C153787 Feasibility Study

• Contract/PO #: C153787
• Contractor Name: Smith Irrigation Ditch
• Contract Type: Loan
• Water District: 44
• County: Routt
• Bill Number: SPL
• Loan Projects - Doc Type: Feasibility Study

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

The new diversion dam will be a 50-foot wide reinforced concrete structure with a 45-
foot long basin and 9.5-foot high sidewalls. Headwell extensions will be located at the
upstream end of the basin with wingwalls at the downstream end. Baffle blocks will be
placed near the downstream end of the basin for energy dissipation before the flow enters
the natural channel. The basin is designed to pass a flow of 2,400 cfs which essentially
corresponds to the 25-year flood event.

An adjustable Obermeyer gate will be installed near the upstream end of the basin. The
gate will be hinged at the floor of the basin and can be raised to a height of 8 feet
resulting in a sufficient water level (at elevation 6,278.2) to allow the use of the existing
headgate. The resulting pool behind the gate will extend about 1500 feet upstrearn.

The gate will operate by means of a compressor and an inflatable bladder. A control
device upstream of the gate will provide automatic regulation of gate operation with only
occasional monitoring by the owners.

During periods of very high flows, the gate will be lowered to the floor of the basin to
allow unimpeded passage of flood waters with minimal impact on the structure. During
the irrigation season, the gate will be in the raised position to allow diversions through
the existing headgate.

The NRCS estimates the costs of construction at $168,646. The NRCS cost breakdown
for the project is given below in Table 2. A contingency of 15 percent has been added to
the cost of all items, with the exception of the Obermeyer Gate, bringing the total cost
estimate to $183,046. Operation and maintenance costs for the structure are expected to
be minimal over the next twenty years.

Table 2. Smith Ditch Diversion Dam Cost Estimate

Item Quantity Unit Unit Price Amount
Mobilization 1 Job $6,000 $6,000
Removal of Water 1 Job $4,000 $4,000
Piling 1449 S.F. $9 $13,041
Earthfill 2210 C.Y. $4 $8,840
Concrete 140 C.Y. $350 $49,000
Rock Riprap 211 Tons $40 $8,440
Sand/Gravel Filter 55 Tons $25 $1,375
Install Gate I Job $2,200 $2,200
Obermeyer Gate 1 Each $72,750 $72,750
Control Enclosure 1 Each $3,000 $3,000
Subtotal $168,646
Contingency at 15% $14,400
Total $183,046

7