It sounds
simple enough. Collected waste is hauled to a centrally located facility, called
a transfer station, instead of being taken directly to a
landfill. At the transfer station, the waste from multiple collection routes
gets deposited on a tipping floor, where front-end loaders and other equipment
push it into large, open-topped transfer trailers parked and waiting in a bay
below.
The aim is
basic to any successful business: save money. Consolidating larger amounts of
waste into fewer transport platforms achieves economies of scale that reduce
overall transportation costs. Measured in cost per ton-mile, it is far cheaper
to move waste in larger semi-trailers designed for long-distance hauling than in
multiple waste-collection trucks designed to gather and compact waste at pickup
points along a relatively short collection route. The former requires less labor
(fewer drivers), less maintenance (fewer and simpler vehicles requires less
extensive maintenance), and a more efficient power plant (utilizing fewer
gallons of diesel per mile when loaded).
However, the
devil is always in the details. Creating a work space where the waste from
multiple collection trucks can be consolidated and transferred to fewer, larger
transport trucks involves more than just pouring the concrete for a tipping
floor and pushing the waste into the transport truck with a front-end loader.
The waste material has to be prepared for shipping and accurately weighed;
loading and offloading waste has to be done in the most efficient manner
possible; communication with the hauling trucks has to be continuous to ensure
timely routing and dispatching; access and exit movements by trucks have to be
properly choreographed to ensure steady material flows.
Why
Transfer Stations?
It is too often
forgotten that companies—even waste management companies—are in business to make
money. It is inherently inefficient (that is, expensive) in term of dollars per
ton of waste times the mileage traveled to the haul waste long distances in
relatively small waste-collection trucks. The trucks that pull up to your curb
once a week and pick up your household waste are not designed for long-haul
transport. They are designed to efficiently gather and compact relatively large
quantities of loose waste and then haul it the comparatively short distance to
the local landfill.
Transfer
stations are relatively compact structures consisting of a few basic structural
elements. Entrance to the facility is via an access roadway or ramp that directs
truck traffic to the open bay(s) of the transfer station. These bays typically
consist of reinforced concrete floors enclosed by prefabricated metal building
structures. The floors are not reinforced with steel rebar only. Further
protection from the impacts of dropping and pushing waste and the movement of
heavy equipment is often provided by steel rails set in the surface of the
concrete floors. These rails are oriented in the direction of waste movement
(towards the lower bay) and extend slightly above the concrete surface.
Depositing
waste from collection trucks and loading waste into transfer trucks both occur
on the transfer station’s tipping floor. Adjacent to and below the tipping floor
is the receiving bay. This is a recessed ramp long enough to contain at least
one transfer truck and deep enough so that the surface of the tipping floor is
somewhat higher than the top of the truck’s trailer. Safety rails and guide bars
are used to direct personnel and workflow. The preferred method of moving
deposited waste from the tipping floor to the trucks is the front-end
loader.
Loading and Offloading
This front-end
loader is the workhorse of the transfer station. Unlike its tracked cousin
operating at the working face of a landfill, the front-end loaders utilized by
transfer stations are equipped with wheels to prevent damage to the concrete
surface of the tipping floor. Equipped with an oversized bucket originally
designed to scoop up and lift large quantities of relatively low-density
materials, the front-end loader can be easily modified for operations in a
transfer station. The first modification would be to replace the standard bucket
with a specially designed refuse bucket. The refuse bucket has an additional
spill plate welded onto the back of the bucket to protect the operator from
being struck by spillage.
This is
especially important since waste is very heterogeneous, both in material
characteristics and object sizes. Often, parts of the waste material are so
light and low-density that they can easily fall off or even get blown off the
heaped pile of waste being pushed by the bucket. Airborne parts and materials
can cause serious damage to the front-end loader’s drive train by clogging air
intakes and covering up the radiator, causing he engine to overheat. In addition
to protecting the driver and the cooling system, wheeled front-end loaders are
also equipped with strike bars that prevent waste from wrapping around the
axles.
Material Preparation
Some material
preparation occurs in the waste-collection trucks themselves as they compact
their loads during pickup and delivery. On average (with wide variations,
however) waste at the curbside has an average density of 0.10 to 0.17 tons per
cubic yard (approximately 7–12 pounds per cubic foot). Compactors inside the
waste-collection trucks reduce the volume of waste by about 50%, effectively
doubling the density of the waste to approximately 0.20 to 0.35 tons per cubic
yard (roughly 15–25 pounds per cubic foot). Additional compaction is rarely done
at transfer stations that utilize truck transport. However, baling operations
that compact and bundle waste into tight “bricks” are often performed at rail
transfer stations. The loads of compacted waste are lifted via a fixed crane
into the open top of the train’s freight cars.
