PARACHUTE CREEK, Colorado - Work crews at the site of a hydrocarbon leak have found evidence that unknown hydrocarbons are present in ground water on both sides of Parachute Creek.
According to an update provided by the state, new evidence of hydrocarbons has appeared in a monitoring well on the south side of the creek, although test results to identify the compounds were not available as of Monday evening.
Earlier tests had found the carcinogenic compound benzene at dangerous levels in ground water on the north side of the creek.
Crews from two natural-gas development companies - Williams Midstream and WPX Energy - have been investigating the plume since it was discovered by Williams workers on March 8, according to statements from the Colorado Oil and Gas Conservation Commission and Williams.
A leak from a pipeline, storage tank or other equipment in the area is believed to have caused the plume, although the precise source of the hydrocarbon leak has yet to be found, according to Williams.
Early reports from the plume site, about four miles up the creek from the town of Parachute, had put the size of the plume at 200 feet by 70 feet by 14 feet deep.
Some unofficial reports have expanded the estimate to nearly twice that size, but a spokesman for the state Department of Natural Resources said on Monday that any estimate at this point would be sheer guesswork.
"We don't know the extent of this thing yet," said Todd Hartman, public information officer for the DNR and the commission.
According to reports, water samples from several wells have shown benzene in the water at levels ranging from 1,900 parts per billion to 18,000 parts per billion.
The maximum safe level of benzene for human exposure is 5 parts per billion, according to the U.S. Centers for Disease Control. Benzene has been linked to leukemia and birth defects in scientific tests, according to the CDC.
In addition to the new wells, according to Hartman's statement, Williams has begun digging a series of trenches "designed to lower the ground water level and remove liquid hydrocarbons and contaminated water from near the stream's edge."
Some of the test wells are just 10 feet from the bank of Parachute Creek.
Hartman also reported the appearance of a form of diesel fuel or diesel oil, known as "diesel range organics" or DRO, attached to the absorbent "booms" deployed by Williams in case hydrocarbons are spotted in the creek.
According to Hartman's report, samples taken on March 9, one upstream of the site and the other adjacent to the site, both showed the presence of the diesel-like substance.
But, the report continued, "subsequent sampling at the March 9 locations have not revealed DRO, nor has DRO been detected in any other surface water sampling locations throughout the investigation."
No explanation for the appearance of the DRO sheen was available at press time.