OSV capsizes and sinks after getting trapped by ice against leg of oil rig in Cook Inlet

A supply boat flooded, capsized and sank in Alaska’s Cook Inlet after being trapped in ice against the leg of an offshore oil rig.

Seven crewmembers were aboard the 166-foot Monarch when the accident happened Jan. 15. They evacuated to the Granite Point oil platform. The engine room immediately flooded after the vessel was catastrophically holed. “The Monarch was tied off to the platform when ice encroached, piercing the hull and the engine room,” said Coast Guard Capt. Mark Hamilton, sector commander and captain of the port for Western Alaska.

“The crew was fortunate in that the leg of the platform that was hit had a ladder attached, so the crew climbed the ladder to safety,” said Coast Guard spokeswoman Petty Officer Sara Francis.

“After the crew left the supply boat, it rolled to starboard and turned turtle,” Francis added. The accident happened at about 0600, and by noon only the bow remained above water.

“We flew over the scene confirming the bow of the vessel was barely out of the water and a couple of hours later the vessel had sunk to the bottom of Cook Inlet, but did turn and landed on her keel,” Francis said.

Along with seven workers from the oil platform, Monarch’s crewmembers were helicoptered to shore as a precaution. Chevron Corp., the operator of the platform, left only essential personnel on the platform.

Monarch was carrying about 35,000 gallons of diesel, which was not contained because of the ice and extreme tides in Cook Inlet, 45 miles southwest of Anchorage. With the ice, wind and tides, the fuel dispersed quickly, the Coast Guard said.

“We do not know how much diesel fuel the Monarch took to the bottom of Cook Inlet,” Francis said.

Monarch, built in 1970 by VT Halter Marine, is owned by Ocean Marine Services Inc. of Kirkland, Wash. Although the vessel was almost 40 years old, it probably was in good condition, the Coast Guard said.

“The Monarch had just completed its five-year inspection and had a lot of steel added while the boat was in dry dock,” Hamilton said.

Ocean Marine Services and the Alaska Environmental Coordination Office participated in the incident response command post.

After the supply boat went down, a bit of its bow remained visible near the oil platform. Courtesy U.S. Coast Guard
Two days after the accident, the tug Vigilant and the motor vessel Champion found the supply boat using side-scanning sonar. The boat was located near the leg of the platform it struck in about 86 feet of water. “We are still watching the vessel on sonar to be sure its position does not change, or if it does we know where it is,” Francis said in March.

“Considering the ice flow, the tides and the overall weather in the area, it will be April or later before we can begin a salvage operation,” Hamilton said.

The oil platform was shut in for approximately 30 hours before resuming normal operations. Ocean Marine Services didn’t respond to requests for comment on the accident. •

By Professional Mariner Staff