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~~~ September 19, 2000 Public Service Company of Colorado 1225 17"' Street, Suites 600 P.O. Box 840 Denver, Colorado 802:01-0840 Attention: Ms. Lissi Lett Subject: GeotechnicalOpinion Ames Hydro Penstock Embankment Fill San Miguel County, Colorac_ Job No. 31,848 Introduction SEP 1 9 2000 Division of R.4inerals and Geology At your request, on August 18, 2000 our Mr. Glater observed an Embankment containing the Ames Hydro Penstock. The purpose of the site visit s to gather information to evaluate concerns expressed by Public Service Company (PSCO) regarding stability of the embankment and related risk of damage to the pipeline caused by movement of the embankment or movements resulting from traffic loads: The area of concern for this study is located about 4100 feet south of the Ames Hydro Plant (Fig. 1, Vicinity Map), where an embankment of about 400 feet in length crosses a natural drainage about 400 feet west of Colorado Highway 145. Photographs of the general area of focus are shown on Figs. 2-4. The Ames Hydro Penstock is a pipe that carries water to the Ames Hydro Power Plant from two lakes located upstream on the Lake Fork of the San Miguel River. In the area of focus, the penstock is 30 inch diameter fiberglass pipe. We understand the penstock consists of steel pipe outside this reach of 2,208 feet of fiberglass pipe. Site History Through conversations with representatives of PSCO and review of documents provided, our understanding of the history of the embankment and penstock in the area of concern is as follows: The drainage crossing at one tirtfe contained a timber trestle supporting a railroad track, probably dating to the 1890's, No evidence of the trestle was apparent at the time of our site visit. It is unknown whether the trestle remains under the embankment. PUBLIC SERVICE COMPANY OF COLORADO AMES HYDRO PENSTOCK CTL/T 31,BQB CTL/THOMPSON, INC. CONSULTING "-NGINEERS 1971 WEST 12TH AVENUE ' DENVER, COLORADO E~ • (303) 825-0777 V