83 barge trips later

A bird finds a perch as dredging of the outer boat basin continues at Crescent City Harbor. Del Norte Triplicate/Bryant Anderson

Dredging of tsunami-deposited silt from the inner boat basin was finished Friday, and the overall project might be completed this week.

Dutra Group scooped more than 120,000 cubic yards of silt and sediment from the inner boat basin and an estimated 4,000–5,000 cubic yards will be pulled out of the outer boat basin before the project ends, said Ward Stover of Stover Engineering, which is overseeing the reconstruction of the inner boat basin.

A full-fledged dredging project for the outer boat basin is slated for next year, but digging a channel to the syncrolift was included in the current project.

The March 2011 tsunami deposited about 90,000 cubic yards of silt in the inner boat basin. The extra 30,000 yards that Dutra hauled away came from “over depth,” the material removed two feet deeper than the target depth requested, Stover said. 

“The way you dredge, you can’t see where you’re digging, so it doesn’t mean you’re going to hit  it right at the design depth, you might go a little over,” Stover said. “If he digs more than two feet over, he doesn’t get paid for that additional material.”

The scows, barge-like boats used to haul the dredged material, made 14-hour round trips to Eureka to dispose of the material — 83 trips for the inner boat basin.

The Humboldt Open Ocean Dredged Site is the closest dumping zone in Environmental Protection Agency Region 9, which encompasses the Pacific Southwest. The site is roughly three miles from the entrance to Humboldt Bay and has been used since 1995.

“It’s an unusual situation for Crescent City because there is no ocean disposal site that would be closer and more economical,” said Allan Ota, the regional ocean dumping coordinator for Region 9. Without Federal Emergency Management Agency funds, Crescent City could not afford such a distant dump site, Ota said.

The scows dump the dredged material within seconds — 1,300 to 1,500 cubic yards per load.

“Each half of the scow can float on its own, so the whole scow splits apart into two pieces — it’s hydraulically run,” Stover said.  “It’s a matter of seconds that it can drop 1,500 yards.”

A third-party company tracked the scow’s transport and reported the information to the EPA, to make sure the material was dumped in the right place.

For material too close to the syncrolift for the excavator to grab, a dive crew sucked out the material and placed it where it could be picked up, Stover said.

Due to material still in the outer boat basin, some very large vessels, when loaded with crabs, will have to wait for high tide to enter the harbor, Stover said.

“It’s not a huge impact,” Stover said. “The contractor just barely had enough time to get the work done that we needed to get done before the winter season.”

The outer boat basin will have to get done next year to use the funding that has been secured for the project, but the dredging thus far has been successful, Stover said.

“We’ve been happy with Dutra’s work,” Stover said.