Transfer Stations
Planning and Designing Transfer Station and Materials Recovery Facilities to Support Zero Waste Initiatives
Jim Miller, Douglas Drennen and Stu Clark
Zero Waste initiatives, which seek to maximize solid waste materials recovery and minimize disposal of materials into landfills (i.e., maximize landfill diversion), are at an all-time high. These days, 鈥淶ero Waste鈥� is in the vocabulary of nearly every state, municipality and governmental agency. Maximizing landfill diversion requires significant commitment and efforts at many levels. Public and private participation, on the parts of individuals as well as businesses, are essential. It is evident that this commitment and these efforts are in place in many locations throughout the U.S., leading to the profound growth in landfill diversion regulations and Zero Waste initiatives.
History
The Clean Air Act of 1963 and its significant amendments, the creation of the EPA in 1970, and the passage of the Resource Conservation and Recovery Act (RCRA) in 1976 have transformed the solid waste industry. During the same general time frame as the passage of the original Clean Air Act, the public鈥檚 awareness and concern for the environment led to the 鈥淓nvironmental Movement鈥�, a significant, driving political force. Helping to launch the Environmental Movement was Rachel Carson鈥檚 1962 New York Time鈥檚 bestselling book, Silent Spring.Although, not directly related to solid waste, this book opened a previously non-existent public conversation on environmental concerns and the effect human behavior can have on the world we live in.
The next significant event that helped institutionalize the Environment鈥攁nd made it something policy makers would start (and continue) to pay attention to鈥攚as the first Earth Day on April 22, 1970. This achieved a rare political alignment, enlisting support from Republicans and Democrats, and people from all walks of life and social persuasion. The success of this first Earth Day was no doubt an influencing factor leading to the passage of the significant 1970 amendments that strengthened the Clean Air Act. In a few years the momentum would lead to the passage of RCRA, which included Subtitle D that specifically addressed the design, operations and closure of landfills. Hundreds of landfills closed rather than comply with Subtitle D requirements.
A consequence of these widespread landfill closures was the perception that the U.S. was 鈥渞unning out鈥� of landfill capacity. The icon for this publicly perceived 鈥渃risis鈥� became the Mobro 4000, a barge that made headlines for hauling more than聽3,000聽tons聽of聽trash聽from聽New York聽to聽Belize聽and then back again. The 1987 Mobro 4000 incident was widely cited by environmentalists and the media as emblematic of the 鈥渟olid-waste disposal crisis鈥� in the U.S. 鈥渄ue to a shortage of landfill space鈥�. It triggered much national public discussion about waste disposal, and has been credited as a contributing factor to recycling rate increases in the late 1980s and after.
The combination of all of these factors鈥攈eightened environmental consciousness, perception of shortage of landfill space, and increased costs for landfill disposal resulting from Subtitle D requirements鈥攑rompted many states and municipalities to initiate recycling regulations. Typically, early recycling programs had modest goals. However, over time, and in response to increased public interest, states and jurisdictions have expanded their recycling goals. Zero Waste initiatives are the latest attempt to capture the public and political will to maximize diversion and recycling.
The Recycling Industry
Most communities began with simple residential 鈥渃urbside鈥� recycling programs that included glass bottles, tin and aluminum cans and newspaper. However as the benefits of landfill diversion and recycling became clearer, these programs were expanded over time to add more and more commodities. Another contribution to the growth of recycling was the rise of commodities markets which started to expand and stabilize, creating a demand for materials.
Eventually the practical limits of being able to add more and more compartments on collection vehicles limited any further ability to expand collection services for recyclables. The obvious efficiency of collecting mixed (commingled) recyclable materials created the need to innovate on the processing side. This led to the development of the sophisticated sorting technology that exists today. This current technology has enabled, among other things, 鈥渟ingle-stream鈥� residential collection and processing to become a reality.
As single stream collection and processing have matured, the amount of targeted materials diverted from landfills has risen significantly. Many municipalities have adequate collection and processing for source separated recyclable materials from residential and sometimes commercial sources. However, the amount of these materials generated by the residential sector is generally limited to approximately 20 percent of the total waste stream.
Other strategies and processes that have gained momentum for diverting these additional materials include: accepting food waste for composting, processing commercial waste to recover recyclables in a mixed waste (dirty) MRF, improved specialty MRF鈥檚 for increased recovery of C&D materials and energy-from-waste conversion technologies.
The Role of the Transfer Station
As landfills closed and population grew rapidly starting in the 1960s, transfer stations became vital components of many solid waste systems. Early transfer stations were designed strictly to receive waste from collection trucks and self-haulers and then transfer that waste to larger vehicles for transportation to landfills. The tipping floor area required for the simple dump and load operation was comparatively small, and early transfer stations were often designed for 鈥渄irect dump鈥� or had receiving pits to facilitate the dumping process.
As population has continued to increase, demand for more transfer station space has increased proportionately. Adding to this is the need to incorporate more space for waste material unloading and staging of non-residential materials typically destined for disposal into landfills. Placing operations to recover those materials at the location where they are already received enables the operator to more fully use existing infrastructure and staff. For instance, source separation is effective in diverting certain waste stream portions, including C&D, green waste and food waste. When these materials are received at transfer stations, segregating and staging them require tipping floor space that may already exist and the existing loading equipment, staff and infrastructure can be used to transfer them to recyclers or to energy conversion facilities.
