international: From Roof to Rubble: Studying Florida's C&D Waste

Banning construction and demolition (C&D) wastes from unlined landfills in several Florida counties has forced the use of other options such as recycling. The state of Florida is helping during this transition by studying C&D recycling at residential, commercial and demolition demonstration sites. Its primary goals are to determine the advantages and disadvantages of recycling on-site versus a processing plant and to produce a job site C&D recycling guide.

So far, two of the three projects - the residential and commercial - are underway or completed. The residential project studied the waste materials at two side-by-side home construction sites at the Mentone sub- division in Southwest Gainesville. Here, containers were placed for excess materials including wood, drywall, metal, plastic, insulation and asphalt roof waste.

Normally, during the early construction stages, no containers are placed for waste. Aside from the material remaining in the cement trucks and the wood used for boards (often reused), pouring foundation results in little waste.

The remaining cement generally is poured out and allowed to harden. The small amount of this material produced per lot minimizes the recycling potential. However, if all of the cement for an entire development was poured in one common area, recovery might be feasible.

During the houses' initial framing period, waste (predominately wood) is stacked around the site, permitting reuse of scraps. The first waste container usually is placed toward the framing's end. At the Mentone demonstration site, a 20-cubic yard roll-off box was placed for wood waste and a 95-gallon cart was placed for metals. After framing, a partitioned, 14-cubic yard container was placed between the two houses with a section dedicated to drywall, plastic, asphalt roof waste (shingles and felt) and insulation.

All containers were labeled, the contents inspected and logged and most contamination was removed.

The largest amount of waste recovered was wood, followed by drywall. Cardboard is not counted since cardboard recycling containers were already in the development, making it difficult to predict this type of waste.

The results of the study showed that the coordination of container placement and pickup was crucial. The space available for a container was limited due to the small lot sizes. While wood was the largest fraction collected, a large amount had nails attached, limiting reuse.

Coordinating recycling efforts in a large residential development is potentially beneficial. For example, moving containers from site to site and the general oversite of the recycling would further its success.

The second project, building a 15,500-square-foot drug store in Southeast Gainesville, was the site of the commercial construction demonstration recycling project. The structure was made with 27-foot concrete block walls and the contractor had 90 days to complete construction.

Since the predominant waste in the early phases is concrete block and rubble, the first containers included one 20-cubic-yard roll-off box for concrete and a second for miscellaneous waste. Two 90-gallon tanks also were provided for construction crew food waste. Later into the project, containers were placed for drywall (roll-off boxes), metal (8 cubic yards) and asphalt roof waste (8 cubic yards).

Overall, concrete was the largest waste material by mass. The county public works department used the concrete as road base. Metal was sent to a local metal salvage company. Drywall was separated though no local markets existed at the time. The general waste container was hauled to the county landfill where a waste composition study was performed.

Difficulties that were encountered in the recycling program's daily operation included:

* the site's size restrictions;

* container drop-off and pick-up scheduling;

* training of the various crews; and

* contamination of recovered waste containers.

The number of containers which could be placed at the site was limited due to the congested working area. Plus, allowance had to be made for changing site conditions, vehicle traffic and material storage. The containers often were moved around the site, which meant bringing in special equipment.

Because of the construction's rapid pace, there were several times when the delivery or pick up of the containers was insufficient. Time and location constraints are important considerations in planning and can easily discourage recycling efforts if not handled appropriately.

Similar to the residential site, crews and subcontractors training is a necessity. Containers must be clearly labeled. The site was relatively successful in minimizing contamination and encouraging cooperation because of the responsibility taken by the site foreman.