A transfer station can be likened to the center of a spider’s web with strings of roads carrying waste hauler traffic to the station. The extent of the web is the transfer station’s service area. As smaller hauling trucks feed waste to the station, the transfer station combines these loads for shipping in larger (usually open-topped) transport trucks for long-haul transport to a remotely located landfill for final disposal. These larger trucks allow for cost-effective shipping, as measured by cost per ton-mile. Such cost savings are important, especially with the increasing cost of diesel fuel.
Often lumped in together with materials recovery facilities (MRFs), transfer stations by comparison tend to be smaller in size. They therefore require a smaller property tract and use less floor space. Simpler in design than a typical MRF, a transfer station is usually not much more than a heavily reinforced concrete tipping floor enclosed with a prefabricated metal shed building and surrounded by access roadways and parking lots.
In addition to the tipping floor, the transfer station floor plan can include loading bays and access ramps. Impact loading from heavy equipment (usually wheeled front-end loaders) used to pick up the trash and load or push it to a desired location necessitate the use of heavy reinforcement in the form of railroad ties embedded in the concrete surface. Despite their differences in size, MRFs and transfer stations have several similarities (one type of facility can often be remodeled and transformed into the other). Material recovery can also be performed at modified transfer stations that have been equipped with sorting bins and separation equipment.
As well as the designed layout, the siting of a transfer station is critical to its performance. Regulations and operational concerns determine the proper siting of a transfer station. On the operating side, siting must ensure that the transfer station has enough area to enclose the facility, provide necessary buffers, sight screening, anticipated truck queuing so that truck movements do not interfere with local traffic patterns. Some inconvenience to local communities may result (especially in urban settings where area is at a premium), but this needs to be balanced by the job opportunities, economic growth, and tax revenues generated by the transfer station.
On the regulatory side, siting criteria set by local and state governments are typically exclusionary in nature. Therefore, transfer stations will not be allowed within other management operations. These usually preclude siting a transfer station in wetlands, 100-year floodplains, parks, bird sanctuaries and wildlife habitats, parks. There are usually set-back distances required for proximity to hospitals or domiciles. Transfer stations located in urban areas will also be limited to neighborhoods that have been zoned industrial or commercial.
On a larger scale, the location of the transfer station must be strategically positioned so as to minimize the costs of both short-distance waste hauling to the facility and long-distance waste transport from the facility to its final landfill disposal. Besides being centrally located as much as possible within the transfer station’s service area, transport costs both coming and going can be reduced by locating the transfer station next to a freeway and other major arterial roadways, provided the weight of the trucks do not adversely impact the pavement of the roads being used.
Whether or not a transfer station makes financial sense can be determined by a simple formula:
BEM = FC Ã· (CHC – THC)
BEM = Breakeven mileage, the distance from the transfer station to the landfill
FC = Fixed capital costs of the construction of the transfer station, as determined by the transfer station’s siting and design
CHC = Collection truck hauling costs, total for all trucks bringing waste to the transfer station
THC = Trailer hauling costs, total for all trucks shipping waste to the landfill
If the distance from the landfill to the transfer station is less than the BEM, the construction and operation of a transfer station is not financially justified. And to take advantage of economies of scale, much greater distances should be served by larger transfer stations.
EDGE Design & Engineering Innovation is a global leader in the design and distribution of a range of equipment including track conveyors and mobile conveyors used at transfer stations, MRFs, bulk materials handling facilities, and quarries. They specialize in the design and distribution of such equipment as track conveyors, mobile conveyors, trommels, direct-feed conveyors, quarry equipment, mobile screening equipment, bulk materials handling equipment, radial conveyors, radial stock pilers, radial telescopic conveyors, tracked telescopic conveyors, and wheeled stockpiling conveyors.
Tipping Floors and Associated Infrastructure
At the center of transfer station operations is the tipping floor. A general rule of thumb requires a minimum floor space of 4,000 square feet with an additional 20 square feet for each ton of waste to be received each day. For example, a 200-ton-per-day facility would require double the minimum size of 8,000 square feet. The initial facility design should also allow for the possibility of future expansion to allow for increased rates of waste receipt. The actual building itself is only a fraction of the overall facility size.
