IV. ENVIRONMENTAL IMPACT ANALYSIS F. HYDROLOGY & WATER QUALITY

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1 IV. ENVIRONMENTAL IMPACT ANALYSIS F. HYDROLOGY & WATER QUALITY INTRODUCTION This section was prepared by staff at Balance Hydrologics, Inc. (Balance). Documents reviewed by Balance staff during preparation of this section include the following: Revised Geotechnical Feasibility Study (Letter), Treadwell & Rollo, November 10, Geotechnical Feasibility Study, Treadwell & Rollo, December 3, Supplementary Geotechnical Feasibility Study, Treadwell & Rollo, March 22, Flood Insurance Rate Map, City of Berkeley, FEMA, Stormwater Drainage Plan, City of Berkeley, City of Berkeley Public Works Dept., Hydrology and Hydraulics Criteria Summary for Western Alameda County, D.J. Labelle and O.H. Kawar, Phase I Environmental Site Assessment, Levine-Fricke, November 18, Results of Limited Soil and Groundwater Investigation, Levine-Fricke, January 21, Soil Survey of Alameda County, Western Part, L.E. Welch, ENVIRONMENTAL SETTING Regulatory Setting Water Quality The California State Water Resources Control Board (SWRCB) and the nine Regional Water Quality Control Boards (RWQCBs) have the authority in California to protect and enhance water quality, both through their designation as the lead agencies in implementing the Section 319 non-point source program of the Federal Clean Water Act and from the State s primary water-pollution control legislation, the Porter-Cologne Act. The San Francisco Bay RWQCB Region 2 office guides and regulates water quality in streams and aquifers within portions of the nine counties surrounding the San Francisco Bay through designation of beneficial uses, establishment of water-quality objectives, administration of the National Pollution Discharge Elimination System (NPDES) permit program for stormwater and construction site runoff, and Section 401 water-quality certification where development results in fill of jurisdictional wetlands or waters of the U.S. Page IV.F-1

2 The 1987 amendments to the Clean Water Act [Section 402(p)] provided for U.S. Environmental Protection Agency (U.S. EPA) regulation of several new categories of non-point pollution sources within the existing NPDES program. Phase I of the stormwater runoff program relied on NPDES permit coverage to address urban runoff discharges from medium to large municipal separate storm systems (MS4s) located in cities or counties with populations of 100,000 or more, from plants in industries recognized by the U.S. EPA as being likely sources of stormwater pollutants, and from construction activities that disturb more than five acres. The U.S. EPA has delegated management of California s NPDES permit program to the SWRCB and the RWQCB. The Phase II Final Rule, which took effect on March 10, 2003, extended permit coverage to certain regulated small MS4s and construction sites that disturb one or more acres, including smaller sites that are part of a larger common plan of development or sale. For those projects that result in the disturbance of more than one acre of land during construction, the applicants of those projects are required to apply for coverage under the NPDES Construction Activities general permit by submitting a Notice of Intent to the State Board. Administration of these permits has not been delegated to cities, counties, or the RWQCBs but remains with the SWRCB. San Francisco Bay Water Quality Control Plan In addition to the NPDES permitting program, the RWQCB regulates water quality in the Bay Area in accordance with the 1995 Water Quality Control Plan (Basin Plan). The Basin Plan presents the beneficial uses that the RWQCB has designated for significant surface waters, aquifers, and wetlands, as well as the water-quality objectives and criteria that must be met to protect these uses. The Basin Plan designates specific existing beneficial uses for the Central San Francisco Bay, including: a) ocean, commercial, and sport fishing, b) estuarine habitat, c) industrial service supply, d) fish migration, e) navigation, f) preservation of rare and endangered species, g) non-contact water recreation, h) shellfish harvesting, i) fish spawning, and j) wildlife habitat. Project storm runoff will be discharged to the existing stormwater drainage system and subsequently the San Francisco Bay. High flows within the University Avenue storm drain, downstream of the project site, are diverted to Aquatic Park and subsequently to the San Francisco Bay. Wildlife habitat, particularly fish and waterfowl habitat, is the beneficial use most sensitive to water quality impacts from the proposed project. Pollution from pesticides, fertilizers, metals, and hydrocarbons in urban runoff can directly and indirectly affect sensitive fish and bird species and their offspring. Provision C.3 Municipal Stormwater Permit The Alameda Countywide Clean Water Program (ACCWP), a consortium of local municipalities and County agencies, was first issued a county-wide NPDES permit in The Program s comprehensive stormwater management plan included a model stormwater ordinance, which the City of Berkeley adopted and promulgated in the Berkeley Municipal Code Chapter 17.20, and conditions of approval for development and redevelopment projects to reduce impacts to stormwater quality and local waterways Page IV.F-2

