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Bridging the gap

Features - Concrete & Asphalt Recycling, Concrete and Aggregates

Contractors working with the Oregon Department of Transportation are maximizing their return by recycling and reuse.

Jim Cox July 10, 2012

When motorists drive across a temporary bridge like the one currently carrying eastbound traffic on Interstate 84 over the Sandy River east of Portland, Ore., they probably have no idea that much of that structure will one day serve the same purpose at a different location. Nor do they realize that materials recovered from the old demolished eastbound bridge are also on their way to new uses.

But these are examples of how contractors are planning ahead to use salvaged materials where possible and save others for reuse. These efforts are not just good business practices—they are aligned with the Oregon Department of Transportation’s (ODOT) standards focused on smart, sustainable outcomes that benefit the environment.

The passage of the third Oregon Transportation Investment Act (OTIA) in 2003 created Oregon’s largest infrastructure investment in five decades. As part of OTIA III, the 10-year, $1.3 billion State Bridge Delivery Program is repairing and replacing hundreds of bridges, and its statewide scope has provided an opportunity to make the three “Rs” of reduce, reuse and recycle standard practice in bridge and highway construction.


Setting a Standard

In 2005, a stakeholder group comprising ODOT, the Oregon Department of Environmental Quality and the Associated General Contractors developed a set of environmental performance standards for the bridge program. These standards direct contractors to handle construction scrap to achieve the “highest and best end use,” minimizing waste generation and reducing disposal in landfills.

To ensure the bridge program and its contractor partners are meeting their goals, environmental team members at ODOT track statistics on reused and recycled materials. Until recently, those numbers were hard to come by, making it difficult to set goals for improving recycling in bridge construction projects. But reporting requirements enacted in recent years are making their work easier.

For example, they can now tell you that in 2010 the bridge program reused or recycled 33,438 tons of asphalt paving, 150,848 tons of clean fill, 60,237 tons of concrete, 15,667 tons of metal and 1,053 tons of wood. The total estimated value was approximately $9.4 million. (The actual value is likely higher; though reporting compliance is many times greater than when the program first recognized the challenge in capturing reuse, recycling and fuel use data in 2007, some savings could not be estimated due to missing information from contractors.)

What’s noteworthy about the materials and contamination environmental performance standards is the emphasis on reporting.

“We set reuse and recycling targets, but until we started getting consistent data from the contractors, we really weren’t certain how achievable they were,” said Geoff Crook, the environmental manager for ODOT’s bridge program.


A Prime Example
ODOT’s work replacing two bridges on I-84 over the Sandy River is an example of a project providing Crook and his team with recycling results along with plentiful, reliable data.

“We’ve been recycling for years, but now we’re reporting what we do to meet ODOT’s needs,” says Wendell Snook, project manager for Hamilton Construction Co., ODOT’s prime contractor on the Sandy River project.

The old eastbound bridge over the Sandy River was built in 1949. About half of its 772-foot length was reinforced concrete deck girder; the remainder was steel deck girder. When it was demolished to make way for its replacement, about 10 percent of the old concrete was incorporated onsite for roadway fill; the remainder goes to a materials supplier that crushes it for aggregate base or general fill. The westbound bridge rubble will find similar uses when it comes down in 2012.

Steel scrap from the Sandy River project goes to Schnitzer Steel, a Portland, Ore.-based company that in its most recent fiscal year processed more than 4.2 million tons of iron and steel scrap.

On the freeway bridges at the Sandy River, construction staging and mobility requirements call for a temporary detour bridge and a work bridge. To reduce costs and increase opportunities for reuse, Hamilton custom fabricates modular components. Hamilton’s temporary works are all made to be reused. Decking, timbers, stringers, bracing and the like are configured in a modular fashion, making it easier to truck goods from site to site and reuse them multiple times.

Hamilton fabricates all of its products for temporary work and detour bridges, including K-frame bracing, pile caps and beams. They are created in a steel fabrication shop powered in part by a 75-kilowatt solar energy system.

ODOT is interested in reducing the number of piles put into the ground or river to build a temporary bridge. Hamilton responded by creating its own standard materials specifications to achieve maximum span distance that is still suitable for fabricating, transporting and erecting. Later, crews disassemble the components and reuse them on other temporary structures.


Optimizing Return
Snook says Hamilton is always looking to get as much value as safely possible out of its materials. Precast concrete slabs on a temporary detour bridge, for example, are hauled off and reused or sold; they might someday find their way onto logging roads or remote parks or ranches.

On a work bridge, the plywood deck is typically single-use. The contractor takes it to a recycler, who turns it and other scrap lumber into hog fuel, mulch, compost or other landscape uses. But ODOT and its contractors use timbers and piles three to four times before they have to be considered scrap. Steel sees virtually unlimited use.

Such attention to reuse and recycling opportunities has become more common under the Materials and Contamination directives for environmental performance standards, according to ODOT’s Crook. Bridge program contractors are required to submit an initial Construction Waste Reuse and Recycling Plan, including baseline estimates of reuse, recycling and disposal quantities. Crook believes contractors are thinking more critically about recycling as a result.

“Data like this informs our business practices and helps ODOT set realistic goals for the future,” Crook said.

Because of the reporting from contractors like Hamilton, and their environmental commitment on projects like the Sandy River Bridge, ODOT has begun to compile the baseline data to determine what can feasibly be achieved in different areas of the state, depending on contractors’ access to materials and recyclers. By consistently capturing information like this, the agency is gaining a better understanding of what’s possible and can develop realistic goals for recycling and reuse that can be incorporated into future contracts.

 


The author is OTIA III Bridge Delivery Unit Manager for the Oregon Department of Transportation’s Major Projects Branch.

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