3.8 HYDROLOGY AND WATER QUALITY

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3 This section of the Draft EIR addresses the potential environmental impacts of the proposed project related to hydrology and water quality. The existing surface water and groundwater hydrologic conditions of the project site and surrounding area are characterized and a summary of relevant law and regulations as they apply to the proposed project is provided. The impact analysis focuses on potential degradation of water quality, alteration of existing drainage patterns, and flooding hazards. Information used in the preparation of this section was obtained primarily from the General Plan and Zoning Code, as well as from Federal Emergency Management Agency (FEMA) flood data EXISTING SETTING REGIONAL CLIMATE AND TOPOGRAPHY Santa Rosa is located in a Mediterranean climate zone typical of central coastal California. This climate zone is characterized by cool, wet winters and warm, dry summers. The city receives a mean annual precipitation of approximately 30 inches in the lower elevations and about 45 inches in the higher elevations. The majority of the rainfall typically occurs between October 1 and April 1. Influenced by marine air about 85 percent of the time, the region is generally protected from the hot weather of the Central Valley by the interior Coast Ranges. Although the Pacific Ocean moderates temperatures, they have a wider range than along the coast, occasionally exceeding 100 degrees Fahrenheit and sometimes falling as low as several degrees below freezing for several consecutive nights. (Santa Rosa General Plan 2035 DEIR, 2009) Santa Rosa is located within the Santa Rosa Plain, an alluvial plain that stretches into Sonoma Valley on the east and spills into the Laguna de Santa Rosa catchment basin to the west. The city is located at the foot of the Mayacamas Mountains where elevations are as high as 220 feet above mean sea level in the easternmost portion of the city limits and slope down to 120 feet above mean sea level at the furthest westernmost end of the city. Santa Rosa Creek flows east to west and runs generally through the center of the city. (Santa Rosa General Plan 2035 DEIR, 2009) REGIONAL HYDROLOGY The entire city is located within the Laguna de Santa Rosa watershed, which originates at Hood Mountain in the Mayacamas Mountains to the east and discharges to Laguna de Santa Rosa, a large wetland complex downstream of the Santa Rosa urban area. Tributary basins to Santa Rosa Creek that lie primarily in the city are Brush Creek, Matanzas Creek, Paulin Creek, Roseland/Colgan Creek, and Piner/Peterson Creek. Mark West Creek drains the northern portion of the city, Naval Creek the westernmost portion, and Todd Creek the southernmost portion of the city. All of these tributaries ultimately drain to Laguna de Santa Rosa, which in turn drains into the Russian River and out to the ocean. Other waterbodies located in or around the city include Fountaingrove Lake, Lake Ralphine, and Santa Rosa Creek Reservoir. SURFACE WATER QUALITY Surface water quality in Sonoma County is monitored by the North Coast Regional Water Quality Control Board (RWQCB) and the. The Water Quality Control Plan for the North Coast Region (Basin Plan), prepared by the North Coast RWQCB, identifies the beneficial uses of surface waters in its region and specifies water quality objectives to maintain the continued beneficial uses of these waters. According to the Basin Plan, beneficial uses of the Santa Rosa subarea of the Russian River include municipal, agricultural, and industrial supply; groundwater recharge; warm and cold freshwater habitat; navigation; spawning, reproduction, and April Draft Environmental Impact Report

4 development; water contact recreation; non-water contact recreation; wildlife habitat; rare species; and possible shellfish and aquatic plant and animal harvesting. (Santa Rosa General Plan 2035, 2009) The Russian River hydrologic unit that includes the Laguna de Santa Rosa watershed is listed under Clean Water Act Section 303(d) as impaired for indicator bacteria, low dissolved oxygen, mercury, nitrogen, phosphorus, sediment, and temperature. Santa Rosa Creek is listed for impairments associated with indicator bacteria, sediment, and temperature. The Laguna de Santa Rosa unit of the Russian River is also listed for impairments associated with low dissolved oxygen, mercury, nitrogen, phosphorus, sediment, and temperature. (Santa Rosa General Plan 2035, 2009) GROUNDWATER RESOURCES The Santa Rosa Plain Subbasin of the Santa Rosa Valley Groundwater Basin covers an area of 80,000 acres, or approximately 125 square miles. It is the largest subbasin of the Santa Rosa Valley Groundwater Basin and is characterized by low relief with an average ground surface elevation of approximately 145 feet above mean sea level. (Existing Conditions Report for the, 2012) The Santa Rosa Plain Subbasin is approximately 22 miles long and 0.2 miles wide at the northern end, approximately 9 miles wide through the Santa Rosa area, and about 6 miles wide at the south end of the plain near Cotati. The Santa Rosa Plain Subbasin is bounded on the northwest by the Russian River plain approximately 1 mile south of Healdsburg and the Healdsburg Subbasin. Mountains of the Mendocino Range flank the remaining western boundary. The southern end of the subbasin is marked by a series of low hills, which form a drainage divide that separates the Santa Rosa Valley from the Petaluma Valley basin south of Cotati. The eastern subbasin boundary is formed by the Sonoma Mountains south of Santa Rosa and the Mayacamas Mountains north of Santa Rosa. (Existing Conditions Report for the North Santa Rosa Station Area Specific Plan, 2012) The Santa Rosa Plain Subbasin is drained principally by Santa Rosa Creek flowing westward into Laguna de Santa Rosa. Laguna de Santa Rosa flows into Mark West Creek, which discharges into the Russian River. Annual precipitation in the Santa Rosa Plain ranges from approximately 28 inches in the south to about 40 inches in the north. (Existing Conditions Report for the North Santa Rosa Station Area Specific Plan, 2012) The major geologic formations comprising the Santa Rosa Plain Subbasin are, from youngest to oldest, Younger Alluvium, Older Alluvium (alluvial fan deposits), the undifferentiated Glen Ellen, Huichica Formations and related continental deposits, the Sonoma Volcanics, the Wilson Grove (formerly Merced) Formation, and the Petaluma Formation. The Tolay Volcanics may also be present in the subsurface. The groundwater subbasin is floored by low permeability rocks of the Franciscan Formation. (SB 610 WSA for the, 2012) WATER QUALITY Two creeks run through the project area: Paulin Creek and Steele Creek. Steele and Paulin creeks within the project boundaries are identified in the Citywide Creek Master Plan as modified-natural creeks. There is an unpaved/gravel trail along the east side of Steele Creek from Guerneville Road to 300 yards south of Jennings Avenue. Paulin Creek has an unpaved/gravel path running along the north side of the creek from McBride Lane to Hardies Lane. The unpaved/gravel path continues on the southern side of the creek from Hardies Lane Draft Environmental Impact Report April

