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HomeMy WebLinkAbout02160029_Sec05-07 Hydrology and Water Quality Project Impacts West Ming Specific Plan - Draft EIR Hydrology and Water Quality Michael Brandman Associates 5.7-1 H:\Client (PN-JN)\0216\02160029\DEIR 9-1\02160029_Sec05-07 Hydrology and Water Quality.doc 5.7 - Hydrology and Water Quality 5.7.1 - Introduction This section of the Draft EIR includes information related to surface water hydrology, flooding, groundwater, and water quality. Preparation of this section of the Draft EIR conforms to the recommendations contained in the Metropolitan Bakersfield General Plan and evaluates additional information specific to the project site. This section is based upon the following documents. • Flood Study, McIntosh and Associates, May 12, 2005. The complete report is contained in Appendix I of the Technical Appendices of the DEIR. • West Ming Specific Plan Lake Report, McIntosh and Associates, August 2005. The complete report is contained in Appendix I of the Technical Appendices of the DEIR. • Hazardous Materials Evaluation, April 2005, McIntosh and Associates. The complete report is contained in Appendix G of the Technical Appendices of the Draft EIR. • Addendum #1 to Geotechnical Feasibility Study and Geological Hazard Study for the West Ming Specific Plan (Sections 11, 13, 14 & portions of 10 &15) In Bakersfield, California. The complete report is contained in Appendix F of the Technical Appendices of the Draft EIR. • Metropolitan Bakersfield General Plan, December 2002. This document is available for review at the City of Bakersfield Planning Department at 1715 Chester Avenue in Bakersfield, CA 93301. • Metropolitan Bakersfield General Plan Final EIR, June 2002. This document is available for review at the City of Bakersfield Planning Department at 1715 Chester Avenue in Bakersfield, CA 93301. 5.7.2 - Environmental Setting Regional Conditions The project site is located within the Kern River watershed. The Kern River drains an approximately 2,420 square mile area in the Sierra Nevada Mountains. Water runoff from the Sierras flows northeast to southwest and enters the San Joaquin Valley through the Kern River Canyon. The Kern River currently has a regulated flow due to the Isabella Dam and Reservoir. The primary purpose of the dam is flood control with the ability to hold back approximately 570,000 acre-feet of water in the reservoir. Downstream of the Kern River Canyon, there are seven diversion weirs in the Bakersfield area. During very wet years, water flows in the river to Buena Vista Lake Bed and then north to Tulare Lake or into the California Aqueduct (City of Bakersfield 2002 GPEIR p.4.8-1). The Metropolitan Bakersfield General Plan area is located above a series of aquifers. These aquifers are part of the larger groundwater basin called the Southern San Joaquin Groundwater Basin. The Project Impacts Hydrology and Water Quality West Ming Specific Plan - Draft EIR 5.7-2 Michael Brandman Associates H:\Client (PN-JN)\0216\02160029\DEIR 9-1\02160029_Sec05-07 Hydrology and Water Quality.doc primary groundwater aquifer below the Metropolitan Bakersfield area is made up of unconsolidated sediments (City of Bakersfield 2002 GP V-16). Surface Water Hydrology and Drainage The natural drainage of the project site is generally to the southwest, along and parallel to the main drainage channel of the Kern River. Relief across the site is fairly gentle, with only minor variations in elevation, which do not concentrate flows on the project site. The project site does not currently contribute surface flows off-site. The only natural drainage feature in the vicinity of the project site is the Kern River, which is located adjacent to the northwestern portion of the project site. The Kern River consists of primary and secondary floodways: The primary floodway is the minimum channel area required to contain a 100-year flood flow of 10,200 cubic feet per second (cfs); and, the secondary floodway is the area where floods would occur if various flood structures, such as dikes or levees, were to fail. The project site is traversed by a portion of the Kern River Canal, as discussed below. The nearest water bodies are as follows: Buena Vista Lake is located approximately 8 miles southwest of the site and Lake Isabella is located approximately 40 miles northeast of the site. The Pacific Ocean is located approximately 70 miles southwest of the site. The Kern River Canal is the only major surface water feature existing on the project site. It is a concrete lined, trapezoidal channel that conveys water across the site. It enters the project site near the northeast corner and flows southwesterly, exiting the project area approximately 4,000-feet south of the extension of Ming Avenue. The Kern River Canal runs parallel to the Kern River Channel in a northeast to southwest direction. The Kern River Canal crosses Allen Road and the dirt