Transcript
Page 1: IV.F. Hydrology and Water Quality - LA City Planning. Hydrology and Water... · Source: Storm Water Hydrology Study, Stantec. Prepared April 2011 65 cfs into the County storm drain

City of Los Angeles Boyle Heights Mixed-Use Community Project SCH. No. 2008061123 October 2011

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IV. Environmental Impact Analysis F. Hydrology and Water Quality

1. Introduction

This section provides an analysis of the project’s potential impacts associated with hydrology and water quality. The analysis is based in part on the Storm Water Hydrology Study prepared for the project site in April 2011 and the Surface Water Quality Study prepared for the project site in January 2011, both of which were prepared by Stantec. These reports are provided in Appendices G-1 and G-2 of this Draft EIR, respectively.

2. Environmental Setting

a. Existing Conditions

(1) Surface Water Hydrology

The project site includes approximately 68.8 acres located within the Boyle Heights community of the City of Los Angeles. In a hydrologic context, the project site lies within the Los Angeles River Watershed, a drainage area that is shaped by the path of the Los Angeles River and covers approximately 871 square miles. The Los Angeles River Watershed encompasses the Santa Susanna Mountains to the west, the San Gabriel Mountains to the north and east, the Santa Monica Mountains and Los Angeles coastal plain to the south, and ends at the Long Beach Harbor. Within this watershed, stormwater that does not percolate through the ground into the groundwater table is directed into storm drains that eventually discharge into the Los Angeles River, which in turn discharges to the Pacific Ocean.

The topography of the project site presents a westward increase in elevation of approximately 65 feet over a distance of nearly 3,000 feet. The highest elevation of the project site is at the northwest corner, with the lowest point at the northwest corner at the intersection of S. Grande Vista Avenue and Lydia Drive. Approximately 54 percent of the project site is currently developed with impervious surfaces, including several apartment buildings and accessory structures as well as surface parking lots and public streets/sidewalks. The remaining 46 percent of the project site consists of pervious surfaces including lawn and landscaped areas interspersed around buildings as well as “The Mall,” a landscaped open space/drainage channel running from east to west, with a

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IV.F Hydrology and Water Quality

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perpendicular section bisecting the channel from north to south. The project site is located in the southern portion of an approximately 1,000 acre regional drainage area that is bounded by the Santa Monica Freeway (I-10) to the north, the I-10/Golden State (I-5) Freeway connector to the west, Grande Vista Avenue to the east, and Olympic Boulevard to the south.1

The project site is underlain by fill soils to a maximum depth of 18 feet. The fill soils consist primarily of moist, stiff to medium density, fine-grained silty to sandy clays and clayey to silty sands which are yellowish brown to brownish grey, mixed with some gravel. The native soils underlying the fill on-site consist predominantly of sands, silty sands, clayey sands, and sandy silts. The native soils are generally fine-grained with some gravel and cobbles, range from orange brown to yellowish brown to brownish grey in color, and are dense to very dense and hard. The geologic materials consist predominantly of alluvial sediments deposited by rivers and streams, typical of the Los Angeles County area.

The project site is part of an approximately 80.9 acre drainage area and is served by two distinct storm drain networks. The first is a major public storm drain owned by the City of Los Angeles that traverses the site from west to east. This 75- to 84-inch concrete pipe has a capacity of approximately 410 cubic feet per second (cfs) where the pipe is 84 inches in diameter and enters the project site from the northwest at the intersection of Glenn Avenue and 8th Avenue and exits the project site to the east at Grande Vista Avenue before draining into the Los Angeles River to the southeast. The second storm drain network that serves the project site is a major County of Los Angeles storm drain comprised of an 11-foot by 6.5-foot concrete box with a capacity of approximately 588 cfs. This County storm drain is located immediately adjacent to the east boundary of the project site in Grande Vista Avenue and flows south to the Los Angeles River.

The site consists of two separate primary drainage areas. The first drainage area connects to the City of Los Angeles storm drain that traverses the site. Four public storm drain inlets on-site connect to the City storm drains and are located at Glenn Avenue and Camulos Place; Glenn Avenue and Hostetter Street; Glenn Avenue and Camulos Street; and Rosalind Place near Lydia Drive. The tributary areas associated with these inlets comprise an area of 34.2 acres within the project boundary as well as 7.3 acres beyond the project boundary. The second drainage area within the project site flows to the County drainage system and includes the central open space area in Wyvernwood known as The Mall. The Mall does not have an underground storm drain but is surface drained by a grassy swale. This open space area is comprised of 34.5 acres. Two additional small portions of the site drain to 8th Street and Olympic Boulevards. These streets are served by other City of Los Angeles inlets and storm drains that drain to the Los Angeles River. 1 Storm Water Hydrology Study, Stantec. Prepared April 2011.

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IV.F Hydrology and Water Quality

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Drainage of the project site can be further divided into seven subareas as shown in Figure IV.F-1 on page IV.F-4. Subarea 1 is located within the northwestern portion of the project site and is comprised of approximately 16.2 acres. Subarea 2 is located immediately adjacent to the project site to the southwest and is approximately 7.3 acres. Subarea 3, which is partially outside of the project site, is located to the south and consists of approximately 10.6 acres. Subarea 4 is within the southeastern portion of the project site and is comprised of approximately 7.4 acres. Subareas 1, 2, 3, and 4 drain to on-site streets and storm drain inlets which are connected to the City storm drain that runs through the project site. Thus, the City storm drain currently provides drainage for approximately 34.2 acres within the project site and approximately 7.3 acres outside of the project site, or a total of approximately 41.5 acres. Subarea 5 within the central and eastern portion of the project site consists of approximately 34.5 acres and drains to The Mall where a surface swale conveys runoff to the east and eventually to the County storm drain in Grande Vista Avenue. Subarea 6, which is located in the southeastern portion of the project site, consists of approximately 2 acres and drains off-site to additional City storm drains in Olympic Boulevard. Subarea 7, which is located in the northern portion of the project site, consists of approximately 2.9 acres and drains off-site to additional City storm drains in 8th Street. Existing storm drain facilities are shown in Figure IV.F-2 on page IV.F-5. The existing City and County storm drain systems that serve the project site accommodate existing runoff and have no deficiencies.2 While The Mall may have local areas that pond stormwater during storm events, no incidents of on-site flooding have been noted that endanger structures or public streets. Furthermore, the project site is not located within a 100-year flood plain.3

To estimate the existing stormwater runoff rates at the project site, hydrology calculations were performed using the Los Angeles County of Public Works 2006 Hydrology Manual. Runoff rates were calculated for 50-year storm events. As shown in Table IV.F-1 on page IV.F-6, the existing stormwater runoff rate at the project site is approximately 152.5 cfs during a 50-year storm event. Of this amount, approximately 78.2 cfs drains to the City storm drain that runs through the project site, 65 cfs drains to the County storm drain, 3.8 cfs drains to the off-site City storm drain located in Olympic Boulevard, and 5.5 cfs drains to the off-site City storm drain located in 8th Street.4 The Los Angeles County of Public Works has indicated that a maximum of 2.9 cfs per acre may be directed to the County storm drain from the project site. As discussed above, 34.5 acres of the project site drain to the County storm drain system, which provides for a maximum discharge of 100 cfs into that system. The project site currently discharges approximately

2 Ibid. 3 Ibid. 4 Ibid.

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Source: Stantec Consulting Inc., April 30, 2009.

Figure IV.F-1Existing Hydrological Conditions

Boyle Heights Mixed-Use Community Project

Page IV

.F-4

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Source: Stantec Consulting Inc., June 8, 2011.

