Dredges Essayons and Yaquina in dry dock together

Jeffrey Henon
Public Affairs Office

The Dredge Essayons facing landward in Vigor Shipyard’s dry dock for her annual maintenance.

The Dredge Essayons facing landward in Vigor Shipyard’s dry dock for her annual maintenance.

For the first time ever, Portland District dredges Essayons and Yaquina went into the same dry dock for maintenance at Vigor Shipyard, Dec. 16, 2016. Vigor Shipyard is located on Swan Island in Portland, Ore. The dredges received scheduled maintenance and some planned upgrades.

When the dredges aren’t in dry dock they’re working. Jon Blake, who has been on the Yaquina since 1985, serving the last four years as the master of the second crew, says, “When we’re underway from March through November, if there’s work to be done, we’re out there 24/7.”

Both vessels have two alternating crews that enable the ships to work around the clock during dredging season. Chris Gibbons, the Essayons’ port engineer explains, “Any vessel in continuous operation is going to have crew changes. If we’re operating in the Oregon-Washington area, the normal crew change-out is every Tuesday, so basically eight days on, six days off.”

The Dredge Yaquina facing seaward in Vigor Shipyard’s dry dock.

The Dredge Yaquina facing seaward in Vigor Shipyard’s dry dock.

Gibbons started working on the Essayons 28 years ago as a Vigor Shipyard employee and was hired by the Corps a year-and-a-half ago to plan the Essayons’ maintenance.

“Because of the nature of the work we don’t have downtime during the season to do maintenance.” Gibbons says, “We’re taking waves over the bow.”

There are many components of a ship that can only be inspected while in dry dock. Crews inspect everything below the waterline visually for any damage that may have occurred to the hull, propellers, rudders and bow thruster. Some components like seawater valves and the steering equipment require inspection and testing that can only be done while out of the water.

Both the Yaquina and Essayons are hopper dredges, which means they operate like giant vacuums with pipes suspended from the sides that suck sediment up from the channel bottom into storage compartments within the ship’s hull. The sediment is abrasive to the all of the components it passes through.

Portland District dredges Yaquina (left) and Essayons (right) sit stern-to-stern in Vigor Shipyard’s dry dock for their annual maintenance.

Portland District dredges Yaquina (left) and Essayons (right) sit stern-to-stern in Vigor Shipyard’s dry dock for their annual maintenance.

The abrasive nature of the sediment – typically sand – combined with the corrosive effects of the salt and brackish waters that the dredges operate in means keeping rust at bay is an ongoing battle. Rust on both ships is being addressed in multiple areas including the dredge piping, hoppers, decks and towers.

The first step in the process is abrasive blasting to remove the rust and protective coatings to reveal the condition of the steel underneath. Weakened areas will be rebuilt and re-welded with new steel before receiving a new protective coating.

Blake sums it up simply, “It’s steel, it’s rusting. You have to address it, or you won’t have a dredge very long.”

Planning the maintenance for dry dock happens all year long. Besides routine maintenance and necessary repairs, there are upgrades that are often planned years in advance. Port engineers must balance their dredge’s most pressing needs with available funding and the ability to complete the work within the dry dock time window.

The Dredge Essayons starboard side propeller. Ship components that sit below the waterline like the hull, propellers, rudders and bow thruster can only be inspected for damage while in dry dock.

The Dredge Essayons starboard side propeller. Ship components that sit below the waterline like the hull, propellers, rudders and bow thruster can only be inspected for damage while in dry dock.

Replacing the entire steering system on the Essayons is one upgrade that has been a few years in the making. Essayons has been using the original rotary vane steering system since the vessel was christened in 1982. Thirty-five years later, it is becoming difficult to find replacement parts.

The steering system is being modernized with a simpler mechanism that consists of two hydraulic cylinders that have less points for failure and greater parts availability.

Gibbons describes the system as, “Two seals and a piston. Very little moving parts, very little maintenance concerns. We’ll have spares sitting on the shelf that, if we have a failure, we’ll just swap one out.”

Blake has been on the Yaquina for most of the dredge’s life. He joined the crew as a third mate in 1985, when the Yaquina was only four years old and has witnessed many upgrades over the years. Some of the most visible changes have happened on the bridge where change is the only constant when it comes to the electronic equipment used to navigate and monitor the Yaquina.

The Dredge Essayons receives an entirely new steering system that requires cutting holes on both sides of the ship.

The Dredge Essayons receives an entirely new steering system that requires cutting holes on both sides of the ship.

“Almost everything on board has been changed,” Blake says. “From communications to navigation equipment, it doesn’t look anything like it did 35 years ago.”

Regardless of whether the dredges are operating or are in dry dock, the dredge crews and the

staff that support them work year-round. When the dredges are in dry dock, the crews still rotate, living on the ships when it’s their shift.

When the dredges are refloated and dredging season starts, port engineers like Gibbons don’t get a break. He’ll leave his temporary office at Vigor Shipyard and return to his permanent desk at the U.S. Moorings to repeat the process.

“Part of the mission of this year’s dry dock is to fine tune next year’s plan,” Gibbons says.

Inside the Dredge Essayons steering gear room, two workers weld in the port-side rudder bearing assembly.

Inside the Dredge Essayons steering gear room, two workers weld in the port-side rudder bearing assembly.