Appendix G.2. Surface Water Quality Study

Transcription

1 Appendix G.2 Surface Water Quality Study

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3 SURFACE WATER QUALITY STUDY The following report is an analysis of the existing and proposed Surface Water Quality of a proposed Mixed Use project in Boyle Heights, a community within the City of Los Angeles, California. The project consists of the redevelopment of an existing 70-acre rental apartment project known as Wyvernwood Garden Apartments. The intent of this report is to explore the existing site and identify possible existing sources of adverse impacts to surface water quality, determine possible adverse impacts to surface water quality by the proposed project, and present proposed improvements and practices to mitigate adverse impacts in the proposed project. 1) EXISTING CONDITIONS a) Identify regional and local surface water resources. The project site lies within the Los Angeles Basin. The Los Angeles Basin is a coastal sediment-filled plain located between the peninsular and transverse ranges containing the central part of the City of Los Angeles as well as its southern and southeastern suburbs (both in Los Angeles and Orange counties). It is approximately 35 miles (56 km) long and 15 miles (24 km) wide, bounded on the north by the Santa Monica Mountains and Puente Hills, and on the east and south by the Santa Ana Mountains and San Joaquin Hills. The Palos Verdes Peninsula marks the outer edge of the basin along the coast. In particular, the project site is located within the Los Angeles River Watershed, an 871-square mile watershed encompassing the Santa Susanna Mountains to the west, the San Gabriel Mountains to the north and east, and the Santa Monica Mountains and Los Angeles coastal plain to the south. The Los Angeles River Watershed has diverse patterns of land use. Forest or open space covers the upper half of the watershed, while the remaining watershed is highly urbanized with commercial, industrial, or residential uses. There are 22 lakes within its boundaries. In addition, there are a number of spreading grounds in the watershed including sites at Dominguez Gap, the Headworks, Hansen Dam, Lopez Dam, and Pacoima Dam. The Los Angeles River is hydraulically connected to the San Gabriel River through the Rio Hondo, although this occurs primarily during large storm events. The Los Angeles River has evolved from an uncontrolled, meandering river to a major flood protection waterway. The Federal Clean Water Act Section 303(d) requires that States assess the quality of their waters every two years and publish a list of those waters not meeting the water quality standards established for them. Water quality standards include beneficial uses, water quality objectives necessary to protect these uses and the antidegradation policy, and are found in the Basin Plan. For water bodies placed on the 303(d) List of Water Quality Limited Segments, states are required to develop Total Maximum Daily Loads (TMDLs) for the pollutant(s) that are causing standards impairment. Page 1 of 13

4 The project site drains to the Los Angeles River Reach 2 via existing storm drains. The Los Angeles River at this point is a trapezoidal concrete storm drain channel. At its closest point, the Los Angeles River is 1/3 mile west of the site. Storm water runoff from the site travels approximately 1 mile through storm drains to reach the river. According to the Los Angeles Region Integrated Report Clean Water Act Section 305(b) Report and Section 303(d) List of Impaired Waters, 2008 Update, the Los Angeles River Reach 2 is polluted by Ammonia, Coliform Bateria, Copper, Lead, Nutrients (Algae), Oil and Trash. b) On-site surface water characteristics i) Identify runoff tributary areas and conveyance systems Approximately half the surface area of the site drains to existing paved streets where storm water runoff is collected in storm drains and conveyed to an existing City owned 84 diameter storm drain that traverses the site. Approximately half the surface area of the site drains to a grassy swale known as the Mall. Storm water in the Mall is conveyed to an existing County owned 11 wide x 6.5 high storm drain in Grande Vista Avenue. ii) Identification of potential point and non-point discharge sources generated within the project site. Contaminated stormwater washed off of parking lots, roads and highways, called urban runoff, is sometimes included under the category of non-point source pollution. However, this runoff is typically channeled into storm drain systems and discharged through pipes to local surface waters, and is a point source to the Los Angeles River. (a) (b) (c) (d) Limited covered parking on the existing site. Covered parking areas reduce the amount of pollution from surface water run-off as compared to uncovered parking areas. This is because the covering limits the amount of oil and other hazardous fluids that leak from vehicles from being introduced into the surface run-off. The contamination would be considered a point-source pollution where the storm water is introduced into the LA River. No covered trash enclosures on existing site. Rotting food and trash often contain high levels of bacteria. If this trash/waste is spilled in the street or gutter or on the ground, it may ultimately be washed into our creeks and into the ocean untreated as a point source pollutant. Unlike our sewer system, storm drains flow directly into our creeks and the ocean without any disinfection. High bacteria levels can cause health risks to humans who come into contact with this water. In addition, high bacteria levels result in beach closures. Use of chemicals, paint, hazardous materials, etc., may find their way into our storm drain system. This runoff may be channeled into storm drain systems and discharged as a point source pollutant. Waste disposal and potential illegal dumping may find their way into our storm drain system. This runoff may be channeled into storm drain systems and discharged as a point source pollutant. Page 2 of 13