road extension of South. Renfro Road and is present within the northern portion of the project site, north of White Lane. This canal is operated by the City of Bakersfield and is contracted to deliver water to the Buena Vista Water Storage District for 6 months of the year. The canal is empty the remaining six months. There are no documented cases or recorded floods for the project area along the Kern River Canal. An abandoned canal, the former James Canal, is located just north of White Lane, which crosses South Allen Road, traversing from southwest to northeast. Flooding Kern River Due to the proximity of the project site, topography, and current levee system, a portion of the project site is designated by the Federal Emergency Management Agency (FEMA) on the Flood Insurance Rate Map (FIRM) as being within the 100-year frequency flood zone (see Exhibit 5.7-1). Exhibit 5.7- 1 shows the northwest portion of the site, north of the Kern River Canal as well as a small area in the southwest portion of the site as currently within a FEMA Zone A which is defined as an area within a 100-year flood. The remainder of the project site is located in FEMA Zone B which is an area of 500-year flood and FEMA Zone C which is an area determined to be outside the 500-year floodplain. FEMA requires a Letter of Map Revision for development within Zone A in order to remove requirements for flood insurance, which includes a flood study and plans for levee construction. Project Impacts West Ming Specific Plan - Draft EIR Hydrology and Water Quality Michael Brandman Associates 5.7-5 H:\Client (PN-JN)\0216\02160029\DEIR 9-1\02160029_Sec05-07 Hydrology and Water Quality.doc An existing levee system is parallel to the Kern River. The existing levee is located along Ming Avenue adjacent to the northern boundary of the project site. The levee extends from Stockdale Highway and terminates approximately one mile west of South Allen Road along Ming Avenue. The existing levee does not extend along the entire 1.5 mile length of the northern boundary along Ming Avenue. Lake Isabella Dam Lake Isabella Dam is located approximately 40 miles northeast of the project site. According to the Metropolitan Bakersfield General Plan, the project site is located within the Lake Isabella Dam Failure Inundation Area. Inundation of the project site from dam failure would take 8 hours. According to the Metropolitan Bakersfield General Plan EIR, failure of the dam would result in flooding 60 square miles of the Metropolitan Bakersfield area. The City of Bakersfield Flood Evacuation Plan provides procedures for the protection of health, safety, welfare of the people and property from potential dam inundation areas. Groundwater The City of Bakersfield operates a 2,800-acre recharge facility located southwest of the project site. This recharge facility allows the City to bank water during surplus rainfall years by recharging the groundwater table. “Safe Yield” is an important goal of the City to ensure that groundwater levels remain stable and to regulate the use of groundwater supplies to prevent depletion of recharge volume. The northwest portion of the project site has been used for groundwater recharge by the Kern County Water Agency. Due to the fluxuations in the amount of surface water that is recharge into the groundwater basin in the project vicinity, the depth of the groundwater table below the project site varies. According to the Kern County Water Maps (Kern County Water Agency 2003), the depth to the unconfined aquifer in the fall of 2000 was approximately 80 feet below ground surface. In the northwestern corner of the project site, groundwater was encountered at a depth of 15 feet below ground surface (SEI, April 2005). According to SEI, the normal groundwater levels at the project site are greater than 50 feet below ground surface. Water Quality Existing and past farming and oil-related activities on the project site have reduced surface water quality on the project site. Another source of surface water degradation is from typical automobile- related contaminants (i.e., oil, grease, and tire particles) as may be deposited on the onsite access roads. Project Impacts Hydrology and Water Quality West Ming Specific Plan - Draft EIR 5.7-6 Michael Brandman Associates H:\Client (PN-JN)\0216\02160029\DEIR 9-1\02160029_Sec05-07 Hydrology and Water Quality.doc 5.7.3 - Thresholds of Significance According to Appendix G of the State CEQA Guidelines, a project would normally have a significant effect on the environment 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 (e.g., the production rate of pre-existing nearby wells would drop to a level which would not support existing land uses or planned uses for which permits have been granted); • Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, in a manner which would result in substantial erosion or siltation on- or off-site; • 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; or • Create Inundation by seiche, tsunami, or mudflow. 