PARACHUTE, Colorado - Officials continue to detect benzene, a carcinogenic compound often associated with natural gas activities, in the area where a leak of natural gas liquids has contaminated an unknown volume of soil and groundwater alongside Parachute Creek.
According to a report on Monday from the Colorado Oil and Gas Conservation Commission, benzene was detected during last weekend at the same three sites where it was first found on April 18.
The water sampling and analysis is being conducted by personnel working for Williams Midstream, the company that owns a natural gas processing plant and some of the pipelines running underground in the area of the leak.
The sampling sites, according to COGCC spokesman Todd Hartman, are at locations 1,800 feet, 2,500 feet and 3,700 feet, respectively, downstream from an above-ground valve set believed to be the source of leaking natural-gas liquids first discovered on March 8.
According to Hartman's report on Monday, the concentration of benzene at the closest point to the valve set, 1,800 feet away, on Saturday was three parts benzene per billion parts water.
In the subsequent two days, according to Hartman's report, no benzene was detected at that location on Sunday, and 3 ppb was reported by Williams on Monday.
Analysis of samples taken at the more distant sites showed the concentration of benzene decreasing at each site and decreasing as samples were taken farther from the supposed source of the leak.
At the 2,500-foot distance, according to results supplied to the COGCC by Williams, analysis detected 1.5 ppb on Saturday, and 1.4 ppb on Sunday. Results from Monday's sampling were not available on Monday.
At the site furthest from the leak, 3,700 feet downstream, samples tested out at 1.1 ppb on Saturday, and 1.2 ppb on Sunday. No results were available from Monday's sampling.
Hartman noted that the safe drinking water standard for benzene is 5 ppb, according to the Colorado Department of Public Health and Environment.
But Parachute Creek is not designated as a drinking-water supply by the state, so the standard for exposure is 5,300 ppb "to protect aquatic life," Hartman reported.
He also reported that water sampling from the creek at a point about 2.7 miles downstream from the leak, where the town of Parachute diverts water for irrigation purposes, showed negative for the presence of benzene.
Hartman's report stated that Williams is working to build an "interceptor trench to strip benzene from the ground water prior to the point where it's believed ground water enters the stream," along with other efforts to clear the toxic chemical from the water.