Crescent City on its way to a stronger harbor; Reconstruction will make harbor able to withstand 15-foot waves
Reconstruction work is underway at the Crescent City Harbor to ultimately make it capable of withstanding the strongest possible tsunami generated in a 50-year period.
Crescent City engineer Ward Stover said rock and other materials are currently being delivered to the harbor for the reconstruction project, which recently broke ground. he said the reconstruction design will give the harbor 50-year protection, meaning the infrastructure will be able to withstand the strongest tsunami that has a 2 percent chance of occurring any year during a 50-year timeframe.
”A 2 percent occurrence has a (wave) height of about 15-feet,” Stover said.
Construction is focused on rebuilding the inner boat basin, which was damaged by tsunamis in 2006 and 2011. on March 11, 2011, a tsunami generated by a 9.0-magnitude earthquake in Japan decimated the harbor, with the largest wave measuring more than 8-feet high. at that time, damage done by a smaller tsunami on Nov. 15, 2006, had not been repaired.
Right now, construction consists of updating the harbor’s rock slope protection and reviewing the structural design of the floats. Stover said pipe piles and other materials are continuing to arrive at the harbor.
”We’re going through the review and approval process of all the materials before they get them ordered,” Stover said.
Harbormaster Richard Young said the project will ultimately make the harbor stouter, with bigger and more closely placed pilings. he said it has been a long road to get all the geotechnical, permitting and design components in place before any actual construction occurs.
”We’re right at the beginning of things that will be visible to people,” Young said.
He said a barge with a crane is expected to start making its way from San Francisco to Crescent City soon. The barge will be used to install the pilings.
The first phase of the project — which involves updating the westerly side of the inner boat basin — is expected to be completed by Nov. 15. Stover said the contractor is required to have the first phase completed in time for the winter crab season.
”We’ll have some permanent facilities to put boats at,” Stover said.
The $33.8 million reconstruction project is contractually scheduled to be completed by February 2014, Stover said. The Dutra Group, a Bay Area company that specializes in marine construction, is doing most of the work and will be providing the barge. Eureka business Maple Service Plumbing, Heating and Air is doing all of the water utility work. Stover said both businesses’ tasks are highly specialized.
The majority of the project will be paid for with California Emergency Management Agency and Federal Emergency Management Agency funds. Because the 2006 tsunami was only deemed a state emergency, FEMA funds aren’t involved and the coverage rate for damage is lower. In addition, the harbor still has to cover 6.25 percent of the rebuilding costs for the March 2011 event.
Young said the Crescent City Harbor District is in the process of negotiating a $5 million to $5.5 million loan with the U.S. Department of Agriculture and its rural development program to help pay for the project. he said the harbor already has about $600,000 in existing debt that it needs to cover, and has been unsuccessful in obtaining grant funding.
”It’s really going to be financially trying for the district to make those (loan) payments, but we really have no choice,” Young said.
It’s estimated the entire project and future outer basin projects will cost a total of $50 million, Stover said. he said the harbor is working on getting the permitting in place to dredge the outside of the basin and improve the outer rock slope protection.
While officials hope the improvements will protect the harbor for decades to come, there is no denying that the Del Norte County coast is a hotspot for dangerous tsunamis. In 1964, an 8.8-magnitude earthquake in Alaska triggered a more than 20-foot wall of water that killed 11 people in Crescent City, according to the U.S. Geological Survey.
National Weather Service spokesman and meteorologist Troy Nicolini said there are a number of factors that make the city and its harbor a natural conveyer of the surges. he said the harbor’s shape and design — with steep rock walls — traps wave energy, making it nearly impossible for entering waves to break.
”The waves tend to bounce around inside and not dissipate,” Nicolini said. “It’s almost like kids playing in the bathtub and the waves double up and then break over the (side of the) tub.”
He said the Crescent City Harbor tends to amplify incoming waves, while Humboldt Bay does the exact opposite.
”If a tsunami comes inside the bay, that wave is going to break on the mudflats,” Nicolini said.
The shape of the ocean floor and surrounding sea features also play into Crescent City’s susceptibility. Nicolini said the reef off Point St. George is a shallow area of the ocean that can push waves coming from Alaska into the harbor. he said the waves tend to bend and wrap around shallow water, refracting right into the inner boat basin.
Deep in the Pacific Ocean, Nicolini said the focus still seems to be on the Del Norte coast.
”The shape of the ocean floor halfway across the Pacific has wave features that tend to concentrate the wave energy toward Crescent City,” Nicolini said.
Unable to protect the harbor from every catastrophic ocean event, harbor officials said they’re happy to at least be putting the 50-year protection model in place. Stover said there’s no easy way to plan for a larger event or a 75-year design as structures around the harbor and in the city would need to be moved and built above tsunami inundation areas.
Despite its higher cost, Young said the 50-year design project is a good investment.
”Over the life of the project, the cheapest thing to do was build it to a 50-year standard,” Young said. “it minimizes the life-cycle cost.”
Megan Hansen can be reached at 441-0511 or .
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