Oregon port works to remove silt from March 2011 tsunami

BROOKINGS, Ore. (AP) — Crews are getting ready to suck out nearly 28,000 cubic yards of silt that were deposited at Port Brookings-Harbor in the aftermath of the 2011 Japanese tsunami.

The debris will be dredged and pumped through a pipe floating atop the Pacific to a federally approved undersea dump site about a mile southwest of the Chetco River mouth, The Mail Tribune reported Sunday.

Large dredges such as the one now removing silt and cobbles in the Chetco River bar could never get into this tiny basin, where strings of docks and pilings are used by a robust recreational fleet as well as commercial vessels.

But the tsunami-fed silt, along with other underwater gunk built up over decades, has left the basin's waters dangerously shallow for even private boats that risk breaking propellers at low tide.

So a Jacksonville engineer has led to a plan for using a smaller dredge to remove the material and a series of pumps to funnel it to an offshore dump site normally visited by large barges.

"We never tried it before," port Manager Ted Fitzgerald said. "What it came down to is that we had to devise our own plan."

The buoyant pipe is designed to be held aloft and in place either on large floats specially built for this project or anchored to the sea floor, which averages about 70 feet deep along its path. Beacons will warn marine traffic of its placement.

"It'll look like a Christmas tree out there," said Jack Akin, the Jacksonville environmental engineer who designed the project.

A better idea of exactly what it will look like may be finalized Thursday when Akin and port officials meet with the U.S. Coast Guard.

The Oregon State Marine Board did a post-tsunami mapping and identified about 28,000 cubic feet of silt attributed to the event. The mapping helped land the port a $673,000 Federal Emergency Management Agency grant for removing it.

Construction and testing is scheduled to begin Sept. 4 and pumping could begin as early as Sept. 7, Akin said. Pumping is expected to take 28 days, but the plan calls for it to last as long as 45 days, depending upon how much debris, dead crab pots and other materials delay operations, he says.

"We expect to have several breakdowns," said Akin.

Ports such as Crescent City regularly dredge in this fashion, but they pump their silt onto dry land.

At Oregon ports, the silt is typically pumped into barges that are towed offshore to any of a series of release sites approved for dumping by the federal Environmental Protection Agency.

Pumping projects like this one haven't been tried off the Oregon Coast largely because the release sites are too far from most ports.

With no land available for the dredge spoils and the boat basin only a mile from the release site, the piping project rose to the surface as the best way to deal with the tsunami-caused silt.

The silt removal is one of the least expensive of the projects undertaken to fix the nearly $7 million worth of damage caused March 11, 2011, when a 9.0-magnitude earthquake rocked Japan. It triggered a tsunami, or series of large ocean surges, that hit the Oregon Coast that morning.

The surges came amid high and dirty flows out of the Chetco River. The tsunami blocked the Chetco's flows to the sea, pushing that water into the port.

Nearly 70 percent of the port's docks were destroyed along with a seawall and several boats. Many commercial craft were alerted to the tsunami and motored out of the boat basin to ride out the storm in relative ease.

Repairs to damaged docks and infrastructure were finished last week, leaving port managers wondering what to do with the mounds of silt that create navigational hazards within the boat basin's tiny pathways.

Copyright 2012 The Associated Press.