Figure IV.F-2Existing Storm Drain Facilities

Boyle Heights Mixed-Use Community Project

Page IV

.F-5

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IV.F Hydrology and Water Quality

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Table IV.F-1 Estimated 50-Year Storm Event Runoff Rates Based On Existing Conditions

Storm Drain System Subarea Acres Q50 (cfs)

On-Site City Subarea 1 16.2 30.5 Subarea 2 7.3 13.8 Subarea 3 10.6 20 Subarea 4 7.4 13.9 Subtotal 41.5 78.2

On-Site County Subarea 5 34.5 65 Subtotal 34.5 65

Olympic Blvd. gutters, then eventually Subarea 6 2.0 3.8 to off-site City storm drain Subtotal 2.0 3.8

8th Street gutters, then eventually to Subarea 7 2.9 5.5 off-site City storm drain Subtotal 2.9 5.5

Total 80.9a 152.5 a The subareas include portions of the public right-of-way. Hence the total acreage for the

subareas is greater than the total acreage for project site.

Source: Storm Water Hydrology Study, Stantec. Prepared April 2011

65 cfs into the County storm drain system, which is below the maximum discharge of 100 cfs.5

(2) Water Quality

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. As described above, in particular, the project site is located within the Los Angeles River Watershed, an 871-square mile watershed encompassing the

5 Ibid.

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IV.F Hydrology and Water Quality

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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 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 0.33 mile west of the site. Stormwater 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.

Existing stormwater runoff from the project site has the potential to contribute oil and grease, suspended solids, gasoline, pesticides, and pathogens to the stormwater conveyance system. Stormwater from the project site is currently not treated prior to entering the storm drain system.

Based on the California Division of Mines and Geology Historically Highest Groundwater Contours Report, groundwater at the project site has a historic high groundwater level on the order of 150 feet below grade. In addition, 12 exploratory borings, which varied in depth from 40 to 100 feet below the existing ground surface, did not encounter groundwater at the project site. However, some soils exposed by exploratory borings were found to be above optimum moisture content.

b. Regulatory Framework

(1) Federal

(a) Clean Water Act

The Clean Water Act was first introduced in 1948 as the Water Pollution Control Act. The Clean Water Act authorizes Federal, state, and local entities to cooperatively create comprehensive programs for eliminating or reducing the pollution of state waters and

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IV.F Hydrology and Water Quality

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tributaries. The primary goals of the Clean Water Act are to restore and maintain the chemical, physical, and biological integrity of the nation’s waters and to make all surface waters fishable and swimmable. As such, the Clean Water Act forms the basic national framework for the management of water quality and the control of pollutant discharges. The Clean Water Act also sets forth a number of objectives in order to achieve the above-mentioned goals. These objectives include regulating pollutant and toxic pollutant discharges; providing for water quality which protects and fosters the propagation of fish, shellfish and wildlife; developing waste treatment management plans; and developing and implementing programs for the control of non-point sources of pollution.6

Since its introduction, major amendments to the Clean Water Act have been enacted (e.g., 1961, 1966, 1970, 1972, 1977, and 1987). Amendments enacted in 1970 created the U.S. Environmental Protection Agency (EPA), while amendments enacted in 1972 deemed the discharge of pollutants into waters of the United States from any point source unlawful unless authorized by an EPA National Pollutant Discharge Elimination System (NPDES) permit. Amendments enacted in 1977 mandated development of a “Best Management Practices” Program at the state level and provided the Water Pollution Control Act with the common name of “Clean Water Act,” which is universally used today. Amendments enacted in 1987 required the EPA to create specific requirements for discharges.

In response to the 1987 amendments to the Clean Water Act and as part of Phase I of its NPDES permit program, the EPA began requiring NPDES permits for: (1) municipal separate storm sewer systems (MS4) generally serving, or located in incorporated cities with 100,000 or more people (referred to as municipal permits); (2) 11 specific categories of industrial activity (including landfills); and (3) construction activity that disturbs five acres or more of land. Phase II of the EPA’s NPDES permit program, which went into effect in early 2003, extended the requirements for NPDES permits to: (1) numerous small municipal separate storm sewer systems;7 (2) construction sites of 1 to 5 acres; and (3) industrial facilities owned or operated by small municipal separate storm sewer systems. The NPDES permit program is typically administered by individual authorized states. As further discussed below, in the State of California, the program is issued through the State Water Resources Control Board and the nine Regional Water Quality Control Boards.

6 Non-point sources of pollution are carried through the environment via elements such as wind, rain, or

stormwater and are generated by diffuse land use activities (such as runoff from streets and sidewalks or agricultural activities) rather than from an identifiable or discrete facility.

7 A small municipal separate storm sewer system (MS4) is any MS4 not already covered by the Phase I program as a medium or large MS4. The Phase II Rule automatically covers on a nationwide basis all small MS4s located in “urbanized areas” as defined by the Bureau of the Census (unless waived by the NPDES permitting authority), and on a case-by-case basis those small MS4s located outside of urbanized areas that the NPDES permitting authority designates.

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IV.F Hydrology and Water Quality

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In addition to regulating non-stormwater discharges, the Clean Water Act sets forth water quality standards and criteria based on a water body’s designated beneficial uses. Section 305(b) of the Clean Water Act requires preparation of a 303(d) list (list of water quality limited or impaired water bodies). This list identifies what water bodies that are not achieving water quality standards or receiving beneficial uses and for what pollutants. Once a water body is identified as impaired, a Total Maximum Daily Load (TMDL) for the constituent of concern (pollutant) must be developed for that water body. A TMDL specifies the maximum amount of a pollutant that a water body can receive and still meet water quality standards. Those facilities and activities that are discharging into the water body, collectively, must not exceed the TMDL. The EPA oversees the 303(d) program and either the EPA or the State Water Board establishes the TMDL schedule for individual constituents. 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) Federal Anti-Degradation Policy

The Federal Anti-degradation Policy (40 Code of Federal Regulations 131.12) requires states to develop statewide antidegradation policies and identify methods for implementing them. Pursuant to the Code of Federal Regulations (CFR), state antidegradation policies and implementation methods shall, at a minimum, protect and maintain: (1) existing in-stream water uses; (2) existing water quality, where the quality of the waters exceeds levels necessary to support existing beneficial uses, unless the state finds that allowing lower water quality is necessary to accommodate economic and social development in the area; and (3) water quality in waters considered an outstanding national resource.

(2) State and Regional

(a) Porter-Cologne Water Quality Control Act (California Water Code)

The Porter-Cologne Water Quality Control Act (Porter-Cologne Act) was enacted in 1969 by the State of California. The Porter-Cologne Act includes provisions to address requirements of the Clean Water Act. These provisions include NPDES permitting, dredge and fill programs, and civil and administrative penalties. Regulations promulgated as a result of the Porter-Cologne Act are codified in Sections 13000–14958 of the California Water Code. The Porter-Cologne Act addresses issues relating to the conservation, control, and utilization of the water resources of the state. The Porter-Cologne Act states that the quality of all the waters of the state (including groundwater and surface water) shall be protected for the use and enjoyment by the people of the state.

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IV.F Hydrology and Water Quality

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The State Water Resources Control Board and its nine Regional Water Quality Control Boards are agencies within the umbrella structure of the California EPA. The State Water Resources Control Board has the principle responsibility for the development and implementation of California water quality policy and must develop programmatic water quality control procedures to be followed by the Regional Water Quality Control Boards. Based on the State Water Resources Control Board procedures, the regional boards develop local water quality control plans. The project site is located in Region 4, also known as the Los Angeles Region governed by the Los Angeles Regional Water Quality Control Board (LARWQCB).

