PARACHUTE — Benzene levels in Parachute Creek, considered potentially dangerous after a large spill of hydrocarbons from natural gas facilities near here, have dropped to the point where three reports in August showed “non-detect” for the cancer-causing chemical, according to the Colorado Department of Public Health and Environment.
According to an update issued on Friday by CDHPE spokesman Mark Salley, water samples taken from the creek on Aug. 8, 12 and 15 were all negative for benzene.
Only one test in August detected benzene in the creek, but at a level of 1.5 parts per billion (ppb) far below the level considered hazardous to human health.
Although other potentially toxic chemicals were spilled, officials concluded early on that benzene could be used as an easily identified and monitored indicator.
Local, state and federal health officials have been monitoring the status of Parachute Creek since a broken gauge on a gas pipeline caused the spill, probably late last year, although the spill was not reported to the Colorado Oil and Gas Conservation Commission until March.
According to monitoring reports, the spill dumped tens of thousands of gallons of potentially toxic chemicals into the soils and groundwater near a natural-gas processing plant owned by the Williams Midstream company. At one point monitoring wells recorded concentrations of benzene in the groundwater at up to 18,000 parts per billion.
According to state and federal health officials, because Parachute Creek is classified as a non-drinking water source, the safety standard is 5,300 ppb, mainly as a protective measure for aquatic life in the creek.
If Parachute Creek were a source of drinking water, the safety standard would be 5 ppb, still higher than any benzene found since mid-July.
The creek continues to be monitored by the CDPHE, which reported on Friday that as of Aug. 13, all the contaminated groundwater and soils that had been removed from the site during several months of remedial efforts had been dealt with. The soil was taken to an industrial waste landfill in Utah, and the groundwater was treated in a groundwater treatment system to the point where the water meets the limits specified for a state-issued discharge permit, according to the CDPHE.
Williams continues to pump water from recovery wells, and to recover hydrocarbons from the water. The groundwater will continue to be treated in a Hydrocarbon Recovery System and, ultimately, be discharged back into the Parachute Creek aquifer.