3.9 HYDROLOGY AND WATER QUALITY

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1 3.9 HYDROLOGY AND WATER QUALITY Introduction The Hydrology and Water Quality section evaluates the Program s impacts on water resources. The environmental setting provides a general overview of the surface water hydrology, water quality, and groundwater within the Program area. The impact analysis describes Program impacts on water resources that can be identified at this first-tier stage of review. Mitigation measures, and impact significance after mitigation, are also described. The discussion also identifies mitigation measures that may be used in the context of individual projects to mitigate site-specific impacts Environmental Setting Hydrology The LAUSD is located within western Los Angeles County extending from San Pedro in the south to the San Fernando Valley in the north. The climate is mild, with dry summers and moderately wet winters. Total annual rainfall averages approximately 14 inches per year. Annual rainfall generally increases from south to north. Representative annual rainfall amounts for specific areas within the LAUSD are as follows: San Pedro 11.8 inches; Santa Monica (pier) 12.5 inches; Los Angeles Civic Center 14.7 inches; and San Fernando 16.2 inches (Western Regional Climate Center, 2003). Nearly all of this rainfall comes in the form of winter storms. Approximately 75 percent or more falls within the months of December to March, with very little falling in the summer. The Program area is generally flat in topography. Drainage into the LAUSD from the surrounding area originates from the Santa Susana Mountains to the north and from the San Gabriel Mountains to the north and east. The Santa Monica Mountains and Hollywood Hills, which basically form the boundary between the Valley and Central areas of the LAUSD, also contribute drainage. These mountains, the San Gabriels in particular, are high and steep, and produce high, flash flood peaks with the potential for large, destructive debris flows. Flood detention and debris collection reservoirs have been constructed at the mouth of most large canyons to protect the downstream urban areas from flooding and debris. Since virtually the entire LAUSD area is densely urbanized, drainage is primarily conducted through an extensive network of underground storm drains. These drains generally originate at curb inlets on city streets and increase in size as they progress in the downstream direction to an open channel or detention basin. Large drainage ways, including those originating in the adjacent mountains, are typically conveyed through the LAUSD area in large, open, concretelined channels. Major drainageways include the Los Angeles River, Tujunga Wash, Pacoima Wash, Ballona Creek, and Dominguez Channel. The Los Angeles River is the largest watercourse within the LAUSD area (Figure at the end of this section). This river, draining a total watershed of approximately 824 square miles, begins in the western San Fernando Valley and runs eastward through the Sepulveda Flood LAUSD New School Construction Program Hydrology and Water Quality

2 Control Basin, then turns southward around the Hollywood Hills. The river continues to run southward approximately along the eastern boundary of the LAUSD to enter the Pacific Ocean at Long Beach. Although the majority of the Los Angeles River is surrounded by urbanized areas and lined with concrete, a portion of the watershed originates in the San Gabriel, Santa Monica and Santa Susana mountains and is relatively unaltered. There are also segments of the Los Angeles River near the Sepulveda Flood Control Basin and Griffith Park that are not lined. The Tujunga Wash and Pacoima Wash are tributaries to the Los Angeles River in the San Fernando Valley. The Dominguez Watershed drains an area of approximately 118 square miles comprising all or portions of the cities of Gardena, Carson, Lomita, and Los Angeles. The Dominguez Channel watershed is entirely urban. The channel begins in Hawthorne and drains south to enter the Pacific Ocean at the Los Angeles Harbor. The third major watershed is the Santa Monica Bay watershed of which Ballona Creek is a part. The communities of Pacific Palisades, Venice, and Westchester are within this watershed. Ballona Creek originates in the City of Los Angeles and runs approximately eight miles southwest to enter the Pacific Ocean at Marina del Rey. A review of FEMA maps for representative areas within the LAUSD indicates that most major drainage channels, for instance the Los Angeles River and Dominguez Channel, contain the 100-year discharge. Most flooding within the LAUSD is primarily local in nature, generally resulting from inadequate street drainage or inadequate local drains. Exceptions include (but are not necessarily limited to) the upper Ballona Creek and tributaries, and the east side of the Los Angeles River in the downtown area, in which there are fairly extensive floodplains. Flood hazard maps are available from the FEMA area, from Los Angeles County, and (if applicable) from local cities. Water Quality Surface water quality has been degraded within the LAUSD area, mostly through nonpoint source pollutants. Pollutants from industrial and municipal effluents are also a problem. The Los Angeles River watershed alone has 1,307 permitted industrial dischargers to the river. All large watersheds within the LAUSD are affected. The Los Angeles Regional Water Quality Control Board (RWQCB) considers uncontrolled pollutants from nonpoint sources to be the greatest threat to the rivers and streams within the region (RWQCB, 1994). The RWQCB lists certain surface waters as impaired as required in 303(d) of the federal Clean Water Act. The RWQCB establishes priority rankings for waters on the list, and develops action plans, called Total Maximum Daily Loads (TMDL), to improve water quality. Water quality is improved through such measures as the imposition of waste discharge requirements, urban runoff control programs, and remediation of pollution. The majority of the Los Angeles River Watershed is considered impaired due to a variety of point and nonpoint sources. Pollutants resulting in 303(d) listing include ph, ammonia, metals, LAUSD New School Construction Program Hydrology and Water Quality

