NASHVILLE, Tenn. (June 22, 2012) – The U.S. Army Corps of Engineers Nashville District announces today Highway 96/141 over Center Hill Dam is being restricted to one lane starting July 9, 2012. The restriction is necessary to enlarge work space on the dam to support the next construction phase of the Center Hill Dam Foundation Remediation Project, installation of the foundation barrier wall. During the two-year duration of the lane restriction, an automated traffic control system will safely manage vehicles across the dam. The maximum wait time is five minutes.
“We regret the inconvenience to the public; however, this barrier wall, constructed by Bauer Foundation Corporation, is the major protective feature to keep the earthen portion of the dam safe for many years to come,” said Project Manager Linda Adcock. In addition to the lane closure, motorists can expect occasional traffic delays along Highway 96 as large equipment is transported to the site.
The seepage rehabilitation plan is a combination of grouting, completed between 2008 and 2010, and construction of a continuous concrete barrier wall for long-term stability, which is being installed between 2012 and 2014. “A vertical concrete wall, at least two-feet thick, will be constructed through the earthen dam and deep into the rock foundation below to prevent seepage from harming the earthen dam,” Adcock added.
Awarded in March 2008, the grouting filled voids and soil-filled openings in the rock foundation and left rim to southwest of the dam. More than one-and one-half million gallons of grout have been successfully placed in the rock foundation along the 800-foot-long earthen dam, 2,700-foot-long left rim and 700 feet downstream of the earthen dam, making the dam safer according to Adcock, and preparing the rock foundation for construction of the permanent concrete barrier wall.
The Corps identified the seepage problem through long-term dam monitoring, which stems from the type of karst limestone rock surrounding the foundation of the dam when constructed in the late 1940s. A study is underway to determine the optimum repair plan for the final phase, the earthen saddle dam, built to fill a low area about 1,500 feet east of the main dam. The study is expected to be concluded by the end of 2012.
Total cost of the project is estimated at $295 million, with about $140 million spent to date on investigations, design and construction. The Corps currently manages Center Hill Lake levels targeting a summer high of 630 feet above mean sea level and a winter pool of about 620 feet; however, day-to-day lake levels are highly dependent on the weather. These target elevations are 10-15 feet lower than normal and are part of risk management until the repairs are complete in late 2015.
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