5 (e) (f) (g) Spills of various materials could find their way into our storm drain system. This runoff may be channeled into storm drain systems and discharged as a point source pollutant. Illicit connections to storm drain and sewer systems can be detected by observing abnormal water flow during the dry weather season, unusual flows in sub drain systems used for dewatering, pungent odors coming from the drainage systems, discoloration or oily substances in the water or stains and residues detained within ditches, channels or drain boxes, and excessive sediment deposits, particularly adjacent to or near active offsite construction. It is not known whether or not there are any illicit connections on the existing project site. Leaking sewers may be an existing point source pollution found on the existing project site due to the age of existing sewer lines. c) On-site groundwater characteristics Soils and geotechnical investigations were performed by the project s soils consultant consisting of twelve exploratory borings. According to the consultant s report, these borings varied in depth from 40 to 100 feet below the existing ground surface. As reported, groundwater was not encountered during excavation. Further, the historic high groundwater level was established by review of California Division of Mines and Geology Open File Report 98-20, Plate 1.2, entitled Historically Highest Ground Water Contours. This information indicates that the historically highest groundwater level is on the order of 150 feet below grade. The maximum depth of cut for the project s grading operations is 55 feet below existing grade. This maximum dimension is associated with excavation of the subterranean garage for one of the larger buildings. This garage and other shallower project elements are substantially above the reported historically highest groundwater level and are not anticipated to expose groundwater or affect its water quality characteristics. The consultant s report did note that some soils exposed by exploratory borings were locally found to be above optimum moisture content. However, no recommendation for de-watering was noted. 2) PROJECT IMPACTS a) Existing potential pollution sources are to be removed as a result of the development project and the implementation of BMP s. i) Covered parking will be provided to reduce the amount of oil and other vehicle fluid leaks from being introduced into urban run-off leaving the site. Parking lot design and associated maintenance programs may further reduce runoff issues through the use of permeable surfaces, green landscape strips and other such devices. ii) Trash enclosures will be covered. Storm water and wastewater runoff from trash areas will be reduced. Wastewater from trash enclosures will be directed to sewers. Page 3 of 13

