Lack of Cook Inlet ice allows Port of Anchorage dredging to start early

Dredging at the Port of Anchorage, the perpetual task of digging silt out of the port's waters so ships can dock without hitting bottom, started early again this year to handle the extra silt built up because of the current configuration of the port.

A lack of ice this past winter in Cook Inlet allowed dredging equipment to come in and start the process months ahead of the usual schedule, ramping up March 23.

Previously, the dredging started around May and ran through October, but the past three winters it has started earlier and run longer since the port was reconfigured during a now-stalled modernization project. This year, it will run through mid-November.

Because of the changes made at the port, more silt now settles to the bottom in the nook where ships dock, especially at the terminal where Tote Maritime parks its huge cargo ships that regularly bring crucial goods to Alaska.

"We consider this a temporary problem, and when they finish their modernization, we don't expect to have these problems every year," said Julie Anderson, chief of operations at the U.S. Army Corps of Engineers' Alaska District.

The silt is created by nearby glaciers, and it flows in meltwater into Knik Arm and Turnagain Arm. Too much silt built up makes it difficult or impossible for large container ships to dock, especially when the tide is low.

The modernization, originally called an expansion project, started years ago but stalled by 2011 before major construction even started. It was meant to add dozens of acres of land to the port to provide more space for operations.


Before stalling, however, work had started on a sheet pile wall in the water along the port. That wall was found to be failing.

Now an area on the north end of the port juts into the water farther than the area where boats dock, causing the tide to flow in such a way that it slows down around the port, trapping more silt. The rest of the port was supposed to be built out farther into the water, which would have brought it into alignment, before the project was delayed.

That extension into the water on the north end of the port is both a navigational hazard for ships and an earthquake hazard, said Jim Jager, external affairs director for the port.

In 2013, the city sued three firms over the stalled project, and added another firm to that list in 2014. Anchorage Mayor Ethan Berkowitz is now making the modernization a priority and asking the Legislature for $290 million to fund it.

Anderson said that once the project is finished, less dredging will be needed and work will go back to the usual schedule.

Seattle-based Manson Construction Co. signed a three-year contract two years ago with the Army Corps to do the dredging work, originally for $8.5 million (that amount has since changed and the Corps will not specify the terms of the contract), and has also been the dredging contractor for many years prior.

Manson removes the silt using Westport, a massive hopper dredge -- essentially a vacuum that sucks up the mucky matter from along the docks and sends it gushing into what's basically a huge bathtub that takes up much of the 180-foot-long dredge. Then Manson drops the silt back into the water in another part of Cook Inlet not far from the port, where the current is strong enough to sweep it away.

The Manson dredge moves up and down along the port, using digital maps to spot the worst silt buildup and determine where it needs to dig. Manson has 12 people constantly working on the dredging project for months.

Manson tugboat captain Mike Benton said that the operation moves between 1 million and 1.2 million cubic yards of silt each year.

The port tries to maintain a minimum depth of 35 feet between the bottom of the Inlet and the low tide mark, said Jager.

"We've had more sedimentation this year than we would typically have," he said. "One of the reasons we brought the dredge up earlier is we we're getting spots where the water wasn't high enough."

On Wednesday, Manson focused on dredging the area in front of Terminal 3. In that specific part of the port's waters, tides move more slowly.

Because of the large amount of silt in waters at the Port of Anchorage and the large tides in the area, Benton said that this is one of the toughest ports to do this dredging work.

"It comes in faster than we can dig it at certain times," he said.

Annie Zak

Annie Zak was a business reporter for the ADN between 2015 and 2019.