Tennessee Valley Authority
Bear Creek Dam Rehabilitation
October 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
Continued emphasis is being placed on Safety and Environmental Performance at Bear Creek. To date, contractors have experienced two minor incidents resulting in one lost time event.
Excavation and Soldier Pile Walls
Work on the vertical soldier pile walls at the sluice outlet structure and along the spillway wall has been completed and the contractor has left the site. All earthen material within the excavation has been removed. The Phase 5 area was recently excavated after the completion of the spillway soldier pile wall and the rock features are currently being cleaned and mapped.
There have been no significant rainfall events, so the dewatering system is removing a minimal amount of water at this time.
Grouting:
The drilling and grouting program is nearing completion in all areas, except for the area in Phase 5 near the existing spillway due to the work described above.
Several areas were identified that could not be mitigated by the grouting work and required concrete cutoff walls installed into the rock. Panels 2 and 4 have been excavated, mapped and filled with concrete. Work is ongoing in panels 1, 3a and 3b.
Current Activities:
- Installation of soldier pile walls near the sluice and spillway structures is completed.
- Drilling and grouting of the foundation is nearing the completion.
- Final excavation and dental concrete placement in phase 5 by the spillway wall is nearing completion.
- Cutoff wall panels 2 and 4 in the areas of large features are completed. Work is ongoing in areas 1, 3a, and 3b.
- The foundation for the concrete grade beams over the sluice outlet structure is nearing completion.
- The RCC contract will be awarded and contractor mobilization is to begin this month.
View of a hoe ram excavating the rock down in panel 3a of the cutoff wall.
