State hears request to pump Moneta pollutants into aquifer

Wyoming’s Oil and Gas Conservation Commission today considers more than 110 letters opposing Aethon Energy’s request to pump up to 180 million barrels of pollutants into the Madison aquifer beneath Shoshoni.

The letters, posted to the OGCC website Monday, seek to protect an underground reservoir conservationists say is a valuable drinking resource. Aethon contends the 15,000-foot-deep aquifer is naturally polluted with benzene and would be uneconomic to develop for domestic use in nearby communities. The company, which has approval to develop the nearby Moneta Divide gas- and oilfield, needs approval to dispose of tainted water pumped from the field.

The hearing is the latest confrontation in a yearslong fight over the Marlin Well, drilled 15,364 feet deep for potential disposal of the briny waste. The Moneta Divide field could produce up to 58.8 million gallons of wastewater a day, the U.S. Bureau of Land Management said when it approved development of the field this year.

Aethon, however, has no specific public plans, approvals or permits for disposing about 73% of that — about 43 million gallons a day.

The BLM did not specify or authorize how to properly dispose of the bulk of the flows. It said Aethon might have to slow the pace of production to match the level of disposal the state and federal Environmental Protection Agency approve.

An “aquifer exemption” for Aethon’s Marlin Well, which the OGCC considers today, would resolve the disposal of less than 1% of full production flows from the Moneta field, according to WyoFile calculations made from various documents.

Conservationists are fearful, however, that approval of one Madison disposal well would open the door for others. 

“Aethon’s request to exempt this viable freshwater aquifer in the Madison Formation… still fails to meet the regulatory and legal criteria,” the Powder River Basin Resource Council and Wyoming Outdoor Council wrote to the commission.

The recent tranche of letters released by the OGCC includes one from a former member of the Wyoming Water Development Commission who called the aquifer a “viable source” of domestic water for the Wind River Basin. “Impacts to our finite potable drinking water sources,” William Bensel wrote, “…must absolutely be avoided.”

Disposal in the Madison is justified, Aethon says, because the benzene, a carcinogen, discovered there is naturally occurring. That benzene combined with the depth of the aquifer, Aethon argues, make it unlikely that nearby cities, from Riverton to Casper to Thermopolis, could use the water domestically.

Disposal plan

Gov. Mark Gordon chairs the five-member commission that is holding the hearing. The U.S. Environmental Protection Agency, however, also has authority over the aquifer; the state administers federal law and regulation.

“The state recommends an action but final approval rests with EPA to determine whether [the decision] meets the requirements of the federal rules,” Shannon Anderson, an attorney with the PRBRC, wrote to WyoFile.

The meeting will be live-streamed on YouTube at 8:30 a.m. Information on how to attend the hearing remotely and comment can be found at the commission website.

Aethon’s 282-page application is at least the third bite at the Madison apple. Although state officials have twice rejected requests to use the Marlin Well for disposal, Aethon says it has new information to justify an exemption.

Among other things, company consultants reprocessed data used in earlier requests and acquired new seismic data. The information better defined the Marlin well geology to ensure pollutants would remain within about three miles for thousands of years, the application states.

Aethon quoted 2012 data that showed samples from the well had between 18 and 110 micrograms of benzene per liter — a figure above the federal maximum contaminant level of 5 ug/l. Such concentrations, if naturally occurring, would support the company position that the aquifer can’t be used domestically.

Conservationists believe the benzene could have been introduced into the well during drilling, a possibility raised years ago by an Oil and Gas Conservation Commission member. Aethon rejects that idea.

The Madison “is not contaminated by man-made chemicals or activities,” Aethon wrote in its permit application. The company did not respond to an email requesting amplification of that position.

Oil and Gas commission records show that drilling mud flowed into the Madison as Encana, the energy firm that owned the Moneta field before Aethon, drilled the Marlin well. Drilling mud can contain benzene.

“During the drilling through the Madison, the drilling log notes multiple occasions of mud lost to the formation,” a 2013 memo from an Encana consultant, EnSci, Inc., reads. At least 6,720 gallons (160 barrels) of drilling mud flowed into the aquifer instead of remaining in the bore hole.

The flows caused the driller to use lost-circulation material, additives to drilling mud used to plug well-hole leaks, while drilling through parts of the 300-foot-thick formation. All told, at least 6,720 gallons (160 barrels) of drilling mud flowed out of the well while drilling through the Madison formation, according to the memo.

Conservation groups weigh in

The Madison is “one of the most important aquifers serving as both a current and future water source,” the PRBRC and WOC wrote in a letter opposing the exemption. The groups hired their own consultants to review Aethon’s application and submitted 18 pages of comments and supporting documents.

Even though the aquifer is deeper and thinner near Shoshoni than in other parts of the state, in the Wind River Basin it is nevertheless “considered the primary target for municipal water supply wells funded by the [Wyoming Water Development Commission],” the groups wrote.

Deep domestic wells “are not uncommon in Wyoming,” the conservation groups wrote, challenging Aethon’s assertions and calling depth a “secondary criterion” to siting.

The groups cite data that show four domestic-use wells in the state deeper than 15,000 feet, 27 that are 10,000 feet or deeper and 240 that are deeper than 5,000 feet.

Conservation consultants also wrote that the benzene measurements from 2012 indicate the hydrocarbon is unlikely to be naturally occurring. That, too, challenges Aethon’s claims.

“If the benzene is naturally occurring it is unlikely that the concentrations would vary this much,” between 18 ug/l and 110 ug/l, the conservation review states. “It is much more likely that the presence of benzene is a result of contaminants introduced during drilling and well construction than naturally occurring in the formation water.” 

Consultants found other faults with Aethon’s request, including “extremely sparse” data used in hydrographic models that produce “great uncertainty” and results that “could vary significantly” from actual conditions.

Aethon failed to demonstrate it is economically and technically impractical to develop the aquifer for water consumption, the groups state.

“We believe that the Moneta Divide field should be developed in a responsible fashion which includes a water management plan that entails the treatment and reuse of produced water rather than a plan that proposes to dump millions or billions of barrels of produced water into freshwater streams or fresh water aquifers,” the groups wrote.

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