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MOUNTAIN HOUSE PROPOSED MACHADO TENTATIVE MAP 4. ENVIRONMENTAL CHECKUST 4.8 HYDROLOGY AND WATER QUALITY disturb five acres or more of land are required prepare a SWPPP to implement BMPs to reduce the off-site impacts of sediment-laden runoff(EDAW,2005b). In addition,MHMP Policies 4.2.2(a)and(b)requires control of runoff, erosion, and sedimentation during grading. MHMP Policy 6.8.3(b)requires that adequate efforts be made to control or eliminate soil erosion and sedimentation associated with construction activities. V Upon completion of construction of the proposed project, existing WQB No.1 would treat storm water runoff from the proposed project prior to discharge to Mountain House Creek and Old River. WQB No. 1 would help to settle out sediment and particulates from runoff, as %W well as trace metals,nutrients and hydrocarbons,as these pollutants tend to adhere to soil 44„ particles. WQB No. 1 would require periodic maintenance including desilting,vegetation clearing, and trash and debris removal. A Maintenance and Operations Manual for WQB No. 1 has been prepared by the Mountain House Community Services District(MHCSD)as �- required by the MHMP(EDAW,2005b). MHMP Policy 15.7 (Implementation [a]) states that Mountain House(i.e.,the MHCSD) shall implement a long-term Storm Water Management Plan(SWMP)to reduce the discharge of �. pollutants from the storm drain system to the maximum extent practicable and protect water quality in the receiving waters. At a minimum,the MHMP states that the SWMP shall include the following elements: (1)public education and outreach on storm water impacts; (2)public involvement/participation; (3)illicit discharge detection and elimination; �. (4)construction site storm water runoff control; (5)post-construction storm water management; and(6)pollution prevention/good housekeeping for municipal operations. West Yost and Associates prepared a SWMP for the MHCSD in April 2001. The SWMP %W identifies a list of water quality BMPs and provides recommendations for the MHCSD's `, storm water quality ordinance. A storm water quality ordinance has not been adopted by the %W MHCSD,but will be when the State of California designates the Mountain House Community as a Phase II MS4 area(Karam,2006). Vr %W Mitigation Measures %' With implementation of the mitigation measures and policies cited above, there would be no v, violation of any water quality standards or waste discharge requirements. The impact of the proposed project would be less than significant. No additional mitigation measures are required. `, b) 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 ofpre-existing nearby wells Iftw would drop to a level which would not support existing land uses or planned uses for `, which permits have been granted)? %W No groundwater would be used for the proposed project's water supply,so the project would *ar not substantially deplete groundwater supplies. The Initial Study for the SPIIIEIR states that %, complete development of Specific Plan III(including the proposed project)would result in covering less than 0.2 percent of the Tracy groundwater subbasin with impervious surfaces. This would result in a negligible reduction in percolation to the subbasin as a whole. 445