SILT — A geological consultant says increased methane in domestic wells near natural gas development in Garfield County is part of a much larger problem of drilling-related water contamination that’s just starting to come to light.

“The tip of the iceberg is emerging,” Geoffrey Thyne told residents at a meeting in Silt on Thursday night.

Thyne, a geology professor consulting for Garfield County, said he thinks evidence is piling up in Colorado and elsewhere in regard to water contamination related to oil and gas development.

“I think it’s a mess. I think it’s going to get worse before it gets better,” he said.

Thyne and Garfield County oil and gas liaison Judy Jordan met with residents to discuss results from the second part of a hydrogeological study being conducted for the region south of Rifle and Silt.

That study revealed increasing methane in some domestic water wells in that region, where there are about 1,000 gas wells. Most of the high concentrations of methane in water are in the Divide Creek area. That area has underground geological faults, and gas contaminated surface waters there in 2004.

Some residents voiced anger Thursday in connection with the study’s second phase, which involved retesting water wells where initial tests raised concerns. Marcia Davis-Durnil said residents shouldn’t have had to wait until now to be told about those concerns and consider water treatment options.

“That could have affected a pregnancy, a special needs child, an autistic child,” she said.

The water test results found some wells with unhealthy levels of selenium, nitrates and other substances not connected with natural gas development. Some wells also contained as much as 6 percent water produced from gas-bearing underground formations during drilling.

None of the study’s results of water well testing showed any levels of benzene or other drilling-related contaminants requiring regulatory action. Methane in water isn’t regulated and vents away through bubbling in high concentrations, but can cause a danger of explosion in enclosed areas.

Thyne believes contamination could be reduced if the state required that the space between gas well casings and drill holes be sealed with cement all the way from the top to the bottom of wells.

Thyne also said he shared the concern expressed by some at Thursday’s meeting about the fact that fluids used to fracture gas formations were exempted by Congress in 2005 from federal clean water regulations.

“A lot of people, including myself, took exception to that issue,” he said.

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