(b) California Antidegradation Policy

The California Antidegradation Policy, otherwise known as the Statement of Policy with Respect to Maintaining High Quality Water in California was adopted by the State Water Board (State Board Resolution No. 68-16) in 1968. Unlike the Federal Antidegradation Policy, the California Antidegradation Policy applies to all waters of the State, not just surface waters. The policy states that whenever the existing quality of a water body is better than the quality established in individual Basin Plans, such high quality shall be maintained and discharges to that water body shall not unreasonably affect present or anticipated beneficial use of such water resource.

(c) California Toxic Rule

In 2000, the EPA promulgated the California Toxic Rule, which establishes water quality criteria for certain toxic substances to be applied to waters in the State. EPA promulgated this rule based on the EPA’s determination that the numeric criteria are necessary in the State to protect human health and the environment. The California Toxic Rule establishes acute (i.e., short-term) and chronic (i.e., long-term) standards for bodies of water such as inland surface waters and enclosed bays and estuaries that are designated by the LARWQCB as having beneficial uses protective of aquatic life or human health.

(d) Board Basin Plan for the Coastal Watersheds of Los Angeles and Ventura Counties

As required by the California Water Code, the LARWQCB has adopted a plan entitled “Water Quality Control Plan, Los Angeles Region: Basin Plan for the Coastal Watersheds of Los Angeles and Ventura Counties” (Basin Plan). Specifically, the Basin Plan designates beneficial uses for surface and groundwaters,8 sets narrative and 8 Designated beneficial uses of water include, but are not limited to: domestic, municipal, agricultural and

industrial supply; power generation; recreation; aesthetic enjoyment; navigation; and preservation and enhancement of fish, wildlife, and other aquatic resources or preserves. Such uses may be past, present and probable future beneficial uses of water.

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IV.F Hydrology and Water Quality

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numerical objectives that must be attained or maintained to protect the designated beneficial uses and conform to the State’s antidegradation policy, and describes implementation programs to protect all waters in the Los Angeles Region. In addition, the Basin Plan incorporates (by reference) all applicable State and Regional Board plans and policies and other pertinent water quality policies and regulations.

The Basin Plan is a resource for the Regional Board and others who use water and/or discharge wastewater in the Los Angeles Region. Other agencies and organizations involved in environmental permitting and resource management activities also use the Basin Plan. Finally, the Basin Plan provides valuable information to the public about local water quality issues.

(e) National Pollutant Discharge Elimination System (NPDES)

In the state of California, the State Water Resources Control Board (SWRCB) and the nine Regional Water Quality Control Boards (RWQCB) are responsible for implementing the NPDES permit program.

(i) Construction

Pursuant to the Clean Water Act Section 402(p) (which requires regulations for permitting of certain stormwater discharges), the SWRCB has issued one statewide NPDES General Permit for Stormwater Discharges Associated with Construction Activity (Construction General Permit) to apply to all construction activities. Under the Construction General Permit (2009-0009-DWQ), effective July 1, 2010, stormwater discharges from construction sites with a disturbed area of one or more acres are required to be covered by the Construction General Permit. Coverage under the Construction General Permit is initiated by completing a Risk Assessment and submitting electronically a project’s Permit Registration Documents through the SWRCB’s Stormwater Multi-Application and Report tracking System. The Permit Registration Documents include a Notice of Intent (NOI), a Risk Assessment, a Site Map, a Stormwater Pollution Prevention Plan (SWPPP), an annual fee, and a Signed Certification Statement.

Landowners are responsible for obtaining and complying with the Construction General Permit, but may delegate specific duties to developers and contractors by mutual consent. For construction activities, the Construction General Permit requires landowners or their designated agent to: (a) eliminate or reduce non-stormwater discharges to stormwater systems and other waters of the United States; (b) develop and implement the SWPPP prior to grading and during construction; and (c) perform inspections of stormwater control structures and pollution prevention measures. The primary objective of the SWPPP is to identify, construct, implement, and maintain BMPs to reduce or eliminate pollutants in stormwater discharges and authorized non-stormwater discharges from the construction

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site during construction. SWPPPs prepared in compliance with an NPDES Phase I Permit describe site erosion and sediment controls, runoff water quality monitoring, means of waste disposal, implementation of approved local plans, control of post-construction sediment and erosion control measures and maintenance responsibilities, and non-stormwater management controls. Dischargers are also required to inspect construction sites before and after storms to identify stormwater discharge from construction activity, and to identify and implement controls where necessary.

Once construction of a project is complete, a Notice of Termination would need to be filed with the Regional Water Quality Control Board certifying that all State and local requirements have been met in accordance with the requirements of the Construction General Permit.

(ii) Operation

Under Section 402(p) of the Clean Water Act, municipal NPDES permits shall prohibit the discharge of non-stormwater except under certain conditions and require controls to reduce pollutants in discharges to the maximum extent practicable. Such controls include BMPs, as well as system, design, and engineering methods. A municipal NPDES permit was issued to the County of Los Angeles and 84 incorporated cities including the City of Los Angeles, in December 2001. The Los Angeles County Municipal NPDES Permit required implementation of the Storm Water Quality Management Program prepared as part of the NPDES approval process. The Storm Water Quality Management Program requires the County of Los Angeles and the 84 incorporated cities to:

Implement a public information and participation program to conduct outreach on stormwater pollution;

Control discharges at commercial/industrial facilities through tracking, inspecting, and ensuring compliance at facilities that are critical sources of pollutants;

Implement a development planning program for specified development projects;

Implement a program to control construction runoff from construction activity at all construction sites within the relevant jurisdiction;

Implement a public agency activities program to minimize stormwater pollution impacts from public agency activities; and

Implement a program to document, track, and report illicit connections and discharges to the storm drain system.

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Under the Los Angeles County Municipal NPDES Permit, permittees are required to implement a development planning program to address stormwater pollution. These programs require project applicants for certain types of projects to implement Standard Urban Stormwater Mitigation Plans (SUSMP) throughout the operational life of their projects. The purpose of a SUSMP is to reduce the discharge of pollutants in stormwater by outlining BMPs which must be incorporated into the design plans of new development and redevelopment. A project is subject to SUSMP if it falls under one of the categories listed below:

Single-family hillside residential developments of one acre or more of surface area;

Housing developments of 10 units or more;

Industrial/commercial development with an impervious surface area of 100,000 square feet or larger;

Automotive service facilities [5,000 square feet or more of surface area];

Retail gasoline outlets [5,000 square feet or more impervious surface area and with projected averaged daily traffic of 100 or more vehicles];

Restaurants of 5,000 square feet or more of surface area;

Parking lot of 5,000 square feet or more of surface area or with 25 or more parking spaces;

Projects located adjacent to or discharging directly to an Environmentally Sensitive Area that meets the following threshold conditions: discharge stormwater and urban runoff that is likely to impact a sensitive biological species or habitat; and create 2,500 square feet or more of impervious surface area; and

Redevelopment projects in subject categories that meet redevelopment thresholds.

(3) Local

(a) City of Los Angeles Water Quality Compliance Master Plan for Urban Runoff

On March 2, 2007, City Council Motion 07-0663 was introduced by the City of Los Angeles City Council to develop a water quality master plan with strategic directions for planning, budgeting and funding to reduce pollution from urban runoff in the City of Los Angeles. The Water Quality Compliance Master Plan for Urban Runoff was developed by the Bureau of Sanitation, Watershed Protection Division in collaboration with the

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stakeholders to address the requirements of this Council Motion. The primary goal of the Water Quality Compliance Master Plan for Urban Runoff is to help meet water quality regulations. Implementation of the Water Quality Compliance Master Plan for Urban Runoff over the next 20 to 30 years will result in cleaner neighborhoods, rivers, lakes and bays, augmented local water supply, reduced flood risk, more open space, and beaches that are safe for swimming. The Water Quality Compliance Master Plan for Urban Runoff also supports the Mayor and Council’s efforts to make Los Angeles the greenest major city in the nation.

