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5.ENVIRONMENTAL CHECKLIST MOUNTAIN HOUSE NEIGHBORHOODS K AND L INITIAL.STUDY 8.HYDROLOGY AND WATER QUALITY areas typically results in increases in the peak flows and the volume of storm . water runoff generated on a site. Mountain House Storm Water Master Plan Addendum II (PACE, 2006) presents the results of HEC-1 modeling conducted for the SPII area, including - Neighborhoods K and L, and forms the basis for the proposed drainage improvements.The proposed storm water drainage system is designed to accommodate the 100-year flood event, and the lake features proposed in Neighborhoods K and L are designed with sufficient storage to detain 100-year flood flows without overtopping.The proposed flood storage in the lakes, coupled with the completed restoration improvements to Mountain House Creek and the placement of engineered fill to remove all building pads in Neighborhoods K and L from the 100-year flood hazard zone for Old River,would ensure that implementation of the proposed project would not result in on-site flooding. (Also,see discussion under Item(g) below.) There are no other structures or properties in the vicinity of Neighborhoods K and L that could experience flood problems due to project development. Therefore, project development would not result in an increase in off-site flooding. Issues related to potential flooding are also addressed in the following Master Plan policies: 4.3.1 (Policy[e]) (Community Edges); 5.1.4(Policy[d])(School Siting Criteria); 6.5(Implementation Measure [b])(Emergency Preparedness); 7.2.8(Objective [c], Policies[a]and [e], and Implementation Measures[a[and [g])(Mountain House Creek Park); 15.4(Policy[a]) (Primary Storm Drain Collection System); 15.5(Policy[a]) (Secondary Storm Drain Collection System); 15.6(Policy[a] and Implementation Measures[a](1)and [a])(9))(Mountain House Creek Improvements); 15.8(Flood Protection); and 15.11.2(a) (Operations and Maintenance). No additional mitigation measures are required related to on-and off-site flooding. e) Would the project 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'? As described above under Item(d),the proposed storm water drainage system is designed to accommodate the 100-year flood event. The storm drain system would also be designed to accommodate runoff resulting from a sudden and complete failure of earthen dams located upstream of the project site in Alameda - County. The lake features proposed in Neighborhoods K and L are designed with sufficient storage to detain 100-year flood flows without overtopping. Thus, project implementation would not create or contribute runoff that would exceed the capacity of the proposed storm water drainage system. As discussed above under Item (a),while the conversion of the Neighborhoods K and L sites from agricultural uses to suburban uses could result in an increase in Isnn 1 I 5-116