For the second straight day, the cancer-causing chemical benzene has been detected in Parachute Creek, a tributary of the Colorado River, downstream from a hydrocarbon leak at a Williams Gas facility that was first detected more than a month ago.
Sampling of the creek on Friday detected benzene at 2.7 parts per billion, similar to Thursday’s detection of benzene at 2.8 parts per billion — the first time benzene, which has been found in much higher and hazardous concentrations in groundwater just feet from the creek, has been detected in surface water.
The state drinking water standard for benzene is 5 ppb. While the current samples are just trace amounts below that standard, the groundwater contamination levels were 3600 times the standard last month. “Sampling at three more points downstream of those detections did not detect benzene,” said Todd Hartman with the Colorado Dept. of Natural Resources, in an email to reporters Friday. “Sampling back upstream, above the initial benzene detection, also did not reveal contamination.”
Samples for benzene taken at the point where the town of Parachute diverts water for its irrigation supply 2.7 miles downstream of the gas facility continued to show no detection of benzene.
From The Grand Junction Daily Sentinel (Dennis Webb):
Benzene has been found in Parachute Creek for the first time since testing began in response to a natural gas liquids leak north of Parachute. Williams and the state Department of Natural Resources said in news releases that the carcinogen was found Thursday at multiple locations, but in amounts below Environmental Protection Agency safe drinking water standards of 5 parts per billion.
Williams said an initial result came back Thursday showing a detection of 2.8 parts per billion. The state said another detection at the same location was 2.7 ppb. Williams said the initial detection was about 1,200 feet downstream from where a pressure gauge on a natural gas liquids line leaked thousands of gallons. The state said the point was about 1,800 feet downstream. No benzene has been found upstream of the leak site.
In response to the detections, Williams did real-time sampling farther downstream Thursday and tests showed benzene at 1.5 ppb 680 feet from the first detection point, and 1.1 ppb 1,900 feet from the first point. Samples taken Thursday where Parachute diverts water for its irrigation supply showed no benzene. Williams said benzene floats on water, dissolves only slightly in it and evaporates quickly from the surface.
Williams is installing aeration, or air-sparging, technology to remove benzene near the initial detection point and 1,900 feet farther downstream. It also has added an additional boom below the initial detection point.
Parachute’s diversion site is 2.7 miles downstream of Williams’ gas plant.
High benzene levels have been found in groundwater on either side of the creek, but benzene hadn’t previously been detected in the creek despite frequent testing. Authorities have said that’s because the groundwater below the creek apparently flows away from it. But the state said the situation appears to be different at the initial point of benzene detection in the creek, with groundwater flowing toward the stream. That point is the farthest downgradient from the valve site where benzene has been detected in groundwater, and the groundwater detection there was 440 ppb Monday, prompting surface water sampling nearby the next day, the state said.
Part of Williams’ response is building a 200-foot-long groundwater interception trench adjacent to the creek at that point, , the state said.
Williams said that it is continuing twice-daily sampling at Parachute’s diversion point. “As a precautionary measure, the city of Parachute’s irrigation gate on Parachute Creek will remain closed until additional data is collected,” it said.
From The Grand Junction Daily Sentinel (Dennis Webb):
The discovery of benzene in Parachute Creek this week is causing heightened anxiety about the possible ramifications of the natural gas liquids leak in that watershed.
“It is of great concern to see it in the creek,” said Kirby Wynn, oil and gas liaison for Garfield County. He said the county is hoping to organize a public meeting in the Parachute area as early as next week and to have investigating agencies along with Williams, the company that has said it is responsible for the leak, provide updates and answer questions.
Williams and the state Department of Natural Resources on Thursday reported the first detection of benzene in the creek since monitoring began last month. The benzene levels were within the Environmental Protection Agency standard for safe drinking water. Groundwater monitoring wells on each side of the creek have shown much higher benzene levels.
Williams says the leak is the result of a faulty pressure gauge on a valve set for a liquids pipeline from its natural gas plant up the creek valley. It discovered the faulty gauge and removed it Jan. 3 but thought that less than 25 gallons had leaked. It now estimates that some 10,000 gallons entered the soil and groundwater, of which about 6,000 gallons has been recovered.
The town of Parachute’s diversion point for its irrigation supply is about 2.7 miles downstream of the valve area.
Judith Hayward, a former Parachute town trustee, previously has expressed concern about the safety of using the irrigation water for gardening once the watering season begins. She said Friday she also worries that some town residents may not be fully informed about the continuing developments involving the leak. “It seems like every other day or so there’s a new finding. I just have so many questions as to what a community can really do to protect themselves,” she said.
A benzene measurement Friday at the point where the substance was first detected in the creek earlier this week 1,800 feet downstream of the valve set was 2.7 parts per billion. That’s little changed from an earlier reading of 2.8 ppb. A sampling site 680 feet downstream of the point of initial detection showed benzene at 1.5 ppb Friday, and one farther downstream read 1.2 ppb. Sampling sites even farther downstream, including at the town diversion point, show no benzene.
Williams spokeswoman Donna Gray said the detections in the creek are “well below the regulatory standard, the allowable standard.” The EPA drinking water standard for benzene, a carcinogen, is 5 ppb.
Steve Gunderson, director of the state Water Quality Control Division of the Colorado Department of Public Health and Environment, said in a prepared statement Friday, “Although the benzene levels in the creek are below state drinking water standards, their presence reinforces the need to assure that the cleanup of this spill is done as expeditiously as possible.”
CDPHE is meeting regularly with the Colorado Oil and Gas Conservation Commission and EPA “to discuss the cleanup and the appropriate measures to be taken,” he said.
Williams and regulators on Friday finalized plans that workers will begin implementing over the weekend to address benzene in the creek, including air-sparging systems that remove benzene through aeration.
Samples upstream of the valve area continue to show no sign of benzene that would indicate a possible source separate from the natural gas liquids leak.
Bob Arrington is a retired engineer in Battlement Mesa who pointed to the pressure gauge as the likely source of the large volume of contamination first found in March, even when Williams still thought the gauge had leaked only a small amount. He also predicted benzene ultimately would show up in the creek where it did, at a gradient pinch point where groundwater was more likely to flow into the creek rather than away from it. He said Friday that even benzene below EPA standards can cause some cancer cases. He thinks Williams should begin doing groundwater monitoring where the creek enters the Colorado River and work its way upstream, as a precautionary measure.
Gray said Williams already has tested groundwater downstream to the point where it is getting readings of no benzene in the groundwater.
Given the extent of the groundwater contamination that has been discovered, Arrington also challenges Williams’ contention that about 80 percent of what it calculates escaped from the gauge, or about 40,000 gallons, vaporized into the atmosphere rather than reaching the ground. He thinks a lot less may have vaporized because of the cold weather at the time of the leak. “I think when you have something like that you have to look at it from the worst possible case and do your planning accordingly,” he said.
Gray said the estimate of the percentage that vaporized and evaporated comes from a standard industry model created using EPA guidance.
Meanwhile, Hayward is concerned about Williams’ plans to build another natural gas liquids line that will go under the creek in the same corridor that holds the existing line that had the leaky gauge. “The fact that these pipelines are going under our creek … who let that happen?” she asked.