City of Boston: Sullivan Square Underpass

Project Overview:

• Concrete repairs to the boat walls and ceiling including the addition of shotcrete repairs mid-way through the project.
• Trimming trees and shrubs that hung over the boat walls quickly changed to a full clearing of the areas north of Sullivan Square.
• Replacement of the outdated highway guardrail system that ran the length of the underpass. 340+ yards of concrete were poured to make a new median and 2,700+ feet of new precast concrete barrier was installed on top of the new concrete median. A guardrail subcontractor was used to install transitions from existing systems outside of our scope of work to new concrete barriers.
• Clearing and upgrades to the existing drainage system, including running cameras through the system to identify blockages.
• Full mill and pave of the underpass.
• Pavement markings for the entirety of the underpass following the paving operation.
• Replacement of the entire underpass and roadway lighting systems.
• Beam end repairs and a full clean and paint of the Mishawum St bridge that crossed overhead.
• New Emseal joints and headers on each end of Mishawum St bridge.
• Installed a temporary bus lane and implemented intersection changes that ended up being permanent to accommodate the MBTA bus facility – added work
• Full replacement of the trough system in the tunnel – originally called to only replace sections that were in the areas of excavation.
• Shotcrete
• Impact attenuator replacements
• Fence rehabilitation in various areas

 

Key Challenges Overcome:

• Short Contract Duration – The NTP was issued in November 2024, the underpass was closed on January 2, 2025 and had to be reopened by June 1, 2025.
• Winter Weather – Temperatures and winter weather impacted the work for more than half of the project duration.
• Added Work – Nine EWOs were processed including shotcrete repairs to repair boat wall excavation areas that the plans originally specified being excavation only. When the City realized what the underpass would look like with all of the excavated areas remaining, we rushed to come up with a solution. Additional excavation to use ready mix concrete that would be more in line with standard substructure repairs was not an option.
• Subcontractor Coordination – Multiple scopes of work required subcontractors on site, moving around the jobsite became an issue especially once the median was poured since lanes were one vehicle wide. Lead to lots of coordination between SPS and the various subs on site about who needed vehicles at certain areas throughout each shift.
• Material Lead Times – Light poles for the roadway lighting were ordered very early in the job but the exact model specified by the plans/specs carried a 4-5 month lead time. Fabrication was completed in Houston and a hurricane knocked power out at the plant which led to additional in getting the poles installed.

 

Interesting Facts / Figures

• 26,000 people travel through the underpass daily. It was shut down to traffic for 6 months during SPS’s repairs.