PARACHUTE, Colo. - Now that the Williams Midstream company believes it has found the source of the so-called Parachute Creek plume, the company has turned its attention to cleaning up what the failed pressure gauge left behind.
But state overseers of the oil and gas industry are still watching closely.
An April 10 statement from Todd Hartman, communications officer for the Colorado Oil and Gas Conservation Commission, noted that Williams' identification of a faulty gauge attached to an above-ground valve as the source "provides a possible explanation of a release in this area."
But, Hartman's statement continued, "The investigation of the cause or causes of the impacts to soil and groundwater will continue until we can determine whether the release described by Williams accounts for the situation on the ground."
According to statements from the commission and Williams, the company has continued drilling new monitoring wells along the banks of Parachute Creek to determine the overall size of the plume and to check for groundwater contamination.
According to the commission's April 10 bulletin, three new groundwater monitoring wells about 50 feet south of Parachute Creek showed benzene at concentrations between 51 parts per billion (ppb) and 450 ppb. That is considerably lower than the levels of benzene found closer to the reported source of the leak.
Hartman also reported that surface water samples taken from the creek itself, about two and a half miles downstream from the plume, showed no sign of contamination.
The samples were taken at about the spot where the town of Parachute takes irrigation water out of the creek.
Williams, in its own assessment of the situation on April 10, estimated that a total of 241 barrels of "natural gas liquids" or -NGLs - made it into the ground from the leak over a period of approximately two weeks in late 2012 and early 2013.
Williams has been working since March 8, with the support of state and federal monitoring agencies, to find the source of the leak, which was discovered by workmen preparing to expand a nearby natural gas processing plant.
During the monthlong cleanup process, Williams has pulled roughly 143 barrels (or roughly 6,000 gallons) of hydrocarbons from the ground, along with nearly 4,300 barrels (180,000 gallons) of contaminated water.
Benzene, a known carcinogen and a commonly used industrial chemical compound often found alongside natural gas, was discovered in monitoring wells near the site of the leak.
In addition, reports from Williams and the state commission have indicated the presence of hydrocarbons in monitoring wells on both sides of Parachute Creek.
Industry and state officials have consistently said the creek itself is not contaminated.