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-9- <br />an./sec. Based on the laboratory testing, the permeability of the <br />• overburden alluvium is on the order of 1 x 10_S ctn./sec. Since the <br />bedrock in the area is primarily consisting of cohesive material and is <br />medium hard to hard, the permeability of the bedrock is of the same <br />order as that of the alluvium. ' <br />Zhe small portion of water that penetrates the compacted cover <br />will enter the refuse pile and will flow towards the face of the pile <br />and collect in the sedimentation pond. Any water readiing the <br />overburden alluvium below the pile will flow along the interface <br />between the refuse and natural soils and would drain into the <br />sedimentation pond. The water collected in the sedimentation pond <br />would be detained to remove sediments before being siphoned into <br />4honpeon Creek downstream of the dam. <br />• <br />II. SIDIMENfATICN Fn[~ID DAM <br />General Description: Presently, the water in the retention pond dam is <br />retained by an earth embankment 10 to 15 feet high. 4he crest width <br />varies from 10 to 15 feet, with the slopes of approximately 2H:1V. <br />Subsurface Conditions: Geoted~nical conditions of the retaining pond <br />dam and foundation were investigated by drilling four soil borings at <br />the locations shown on Figure 2. As shown by the logs of holes <br />(Fig. 4 ), the ertbanlooent consists of 10 to 15 feet of medium stiff to <br />stiff clay fill mixed with rardanly scattered gravel, claystone and <br />wood. Below these depths, natural clays with occasional gravel lenses <br />extend to depths of 19 to 24.5 feet. Numerous pieces of wood were <br />found at the contact of the fill and natural soils. <br />• <br />