Trace amounts of DDT found at Tahoe Keys
The discovery of small amounts of a pesticide banned 32 years ago has delayed plans for a third time to dig out the west channel of the Tahoe Keys.
The channel fills with sand about every 10 years and has to be dredged to make room for boats. The issue of where to dispose of the sand removed from the channel caused the two previous delays.
The Tahoe Keys Property Owners’ Association hit its third brick wall early last week when sample water tests showed a small amount, about .03 parts per billion, of DDT.
Dichlorodiphenyltrichloroethane was a popular pesticide in the United States before it was banned in 1972 because of “unacceptable risks to the environment and potential harm to human health,” according to the U.S. Environmental Protection Agency.
The chemical takes up to 15 years to degrade in the environment. It accumulates in fish and birds that ingest it and can affect their ability to reproduce. The chemical is listed by the EPA as a “probable carcinogen” for humans.
The Tahoe Keys Property Owners’ Association and the Lahontan Regional Water Quality Control Board have been working together to determine where the chemical came from, said Doug Smith, a senior engineering geologist for the water board.
Initial tests indicate the DDT did not come from sand or water in the channel.
“We’ve collected samples of water in each step of the water treatment plant,” said Dominic Meo III, a consultant working on the project for Geotechnical Support Services. “Everyone is cooperating in an open and honest way to find the source of the chemical.”
Tests to determine if the DDT came from the 1,500 feet of pipe or the sand/water separating equipment that are part of the dredging project are expected soon. The pipe is needed to send dredged sand and water from the channel along a beach and into the parking lot of the association where treatment equipment is set up.
Even without the test results the association will move forward on the project by fitting a $37,000 carbon filtering machine to the dredging equipment. It will ensure that DDT is stripped from the water involved in the project before it is returned to a Tahoe Keys lagoon.
The project, now slated to start this week, will take up to 14 days to complete. If it turns out the small amount of DDT came from equipment, the association will take action to make sure responsible parties cover the extra cost incurred by the detection and cleanup of the chemical, said Jill Southerland, administrator for the Tahoe Keys Property Owners’ Association.
“There’s been many bumps and mountains in this project,” Southerland said. “Our intention is certainly to abide by all the regulations and do our due diligence. It was almost nondetect but there was enough (DDT) that Lahontan has to figure out where it’s coming from and why it’s there.”
El Dorado County started its mosquito control program in 1963. Records do not mention the use of DDT prior to it being banned in 1972, said Virginia Huber, manager of the county’s mosquito control program. County Agricultural Commissioner Bill Stephans said records regarding chemical use in the county only date to the 1980s, when state law began requiring that those records be kept.
The 6,000 cubic feet of sand to be dug from the channel will leave the entrance to the channel and the channel 3 to 8 feet deeper for boats. Environmental regulations require the sand to be deposited outside the basin. An asphalt company was going to take it but that arrangement fell through. Now the plan is to provide it to a landscape company in Minden, Meo said.
The dredging will be done by a boat fitted with a suction device. The work will cost more than $500,000 with the addition of the carbon filter.
The more than 1,500 property owners in the association will not have to pay a special fee to finance the work. The money will come from a reserve fund. Initial estimates for the project came in between $400,000 and $600,000, Southerland said.
– Gregory Crofton can be reached at (530) 542-8045 or by e-mail at firstname.lastname@example.org
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