Document Anaheim_doc_2f5d0ca92b

5. Environmental Analysis Anaheim General Plan/Zoning Code Update EIR City of Anaheim • Page 5-105 5.7 HYDROLOGY AND WATER QUALITY 5.7.1 Methodology Hydrology deals with the distribution and circulation of water, both on land and underground. Water quality deals with the quality of surface and groundwater. Surface water is water on the surface of the land and includes lakes, rivers, streams, and creeks. Groundwater is water below the surface of the earth. Implementation of projects as set forth in the General Plan and Zoning Code Update has the potential to affect water systems with respect to natural hydrology, and the use and quality of, or demand for, water resources. The character and quality of the natural water systems affect other major components of the environment. Water is managed within the City of Anaheim for a variety of purposes. It is managed for human use and consumption; as a potential hazard; as a source of recreation; as a resource supporting natural habitats; and as a receiver and conveyor of pollutants. This section discusses the existing characteristics, and the potential effects of the proposed project on groundwater and surface water. This section also discusses the importance of water as a fundamental component of the environment, beginning with physical characteristics of the hydrological water systems as they currently exist. 5.7.2 Environmental Setting Existing Conditions Related to Surface Waters Existing Watercourses The City of Anaheim lies within Region 8 (Santa Ana) of the California Regional Water Quality Control Board jurisdiction. Region 8 covers approximately 2,800 square miles and includes portions of Orange, San Bernardino, and Riverside Counties. The Santa Ana River is the main surface watercourse within the City of Anaheim. The Santa Ana River is the largest river within Region 8, at approximately 75 miles in length, and provides roughly 70% of the total groundwater recharge for the Santa Ana River basin. Water flow within the river is regulated by the Prado Dam, Seven Oaks Dam, and other flood-control facilities in the river and tributary area. The Santa Ana River is the also Orange County’s main river system. The portion of the system within the City of Anaheim includes the area from just west of Imperial Highway to Ball Road. The river’s unlined channel bottom along this stretch consists of permeable sandy material and is directly connected to previous alluvial materials that allow for the transfer of water into the underlying aquifers. Existing Drainage Facilities Drainage patterns within the City are varied and are mostly conveyed on street surfaces as well as local storm drainage facilities, which convey runoff to the regional facilities owned and maintained by the Orange County Flood Control District. The topography of the City is relatively flat, with the exception of the eastern area of the City and its Sphere-of-Influence (south of SR-91), which is comprised of hills and canyons. The existing storm drain system is illustrated in Figure 5.7-1, Existing Storm Drain System Map. ---PAGE BREAK--- 5. Environmental Analysis Page 5-106 • The Planning Center May 2004 The storm water facilities in the City are divided into three categories: • Regional Facilities: Santa Ana River and major channels • Intermediate Facilities: Lesser channels and detention facilities • City Facilities: Local storm drains and appurtenant facilities Regional facilities are owned and maintained by the Orange County Flood Control District (OCFCD). The largest facility, the Santa Ana River, is supplemented by the following major channels: • Carbon Creek Channel • Anaheim-Barber City Channel • East Garden Grove-Wintersburg Channel The following lesser channels (Intermediate Facilities) are also owned and maintained by the OCFCD: • Carbon Canyon Diversion Channel • Carbon Canyon Channel • Atwood Channel • Richfield Channel • Southeast Anaheim Channel • Esperanza Channel • Gypsum Creek Channel • Walnut Canyon Storm Drain • Deerfield Storm Channel • Chantilly Storm Channel • West Anaheim Storm Drain Historically, all local streets and arterial highways in Orange County, including Anaheim, functioned as drainage conveyances, in addition to their primary function of transportation. However, with the urbanization of the area, the need for drainage systems became more apparent and storm drain construction began in the late 1950s and early 1960s. ---PAGE BREAK--- ---PAGE BREAK--- 5. Environmental Analysis Page 5-108 • The Planning Center May 2004 This page intentionally left blank. ---PAGE BREAK--- 5. Environmental Analysis Anaheim General Plan/Zoning Code Update EIR City of Anaheim • Page 5-109 Drainage Standards and Criteria The following is a summary of existing storm design frequency requirements within the City based on the City’s Drainage Design Manual: • 100-year design storm shall be used for arterial highways in hillside areas and storm drains connecting to the Santa Ana River. • 25-year design storm shall be used for arterial highways in flatland areas, local streets in hillside areas, and all storm drains in sump conditions. • 10-year design storm shall be used for local streets in flatland areas, and onsite private drainage systems. The County of Orange’s minimum criteria for County channels is to provide at least a 20-year channel capacity, provided that buildings are protected from inundation for a 100-year storm event. Major regional drainage facilities such as the Santa Ana River are designed to provide protection against major loss of life and property for a 100-year event. It is the goal of the County of Orange and the Orange County Flood Control District (OCFCD) to provide 100-year flood protection for all buildings. To provide for this goal, OCFCD attempts to design facilities to convey 100-year flows where feasible. Several OCFCD’s facilities are a mixture of segments built at different times. Improvements of deficient OCFCD facilities are programmed in OCFCD’s Seven-Year Flood Control Projects Plan subject to annual review and revision based on Countywide prioritization. The County recommends that Cities condition developments located adjacent to flood control channels to participate in funding to implement improvements to OCFCD’s deficient flood control channels so that the needed protection for the proposed developments may be provided. With the exception of the South Central Anaheim area, which drains into the Anaheim-Barber City Channel, a 25-year storm design standard should be used for all other City-owned and maintained channels (and their tributary areas) within the City. Because the Anaheim/Barber City Channel can only convey the maximum flow of a 10-year storm, the facilities that are tributary to the channel are master planned to accommodate only a 10-year storm. Local Drainage Facilities In 1973, a Master Plan of Drainage was developed for the entire City. In this Master Plan, the City was divided into 44 distinct watershed areas, designated as Districts. Storm drain deficiencies and the needed drainage facilities were also identified. Since then, significant improvements to the system of drainage facilities have occurred. Due to changes in drainage patterns development conditions and hydrologic criteria in certain areas of the City since 1973, updated Area Master Plans of Drainage have been prepared and approved. These Area Master Plan Revisions, which revised the 1973 Master Plan for selected areas of the City are: District 27, South Central Area and Northeast Industrial Area. The discussion of drainage conditions has been organized according to seven geographic areas