Bourne Bridge Replacement, Cape Cod Canal

The Bourne Bridge won a steel industry beauty award in 1934, a year before it opened. Ninety-one years later it’s functionally obsolete, and Massachusetts has a plan to replace it that is fully designed in concept and not yet funded. The Cape Cod Bridges Program puts the Bourne element at roughly $2.37 billion inside a $4.5 billion two-bridge programme. Its sibling, the Sagamore, is fully funded and already in procurement. Bourne is a year behind and still waiting on a $1.183 billion federal application.

Project Scope

The existing bridge is a steel arch with a suspended deck, 2,384 feet long with a 616-foot main span and 135 feet of clearance over the canal. It’s 45 feet wide, carries four travel lanes with no shoulders, and has a single six-foot raised sidewalk on the west side with no barrier. The Public Works Administration built it for the Army Corps between 1933 and 1935 to suit the widened canal, and it opened on 22 June 1935. It was designed for about a million trips a year. The two canal bridges now carry something near 38 million crossings annually between them. The replacement is twin network tied-arch structures, one per direction, with a 720-foot mainline span, four through lanes plus two auxiliary lanes, full shoulders, a median and a barrier-separated shared-use path on each crossing, built to a 100-year design life. Arch spans get fabricated off site, floated in on barges and lifted into place while approach spans are built on land, which keeps the navigation channel working. Splitting the crossing into two structures is what lets MassDOT stage the job with two lanes per direction open the whole time. There is no acceptable alternative: these are the only two road links to Cape Cod. HNTB leads programme management and the NEPA documentation. No contractor has been procured.

Why It Matters

Funding is the whole story. A 2023 application covering both bridges was denied at $1.88 billion. Sagamore came together afterwards from a $993 million Bridge Investment Program award, a $372 million Mega grant, $350 million from the Corps and around $750 million from the Commonwealth. Bourne has the environmental clearances, with a MEPA certificate on 17 April 2026 and a federal Record of Decision that June, and not much else. Construction is sequenced for roughly 2032, completion around 2037.

Project Team & Details