From The Grand Junction Daily Sentinel (Dennis Webb):
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.
From Aspen Public Radio (Marci Krinoven):
Donna Gray with the energy company Williams says the system erected [last] Sunday is one of seven aeration and vapor extraction systems. The process is also called air sparging. “That involves introducing air or oxygen to both the surface area and groundwater in the soil, in the spill area,” Gray says.
The technology goes after contaminants like benzene that have been absorbed in soil and dissolved in groundwater. The process is similar to blowing bubbles with a straw into a bowl of water. Once the contaminants make contact with air, they disappear from the water.
From The Denver Post (Bruce Finley):
Contamination of Parachute Creek worsened this week, more than six months after an oil and gas industry spill, with levels of cancer-causing benzene exceeding the federal safe drinking water limit. Water samples drawn near the spill at a Williams Co. gas-processing plant near Parachute showed benzene levels at 5.5 parts per billion on July 11 and 9.2 ppb on July 15, according to data provided Thursday by the Colorado Department of Public Health and Environment.
These are the first test results since May showing benzene levels in surface water exceeding the federal standard of 5 ppb. Benzene levels in groundwater remain much higher than the limit. CDPHE water quality overseers have set a state limit for benzene in Parachute Creek at 5,300 ppb, based on aquatic life, because the creek isn’t designated as a water source for people.
Benzene dissipates at sampling locations downstream toward a gate where the town of Parachute can divert creek water for irrigation. CDPHE spokesman Mark Salley said the increasing benzene levels “do not represent a risk to public health.”
Williams last weekend began running new aeration systems to extract benzene vapors – part of a cleanup. Salley said an additional aeration and vapor extraction system will be activated next week in an effort to treat contaminated groundwater closer to the source of the spill and speed the overall cleanup.
Tons of contaminated soil are being hauled to a facility in Utah.
The benzene sampled near the spill “is isolated and does not appear to be traveling,” Salley said. CDPHE officials expect the new system will bring levels down.
Williams has blamed the spill on a mechanical failure. It released more than 10,000 gallons of hydrocarbon liquids from a valve on a pipeline, contaminating soil and groundwater. When the spill was revealed, companies and state and federal agencies scrambled to protect Parachute Creek, which flows into the Colorado River.