iv.e. hydrology and water quality. hydrology and water quality.pdf · e. hydrology and water...

Los Angeles Community College District LAMC Master Plan and Public Recreation Improvement Program PCR Services Corporation October 2005

Page IV-163

PRELIMINARY WORKING DRAFT – Work in Progress

IV. ENVIRONMENTAL IMPACT ANALYSIS E. HYDROLOGY AND WATER QUALITY

This section describes the potential impacts on water quality, drainage, and flooding that may occur as a result of the proposed project. This section is based on the Water Resources Technical Report dated September 7, 2004 prepared by PSOMAS for the proposed project. The report is contained in its entirety in Volume III, Appendix I, of this EIR. Also incorporated into this section is the Pacoima Wash Hydrology Report prepared by the County of Los Angeles and dated June 1, 2005, which provided updated hydrologic information to address the Capital Flood and the 100-year frequency design storm at Pacoima Wash.73

1. ENVIRONMENTAL SETTING

a. Existing Conditions

(1) Hydrology

As shown in Figure IV-26 on page IV-164, the project site is located within the Pacoima Wash Watershed, which is situated within the Upper Los Angeles River Watershed. Runoff in this area stems from the Angeles National Forest and flows in the Pacoima Canyon Creek, which becomes the Pacoima Wash downstream of the Pacoima Reservoir located approximately two miles upstream of the project site. The Pacoima Wash flows downstream in a southerly direction from the Pacoima Reservoir and passes along the southeastern boundary of the project site (PA 2). Approximately four miles downstream of the project site, the Pacoima Wash Diversion Channel discharges into the Tujunga Wash which extends another three miles before it ultimately converges with the Los Angeles River. The Pacoima Wash Watershed has a total tributary area of 21,716 acres (33.93 square miles), which includes 18,1567 acres (28.37 square miles) upstream of Pacoima Dam and a tributary area of 3,560 acres (5.56 square miles) downstream of Pacoima Dam. The upstream watershed is 100 percent undeveloped. The downstream watershed is 16 percent residential, 8 percent recreational parks, and 76 percent undeveloped.

73 Capital Flood refers to runoff from a 50-year rainfall storm event falling on a saturated watershed. A 50-year

storm event is a flood that is equaled or exceeded once in 50 years on the average; equivalent to the two percent annual chance.

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IV.E. Hydrology and Water Quality


Page IV-165


Using Los Angeles County Hydrology Methodology, runoff from a 25-year storm event was calculated for each of the drainage areas. Runoff quantities are provided in Table IV-21 on page IV-166. As shown, under existing conditions, the drainage areas would generate a total clear flow rate of 268 cubic feet per second (cfs) during a 25-year storm event.74

The increase in runoff will depend on the type of soil and its response to rainfall.75 Some soils can absorb 100 percent of the rainfall of a small storm, such as soil type 15 (Tujunga Fine Sandy Loam), found in the Pacoima Wash Watershed. According to the LACDPW Hydrology Manual, soil types 5 (Hanford Fine Sandy Loam) and 15 are found in this watershed. Annual rainfall in the area is typically low (approximately 23 inches) and usually occurs in the winter months. The combination of soil characteristics and high magnitude low frequency storms typical of the region produces conditions conducive to rapid accumulation of surface water and high storm peak runoffs.76

Two drainage features, the May Canyon Channel and Channel C, traverse the project site. The May Canyon Channel commences near the intersection of Hubbard Street and Garrick Avenue and extends underground through the County Recreation Area to the southern portion of PA 2A, where it surfaces and converges with the Pacoima Wash. Channel C commences at Hubbard Street and extends aboveground along the northern boundary of the existing LAMC campus (PA 1). Once the channel reaches the northeast corner of the campus, it becomes an underground channel that drains to a pond on the El Cariso Golf Course.

According to the Flood Insurance Rate Map, PA 1, PA 3, and PA 4 are not located within a 100-year flood plain.77 PA 2 (Parkland Expansion Parcels) is located within a 100-year flood plain as, depicted in Figure IV-27 on page IV-167. Portions of PA 2 are located within Zone AO and Zone A. Zone AO is defined as areas of 100-year shallow flooding where depths are between 1 and 3 feet as indicated, but flood hazard factors have not been determined. Zone A is defined as areas of 100-year flood, where base flood elevations and flood hazard factors have not been determined. The project site is located within a levee or dam failure-related inundation area.

74 A 25-year flood is a flood that is equaled or exceeded once in 25 years on the average; equivalent to the

four percent annual chance. 75 PSOMAS, Water Resources Technical Report for Los Angeles Mission College (September 7, 2004); p. 28. 76 Ibid, p. 29. 77 FEMA, Managing Floodplain Development in Approximate Zone A Areas—A Guide for Obtaining and

Developing Base (100-year) Flood Elevations (April 1995); pp. A1-1 and A1-2, http://www.fema.gov./pdf.fhm/frm_zna.pdf [February 5, 2005]. A 100-year flood is a flood that is equaled or exceeded once in 100 years on the average; equivalent to the one percent annual chance. A floodplain is any land area, such as the lowland areas adjoining inland waters, susceptible to being inundated by water from any source.



Page IV-166


In order to estimate runoff volumes for the project site, the project site was divided into several sub-basins/drainage areas. The drainage areas, which total approximately 212 acres, are depicted in Figure IV-28 on page IV-168. All of the drainage areas ultimately discharge to the Pacoima Wash. Runoff from the residential areas located north of the project site is intercepted by the drainage facilities in Hubbard Street. Runoff from areas northwest of the project site as well as portions of the existing County Recreation Area drains into the May Canyon Channel. There are no known existing hydrologic or drainage issues on the project site or its tributary watersheds.

(2) Water Quality

There is no water quality monitoring data available for the project site or its upstream watershed. Therefore, existing water quality conditions were modeled using land use specific storm water quality data provided by Los Angeles County, as well as data from other recent studies in Los Angeles County. The constituents chosen for the water quality modeling analysis were selected based on the existing land use types at the project site (open space, golf course, educational). The constituents, which include total phosphorus (TP), total nitrogen (TN), nitrate, ammonia, dissolved copper (Cu), total lead (Pb), dissolved zinc (Zn), total aluminum (Al), and

Table IV-21

Existing Runoff Volumes

Sub-Basin/Drainage Area Associated

Project Area (PA) Area

(acres) Q25c a

(cfs) EB-1 PA 1 8.4 15.1 EB-2 PA 1 8.8 16.8 EB-3 PA 1 6.2 12.0 EB-4 PA 4 10.8 12.4 EB-5 PA 3B 18.5 19.2 EB-6 PA 3B 41.1 41.3 EA-1 N/A b 8.9 13.3 EA-2 N/A b 10.6 17.1 EA-3 PA 3 28.3 30.8 EA-4 PA 3A 17.0 23.1 EA-5 N/A b 36.0 37.8 EA-6 PA 2A 7.7 12.0 EC PA 2B 9.6 17.1

Total - 211.9 268.0 a Quantities are presented in cubic feet per second based on a 25-year storm event. b Not applicable because the drainage area identified does not include land within a project site. Source: PSOMAS, Water Resources Technical Report for Los Angeles Mission College, September 2004.

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Page IV-169


fecal coliform, are commonly found in runoff from these types of land uses. The percent of impervious surface for each drainage area was estimated based on the distribution of existing land uses and land use specific percent impervious values presented in the Los Angeles Hydrology Manual.78 No water quality control improvements currently exist within the project site. Table IV-22 on page IV-170 summarizes the results of the Event Mean Concentration (EMC) values used to characterize existing storm water quality at the project site.79 Table IV-23 on page IV-171 presents the existing pollutant loads for each of the constituents based on a runoff volume of 4,561,406 cubic feet year.

The project site is within the overall Upper Los Angeles River Watershed, which includes many uses from vacant and open space to urban developments. Constituents found in storm water runoff in urbanized areas include sediment, nutrients, petroleum hydrocarbons, metals, pathogens, as well as trash. Many of these pollutants are listed as priority pollutants for reaches of the Los Angeles River. As noted above, the downstream reaches of the Los Angeles River are included on the 303(d) list and are subject to TMDL limits. The current constituents listed for TMDL priority scheduling include aluminum, ammonia, cadmium, copper, lead, zinc, high coliform count, nutrients (algae), pH, scum/foam-unnatural sources, and oil. The following is brief overview of the potential construction type key pollutants.

