The municipality of Anchorage, Alaska knew one thing: A dilapidated 19-building apartment complex had to be destroyed. However, once the wrecking ball struck, the resulting rubble would be a disposal headache.
With the local landfill nearing capacity in an estimated 10 to 15 years, Anchorage faced steep tipping fees and possible buried profits if it landfilled the C&D debris.
It needed an innovative solution, and during the bidding process, it found one: Alcan Environmental Inc. proposed a plan that promised a 95 percent diversion rate. The reduced waste not only would conserve the landfill's life and reduce costs, but also would produce a myriad of salable products.
According to project manager Les Boczonadi, Alcan realized during bidding that it would not be feasible to landfill the estimated 18,000 tons of debris from he demolished apartments.
By salvaging and processing marketable waste, Alcan saved the municipality an estimated $475,000 in landfill tipping fees.
Alcan's demolition plan focused first on segregating asbestos from each building. In the project's early stage, the company realized that the buildings contained large quantities of ferrous metals and aluminum siding that could be recycled. During demolition, the various waste streams were segregated.
"As we were bringing the buildings down, we were concentrating on as much of the large dimensional segregation as possible," Boczonadi says. "The wood beams we uncovered were old-growth Douglas Fir, number two or better. Material like that isn't used these days."
Aluminum siding, non-galvanized piping, cast iron and black iron were separated from the wood debris.
Alcan demolished each building in about one day. One track excavator tackled the initial demolition, while another separated the materials. A third excavator loaded a tumble grinder with wood and other grindable materials, which included flooring, wood and sheet rock.
Prior to grinding, high-inertia swinging hammers provided high production with the tolerance to pass through small pieces of contaminant that may not have been separated. In addition, carbide-surfaced hammertips were used to provide long wear life.
A tumble grinder was used in temperatures ranging from -5 degrees F to 20 degrees F. Alcan tented the tumble grinder and put two 300,000-BTU propane heaters beneath the unit.
Operating at up to 1,100 cubic square yards per hour, the grinder processed wood materials from one 16-unit apartment building in just under two, seven-hour days.
Inclined at 30 degrees, its tumble tub has more than 200 square feet of prescreening area to separate the fines before they came in contact with the rotor.
In addition, the rotating screen acted as a cage to prevent the debris from reversing out of the tub, and feeding it back to the rotor below.
With only oversized materials contacting the hammer- tips, the wear costs were reduced.
95 Percent Recovery The initial phase was completed by the end of 1996 - a few months ahead of schedule.
The results were impressive: While the wrecking ball caused 11,000 tons of debris, only 500 tons were landfilled.
Wood and metals, the highest-quantity materials salvaged, had significant resale value. "There is a large market for recycling dimensional lumber and turning it into furniture," Boczonadi notes.
Alcan salvaged more than one mile of 16" x 16" wood beams and at least a half mile of 8" x 16" wood beams.
It also recovered 4,500 2" x 10" x 18" floor and roof joists. The company denailed the wood material, in preparation for auction to the furniture market, according to Boczonadi.
Much of the remaining wood was stockpiled at a regional composting facility. A portion will be mixed with a high-quality potting soil, while the remainder awaits the results of a feasibility study examining its market potential as compressed chip logs for fireplaces.
After the project is completed, compost remaining at the site will be spread as seed cover for grass on the 18-acre lot, which will be rezoned for a new building project.
Since Alaska has no smelting facility, the metals had to be hauled to the lower 48 states for processing. After the metals were recycled, they were sold to a buyer.
In the final phase, the concrete foundations were removed. The concrete will be excavated and crushed, and the crushed product will provide fill material to extend an existing land bridge at the Port of Anchorage.