An Adventure in Coordination – the Replacement of the Lubbers Brook Culvert

The goal of this project was to replace two structurally deficient pipe culverts that carry Lubbers Brook beneath Middlesex Avenue (Route 62) in Wilmington.  The two pipes and adjoining headwalls were constructed in 1960.  The culvert barrels had begun to fail with sinkholes opening within the roadway above the top of the culverts. Due to the skew of the brook to the roadway and the sensitive environmental areas on each side of the road, the design team settled on a corrugated metal arch culvert with cast-in-place concrete headwalls and wingwalls.  The two existing pipe culverts measured 7-6” in width, 5’-2” in height while the proposed, single span arch measured 25’-6” long by 7’-9” high.  From a purely structural analysis and design perspective, this project was straightforward.  From a geometry, logistics and execution perspective, it was anything but.

The key concern regarding this project was traffic flow.  Middlesex Avenue cuts through the heart of Wilmington and connects commuters with local destinations as well as I-93 and the North Wilmington MBTA station. This stretch of Middlesex Avenue sees about 26,000 vehicles per day.  In addition, the detour route took many commuters on to I-93 and forced large trucks into awkward turns.  Middlesex Avenue is also essential for first responders in the town of Wilmington to reach residents in the northern part of town. Due to these aspects, the project team coordinated early with MassDOT and permits were filed with the district to allow a detour route on to I-93. 

In addition, early in the project, the team looked for ways to stage the project to always allow for at least one lane of through traffic. However, due to the large excavations required, environmentally sensitive land upstream and downstream and the presence of obstructions found when doing early geotechnical investigation, these approaches were deemed to be unfeasible.  The design team then pivoted and focused on ways to reduce the closure time as much as possible.  These efforts were hampered to an extent due to the large skew.  The large skew (52°) precluded the use of a precast concrete culvert or a precast headwall.  Options for design were further limited by the adjacent homes, businesses, and MBTA commuter rail line that was approximately 500-feet from the western end of the project.

Setting the culvert atop the footings

Accounting for these design constraints, the team moved forward with the design utilizing as much available width as possible and thinking of alternative solutions. The solution proposed by the design team consisted of a full closure for 30 days. This would be followed by a 42-day period of single lane, alternating flow traffic, controlled by a temporary signal. At the end of the 42-day closure, two lanes of traffic and a single pedestrian access route would be available to the traveling public while the contractor continued to work in the shoulder areas.

Once the contract was awarded, several residents of the town of Wilmington and the town of Wilmington emergency services personnel began to grow concerned about the 42-day single lane closure. There was concern that traffic at the temporary signal could backup on to the adjacent MBTA commuter rail line. This was discussed amongst the project team. The contractor (J. Tropeano Inc.) proposed a different solution.  The contractor chose to utilize a 44-day full closure, but at the completion of that 44 days, two lane traffic would be open on Middlesex Avenue.  This solution was accepted by the town and a full closure was implemented on July 18.  

It was critical that the contractor stay on this schedule as the first day of school for the Town of Wilmington was August 31.  If the contractor kept their commitment to 44 days, Middlesex Avenue would be open to two lane traffic on the evening of August 30. Also, due to the loss of connectivity and increased response times as a result of the full closure, temporary housing quarters (RV) were procured by the town for the Wilmington fire department. A temporary substation was setup to the north of the culvert to limit response times within North Wilmington.

Through hard work and close collaboration from all members of the project team the road was opened to traffic at 5:00PM on August 30.  All buses were able to cross the new structure the next morning and deliver their passengers to their first day of school (whether they liked it or not).

North elevation of the culvert with headwall and wingwalls complete

Although the road was now open to traffic, the work was far from complete. The contractor continued to work to infill the culvert below the road, finish grading at the wingwalls, install the steel support brackets for the mounted waterline and gas line, remove the control of water equipment and return normal stream flow, install the bridge rail and approach guardrail, install sidewalks at the north and south side, wetland restoration and replication, final grading, paving and striping.  This work was completed expeditiously using single lane closures with police details as needed.

In addition to the complex geometry and the accelerated project schedule, utilities within the project limits added layers of complexity. Overhead lines were located adjacent to the south sidewalk. One pole was in close proximity to the southwest corner, necessitating the use of a stepped wingwall footing to reduce the excavation depth. The existing water line that traversed the top of the culvert in the existing condition was cut and capped during construction and relocated to steel brackets in the final condition. The gas line within the north shoulder was cut and capped during construction and was also relocated to the north headwall at the end of construction.  Timing was critical on this work to get the line reconnected before the weather changed for the winter. A telecommunications duct bank was located beneath the north sidewalk.  This concrete encased duct bank was supported in-place throughout construction by a strongback system consisting of two pile bents, concrete pad abutments and HP pile beams utilizing nylon straps. Finally, temporary drainage systems were required due to the town drainage structures that outlet into Lubbers Brook within the cofferdams that were installed.

Even though the structural analysis and design of this project was straightforward, the coordination and consideration required to keep the project moving forward was immense. Several aspects that were closely considered during design and construction include the structural geometry, utility considerations and impacts, maintenance and control of traffic, construction staging areas and maintenance of town services. Close coordination during design between several town stakeholders and the design engineer allowed for the production of detailed and concise bid documents. Then, throughout construction, weekly coordination meetings allowed the project team to quickly identify and overcome challenges.  Only through open communication and cooperation was this project possible.

Project Team
Owner and Project Proponent: Town of Wilmington
Engineer of Record/Construction Oversight: TEC, Inc.
General Contractor: J. Tropeano, Inc.
Culvert Supplier: ConTech Engineering Solutions LLC