• Nutrients. Nitrogen, phosphorous, and potassium are the major nutrients used for fertilizing new landscape at construction sites. Heavy use of commercial fertilizers can result in discharge of nutrients to water bodies where they may cause excessive algae growth.

• Trace Metals. Over half of the metal load carried in storm water is associated with sediments (Schuler, 1987) as metals both adsorb to solids particulate matter (total suspended solids) and get washed off in dissolved forms. Many of the uses during a construction project such as galvanized metals, paint, or preserved wood may contain metals. If uncontrolled these metals may enter the storm water and impact the downstream receiving waters.

• Pesticides. Unnecessary or improper application of pesticides may result in direct surface water contamination and/or indirect pollution by transport off soil surfaces into surface water.

78 Los Angeles County Department of Public Works, Hydrology Manual for Flood Control, December 1991. 79 An EMC is the average concentration of a pollutant in the runoff from a storm event, equal to the total mass of

pollutant divided by the total volume of storm runoff.



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• Other Toxic Chemicals. If improperly stored and/or disposed of, synthetic organic compounds (such as adhesives, cleaners, sealants, and solvents) that may be used at construction sites will have a significant impact on receiving waters.

• Miscellaneous Wastes. These may include wash water from concrete mixers, paints and painting equipment cleaning activities, solid wastes from land clearing activities, wood and paper material from packaging of building material, and sanitary wastes. Improper/illegal disposal of these wastes can lead to polluted waterways.

b. Policy and Regulatory Environment

Development that discharges storm water runoff into and/or results in encroachment upon natural drainages, wetlands, and/or floodplains is subject to the requirements of federal, state, and local agencies, including the U.S. Army Corps of Engineers (USACE) and the Regional Water Quality Control Board (RWQCB) pursuant to the federal Clean Water Act (CWA), the California Department of Fish and Game (CDFG) pursuant to the California Fish and Game Code, and the Los Angeles County Department of Public Works (LACDPW).

Table IV-22

Land Use Representative Event Mean Concentrations a Pollutant EMCs

Land Use b TP

(mg/L) TN

(mg/L) Nitrate (mg/L)

Ammonia(mg/L)

Cu (diss)(mg/L)

Pb (mg/L)

Zn (diss)(mg/L)

Al (mg/L)

Fecal Coliform g

(MPNh/100mL)Golf Course c 1.43 8.69 f 4.44 1.1 N/A j 0.0025 N/A j N/A j 17,950 Institutional d 0.31 2.2 0.51 0.28 0.013 0.0049 0.066 0.881 N/A e Open Space e 0.16 1.89 1.05 0.11 N/A i N/A i N/A i 1.681 1,397 a An Event Mean Concentration (EMC) is the average concentration of a pollutant in the runoff from a storm event,

equal to the total mass of pollutant divided by the total volume of storm runoff. b EMCs for each land use are based on L.A. County Storm Water Monitoring Data (1994-2000), unless otherwise

noted. c Calculated mean concentrations for golf course land uses are based on an analysis conducted by Geosyntec, 2002.d Los Angeles County 1994-2000 Integrated Receiving Water Impacts Report, Table 4-12, Educational Land Use. e Los Angeles County 1994-2000 Integrated Receiving Water Impacts Report, Table 4-12, Vacant Land Use. f Total nitrogen estimated from sum of Total Kjeldahl Nitrogen (TKN) and nitrates. g Fecal coliform levels based on Center for Watershed Protection data, unless noted. h MPN – Most Probable Number. i Statistically invalid data (S.I.D.); data collected is below detection limit. j No information available. Source: PSOMAS, Water Resources Technical Report for Los Angeles Mission College, September 2004.



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(1) Hydrology

(a) Federal Statutes and Programs

With the passage of the National Flood Insurance Act of 1968, the U.S. Congress established the National Flood Insurance Program (NFIP), enabling property owners in participating communities to purchase insurance as a protection against flood losses in exchange for State and community floodplain management regulations that reduce future flood damages. Participation in the NFIP is based on an agreement between communities and the federal government. If a community adopts and enforces a floodplain management ordinance to reduce future flood risk to new construction in floodplains, the federal government will make flood insurance available within the community as a financial protection against flood losses. This insurance is designed to provide an insurance alternative to disaster assistance to reduce the escalating costs of repairing damage to buildings and their contents caused by floods.80

The Flood Disaster Protection Act of 1973 prohibits federal agencies from providing financial assistance for acquisition or construction of buildings and certain disaster assistance in the floodplains in any community that did not participate in the NFIP by July 1, 1975, or within 1 year of being identified as flood-prone. This law required federal agencies and federally insured or regulated lenders to require flood insurance on all grants and loans for acquisition or construction of buildings in designated Special Flood Hazard Areas (SFHAs) in communities that participate in the NFIP. This requirement is referred to as the Mandatory Flood Insurance Purchase Requirement. The SFHA is that land within the floodplain of a community subject to a 1 percent or greater chance of flooding in any given year, commonly referred to as the 100-year flood. The 1-percent-annual-chance flood (or 100-year flood) represents a magnitude and

80 Federal Emergency Management Agency; Federal Insurance and Mitigation Administration, National Flood

Insurance Program Description (August 1, 2002).

Table IV-23

Existing Pollutant Loads

Modeled Constituents

Drainage Area

(acres)

Runoff Volume (ft3/yr)

TP (lbs/yr)

TN (lbs/yr)

Nitrate(lbs/yr)

Ammonia(lbs/yr)

Cu (diss)

(lbs/yr)Pb

(lbs/yr)

Zn (diss)

(lbs/yr) Al

(lbs/yr)

Fecal Coliform

(109 MPN/yr)

212 4,561,406 142.29 1,019.21 486.82 110.70 0.97 0.54 4.94 305.63 6,398

Source: PSOMAS, Water Resources Technical Report for Los Angeles Mission College, September 2004.



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frequency that has a statistical probability of being equaled or exceeded in any given year, the 100-year flood has a 26 percent (or 1 in 4) chance of occurring over a 30-year period.81

In 1994, Congress amended the 1968 Act and the 1973 Act with the National Flood Insurance Reform Act (NFIRA). The 1994 Act included measures to increase compliance by mortgage lenders; increase the amount of flood insurance coverage that can be purchased; provide flood insurance coverage for the cost of complying with floodplain management regulations by individual property owners; establish a Flood Mitigation Assistance grant program to assist States and communities to develop mitigation plans and implement measures to reduce future flood damages to structures; codify the NFIP’s Community Rating System; and require FEMA to assess its flood hazard map inventory at least once every 5 years.82

(b) Los Angeles County Department of Public Works

In 1986, the LACDPW issued a memorandum entitled “Level of Flood Protection and Drainage Protection Standards” for development projects in Los Angeles County. The memorandum establishes Los Angeles County policy on levels of flood protection and requires that designated facilities (i.e., facilities not under State of California jurisdiction that intercept flood waters from natural drainage courses) be designed for the Capital Flood (i.e., 50-year storm event). The project would intercept flood flows from natural areas; therefore, storm drainage facilities proposed to accept these flows must be sized and designed for the Capital Flood.

(2) Water Quality

The federal CWA is the cornerstone of surface water quality protection in the United States. The statute employs a variety of regulatory and non-regulatory tools to sharply reduce direct pollutant discharges into waterways, finance municipal wastewater treatment facilities, and manage polluted runoff. These tools are employed to achieve the broader goal of restoring and maintaining the chemical, physical, and biological integrity of the nation’s waters. The nationwide implementation of the CWA is the responsibility of the United States Environmental Protection Agency (USEPA).

