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Page 28 V <br /> ENVIRONMENTAL IMPACT MITIGATION MEASURE LEVEL OF <br /> SIGNIFICANCE <br /> AFTER <br /> MITIGATION <br /> to effects of the 100-year flood. provision of replacement floodplain area <br /> (SIGNIFICANT) and storage volume in an easement along <br /> the relocated North Branch of the South <br /> Fork of Little Johns Creek. <br /> (c) The channel and floodplain storage <br /> easement are designed to accommodate the <br /> 100-year,24-hour storm. The design also <br /> includes a three foot freeboard. <br /> K.3. Stormwater runoff from landfill (a) The surface water conveyance system, LS <br /> surfaces,if not properly controlled,could including the detention pond would be <br /> contribute to increased peak flows designed to handle the 100-year storm. <br /> downstream,or degrade surface water in <br /> receiving waters. (SIGNIFICANT) (b) Stormwater runoff from the working <br /> face would be collected at the edges of the <br /> landfill and routed to the perimeter <br /> leachate collection trenches. <br /> (c)The timing of the pumped discharge <br /> from the detention ponds must not occur <br /> with the peak flow rate of Little Johns <br /> Creek as this would impact downstream <br /> locations by increasing the flood hazard. <br /> Telemetry,which monitors the flow in the <br /> Creek to determine the peak, should then <br /> be used to coordinate the start up of the <br /> pumps. <br /> KA. Uncontrolled erosion from soil (a)The final bridge design shall include LS <br /> stockpiles and landfill surfaces,or structural controls to prevent spilled or <br /> inadvertent spills of refuse or other tracked sediment from entering the stream <br /> substances on-site could contaminate channel,and shall be regularly cleared of <br /> surface water. (SIGNIFICANT") accumulated sediment and refuse. <br /> Accumulated material shall be properly <br /> disposed of in the landfill. <br /> (b)Additional measures described in <br /> Section III.G,Air Quality,Mitigation <br /> Measure G.1,would also minimize dust <br /> impacts. <br /> K.5, Groundwater contamination would (a) Landfill design includes a separation LS <br /> result if the liner and leachate collection between the liner and groundwater that <br /> system for the expansion failed. meets all regulatory standards. <br /> SIGNIFICAN <br /> GR,4S5ETTI ENVIRONMENTAL CONSULTING <br />