of the City. The areas and the encompassing Drainage Districts from the City’s Master Plan of Drainage are illustrated in Table 5.7-1. The location of each of the districts can be found on Figure 5.7-1, Existing Storm Drain System Map, found earlier in this chapter. ---PAGE BREAK--- 5. Environmental Analysis Page 5-110 • The Planning Center May 2004 TABLE 5.7-1 DRAINAGE DISTRICTS Geographic Area Drainage Districts West Anaheim Districts 1 through 14 North Central Anaheim Districts 15 through 17 and 28 South Central Anaheim Districts 18 through 26 Northeast Industrial Districts 29 through 35 The Platinum Triangle District 27 Hill and Canyon Area Districts 36 through 43 East Anaheim Undeveloped Hills and Canyons District 43 and Districts 98 and 99 (Gypsum and Coal Canyons) Source: PSOMAS City of Anaheim General Plan Update Drainage Report: Baseline Conditions, Opportunities and Constraints (December 2001). Condition of Existing Drainage Facilities Statistical techniques, through a process called frequency analysis, are used to estimate the probability of the occurrence of a given precipitation event. The recurrence interval is based on the probability that the given event will be equaled or exceeded in any given year. For example, a 100-year storm event has a 1% chance that it will be equaled or exceeded in any given year, or a 100% chance that it will occur within 100 years. Therefore, a 100-year storm event will have a larger peak flow than a 10-year storm event or a 25-year storm event. The estimated storm runoff for 10-, 25-, and 100-year storms were computed for the 12 districts within the City, for which post-1986 studies or master plans (listed in Appendix N) were not available. Results from the hydrologic analysis are summarized in Table 5.7-2. TABLE 5.7-2 SUMMARY OF HYDROLOGIC RESULTS (PEAK FLOWS) District Tributary Area (acres) Q-10 (cfs 1) Q-25 (cfs) Q-100 (cfs) 5 371 300 380 503 9 319 212 278 379 14 622 587 707 944 28 956 770 986 1,340 36 448 332 709 333 875 422 1,150 568 37 307 371 286 551 660 563 678 813 691 893 1,072 908 38 683 1,146 1,415 1,871 39 1,639 2,233 2,791 3,683 40 536 184 802 346 991 425 1,300 558 41 940 1,519 1,876 2,478 43 1,326 143 311 2,379 328 614 2,896 400 759 3,780 525 1,001 Source: PSOMAS City of Anaheim General Plan Update Drainage Report: Baseline Conditions, Opportunities and Constraints (December 2001). 1 cfs = cubic feet per second. Existing storm drain system capacities within the City (for all areas except for the area tributary to the Anaheim-Barber City Channel) were evaluated relative to 25-year flows. Drainage areas tributary to the Anaheim-Barber City Channel were evaluated relative to 10-year flows. Table 5.7-3 presents a summary of local (City) facility baseline drainage conditions. Figure 5.7-2, Existing Storm Drain Conditions Map, provides an overview of the condition of existing City-owned and maintained drainage systems within the City. ---PAGE BREAK--- ---PAGE BREAK--- 5. Environmental Analysis Page 5-112 • The Planning Center May 2004 This page intentionally left blank. ---PAGE BREAK--- 5. Environmental Analysis Anaheim General Plan/Zoning Code Update EIR City of Anaheim • Page 5-113 TABLE 5.7-3 LOCAL FACILITY BASELINE CONDITIONS SUMMARY Geographic Area Conditions Summary West Anaheim (Districts 1-14) The majority of the storm drain system within each of the Districts in this area appears to be inadequate. North Central Anaheim (Districts 15-17 and 28) Most of the systems appear to be adequate except for small segments in the westerly portion of Districts 16 and 17. South Central Anaheim (Districts 18-26) The majority of the main collector facilities in the north and central portions of the area appear to be inadequate. The remaining areas appear to have generally adequate drainage systems, except for limited segments. Northeast Industrial (Districts 29-35) The majority of the systems in this area appear to be inadequate. The Platinum Triangle (District 27) Most of the storm drains in this District appear to be inadequate. Anaheim Hills/Santa Ana Canyon (Districts 36-43) The majority of the systems appear to be adequate. Districts 37, 41, 42, and 43 appear to be in the best condition. East Anaheim Undeveloped Hills and Canyons (Gypsum and Coal Canyons) This area is mostly undeveloped and consequently there are no existing drainage improvements in the area. Caltrans does have a box culvert located near Gypsum Canyon and the SR-91 Freeway. Source: PSOMAS City of Anaheim General Plan Update Drainage Report: Baseline Conditions, Opportunities and Constraints (December 2001). Flood Hazards As part of the National Flood Insurance Program, floodplain studies have been performed for various communities in Orange County including the City of Anaheim. In order to provide a national standard without regional discrimination, the 100-year flood has been adopted by the Federal Insurance Administration as the base flood for purposes of floodplain management measures. The 500-year flood is employed to indicate additional areas of flood risk in the community. The results of these studies are presented in the floodplain boundary maps and Flood Insurance Rate Maps (FIRMs). These maps contain official delineation of flood insurance zones and base flood elevation lines. Regional Drainage in the City initiates from natural and undeveloped mountains to the north and northeast. If uncontrolled, this drainage could cause severe flooding throughout the City. The Federal Emergency Management Agency (FEMA) prepares Flood Insurance Rate Maps (FIRMs) that show the extent of Special Flood Hazard Areas (SFHAs) and other thematic features related to flood risk assessment. Flood areas are illustrated in Figure 5.7-3, Flood Hazard Areas. SFHAs are areas at or below a flood elevation that have a 1% or greater probability of being equaled or exceeded during any given year (this is also known as a 100-year flood event). This flood, which is referred to as the base flood, is the national standard on which the floodplain management and insurance requirements of the National Flood Insurance Program (NFIP) are based. The flood hazard zones within the City of Anaheim include Zone A, Zone X 500 (shaded) and Zone X (un- shaded). The following is a brief overview of constraints in each zone: • Zone A: Special flood hazard areas inundated by the 100-year flood, where no base flood elevations have been determined. Mandatory flood insurance purchase requirements apply. • Zone X 500 (shaded): Areas of 500-year flood; areas of 100-year flood with average depths less than one foot or with drainage areas less than one square mile; and areas protected by levees from a 100-year flood. • Zone X (un-shaded): Areas determined to be outside the 500-year floodplain. ---PAGE BREAK--- 5. Environmental Analysis Page 5-114 • The Planning Center May 2004 This page intentionally left blank ---PAGE BREAK--- ---PAGE BREAK--- 5. Environmental Analysis Page 5-116 • The Planning Center May 2004 This page intentionally left blank. ---PAGE BREAK--- 5. Environmental Analysis Anaheim General Plan/Zoning Code Update EIR City of Anaheim • Page 5-117 Existing Conditions Related to Groundwater Groundwater is water that is found below the ground surface in water bearing formations called aquifers. An aquifer is a geologic formation that is sufficiently permeable to conduct groundwater, and to yield significant quantities of water to wells and springs. Perched groundwater is a body of water located above a permanent groundwater zone and separated from it by a soil or bedrock zone of low permeability. Groundwater basins are areas with highly permeable soils that allow