C150187 Feasibility Study

• Contract/PO #: C150187
• Contractor Name: Young Creek Reservoir Company
• Contract Type: Loan
• Water District: 40
• County: Delta
• Loan Projects - Doc Type: Feasibility Study

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9I\C.

SMITH WILLIAMS CONSULTANTS, INC.

as is true with row crops in the area. A vicinity map showing the reservoir location and a blowup of the
dam area and area of rehabilitation are included on Figures 1 and 2.

Hydrology and Water Rights

The source of water for the Young Creek Reservoir Company is diversion flows out of the Young Creek
drainage, which is a tributary to the Forked Tongue drainage on the Grand Mesa in Delta County,
Colorado. Impoundment rights totaling approximately 781.92 acre-feet in Young Creek Reservoir 1-2 and
230.46 ac-ft in Young Creek Reservoir No.3 were obtained through legal appropriation between the
dates of 1907 and 1960. The total decreed annual storage amounts to 1012.38 ac-ft. A summary of
water rights are presented in Appendix B.

Project Description and Alternatives

The purpose of this project is to provide rehabilitation to Young Creek Reservoir 1-2 for mitigation of
sinkholes that have historically occurred within the basin. This rehabilitation is necessary to minimize the
potential for future damage to the reservoir basin area thereby limiting impoundment capacity within the
reservoir. To address rehabilitation of the reservoir area in question, the four alternatives listed below
were considered:

1. The no-action alternative.
2. Line the left abutment and reservoir area with 60-mil HDPE liner ($174,474.50).
3. Line the left abutment and reservoir area with geosynthetic clay liner ($180,428.00).
4. Line the left abutment and reservoir area with a compacted clay liner ($176,114.00).

Alternative No. 1 is considered unacceptable since no action will result in storage restrictions by the
state thereby impairing the Young Creek Reservoir Company's ability to supply irrigation flows to its
shareholders.

Alternative No.2: This alternative involves lining the area of proposed rehabilitation with a High Density
Polyethylene (HDPE) liner. The area along the left abutment of the reservoir between elevations 84 ft.
and 102 ft. extending from the dam face approximately 200 ft. into the reservoir basin is the area of
treatment. The area will be stripped and shaped prior to placement of liner. The liner will be anchored
along the limits of the rehabilitation area. A rip rap bedding material (12") will be placed over the liner and
24 inches of Rip Rap (D50=12") will be placed over the bedding material.

Alternative No.3: This alternative involves lining the area of proposed rehabilitation with a
Geosynthetic Clay Liner (GCL). The area of treatment is identical to that described above. The area will
be stripped and shaped prior to placement of liner. The liner will be anchored along the limits of the
rehabilitation area. A rip rap bedding material (12") will be placed over the liner and 24 inches of Rip Rap
(D50=12") will be placed over the bedding material.

Alternative No.4: This alternative involves lining the area of proposed rehabilitation with a Compacted
Clay Liner (CCL). The area of treatment is identical to that described above. The area of treatment will
be stripped and clay will be excavated and stockpiled for reuse in the liner system. A 12" layer of filter
material will be placed against the exposed slide rock. The filter material will be compacted and covered
by 18 inches of compacted clay liner material salvaged from the basin excavation in the area of treatment
and from sources within the basin area. A rip rap bedding material (12" thick) will be placed over the CCL
and a 24" layer of Rip Rap (D50=12") will be placed over the bedding material.

Young Creek Reservoir 1-2
Reservoir Rehabilitation Feasibility Study
July 2004

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