3 to the maximum extent practicable. The C.3 provisions of the recently-amended (February 2003) NPDES permit further enhance these requirements by requiring that best management practices (BMPs) to treat stormwater runoff be designed to meet specific criteria. Existing Site Conditions Balance staff visited the project site on September 14, Based on existing site topography 1, the elevation of the site is approximately 18 feet above mean sea level. The project site is currently occupied by two buildings operated as restaurants (Brennan s and Celia s) and a vacant historic former Southern Pacific Railroad train depot (former train depot) with ground-level, asphalt parking throughout. The three existing structures have limited landscaping around the perimeter of each building. In fact, approximately 90 to 95 percent of the property is impervious and covered by concrete or asphalt pavement from prior development. Stormwater runoff sheetflows across the site and towards adjacent streets and subsequently to the municipal storm drain. Existing on-site stormwater BMPs to control the quantity and/or quality of stormwater runoff from the site are limited or do not exist. Only small portions (approximately 15 to 20 percent) of roof runoff from existing buildings drain to a planter or gravel substrate. The remaining roof runoff is drained directly to the parking lot or an adjacent street. A few raised planters on site (less than five percent of total project area) support full grown trees, but do not receive stormwater runoff. Balance observed that the area on the south side of Brennan s Restaurant, used for trash storage and disposal, drains to the street and subsequently to the stormwater drain on University Avenue. These observations suggest that the existing stormwater runoff quality may be degraded as a result of contact with pollutants likely associated with trash storage and disposal areas. Recent renovations of the train platform, under University Avenue Bridge, have improved drainage of a pedestrian walkway and improved (planted) pervious areas immediately around the former train depot. Drainage According to the City of Berkeley Stormwater Drainage Plan, the project site has access to the existing stormwater system, surrounding three sides of the property and contiguous: 1) a 12-inch diameter storm drain beginning at the intersection of Fourth Street and Addison which drains to; 2) an 18-inch diameter storm drain along Third Street (Union Pacific Railroad), which in turn, drains to; 3) a 7.5-foot diameter storm drain along University Avenue 2. Ultimately, the storm drain system discharges into the central San Francisco Bay several blocks to the west 3. Although the municipal stormwater system surrounds three sides of the property, the City of Berkeley s stormwater drainage plans and field observations by Balance staff identify only two storm drain inlets. Runoff from the majority of the project site drains via sheet and gutter flow until they reach the two identified storm drain inlets at: 1) the corner of Addison and Third Christiani Johnson Architects, site survey, unknown scale, 6/8/05. City of Berkeley Stormwater Drainage Plan, City of Berkeley, 1974, revised Akagi, Daniel, City of Berkeley Public Works Department, personal communication with Balance staff, September 15, Page IV.F-3

