PROJ00147

• Contract/PO #: C153637
• Contractor Name: North Poudre Irrigation Company
• Contract Type: Loan
• Water District: 3
• County: Larimer
• Bill Number: SB 92-87
• Loan Projects - Doc Type: Feasibility Study

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Chapter V: PLAN OF DEVELOPMENT

A. RESERVOIR NO. 6

A.I. PHYSICAL PLAN

North Poudre Reservoir No. 5 and No. 6 were originally constructed around 1900
for the purpose of storing agricultural Irrigation water. The dams for both
reservoirs have been modified at least once and raised since the initial con-
struction. The main dam embankment for No.6 was raised 4.5 feet in 1910 and
the outiet was lowered 7.5 feet. Other miscellaneous modifications have been
made over the years and No. 5 underwent a major rehabilitation in 1980.

1. Existing Facilities - Reservoir No.6. Reservoir No. 6 Is Impounded by two
dams. The main dam runs in approximately an east to west direction and the
saddle dam runs In a north to south direction as shown on the plan on Figure
V-I. The main dam Is approximately 1150 feet long with a structural height at
the outiet of approximately 42 feet. The saddle dam is approximately 800 feet
long with a structural height at the deepest section of approximately 7 feet.

The main dam embankment slopes are approximately 3H (horizontal) to 1 V
(vertical) with a 20 foot dam crest width. The saddle dam embankment slopes
are 3H to 1 V and in some areas as fiat as 4H to 1 V with a 20 to 25 foot crest
width. An access roads run across the crest of both dams and the crest is
sllghtiy rutted or depressed in some areas.

Currently there is no spillway for the reservoir. The two dams are at approxi-
mately elevation 5162 feet and are lower than the abutments. There may be a
slight depression to the east of the main dam but In general any severe fiooding
that could not be retained by the dam would overtop the dam.

The outlet works consists of an Inlet box. 2-36 Inch concrete box culvert type
conduits, and a concrete gate house in the center of the dam containing the gates
and operator. The outlet has no outlet structure or energy dissipation structure.
The outlet pipe is approximately 290 feet in overall length and has minimal
slope. The date of installation of this outlet works Is not known. The outlet
gates are in very poor condition and were opened and the operator stem removed
in 1987 such that the reservoir could not be filled.

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

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Chapter V - No. 6 l'euibility