for the replenishment of the aquifers. These basins are usually located along streambeds and in alluvial fans where permeable soils are generally found. The quantity of groundwater found in an aquifer is dependent upon the specific geologic and hydrologic conditions in an area. Most of the readily extractable groundwater is obtained from aquifers consisting of recent alluvium, with smaller quantities of groundwater found in jointed bedrock and residuum. In Orange County, groundwater conditions are influenced by natural conditions such as rainfall, outflow from underground reservoirs to the ocean and other basins, and stream flow. Artificial conditions including water extraction through wells, and the infusion of imported or treated water to replenish groundwater supplies also influence the basin’s groundwater. The elevation of groundwater varies with the amount of pumping and the amount of recharge. Groundwater basins may be recharged naturally through filtrating precipitation, or artificially with imported or reclaimed water. Because groundwater moves through the earth slowly, in most cases a meter or two per year, polluted water is given an opportunity to filter and purify before being used. Artificial recharge with imported water is practiced as a means of offsetting declining groundwater levels and providing storage for use in times of drought. The Orange County groundwater basin underlies the northern half of Orange County, covering approximately 310 square miles, bordered by the Coyote and Chino Hills to the north, the Santa Ana Mountains to the northeast, the Pacific Ocean to the southwest, and terminating near the Orange County line to the northwest, where it connects to the Central Basin of Los Angeles. Based on well data from the Orange County Water District (OCWD), groundwater levels in the Anaheim area generally range from approximately 20 feet below mean sea level (MSL) at the western limits to approximately 300 feet above MSL along the eastern limits in the Santa Ana River channel area (OCWD, 2000). Groundwater in the hillside areas of Anaheim is generally present in the sedimentary formations, which typically have low permeability and do not produce sufficient flow for groundwater production wells. Accordingly, little data regarding the occurrence of groundwater in the hillside areas are available. The depths of groundwater may vary significantly by locality. The California Department of Water Resources divides the Orange County groundwater basin into two primary hydrologic divisions, the Forebay and Pressure areas. The City of Anaheim spans both divisions. The boundary of these two areas generally delineates the areas where surface water or shallow groundwater can or cannot move downward in significant quantities to the first producible aquifer. This boundary represents a transition zone where low-permeability clay and silt deposits increasingly occur in near-surface sediments southwest of the boundary of these two areas. The Forebay refers to the area of intake or recharge where the majority of recharge to the basin occurs primarily by direct percolation of Santa Ana River water. The Forebay Area, which encompasses much of the cities of Garden Grove (eastern side), Santa Ana, Orange, and Tustin, is characterized by highly permeable sands and gravels with relatively few and discontinuous clay and silt deposits. ---PAGE BREAK--- 5. Environmental Analysis Page 5-118 • The Planning Center May 2004 The Pressure Area is defined as the area in the basin where surface water and near-surface groundwater are prevented from percolating in large quantities into the major producible aquifers by clay and silt layers at shallow depths (upper 50 feet). Most of the central and coastal portions of the basin fall within the Pressure Area, including the cities of Garden Grove (western half), Westminster, Seal Beach, and Los Alamitos. Because the principal and deeper aquifers within the Pressure Area are under “confined” conditions, the water levels in wells penetrating these aquifers exhibit large seasonal variations in response to pumping. The Santa Ana River serves as OCWD’s main source for groundwater recharge. Beneficial uses for the Lower Santa Ana River Basin groundwater sub-basins include municipal and domestic supply, agricultural supply, industrial service supply, and industrial process supply. The OCWD currently services over two million people, with an expected increase of over half a million by 2020. Water demand is anticipated to rise from approximately 515,000 acre-feet per year to approximately 686,000 acre-feet per year in that same time frame (OCWD, Engineer’s Report, 1998). Currently, OCWD is focusing on reducing their customers’ reliance on imported water by improving the quality and availability of the groundwater in Orange County. To increase local supplies, OCWD is working to increase the capacity of its existing recharge facilities, as well as develop more areas where water can be percolated into the underground aquifers. Water Quality Regulations Federal and State Programs. Federal Clean Water Act In 1972, the Federal Water Pollution Control Act, later referred to as the Clean Water Act (CWA), was amended to require that the discharge of pollutants to waters of the United States from any point source be effectively prohibited, unless the discharge is in compliance with a National Pollutant Discharge Elimination System (NPDES) permit. In 1987, the CWA was again amended to require that the EPA establish regulations for permitting of storm water discharges (as a point source) by municipal and industrial facilities and construction activities under the NPDES permit program. The EPA published final regulations regarding storm water discharges on November 16, 1990. The regulations require that municipal separate storm sewer system (MS4) discharges to surface waters be regulated by a NPDES permit. In addition, the CWA requires the States to adopt water quality standards for water bodies and have those standards approved by the EPA. Water quality standards consist of designated beneficial uses for a particular water body (e.g. wildlife habitat, agricultural supply, fishing etc.), along with water quality criteria necessary to support those uses. Water quality criteria are set concentrations or levels of constituents – such as lead, suspended sediment, and fecal coliform bacteria – or narrative statements which represent the quality of water that support a particular use. In 2000, EPA established numeric water quality criteria for toxic constituents in waters with human health or aquatic life designated uses in the form of the California Toxics Rule (“CTR”) (40 CFR 131.38). When designated beneficial uses of a particular water body are being compromised by water quality, Section 303(d) of the Clean Water Act requires identifying and listing that water body as “impaired”. Once a water body has been deemed impaired, a Total Maximum Daily Load (“TMDL”) must be developed for each water quality constituent causing the impairment. A TMDL is an estimate of the total load of pollutants, from point, non-point, and natural sources, that a water body may receive without ---PAGE BREAK--- 5. Environmental Analysis Anaheim General Plan/Zoning Code Update EIR City of Anaheim • Page 5-119 exceeding applicable water quality standards (with a “factor of safety” included). Once established, the TMDL is allocated among current and future dischargers into the water body. The primary receiving waters within the City of Anaheim are dry much of the year. None of the receiving waters within the City are listed as impaired under Section 303(d) of the Clean