Marine: Less Than $500,000 Terminal 3 Headline Dolphin

The new Terminal 3 Headline Dolphin is a concrete structure supported by steel piling with a mechanical capstan for vessels to use for their headline mooring line. A new 200-foot-long, two-span gangway was installed on the new dolphin to the existing terminal with one intermediate concrete cap supported by steel piling. Logging vessels that load on Terminal 3 can now utilize the new headline dolphin to keep the forward part of their vessel against the dock during loading operations. With the location of the dolphin being more than 200 feet from the existing terminal, Legacy Contracting was required to preform the work on a modular float barge.
Eight 24 x 0.625 x 123-foot piles painted with a marine grade coating system supports the concrete dolphin. These piles were driven full length at a 3:1 batter slope out from the center of the dolphin. With the steep batter, Legacy Contracting fabricated a driving template that was supported by one center pile and used to achieve correct spacing and batter to meet the tight tolerance required. The template also had to be designed so it could be easily disassembled to remove it after all the piles were driven. The piles were PDA tested to ensure they met specified bearing capacities of 600 kips in compression and 440 kips in tension.
Two 24 x 0.625 x 104-foot piles painted with a marine grade coating system supports the concrete intermediate cap, which in turn supports the gangway mid-span. These piles were driven at a 4:1 batter sloped out from the center of the cap. Legacy Contracting fabricated a different template to meet the tight tolerance required.

This project had strict marine mammal monitoring and the permit only allowed a certain number of blows per day from impact driving, which proved challenging during the course of the project. Having to construct a template to drive within allowable tolerances while also making sure not to damage the coating was an added difficulty. Legacy Contracting also drove the pile full length without splicing them, to minimize construction time and environmental impacts. Legacy Contracting, Inc. was able to overcome these challenges and deliver the owner a great end product.

Posted in PileDriver Magazine. Tagged as Issue 5, 2018.

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