The following incidents in CIRCAC’s area of responsibility and concern have warranted monitoring and/or advice, recommendations, data and expertise. This page contains the information released through the Unified Command as well as descriptions of the most recent incidents in our areas of responsibility and concern.

Note: Click here to see documented Drills and Exercises.




CIRCAC Staff received information on June 5, 2018, about a crude oil discharge that occurred during work on the Hilcorp owned Middle Ground Shoal (MGS) subsea pipeline. The release was in the vicinity of Platform A as divers were working on the Platform-A subsea pipeline reconfiguration project. They were disconnecting a flange on a confirmed closed valve line. At approximately 11:00, topside crew on the platform noticed approximately 10 to 15 (up-to 1 inch in size) tar balls floating on the surface near the platform. The flange was secured with a blind flange. Hilcorp had CISPRI response assets standing by with its skimmers deployed throughout the operation as part of their response protocols for the operation. CISPRI responders recovered the tar balls and any recoverable sheen. Estimated recovered crude oil (tar balls and sheen) was approximately 1 cup. Hilcorp notified all appropriate agencies.

Prior to the project start, Hilcorp had submitted to the Alaska Department of Environmental Conservation (ADEC) their “2018 MGS Pipeline Removal and Replacement Spill Mitigation Plan.” As part of that plan Hilcorp implemented the following spill prevention/mitigation measures for the work scheduled.

  • An open-cell sponge and temporary blind flange equipped with a neoprene gasket will be installed at pipeline breaks to contain and seal the pipelines.
  • Oil spill response equipment including a Cook Inlet Spill Prevention & Response, Inc. (CISPRI) vessel will be on stand-by one hour before, during, and one hour after pipeline disconnection activities.
  • Over-flights will be conducted over the project area during slack tide to monitor for a sheen each day that pipelines are non-continuous (while any portion of the sub-sea pipeline is not continuously connected at flanges or valves). Results of daily overflights will be recorded.
  • Platform personnel on Platform A and Platform C will visually inspect the area during slack tide to monitor for a sheen each day that pipelines are non-continuous. Results of daily visual inspections will be recorded.


Platform Anna

The cause of this incident, and quantity of release, are under investigation.

Note: Throughout this incident, CIRCAC participated in the Unified Command to monitor the response and provide advice, recommendations and resources.

April 3, 2017


Nikiski, Alaska – The Unified Command comprised of the United States Coast Guard (USCG), Alaska Department of Environmental Conservation (ADEC), and Hilcorp Alaska (Hilcorp) responding to a reported sheen in Cook Inlet stood down this morning at 9am after a final overflight this morning confirmed no sheening.

Hilcorp crews successfully and safely evacuated all crude oil from the suspected leaking pipeline by displacing it with filtered seawater.  The pipeline is an oil gathering line connecting the Anna and Bruce platforms. Cook Inlet Spill Prevention and Response (CISPRI) remained on scene and USCG and ADEC Observers were on board the Anna platform for the purging operation.

Overflights were conducted at 700pm Sunday evening and at 750am this morning. No sheen was observed. The Perseverance, a CISPRI vessel, remained on standby through the evening and will do a final survey of area later today.

A diving crew is assembling in the region accompanied by the appropriate support vessels.  Use of divers to investigate and perform any necessary repairs will be initiated as soon as it is safe to do so.

At this time, the exact cause of the release is unknown and remains under investigation.


Media can reach the Unified Command Information office by contacting:
Lori Nelson   Candice Bressler   Coast Guard Public Affairs  907-777-8392   907-465-5009    907-209-8731



Nikiski, Alaska – A Unified Command comprised of the United States Coast Guard (USCG), Alaska Department of Environmental Conservation (ADEC), and Hilcorp Alaska (Hilcorp) has been established in response to reports of a sheen near the Anna Platform.

The Anna Platform is located in the Granite Point Field of Cook Inlet. A sheen was discovered by Hilcorp personnel at 11:20am on Saturday, April 1. Production was shut in immediately and the incident was reported to ADEC at 12:05pm on the same day.

Three flyovers were conducted yesterday. During the first flyover at approximately 11:30am, several sheens were spotted approximately 3 miles downstream from the platform. The other two flights did not identify any sheen in the area. Two additional flyovers were completed today at 10:45am and 2pm. No sheen was sighted in the area.

The suspected source of the release is an oil pipeline running between the Anna and Bruce platforms. In order to reduce the risk of a further spill, platform crews are displacing the existing oil in the pipeline with seawater. USCG and ADEC personnel have boarded the Anna platform and will be observing the operation. The Perseverance, a Cook Inlet Spill Prevention and Response (CISPRI) vessel, is also on scene and will remain there until the oil is removed from the line.

At this time, the cause of the release and sheen is unknown. Further updates will be provided when they become available.


Media can reach the Unified Command Information office by contacting:

Lori Nelson


Candice Bressler


Coast Guard Public Affairs


Platform A Gas Pipeline Leak (Hilcorp)

CIRCAC’s congressional mandates specify our role in crude oil transportation and facility operations. Though natural gas supply lines do not specifically fall within those mandates, we are concerned any time a hazardous substance is introduced into the Inlet. We’re providing our data and expertise in any way that can improve decisions being made about this incident, which is a reminder of Cook Inlet’s aging infrastructure, specifically subsea pipeline integrity.

CIRCAC’s Director of Science and Research, Susan Saupe, has been contacted as a subject matter expert about parts of the monitoring plan based on her experience sampling in Cook Inlet, including in the high current scenarios north of the Forelands.  She has provided her recommendations to the state and resource agencies.  As we understand, the State’s final recommendations to Hilcorp are still being considered.  We’re also providing access to the ice camera network to assist.


Drift River Oil Terminal Spill

In July, Hilcorp Alaska reported a crude oil discharge associated with the piping system at the Drift River Oil Terminal tank farm. During investigation, a valve misalignment was discovered and the pump shut down. The investigation uncovered four different sites where oil contamination levels required excavation, ground water recovery and site remediation. The response continued until weather forced the suspension of operations and will be resumed this spring.

Beaver Creek

In July, Hilcorp reported a small leak from a buried crude oil line at the facility. The Beaver Creek Production Facility is located near Kenai in the Kenai National Wildlife Refuge. The leaking line had been isolated and approximately 25 gallons were spilled, 850 cubic yards of solids removed, five groundwater monitoring wells installed and over 30 confirmation samples collected. The case was transferred to ADEC’s Contaminated Sites Program for cleanup monitoring and evaluation due to its possible impacts to groundwater.

Nikiski KPL Dock
In December, a pipe ruptured at the KPL facility Tank 2400 waste water tank. The resulting discharge did not impact Cook Inlet nor were there any injuries. The ruptured pipe was isolated and contractors have been cleaning up the discharge. The Alaska Department of Environmental Conservation responded to the incident and investigated. The rupture was likely caused by freezing water in the pipe combined with pressure when put into service; 12.5 barrels of water and .6 barrels of hydrocarbons were recovered.