How much radioactive contamination is too much? The Colorado Oil and Gas Conservation Commission (COGCC) will wrestle with that question over the next few months as it sorts out whether to allow producers to explore the natural gas-prone area near the nuclear blast site at Project Rulison.

Using hypothetical drilling data, the U.S. Department of Energy (DOE) determined that a 95% chance exists of no contamination by the radioactive isotope tritium near Rulison's drilling exclusion area. Drilling near the area, said DOE, would be "relatively safe" (see NGI, Sept. 24).

The DOE detonated a 40-kiloton nuclear bomb 8,426 feet underground in September 1969 outside Rulison and Battlement Mesa, which is about eight miles from Rifle, CO, in an attempt to free up commercially marketable quantities of natural gas, but the gas it produced proved to be too contaminated.

Tom Pauling, an environmental team leader for DOE's Office of Legacy Management, reviewed the DOE data with the COGCC during an information session for the public. The DOE now prohibits drilling lower than 6,000 feet in a 40-acre area around the site. In addition, the COGCC requires a hearing for any gas wells proposed to be drilled within a half-mile of the site, and it notifies the DOE of wells to be drilled in a three-mile radius.

The DOE has not made any new recommendations, but Pauling told commissioners the agency was "comfortable with [the current rules] going forward until we can come to a more definitive path forward."

The DOE studied a hypothetical well site that would be about 258 meters west of the blast site. The federal agency conducted more than 500 different models before determining that in 95% of the cases, contamination of the well by the radioactive tritium isotope would not occur.

COGCC Chairman Harris Sherman said the commission plans to study the DOE data and review all of the scientific studies before making any decisions about whether additional drilling should be permitted.

"We really are trying to educate ourselves in a preliminary way about these issues," said Sherman.

COGCC Director Brian Macke, who has authored a past COGCC report on Project Rulison, said the geological character of the underground formations, which consist of stacked sandstone "lenses" limits the possibility of nuclear contaminants reaching wells drilled in nearby areas. The lenses are estimated to be 300-400 feet across and in general are not connected, he noted.

Representatives from Noble Energy Corp., Williams and EnCana Oil & Gas (USA) also spoke at the hearing. Several producers are interested in pursuing gas exploration close to the restricted area.

"We are certain that we can operate in this area safely," said Noble's Michael Wozniak. He said Noble "first of all" wanted to "protect our workers and the people who are right there on site." He recommended the COGCC review the history on the blast site, and he urged the COGCC to put its faith in government and industry scientists before drawing any conclusions.

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