MassDOT Explores Bourne Bridge Interchanges
The Cape Cod Bridges Program will not receive any funding from the three grant opportunities it applied for under the president’s Infrastructure Investment Jobs Act.
The Massachusetts Department of Transportation made the formal announcement at a virtual informational session on interchange alternatives for the Bourne Bridge held Wednesday evening, March 22. Program manager Bryan Cordeiro said that as of that day, MassDOT and the US Army Corps of Engineers were informed that applications to the Mega, INFRA and Bridge Investment programs had been denied for Fiscal Year 2022.
That being said, Mr. Cordeiro said that MassDOT and the Army Corps are already preparing applications for the next round of funding from all three programs.
“We expect to submit a stronger application this time around to USDOT,” he said, citing progress made by the program since the last application round and feedback gathered since then.
The meeting introduced five conceptual roadway designs relating to the new Bourne Bridge, with three alternatives for the northern off-Cape side and two for the southern on-Cape side. Mr. Cordeiro said MassDOT has preliminarily recommended that both bridges be constructed inboard of the current spans and not overlap the existing footprint.
Joe Cahill, lead civil designer with civil design firm HNTB, presented the interchange options.
For “Bourne North,” meaning the off-Cape side, the following three interchange options were introduced.
The northbound on-ramp alternative configuration is similar to what exists today, Mr. Cahill said. A major change would be the introduction of a northbound on-ramp from the Scenic Highway near the Bourne Scenic Park entrance to northbound Route 25. This configuration would remove traffic from Belmont Circle and is anticipated to improve safety and traffic operations in that area. Mimicking the current configuration, Mr. Cahill said, would minimize property impacts.
The single-exit partial interchange alternative builds on the northbound on-ramp option, Mr. Cahill said, but adds an off-ramp from southbound Route 25 that connects directly to the Scenic Highway, just to the west of the relocated Route 25. This configuration would also allow drivers to bypass Belmont Circle and improve safety and operations there. Property impacts due to the additional ramp would be mitigated by keeping the ramps close to the relocated Bourne Bridge and Route 25 approach road, Mr. Cahill said.
The directional interchange alternative is also similar to previous options but introduces directional ramps, allowing vehicles traveling south on Route 25 to eastbound Scenic Highway and west on Scenic Highway to northbound Route 25 to do so without stopping. Like the other options, this interchange is anticipated to remove traffic from Belmont Circle. Mr. Cahill said this design would likely require more right-of-way impacts than the previous two designs, particularly where the new ramps run along Scenic Highway.
The following two options were introduced for the “Bourne South” connections. Mr. Cahill said that while these designs do not currently show any alterations to the Upper Cape Cod Regional Technical School driveway (pictured in the upper right of the plan), officials do plan to evaluate the driveway entrance to Sandwich Road as the design development progresses.
A diamond interchange alternative is one of the most commonly used designs, Mr. Cahill said. The mainline roadways—Routes 25 and 28—would cross over the local road to separate through traffic from local traffic. Turning is done using ramps that connect to the local road, resulting in the removal of the Bourne Rotary. This alternative also introduces a frontage road along southbound MacArthur Boulevard to provide access to the businesses there. The frontage road is anticipated to connect to both Trowbridge Road and southbound MacArthur Boulevard. Property impacts would be largely concentrated on undeveloped parcels east of Route 25 and MacArthur Boulevard.
The single-point interchange alternative is built on a concept similar to the diamond interchange, Mr. Cahill said. Route 25 would come off the Bourne Bridge, spanning over Trowbridge Road, while all movements on and off that roadway are handled with on- and off-ramps. The rotary would be removed, and a frontage road would be provided for southbound MacArthur Boulevard businesses, and property impacts would be the same as the previous alternative. The key difference here, Mr. Cahill said, is how the intersections of the on- and off-ramps would be handled at Trowbridge Road. Here, there would be one centralized intersection of ramps, which would provide for a more efficient intersection but also provide drawbacks, such as difficult sightlines to the traffic signal under the bridge. Mr. Cahill said it is also likely that the frontage road would not be accessible from Trowbridge Road, and the only access would come off the southbound on-ramp.
The entire presentation from MassDOT will be available soon on the Cape Cod Bridges Program website.
An important clarification in terms of bridge construction and traffic was made during the meeting. Mr. Cordeiro said a key goal of the program is to maintain all existing roadway connections at all times during construction. The duration will be long, he said, so it is important that traffic is not disrupted and that all connections remain open.
HNTB’s lead bridge designer, John Smith, said the plan is to keep the existing bridges functioning until traffic is able to be switched over to the first of the new twin bridge spans. Two travel lanes in each direction will be functional on the existing bridge until all four lanes can be transferred over to the first of the new spans. Then the second bridge and final connections will be completed, he said.
“There will never be a time where there won’t be two lanes going across the canal [in each direction] on either the existing bridge or the first of the new bridges and all of the connections will remain operational,” Mr. Smith said. “Sometimes they’ll be in a temporary configuration but there will never be a timeframe when we don’t have the connections.”
Bourne Select Board member Judith M. Froman asked for clarification during the public comment portion, referencing the current Sagamore Bridge work, which limits traffic to one lane in each direction, and asked if it would be anything similar to that. Mr. Smith said it would not and explained that the new bridge spans will actually be wider than the current ones. Lanes will be 11 feet wide on the new spans, wider than the current 10-foot lanes, he said, so even the temporary configuration across one of the twin spans will function better than the existing bridges, he said.