After 15 years, the pipe dream is becoming tantalizingly real — the seawater pipe dream, that is.

Honolulu Seawater Air Conditioning LLC is on the cusp of constructing a project that could take Hawaii closer to our recyclable-energy goals: a $250 million system that would suck in seawater from about 5 miles offshore, to be used to air-condition buildings in downtown Honolulu. The company has reached agreement with the state Department of Land and Natural Resources on mitigations for its proposed 4.7-mile undersea pipeline on coral and marine rocks.

What’s also bringing the project closer to ground-breaking is the growing number of customers to use this technology to cool their structures. If the city commits its municipal buildings by year’s end, as expected, it would join earlier sign-ups such as the state Capitol and seven other state buildings, The Queen’s Medical Center, Hawaiian Electric Co., the University of Hawaii John A. Burns medical school, the federal courthouse and First Hawaiian Bank.

Such high-profile clients means there’ll be little room for error, once the new pipeline and plant makai of the old Gold Bond Building come on line in 2022, as targeted. The pitch is that the seawater system, annually, could cut building owners’ AC costs by up to 75%, cut 77 million kilowatt-hours of electricity use, reduce dependency on oil and save up to 178,000 barrels of oil, conserve over 260 million gallons of potable water, and reduce carbon dioxide emissions.

All this, of course, would align with Hawaii’s law to have 100% clean energy by 2045. Pipe dreams are good; making them come true, even better.