State finalizing Hilcorp Endicott permit with chlorine mixing zones

The Alaska Department of Environmental Conservation issued a final wastewater discharge permit on March 19 for Hilcorp Alaska's Endicott Operations that authorizes mixing zones for chlorine, temperature, and pH in the Beaufort Sea. The permit allows pollutants to exceed water quality standards within designated areas before dilution occurs.

Hilcorp operates a seawater treatment plant on Duck Island in Stefansson Sound that produces waterflood for injection into oil formations. The facility discharges treated seawater, domestic wastewater, and continuous flush system effluent into Arctic waters.

The permit authorizes chronic mixing zones for temperature, total residual chlorine, pH, and whole effluent toxicity. It also includes an acute mixing zone for chlorine.

Public comments were accepted from March 23 through April 24. A review period from May 11 through May 15 was restricted to the permittee only. The general public could not submit comments during that final stage.

DEC received the permit reissuance application from Hilcorp on May 4, 2023. Contact Amy Wockenfuss at 907-269-8874 or [email protected] for additional technical documents.