Weighing
Waste loads are
weighed by having the waste-collection trucks drive over truck scales installed
at the transfer station. In-ground scales can be installed in recessed pits or
else directly on flat ground. In the first case, the elevation of the surface of
the scale is flushed with the adjacent pavement. In the second case, the scale’s
surface is somewhat higher than the pavement and can be accessed by means of
approach ramps.
The weight of
the truckload is measured by a series of load cells attached to strategic points
on the frame of the scale structure. The weight of the loaded truck either
deforms the load cells or increases their internal pressures. Deformation is a
function of the stiffness of the load cell’s materials. In most cases, the load
cells deform slightly under the applied loads and elastically return to their
original shape once the load is removed. Electrical sensors measure the
deformation of the load cells’ body and send electrical or (if the load cell is
pressure activated) hydrostatic signals to a monitoring station. By tallying the
readings from all the individual load cells in the scale, relating the measured
deformations to the load cell material’s elasticity, the station can determine
and display the vehicle’s weight. The trucks are weighed twice: once when they
enter the facility to get a weight when fully loaded and once when leaving the
facility to get a weight when empty. The difference between the two weights is
the weight of the waste load deposited at the transfer station.
A good example
of a truck-weighing system that has been successfully integrated into transfer
station operations is that of the Survivor truck scales manufactured by Rice
Lake Weighing Systems. Designed for durability and long-term performance, these
scales are constructed of structural steel arranged in a support structure whose
innovative design is intended to promote greater accuracy, less downtime, and
greater operational lifetime. Several different models are available
(aboveground, recessed pit, and portable) and can be custom built to exact
specifications.
Results of the
weighing operations are clearly indicated (even in direct sunlight) on the
unit’s M-Series remote display. Its Intellibright feature uses a photo sensor to
read available ambient light and adjusts the brightness of the display
accordingly. The display apparatus provides readings from the unit’s MHMI
digital weight indicators. The company’s Model 920i programmable HMI
Indicator/Controller provides open connectivity to standard networking
interfaces. A single 920i indicator is capable of handling multiple scales,
storing, manipulating, and reporting data. Hard copies of this accumulated data
are issued from Rice Lake’s ATK automated ticketing kiosks. The quick
availability of weight tickets produced by a user-friendly interface reduces
truck queuing and increases material movement efficiencies.
Dispatching
Communications
with incoming waste-collection trucks and outgoing waste-transfer trucks is
important to avoid unnecessary waiting caused by queues. Timing is everything,
and detailed scheduling is established and ensured by communications and GPS
tracking of incoming and outgoing traffic to ensure proper timing. Communicating
with your vehicle fleet is not just a simple matter of talking to the driver
over a two-way radio; a traditional CB radio will do that.
Today’s
dispatching operations require more sophisticated tools to facilitate broader
integration between operations and real-time data transfer. As solid waste
operators continue to struggle with rising costs, the need to integrate systems
and measure performance has never been greater. An example of a product that
allows for this higher level of communication is the system provided by
Routeware. Led by experienced solid waste industry veterans, Routeware recently
unveiled its “Smart Truck” technology, which is designed to manage key operating
variables in real time. What’s more, the system is capable of integrating with
key elements of a transfer station operation to seamlessly link truck weights
and scale systems.
The fully
integrated “brains” of the system, the DMS 5000, integrates with a GIS-based
routing system to route vehicles and show locations efficiently, all in real
time, while capturing relevant service data and exceptions. This data enables
the fleet to operate and dispatch more effectively from pickup to the transfer
station. Routeware also has the ability to create custom packages and reports
that leverage a wide array of add-on features, including: scale integration,
digital camera and video capability, maintenance diagnostics, and RFID
technology for service verification or container inventory purposes. The DMS
5000 is capable of organizing operational data into one
easy-to-access-and-utilize package that is based on the operational and
reporting needs of the customer. Wi-Fi allows for the real-time transmission of
all of the integrated activities, making it simple to monitor the progression of
routes and facilitate changes.
The addition of
scale integration is a significant feature of the Smart Truck technology because
it allows for onsite verification of container weight and collation of customer
data, which can be critical to maintaining proper customer pricing. In addition,
the scale integration feature can provide the means to monitor and optimize
available truck capacity and to avoid dangerous and costly overweight situations
on route and transfer vehicles. Weight data captured by the onboard scale system
can also be directly integrated with third-party scales at a transfer station,
landfill, or other destination.