(a) Federal Clean Water Act

The USACE regulates “discharge of dredged or fill material” into “waters of the U.S.,” which includes tidal waters, interstate waters, and all other waters that are part of a tributary

81 Ibid., p.5. 82 Ibid., p. 4.



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system to interstate waters or to navigable “waters of the U.S.,” as well as the use, degradation, or destruction of which could affect interstate or foreign commerce or which are tributaries to waters subject to the ebb and flow of the tide (33 C.F.R. 328.3(a)), pursuant to provisions of Section 404 of the CWA. The USACE generally takes jurisdiction within rivers and streams to the “ordinary high water mark” determined by erosion, the deposition of vegetation or debris, and changes in vegetation. The USACE defines jurisdictional wetlands as areas that contain hydrophytic vegetation (i.e., aquatic vegetation), hydric soils (i.e., soils that are sufficiently wet in the upper part to produce anaerobic conditions), and wetland hydrology, in accordance with the procedures established in the USACE Wetland Delineation Manual.83 On January 9, 2001, the United States Supreme Court ruling in the Solid Waste Agency of Northern Cook County v. United States Army Corps of Engineers (No. 99-1178) held that the CWA does not give the federal government regulatory authority over non-navigable, isolated, intrastate waters. As a result of this decision, some previously regulated depressional areas, such as mudflats, sandflats, wetlands, prairie potholes, wet meadows, playa lakes, natural ponds, and vernal pools, which are not hydrologically connected to other intrastate or interstate “waters of the U.S.,” are no longer regulated by the USACE.84

The Pacoima Wash, which is located immediately east of PA 2, has been identified as a “water of the U.S.” Any activity in the wash may be subject to federal permit requirements pursuant to Section 404 of the CWA. Potential impacts to the Pacoima Wash and/or other designated “waters of the U.S.” are discussed in subsection IV.C., Biological Resources of this EIR.

Section 401 of the CWA requires that any applicant for a federal permit that involves activities resulting in a discharge to “waters of the U.S.” shall provide a certification from the State in which the discharge is proposed. The State certification needs to conclude that the discharge will comply with the applicable provisions under the federal CWA. Therefore, before the USACE will issue a Section 404 permit, applicants must apply for and receive a CWA Section 401 Water Quality Certification. In the State of California, the overall regulation, protection, and administration of water quality is carried out by the State Water Resources Control Board (SWRCB).

83 U.S. Army Environmental Laboratory, Wetlands Delineation Manual, 1987 Edition. 84 These areas may still be regulated by CDFG under Fish and Game Code Section 1600 or by the RWQCB under

the Porter-Cologne Act. Legislation has been introduced to the State Assembly to revise the Fish and Game Code to specifically regulate isolated waters affected by the SWANCC case.



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(b) National Pollutant Discharge Elimination System Program

The USEPA established the National Pollutant Discharge Elimination System (NPDES) Program as the primary implementation program for regulating surface water quality. The NPDES Program requires permits for storm water discharge from storm drain systems into “waters of the U.S.” The NPDES Program addresses storm water discharge during both pre- and post-construction activities.

Construction activities disturbing one acre or more are required to comply with the SWRCB General Construction Activity Storm Water Permit (NPDES No. CAS000002, Order No. 99-08-DWQ). This requires the preparation and approval of a Storm Water Pollution Prevention Plan (SWPPP). The SWPPP must include the implementation of Best Management Practices (BMPs) that would reduce the potential for discharge of accidental and/or implicit pollutants into the storm drain system during grading and construction. The BMPs should be designed to maintain construction areas in such a condition that storm flows do not carry wastes or pollutants off-site. The General Construction Activity Storm Water Permit requires that these BMPs be in place prior to issuance of a grading permit.

Under the General Construction Activity Storm Water permit, project applicants are also required to implement a Standard Urban Storm Water Mitigation Plan (SUSMP) during the operational life of a project to ensure that storm water pollution is addressed through the incorporation of BMPs in the design of the development. This requirement provides numerical water quality design standards to ensure that storm water runoff is managed for water quality concerns in addition to flood protection. Project applicants are required to select source control and treatment control BMPs from the list approved by the RWQCB. In combination, the treatment control BMPs must be sufficiently designed and constructed to treat, infiltrate, or filter the first 3/4-inch of storm water runoff from a storm event.

(c) State of California Water Quality Requirements

(i) Porter-Cologne Water Quality Control Act

Division 7 of the California Water Code, also known as the Porter-Cologne Water Quality Control Act, contains provisions that cover water quality protection and management for California’s waters. The Porter-Cologne Act establishes the SWRCB and the nine Regional Water Quality Control Boards (RWQCBs) as the principal state agencies responsible for the protection and, where possible, the enhancement of the quality of California’s waters. The SWRCB sets statewide policy, and together with the RWQCBs, implements state and federal laws and regulations. In California, the NPDES permit program is administered by the SWRCB, through the RWQCBs.



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Under the Porter-Cologne Act, a RWQCB may choose to regulate discharges of waste (dredge or fill materials) by issuing Waste Discharge Requirements (WDR), a type of state discharge permit, instead of issuing a CWA Section 401 Water Quality Certification. The SWRCB must review the WDR and certify, condition, or deny any activity if it does not comply with state water quality standards. Each RWQCB may waive WDRs for a specific discharge or category of discharges as long as the conditions stated in the respective RWQCB’s Water Quality Management Plan are followed. Processing of a WDR is similar to that of a Section 401 certification; however, the RWQCB has slightly more discretion to add conditions to a project under the Porter-Cologne Act than under the CWA. The project site is located within Region 4 and, thus, would obtain a WDR permit or CWA Section 401 Water Quality Certification for the proposed project from the Los Angeles RWQCB.

(ii) Water Quality Control Plan for the Los Angeles Region

The project is subject to the RWQCB’s Water Quality Control Plan (Basin Plan). Under the SWRCB, each RWQCB has adopted a Basin Plan, which is designed to preserve and enhance water quality and protect the beneficial uses of the region’s ground and surface waters. Region 4’s Basin Plan, Water Quality Control Plan for the Los Angeles Region designates beneficial uses of water bodies, sets water quality objectives to protect those uses, addresses localized water quality problems, and lays out a plan for water quality protection.85 Accordingly, water quality criteria for selected constituents have been established for the types of water uses designated under the Basin Plan.

As identified in the Basin Plan, the project site falls within Reach 8 of the Upper Los Angeles River Watershed (Pacoima Wash above Pacoima Spreading Grounds) and within the Pacoima Wash Hydrologic Unit (HU 405.21). Beneficial uses identified for Reach 8 of the Upper Los Angeles River include municipal and domestic supply, groundwater, contact water recreation, non-contact water recreation, warm freshwater habitat, wildlife habitat, and rare, threatened, or endangered species. Reach 8 is not included on the 2002 CWA Section 303(d) list of impaired reaches of the Los Angeles River. However, downstream reaches of the Los Angeles River are included on the list and are subject to Total Maximum Daily Load (TMDL) limits. The current constituents listed for TMDL priority scheduling include aluminum, ammonia, cadmium, copper, lead, zinc, high coliform count, nutrients (algae), pH, scum/foam-unnatural sources, and oil. These pollutants were designated on the priority list mainly because of their current non-compliance with the beneficial uses. Future development of vacant/open space lands within the Los Angeles River Watershed may further degrade water quality if not properly mitigated.

85 California Regional Water Quality Control Board, Los Angeles Region, Water Quality Control Plan, Los

Angeles Region, adopted June 13, 1994.



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(iii) California Fish and Game Code

Section 1602 of the California Fish and Game Code requires any entity (e.g., person, State or local government agency, or public utility) who proposes a project that will substantially divert or obstruct the natural flow of, or substantially change or use any material from the bed, channel, or bank of, any river, stream, or lake, or deposit or dispose of debris, waste, or other material containing crumbled, flaked, or ground pavement where it may pass into any river, stream, or lake, it must first notify the CDFG of the proposed project.86 This includes rivers or streams that flow at least periodically or permanently through a bed or channel with banks that support fish or other aquatic life and watercourses having a surface or subsurface flow that support, or have supported, riparian vegetation. The CDFG’s jurisdiction extends to the river, stream, or lake’s top of bank, or to the outer edge of the adjacent riparian vegetation (i.e. riparian “drip line”), whichever is greater. If the CDFG determines that a proposed project may substantially adversely affect existing resources, a Lake or Streambed Alteration Agreement will be required.

Any activity in the Pacoima Wash may be subject to regulations administered by the CDFG. Impacts to the Pacoima Wash and/or other water resources are discussed in subsection IV.C., Biological Resources, of this EIR.

