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Clean-up of underground chemical plume set to begin

POSTED July 22, 2011 8:49 p.m.

A potentially hazardous plume of dry cleaning fluid has sat beneath downtown Turlock for years.

This week, the cleanup effort kicks off in earnest, with construction completing on a pump-and-treat cleaning system.

“It’s not a public health risk at all, it’s just one of those things that’s there, and we need to take care of it,” said Turlock Regulatory Affairs Manager Michael Cooke.

Tetrachloroethylene, also known as PCE, is a solvent most often used as part of the dry cleaning process. The city discovered an underground plume of the chemical, near downtown Turlock, in the early 1990s.

To this day, city officials remain unsure exactly how PCE reached Turlock’s soil. The most likely explanation suggests that some drycleaner expelled PCE into the city’s sewer system, and then that PCE somehow leaked from the sewer system into the ground below.

Because the source was never conclusively determined, in 2009 the City of Turlock volunteered to lead the cleanup effort, with monetary assistance from the State Water Resources Control Board’s Clean Up and Abatement Account. The $455,000 obtained from the state is expected to cover costs for the entire remediation effort.

While the chemical is considered hazardous, and can be toxic if ingested, the plume currently poses no danger to Turlock’s drinking water supply, according to Cooke.

“It’s kind of isolated in the downtown area,” Cooke said. “It’s not affecting drinking wells.”

The plume is currently between 15 and 50 feet underground, far from the 200-300 foot deep water wells utilized by Turlock.

The cleanup will rely on a “pump-and-treat” system, which pumps contaminated groundwater to the surface, then blows air through the water which causes the PCE to evaporate. The leftover water is then pumped to the wastewater treatment plant for further treatment.

Construction on the system finished this week, built in a corner of the City of Turlock employee parking lot, directly over the PCE plume. The system will be tested next week, and then turned on for good about a month after that.

But when will the pump turn off?

“That’s what we don’t know,” Cooke said.

The cleanup effort could be complete in two years, or it could take 10, Cooke said. Monthly samples will be taken to determine progress in the cleanup.

The State Water Resources Control Board will have the final say as to when the cleanup is complete.

To contact Alex Cantatore, e-mail acantatore@turlockjournal.com or call 634-9141 ext. 2005.

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