Williams to treat millions of gallons of groundwater
Williams expects to remove and treat as many as 26 million gallons of groundwater over a half-year to a year at the site of its natural gas liquids leak alongside Parachute Creek.
That’s according to a water management plan recently approved by the Colorado Department of Public Health and Environment’s Hazardous Materials and Waste Management Division.
The approval comes as Williams has been dealing with a recent spike in benzene levels at a monitoring site in the creek, including a reading of 9.2 parts per billion on Monday.
That’s the highest reading in the creek since testing began following discovery of the leak, and follows a reading of 5.5 ppb July 11.
That had been the first reading in the creek above the state drinking water standard of 5 ppb since May 1. However, the state doesn’t consider the creek to be a drinking water source, and instead a maximum standard of 5,300 ppb applies to protect aquatic life there.
Health Department spokesman Mark Salley noted in a recent media update that the contamination is isolated to one creek test location and does not appear to be traveling.
“All other sample points remain non-detect for contamination, including the town of Parachute’s diversion point for irrigation water,” he said.
On July 13, Williams began operating new air sparge wells to upgrade a sparge/vapor extraction system.
The new wells were placed to stop the flow of benzene-contaminated groundwater around the east end of the system. That flow may be causing the increased benzene readings. A new air sparge/vapor extraction system farther upstream also is scheduled to be activated next week.
“The intent of this system will be to treat contaminated groundwater closer to the original source area and speed up the overall cleanup process,” Salley said.
Williams estimates about 10,000 gallons of hydrocarbons in a natural gas liquids pipeline leaving its adjacent gas processing plant leaked from a faulty gauge into soil and groundwater this winter, and that it has recovered about 7,600 gallons.
It plans to remove millions of gallons of groundwater at a rate of 50 gallons per minute, clean it and return it to the aquifer under a system that it has installed and been testing.
About 155,000 gallons of tainted groundwater removed in March has been disposed of in an injection well in Grand County, Utah.
Williams also has been shipping about 1,500 cubic yards of excavated soil to a landfill in East Carbon, Utah.