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Hilcorp Natural Gas Leak from 8‐inch Pipeline in Cook Inlet

SITREP #: 1 | SPILL #: 17239903801


TIME/DATE OF DISTRIBUTION:  4:30 p.m. February 15, 2017




INCIDENT LOCATION: Cook Inlet between Platform A and Nikiski. (Lat/Long: 60.776367, ‐151.43365)




HOW/WHEN SPILL WAS DISCOVERED AND REPORTED: A Hilcorp helicopter flying between Nikiski and Platform A around 3 p.m. on February 7, 2017, identified bubbles resulting from a natural gas leak. Hilcorp reported the gas leak to the National Response Center and to the Alaska Department of Environmental Conservation (ADEC) at 4 p.m. on the same day.


TYPE/AMOUNT OF PRODUCT SPILLED: The natural gas being released is not natural gas from the platform. The gas is processed dry natural gas (98.67% Methane), providing fuel gas to four platforms: Platform A, Platform C, Dillon Platform and Bakers Platform. The exact amount of gas released to water is unknown at this time.

Hilcorp reported the line pressure up to February 13 was approximately 195 psi. As of February 14, Hilcorp reported the line pressure was reduced to 185 psi with an estimated leak rate between 225,000 to 325,000 cubic feet per day.


CAUSE OF SPILL:  The cause of the leak is unknown at this time and is being investigated.


SOURCE CONTROL: The 8‐inch pipeline is an underwater pipeline at approximately 80 feet below Cook Inlet waters.  No source control has been achieved at this time.


RESPONSE ACTION: Hilcorp conducted overflights on February 8th, 9th, 11th, 12th, and 14th to ensure the gas leak was not increasing in size. The overflight conducted on February 8th and 9th showed continued gas release.

Bubbles from the natural gas leak could not be detected on February 11th, 12th or 14th because of the ice pans that cover the affected area. Overflights could not be conducted on February 10th or the 13th due to weather. Hilcorp activated a diving company to assess the pipeline damage when the gas release was discovered; however, due to the current ice conditions, diving at this time was determined to be unsafe due to ice conditions in Cook Inlet. Hilcorp is continuing to monitor the pressure and flow rate on the line to ensure there is indication of an increase in the rate of release.

ADEC has been actively communicating with Hilcorp and resource agencies to determine path forward and to address potential resources at risk in Cook Inlet.




Shorelines ‐ Shoreline type varies throughout upper Cook Inlet. Shorelines around the East Forelands area include mixed sand and gravel beaches, coarse‐grained sand, and exposed tidal flats. Redoubt Bay and Trading Bay on the west side of Cook Inlet include salt and brackish‐water marshes and sheltered tidal flats which are of high importance to bird and invertebrate species.


Marine Mammals ‐  Species likely to be present in upper Cook Inlet include Cook Inlet beluga whale (Endangered Species Act [ESA]‐listed as endangered), western Distinct Population Segment (DPS) Steller sea lion (ESA‐listed as endangered), Mexico DPS humpback whale (ESA‐listed as threatened), harbor seals, killer whales, Hawaii DPS humpback whales, harbor porpoise, and Dall’s porpoise. The Southwest Alaska DPS Northern sea otter (ESA‐listed as threatened) is known to occur in lower Cook Inlet. The discharge location is within designated Critical Habitat for Cook Inlet beluga whales. Cook Inlet beluga whales are likely utilizing offshore waters in upper Cook Inlet during winter and will concentrate near forage fish locations as those populations arrive.


Birds ‐ Steller’s eiders are ESA‐listed as threatened and are known to overwinter south of the gas release along both the eastern and western shores of lower Cook Inlet; however, a small portion of this species has been known to overwinter in the Nikiski area. Waterfowl and shorebirds are overwintering in upper Cook Inlet.

Notably, rock sandpipers are known to overwinter in upper Cook Inlet feeding on bivalves, including almost the entire population of the subspecies Calidris ptilocnemis ptilocnemis. Bald and golden eagles are also present in Cook Inlet year round. Migratory birds, including waterfowl, seabirds, and shorebirds will likely begin arriving in high numbers in the Cook Inlet area in late March to early April.


Fish ‐ Several species and different life stages of fish are likely present in Cook Inlet near the vicinity of the gas release, including all five species of Pacific salmon (Chinook, coho, sockeye, chum, and pink salmon), Dolly Varden, rainbow trout, Pacific eulachon, Pacific halibut (spawning and hatching occurs in winter months), Pacific herring, Bering cisco, Humpback whitefish, American shad, Walleye pollock, sablefish (adults spawn in winter in deep waters, larvae are present at the water surface, and juveniles are found in nearshore waters), Pacific and saffron cod, yellowfin sole, and smelt. This area is Essential Fish Habitat for all five species of Pacific salmon.


FUTURE PLANS AND RECOMMENDATIONS: Hilcorp is continuing to monitor ice conditions to determine when it will be safe for diving activities. Continue to monitor the pipeline pressure to ensure there is no sudden decrease in pressure to indicate increased leak. Coordinate overflight with wildlife resource agencies to assess potential impacts.  Continue to explore safe options to control the source.


WEATHER: Today: Snow showers; temperatures nearly steady in the low to mid 30°F; winds northeast at 5 to 10 mph; chance of snow 50 percent; one to three inches of snow expected. Tonight: Cloudy; low 24°F; winds northeast at 15 to 25 mph. Tomorrow: Cloudy with snow showers becoming a steady accumulating snow later on; high 33°F; winds northeast at 15 to 25 mph; chance of snow 80 percent; snow accumulating one to three inches.



SOSC:  Geoff Merrell, ADEC



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