The Water Quality Compliance Master Plan for Urban Runoff identifies and describes the various watersheds in the City, summarizes the water quality conditions of the City’s waters, identifies known sources of pollutants, describes the governing regulations for water quality, describes the BMPs that are being implemented by the City, discusses existing TMDL Implementation Plans and Watershed Management Plans. Additionally, the Water Quality Compliance Master Plan for Urban Runoff provides an implementation strategy that includes the following three initiatives to achieve water quality goals:

Water Quality Management Initiative, which describes how Water Quality Management Plans for each of the City’s watershed and TMDL-specific Implementation Plans will be developed to ensure compliance with water quality regulations.

The Citywide Collaboration Initiative, which recognizes that urban runoff management and urban (re)development are closely linked, requiring collaborations of many City agencies. This initiative requires the development of City policies, guidelines, and ordinances for green and sustainable approaches for urban runoff management.

The Outreach Initiative, which promotes public education and community engagement with a focus on preventing urban runoff pollution.

Finally, the Water Quality Compliance Master Plan for Urban Runoff includes a financial plan that provides a review of current sources of revenue, estimates costs for water quality compliance, and identifies new potential sources of revenue.

(b) City of Los Angeles Proposition O

On November 2, 2004, Los Angeles voters passed Proposition O with a majority of 76 percent. The $500 million bond authorizes the City to fund projects that protect public health, capture stormwater for reuse and meet the Federal Clean Water Act through removal and prevention of pollutants entering regional waterways. A number of projects targeted at improving water quality have been authorized using Proposition O funds,

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including but not limited to: the Temescal Canyon Park Stormwater BMP, Los Angeles Zoo Parking Lot, the Westchester Stormwater BMP, Echo Park Lake Rehabilitation Project, and the Hansen Dam Recreational Area Parking Lot and Wetlands Restoration.9

In addition, Proposition O funds were utilized for Catch Basin Screen Cover and Insert Project which provided for the installation of catch basin inserts and screen cover throughout the City beginning in 2005 with completion on September 30, 2007 (Phase I and Phase II). Phase III began in the spring of 2008 and will retrofit approximately 34,000 remaining catch basins with opening screen covers.10

(c) City of Los Angeles Stormwater Program

The City of Los Angeles Development Best Management Practices Handbook, Part A Construction Activities, 3rd Edition, adopted by the City of Los Angeles Department of Public Works in September 2004, and associated ordinances reinforce the policies of the Construction General Permit.11 The handbook and ordinances also have specific minimum BMP requirements for all construction activities and require dischargers whose construction projects disturb 1 acre or more of soil to prepare a SWPPP and file a NOI with the RWQCB.

Requirements of the Los Angeles County Municipal NPDES permit are mirrored within the City of Los Angeles’ Development Best Management Practices Handbook, Part B Planning Activities, 3rd Edition, adopted by the City of Los Angeles Department of Public Works in June 2004. The manual provides guidance for developers in complying with the requirements of the Development Planning Program regulations of the City’s Stormwater Program. Compliance with the requirements of this manual is required by City of Los Angeles Ordinance No. 173,494.

The requirement to incorporate stormwater BMPs into the SUSMP is implemented through the City’s plan review and approval process. During the review process, project plans are reviewed for compliance with the City’s General Plans, zoning ordinances, and other applicable local ordinances and codes, including stormwater requirements. Plans and specifications are reviewed to ensure that the appropriate BMPs are incorporated to

9 City of Los Angeles Stormwater Program, Proposition O, website www.lapropo.org/index.htm; accessed

November 22, 2010. 10 City of Los Angeles Stormwater Program, What’s New, website www.lastormwater.org/siteorg/events/

PropO/121307.htm; accessed November 22, 2010. 11 Revised State Water Resources Control Board Construction General Permit (Order No. 09-09DWQ,

effective July 1, 2010) supersedes the requirements of the City of Los Angeles Development Best Management Practices Handbook, Part A Construction Activities, 3rd Edition.

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address stormwater pollution prevention goals. Based on the Development Best Management Practices Handbook, the proposed project falls into the following categories that are subject to the SUSMP requirements:

Industrial/commercial development with one acre or more of impervious surface area;

Restaurants;

Parking lots with 5,000 square feet or more of surface area or with 25 or more parking spaces;12

Housing developments of 10 units or more.

Several SUSMP provisions that are applicable to these and other land use categories may include, but are not limited to, the following:

Peak Stormwater Runoff Discharge Rate:13 Post-development peak stormwater runoff discharge rates shall not exceed the estimated pre-development rate for developments where the increased peak stormwater discharge rate will result in increased potential for downstream erosion;

Minimize stormwater pollutants of concern;

Protect slopes and channels;

Provide storm drain system Stenciling and Signage (only applicable if a catch basin is built on-site);

Properly design outdoor material storage areas to provide secondary containment to prevent spills;

Properly design trash storage areas;

Provide proof of ongoing BMP Maintenance of any structural BMPs installed;

Conserve natural and landscaped areas;

Properly design loading/unloading dock areas;

12 “Parking lot” means land area or facility for parking or storage of motor vehicles used for business,

commerce, industry, or personal use, with a lot size of 5,000 square feet or more of surface area, or with 25 or more parking spaces.

13 Peak Stormwater Runoff Discharge Rate is expressed in terms of rate of flow.

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Properly design vehicle/equipment/accessory wash areas;

Design Standards for Structural or Treatment Control BMPs.

In addition, under the SUSMP, restaurant and parking lots are also subject to specific prescriptive methods.

The BMPs must control peak flow discharge to provide stream channel and over bank flood protection, based on flow design criteria selected by the local agency. Further, the source and treatment control BMPs must be sufficiently designed and constructed to collectively treat, infiltrate, or filter stormwater runoff from one of the following:

– The 85th percentile 24-hour runoff event determined as the maximized capture stormwater volume for the area, from the formula recommended in Urban Runoff Quality Management, Water Environment Federation Manual of Practice No. 23/ASCE Manual of Practice No. 87, (1998);

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

– The volume of runoff produced from a 0.75-inch storm event, prior to its discharge to a stormwater conveyance system;

– 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.

Per the City’s SUSMP Infiltration Requirements and Guidelines, the order of preference specified below shall be followed in determining the appropriate type of SUSMP improvement for the project site.

1. Infiltration Systems (design based on the volume of stormwater)

2. Bio-Filtration/Retention Systems (design based on flow of stormwater)

3. Stormwater Capture and Re-Use (optional; subject to County Health Department approval)

4. Mechanical/Hydrodynamic Units

5. Combination of any of the above

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(d) County of Los Angeles Hydrology Manual

Drainage and flood control in the area of the project site is regulated by the Los Angeles County Department of Public Works and the City of Los Angeles Department of Public Works. The Los Angeles County Department of Public Works’ Hydrology Manual requires that a storm drain conveyance system be designed for a 25-year storm event and that the combined capacity of a storm drain and street flow system accommodate flow from a 50-year storm event. Areas with sump conditions are required to have a storm drain conveyance system capable of conveying flow from a 50-year storm event.14 The County also limits the allowable discharge into existing storm drain facilities based on the MS4 Permit unilaterally enforced on all new developments that discharge directly into the County’s storm drain system. Any proposed drainage improvements of County owned storm drain facilities such as catch basins and storm drain lines requires the approval/review from the County Flood Control District.

(e) City of Los Angeles Storm Drain Design Manual

Part G of the City of Los Angeles Storm Drain Design Manual provides further guidelines for the design of storm drains in the City including design criteria, standards, policies, and procedures. In general, the frequencies selected for storm drain design in areas zoned for urban residential or more impervious types of improvements are as follows:15

1. A 10-year storm frequency for areas without sumps.

2. A 50-year storm frequency for sump areas.

3. A 10-year storm frequency for closed conduits in natural watercourses, if the watercourse is maintained in place. The combined capacity of watercourse and conduit must contain a storm of 50-year frequency.

