PROJ00015

• Contract/PO #: C153631
• Contractor Name: Beaver Reservoir Company
• Contract Type: Loan
• Water District: 59
• County: Gunnison
• Bill Number: FSA
• Loan Projects - Doc Type: Feasibility Study

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Woodward.Clyde
Consultants

will include a combination of selected profile plotting and contouring of all SP results
with interpretation of seepage patterns.

2.2.4 Drilling, Sampling, and Field Testing

The proposed drilling program consists of four boreholes. Three are located on the
existing dam crest and one at the dOWIl5tream toe on the right abutment. The purpose
of the drilling program is to determine the subsurface stratigraphy, engineering
classifications, and engineering properties for the materials in the embankment and its
foundation. Samples of these materials will betaken at selected intervals and depths for
field classification purposes and later laboratory testing. Field permeability tests using
borehole packers and flow meters will be conducted at various depths in selected
boreholes to evaluate the relative permeability of the various strata. The test results will
be used to develop a conceptual model of the possible subsurface flow patterns which
are possibly related to the historical sinkhole development. If water losses during the
permeability testing are large, dye injection tests may be conducted at selected depths
in an attempt to determine the flow path(s) and possible outlet points.

The proposed boreholes are lo~ated either on the dam crest or at the downstream toe.
The borehole pattern will be refined based on the results of the site inspection and
surface geophysical investigations to maximize the efficiency and minimize the costs of
the drilling program. Borehole depths are expected to range from 40 to 60 ft with a
maximum embankment penetration of approximately 30 ft and a maximum foundation
penetration of approximately 50 ft. Standpipe piezometers will be installed in selected
boreholes located along the dam crest to allow monitoring of water levels and water
temperatures within the dam foundation and embankment.

Special emphasis will be placed on the sampling of clays, claystones, and shales in the
lower embankment and foundation as these materials, if classified as dispersive or
susceptible to slaking, may be contributing significantly to sinkhole development.

92D227PIP227 06-25.92(10:17pm)/PRO/54

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