Clovis Public Works Director Harry Wang said Thursday the city may have to spend more than $600,000 to treat a half-mile-long plume of toxic solvent that is contaminating groundwater to the east of the old city landfill.
City and state officials said the contaminated water is not used for human consumption.
The solvent, perchloroethylene, has been found in concentrations of about 50 parts per billion — 10 times the groundwater standard set by the U.S. Environmental Protection Agency.
The plume has been found in groundwater about 270 feet below the surface. It is about a half-mile long and a quarter-mile wide, Wang said.
Beginning somewhere under the site of Clovis’ old city landfill, the plume is heading east in the Ogallala Aquifer and appears to be moving at about 20 feet per year, said Ed Hansen, a hydrologist with the state Environment Department.
At concentrations of 5 ppb and with a lifetime of exposure, perchloroethylene has a one in 100,000 to one in 1 million chance of producing cancer in humans, Hansen said. However, the solvent contaminating the groundwater under the landfill is at10 times that concentration, he said.
“There’s no immediate danger. No one is consuming the groundwater in that area. However, the plume is moving, so we want to get it under control as soon as possible,” Hansen said.
The city and the New Mexico Environment Department will hold a public meeting at 7 p.m. June 10 in the Clovis-Carver Public Library to discuss the remediation plans.
Wang said the city is considering two methods of dealing with the contamination: pumping the contaminated water from the aquifer, then either carrying it by truck or pumping it through a pipeline and dumping it into the city’s wastewater treatment plant; or using “bioremediation,” in which bacteria capable of eating the solvents are pumped directly into the plume. The two methods also could be used together, he said.
Wang said building costs for the pump-and-treat method would be $600,000, plus an additional $100,000 per year for pumping. He said he does not yet have figures for the bioremediation system.
Wang said the plume is under city-owned land and the city owns all the land to the southwest for more than a half-mile. In addition, the city has a number of monitoring wells around the site, he said.
Although the city leases the land south of the site for agricultural purposes, so far no solvent has been detected in any agricultural wells, Wang added.
Perchloroethylene, also called Tetrachloroethylene, is commonly used as a dry-cleaning solvent, but also is used as a grease remover by mechanics, Wang said.
Clovis Public Works personnel think that sometime between the mid-1930s and the late 1970s, an unknown party or parties dumped a large quantity of the solvent in the old city wastewater treatment system or at the old landfill site, Wang said.
Wang said two water wells owned by the New Mexico-American Water Company located north of the area were shut down in the early 1990s after traces of perchloroethylene were detected. No traces of solvent have been discovered in any drinking water wells since then, he added.
Jim Bonner, New Mexico-American Water Co.’s operations manager, said the company continues to monitor the wells but takes no water out of them. He said the wells continue to show traces of perchloroethylene and nitrates.
The city of Clovis found the perchloroethylene plume when it drilled a series of monitoring wells in response to New Mexico-American Water Co.’s discovery. City officials reported the problem to the Environment Department’s Solid Waste Bureau in 1996, Wang said.