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Water Quality Management Plan (WQMP) <br />Mainplace Mall Specific Plan <br />In its preliminary engineering investigations, the soils engineer has determined that the top <br />30 feet of soil lacks the permeability to effectively infiltrate stormwater runoff. The <br />underlying soils below a 30-foot depth tend to be more permeable in nature are feasible for <br />infiltration. Additionally, the current groundwater table is in excess of 100 feet deep, <br />allowing for potentially significant infiltration depths. However, the historical high <br />groundwater levels are closer to 30 feet to 40 feet deep. Many agencies require the use of <br />the historic high groundwater levels for the analysis of stormwater infiltration. In the <br />event that the historic high groundwater is required for feasibility analysis, infiltration will <br />not be feasible on -site and biofiltration BMPs will be required. If the historic high <br />groundwater level is disregarded as a feasibility criterion, then deep infiltration through <br />the use of dry wells or similar measure will likely be utilized across the site. Both <br />infiltration and biofiltration BMPs sized per the TGD and MWQMP will reduce the <br />pollutants in the developed condition stormwater runoff to the MEP standards set forth in <br />the TGD. <br />Centennial Section II <br />Conceptual Specific Plan WQMP Page 11 <br />