Benzene levels in groundwater 800 times higher than safe level
Authorities on Wednesday installed and sampled three new monitoring wells within 10 feet of Parachute Creek, one day after high benzene levels were reported within the same distance of the creek.
The results of those samples, along with another round of samples taken from the surface of the creek itself, were not available.
Benzene levels as much as 800 times more than the federal drinking water standard were found Tuesday in shallow groundwater in a monitoring well just 10 feet from the banks of the creek at the site of a liquid hydrocarbon leak.
State officials continue to say that testing of the creek water continues to show no signs of contamination from the leak.
Sampling results from well completed Tuesday show benzene levels of 1,900 to 4,100 parts per billion. The Environmental Protection Agency’s maximum allowable level for benzene, a carcinogen, in drinking water is 5 ppb.
Readings from three other wells farther from the creek and closer to the contamination site have shown readings ranging from 5,800 ppb to 18,000 ppb.
The highest reading is near a recovery trench dug as part of the leak cleanup. That trench, and the area around an above-ground valve set for a 4-inch-diameter natural gas liquids line from Williams’ nearby gas processing plant, are being investigated as possible sources of what investigators think may have been historic releases of hydrocarbons. No active leak sources have yet been found.
Williams spokeswoman Donna Gray said Tuesday the 4-inch line went into service in 2008.
The contamination was discovered by Williams in a pipeline corridor March 8 as it was doing location work. Some 6,000 gallons of hydrocarbons were recovered.
Colorado Department of Natural Resources spokesman Todd Hartman said the new monitoring well is about 325 feet southeast of the valve set and recovery trench.
Investigators for the Colorado Oil and Gas Conservation Commission believe groundwater is flowing from the creek toward the contamination site, rather than vice versa, which is helping protect the creek from contamination.
Parachute Creek provides irrigation water to the town of Parachute. Town Administrator Bob Knight said Tuesday the town usually releases water from the creek into its irrigation reservoir on April 15.
“We are hoping this matter is resolved long before that. But I have no intention of turning water into the reservoir until it is cleaned up and the leak has been found or whatever is causing that,” he said.
He said some residents probably will use the town’s domestic water system for irrigation, which will put more strain on the system’s treatment plant.
“But we believe we can handle it for the interim,” he said.