Results of a nearly nine-year-long study to help determine the potential impacts of natural gas development on groundwater south of Silt will be presented to Garfield County commissioners and the public on Tuesday.
The three-phase study has been in the works since 2004 after a faulty gas well operated by Encana Oil and Gas was determined to be the source of methane gas that was bubbling up in West Divide Creek.
However, the latest study determined that there is a significant amount of naturally occurring biogenic methane contributing to the methane gas that has been showing up in domestic water wells in the larger Mamm Creek region.
That’s according to a summary report on the Phase III findings from hydrologic consultants Tetra Tech out of Louisville.
The first two phases of study was paid for in part using funds from a $371,200 Colorado Oil and Gas Conservation Commission fine levied against Encana as a result of the faulty well. Garfield County paid for the Phase III study.
“This study is an attempt to improve understanding of the nature of groundwater chemistry in the vicinity of the installed monitoring wells,” according to an executive summary of the Phase III Hydrogeologic Study of the Mamm Creek area.
The study used three pairs of wells, one about 400 feet deep and the other about 600 feet deep. That’s roughly 200 to 400 feet deeper than the typical domestic water well.
Four water quality samples were taken from each well during the course of the third phase, as well as one from a nearby residential well, according to the report.
Concentrations of biogenic methane, which results naturally from shallow microbial activity, was detected in the shallower wells, according to the findings.
The deeper wells contained concentrations of what appears to be thermogenic gas, the type sought by energy companies and which comes from geologic formations deep in the ground, according to the report summary.
The report indicates that it’s unlikely the thermogenic methane observed in the deeper wells is the source of the shallow biogenic methane.
The carcinogen benzene was also found in several of the monitoring wells, though mostly below the threshold of 5 parts per billion considered safe for drinking water. One sample did exceed that level, at 5.3 ppb, according to the study.
A full presentation of the Mamm Creek hydrogeologic study was to be given during the morning session of the regular Garfield Board of County commissioners meeting, beginning at 8 a.m. Tuesday at the county administration building in Glenwood Springs.