Project of the Year - Highway

Interchange 8 Reconstruction Project

One judge called the Interchange 8 reconstruction project "one of the most complex highway projects ever executed, especially because of the traffic management issues." That helped it to not only earn project of the year honors for the highway category but also place it among top five finalists overall.

"They took down a mountain," said another judge. "And it works nicely."

The $187 million project involved the reconstruction of Interchange 8, which links Interstate 87 and Interstate 287 in Tarrytown and Greenburgh, N.Y., on the eastern side of the Tappan Zee Bridge. The project's reach extended to the bridge toll plaza and the Saw Mill River Parkway that runs north and south through Westchester County.

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The massive job entailed the construction of new roadways and bridges through an environmentally sensitive wetland area and the building of retaining walls and noise barriers. It also involved drainage improvements, utility relocations, installation of Variable Message Signs and Intelligent Transportation Systems, and full-depth asphalt paving and resurfacing.

The stretch of highway the project improved is one of the most congested and highly traveled corridors in southern New York State. The Tappan Zee alone handles more than 138,000 vehicles per day. Interchange 8 serves as the main distributor for that vehicular flow.

"The amount of traffic that goes through that knuckle of roadways is amazing," said a judge.

The project aimed to ease congestion with the addition of an auxiliary lane in each direction. Other goals were to enhance safety by eliminating collector-distributor lanes to help to clear the mainline roadway. The project also aimed to install noise barrier walls, reduce air pollution with less idling traffic, and improve traffic movement through the toll plaza with the installation of E-ZPass toll lanes.

In addition to that long checklist, the project team had another major chore - maintaining normal traffic flow on I-87 and I-287 as well as local roads such as Route 119 and Route 9. The team aimed to not have any long-term lane closures, with a goal of maintaining six lanes of traffic throughout the duration of the project.

The team tightly orchestrated its work in each construction zone, reconfiguring every highway section to improve capacity. The plan minimized traffic flow disruptions through intensive planning and scheduling, combined with a community outreach program and a project-specific Web site designed to keep motorists informed of ongoing work.

Those traffic flow constraints made some portions of the job especially difficult. The team could only take on rock blasting within 20-minute traffic stoppage windows from 10 a.m. to 2 p.m., Monday through Thursday. In those windows, the team would halt traffic, conduct the blasts, clear the roadway, and reopen the road.

Other operations - such as traffic switches, retaining wall construction, drainage work, and median installation - took place during off-peak hours or behind barriers.

During work on the Tappan Zee Bridge toll plaza area - where the team could only close a single lane of the 12-lane plaza Monday through Thursday - the project team had to find innovative ways to reduce construction time. The team chose laser screed machine technology to set final road grades in the area. It also opted to rebuild the new toll plaza with precast concrete pavement panels. Demolishing the existing pavement, and placing and grouting the new precast panels, took four days, which allowed the team to tackle one lane a week.

The project also involved construction of auxiliary lanes between the interchange and the Tappan Zee, including a section that passes through the environmentally sensitive Tallyrand Swamp. In order to prevent longstanding embankment settling problems, the project team chose to stabilize the area with EPS Geofoam, a strong, low-density cellular plastic material produced in block form and positioned onsite. Though widely used in European road projects, the foam is relatively new to the United States.

Throughout all phases of the project, the team monitored operations to ensure that the new roadway was stable and that the work was not damaging the sensitive ecosystem. The team installed permanent survey stakes along the length of the retaining wall to monitor settlement, showing none so far.

The project from the start included extensive community outreach, including a series of public open houses in Westchester and Rockland counties. The team also held quarterly informational sessions with the region's government and business leaders as construction progressed. The project also had a full-time community liaison, a toll free information line, daily radio highway advisory updates, and the Web site.

"It's a very 'civil' project - from the congestion [relief] to the communication to users to obviously the engineering," said one judge.