Current phase of Clearwater Dam construction almost half complete

PIEDMONT, Mo. -- Nearly half of the concrete panels needed to complete the cutoff wall have been installed at Clearwater Dam, according to a news release from the U.S. Army Corps of Engineers office in Little Rock, Ark.

About 122 of the 273 panels have been excavated and back filled with concrete. Work is ahead of schedule and should be completed in 2014.

Once the cutoff wall is complete, it will resolve chronic seepage that has threatened the dam's stability. The wall will be as much as 195 feet deep, or 40 feet into competent rock. The rock elevation fluctuates; therefore, the bottom of the wall will vary with the depth of the rock.

Seepage was detected as early as the 1950s. As a result, modifications were made over the years, including changes to the management of lake levels. In 1989, a seepage berm was constructed. However, seepage continued. In January 2003 during a routine inspection of Clearwater Dam, a sinkhole was discovered about midway along the upstream surface of the dam. The sinkhole was 10 feet across and eight to 10 feet deep. It was repaired, and intensive studies were begun to find a permanent solution.

The rehabilitation project is being constructed in multiple phases. The exploratory drilling and grouting phase was known as Phase I. After gathering information from the exploratory drilling, the need was identified to perform more extensive grouting treatment of the dam, which became Phase Ib. Construction of the actual concrete cutoff wall is Phase II.

Today, Corps personnel continue to perform frequent inspections, and a number of other Interim Risk Reduction Measures continue in place. No further detrimental changes have been observed. The inspections monitor seepage conditions, settlement and movement. In addition, officials increase inspections when heavy rain occurs and the lake elevation rises. They monitor through instrumentation and "eyes on" inspections.

As confidence in the dam's stability increases, Corps officials caution against becoming complacent about the risks of living, working or recreating downstream of any dam. Complacency can cause people to fail to take action or even cause them to take inappropriate action in the event of an emergency and increase the risk to their property or lives.

Also, once the rehabilitation project is completed and the dam is functioning properly, there will still be inherent risk to those downstream in the floodplain of the Black River. Clearwater Dam reduces downstream flood losses in most circumstances. But it has limitations, and flooding, even severe flooding, will still occur in the floodplain from time to time.

For more information about Clearwater's rehabilitation project, please call the Clearwater Project Office at 573-223-7777.

Pertinent address:

Clearwater Dam, Piedmont, MO