Brookhaven officials have postponed the planned dredging of Lower Lake in Yaphank over concerns that the cleanup of nearby Upper Lake has fed excessive amounts of sediment into the millpond.

Supervisor Edward P. Romaine said he hopes Lower Lake will be dredged next year. But the delay, and expected adjustments to the dredging plan, will increase the cost of the $4 million project, he said.

Officials could not estimate how much the delay would boost costs.

But Romaine said the postponement has thwarted the town's plans to control costs by dredging both lakes in the same fiscal year. "It will cost us twice for the thing that was supposed to happen once," Romaine said.

Both bodies of water were to have been dredged this year to remove invasive plants and hundreds of tree stumps that had been left in the lake beds more than two centuries ago when forests were cleared to create the man-made millponds.

But sediment stirred by contractors dredging Upper Lake this summer caused turbidity, or cloudy water, said project consultant Chic Voorhis. Sediment is considered a pollutant under the federal Clean Water Act, officials said.

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In addition, the lake bottom was littered with more stumps than anticipated, Voorhis said. "It was amazing how much material had to be removed," he told the town board.

Officials involved in the project decided that dredging Lower Lake was too risky because sediment likely had drained into it from Upper Lake, Voorhis said.

Councilwoman Connie Kepert, whose district includes the two lakes, said she was "disappointed that Lower Lake could not be done this season. I'm very hopeful that it can be done next season."

Upper Lake dredging began on June 1 and was completed on Sept. 5, Voorhis said. Under rules set by a state permit for the project, Lower Lake dredging was to have been completed by Oct. 31.

Voorhis said alternative methods of cleaning Lower Lake were rejected as impractical. "I'm really not aware of an effective option," he said.

Yaphank resident Johan McConnell said invasive species in the lakes have become a critical issue in the past eight years. She said she won't let her Labrador retriever swim in Lower Lake, and residents no longer use it for boating, fishing and swimming, "because it's so choked with the invasive species you really can't do any of that."

With Deon J. Hampton