Water Act and no apply.] Basin Plan In the State of California, the State Water Resources Control Board and nine Regional Water Quality Control Boards are responsible for implementing the CWA and the state Porter-Cologne Water Quality Control Act. Under the CWA and Porter Cologne, the Region 8 Santa Ana Regional Water Quality Control Board adopted the Water Quality Control Plan for the Santa Ana River Basin (Santa Ana Basin Plan) 1995). The Santa Ana Basin Plan provides quantitative and narrative criteria for a range of water quality constituents in receiving waters. Specific criteria are provided for certain designated water bodies within the region and general narrative and numeric water quality objectives are provided for ocean waters, bays and estuaries, inland surface waters, and groundwaters. In general, the narrative criteria require that degradation of water quality does not occur due to increases in pollutant loads that will impact the designated beneficial uses of a water body. Table 5.7-4 lists the beneficial uses designated for certain receiving waters within the City of Anaheim. For example, the Santa Ana Basin Plan requires that “Inland surface waters shall not contain suspended or settleable solids in amounts which cause a nuisance or adversely affect beneficial uses as a result of controllable water quality factors.” TABLE 5.7-4 BENEFICIAL USES OF RECEIVING WATERS Beneficial Uses Water Body MUN AGR GWR REC 1 REC 2 WARM WILD RARE Santa Ana River Reach 2 E P P P P P P P Santa Ana River Reach 1 E P1 P I I Carbon Creek Canyon E P P P P P P P – Present or potential beneficial use E – Excepted from MUN designation 1 – Access prohibited in all or part by OCEMA I – Intermittent Beneficial Use 1 Access prohibited in all or part by OCEMA. California Toxics Rule The California Toxics Rule (CTR) is a federal regulation issued by the federal EPA providing water quality criteria for potentially toxic constituents in receiving waters with human health or aquatic life designated uses in the State of California. CTR criteria are applicable to the receiving water body and therefore must be calculated based upon the probable hardness values of the receiving waters for evaluation of acute (and chronic) toxicity criteria. At higher hardness values for the receiving water, copper, lead, and zinc are more likely to be complexed (bound with) components in the water column. This in turn reduces the bioavailability and resulting potential toxicity of these metals. The Basin Plan objectives and the CTR criteria do not apply directly to discharges of urban runoff, but rather to specified receiving waters described above. ---PAGE BREAK--- 5. Environmental Analysis Page 5-120 • The Planning Center May 2004 NPDES Permits: The MS4 NPDES Permit The Santa Ana Regional Water Quality Control Board issued the third term permit (Order No. R8-2002-0010) governing the public storm drain system discharges in northern Orange County from the storm drain systems owned and operated by the northern Orange County cities and Orange County (collectively “the Co-permittees”) in January 2002. This permit regulates storm water and urban runoff discharges from development to constructed and natural storm drain systems in the City of Anaheim. Among other requirements, the NPDES permit specifies requirements for managing runoff water quality from new development and significant redevelopment projects, including specific sizing criteria for treatment Best Management Practices (BMPs). This particular program is discussed below, with others required by the MS4 NPDES Permits following below. New Development Significant Redevelopment Program To implement the requirements of the NPDES permit, the Co-permittees have developed a 2003 Drainage Area Management Plan (DAMP) that includes a New Development and Significant Redevelopment Program 2003). This New Development and Significant Redevelopment Program provides a framework and a process for following the NPDES permit requirements and incorporates watershed protection/storm water quality management principles into the Co-permittees’ General Plan process, environmental review process, and development permit approval process. The New Development and Significant Redevelopment Program includes a Model Water Quality Management Plan (WQMP) that defines requirements and provides guidance for compliance with the NPDES permit requirements for project specific planning, selection, and incorporation of BMPs in new development or significant redevelopment projects. Local jurisdictions, including the City of Anaheim, have adopted a Local Implementation Plan (LIP) based upon the County’s DAMP which includes the model WQMP. Using the local LIP as a guide, the City approves project-specific as part of the development plan and entitlement approval process for discretionary projects, prior to issuing permits for ministerial projects. The requirements of the Model WQMP are located in Section 7.6 and Exhibit 7.II of the DAMP. Consistent with the LIP and the Model WQMP, all priority new development and significant redevelopment projects are required to develop and implement a Project WQMP that addresses: • Regional or watershed programs (if applicable) • Routine structural and non-structural Source Control BMPs • Site Design BMPs (as appropriate) • Treatment Control BMPs (Treatment Control BMP requirements may be met through either project specific (on-site) controls or regional or watershed management controls that provide equivalent or better treatment performance • The mechanism(s) by which long-term operation and maintenance of all structural BMPs will be provided Illegal Discharge Illicit Connection Elimination Program As part of the New Development/ Significant Redevelopment Program and as a stand alone program, the Illegal Discharge Illicit Connection (IDIC) Program was developed to provide the legal authority and the ---PAGE BREAK--- 5. Environmental Analysis Anaheim General Plan/Zoning Code Update EIR City of Anaheim • Page 5-121 framework to enforce against violations of local Surface Water Quality Regulations. This program has evolved over time and from a broad standpoint can be considered to involve Chapters 10, 9 and 4 of the DAMP and LIP. These chapters guide the efforts of Co-permittees and the City of Anaheim, respectively, in preventing the discharge of pollutants to the storm drain system – and subsequently the waters of the state – and ensures proper and adequate enforcement actions are implemented to prevent future occurrences. Public Education Program Closely related to the IDIC Program, the Public Education Program (chapter 6 of the DAMP and LIP) as its name suggests, is focused on assessing the demographics, mindset and potentially activities of the population of Orange County and, based on this information, providing information and guidance to both change these behaviors and provide guidance to do so. As in most enforcement programs, the educational step is considered a crucial preliminary stage in a successful enforcement program. Municipal Activities Program In order to ensure that City activities do not pose a threat to surface water quality and to remediate those, which do or have caused a violation, the Municipal Activities Program (Chapter 5 of the DAMP and LIP) has been developed. This program includes the development of an inventory of all municipal fixed facilities (buildings and grounds) and field activities (landscape maintenance, roadway work, etc.) followed by the implementation of an inspection and internal enforcement program based on these inspections. Definition: “Maximum Extent Practicable” (MEP) is a technology-based