Dredges tackle volcano's debris blocking access to major seaports
Volcanic ash, mud, silt, and timber from the eruption of Mt. St. Helens have shut down the important ports of Portland, Ore., and Vancouver, Wash., by rendering a three-mile stretch of the Columbia River impassable to shipping. The depth of the river channel leading to the ports has been reduced from a normal 40 feet to 15 feet.
Every day the ports are closed, says Louis Holcomb, executive director of the port of Vancouver, it results in a direct and indirect loss to the region of $3. 25 million.
Lloyd Anderson, director of the port of Portland, says he is optimistic that the ports will get by without major losses, since dredging activities are going faster than originally expected.
According to Portland officials, 24 ships are trapped in port and 25 are tied up at the mouth of the Columbia, waiting to get in.
The ports normally handle well over 5 million tons of cargo annually. Last year 250,000 Toyota and Honda autos passed through Portland's docks, as well as tons of steel and electronic equipment.
The neighboring ports (Vancouver is on the Columbia, Portland farther inland on the Willamete, a major tributary) also serve as export centers for lumber bound for the Far East and grain shipped from the Midwest.
So far, only two ships bound for the Columbia have been diverted to Seattle, says Mr. Holcomb.
A spokesman for the US Army Corps of Engineers, Pacific Division, in Portland estimates that it will take a week to clear a 25-foot-wide channel. This would permit one-way, daytime ship traffic. To get the channel back to its previous 600-foot width and normal depth, he estimates it will take most of the summer. The corps puts the cost of the dredging at about $24 million.
Some estimates place up to 10 million cubic yards of debris in the channel.This is equivalent to the usual amount of dredging done by the corps on the Columbia in one year. In order to dredge this mass of mud, ash, and silt, the corps has moved four dredges up from California and is planning on hiring an additional three or four private dredges.
Although the Corps of Engineers hopes to restore limited navigation in two to three weeks, a lot depends on how easily the dredging goes. If the dredges encounter a lot of rocks or buried timber, the effort could be delayed. Also, one corps spokesman said, the volcanic ash has a propensity to set like concrete when it settles.
Not only will the corps have to dredge the Columbia, it will also have to clean out the Cowlitz River to its normal depth of eight feet. The debris currently jamming up this Columbia tributary creates a major flood hazard.
The Toutle River is also backed up with mud and debris, forming a lake 200 feet deep and 20 miles long. There is some concern that if an earthen dam holding this water back were to break it would cause additional problems on the Columbia, not to mention the damage it would do to the river valley.