3 coliform, trash, scum, algae, oil, chlorpyrifos (a component of pesticides), other pesticides, and volatile organics. Some of these pollutants are constituents of concern throughout the length of the river, while others are of concern only in certain reaches (RWQCB, 2003). Ballona Creek pollutants include high levels of dissolved solids (chlorides, sulfates, heavy metals), organic chemicals, and bacteria, for which the creek is listed as impaired. Untreated sewage has discharged into Ballona Creek during heavy rainfalls. Dry weather and storm runoff from the main channel and two major tributaries have been found to be toxic to marine organisms (RWQCB, 2003). The Dominguez Channel drains a highly industrialized area, resulting in very poor water quality. Ten major NPDES discharges, one wastewater treatment plant, two generating stations, six refineries, 58 minor discharges, and 424 dischargers are covered under an industrial storm water permit. The Dominguez Channel is listed as impaired for chlordane, DDT, polychlorinated biphenyls (PCBs), aldrin, dieldrin, polycyclic aromatic hydrocarbons, chromium, ammonia, benthic community effects, ChemA, coliform, lead and zinc (RWQCB, 2003). Groundwater The major groundwater basins within the LAUSD (Figure 3.9-2) are the Los Angeles Coastal Plain Basin, the San Fernando Basin, and the Main San Gabriel Valley Basin (RWQCB, 1994). The Los Angeles region in general, and the LAUSD area in particular, have relied on groundwater to supply irrigation demands since the 1870s (USGS, 1995). The draw of groundwater over the years has altered the characteristics of the groundwater basins of Southern California. Today, the predominant use of groundwater is for public supply. The public demand for water has outpaced groundwater as a continuing replenishable source of potable water. The groundwater used for public supply is supplemented by water from Owens Valley, Northern California, and the Colorado River. Groundwater is also protected from the intrusion of salt water from the ocean by the injection of reclaimed water into aquifers adjacent to the coastline (USGS, 1995). Water in the main aquifer or groundwater basin beneath the LAUSD moves toward the ocean before extraction wells alter the flow direction. Extraction increases during dry years and periods of drought (MWD, 2003). Generally, the aquifer beneath the LAUSD is defined by alternating horizontal layers of confining units and permeable units. In most places the top most layer, the exposed ground layer, is a confining layer of clay and silt. This confining layer ranges from less than 1 foot to about 180 feet in thickness. The main freshwater body is generally found in a permeable layer below the confining layer (where the confining layer exists) at depths of 100 to 4,000 feet. Below this level the water is saline and unpotable (USGS, 1995). The water in the aquifer moves slowly toward the ocean or toward extraction wells within the permeable unit. Saltwater can exist in the permeable units and is drawn landward through the fresh water aquifer toward extraction wells that draw down the fresh water table. To counter the intrusion of saltwater into the fresh water aquifers, injection wells LAUSD New School Construction Program Hydrology and Water Quality