5.7.4 - Project Impacts and Mitigation Measures The proposed project would have the potential to affect surface hydrology, flooding, groundwater, and water quality. Following is a discussion of the project impacts that correspond to the thresholds previously identified in Section 5.7.3. Impact 5.7.A: The proposed project could violate water quality standards or waste discharge requirements. Short-Term Construction Impacts Implementation of the proposed project would result in construction activities that could have the potential to contribute to pollutants in surface waters off-site potentially impacting the water quality within the Kern River. Generally, construction-phase activities could generate pollutants such as increased silts, debris, chemicals, and dissolved solids related to the following activities: Project Impacts West Ming Specific Plan - Draft EIR Hydrology and Water Quality Michael Brandman Associates 5.7-7 H:\Client (PN-JN)\0216\02160029\DEIR 9-1\02160029_Sec05-07 Hydrology and Water Quality.doc • Grading - disruption of surface soils and increased susceptibility to erosion; • Building Construction - Use of sealants, glues; wood preservatives, oils, concrete and the generation of debris related to construction activities; • Painting - Paint fragments and stucco flakes; • Construction Equipment and Vehicle maintenance -Washing, chemical degreasing Since construction activities could result in increased pollutants to surface water, the proposed project could result in a short-term potential to degrade surface water quality that could eventually be conveyed offsite and potentially to the Kern River. This is a potentially significant impact. Long-Term Operational Impacts Long-term operations of the proposed project would increase the potential of stormwater runoff transporting contaminants from roadway surfaces, lawns, driveways, parking lots, and other exposed structural and landscape surfaces into the storm drain system. Typical urban runoff contaminants (i.e., oil, grease, surfactant, heavy metals, solvents, pesticides, nutrients, or fecal coliform bacteria) can be expected within runoff. The proposed project includes a drainage system that includes retention and detention basins so that stormwater flows from the project site are retained on the site. The project’s basin system includes at least one basin for each 80 acres which is consistent with the City of Bakersfield requirements. In addition, the retention basins would be constructed so that they could fully drain within 7 days after a storm event to be consistent with City policy. There are some detention basins proposed that will detain water until the storm event passes and then pumps the stormwater to a retention basin. The detention basins proposed adjacent to the Kern River Canal include pumps that would convey water to the Kern River Canal during high frequency storm events. The system of detention and retention basins on the project site would retain the majority of the surface water generated during storm events. During the low frequency storm events, the storm water flows generated on the project site would be retained onsite in the retention basins and percolate to the groundwater basin. This percolation would retain the contaminants within the retention basins. During the high frequency storm events, the retention basins would continue to allow stormwater to percolate in the groundwater basin while the pumps at the proposed detention basins facilities would regulate the amount of stormwater that is retained onsite. The detention basins would provide an enhancement of the surface water quality through the settlement of contaminants prior to pumping the stormwater into the Kern River Canal. The system proposed as part of the project would reduce potential long-term surface water quality impacts to less than significant. Mitigation Measures 5.7.A.1 Prior to grading plan approval, the project applicant shall prepare a Stormwater Pollution Prevention Plan (SWPPP) that conforms to the State Water Resources Project Impacts Hydrology and Water Quality West Ming Specific Plan - Draft EIR 5.7-8 Michael Brandman Associates H:\Client (PN-JN)\0216\02160029\DEIR 9-1\02160029_Sec05-07 Hydrology and Water Quality.doc Control Board NPDES permit in which the City of Bakersfield is a co-permitee. The SWPPP shall specify Best Management Practices (BMPs) to prevent construction- related pollutants from reaching storm water and all products of erosion from moving off-site. The SWPPP shall require approval by the State Water Resources Control Board and verification of approval provided to the City of Bakersfield Planning Department. Level of Significance After Mitigation Less than significant. Impact 5.7.B: The proposed project could deplete groundwater supplies or Interfere with groundwater recharge. Project implementation will require