WSP03098 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I 002591 constructed in the porous upper portions of the bedrock to prevent seepage, The cutoff trench will be backfilled with select impervious material (1). 2. Bedrock Geology The reservoir basin behind the proposed Taylor Draw Dam lies on a bedrock of Mesa Verde Group sandstones, shales, and claystones. These rocks are exposed as rims and ledges of the more resistent sand- stone beds, and surround the broad valley of the meandering White River (1), The dam site is founded on bedrock of the lowermost Iles formation of the Mesa Verde Group and the uppermost Mancos Shale, both of late Cretaceous Age. The contact is conformable and indistinct as the gray marine shales of the Mancos formation grade upward into thin bedded sandstones, claystones, and sandy shales, and finally to the thick massive sandstones of the lower Iles formation. In the vicinity of the dam these rocks dip about three or four degrees north- east, or generally upstream and toward the left abutment. Thick beds of Iles formation sandstones outcrop at the right abutment and along the edge of a terrace near the left abutment, Moving the axis of the dam slightly upstream from the site originally proposed for the Rangely Project will decrease the slope of the right abutment and considerably reduce the cutting necessary to flatten the slope of this abutment. It will be necessary to reduce the slope of the right abut- ment in order to obtain a positive seal between the impervious'core of the dam and the bedrock (1), Drilling and water tests performed during previous investiga- tions of the site revealed the bedrock to' be primarily interbedded 11-11 -'~