UPSTREAM SLOPE PROTECTION REPAIR JACKSON LAKE RESERVOIR DAM, MORGAN COUNTY, COLORADO

摘要

Jackson Lake Reservoir Dam was constructed about 100 years ago as an off-channel storage reservoir for agricultural purposes. The reservoir has a maximum storage capacity of 35,000 acre-feet. The dam embankment is approximately 2 miles in length with a structural height on the order of 20 feet. The embankment is earthfill consisting of granular material overlying a foundation of similar soils. The slope protection consists of cast-in-place concrete slabs, the oldest of which date from around 1912. In recent years, repairs consisting of filling sinkholes or voids on the dam crest and beneath slabs, and repair and replacement of damaged concrete slabs have been made on a continual basis. Considerable effort was spent on the maintenance, primarily due to failing slope protection. The causes of sinkhole development and the need for continual maintenance were studied and determined to be due to the lack of an upstream cutoff and failing concrete slabs. Several rehabilitation alternatives were studied and rehabilitation by use of soil cement was selected due to the presence of suitable sand aggregate on the beach near the embankment. The cost of rehabilitation was reduced when the contractors selected the placement alternative of a 6-foot wide soil cement layer. Laboratory mix design was performed using lake water. Quality control and testing indicated strength exceeding the Portland Cement Association (PCA) and U.S. Bureau of Reclamation (USBR) criteria. The field test results and photographs were transmitted electronically and available on a daily basis along with data and production summaries.