6 iii) iv) Roof drain water will be collected and treated before discharge to the storm drain system. Material use controls will include promoting efficient and safe housekeeping practices when handling potentially harmful materials. v) Material exposure controls will include proper material storage to prevent or reduce the discharge of pollutants to storm water by storing materials in a designated area, installing secondary containment, etc. vi) vii) Material disposal and recycling BMP s will reduce pollutants in storm water. These may include stenciling storm drain system sign with prohibitive language to discourage dumping, and establishing household hazardous waste/used oil collection centers. Illegal dumping controls implement measures to detect, correct, and enforce against illegal dumping of pollutants on streets and into the storm drain system. viii) Illicit connection controls will prevent unwarranted physical connections to storm drain system. ix) Street and storm drain maintenance will reduce the discharges of pollutants to storm water from street surfaces, catch basins and storm water inlets by conducting cleaning on a regular basis. x) Vegetation controls typically involve a combination of chemical application and mechanical methods which reduce the introduction of pollutants into the storm conveyance system. xi) xii) Sewers replacement will limit the number of any potential existing sewage leaks or sanitary overflow into the storm drain conveyance system. Hydrocarbons, oil and other vehicle fluid leaks associated with streets and driveways will be mitigated and treated using bioswales, biofilters, media filters, and/or percolation devices, reducing the discharges of pollutants to storm water. b) New pollutant sources that may be introduced and the implementation of BMP s. i) Construction phase (a) Point and non-point sources (i) (ii) (iii) Grading operations may generate sediment discharge into storm waters. BMP s for reducing erosion and sediment control include site planning considerations, vegetative stabilization, physical stabilization, diversion of runoff, velocity reduction of runoff, and sediment trapping/filtering. Dewatering operations may generate two classes of pollutants: sediment, and toxics/petroleum products. Appropriate sediment controls and groundwater testing can prevent or reduce the discharge of pollutants. Paving operations may pollute surface water with sediment, toxic materials, and oil/grease. Controls may be implemented to prevent runon and runoff pollution. Page 4 of 13

7 (iv) Structure construction and painting may generate toxic materials, floatable materials and other construction waste. Discharge of pollutants into surface waters can be prevented or reduced by covering or berming building material storage areas, using good housekeeping practices, using safer alternative products, and training employees and subcontractors. (v) (vi) Page 5 of 13 Material delivery and storage may generate sediment, nutrients, toxic materials, oil/grease, and floatable materials. Pollutants to storm water may be prevented or reduced by minimizing the storage of hazardous materials onsite, storing materials in a designated area, installing secondary containment, conducting regular inspections, and training employees and subcontractors. Material use may generate nutrients, toxic materials, oil/grease, and floatable materials. Discharge of pollutants into surface waters can be prevented or reduced by using safer alternative products, minimizing hazardous material use on-site, and training employees and subcontractors. (vii) Spill prevention and control may limit toxic materials and oil/grease from polluting storm water by reducing the chance for spills, stopping the source of spills, containing and cleaning up spills, properly disposing of spill materials, and training employees. (viii) Solid waste management may prevent or reduce the discharge of sediment, floatable materials, and other construction waste pollutants to storm water by providing designated waste collection areas and containers, arranging for regular disposal, and training employees and subcontractors. (ix) Contaminated soil management prevents or reduces the discharge of sediment, hydrocarbons, and toxic materials to storm water from contaminated soil and highly acidic or alkaline soils by conducting pre-construction surveys, inspecting excavations regularly, and remediating contaminated soil promptly. (x) Concrete waste management prevents or reduces the discharge of pollutants to storm water from concrete waste by conducting washout off-site, performing on-site washout in a designated area, and training employees and subcontractors. (xi) Septic waste management prevents or reduces the discharge of pollutants to storm water from sanitary/septic waste by providing convenient, well maintained facilities, and arranging for regular service and disposal. (xii) Vehicle and equipment cleaning prevents or reduces the discharge of hydrocarbons, toxic materials and oil/grease to storm water from vehicle and equipment cleaning by using offsite facilities, washing in designated areas only, eliminating discharges into the storm drain by infiltrating or recycling the wash water, and/or training employees and subcontractors.

