Oxygen plan starts on Thurmond Lake

MODOC, S.C. --- A long-awaited project to improve oxygen levels -- and striper fishing -- on lower Thurmond Lake passed a milestone last week as workers installed the first of set of submerged distribution lines.

• Photos

Rob Pavey/Staff

Workers with Mobley Engineering attach concrete anchors to one of nine oxygen lines to be submerged in Thurmond Lake, as an Army Corps of Engineers boat patrols behind them.

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"This is one of nine lines," said Jamie Sykes, a fisheries biologist for the Army Corps of Engineers. "We expect to have three lines in by September, so that we can do some testing."

The $11.3 million project won't go into actual operation until sometime in 2011, when a shore-based oxygen plant will be able to pump 20 to 100 tons of oxygen per day through seven miles of perforated pipes submerged 80 to 90 feet below the lake's surface.

The yellow diffuser line deployed last week by contractors and corps officials was anchored to the lake's bottom. A temporary oxygen tank at the Modoc boat ramp will be used to evaluate its effectiveness before additional lines are placed in the lake.

The project is expected to increase dissolved oxygen levels by up to 3 parts per million along a five-mile swath from Modoc downstream to the face of Thurmond Dam. Current oxygen levels in that area can fall to as little as 1 part per million during warm weather.

Typically, large striped bass migrate upstream when hot weather reduces oxygen. They often congregate in the tailrace of Russell Dam, where there is more oxygen, but where the dam's reversible turbines have been shown to kill fish and also raise water temperatures in Thurmond Lake.

The corps agreed in 2002 that only two of the four reversible units would be operated during warmer months to avoid heating up the tailrace area and disrupting striper activities.

Once the oxygen system is active on the lower lake, that restriction will be lifted.

As part of the testing program, biologists have attached transmitters to about two dozen striped bass. Their movements will be tracked this year, especially during hot weather.

Next year, when the oxygen system is in use, the same fish will again be tracked to see if they tend to stay in the lower lake instead of moving upstream.