The trend in landfills is towards bigness. According to Richard Porter in The Economics of Waste, “At the start of the 1970s, there were 20,000 landfills in the United States, but by the end o the 1980s only 6,000, and by 1998 barely 2,000.” Small, municipally run landfills have been replaced by large regional landfills, largely because more stringent regulations have made small-scale landfilling very expensive.
One such regional landfill is just outside of Arlington, Oregon. We visited Columbia Ridge Landfill, operated by Waste Management, where all of Seattle’s garbage goes. The Columbia Ridge Landfill is big, with a 700-acre permitted footprint and a 12,000 acre facility footprint. They receive about 2 million tons of garbage every year.
The District Manager, a man named Kelly, gave us a tour of the facility. Usually they drive a suburban for small tours, but someone else was using it so we got the tour in their tour bus. Kelly said they didn’t have tours that often, maybe a dozen every year.
First, Kelly drove us out to the landfill’s rail yard. Columbia Ridge receives six trains a week from Seattle, each train holding 60 to 140 containers. The containers usually weigh between 25 and 27 tons. Kelly said they can empty 100 containers in a ten hour shift if they are operating at full capacity. And that’s only what’s arriving by train: they also receive waste by trucks along I-84 and other routes.
The containers are taken off the trains by an overhead loader and placed on tractor trailers. These trucks haul the containers the two miles up to the working face where they are tipped. The containers are loaded onto machines that raise the containers up almost to 45 degree angles before they dump their load of garbage.
Once the garbage falls out of the containers, it is pushed into position by bulldozers with giant blades. Compactors with steel spiked wheels roll back and forth over the garbage compacting it into place. Kelly told us that four passes usually achieves optimal compaction. At the end of the day, dirt or an alternative daily cover is laid down on top of the working face to keep down odor and keep away birds and rats. Alternative daily cover can be any EPA approved material, such as petroleum contaminated soils.
The garbage in landfills is laid down in lifts. After a new cell has been prepared with its clay and plastic liners and leachate collection system, a five foot thick layer of garbage is put down. This is called a floating lift and isn’t compacted because they don’t want to damage the liner or collection pipes. After the floating lift is put down, garbage is put down in fifteen to twenty foot deep lifts and compacted.
Building a landfill is like building a very complex pyramid: each cell can only be built up to a certain height before the adjoining areas are also built up. Designers also have to account for roadways to and from the working face as well as landfill gas collection pipes.
Columbia Ridge does have a landfill gas collection system. Currently they have eight engines generating about 6.4 Megawatts of electricity. They are planning to expand their capacity in the near future. Landfill gas collection essentially consists of pipes shoved into the landfill hooked up to a vacuum system.
Kelly told us that Columbia Ridge was a good location for a landfill because it wasn’t very close to its neighbors and because they only receive 9 inches of rain a year. When it comes to landfills it seems that location is one of the most important factors. Nobody wants it nearby.