Truck-mounted
cameras can record virtually all route activities and serve as proof of service
exceptions, eligible for additional charges. The digital photo function allows
the operator to save and organize photos by customer, location or other service
records specified by the operator, creating a visual record of the service
rendered. The DMS 5000 can be integrated with a maintenance diagnostics program
to monitor engine hours as a precursor to preventative maintenance schedules.
The RFID feature automatically reads passive tags on containers to match and
verify loads to customers and locations, and to create a daily log relative to
containers or other assets located in the field.
Routing
Routing is the
planning performed prior to dispatching the trucks on their collection and
hauling routes. It is done to determine the optimum routes to be traveled by the
collection and transfer trucks entering and leaving the transfer station. Until
the advent of intelligent software, this task was usually more art than science.
Routing software searches out the most efficient routes possible (routes that
avoid dead ends and backtracking). Any truck movement that results in a truck
retracing its steps is wasted movement and a loss of time and money.
Soft-Pak Inc.
provides an entire suite of software management systems for the waste industry
in general and truck routing in particular. Its “i-Pak” integrated software
system that emphasizes inventory tracking, routing, and productivity. i-Pak’s
Vehicle Management module tracks the performance of rolling stock (trucks,
equipment, and vehicles) and stationary support equipment (bailers, compactors
and container). So, in addition to choosing the most profitable route from a
time and distance point of view, i-Pak can also track the actual productivity of
individual trucks and the profitability of their various routes. e-Pak is a
secure Web-based extension of the i-Pak system that allows complete i-Pak
functionality without the need for additional hardware. e-Pak can work with
existing personal computers with the option to use offsite data backups.
MarBorg
Industries is a 75-year-old Santa Barbara, CA–based solid waste and recycling
company that has utilized Soft-Pak systems since 1997. Derek Carlson, business
manager for MarBorg, has this to say about Soft-Pak and the advantages it
provides his company:
“Many things
have changed in the industry in the past decade, but Soft-Pak has always enabled
us to stay ahead of the curve. The most valuable benefit of using Soft-Pak is
that it is a comprehensive turnkey system that links and tracks every line of
our business so we do not have to waste time and money duplicating our efforts
across different systems. A prime example of this integration is the development
of the company’s Scale-Pak module, which takes the transactions from transfer
stations, landfills, and recycling centers and automatically updates customer
accounts for billing, tracks material inventory in and out, gives jurisdictional
reporting and, of course, generates certified weight tickets. Before we utilized
Scale-Pak, we would have to double- and triple-enter the same information to get
all the benefits that we now receive automatically by using Soft-Pak in
conjunction with Scale-Pak. We used to take the weight tickets that were
generated at the various facilities and re-enter them into our billing system
and then enter the information again in order to track inventory and perform our
diversion reporting. Now, once the transaction has been completed at the scale,
all of this information is automatically disseminated throughout the system,
updating customer accounts, inventory, and diversion reports. We have saved
hundreds of thousands of dollars in operational and administrative efficiencies
over the past several years by using the fully integrated Soft-Pak systems.”
Desert Micro
also provides a software package that can be utilized by waste haulers to
optimize collection truck routes. Its Route Manager combines the tasks of
managing billing, collections, dispatching, routing, and operations.
In addition to
a complete customer database and the daily tracking of truck operations, Route
Manager provides routing layouts and a transaction history of route changes and
their effects on the bottom line. It can mange and integrate an unlimited number
of routes. Route sequencing can be done in real time with stop highlighting,
route splitting, or route combination. Each stop along the truck route can be
annotated with detailed notes and comments, facilitating both operations and
planning.
Operations
Inside the
transfer station, waste-handling operations are performed to efficiently
transfer waste from the smaller collection trucks to the larger transfer trucks.
Here, the human element comes into prominence, as spotters and operators must
coordinate and communicate effectively to prevent waste from building up on the
tipping floor.
Transfer
trailers are the end point of the station operations. All the deposited waste is
directed to the open top of a transfer trailer parked in a lower bay adjacent to
the tipping floor. The ability to quickly and efficiently top-load a transfer
trailer increases dramatically with an East Manufacturing Genesis
tipping-platform transfer trailer. The design of the Genesis sidewall eliminates
the need for the center bar or pipe that has traditionally bridged the
sidewalls’ midsection across the top.
To avoid damage
to the cross-pipe when top-loading a trailer, an equipment operator is forced to
load at the front and the back of the trailer, creating two uneven mounds of
material. A center bar decreases loading efficiency by effectively splitting the
trailer’s loading zone in two and making packing a challenge.
Without a
crossbar in the way, East Genesis tipping-platform transfer trailers can be
loaded faster, cleaner, and more efficiently. And a more even distribution of
the load allows operators to improve load densities, yielding higher
profits.
