Situated on a remote island in the Aleutian chain on the stormy Bering Sea, the International Port of Dutch Harbor has become one of the busiest commercial fishing ports in the United States. It sits on a mile-long spit of land extending from the northeast end of Amaknak Island. The port, owned and operated by the city of Unalaska, is the economic heart and soul of this remote hamlet that spans both Amaknak and Unalaska islands.

Docks in need of modernizing
In recent years, the demand for Dutch Harbor's services has steadily grown. Port authorities and the city council decided a major upgrade of the Unalaska Marine Center (UMC) was needed. They contracted with PND Engineers, a firm specializing in waterfront engineering, to begin conceptual planning that focused on two dock positions.

 
To achieve a continuous, high-capacity dock along the entire dock structure, a PND proprietary Open Cell Sheet Pile????EUR??,,?>>???? bulkhead design was employed, a platform that matched several adjacent marine facilities. The upgrade included 105,000 square feet of paver surfacing. PND performed planning, design, permitting, construction administration and inspection. Onsite work began in May 2017 and was completed in January of 2019, a noteworthy achievement for all parties.

Dock surfacing challenges in the Aleutian Islands
The challenges, were daunting: design a pavement behind a 50-foot-tall bulkhead fill dock that would perform well under the unusually high stress loads of large forklifts that maneuver ocean cargo containers, accommodate minor seismic activity settlement, withstand the test of time in unfavorable climate conditions. And conform to the project budget.

The location posed other obstacles: lack of quality raw materials for concrete construction on the island, few suppliers, no asphalt plants, heavy annual rain, snowfall, and low overnight temperatures that make scheduling poured-in-place concrete problematic; all resulting in a high cost of ready-mix concrete.

This had PND examining alternatives to concrete or asphalt surfacing. The bulkhead dock fill structure design provided a stiff subsurface, which meant that a system using pavers could be considered as a surface for the entire 2.5-acre dock extension.

After a comprehensive design-phase evaluation, PND chose and implemented the lower-cost and more efficiently installed technology, new to Alaska marine industries, which saved the city an estimated $2 million. They selected Keystone Hardscapes MaxLock L-10, a dentated paver with a 120 mm (4.72-inch) thickness. Its superior lockup properties and resistance to rotation and displacement made it a practicable choice.

The paver mold was fabricated so the pavers could be machine-installed in a herringbone pattern to offer the greatest performance interlock. Manufactured in Portland, Oregon, and transported to Seattle, when all 100 truckloads were staged, Turnagain Marine Construction arranged for a single barge to make the 1,800-mile voyage. BC Pavers of Renton, Washington, began installation in October 2018 and finished before year-end.

Great expectations for Unalaska's port
A novel design approach to the surfacing of the dock proved to be an important innovation. At a ribbon-cutting ceremony, optimism abounded. Port director Peggy McLaughlin and city engineer, Robert Lund, pronounced the paver surfacing a success. Administrators for other Alaskan ports noted this first-time use of interlocking concrete pavers with an eye toward future renovation projects.

As seen in LASN magazine, February 2020.