DEC issues proposed final APDES permit for Hilcorp's Prudhoe Bay discharge

The Alaska Department of Environmental Conservation issued a proposed final discharge permit that would continue Hilcorp Alaska's authorization to release up to 12.4 million gallons of strained seawater per day into Stefansson Sound from the Prudhoe Bay Seawater Treatment Plant at the West Dock Causeway, about 20 miles northeast of Nuiqsut. The notice is a procedural step in the reissuance of an existing discharge authorization, not a final permit issuance.

The plant has operated under an administratively extended permit since December 31, 2022, when the prior authorization expired. Hilcorp submitted the reissuance application on August 30, 2022. DEC published a fact sheet on the proposed reissuance on April 17, 2026.

Hilcorp has until July 24 to review the proposed permit. Public comments were accepted from June 10 through July 10, 2026. The permit documents, including the preliminary draft permit and fact sheet, are available for public review at DEC offices in Anchorage, Fairbanks, Juneau, Soldotna, and Wasilla.

The Native Village of Nuiqsut has raised concerns that Beaufort Sea mixing zones risk harming marine mammals and subsistence resources. The permit authorizes acute and chronic mixing zones at Outfall 001 in Stefansson Sound and sets effluent limits including pH, temperature differential, and total residual chlorine caps.

As broader context, the Alaska Oil and Gas Conservation Commission found in November 2025 that Hilcorp "has a substantial history of noncompliance with AOGCC regulations," citing violations at the Polaris Oil Pool in the Greater Prudhoe Bay Unit. That finding was separate from DEC's permitting process for the seawater treatment plant.