5 to Coffey Lane. The RWQCB has identified toxic contaminants on several industrial properties located adjacent to Paulin Creek. Although high iron, manganese, and hardness have been reported in groundwater for some portions of the Santa Rosa Plain Subbasin, the overall quality of groundwater in the subbasin is good. Groundwater underlying the City s service area generally meets primary and secondary drinking water standards for municipal use. The City s Farmers Lane wells have historically exhibited slightly elevated concentrations of both iron and manganese, exceeding secondary drinking water standards. (SB 610 WSA for the, 2012) DRAINAGE AND FLOODING Flooding Hazards Flooding is inundation of normally dry land as a result of a rise in the level of surface waters or rapid accumulation of stormwater runoff. Regional flooding hazards are generally evaluated by FEMA and presented in community Flood Insurance Rate Maps as part of the floodplain mapping program. Following a very severe flood in 1955, local improvement programs were developed and focused on increasing the flood capacity of Santa Rosa Creek, Matanzas Creek, Piner Creek, Paulin Creek, Brush Creek, and Spring Creek. However, following the construction of 25 miles of flood control channels in the 1960s, the lower reach of Spring Creek continued to consistently overflow. (Santa Rosa General Plan 2035, 2009) FEMA maps are currently being finalized for the southern Santa Rosa area, including Naval, Roseland, and Colgan creeks, and are anticipated to become effective in late In addition, the US Army Corps of Engineers has partnered with FEMA to develop flood hazard maps for Santa Rosa Creek and its tributaries. This study is currently under way, and draft flood hazard maps are not yet available. Once completed, federal flood hazard mapping will exist for both Paulin and Steele creeks in the project area. Dam Inundation In addition to natural flood hazards, flooding can also occur as a result of dam inundation caused by dam failure. Structural failure may be caused by seismic activity. The most extreme flood risk to the would be from an uncontrolled release from a failure at Matanzas Creek Reservoir, or to a lesser degree Lake Ralphine or Fountaingrove. However, all of these dams are annually inspected by the California Division of Safety of Dams (DSOD) engineers to ensure they are performing and being maintained in a safe manner. Figure 12-4 of the General Plan 2035 shows that the Specific Plan area is not located within a sam inundation area. When determined to be structurally inadequate to withstand anticipated ground shaking, dams under the jurisdiction of the DSOD are required to undergo seismic retrofitting. With annual DSOD inspection and oversight, the potential for catastrophic failure is considered to be very low. (Santa Rosa General Plan 2035, 2009) Tsunami and Seiche Inundation Flooding can also occur due to tsunamis, seiches, or mudflows. Tsunamis are waves caused by an underwater earthquake, landslide, or volcanic eruption. Since the project site is located inland, it could not experience a tsunami. A seiche is a rhythmic motion of water in a partially or completely landlocked waterbody caused by landslides, earthquake-induced ground accelerations, or ground offset. There are several reservoirs located within or near the city limits that could potentially experience seiche waves from a significant seismic event. However, none April Draft Environmental Impact Report