Fortunately, many transfer stations have adequate site space to accommodate expansion if needed, and recovery operations can typically be added within the limits of existing facility operating permits or with minor permitting revisions, whereas permitting a new facility could be lengthy and costly. Unfortunately many existing transfer stations are too small and improperly configured to accommodate the necessary operational changes for the needed services. The archaic direct dump and pit designs are especially ineffective and unsafe for added recovery operations.
Achieving maximum diversion typically requires providing additional public services including convenient and safe recycling and household hazardous waste drop-off centers. While these services usually are not conducted within transfer stations, they are often located at transfer station sites, further complicating site traffic flow and safety.
Moving Towards Making Modifications
Zero Waste initiatives and the desire to recycle are here to stay. As jurisdictions continue to develop new policies and strategies for recycling more materials, additional tipping floor space and improved operational flow will become essential. To meet the demands, transfer stations will no longer be single-purpose facilities and will need to transform into multi-functional solid waste processing facilities, and many municipalities have been or will be forced to modify, expand or add new facilities to meet their needs. The ability to successfully modify existing transfer and recovery facilities will significantly affect how much of the total waste stream can be diverted and recycled and the ultimate success of Zero Waste initiatives.
Jim Miller is CEO of J.R. Miller & Associates (Brea, CA). He ca be reached at (714) 524-1870.
Doug Drennen is Principal of Environmental Engineering Services for J.R. Miller & Associates. He can be reached at (714) 524-1870 or via e-mail at ([email protected].
Stu Clark is Principal at D. Edwards, Inc. (Brea, CA). He can be reached at (707) 395-0213 or via e-mail at [email protected].
Shoreway Center for the Environment, South Bayside Waste Management Authority, San Carlos, CA (SBWMA)
SBWMA operates as a special district responsible for managing recycling and solid waste services for 12 jurisdictions in the San Francisco Bay Area. Built in 1982, the original transfer station is situated on a 10-acre site located halfway between San Francisco and San Jose. Prior to the improvements, the Transfer Station was a 58,000 sq ft building with a large commercial tipping floor and a small self-haul tipping area. In the early 1990鈥檚, SBWMA started collection services consisting of dual-stream recyclable pick-up and yard waste on a bi-weekly basis for residents in each of its member jurisdictions. To process the dual stream recyclables, equipment was installed in an existing 48,000 sq ft building adjacent to the transfer station site. As SBWMA continued to add programs, new operations were added at the site, including a public drop-off for recyclables, e-waste drop off and segregated construction debris (see Figure 1).
The primary access road to the inbound scale was located between the two operations, requiring all traffic to use one access road. Both commercial collection and general public vehicles travelled in two lanes to one scale house. This single entrance caused several undesirable traffic circulation conflicts that created significant safety problems and operational inefficiencies. The situation was aggravated by the fact that the added new services increased customer traffic.
In 2005, with the goal of increasing participation and recovery/diversion, the Authority decided to convert to single-stream collection. To process the different material stream plus clean commercial and handle the anticipated increase in volume, the existing MRF system would have to be replaced by a new processing system and substantial changes to the MRF building would be required.
The Authority also wanted to enlarge the self-haul tipping floor because its small size created an unsafe and inefficient operation with little opportunity for materials recovery. This need for a significant capital improvement presented a fortuitous opportunity to consider other pressing needs, such as overall operational efficiency, employee and customer safety, more efficient traffic circulation, and better materials handling. The Authority sought to construct an educational center with viewing gallery and to gain as a minimum, LEED Silver certification.
Completed Improvement
The existing MRF building was demolished and replaced with a new 71,000 sq ft building. This size and configuration provided sufficient floor area for the single-stream and clean commercial MRF system, including staging for the increased volume of collected materials (see Figure 2). The existing 12,000 sq ft self-haul portion of the Transfer Station building was removed and replaced with a 21,000 sq ft building addition. This increased building area doubled the number of unloading stalls from six to 12 and provided a significant increase in material staging capacity. In addition, customer safety and the ability to recover self-haul materials were greatly increased (see Figure 3).
Other improvements included a relocated recyclables and E-waste drop-off in front of the MRF near the street鈥攁nother significant increase in customer safety as well as convenience. Now those customers using only these services will not need to drive to the back of the site, thus eliminating unnecessary traffic and congestion. A new Education and Environmental Center was also provided for conducting tours and providing educational events for schools or other civic organizations. In addition, the facility received LEED Gold certification.
Diversion Data
The improved facility and new processing system has produced the following increases in recovery/diversion:
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Converting to single stream residential collection resulted in a 29.5 percent increase in recyclables that were processed in the new MRF.
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Weekly residential pickup of organics resulted in 29.4 percent increase in recoverable materials over the previous year.
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Additional floor space provided by the transfer station expansion resulted in an additional recovery of wood, metals, OCC and used carpets from C/D waste.
The following is a comparison of the amount of materials recovered between the original and the improved facilities:
Volumes (TPY)
Waste/ Stream 2006 2011-12
Residential SS 32,000 41,000
Organics
(green + food wastes) 88,000 102,000
C/D waste 18,300 38,200
Total 138,300 181,200
After one full year of operating the new Shoreway Environmental Center, SBWMA has increased recycling by 31% or about 43,000 TPY. The Authority expects this number to increase as new programs and services mature (see Figure 4).
Figure 1
Existing SBWMA facilities.
Figure 2
New S.E.C. facility.
Figure 3
New transfer station floor plan.
Figure 4
New S.E.C. MRF and Education Center.