For most of their history, the World War II-era storage bunkers in Waikele Gulch provided safekeeping for military munitions, including nuclear warheads.

In 2003, the Navy sold the 515-acre site to a private company that converted it into a successful storage facility that is now 94 percent occupied.

Most of the 128 bunkers cut into the sides of the gulch are leased to industrial companies, including manufacturers, construction firms and painting contractors that store their materials there, said Mark Ambard, the facility’s leasing agent.

"At 39 cents a square foot, the space is cheap," he said of the 4,000-square-foot bunkers.

The location of the bunker rented by Donaldson Enterprises was chosen because it met requirements set by the Bureau of Alcohol, Tobacco and Firearms regarding the distance fireworks must be stored from an inhabited area, Ambard said.

"This is a terrible situation, but it would have been a lot worse if it happened in an area like Mapunapuna," he said.

The site, formerly known as the Naval Ammunition Depot, Waikele Branch, was bought in 2003 by Ford Island Properties, a joint venture of mainland firms Hunt Building Co. and Fluor Federal Services LLC. Ford Island Properties also bought or secured leases for several other underused Navy properties on Oahu under a deal made possible by special legislation approved by Congress in 1999.

The sprawling Waikele complex was used for weapons storage from 1940 until 1993, according to the Navy. The bunkers housed as much as 56,000 tons of explosives, including nuclear warheads during the 1960s.

The property lay unused from 1993 until Ford Island Properties bought the site in 2003. Ford Island brought in an affiliate of local real-estate development firm Hawaiian Island Development Co. headed by Peter Savio to market the property as storage space.

A partnership led by local publishing executive and entrepreneur Peter W. Cannon leased 23 of the tunnel-like bunkers and built storage lockers inside them ranging from 25 square feet to 300 square feet. The venture, which operates as Waikele Self Storage, offers space at prices that are as much as 25 percent lower than conventional storage facilities on Oahu.

The other 105 bunkers, including the one rented by Donaldson Enterprises, are unimproved spaces with no electricity or running water. The bunkers rent for about $1,600 a month with a minimum lease of three years.