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11ur 29, 2009 1"tw I I <br />During the clearing and gn?bbing operation in the Fall of 2008, there was no evidence of <br />subsurface water in the topsoil nor was there any evidence of surface seeps (Figure 10). There <br />was what could only be described as a trickle of water entering the Horse I Pond. <br />The Horse Gulch drainage basin is relatively small at just over 190 acres and the <br />topography facilitates good drainage. The bedrock slopes toward the northeast which does not <br />allow the creation of perched water near the soil-rock interface. The highly plastic clays further <br />hinder migration of surface water into the bedrock. <br />The FLAC'3D model was first run as if water did not affect the site. A second model was <br />run With the same material properties but with the phreatic surface at the top of the native <br />materials. The material below the phreatic surface was assumed fully saturated, and its saturated <br />density was based oil all average porosity of 0.05. Groundwater flow' was not simulated, rather <br />only pore water pressures were used to compute effective stresses. <br />3.0 Motm. RESULTS <br />The first model was run using the average properties for a spoil embankment comprised <br />of soil and ruck with no phreatic surface. The results are shown in Figures i I through 13. <br />Agapito Associates. Inc. <br />Figure 10. No Expression of Near-Surface Water Fall 2008