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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DESCRIPTION OF SELECTED PLAN

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The selected project is Option 4-6 - Resurface the Upstream Slope with a Soil
Cement Overlay, Limited Length. The major structural component for the project is the
soil cement facing placed at the toe of the existing upstream facing and continued up
the slope to the elevation 36.5, the base of the parapet wall. The project length would
be limited to approximately 8,100 feet with a soil cement placement width of 9.0 feet,
and the actual length based upon the unit price for construction of soil cement and
placement width. The project is proposed with a minimum soil cement placement width
of 6.0 feet, Placement width at less than about 8.0 to 9.0 feet requires non-
conventional placement methods such as a conveyor system, which would more than
likely increase the unit cost for the soil cement, but may yield a net overall increase in
the placement face surface area. This alternative would be explored in bid options.

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The major preparatory work for the project includes the investigation for voids
behind the existing slabs and the excavation of the toe trench for placement of the soil
cement foundation. Figure 7 details the major project components. Essentially, the
project requires the same construction across the entire length of the dam.

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Desiqn Criteria

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Design criteria for the stability analyses and general geotechnical considerations
have been summarized in the previous section, Recent Field Investigations, and are
included in the October 2000 report by Kumar and Associates, attached in Appendix D.
The design and laboratory investigations for soil cement are also included in that
section. Additional subsurface investigations are proposed for the final design to obtain
material properties of the existing embankment and dam foundation soils, verifying the
soil design assumptions made for the ~eotechnical investigation which were based on
the limited information in the Smith Feasibility Report.

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Final design laboratory investigations may investigate the soil cement design

using hammer compaction or modified proctor density methods, which may better

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represent field compaction results, and substitution of fly ash for a portion of the

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