Rehabilitation of the Route 139 Hoboken Viaduct: A Case Study in Accelerated Bridge Construction

The Federal Highway Administration (FHA) defines ABC as a plan to accelerate bridge construction projects using a combination of innovative planning, design, cost estimation, procurement, project management, and construction methods that reduce on-site construction time and can be implemented safely and in a cost-effective manner.

To help quantify the benefits of accelerating a bridge construction project, we must first define two recognized time metrics.

The first-time metric is on-site construction time (OCT). This is defined as the period that starts when the contractor arrives at a project site and ends when the contractor completes the work and leaves the project site. OCT is the full time necessary to make all the proposed improvements to the project site.

The second time metric is mobility impact time or MIT. It’s a subset of on-site construction time, and it represents the period of time that the contractor’s operations impede traffic flow through the construction site. We’ve all been caught in construction traffic and can relate to the need to minimize MIT as much as possible to cause the least disruption to the traveling public.

According to the FHA, the reduction of MIT falls into six tiers or categories:

• Tier 1: Traffic impacts within one day.
• Tier 2: Traffic impacts within three days.
• Tier 3: Traffic impacts within two weeks.
• Tier 4: Traffic impacts within one month.
• Tier 5: Traffic impacts within three months.
• Tier 6: Overall project schedule is significantly reduced by months to years.

To appreciate the various tiers of ABC, it’s best to start with the traditional construction benchmark. In general terms, when you’re constructing or replacing a bridge, it’s common for such a project to take at least 12 months or more to complete using traditional construction techniques.

While it’s common for traffic impacts to exceed three months for a typical overpass project, ABC techniques reduce the overall project schedule. Tiers 5, 4, and 3 are progressively more aggressive ABC projects.

Getting even more ambitious, Tier 2 ABC projects limit traffic impacts to fewer than three days, and you can think about a Tier 2 project as one that could occur over a long weekend, such as a bridge detour that’s put in on a Friday evening that stays in place until the following Monday morning.

Finally, there’s Tier 1, the most aggressive type of ABC project, defined as a project that limits MIT to less than 24 hours. Bridges that fall into Tier 1 often require unique or complicated construction equipment to pull off such an aggressive schedule.

There are many ways to accelerate a bridge project, including alternative contracting methods. This is where a contractor builds the bridge and takes the lead in its design. This method provides a way to build innovation into the design from the outset.

Another way to accelerate bridge construction is to use prefabricated bridge elements and systems (PBES). Unlike traditional construction methods, ABC projects tend to veer away from on-site material placement in favor of prefabrication. You can think of ABC as a modular home instead of a conventional stick-built house.

Other bridge construction methods include constructing a new structure to the side of its final position and using large-scale placement techniques for installation. After the new bridge is built next to the old one, the existing bridge is demolished. The new bridge is slid into place or pushed into place such that traffic impacts above are significantly reduced.

You may be asking at this point, “How popular is ABC within the industry?” And while ABC may only be suitable for some projects, it’s become very popular in some locations. Let’s take a look at one such project.

The Hoboken Viaduct is a fairly large, complex, aging structure in need of rehabilitation. The rehab concept was originally designed assuming conventional construction techniques, but due to extenuating circumstances, the bridge was redesigned to incorporate ABC methodology. This provides a unique opportunity to compare the conventionally designed bridge with one designed using ABC techniques.

Owned by the New Jersey Department of Transportation (NJDOT), the Hoboken Viaduct is located between Jersey City and the City of Hoboken. It is part of a complex network of roadways and structures that connect the New Jersey Turnpike and points west to the Holland Tunnel that leads into Manhattan. It’s a 3,200-foot-long, cut-and-cover structure constructed in 1926 that looks like a tunnel but is a bridge with the lower express roadway placed below the surface street network.

The structure consists of approximately 220-floor beams that span north to south over the Route 139 express lanes below. Span lengths are each about 60 feet and spaced about every 20 feet along the length of the structure. These beams support longitudinal steel stringers that, in turn, support the deck of the upper eastbound local roadway.

The conventional wisdom at the time was that all four upper lanes had to be maintained through the project site during construction. Due to site congestion, the two eastbound local lanes would need to be supported by floor beams throughout the project. To reuse these floor beams, their concrete encasements would need to be removed, and the exposed steel would then need to be cleaned and painted. In some cases, several floor beams also needed to be repaired or even strengthened.

Something to keep in mind is that all the floor beam work, to all 220 floor beams, would have to have been done in 12-foot-long sections along their length since the work zone below the structure was limited to a single-lane outage controlled by a movable construction barrier curve.

The beam rehabilitation was anticipated to be a very tedious, time-consuming process but was necessary because they needed to remain in service due to the traffic staging. During a shutdown period, the design team approached NJDOT with a suggestion to consider incorporating ABC. The question became, “What kind of method should we incorporate to reduce the construction schedule?”

The team determined that using prefabricated components had some potential but would probably require a completely different traffic staging scheme. NJDOT scheduled a smart solutions workshop aimed at value engineering the project through a collaborative process with the various design parties.

We determined that a temporary roadway constructed at the east end of the structure could connect that temporary roadway with the city grid through a series of progressive detours. It would be possible to get the upper eastbound roadway off the structure in sections. If we could do that, the concept’s immediate benefits would be clear from the start.

If the floor beams were no longer needed to support traffic during construction, they could then be replaced in their entirety rather than rehabilitated in a piecemeal faction. The concept would also provide larger work zones for the contractor to fit the new stringers into the new floor beams. Based on the workshop, we estimated the project could be completed 12 months sooner than the original design, saving approximately $30 million in construction costs.

The potential time and cost savings were too significant to ignore. NJDOT directed the design team to incorporate the changes and convert the project from a conventional deck replacement and rehabilitation concept to a full superstructure replacement using ABC techniques.

The Hoboken Viaduct is a vast structure, so the original design would have involved numerous traffic impacts and a significant construction duration. Following the smart solutions workshop, public feedback indicated that motorists might be willing to endure some of the inconveniences of the detours at the beginning of construction, provided the result would significantly reduce the construction schedule.

The ABC concept allowed more predictable construction management by removing the guesswork regarding the condition assessment of the existing steel beneath the concrete encasement. Lifecycle benefits were realized by removing traffic from the bridge decks, not only with the floor beams and the superstructure but also by providing new columns and substructures.

The construction cost estimate for the original rehabilitation was $97 million. By incorporating ABC techniques, including removing traffic from the structure, the revised concept structural estimate was $69 million. The project was ultimately awarded at a bid price of $62 million, a savings of $35 million from the original rehabilitation estimate.

The Hoboken Viaduct is a great example of how ABC techniques can generate substantial time and cost savings. The 12-month schedule translated to millions of dollars saved. In doing so, it also improved safety during construction and resulted in more durable, higher-quality construction, which was more efficient than the previous rehabilitation scheme. It also demonstrated the successful outcomes possible when all project stakeholders are committed to collaborative partnering throughout the life of a project.