IN MOST JURISDICTIONS, the coup de grace for trash usually comes when it is flung into a landfill. Not so in Hennepin County, Minn., which has no landfills. Here, trash disposal has morphed into a resource recovery operation anchored by two transfer stations: Brooklyn Park, located south of Minneapolis, and the Freeway Transfer Station on the other side of the county.
Of the approximately 630,000 tons of waste handled annually by the county, only 79,000 tons go to landfills located outside the county. The rest either fuels generators at a local utility that burns the waste as refuse derived fuel (RDF) or goes to a county-owned waste-to-energy (WTE) facility. The Freeway Transfer Station handles about 112,000 tons of the waste, and Brooklyn Park receives 171,000 tons of trash per year from municipal and private haulers.
Brooklyn Park is located midway between the WTE mass burn facility and the RDF plant. The enclosed, rectangular transfer station and recycling center are designed to speed the movement of materials. The transfer station occupies the eastern half of the space, while the recycling floor lies on the west side.
The transfer tipping floor, which measures approximately 30,000 square feet (sq. ft.), accommodates up to six collection trucks at once. The trucks dump trash into a 17,500 sq. ft. pit that drops 12 feet below the tipping floor.
In the pit, Volvo L120C and Caterpillar 950F loaders shove the trash into two hoppers that funnel material into two 19-ton transfer trailers located in tunnels below the hoppers. The loaders work there to avoid crowding collection trucks off the tipping floor. Also in the pit, two Builtrite Model 2100 tamping cranes, one for each hopper, compress the waste in the trailers. Fairbanks axle scales measure the loads.
The pit allows waste to be stored overnight to enable the facility to schedule trailer movements for light periods of traffic and short waiting periods at delivery destinations. Moreover, the trash in the pit can be misted with dust and fire suppression products. In most transfer stations, wetting the tipping floor would create skids, trips, falls and other safety hazards. Finally, the pit contains a concrete bunker where the loaders can place materials just in case they catch on fire.
According to Randy Kiser, principal planning analyst with Hennepin County Environmental Services, the efficient tipping operation enables haulers to move from the scalehouse to the floor, dump their loads and exit the facility in an average of 9.5 minutes.
Collection trucks enter the facility from a 350-foot queue located on the west side of the building. The scale-house helps to weigh entering and departing trucks. After passing over the scales, inbound trucks move along a concrete road to enter the transfer tipping floor. The trucks dump their loads then continue back to the outbound scale lane and then off the grounds.
Public traffic enters the facility on the same side as the commercial trucks and passes through a second scale house designed for smaller vehicles. People with hazardous materials follow the truck route north to a household hazardous materials drop-off located in a 5,000 sq. ft. addition to the main building. People dropping off recycling materials, trash, tires or bulk wastes do so at the stations set in the front of the building.
One drawback to the route is customers must buck traffic by turning south from the scalehouse. “There is some cross over,” Kiser says. “But we've just begun a project to redo the traffic patterns.”
Brooklyn Park charges a commercial tipping fee of $40.60 per ton, less than half the $95 per ton fee of 10 years ago when flow control was in effect and haulers were forced to use the facility.
The Hennepin facility is close to Wisconsin and Iowa. Both states offer large landfills with low tipping fees. Following court decisions that prohibited local governments from requiring waste deliveries to their facilities, Hennepin haulers began to develop an infrastructure to move their trash out of state. Some ended their relationship with Brooklyn Park. Others, however, responded favorably when the facility cut its tipping fee, first to $60 and later to the $40 range. The lower tipping fees attract haulers who bring in a combined total of 170,000 to 177,000 tons (Brooklyn Park's capacity) of waste per year.
Ticket Prices Rising
However, paying for disposal has grown challenging. According to Kiser, operations, maintenance, transfer costs and debt service cost $19.72 a ton in 2002. While efficient operations leave Brooklyn Park with $20.88 per ton from its tipping fee, an expensive contract with the RDF plant consumes all of the leftover cash, and then some.
A local utility built the RDF plant in 1989, when Hennepin constructed Brooklyn Park. The utility agreed the plant would accept waste from the transfer station and produce RDF, which the utility then would use as a fuel to replace coal. But the utility insisted its costs for making and burning RDF could not exceed the cost of burning coal. Hennepin agreed to pay for processing waste into RDF, about $70 per ton.
“The county has to subsidize the production of RDF,” Kiser says. “It isn't the best financial deal, but this was done at a time when the utility and the county were exploring these kinds of ideas. There was no history of costs, and we couldn't expect the utility to take a financial risk. We developed a contract that would equalize their fuel costs. In five years, when we renegotiate the contract, we'll be looking to close out some of these inequities.”
Kiser also points out that Brooklyn Park is not in business to make profits. Its goal is to write a new script governing waste disposal. The facility's role as the hub of a large resource recovery operation achieves part of the goal, he says.
The facility also helps educate the public about alternatives to landfill disposal. Inviting public areas line the facility. Public drop-off locations for recyclables and trash attract 50,000 local residents per year to Brooklyn Park. Near the drop-off locations is a conference room, with floor-to-ceiling windows that look out onto the recycling and transfer tipping floors. Adjacent to the building is an eco-yard.
Residents dropping off materials often pause to take in the exhibits in the eco-yard, pick up literature about controlling waste and speak with attendants. In addition, six members of Kiser's staff conduct 10 to 15 public tours of the facility each year.
“We talk about why we separate trash, recyclables and hazardous materials,” Kiser says. “We stress the importance of reducing waste through recycling.” Attendees include civic groups and students of all ages, from elementary schools and community colleges. Before constructing the eco-yard, the landscaping around the facility struggled because of poor soil and growing conditions. Maintenance was expensive. County officials wanted to upgrade the landscaping to bring it more in line with the facility's educational goals. The eco-yard was conceived as an outdoor classroom and designed by a landscape ecologist to illustrate a functional, cost-effective, environmentally sound and visually pleasing back yard.
“It contains a number of different kinds of plants that you can grow and use instead of grass — which creates lawn wastes,” Kiser says. “We have low-maintenance lawns that reduce yard waste, a composting bin that illustrates how to dispose of organic materials at home, and a rain garden that illustrates ways to collect and use rain water.”
Exhibit signs throughout the eco-garden enable self-guided tours. A brochure and Web site provide educational resources. “We've designed our facility to do a lot more than just transfer garbage,” Kiser says, pointing out the transfer operations are part of a comprehensive county resource recovery system. Indeed, “Hennepin County operates a state-of-the-art transfer station with several features,” says John Skinner, executive director and CEO for the Solid Waste Association of North America, Silver Spring, Md. The association awarded the facility with a gold excellence award in 2003.
Michael Fickes is Waste Age's business editor.