Thu January 10, 2013
Construction Debris: Where Seattle's Old Buildings Go To Die
Close to half of the garbage generated in America doesn’t come from individual homes or businesses. It comes from construction sites.
The construction industry has been down in the dumps for several years, but on the University of Washington campus, it’s booming. As part of a $475 million surge in construction, new dormitories have been cropping up left and right at UW. That means old buildings have been coming down.
For more than half a century, UW's Lander Hall stood nine stories tall and covered most of a city block. Tearing down the old dorm last year took weeks.
Day after day, excavator machines with huge hydraulic jaws stretched toward the sky and chewed into the dorm. Floor by floor, chunks of concrete, rebar and wood plummeted toward the ground.
One operator was seriously injured last summer when a 20-ton slab of concrete fell on the cab of his excavator.
Convoys of trucks carted all that very heavy debris away. In the end, Lander Hall was reduced to 7,600 tons of concrete and 850 tons of iron.
Where Does All That Waste Go?
About 40 percent of America’s waste comes from construction sites. In Washington state, construction and demolition debris peaked in 2006 before the construction sector imploded. As the state's economy climbs out of its doldrums, construction waste is again approaching record levels.
Seattle’s old buildings often end up in a mountainous landscape on the city’s outskirts. But it’s not in the Washington Cascades.
Dickie Allen walks through the shade of a sort of manmade canyon in south Seattle near the border with Tukwila. He points to a mountain made mostly of concrete slabs with odd bits of rebar sticking out.
"This is everything that’s been dumped," he says. "It’s a large pile -- it’s probably eight, 10 stories."
A second mountain, made of concrete rubble, towers behind him.
“We have the boys pick all the steel, all the garbage," Allen says. "We try to separate as much clean wood as we can.”
Allen works for Contractors Concrete Recycling. It’s where old buildings go to die and to get something of a second life.
Allen shouts to be heard over a concrete-crushing machine about the size of a mobile home. Concrete slabs go in; a stream of inch-wide pieces of rubble comes out on a conveyor belt. Later that rubble will be used as fill beneath new buildings or road projects.
Every year in Washington state about 6 million tons of old buildings get torn down, according to the Washington Department of Ecology. About two-thirds of the tonnage gets recycled or used somehow. The rest ends up in a landfill.
Allen says he’s been working in demolition since the mid-'90s, when he helped tear down the old Seattle City Light building on Lake Union.
“Ever since then, just been ripping and tearing, you know? Tearing down buildings,” Allen says. “I’ve seen a lot of change in Seattle -- helped change it, too.”
He says when he started in demolition, little debris was recycled, mostly just the scrap metal.
“Now, they’re doing wood and everything,” he says.
Recycling Numbers Overstate The Case
King County now keeps 83 percent of its demolition debris out of the landfill, either by recycling it or burning it for fuel. Trains haul the rest to landfills in eastern Washington and eastern Oregon.
Most people would agree that recycling is a good thing, but it doesn’t necessarily make a big dent in the building sector’s appetite for raw materials and energy.
A lot of the debris gets recycled into low-value products like rubble. That means new construction keeps needing new, high-value materials like concrete and lumber.
Recycling rates reported by the construction industry and government agencies tend to overstate how much debris is saved from landfills. Old buildings typically contain hazardous materials like asbestos insulation or items covered in lead paint. That hazardous waste is hauled away to specialized landfills before demolition begins. It isn’t even counted in recycling statistics.
Sometimes old buildings' debris can wind up in a landfill and developers get to say they kept it out of a landfill.
The only active landfill remaining in King County is the Cedar Hills Regional Landfill in Maple Valley. It doesn’t take a lot of construction debris, but it does take truckload after truckload of household waste.
Cedar Hills landfill ingests some 3,000 tons a day. It covers more than 400 acres.
“If you look to the north, you see hills all around us," says landfill manager Dean Voelker. "Well, these hills are all garbage.”
Even at a landfill covering hundreds of acres, space is a concern. Bulldozers with six-foot high wheels covered in rows of metal spikes run back and forth over the newly dumped garbage. They crunch the garbage down so it takes up less space.
The Landfill Cover-up
Cedar Hills doesn’t smell nearly as bad as you might guess. Most of its trash is covered up.
“Instead of having exposed garbage all over the landfill," Voelker says, "the federal requirements ask us to put six inches of daily cover over the refuse every single day.”
That six-inch cover suppresses fires, keeps odors down and keeps animal scavengers -- at Cedar Hills, that means gulls, starlings, rats and even bears -- away.
Many landfills cover up their fresh, stinky garbage with demolition debris, after it's been sorted and processed at a recycling plant.
For now, it’s considered a “green building” practice to send demolition debris into a landfill that way. King County counts the use of debris for a landfill's daily cover as one way to divert debris from landfills. County officials say they're looking to change that.
"It's not going in as waste, but with a purpose," says Kinley Deller with King County's solid waste division. "But it's still ending up in a landfill."
The nation’s most popular green building program, known as LEED, also gives its seal of approval to layering demolition debris into a landfill. LEED certification, from the US Green Building Council, can add thousands of dollars to a property's market value since many potential buyers value environmental protection. The building council is considering dropping the practice of landfill covering from its list of approved green practices.
Covering Up Without Waste
To keep the Cedar Hills landfill from filling up too quickly, Dean Voelker says they stopped adding a six-inch thick cover to the landfill every day.
Instead, at the end of each day, landfill workers spread out 40-foot-wide tarps with a machine called a Tarpomatic. They roll the tarps back up in the morning.
King County’s only landfill has 11 years left before it’s full and the garbage will have to go somewhere else.
The University of Washington requires its major construction projects to recycle or divert at least 75 percent of their waste from the landfill. That's enough to help the projects earn LEED certification from the U.S. Green Building Council.
Even with 100 percent recycling, demolition turns an old building into something much less valuable. UW officials say they considered renovating the half-century-old Lander Hall. But they found it would be cheaper to build a 21st-century Lander Hall from scratch.
Trash Experiment Ends
Preserving Historic Buildings