Repairing Dartmoor's drawdown assembly requires funding

By Harvey Hoffman / Sun contributor

Harvey Hoffman is the general manager of the Fairfield Glade Community Club.

The Fairfield Glade Community Club (FGCC) will hold a Special Board Meeting for the purpose of voting on approving expenditures related to the repair of the Lake Dartmoor dam drawdown assembly. The meeting is scheduled for Monday, June 15, 11 a.m., at the Community and Conference Center.

During the heavier than usual rain falls in early May, the drain valve in the dam was opened by club staff. The reasons for opening the valve were related to the rising lake level caused by the extreme rainfall. The lake water was over riding sea walls, docks, golf course pathways and other structures.

Partially opening the drain valve allowed excess water in the lake to be released. After a few days, the valve was closed. This action, unfortunately, caused a previously repaired area on the drawdown pipe to be damaged. When the valve was closed, water was flowing out of the 30-inch outlet pipe at the bottom of the dam.

In an effort to arrest the unwanted flow of water, underwater divers placed numerous bags near the hole(s). The extent of the size and number of holes has not been determined, as the divers were not able to safely inspect the area as the water flow was too heavy. The bags were made of various flexible and inflexible materials and filled with concrete, foam, sand, sawdust and other materials. Specialized concrete was also shot into the area. Those efforts were only partially successful in reducing the to 11 inches flow to 6 inch level in the 30-inch outlet pipe. As of the end of the week, June 6, the flow was 6 inches deep in the pipe, or approximately 2,000 gallons per minute.

A large pump has been installed for the purpose of recycling the lake water that is being lost. Until the pipe was buried under the surface of the roadway, the roadway was closed.

There have been many meetings with the Geotek Engineering Company, Inc., of Nashville TN, the club’s "Engineering Firm of Record," as well as a number of experienced repair companies. A solution has been identified. Our challenge is to block the flow and then effect a permanent solution. A blockage or other type of flow control needs to be placed in the pipe before the repair can be safely effected. An inflatable packer “donut” will be placed approximately 300 feet upstream from the outlet. The full length of the outlet pipe is approximately 600 feet. Extending 5 feet through the “donut,” a 12-inch pipe will be placed, affording a path for the water to flow, until the repair can be effected. The outlet end of the 12-inch pipe will be closed with a gate valve, allowing for the pipe to be used in the future, in cases of an emergency. A second perforated pipe will be installed along with the 12-inch pipe. but ending before the “donut.” Through the second pipe, concrete will be injected filling the 30-inch pipe from the location of the packer to the downside opening creating a permanent plug.

We have spoken to John Mishu, P.E., principal of Geotek engineer firm, that has worked with the club for many years, and he assured the club that the integrity of the dam is currently not at risk. Jeff Warren, FGCC director of community services, has been in communication with an official of the Tennessee Department of Safe Dams.

Boat owners on Lake Dartmoor may want to consider moving or removing their boat to a location where the water will be deeper. It is estimated that the lake could drop approximately 30 inches. The extent of the drop in lake level is not appreciably lower than was observed during the past few years of unusual low rainfalls.

The projected completion of the repairs is estimated to take up to four weeks, dependent on approval of the Tennessee Department of Safe Dams and the Department of Water Pollution Control.

During the storms, water was flowing over the spillway located on Catoosa Blvd. This spillway is the severe "flood control" mechanism for Lake Dartmoor Blvd. The flow was at the overflow level and could have endangered vehicle traffic on Catoosa Blvd. if the rainfall had continued. As a second phase of the project, it is expected that the spillway structure will be altered in the near future, as a further precaution to similar events.

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