4 are used to pump reclaimed or other surface water between the saltwater and fresh water aquifers (RWQCB, 1994). The geology of the confining and permeable units varies locally. Generally, the quality of water in the Los Angeles Basin is suitable for most uses. Dissolvedsolids concentrations in the water are generally less than 500 milligrams per liter and concentrations of chloride do not exceed drinking-water standards recommended by the USEPA. Water imported from the Owens Valley and the Colorado River for recharge has larger concentrations of dissolved solids, chloride, and sulfate than the groundwater, but the quality of the mixed native groundwater and imported water is within State and federal standards for drinking water (USGS, 1995). Valley Area The Valley area consists of the LAUSD s Local Districts A, B and C, and generally comprises the area of Los Angeles known as the San Fernando Valley. The urban valley is bounded on the south by the Santa Monica Mountains and the Hollywood Hills, on the west by the Simi Hills, on the north by the Santa Susana Mountains and foothills of the San Gabriel Mountains, and on the east by the San Gabriel and Verdugo Mountains. Drainage flows from the mountains into the Valley, then east along the Los Angeles River. Major tributaries to the Los Angeles River include, among others, the Pacoima Wash, the Tujunga Wash, Arroyo Calabasas, and Browns Canyon Creek. The Los Angeles River flows through the Sepulveda Flood Control Basin in the south central San Fernando Valley. The mountains surrounding the San Fernando Valley are capable of producing high flood peaks and sudden debris flows. Depending on the area and steepness of terrain, some areas within the San Gabriel Mountains are capable of producing more than 300 cubic yards of debris per acre of watershed in the form of mud and rocks (LADPW, 1993). These debris flows can be very hazardous to life and property. The Los Angeles County Department of Public Works maintains a series of flood detention and debris collection basins at the base of the mountains that surround the San Fernando Valley, particularly along the base of the San Gabriel Mountains. Hansen Dam and Lopez Dam, located in the San Fernando area, are examples. These flood control and debris basins provide protection against debris flows originating in the mountains. However, some small canyons may not have adequate debris and flood protection. The constructed flood control channels for the major rivers within the Valley are generally adequate to contain the 100-year discharge. However, there are flood-prone areas, mostly local in nature, that are delineated on FEMA flood maps. The groundwater basin under this area of the LAUSD is the San Fernando Basin. This groundwater basin is between the Santa Susana Mountains, San Gabriel Mountains, Verdugo Hills, San Raphael Hills, Elysian Hills, Santa Monica Mountains, and the Los Angeles Coastal Basin. Sub-basins within the San Fernando Basin are the Sylmar and Verdugo Basins (RWQCB, 1994). LAUSD New School Construction Program Hydrology and Water Quality

5 Central Area The Central area consists of the LAUSD Local Districts D, E, F, and H, and basically comprises the City of Los Angeles, including downtown Los Angeles, south of the Santa Monica Mountains and the Hollywood Hills. Topography is generally flat through most of this area. This area contains the Ballona Creek channel described above, as well as a portion of the Los Angeles River. A potential for debris production from the mountains to the north of the Central area exists, but this potential is moderate. Flood-prone areas are along Ballona Creek and in the Ballona Creek watershed, along the west side of the Los Angeles River north of the I-10 freeway, at the Venice area on the coast, and at other local areas throughout the Central area, as delineated on FEMA maps. The groundwater basins under this area of the LAUSD are the San Fernando Basin, Los Angeles Coastal Basin and Main San Gabriel Valley. Only small sections of the San Fernando Basin and Main San Gabriel Valley Basin are in the LAUSD. The northern part of Local District E is in the San Fernando Basin. The eastern part of Local Districts F and H are in the Main San Gabriel Valley Basin. The part of the Los Angeles Coastal Basin in the central area is between the Santa Monica Mountains and the Elysian Hills. Sub-basins within this part of the Los Angeles Coastal Basin are the Santa Monica Basin, Hollywood Basin, Central Basin, and West Coast Basin (RWQCB, 1994). South Area The South area is comprised of the Local Districts G, I, J and K, and generally consists of most of the area south of the I-10 Freeway and west of the 710 Freeway, not including Torrance, Inglewood, and Compton. Major drainage ways include the Dominguez Channel and the Los Angeles River, which runs along the eastern boundary of the South area. Both channels drain to the south to enter the Pacific Ocean in the vicinity of the Long Beach and Los Angeles Harbors. Flood control channels within this area generally convey the 100-year discharge. Most flood-prone areas are local and due to inadequate local drainage. The groundwater basin under this area of the LAUSD is the Los Angeles Coastal Basin. This part of the groundwater basin is between the Pacific Ocean, Palos Verdes, and the Baldwin Hills. Sub-basins within this part of the Los Angeles Coastal Basin are the West Coast Basin and the Central Basin (RWQCB, 1994) Applicable Regulations, Plans, and Standards Federal Clean Water Act. The federal Clean Water Act (CWA) requires states to set standards to protect, maintain, and restore water quality through the regulation of point source and certain non-point source discharges to surface water. Section 401 of the CWA states that any applicant for a federal license or permit to conduct any activity including, but not limited to, the construction or operation of facilities that may LAUSD New School Construction Program Hydrology and Water Quality