4. A 10-year runoff frequency for open channels in natural watercourses with freeboard to contain a storm of 50-year frequency.

5. A 50-year storm frequency for any storm drain in a natural watercourse if the watercourse is eliminated.

14 Los Angeles County Department of Public Works Hydrology Manual, January 2006, ladpw.org/wrd/

Publication/engineering/2006_Hydrology_Manual/2006%20Hydrology%20Manual-Divided.pdf, accessed November 22, 2010.

15 Los Angeles Bureau of Engineering, City of Los Angeles Storm Drain Design Manual, Part G Storm Drain Design, Section G 222, Design Frequencies.

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6. Flow from a 50-year storm frequency shall not do any damage to private property, such as flows which overflow the curb on hillside streets.

(f) Los Angeles Municipal Code

Earthwork activities, including grading, are governed by the Los Angeles Building Code, which is contained in Los Angeles Municipal Code (LAMC), Chapter IX, Article 1. Specifically, Section 91.7013 includes regulations pertaining to erosion control and drainage devices and Section 91.7014 includes general construction requirements as well as requirements regarding flood and mudflow protection.

Section 64.70 of the LAMC sets forth the City’s Stormwater and Urban Runoff Pollution Control Ordinance. The ordinance prohibits the discharge of the following into any storm drain system:

Any liquids, solids, or gases which by reason of their nature or quantity are flammable, reactive, explosive, corrosive, or radioactive, or by interaction with other materials could result in fire, explosion or injury.

Any solid or viscous materials, including oil and grease, which could cause obstruction to the flow or operation of the storm drain system.

Any pollutant that injures or constitutes a hazard to human, animal, plant, or fish life, or creates a public nuisance.

Any noxious or malodorous liquid, gas, or solid in sufficient quantity, either singly or by interaction with other materials, which creates a public nuisance, hazard to life, or inhibits authorized entry of any person into the storm drain system.

Any medical, infectious, toxic or hazardous material or waste.

Additionally, unless otherwise permitted by a NPDES permit, the ordinance prohibits industrial and commercial developments from discharging untreated wastewater or untreated runoff into the storm drain system. Furthermore, the ordinance prohibits trash or any other abandoned objects/materials from being deposited such that they could be carried into the storm drains. Lastly, the ordinance not only makes it a crime to discharge pollutants into the storm drain system and imposes stiff fines on violators, but also gives City public officers the authority to issue citations or arrest business owners or residents who deliberately and knowingly dump or discharge hazardous chemicals or debris into the storm drain system.

Any proposed drainage improvements within the street right of way or any other property owned by, to be owned by, or under the control of the City requires the approval of

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a B-permit (Section 62.105, LAMC). Under the B-permit process, storm drain installation plans are subject to review and approval by the City of Los Angeles Department of Public Works Bureau of Engineering.16 Additionally, any connections to the City’s storm drain system from a property line to a catch basin or a storm drain pipe requires a storm drain permit from the City of Los Angeles Department of Public Works, Bureau of Engineering.

(g) City of Los Angeles Proposed Low Impact Development Ordinance

The City of Los Angeles Bureau of Sanitation (BOS) has proposed to amend the Los Angeles Municipal Code to expand the existing SUSMP requirements through the provision of stormwater Low Impact Development (LID) strategies for development projects that require building permits. The proposed LID Ordinance expands upon the City’s SUSMP program by incorporating environmental practices such as infiltration, capture and use, and biofiltration. The LID Ordinance proposes the use of softscape and hardscape surfaces to retain, detain, store, and change the timing or filtering of stormwater and urban runoff. The use of small-scale, natural drainage features is emphasized to maximize infiltration and capture on-site, in lieu of end-of-line treatment methods. As currently proposed, the LID Ordinance would require that projects be designed to capture and manage stormwater runoff from the first 0.75-inch storm using the various methods, with infiltration being one of the preferred methods. Under the Ordinance, projects would be required to prepare a LID Plan for submittal to the BOS for review and approval. The LID Ordinance was approved by the City of Los Angeles Board of Public Works on January 15, 2010. The Ordinance remains under consideration by City Council Committees and will need to be considered by the full City Council.

3. Project Impacts

a. Methodology

As indicated above, this analysis of hydrology and water quality impacts is based in part on the Storm Water Hydrology Study prepared for the project site in April 2011 and the Surface Water Quality Study prepared for the project site in January 2011, both of which were prepared by Stantec. These reports are provided in Appendix G-1 and G-2 of this Draft EIR, respectively. The reports were prepared based on a review of documents from and methodologies specified by the Los Angeles County Department of Public Works and the City of Los Angeles Department of Public Works.

16 Los Angeles County Department of Public Works, Bureau of Engineering, http://eng.lacity.org/index.cfm;

accessed November 22, 2010.

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(1) Surface Water Hydrology

The analysis of hydrology impacts includes a calculation of pre-project and post-project runoff rates during a 50-year storm event. Potential impacts to the storm drain system were analyzed by comparing the calculated pre-project runoff rates to the calculated post-project runoff rates, taking into consideration the capacity of the existing storm drain system serving the site.

(2) Water Quality

For purposes of the water quality analysis, impacts were assessed by evaluating the types of pollutants and/or effects on water quality likely to be associated with construction and operation of the project. Project consistency with relevant regulatory permits/requirements, including BMPs and applicable plans, is evaluated to demonstrate how compliance would ensure that the project would not significantly degrade existing water quality.

b. Thresholds of Significance

(1) Surface Water Hydrology

Appendix G of the CEQA Guidelines provides a set of sample questions that address impacts with regard to hydrology. These questions are as follows:

Would the project:

Substantially deplete groundwater supplies or interfere substantially with groundwater recharge such that there would be a net deficit in aquifer volume or a lowering of the local groundwater table level (e.g., the production rate of pre-existing nearby wells would drop to a level which would not support existing land uses or planned uses for which permits have been granted)?

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 that would result in flooding on- or off-site?

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

Place housing within a 100-year flood hazard area as mapped on federal Flood Hazard Boundary or Flood Insurance Rate Maps or other flood hazard delineation maps?

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

Expose people or structures to a significant risk of loss, injury or death involving flooding, including flooding as a result of the failure of a levee or dam?

Inundation by seiche, tsunami, or mudflow?

In the context of these questions from Appendix G of the CEQA Guidelines, the City of Los Angeles CEQA Thresholds Guide states that a project would normally have a significant impact on surface water hydrology if it would:

Cause flooding during the projected 50-year developed storm event which would have the potential to harm people or damage property or sensitive biological resources;

Substantially reduce or increase the amount of surface water in a water body; or

Result in a permanent, adverse change to the movement of surface water sufficient to produce a substantial change in the current or direction of water flow.

(2) Surface Water Quality

Appendix G of the CEQA Guidelines provides a set of sample questions that address impacts with regard to water quality. These questions are as follows:

Would the project:

Violate any water quality standards or waste discharge requirements?

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?

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

Otherwise substantially degrade water quality?

In the context of these questions from Appendix G, the City of Los Angeles CEQA Thresholds Guide states that a project would normally have a significant impact on surface water quality if it would:

Result in discharges that would create pollution, contamination or nuisance as defined in Section 13050 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.

As defined in the CWC:

“Pollution” means an alteration of the quality of the waters of the State to a degree which unreasonably affects either of the following: 1) the waters for beneficial uses or 2) facilities which serve these beneficial uses. Pollution may include contamination.

“Contamination” means an impairment of the quality of the waters of the State by waste to a degree which creates a hazard to the public health through poisoning or through the spread of diseases. Contamination includes any equivalent effect resulting from the disposal of waste whether or not waters of the State are affected.

