Palm Beach County, Fla.
The Solid Waste Authority of Palm Beach County, Fla., operates five transfer stations that serve a population that fluctuates between 1.1 million to 1.4 million residents. Additionally, the authority operates a landfill, waste-to-energy facility and materials recovery facility. The distance from the transfer stations to the disposal site ranges from 15 miles to 40 miles.
According to Mark Hammond, the authority's managing director, equipping transfer stations evolved based on the authority's experience. “The two earliest stations that we built in the 1980s were a combination of open top-loading and two stationary compactors,” he recalls. “After we'd had a chance to operate these earlier transfer stations, we found that it was much more efficient and reliable to use open top-loading.”
Consequently, the authority's subsequent stations were built as open top-loading facilities capable of handling up to 2,000 tons per day, compared to the first two stations' throughput of 1,200 tons per day.
Another lesson learned by the authority was about the type of equipment to load and tamp the transfer trailers. “The earlier stations had fixed pieces of equipment to tamp the loads down and assist with loading,” Hammond says. “These had a grabber arm that spread the waste around the open top and also [helped with unloading] if the trailers were overloaded. But these [units] depended on electricity.” Thus, Hammond says the newer stations feature a space behind the pit where a backhoe does the loading.
“We like that arrangement a little better because if we have a power interruption, it isn't going to affect operations,” Hammond says. “We also found that from a maintenance standpoint, they are a little easier to work on. If one breaks down, it's easier to bring in a back-up piece of equipment.”
Hammond says the authority uses Samsung 250 rubber-tired loaders to move waste from the tipping floor to the pit, and uses Caterpillar M318s to load the trailers. “The reason we picked the Cats was because [the company could] modify the cabs,” he says. “We originally had different loaders, but the visibility wasn't really good for the operators.”
Consequently, Hammond says the authority asked different manufacturers if they could modify the cabs to increase visibility. Caterpillar came up with a system that elevated the cab 3 feet higher than normal. “That allows our operators to sit in the cab and look down into the trailers as they load them,” he says.
One of the challenges the authority now is facing is replacing the compactors in the two earliest transfer stations. “We would have preferred to tear out the compactors completely and make the stations an open top type,” says John Booth, authority inspector of engineering and public works. However, that would have required tearing the building down. “The limitations of our site didn't allow us to do that,” Booth says, “so we put in a custom compactor that fit our site. Although we're going to have compactors, they will work better than our old ones.”
The city of Dallas operates three transfer stations and a landfill. The Bachman transfer station, with a design capacity of 2,000 tons per day and a daily volume of 800 tons per day, is the largest of its three stations. The other two stations, Fair Oaks and Oak Cliff, handle on average 400 tons per day. The distance from the Bachman station to the city's McCommas Bluff landfill is 46 miles round trip.
At the Bachman station, transfer trailers enter the facility for loading through a tunnel. In the tunnel, the trailers rest on scales that are monitored by the equipment operators loading the trailer to ensure the trucks don't exceed the legal weight limits.
Recently, the city purchased front-end wheel loaders equipped with a transfer station package. Developing good specifications is critical to getting the right equipment, says Frank Sturgeon, city transfer operations manager.
“We're very detailed because we've learned in the past that if you are vague, some vendors will take advantage of you,” Sturgeon says. What one manufacturer's specs identify as a transfer station package could be very different from what Dallas needs. So “you have to get into some fine detail when you spec out a piece of equipment, and you have to watch what you write,” he says.
Republic Services subsidiary Taormina Industries, Anaheim, Calif., operates a 6,000 ton per day facility that was built in 1984. The facility combines both a 40,000-square-foot transfer station, plus a 210,000-square-foot materials recovery facility that handles commingled recyclables, green waste, and construction and demolition (C&D) debris. The transfer station moves approximately 3,000 tons of waste per day to the Brea-Olinda landfill, a 26-mile round trip.