6 of these reservoirs are in the vicinity of the Specific Plan area. A mudflow or mudslide is the most rapid and fluid type of downhill mass wasting. It is a rapid movement of a large mass of mud formed from loose earth and water. Similar terms are debris flow (e.g., in high mountains) and mudslide (not very liquid). (Santa Rosa General Plan 2035, 2009) REGULATORY FRAMEWORK FEDERAL Clean Water Act The Clean Water Act (CWA) regulates the water quality of all discharges into waters of the United States, including wetlands, as well as perennial and intermittent stream channels. Section 401, Title 33, Section 1341 of the CWA sets forth water quality certification requirements for any applicant applying for a federal license or permit to conduct any activity including, but not limited to, the construction or operation of facilities, which may result in any discharge into the navigable waters. Section 404, Title 33, Section 1344 of the CWA in part authorizes the U.S. Army Corps of Engineers to: Set requirements and standards pertaining to such discharges: subparagraph (e); Issue permits for the discharge of dredged or fill material into the navigable waters at specified disposal sites : subparagraph (a); Specify the disposal sites for such permits: subparagraph (b); Deny or restrict the use of specified disposal sites if the discharge of such materials into such area will have an unacceptable adverse effect on municipal water supplies and fishery areas : subparagraph (c); Specify type of and conditions for non-prohibited discharges: subparagraph (f); Provide for individual state or interstate compact administration of general permit programs: subparagraphs (g), (h), and (j); Withdraw approval of such state or interstate permit programs: subparagraph (i); Ensure public availability of permits and permit applications: subparagraph (o); Exempt certain federal or state projects from regulation under this Section: subparagraph (r); and Determine conditions and penalties for violation of permit conditions or limitations: subparagraph (s). Section 401 certification is required prior to final issuance of Section 404 permits from the U.S. Army Corps of Engineers. Section 303(d) of the federal Clean Water Act requires that all states in the U.S. identify waterbodies that do not meet specified water quality standards and that do not support intended beneficial uses. Identified waters are placed on the Section 303(d) List of Impaired Waterbodies. Draft Environmental Impact Report April

7 Once placed on this list, states are required to develop a water quality control plan for each water body and each associated pollutant/stressor. (Santa Rosa General Plan 2035, 2009) National Pollutant Discharge Elimination System Since 1972, the CWA has regulated the discharge of pollutants to waters of the U.S. from all point sources. Section 402(d) of the CWA establishes a framework for regulating nonpoint source stormwater discharges under the National Pollutant Discharge Elimination System (NPDES). Established in 1990, Phase I of the NPDES stormwater program regulates stormwater discharges from major industrial facilities, large and medium-sized municipal separate storm sewer systems (those serving more than 100,000 persons), and construction sites that meet certain established criteria. In 1999, the NPDES stormwater program was expanded to include Phase II communities. Activities that result in the disturbance of 1 acre of land or more must also apply for coverage under the statewide NPDES General Construction Activities Permit. To comply with the NPDES General Construction Permit, a project applicant is required to submit a Notice of Intent to the State Water Resource Control Board s (SWRCB) Division of Water Quality. The Notice of Intent includes general information on the types of construction activities that will occur on the site. The applicant (for a site-specific project) is also required to submit a site-specific plan called the stormwater pollution prevention plan (SWPPP) to minimize the discharge of pollutants during construction. The SWPPP must include a description of best management practices (BMPs) for preventing the discharge of silt and sediment from the site. The SWPPP must also include BMPs for preventing the discharge of other nonpoint source pollutants besides sediment (e.g., drilling lubricant, oil, concrete, cement) from the site, as well as a detailed description of (and schedule for) all sampling and monitoring. Construction activities that are subject these requirements include, but are not limited to, clearing, grading, demolition, excavation, construction of new structures, and reconstruction of existing facilities involving removal and replacement that results in soil disturbance. The Sacramento Trial Court ordered the SWRCB to set aside the numeric effluent limits for ph and turbidity established in the general construction permit for Level 3 construction sites and to refrain from enforcing those limits until the SWRCB adopts new limits based on specified best control treatments assessed in accordance with the factors contained in Section 304(b)(4)(B) of the Clean Water Act. If and when new ph and turbidity NELs are adopted, the SWRCB must also determine the appropriate size of a compliance storm event exemption from the numeric effluent limits. The remaining portions of the permit were deemed valid and enforceable. (Abbott & Kindermann 2011) Federal Emergency Management Agency FEMA administers the National Flood Insurance Program (NFIP) to provide subsidized flood insurance to communities that comply with FEMA regulations limiting development in floodplains. FEMA also issues Flood Insurance Rate Maps identifying which land areas are subject to flooding. The maps provide flood information and identify flood hazard zones in the community. The design standard for flood protection is established by FEMA, with the minimum level of flood protection for new development determined to be the 1-in-100 annual exceedence probability (i.e. the 100-year flood event). April Draft Environmental Impact Report

