Tennessee Valley Authority
Bear Creek Dam Rehabilitation
May 2008
Since its completion in 1969, the earthen Bear Creek Dam has experienced foundation leaks. Previous efforts to control leaks have been ineffective over the long term.
Following periods of heavy rainfall, the reservoir level can rise, and increase the risk of dam failure. To reduce this risk, TVA prepared an Environmental Impact statement to evaluate alternatives for a long-term solution. After thorough study, public involvement, and several opportunities to provide comment, TVA signed a Record of Decision on September 10, 2007 stating it would build a roller compacted concrete structure at the downstream toe of the existing dam along with a water cutoff "wall" under the new structure to block water passage under the dam. Site preparation began in September 2007.
Construction Report Update
Safety and Environmental Issues
The Safety and Environmental Performance at Bear Creek has been perfect to date, with no reportable events.
Excavation
All of the soil and deteriorated rock has been removed from the upper half of Phase 2. The rock surface has been cleaned and 16,500 square feet of surface covered with shotcrete for protection. The area was inspected, photographed and mapped before placement of the shotcrete. Ramps and level areas for the grout drill rigs are currently being constructed.
The excavation of Phase 3 is now complete. Most of the rock bottom of Phase 3 did not have the extensive network of features that were found in Phase 1. Cleaning of the rock surface and dental grout at the south end of Phase 3 is beginning.
The dewatering system that was previously installed is successfully keeping the water out of the Phase 3 excavation.
Grouting
The drilling and grouting in the spillway and the south embankment dam is nearing completion. Currently, grout operations are ongoing in Phase 1. Verification holes will be drilled and tested to determine the acceptability of the grout curtain.
Current Activities
- The upper half of Phase 2 is nearing completion and being covered with a protective shotcrete surface. Ramps for drill rigs are being constructed.
- Phase 3 excavation work is complete, and cleaning and dental grouting has started at the south end of Phase 3.
- Drilling and grouting is nearing completion in the spillway and left embankment.
- Drilling and grouting is ongoing in Phase 1.
View of the exposed rock surface covered with mud and water near the bottom of the Phase 3 excavation.
