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• and southeast with slopes on [he order of 5 [0 15 percent. A maximum elevation difference of approximately 25 <br />feet exists across the project site. <br />SUBSURFACE CONDITIONS <br />A formal geotechnical investigation has not been completed at this site; however, based on our experience with <br />the substtrface conditions encountered along the access road, which was constructed to the dewatering borehole <br />site, we believe [hat the subsurface conditions encountered at the site will generally consist of a thin layer of <br />topsoil overlying natural clays and claystone bedrock. The clays and claystone bedrock will be low to <br />moderately plastic and should be fairly impervious in the natural state and when properly recompacted. <br />We do not anticipate that free groundwater will be encountered during the construction of the proposed ponds. <br />However, it should be Doted that groundwater conditions can be expected to fluctuate with changes in <br />precipitation and runoff. <br />EMBANKMENT DETAILS <br />Foundation: The embankments will be placed on [he overburden soils and bedrock described in the previous <br />section. The dam should consist of a "homogeneous embankment" constructed with [he relatively impervious <br />on-site overburden soils and underlying bedrock. The subsoils, exclusive of the topsoil, are suitable for support <br />of the structure. Prior to placement of the fill materials, all of the topsoil and vegetation should be removed <br />and the exposed soils should be scarified to a depth of at least 8 inches, brought to within 2 percent of the <br />• optimum moisture content and then recompacted [o at least 95% of the standard Proctor density as determined <br />by ASTM D698. A negligible amount of settlement can be anticipated for the overburden soils and bedrock. <br />Some minor settlement of the embankment materials should be anticipated. The settlement will be discussed <br />further in the overbuild section. <br />Cross Section: The proposed dam embankments will be approximately 8 feet high at the deepest point. The <br />cu[ and fdl slopes along the exterior of the embankments will be constructed [o a 2 (horizontal) to 1 (vertical) <br />slope configuration. Whereas, the interior embankment slopes will be constructed ro 3 (horizontal) to L <br />(vertical) slope configuration. The embankments will be constructed with crest widths of 15 feet. The dams will <br />be a "homogeneous embankment" constructed with [he relatively impervious clays or bedrock materials <br />excavated from the west end of the ponds. <br />Compaction: We recommend [hat all of the embankment materials be compacted to at least 95% of [he <br />maximum standard Proctor density and within 2 percent of the optimum moisture content, as determined by <br />ASTM D698. The fill should be placed under controlled conditions and observed and tested by a qualified soils <br />engineer during placement. The fill lifts should no[ exceed 12 inches in loose thickness. The fdl materials <br />placed in the embankment should be free of topsoil, vegetation, brush and other deleterious substances, and <br />should not contain rocks or lumps of soil greater than 6 inches in size. In addition, the fill materials should no[ <br />be frozen. <br />[n our opinion, excavation of [he near surface bedrock and overburden soils should be possible with heavy duty <br />. conventional excavation equipment. The use of equipment with rippers may be required if the more highly <br />cemented layers of bedrock are encountered. <br />Job No. 9b25P_ Northwest Colorado Consultants. Inc. Page ? <br />