PROJ02019

• Contract/PO #: FS0069FX
• Contractor Name: Fountain, City of
• Contract Type: Loan
• Water District: 0
• Loan Projects - Doc Type: Feasibility Study

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SELECTED ALTERNATIVE

The preferred project is Alternative F. This alternative provides an off-
channel pool, allowing the channel sediments to be routed around the pool and
limiting future sediment deposition in the lake. A schematic view of the proposed
alternative is shown on Figure 4. A preliminary layout of this alternative is also
shown on Figure 3.

In this alternative it is proposed to reconstruct and lower the crest of the
existing emergency spillway at the south side of the reservoir by roughly 12.5 feet
to elevation 6416.5, approximately 17 feet below the existing dam crest elevation
of 6433.5 and a maximum structural height of about 20 feet. The lowered spillway
results in a structural height of less than 20 feet, the upper limit which would allow
the dam to be reclassified as a Minor Size Dam with a Hazard Class of 2, 3 or
possibly even 4. Under the State Engineer's Rules and Regulations, the failure of a
Class 2 dam (the most severe classification expected) with the water pool at the
normal waterline will cause no loss of human life, but significant property damage
may be expected.

The spillway proposed for this alternative would extend from the upstream
end of the lake to the existing spillway located on the south abutment of the dam.
The spillway would intercept the stream at the upper end of the remnant reservoir
pool and direct it around the lake, isolating the remnant reservoir pool from the main
stream channel. The remnant reservoir pool will remain to prevent freezing of the
pipe intake and provide additional protection from sedimentation.

The spillway of a minor, Class 2 dam is required to pass a 100-year flood.
The 100-year flood was estimated to be 6,400 cfs (reference Wheeler's Flood
Hydrology Study for Keeton Dam, dated October 1991). It is proposed to design
the spillway for twice the 100-year flood discharge, even if a lower hazard

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