Benzene found at gas storage site

Benzene has been identified as one of the contaminants found in shallow groundwater at a natural gas storage well pad southwest of Glenwood Springs this summer, and low levels of unidentified hydrocarbons were found in groundwater near another nearby pad.

However, recent testing at two other pads in the area revealed no soil or water contamination, according to SourceGas, the company that operates the Wolf Creek Natural Gas Storage Field. There also continues to be no indication of ground or surface water contamination beyond the immediate areas where contamination has been found.

The contamination is thought to be historic in nature, and SourceGas discovered it as it has been making safety and reliability improvements to the field. SourceGas uses old, depleted gas wells to store gas to meet area customers’ winter needs.

The storage field is part of what’s called the Thompson Divide, which is the focus of ongoing debate over whether new oil and gas drilling should occur there.

Last summer soil contaminated with hydrocarbons was excavated from one of the pads where discolored soil was found. Subsequent sampling at that site has found no soil or water contamination, and the same goes for sampling at another pad where discolored soil also was found.

Sampling at 11 temporary groundwater monitoring wells near a third such pad has revealed no contamination in nine wells. But what SourceGas calls “very low levels” of hydrocarbons were found in the two of the wells closest to the pad.

Tests are continuing to determine if those are natural in origin or are related to oil and gas development.

On June 20, SourceGas found contamination at another pad. Subsequent tests have determined the contaminants consist of diesel-range organics, ethylene glycol and benzene. The benzene levels ranged from 7 to 25 parts per billion. When regulated in drinking water supplies, benzene, a carcinogen, must be kept no higher than 5 ppb.

That contamination was in soil and what SourceGas and the Bureau of Land Management call “shallow, perched groundwater.” BLM spokesman David Boyd said that’s water that had seeped down a bit but is separated by dry soil from deeper, flowing groundwater.

SourceGas cleaned up the site by removing about 375 cubic feet of soil, company spokeswoman Natalie Shelbourn said. The cleanup included the perched groundwater area, which Boyd said had dried up. Inspections within a quarter-mile of the pad found no detectable hydrocarbons in seeps or springs, SourceGas says.

It said none of those water sources flows into the section of Wolf Creek between the pad and its confluence with the Thompson Creek ditch.

Sampling earlier this summer at a ditch running to Divide Creek three-quarters of a mile away also found no contamination.



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