8 (b) ii) Post-construction (a) (xiii) Vehicle and equipment fueling may introduce hydrocarbons, toxic materials and oil/grease to surface waters. Controls prevent fuel spills and leaks, and reduce their impacts to storm water by using off-site facilities, fueling in designated areas only, enclosing or covering stored fuel, implementing spill controls, and training employees and subcontractors. (xiv) Vehicle and equipment maintenance prevents or reduces the discharge of hydrocarbons, toxic materials and oil/grease to storm water from vehicles and equipment maintenance by running a dry site. This involves using off-site facilities, performing work in designated areas only, providing cover for materials stored outside, checking for leaks and spills, containing, and cleaning up spills immediately, and training employees and subcontractors. Compliance with NPDES and other applicable requirements The California Storm Water Quality Association Handbooks provide general guidance for selecting and implementing Best Management Practices (BMP s) that will eliminate or reduce the discharge of pollutants from project sites to waters of the state and developing and implementing storm water pollution prevention plans (SWPPPs) that document the selection and implementation of BMP s for a particular construction project. The 2004 errata for the handbooks are available on BMP fact sheets were last updated 1/1/2003. Subsurface exploration and borings indicate that groundwater should be well below the depth of project excavation efforts. However, if dewatering were necessary during construction, the following would be required: Prepare and submit a dewatering plan to the Los Angeles City Bureau of Sanitation (BOS), the Regional Water Quality Control Board, and the National Pollutant Discharge Elimination System for plan check, approval, and permit. Obtain a BOS Industrial Waste Permit for disposal of dewatering effluent to the sanitary sewer. Please note that sewers are the primary disposal method for dewatering operations. Disposal to storm drains should only be used as a last resort and would be subject to significant regulation. Point and non-point sources (i) Non-storm water discharge (dry weather runoff) to drains may emit nutrients, heavy metals, toxic materials, floatable materials, oxygen demanding substances, oil/grease, and bacteria/viruses. BMP s eliminate non-storm water discharges to the storm water system. Non-storm water discharges may include: process waste waters, cooling waters, wash waters, and sanitary wastewater. Page 6 of 13

9 (ii) (iii) Vehicle and equipment use: Fueling and maintenance could introduce heavy metals, toxic materials, and oil/grease into storm waters. BMP s prevent fuel spills and leaks, and reduce their impacts to storm water; Washing and cleaning may produce sediment, nutrients, heavy metals, oxygen demanding substances, and oil/grease. BMP s prevent or reduce the discharge of pollutants to storm water from vehicle and equipment washing. Outdoor loading/unloading of materials may generate nutrients, heavy metals, toxic materials, floatable materials, oxygen demanding substances, and oil/grease. BMP s should prevent or reduce the discharge of pollutants to storm water from outdoor loading/unloading of materials. (iv) Outdoor container storage of materials may emit heavy metals, toxic materials, and oxygen demanding substances into storm drainage. Prevent or reduce the discharge of pollutants by installing safeguards against accidental releases, installing secondary containment, conducting regular inspections, and training employees in standard operation procedures and spill cleanup techniques. (v) Outdoor process equipment operations and maintenance could emit sediment, heavy metals, toxic materials, and oil/grease into storm waters. Prevent or reduce the discharge of pollutants to storm water from outdoor process equipment by reducing the amount of waste created, enclosing or covering all or some of the equipment, installing secondary containment, and training employees. (vi) Waste handling and disposal prevents or reduces the discharge of heavy metals, toxic materials, and oil/grease to storm water from waste handling and disposal by tracking waste generation, storage, and disposal; reducing waste generation and disposal through source reduction, re-use and recycling; and preventing runon and runoff from waste management areas. (vii) Contaminated or erodible surface areas may discharge sediment, nutrients, heavy metals, toxic materials, floatable materials, oxygen demanding substances, and oil/grease into storm waters. Prevention or reduction can be accomplished by leaving as much vegetation onsite as possible, minimizing soil exposure time, stabilizing exposed soils, and preventing storm water runon and runoff. (viii) Building and grounds maintenance prevents or reduces the discharge of pollutants to storm water from buildings and ground maintenance by washing and cleaning up with as little water as possible, preventing and cleaning up spills immediately, keeping debris from entering storm drains, and maintaining the storm water collection system. Other measures may include use of non-toxic insecticides and fertilizers. Page 7 of 13