Once the waste is deposited on the tipping floor, a front-end loader (with an oversized bucket to accommodate large waste objects) is used to push, lift, and load the waste across the floor to the next stage in the process. To prevent damage to the tipping floor, wheeled loaders are used instead of tracked vehicles.
The actual designs of transfer stations can vary widely in complexity. The simplest designs include simply the tipping floor and an open-topped transfer trailer parked adjacently and set at a lower level. More complicated designs incorporate waste separation or waste compaction operations.
L&M Construction Chemicals makes specialized concretes and concrete surface finishes. Especially applicable to transfer station tipping floors is the company’s Emerytop 400. This material utilizes emery aggregate to create a surface that can withstand the pounding received by wheeled loaders and waste dumping operations. Most domestic emery aggregates have a low aluminum oxide and iron oxide content. While they provide good abrasion resistance, they are inadequate to resist impact conditions. The select emery aggregates used in L&M’s Emerytop 400 topping have a high aluminum oxide content of 58% for hardness, and a minimum iron oxide content of 25% for malleability. Emerytop 400 has very low drying shrinkage, making for good bonding to the substrate concrete. As a hardened cement paste, this material ensures a longer-lasting cement matrix paste to hold the high-grade emery aggregates in place for even wear. It also ensures that the penetration of chloride and other contaminants will be very low, offering unique protection from the penetration of chemicals (commonly found in waste) that deteriorate cement-based toppings from the inside, shortening their useful life. Overall, Emerytop 400 is durable under harsh transfer station conditions, providing protection against impact, abrasion, and chemical attack.
Delta Pacific (a subsidiary of Structural Preservation Systems) operates as a concrete restoration, chemical construction, and floor system contracting company. It specializes in chemical grouting, chemical-resistant linings, concrete repairs, epoxy floor and wall systems, epoxy injection, expansion joints, grouting solutions, joint sealants, protective coatings, and waterproofing. It offers services essential to preserving the integrity of concrete transfer station tipping floors, such as portable water blasting, concrete overlay, concrete restoration and preservation, concrete sealers, surface preparation and restoration, industrial floor repair, and spall repairs. Delta serves waste treatment industries in various markets nationwide.
A Canadian firm, MegaDome is a supplier of large tension fabric membrane buildings for transfer stations and similar enclosed facilities. These large yet light and flexible buildings provide an inexpensive method to protect tipping floor operations from wind and weather. Their module design allows for operational flexibility and ease of site expansion.
Waste Management and Separation
As mentioned above, transfer stations can also be used to perform auxiliary waste separation operations. Normally performed at MRFs, waste separation can be performed in section adjacent to the tipping floor. The size and configuration of this work area will depend on the type of waste to be segregated (ferrous and nonferrous metals, paper, plastics, glass, etc.). In general, the size of the waste separation operation will be limited by the need to perform the facility’s main task of waste transfer.
Once the waste is deposited on the tipping floor, a front-end loader (with an oversized bucket to
accommodate large waste objects) is used to push, lift, and load the waste to the next stage.
Schuyler Rubber Co. Inc. manufactures essential if not so glamorous products, such as laminated rubber cutting edges and rubber facility bumpers. Attached to the bottom edge of a wheel loader’s bucket, laminated rubber cutting edges are used in transfer stations and recycling facilities to prolong the wear life of concrete tipping floors. By softening the contact between concrete surface and hard metal edge of the bucket, laminated rubber cutting edges can cut the cost of repairing and replacing a tipping floor. This saves on the facility’s maintenance budget as well as operational downtime associated with the repairs. Each cutting edge is built to accommodate a specific bucket size. All of the rubber cutting edges have an innovative sliding T-track mounting channel for easy installation and replacement. Facility bumpers can be installed on walls, tipping floors and dumpsters to reduce noise and hard contact with these surfaces.
