Materials Get Recycled on the Sam Rayburn Tollway

The NTTA is using recycled material on its new interchange at the Sam Rayburn Tollway and U.S. 75 to minimize the project’s impact on the environment. The green initiative translates to a savings of time and money while furthering the NTTA’s sustainability efforts.

The recycled material is concrete and asphalt from U.S. 75 and the Sam Rayburn Tollway (SRT), which the NTTA is reusing on the interchange project. The NTTA’s contractor, W.W. Webber LLC, has set up three concrete recycling machines on site so that the old concrete can be crushed and repurposed into three different-sized materials. The crushed material then is used in project locations such as pipe bedding or various fill material.

“The NTTA is extremely proud of this on-site recycling effort, which supplies reprocessed materials back into our own project,” said Gerry Carrigan, NTTA assistant executive director of project delivery. “Not only are we helping the environment, but we are cutting costs and saving time by using fewer trucks to haul in materials.”

Here’s how the NTTA’s recycling effort works: A machine called a stomper crunches up the old concrete roadway and underlying asphalt in 18-foot-wide sections. The stomper crushed the old northbound U.S. 75 main lanes and underlying asphalt from Ridgeview Drive to the new SRT interchange. It also crushed old asphalt on Medical Center Drive.

Workers using hydraulic excavators then rake out the concrete and remove the reinforcing steel. The underlying asphalt is then removed. The concrete is recycled on site, and the asphalt goes to the asphalt plant, where a percentage of the original material is put right back into new asphalt sub-grade on the SRT/U.S. 75 interchange project. The remaining recycled asphalt is available for use on other projects. Meanwhile, the steel goes to a steel mill, where it is recycled for use in construction projects throughout North Texas.

So far, the NTTA and its contractor have recycled approximately 27,000 cubic yards of concrete, enough to bury a regulation NFL football field under 12 ½ feet of concrete. In addition, an estimated 1.9 million pounds of steel have been recycled during this effort.

The NTTA’s project involves building the new, four-level SRT/U.S. 75 interchange in the communities of Allen, Fairview and McKinney, and rebuilding the main lanes and frontage roads from Hardin Boulevard to east of Medical Center Drive.

Recycled concrete is used in different ways on the project:
• as fill for new embankments that serve as the approaches to new interchange bridges; and
• as pipe bedding around new storm sewer pipes.

The use of recycled concrete and asphalt are among the NTTA’s ongoing sustainability efforts. System-wide, these efforts include the NTTA’s use of uncoated, environmentally friendly concrete during construction; landscaping with native and adapted plants; storm water management and recycling; and the use of hybrid vehicles. In fact, the NTTA was recognized by the  International Bridge, Tunnel and Turnpike Association (IBTTA) for its sustainability efforts in June with the 2009 Toll Excellence Award in Social Responsibility.

On the SRT project, additional sustainable initiatives include all-electronic toll collection, which improves air quality because motorists don’t have to stop to pay tolls while their vehicles idle. In addition, SRT creek bridge substructures have been widened to eliminate the need to re-enter sensitive watershed areas during potential future road expansions.

Currently, the SRT/U.S. 75 interchange project is approximately 42 percent complete. The NTTA expects to open the new interchange to traffic in January 2011.