Laserfiche WebLink
2.0 MITIGATION STRATEGY <br />2.1.SEEPAGE BARRIER CUTOFF WALL <br />If mitigation is required as indicated above, FARFRUMWURKIN LLLP proposes <br />to install a seepage barrier between the gravel pit and the Ditch. The seepage <br />barrier will isolate the drop in the water table at the pit from the hillslope, due to <br />dewatering. The approximate location of the seepage barrier is shown on Sheets <br />1 and 2. The actual location of this barrier may vary depending on the observed <br />drawdown. <br />The seepage barrier will be constructed by trenching through the upper <br />hydrologic unit (sandy silt layer) down to bedrock shale, approximately 6 to 8 feet <br />deep. The trench will be filled with low permeability clay or other impermeable <br />materials such as geo-membrane and compacted to form a hydrologic barrier. <br />Compaction of the clay barrier, if chosen as the impermeable barrier material, will <br />occur to within 90 % maximum dry density and within 3% optimum moisture <br />content. <br />The seepage barrier will cause the water table to mound between the barrier and <br />the ditch thereby decreasing the water table gradient and reduce canal seepage <br />rates to historic or less. <br />