10 (b) (ix) Building repair, remodeling and construction activities may discharge pollutants to storm water. Prevention or reduction of pollutants can be accomplished by using soil erosion controls, enclosing or covering building material storage areas, using good housekeeping practices, using safer alternative products, and training employees. (x) Other potential pollution sources include: Automobile and atmospheric deposits; Urban housekeeping and landscaping practices; Commercial activities; and Accidental spills and illegal dumping. Compliance with NPDES and other applicable requirements The California Storm Water Quality Association Handbooks provide general guidance for selecting and implementing Best Management Practices (BMP s) that will eliminate or reduce the discharge of pollutants from project sites to waters of the state and developing and implementing storm water pollution prevention plans (SWPPPs) that document the selection and implementation of BMP s for a particular construction project. The 2004 errata for the handbooks are available on BMP fact sheets were last updated 1/1/ ) CITY OF LOS ANGELES STANDARD URBAN STORMWATER MITIGATION PLAN (SUSMP) Based on the City of L.A. CEQA Thresholds Guide (2006), the project would have a significant impact on surface water flow and quality if it would: Result in discharges that would create pollution, contamination or nuisance as defined in Section of the California Water Code (CWC) or that cause regulatory standards to be violated, as defined in the applicable NPDES stormwater permit or Water Quality Control Plan for the receiving water body. The municipal storm water National Pollutant Discharge Elimination System Permit (NPDES Permit No. CAS004001) issued to Los Angeles County and 84 cities (Permittees) by the Los Angeles Regional Water Quality Control Board (Regional Board) on December 13, 2001 under Order No requires the development and implementation of a program addressing storm water pollution issues in development planning for development and redevelopment projects. a) Requirements for Standard Urban Stormwater Mitigation Plan (SUSMP) i) Peak Storm Water Runoff Discharge Rates [further discussed in separate Storm Water Hydrology Study ] Post-development peak stormwater runoff discharge rates shall not exceed the estimated pre-development rate for developments where the increased Page 8 of 13

11 peak storm water discharge rate will result in increased potential for downstream erosion On May 31, 2007, the project team met with Ammar Ibrahim Altawill of the City of Los Angeles Watershed Protection Division. The following requirement was given: The Watershed Protection Division will not require runoff Peak reduction because the site currently flows directly to storm drains and the L.A. River. The project will not increase the potential for erosion. The Los Angeles county Department of Public Works has directed that a maximum of 2.9 cfs per acre may be directed to the County storm drain system from this project. Currently 34.5 acres drains to the County storm drain system; therefore maximum discharge allowed to the County system is 100 cfs. ii) Conserve Natural Areas If applicable the following items are required and must be implemented in the site layout during the subdivision design and approval process, consistent with applicable General Plan and Local Area Plan polices: Concentrate or cluster development on portions of a site while leaving the remaining land in a natural undisturbed condition Limit clearing and grading of native vegetation at a site to the minimum amount needed to build lots, allow access, and provide fire protection. Maximize trees and other vegetation at each site by planning additional vegetation, clustering tree areas, and promoting the use of native and/or drought tolerant plants. Promote natural vegetation by using parking lot islands and other landscaped areas. Preserve riparian areas and wetlands The existing site consists entirely of urban multi-family development and does not include any areas of natural undisturbed condition, native vegetation, riparian areas, or wetlands. To maximize trees and other vegetation at the site the project will create landscaped areas including vegetation, trees, and native and/or drought tolerant plants. iii) Minimize Storm Water Pollutants of Concern Stormwater runoff from a site has the potential to contribute oil and grease, suspended solids, metals, gasoline, pesticides, and pathogens to the storm water conveyance system. The development must be designed so as to minimize, to the maximum extent practicable, the introduction of pollutants of concern that may result in significant impacts, generated from site runoff of directly connected impervious areas (DCIA), to the storm water conveyance system as approved by the building official. Pollutants of concern, consist of any pollutants that exhibit one or more of the following characteristics: Page 9 of 13