“Nuisance” means anything which meets all of the following requirements: 1) is injurious to health, or is indecent or offensive to the senses, or an obstruction to the free use of property so as to interfere with the comfortable enjoyment of life or property; 2) affects at the same time an entire community or neighborhood, or any considerable number of persons although the extent of the annoyance or damage inflicted upon individuals may be unequal; and 3) occurs during or as a result of the treatment or disposal of wastes.

The City of Los Angeles CEQA Thresholds above are used in the following analysis.

c. Project Design Features

As part of the project, the existing 84-inch diameter City storm drain would be protected in place or relocated as required to conform to the proposed street alignments.

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Relocated portions of the pipe would be replaced with pipe of equal size. The existing storm drain would remain in service at all times to convey flows from off-site areas. All on-site drainage facilities, except the 84-inch diameter City storm drain, would be removed. Proposed storm drains would range from 24 inches to 54 inches in diameter and would be located within the project’s new street alignments or within easements established in the project site. All site water would be collected on-site in catch basins. In addition, the existing drainage channel running through the site from west to east (generally corresponding to The Mall) would be maintained and improved with a series of urban bioswales designed to collect surface water and provide first flush treatment prior to discharge to the local storm drain system. Water leaving the site to surrounding streets and gutters would be eliminated.

The project would comply with the regulatory requirements above regarding hydrology and surface water quality, including those regarding implementation of a SWPPP during construction of the project, SUSMP requirements during operation of the project, and LID requirements. In compliance with these requirements, BMPs would be implemented to address water quality issues during both construction and operation of the project. Such BMPs would include but not be limited to the following:

Covered parking would 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.

Trash enclosures would be covered. Wastewater from trash enclosures would be directed to sewers.

Roof drain water would be collected and treated before discharge to the storm drain system.

Material use controls would include promoting efficient and safe housekeeping practices when handling potentially harmful materials.

Material exposure controls would include proper material storage to prevent or reduce the discharge of pollutants to stormwater by storing materials in a designated area, installing secondary containment, etc.

Material disposal and recycling BMP’s would reduce pollutants in stormwater. These may include stenciling storm drain system sign with prohibitive language to discourage dumping, and establishing household hazardous waste/used oil collection centers.

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Illegal dumping controls would include measures to detect, correct, and enforce against illegal dumping of pollutants on streets and into the storm drain system.

Illicit connection controls would prevent unwarranted physical connections to storm drain system.

Street and storm drain maintenance would reduce the discharges of pollutants to stormwater from street surfaces, catch basins and stormwater inlets by conducting cleaning on a regular basis.

Vegetation controls would reduce the introduction of pollutants into the storm conveyance system.

Sewer replacement would 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 would be mitigated and treated using bioswales, biofilters, media filters, and/or percolation devices, reducing the discharges of pollutants to stormwater.

Site planning considerations, vegetative stabilization, physical stabilization, diversion of runoff, velocity reduction of runoff, and sediment trapping/filtering.

Covering or berming building material storage areas, using good housekeeping practices, using safer alternative products, and training employees and subcontractors.

Minimizing the storage of hazardous materials onsite, storing materials in a designated area, installing secondary containment, and conducting regular inspections.

Reducing the chance for spills, stopping the source of spills, containing and cleaning up spills, and properly disposing of spill materials.

Providing designated waste collection areas and containers and arranging for regular disposal.

Conducting pre-construction surveys, inspecting excavations regularly, and remediating contaminated soil promptly.

Conducting washout off-site and performing on-site washout in a designated area.

Providing convenient, well maintained facilities, and arranging for regular service and disposal.

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Additional operational BMPs would be designed to infiltrate and filtrate on-site stormwater runoff in accordance with NPDES and City requirements. In addition, 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 stormwater.

d. Analysis of Project Impacts

(1) Construction

(a) Surface Water Hydrology

Construction of the proposed project would require the removal of existing buildings, paving, and landscaping on the site as well as earthwork activities (i.e., grading, excavation). As a result, underlying soils would be exposed, making the site temporarily more permeable. However, this increase in permeability would not have a substantial impact on existing drainage patterns and flows, particularly since runoff would be properly controlled through the implementation of appropriate BMPs. Therefore, construction-related impacts to surface water hydrology would be less than significant.

(b) Surface Water Quality

Construction of the project would involve site preparation activities including demolition, excavation, and grading. Such activities would temporarily alter the existing drainage patterns and water flows within the project site. During construction, approximately 1,084,400 cubic yards of soil would be excavated, of which approximately 123,200 cubic yards would be used for fill on-site and the remaining 961,300 cubic yards would be exported off-site. Exposed and stockpiled soils could be subject to erosion and conveyance into nearby storm drains during storm events. In addition, on-site watering activities to reduce airborne dust could contribute to pollutant loading in runoff. However, as the construction site would be greater than one acre, the project would be required to file a NOI and obtain coverage under the NPDES General Construction Activity Permit (Order No. 99-08-DWQ). In accordance with the requirements of the permit, the project would prepare and implement a site-specific SWPPP, which would specify BMPs and erosion control measures to be used during construction to minimize pollution in runoff. BMPs would include but not be limited to proper scheduling to avoid mass grading during the rainy season; covering materials such as bags of cement, paint, etc.; designating wash pits for washing paint, stucco, etc.; berming the site to control effluent from leaving a site during a rain event; establishing sediment traps. These and other BMPs would eliminate or reduce pollutant levels in runoff during construction activities. In addition, the project would be required to comply with City grading permit regulations, which require necessary measures, plans, and inspections to reduce sedimentation and erosion. Therefore, with

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compliance with NPDES requirements and City grading regulations, construction-related impacts to hydrology and water quality would be less than significant.

(c) Groundwater

The maximum depth of cut for the project’s grading operations is 55 feet below existing grade. This maximum depth 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 of 150 feet below grade and are not anticipated to expose groundwater or affect its water quality characteristics. Additionally, subsurface exploration and borings indicate that groundwater should be well below the depth of project excavation efforts and de-watering would not be necessary. However, if dewatering were necessary during construction, compliance with City de-watering requirements would ensure that the quality of groundwater is maintained. Therefore, construction-related impacts to groundwater would be less than significant.

(2) Operation

(a) Surface Water Hydrology

The project would result in a 4.7 percent net increase in impervious surfaces on-site. However, as discussed in Section II, Project Description, of this Draft EIR, the project would include a substantial amount of landscaped open space and recreational areas, much of which would be comprised of pervious surface area. Specifically, the project would include a civic plaza, an expansive central park, active parks, neighborhood greens, neighborhood playgrounds, and landscaped courtyards and pathways. After project implementation, pervious areas on the ground level and podium level would constitute approximately 10 percent of the site.17 The drainage area would continue to consist of the same seven subareas as existing conditions, none of which would change in size. Proposed drainage for the project site is shown in Figure IV.F-3, Proposed Hydrological Conditions, on page IV.F-28.

Moreover, the distribution of flows as well as on-site drainage systems would be slightly altered as shown in Figure IV.F-4 on page IV.F-29. Existing on-site storm drains would be retained in place or relocated as required to conform to the proposed street alignments. Relocated portions of the storm drains would be replaced with pipes of equal size as existing conditions. The existing storm drain system would remain in operation at all times during project construction and operation to ensure the adequate removal of stormwater flow. Additional storm drains would also be located within the project’s new

17 Storm Water Hydrology Study, Stantec. Prepared April 2011.

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Source: Stantec Consulting Inc., April 30, 2009.

Figure IV.F-3Proposed Hydrological Conditions

Boyle Heights Mixed-Use Community Project

Page IV

.F-28

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Figure IV.F-4Proposed Storm Drain Facilities

Boyle Heights Mixed-Use Community ProjectSource: Stantec Consulting Inc., June 8, 2011.