6 result in any discharge to navigable waters shall provide the licensing or permitting agency a certification from the state in which the discharge originates or would originate, or, if appropriate, from the interstate water pollution control agency having jurisdiction over the navigable water at the point where the discharge originates or would originate, that any such discharge would comply with the applicable provisions of Sections 301, 302, 303, 306, and 307 of the Clean Water Act. This State certification is referred to as "Section 401 Water Quality Certification." In California, the nine RWQCBs administer Section 401 certification. Section 402(p) of the CWA establishes a framework for regulating municipal and industrial storm water discharges under the NPDES Program. USEPA NPDES regulations require that discharges of storm water to waters of the United States from construction projects that encompass one or more acres of soil disturbance comply with an NPDES Permit (United States Congress, 1948 (as amended), 33 U.S.C ). Section 404 of the CWA authorizes the US Army Corps of Engineers (USACE) to regulate the discharge of dredged or fill material within the waters of the U.S. and adjacent wetlands. Most watercourses within the United States, including those within the LAUSD boundary, qualify as waters of the U.S. Nationwide 404 permits are available in certain cases to streamline the 404 process. For instance, Nationwide Permit #39, Residential, Commercial and Institutional Developments, could apply to school construction provided the impacts to waters of the U.S. are ½ acre or less and involve less than 300 linear feet of stream. Notification of the USACE is required. Mitigation for impacts may also be required. The Flood Disaster Protection Act of The Flood Disaster Protection Act requires local municipalities to adopt and enforce floodplain regulations to manage development and encroachment into floodplains as a condition of participating in the national flood insurance program. Floodplain management is achieved through the aid of Federal Flood Insurance Rate Maps, which delineate and describe 100-year flood hazard areas for selected rivers and streams within the local jurisdiction. Development within these flood hazard areas is generally prohibited unless it can be accomplished without being subject to flooding from the 100-year flood, or increasing the flood risk on other property. New schools would be required to be located outside the floodplain, or be protected by elevating the lowest floor above the 100-year flood level. State National Pollutant Discharge Elimination System General Permit For Storm Water Discharges Associated With Construction Activity. The SWRCB has adopted a Statewide General NPDES Permit that applies to all storm water discharges associated with construction activity, except from those on Tribal Lands, in the Lake Tahoe Hydrologic Unit, and those performed by the California Department of Transportation (Caltrans). This General Permit requires all dischargers where construction activity disturbs one acre or more to: LAUSD New School Construction Program Hydrology and Water Quality