8 STATE Porter-Cologne Water Quality Act In 1969, the California Legislature enacted the Porter-Cologne Water Quality Control Act to preserve, enhance, and restore the quality of the state s water resources. The act established the State Water Resources Control Board and nine Regional Water Quality Control Boards as the principal state agencies with the responsibility for controlling water quality in California. Under the act, water quality policy is established, water quality standards are enforced for both surface water and groundwater, and the discharges of pollutants from point and nonpoint sources are regulated. The act authorizes the State Water Resources Control Board to establish water quality principles and guidelines for long-range resource planning including groundwater and surface water management programs and control and use of recycled water (USDOE 2012). State Water Resources Control Board The five-member State Water Resources Control Board allocates water rights, adjudicates water right disputes, develops statewide water protection plans, establishes water quality standards, and guides the nine regional water quality control boards located in the major watersheds of the state. The joint authority of water allocation and water quality protection enables the SWRCB to provide comprehensive protection for California s waters (SWRCB 2012). The SWRCB is responsible for implementing the Clean Water Act, issues NPDES permits to cities and counties through Regional Water Quality Control Boards, and implements and enforces the General Construction Permit. REGIONAL Regional Water Quality Control Board, North Coast Region Each RWQCB is required to develop, adopt, and implement a Water Quality Control Plan (Basin Plan) for its respective region. The Basin Plan is the master policy document that contains descriptions of the legal, technical, and programmatic bases of water quality regulation in each region. Basin Plans identify beneficial uses of surface waters and groundwater within the corresponding region; specify water quality standards, known as water quality objectives, for both surface water and groundwater; and develop the actions necessary to maintain the standards to control nonpoint and point sources of pollutants to the state s waters. All discretionary projects requiring permits from the RWQCB (i.e., waste and pollutant discharge permits) must implement Basin Plan requirements (i.e., water quality standards), taking into consideration the beneficial uses to be protected. The Specific Plan aea is within the jurisdiction of the North Coast RWQCB. The North Coast RWQCB also issues the NPDES Municipal Separate Storm Sewer (MS4) Phase 1 permit to the City requiring post-construction stormwater quality measures and site design consistent with the Storm Water Low Impact Development Technical Design Manual. LOCAL General Plan The Santa Rosa General Plan 2035 serves as the overall guiding policy document for the City of Santa Rosa. The following is a list of applicable General Plan goals and policies most pertinent to the Specific Plan in regard to hydrologic or water quality and flooding issues. Draft Environmental Impact Report April

9 Public Services and Facilities Element Goal PSF-I: Manage, maintain and improve stormwater drainage and capacity. Policy PSF-I-1: Require dedication, improvement and maintenance of stormwater flow and retention areas as a condition of approval. Policy PSF-I-2: Require developers to cover the costs of drainage facilities needed for surface runoff generated as a result of new development. Policy PSF-I-3: Require erosion and sedimentation control measures to maintain an operational drainage system, preserve drainage capacity and protect water quality. Policy PSF-I-4: Require measures to maintain and improve the storm drainage system, consistent with goals of the Santa Rosa Citywide Creek Master Plan, to preserve natural conditions of waterways and minimize paving of creek channels. Policy PSF-I-5: Cooperate with the Sonoma County Water Agency and the Northern California Regional Water Quality Control Board to conduct regular assessment of stormwater drainage facilities, to ensure that adequate drainage capacity is maintained throughout the system to accommodate increases in residential and commercial development. Policy PSF-I-6: Require implementation of Best Management Practices to reduce drainage system discharge of non-point source pollutants originating from streets, parking lots, residential areas, businesses, industrial operations and those open space areas involved with pesticide application. Policy PSF-I-7: Prepare and distribute information to increase awareness of businesses and residents about the need to reduce drainage system discharge of non-point source pollutants. Policy PSF-I-8: Implement the Standard Urban Stormwater Mitigation Plan (SUSMP) in order to reduce pollutants and runoffs flows from new development and significant redevelopment projects. Policy PSF-I-9: Consider installation of creekside pathways, consistent with the Citywide Creek Master Plan and Bicycle and Pedestrian Master Plan, when possible as part of stormwater improvement projects along the city s creek corridors. Noise and Safety Element Goal NS-C: Prohibit development in high-risk geologic and seismic hazard areas to avoid exposure to seismic and geologic hazards. Policy NS-C-7: Require inspection for structural integrity of water storage facilities, water conveyance facilities, electricity transmission lines, roadways, water detention facilities, levees, and other utilities after a major seismic event, especially on the San Andreas or Rodgers Creek faults. Goal NS-D: Minimize hazards associated with storm flooding. Policy NS-D-1: Ensure flood plain protection by retaining existing open areas and creating new open areas needed to retain stormwater, recharge aquifers and prevent flooding. April Draft Environmental Impact Report

