Pickwick Landing Dam South Embankment Seismic Upgrade Project

ABSTRACT ONLY - Located on the Tennessee River, the Pickwick Landing Dam South Embankment is a 3,000 foot-long, 65-foot tall, hydraulic fill dam constructed in the 1930s. As part of their valley-wide dam safety seismic hazard assessment program, the Tennessee Valley Authority identified the need to improve the seismic performance of the south embankment. An alternative evaluation process was used to select a preferred design alternative that included upstream and downstream buttresses to address the potential liquefaction-induced strength loss of both foundation and embankment soils. The final design of the buttresses was developed to achieve safety factors of at least 1.1 for post-seismic slope stability and to limit post-seismic deformations to less than 2-feet in both the upstream and downstream directions. The upstream buttress included over 825,000 tons of rockfill installed through up to 14-feet of soft sediments. The downstream buttress included over 725,000 cubic yards of soil and aggregate filter materials. The project also included installing a dewatering system which included a series of deep wells, downstream toe drains and stream channel modifications. A comprehensive instrumentation monitoring system was developed and installed prior to beginning construction to monitor dam behavior during construction. This paper will provide an overview of the project and will describe some of the challenges the project team encountered and how they were handled during design and construction.