Shrewsbury, Mass., concludes Toblin Hill Bridge project
The Toblin Hill Bridge in Shrewsbury, Mass., has been reconstructed and reopened after the original had to be demolished following the discovery of a sinkhole.
Originally built as part of the Toblin Hill Estates subdivision in 1998, a private developer was in charge of the bridge’s design and build. After the discovery of a sinkhole in 2015, it was finally decided the bridge needed to be demolished. After sitting for a few years, the Town of Shrewsbury was able to gather the funds necessary to begin the process of designing and eventually building a new bridge in its stead. This new bridge was completed and reopened in the fall of 2023.
A sinkhole was discovered on the north side of the bridge on a sidewalk in 2015. The highway department attempted to fix it by throwing gravel in, but the situation continued to worsen. That summer the town’s consultant, GZA Geoenvironmental, visited the original Toblin Hill bridge site to check the sinkhole and review the damage, leading to the closure of the bridge. It was discovered that the damage from the sinkhole, as well as numerous structural failures, made the bridge unable to be repaired. The concrete arches had begun to bow out and could not be fixed. The engineer and developer had also gone out of business.
This engineering review led to the conclusion that the bridge was failing and needed to be demolished. The best guess for the failure was a lack of coordination between engineering for the arches, T walls and earthwork. In December 2017, a bid was put out by the town for partial demolition and the demolition was completed in 2018. The town decided the best course of action was to tear the bridge down before it fell down. Since the bridge was only one of two routes into that subdivision and spans an existing wetland, it did not cause a bother for the residents.
Following the demolition of the bridge, the town hired its consultant GZA in 2019 to design and review multiple design options to rebuild the bridge. The estimated cost of bridge replacement was over $1 million. This led to the demolished bridge site staying that way until the proper funds could be budgeted.
“We had rough estimates but no funds to move forward,” Andy Truman, PE, Shrewsbury town engineer and engineering and conservation division manager, explained. Once funds became available in 2021, the town put the preferred replacement bridge option to bid. These funds came from the cash proceeds the town received from the sale of land. That bid was awarded in spring 2022.
In order to prevent a similar situation from occurring with the new bridge, the town spent most of 2022 working with GZA and the contractor coordinating the various details, design elements and drawings for the new bridge.
“We took the time ahead of construction to make sure everything worked with everything else,” Truman described. Structural steel, abutments and T walls were all analyzed and coordinated to ensure they would work well together and that all engineers on the project were on the same page. By fall 2022, all necessary reviews for the plans were completed, but the town thought it best to wait until the spring to begin construction.
The city of Shrewsbury took the majority of 2022 to work on design and conceptualization coordination so that all engineers and contractors working on the Toblin Hill Bridge project would be on the same page. This helped the project go smoothly with an end goal to prevent any failures in the future. (Photo provided by the city of Shrewsbury, Mass.) 
Besides the sinkhole that continued to worsen despite multiple attempts by the street department to fix it, there were also multiple structural failures with the bridge. The concrete arches had even begun to bow out. (Photo provided by the city of Shrewsbury, Mass.) 
After demolition, a gantry had to be hung and insulated for a sewer line that was part of the original bridge. The new bridge needed a new conduit for street lights as well. (Photo provided by the city of Shrewsbury, Mass.) 
Spanning 40 feet between abutments, the new Toblin Hill Bridge has finally opened to the public after being shut down and then demolished. The bridge spans a wetland. (Photo provided by the city of Shrewsbury, Mass.)
The Toblin Hill Bridge has a 40-foot span between abutments, and the town could salvage many of the original abutments. Almost all the T wall sections could be kept as well. However, this created one of the biggest issues of building the new bridge, which was finding a T wall manufacturer that could make new ones similar to the original ones. The steel arch needed completely replaced. Since the original bridge had an existing sewer line going across it, a gantry had to be put in so that the sewer line could be hung and insulated after the original bridge was demolished. A new conduit for streetlights also had to be put in.
Construction on the new Toblin Hill Bridge began in spring 2023 and was completed by the fall. Overall, primarily due to the time taken ahead of time to ensure everything would work well together, the building of the new bridge went very smoothly. The project’s final cost was approximately $1.2 million. It is now open to the public and has received a strong positive response from the community.
Next Article: The Hamilton, Ohio, Public Works Department recognized with accolades
