C153379 Feasibility Study

• Contract/PO #: C153379
• Contractor Name: Brook Forest Water District
• Contract Type: Loan
• Water District: 9
• County: Jefferson
• Bill Number: SB 80-67
• Loan Projects - Doc Type: Feasibility Study

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are usually loose to medium dense in the upper 5 to 10 ft and become medium
dense to dense below that depth.

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The ground-water condition in the flood-plain alluvium is closely

tied to the level of water in the South Platte River. It appears that some

ground-water flow is in the direction of the river which is probably due to

recharge from irrigation in the flood-plain and water flow toward the river on

top of the bedrock surface. In most cases when the test pits were excavated

in the Hurley Terrace and Louviers Alluvium, the ground water was within

several feet of the surface. The water levels recorded for the test pits and

the borings are presented in Appendix A, on the Log of Borings and Log of Test

Pits on Plates A-IA through A-1M and Plates A-2A through A-2C. The water

levels in the areas of the abutments are located just above or on the surface

of the weathered bedrock.

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4. Geotechnical Design Parameters

The purpose of the geotechnical exploration and laboratory testing

program was to estimate the engineering properties of the in situ soils

encountered below the dam and to quantify the engineering properties of the

materials identified as potential construction materials for the dam. The

in situ soils encountered below the dam are the Sand Hills Formation, the

Hurley Terrace (flood-plain alluvium), the Fox Hills Formation and the Pierre

Shale Formation. The potential borrow materials are the Hurley Terrace, the

Louviers Alluvium, the Sand Hills Formation, the Fox Hills Formation and the

Pierre Shale Formation.

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A summary of the physical properties of the materials tested is presented

on Table 111-4. The detailed results of the laboratory testing are included

in Appendix A. These test results have formed the basis of the design data

for the appraisal-level design of the Hardin Dam and ancillary facilities.

The results of the field and laboratory program were rewarding because suitable

construction materials were identified for the embankment core, shell and

internal drains in the immediate vicinity of the site. The design procedurE!

and the resulting structures are presented in Chapter VI.

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III-18

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