PROJ00170

• Contract/PO #: C153481
• Contractor Name: Colorado River Water Conservation District
• Water District: 0
• Bill Number: XB 99-999
• Loan Projects - Doc Type: Feasibility Study

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In 1984, the CD OW performed a hydrologic analysis of the Elkhead Lake drainage
basin in accordance with the SEO guidelines. The inflow design flood
approved by the SEO was 37,387 cfs, which exceeded the primary spillway
capacity by over 20,000 cfs.

In April of 1985, the CDOW contracted wi th r~orri son-Knudsen Engi neers, Inc.
(MKEl to explore the feasibility of constructing a lining of roller compacted
concrete (RCCl over the crest and downstreaM face of the Elkhead Lake Dam to
act as an aux il i ary spi 11 way that woul d sati sfy the overtoppi ng requi rements
of the SEO. A report entitled "Feasibility of Expanding Spilll~ay Capacity
with RCC Overflow Section" was produced. The report concluded that it was not
economically feasiole to protect the embankment against overtopping using RCC
wi thi n the budget constrai nts of the CDOW. The report suggested, however,
that an alternative design utilizing an auxiliary spillway channel through the
1 eft abutment controlled by a fuse plug embankment mi ght be economi ca lly
feasi b 1 e.

In November 1985, MKE was awarded a contract by the CDOW for final design of
the auxiliary spillway. The construction drawings, specifications, final
desi 9n report, and cost estimate for thi s ;>roject were submi tted to the SEO
for approval in April of 1986.

While preparing the final design of the modification to Elkhead Lake Dam, it
became evident that if required excavation material from the auxiliary
spillway channel was used directly to raise the existing dam, additional
reservoir storage could be provided at a reasonable cost. With the approval
of the CDOW and the SED, r~KE and the Colorado River Water Conservation
District (CRWCDl attempted to ascertain which water users in the region would
be interested in relatively inexpensive storage. The City was the prime
candi date because of the deferment of the Estey-Simpson Project.

Based on preliminary cost estimates, the state legislature authorized the
Colorado Water Conservation Board (CWCBl to make matching funds available to
the City, up to $750,000, for construction of the project. The CRWCD and CWCB
agreed to divide the cost of preparing a study to determine the feasibility of

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