The First Line of Defense
Modern toll plazas are not the stop-and-pay booths of yesteryear. With electronic tolling, some vehicles move through the plaza at near-highway speeds. So, when the Maine Tollway Authority was ready to upgrade the Interstate 95/295 plaza near Portland, the safety of its workers was a big concern. A tunnel under the tollway would be the best way to move toll workers safely from the administration building to toll booths on the other side of the plaza and also protect the high-tech equipment that makes electronic tolling possible.
To construct the tunnel, the Tollway Authority turned to Reed & Reed, one of northern New England’s largest and most versatile contractors. A precast concrete box culvert tunnel was the obvious answer. The box culvert job went to Michie Corporation, a New England powerhouse in its own right. And when Michie needed a watertight seal for the 29 box culvert sections that would comprise the 200-foot-long tunnel, they turned to Hamilton Kent.
Chad Poland, engineering manager for Michie, said a primary requirement was a watertight tunnel. It is a relatively low-lying area, so groundwater was a major issue.
“The Turnpike Authority had a lot of concern because they’ve got a lot of utilities going through the tunnel, so it needed to be kept dry,” he said. “It was a multi-faceted approach, the first of which was the connections between the tunnel sections. That’s where we used the Hamilton Kent gasket. We also membraned the whole thing and took a couple other steps to keep it tight, but the first line of defense was that gasket.”
Michie Corp., based in Henniker, N.H., manufactured the 8’ x 10’ box culvert sections along with several other components for the toll plaza. Michie Corp. worked closely with Hamilton Kent to coordinate the design of the box culvert joints with the style of the gasket.
“The boxes were cast with a custom joint that specifically works with this gasket,” Poland said. “The gasket seats against a step, then we glue it in. It’s all applied at the manufacturing facility.”
Applying the gasket at the precast plant saves time in the field and simplifies the installation because they are ready upon delivery.
“They arrive onsite with a gasket in place, and there are other measures you take to make sure the pieces line up, but you basically suck the two pieces together with hydraulic jacks,” Poland said. “This particular gasket – once you make contact with the piece that you’re drawing into – it just kind of rolls with the piece to provide a pretty tight seal.”
Steve Gard, precast division manager, said the project required a high-quality gasket, which proved no problem for Hamilton Kent. “It’s not a typical box culvert joint ring,” he said. “That ring is specially machined. It’s a very high tolerance, like within 5-thousandths of an inch.”
Gard stayed on-site with the contractors throughout the installation, “to make sure all the pieces fit together,” he said, and also worked with James Fuoco at Hamilton Kent in the development of the gasket.
“We were very satisfied, and they were very supportive in getting us up and going – helping us along with the process,” Gard said. “We hadn’t done this before, so they came down and helped us test-fit everything and size it properly.”
Brian Holmes, project manager for Reed & Reed, said that the tunnel installation went as planned.
“For a piece of work that is critical, it was probably one of the smoother operations of the entire project, and a lot of that was due to the pre-planning, the manufacturing tolerance of the gaskets, and the gasket installation at the precast facility,” Holmes said. “Both the quality of the gasket and the quality of the installation on the cast pieces was evident. We didn’t have any issues.
The pedestrian and utility tunnel comprised the first phase of the $17.9 million Exit 44 Open Road Tolling Project, which started in 2017. After completing the underground work, the demolition of the former site, construction of the administration building and plaza grounds took an additional two years, with the E-ZPass tollway completed in November, 2019.
As the motorists cruise through the tollway, Turnpike Authority officials can rest easy knowing that their employees have safe passage through a brightly lit precast concrete tunnel, kept dry by Hamilton Kent watertight gaskets – the first line of defense.
Hamilton Kent provides technical support and innovative solutions for today’s environmentally conscious infrastructure projects. Contact our expert team to learn more about soil-tight and watertight gaskets and connectors for standard and custom structures.
For additional information: https://precast.org/2020/01/protecting-what-matters-most/