Currently, the company is planning to construct a new transfer station to service its customers in Colton, Calif. According to Tom Vogt, president of Taormina Industries, the design of the Colton facility will be based on lessons learned from the Anaheim transfer station.
“We have the attitude that [operators] really become the experts,” Vogt says. “You have to rely on your own experience and then the support of the various vendors who know what products they're selling can solve your needs. We take that information and combine it with our own experience, and that's how we come up with the [transfer station] designs. Luckily, we have the large facility [in Anaheim] that is kind of our laboratory.”
However, the Anaheim facility taught Taormina what not to choose. “Our transfer station in Anaheim is a pit-type transfer station as opposed to a flat-deck,” Vogt explains. Thus, in building the Colton site, the company looked at the time requirements for loading and decided to construct a flat-deck station instead.
Additionally, because the Colton facility will process a lower volume of material, new equipment will be installed in the Anaheim site first, where it would be used more. “We probably will put equipment that already has seen its most productive time in the high-capacity facility, then move it out to [Colton] where it will be operated a few hours a day instead of two shifts per day,” Vogt says.
The Central Los Angeles transfer station, owned and operated by Browning-Ferris Industries (now Allied Waste Industries), collects 2,600 tons per day from commercial operators and the city of Los Angeles. Permitted to handle 4,025 tons per day, the station is designed with two ports that allow the simultaneous loading of two transfer trucks. Once waste is processed through the station, it is trucked to one of two landfills: one located 22 miles away and the other located 31 miles away.
According to Doug Moore, BFI general manager, when the company purchased equipment for the transfer station, it required vendors to bring in their equipment to demonstrate it.
“We brought in test equipment that we actually operated for a couple of weeks,” Moore recalls. “Most of the vendors were open to letting us try their equipment out. That is really where we got the sense of which equipment was the best — most user friendly, most comfortable and most productive.”
If an equipment test isn't possible, “The best thing to do is to let the equipment dealers put you in touch with customers,” Moore adds. Dealers should be able to provide a good reference, and the customer should be able to verify whether the equipment can do what the manufacturer says it is capable of.
Based on its tests, BFI chose four rubber-tired bucket loaders: three small loaders and one large. But to improve the loading capability of the loaders, the company ordered buckets with two-foot extensions that allow the bucket to reach down farther into the pit to dress the load. Because the materials are somewhat compacted by the collection vehicles, Moore says an additional compaction vehicle was not necessary to ensure a full load.
Overall, knowing what type of equipment will work in your specific transfer operation will result from years of experience, the city of Dallas' Sturgeon says. “It's just trial and error, and studying other transfer operations.” Because by watching what others do and learning from mistakes, you can gather knowledge, compile it into one package and go from there, he says.
Lynn Merrill is the director of public services for the city of San Bernardino, Calif.
The Transfer Station Process
Each transfer station is unique in terms of the customers it serves, its physical location and the material volume it handles. What might work in one station may be a poor choice at another location — even if the facilities are located within the same area.
Despite some differences, though, most transfer stations operate in the same way.
Like collection trucks, transfer trailers begin their visit to a transfer station at the scalehouse. Depending on the trailer types used, there may be an area outside of the station where truck operators may stop and untarp the trailers, then inspect them prior to loading.
The truck will then pull into the station and onto a second scale designed to monitor the trailer weight as it is being loaded.
Some transfer stations also have a separate location with platforms to allow the operator to check the load and place a tarp over the trailer.
— Lynn Merill
Choosing the appropriate equipment for each transfer task is an important consideration. Fortunately, there are only a few key components to a transfer station system.
For example, you need a scale system to weigh inbound collection vehicles at the facility gate. This system may be tied into a computer reporting and billing system, which can help quickly record and report the weight and costs of each load.
Once the load is dumped on the floor, a wheel loader or grapple system is needed to physically move the garbage from the tipping floor to the transfer trailers.
Support equipment may include dust suppression systems, odor control systems and miscellaneous cleaning apparatus such as power brooms and pressure washers for end of the day cleanup.
— Lynn Merill