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Managing C&D debris

Managing C&D debris

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    Metal pipes and related components removed during construction, like the cast iron water main and valve shown above, can be taken to salvage yards and recycled. Photos: Pam Broviak

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    The National Association of Home Builders Research Center estimates that construction of a typical 2000-square-foot single-family home creates 8000 pounds of waste. This consists of wood, gypsum, metal, siding, cardboard, plastic, asphalt roofing, and miscellaneous materials.

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    Black coal tar residue from an old gasification plant was discovered in excavations for this pipeline job. Surprises like this can be avoided by conducting environmental assessments during the planning phase of infrastructure projects.

Recycling Road Rubble

Construction of a city's infrastructure can generate substantial amounts of C&D debris. But there is a long, successful history of recycling, reuse, and salvage operations in the road-building industry. For many years contractors have realized the economic benefits of reusing bricks, concrete, and asphalt removed from roadways. Two readily accepted and popular applications of broken-up concrete are as road base and riprap.

Many cities have chosen to keep the grindings and other materials removed during the course of a roadway project for reuse in other projects. “Our city's specifications require milled materials to remain city property, and the contractor is directed to store these grindings at a city-designated site,” said Gene Hewitt, city engineer for Peoria. III. “Public works employees later use the material on other jobs within the city.” Peoria retains the option on each project to keep any material that might otherwise have been disposed of.

In addition to roadway surface materials, some contractors also make arrangements to reuse excavated material. This dirt can be hauled to a different jobsite and used as fill.

Reuse and recycling of materials is an established practice for sewer and water main installations. In areas requiring trench backfill or select granular fill, material excavated from the trench can often be used. This avoids having to haul in material from a quarry and provides an economic savings to the city.

Roadway and pipeline projects also can generate debris consisting of metal pipes and castings. If these items are not salvaged by the contractor or city, local salvage companies or individuals are ready and willing to haul them from the jobsite.

Considering environmental impacts

Although employees in public works have been recycling materials generated from infrastructure projects for years, increasing environmental awareness and stricter regulations are requiring everyone to think twice before hauling the next load of excavated material to another jobsite or dump site.

Although state DOTs have been conducting thorough environmental assessments for years on projects managed by individual states, these policies are now being extended to local agencies. Last year, Illinois established special waste procedures for local highway improvements funded with state or federal monies.

For any project in Illinois involving excavation or building demolition/modification, cities must follow the procedures' screening criteria to determine if a Preliminary Environmental Site Assessment (PESA) is required. If this PESA results in a finding of moderate or high risk of the presence of regulated substances—and avoidance of the area is not possible—a more detailed report called a Preliminary Site Investigation (PSI) is required. A PSI determines the nature and extent of contamination. If the PSI recommends removal of the excavated material, it would typically be addressed in the contract.

Although project designers in larger cities may already know how to prepare an environmental assessment, officials in smaller communities need to be aware of any special waste policies established in their state and allocate the necessary funds and time to achieve compliance and meet the project deadlines.