7 Develop and implement a Storm Water Pollution Prevention Plan (SWPPP) that specifies BMPs that would prevent all construction pollutants from contacting storm water and with the intent of keeping all products of erosion from moving off site into receiving waters. Eliminate or reduce non-storm water discharges to storm sewer systems and other waters of the nation. Perform inspections of all BMPs. The General NPDES Permit in the LAUSD area is implemented and enforced by the Los Angeles RWQCB. An SWPPP must include: (1) a site description, (2) BMPs for erosion and sediment controls, (3) BMPs for construction waste handling and disposal, (4) implementation of approved local plans, (5) proposed post-construction controls, and (6) provisions for nonstorm water management. A full description of the required contents of an SWPPP is provided in State Water Resources Control Board, 1999, National Pollutant Discharge Elimination System General Permit For Storm Water Discharges Associated With Construction Activity available from the RWQCB. LAUSD must comply with the General Permit in implementing the Program. Typically, a developer will comply with the General Permit by issuing site-specific notices of intent and preparing site-specific SWPPP s. As discussed below, however, it would be more effective for LAUSD to develop a master SWPPP for the Program, under RWQCB supervision, which could be adapted as necessary for specific sites as those sites are designed and built. The Clean Water Act also prohibits the discharge of pollutants to waters of the United States from any point source unless the discharge is in compliance with an NPDES permit. Porter-Cologne Water Quality Control Act. The Porter-Cologne Water Quality Control Act of 1967, Water Code et seq., requires the SWRCB and the nine RWQCBs to adopt water quality criteria to protect State waters. These criteria include the identification of beneficial uses, narrative and numerical water quality standards and implementation procedures. The criteria for the project area are contained in the Water Quality Control Plan for the Los Angeles Region (RWQCB, 1994). This plan sets numerical and/or narrative water quality standards controlling the discharge of wastes to the State s waters and land. California Fish and Game Code (Streambed Alteration Agreement). Prior to undertaking any construction activity within streambeds, including all intermittent as well as perennial streams, a Streambed Alteration Agreement must be obtained from the Department of Fish and Game. Through this agreement, the Department attempts to ensure that any approved construction activity is protective of stream resources through design, construction planning, and specific mitigation measures. California Water Code requires that any person discharging waste, or proposing to discharge waste, within any region that could affect the quality of the waters of the State, other than into a community sewer system, must submit a report of waste discharge to the RWQCB. LAUSD New School Construction Program Hydrology and Water Quality

8 California Government Code requires school districts to comply with any city or county ordinance regulating drainage improvements. Section also requires school districts to comply with ordinances requiring review and approval of grading plans as they relate to design and construction of onsite improvements that affect drainage. Local In order to participate in the National Flood Insurance Program (see Flood Disaster Protection Act of 1973 above), local jurisdictions, including cities and counties, must enact floodplain development regulations. These regulations generally prohibit development within a floodplain unless the lowest floor of the structure is above the predicted flood level. Some flood-prone areas, known as floodways, are set aside specifically for the conveyance of flood flows, and development in these areas is prohibited or severely restricted. Los Angeles County, the City of Los Angeles, and most other cities, have floodplain and water quality regulations for new development Environmental Impacts and Mitigation Measures Thresholds of Significance The Program would result in a significant adverse impact relating to hydrology and water quality if: The Program causes a violation of any water quality standard or waste discharge requirement, or creates a condition of pollution, contamination, or nuisance as defined in California Water Code The Program depletes groundwater supplies or interferes substantially with groundwater recharge such that the production rate of pre-existing wells would be caused to drop to a level which would not support existing land uses or planned uses for which permits have been granted. The Program substantially alters the existing drainage pattern of an area, including through the alteration of the course of a stream or river, in a manner that would result in substantial erosion or siltation, or impede or redirect flood flows within a 100-year flood hazard area such that the flood hazard on adjacent property is increased. The Program results in runoff volume increases that cause the capacity of the existing drainage system to be exceeded. The Program exposes people or structures, including those within the proposed the LAUSD schools, to a risk of loss, injury or death within the 100-year floodplain, as a result of the failure of a levee or dam, or as a result of seiche, tsunami, or mudflow Environmental Impact Analysis Impact HWQ-1: Water quality degradation is considered a significant impact if the Program causes a violation of any water quality standard or waste discharge requirement, LAUSD New School Construction Program Hydrology and Water Quality

