State regulators of the oil and gas industry will be debating next month over how gas drilling companies should deal with large and potentially toxic pit liners.

The liners are giant sheets of synthetic, impermeable material used to keep fluids and slurries from seeping into the ground during drilling operations.

Under rules adopted in 2008, pit liners must be removed once the pits are no longer in use, and disposed of in accordance with solid waste regulations, which means in landfills.

But the oil and gas industry wants to be able to bury the liners in place, a practice allowed prior to the 2008 rule change.

Critics of the industry have argued that the pit liners, once they have been used, are coated with potentially lethal chemicals and hydrocarbons that pose a threat to the environment.

As a result, said Frank Smith, energy organizer for the Western Colorado Congress, a nonprofit alliance of Western Slope community groups, burying liners in the ground could lead to contamination of soil and groundwater.

Or, Smith said, if the site in question returns to agricultural use, "There might be a liner coming up out of the ground with the plow."

Currently, the rules of the Colorado Oil and Gas Conservation Commission require that drilling rig operators must construct holding pits "to protect public health, safety and welfare and the environment, including soil, waters of the state and wildlife" from adverse impacts from wastes generated in exploration and production activities.

Any pits built after 2008, when the state adopted new, stricter rules for overseeing the industry, must be lined in most circumstances.

Such pits often are used to store hydrocarbons, fluids used for drilling, hydraulic fracturing or other "completion" activities.

Some of the chemical components associated with those fluids are considered potentially hazardous to human health, such as benzene, a known carcinogen.

Since 2008, the rules require that synthetic liners used for those pits be disposed of "in accordance with applicable legal requirements for solid waste disposal," but receiving sites are not always near the gas fields.

The Garfield County landfill, following a decision by the county commissioners in 2009, will not accept used liners because they are too bulky and hard to handle and because of uncertainty about the toxicity of the fluids adhering to the liners.

As a result, liners used in Garfield County must be trucked to distant disposal sites, specially designed to deal with materials of this sort, or they must be recycled.

Recycling is the route taken by the Williams Production drilling company, according to spokeswoman Susan Alvillar. She said the company bales its used liners and ships them to a recycling company in Denver.

Early in 2010, the Colorado Petroleum Association, an industry lobbying group, petitioned the state oil and gas commission to permit the industry to bury the liners in place, at the drilling site.

Discussion of the issue has been delayed several times by the commission, but is due to come up at its April 4-5 meetings in Denver.

Operators were permitted to dispose of the pit liners at the drilling site, once drilling was finished, prior to the enactment of the new and stricter rules in 2008.

The Petroleum Association's proposal is for the state to once again permit pit liners to be buried "on non-crop lands and non-irrigated crop lands," if certain criteria are met.

Those criteria include notification of the surface landowner and making sure any wastes remaining in the pit meet state guidelines for allowable disposal at the site.

The industry proposal, however, met some resistance when the U.S. Environmental Protection Agency (EPA) issued a finding last September that the disposal of pit liners is subject to hazardous waste regulation and is not under the sole purview of the COGCC.

Essentially, explained Smith of the WCC, the EPA believes the rules should stay as they are, and not be revised to allow on-site disposal of pit liners.

The Colorado Petroleum Association responded that the disposal of pit liners is within the jurisdiction of the COGCC, not the EPA, and is moving forward with its proposal.

The association argues, in its petition, that reverting to the old disposal rule would provide a balance between the state's "interest in fostering oil and gas development" and its mission to minimize environmental damage by the industry.

jcolson@postindependent.com