The U.S. Army Corps of Engineers, Nashville District, announced today that Center Hill Lake elevations will be lower during remediation work on Center Hill Dam. The Corps plans to target Center Hill Lake levels between elevation 630 feet above mean sea level (msl) in the summer and no lower than elevation 618 msl during the late fall and early winter.
These elevations are approximately five to ten feet lower than recent pool operating levels, and as much as eighteen feet lower than normal operating levels. Since early 2007, the Corps has targeted the lake levels at the lower boundary of the operating guide curve, which is elevation 640, summer pool, and elevation 623.5, winter pool.
At the new lowered levels, all marinas will be operable. However, access to the marinas may be affected and in some cases, restricted, particularly during the fall, winter and early spring months. At elevation 630, 24 of the 35 boat ramps will be usable.
At elevation 618, all 35 launching ramps will be unusable. Information on each specific ramp is available on the website.
The lowering of Center Hill Lake is intended to decrease pressure on the foundation, reducing the progression of seepage, as well as lessening downstream damages in the unlikely event of a dam failure. The chosen levels are the result of an Environmental Impact Statement (EIS) developed over the past year. The EIS evaluated potential impacts caused by each of nine lake level alternatives.
The process included consideration of safety concerns, potential impact to project purposes, and the views of the State of Tennessee, other federal agencies, affected stakeholders, and the public. The goal of the EIS was to identify an alternative that balanced the safety of the downstream human and natural environment against the reduction of project benefits from water supply, water quality, recreation, navigation, and hydropower.
During the five year repair period, this interim pool operation will be periodically re-evaluated to determine if Center Hill Lake can be safely raised, maintained, or if further lowering is necessary to ensure safety. Completion of the dam repairs will extend the project life well into this century, resulting in continued long-term project benefits.
The lake restriction at Center Hill reservoir coupled with ongoing lake restrictions at Wolf Creek reservoir upstream significantly reduce the amount of water in storage in the Cumberland River Basin reservoir system. The impacts of reduced water availability are most likely to be experienced in the summer and fall.
The Corps has developed an Interim Operating Plan (IOP) for management of the reservoir system during the time these pool restrictions are in place. The IOP establishes priorities that water managers will follow during this period of limited water resources. The priorities are: 1) water supply; 2) water quality; 3) navigation; 4) hydropower; and 5) recreation. The Corps operated according to these guidelines in 2007 when severe drought and excessive summer heat accompanied less restrictive pool restrictions.
Further information regarding the seepage problems, remediation, Environmental Impact Statement (EIS) and Cumberland River Reservoir Interim Operating Plan (IOP) may be found on the Nashville District website at http://www.lrn.usace.army.mil/CenterHill/.
U.S. Army Corps of Engineers awards first construction contract at Center Hill Dam
The Corps announced the awarding of the first large construction contract today as part of ongoing rehabilitation of the foundation of Center Hill Dam. The foundation grouting contract was awarded on Friday, February 22 to Kiewit – A.C.T., J.V., a joint venture between Kiewit Southern Co., and Advanced Construction Techniques, Ltd. at a price of $87.4 Million.
The main components of work are:
1. Construction of a work surface along the upstream (lake) side of the main dam earthen embankment
2. Construction of a work surface along the left rim (just west of the dam). This requires excavation similar to a road cut through the hill just west of the dam.
3. Drilling small diameter holes into the rock foundation and pumping grout (a flowable cement slurry) in the foundation to fill any voids.
4. Installation of an approximate 3, 500 foot-long continuous grout line into the main embankment and left rim
5. Filling a cave feature in the rock foundation of the left rim
Center Hill Recreation Area (also known as Ike Park), which is located immediately adjacent to the dam and contains a boat launching ramp and picnic facilities, will be closed to public use once the contractors arrive on site and construction begins. This area will be used as a staging area for construction.
Although long-term road closures are not expected, brief interruptions to traffic along the roadways near the dam may result from the planned construction work.
Center Hill Dam has been identified by the Army Corps of Engineers as a high risk dam due to worsening foundation seepage. This grouting contract is an important first step to significantly improve the long-term reliability of the dam and public safety.