DESPITE ACCOLADES IT HAS received, the city of Phoenix knows there is always room for improvement — particularly in transfer station design. In 1995, the city opened its first transfer station/materials recovery facility (TS/MRF), which received national and international acclaim for its innovative, attractive and multi-functional design. However, what was seen as a state-of-the-art design led to unforeseen operational problems. So as the city began designing a new TS/MRF, it decided to incorporate the city's value of “learn, change and improve.”
Phoenix formed three committees of experts to develop a list of ways to learn from the past. Many elements on the list are being incorporated into the construction of a new TS/MRF facility, called the North Gateway Transfer Station and Materials Recovery Facility.
When Phoenix developed its first TS/MRF, called the 27th Avenue facility, the design focused on building a facility for the community, its people, the environment, education, and, of course, recycling and managing solid waste. The facility used recycled materials in the construction. Solar lighting was captured through skylights equipped with computerized solar tracking devices, and a truck wash was built that used recycled wash water. A misting system above the transfer hoppers was designed to suppress dust and, in the hot summer, to double as an evaporative cooling system for the operating floor.
However, building a “green” facility that also was interactive for students and community organizations led to some problems. So as Phoenix began designing its new TS/MRF, it wanted to learn from its operational experiences and not duplicate design features that negatively affected operations.
The city created a committee comprised of 25 people involved with TS/MRF operations to develop a list of design features that could be improved. The following are suggestions transfer station designers might want to consider.
Can't Change Behavior
At Phoenix's 27th Avenue facility, the city designed a 43,600-square-foot tipping floor to save capital. The city believed a smaller tipping floor would be adequate because it wrongly assumed customers would stagger their disposal trucks' schedules to avoid arriving simultaneously with other trucks. This was a major mistake, staff learned, because customer delays occurred when everyone arrived at the facility at the same time. Assuming customers will alter their operations should not become the basis of a TS/MRF design.
At the North Gateway TS/MRF, Phoenix is constructing a large vehicle tipping floor that is more than 10,000 square feet larger. A separate small vehicle tipping area (self-haul) has been added that is configured to improve traffic flow and be more customer-friendly. The MRF processing and tipping floors are approximately 6 percent larger than those at the 27th Avenue Facility. The biggest difference is the separation of the processing and large and small vehicle areas, which will improve vehicle queuing, provide more visibility in the viewing areas and create separate entrances for the tipping areas.
In addition to addressing changes in size and configuration, the Equipment Management Division (EMD) focused on the specialized equipment required, as well as the needs of staff working on the equipment.
EMD suggested ramps at the new facility's entrance have a non-slip surface for traction. Precautions should be taken at the bottom of the ramp to allow for runaway vehicles when brakes fail, the group said. There should be room on the ramp for parking a disabled vehicle out of the way of the traffic flow.
To help reduce damage to vehicles, EMD also suggested installing replaceable bumper material along ramp walls and door openings (rubber pads or wood rails, all of which could be made of recycled material). This also would minimize wall repair costs. Inside the building, EMD suggested the tipping area be large enough to minimize turning of waste haulers to decrease the scrubbing of the tires on the floor. The group recommended allowing for a 60-degree angle tipping instead of a 45-degree one, in relation to the building entrance.
EMD suggested constructing a staging area that could accommodate solid waste collection equipment. Phoenix uses Starr trailers, which are actually two trailers. One trailer is parked while the other is being emptied.
The Facilities Management Division (FMD) focused on building requirements and improving future operations and maintenance at the new facility. Its suggestions could help to improve operations, reduce costs and boost safety.
For example, FMD suggested skylights be eliminated. Skylights at the 27th Avenue facility caused water leakage. Moreover, with the amount of dust and dirt that accumulated on skylights, the natural light provided was minimal.
To minimize damage to electrical conduits, the group recommended all raceways be concealed, with emphasis in the tunnels and tipping area. Adequate cooling and single-door access should be provided to the electrical equipment room, the group said.
Ceiling lights should be placed so that they are accessible for repairs (not directly above conveyors) and should be in sealed units where water is sprayed to prevent damage to hot lamps. The group also recommended ceiling lights be controlled by time clocks with override capabilities.
To improve safety, the group recommended all junction boxes in the plant area should be water tight to protect them from dust and water. FMD also noted that lighting should be increased in all public areas. Light poles in the self-haul area and in the parking lots could be placed on the perimeters to prevent damage by vehicles and equipment.
For efficiency, a separate meter section for interior and exterior lighting could be installed. An energy management system (EMTCS) to control the cooling and heating equipment, as well as the site lighting, would be helpful, FMD said. This system would also control the dust suppression system but would need to be integrated with the fire protection system.
The roof, FMD said, should be built up with as few penetrations as possible. Minimizing trees and vegetation near the roof would limit the amount of leaves and other debris clogging the roof drains. And adequate walk pads surrounding all roof-mounted equipment would ease maintenance.
In office areas, FMD recommended the city consider where the administrative offices are located, as well as the use of sun shading. FMD suggested vinyl tile flooring in the office areas. This would help to keep employees safe.
Additionally, FMD recommended observation areas be enclosed, and employee break areas and restroom facilities be separate from the facilities for the public and contractors.
Among the items the Solid Waste Disposal Management Division (SWDMD) determined it needed was a high-pressure wash rack for heavy equipment to clean off garbage prior to daily post-trips. The group said the city also needed a larger tipping floor and more waste storage floor space. The 27th Avenue Facility floor was too small to handle the volume of vehicles that comes in daily and too small for the amount of waste that is stored on the floor during peak delivery times. A separate tipping area for recycling operations would reduce traffic congestion and the volume of material on the floor. Separating commercial and residential tipping areas would cut down on the time spent waiting in lines for the scales and to dump loads, while addressing safety.