4 Streets, and 2) University Avenue between Third and Fourth Streets. Approximately 25 to 30 percent of the site drains towards Addison Street and discharges to the storm drain inlet identified at Addison/Third Streets. Approximately 70 to 75 percent of the site drains toward the University Avenue storm drain inlet. Because no storm drains exist along Fourth Street, runoff from the site is conveyed along Fourth Street via gutter flow to University Avenue and south to the storm drain inlet between Third and Fourth Streets. An estimated one percent of the site, the parking area just south of the former train depot, appears to have no positive drainage and likely ponds storm runoff on-site. Evaporation appears to be the only means of removing ponded water from this area. The University Avenue storm drain, which is sufficient to convey storm flows from large portions of downtown Berkeley, discharges to the San Francisco Bay immediately west of Interstate-80. Downstream of the project site the University Avenue storm drain is equipped with a high flow 4 bypass weir at Second Street west or downstream from the project site. During high runoff events, a portion of flow is allowed to bypass to a culvert that discharges to Aquatic Park lagoon and subsequently to the San Francisco Bay. The University Avenue storm drain west of Second Street is susceptible to tidal influence because of its location and elevation at the Bay. Flooding The Flood Insurance Rate Map for West Berkeley indicates that the site is not located within the 100-year flood hazard area 5. Thus, the risk of flooding within the project area is limited to shallow ponding during intense or prolonged rains. Geology and Soils The project site lies approximately 2,000 feet east of the San Francisco Bay on an alluvial plain a thick layer of earthen materials transported and deposited by streams draining the East Bay Hills. The area likely fluctuated historically between lagoon-type waters and depositional environments. The National Resource Conservation Service (NRCS) 6 soil survey for Alameda County, Western Part, classifies the area including the project site as urban land, mainly heterogeneous fill which has not been assessed for engineering properties. 7 During development, fill was commonly used to extend the West Berkeley shoreline westward into the Bay to accommodate urban expansion. The Treadwell & Rollo geotechnical feasibility study identified 4 to 8 feet of fill on the project site with a ground surface elevation of High flow was not specifically defined by the City of Berkeley Public Works Department but based on experience by our engineering staff. It is assumed to be equivalent to a flow greater than the 2.0 year recurrence event. Flood Insurance Rate Map, City of Berkeley, California, FEMA, Formerly the Soil Conservation Service (SCS) Soil Survey of Alameda County, California, Western Part, Welch, L.E., Page IV.F-4

5 approximately 15 feet above mean sea level. The fill is characterized as dense sand and/or clayey sand. A two-foot thick stiff clay layer was encountered at a depth of about seven feet. Geotechnical analysis of this layer estimates it to be moderately to highly compressible under a moderate increase in overburden stress. Beneath the fill, soil conditions exhibit alternating layers of stiff clay and sandy clay to dense clayey sand to the maximum explored depth of 50.5 feet. Groundwater Based on the Phase I Environmental Site Assessment (Phase I ESA) completed in 2003 by Levine-Fricke, there are no existing monitoring or water wells on site. Treadwell & Rollo completed two separate onsite subsurface investigations as part of a geotechnical feasibility study and recorded depths to groundwater. Initial ground-water levels were measured between 9.5 and 10 below ground surface in early October 2003, a period when we might suspect the deepest annual depth to ground-water because it is the end of the dry season. The 2003 water year 8 registered 19 inches in Berkeley 9, which is nearly five inches below the annual long-term average (23.5 inches). 10 This fact might also contribute to the greater distance or depth to groundwater. In March of 2004, during the wet season, ground-water levels rose to 7.5 feet below ground surface. However, March of 2004 was a dry month and the 2004 water year was, again, a below average precipitation year (18.5 inches) 11. Therefore, in wet or very wet years (e.g., 1982, 1998) we might suspect shallower depths to ground water on-site. The City of Berkeley has observed ground water near the surface within the near vicinity of the site in a very wet year (1998) 12. Based on existing ground-water studies and on site investigations it is reasonable to assume groundwater fluctuates season to season and/or dry year to wet year. Water Quality The site is currently occupied with two restaurants and the vacant former train depot. The Phase I ESA conducted for the site by Levine-Fricke did not identify any recognized environmental conditions (RECs) on-site or any documented unremediated hazardous material cases within proximity of the site or hydraulically upgradient of the site. However, it is possible that the adjacent or surrounding properties could use, store, generate or dispose of regulated hazardous substances or waste or have the potential to alter water quality. Therefore, a limited soil and ground-water investigation was conducted by Levine- Fricke in 2004 to assess the current soil and ground-water quality. Levine-Fricke analyzed subsurface The 2003 water year is defined as the period of measured rainfall beginning on October 1, 2002 and ending September 30, Balance rain gauge, Balance Hydrologics Office, 841 Folger Avenue, Berkeley, CA Berkeley, California, period of record: 86 years, National Climate Data Center COOP station No Balance rain gauge, 2004 water year (October 1, 2003-September 30, 2004). Aikenhead, Diana, City of Berkeley Public Works Department, personal communication with Balance staff, September 12, Page IV.F-5