McCloskey International’s 621/628 Trommel Screener is suited for large heavy-duty applications where production rates can reach 200 to 300 tons per hour, depending on the type of material being processed. It uses a 174-horsepower Tier III Cat engine, accessible engine bay, and high-efficiency diesel hydraulic system. Its 6-foot diameter ensures strong screening action from its rotation while its 21-foot length ensures high-quality production. For a longer screening time, the 628 trommel offers a drum that is 4.5 feet longer.
Krause Manufacturing engineers and builds high-quality, long-lasting automated sorting systems for construction-and-demolition (C&D) waste. These systems have been used at dropoff box services, transfer stations, C&D recyclers, and MRFs. The company can custom design, fabricate, and install to an operator’s exact specifications. A turnkey system from Krause is built to survive the harsh environment of a transfer station. Krause Manufacturing and its sister company, CP Manufacturing, have a combined total of over 80 years of machinery and recycling equipment experience. Their engineering departments use the latest in CAD development software, including SolidWorks 3D. Krause’s fabrication shop utilizes a plasma cutter; a 600-ton, 20-foot capacity, numerically controlled press brake; a 36-foot swing, 10-feet-between-centers lathe; and a 318-foot by 10-foot capacity shear. Krause’s product lines now include turnkey conveyor systems, disc and trommel screens, catwalks. and very heavy-duty conveyors.
Northshore provides Builtrite handlers and attachments for waste handling equipment used in transfer stations. The company’s Model 80 and Model 2100 remotely operated handlers are designed to reduce operating costs by streamlining the material handling facet of the job. In transfer stations this can be done by maximizing weights in trailers leaving the site and by improving sorting, loading, leveling, and topping. The remote operation system improves onsite safety while providing superior separation and sorting capability. Unlike wheeled loaders which can only push and lift material, Builtrite Handlers allow operators to reach below grade for better trailer topping and tamping
Movement and Compaction
Some transfer stations also use waste compaction equipment in order to maximize the waste’s density. Such a facility uses a surge pit, a lower level of the tipping floor that allows for temporary storage of waste from peak inflows. In the confined space of the surge pit, equipment can push waste up against a side wall, increasing its density and reducing the number of truck needed for hauling waste to the landfill. This reduces the overall cost of long distance hauling associated with the transfer station operations.
Some surge pits dispense with the need for equipment compaction by utilizing hydraulic rams and precompactors to achieve even higher densities. Installed in one side of the surge pit, hydraulic rams exert very high pressures as they push the accumulated waste into the opposite wall. Precompactors take this further by pushing waste into a tube, achieving a very high density waste “log” that is then ejected into the back of the transfer trailer by the truck bed’s walking floor.
Volvo’s wheeled loaders come with such standard features as the high-efficiency Volvo power train, including a high-torque at low-rpm (1,100- to 1,600-rpm) engine, designed together with high-flow, load-sensing hydraulics providing fast hydraulic speeds and high fuel efficiency, a fuel-efficient lockup torque converter, high-traction differential locks for both axles, and a hydrostatic infinitely variable transmission. Operator comfort and efficient productivity is ensured by cab filtration, ergonomically placed switches, adjustable seat and steering wheel, low internal sound levels, CareTrack telematic monitoring system, and the Contronics/MATRIS, onboard diagnostic systems.
The Case 621F and 721F wheeled loaders are well designed for efficient transfer station operations. They come equipped with factory installed protective guards in 16 key areas, a mid-mounted cooling module, and advanced air filtration components for working in concentrated dust-and-debris-filled environments like a transfer station tipping floor. It uses proven selective catalytic reduction (SCR) technology to meet Tier 4 interim emissions standards while also delivering increased power and improved fuel efficiency. Meeting these stricter emission standards can be very important to a transfer station sited in an urban area. The Case 721F wheel loader features a 6.7-liter engine, rated at 179 horsepower for heavy-duty applications. “Case developed an unobtrusive factory-born waste handling package because our waste and scrap customers want an OEM solution purpose-built just for their jobs,” says Rob Marringa, brand marketing manager, Case Construction Equipment. “Reliability and durability are their utmost concerns. They want the reassurance that their wheel loaders will survive the operating environment, and a factory-installed solution, backed by Case, gives them that confidence.”