The group also recommended the city look into using a material for the push walls that will not deteriorate with force. The concrete push walls at the 27th Avenue facility deteriorated. The loader operator also is unable to get close enough to the wall to remove material, so manual labor has been used to remove material close to the wall. This makes the task labor-intensive and costly.
To prevent accidents, SWDMD recommended the city install an intercom system at the entrance door to communicate with vehicles and potentially eliminate the need for a spotter. Keeping roads and ramps going in and out of the facility as straight as possible also would help, they said.
The SWDMD suggested Phoenix install air lines and couplings in the excavator areas to allow the excavator to blow out the radiator between trailers, reducing the number of times it overheats and the number of times it has to leave the floor. Evaporative coolers could be installed on the walls blowing directly on the tipping floors. It gets very hot on the tipping floor, so coolers would improve airflow and lower the temperature inside the facility, the group explained. Adequate ventilation also would help to control dust.
SWDMD said the city needs to provide an onsite maintenance area for off-road equipment. The facility also needs a fueling station for off-road equipment and other equipment.
And finally, the group said the office areas and common use areas should be close together. At the 27th Avenue Facility, the areas are too spread out, making it difficult for visitors to find anyone.
Tackling the Trash
The Solid Waste Field Services Division (SWFSD) had specific requirements for operators, vehicles and the facility. This group was not only concerned about the high-volume of vehicles, but it also was concerned about the larger collection vehicle sizes and agreed a larger tipping floor is necessary. Trucks arriving at the facility are 32 feet long plus the trailer, the group explained, so 65 feet are needed to pull the truck onto the floor. A large area would help drivers to swing the doubles around so the rear trailer could be dropped after it is dumped.
SWFSD suggested having a separate dumping area for city and contracted crews, away from other users. If operators cross the scale faster but have to wait to dump, no time is gained. Also, dumping next to small residential self-haulers is unsafe.
If the city can keep refuse and recycling lines separate, when one side is backed up on the tipping floor, the other area will not be affected.
Other tipping area improvements the group suggested were to improve ventilation and lighting; to have a separate scale for city trucks using transponders; and to create an onsite staging area that has room to park approximately 10 solid waste collections trucks. Having a large area for truck cleanout would help operators get back on their routes faster.
Phoenix's Solid Waste Recycling Contracts staff wanted a larger tipping floor, as well as separate entrances for the transfer station and MRF. Traffic needs to be in different areas to reduce wait times for vehicles and improve safety, the group said. Instead of one entrance into the facility, they suggested having an open side design similar to other transfer facilities. This would alleviate traffic by allowing several vehicles to tip at once. A facade wall could be used to hide activity from public view.
To manage recyclables, the committee recommended the self-haul area be attached to the transfer building so material can be pushed in without double handling. And the bale storage area for the MRF and the loading dock should be close to each other.
The staff also suggested a dedicated recyclables scale would help to eliminate mistakes with the card readers.
A Better Facility
To ease operations, the engineers suggested:
cross traffic between residential loads and collections vehicles be eliminated;
two scalehouses be built to separate transfer station and MRF functions;
the self-haul area be part of the transfer station floor and adjustable to meet the overflow needs of busy weekends;
the hoppers be placed in between self-haul and collections;
slanted plates on interior facility walls be built to avoid trapping the trash, which would make cleanup easier; and
exposed structural steel be avoided in the design because it requires frequent painting, which becomes expensive.
Outside the facility, engineers suggested user-friendly and low-maintenance landscaping that make cleaning the facility easier and less time-consuming.
The education staff believed using recycled building products in the facility's design helped the public understand and observe recycling practices. To bring the recycling message home, they suggested centralizing trash areas while expanding recycling areas. They also suggested landscaping incorporate aspects of green waste recycling, mulching and composting. For example, the city could create a one-stop-shop for buying composters, mulch and other essentials, and a demonstration garden, they said.
The key to educating visitors is having a well-designed tour for students and adults, so educators suggested installing a sound system into the building design, placing easy-to-read signage throughout tour areas, and ensuring that windows in the viewing areas are clear and low enough for small children.
Viewing windows also need to be easy to access from the inside, or to turn and be cleaned, then locked into place, the educators said. Outside windows, they added, should be designed to avoid reflecting daylight and glares. And tour areas should meet American Disabilities Act (ADA) accessibility guidelines.
The education room, the staff said, does not need to be an amphitheater but should seat 40 people comfortably. The room should be used for educational purposes and meetings only — not employee break rooms. The staff wanted space to change existing exhibits and distribute brochures. They also wanted an area big enough to store hard hats and vests for visiting guests, props and education materials. A computer lab, classroom and telephone also would be beneficial, they said.
To further accommodate visitors, the group suggested more drinking fountains and vending machines with competitive pricing. And, they said, there should be adequate restrooms for public use only. A picnic/eating area for school groups with a pleasant barrier or surrounding view would be appreciated.
The bus turnaround and parking area at the 27th Avenue facility, which is designed for three buses, should be replicated at the new facility, the staff concluded.
Bruce Henning is a deputy public works director for the city of Phoenix in charge of the solid waste disposal management division. This article is based on a presentation Henning made at SWANA's WASTECON 2004 in Phoenix.