standard established by Congress in CWA Section 402(p)(3)(B)(iii) that applies to MS4s and the Co-permittees. According to the definition in the Orange County MS4 Permit, MEP means to the maximum extent feasible, taking into account considerations of synergistic, additive, and competing factors, including but not limited to, gravity of problem, technical feasibility, fiscal feasibility, public health risks, societal concerns, and social benefits.” By its compliance with the MS4 NPDES Permit, DAMP requirements for site design, source control, and treatment control BMPs satisfy the MEP standard as per the MS4 NPDES Permit. NPDES Permits: General Construction Permit Pursuant to the CWA Section 402(p), requiring regulations for permitting of storm water discharges, the State Water Resources Control Board has issued a statewide general NPDES Permit for storm water discharges from construction sites (NPDES No. CAS000002). California Water Resources Control Board Resolution No. 2001-046, Modification of Water Quality Order 99-08-DWQ State Water Resources Control Board National Pollutant Discharge Elimination System (NPDES) General Permit for Storm Water Discharges Associated with Construction Activity, was adopted by the on 26 April 2001. Under this General Construction Activity permit, discharges of storm water from construction sites with a disturbed area of one or more acres are required to either obtain individual NPDES permits for storm water discharges or to be covered by the General Permit. Coverage by the General Permit is accomplished by completing and filing a Notice of Intent with the and developing and implementing a Storm Water Pollution Prevention Plan. Each applicant under the General Construction Activity Permit must ensure that a Storm Water Pollution Prevention Plan is prepared prior to grading and is implemented during construction. The primary objective of the is to identify, construct, implement in accordance with a time schedule, ---PAGE BREAK--- 5. Environmental Analysis Page 5-122 • The Planning Center May 2004 and maintain BMPs to reduce or eliminate pollutants in storm water discharges and authorized non- storm water discharges from the construction site during the construction phase. The should contain a site map which shows the construction site perimeter, existing and proposed buildings, lots, roadways, storm water collection and discharge points, general topography both before and after construction, and drainage patterns across the project. The must list BMPs the construction site will implement to protect storm water runoff and the placement of those BMPs. Additionally, the must contain a visual monitoring program; a chemical monitoring program for "non-visible" pollutants to be implemented if there is a failure of BMPs; and a monitoring plan if the site discharges directly to a water body listed on the 303(d) list. The City of Anaheim grading ordinance requires that all construction projects of one acre or more must file an NOI and prepare a NPDES Permits: General Industrial Permit Similar to the General Construction Permit, the General Industrial Permit requires the submittal of a Notice of Intent (for industrial activities) and development and implementation of a However, the difference is that this permit applies to the operation of certain industrial sites. The similar to that for Construction Activities, identifies BMPs which are to be put in place to prevent pollution generating activities and to reduce or eliminate the exposure of materials to wind, rain or other means of transport offsite. Additionally, the requires inspection and sampling to be performed as well as proper tracking of paperwork relative to this and related pollution prevention activated (i.e. staff training, material management/disposal, etc.). Sewer Waste Discharge Requirements for Orange County In 2001 the Orange County Grand Jury conducted an investigation into the contamination of the County’s surface waters, particularly the beaches. This investigation was, in part, in response to a significant number of beach closures in 1999 at and near Huntington Beach (which is between the outfall of the San Gabriel and Santa Ana Rivers). Among the findings were that Sanitary Sewer Overflows (SSOs) were likely a major contributor to this contamination. Additionally, the findings pointed to “Fats Oils & Grease” as a primary cause of the sanitary sewer line obstructions which result in these SSOs. In response to this investigation and pressure from the State, the Santa Ana Regional Water Quality Control Board issued a permit (Order No. R8-2002-0014), in April 2002, governing capacity, management, operation and maintenance of the publicly owned sanitary sewer collection system in northern Orange County. This permit is commonly referred to as the Sewer WDR and was generally based on pending Federal Regulations called CMOM (Capacity Management, Operations & Maintenance) for Sanitary Sewer Collection Systems. All Collection Agencies (Municipalities and Districts which own and/or operate publicly funded sanitary sewers) in North Orange County are individual Permittees under the Sewer WDR and are currently in the middle of a five year schedule of program of development and implementation. Similar to the MS4 NPDES Permit, the programs required by this Order include, establishing legal authority, implementing education and enforcement programs, and developing or refining municipal maintenance programs and emergency response. In addition, however, the Sewer WDR requires that sanitary sewer system capacity be ensured for reasonable anticipated flows, in order to ensure an capacity is not exceeded resulting in sewer spills. 5.7.3 Thresholds of Significance The criteria used to determine the significance of impacts on hydrology and water quality are taken from City-approved Thresholds of Significance based on the City's Initial Study and the model Initial Study ---PAGE BREAK--- 5. Environmental Analysis Anaheim General Plan/Zoning Code Update EIR City of Anaheim • Page 5-123 checklist in Appendix G of the State CEQA Guidelines. The project would result in a significant impact to hydrology or water quality if it would: • Violate any water quality standards or waste discharge requirements; • 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 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 a substantial erosion or siltation on- or off-site; • Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, or substantially increase the rate or amount of surface runoff in a manner which would result in flooding on- or off-site; • Create or contribute runoff water which would exceed the capacity of existing or planned storm water drainage systems or provide substantial additional sources of polluted runoff? • Otherwise substantially degrade water quality; • Place housing within a 100-year flood hazard area as mapped on a federal Flood Hazard Boundary or Flood Insurance Rate Map or other flood hazard delineation map; • 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; 5.7.4 Analysis of Environmental Impacts IMPACT: WOULD THE PROJECT VIOLATE ANY WATER QUALITY STANDARDS OR WASTE DISCHARGE REQUIREMENTS Impact Analysis: Both point sources, such as direct drainage sources, and nonpoint sources of water pollution, such as urban runoff, are usually discharged via separate storm drains to “waters of the United States” and are therefore regulated under the Federal Clean Water Act (CWA). The City of Anaheim must therefore comply with Federal water quality, waste discharge, and total maximum daily load standards defined in the CWA. In addition, any projects or construction