additional levees to be constructed by the developer along the northern and western boundaries of the project along Ming Avenue and along the westerly alignment of the future alignment of the West Beltway. The project will include the development of urban uses in an area of the project site that is currently being used for groundwater recharge by the Kern County Water Agency. These northwestern areas on the project site are known as the Pioneer-Central Recharge Area and are currently located within the FEMA 100-year Flood Zone A; however, with the extension and improvement of the existing levee, the project site would be removed from the 100- year flood zone. The northwestern portion of the project site, which is currently functioning as a recharge basin during the rainy season, will be replaced with urban uses that have impervious surfaces and therefore could interfere with groundwater recharge. However, according to Castle & Cooke, there is an agreement in place between Castle & Cooke and the Kern County Water Agency which allows for the property within this recharge area to be developed in accordance with the Specific Plan; in exchange, Castle & Cooke is providing additional groundwater recharge areas to the Kern County Water Agency. Pre-existing water wells would not experience a decline in production that would prevent the support of existing or planned land use for which water use permits have been granted (McIntosh and Associates 2005). The project will increase water demand for residential, commercial, and industrial uses. This is discussed in more detail in Section 5.12, Utilities and Service Systems. A portion of this increased demand will be met with groundwater supplies. The City of Bakersfield will implement policies of the Metropolitan Bakersfield General Plan related to “Safe Yield” as well as the City of Bakersfield’s Urban Water Management Plan during Site Plan Review. According to McIntosh and Associates, the implementation of the proposed project would not result in net deficit in aquifer volume or the lowering of the local groundwater table. Therefore, the proposed project would result in a less than significant impact on the depletion of groundwater supplies. (McIntosh and Associates 2005). Mitigation Measures No mitigation measures are required. Project Impacts West Ming Specific Plan - Draft EIR Hydrology and Water Quality Michael Brandman Associates 5.7-9 H:\Client (PN-JN)\0216\02160029\DEIR 9-1\02160029_Sec05-07 Hydrology and Water Quality.doc Level of Significance After Mitigation Less than significant. Impact 5.7.C: The proposed project could alter the existing drainage pattern of the site or area in a manner which would result in erosion or siltation on- or off-site. Implementation of the proposed project would result in incremental grading on the project site. The grading would alter the existing drainage of the project site. Onsite stormwater flows would be conveyed to the series of detention and retention facilities that are proposed onsite. Construction activities associated with the project could have the potential to cause erosion or siltation leaving construction sites. Erosion could occur if graded slope areas are not stabilized when storms occur. Silt leaving a construction site could be transported within stormwater flows or carried offsite by construction vehicles. Construction activities associated with the project could result in a significant erosion or siltation impact. After construction activities on the project site are completed, the site soils would be stabilized with installation of landscaping and impervious surfaces. The project would substantially increase the area of impervious surfaces on the project site. This increase would result in a substantial increase in the rate and volume of runoff from the developed areas as compared with the agricultural and oil production uses on the site. Although the proposed project would increase stormwater runoff, the landscaping and impervious surfaces that would be installed on the project site would reduce the potential for erosion and siltation on and off the project site. Therefore, implementation of the project would not result in significant long-term erosion or siltation impacts on or off the project site. Mitigation Measures Implementation of Mitigation Measure 5.7.A.1 is required. Level of Significance After Mitigation Less than significant. Impact 5.7.D: The project would not create or contribute runoff water which would exceed the capacity of existing or planned stormwater drainage systems; however, the project could provide additional sources of polluted runoff. The proposed project includes the development of residential, commercial, and industrial uses. These land uses would include a substantial amount of impervious surfaces that would increase surface water runoff during storm events. The project includes a storm drain plan that would convey stormwater into a system