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

I
I
I
I
I
I

stability of the upstream slope would not be addressed. The existing parapet wall is not
replaced, providing some uncertainty for future repair. The life span for the work is
expected to be 50 years, and a new slab replacement program, excepting the
cutoff/foundation toe construction, would be initiated around 2051.

I
I
I
I
I
I
I
I
I
I
I
I
I

Option 4 - Resurface the Upstream Slope with a Soil Cement Overlay
This option would consist of overlaying the existing concrete slabs with
horizontally placed layers of soil cement. Horizontal layer width of the soil cement
would range from 6.0 to 9.0 feet, resulting in a placement thickness normal to the slope
of approximately 2.7 to 4.2 feet. Placement would include a soil cement cutoff wall at
the upstream toe of the dam. This wall would serve as a seepage cutoff as well as the
footing for the additional soil cement placement against the existing facing, Soil cement
placement would extend up the dam slope to the top of parapet wall at gage height
40.5 (Option 4-4) or up to the base o'f the parapet wall at gage height 36.5 (Option 4-1
and 4-6). Option 4-4 is structured to provide a complete project with the facing carried
to the top of the parapet wall. Option 4-1 is structured to provide a complete project
with the facing carried to the base of the parapet wall. Option 4-6 is structured to limit
expenses to the expected available funding, and addresses approximately 8,100 feet of
the dam length with the soil cement placed up to the base of the parapet wall. The
. '
limits of the soil cement .facing for Option No. 4-6 would be set to address the areas of
historic problems with sink holes,

For all Options 4. a major program to investigate voids under the existing slabs
may be undertaken. This program could include drilling into the slabs and probing for
voids. If voids were encountered, the site would be further explored. It is expected
that the voids would be grouted, but in some instances it may be necessary to entirely
remove the existing slabs. Figure 7 shows the design concept for this option.

This program would be completed in one season without severe impact on the

use or storage of reservoir water. The soil cement is massive and durable, and has a

life expectancy of more than 100 years with little maintenance required. Soil cement

has been in service at Bonnie Dam in eastern Colorado for about 50 years, and is still

27