One of three interceptor wells that have been pumping millions of gallons of water daily into the Muskingum River for 26 years has been shut off by Marietta's water department due to improved water quality at the site.
"We tested interceptor well 2 in March and April this year and found no contamination, and we're monitoring it regularly to see if any problem still exists," said Jeff Kephart, city water superintendent.
The three wells were installed during the 1980s after a chemical called tetrachloroethylene (PCE) was discovered in groundwater near a portion of the city's well fields.
The substance is widely used for dry-cleaning fabrics and metal degreasing operations.
The city well fields, generally located between the Washington County Fairgrounds and the Marietta Aquatic Center, contain seven production wells that draw the city's drinking water from the sand and gravel aquifer.
Kephart said the city is blessed with plenty of safe drinking water supplied by the production wells, and that water is in no danger of contamination.
"But tetrachloroethylene is considered a volatile organic chemical," he said. "The three interceptor wells were installed to pump off any contaminated water before it reached the production well field."
Until March of this year all three interceptors were pumping water into the Muskingum 24 hours a day.
"Interceptor well 1 pumps about a million gallons a day, while the others (interceptors 2 and 6) were together pumping a total of about 1.3 million per day," Kephart said.
Although interceptor 2 has been shut down, wells 1 and 6 will continue to pump off the contaminated water.
"Our major area of concern now is in the area of the old mini-golf facility at the fairgrounds," Kephart said, noting contaminated groundwater there likely means interceptor well 1 at that location will have to be operated indefinitely.
He said the shutdown of interceptor well 2 will also save the city between $300 and $400 a month on electricity required to run the pumping equipment.
Kathy Davis, stormwater specialist with the Washington Soil and Water Conservation District, said closing down one of the interceptor wells due to the lack of contamination is good news, but monitoring of groundwater in that area will have to continue to make sure the contaminant is gone.
"And it's important that people be mindful of the location of the city's well fields," she said. "That's why any spill of materials in that area, no matter how small, must be thoroughly cleaned up. The well fields are on very sandy soils, and the (Ohio Environmental Protection Agency) requires a 300-foot isolation zone around each of the city's potable wells."
Davis said no construction or other potential contamination activity can be performed within the isolation zone.