6 soils to five feet below ground surface for a suite of metals and pesticides and groundwater for volatile organic compounds, solvents, and petroleum hydrocarbons. The analytical results found the presence of pesticides and metals in soil samples but at concentrations below environmental screening levels. Environmental screening levels were established by the RWQCB. Constituents detected below environmental screening levels are assumed to not pose a significant threat to human health and the environment. Constituents analyzed in ground water were not detected above laboratory reporting limits. Sediment is another water quality concern. However, existing sediment contributions are likely minimal due to the relatively flat topography, impervious cover, and low erosion potential of soils on the project site. ENVIRONMENTAL IMPACTS Thresholds of significance In accordance with Appendix G of the CEQA Guidelines, the proposed project could have a significant environmental impact if it would: Violate any water quality standards or waste discharge requirements; Substantially deplete ground-water supplies or interfere substantially with ground-water recharge such that there would be a net deficit in aquifer volume or a lowering of the local ground-water table level (e.g., the production rate of preexisting nearby wells would drop to a level which would not support existing land uses or planned uses for which permits have been granted); Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, in a manner which would result in substantial erosion or siltation on- or off-site; Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, or substantially increase the rate or amount of surface runoff in a manner which would result in flooding on- or off-site; Create or contribute runoff water which would exceed the capacity of existing or planned stormwater drainage systems or provide substantial additional sources of polluted runoff; Otherwise substantially degrade water quality; 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; Page IV.F-6

7 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; Be inundated by seiche, tsunami, or mudflow. Hydrology & Water Quality Issues Not Further Discussed Violate Water or Wastewater Discharge Standards As discussed in the Initial Study (refer to Appendix I), the proposed project does not include any pointsource discharge. Project development would conform to all requirements of the Regional Water Quality Control Board, Uniform Building Code and Berkeley Municipal Code Title 17 (Water and Sewers) and would not result in un-permitted discharges into the sanitary sewer and stormwater systems. Thus, the project would not violate any water quality or waste discharge standards. No further analysis of this issue is required. Deplete Ground-water Supplies Much of the project site is currently impervious, and the limited exposed soils have low permeabilities; infiltration of runoff is negligible. Most stormwater sheet flows across the site and enters the municipal storm drain system serviced by East Bay Municipal Utilities District (EBMUD). The existing landscaping might increase recharge to the local ground-water aquifer. However, low soil permeability of local soils prevents or greatly reduces infiltration and percolation of stormwater. According to the preliminary site plan the proposed project would slightly decrease the amount of impervious surface at the project site through the use of porous concrete, vegetated biofilters, landscape plantings, and pavers 13. Based on these findings, project impacts to groundwater and ground-water recharge would be less than significant. No further analysis of this issue is required. Impact Ground-water Quality The groundwater within the local of the site is not useable for potable domestic supply. Pervious areas of the proposed project will be underlain by closed treatment systems which are underdrained to the municipal storm drain system. Given these proposed project elements and the soil properties discussed above, storm water is unlikely to impact groundwater. Therefore, project impacts to ground water quality would be less than significant. 13 David Johnson, Christiani Johnson Architects, personal communication with Balance staff, September 20, Page IV.F-7

8 Alter Drainage Patterns The proposed project would change the drainage patterns on the project site by grading the project site, removing existing structures, and adding new structures. The project site in its current condition is 95 to 98 percent impervious, and all drainage is directed to two municipal storm drains, one located at the corner of Addison Street and Fourth Street, and the other is located along University Avenue between Third and Fourth Streets. All the runoff associated with the proposed project would be either directed to landscaped areas and/or pre-manufactured stormwater quality best management practices (BMPs) for infiltration and water quality purposes or directed to the two existing storm drains. As such, the alteration of the existing drainage pattern would not result in substantial erosion or siltation on- or off-site. Therefore, project impacts related to this issue would be less than significant, and no further analysis of this issue is required. 100-year Flood Hazards As discussed in the Initial Study and previously, the project site is not located 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. Thus, no further discussion of this issue is required. Exposure to Flooding As discussed in the Initial Study, no dams or levees are located in the project site area. Therefore, the project would not expose people or structures to a significant risk or loss, injury or death involving flooding, as a result of the failure of a levee or dam. Inundation by Seiche, Tsunami, or Mudflow As discussed in the Initial Study, seiches are standing waves created by seismically induced ground shaking (or volcanic eruptions or explosions) that occur in large, freestanding bodies of water. A tsunami is a series of waves that are caused by earthquakes that occur on the seafloor or in coastal areas. The project site is not located near the open ocean of the Pacific Ocean, and therefore, would not be subject to inundation by seiche or tsunami. The project area is relatively flat and does not contain any hillside terrain; therefore, there is no potential for the project site to be inundated by a mudflow. Thus, no further discussion of this issue is required. Page IV.F-8