(d) County of Los Angeles

Applicants for development projects have two major responsibilities under the General MS4 permit. The first is to submit and then implement a Standard Urban Storm Water Mitigation Plan (SUSMP) that contains design features and BMPs appropriate and applicable to the project. The Los Angeles Region RWQCB approved Los Angeles County’s SUSMP that requires new construction and development projects to implement BMPs (as of March 8, 2000). The second responsibility is to prepare a Storm Water Pollution Prevention Plan (SWPPP) for all construction projects with disturbed areas greater than 1 acre. The proposed project would be subject to these requirements and proper development and implementation of a SUSMP and a SWPPP.

Design standards for post-construction structural or treatment control BMPs have been established in the SUSMP for Los Angeles County. The SUSMP requires that new developments and re-development projects employ a variety of general and land use specification measures to reduce the post-project discharge of pollutants from storm water conveyance systems to the maximum extent practicable. The County’s Manual for the Standard

86 Senate Bill No. 418, approved by the Governor October 8, 2003, includes revisions to the Streambed Alteration

Agreement process.



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Urban Storm Water Mitigation Plan includes the requirements of the SUSMP. Projects that fall into any of the seven SUSMP development categories are required to incorporate appropriate SUSMP requirements into project plans as part of the development plan approval process for building and grading permits.87 The SUSMP numerical sizing criteria states that all post-construction structural or treatment control BMPs shall collectively be designed to comply with the following:

• Mitigate (infiltrate or treat) storm water runoff from either:

o the 85th percentile 24-hour runoff event determined as the maximized capture storm water volume for the area, from the formula recommended in Urban Runoff Quality Management, WEF Manual of Practice No. 23/ASCE Manual of Practice No. 87, (1998), or

o the volume of runoff based on unit basin storage water quality volume, to achieve 80 percent or more volume treatment by the method recommended in California Stormwater Best Management Practices Handbook—Industrial/Commercial (1993), or

o the volume of runoff produced from a 0.75 inch storm event, prior to its discharge to a storm water conveyance system, or

o the volume of runoff produced from a historical-record based reference 24-hour rainfall criterion for “treatment” (0.75 inch average for the Los Angeles County area) that achieves approximately the same reduction in pollutant loads achieved by the 85th percentile 24-hour runoff event; and

• Control peak flow discharge to provide stream channel and over bank flood protection, based on flow design criteria selected by the local agency.

In addition, compliance with the following local flow-based design criteria outlined in the General MS4 Permit would be required:

• The flow of runoff produced from a rain event equal to at least 0.2 inches per hour intensity; or

• The flow of runoff produced from a rain event equal to at least two times the 85th percentile hourly rainfall intensity for Los Angeles County; or

87 County of Los Angeles, Manual for the Standard Urban Storm Water Mitigation Plan, May 2000.



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• The flow of runoff produced from a rain event that will result in treatment of the same portion of runoff as treated using volumetric standards above.

2. ENVIRONMENTAL IMPACTS

a. Methodology and Significance Thresholds

(1) Methodology

As identified in the Initial Study for the project, groundwater impacts would be less than significant and, therefore, further analysis of this issue is not required in this EIR. Consequently, the analysis presented below addresses impacts on surface water hydrology and surface water quality and is based on information provided in the Water Resources Technical Report prepared by PSOMAS. This report provides an analysis of the impacts that would occur during construction and operations of the project.

(a) Runoff

The methodology for determining runoff impacts considered both existing and future (or post-project) conditions for the project watershed, the Pacoima Wash watershed. The analysis of impacts relative to hydrology considered the following: whether existing drainage patterns would be substantially altered, the ability of existing and proposed infrastructure to accommodate estimate post-project runoff, and whether the project would result in high flood risks. As discussed above, in order to estimate runoff volumes for the project site, the Pacoima Wash watershed was divided into several sub-basins/drainage areas. Using the Los Angeles County Hydrology Methodology, runoff from the 25-year storm event was estimated for existing and proposed conditions. Estimates of runoff volumes for existing conditions are based on the Rational Equation formula, which calculates runoff based upon the imperviousness of the watershed, rainfall depth, and the drainage area. The imperviousness of the watershed is determined from the Los Angeles Hydrology Manual based on the distribution of land use types. Rainfall depth data were obtained from the Pacoima Dam rain gauge. Rainfall record is available for the period between 1996 to 2001 and includes an analysis of the average annual rainfall for events larger than 0.1 inches.

(b) Event Mean Concentrations (EMC)

EMC is the average concentration of a pollutant in the runoff from a storm event. As discussed above, the pollutants chosen for analysis are Total Phosphourous, Total Nitrogen, Nitrate, Ammonia, Dissolved Copper, Total Lead, Dissolved Zinc, Total Aluminum, and Fecal



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Coliform. The Los Angeles County Storm Water Monitoring Program conducts comprehensive wet weather monitoring and publishes EMCs for several different constituents and a variety of land uses. These numbers were used to provide EMCs for the existing and proposed land use types, because of the relatively close location of the Los Angeles County monitoring stations to the project site.

(c) Pollutant Load

The analysis of impacts relative to water quality is defined by pollutant load. The pollutant load is calculated from estimated runoff volumes and EMC values based on the existing and proposed land use types (open space, institutional, golf course). Post-project pollutant load was compared with existing pollutant load and regulatory criteria/standards to determine project impacts to surface water quality.

(2) Significance Thresholds

The District has design and construction responsibilities over the entire project and long-term operations and maintenance responsibility over PA 1 (LAMC Campus) and PA 4 (LAMC Expansion Parcel). The County of Los Angeles has design and long-term operations and maintenance responsibilities over PA 2 (Parkland Expansion Parcels) and PA 3 (El Cariso Recreation Area Improvements). Both the District and the County use the California Environmental Quality Act (CEQA) Guidelines Appendix G questions as guidance for determining the significance of an environmental impact.

(a) Surface Water Hydrology

With CEQA Guidelines Appendix G as a foundation for this impact analysis, the impact on surface water hydrology will be considered significant if the proposed project would:

• Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, in a manner which would result in substantial erosion or siltation on- or off-site;

• Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, or substantially increase the rate or amount of surface runoff in a manner which would result in flooding on- or off-site;

• Create or contribute runoff water which would exceed the capacity of existing or planned storm water drainage systems or provide substantial additional sources of polluted runoff;



Page IV-180


• Place within a 100-year flood hazard area structures which would impede or redirect flood flows;

• Expose people or structures [or sensitive biological resources]88 to a significant risk of loss, injury or death involving flooding, including flooding as a result of the failure of a levee or dam; and/or

• Result in inundation by seiche, tsunami, or mudflow.

(b) Water Quality

With CEQA Guidelines Appendix G as a foundation for this impact analysis, the impact on water quality will be considered significant if the proposed project would:

• Violate any water quality standards or waste discharge requirements; and/or

• Substantially degrade water quality.

Concerning surface water quality, the City of Los Angeles would normally find an impact to be significant if discharges associated with the project would create pollution, contamination or nuisance as defined in Section 13050 of the California Water Code or that cause regulatory standards to be violated, as defined in the applicable NPDES storm water permit or Water Quality Control Plan for the receiving water body.89 These regulations are used to determine the significance of project-related impacts on water quality.

b. Project Features

The project proposes the following features to reduce construction and post-construction surface hydrology and water quality impacts to the extent practicable:

(1) Surface Water Hydrology

• Existing drainage facilities within PA 1 and PA 4 would be replaced with appropriately sized drainage systems, including the proposed Arroyo.

88 Expanded to include a feature of the significance threshold of the City of Los Angeles. 89 City of Los Angeles, Draft L.A. CEQA Thresholds Guide (May 14, 1998); p. D.2-4



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• The proposed Arroyo feature on PA 1 (LAMC Campus) and PA 4 (LAMC Campus Expansion Parcel) is functionally a set of detention basins traversing the project site as well as a water quality BMP. The 25-year flows will be contained within the basin, while 50-year flows will be channeled through a series of spillways. It is not a “water of the U.S.” and can therefore be utilized as a water quality BMP.

• The on-site storm drainage system shall be designed for the 25-year storm event, as approved by the County. Catch basins will be installed to intercept flows beyond the 25-year storms and at strategic locations to minimize flooding on PA 1 (LAMC Campus) and PA 4 (LAMC Campus Expansion Parcels).

