CAGE November Monthly Meeting November 14, 2018 Lakewood Country Club
6800 W 10th Ave
Lakewood, CO 80214
11:30am-1:00pm
Clear Lake Dam Replacement: RCC Dam on a Challenging Soil Foundation
Clear Lake Dam is a high-hazard-potential dam located on Guanella Pass Road, about 3 miles south of Georgetown, Colorado. The original dam, constructed in about 1902, was a timber-crib embankment dam with a history of seepage issues. It was supported on a foundation composed of unstratified glacial till, alluvium, landslide debris, rockfall, and can potentially include zones of “internally unstable” gap-graded deposits where finer-grained particles are not filter-compatible with coarser-grained particles and can be prone to internal erosion where high-gradient seepage flows are present. In 2011, seven sinkholes were discovered near the upstream slope of the dam, and leakage was identified in the outlet conduit beneath the upstream toe. In 2013, after considering several alternatives, the dam owner decided to replace the dam with a new roller-compacted concrete (RCC) dam. Greg Monley will summarize the geotechnical investigations and analyses performed for the design of a new RCC replacement dam supported on a challenging soil foundation, including the design of a filter/drain system that addressed potentially unstable foundation soils. Foundation design features to minimize settlement, cracking, and RCC dam contraction joint leakage will also be discussed along with a summary of the initial performance of the dam.
Greg Monley, P.E., Senior Geotechnical Engineer
W. W. Wheeler & Associates, Inc.
Greg Monley is a registered professional engineer with over 30 years of geotechnical engineering and engineering geology experience in design, construction, and rehabilitation of dams and hydraulic structures, other earth structures, and geologic hazard evaluations and mitigation. He has worked on large dam projects, including rock slope and landslide stabilization designs for dams, throughout Colorado and the western United States. Greg was employed by Kumar & Associates during the subject work.