12 current loadings or historic deposits of the pollutant are impacting the beneficial uses of a receiving water, elevated levels of the pollutant are found in sediments of a receiving water and/or have the potential to bioaccumulate in organisms therein, or the detectable inputs of the pollutant are at concentrations or loads considered potentially toxic to humans and/or flora and fauna. In meeting this specific requirement, minimization of the pollutants of concern will require the incorporation of a BMP or combination of BMPs best suited to maximize the reduction of pollutant loading in that runoff to the Maximum Extent Practicable. The proposed project takes into consideration several BMP s to minimize pollutants of concern associated with water runoff. Section 2 of this report categorizes these BMP s as either existing pollution sources or new pollution sources. The existing pollution sources described in Section 2 a) indicate how proper project design and promoting efficient and safe housekeeping practices can minimize pollutants to water runoff. The new pollution sources described in Section 2 b) detail BMP s for both construction and post-construction sources of polluted water runoff. iv) Protect Slopes and Channels Project plans must include BMPs consistent with local codes and ordinances and the SUSMP to decrease the potential of slopes and/or channels from eroding and impacting stormwater runoff. Permanent slopes will be landscaped to reduce the potential for erosion. The project does not include channels. v) Provide Storm Drainage System Stenciling and Signage All storm drain inlets and catch basins within the project area must be stenciled with prohibitive language (such as: NO DUMPING DRAINS TO OCEAN ) and/or graphical icons to discourage illegal dumping. Signs and prohibitive language and/or graphical icons, which prohibit illegal dumping, must be posted at public access points along channels and creeks within the project area. Legibility of stencils and signs must be maintained. All storm drain inlets and catch basins within the project area will have prohibitive language as required by the SUSMP. Legibility of stencils will be maintained per a recorded covenant and agreement. vi) Properly Design Outdoor Material Storage Areas Outdoor material storage areas refer to storage areas or storage facilities solely for the storage of materials. Improper storage of materials outdoors may provide an opportunity for toxic compounds, oil and grease, heavy metals, nutrients, suspended solids, and other pollutants to enter the stormwater conveyance system. Where proposed project plans include outdoor areas for storage of materials that may contribute pollutants to the Page 10 of 13

13 storm water conveyance system, the following Structural or Treatment BMPs are required: Materials with the potential to contaminate storm water must be: (1) 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 stormwater conveyance system; or (2) protected by secondary containment structures such as berms, dikes, or curbs. The storage area must be paved and sufficiently impervious to contain leaks and spills. The storage area must have a roof or awning to minimize collection of stormwater within the secondary containment area. This project does not propose outdoor material storage areas. vii) Properly Design Trash Storage Areas A trash storage area refers to an area where a trash receptacle or receptacles are located for use as a repository for solid wastes. Loose trash and debris can be easily transported by the forces of water or wind into nearby storm drain inlets, channels, and/or creeks. All trash container areas must meet the following Structural or Treatment Control BMP requirements. Trash container areas must have drainage from adjoining roofs and pavement diverted around the areas Trash container areas must be screened or walled to prevent off-site transport of trash To mitigate the potential harmful effects of trash storage (for residential as well as all commercial and office uses) all such areas will be covered and wastewater will be directed to sewers. Refer to Section 2 a) ii) of this report. viii) Provide Proof of Ongoing BMP Maintenance Improper maintenance is one of the most common reasons why water quality controls will not function as designed or which may cause the system to fail entirely. It is important to consider who will be responsible for maintenance of a permanent BMP, and what equipment is required to perform the maintenance properly. As part of project review, if a project applicant has included or is required to include, Structural or Treatment Control BMPs in project plans, the applicant shall be required to provide verification of maintenance provisions through such means as may be appropriate, including, but not limited to legal agreements, covenants, CEQA mitigation requirements and/or Conditional Use Permits. For all properties, the verification will include the developer s signed statement, as part of the project application, accepting responsibility for all structural and treatment control BMP maintenance until the time the property is transferred and, where applicable, assigned agreement from the public entity assuming responsibility for Structural or Treatment Control BMP maintenance. The transfer of property to a private or public owner must have conditions requiring the recipient to assume responsibility for maintenance of Page 11 of 13