• On PA 2 (Parkland Expansion Parcels), the buildings shall be raised to four feet above existing grade.

• All buildings and structures on PA 2 will be designed and constructed to meet “floodable” design criteria. This design feature would allow flood waters associated with a 50-year rainfall storm event to flow through the buildings and structures, thereby sustaining reduced structural damage due to flooding.

• Existing sheet flow patterns in PA 2 and PA 3 will be maintained while low-flows are diverted to water quality BMPs.

• Erosion and sedimentation control plans shall be prepared for the project to ensure that no significant erosion or sedimentation impacts would occur during or after development of the project. Temporary erosion control measures to be implemented during construction may include minimizing existing vegetation removal; using temporary soil covers, such as hydro seeding, to protect exposed soil from wind and rain; and installing silt fencing, berms (i.e., sandbagging), and dikes to protect storm drain inlets and drainage courses.

(2) Water Quality

The proposed project includes two categories of BMPs: source control and treatment control. Source control BMPs to prevent pollutants from entering storm and non-storm runoff and will include materials management, spill prevention and cleanup, and good housekeeping practices. Treatment control BMPs include a combination of physical treatment of the runoff through structural means such as catch basin inserts, infiltration systems (i.e., ponds, vaults, trenches, dry wells, porous pavement, and concrete grids), biofilters and grass swales comprised of vegetated strips of land, extended detention facilities. For purposes of this report, discussion of water quality improvements is limited primarily to structural BMPs, as these BMPs include treatment control functions that can be assessed for the water quality impact analysis. In accordance with NPDES requirements and local regulations implementing such requirements, an



Page IV-182


overview of the types of BMPs that are anticipated to be implemented as part of the project is provided below.

(a) Construction BMPs

• Erosion Control. During construction, erosion control techniques to retain soil and sediment on the site will be implemented. Particular attention will be paid to graded construction project sites where there is a potential for soil exposure to the erosive effects of rainfall and wind. Typical measures may include appropriate vegetation of exposed areas, diversion of runoff (such as earth dikes, temporary drains, slope drains), velocity reduction (outlet protection), and dust control measures (watering).

• Stabilization. All disturbed areas of the construction site will be stabilized during project construction. Example measures may include: blankets, reinforced channel liners, soil cement, fiber matrices, geotextiles, or other erosion resistant soil coverings or treatments. The construction entrance/exist will also be stabilized (e.g., aggregate underdrain with filter cloth).

• Sediment Control. These measures include BMPs that will prevent a net increase of sediment load in storm water discharge relative to pre-construction levels. Sediment control BMPs are recommended at appropriate locations along the site perimeter and at all operational internal inlets to the storm drain system at all times during the rainy season. Sediment control practices may include filtration devices and barriers (such as fiber rolls, silt fence, straw bale barriers, and gravel inlet filters) and/or settling devices (such as sediment traps or basins).

• Non-Storm Water Management. Possible non-storm water discharges from the construction project sites to receiving waters will be properly controlled. Examples of non-storm water discharges include watering for dust control purposes, and vehicle and equipment wash down wastes. Non-storm water discharges will be eliminated or reduced to the extent practicable.

(b) Post-Construction BMPs

• Bio-filtration/Grass Swales. For the proposed project, bio-filtration/grass swales are proposed to be located in the westerly portion of PA 1, PA 2, and PA 3.90 Bio-filtration/grass swales are typically vegetative lined features engineered to provide the dual purpose of water quality treatment and conveyance of storm water runoff.

90 Refer to Figure IV-23, drainage areas DA-4 (PA 3), DA-6 (PA 2A), DB-1 (PA 1), and DC (PA 2B).



Page IV-183


Swales are vegetated channels specifically designed to remove particulate pollutants and reduce flow velocities of storm water runoff. Swales typically provide low to moderate treatment efficiencies and are mainly effective at removing debris and solid particles. Incorporating vegetated swales into site design helps reduce the overall impervious surface for a project site and can help minimize overland and concentrated flow depths and velocities. There are no minimum dimensions required for design of bio-filtration/grass swales or strips, although it is recommended for treatment efficiency to maximize length and minimize depths. Slopes will be kept to between 2 and 5 percent to prevent scouring. Anticipated maintenance and monitoring requirements for the proposed swales include: 1) vegetation management to maintain adequate hydraulic functioning and to limit habitat for disease-carrying animals; 2) animal and vector control; 3) periodic sediment removal to optimize performance; 4) trash, debris, grass trimmings, tree prunings, and leaf collection and removal to prevent obstruction; 5) removal of standing water, which may contribute to the development of aquatic plant communities or mosquito breeding areas; and 6) erosion and structural maintenance to prevent the loss of soil and maintain the performance of the swale.

• Infiltration Basins. Infiltration basins are proposed within PA 2 and PA 3.91 Infiltration basins are generally designed with a volume equal to at least the water quality treatment volume and may be designed to accommodate up to 20 percent in excess of the volume to account for sediment deposition. As a minimum, the basins will be designed to satisfy the Los Angeles County SUSMP criteria. The SUSMP water quality design storm is representative of approximately the 85th percentile rainfall, resulting in approximately 70 percent runoff capture (or the volume of runoff produced from a 0.75 inch storm event). To determine optimum BMP placement, a flow-path-to-width ratio of at least 2:1 for detention basin design will be employed. Baffles or interior berms can be used to accomplish this ratio to accommodate the geometry of the site.

• Detention Basins. The arroyo system proposed for PA 1 and PA 4 (drainage areas DB-2a, DB-2b and DB-3), is an Extended Detention Basin (EDB) that will be designed to detain peak flows and release detained flow gradually so that proposed peak flows will be about half of the existing 25-year peak flows. An EDB is generally designed with a volume equal to at least the water quality treatment volume and may be designed to accommodate up to 20 percent in excess of the volume to account for sediment deposition. As a minimum, the EDB would be designed to

91 An infiltration basin is a surface pond, which captures first-flush stormwater and treats it by allowing it to

percolate into the ground and through permeable soils. As the stormwater percolates into the ground, physical, chemical, and biological processes occur which remove both sediments and soluble pollutants. Pollutants are trapped in the upper layers of the soil, and the water is then released to groundwater.



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satisfy the Los Angeles County SUSMP criteria. The SUSMP water quality design storm is representative of approximately the 85th percentile rainfall, resulting in approximately 70 percent runoff capture (or the volume of runoff produced from a 0.75 inch storm event). Extended detention basins are designed to receive and detain stormwater runoff for a prolonged period of time, typically up to 48 hours. Extended detention is achieved by use of an outlet device regulating the flow from the basin at a rate which minimizes downstream erosion, reduces flooding, and provides for enhanced pollutant removal.

• Catch Basin Inserts. Catch basin inserts are proposed for use at two locations in PA 1 (drainage area DB-1), and would be installed within existing or new storm drains to treat storm water runoff before entering the storm drain system. Catch basin inserts typically filter or screen out sediments and associated storm water pollutants during dry weather and low flow events.

• Hydrodynamic Separation Systems (HSS). HSS, Gross Solids Removal Devices (GSRDs), and Continuous Deflective Separator (CDS) units are flow-through BMPs installed in-line to remove large sediment particles and associated storm water pollutants as well as floatable trash, oils, and grease from the storm drain system. The systems are typically designed to allow particulate matter to fall out of suspension and settle in a collection chamber, while floatable materials are collected above the water surface. A CDS or its equivalent is proposed for treatment of runoff from the easterly portion of PA 4 (drainage area DB-4).

