discharge. All PDPs must meet the hydro modification requirements unless: The project site discharges into an underground storm drain system that discharges direct to a bay or ocean; or The project site discharges into a conveyance channel whose bed and bank are concrete lined all the way from the point of discharge to ocean waters, enclosed bays, estuaries or water storage reservoirs and lakes. In the City of Dana Point, any priority project that discharges to natural bottom creeks, such San Juan Creek and Salt Creek are subject to the hydro modification requirements. There may be City of Dana Point Local Implement 7-13 Revised February 2011

14 projects near the coastline that may discharge into an underground storm drain system that discharges directly into ocean waters where the hydro modification projects do not apply and those will be evaluated on a case by case basis. Interim hydro modification criteria apply until a Hydro modification Management Plan is adopted by the SDRWQCB. PDPs must implement the following criteria by comparing the predevelopment (naturally occurring) and post-project flow rates and durations using a continuous simulation hydrologic model: For flow rates from ten percent of the two-year storm event to the five-year storm event, the post-project peak flows shall not exceed predevelopment (naturally occurring) peak flows. For flow rates from the five-year storm event to the ten-year storm event, the postproject peak flows may exceed predevelopment (naturally occurring) flows by up to ten percent for a one-year frequency interval. Pre-development is defined as the naturally occurring (pre-human disturbance) conditions per the Order (i.e. pre-development, not pre-project). Although LID, treatment control, and hydro modification control requirements are stated independently in the Order, and PDPs must demonstrate compliance with each individually, these provisions overlap significantly and some management practices may fulfill or partially fulfill a portion of one or more of each of these requirements. LID and hydro modification control requirements are also interrelated as both are based on reduction of runoff volume as their first priority. Implementation of hydro modification requirements inherently results in compliance with treatment control requirements. LID site design should be considered as the first priority in the hierarchy of LID implementation, beginning with the earliest phases of a project. The use of effective site design practices can result in smaller hydro modification and treatment control BMPs. Including space for BMPs in the site design at the earliest phases of the project planning process can allow projects to more easily satisfy numeric performance criteria. The project proponent may use the South Orange County Hydro modification Control BMP Sizing Tool, Exhibit 7.2, also available on the City website at: to design and select the hydro modification BMPs, until a Hydro modification Management Plan (HMP) is approved by the San Diego Regional Water Quality Control Board. Upon approval, the Hydro modification Management Plan will be in effect and replace the Interim Hydro modification BMP Sizing Tool and be incorporated by reference into the City s LIP and WQMP Template Low Impact Development (LID) Best Management Practices (BMPs) All PDPs are required to develop and implement a Preliminary and Final WQMP that includes LID BMPs, intended to collectively minimize directly connected impervious areas, limit loss of existing infiltration capacity, and protect areas that provide important water quality benefits City of Dana Point Local Implement 7-14 Revised February 2011

15 necessary to maintain riparian and aquatic biota, and/or are particularly susceptible to erosion and sediment loss, as feasible. Please refer to Section for LID BMP requirements Treatment Control BMP Requirements PDPs are required to implement a single or combination of storm water Treatment Control BMPs that will remove anticipated pollutants of concern, as identified by the procedure in Section Treatment Control BMPs must be implemented unless a waiver is granted to the project by the City, based on the infeasibility of any Treatment Control BMP (see Section ) or are specifically exempted by the limited excusions listed as the end of Section As noted earlier in this Section, Hydro modification Control and/or LID BMPs may inherently achieve the required treatment. The project application should assess the project s BMPs and demonstrate compliance with the treatment BMP performance criteria as described in Section and/or use the Hydro modification BMP Tool to demonstrate performance. Structural Treatment Control BMPs required by this section shall be operational prior to project final acceptance and utilization, and shall be located and designed in accordance with the requirements here in this section Treatment Control BMP Performance Criteria The performance criteria for designing Treatment Control BMPs are to treat the Stormwater Quality Design Flow (SQDF) or the Stormwater Quality Design Volume (SQDV) of the storm water runoff. Table 7.4 lists BMPs along with the basis of design, SQDF or SQDV, to be used for designing the BMP. The WQMP Template in Exhibit 7.1 provides detailed guidance and tools for determining the SQDV and SQDF for a project. Table 7.4 Basis of Design for Treatment Control BMPs Treatment Control BMP Vegetated (Grass) Strips Vegetated (Grass) Swales Proprietary Control Measures Dry Detention Basin Wet Detention Basin Constructed Wetland Detention Basin/Sand Filter Porous Pavement Detention Porous Landscape Detention Infiltration Basin Infiltration Trench Media Filter Design Basis SQDF SQDV City of Dana Point Local Implement 7-15 Revised February 2011

