PROJ00116

• Contract/PO #: C153477
• Contractor Name: Victor, City of
• Water District: 0
• County: Teller
• Bill Number: XB 99-999
• Loan Projects - Doc Type: Feasibility Study

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stream of the dam indicate that the reduction from the full PMF to the 1/2 P/1F is
well justified for this case. Further reduction in the spillway size may be
justifiable from a downstream flood damage basis, but is not recommended at this
time for the following reasons:
1.) Placement of additional fill material on the dam must be made regardless
of the spillway size to stabil ize the embankment. Material for this
fill may be excavated from the spillway site thereby enlarging the
spillway not just for flood control purposes but to provide material
for the embankment.
2.) Further reduction of the spillway capacity to less than 1/2 the PMF
involves acceptance of risk for dam overtopping that is not acceptable
in light of item 1 above.
3.) Until the State Engineer's criteria are officially implemented, down-
sizing of the spillway may be premature.
A tradeoff on spillway width, material required for embankment and the resulting
safety of the emergency spillway channel is also required due to the steepness of
the spillway left bank adjacent to and downstream of the dam. Generally speaking,
the wider the required spillway, the more excavation required and thus the more
material would be available for the dam stability embankment. Excavation into
the left bank of the spillway does, however, present the possibility of an overly
steep and unstable channel side slope. This is of particular COncern for all
alternatives except alternative 4 above. Alternative #4 was considered to be the
most advantageous of the alternatives. By raising the dam and increasing it's
cross-section, the stability of the dam can be increased to meet dam safety
standards. In addition, the added head provided by raising the dam embankment
allows for a smaller width emergency spillway to be constructed and yet still be
the major Source of required embankment material. The raise in the embankment
does not increase water storage since the emergency spillway crest is set at the
previous elevation for full water storage. An increase in dam height only provides
additional storage during large flood events. A more detailed discussion of the
preliminary design and stability of the dam follows.

Three additional alternatives were evaluated and rejected from further considera-
tion. These alternatives were:

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