Caterpillar is famous as a manufacturer of rugged construction equipment, the kind of equipment perfectly suited for the harsh environment of a transfer station. Caterpillar wheel loaders come with both standard and optional guarding on major components and systems. These wheel loaders are referred to as having waste handling arrangements which provide increased productivity, reliability, operator comfort and safety. Optional features include a radiator guard which provides protection to the grill, cooling fan, radiator and condenser cores. An external add-on, this guard is easily hinged to allow easy access for cleaning and maintenance. An often neglected part of the wheel loaders are the wheels themselves. Caterpillar wheel loaders can be fitted with Flexport Extreme Duty solid tires. These are designed with holds molded through the outer ring of the tire’s sidewalls. These holds improve tire flexibility and stability, allowing the tires to handle tipping floor surfaces with a greatly improved ride compared to that of other solid tires.
Waste from the tipping floor can be fed into a baler, which then compacts the waste into a high-density bale that is then often wrapped in wire mesh. This shape is usually a rectangular block whose dimensions can vary from 3 feet to 8 feet. The waste bales are then lifted into the back of the transfer trailers by means of forklifts.
Enterprise Baler Co. is a 49-year-old family owned and operated business. Based in California, Enterprise is a company with worldwide sale having established 1,600 operations from China to Latin America, and in the US from Anchorage to San Diego to Boston. One of the company’s largest facilities is a three-stream sort system in San Francisco that processes 2,500 tons per day, making it one of the largest in the country. The balers come equipped with a floating feeder that is designed to provide the baler with a constant, optimal flow of material even when fed from bunkers, overhead storage, or walking floor hoppers. Not just an equipment supply company, Enterprise has an experienced team of engineers that can design a sorting system for transfer stations and MRFs to an owner’s specifications.
International Baler Corp. produces a wide variety of configurations, sizes, and costs based on the materials being recycled and the output demands (such as multiple materials, custom-size bales, or super-high production). IBC can custom build a cost effective application that fits a transfer station’s specific needs. IBC offers over 200 different standard models of baling equipment including vertical balers, horizontal balers, auto-tie balers, and two-ram balers that are engineered to custom-fit each customer’s specific needs. The company also offers many models of specialty baling equipment for products like foam, textiles, and rubber, as well as such ancillary equipment as conveyor systems, fluffers, and dumpers.
The American Baler Co.’s 42WS Balers are designed for small to medium MRFs, transfer stations, and independent paper brokers. The 42WS Balers, with their wide-mouth feed openings, are useful for bundling flattened OCC. Three types 42WS Balers offer three different cylinder sizes and production rates (from 5 tons per hour to 25 tons per hour) and wide-mouth feed openings to handle the majority of materials that are found in a transfer station.
The waste that arrives at a transfer station eventually finds its way into open-topped transfer trailer trucks parked in bays adjacent to the tipping floor and sure pit. These bays are set with floor elevations lower than the tipping floor, low enough to allow easy loading from the top as a front-end loader pushes the waste from the floor. Sometimes, waste is loaded horizontally from the rear of the truck either by hydraulic machinery, forklifts, or a live floor installed in the truck bed. The bays are large enough to accommodate one or more trucks. The trailers are often parked for extended periods of time, providing storage until the waste is transported to the landfill.
The rate at which waste can be unload from collection trucks and the rate it can be loaded into the transfer trailers both affect the size of the landfill. The two rates (incoming and outgoing) depend on the collection vehicle payloads, area of the tipping floor, hours of operation each work day, the ratio of the peak number of arriving trucks to the average number of trucks during a 30-minute work interval, transfer trailer capacity, the number of trailers that can be loaded at the same time, the productivity of the equipment loading the transfer trailers, as well as their queuing and positioning times.
