ILWACO — There’s a lot more than silt sitting at the bottom of two local ports.
Each year discoveries are made during the annual dredging season as port maintenance crew work to remove thousands of cubic yards of accumulated silt clogging access and moorage at the Port of Ilwaco and Chinook.
Operating a hydraulic dredge is complex and can take months to master. The main controls feature eight identical manual levers and six primary gauges that the operator must observe and maneuver to operate the dredge effectively.
“It takes several months to be an efficient operator,” said John Demase, marina operations manager for the Port of Ilwaco. “There’s obviously no school for it.”
The dredge is typically a two-man operation, with one person manning the controls and another keeping the suction and cutter-head free of debris. The season brings new roles and responsibilities as boatyard staff handle dredge duties and the maintenance crew split boatyard and regular maintenance responsibilities.
“When it comes dredge season we completely change everybody’s roles,” Demase said.
Those on dredge duty work a different schedule largely determined by the tides, when work conditions are optimal.
“This year we are running two shifts a day, coinciding with low tides, to maximize our production within our limited timeframe,” said Port Manager Guy Glenn, Jr.
The Port of Ilwaco started a maintenance dredging program nearly 20 years ago. Between 15,000 and 30,000 cubic yards of material are removed annually from the marina.
Once the dredge is started a trail of bubbles signify the spot where silt is being removed in steady, sweeping motions through a 10-inch suction hose. Soon strips of dock bumper, pieces of wood pilings and old soda bottles begin to bubble to the surface. Rusty remnants of power tools and miscellaneous marine engine parts are common. The crew regularly finds old tires, once frequently used as boat and dock fenders; the record stands at 12 tires in a single day, according to Glenn. Crab pots, carpet, tattered rope, metal fish carts and five-gallon buckets often cling to the cutter-head. The biggest pieces must be removed manually to prevent damage to the dredge as the silt is deposited in a temporary hopper.
Each week, crew focus on a different section of the marina following a coordinated dredge plan. The goal is to accomplish as much as possible during the permitted in-water work window. Work started Nov. 1 in Ilwaco and will eventually move to Chinook, likely in late December, and continue through Feb. 28, the permitted in-water work window for the projects. Careful calculations are made considering the amount of silt that needs to be removed from the shallowest areas, how long it will take and where it will go. On average the dredge can move 50 to 75 cubic yards of silt per hour. The dire spots are dredged first, but an efficient season requires precise planning.
“A lot goes into dredging that people don’t realize,” Demase said. “Beforehand we’re doing depth surveys and adjust them for tide, then based off that I get with the port manager [Glenn] and we make a dredge plan.”
The silt and sediments are unique to each port on either side of the river. The Port of Ilwaco and Chinook both are approximately 80 percent silt, mostly clay with a little sand.
“If you go across the river to Astoria, it’s completely different,” Demase said. “It’s really sand heavy.”
In March 2018, Washington state legislators finalized Senate Bill 6095, including $450,000 to help the ports of Ilwaco and Chinook with marina maintenance dredging. Chinook and Ilwaco received $275,000 and $175,000, respectively. Lawmakers also provided $77,000 to explore options for sediment disposal, a crucial need as disposal sites have reached or are near capacity. Areas in the Chinook marina have silted in more than six feet from their original authorized depths over the last 10 to 20 years leading lead to moorage slips becoming restricted or even becoming unusable.
“We would not have been able to dredge in the Port of Chinook marina without funding from the State of Washington this year,” Glenn said.
“We hope to remove enough material this season to buy us time to develop alternatives for managing our dredge material. This is why we are pursuing a long-term marina maintenance dredging plan at both ports.”
One of the primary objectives of the plan is to help identify alternatives to manage dredge material placement since the lack of capacity at the upland sites will constrain future dredging efforts at both ports. The combined dredging plan is currently being developed with the leadership of Vladimir Shepsis, a hydraulic engineer from Mott MacDonald/Coast and Harbor Engineering.