Mad River Union
WOODLEY ISLAND – Humboldt Bay will soon have its own dredge, allowing the harbor district to maintain local marinas on a regular basis. The vessel will also save taxpayers millions of dollars in dredging costs, if all goes as planned.
The Humboldt Bay Harbor, Recreation and Conservation District (HBHRCD) Commissioners voted unanimously, with Commissioner Mike Wilson absent, at its April 24 meeting to purchase the 70-foot vessel for $950,000. The district may spend an additional $450,000 making improvements to the dredge.
The entire cost of the cutter-head dredge is being paid for by Pacific Gas & Electric. As part of the decommissioning of its Humboldt Bay Nuclear Power Plant, PG&E gave the district $2 million to buy the vessel and dredge Fisherman’s Channel, located adjacent to the power plant in King Salmon. The channel was used as a source of cooling water for the now-defunct reactor. The nuclear power plant was closed down in 1976 and is now the site of the Humboldt Bay Power Plant, which is fueled mostly by natural gas.
After the district trains its staff to operate the dredge, figures out where to dump the spoils and obtains the necessary environmental permits, dredging may begin in late 2015. To protect salmon, dredging can only take place during the winter months.
HBHRCD Chief Executive Officer Jack Crider said the dredge will be used about four months out of the year. The rest of the time it will be dry docked in Fields Landing.
The first project will be the dredging of Fisherman’s Channel, which will give district staff time to learn the ins and outs of dredging.
Eventually, the dredge will be deployed at the Woodley Island Marina, Eureka Public Marina and all of the public and private docks around the bay.
The main channels, Crider explained, are maintained by the U.S. Army Corps of Engineers, which brings in its own dredge every year.
The harbor district, Crider said, should see substantial savings by doing its own dredging. The marinas will also be better maintained.
Traditionally, Crider said, the Woodley Island and Eureka marinas have been dredged every eight to 10 years. The last dredging in 2007 cost $3.2 million, he said. Part of that cost included $600,000 just to get the dredge moved to Humboldt Bay, along with all the associated equipment.
That brings the cost of dredging to about $400,000 a year. Crider said he expects that by the district doing the dredging itself, it will cut that cost by 50 to 60 percent or more.
Besides saving money, the district will also have better maintained facilities, Crider said. Bay sediment fills the marinas by about six inches a year, eventually rendering some slips unusable.
One of the most challenging details that the district needs to work out before it can dredge is where to dewater and dispose of the spoils.
The district is still studying its options. One possibility is to use the spoils to build up levees. Another option is to temporarily deposit the spoils in the navigation channel and allow the U.S. Army Corps of Engineers to suck up the sludge when it brings in its massive dredge.
Another option, Crider said, is to pump the dredge materials to the harbor district’s ponds, located on 23 acres north of the Samoa Cookhouse. The sediment would drop out, then the seawater could be disposed of by either pumping it to the ocean, or using the old pulp mill’s ocean outfall line.
The dredge comes with 11,000 feet of piping. The dredge’s 750 hp motor, along with a separate 750 hp booster engine, can pump the sludge and water through pipes that are temporarily placed on the floor of the bay and connected to the dredge with a floating portion of pipe.
The pipes can then dump the spoils at the chosen disposal site.