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-11- <br />• <br />can be constructed with a partial cutoff trench which extends 5 feet below <br />the bottom of the embankment foundation. If a complete cutoff is desired <br />to minimize seepage, it will be necessary to extend the embankment cut- <br />off trench approximately 2 feet into the underlying claystone bedrock. <br />The potential for underseepage will be far exceeded by the surface <br />evaporation losses because of the relatively low head and long seepage <br />path involved at this site. In order to control the points of exit <br />of underseepage, and seepage through the structure, we recommend provision <br />of a blanket drain downstream within the embankment. <br />EMBANIQIENT <br />The embankment will be constructed at approximately the location in- <br />• dicated on Fig. 2 We anticipate a two-stage construction. During the <br />initial construction, an earth dam with the general configuration shown <br />on Fig. 8 will be constructed. At a later date a large embankment will <br />be constructed downstream from the dam embankment for use as a haul <br />road. The haul road embankment will be constructed with sedimentary rock <br />spoil from the initial box cuts for the mine. Recommendations for con- <br />struction of the haul road embankment are presented in our report for haul <br />road construction in the Eckman Park area. <br />General <br />The proposed dam embankment for the sedimentation reservoir <br />will have a maximum height of 30 feet above the bottom of the valley. <br />Crest length will be approximately 600 feet and we estimate the <br />• <br />