BEAUFORT--The State Ports Authority is studying proposals from 15 companies who want to help the agency expand the Port of Charleston, develop a new port in Jasper County or do both.

Agency officials said Wednesday that the companies have offered ideas on financing and operating either a three-berth container terminal on a 280-acre site at the former Navy Base in Charleston or an 1,800-acre site in Jasper County that would serve shipping lines on the Savannah River.

The authority began its search for a private partner after suing to bar Jasper County from developing its own $450 million deep-water shipping terminal on the Savannah River.

In a legal brief filed with the state Supreme Court, the State Ports Authority argues it has exclusive power to develop ports in South Carolina. But attorneys for Jasper County say its operation of a port does not violate State Ports Authority regulations.

The Supreme Court is expected to hear opening arguments in the suit on Sept. 20, according to the court's Web site.

Jasper County has fostered its own agreement with private port builder SSA Marine to develop and manage the port through private funding. Under the agreement, the county would maintain ownership of the property and receive fees and ancillary tax revenue.

SSA submitted an identical development plan to the state for consideration, said regional vice president Jake Coakley. "What we're trying to do is move the process forward," he said.