Client: BP Exploration (Alaska), Inc.
Owner: BP Exploration (Alaska), Inc.
Cost of Work: $25 million

The Endicott Causeway Breach, a twin torsional box-girder bridge made of A-588 weathering steel, was proposed as a value-engineered design alternative, reducing overall project costs by $8 million, and allowing shipment of materials by truck instead of shipping completed assemblies by barge. Modular design allowed quick assembly of box girders with high-strength bolted splice plates. In addition, use of weathering steel eliminated initial and maintenance costs for protective coatings.

This special-purpose bridge provides access for oil field service traffic, including light to heavy-duty vehicles, and supports the 100,000+ BBL/day Endicott oil field pipeline. The water velocities through existing breach openings along this 5-mile causeway have been known to cause 30 feet of sea bed erosion in a single storm; movements of sea ice can apply major forces to foundations during the winter months. Foundations consist of two conical piers with beveled sides to reduce ice forces. Pier piles consist of six 30-inch-diameter steel pipe piles driven at a batter using a welded template. The piles fit under each 12-foot-diameter by 3-foot-deep prewelded pier cap, which is fabricated with top and bottom plates and a series of radial stiffeners and face plates to make the cap rigid to withstand ice contact forces. The conical pier is covered with a thin steel cone and the area between the conical pier cap and outside cone was grouted for strength. The piers are designed for -45 feet of scour and an estimated maximum ice force of 250 tons horizontal. There are two piers for the 650-foot span.