Page 152 - Materials Chemistry, Second Edition

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Municipal Solid Waste Collection 123
W width of each dumping space (ft)
H hours per day that waste is delivered
W
T time to unload each collection vehicle (min)
C
F peaking factor (ratio of number of collection vehicles received during an average 30-min
period to the number received during a peak 30-min period)
P transfer trailer payload (tons)
t
N number of transfer trailers loading simultaneously
H hours per day used to load trailers (empty trailers must be available)
t
B time to remove and replace each loaded trailer (min)
T time to load each transfer trailer (min)
t
N number of hoppers
n
L length of each hopper
n
L length of each push pit (ft)
p
N number of push pits
p
B total cycle time for clearing each push pit and compacting waste into trailer
C
5.3.13 TRANSFER VEHICLES
Most transfer systems use tractor trailers for hauling wastes; however, other types of vehicles may
also be used.

5.3.13.1 Trucks and Semitrailers
Trucks and semitrailers are often used to carry wastes from transfer stations to disposal sites. These
vehicles are flexible and effective because they can be adapted to serve the needs of individual com-
munities. Truck and trailer systems should be designed to meet the following requirements:

• Wastes must be covered during transport.
• The vehicles should be designed to operate safely in the traffic conditions encountered
on the hauling routes.
• Truck capacity should be designed so that road weight limits are not exceeded.
• Unloading methods should be simple and reliable.
• Truck design should prevent the leakage of liquids during hauling.
• The materials used to make the trailers and the design of sidewalls, floors, and suspen-
sion systems should be able to withstand the MSW loads.
• The number of required tractors and trailers depends on peak inflow, storage at the facil-
ity, trailer capacity, and the number of hauling hours.

Two types of trailers are used to haul wastes from the transfer station to the final disposal facil-
ity: compaction and noncompaction trailers. Noncompaction trailers are used with pit or direct-
dump stations, and compaction trailers are used with compaction stations. Noncompaction trailers
can usually haul higher payloads than compaction trailers because the former do not require an ejec-
tion blade for unloading. Based on a maximum gross weight of 80,000 lb, legal payloads for com-
paction trailers are typically 16 to 20 tons, while legal payloads for open-top live-bottom trailers are
20 to 22 tons (U.S. EPA, 2003).
Transfer vehicles should be able to negotiate the rough and muddy conditions of landfill access
roads.

5.3.13.2 Rail Cars
Railroads carry only about 5% of transferred wastes in the United States (Lueck, 1990). As the dis-
tance between sanitary landfills and urban areas increases, however, railroads tend to become more
appealing for transporting wastes to distant sites. Rail transfer stations are usually more expensive