EcoFlight provided the aerial images for this story published in the Denver Post on 3-28-13
Benzene is polluting groundwater near a plume of hydrocarbons leaking from the Williams Midstream natural gas plant north of Parachute, in some places 3,600 times greater than the level considered safe for drinking, the state Oil and Gas Conservation Commission reported Thursday.
Samples of water from nearby Parachute Creek — a source of water for the town and irrigators — have shown no evidence of contamination, COGCC said.
Tests of water from three monitoring wells, about 30 feet from the creek, showed benzene levels ranging from 5,800 parts per billion to 18,000 ppb in a well closest to a trench dug to recover fouled water and oil. The state health standard is 5 ppb.
The company has recovered about 176,400 gallons of contaminated water and about 6,000 gallons of hydrocarbons, COGCC said Thursday.
Hydrological consultants for plant operators Tulsa-based WPX and Williams have analyzed groundwater flow in the area and determined that groundwater is recharged by the creek, rather than groundwater feeding the creek.
However, company workers are drilling another set of test wells about 10 feet from Parachute Creek to confirm the pollution is not moving toward the stream. Three wells already in place are about 30 feet from the creek.
COGCC said the water being pumped from the recovery trench is "enhancing groundwater flow away from Parachute Creek."
Since the spill was reported, company workers have been excavating to determine its origin. Earlier this week, the company reported a valve box for a pipeline carrying natural gas liquids away from the plant may be the source.
The spill was originally reported to state regulators as contaminated soil. On March 15, the groundwater contamination was reported.
Since then, both COGCC and the U.S. Environmental Protection Agency have issued clean up orders for the spill. Both agencies are providing direction and oversight of the clean up being managed by the companies.