An independent peer reviewer hired by Garfield County concurs with the findings of a recently completed study showing that methane gas found in the most recent round of groundwater samples in the West Divide and Mamm creek areas south of Silt is mostly natural and not related to drilling activity.
“I cannot say with absolute conviction that gas wells haven’t contributed to that,” Geoffrey Thyne, a hydrologist and consultant with Science Based Solutions, told county commissioners on Monday.
“Most wells do still have very small amounts of leakage, and you just can’t build them any better,” he said.
But the vast majority of methane gas that has been detected recently is not of the thermogenic variety, which is the deep-earth gas sought by energy producers for commercial purposes, he said.
Rather, it is a “naturally occurring, biogenic component of the water,” and is part of a natural microbial process, Thyne said.
Thyne was hired by the county to review the findings of the Phase III Mamm Creek Area Hydrogeologic Study presented to the county by another group of consultants, Tetra Tech, last fall.
That study was an extension of a nine-year effort to determine the potential impacts of natural gas development on groundwater, after Encana Oil and Gas was found to have a faulty well casing that caused methane gas to eventually bubble up in West Divide Creek in 2004.
The company was ultimately fined $371,200 by the Colorado Oil and Gas Conservation Commission, and that money helped fund the first two phases of the study.
The third phase of the study, funded by the county, suggested that seven to eight years later, the methane found in the shallower test wells is naturally occurring.
Thyne also concurred that diminishing levels of hydrocarbons such as benzene that have been detected in more recent years suggest a single, one-time source of contamination, rather than a continuing source.
“What we have seen with these results indicates there was a single, big source that has been gradually dissipating over time,” he said.
The West Divide Seep resulted in numerous steps being taken by the state to change the way well casings are constructed, as well as recently adopted pre- and post-drilling water quality testing requirements to ensure groundwater is not contaminated by new wells.
Thyne, as well as COGCC officials who were on hand Monday, said they see no reason why the county should continue to study groundwater in the Mamm and Divide creek area, beyond the monitoring and testing that’s already now required of the industry.
However, Divide Creek-area resident Lisa Bracken, who was among the first to notice the 2004 seep and report it to state officials, maintained that ongoing monitoring is needed.
“The new stipulations [on the industry] are helpful, and every effort forward has been helpful,” she said. “But it’s still not as good as it can be.”
Bracken said the groundwater test well monitoring done to date has been too broad, and too little attention has been paid to the experiences of residents in the area that suggest groundwater is still being impacted.
“Eye-witness accounts have been consistently marginalized and discredited by the COGCC, and in some cases by the county,” she said. “There are a lot of things here that are not being said, and the issue is far more detailed and complex than is being presented here today.”
Silt resident Peggy Tibbetts also called for broader water quality testing, not just in areas adjacent to natural gas activity but as it involves municipal water quality.
“I don’t drink Silt’s water, because it makes me sick,” she said. “There is not special testing done to make sure our water is not impacted by these situations.”
A copy of Thyne’s report and information provided by the COGCC on Monday can be found on the Garfield County website, www.garfield-county.com, on the Oil and Gas Liaison page.