Colorado - Old Dillon Reservoir Enlargement_Water Activity Summary

• Basin Roundtable: Colorado
• Applicant: Summit County
• Description: Old Dillon Reservoir Enlargement
• Account Source: Basin
• Board Meeting Date: 3/19/2008
• Contract/PO #: 09000000026
• WSRA - Doc Type: Water Activity Summary Sheet - CWCB Evaluation/Approval Documents

Water Supply Reserve Account – Grant and Loan Program
Water Activity Summary Sheet

Applicant:
Summit County Governments
Water Activity Name:
Old Dillon Reservoir Enlargement
Water Activity Purpose:
Structural
County:
Summit
Drainage Basin:
Colorado River
Water Source:
Salt Lick Gulch (Tributary to Blue River)
Amount Requested:
$100,000 (Colorado River Basin Account)
Matching Funds:
$49,360 or 33% of Project cost provided by the Old Dillon Reservoir Group

Water Activity Summary:

In 2008 the Old Dillon Reservoir (ODR) group plans to complete the NEPA environmental permitting
required for both the USFS Special Use Permit and the USACE 404 permit. The work for which this grant is
requested is specifically to help fund the NEPA and permitting components of the work and also to fund
preliminary engineering work including a wildland hydrology study, probable maximum flood study and a
dam break analysis (estimated to cost $149,360). Summit County does not have any TABOR issues with
regards to this grant since the Summit County voters passed a general revenue retention measure years ago.

The project will be designed and put out to bid during the winter of 2008-2009. If all permits are obtained by
spring of 2009, the group plans to start construction in April or May of 2009. To date the overall cost of the
Old Dillon Reservoir Enlargement project has been about $190,000. The budget for permitting and
engineering activities in 2008 is $500,000 and the budget for construction activities in 2009 may approach $7
million.

Discussion:

Old Dillon Reservoir is currently a 46.14 acre-foot impoundment owned and operated by the Town of Dillon
and located between the Denver Water Board's Dillon Reservoir and 1-70 in Summit County just west of the
corporate boundaries of the Town of Dillon and the Town of Silverthorne. The Reservoir is fed by Salt Lick
Gulch through the Dillon Ditch and is operated and maintained on USFS property under a Special Use
Permit. Salt Lick Gulch is a tributary to the Blue River which is located downstream of the Dillon Reservoir.
Use of surface waters from Salt Lick Gulch has no impact on Denver Water's ability to fill their Dillon
Reservoir facility.

Flows in Salt Lick Gulch will be affected when the Dillon Ditch operates to provide the existing direct-flow
right of 10 cfs, but those diversions can occur under the existing authorization for the Ditch. The ODR group
estimates that Salt Lick Gulch can provide an annual yield of 400 acre- feet in dry years and 1,200 acre-feet
in wet years. The reservoir will be filled annually in the spring and during other times of the year to the
extent that water is legally and physically available.

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