PROJ00243

• Contract/PO #: C153680
• Contractor Name: Santa Maria Reservoir Company
• Water District: 0
• County: Hinsdale
• Bill Number: SB 94-029
• Loan Projects - Doc Type: Feasibility Study

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Geotechnical Engineering Investigation

After the completion of drilling, 2-inch PVC stand-pipes were installed in all boreholes.
The lowest 10 or 20 feet consisted of a screened section with a coarse sand backfill around it.
The remainder of the pipe consisted of solid sections with a bentonite and / or cement backfill to
serve as a seal in order to isolate the screen section from the upper part of the borehole.

The attached boring and well construction logs, Appendix A, show our interpretation of
the subsurface conditions at the dates and locations indicated. They may not be representative of
subsurface conditions at other locations and times. Photographs taken of samples collected from
the boreholes are included in Appendix A.

B. Permeability Tests

Falling head penneability testing was conducted or attempted in four borings, B-2, B-3, B-
3A and B-4, at intervals between 10 and 20 feet, depending on drilling water or mud loss. In all
attempts the borehole could not be filled with water even though the pumping rate ranged
between 10 and 12 gallons per minutes for up to 30 minutes. This indicates a high degree of
penneability in the surrounding materials.

C. Laboratory Testing

The laboratory testing program was directed toward a quantitative and qualitative
evaluation of the physical and mechanical properties of the soils underlying the site and within the
dam shell.

Gradation tests were perfonned on all retrieved soil samples of the subsurface soils in
accordance with ASTM Test Designations D-421 and D-422. These tests were perfonned to
assist in the classification of the soils and to determine their grain size distribution. The results of
these tests are presented on Figures B-1 through B-22, in Appendix B.

Continental Dam

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