In addition,
the Genesis has a smooth-sided design that maximizes load capacity and improves
operational aerodynamics to improve gas mileage. Structural strength is ensured
by 2-inch-thick sidewalls supported by internal ribs every 3 inches. Additional
width of up to 4 inches increases the overall volume capacity of this model by
up to 5.75 cubic feet compared to a traditional sheet-and-post sidewall. The
East Genesis Tipper’s advanced design—extruded sidewall panels, floor-to-wall
junction, and heavy-duty top rail—combine to add the extra strength needed to
keep wall flexing to a minimum.
Unloading the
transfer trailers when they reach their destination is made simpler with the use
of live floors. Live floors may seem complex, but in principle they are actually
quite simple. The floor of the transfer trailer is equipped with planks or slats
that extend horizontally along the trailer floor. The planks are grouped
together in units of three and move back and forth lengthwise in the trailer.
The first group
of every third plank moves back toward the truck cab and away from the discharge
opening in the trailer rear. Then, the second group of every third plank moves
into position, which is then followed by the third group. By doing this movement
in intervals of three, the truck’s load is not forced back into the trailer
since two out of the three planks (and the loads on top of them) remain
stationary. When all three groups have been moved back into the trailer, all the
planks then move forward toward the open end of the trailer. This carries out
the load toward the open end, where it is partially discharged. The truck itself
inches forward as the load comes out the back. The process is repeated until the
entire load is discharged. This mechanism allows for the easy offloading of
large transfer-trailer loads without the need for hydraulic jacks to tilt the
load like a dump truck.
Keith
Manufacturing Co.’s Walking Floor system uses fewer moving parts in order to
minimize wear and tear, maintenance, and repair. This hydraulically powered
system stores waste material until it is ready to be conveyed to a compactor or
other processing equipment.
Custom-engineered to the specific
needs of each transfer station, Keith systems can withstand the impact of heavy
materials and loading equipment. Power requirements are low, and no additional
energy is needed for startup. In addition to municipal solid waste, the Walking
Floor systems are suitable for scrap tires, scrap metal, cardboard, plastic,
aluminum, and baled paper. A wide variety of floor slats are available to handle
highly abrasive loads, such as construction and demolition debris.
Trailers
outfitted with a Keith Walking Floor unloader improve transfer station
efficiencies through the ability to unload quickly and indoors. Floor slats run
the length of the trailer and are powered by a tractor-mounted power takeoff
hydraulic pump to unload the material.
Trailers
located at the dumping areas in the transfer station provide an inexpensive and
simple solution to waste collection and disposal. Trailers store the waste until
it is ready to be transported to the landfill. Then the trailers are taken to
the landfill, where the waste is easily unloaded.
Once fully
loaded, the semi-trailers carrying the accumulated waste are usually covered
with tarps. Tarps perform double duty, protecting the load from the elements
while they protect motorists from objects falling from the truckloads. The need
for tarps is codified into every state law and regulation concerning roadway
safety and protection from litter.
Tarps can be
manually deployed and tied down by the station crew, or else mechanically
deployed by the truck driver, as with rolling tarps. In most cases, automated
rolling tarps are preferred for their greater efficiency and enhanced
operational safety. These rolling tarps consist of a support structure made of a
series of bowed frames, each of which is anchored to the truck sidewalls by
rollers that allow them to slide forward and backward—expanding and contracting
like an accordion. Being bowed or arched allows the frame to avoid contact with
(and abrasive wear and tear from) the accumulated waste load.
Cramaro
Tarpaulin Systems of Newark, NJ, provides a complete product line of tarp covers
for transfer trailers.
The company’s
“Slide ‘N Go” system covers and uncovers a heaped waste load in only a few
seconds. A flexible cable design allows for safe on-ground operation.
The opening and
closing operation is performed manually by a foldaway hand crank connected to a
belt or chain drive, or else by a 1.3- to 1.8-horsepower electrical motor with
heavy-duty gearing and 6-gauge duplex wiring for high-current loads. The bows of
the cover frame are designed for long-term durability, covered with plastic
sleeves and arranged in a configuration that allows compaction to a width of
only 18 inches when not deployed. The tarps are vinyl, waterproof, one-piece
construction sheets with out seams.
Landfill Gatekeeping
A
transfer station, like any other industrial or construction site, is inherently
dangerous to people who are unfamiliar with its operations. In order to protect
the public, transfer stations are usually sited in isolated locations and/or
surrounded by security fencing. The use of security fencing can also serve to
keep blown litter in as it keeps trespassers out. Fences can also be equipped
with litter-screen extensions made out of fine mesh that will protect adjoining
properties from blown debris. A properly installed fence will also be dug into
the ground to help repel burrowing vermin.