• Source Control BMPs. Landscaping will consist of native and non-invasive plants that require minimal irrigation, fertilizing, and pest control. The use of pesticides and herbicides will be kept to a minimum and guidance for landscaping contractors will be developed to minimize the amount of such applications and maximize the benefits. An education program on water quality issues and pollution prevention for students, employees, park patrons, landscape contractors and visitors will be made available prior to operation of the project.

c. Project Impacts

(1) Surface Water Hydrology

(a) Construction

Impacts to surface water hydrology could occur during construction activities as initial clearing and grading would expose much of the surface soils. Construction would alter the existing drainage facilities within PA 1 (LAMC Campus) and PA 4 (LAMC Campus Expansion



Page IV-185


Parcel) by replacing drainage systems with appropriately sized facilities, including the proposed Arroyo. The Arroyo would function as a set of detention basins traversing the project site. This new drainage feature would direct and control storm water flows associated with proposed development on the LAMC campus. The 25-year flows will be contained within the project sub-basins, while 50-year flows will be channeled through a series of spillways. Catch basins would be strategically located to intercept flows beyond the 25-year storms thereby reducing the impact of storm water flows. To ensure that potential erosion and siltation impacts are reduced to a less than significant level, mitigation measures have been prescribed that include the project design features described above, which will further ensure their implementation.

PA 2 (Parkland Expansion Parcels) is located within a 100-year flood hazard area as currently depicted on the Flood Insurance Rate Map (See Figure IV-21). Although small structures would be constructed on PA 2, the project also proposes to raise the elevation of the structures by up to four feet, which exceeds the FEMA criteria (three feet above existing elevation), as well as the minimum estimated elevation necessary to protect the structures from flood waters. In addition, all buildings and structures on PA 2 would be designed and constructed to meet “floodable” design criteria. This design feature would allow flood waters associated with a 100-year rainfall storm event to flow through the buildings and structures, thereby reducing the potential for structural damage due to flooding and the potential to impede or redirect flood flows associated with a 100-year storm event. The project would maintain existing sheet flow patterns in PA 2 and PA 3, while low-flows for these areas would be diverted to water quality BMPs.

The Pacoima Dam, which is located less than two miles upstream from the project site, specifically PA 2, is owned and operated by the LADPW for flood control and water conservation purposes. The dam is equipped with various instruments to monitor the structural, geotechnical, and hydraulic conditions in and around the dam. LADPW routinely monitors these instruments to ensure the safe operation of the dam. According to LADPW, there have been no conditions noted in the dam, foundation, or abutments that would adversely affect its continued safe operation.92 Furthermore, the California Division of Safety of Dams (DSOD) inspects the dam annually and it has not imposed any operating restrictions on the dam. DSOD finds the dam, reservoir, and appurtenances satisfactory for continued use. In April 2004, construction to expand the spillway of the dam to accommodate a probable maximum flood event was completed. Therefore, construction and operation of the proposed ball fields on PA 2, the proposed easement over the on-site drainage channel and riparian habitat, and implementation of all other aspects of the proposed project are not expected to expose people, structures, or

92 Electronic communication with John Burton, Civil Engineer, Dam Surveillance, Los Angeles County Department

of Public Works, November 8, 2004.



Page IV-186


sensitive biological resources to a significant risk of loss, injury or death involving flooding, including flooding as a result of the failure of a dam.

Mudflows result from the down slope movement of soil and/or rock under the influence of gravity. The project site is not located within an area that is subject to high debris and mudflow conditions. However, because the proposed ball field sites (PA 2) are adjacent to an alluvial wash, there is the potential for sediment laden flood flows to impact PA 2 during extreme events. The proposed finished elevation (above the base flood), building setbacks, and debris control facilities would ensure that debris flows during extreme conditions would be less than significant.

Construction BMPs would include, but not necessarily be limited to, sediment control, soil stabilization, scheduling grading activities during dry weather months, preservation of existing vegetation, storm water conveyance controls, erosion control, temporary stream crossings, and waste management as appropriate. To ensure that hydrologic and flood-related impacts during construction are less than significant, project design features described in section 2.b.(1) and BMP’s described above will be implemented. Therefore, potential impacts would be less than significant and no mitigation measures would be required.

(b) Operation

The proposed project would alter the existing drainage pattern of the project site, as shown in Figure IV-29 on page IV-187. Using Los Angeles County Hydrology Methodology, runoff from a 25-year storm event was calculated based on the proposed development of the project site. Runoff quantities are provided in Table IV-24 on page IV-188. As shown, the proposed project would generate a total flow rate of 284.6 cfs during a 25-year storm event. This represents an increase in flow rate by 16.6 cfs when compared to existing conditions. To manage the increase in runoff, the project proposes a combination of drainage systems, including a man-made arroyo, grassy swales, storm drainpipes, catch basins, area drains, and outlet structures as summarized in section 1(a), Construction, above. The 25-year storm design would be used to design all on-site drainage systems carrying runoff from developed areas. These drainage systems would detain and gradually release peak flows, thereby, reducing them. The Arroyo alone would reduce runoff by approximately 20.0 cfs. As a result, the proposed project would effectively reduce the amount of runoff during a 25-year storm event compared to existing condition, as shown in Table IV-25 on page IV-189.

Furthermore, based on the June 2005 hydrologic information provided by the County of Los Angeles, the collected peak flow rate from a Capital Flood for Pacoima Wash at Harding Street is 7,300 cubic feet per second (cfs). The collected peak flow rate from a 100-year frequency design storm for Pacoima Wash at Harding Street is 8,500 cfs. These flow rates are

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Page IV-188


Table IV-24

Proposed Project Runoff Volumes

Sub-Basin/Drainage Area Associated

Project Area (PA) Area

(acres) Q25c a

(cfs) DB-1 PA 1 8.4 15.1 DB-2a PA 4 5.2 11.3 DB-2b PA 1 8.6 16.7 DB-3 PA 1 6.3 12.9 DB-4 PA 4 5.6 10.5 DB-5 PA 3B 18.5 19.2 DB-6 PA 3B 41.1 41.3 DA-1 N/A b 8.9 13.3 DA-2 N/A b 10.6 17.1 DA-3 PA 3 28.3 30.8 DA-4 PA 3A 17.0 26.5 DA-5 N/A b 36.0 37.8 DA-6 PA 2A 7.7 13.2 DC PA 2B 9.6 18.9

Total - 212 284.6 a Quantities are presented in cubic feet per second based on a 25-year storm event. b Not applicable because the drainage area identified does not include land within a Project Area. Source: PSOMAS, Water Resources Technical Report for Los Angeles Mission College, September 2004.

much lower than the flow rates that were originally used to estimate the project’s impact. Therefore, hydrologic impacts during operation of the proposed project would be less than significant.

PA 2 is currently located within a 100-year flood plain (Zone AO/A), as depicted on the existing Flood Insurance Rate Map. With implementation of the proposed grading concept, the proposed ballfields, bleachers, concession stands, and restrooms (non-habitable structures) would be above the base flood elevation. This project feature combined with adherence to “floodable” design criteria would ensure that flood-related structural damage and potential obstruction or redirection of flood waters would not occur. Therefore, potential impacts would be less than significant and no mitigation measures would be required.

Post-construction erosion, sedimentation, and debris production would be reduced through the installation of non-erodable vegetation and surfaces on the project site, use of



Page IV-189


erosion control measures, and debris basins. As a minimum, the proposed project would comply with the requirements of Order No. 01-182 (NPDES Permit CAS004001) issued by the Los Angeles RWQCB for Los Angeles County.93 To ensure that hydrologic and flood-related impacts during project operations are less than significant, design features have been incorporated into the project. As a result, potential impacts would be less than significant and no mitigation measures would be required.

93 Los Angeles County Department of Public Works, Development Planning for Storm Water Management—A

Manual for the Standard Urban Storm Water Mitigation Plan (SUSMP), September 2002.

Table IV-25

Hydrology Impacts

Drainage Area a Associated

Project Area Area

(acres) Existing Q25c

(cfs) Proposed Q25c

(cfs)

Proposed Q25c

Post-BMP (cfs)

Increase in Q25 Due to the

Project (cfs)

B-1 1 8.4 15.1 15.1 N/A 0.0 EB-2/DB-2b 1 8.8/8.6 16.8 16.7

B-3 1 6.2/6.3 12.0 12.9 Arroyo Tributary Area 1 15.0 24.0 32.0 13.0 -11.0

DB-2a 2 5.2 12.4 11.3 Arroyo Tributary Area 2 20.2 24.0 26.0 15.0 -9.0

EB-4/DB-4 b 2/3 10.8/5.6 12.4 10.5 N/A -1.9 B-5 2 18.5 19.2 19.2 <19.2 0.0 B-6 N/A 41.1 41.3 41.3 N/A 0.0 A-1 N/A 8.9 13.3 13.3 N/A 0.0 A-2 N/A 10.6 17.1 17.1 N/A 0.0 A-3 N/A 28.3 30.8 30.8 N/A 0.0 A-4 2 17.0 23.1 26.5 N/A 0.0 A-5 N/A 36.0 37.8 37.8 N/A 0.0 A-6 2 7.7 12.0 13.2 <12.0 0.0 C 2 9.6 17.1 18.9 <17.1 0.0

a Existing/proposed notation where drainage area numbering system differs between the two scenarios. b Portion of EB-4 redirected to Arroyo as drainage area DB-2a. Source: PSOMAS, Water Resources Technical Report for Los Angeles Mission College, September 2004.



