Wyoming DEQ's investigation into Pavillion well water quality exceeds $1.2 million - Casper, WY Oil City News
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Wyoming DEQ’s investigation into Pavillion well water quality exceeds $1.2 million

January 2010 sampling. (United States Environmental Protection Agency)

CASPER, Wyo. — An investigation into “drinking water quality issues in the rural area east of the Town of Pavillion” has exceeded $1.2 million in total costs.

The Wyoming Department of Environmental Quality released their 4,266 page 2019 Final Report on Monday, Dec. 23. That is a follow-up to an over 80,000 page report completed in 2016.

In addition to the cost of the investigation, the DEQ says that $929,268 was spent on a Pavillion East Water Supply Project to install cistern systems to landowners who requested them.

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The project was authorized via legislation and lasted from January 2014 through February 2015. The DEQ says 31 cisterns for 28 landowners were installed.

For landowners who didn’t participate in the cistern program, a bottled water delivery program was available through March 31, 2017.

Four out of eight pit sites in the Pavillion Gas Field involved in the DEQ’s Voluntary Remediation Program have been granted a “Certificate of Completion.”

The remaining sites are being “actively investigated” and will be entered into the VRP as information becomes available and if groundwater is impacted.”

The DEQ’s investigation dates back to 2013.

Their investigation “included the collection of water quality and operational data for the water-supply wells (domestic, irrigation and stock), in order to assess water quality and identify parameters or conditions that might cause palatability or toxicity issues.”

“An evaluation of the integrity of nearby oil and gas wells and the historic use of surface pits in the Pavillion Gas Field was also performed,” the DEQ adds in a fact sheet on the investigation.

The 2019 report follows up on a number of things that the DEQ’s 2016 Final Report identified for further investigation.

DEQ sampling of 13 wells in 2014 indicated organic compounds in excess of “applicable” drinking water standards. Those included an “organochlorine” pesticide and a “phthalate ester.”

“Phthalate is used as a plasticizer in flexible PVC plastics and is a common laboratory contaminant,” the DEQ says.

However, in the 2019 report, DEQ says that testing in 2017 and 2018 did not indicate the presence of either of these organic compounds, suggesting that the concentrations detected in 2014 may have been “artifacts of sampling or analysis processes.”

The DEQ says that elevated levels of salts, metals and radionuclide concentrations in the wells were confirmed in both 2017 and 2018.

While such compounds can be naturally occurring, the DEQ adds that “industrial applications may use some of these same compounds (e.g. oil and gas drilling mud contains chloride and potassium).”

The DEQ does not think that hydraulic fracturing is responsible for any water problems with the wells.

“Evidence does not indicate that hydraulic fracturing fluids have risen to shallow depths utilized by water-supply wells,” their fact sheet states. “Also, based on an evaluation of hydraulic fracturing history, and methods used in the Pavillion Gas Field, it is unlikely that hydraulic fracturing has caused any impacts to the water-supply wells.”

Rather, the DEQ thinks that gas seepage may be responsible for water quality concerns.

“Gas in the upper Wind River Formation appears to have originated mainly from upward migration from deeper commercial gas-bearing zones and evidence suggests that upward gas seepage (or gas charging of shallow sands) was happening naturally before gas well development,” the DEQ says.

While the seepage may have preceded gas well development, the seepage may have continued after gas wells were in place.

“Some gas wells are experiencing slow gas seepage,” the DEQ says. “The relative contribution of potential gas seepage along gas wells versus natural upward migration of gas is undefined and would be very difficult to quantify.”

The DEQ says that the “palatability” of the water may be affected by another factor.

“Geochemical changes associated with the biodegradation of dissolved organic compounds likely have produced constituents associated with poor water palatability, and appear to be linked to declining well yields,” they say.

Reaching firm conclusions about the cause of water quality issues may not be possible.

“Limited baseline water quality data, predating development of the Pavillion Gas Field hinders reaching firm conclusions on causes and effects of reported water quality changes,” the DEQ says.

Further information and background about the investigation into Pavillion water quality is available from the United States Environmental Protection Agency.