For over 20 years, Mr. Bult’s Inc. (MBI) has been the largest provider of long-haul waste transportation in North America. As experienced providers of equipment for waste transport, transfer stations and landfill tipping operations, MBI has the most extensive fleet of equipment in the industry. It has over 4,000 total pieces of equipment, including 1,300 trucks (over half of which are less than 3 years old), 2,500 trailers of all types (tipper, walking floor, van, flat bed, lowboy, and intermodal), over 100 pieces of loading equipment (wheel loaders, skid steers, etc.) and nearly 100 Columbia trailer tippers, as well as various service trucks and support equipment.
Transfer Trailers and Waste Transport
If collection trucks are the workhorses of transfer station operation, transfer trailers are the show horses. These trucks make building and operating a transfer station worthwhile, since their larger capacities achieve economies of scale that greatly reduce overall transportation costs. It is far cheaper to move large quantities of waste long distance in fewer transfer trailers than smaller quantities of waste in more numerous collection trucks. Fewer trucks also means lower overhead with less maintenance and greater fuel efficiency.
Cardinal Scale’s Guardian Hydraulic Truck Scale is designed for a high degree of weighing accuracy and longevity in hostile environments, such as tipping floor applications in transfer stations. These scales are impervious against lightning and water damage, two of the most common issues to affect electronic load cell truck scales. These NTEP legal-for-trade truck scales are available in concrete or steel decks and low-profile or pit-mount types up to 135 tons. As a solution for the problem of truck scale operations in hostile environments, Cardinal Scale’s Guardian hydraulic truck scale is designed with a 24-inch I-beam structure and 7-inch-thick concrete platform that utilizes 75,000-pound hydraulic stainless-steel load cells. In addition to the Guardian, Cardinal provides the SnapStream, a fully integrated NTEP legal-for-trade wireless scale system for commercial applications. SnapStream allows a scale to send weight data wirelessly to an indicator and the indicator in turn to send that data wirelessly to a host of peripheral equipment such as remote displays, printers, PC’s and networks that are commonly used in transfer station truck scale applications. A digitally controlled weighing and diagnostic system, SnapStream may be used with Cardinal’s model 205, 210, and 225 digital weight indicators, where scale diagnostics can be viewed directly on the indicator without having to go to the scale itself.
Mac Trailer Manufacturing is a foremost leader in the manufacturing of tipper and moving floor transfer trailers. Its designs recognize the importance of constructing a trailer that will withstand the impacts and abrasive operations associated with the loading and unloading of waste and other bulk materials. Their moving floors are made of fully welded aluminum sheet and post with side skins to a gauge of 0.250, or the smooth sided “MVP” (Mac Vertical Panel) Maclock configuration that incorporates two-and-a-quarter-inch hollow core aluminum extruded panels. The company’s Mac Tipper, which maximizes volume with tare weight, utilizes tapered designs with lengths to 53 feet and volume capacities up to 148 cubic yards. Mac provides axle configurations from triaxle to eight axles, to multiple spreads and lifts or sliders.
Vulcan On-Board Scales’s product line includes truck scales specifically designed for transfer trailers. The Vulcan transfer vehicle scale system includes fifth-wheel load cells plus a unique center hanger mounting kit and Super-Beam load cell. Rugged, all-digital Vulcan air sensors are also available if the truck or trailer utilizes an air suspension instead of spring suspensions. Vulcan VSL electronics allow unlimited mixing of trucks and trailers without any adjustment. Options are available to provide weight information to loaders or scoreboards in the transfer station.
East Manufacturing Corp. is a provider of transfer trailers as well as associated equipment such as sheet-and-post tipping platforms and live floors, as well as the company’s Genesis tipping platform and live floor. Its Genesis systems provide a smooth-side design that maximizes both payload capacity and durability while ensuring operational savings. With an aerodynamic design, Genesis transfer trailers use less fuel, achieving 5% to 10% better mileage.
