Drilling in a natural gas-prone area of western Colorado where an underground nuclear test took place nearly 40 years ago is "relatively safe," a U.S. Department of Energy (DOE) study concluded.

The long-awaited study on Project Rulison, located eight miles southwest of Rifle, CO, was based on computer-simulated models. The results are expected to be at the heart of an ongoing debate between area landowners concerned about safety issues and exploration and production companies that are interested in recovering the gas reserves.

Project Rulison was part of the federal government's Plowshare Project, which sought peaceful uses for nuclear devices. Ironically, the former Atomic Energy Commission detonated the 43-kiloton bomb as a test to blast shale and free gas in the Williams Fork Formation. A well then drilled by DOE produced gas, but it was considered too radioactive to be sold. DOE began deactivating and cleaning the area in the 1970s.

Tom Pauling of the DOE's Office of Legacy Management in Grand Junction, CO, said the study determined that no radioactive contamination above naturally occurring levels reached the gas well in 95% of the computer simulations in the study. In the other 5% of the tests, the radioactivity level was "extremely" low.

DOE's study focused on tritium because it is the radioactive byproduct most likely to migrate. "Based on the mathematical model, it's very unlikely for tritium to migrate to a production well based on the current restrictions," Pauling said.

The federal agency's conclusions are based on years of monitoring the site, Pauling noted. Even though the DOE "can't know everything about the subsurface," he said it was confident that the study was thorough. "But we think there's room to raise questions...We don't propose resting entirely on this study."

Rulison's long-term management is handled by the DOE's Office of Legacy Management, but Colorado is in charge of issuing drilling permits. Producers now are allowed to drill within about one-half mile of the blast site, which is the buffer set up by state and federal officials. However, the Rulison site is in one of the most gas-prone areas of the state. State regulators plan to review the DOE data to determine if the buffer should be reduced.

"Any information that the commissioners and staff can gather regarding Project Rulison is very helpful in our decision-making process that includes this DOE model," said Colorado Oil and Gs Conservation Commission (COGCC) Director Brian Macke.

The COGCC will hold an informational hearing with DOE officials on Oct. 2 in Grand Junction to discuss the Rulison site. According to the COGCC, no applications are pending to drill in the disputed area.

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