of detention and retention basins. The storm drain plan would be designed to accommodate a 100-year flood. As discussed under Impact 5.7.A, the proposed retention and detention facilities would reduce contaminants exiting the site from the long-term operation of the project because the basins would be designed for the stormwater to percolate into the groundwater and the contaminants would remain in the basins. As a result, the project would not impact existing Project Impacts Hydrology and Water Quality West Ming Specific Plan - Draft EIR 5.7-10 Michael Brandman Associates H:\Client (PN-JN)\0216\02160029\DEIR 9-1\02160029_Sec05-07 Hydrology and Water Quality.doc drainage infrastructure. In addition, the project would result in a less than significant impact from the project’s additional sources of pollutant runoff conveyed to offsite areas. Mitigation Measures No mitigation measures are required. Level of Significance After Mitigation Less than significant. Impact 5.7.E: The proposed project could degrade water quality within the proposed onsite 5-acre lake. The proposed project includes a lined 5-acre manmade lake. The lake has two primary functions; one to enhance aesthetics and the second to provide recreation opportunities for the residents of the project vicinity. Accordingly, the applicant is proposing active recreational uses at the lake including fishing, boating (i.e., sail, human-powered, and electric motor-powered), and other types of surface aquatic activity; however, swimming at the lake would be prohibited. The initial lake water as well as the long-term maintenance of the water level at the lake would be by the use of domestic water. The proposed uses of the lake could result in reductions of the quality of the lake water. These uses could result in floating debris, water clarity issues, dissolved oxygen, algae, aquatic plant growth, and insect growth. Activities surrounding the lake could also degrade the water quality of the lake. These activities could result in trash, leaves, oil, grease, and fertilizers from adjacent landscape areas. Therefore, implementation of the proposed project could result in a significant water quality impact on the proposed 5-acre lake. Mitigation Measures 5.7.E.1 Concurrently with submittal of a tentative subdivision map application or other development plan in the northwestern corner of the project site, whichever occurs first, the project applicant shall submit and receive approval of a lake management plan for the proposed 5-acre lake. The management plan shall provide specific methods to achieve a balanced aquatic ecosystem and an aesthetically pleasing lake with minimal insect infestations and uncontrolled algae blooms. The implementation of these methods shall result in water quality that can support the proposed uses of the lake. In addition, the management plan shall provide information on the personnel responsibilities of the long-term maintenance of the lake as well as the entity that will assume financial responsibility for the long-term management of the lake. Level of Significance after Mitigation Less than significant with mitigation. Project Impacts West Ming Specific Plan - Draft EIR Hydrology and Water Quality Michael Brandman Associates 5.7-11 H:\Client (PN-JN)\0216\02160029\DEIR 9-1\02160029_Sec05-07 Hydrology and Water Quality.doc Impact 5.7.F: The proposed project includes the placement of housing and potentially other structures within an area currently designated as a 100-year flood hazard area as mapped on the Federal Emergency Management Agency Flood Insurance Rate Map. A portion of the project site is designated by the Federal Emergency Management Agency (FEMA) on the Flood Insurance Rate Map (FIRM) as being within the 100-year frequency flood zone (see Exhibit 5.6-1). The project includes residential uses and potentially other structures within areas that are currently within the 100-year frequency flood zone. According to FEMA regulations, a Letter of Map Revision that redefines the flood zone based on hydraulic and levee information is required to be submitted to FEMA to show that the proposed housing would be located outside the 100-year flood zone. Since the proposed project includes residential uses and potentially other structures within an area currently designated as a 100-year flood hazard zone, the proposed project could result in a significant flood impact. Mitigation Measures 5.7.F.1 Prior to recordation of a final map, or as otherwise determined by the Building Director, for onsite areas that are currently in 100-year flood hazard area, the project applicant is required to obtain a Letter of Map Revision (LOMR) from the Federal Emergency Management Agency (FEMA). The LOMR shall identify that the area of the proposed development has been removed from the Zone A FEMA designation and submitted to the City of Bakersfield Building Department. Based on the Flood Study prepared by McIntosh