The U.S. Army Corps of Engineers Nashville District announced today a normal decrease in construction activity at Center Hill Dam as the Seepage Rehabilitation project transitions from first phase grout placement to the next phase of constructing a foundation barrier wall.
"We want to assure the public there is no reason for concern if they notice a lull in activity," said Project Manager Linda Adcock. "The grouting contract is basically complete and proposals for constructing a foundation barrier wall are currently being evaluated."
The seepage rehabilitation plan is a combination of grouting and construction of a continuous concrete barrier wall for long-term stability. The District anticipates awarding the 2.5-year-long contract to construct the permanent seepage barrier for the earthen dam's foundation in the spring of 2011.
"A vertical concrete wall, at least 2-feet thick, will be constructed through the earthen dam and into the rock foundation below to prevent seepage from harming the foundation," Adcock added.
Awarded in March 2008, the grouting contract was the first major contract of the seepage rehabilitation effort and is essentially complete. The grouting filled voids and soil-filled openings in the rock foundation and prepared for the safe construction of a concrete barrier wall. More than 1.5 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.
The problem was identified through long-term dam monitoring and stems from the type of karstic limestone rock on which the dam was constructed in the late 1940s.
A study is also underway to determine if rehabilitation is needed in the foundation for the earthen saddle dam built to fill a low area about 1,500 feet east of the main dam and should be concluded in early 2011.
Total cost of the project is estimated at $295 million, with about $120 million spent to date on investigations and construction.
The Corps plans to maintain Center Hill lake levels as it has in recent years, 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 weather-dependent.
Additional information is available at http://www.lrn.usace.army.mil/CenterHill/index.htm.