10 Policy NS-D-2: Maintain current flood hazard data and coordinate with the Army Corps of Engineers, FEMA, Sonoma County Water Agency and other responsible agencies to coordinate flood hazard analysis and management activities. Policy NS-D-3: Require that new development incorporate features into site drainage plans that would reduce impermeable surface area, increase surface water infiltration and minimize surface water runoff during storm events. Such features may include: Additional landscape areas, Parking lots with bio-infiltration systems, Permeable paving designs, and Stormwater detention basins. Policy NS-D-4: Incorporate features and appropriate standards that reduce flooding hazards, as described in Policy NS-D-3, into the City s design standards. Policy NS-D-5: Apply design standards to new development that help reduce project runoff into local creeks, tributaries, and drainage ways. Policy NS-D-6:Locate new essential public facilities such as hospitals and fire stations outside of flood areas or areas subject to dam inundation. Goal NS-E: Provide protection of public and private properties from hazards associated with dam inundation. Policy NS-E-1: Support efforts to conduct periodic inspections of local dams to ensure all safety measures are in place. Sonoma County Water Agency Flood Control Design Criteria The Sonoma County Water Agency (SCWA) was formed in 1949 with the primary responsibility to produce and furnish water for beneficial uses, water conservation, and flood management. Nine geographical zones, each encompassing a major watershed, were proposed in 1958 as a means of financing the construction and maintenance of flood control works in the county. The SCWA works cooperatively with the incorporated cities, unincorporated communities, and the state and federal governments to oversee flood control channel modifications and flood control revenue collection in the six active zones. The is located in Flood Zone 1A Laguna de Santa Rosa Mark West Creek Watershed. Storm drainage infrastructure in unincorporated Sonoma County is designed using the SCWA Flood Control Design Criteria. In compliance with the SCWA criteria, all culverts and drainage systems must be designed to accommodate the runoff from a 25-year recurrence interval storm event and protect finished floors from the 100-year recurrence interval storm. The SCWA reviews project plans for proposed drainage improvements. In addition, the SCWA is in the process of revising and updating the Flood Control Design Criteria. Storm Water Low Impact Development Technical Design Manual The Storm Water Low Impact Development Technical Design Manual (LID Manual), adopted by the in October 2011 and implemented in 2012, applies to both privately sponsored projects and capital improvement projects. The LID Manual requires applicable projects to design and implement post-development measures to reduce stormwater pollution. Draft Environmental Impact Report April

11 Under the LID Manual, applicable projects are required to design and implement postdevelopment measures for the management of stormwater quality and stormwater volume for the entire development site. The LID Manual emphasizes managing stormwater runoff through landscape-based treatment methods to reduce the potential impacts to local drainage systems. The goal of the manual is to reduce pollution and runoff flows to the best practicable extent for all new capital improvement program and development projects meeting the following criteria: Development that creates or replaces a combined total of 1 acre or more of new impervious surface. Street, road, highway, or freeway construction or reconstruction, creating or replacing 10,000 square feet or more of impervious surface. All development that includes four or more dwelling units. Industrial parks, commercial strip malls, retail gasoline outlets, restaurants, or automotive service facilities creating or replacing 10,000 square feet or more of impervious surface. Parking lots, 25 or more spaces or 10,000 square feet not associated with other projects. Parking lots with 25 or more spaces or 10,000 square feet not associated with other projects. As new developments are planned, measures for treatment of erosion and stormwater are addressed at the source. As sites are developed each site must establish acceptable source control methods. Varied methods can be employed to satisfy the requirements set forth by the Storm Water Management Plan. The works in conjunction with Sonoma County and the SCWA to ensure the requirements are met. California Green Building Standards Code The California Building Standards Code (CALGreen) is published in its entirety every three years by order of the California Legislature. The California Legislature delegated authority to various state agencies, boards, commissions, and departments to create building regulations to implement the state s statutes. These building regulations or standards have the same force of law and take effect 180 days after their publication unless otherwise stipulated. The California Building Standards Code applies to all occupancies in the State of California as annotated. A city, county, or city and county may establish more restrictive standards reasonably necessary because of local climatic, geological, or topographical conditions. For the purpose of this code, these conditions include local environmental conditions as established by a city, county, or city and county. Findings of the local condition(s) and the adopted local building standard(s) must be filed with the California Building Standards Commission to become effective and may not be effective sooner than the effective date of this edition of the California Building Standards Code. Local building standards that were adopted and applicable to previous editions of the California Building Standards Code do not apply to this edition without appropriate adoption and the required filing. April Draft Environmental Impact Report

12 Citywide Creek Master Plan Background The Santa Rosa Citywide Creek Master Plan, adopted by the City Council on March 27, 2007, implements General Plan 2035 Policy OSC-D-13 and provides guidelines for the care, management, restoration, and enhancement of nearly 90 miles of creeks in Santa Rosa. The master plan is intended for use by city and county staff when planning creek enhancement and restoration activities, coordination and expansion of creekside trail systems, making broader land-use planning decisions concerning creeks, and in the development approval process for projects proposed adjacent to a waterway. The Citywide Creek Master Plan consolidates previously adopted creek policies that are contained in numerous city documents adopted over a span of several decades. The master plan presents these policies in a comprehensive and illustrative form that includes recommendations for habitat preservation, enhancement, restoration, and development of trails by each watershed. Project recommendations are based on community input, literature reviews, and extensive field research. Site-specific recommendations are presented in the text as well as on a set of geographical information system (GIS)-based maps, organized by watershed area. Detailed conceptual plans were developed for two locations: Upper Colgan Creek and Roseland Creek. Previously adopted concept plans incorporated into the master plan include Pierson Reach of Santa Rosa Creek and Lower Colgan Creek. Implementation of the Citywide Creek Master Plan will occur over several years, perhaps decades, and will be accomplished through partnerships with citizens, organizations, agencies, and the development community. Project funding will come primarily from grants or other funding sources designated for restoring fish and wildlife habitat and for improving creekside recreation, access, and transportation opportunities. The proposed project includes an amendment to the Citywide Creek Master Plan to incorporate the proposed bicycle and pedestrian trails along Paulin and Steele creeks IMPACTS AND MITIGATION MEASURES STANDARDS OF SIGNIFICANCE The impact analysis provided below is based on the following State CEQA Guidelines Appendix G thresholds of significance. An impact to hydrology and water quality is considered significant if the project would: 1) Violate any water quality standards or waste discharge requirements. 2) Substantially deplete groundwater supplies or interfere substantially with groundwater recharge such that there would be a net deficit in aquifer volume or a lowering of the local groundwater table level (e.g., the production rate of pre-existing nearby wells would drop to a level which would not support existing land uses or planned uses for which permits have been granted). 3) Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, in a manner which would result in substantial erosion or siltation on- or off-site. Draft Environmental Impact Report April