16 Treatment Control BMP Proprietary Control Measures Design Basis Alternative storm water Treatment Control BMPs not identified in Table 7.4 may be approved at the discretion of the City, provided the alternative Treatment Control BMP is as effective in removal of pollutants of concern as other feasible BMPs. All treatment control BMPs for PDPs must be selected and sized to comply with the following criteria: Volume-based treatment control BMPs shall be designed to mitigate (infiltrate, filter, or treat) the volume of runoff produced from a 24-hour 85th percentile storm event, as determined from the County of Orange s 85 th Percentile Precipitation Isopluvial Map. The 24-hour 85 th percentile runoff for Dana Point ranges from approximately 0.76 to 0.8 inches, please refer to the Map provided in Exhibit 7.3 to determine the volume for your site; or Flow-based treatment control BMPs shall be designed to mitigate (infiltrate, filter, or treat) either a) 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 b) 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. Treatment control BMPs for all PDPs must mitigate (treat through infiltration, settling, filtration or other unit processes) the required volume or flow of runoff from all developed portions of the project, including landscaped areas. All treatment control BMPs must be located so as to remove pollutants from runoff prior to its discharge to any waters of the U.S. Multiple Priority Development Projects may use shared treatment control BMPs as long as construction of any shared treatment control BMP is completed prior to the use or occupation of any Priority Development Project from which the treatment control BMP will receive runoff. All treatment control BMPs for Priority Development Projects must, at a minimum: (i) Be ranked with high or medium pollutant removal efficiency for the project s most significant pollutants of concern (as determined per Section 7.7.2) as indicated in Table 7.5 below. This applies only to those PDPs not implementing LID or hydro modification control BMPs capable of meeting the design storm criteria for the entire site. Low-Impact Development (LID) and other site design BMPs that are correctly designed to effectively remove pollutants from runoff are considered treatment control BMPs. Treatment control BMPs with a low removal efficiency ranking may only be approved when a feasibility analysis has been conducted which exhibits that implementation of treatment control BMPs with high or medium removal efficiency rankings is infeasible for all or a portion of the PDP. (ii) Be correctly sized and designed so as to remove storm water pollutants to the MEP. Be implemented close to pollutant sources, and prior to discharging into waters of the U.S. City of Dana Point Local Implement 7-16 Revised February 2011

17 Not be constructed within a waters of the U.S. or waters of the State. Include proof of a mechanism under which ongoing long-term maintenance will be conducted to ensure proper maintenance for the life of the project. Be designed and implemented with measures to avoid the creation of nuisance or pollution associated with vectors, such as mosquitoes, rodents, and flies. Limited Exclusions: Proposed restaurants, where the disturbed land area for development or redevelopment is less than 5,000 square feet, are excluded from the Treatment Control BMP and numerical sizing criteria requirements, but are still required to prepare a Project WQMP and implement LID features and applicable source control BMPs. 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 WQMP requirements, the Treatment Control BMP and numeric sizing criteria discussed in this section apply only to the addition, and not to the entire development. City of Dana Point Local Implement 7-17 Revised February 2011

18 Table 7.5: Treatment Control BMP Selection Matrix (1) Treatment Control BMP Categories Pollutant of Concern Biofilters Detention Basins Infiltration Basins (2) Wet Ponds or Wetlands Filtration Hydrodynamic Separator Systems (3) Sediment Turbidity H/M H/M H/M H/M H/M H/M Nutrients L H/M H/M H/M Organic Compounds U U U U H/M H/M L L Trash & Debris Oxygen Demanding Substances L L H/M H/M U H/M U H/M H/M H/M H/M L Bacteria & Viruses U U H/M U H/M L Oil & Grease H/M H/M U U H/M L/M Pesticides (non-soil bound) U U U U U L (1) Cooperative periodic performance assessment may be necessary. This Treatment Control BMP table will be updated as needed and as knowledge of stormwater treatment BMPs improves. (2) Including trenches and porous pavement. (3) Also known as hydrodynamic devices and baffle boxes. L: Low removal efficiency H/M: High or medium removal efficiency U: Unknown removal efficiency Sources: Guidance Specifying Management Measures for Sources of Nonpoint Pollution in Coastal Waters (1993), National Stormwater Best Management Practices Database (2001), and Guide for BMP Selection in Urban Developed Areas (2001). Biofilters include: Grass swales Grass strips Wetland vegetation swales Bioretention Detention Basins include: Extended/dry detention basins with grass lining Extended/dry detention basins with impervious lining Infiltration Basins include: Infiltration basins Infiltration trenches Wet Ponds and Wetlands include: Wet ponds (permanent pool) Constructed wetlands Filtration Systems include: Media filtration Sand filtration Hydrodynamic Separation Systems include: Swirl Concentrators Cyclone Separators City of Dana Point Local Implement 7-18 Revised February 2011

