PROJ00202

• Contract/PO #: C153474
• Contractor Name: Oak Creek, Town of
• Water District: 0
• County: Rio Blanco
• Bill Number: XB 99-999
• Loan Projects - Doc Type: Feasibility Study

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1. Access road improvements to allow access of construction equipment and
vehicles to the site.

2. Clearing, grubbing, and topsoil stripping and general preparations in
the construction staging area, as well as the area where modifica-
tions will be constructed.

3. Open-cut excavation and grading of the downstream face and toe area
of the dam for construction of an underdrain system and the soil-
cement overtopping protection.

4. Construction of overtopping protection on the overflow section of the
crest and downstream face of the dam and in a downstream apron area.

5. Construction of a 4- to 5-foot raising of the dam crest outside the
overflow section.

6. Disposal of excess excavated materials in the right abutment area.

7. Modifications to the existing spillway to provide increased hydraulic
capacity consistent with the increase in dam crest height. There
will also be minor modifications to the outlet works discharge at the
toe of the dam in the area of new soil-cement construction.

8. Reclamation of all areas disturbed during construction including the
construction staging area and the waste excavation disposal area in
the right abutment of the dam but excluding the soil-cement over-
topping protection section.

The overflow section is located in the central portion of the dam. This
section will be approximately 300 feet wide. The elevation of the overflow
section will be set between elevation 9733 to 9736, as required to provide the
necessary discharge capacity. The total discharge capacity of the overflow
section will be 12,000 to 14,000 cfs, which, when combined with the discharge
capacity of the existing spillway, will provide the required total discharge
capacity of approximately 16,500 cfs. Riprap materials recovered from pro-
cessing excavated materials from the toe of the dam will be used, as
appropriate, in the area downstream of the existing spillway stilling basin
and the soil-cement apron to provide additional erosion protection.

Geotechnical Explorations - Three exploratory test pits were excavated on
September 30, 1986 at locations above the left side of the existing spillway
channel, as shown on Figure 9. Summary exploration logs for these test pits
are given in Appendix E.

Material found in the test pits generally consisted of silty and clayey
sands and gravels. The Unified Soil Classification would be SC-SM to GC-GM.
Cobbles and boulders up to 3 feet in maximum dimension were found in all test
pits. The estimated cobble and boulder content of the materials removed from
the pits ranged from 25 percent in test pit TP-1 to 10 to 15 percent in test
pit TP-3. The cobbles and boulders were of basaltic composition and ranged
from subangular to sub rounded in shape. The estimated specific gravity of the