Open lines of communication between the project owner, engineer, precaster and contractor drove the success of a $75 million DelDOT roadway reconstruction project.
By Bridget McCrea
Photos provided by R.E. Pierson Construction Co.
It’s not often that a $75 million roadway reconstruction project spanning many months and involving dozens of different organizations goes smoothly and comes in both under budget and faster than expected, but that’s exactly what happened with the rebuilding of Delaware’s State Road 141/Interstate 95 interchange.
There were some hiccups along the way, of course, but when you get the project owner, engineer, designer and precaster in the same room (albeit a virtual one), it is clear that for this particular project, having everyone synced up and operating from the same playbook produced a positive outcome.
The project started in August 2019 and involved the complete roadway reconstruction and widening of SR 141, a major Delaware route. Owned and managed by the Delaware Department of Transportation (DelDOT), this route includes a major intersection and interchange with southbound I-95 just south of Wilmington. At that junction, three different interstates (Interstate 295, Interstate 495 and I-95) merge into one and are reduced to five traffic lanes.
“The area had a significant accident and congestion rate,” said Nick Hetrick, P.E., the Delaware/Maryland region general manager for Pilesgrove, N.J.-based R.E. Pierson Construction Co Inc., the construction firm that managed the project. “The goal was to help relieve those issues while also improving the function of the interchange and replacing the bridges.”
DelDOT project engineer Nicholas Dean, P.E., said the average daily traffic (ADT) numbers for the interchange are projected to hit nearly 110,000 by 2040, up from 85,200 in 2015. The highway bridges were “structurally deficient,” he added, and not quite wide enough to handle the increase in traffic and DelDOT’s target traffic pattern adjustments.
“This project was a good opportunity for us to get in and make the necessary adjustments,” Dean said.
According to Hetrick, the bridge crossings for SR 141 northbound and southbound from I-95 consisted of two structures, each of which included three different spans that were about 85 feet long and just more than 80 feet wide. These spans allow I-295’s merge point to extend past the interchange via a slip lane. Interstate 95 runs beneath the center span, with a slip lane for the on and off movements for northbound and southbound SR 141 traffic (over the third span).
At the start of the project, the existing bridges were demolished while a phased construction strategy allowed DelDOT to maintain SR 141 traffic flow. The new bridge was constructed in halves, with precast concrete comprising both pier columns and caps. Upon delivery to the jobsite, the precast columns were set on the cast-in-place footings. The caps were set up on top of the columns and then connected into place.
The bridge deck superstructure, designed by Exmore, Va.-based Precast Systems Engineering encompasses a hybrid assembly of steel girders with precast concrete deck panels. The girders were shipped to the precast manufacturer, Precast Systems Inc. of Allentown, N.J., where the panels were cast on the girders and the entire assemblies shipped to the site.
The 85-foot-by-9-foot precast pieces spanned pier-to-pier and pier-to-abutment. The project required a total of seven modules per span (for a total of 21 per bridge) that were installed across the complete width of the bridge.
R.E. Pierson also had precast concrete parapets cast for the exterior deck modules.
“That eliminated a lot of the field work that we originally anticipated having to do,” Hetrick said.
The contractor was able to complete one bridge span per night, which entailed setting four pieces (as they were trucked in), positioning them with a crane and then setting them in place across the roadway.
For the size and scope of the project, the actual impact on traffic and the surrounding area was fairly minimal.
“DelDOT did have to shut I-95 down for one night using detours and slip lanes, but we were able to get everything installed in just three nights by setting half the bridge during the first phase and then another three nights for the rest of it,” Hetrick said. “We also did some form work and UHPC closure pours to link all of the slabs together, put a PPC wearing surface on top of it, and then opened the road up to traffic.”
Designing for Success
From the design perspective, Dean said DelDOT wanted to avoid conflict with any existing footers within the piles that were already in place. To achieve that goal, he and Scott Walls, P.E., a DelDOT project engineer, designed it so that all of the piles could be moved one foot in any direction without the need for a review process.
“If the contractor realized that a pile it was about to drive was in conflict with something, it could slide that pile over a foot without having to stop and call us about it,” Dean said. “That really helped to speed up the process for this accelerated bridge construction project.”
Walls said this also was the first project where DelDOT used modular superstructure units, which allowed it to create a functional module that was also practical from an installation perspective.
“We wanted the contractor to be able to pick the structure up and handle it using efficient cranes, versus needing a specialty contractor to handle that aspect of the project,” Walls said. “We paid close attention to those types of details.”
He said much attention was paid to the stresses that would be placed on the huge precast pieces and any negative impacts of movement on those structures during transport.
“In design, we put in a lot of time detailing the efforts to prevent those issues,” Walls said. “We worked very closely with the precast team and their shop, going through their procedures and methods of picking up, carrying and transporting the pieces. It ended up working out phenomenally.”
Precast Makes the Cut
After considering the different concrete options for the highway improvement project, DelDOT chose precast for its fast installation times.
“It allowed us to take the bridge work off the critical path and accelerate the schedule,” Dean said. “To the contractor’s credit, they actually accelerated the schedule much farther than we would have anticipated (by a full six months, in fact) them being able to do. That was a feather in their cap.”
Walls said DelDOT already had used precast elements in different ways on previous projects, including both precast abutments and precast beams. With the interchange improvement project, he said the agency wanted to build upon its existing knowledge of and experience with precast.
“We felt really comfortable with the material and the system,” Walls said. “We pushed the limits a bit with the modules and pier caps, but based on our previous experience — where we didn’t run into any issues — we wanted to use precast with this project as well.”
Precast Systems Engineering answered that call after completing the Christina River Bridge project for DelDOT in Wilmington. The precaster had produced similar modules in the past, only using double T units versus steel beams (and on a smaller scale).
“For the SR 141 interchange project, we basically took some different approaches we’d used on past projects and married them together,” said Chad Saunders, vice president at Precast Systems.
One innovative precast feature was the barrier with the form liner finish, which included both recesses and picture framing, versus just a standard barrier. From the precast perspective, Saunders said the unit weight of the exterior pieces made the project challenging and required excellent coordination between all the parties.
“That took a lot of good engineering on the part of Precast Systems Engineering,” Saunders said, “which had to figure out how everything was going to be lifted and handled.”
JP Binard, P.E., owner and manager at Precast Systems Engineering, concurs, and says the construction engineering and fine details took time to develop, but the end result was well worth the effort.
“We designed lifting to validate that DelDOT’s desired approach was acceptable, and to factor in some of the unique considerations the precaster used to handle and ship the pieces,” said Binard, who also developed the integrated shop drawings for the project. Those drawings were unique in that they incorporated the precast, steel fabrication and barriers. “We used 3D detailing methods to ensure that there were no clashes.”
All on the Same Page
Substantially completed in December 2021, the interchange project went smoothly overall thanks to the coordinated effort of everyone involved. Dean and Walls both liked the open lines of communication between DelDOT and all three vendors (contractor, precaster and precast engineer) throughout the process.
In a few instances, this high level of collaboration led to project simplifications. With the precast barrier, for example, the precaster and contractor worked together to make a few modifications that simplified the closure pour process.
“It was great to have that back-and-forth with the precaster and contractor, which really helped align with design and construction sides of the project,” Dean said. “The communication between all parties made this project a success, quite honestly. That was the biggest thing that we noticed on this one — that open lines of communication really drove the success of the project.”
Bridget McCrea is a freelance writer who covers manufacturing, industry and technology. She is a winner of the Florida Magazine Association’s Gold Award for best trade-technical feature statewide.