PROJ00259

• Contract/PO #: C153424
• Contractor Name: Colorado River Water Conservation District
• Water District: 0
• Bill Number: XB 99-999
• Loan Projects - Doc Type: Feasibility Study

2. Engineering Geology

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· Tunnels, pipelines and new canals should be avoided where
possible, in favor of using the existing water distribution
system.

The West Divide Project includes a potential series of dams
and canals on tributares to the Colorado River south of the Colorado
River, and west of the Crystal River and the Roaring Fork, between
Glenwood Springs and Parachute, Colorado. Physiographically, the area
is south and west of the Grand Hogback and southeast of Piceance Basin
(Ref. 33). The Grand Hogback is a monocline that flanks the White
River Plateau and the northern end of the Sawatch Range, major struc-
tural elements of the Southern Rock Mountain. The formations along
the Grand Hogback are of Late Creta(:eous age and include, from oldest
to youngest, the Dakota Group, the Colorado Group, the Mancos Shale
and the Mesa Verde Formation. These formations along the hogback dip
steeply west to southwest.

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Unconformably overlying the Late Cretaceous Formations along
the southern and southeastern margins of the Piceance Basin are the
Ohio Creek and Wasatch Formation. The Wasatch formation is overlain
by the Green River Formation, which was deposited in the Piceance
Basin. Locally in the Battlement Mesa area along the south and south-
west limits of the Divide Creek area are basaltic lava flows and
dikes. The Ohio Creek, Wasatch and Green River Formations are
generally about horizontal but hav" locally been folded into broad
synclines and anticlines wi th their axes approximately parallel to the
Grand Hogback. Major faults are limited to the area of the Grand
Hogback.

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The bedrock formations are for the most part concealed by
surficial deposits. These deposits Include colluvium derived from the
in-place weathering of the bedrock. Locally, the thick deposits of
colluvium have failed, forming landslide deposits. Alluvium,
including terrace deposits that were formed at periods when the
streams were at higher levels than at present, occur along the
streams..

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The engineering properties of the geologic materials are
related to their origin. The bedrock formations, for the mos t part,
are composed of easily weathered and eroded shales, claystone, silt-
sones and sandstones. The topography, as a result, is for the most
part gently rolling. Steep slopes occur where hills are capped by

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