9 or creates a condition of pollution, contamination or nuisance as defined in California Water Code Impact Determination Less than Significant with Mitigation. Construction Impacts The Program would result in new school construction; reconstructions or additions to existing campuses; construction of small satellite academies; and retrofitting non-school buildings to school use. These types of projects include grading and other construction activities that could cause deterioration of water quality if sediments or construction-related pollutants wash into the surface water system. The LAUSD construction BMPs (Section 2.4) incorporated into the Program require that LAUSD take the following steps for all for new construction projects: Prepare and implement a sediment and erosion control plan that follows the BMPs outlined by the State Water Resources Control Board to comply with the Stormwater Construction Activities General Permit; Develop and implement a SWPPP, with BMPs for new construction, as required by RWQCB NPDES regulations; Discharge water accumulated within the construction excavation pits in accordance with BMPs and a dewatering plan that must be developed and approved prior to construction as part of the NPDES General Construction Stormwater Permit; and, Prevent construction-related sediment flows from entering storm drainage systems by constructing temporary filter inlets around existing storm drain inlets prior to the stabilization of construction site areas. The commitment to comply with NPDES regulations would avoid significant water quality impacts based on construction runoff in most cases. Where construction sites are smaller than one acre, however, there is no requirement to prepare a SWPPP. Some school additions and school facilities constructed under this Program could be less than one acre. The aggregate runoff from sites that are less than one acre could create a condition of pollution, contamination, or nuisance as defined in California Water Code Considered in the aggregate, the total of these sites would be greater than one acre, all constructed without the benefit of compliance with an SWPPP. Therefore, water quality impacts from these sites in the aggregate could be significant. Mitigation Measure HWQ-1, intended for the school program in the aggregate, would mitigate the impact of all school construction under the Program. Operational Impacts New schools constructed under the Program would not produce or discharge industrial wastes to surface or groundwater. New schools built under the Program may create additional sources of non-point source or storm water pollution from vehicular-related contaminants washing into the drainage system during wet weather. In some cases, new schools would replace LAUSD New School Construction Program Hydrology and Water Quality

10 existing uses and/or impervious ground coverage. Most, if not all, of the new schools would be constructed in areas that are already developed and already producing non-point-source pollutants. Mitigation Measure HWQ-1 The LAUSD shall ensure that the aggregate stormwater runoff from school construction projects built on sites of less than one acre does not create a condition of pollution, contamination, or nuisance as defined in California Water Code In order to implement this mitigation measure, the LAUSD, in consultation with the Los Angeles RWQCB, shall develop a Program-wide approach and SWPPP for all construction to be conducted under the Program, regardless of site size. Guidelines shall be developed under this Program-wide SWPPP for development of individual construction SWPPPs for individual sites. This mitigation measure would reduce the impact to less than significant if it achieves the following performance standard: All new school construction, including school ancillary facilities, regardless of size, is performed according to best management practices described in an SWPPP. Residual Impact. If Mitigation Measure HWQ-1 achieves the identified performance standards at specific sites, then site-specific impacts would be mitigated to insignificant. The LAUSD will conduct site-specific determinations of significance during the second-tier stage of review. Impact HWQ-2: Groundwater depletion is considered a significant impact if the Program depletes groundwater supplies or interferes substantially with groundwater recharge such that the production rate of pre-existing wells would be caused to drop to a level which would not support existing land uses or planned uses for which permits have been granted. Impact Determination Less than Significant. The Program is not growth-inducing, and therefore will not have an impact on groundwater levels. Water use by the LAUSD, including groundwater, is based on the number of students in the district. Students in the Program will be in the LAUSD regardless of the existence of the Program; therefore, there is no groundwater impact. Mitigation Measures: No mitigation is required. Impact HWQ-3: Alteration of drainage patterns is considered a significant impact if the Program alters drainage patterns in such a manner as to induce or worsen flooding, erosion or siltation on non-lausd property. Impact Determination Less than Significant. Drainage patterns within this area are well established, with most drainage channels owned and operated by Los Angeles County and local cities, resulting in low potential for drainage alteration in most areas. However, schools constructed in outlying areas could potentially alter LAUSD New School Construction Program Hydrology and Water Quality