Page IV-190


(2) Water Quality

(a) Construction

Proposed construction activity would include clearing, excavation, stockpiling of materials, earth movement to create level building pads and play fields, and other disturbances of soil. Pollutant export could increase significantly during construction activities as initial clearing and grading would expose much of the surface soils. Sediment resulting from excessive erosion of disturbed soils is the primary pollutant of concern. Unless adequate erosion controls are installed and maintained at the site, significant quantities of sediment may be delivered to the downstream receiving water, along with attached soil nutrients and organic matter. Other pollutants of concern are metals, nutrients, pesticides, construction chemicals, and miscellaneous waste from construction sites.

The preparation and implementation of the SWPPP would effectively address control of pollutants from the numerous construction activities. The SWPPP would establish effective BMPs that would control pollutants during all stages of construction, from initial mobilization through completion of construction. The following are typical BMPs that would be considered in the project SWPPP to address construction activities:

• Erosion and sediment control measures during grading and construction; including gravel bags, de-silting basins, stabilized construction entrances, dust control and street sweeping;

• Equipment staging areas to localize and establish BMPs for control of pollutants associated with equipment refueling, operation and maintenance;

• Material staging areas to localize and establish BMPs for control of pollutants associated with storage or stockpiling of construction materials;

• Proper application and use of construction materials, including paint, thinners, polymers, adhesives, fertilizers, pesticides, weed-killers; and

• Concrete truck washout, procedures to control residue from concrete truck washout, which shall be disposed of in designated sites.

BMPs would include, but not necessarily be limited to, sediment control, soil stabilization, scheduling, preservation of existing vegetation, conveyance controls, wind control, temporary stream crossings, and waste management as appropriate. All BMPs would be consistent with the requirements set forth in the General Construction Permit. As such, implementation of construction BMPs would reduce the potential for the discharge of pollutants or substantial erosion or siltation during project construction. In addition, proper engineering



Page IV-191


techniques would be applied to reduce erosion and sediment discharge to affect stormwater quality. Design features have been incorporated into the project, which include the BMP’s described above, to ensure that impacts to water quality during construction is not affected. Therefore, impacts to water quality would be less than significant and no mitigation measures would be required.

(b) Operation

The proposed project would increase the amount of urban contaminants in runoff, particularly in PA 2 and PA 4, which are currently vacant/open space areas. Employing the same model used to establish existing water quality conditions in subsection 1.b.(2), future water quality conditions resulting from implementation of the proposed project were estimated. Table IV-26 on page IV-192 presents the future pollutant loads for each of the constituents based on a runoff volume of 4,914,600 cubic feet per year at project build-out. As shown, the proposed project would result in increases in total phosphorus (TP), total nitrogen (TN), ammonia, dissolved copper (Cu), total lead (Pb), and dissolved zinc (Zn) loads. The proposed project would result in decreases in nitrate and total aluminum (Al) loads, and a negligible decrease (less than 0.002 percent) of fecal coliform. The project proposes to incorporate a number of water quality improvements (treatment control BMPs) to reduce the pollutant loading in storm drain systems. Treatment control BMPs involve physical treatment of the runoff, primarily through structural means. The BMPs proposed for the project include infiltration basins, grass swales/biofilters, extended detention basins (EDBs), catch basin inserts, and gross solid removal devices (GSRDs) as described above (section 2.b(2), and in further detail below.

(i) Grass Swales/Biofilters

As shown in Figure IV-29, grass swales/biofilters are proposed within PA 1, PA 2, and PA 3A. Grass swales/biofilters are vegetative lined features engineered to provide the dual purpose of water quality treatment and conveyance of storm water runoff.

Implementation of this structural BMP would assist in reducing the overall impervious surface of the project site and minimizing overland and concentrated flow depths and velocities. The swales would be sized to meet the minimum Los Angeles County SUSMP criteria based on a 0.75-inch runoff event.

(ii) Infiltration Basins

As shown in Figure IV-29, infiltration basins are proposed in PA 2 and PA 3A. Infiltration basins are surface ponds that capture first-flush storm water and treat it by allowing it to percolate into the ground and through permeable soils. As the storm water percolates into the



Page IV-192


ground, physical, chemical, and biological processes occur which remove both sediments and soluble pollutants.

(iii) Extended Detention Basins (EDB)

As shown in Figure IV-29, an EDB in the form of a man-made arroyo is proposed within PA 1 and PA 4. The man-made arroyo would be constructed to capture runoff from within PA 1 and PA 4 and eventually outlet to Eldridge Avenue. Storm water would flow naturally within the arroyo to a detention pond that would be constructed at the lowest elevation of the site, between future Parking Structure A (previously approved project) and Eldridge Avenue. The arroyo would be designed to detain the 25-year storm event and release the detained flow gradually, thereby, reducing peak flows into Eldridge Avenue. The arroyo would also channel 50-year flows through a series of spillways.

(iv) Catch Basin Inserts

As shown in Figure IV-29, catch basin inserts are proposed at two locations within PA 1. Catch basins inserts are installed into storm drains to treat storm water runoff via a filter or screen before entering the storm drain system.

(v) Gross Solid Removal Devices (GSRD)

As shown in Figure IV-29, a GSRD is proposed within PA 4. GSRDs are flow-through units installed in-line to remove large sediment particles and associated storm water pollutants as well as floatable trash, oils, and grease from the storm drain system. The systems are designed to allow particulate matter to fall out of suspension and settle in a collection chamber, while floatable materials are collected above the water surface.

Table IV-26

Comparison of Pollutant Loads Under Existing and Proposed Conditions


Timing


TP (lbs/yr)

TN (lbs/yr)

Nitrate(lbs/yr)

Ammonia(lbs/yr)

Cu (diss)

(lbs/yr)Pb

(lbs/yr)

Zn (diss)

(lbs/yr) Al

(lbs/yr)

Fecal Coliform

(109 MPN/yr)

Existing 4,561,406 142.29 1,019.21 486.82 110.70 0.97 0.54 4.94 305.63 6,398 Future 4,914,600 155.03 1,079.93 476.80 123.57 1.77 0.84 8.99 293.56 6,387

% Change +8% +9% +6% -2% +12% +82% +56% +82% -4% 0%

Source: PSOMAS, Water Resources Technical Report for Los Angeles Mission College, September 2004.



Page IV-193


The removal efficiencies for each of these treatment control functions can be quantified and, thus, were applied to the future pollutant loads. Table IV-27 on page IV-194 presents the future pollutant loads for each of the constituents with the structural BMPs in place. As shown, the BMPs would help reduce pollutant loads of total phosphorus (TP), dissolved copper (Cu), total lead (Pb), dissolved zinc (Zn), and total aluminum (Al). However, concentrations of total phosphorus (TP), dissolved copper (Cu), total lead (Pb), and dissolved zinc (Zn) would still exceed existing conditions. Removal efficiencies for nitrate and ammonia are not available.

In addition to the treatment control BMPs, the project also proposes to incorporate a number of source control BMPs to help reduce the pollutant loading in storm drain systems. Source control BMPs involve reducing the amount of pollution before it occurs. The BMPs proposed for the project include street sweeping, “low-impact” vegetation, and educational programs for faculty, students, and landscaping contractors. Although the removal efficiencies cannot be quantified, source control BMPs are usually the most effective and economical in preventing pollutants from entering storm and non-storm runoff. It is anticipated that with proper implementation of these source control BMPs, impacts to water quality would be further reduced.

