From The Grand Junction Daily Sentinel (Dennis Webb):
Benzene has again been detected, but at barely detectable levels, in Parachute Creek at the site of a natural gas liquids leak.
The carcinogen was measured at 1.4 to 1.5 parts per billion at a single location in the creek in daily samples between Saturday and Tuesday, according to updates from the Colorado Department of Public Health and Environment and Williams, the company responsible for the leak.
Benzene hadn’t been detected for more than two and a half weeks in the creek after previously having been measured at levels that briefly and barely topped 5 parts per billion. That’s the drinking water standard for the contaminant, although the creek isn’t regulated as a drinking water source by the state.
The contamination resulted from a leak from a faulty pressure gauge on a pipeline leaving Williams’ natural gas processing plant northwest of Parachute. Williams believes about 10,000 gallons of natural gas liquids contaminated soil and groundwater, with benzene also eventually reaching the creek.
The weekend benzene detections were at just the one location where benzene in groundwater has been sporadically entering the creek. Samples up and downstream aren’t currently showing any benzene contamination, and no hydrocarbon sheen has ever been seen on the creek, CDPHE says.
It says the sampling shows the size of the groundwater contamination plume remains stable, with benzene concentrations at the plume’s end staying constant.
Williams continues to operate a groundwater aeration system to remove benzene, and work continues on construction of a new facility to remove and treat contaminated groundwater so it can be returned to the watershed. The system’s major components are on site, and work is being completed on plumbing and electrical systems and on obtaining state water discharge and air emission permits.