Page IV

.F-29

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street alignments or within easements established in the project site.18 In addition, two major easements associated with an existing Los Angeles County Flood Control District (LACFCD) storm drain and a Metropolitan Water District (MWD) water line that traverse the site would be maintained, with a segment of the storm drain realigned within the site to accommodate project development.19 Additionally, the existing drainage channel running through the site from west to east (generally corresponding to The Mall) would be maintained and improved with a series of urban bioswales designed to collect surface water and provide first flush treatment prior to discharge to the local storm drain system.

To estimate the post-project stormwater runoff rates at the project site, hydrology calculations were performed using the Los Angeles County of Public Works 2006 Hydrology Manual. Runoff rates were calculated for the 50-year storm events. As shown in Table IV.F-2 on page IV.F-31, the estimated post-project runoff rate at the project site would be approximately 152.60 cfs during a 50-year storm event. Thus, the runoff rate during a 50-year storm event upon project completion would be approximately 0.1 cfs greater than the existing runoff rate. Of this amount, approximately 78.96 cfs would drain to the City storm drain that runs through the project site, and 73.64 cfs would drain to the County storm drain. As discussed in further detail below, the small subareas that currently drain to the Olympic Boulevard and 8th Street gutters (i.e., Subareas 6 and 7) would be connected directly to the County storm drain, with no runoff flow to the Olympic Boulevard or 8th Street gutters.20

The City storm drain that runs through the project site would continue to serve Subareas 1, 2, 3, and 4. The amount of runoff to the City storm drain would increase from 78.2 cfs to 78.96 cfs upon completion of the project. As the City storm drain serving the project site has a capacity of approximately 410 cfs, this nominal increase would be adequately accommodated by the City storm drain system. Subarea 5 would continue to drain into the County storm drain in Grande Vista Avenue. However, the amount of runoff would increase from 65 cfs to 73.64 cfs due to the elimination of the discharge from Subareas 6 and 7 to Olympic Boulevard and 8th Street and redirection of this discharge to the County storm drain. As the total allowable discharge to the County storm drain from the project site is 100 cfs, the existing County storm drain system would be able to accommodate runoff from the project site.21 Overall, the ratio of drainage areas connected to each storm drain system would remain the same. Both storm drains eventually connect to the Los Angeles River in close proximity to each other, resulting in no significant impacts

18 Ibid. 19 The MWD water line is part of the regional water system and does not serve the site. 20 Storm Water Hydrology Study, Stantec. Prepared April 2011. 21 Ibid.

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IV.F Hydrology and Water Quality

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Table IV.F-2 Estimated 50-Year Storm Event Runoff Rates Based On Project Conditions

Storm Drain System Subarea Acres Q50 (cfs)

On-Site City Subarea 1 16.2 30.88 Subarea 2 7.3 13.92 Subarea 3 10.6 20.21 Subarea 4 7.4 13.95 Subtotal 41.5 78.96

On-Site County Subarea 5 34.5 64.30 Subarea 6 2.0 3.81 Subarea 7 2.9 5.53 Subtotal 39.4 73.64

Total 80.9a 152.60 a The subareas include portions of the public right-of-way. Hence the total acreage

for the subareas is greater than the total acreage for project site.

Source: Storm Water Hydrology Study, Stantec. Prepared April 2011.

by diverting drainage patterns. The amount of surface water reaching the downstream body of water, the Los Angeles River, would remain the same. In addition, it is important to note that the project would include stormwater quality measures that may include infiltration devices. These and other devices would further reduce runoff leaving the site. However, the analysis provided above is conservative and does not account for the reduction in flows associated with these project features.

Based on the above, the project is not anticipated to substantially increase the volume or rate of stormwater runoff discharged from the site as compared to existing conditions. As such, the project would not cause on-site flooding during the projected 50-year developed storm event, substantially reduce or increase the amount of surface water in a water body; or produce a substantial change in the current or direction of water flow. Project impacts associated with hydrology during operation would be less than significant.

(b) Water Quality

During the operational phase of the project, urban-related pollutants could potentially be conveyed by stormwater runoff into municipal storm drains. Urban related pollutants may include grease, oil, suspended solids, metals, solvents, phosphates, and pesticides/fertilizers. However, in accordance with NPDES requirements, a SUSMP would be required to be in place during the operational life of the project to reduce the discharge

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IV.F Hydrology and Water Quality

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of polluted runoff from the site. The SUSMP would set forth BMPs that would be implemented during the operational life of the project and would be subject to City review for compliance with the Development Best Management Practices Handbook, Part B Planning Activities. As described above, these BMPs could include, but are not limited to, the following: stenciling storm drains with prohibitive language to discourage dumping; establishing household hazardous waste collection centers; collecting and treating roof drain water before it is discharged to the storm drain system; providing covered parking areas; and providing covered trash enclosures.

Implementation of SUSMP requirements, inclusive of BMPs, would ensure that discharges from the project would not violate water quality standards. The project would also implement the City’s LID requirements. Furthermore, the project would also be designed in compliance with the Clean Water Act (CWA) and Order No. 90-079 of the RWQCB, which regulates the issuance of waste discharge requirements. Operation of the project would not result in discharges that would create pollution, contamination or nuisance or that cause regulatory standards to be violated for the receiving water body. Therefore, project impacts on water quality during operation would be less than significant.

4. Cumulative Impacts

Cumulative impact analysis on surface water quality is evaluated for the Los Angeles River Watershed. As identified in Section III, Environmental Setting, of this Draft EIR, there are 37 related projects within the project vicinity. These projects could potentially increase the volume of stormwater runoff and contribute to pollutant loading in stormwater runoff, resulting in cumulative impacts to hydrology and water quality. Forecasted growth in the Los Angeles River Watershed is subject to City and 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 hydrology. It is also anticipated that related projects would be subject to SUSMP requirements and implementation measures. In addition, the City of Los Angeles Department of Public Works reviews all construction projects on a case-by-case basis to ensure that sufficient local and regional drainage capacity is available. Thus, the combined cumulative hydrology and surface water quality impacts associated with the project’s incremental effect and the effects of other related projects would be less than significant.

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IV.F Hydrology and Water Quality

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5. Project Design Features and Mitigation Measures

a. Project Design Features

Project Design Feature F-1: The Applicant shall replace existing and construct new storm drains as needed that shall be designed and sized using the Los Angeles County Hydrology Manual and the City of Los Angeles Storm Drain Manual to provide for a minimum 10-year frequency storm event.

Project Design Feature F-2: Upon completion of the project, the total amount of impervious surface area on the 68.8-acre project site shall not exceed 90 percent of the site. The Applicant shall construct prior to build-out of the Specific Plan Area a stormwater system of bioswales, bio-filtration, infiltration, and native plants identified in the Specific Plan Design Guidelines Illustrative Site Plan as “the Arroyo Walk.” This 3.5-acre linear stretch of open space would weave through and link the various open space systems, generally following the northern contour of Glenn Avenue. The exact size and location of the final stormwater features shall be determined prior to construction of Phase 3 of the project. Vegetation controls typically involve a combination of chemical application and mechanical methods, which reduce the introduction of pollutants into the storm conveyance system.

Project Design Feature F-3: Parking facilities shall be designed in either of the following two configurations: Covered parking shall be provided to reduce the amount of oil and other vehicle fluid leaks from being introduced into urban run-off leaving the site, or parking lots designed to reduce runoff issues through the use of permeable surfaces, green landscape strips and other such devices.

Project Design Feature F-4: Roof drain water shall be collected and directed into planter boxes before discharge to the storm drain system. Roof water shall be treated to remove trash before directed to planter boxes.

