Low benzene levels persist in part of Parachute Creek
Post Independent Contributor
PARACHUTE — Efforts to clean up a hydrocarbon plume discovered in March near a gas plant owned by Williams Midstream north of Parachute may be pushing small amounts of the toxic compound benzene into one section of Parachute Creek, according to a recent update from state regulators.
Benzene concentrations of between 1.5 and 1.8 parts per billion (ppb) have been detected at a monitoring station close to the origin of the plume, according to a June 18 report from the Colorado Department of Public Health and Environment.
“While the remediation efforts are underway and they are doing some skimming and pumping, it was expected that that disturbance might cause the groundwater to find an alternate pathway to the creek,” said Mark Salley, communications director for the department.
Salley noted that the benzene levels recently detected are “infinitesimal” compared to the level at which benzene, a carcinogen, is defined by federal law as posing a threat to wildlife: 5,300 ppb.
Concentrations of benzene in excess of 5 ppb are thought to pose a threat to human health.
Since the leak was first reported to state regulators in March, concentrations of benzene in the groundwater around Parachute creek have ranged as high as 18,000 ppb, and levels just over 5 ppb were detected in the creek itself for a short period earlier this spring.
For about two weeks starting in late May, no benzene was detected at any of the six monitoring sites that sit directly in Parachute Creek. Low levels of benzene resurfaced on June 8 at the monitoring site close to the source of the plume, and have persisted since.
The company Bargath, a Williams Midstream subcontractor, is now operating a groundwater treatment system near the source of the hydrocarbon plume. The system separates water from hydrocarbons and pushes hydrocarbons into recovery wells, then filters the groundwater and releases it again.
Cleanup workers are also “sparging” groundwater near the end of the benzene plume, a technique that involves injecting air into the groundwater and stripping it of any contaminants. In places where the levels of benzene pushed in the air violate state air quality standards, air filters are used, according to state Environmental Protection Specialist David Walker.
Williams Midstream officials have said previously that the plume may have started in December 2012, when a faulty gauge on a pipeline near the gas plant broke.
Williams’s workers plugged the gauge in January, believing that a report to state officials wasn’t required since only a small amount had leaked.
By early March, though, it became apparent that more hydrocarbons had leaked than previously thought, officials have said. The liquid is a mixture of hydrocarbons and water, and it has formed a plume approximately 1,675 feet long, 435 feet wide and 10 feet thick.
It may take years to complete cleanup of the groundwater around the hydrocarbon plume, but state officials hope to have Parachute Creek itself free of contaminants by summer’s end, according to Salley.
Williams Midstream has faced no financial penalties from the state health department in connection with the plume, and likely won’t unless they violate the terms of a “compliance order” from the state governing the terms of the cleanup, Salley said.
A state panel called the Natural Resources Damages Trustees, which operates under the umbrella of the state attorney general, might still impose penalties, according to Salley.
A spokeswoman for that group did not immediately respond to a request for comment.
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