With powerful diesel engines throbbing, the dredging vessel Yaquina inches its way through the mouth of Morro Bay harbor.
As it progresses, the ship drags two suction dredging arms along the bottom of the ocean, sucking up sand and silt along a 25-foot-wide swath. The brown, frothy dredge material is pumped into a huge hopper in the middle of the ship.
“How we clean out an area is through repetition,” said Capt. Mark Keen, the Yaquina’s skipper. “We just keep going over the same area.”
The Yaquina is an annual visitor to Morro Bay. The Army Corps of Engineers ship comes to Morro Bay every year to deepen the harbor entrance. At 200 feet long, it dwarfs every other vessel in the harbor.
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The ship arrived on Friday and will stay until June 2 or 3. The ship and its crew will work around the clock during that time.
The goal of the dredging is to deepen the harbor entrance to between 30 and 40 feet, so that vessels of all sizes can safely access the harbor, Keen said. The ship also deepens the channel within the harbor.
When working at the mouth of the harbor, the ship creeps along at about 1.5 knots so it can handle any big swells without losing headway. When working inside the harbor, the ship goes even slower.
“The cardinal rule of operating a hopper dredger is: Don’t go backwards,” Keen explained. “Because the drag arms are on the bottom, you break something if you go backwards.”
It takes about an hour and a half for the suction arms to fill the hopper with 1,025 cubic yards of dredge material. The ship then motors out to a disposal site south of the harbor just off the Morro Bay Sandspit and dumps the dredge material in about 40 feet of water.
In addition to keeping the harbor navigable, the dredge material also aids in beach replenishment, Keen said. He estimates that the ship will make about 200 round trips between the harbor mouth and the disposal site during the two and half weeks it is here.
The Yaquina made its first visit to Morro Bay in 1990 and has made annual visits since about 2000. About every five or six years, the Army Corps of Engineers does a more thorough dredging of the harbor.
Dredging of Morro Bay harbor is funded through the federal budget. The annual dredging costs about $2.5 million, and the price tag for the larger dredging is nearly $6 million, said Eric Endersby, harbor manager.