19 7.7.9 Infiltration Restrictions Grading permits may limit or prohibit the use of infiltration BMPs in hillside or other special situations where slope stability and subsurface stability are of concern. Over time, infiltration may affect pre or post-development subsurface conditions, creating potential for instability. To protect groundwater quality, the City applies restrictions to the use of any BMPs that are designed to primarily function as centralized infiltration devices (such as large infiltration trenches and infiltration basins). The restrictions are not intended to be applied to small infiltration systems dispersed throughout a development project. The implementation of these infiltration BMPs must not cause or contribute to an exceedance of groundwater quality objectives and must meet the restrictions below, unless it is demonstrated that a restriction is not necessary to protect groundwater quality. Structural infiltration Treatment Control BMPs shall not cause a nuisance or pollution, as defined in Water Code Section Urban runoff from commercial developments shall undergo pretreatment to remove both physical and chemical contaminants, such as sedimentation or filtration, prior to infiltration. All dry weather flows containing significant pollutant loads must be diverted from infiltration devices and treated through other BMPs; Pollution prevention and source control BMPs must be implemented at a level appropriate to protect groundwater quality at sites where infiltration treatment control BMPs are to be used; Infiltration treatment control BMPs must be adequately maintained so that they remove storm water pollutants to the MEP; The vertical distance from the base of any infiltration treatment control BMP to the seasonal high groundwater mark must be at least 10 feet. Where groundwater basins do not support beneficial uses, this vertical distance criteria may be reduced, provided groundwater quality is maintained; The soil through which infiltration is to occur must have physical and chemical characteristics (such as appropriate cation exchange capacity, organic content, clay content, and infiltration rate) which are adequate for proper infiltration durations and treatment of runoff for the protection of groundwater beneficial uses; Infiltration treatment control BMPs must 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 each Co-permittee unless first treated or filtered to remove pollutants prior to infiltration and a comprehensive site-specific evaluation has been conducted; and Infiltration treatment control BMPs must be located a minimum of 100 feet horizontally from any water supply wells. City of Dana Point Local Implementation Plan 7-19 Revised February 2011

20 Structural Source Control BMPs Source Control BMPs reduce the potential for storm water runoff and pollutants from coming into contact with one another. Source Control BMPs are defined as any administrative action, design of a structural facility, usage of alternative materials, and operation, maintenance, inspection, and compliance of an area that aims to eliminate or reduce storm water pollution. Each new development and significant redevelopment project is required to implement appropriate Source Control BMP(s). Applicable structural and non-structural source control BMPs are required within all new development and redevelopment projects regardless of their priority, unless they do not apply due to the project characteristics. If any of the following Source Control BMPs that would otherwise apply to the project are not included in the project, an explanation of why must be included in the Project WQMP. The following list of Structural and Non-Structural Source Control BMPs are referenced by the CASQA BMP Handbook reference number in parenthesis, where applicable, refer to Provide Storm Drain System Stenciling and Signage (CASQA BMP Handbook SD-13) Provide stenciling or labeling of all storm drain inlets and catch basins, constructed or modified, within the project area with prohibitive language (such as: NO DUMPING-DRAINS TO OCEAN ) and/or graphical icons to discourage illegal dumping. 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. Maintain legibility of stencils and signs. Use Efficient Irrigation Systems and Landscape Design (CASQA BMP Handbook SD-12) Compliance with the City s Water Efficient Landscape Standards and Requirements, Dana Point Municipal Code (DPMC) 9.55 and Water District standards are also required, when applicable. Projects shall design the timing and application methods of irrigation water to prevent the runoff of excess irrigation water into the municipal storm drain system, which starts at the curb and gutter. The following methods to eliminate excessive irrigation runoff shall be incorporated. Employing rain shutoff devices to prevent irrigation during after precipitation. Designing irrigation systems to each landscape area s specific water requirements. Using flow reducers or shutoff valves triggered by a pressure drop to control water loss in the event of broken sprinkler heads or lines. The timing and application methods of irrigation water shall be designed to prevent runoff of excess irrigation water into the municipal storm drain system. Employing other comparable, equally effective, methods to reduce irrigation water runoff. Group plants with similar water requirements in order to reduce excess irrigation runoff and promote surface filtration. Choose plants with low irrigation requirements (for example, native or drought tolerant species). Consider other design features, such as: Use mulches (such as wood chips or shredded wood products) in planter areas without ground cover to minimize sediment in runoff. City of Dana Point Local Implementation Plan 7-20 Revised February 2011