Chugach Electric; Knik Arm, Upper Cook Inlet, Alaska

Knik Arm, Upper Cook Inlet, Alaska | 1986-Jul-22

Initial Notification: On May 12, 1986, Chugach Electric Utility Co. noticed an abnormal fluid pressure drop in one of its undersea 138 KV transmission cables extending between Pt. McKenzie and Pt. Worzonoff in Upper Cook Inlet. The pressure drop was interpreted as a leak in the cable dielectric fluid, dodecylbenzene (DD), which is maintained at a positive pressure to prevent any salt water intrusion into the cable. The subsequent release of DDB into the marine environment was calculated by Chugach to be 5-10 gallons per day. As a result, on June 2, 1986, Chugach voluntarily de-energized and depressurized its cable, reducing fluid loss to 1-2 gallons per day and commenced an inspection program. On June 4, 1986, the U.S. Coast Guard Marine Safety Office (MSO), Anchorage, and the Alaska Department of Environmental Conservation (DEC) were notified of the situation. USCG district 17.