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Memo to Gregg Squire 2 March 13 2001 <br />the Division; the Urban Drainage document may also still be available from Urban Drainage and <br />Flood Control District. <br />2. Issues Related to the Proposed Pit Liner <br />The following cross - section will be used with subsequent narrative to illustrate the issues to be <br />resolved with the proposed pit liner. The cross section depicts the typical reclaimed configuration <br />based on descriptions included in the permit application. <br />1 inch = 12 feet horizontal; 1 inch = 6 feet vertical <br />a) As illustrated in the cross section, the proposed reclamation plan does not provide for a keyway to <br />tie the compacted clay liner into the impermeable shale bedrock. This differs from the plan for <br />Coulson Excavating Company's R &O Pit approved last year. In fact, as the cross section <br />illustrates, the plan proposed for the Bonser Pit provides a direct flow pathway for alluvial ground <br />water to enter the gravel fill located stratigraphically below the clay liner. The ground water <br />present beneath the clay liner would be under varying degrees of hydrostatic pressure depending <br />on the elevation of the water table, and the pressurized ground water could create sand boils on the <br />O )Y -01 <br />mmumimaiimimilililmmliulu <br />0018499 <br />