Morro Bay is ready to embark on its largest harbor dredging operation in nearly a decade.
The dredging is needed to keep the harbor open and navigable to deeper-draft ships and increase boating safety, said Rick Algert, harbor manager. Over the next several months, workers with the U.S. Army Corps of Engineers will remove an estimated 600,000 cubic meters of sand and silt from the harbor and its entrance, enough to fill 240 Olympic-sized swimming pools.
The entrance to the harbor is dredged every year, but a dredging of the entire navigable channel in the bay is much less common and overdue about four years because of federal budget restrictions.
“This is a big deal for us,” Algert said. “We haven’t done a big job like this since 2001.”
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Most of the dredged sand will be deposited on Morro Strand State Beach north of Morro Rock from Highway 41 to Azure Street. The additional sand will bolster the beach against storm erosion and protect habitat for snowy plovers, small shorebirds that nest on the beach.
The $8.6 million project is set to begin early this week and is expected to last through January, said Jim Mills, federal engineer in charge of the project. They will try to get the work done as quickly as possible and minimize inconvenience to Morro Bay residents and visitors.
“We want to get in and get out,” he said.
Morro Bay city officials have been fielding some concerns from beach-goers that the dredged material may be toxic. The sand is full of decaying organic matter and stinks for several days after it has been deposited on the beach, but it is not toxic, Mills said.
The Army Corps of Engineers has repeatedly tested the dredge material. It contains elevated levels of some metals common in the watershed, such as nickel, but nothing at toxic levels.
City officials concede that the dredging is an inconvenience to beach-goers but the benefits of dredging far outweigh the inconvenience. It would only take a couple of years of no dredging before the harbor was navigable to only smaller, shallow-draft vessels.
“We should be very grateful for this activity even if it is unattractive for a short time,” said Morro Bay Mayor Janice Peters in an e-mail to a worried resident.
Tides flowing in and out of the bay would maintain a small, shallow channel. But fishing vessels, and more importantly, Coast Guard patrol boats would not be able to use the harbor.
Hosting the Coast Guard station is a vital job of the harbor, said commercial fisherman Jeremiah O’Brien. Monterey and Santa Barbara are the closest other Coast Guard stations, each about 70 miles away.
As the recent accidental death of fisherman David Kubiak demonstrates, commercial fishing is a dangerous occupation, and fishermen rely on the Coast Guard for support during emergencies.
“The consequences of not dredging can literally be fatal,” O’Brien said.
Coast Guard patrol boats from Morro Bay also make frequent trips to Diablo Canyon nuclear power plant to enforce a one-nautical-mile exclusion zone around the plant.
This year’s expanded dredging operation will include the annual dredging of the harbor entrance. The goal is to keep the depth of the harbor entrance about 40 feet, Algert said.
In addition to keeping the harbor accessible to deeper-draft vessels, dredging minimizes the number of days the entrance is closed because of high surf.
If the channel is properly dredged, fewer waves break across the entrance. Breaking waves make entering and exiting the harbor dangerous.
“Historically, there have been 18 or 20 deaths since World War II from transiting the harbor entrance,” Algert said.
This year’s dredging operation will feature two new pieces of technology. One is an electric suction dredge that will reduce the amount of air pollution the project generates compared to diesel-powered dredges used in the past.
The other is a hopper dredge that will remove sediment from the upper reaches of the bay that the suction dredge cannot access, Algert said. The suction dredge will deposit its sediment on the beach north of the Rock, while the hopper dredge will dispose of its sand at a near-shore location.
The near-shore location is one nautical mile south of the harbor jetty in 20 to 40 feet of water off Montaña de Oro State Park. This is also where sediment is deposited from the annual dredging of the harbor entrance.
Harbor officials monitor this location and have found no evidence that dredge material is building up on the ocean floor, Algert said. Powerful lateral currents quickly disperse the sand.
These currents are one of the main reasons the harbor mouth has to be dredged annually. Engineers have named the pocket of the entrance between the two jetties protruding from the sand spit the “sand trap” because large volumes of current-driven sand build up there.
Inside the harbor, the main sources of sediment are the two creeks that flow into the bay — Chorro and Los Osos creeks. These creeks bring sediment into the harbor from the entire Morro Bay watershed that extends inland to the outskirts of San Luis Obispo.
Controlling sedimentation of the bay is one of the main challenges of the Morro Bay National Estuary Program and land management agencies.
Reach David Sneed at 781-7930.