and Associates in May 2005, the following improvements are required to remove the majority of the project site from the Zone A FEMA designation. Along the northern boundary of the site, the recently constructed levee shall be extended along Ming Avenue to intersect the proposed West Beltway. The recommended elevation at the intersection, based on the Revised Conditions Model, is 354.0 feet. From the northwestern boundary of the project site, the levee system shall continue to be constructed along the westerly boundary of the site along the proposed West Beltway alignment to 2,800 feet south of the Kern River Canal where it would blend into the natural ground elevation of approximately 349.0 feet. This portion of the levee may be a separate embankment or it may be incorporated into the proposed Beltway. In either case, the project applicant shall construct the levee in accordance with the FIRM - 2 evaluation in the Flood Study prepared by McIntosh and Associates in May 2005. The evaluation established the water surface elevation for the 100-year frequency event. The required levee elevation to meet the requirements of the FEMA is three-feet above the water surface elevation. Project Impacts Hydrology and Water Quality West Ming Specific Plan - Draft EIR 5.7-12 Michael Brandman Associates H:\Client (PN-JN)\0216\02160029\DEIR 9-1\02160029_Sec05-07 Hydrology and Water Quality.doc Due to the need for the Kern River Canal to extend through the future West Beltway alignment, the project applicant shall raise the existing canal levee east of the proposed West Beltway alignment to elevation 351.6 feet and maintain that elevation until the levee blends into the existing embankment at elevation 351.6 feet. 5.7.F.2 Prior to recordation of a final map, or as otherwise determined by the Building Director, for the small area of the southwestern portion of the site that is currently within a 100-year flood hazard area, specific improvements to remove this area from the Zone A FEMA designation are required to be submitted to FEMA for approval and then submitted to the City of Bakersfield Building Department. Level of Significance After Mitigation Less than significant. Exhibit 5.7-2 illustrates the proposed flood zones on the project site after implementation of the above levee system and other improvements. Impact 5.7.G: The proposed project could expose people or structures to a risk of loss, injury or death involving flooding as a result of the failure of the Lake Isabella Dam. If there was a failure of the Lake Isabella Dam, floodwaters could inundate a large portion of the City of Bakersfield including the project site. According to the State Office of Emergency Services, the project site and vicinity could be inundated with one to two feet of water. This inundation of the project site from dam failure would take 8 hours. The City of Bakersfield Flood Evacuation Plan provides procedures for the protection of health, safety, welfare of the people and property from potential dam inundation areas through evacuation of areas that would be inundated. This plan is currently in the process of being updated. The implementation of the Flood Evacuation Plan as well as the relatively shallow depth of flow estimated by the Office of Emergency Services would not expose structures or people to a significant risk of loss. Therefore, the potential dam inundation impacts to the proposed project from Lake Isabella are considered to be less than significant. Mitigation Measures No mitigation measures are required. Level of Significance after Mitigation Less than significant. Impact 5.7.H: The proposed project would not be subject to inundation caused by seiche, tsunami or mudflow. Seiches and Tsunamis are the result of waves in bodies of water created by earthquakes. A tsunami is not likely to impact the project site as the nearest point of the Pacific Ocean is approximately 70 miles away. The nearest water bodies include Buena Vista Lake which is located approximately 8 miles southwest of the site and Lake Isabella which is located approximately 40 miles northeast of the site. Due to the distance of these existing large water bodies, it is unlikely that seiches would cause an 02160029 • 07/2006 | 5.7-2_Future_fld_map.mxd Exhibit 5.7-2Future Flood MapN OR T H Michael Brandman Associates Source: Thomas Guide Digital Edition, 2004. WEST MING SPECIFIC PLAN EIR Project Impacts West Ming Specific Plan - Draft EIR Hydrology and Water Quality Michael Brandman Associates 5.7-15 H:\Client (PN-JN)\0216\02160029\DEIR 9-1\02160029_Sec05-07 Hydrology and Water Quality.doc impact on the proposed project. Since the project site is relatively flat, no mudflow impacts on the proposed project would occur. Therefore, inundation caused by seiche, tsunami or mudflow is considered less than significant. Mitigation Measures No mitigation measures are required. Level of Significance after Mitigation Less than significant.