14 any Structural or Treatment Control BMP to be included in the sales or lease agreement for that property, and will be the owner s responsibility. The condition of transfer shall include a provision that the property owners conduct maintenance inspection of all Structural or Treatment Control BMPs at least once a year and retain proof of inspection. For residential properties where the Structural or Treatment Control BMPs are located within a common area which will be maintained by a homeowner s association, language regarding the responsibility for maintenance must be included in the projects conditions, covenants and restrictions (CC&Rs). Printed educational materials will be required to accompany the first deed transfer to highlight the existence of the requirement and to provide information on what storm water management facilities are present, signs that maintenance is needed, how the necessary maintenance can be performed, and assistance that can be provided. The transfer of this information shall also be required with any subsequent sale of the property. If Structural or Treatment Control BMPs are located within a public area proposed for transfer, they will be the responsibility of the developer until they are accepted for transfer by the County or appropriate public agency. Structural or Treatment Control BMPs proposed for transfer must meet design standards adopted by the public entity for the BMP installed and should be approved by the County or other appropriate public agency prior to its installation. An Operations and Maintenance (O&M) Plan will be provided for each Structural or Treatment Control BMP specified for this project. The O&M Plan will include: Directions for maintenance activities and source control practices Logs for recording the dates and operators of said activities and practices A Covenant and Agreement specifying the party responsible for implementing the Operations and Maintenance Plan will be recorded for each BMP. ix) Design Standards for Structural or Treatment Control BMPs Post-construction Treatment Control BMPs are required to incorporate, at a minimum, either a volumetric or flow based treatment control design standard or both, as identified below to mitigate (infiltrate, filter, or treat) storm water runoff: Volumetric Treatment Control BMP The volume of runoff produced from a 0.75 inch storm event, prior to its discharge to a storm water conveyance system Flow Based Treatment Control BMP The flow of runoff produced from a rain event equal to at least 0.2 inches per hour intensity. The project s design and construction documents and associated SUSMP program will specify methods and requirements to mitigate storm water quality to regulatory standards. Page 12 of 13

15 4) MEETING WITH WATERSHED PROTECTION DIVISION On the May 31, 2007 meeting Ammar Ibrahim Altawill, of the City of Los Angeles Watershed Protection Division, the following requirements were given to the project team: Mitigate the volume of runoff produced from the 0.75 inch storm event prior to its discharge into the storm drain system. Infiltration shall be used to the maximum amount practicable. Bio-filters and/or planter boxes may be used. Mechanical/Hydrodynamic units such as CDS units may be used but are not preferred. Pre-treat roof water before directing to planter boxes to remove trash, etc. Further, project documentation and design materials will specify and incorporate the above measures, BMPs identified in Sections 2 and 3 of this report, and other BMPs from the California Storm Water Quality Association Handbook to assure that storm water quality of project runoff meets agency requirements and standards. 5) CUMULATIVE IMPACTS Cumulative impact analysis on surface water quality is evaluated for the Los Angeles River Watershed. Forecasted growth in this watershed is subject to NPDES requirements regarding water quality for both construction and operation. Additionally, related projects within the Los Angeles River Watershed are generally in an already highly urbanized area, hence, future development is not likely to cause substantial changes in the regional surface water quality. It is also anticipated that related projects would be subject to SUSUMP requirements and implementation measures. Therefore, cumulative impacts to surface water quality should be less than significant when compliant with applicable laws, rules and regulations. Page 13 of 13

16 SURFACE WATER QUALITY STUDY REFERENCES Federal Clean Water Act of 1977 Pub.L , December 27, 1977 and Water Quality Act of 1987, Pub.L , February 4, Los Angeles Region Integrated Report Clean Water Act Section 305(b) Report and Section 303(d) 2008 Update, Adopted July 16, Preliminary Geotechnical Engineering Investigation, Proposed Residential Development, Southeast Corner 8 th Street and Soto Street, Geotechnologies Inc, January 25, California Storm Water Quality BMP Handbook, January 2003, Errata September LA CEQA Threshold Guide, City of Los Angeles National Pollutant Discharge Elimination System Permit (NPDES Permit No. CAS004001), as issued by the Los Angeles Regional Water Quality Control Board, December 13, 2001 under Order No Meeting with Ammar Ibrahim Altawill, City of Los Angeles Watershed Protection Division, May 31, 2007.