PROJ00279

• Contract/PO #: C153572
• Contractor Name: North Poudre Irrigation Company
• Contract Type: Loan
• Water District: 3
• County: Larimer
• Bill Number: HB 85-1042
• Loan Projects - Doc Type: Feasibility Study

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Chapter V: PLAN OF DEVELOPMENT

A. Physical Plan

1. Existina Facilities. North Poudre Reservoir No.2, known
as Demmel Reservoir, was originally constructed in about 1890 for
the purpose of storing agricultural irrigation water. The two
dams that impound the reservoir were raised at least once
following the initial construction.

The reservoir is impounded by two dams that run in ap-
proximately an east-west direction as shown on the plan in
Appendix H. The East Dam is approximately 800 feet long and is
about 12 feet in height. The West Dam is approximately 1200 feet
long and approximately 12 feet in height.

There are two spillways for the reservoir; one on each end of
the two dams. There is one spillway on the far west end of the
West Dam which is very small and is estimated to have a peak
capacity of 300 cubic feet per second. The second spillway is
located on the east end of the East Dam and is estimated to have a
peak capacity of 2600 cubic feet per second. The combined capacity
is less than half of the required capacity to pass the
design flood.

The outlet works consists of a 36 inch corrugated metal pipe
with a concrete gatehouse in the center of the dam and a concrete
headwall type inlet and outlet. The outlet pipe is 367 feet in
overall length and has an average slope of 0.4 percent. The date
of installation of this outlet works is not known for sure but is
estimated to be in the early 1950's. This outlet replaced a cast
iron pipe conduit which is still buried in the dam. The cast iron
pipe was plugged with concrete at the inlet end in 1985.

The upstream slope protection is almost nonexistent on both
dams. In some areas there is no riprap and in other areas the
riprap can best be described as debris. The downstream faces are
well vegetated with no erosion problems apparent.

There are
rehabilitate the
deficiencies.

several problems which contribute to the need to
two dams. Following is a general list of

1. Inadequate freeboard to allow filling to maximum
gage height of 24 feet.
2. Severely deteriorated outlet conduit.
3. Inadequate spillway capacity to pass greater than a
100 year flood.
4. Seepage problems on the West Dam.
5. Inadequate upstream slope protection.
6. Ponding of water at the toe of the East Dam.
7. Locally oversteep face slopes in certain areas.

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