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Aethon permitted to keep dumping oilfield watsewater into Boysen; less chemical testing required

Boysen Dam (WikiMedia)

CASPER, Wyo. — The Wyoming Department of Environmental Quality issued a final permit to Aethon Energy Operating, LLC on Friday, Oct. 2, allowing the company to continue dumping oilfield wastewater into Boysen Reservoir.

Aethon operates a facility which has historically discharged about 2 million gallons of oilfield wastewater per day into Alkali Creek from activity at the Frenchie Draw Gas Field. Alkali feeds into Badwater Creek approximately 40 miles upstream of Boysen, according to the Wyoming DEQ’s final permit.

The Wind River in the canyon below Boysen Reservoir is considered a Class 1 river segment. Under Wyoming Water Quality rules, such waters “are those surface waters in which no further water quality degradation by point source discharges other than from dams will be allowed…the water quality and physical and biological integrity which existed on the water at the time of designation will be maintained and protected.”

The section of the Wind River below Boysen was designated as Class 1 water in 1979, according the Wyoming DEQ. They say that wastewater discharges from the Frenchie Draw Gas Field began in the mid-1960s and “have remained essentially unchanged since the designation of the downstream Wind River segment as a Class 1 water.”

Wyoming DEQ says that contemporary discharge at the Aethon facility “is not considered to be a new or expanded discharge.” Aethon originally proposed expanding the amount of discharge allowed under the permit to allow for up to 400% more flow.

The Wyoming DEQ say, however, that a reverse osmosis unit at the facility has been inoperable since 2019 and that Aethon does not have plans to re-open that unit at this time.

Discharge at the facility “undergoes some passive oil-water separation and settling of solids using retention pits prior to the final points of discharge,” the Wyoming DEQ states. “From 2016 to 2019, this facility employed a reverse osmosis unit (Neptune Plant) used for treating and then blending produced water.”

The Neptune Plant was intended to allow the facility to expand the amount of water that could be discharged under the salt load restrictions in the discharge permit.

“More water could be discharged if salts were removed from the water,” Wyoming DEQ says. “However, the reverse osmosis treatment unit at this facility has become inoperable due to some ongoing technical issues at the plant. Therefore, the facility is reverting to its historic basic operation of discharging untreated (or only passively treated) water at lower volumes.”

The Wyoming DEQ says that an increase to the discharge volume and pollutant load is “not practical or necessary to permit at this time. This permit renewal caps the salt load output at historic levels (908 tons per month). In addition, flows from the facility will remain essentially unchanged from the previous permit term, at around 2 million gallons
per day (2 MGD).”

While the permit doesn’t provide for an increase in discharge volumes or the amount of pollutants allowed, the Wyoming DEQ says that the permit has been revised in several ways.

First, the permit reduces the number of well additive chemicals that must be screened from 14 to four. Wyoming DEQ says this change was made based on public comments they received.

“The concern was that only four of the original proposed fourteen chemicals have reliable enough test methods to yield consistent and accurate analytical results,” Wyoming DEQ says. “After some additional research, WDEQ agrees with this and the list of screened down-hole chemicals is modified accordingly.”

Another change that came about after public comment includes clarification regarding the “total sulfide effluent limit of 20 µg/L.”

“Several comments noted correctly that this calculated effluent limit is below the practical detection limit for total sulfide,” Wyoming DEQ says. “Approved EPA test methods for sulfide detect down to only 50 µg/L. When a calculated effluent limit is below the practical detection limit, the permittee is only required to use the existing approved methods and a result of ‘nondetectable’ is compliant.”

The Wyoming DEQ has also removed proposed instream monitoring stations in Wind River Canyon and in Badwater Bay at Boysen Reservoir.

“These monitoring locations were originally proposed to coincide with a significant increase in discharge flows from the facility,” Wyoming DEQ says. “However, as noted in the Statement of Basis, the project is not authorized to increase its effluent output during the upcoming permit term.”

While those monitoring stations will not be requiring, other stations will still be used for “routine outfall sampling.”

“This permit requires sampling at two downstream locations for TDS (total dissolved solids), chloride, oil & grease, pH, dissolved oxygen and temperature,” Wyoming DEQ says. “Additionally, the uppermost monitoring station (DMP1) includes monitoring for various reasonable potential screening constituents and BTEX constituents (Benzene, Toluene, Ethylbenzene, Xylene).”

“Monitoring station DMP1 is at the very downstream end of the project area on Alkali Creek. Monitoring station BWC1 is on Badwater Creek, below its confluence with Alkali Creek. All instream monitoring locations are for data collection purposes only, and do not constitute regulated discharge points under the permit.”

The Wyoming DEQ provides the full language of the final permit online.

The Wyoming DEQ has also summarized public comments they received and provided responses to those comments online.

This article originally appeared on Oil City News. Used with permission.


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