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(2)protecting downstream storm-drainage inlets from sedimentation;(3)using silt fencing and hay bales to retain sediment on the project site;and(4)any other suitable measures outlined in the Association of Bay Area Governments'Manual for Standards for Erosion and Sediment Control Measures or the San Francisco Bay RWQCB Erosion and Sediment Control Field Manual,the California State Erosion Control BMP Handbook,or acceptable alternative. ► Mitigation Measure 4.7-2(b) (Sedimentation).After construction is completed,all drainage culverts shall be inspected by MHCSD on a yearly basis for accumulated sediment.If sediment has accumulated, these drainage structures of debris and sediment shall be cleared by MHCSD. Funding of these tasks shall be based on a MOU between the District and MHCSD. Mountain House Community Services District Design Manual 2002 - There are no design measures or standards identified in the Mountain House Community Services District Design Manual applicable to drainage. _ SIGNIFICANT IMPACTS IDENTIFIED IN THE 1994 MOUNTAIN HOUSE MASTER PLAN AND SPECIFIC PLAN I FINAL EIR The MHMP EIR identified the following significant drainage impacts before mitigation associated with implementation of the MHMP: Increased sedimentation in Old River caused by runoff from Mountain House Creek and operation of the proposed marina [no longer relevant]; Shallow groundwater presenting adverse conditions for construction of foundations and detention/retention basins.Project could result in elevation of groundwater levels because of removal of subsurface drains; ► Erosion of levees by waves generated by boat wakes as a result of increased boating in Old River and South Delta waterways and operation of the proposed marina [no longer relevant]; and ► Possible deposition of sediment transported by Mountain House Creek in the project site,potentially interfering with flood control and the enhanced habitat the Mountain House Creek corridor. If transported to Old River, sediment could have adverse impacts on downstream water quality. The MHMP EIR did not identify any significant drainage impacts after mitigation(i.e., significant and unavoidable drainage impacts) associated with implementation of the MHMP. 4.7.3 SIGNIFICANCE THRESHOLDS The project would result in significant drainage impacts if it would: ► Substantially alter the existing drainage pattern of the site or area in a manner that would result in substantial on-site or off-site erosion or siltation that could lead to adverse effects on the capacity and performance of the _ storm-drain system; ► Substantially alter the existing drainage pattern of the site or area,or substantially increase the rate or amount of surface runoff in a manner that would result in flooding on-site or off-site, or exceed the capacity of existing or planned stormwater-drainage systems;or ► Require dewatering that would result in on-site or off-site flooding or exceed the capacity of existing or planned stormwater-drainage systems. EDAW College Park at Mountain House Spec'rfic Plan III Draft EIR Drainage 4.7-10 San Joaquin County