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<br />co <br />.~~ <br />.., <br /> <br />at the east end of the dam which it would cross and then con- <br /> <br />tinue up the west side of the reservoir about a mile to the <br /> <br />present road. Estimated cost of road relocation is about $100,000. <br /> <br />Geology <br /> <br />The most unfavorable geological condition at the Rifle Gap <br /> <br />Dam Site is the excessive depth of foundation, stream fill. <br /> <br />Drilling indicates a maximum depth of 128 feet, consisting for <br /> <br />the most part of angular rock and tight interstitial fines con- <br /> <br />taining same more permeable lenses of stream gravels. In general <br /> <br />the surface material is more compact than that at depth. A tight <br /> <br />blanket of side wash mantles the underlying gravels, a blanket <br /> <br />that apparently extends uniformly upstream and over the entire <br /> <br />reservoir area. Water, therefore, has no ready access to the <br /> <br />lower more permeable zones. This natural blanket can probably be <br /> <br />depended on to eliminate the necessity for a cutoff trench to <br /> <br />bedrock. In case the natural fill is not removed, allowance for <br /> <br />compaction and settlement under the dam must be allowed for in <br /> <br />design. <br /> <br />62 <br />