C150063 Feasibility Study

• Contract/PO #: C150063
• Contractor Name: Jackson Lake Reservoir & Irrigation Company
• Contract Type: Loan
• Water District: 1
• County: Morgan
• Bill Number: SB 94-29
• Loan Projects - Doc Type: Feasibility Study

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state of decay. The cracks and holes, and lack of cutoff under the slabs may have
allowed embankment materials to be eroded from behind the slabs due to the wave

action during severe windstorms. Sinkholes have formed on the crest at various times,
and the Company has had to keep diligent watch over the dam to ensure its integrity.
Sinkholes that form are filled by the Company by washing sand and gravel into the
sinkholes to stabilize and fill the possible voids.

Currently the dam is not under restriction by the State Engineer. However, the
State Engineer has been concerned about the deterioration of the concrete slab facing
and the potential formation of sinkholes behind the slabs. The Company has voluntarily
held the reservoir to a level below gage height 27 feet in winter and spring to minimize
potential problems during the time of year that the largest windstorms are prevalent.

Because of the deteriorating conditions of the upstream slope protection, the
owner is concerned with the possibility of future storage restrictions and of
experiencing a major failure of the dam embankment. Over the next few years, the
State Engineer may consider restricting the storage height due to the condition of slope
protection.

Without repair of the dam, tl:Je Company is faced with the potential for failure of

the dam, or may be placed in a situation where they can no longer adequately serve the

stockholders if the reservoir storage is severely restricted by the State Engineer.

Recent Field Investiaations

W. W. Wheeler and Associates and Kumar and Associates have performed
several field investigations in conjunction with or in anticipation of the preparation of
the Feasibility Study. These studies are summarized below.

Site Surveys
Two site surveys were performed by Wheeler in September 1994 and November
1996. The 1994 survey focused on obtaining cross-sections of the upstream slope of
the dam. The 1996 survey obtained ground information on the beach upstream from

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