activities performed within a Caltrans right-of-way must obtain an Encroachment Permit from Caltrans. Implementation of the General Plan and Zoning Code Update would potentially impact the quantity of runoff and other pollutant loadings to receiving waters. Impacts may be significantly greater during the region’s rainy season, which is generally defined as October through May. Policies included in the General Plan and Zoning Code Update would ensure compliance with Federal standards by ensuring adequate storm drainage, and maintaining adequate water and waste distribution capacity. Relevant Goals and Policies Proposed General Plan policies related to reducing polluted runoff and the maintenance of the drainage and sewer system include: • Ensure compliance with the Federal Clean Water Act requirements for National Pollutant Discharge Elimination System (NPDES) permits, including developing and requiring the development of Water Quality Management Plans for all new development and significant redevelopment in the City. (Green Element, Goal 78.1, Policy 1) • Continue to implement an urban runoff reduction program consistent with regional and federal requirements, which includes requiring and encouraging the implementation of the following design features: ---PAGE BREAK--- 5. Environmental Analysis Page 5-124 • The Planning Center May 2004 − Increase permeable areas and install filtration controls (including grass lined swales and gravel beds) and divert flow to these permeable areas to allow more percolation of runoff into the ground; − Use natural drainage, detention ponds, or infiltration pits to collect runoff; and, Divert and catch runoff using swales, berms, green strip filters, gravel beds and french drains; Install rain gutters and orient them towards permeable surfaces; Construct property grades to divert flow to permeable areas; Use subsurface areas for storm runoff either for reuse or to enable release of runoff at predetermined times or rates to minimize peak discharge into storm drains; Use porous materials, wherever possible, for construction of driveways, walkways, and parking lots; and − Divert runoff away Prevent rainfall from entering material and waste storage areas and pollution-laden surfaces. (Green Element, Goal 78.1, Policy 2) • Require new development and significant redevelopment to utilize site preparation, grading, and foundation designs best management practices that provide erosion and sediment control to prevent construction-related contaminants from leaving the site and polluting waterways. (Green Element, Goal 78.1, Policy 4) • Require new construction to include post-construction control measures in site designs to preventRegulate construction practices, including grading, dust suppression, chemical management, and encourage pre-determined construction routes that minimize dust and particulate matter pollution. (Green Element, Goal 8.1, Policy 25) • Coordinate with appropriate Federal, State, and local resource agencies on development projects and construction activities affecting waterways and drainages. (Green Element, Goal 78.1, Policy 57) • Each project/development willEnsure that appropriate sewer system mitigation measures are identified and implemented in conjunction with new development based on the recommendations of prior sewer studies and/or future sewer studies that may be required to conduct a sanitary sewer study to be reviewed and approved by the City Engineer and mitigate its impacts if the study indicates that the project/ development will increase sewer flows programmed in the appropriate master plan sewer study for the area or if the project currently discharges to an existing deficient sewer system. (Public Services and Facilities Element, Goal 5.1, Policy 1) • Minimize the amount of impervious surfaces in conjunction with new development. (Public Services and Facilities Element, Goal 6.1, Policy 3) • Minimize the disturbance of natural water bodies and natural drainage systems, where feasible, resulting from development including roads, highways, and bridges. (Public Services and Facilities Element, Goal 6.1, Policy 4) • Encourage new development to maintain and enhance existing natural streams, as feasible. (Safety Element, Goal 3.1, Policy 3) Existing Codes and Regulations • Projects encompassing an area in excess of 1 acre shall submit for approval to the State Water Resources Control Board, a Notice of Intent to be covered under the Storm Water Permit, in compliance with the National Pollutant Discharge Elimination System (NPDES) program. In addition, future projects shall be required to develop and implement a Storm Water Pollution Prevention Plan which incorporates Best Management Practices (BMPs). • Prior to the issuance of grading permits, project property owner/developers shall submit, and the Public Works Director shall have approved, a Water Quality Management Plan (WQMP) consistent with the requirements of the Orange County Stormwater Program Drainage Area Master Plan ---PAGE BREAK--- 5. Environmental Analysis Anaheim General Plan/Zoning Code Update EIR City of Anaheim • Page 5-125 (DAMP). The WQMP shall identify the Best Management Practices (BMPs) that will be used on site to control predictable pollutant runoff. Level of Significance Before Mitigation: Less than significant. Mitigation Measures: No mitigation measures are necessary. Level of Significance After Mitigation: No significant adverse impacts were identified and no mitigation measures are necessary. IMPACT: 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 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) Impact Analysis: The City receives up to three-fourths of its drinking water from local groundwater, therefore it is critical to protect the Orange County Groundwater Basin. This groundwater basin underlies the northern half of Orange County, covering approximately 310 square miles, and has a recharge area which extends north and east of SR-57/SR-91 interchange, to the SR-91 Freeway and Imperial Highway interchange. The recharge area is so large that it represents two-thirds of the total groundwater recharge in Orange County. Implementation of the General Plan and Zoning Code Update would not potentially increase the demand on groundwater supplies. In order to protect the City’s groundwater and the Orange County Groundwater Basin, the General Plan and Zoning Code Update contains policies directing the City to reduce pollution, enforce water quality management regulations, and conserve water. Relevant Goals and Policies Proposed General Plan policies related to the protection of groundwater resources include: • Develop and disseminate educational materials that describe the importance of protecting groundwater and management techniques for the proper storage and disposal of materials and waste. (Green Element, Goal 67.1, Policy 1) • Include groundwater protection educational outreach efforts with Anaheim Fire Department hazardous materials and waste inspections. (Green Element, Goal 67.1, Policy 2) • Continue to coordinate groundwater protection efforts with the Orange County Water District, neighboring cities and other relevant agencies. (Green Element Goal 67.1, Policy 3) Existing Codes and Regulations • Future projects shall comply with all applicable local, State, and federal regulations relating hydrology and water quality. Level of Significance Before Mitigation: Less than significant. Mitigation Measures: No mitigation measures are necessary. Level of Significance After Mitigation: No significant adverse impacts were identified and no mitigation measures are necessary. ---PAGE BREAK--- 5. Environmental