Basic Transfer Station Technologies

Waste can be unloaded directly into the “open top” of the trailer, but is most
often unloaded on the tipping floor to allow for materials recovery and waste
inspection before being pushed into the trailer. Large trailers, usually 100 cubic
yards or more, are necessary to get a good payload because the waste is not
compacted. This is a simple technology that does not rely on sophisticated
equipment (e.g., compactor or baler). Its flexibility makes it the preferred option
for low-volume operations.
The surge pit is not a loading technology, but an intermediate step normally used
with open-top or precompactor systems. The pit can store peak waste flow, thus
reducing the number of transfer trailers needed. A tracked loader or bulldozer is
used to compact the waste before loading, increasing payload. Because waste is
often unloaded directly into the surge pit, this technology might deter materials
recovery and waste screening efforts.
Precompactor systems use a hydraulic ram inside a cylinder to create a dense
“log” of waste. The log is pushed into a trailer that uses “walking floor” technology
to unload or relies on a tipper at the landfill to unload by gravity. Most precompactor
installations have two units in case one unit requires repair. The capital cost
is relatively high at more than $250,000 per unit, but the superior payload can
offset these initial costs.
Balers are units that compress waste into dense, self-contained bales. Wire straps
may be used to hold the bales intact. They are usually moved by forklifts and
transported by flatbed trailers. The baler units can also be used for recyclables
such as paper and metal. Payloads are very high, but so are capital costs. Most baling
stations have at least two units in case one is down, and they cost more than
$500,000 apiece. This high-technology option is normally used only in high-volume
operations, and special equipment or accommodations might be required at the
landfill (or balefill).
In this alternative, waste is tipped at a transfer station, then loaded into intermodal
containers. These containers typically have moisture- and odor-control features
and are designed to fit on both flatbed trailers and railroad flatcars. The containers
may be loaded directly onto railcars or transferred by truck to a train terminal.
The sealed containers can be stored on site for more than 24 hours until enough
containers are filled to permit economic transport to the landfill. At the landfill,
these containers are usually unloaded by tippers. This option allows for reduction
of total truck traffic on local roads and can make distant disposal sites economically
viable.
Stationary compactors use a hydraulic ram to compact waste into the transfer
trailer. Because the trailer must be designed to resist the compactive force, it is
usually made of reinforced steel. The heavy trailer and the weight of the onboard
unloading ram reduce the payload available for waste. This technology is declining
in popularity[/size]