13 4) 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. 5) Create or contribute runoff water which would exceed the capacity of existing or planned stormwater drainage systems or provide substantial additional sources of polluted runoff. 6) Otherwise substantially degrade water quality. 7) 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. 8) Place within a 100-year flood hazard area structures which would impede or redirect flood flows. 9) Expose people or structures to a significant loss, injury, or death involving flooding, including flooding as a result of the failure of a levee or dam. 10) Inundation by seiche, tsunami, or mudflow. METHODOLOGY The hydrology and water quality analysis presented below is based on a review of published information, reports, and plans regarding regional and local hydrology, climate, topography, and geology obtained from private and governmental agencies as well as from Internet websites. Primary sources include the Santa Rosa General Plan 2035, North Coast RWQCB s Basin Plan, California Stormwater Quality Association Best Management Practice Handbooks, and FEMA Flood Insurance Rate Maps. PROJECT IMPACTS AND MITIGATION MEASURES Violate Water Quality Standards or Waste Discharge Requirements (Standard of Significance 1) Impact Development and redevelopment under the Specific Plan include construction-related activities that could expose soil to erosion during storm events, causing degradation of water quality. This impact is considered to be less than significant. During construction of projects under the Specific Plan, especially during site grading activities, stormwater runoff could remove sediment from exposed soil areas, increasing the chance of runoff or wind mobilization and thereby causing increases in sediment loads in nearby storm drain systems and downstream waterways, including Paulin Creek and Steele Creek. Additionally, the grading process uses heavy construction equipment powered with diesel fuel or gasoline and also requiring motor oil, hydraulic oils, and other potential contaminants. A leak, most common during refueling, could contaminate proximate waterways. A release of construction materials such as concrete, asphaltic emulsion, or paint could also affect downstream water quality through surface runoff or groundwater seepage. However, every project that is subject to the Storm Water Low Impact Development Technical Design Manual is required to apply for coverage and develop and implement a project-specific SWPPP. These SWPPS include erosion control/soil stabilization techniques, BMPs for preventing the April Draft Environmental Impact Report

14 discharge of construction-related pollutants, drainage facility inspections, monitoring and maintenance programs, and training and information programs. Implementation of these requirements would ensure that the potential for violation of water quality standards and waste discharge requirements pose a less than significant impact both during and after construction. Mitigation Measures None required. Deplete Groundwater Supplies or Interfere with Groundwater Recharge (Standard of Significance 2) Impact Development and redevelopment under the Specific Plan would not significantly deplete groundwater supplies or alter the area available for recharge of the groundwater aquifer. This impact would be less than significant. The developments within the Specific Plan area would utilize municipal water sources, which would include the use of groundwater. As discussed in more detail in Section 3.12, Public Services and Utilities, of this DEIR, according to the Water Supply Assessment completed for the Specific Plan, the City will be able to support the growth that would result from the Specific Plan, in combination with existing demands and planned future demands. In addition, the Water Supply Assessment determined that the groundwater supply would be adequate to support the projected amount of groundwater (2,300 acre-feet per year) anticipated to be pumped as a share of the potable water supply needed to support future growth in Santa Rosa, including the Specific Plan area. As a result, the Specific Plan would not substantially deplete groundwater supplies since it would not result in the need to pump more water than can be supported by the local groundwater basin. The areas of development and redevelopment in the Specific Plan area are mainly developed sites and therefore covered with buildings, paving, roadways, or a heavily compacted, otherwise impervious surface. Future redevelopment would not alter the area available for groundwater recharge. Since the Specific Plan would not significantly alter groundwater recharge, there is a less than significant impact to the groundwater of the area. Mitigation Measures None required. Alter Existing Drainage Patterns (Standards of Significance 3 & 4) Impact Development and redevelopment under the Specific Plan could increase impervious surfaces and, as a result, alter drainage patterns and increase drainage rates over existing conditions. This impact is considered to be less than significant. The areas of development and redevelopment in the Specific Plan area are mainly developed sites and therefore covered with buildings, paving, roadways, or a heavily compacted, otherwise impervious surface. As a result, drainage patterns due to development have already been established. None of the projects anticipated under the Specific Plan are likely to require substantial alteration of existing drainage patterns that would cause substantial erosion or siltation. Development would occur on a nearly level terrace with minimal required grading and few channels. The only work near major drainage channels would occur adjacent to Paulin Draft Environmental Impact Report April

