The U.S. Energy Dept. plans to build the next cavern in the Strategic Petroleum Reserve in the salt domes at Richton, Miss., and expand the capacity at three existing sites in Texas and Louisiana.

The total expansion will increase the reserve’s storage capacity by 273 million barrels of crude oil for a total of 1 billion barrels. The project will cost between $3 billion and $4 billion, and take approximately 12 years to complete, says John Grasser, a spokesman for DOE’s fossil energy department.

The Mississippi project will cost about $1 billion to complete, says a spokesman for Rep. Chip Pickering, (R-Miss). It will hold about 160 million barrels of crude oil. The project also includes construction of two pipelines. The first will interconnect with the Capline pipeline system at Liberty, Miss., and the other to refiners and marine facilities in Pascagoula, Miss. The agency could not give details on the construction.

The Mississippi site is the first inland location for the reserve. It will be less vulnerable to hurricanes than the existing sites along the Gulf Coast, say DOE officials. “Hurricanes Katrina, Rita and Wilma demonstrated the need for the U.S. to enhance its energy infrastructure,” says Sen. Thad Cochran, R-Miss., noting that the site also would diversify the locations of the emergency stockpile. Richton was chosen over four other sites considered by the agency.

The U.S. Environmental Protection Agency was set to publish the project’s final environmental impact statement on Dec. 15, ending a 16-month study of the plan. SPR was designed to provide the U.S. with an emergency oil source in the wake of the 1970s oil embargo. The system was last used in June when a ship channel near Lake Charles, La., closed, denying delivery access to refineries. DOE loaned crude from the inventory to private refiners to avoid shutdowns.

The preferred Mississippi site will not be final until after a 30-day comment period.