Many other potential constituents of concern are not easily modeled due to limited or non-existent monitoring data, or difficulty in measuring pollutants concentrations. Some of the constituents listed for TMDL priority scheduling in downstream reaches of the Los Angeles River are a prime example. Oils, pH, and scum/foam cannot be modeled, however the treatment and source control BMPs to be implemented by the proposed project would assist in reducing these constituents to less than significant levels. To ensure that water quality impacts during project operations are reduced to a less than significant level, mitigation measures have been prescribed that include the BMP’s described above and project design features, which will further ensure their implementation

d. Policy and Regulatory Compliance

As part of the proposed project’s review and approval, there are a number of performance criteria and standard conditions that must be met. These include compliance with applicable laws that relate to federal, state, and local regulating agencies for impacts to sensitive plant and wildlife species, wetlands, riparian habitats, and stream courses.

(1) Federal Statutes and Regulations

A jurisdictional delineation of “waters of the U.S.” and wetlands was conducted at the project site on February 10, 2003 by qualified PCR biologists to determine the presence or absence of USACE, CDFG, and/or Regional Water Quality Control Board (RWQCB)



Page IV-194


jurisdiction. The project site contains one jurisdictional feature (Channel B), portions of which are located within PA 3B (underground) and PA 2A (aboveground). The portion of Channel B within PA 2A would be protected by the 200-foot wide flood control easement. Two non-jurisdictional features were also found, one between PA 1 and PA 4 (Channel C) and one within PA 2B (Channel D). Channel B is characterized as an intermittent stream due to the presence of hydrologic inputs from adjacent Golf Course irrigation and residential runoff. Channel C (the concrete-lined v-ditch) and Channel D (the man-made earthen swale) were determined to be non-jurisdictional because they constitute excavations in the uplands, lack biological value, and are not hydrologically connected to a “navigable” “waters of the U.S.” The total jurisdiction within the project site under USACE/RWQCB regulation is 0.11 acre (including 0.03 acre of jurisdictional wetlands) and 0.56 acre under CDFG jurisdiction. Table IV-28 on page IV-195 contains a breakdown of the jurisdictional features within the project site.94 The proposed project would permanently impact approximately 87 square feet (sf) of USACE/RWQCB “waters of the U.S.” and 654 sf of CDFG streambed and associated riparian habitat within Channel B located in PA 2A. In addition, temporary impacts are anticipated beyond the limits of permanent impact. Temporary impacts would include 349 sf of USACE/RWQCB “waters of the U.S.” (including approximately 14.4 sf, of jurisdictional wetlands) and 3,093 sf of CDFG jurisdictional streambed and associated riparian habitat. Impacts are considered potentially significant. Implementation of Mitigation Measure BR-2 would reduce this potentially significant impact to a less than significant level. (Refer to Section IV.C. Biological Resources.)

Before the USACE will issue a Section 404 permit for the proposed project, a Section 401 water quality certification or WDR must be obtained from the RWQCB. With the application, a detailed Water Quality Management Plan would be prepared and submitted which 94 Refer to Figure IV-18 of this EIR for a map of the jurisdictional and non-jurisdictional water features at the

project site.

Table IV-27

Future Pollutant Loads with Structural BMPs in Place


Timing


TP (lbs/yr)

TN (lbs/yr)

Nitrate(lbs/yr)

Ammonia(lbs/yr)

Cu (diss)

(lbs/yr)Pb

(lbs/yr)

Zn (diss)

(lbs/yr) Al

(lbs/yr) Fecal Coliform (109 MPN/yr)

Future 4,914,600 155.03 1,079.93 476.80 123.57 1.77 0.84 8.99 293.56 6,387 Post

BMPs 4,914,600 153.18 1,077.09 N/A a N/A a 1.71 0.80 8.86 264.43 6,387 % Change +8% +8% +6% N/A a N/A a +76% +50% +79% -13% 0% a Not available. Source: PSOMAS, Water Resources Technical Report for Los Angeles Mission College, September 2004.



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covers the key water quality features of the project to ensure the integrity of water quality in the area during and post-construction.

(2) Water Quality Control Plan for the Los Angeles Region

Compliance with Order No. 01-182 (NPDES Permit CAS004001) issued by the Los Angeles RWQCB for Los Angeles County would be demonstrated prior to construction. Any project subject to review by the County may be subject to the requirements of the NPDES Permit. Two aspects of the proposed project trigger NPDES compliance: 1) proposed surface parking lots with 5,000 square feet or more of surface area or with 25 or more parking spaces (all PAs), and 2) construction located within or directly adjacent to or discharging directly to an environmentally sensitive area if the discharge is likely to impact sensitive biological species or habitat and the development creates 2,500 square feet or more of impervious surface area (PA 2). Compliance would be demonstrated to the County prior to construction.

The Regional Boards throughout southern California are developing concepts for the implementation of a Hydro-modification Control Plan (scheduled for completion in 2005) to address downstream erosion impacts from development. Upon final design, if this plan as been competed and approved, it may be necessary to comply with or consider elements of its recommendations.

(3) State of California Fish and Game Code

As noted under d. (1) above, the project includes 0.56 acre of CDFG jurisdictional streambed and associated riparian habitat. The proposed project would permanently impact approximately 654 sf of CDFG streambed and associated riparian habitat within Channel B located in PA 2A. In addition, temporary impacts would include 3,093 sf of CDFG jurisdictional features. Impacts are considered potentially significant. Implementation of Mitigation Measure

Table IV-28

Summary of Jurisdictional Features within the Project Site

Name USACE (acres) a RWQCB (acres) CDFG (acres) Nature Channel B 0.11 (0.03) 0.11 (0.03) 0.56 Intermittent Total Jurisdiction b 0.11 (0.03) 0.11 (0.03) 0.56 a Acres in parenthesis are wetlands, which are a subset of the total acreage (i.e., the wetlands and waters

acreages are not additive). b Agency jurisdictions often overlap (i.e., the totals in each column are not additive for a given category of

aquatic resource). Source: PCR Services Corporation, 2003.



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BR-2 would reduce this potentially significant impact to a less than significant level. (refer to Section IV.C. Biological Resources.)

(4) County of Los Angeles

PA 2 (Parkland Expansion Parcels) is located within a 100-year flood plain, as defined on the Flood Insurance Rate Map. Accordingly, the proposed project incorporates design features consistent with the LACDPW-issued a memorandum on Level of Flood Protection and Drainage Protection Standards. To achieve the level of flood protection for Capital Flood (See section 1.b.(1)(b)), the project design for PA 2 includes:

• Raising the base flood elevation of the structures by up to four feet.

• Designing all buildings and structures on the site to meet “floodable” design criteria. This design feature would allow flood waters associated with a 100-year rainfall storm event to flow through the buildings and structures, thereby reducing structural damage due to flooding.

3. CUMULATIVE IMPACTS

Cumulative impacts could occur when the impacts of the project and impacts of other development in the project area combined would yield an impact more significant than these impacts individually. It is to be expected that any future development in the surrounding area would be required to comply with current development regulations, including the same or similar general flood control and water quality requirements as the proposed project and other site-specific requirements that the LACDPW Flood Control Division, Watershed Management Division, and the LARWQCB would specifically identify for those projects. These requirements serve to avoid the potential for creating flooding, erosion, siltation, and water quality impacts in the Pacoima Wash. Therefore, the potential cumulative impacts with respect to hydrology and water quality would be less than significant.

4. MITIGATION MEASURES

Design features of the proposed project provide specific instructions for: 1) reducing project-related pollutant discharges into waterways; 2) reducing and managing peak post-development runoff volumes; 3) landscaping with vegetation that would reduce the future use of chemicals; 4) reducing the risk of flood damage and hazards to PA 2 through raising the elevation of the structures and constructing floodable structures; and 5) installing facilities within



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the landscaping of all project areas that will contain and treat first flush storm water, such as detention basins, biofilters, infiltration basins, grass swales, and gross solids removal devices. With implementation of the proposed project design features, hydrology and water quality impacts associated with construction and operation of the proposed project would be less than significant. Therefore, no mitigation measures are required.

5. LEVEL OF SIGNIFICANCE AFTER MITIGATION

Implementation of project design features and compliance with standard policies and requirements would ensure impacts on hydrology and water quality are less than significant. No mitigation measures are required.

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