Analysis Page 5-126 • The Planning Center May 2004 IMPACT: WOULD THE PROJECT 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 A SUBSTANTIAL EROSION OR SILTATION ON- OR OFF-SITE OR SUBSTANTIALLY INCREASE THE RATE OR AMOUNT OF SURFACE RUNOFF IN A MANNER WHICH WOULD RESULT IN FLOODING ON- OR OFF-SITE Impact Analysis: Drainage runoff from parcels is dependent on the percent impervious factor assigned to the particular parcel. Increased development throughout Anaheim and its Sphere-of-Influence, especially on currently undeveloped properties, will increase the amount of impervious surfaces, thereby increasing the amount and speed of runoff. Increased runoff volumes and speeds may create nuisance flooding in areas without adequate drainage facilities. The majority of the City is built out and therefore runoff volumes are not expected to increase significantly. The proposed General Plan and Zoning Code Update will create a mixed-use land use designation within The Platinum Triangle, The Colony, and Downtown Area which will allow existing commercial and industrial areas to redevelop with mixed-use projects, including residential uses. Since residential uses often involve a greater amount of landscaping and provide more open area, project implementation may result in a greater amount of acreage available for groundwater recharge. With a decrease in impervious surfaces, runoff volumes will also decrease. However, as shown on previous Figure 5.7-2, a number of drainage facilities within the City are currently deficient. Current deficiencies will be mitigated through implementation of applicable General Plan Goals and Policies and the mitigation measures listed below. The eastern portion of the Hill and Canyon Area is currently undeveloped and will require new drainage facilities as part of development. The specific types and locations of drainage facilities will be determined at the time development applications are submitted. The policies and goals contained in the General Plan direct the City to increase permeable areas, use natural drainage facilities, and employ site preparation and gradation techniques that control erosion, prevent sedimentation and contamination of waterways, and minimize flood risks, thus serving to mitigate any potential impacts to existing drainage facilities. Relevant Goals and Policies Proposed General Plan policies related to the maintenance of the drainage system include: • Cooperate with surrounding jurisdictions and the County of Orange to provide adequate storm drainage facilities. (Green Element, Goal 78.1, Policy 3) • Improve the City’s storm drain system to address current deficiencies as well as long-term needs associated with future development to minimize flood damage and adequately convey rainfall and subsequent runoff from a 25-year frequency storm. (Public Services and Facilities Element, Goal 6.1, Policy 1) • Minimize the amount of impervious surfaces in conjunction with new development. (Public Services and Facilities Element, Goal 6.1, Policy 3) Existing Codes and Regulations • Future projects shall comply with all applicable local, State, and federal regulations relating hydrology and water quality. Level of Significance Before Mitigation: Potentially significant impact. ---PAGE BREAK--- 5. Environmental Analysis Anaheim General Plan/Zoning Code Update EIR City of Anaheim • Page 5-127 Mitigation Measures: 5.7-1 The City shall work with the Orange County Flood Control District (OCFCD) to ensure that flood control facilities are well maintained and capable of accommodating, at a minimum, future 25-year storm flows for City-owned and maintained facilities, and 100-year storm flows for County facilities. Where improvements to local drainage facilities have the potential to increase discharges to County facilities, the City shall analyze potential impacts to County facilities in consultation with the Manager, County of Orange Flood Control Division. Encroachment Permits shall be obtained from the County’s Public Property Permits Section for any activity performed within OCFCD’s right of way. 5.7-2 The City shall require that new developments minimize stormwater and urban runoff into drainage facilities by incorporating design features such as detention basins, on-site water features, and other strategies. Level of Significance After Mitigation: Less than significant. IMPACT: WOULD THE PROJECT CREATE OR CONTRIBUTE RUNOFF WATER WHICH WOULD EXCEED THE CAPACITY OF EXISTING OR PLANNED STORM WATER DRAINAGE SYSTEMS OR PROVIDE SUBSTANTIAL ADDITIONAL SOURCES OF POLLUTED RUNOFF Impact Analysis: As described above, the majority of the City is built out and therefore runoff volumes are not expected to increase significantly. The proposed General Plan and Zoning Code Update will create a mixed-use designation within The Platinum Triangle, The Colony, and Downtown Area which will provide for existing commercial and industrial areas to redevelop with residential uses. Since residential uses often involve a greater amount of landscaping and provide more open area, project implementation may result in a greater amount of acreage available for groundwater recharge. With a decrease in impervious surfaces, runoff volumes will also decrease. However, as shown on previous Figure 5.7-2, a number of drainage facilities within the City are currently deficient. Current deficiencies will be mitigated through implementation of applicable General Plan Goals and Policies and the mitigation measures listed above. Pollution associated with storm water and urban runoff affects the groundwater of Anaheim, as well as neighboring jurisdictions throughout the region, because the Orange County Groundwater Basin spans approximately 310 miles across northern Orange County. Unlike sewage, which goes to treatment plants, urban runoff flows untreated through the storm drain system. Anything thrown, swept, or poured into the street, gutter or a catch basin (the curbside openings that lead into the storm drain system) flows directly into channels, creeks, bays, and ultimately the Pacific Ocean. The problem is particularly acute at the beginning of a heavy rain storm, but can be a problem at any time due to the improper disposal of products associated with home, garden and automotive maintenance. The goals and policies contained in the General Plan direct the City to maintain and improve the City’s stormwater drainage systems to keep pace with growth, minimize runoff, and decrease levels of pollution, thus serving to mitigate any potential impacts to existing drainage facilities. Relevant Goals and Policies • See Relevant Goals and Policies listed above under “Causes or Contributes to a Violation of any Water Quality Standards, Waste Discharge or Total Maximum Daily Load Limitations Standards” and “Substantially Alters The Existing Drainage Pattern of The Site or Area in a Manner That ---PAGE BREAK--- 5. Environmental Analysis Page 5-128 • The Planning Center May 2004 Would Result in Excessive Erosion or Siltation On-Site or Off-Site, or Result in Flooding On-Site or Off-Site.” Existing Codes and Regulations • Future projects shall comply with all applicable local, State, and federal regulations relating hydrology and water quality. Level of Significance Before Mitigation: Less than significant. Mitigation Measures: No mitigation measures are necessary. Level of Significance After Mitigation: No significant adverse impacts were identified and no mitigation measures are necessary. IMPACT: WOULD THE PROJECT OTHERWISE SUBSTANTIALLY DEGRADE WATER QUALITY Impact Analysis: The continued growth and prosperity of Anaheim depends on a reliable and clean water