11 drainage patterns. The LAUSD BMPs, Section 2.3.3, require collecting surface runoff in a storm water collection system designed for 25-year peak runoff rates. This BMP would partially avoid drainage impacts, particularly for on-site flows, but may not adequately address off-site flows. The Education Code, however, requires that school sites not be within a flood zone unless the cost of mitigating the flood or inundation impact is reasonable ( and ). Mitigation in flood hazard areas could include importing fill to elevate the site above the floodplain, or diversion of flows around the site, which could increase the flood hazard onto adjacent properties. This requirement would discourage locating schools in flood zones where drainage patterns could be disturbed. In addition, as noted above, California Government Code requires school districts to comply with city and county ordinances regulating drainage improvements and requiring review and approval of grading plans as they relate to design and construction of on-site improvements that affect drainage. LAUSD will comply with in implementing the Program. This compliance will ensure that school projects in individual cases will not have a significant adverse effect on the local drainage system. No significant adverse impacts have been identified as a result of this first-tier stage of review. The LAUSD will conduct site-specific determinations of significance during the second-tier stage of review. Mitigation Measure. No mitigation is required. Impact HWQ-4: Increased runoff volume is considered a significant impact if the Program results in runoff volume increases that cause the capacity of the existing drainage system to be exceeded. Impact Determination Less than Significant. The Program would involve the construction of buildings, parking lots, sidewalks, and other impervious surfaces that can increase runoff rates through impeding infiltration of rainfall and increasing overland flow velocities. Total impervious area for the new schools under the Program is estimated to be less than 750 acres (assumes 100 new schools, 15 acres or less each, 50 percent impervious). By comparison, the LAUSD school district covers 704 square miles. Total new Program-related impervious area is less than one fifth of one percent of the total area, resulting in a negligible potential for increased runoff volume. Moreover, since the LAUSD area is already heavily urbanized and largely built out, the existing environment already consists largely of impervious areas. Thus, school district construction should generally have little or no impacts. CHPS criteria for high performance schools (Section 2.3) include the following: Managing stormwater with systems to absorb and capture as much runoff as possible Minimizing impervious surface areas to reduce stormwater runoff Distributing runoff from impervious surfaces over large vegetated areas prior to reaching a stormwater conveyance system LAUSD New School Construction Program Hydrology and Water Quality

12 Installing a vegetated roof Using natural or constructed wetlands to provide on-site retention and treatment of stormwater Using rainwater-harvesting systems. While not necessarily mandatory for every school, the CHPS criteria are intended to avoid increasing water quantity and velocity where possible. Further, most schools would drain into a municipal drainage system rather than onto adjacent property. No significant impacts have been identified at this first-tier stage of review. LAUSD will identify and consider site-specific impacts during the second-tier stage of review. Mitigation Measure: No mitigation is required. Impact HWQ-5: Flooding impacts are considered significant if the Program exposes people or structures, including those within the proposed the LAUSD schools, to a risk of loss, injury or death within the 100-year floodplain, as a result of the failure of a levee or dam, or as a result of seiche, tsunami, or mudflow. Impact Determination Less than Significant with Mitigation. Schools constructed in flood-prone areas, including areas subject to coastal flooding, riverine overbank flooding, local flooding and dam inundation are subject to property damage and safety hazards. Building structures and contents, vehicles, playgrounds, ballfields, landscaping, and other improvements associated with the school could all be damaged from flooding. Damage could also occur through inundation or erosion. Flooding of schools and school access roads could present a safety hazard for students and staff at the school facility. The LAUSD site selection criteria (Section 2.3.3) discourage construction of schools in floodplain areas unless the flood hazard is mitigated. Floodplain identification is typically accomplished by reviewing FEMA and other flood maps maintained by local jurisdictions. The FEMA maps provide flood hazard information. The maps show the location of the 100-year floodplain, along with flood depth information and flood zone information. The flood zones, along with the depth information, are intended to depict varying levels of flood hazard and are used for floodplain management and flood insurance purposes. Each community has a separate set of maps. The maps can be obtained at the following website address: fema.gov. For the vast majority of the proposed schools, review of FEMA flood maps would be sufficient since the areas are urban and have been mapped. However, it is possible that a few schools, particularly in the outlying areas of the LAUSD, could be located in areas where the flood hazard is not mapped. In addition to riverine or overland flooding, new schools within 0.62 mile of the coast, and below 100 feet elevation in the Central and South LAUSD areas (specifically Pacific Palisades, Venice, Westchester and San Pedro areas) could be subject to tsunami hazard (see Figures 3.6- LAUSD New School Construction Program Hydrology and Water Quality

