CASA GRANDE — It was a project unlike any other Lonnie Mikkelsen had done before.

A series of large, dome-shaped buildings to sit on a plot of land off Thornton Road, south of Interstate 8. Mikkelsen was part of the construction crew that shaped the Casa Grande domes more than 30 years ago.

He recalled the technical process of raising the domes, which he compared to building an upside-down swimming pool.

The crew used a large, inflatable balloon to form the exterior dome shape. They would then enter the balloon and begin spraying the inside with foam and then added a layer of thin concrete.

Most of that foam has since deteriorated, falling victim to the hot Arizona sun. The domes Mikkelsen helped build would never serve their purpose as a manufacturing plant to produce circuit boards.

InnerConn Technology started the project in 1982, but a bank took ownership of the property after the company reportedly defaulted on a loan.

The domes have sat vacant for decades, drawing the attraction of curious spectators. A section of one of the domes collapsed earlier this month.

Mikkelson said he’s impressed the domes have held their shape considering they were built with little rebar and haven’t been structurally maintained.

It’s anyone’s guess why InnerConn Technology chose to build such unusual buildings, he said, though the business owners from California did seem to be eccentric.

The five dome buildings were estimated to cost $500,000 to build, according to an old Casa Grande Dispatch article.

Owners of InnerConn Technology had reportedly formed a subsidiary company, Dome Industrial Homebuilders Inc., and were planning to market their new dome-building design.

“It’s a different type of building and the insulation qualities are fantastic,” said the vice president of InnerConn in 1982.

Mikkelson said building the domes was an educational experience, though the skills didn’t become too useful since the dome design didn’t take off in Arizona.

But he was involved in constructing another local dome building, located in the 20000 block of West Hopi Drive. The white, igloo-shaped building is currently occupied by Indian Hills Community Church.