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i MOUNTAIN HOUSE NEIGHBORHOODS K AND L INITIAL STUDY 5.ENVIRONMENTAL CHECKLIST S.HYDROLOGY AND WATER QUALITY the levels of oils, grease, metals, and petroleum hydrocarbons in site runoff,the — proposed lake features and water quality BMPs described in the SWMP, as well as regular inspection and maintenance of these lakes and water quality BMPs, would treat the first flush and ensure that post-construction impacts on water quality would be less than significant. Issues related to runoff quality and quantity are also discussed in the following: Master Plan Policies 7.3.6(Implementation Measure[e])(Wetland Management) and 15.7 (Implementation Measures[a], [c], [d], [e], [g[, [h],and [i])(BMPs). 4 j Project impacts related to runoff quality and quantity are considered less than I significant due to mitigation measures in the project description. No additional mitigation measures are necessary. 0 Would the project otherwise substantially degrade water quality? All project-related water quality impacts are addressed above under Item(a). ] ! The Master Plan and the Initial Study prepared for the SPIT discussed the possibility of using reclaimed water for on-site irrigation of landscaped areas.The use of reclaimed water for site irrigation is no longer proposed as part of the Neighborhoods K and L project. Thus, no impact related to the use of reclaimed water for irrigation would result. No mitigation measures are necessary. g) Would the project place housing within a 900-year flood hazard area as mapped on a federal Flood Hazard Boundary or Flood Insurance Rate Map or other flood hazard delineation map? II As discussed above, ground surface elevations in Neighborhoods K and L range from 0 feet above msl along Old River to about 25 feet above msl in the southern portion of the site. Current FEMA maps for San Joaquin County(FEMA, 2011) + indicate that the northern portions of Neighborhoods K and L are located within the 100-year flood hazard zone for Old River. The current 100-year flood elevation for Old River is approximately 10.4 feet above msl. _ As part of the proposed project, building pads within areas that are currently mapped as being within the designated 100-year flood hazard zone for Old River would be elevated above the FEMA 100-year base flood elevation. Approximately 2 million cubic yards of engineered fill would be needed to remove " the northern portions of Neighborhoods K and L from the 100-year flood hazard i zone. Portions of the Neighborhoods K and L project site with ground surface elevations above 10.4 feet above msl would not require fill. In addition,the northern portion of the Neighborhoods K and L project site bordering Old River is proposed as park land,which would provide a flood buffer between Old River and proposed development areas. These improvements would result in the -- removal of all portions of Neighborhoods K and L from the 100-year flood hazard zone and would be consistent with the approved Conditional Letter of Map F Isms ii 5-117 l