Bourne Bridge

The Bourne Bridge is a through steel arch bridge that carries State Route 28 over the Cape Cod Canal in Bourne, Massachusetts. Completed in 1935, it was named the 1934 “Most Beautiful Steel Bridge” in Class A by the American Institute of Steel Construction (AISC), and it carries four lanes of traffic across a 616-foot main span with 135 feet of clearance above the canal, sufficient for large ocean-going vessels. Its approach spans are notably longer than those of its sister span, the Sagamore Bridge, owing to the surrounding terrain. Now nearing a century of service, the Bourne Bridge is slated for replacement with twin arch spans as part of the broader Cape Cod Bridges Program.

Cape Cod Canal

Interest in a canal through this area dates back to the Plimoth Colony in the 1600s, when only about a mile of land separated the Mamomet River (later the Monument River), which flowed into Buzzards Bay, from the Scusset River, which flowed into Cape Cod Bay. ⁸ In 1627, the Pilgrims established a trading post along the Mamomet River, and reaching it by water and a short overland portage proved far more practical than traveling twenty miles by land, though a full water route remained beyond the small colony’s means. General George Washington later recognized the canal’s strategic military value, and in 1776 ordered Continental Army engineer Thomas Machin to conduct the first known survey for the project. Over the following century, repeated surveys and construction attempts failed for lack of funding or engineering resources, while ships continued wrecking along Cape Cod’s outer banks at a rate of roughly one every two weeks by the late 1880s.

In 1904, financier August Belmont II took up the project, organizing the Boston, Cape Cod & New York Canal Company and partnering with civil engineer William Barclay Parsons, who confirmed the canal’s feasibility. ⁸ Construction began in 1909, overcoming obstacles like massive glacial boulders through the use of steam shovels, dipper dredges, and railroad-based material removal.

The canal opened on July 29, 1914, as a privately operated toll waterway, allowing Belmont to beat the Panama Canal’s opening by seventeen days. It was officially completed on April 10, 1916. Frequent accidents and mariners’ fears of its narrow, swift-current bridge openings meant the canal never achieved the traffic or profitability its investors expected.

Following wartime federal oversight during World War I, Belmont resumed control of the canal before selling it to the federal government in 1927 for $11.5 million. ⁸ The U.S. Army Corps of Engineers (USACE) took over operations in 1928, eliminating tolls and surveying shipping companies to understand their reluctance to use the route. The response was clear: the canal’s movable bridges were typically left in the down position, forcing ships to fight the current in a narrow channel while waiting for them to open, a problem that would ultimately drive the push for fixed highway bridges.

Between 1935 and 1940, the USACE spent $21 million widening the canal to 480 feet and deepening it to 32 feet, making it the widest sea-level canal in the world at the time. ^{12 13}

1935 Bourne Bridge

To solve this, the USACE pursued fixed highway bridges instead. Fay, Spofford & Thorndike of Boston oversaw design and construction, with the Cram & Ferguson architectural firm advising on appearance. ⁸ The resulting design featured a 616-foot center span and 135 feet of vertical clearance above mean high water, sufficient for large ocean-going vessels.

Depression-era federal funding supported the project, creating hundreds of jobs for skilled and unskilled workers alike. ⁸ Construction on the Bourne Bridge and its sister span, the Sagamore Bridge, began in 1933 under the Public Works Administration on behalf of the U.S. Army Corps of Engineers. ² Built simultaneously, the two bridges were dedicated on June 22, 1935, and opened to traffic that same day. ³

The Bourne Bridge was named the 1934 “Most Beautiful Steel Bridge” in Class A by the American Institute of Steel Construction (AISC). ¹

The bridge underwent repairs in 1959, followed by minor rehabilitation in 1963 and pressure grouting of cracks in the concrete abutments and piers in 1969. ¹¹ Structural repairs followed in 1976, and a major rehabilitation in 1979–80 replaced the deck with a lightweight, concrete-filled steel grid deck, strengthened and replaced various structural components, and swapped out 3,000 deteriorated rivets for high-strength bolts. New hanger cables were installed in 1986. The substructure underwent major rehabilitation in 2001, the deck was rehabilitated again in 2010, and steel repairs — including the removal of fatigue-sensitive weld details — were carried out in 2012.

Between 1967 and 1977, 36 people died by suicide from the Bourne and Sagamore bridges, and another 24 attempted but survived or were stopped. ⁴ As part of major rehabilitation work between 1979 and 1983, both bridges’ original four-foot railings were replaced with 12-foot suicide-deterrent fencing — round pickets spaced no more than six inches apart, with tops curved inward on a seven-inch radius. In the 28 years following installation, seven suicide deaths were recorded at the bridges, and two further attempts were prevented between 2013 and 2021.

In October 2019, the USACE recommended replacing the bridge with a wider structure featuring four travel lanes, an auxiliary lane in each direction, bike and pedestrian paths, shoulders, and a median, concluding that replacement would be more cost-effective than upgrading the existing bridge and would better address chronic summer traffic backups. ⁵

A six-foot-wide sidewalk currently runs along the bridge’s west side for pedestrian and bicycle use. ⁶ Though slightly raised, it has no barrier separating it from vehicle traffic, and cyclists are advised to walk their bikes across. ⁷

Replacement

To address the aging bridges’ deteriorating condition and the region’s growing multimodal transportation needs, the Cape Cod Bridges Program was launched to replace both the Bourne and Sagamore bridges with modern structures. This replacement effort builds on earlier studies, including MassDOT’s October 2019 Cape Cod Canal Transportation Study and the USACE’s March 2020 Cape Cod Canal Highway Bridges Major Rehabilitation Evaluation Report/Environmental Assessment (MRER/EA), both of which examined the bridges’ condition and the surrounding roadway network’s needs. ¹⁰ MassDOT’s study set out to identify existing and future multimodal transportation needs around the canal, ultimately assessing whether major rehabilitation or full replacement of the bridges offered the more reliable, fiscally sound path forward. That work led to the MRER, published in March 2020, which now serves as the foundational document guiding the Cape Cod Bridges project. On April 3, 2020, the USACE and the Assistant Secretary of the Army for Civil Works formally decided to replace both the Sagamore and Bourne bridges with new structures built to modern standards.

On July 7, 2020, MassDOT and the USACE signed a Memorandum of Understanding (MOU) governing the replacement process. ¹⁰ Under the agreement, USACE will continue owning, operating, and maintaining the existing Bourne and Sagamore bridges until the new bridges open, while MassDOT leads design and construction and will own, operate, and maintain the completed replacements.

The resulting plan aims to modernize the surrounding roadway network and address multimodal transportation gaps. ⁹ Each existing bridge will be replaced with a pair of twin structures, separating traffic by direction onto its own bridge — an approach intended to improve safety and traffic flow while minimizing disruption to drivers and canal navigation, since two lanes of travel in each direction can remain open throughout construction.

The agreed-upon design calls for twin arch-type bridges at both crossings, a choice shaped by strong public support in community engagement and survey results, as well as engineering studies favoring this design over the alternatives considered. ⁹ Approach spans will be built on land, while the arch spans will be fabricated off-site, floated into place, and lifted into position. The new bridges are expected to last 100 years and will be designed to minimize long-term maintenance costs and disruptions.

The project will also add safer pedestrian and bicycle crossings, scenic overlooks, a new loop trail connecting the two bridges, and improved connections to nearby roads, businesses, and multimodal trails. ⁹ Each new crossing will include a barrier-separated shared-use path linking to the canal’s service roads, with additional pedestrian and cyclist accommodations planned along local roadways in line with MassDOT’s Healthy Transportation Policy Directive.