With a key study due out today on a shipping terminal being proposed for North Charleston, the State Ports Authority on Thursday released details of a plan to help offset the environmental consequences of the project.

Valued at $9.6 million, the plan is one of the largest single mitigation efforts in South Carolina history, port officials said.

It includes a $1 million contribution toward efforts to preserve Morris Island and another $1 million to protect land through the Cooper River Initiative, a consortium of environmental agencies and groups.

The SPA is pushing to build a major container terminal on the south end of the former Navy base that would be capable of handling more than 1 million 20-foot-long shipping containers a year.

The $600 million project will affect about 10 acres of tidal marsh, two acres of freshwater wetlands and 57 acres of underwater fill. To offset those effects, the SPA is proposing to spend about $2.5 million to recreate 22 acres of tidal marsh and restore more than five miles of oyster reefs in and around Charleston Harbor, among other measures.

In addition, the ports authority and the city of North Charleston agreed on a $4 million package of community projects. It includes funding for education and job-training programs and the creation of an affordable housing trust.

The SPA also will make available a three-acre site for the Clemson Restoration Institute on the former Navy base.

"The Ports Authority is committed to responsible development," said Bernard S. Groseclose Jr., president and chief executive. "We're addressing the impacts of port development in a fair and very thorough way."

North Charleston Mayor Keith Summey said port officials worked closely with the city and he is satisfied with the results. The neighborhoods that will be most affected by the port expansion also played a key role, he said.

"We involved them very closely," Summey said.

Compared to similar large-scale projects, the ports authority's mitigation proposal is exceptional, said SPA spokesman Byron Miller said. For example, the value of the plan for a new Virginia shipping terminal that is roughly three times the size of the proposed North Charleston port totaled $6.7 million, the SPA said.

The SPA will begin implementing its plan as soon as construction of the terminal begins, Miller said.

The proposal does not include any concessions that could be offered by the state Department of Transportation as part of an access road the DOT is expected to build to serve the new port terminal.

The SPA has waited nearly four years for the go-ahead to expand the Port of Charleston. The SPA had hoped to start construction by now, but transportation and environmental issues have delayed the project.

Nancy Vinson, program director for the Coastal Conservation League in Charleston, said the offer to restore marshlands and oyster reefs seems appropriate. But the mitigation plan lacks a comprehensive traffic study, she said.

Her group has asked for a detailed look at Interstate 26, regardless of whether the terminal is built in North Charleston.

"What good is a port in the middle of gridlock?" Vinson said.

The U.S. Army Corps of Engineers is set to release its final environmental assessment of the SPA's expansion today and take comments from the public. The permitting decision for the project is expected in April.

Reach Peter Hull at 937-5594 or phull@postandcourier.com.