PROJ02027

• Contract/PO #: FS0044FX
• Contractor Name: Larimer County, Board of County Commissioners
• Contract Type: Miscellaneous
• Water District: 0
• Loan Projects - Doc Type: Feasibility Study

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SECTIINSEVEN

Recollllended Project

The Douglas Dam segmented fuseplug was selected based on price and operational benefits.
The fuseplug was the cheapest alternative for flood control above Douglas Reservoir. The
segmented fuseplug does not interfere with the normal operation of the irrigation reservoir.
Another benefit to the segmented fuseplug was normal water storage can not encroach on the
storage available for flood control.

The 2 Dam Alternative (Dam #3 and #5) was selected for the additional downstream storage.
This alternative was selected based on cost. The other alternatives produced the same desired
discharge except at a higher cost.

A preliminary concern with the Willox Lane Diversion was changing the point of diversion for
water rights from the original confluence of Dry Creek. A FEMA conditional letter of Map
Revision (CLOMR) would be required because flood flows would enter the Cache la Poudre
River upstream from the confluence with Dry Creek and potentially impact structures along the
Cache la Poudre River due to increased flood heights. The Willox Lane Diversion was dropped
from consideration in favor of alternatives of similar cost because the other alternative would
provide additional flood control benefits and would not require changing water rights and flood
flows out of the Dry Creek watershed.

The East Vine Diversion was selected as the preferred diversion alternative. The East Vine
Diversion eliminates the concerns of water rights and FEMA issues of the other diversion
alternatives. The cost is higher than the Willox Lane Diversion but provides additional flood
control for the local Dry Creek basin. The East Vine diversion will not solve all conveyance
problems in the Dry Creek local basin. Additional improvements will need to be made in the
Dry Creek local basin but the East Vine diversion is a major component of the solution because
it provides an outlet for the improvements. The Boxelder Creek Diversion is limited due to the
regulations that prohibit the transbasin diversion of flood flows.

7.1 RECOMMENDED PROJECT

The recommended alternative consists of the following design features:

1. Segmented fuseplug for Douglas Dam - $300,000

2. Upgrades to Dry Creek for Irrigation Conveyance - $200,000

3. Downstream Storage (Dam #3 and Dam #5) - $2.3 million

4. Modifications to the Larimer and Weld Canal- $200,000

5. East Vine Diversion Channel- $800,000

6. SCADA System - $150,000

A 30% contingency was included in the quantities cost estimate to account for unlisted items and
the uncertainty of the design based on the existing information.

For the total estimated cost of the recommended alternative, 25% contingency was added to
account for engineering design, permitting and construction fees. The total estimated cost for the
recommended alternative was 4.9 million dollars. The breakdown of the quantity cost estimate is
included in Appendix A of this report.

T:\ProjectsI682466ODry CrkDiversionlarimerCountylSub_00\12.0Word ProcIFIood Control Plan-Rpt.doc 04124100(11:14 AM) 7-1