Natural gas underground storage caverns planned in Millard County

SALT LAKE CITY — Imagine four gigantic man-made caverns, each of them the size of the Empire State Building. That's exactly what's likely to begin taking shape early next year in Millard County.

Pending federal approval, Magnum Development LLC plans to begin creating four enormous underground chambers to store natural gas.

"I mean, it's like a scuba tank. You pop the top and gas comes out," said Tiffany James, Magnum's director of environmental services.

But no scuba tank was ever so big. Magnum will use water to carve the caverns out of a mile-thick salt deposit under the West Desert. Each of the four chambers will be 1,300 to 1,400 feet high and 300 feet in diameter. The tops of the four caverns will be about 4,000 feet below the surface.

"Each of these caverns will be the size, roughly, of the Empire State Building," said John Andrews, associate director of SITLA, Utah's School and Institutional Trust Lands Administration. The agency owns the land under which the caverns will be carved and stands to earn revenue for Utah schools for many years by charging Magnum rental and usage fees.

"So we estimate that this will generate hundreds of thousands of dollars per year for that school trust," Andrews said.

The proposed location is just over a mile from the Intermountain Power Project plant, north of Delta in Millard County. In 1979, an oil drilling crew in the area failed to find oil, but they did discover a deeply buried deposit of salt.

The salt layer is a remnant of an ancient sea that occupied the area millions of years ago.

Magnum will create caverns in the salt on a mind-boggling scale using a technique called "solution mining." The plan is to drill water-injection wells thousands of feet deep into the salt.

"And then we circulate water over and over and over again," James said.

"It dissolves the salt," Andrews explained, "and then the water is brought out of the well and put into an evaporation pond on the site."

Utah's man-made caverns will connect to a natural gas pipeline network. That will require a new 61-mile pipeline from the caverns to the Kern River pipeline near Interstate 15.

Similar storage caverns exist in eastern states, but these will be the first comparable facilities in the west.