13 2 and 3.6-3) (NOAA, 2003). Tsunamis are rare events, but can be catastrophic when they occur. The National Oceanic and Atmospheric Administration (NOAA) operates a tsunami warning system and provides assistance for tsunami hazard mitigation. Mitigation generally involves tsunami hazard awareness, attention to tsunami warning signs, and moving to higher ground if it is suspected that a tsunami is approaching. Schools constructed in or near the mouth of steep canyons in the Los Angeles area could be subject to debris flows. Debris flows can form rapidly, convey boulders, and be very destructive and hazardous. Although most large canyons have debris collection structures at their mouths to prevent this type of damage downstream, some of the smaller canyons may lack such protection. Based on the location of the LAUSD school needs, it is unlikely that any new schools would be subject to this impact. Most (if not all) schools would be located in established urban areas far from the debris-producing areas in the mountains. However, it appears from the LAUSD needs map that some schools, particularly those north of the 210 Freeway in Local District B (Figures 2-1 and 2-2), could possibly be sited in areas subject to debris flows. Impacts from unmapped flooding, tsunami, and debris flow can be mitigated by taking these potential hazards into account in the school siting process, and ensuring that these hazards do not occur or can be mitigated to a less-than-significant level. Mitigation of these effects would be addressed, as applicable, in the site selection and design process for individual schools. Mitigation Measures HWQ-5.1 The siting analysis for new schools shall include evaluation of all possible flood hazards as determined by: (1) review of FEMA flood maps; (2) review of flood information provided by local city or county floodplain managers; (3) review of California Department of Water Resources dam safety information; and, (4) local drainage analysis by a civil engineer. The flood hazard determination shall include consideration of tsunamis and debris flow. Schools should be located outside of these hazard areas. HWQ-5.2 Where placing the school outside the floodplain is impractical, the school shall be protected from flooding by containment and control of 100-year flood flows, elevating lowest floors at least one foot above the expected 100-year flood level, or other methods acceptable to FEMA. HWQ-5.3 New schools and classrooms within 0.62 mile of the coast, and less than 100 feet above mean sea level, or otherwise within a tsunami hazard zone as delineated by NOAA, shall prepare and implement a tsunami awareness program and evacuation plan. HWQ-5.4 New schools and classrooms shall be located outside areas subject to potentially damaging debris flow. The Los Angeles County Department of Public Works, and/or local city officials, as appropriate, shall be consulted regarding the debris LAUSD New School Construction Program Hydrology and Water Quality

14 flow potential at proposed sites near the mouth of or in natural canyons and feasible mitigation measures shall be developed to reduce any potential risk. Residual Impact. No significant adverse impacts have been identified as a result of this firsttier stage of review. Mitigation Measure HWQ-5.1 will mitigate site-specific impacts to a level of insignificance. The LAUSD will conduct site-specific determinations of significance during the second-tier stage of review. LAUSD New School Construction Program Hydrology and Water Quality

15 Ventura Co. Los Angeles Co. Santa Clara River Watershed Ventura River Watershed Calleguas Creek Watershed County Boundary Regional Groundwater Basin Watershed Boundary LAUSD Boundary Santa Monica Bay WMA A C D B Los Angeles River Watershed G E I F H J San Gabriel River Watershed LAUSD New School Construction Figure LAUSD Boundary with Regional Watersheds Aspen Consulting Engineers A Division of Aspen Environmental Group K Dominguez Channel WMA Los Cerritos Channel and Alamitos Bay WMA LAUSD New School Construction Program Draft Program EIR Hydrology and Water Quality March 2004

16 Peace Valley Lockwood Valley Hungry Valley Ojai Eastern Santa Clara Upper Santa Clara Ventura Ventura Central Gillbrand Simi Valley B A San Fernando Valley C LAUSD New School Construction D Los Angeles Coastal Basin G E I F H J San Gabriel Valley Upper Santa Ana Figure LAUSD Boundary with Regional Groundwater Basins Aspen Consulting Engineers A Division of Aspen Environmental Group K LAUSD New School Construction Program Draft Program EIR Hydrology and Water Quality March 2004