The North Carolina Turnpike Authority in the US has released the final environmental impact statement (FEIS) for the proposed $660m Mid-Currituck Bridge in Currituck County.

The project involves building a seven mile long two-lane toll bridge with approach roads. The FEIS showed the MCB4/C1, which places the bridge in the northern (C1) corridor with a second bridge across Maple Swamp and will allow Aydlett Road to remain open to traffic.

North Carolina Turnpike Authority executive director David Joyner said: "The approval of this FEIS marks an important step forward for this project, which has been years in the making. As the environmental planning process nears completion, the Turnpike Authority will determine over the next few months whether to proceed with the public-private partnership option or utilise municipal financing to build the project."

The preferred alternative also includes several design refinements to help avoid and minimise impacts in response to feedback from government agencies and the public.

Terminating the bridge in a roundabout at NC 12 also allowed the C1 bridge alignment to be adjusted to remove curves and consequently reduced its length across Currituck Sound to 24,700ft from 24,950ft.

After completion of the structure, journey time from Norfolk to Corolla is expected to be reduced from two hours to around an hour. It will also reduce congestion in the Currituck Sound area and provide an alternative hurricane evacuation route for the northern Outer Banks.

The project is expected to be financed through a combination of state appropriation bonds, toll revenue and private equity.

The authority will accept comments on the FEIS until 12 March.

Final federal approval of the project is expected this spring when the Federal Highway Administration issues its Record of Decision.

Construction work is expected to begin in late 2012 and the project will open to traffic in 2017.