CASE STUDY: BLAKELY MOUNTAIN DAM

摘要

Blakely Mountain Dam, a 1,100 foot long, 205 foot high earthen dam, which forms LakeOuachita, is located approximately 10 miles NW of Hot Springs, AR. This project wasplaced in service in August 1953 and is currently being evaluated for concerns regardingseepage and piping failure modes of the dam.Blakely Mountain Dam was built with a gravel drain abutting against the impervious corefor 3,300 square feet along the length of the dam. This gravel drain does not meet filtercriteria for the impervious core materials and therefore may lead to piping of the corematerial.Construction of a 2 million dollar seepage collection system consisting of an imperviousberm with 10 manholes, ditches, and a V-notch weir was completed in October 2009 tomonitor flow through the dam. Three manholes were equipped with turbidity meters tomonitor soil particles movement through the system.Between November 2010 and January 2011, the collection system had no flow. Thisprompted the Vicksburg district to test for possible leaks throughout the dam, which maycause water and possible piped material to bypass the seepage collection system. InJanuary 2011, a dye test was performed on the dam. This consisted of pumping highlyconcentrated dye into the blanket drain and monitoring for leakage.To date no evidence of piping has been observed. An Issue Evaluation Study (IES) forBlakely commenced this past March. This presentation will profile the dam’s history,results of recent tests, and the outcome of the IES.