9 Project Impacts Water Quality Construction Impacts During construction, sediment is typically the constituent of greatest potential concern due to potential erosion during grading and removal and re-compaction or replacement of fill areas. Development of the proposed project would require dewatering activities during construction if the final construction plans include excavation below 7 feet below ground surface. Under the Alameda Countywide NPDES Municipal Stormwater Permit conditionally exempted discharges include uncontaminated pumped groundwater and foundation drains. The Phase I and Phase II Environmental Site Assessments indicated groundwater and soil beneath the site were clean or contained constituents of concern at levels below RWQCB established environmental and human health risks. Adjacent properties were not identified as recognized environmental conditions under the local, state, and federal environmental databases. The potential for encountering contaminated ground-water during dewatering is unlikely, but water quality impacts could be significant due to sedimentation. Therefore, project impacts to water quality associated with dewatering, if necessary, could be potentially significant. Other pollutants that could affect surface-water quality during the project construction phase include petroleum products (gasoline, diesel, kerosene, oil and grease), hydrocarbons from asphalt paving, paints and solvents, detergents, fertilizers, and pesticides. As a condition of project approval and prior to obtaining a grading permit, the City of Berkeley would require the project applicant to prepare and submit a Stormwater Pollution Prevention Plan (SWPPP) in accordance with the NPDES General Construction and Municipal Stormwater Discharge Program permits. The SWPPP would detail the treatment measures and BMPs that would be implemented during the construction phase of project development to minimize pollutant discharges such as petroleum products, paints and solvents, detergents, fertilizers, and pesticides in stormwater runoff to the maximum extent practicable. The erosion control plan, which forms a significant portion of the construction-phase controls required in a SWPPP, typically includes components such as: phasing of grading, limiting areas of disturbance, designation of restricted-entry zones, diversion of runoff away from disturbed areas, protective measures for sensitive areas, outlet protection and provision for revegetation or mulching. The plan also prescribes treatment measures to trap sediment once it has been mobilized, at a scale and density appropriate to the size and slope of the catchment. These measures typically include: inlet protection, straw bale barriers, straw mulching, straw wattles, silt fencing, check dams, terracing, and siltation or sediment ponds. The project site is very flat, with clayey soils, and a low risk of erosion. Thus, potential constructionphase impacts due to erosion would be easily avoided through preparation and implementation of the erosion control plan (consistent with recommended design criteria) that would be included as part of the Page IV.F-9

10 SWPPP. Other potential construction-phase pollutants would be controlled to levels below significance through project management and housekeeping measures, as described in the SWPPP that the project applicant would be required to prepare. The City of Berkeley would review the SWPPP to verify that the BMPs are designed in compliance with the appropriate criteria, as set forth in the Alameda Countywide NPDES permit and other recommended guidance, such as the Stormwater Best Management Practices Handbook for Construction. The RWQCB would enforce compliance with the regulatory requirements of the NPDES General Construction and Municipal Stormwater Discharge permits through site inspections. Compliance the permit requirements would ensure that project impacts to water quality associated with other construction activities (other than dewatering) would be less than significant. Operational Impacts Once the project has been constructed, the same types of pollutants mentioned previously could be mobilized in stormwater runoff from roadway areas, driveways, and landscaping, and in dry-season nuisance flows from landscape irrigation and other activities, such as pavement washing. Sediment is not typically a post-construction concern at mixed-use developments because these sites are usually paved, landscaped, and provided with engineered drainage infrastructure. As mentioned above, preparation of a SWPPP would be required. The SWPPP includes post-construction BMPs used to reduce pollutant loadings in stormwater runoff once the site is occupied, sets forth the BMP monitoring and maintenance schedule, and identifies the responsible entities during the construction and post-construction phases. The City of Berkeley would review the SWPPP to verify that the BMPs are designed in compliance with the appropriate criteria, as set forth in the Alameda Countywide NPDES permit and other recommended guidance, such as the Stormwater Best Management Practices Handbook for New Development and Redevelopment. The RWQCB would enforce compliance with the regulatory requirements of the NPDES General Construction and Municipal Stormwater Discharge permits through site inspections and review of annual reports and other ACCWP document submittals. Balance staff reviewed the preliminary project site drainage, grading plans, and site constraints to assess practicality and effectiveness of BMPs (which would be outlined in the SWPPP) in order to comply with the NPDES requirements. Post-construction stormwater treatment controls can be categorized as either flow-based (e.g., biofilters) or volume-based (e.g., detention basin, wet pond). The limited space available at the project site would be insufficient for volume-based control measures for the project. Therefore, flow based controls are only considered for the project site and are discussed below. Post-construction water quality enhancement measures in the Start at the Source handbook and the recently revised California Stormwater BMP Handbook for New and Redevelopment emphasize site design to reduce impervious area coverage, source control to prevent pollutants from becoming entrained Page IV.F-10

