Posted on February 16, 2021
ILWACO — Little noticed but important work is underway, focused on the bottom of local marinas.
Annual dredging has commenced, crucial efforts needed to keep local waterways navigable and preserve access to the Port of Ilwaco and Chinook for commercial and recreational vessels. Annual dredging started in early January and will conclude by Feb. 28, a timeline designed to avoid migrating fish.
In addition to the dredging in and near Pacific County’s two Columbia River marinas, larger-scale sediment removal is maintaining access between Ilwaco and the river’s main navigation channel leading to the ocean.
20 years in the making
The Port of Ilwaco started its maintenance dredging program nearly 20 years ago, improving the overall condition of the marina. Typically between 10,000 to 15,000 cubic yards are removed each year, enough to fill about 1,000 dump trucks.
“Our goal this year is less than previous years,” said port Manager Guy Glenn Jr. “We have done a lot of dredging since 2013 and hope to remove more in the 2021-2022 in water work window, which begins Nov. 1 and ends on Feb. 28. Dredging takes a significant amount of staff time and resources.”
Efficiency is paramount to maximize the impact of the allotted in-water work window, coordinated weeks in advance, taking into account tide conditions and migrating salmon. 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 worst impacted spots are dredged first, but an efficient season requires precise planning.
The silt sitting at the bottom of the ports of Ilwaco and Chinook is up to 80% clay. Roughly four vertical feet of clay-heavy silt will be removed from the port bottom on average. The material will then be deposited at a placement site near the marinas.
“Dredge material from the [Ilwaco] marina is placed in a seven-acre upland placement site next to our boat launch parking area. We operate a 10-inch hydraulic suction dredge and have around 3,000 feet of dredge pipe to pump the dredge material to our upland site,” Glenn said.
Dredging is a necessary annual maintenance endeavor for local ports impacted by accumulating sediment.
“Our entrance channel and marina are essentially ‘navigation infrastructure,’” Glenn explained. “Maintenance dredging is needed for vessels to transit into port and around our marina to offload their catch, get fuel, ice, bait and be hauled out in our boatyard for repairs and maintenance, and to also moor their vessels at our docks. The confluence of the Columbia River and Pacific Ocean is a very dynamic area, between the river currents, tides and wave action. These forces can move sediment around and create shoaling, which in turn can restrict access for vessels requiring more depth. The investment we make in maintenance dredging is not readily visible but critical for our local ports, both Ilwaco and Chinook.”
Repairing wear and tear
The Port of Ilwaco oil depot and boatyard shop building were both in line for renovations last week after seasonal storms took a toll on the structures.
“Our boatyard shop roof was severely damaged during a storm in early 2020,” Glenn said. “We have been working on coordinating the project since early last year. The process took longer than anticipated and we started running into further delays with winter weather. The roof is being completely replaced on the entire building.”
The waste oil depot roof was also severely damaged in a storm in early 2020.
“As a result, the previous structure was replaced due to its age and condition,” Glenn said.