15 Creek and Steele Creek (including the proposed bicycle and pedestrian paths), possibly requiring some bank stabilization or the installation or reconstruction of new storm drain outfalls. While none of these projects are planned to substantially alter the course of the adjacent waterways, unforeseen circumstances, such as uncontrolled grading or placement of fill and unregulated discharge of water, may alter drainage patterns sufficiently to contribute to substantial erosion or siltation. However, development of sites adjacent to Paulin Creek and Steele Creek will require permitting with the California Department of Fish and Game (CDFG) and the Sonoma County Water Agency, where applicable. The following describes the potential permits that may be required: Streambed Alteration Agreement. Any portions of the proposed project occurring along the banks of Paulin Creek or Steele Creek would be subject to the requirements for a CDFG Streambed Alteration Agreement. Restoration and enhancement of bank areas covered by concrete slabs and riprap would be included as part of any project located adjacent to the creek. Sonoma County Water Agency Review. Individual project applicants would be required to submit drainage design plans for review and approval by the SCWA for any portions of the project occurring along the banks of Paulin Creek or Steele Creek. Applicants would be required to obtain a revocable license from the SCWA prior to construction within the agency s property. In addition, proposed projects under the Specific Plan would be required to comply with the City s General Plan goals and policies which require the City to manage, maintain, and improve stormwater drainage and capacity. Two policies most pertinent under this goal are General Plan Policy PSF-I-1 and Policy PSF-I-9. These policies require dedication, improvement, and maintenance of stormwater flow and retention areas as a condition of approval. By complying with existing regulations and permitting processes, the potential impact related to altering drainage patterns and increases in siltation and/or erosion would be reduced to a less than significant. Mitigation Measures None required. Runoff Water, Polluted Runoff, and Water Quality Degradation (Standards of Significance 5 & 6) Impact Development and redevelopment under the Specific Plan could increase impervious surfaces and, as a result, increase runoff over existing conditions. Runoff from urban uses may also contribute to the degradation of water quality in the area. This impact is considered to be less than significant. The areas of development and redevelopment in the Specific Plan area are mainly developed sites and therefore covered with buildings, paving, roadways, or a heavily compacted surface. Non-point source pollutants are washed by rainwater from roofs, landscape areas, and streets and parking areas into the drainage network. Development and redevelopment in the Specific Plan area could increase the levels of non-point source pollutants and litter entering Steele Creek and Paulin Creek. An increase in non-point source pollutants could have adverse effects on wildlife, vegetation, and human health. These pollutants could also infiltrate into groundwater and degrade the quality of potential groundwater drinking sources. April Draft Environmental Impact Report

16 Pollutant concentrations in site runoff are dependent on a number of factors, including land use conditions, site drainage conditions, intensity and duration of rainfall, the climatic conditions preceding the rainfall event, and implementation of water quality best management practices. Due to the variability of urban runoff characteristics, it is difficult to estimate pollutant loads for non-point source pollutants. Increases in the levels of oil, grease, petroleum hydrocarbons, organics and toxicants, metals, and possibly nutrients are likely. The City requires developers to prepare and implement the requirements set forth in the Storm Water Low Impact Development Technical Design Manual (LID Manual), pursuant to NPDES Municipal Separate Storm Sewer (MS4) Permit requirements. As the area is gradually redeveloped consistent with the LID Manual, the water quality associated with stormwater runoff would gradually increase over existing conditions. Implementation of the LID Manual, as described under Impact above, would ensure that impacts related to runoff and water quality degradation are reduced to a less than significant level. Mitigation Measures None required. Change in Flood Potential (Standards of Significance 7, 8 & 9) Impact Development in the Specific Plan area may result in increased runoff and flows to the municipal storm drain system. This impact would be less than significant. The Specific Plan area is not currently within a designated FEMA floodplain (Community Panel Numbers ). However, once the US Army Corps of Engineers and FEMA complete their current analysis, flood hazard areas are expected to exist in the project area. Subsequent development in the Specific Plan area may result in increased runoff and flows to the municipal storm drain system due to new paving or surfacing, the addition or removal of storm drain inlets, or other changes to the existing storm drain system. Flows contributed by the Specific Plan may have an adverse impact on the capacity of storm drain conveyance within the municipal system, ultimately affecting Steele Creek, Paulin Creek, and the Laguna de Santa Rosa watershed. General Plan Policy NS-D-3 requires that new development incorporate features into site drainage plans that would reduce impermeable surface area, increase surface water infiltration, and minimize surface water runoff during storm events. Furthermore, Policy NS-C-7 requires inspection of water storage facilities and water conveyance facilities to minimize the possibility of dam failure. Every project that is subject to the Storm Water Low Impact Development Technical Design Manual is required to develop hydrology and hydraulic calculations, maps, and a report in accordance with the Sonoma County Water Agency flood control criteria. These plans include design drawings and calculations of the capacity of the proposed storm drain system for the project. The plan also includes a hydraulic analysis prepared consistent with Sonoma County Water Agency flood control design criteria to establish whether the existing municipal system has capacity to accommodate any increased flows resulting from the proposed project. In addition, once flood hazard areas are delineated and incorporated into FEMA maps, all subsequent projects will comply with the City s floodplain administrator requirements and Municipal Code. Draft Environmental Impact Report April