11 in runoff, and infiltration to reduce peak flows and enhance water quality. The City of Berkeley prefers stormwater treatment controls that are integrated into the site design (e.g., porous pavement, modular pavers, biofilters) rather than manufactured treatment controls, but they recognize that re-development projects are often space-limited 14. Balance s review of the project site plans noted that the design of the proposed project already exhibits a reduced building footprint (when compared to a single-story building with the same square footage) by creating a multi-story project that also includes a interior parking areas to accommodate a portion of the parking requirement. These two features would reduce water quality impacts by minimizing surface exposure. Balance also recognized the site constraints that inhibit specific water quality BMPs. For example, treatment BMPs that promote infiltration of runoff to the aquifer, such as pervious pavements or infiltration trenches and bioswales, would be of limited use at this site due to the slow permeability of local soils and close proximity to groundwater, so compliance with the ACCWP NPDES permit requirement for runoff treatment prior to discharge would require that other types of stormwater treatment controls be incorporated into the project design. The project would treat 100 percent of the site s stormwater runoff in a two-year return event using a combination of integrated and manufactured treatment controls 15. The project proposes pervious parking stalls for the street level parking, constructed with a porous filter media subdrained to the municipal stormdrain. Other street level impervious areas are proposed to drain to: 1) two biofilters located between the proposed North Building and existing former train depot; and 2) porous concrete with a treatment matrix subdrain located between the proposed South and North Buildings. The biofilters include a grassy swale which infiltrate to a closed system composed of treatment media and subdrained to the municipal storm drain. Pollutant concentrations are reduced by physical filtration, volatilization, plant uptake and adsorption onto soil particles, while the swales also provide aesthetic benefits. Porous concrete drains to a closed treatment system subdrained to the municipal storm drain system. In larger events, these BMPs are equipped with overflow drain inlets with an on-site storm drain system discharging to the municipal storm drain on the corner of Addison and Third Streets. Together, the pervious pavers, the biofilters, and porous concrete BMPs are sized to treat over 20,000 square feet of impervious area up to a two-year recurrence event 16. Given that more than 50 percent of the proposed project would generate stormwater runoff from roof area, a portion of roof runoff, where feasible, would be piped directly to the biofilters via rainwater leaders. Remaining roof runoff that cannot be directed or piped to the biofilters would drain to pre-manufactured mechanical treatment units. These pre-manufactured BMPs are likely to be located on the south and east sides of the proposed buildings, sides opposite from the biofilter and porous concrete BMPs Aikenhead, Diana, City of Berkeley Public Works Department, to Balance staff, July McGuire, Patrick, BKF Engineers,, personal communication with Balance staff, November 3, 2005 McGuire, Patrick, BKF Engineers, personal communication with Balance staff, November 15, 2005 Page IV.F-11