An open-topped transfer trailer needs a cover. And that’s where tarp manufacturer like Roll-Rite LLC comes in. Its Quick-Pick Systems provide a high-capacity tarp housing that can be easily installed on 48-foot by 53-foot transfer trailers. It is a complete, prepackaged electric tarp deployment system that includes electric motor, high capacity tarp spooling housing, 16-spring underbody mount pivot set, tarp bow set, wiring, and other components needed for easy deployment over dump truck and transfer station loads.
Mountain Tarp provides a side-roll tarp deployment system for open topped transfer trailers. The company’s Lock-N-roll tarp system provided waterproof coverage for transfer trailer loads.
Constructed of aluminum framingand a fabric bonnet, the tarp can eitherbe temporarily strapped into place or permanently installed. The permanent installation uses a simple, removable hand crank for ease of deployment. It also comes with attached nose and tail sections, making caps unnecessary.
Live Floors and Landfill Tippers
Once the transfer trailers reach their destination, the problem of how to best off-load these over sized trucks at the landfill working face presents itself. Live floors installed in the truck bed make this operation easier. Live floors operate on a basic principle based on independently moving planks or slats running horizontally the length of the floor bed. By moving in sequence from adjacent to the cab to the open end of the truck bed, live floor planks (usually three at a time) move in sequence to create a kind of wave motion that lifts and pushes the waste towards the open rear. These movements are repeated until the truck is emptied. Live floors eliminate the need for heavy-duty jacks to lift and tilt the load like a dump truck.
Portable and fixed tippers alike are available for the smooth and controlled management of waste disposal at the landfill workface. With a dedicated tipper there is no need for potentially expensive self-unloading trailers. This saves on overall truck weight, allowing the transfer trailers to carry even heavier loads.
Wilkens Industries Inc. has been manufacturing trailers since 1985, providing a wide variety of trailers for multiple needs. The company’s equipment line includes live floor trailers, push-outs, and tippers. It can also build trailers to customized specifications. Wilkens manufactures the X Series transfer trailer. This patent design allows direct transfer into the trailer from the route truck with the use of a loading dock. It represents a new and cost-effective approach to transporting solid waste in rural or remote areas, as well as inner cities. To provide a wider variety of trailers, Wilkens deals in both new and used equipment.
Keith Manufacturing manufactures the Walking Floor unloader, designed for easy removal of waste from a transfer trailer without the need for tipping. The company’s Walking Floor system can handle pallet and bulk material loads because of its unique horizontal unloading/loading design. The company manufactures mobile as well as stationary Walking Floor systems.
J&J Truck Bodies & Trailers provides several models of transfer trailer trucks, including the DynaHauler Steel Push Out (SPO). This steel push-out trailer is designed to haul either municipal waste or commercial/industrial waste. It comes equipped with a hydraulically driven steel push-out plate that allows it to eject waste horizontally directly out of its rear door. Horizontal push out eliminates the need for a tipper at the landfill workface. The DynaHauler/SPO is manufactured from high-grade steel and is available in standard sizes ranging from 65 to 92 cubic yards, or to custom lengths and sizes.
Phelps Industries’ low-profile landfill trailer tipper is designed to be easily moved and relocated via over-the-road transport. It can be quickly modified by unpinning and removing several major components that amount to a second trailer load, which includes its own self-contained diesel-powered hydraulic power unit. The Phelps tipper can then raise itself in front for coupling to a truck/tractor or converter dolly for relocation and setup (which can be accomplished in only 15 minutes). Typically, the tipper is set up at the working face of a landfill. The ease and simplicity of relocating the tipper allows for flexible operations in multiple disposal cells during the operational lifetime of the landfill.So with the right combination of design, equipment, vehicles and process flow any transfer station can be a winner. By tailoring the layout of the tipping floor, truck access, equipment operations to anticipated flows while allowing for future expansion, an operator can ensure that he has a world champion transfer station.