HOST Park Seawater Supply Pipeline
Kailua-Kona, Hawaii
Plunging from the shoreline to a depth of 3,000 feet along the steep coast of the island of Hawaii, the HOST Park Seawater Supply Pipeline is the world?s deepest large-diameter seawater intake pipeline. This 9,100-foot-long pipeline, constructed of high-density polyethylene (HDPE), is unique in its purpose to bring unrefined ocean water back to the island, rather than convey treated wastewater or storm-water overflows to the ocean. The seawater supply system is ready to provide 27,000 gallons per minute of nutrient-rich cold seawater and 40,500 gallons per minute of warm surface water, both for commercial aquaculture and energy research.
The Natural Energy Laboratory of Hawaii Authority (NELHA) labored for a dozen years to see the pipeline built. By bringing cold ocean water to the Hawaii Ocean Science and Technology Park (HOST Park), a research and commercial facility at Keahole Point, NELHA will help the state diversify and expand its economy, which is highly dependant on the unpredictable tourist industry.
Installation of the pipeline was no easy task. The rocky seafloor ruled out construction of a tunnel for the pipeline, so the engineers developed a structural support system that not only suspends 2,000 feet of the pipeline over the seabed, but enables the line to move laterally in the strong currents expected during hurricanes.
Since the pipeline had to be placed at depths as great as 3,000 feet, engineers relied on computer models to predict the pressures that would occur both inside and outside the pipeline as it was lowered. Here the flexibility of the HDPE pipeline was invaluable, but since the strength of HDPE degrades with temperature, deploying it under the hot Hawaiian sun was not an option. The creative solution for this meant that the pipeline was painted white and deployed at sundown, with Global Positioning System receivers tracking its exact location as it sank.
Owner: Natural Energy Laboratory of Hawaii Authority
Entrant: Makai Ocean Engineering, Inc.
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