12 The interior parking facilities would be required to drain to the city sanitary sewer system. Runoff from trash storage and disposal areas would also drain directly to the sanitary sewer system. When the City agrees that the project s water quality treatment BMPs are in compliance with the ACCWP NPDES permit for municipal stormwater discharges, then the project owner and the City of Berkeley shall enter into a Stormwater Treatment Measures Maintenance Agreement. The property owner shall be responsible for all costs associated with proper operation and maintenance of all stormwater BMPs as outlined in a prepared Stormwater Best Management Practices Operation and Maintenance Manual. The Stormwater Best Management Practices Operation and Maintenance Manual shall include a records retention program such that the City of Berkeley would be able to verify that maintenance is performed on a routine basis. Overall, implementation of these proposed drainage improvements in concert with compliance with the SWPPP, City Municipal Code requirements, and the monitoring and maintenance agreement would provide adequate protection of water quality and ensure that project impacts related to water quality would be less than significant. Mitigation Measures (Water Quality) Because the proposed project could potentially result in significant water quality impacts associated with dewatering activities, the following mitigation measure is required: IV.F-1: If construction plans include excavation to seven feet below ground surface, prior to issuance of a grading permit, the project applicant shall prepare and submit to the City for approval a dewatering plan that incorporates the following (at a minimum): Before groundwater can be discharged to the municipal stormdrain system, all dewatering runoff shall be passed through a water quality control device, such as a silt fence to minimize or reduce sediment from entering the stormdrain system. Discharge shall occur under the following conditions: i) dewatering activities are conducted during non-storm time periods; ii) water is discharged directly to the municipal stormdrain and shall not be conveyed via gutter flow or sheet flow to the nearest stormdrain inlet; and iii) water is discharged to a storm drain with adequate capacity to convey the water through the system (e.g., University Avenue storm drain inlet). Increase in Runoff Resulting in Flooding/Insufficient Storm Drain Capacity As discussed above, the proposed project would slightly decrease site imperviousness, an overall benefit of the project. Based on the preliminary site plans, Balance staff modeled pre- and post-project runoff using the Rational Method and following the guidelines set forth by the Alameda County Drainage Page IV.F-12

13 Manual (Table 1). Balance staff modeled pre-project runoff to be 3.9 cubic feet per second for the 5-year recurrence event, and post-project runoff to be 3.8 cubic feet per second for the same event (a 2.6 percent reduction). The pre-project runoff for the 25-year recurrence event was modeled to be 5.5 cubic feet per second and reduced to 5.4 cubic feet per second for post-project runoff (a 1.8 percent reduction). The 100-year recurrence event was reduced from 6.8 to 6.7 cubic feet per second from pre-project to the post project conditions (a 1.5 percent reduction). Based on Balance s analysis, the proposed project appears to maintain or slightly reduce the peak runoff levels for each of these design storms. The site drainage plans propose to mimic pre-project drainage conditions where a portion of the site drains to the University Avenue storm drain inlet and a portion drains to the Addison/Third Streets storm drain inlet. Since post-project flows would be equal to or less than existing conditions and mimic preproject drainage patterns, project impacts related to this issue would be less than significant. Mitigation Measures (Increase in Runoff/Flooding) Because no significant impacts related to increase in runoff resulting in flooding/insufficient storm drain capacity would occur, no mitigation measures are required. Cumulative Impacts Other related development in the City of Berkeley within proximity of the site includes the Read Project, located at 2039 Fourth Street. Similar to the proposed project, this project would result in the disturbance of more than one acre, and as such, the applicant of this project would be required to comply with the NPDES General Construction and Municipal Stormwater Discharge permit requirements, Alameda County design criteria standards, and City Municipal Code requirements to ensure that implementation of these developments would not result in significant water quality impacts. As stated previously, through compliance with the SWPPP, City Municipal Code requirements, and the monitoring and maintenance agreement, water quality impacts of the proposed project would be less than significant. Additionally, the proposed project would maintain or slightly reduce the rate of runoff generated on-site. Therefore, the proposed project would not contribute to cumulative impacts related to water quality or stormdrain capacity/flooding. Therefore, cumulative hydrology and water quality impacts would be less than significant. Mitigation Measures (Cumulative Impacts) Because no cumulative impacts related to hydrology and water quality have been identified, no additional mitigation measures are required. LEVEL OF SIGNIFICANCE AFTER MITIGATION With implementation of the mitigation measure outlined above, project impacts related to hydrology and water quality would be less than significant. Page IV.F-13

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