Project Design Feature F-5: Hydrocarbons, oil and other vehicle fluid leaks associated with streets and driveways shall be mitigated and treated using bioswales, biofilters, media filters, and/or percolation devices, reducing the discharges of pollutants to stormwater.

Project Design Feature F-6: Trash enclosures shall be covered. Stormwater and wastewater runoff from trash areas will be reduced. Wastewater from trash enclosures will be directed to sewers.

Project Design Feature F-7: Property management and home-owners associations shall implement material use controls that promote

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IV.F Hydrology and Water Quality

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efficient and safe housekeeping practices when handling potentially harmful materials.

Project Design Feature F-8: Material disposal and recycling BMP’s shall be implemented to reduce pollutants in stormwater. These shall include stenciling storm drain system sign with prohibitive language to discourage dumping, and establishing household hazardous waste/used oil collection centers.

Project Design Feature F-9: Material exposure controls shall include proper material storage to prevent or reduce the discharge of pollutants to stormwater by storing materials in a designated area, installing secondary containment, etc.

Project Design Feature F-10: Sewer replacement shall limit the number of any potential existing sewage leaks or sanitary overflow into the storm drain conveyance system.

Project Design Feature F-11: The Applicant shall implement measures to detect, correct, and enforce against illegal dumping of pollutants on streets and into the storm drain system.

Project Design Feature F-12: The project shall not construct Illicit physical connections to the storm drain system.

b. Mitigation Measures

While the project would not result in significant impacts to hydrology and water quality, the following mitigation measures are recommended to reflect existing regulatory requirements.

(1) Construction

Mitigation Measure F-1: Prior to the issuance of demolition and building permits for Projects (as that term is defined in the Specific Plan) that are expected to disturb one acre or more of land, the applicant shall provide proof to the City of Los Angeles that a Notice of Intent (NOI) has been filed with the State Water Resources Control Board (SWRCB) for coverage under the General Construction Permit and a project specific Risk Assessment, and Storm Water Pollution Prevention Plan (SWPPP) has been prepared. Such evidence shall consist of a copy of the Notice of Intent stamped by the SWRCB or Regional Board, or a letter from either agency stating that the Notice of Intent has been filed. The SWPPP shall include a menu of Best Management Practices (BMPs) to be selected and implemented based on the phase of construction and the weather conditions to effectively control erosion, sediment, and other construction-related pollutants to meet the Best Available Technology Economically

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IV.F Hydrology and Water Quality

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Achievable and Best Conventional Pollutant Control Technology standards. The Best Management Practices to be implemented during construction shall address the following:

Erosion Control;

Sediment Control;

Waste and Materials Management;

Non-stormwater Management;

Training and Education; and

Maintenance, Monitoring, and Inspections.

As required by the Construction General Permit, during all phases of construction, the Project shall implement BMPs consistent with the Best Available Technology Economically Achievable and Best Conventional Pollutant Control Technology standards. BMPs 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.

Mitigation Measure F-2: 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 shall 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.

Mitigation Measure F-3: The project shall comply with Chapter IX, Division 70 of the LAMC, which addresses grading, excavations, and fills, and Chapter VI, Article 4.4 of the LAMC, Storm Water and Urban Runoff Pollution Control (as modified by Ordinance Nos. 172,176 and 173,494), which requires the application of BMPs.

Mitigation Measure F-4: Excavation and grading activities shall be scheduled during dry weather periods. If grading occurs during the rainy season (October 15 through April 1), diversion dikes shall be constructed to channel runoff around or through the site. Channels

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IV.F Hydrology and Water Quality

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shall be lined with materials in accordance with the BMPs identified by the project’s SWPPP to reduce runoff velocity.

Mitigation Measure F-5: Stockpiles, excavated, and exposed soil shall be covered with secured tarps, plastic sheeting, erosion control fabrics, or treated with a bio-degradable soil stabilizer. Building material storage areas shall be properly covered and bermed to prevent discharge of waste into storm drains.

Mitigation Measure F-6: All waste shall be disposed of properly. Project contractors shall minimize the storage of hazardous materials onsite, storing materials in a designated area, installing secondary containment, arranging regular disposal, conducting regular inspections, and training employees and subcontractors. Vehicle fueling shall be restricted to designated areas, enclosing and covering stored fuels. Non-recyclable materials/wastes shall be taken to an appropriate landfill. Toxic wastes shall be properly characterized and disposed at a licensed regulated disposal site.

Mitigation Measure F-7: Appropriate erosion control and drainage devices such as interceptor terraces, berms, vee-channels, and inlet and outlet structures shall be incorporated in all new construction areas. Outlets of culverts, conduits or channels shall be protected from erosion by discharge velocities by installing rock outlet protection. (Rock outlet protection is a physical device composed of rock, grouted riprap, or concrete rubble placed at the outlet of a pipe.)

Mitigation Measure F-8: Project contractors shall implement concrete waste management by conducting washout off-site, performing on-site washout in designated areas, and training employees and contractors.

Mitigation Measure F-9: Project contractors shall provide convenient, well-maintained septic waste facilities, and arrange for regular service and disposal.

Mitigation Measure F-10: Leaks, drips and spills shall be cleaned immediately to prevent contaminated soil on paved surfaces that can be washed away into the storm drains.

Mitigation Measure F-11: Hosing down of pavement at material spills shall be prohibited. Dry cleanup methods shall be used whenever possible.

Mitigation Measure F-12: Dumpsters shall be covered and maintained. Uncovered dumpsters shall be placed under a roof or covered with tarps or plastic sheeting.

Mitigation Measure F-13: Gravel approaches shall be used where truck traffic is frequent to reduce soil compaction and limit the tracking of sediment into streets.

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IV.F Hydrology and Water Quality

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Mitigation Measure F-14: All vehicle/equipment maintenance, repair, and washing shall be conducted away from storm drains. All major repairs shall be conducted off-site. Drip pans or drop clothes shall be used to catch drips and spills.

(2) Operation

Mitigation Measure F-15: The Applicant shall implement stormwater BMPs to capture and manage 100 percent of the first 0.75 inch of rainfall from a storm event in a 24-hour period in the following order of priority: infiltration, capture and reuse, City approved bio-filtration/retention system BMP or combination of the above. The design of structural BMPs shall be in accordance with the LID Section of the Development Best Management Practices Handbook Part B Planning Activities. If the Bureau of Sanitation Stormwater Protection Division determines that the above 100 percent capture is infeasible, then the Project Applicant shall implement offsite mitigation within the same sub-watershed for the same. Prior to issuance of a building permit, the Applicant shall be required to verify the Stormwater Protection Division’s approval of the LID strategies and submit a signed certificate from a California licensed civil engineer or licensed architect that the proposed BMPs meet this numerical threshold.

Mitigation Measure F-16: The Specific Plan area run-off shall not exceed 2.9 cfs per acre into the County of Los Angeles storm drain system. A signed certificate from a California licensed civil engineer to confirm that the proposed project is designed in such a manner shall be required.

Mitigation Measure F-17: Potentially hazardous materials with the potential to contaminate stormwater shall be: (1) placed in an enclosure such as, but not limited to, a cabinet, shed, or similar structure; or (2) protected by secondary containment structures such as berms, dikes, or curbs. Storage areas shall be paved and sufficiently impervious to contain leaks and spills, and shall have a roof or awning to minimize collection of stormwater within the secondary containment area.

Mitigation Measure F-18: Project documentation and design materials that specify and incorporate all BMPs shall be provided to assure that stormwater quality of project runoff meets agency requirements and standards.

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IV.F Hydrology and Water Quality

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6. Level of Significance After Mitigation

As discussed above, impacts on hydrology and water quality would be less than significant. Additionally, project design features and mitigation measures would further ensure compliance with applicable regulations.


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