It will cost $158.5 million to replace the Sarah Mildred Long Bridge in Kittery, according to a tentative agreement between the states of Maine and New Hampshire and the construction contractor, Cianbro Corporation of Pittsfield.

The agreement is a major milestone for the project, which is scheduled to begin late this year.

The new bridge across the Piscataqua River is designed to have long open spans and to use 11 fewer piers than the existing bridge. In addition, because the bridge is higher, there will be faster and fewer openings for marine traffic.

The bridge will also have a vessel collision system to reduce damage if ships strike the piers. On April 1, 2013, a large tanker ship clipped the bridge, causing severe structural damage and leading to the bridge’s closure to vehicular traffic,

In November of 2012, Figg/Hardesty and Hanover was awarded a contract to design the new bridge as well as coordinate public input meetings to see what local residents wanted reflected with the bridge design. Because of that input, the design will include wider shoulders for bicyclists, a wider opening for marine traffic, and keeping the name, Sarah Mildred Long.

In 1987, the bridge was named to honor Long, who had been an employee of the Maine-New Hampshire Interstate Bridge Authority for 50 years.

In early September, the federal government awarded a $25 million grant to both states to fund the rail portion of the bridge. The rail – a spur off the mainline of Pan Am Railways – is used to move nuclear material out of the Portsmouth Naval Shipyard.

The new bridge is expected to be open to motorists in August of 2017.