The cause of the sinking remains under investigation. We know that it impacted the oil platform – whether or not that was the cause or if it was as a result of ice moving in the inlet is part of the investigation, Coast Guard petty officer Sara Francis told Lube Report. The Monarch operates from Nikiski to the oil platforms, providing them various supplies, totes and lubricants.

The Monarch began taking on water at about 5:51 a.m. on Thursday, the Coast Guard said. The crew evacuated to the platform. A tugboat was dispatched to the scene but was unable to hook up a tow to the ship.

Shortly after noon on Thursday, the Unified Command received a report from personnel on the platform that the Monarch had sunk completely in waters about 86 feet deep. Unified Command includes the Coast Guard, Alaska Department of Environmental Conservation and Ocean Marine Services Inc.

The Monarchs home port is in Juneau, Alaska, but it operated primarily in the Nikiski and Cook Inlet area. Ocean Marine Services Inc. of Kirkland, Wash. operates the vessel.

Union Oil Co. of California, a Chevron company, operates the platform. Personnel on the platform told the Coast Guard Thursday that at low tide there appeared to be no significant damage to the platform legs from the contact with the Monarchs hull.

The Coast Guard said the motor vessel Champion is maintaining an oil response capability onboard and additional equipment is available at the OSK Lines dock in Nikiski, 16 miles away. Divers plan to affix transponders to the hull of the sunken Monarch to monitor the status of the vessel when weather and ice conditions permit.

Unified Command is developing a long term monitoring plan to allow time to develop a suitable removal plan. Removal is expected to take place when ice conditions no longer present a safety hazard to responders or operations, the Coast Guard said.