supply. The City has responsibilities to maintain the quality of groundwater and address the issues associated with storm water and urban runoff pollution. As mentioned in the preceding sections, implementation of the General Plan and Zoning Code Update has the potential to increase levels of water pollution and urban runoff. The General Plan and Zoning Code Update seeks to protect water quality by requiring residents and businesses to engage in water quality management practices and pollution control measures. The General Plan’s Goals and Policies also direct the City to monitor water quality and provide water service that meets or exceeds health standards. Relevant Goals and Policies • See Relevant Goals and Policies listed above under “Causes or Contributes to a Violation of any Water Quality Standards, Waste Discharge or Total Maximum Daily Load Limitations Standards” Existing Codes and Regulations • Future projects shall comply with all applicable local, State, and federal regulations relating hydrology and water quality. Level of Significance Before Mitigation: Less than significant. Mitigation Measures: No mitigation measures are necessary. Level of Significance After Mitigation: No significant adverse impacts were identified and no mitigation measures are necessary. IMPACT: WOULD THE PROJECT PLACE HOUSING WITHIN A 100-YEAR FLOOD HAZARD AREA AS MAPPED ON A FEDERAL FLOOD HAZARD BOUNDARY OR FLOOD INSURANCE RATE MAP OR OTHER FLOOD HAZARD DELINEATION MAP OR PLACE WITHIN A 100-YEAR FLOOD HAZARD AREA STRUCTURES WHICH WOULD IMPEDE OR REDIRECT FLOOD FLOWS Impact Analysis: Figure 5.7-3, Flood Hazard Areas, presents the detailed floodplain areas for the City of Anaheim. Review of this figure and the Flood Insurance Rate Maps (available for reference from the Anaheim Planning Department and FEMA) indicates that there are presently some areas in the 100-year ---PAGE BREAK--- 5. Environmental Analysis Anaheim General Plan/Zoning Code Update EIR City of Anaheim • Page 5-129 Figure 5.7-4 Dam Inundation Map Place on an odd page. Color 11 x 17 ---PAGE BREAK--- 5. Environmental Analysis Page 5-130 • The Planning Center May 2004 This page intentionally left blank ---PAGE BREAK--- 5. Environmental Analysis Anaheim General Plan/Zoning Code Update EIR City of Anaheim • Page 5-131 flood zone that could create a hazardous condition in the City. The 100-year flood areas are generally near the Santa Ana River, reservoirs, and recharge basins. Buildout of the Recommended Land Use Alternative could potentially expose more people and habitable structures to potential flooding. Increased exposure could occur through development of lands within flood zones. The policies contained in the General Plan seek to protect structures and residents within flood zones by requiring all development proposals to undergo an evaluation process to determine flood risks and ensure compliance with local, State, and Federal regulations. Relevant Goals and Policies Proposed General Plan policies related to reduction of the risk to life, property, public investment and social order created by flood hazards include: • Evaluate all development proposals located in areas that are subject to flooding to minimize the exposure of life and property to potential flood risks. (Safety Element, Goal 3.1, Policy 1) • Provide appropriate land use regulations and site development standards for areas subject to flooding. (Safety Element, Goal 3.1, Policy 2) • Continue to participate in the National Flood Insurance Program. (Safety Element, Goal 3.1, Policy 4) • Continue to comply with the Cobey-Alquist Floodplain Management Act requirements and State of California Model Ordinance. (Safety Element, Goal 3.1, Policy 5) • Continue to work with the Orange County Flood Control District and the United States Army Corps of Engineers to receive and implement updated flood control measures and information. (Safety Element, Goal 3.1, Policy 6) • Improve the City’s storm drain system to address current deficiencies as well as long-term needs associated with future development to minimize flood damage and adequately convey rainfall and subsequent runoff from a 25-year frequency storm. (Public Services and Facilities Element, Goal 6.1, Policy 1) Existing Codes and Regulations • Future projects shall comply with all applicable local, State, and federal regulations relating hydrology and water quality. Level of Significance Before Mitigation: Less than significant. Mitigation Measures: No mitigation measures are necessary. Level of Significance After Mitigation: No significant adverse impacts were identified and no mitigation measures are necessary. IMPACT: WOULD THE PROJECT 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 Impact Analysis: In addition to flood hazards associated with 100-year flood zones, flood inundation resulting from dam failure due to strong seismic activity is a potential hazard for the City. General limits of flood hazard due to dam failure are shown on Figure 5.7-45-5, Dam Inundation Map, for the Walnut Canyon Reservoir, the Prado Dam, and the Carbon Canyon Dam. Walnut Canyon Reservoir is located in the Hill and Canyon Area of the City, while the Prado Dam and reservoir are located approximately 2 ---PAGE BREAK--- 5. Environmental Analysis Page 5-132 • The Planning Center May 2004 miles east of Anaheim in Riverside County. The City is also down slope to the Carbon Canyon Dam, which is located in the City of Brea and has the potential to flood areas of the City north of SR-91. Implementation of the General Plan and Zoning Code Update has the potential to increase the number of people and structures exposed to flood hazards. The General Plan contains policies that seek to reduce the threat of catastrophic flood damage through aggressive flood mitigation activities. Relevant Goals and Policies • See Relevant Goals and Policies listed above under “Place Housing or Habitable Structures Within a 100-Year Flood Zone” Existing Codes and Regulations See Existing Codes and Regulations listed above under “Place Housing or Habitable Structures Within a 100-Year Flood Zone” Level of Significance Before Mitigation: Less than significant. Mitigation Measures: No mitigation measures are necessary. Level of Significance After Mitigation: No significant adverse impacts were identified and no mitigation measures are necessary. IMPACT: WOULD THE PROJECT BE SUBJECT TO INUNDATION BY SEICHE, TSUNAMI, OR MUDFLOW There is a low to moderate potential for flooding due to seiche hazards affecting properties adjacent to the Walnut Canyon Reservoir, an enclosed body of water in the Anaheim Hills. The City of Anaheim is not located close enough to the coast to be subject to possible impacts from a Tsunami. The potential for mudflow would be mitigated by the Goals and Policies and mitigation measures described above. Relevant Goals and Policies • See Relevant Goals and Policies listed above under “Place Housing or Habitable Structures Within a 100-Year Flood Zone” Existing Codes and Regulations Existing Codes and Regulations • Future projects shall comply with all applicable local, State, and federal regulations relating hydrology and water quality. Level of Significance Before Mitigation: Less than significant. Mitigation Measures: No mitigation measures are necessary. Level of Significance After Mitigation: No significant adverse impacts were identified and no mitigation measures are necessary. 5.7.5 Significant Unavoidable Adverse Impacts The General Plan Goals and Policies, and mitigation measures identified above would reduce potential impacts associated with hydrology and water quality to a level of insignificance.