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<br />. <br /> <br />, _~., _v'_'_'_"'_-<"~ <br /> <br />" <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />, <br /> <br />0849 <br /> <br />4. "Subsurface investigations. - i:>ubs1.lrface investigations consisted <br /> <br />of fiveccore holes drilled on the axis of the proposed Trinidad Dam and <br /> <br />numerous auger holes in the soil overburden. In addition, seven core <br /> <br />holes were drilled by the Bureau of Reclamation at the Sopris dam site <br />about two miles upstream from the Trinidad dam site. The five core holes <br /> <br />drilled on the Trinidad dam site represent 458 lineal feet of drilling. <br /> <br />The locations of these five core holes are shown on plate 2. Numerous <br /> <br />, ' <br />auger holes were !llade in the vicinity of the proposed dam to obtain samples <br />for determination of borrow sources for embankment materials. The location <br />of these auger hol~s and the delineation of possible borrow areas for <br />pewious and iJnpervious materials are shown on piate 3. <br />5. Geology ofT~inidaq dam site. ~ the rock outcrops alld those <br />recovered from core holes show the dam site to be underlain by Pierre shaJe . <br /> <br />Both abutments are on the Trinidad sandstone and the Vermejo formation. <br /> <br />The Pierre shale, in this area, consists of firm fossiliferous dark-gray <br /> <br />to olive-green clay shale and sandy shale containing thin beds of fine- <br /> <br />grained clayey sandstone. The Trinidad sandstone is a hard, light, gray <br /> <br />sandstone, usually massive, with thin layers of dark-gray sandstone with <br /> <br />shale partings. Exact limits of the two formations are difficult to det- <br /> <br />ermine because of gradual gradation into shale from sandstone and sand- <br /> <br />stone into shale. The Vermejo formation consists of firm amber sandstone' <br /> <br />and sandy shale with thin laminations of carbonaceous shale. The tunnel <br /> <br />for the outlet works would be driven through the left abutment in the <br /> <br />Trinidad sandstone which is sufficiently stable to require little timber- <br />ing during driving operations. The spillway across the left abutment <br /> <br />would be on the Vermejo formation and require no concrete other than the <br /> <br /> <br />proposed ogee weir. All strata have a slight westerly dip conforming <br /> <br />to the general regional trend. <br /> <br />3 <br /> <br />APPENDIX F <br /> <br />