Colorado regulators are investigating recent accusations that oil and gas drilling companies injected 1.3 million gallons of diesel fuel into the ground during gas drilling activities between 2005 and 2009.
The charge was made in a report written for members of a congressional committee, released in late January, which found evidence that more than 32 million gallons of diesel fuel were used by the industry in 19 states, including Colorado.
"We're currently reviewing our records" to determine if the allegation is true, said Dave Neslin, executive director of the Colorado Oil and Gas Conservation Commission, at a meeting on Thursday of the Northwest Colorado Oil and Gas Forum.
The fluids cited in the report were used in a procedure known as hydraulic fracturing, or fracking, in which vast amounts of water, sand and chemicals are injected into gas-well bores under pressure, to break up buried rock formation and make it easier for gas and oil to flow to the surface.
The technique has been used by the industry for decades, and is now used in nearly all wells currently being drilled, including those in Garfield County.
But the procedure has come under growing scrutiny as the industry has converged on a geologic formation known as the Marcellus Shale, a rock bed the size of Greece that lies about 6,000 feet beneath New York, Pennsylvania, West Virginia and Ohio.
The New York Times has published several stories in recent days about the drilling phenomenon, under the title, "Drilling Down," concentrating mainly on the Marcellus Shale operations.
A video report on the Times website, however, focuses on Garfield County and on residents of the Silt Mesa and Rifle areas who say they have been forced to move away because of exposure to toxic chemicals and resulting ill health.
The increased scrutiny on the industry in Garfield County comes as drilling has intensified and one company, Antero Resources, announced plans for drilling hundreds of wells in the unincorporated residential areas of Silt Mesa and Battlement Mesa.
Antero officials have publicly stated that the company has never used diesel in its fracking activities.
Neslin told those at the forum that companies reported using diesel in four wells around the state. He said none of those were located in the Piceance Basin or in Garfield County.
The reports dealt with two frack jobs in 2005 and two in 2007, he said.
During that period, he continued, there were 10,000 wells fracked in general throughout the state, without any proof that nearby water resources were contaminated by the drilling activities.
The congressional study found no evidence that the use of diesel fuel contaminated water supplies in any of the states included in the report.
But the U.S. representatives who led the year-long probe - Reps. Henry Waxman of California, Diana DeGette of Colorado and Edward Markey of Massachusetts, all Democrats - said the findings, if true, constitute a violation of the federal Safe Drinking Water Act.
Neslin said he asked for details from the congressional study, but "they declined for confidentiality reasons."
So the COGCC is now asking the industry to provide greater detail about the use of diesel fuel in their activities.
He said the Colorado Oil and Gas Association, the industry trade group, "has been very helpful" in getting the information from industry sources.
That industry data, Neslin concluded, "should help us to assess whether these activities had any effect on drinking water."
But, he added, the COGCC staff feels "that such impacts have not occurred" in Colorado, because there has been no verified proof of drinking water supplies being contaminated by the industry's actions.