They mostly come out at night: the excavators, the graders, the haulers, the front-end loaders and their operators, the construction crews who are transforming Interstate 35E one mile at a time.
Commuter Julie Leuzinger noticed them after crews began moving in at the end of October.
“Seventeen miles of my commute are on I-35,” she said. “I drive that twice a day from Carrollton to Denton for work.”
The reconstruction of 28.1miles of I-35E between Interstate 635 and U.S. Highway 380 will produce tons of debris in its wake — yards of exhumed soil, slabs of asphalt and hunks of concrete. Between 1,000 and 2,000 cubic yards of excavated road material will be produced per lane-mile.
Depending on the thickness of the pavement, that could be enough to cover someone’s 1-acre backyard in a rock pile 6 inches deep, according to Mike Shenoda, a professional engineer and member of the engineering technology faculty at the University of North Texas.
Where will all that material go? Probably into the next road construction project.
Almost all waste materials created by highway construction can be recycled as long as they are not hazardous, Shenoda said. Whether the road can be recycled depends on its condition, age and composite material.
“Most of the paving materials, the concrete and asphalt, are crushed into aggregate that can be reused,” Shenoda said. “The large stones that comprise the aggregate are then tested for quality.”
Higher-quality material can be used to make pavement for the new road. The lower-quality material can be used for filling in holes and such. These high-quality rocks exhibit strength,resistance to weather and chemicals and a rough texture that provides friction for a drivable surface, he said.
Most asphalt on roadways is about 95 percent rock and 5 percent binder, such as tar.
To recycle, the old asphalt is crushed into aggregate. Construction crews heat and test it, and then add new binder. If not recycled into new pavement, the crushed asphalt can be used as an under layer to the new pavement or as back fill material.
Shenoda adds that most road construction debris is not hazardous and could be disposed of in landfills.
“Volume becomes the issue,”he said.
Texas Department of Transportation officials say that asphalt, concrete and even tire rubber are recycled and used to build Texas roads. The agency also tracks how much recycled asphalt pavement and recycled asphalt shingles it uses.
In fiscal year 2013, 17percent of the 7.5 million tons of asphalt placed by TxDOT was made of recycled materials. All recycled asphalt pavement is used by contractors, TxDOT or by county and municipal governments for use on their roads. Recycling highway construction materials extends landfill life and reduces project costs, TxDOT officials say.
However, TxDOT does not require its contractors to recycle construction materials. That decision belongs to the contractors.
For 35Express — there construction of I-35E through Denton County and part of Dallas County — the recycling efforts will be overseen by AGL Constructors, a consortium of Archer Western Contractors LLC, Granite Construction Co., Lane Construction and their subcontractors. Acting as an adviser, TxDOT officials outline what materials can be salvaged and the processes for salvaging such materials.
According to AGL officials,old asphalt will be recycled into new asphalt for use on I-35E. Concrete aggregate will be crushed and recycled into “flex base,” the foundation for new roadways, and rebar will be sent to a recycling center. Most of the trees removed to make room for the new construction will be mulched and used in landscaping.
“Our goal is to have as little waste as possible and to recycle as much as we can from the project,”said Kimberly Sims, a public information coordinator for AGL.
While neither TxDOT nor AGL could estimate how much road debris would be produced and recycled, AGL does plan to track its waste and recycling efforts, Sims said.
Since Oct. 28, crews have begun preparing sections of I-35E that will be rebuilt. For the next three years, the project will add lanes and streamline frontage roads to alleviate traffic congestion in one of the most heavily traveled roadways in North Texas.
To manage the 28-mile project, TxDOT and AGL divided the task into three segments: a northern segment of 10.5 miles of I-35E from U.S. 380 to FM2181, a middle segment of 12.1 miles from FM2181 to President George Bush Turnpike, and a southern segment from the President George Bush Turnpike to I-635.
The first phase of the project will cost approximately $1 billion and affect eight cities, two counties and countless commuters.
While delays and traffic jams will inevitably occur, Leuzinger wanted to make sure those headaches would be a thing of the past for her. When she and her husband learned last year that the project would soon break ground, they began preparing to relocate.
They signed the papers for their new home the day before Thanksgiving. After commuting to Denton for nine years, Leuzinger has moved to Flower Mound to avoid the construction.
“You could say that I’ve drastically altered my commute by moving,” she said. “Now I’m taking measures so that the construction doesn’t affect my life so much.”