PROJ00137

• Contract/PO #: C153467
• Contractor Name: Greeley, City of
• Contract Type: Loan
• Water District: 0
• County: Weld
• Bill Number: XB 99-999
• Loan Projects - Doc Type: Feasibility Study

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The City, together with MKE, selected Alternative No.1 for feasibility design
because of the substanti al reducti on in long-term operati on and mai ntenance
costs, and its high degree of technical confidence. The major components of
this design and estimated appraisal-level construction cost, including 25
percent contingencies, are as shown above. The feasibility of this solution,
however, is dependent upon locating a suitable source of RCC aggregate.

The possibility of transferring the storage volume of Twin Lakes Reservoir to
Peterson Lake Reservoir was explored by developing two enl argement design
alternatives for Peterson Lake Dam. One alternative consisted of raising the
dam with earth materials and the other alternative included replacing the dam
wi th a new RCC dam. The earth dam enl argement resulted in a total cost of
Peterson Lake Dam of $983,200, and the RCC alternative $1,347,200. An
additional cost of transferring the water, not allowed for in the cost
estimate, would be reclamation of the Twin Lakes Reservoir.

The reservoi r operati on study showed that by provi di ng an addi ti onal storage
capaci ty of 460 acre-feet in Peterson lake Reservoi r, the fi rm yi el d woul d
only increase 167 acre-feet. Based on the appraisal-level cost estimates, the
cost per acre-foot of firm yield would be approximately $2,900 and $1,800
respectively for the earth and RCC alternative. Even without considering the
costs of breeching and reclaiming Twin Lakes Dam and Reservoir, these figures
are substanti ally hi gher than the estimated constructi on cost of $991 per
acre-foot of firm yield obtained by rehabilitating Twin Lakes Dam using cost
figures derived for preliminary alternative No.1.

The possibility of transferring the storage volume of Twin Lakes Reservoir to
Comanche Reservoi r was al so examined. The reservoi r operati on study reveal ed
that by providing an additional storage capacity of 460 acre-feet in Comanche
Reservoir, the firm yield from that reservoir would only increase by 153
acre-feet. From a techni cal standpoi nt, enl argi ng Comanche Dam above that
required to safely route the PMF is not recommended because of the foundation
conditions at the site. Al so, a cursory study of the quantities required to
raise the dam four feet, to store the additional 460 acre-feet, suggested that
it would be uneconomical to transfer the Twin lakes storage decree to Comanche
Reservoi r.

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