17 Mitigation Measures None required. Inundation by Seiche, Tsunami, or Mudflow (Standard of Significance 10) Impact The Specific Plan area would not be subject to substantial impacts related to inundation by seiche, tsunami, or mudflow events. This impact would be less than significant. Tsunamis are waves caused by an underwater earthquake, landslide, or volcanic eruption. Since the project site is located inland, it could not experience a tsunami. A seiche is a rhythmic motion of water in a partially or completely landlocked waterbody caused by landslides, earthquake-induced ground accelerations, or ground offset. There are no large bodies of water near the Specific Plan area to pose a substantial seiche threat. A mudflow or mudslide is the most rapid and fluid type of downhill mass wasting. It is a rapid movement of a large mass of mud formed from loose earth and water. Similar terms are debris flow (e.g., in high mountains) and mudslide (not very liquid). The Specific Plan area is relatively flat, and mudslides are therefore not an issue. This impact would be less than significant. Mitigation Measures None required CUMULATIVE SETTING, IMPACTS, AND MITIGATION MEASURES CUMULATIVE SETTING The cumulative setting for hydrology and water quality is the Laguna de Santa Rosa watershed, which originates at Hood Mountain in the Mayacamas Mountains to the east and discharges to Laguna de Santa Rosa, a large wetland complex downstream of the Santa Rosa urban area. While most of the Laguna de Santa Rosa watershed is in Sonoma County, it crosses the border of Napa County and is therefore affected by the land use practices in both counties. Various cities, water districts, sanitation districts, school districts, public lands, and private lands are also devoted to various resource extraction and other uses within the watershed. CUMULATIVE IMPACTS AND MITIGATION MEASURES Cumulative Water Quality, Runoff, and Flooding Impacts Impact The proposed project, in combination with existing, approved, proposed, and reasonably foreseeable development in the Laguna de Santa Rosa watershed, would alter drainage conditions, rates, volumes, and water quality, which could result in potential flooding and stormwater quality impacts within the overall watershed. This impact is considered less than cumulatively considerable. Development within the Santa Rosa Urban Growth Boundary has the potential to result in a cumulative impact related to hydrology and water quality. However, the General Plan 2035 EIR identified that with the policies included in the General Plan, the General Plan would result in a less than cumulatively considerable impact related to hydrology and water quality. The Specific Plan would be subject to the same General Plan policies. Therefore, the development of the April Draft Environmental Impact Report

18 lands within the Specific Plan area is not expected to contribute to a cumulative hydrologic or water quality impact to the Santa Rosa area. The Specific Plan calls for increased residential, transit village, mixed use, retail, and public/institutional development. Peak runoff could increase gradually, due to increased impervious surface area, as development proceeds. However, these impacts will be reduced through improvements to the storm drain network identified in Section 3.12, Public Services and Utilities and are not expected to contribute to the cumulative effects to stormwater capacity (see subsection for more details). Additionally, General Plan Policy NS-D-3 requires that new development incorporate features into site drainage plans that would reduce impermeable surface area, increase surface water infiltration, and minimize surface water runoff during storm events. The impact to water quality depends almost entirely on the effectiveness of best management practices and engineering controls to prevent pollution, contaminated runoff, leaks, or spills from entering the storm drain system and area waterways, especially Santa Rosa Creek. Adherence to the City s Storm Water Low Impact Development Technical Design Manual in developing a site-specific SWPPP based on current best management practices will not result in a cumulative impact that would reduce water quality. The city s trash receptacles and pet waste bag dispensers would also add a level of protection against increased trash and bacterial concerns in the adjoining waterways. The developments within the Specific Plan area and Santa Rosa would utilize municipal water sources, which include the use of some groundwater to supplement potable water sources. As discussed above, according to the Water Supply Assessment for the North Santa Rosa Station Area Specific Plan, the planned municipal supply is adequate to handle the projected cumulative water demand increase resulting from growth in Santa Rosa as well as in the Specific Plan area, and no depletion of the groundwater aquifer is anticipated. Therefore, the Specific Plan would not contribute to a cumulative impact to groundwater resources. Taken together, existing General Plan policies and requirements reduce the project s potential to contribute to cumulative hydrologic and water quality impacts to a level that is less than cumulatively considerable. Mitigation Measures None required. Draft Environmental Impact Report April