Art might be in the eye of the beholder, but for one Washington community, it lies within a unique transfer station nicknamed "ARTS."

By Karl Hufnagel and Mark Westenskow

As it has become for many counties across the country, keeping up with the times became a challenge in Snohomish County, WA (population 620,000), north of Seattle.

Facing a landfill closure in 1992, Snohomish County restructured its solid waste management program to a long-haul waste-by-rail system. By 2002, however, the county's three recycling and transfer stations were processing more than 440,000 tpy of waste. The two busiest stations were constructed in the 1970s around a direct-dump pushpit and small-compactor transfer concept designed for daily tonnage throughput of less than 200 tpd. These stations had become seriously outmoded and incapable of keeping up with the county's growing waste tonnage. Customers endured lengthy delays, service restrictions, and frequent equipment malfunctions.

In the late 1990s, the county embarked on a program to replace these two stations with state-of-the-art facilities, each capable of handling at least 1,500 tpd - many times the original station capacity.

The new Airport Road Recycling and Transfer Station (ARTS) was sited adjacent to a large commercial airport, which in itself presented some significant design challenges.

In addition, the new station layout completely changed the operational methods used by the county.

During the design phase, the county's consultant team worked to develop a facility that is efficient, can safely accommodate large numbers of commercial and self-haul customers simultaneously, and provides a safe, healthy, and pleasant environment for both customers and staff.

Site constraints for the 10-ac. site did not allow for the development of long, prescale queuing lanes for station customers. This dictated the need for a rapid-transaction scale facility consisting of four shallow-pit truck scales, lane-control lights, scale entrance and exit gates and lights, automated vehicle identification and data capture for scales 1 and 4, unattended ticket receipt printers for scales 1 and 4, and traffic-control modules. The facility is capable of processing peak-period customer arrivals (estimated to be 123 vehicles per hour) while avoiding long queues.

A four-scale plaza with one reversible UniBridge scale (scale 3) is a central element in the design of this area of the facility.

Equally important to the efficient processing of customers is the reliance on a highly automated scale transaction process. The reversible scale, when operated as an inbound scale, provides a total of three inbound scales.

Illuminated lane-availability signs on the face of the scale-plaza canopy identify whether a particular scale is closed (red X), open to self-haul and nonaccount commercial customers (green arrow), or open only to commercial-account customers (yellow X).

On weekdays, commercial-customer traffic at the station predominates. Regular commercial-account traffic uses the outboard scales (scales 1 and 4) when entering and leaving. These two normally unattended scales are fully automated and use PC Automation's Automatic Identification and Data Capture technology to minimize the transaction time and labor costs. Radio-frequency identification equipment (vehicle-mounted transponder and canopy-mounted antennae) provides the necessary link between the truck and the scale data management system. Automated semaphore scale entry and exit gates backed by red and green "stop" and "go" lights are linked to the scale data management system through one PC Automation microprocessor-based Traffic Control Module per scale. Digital readouts and remote ticket printers at the normally unattended outboard scales complete the automation package.

Self-haul and nonaccount commercial customers are guided through scale 2, an attended scale. This scale also is equipped to operate in a highly automated mode. For example, even when the scale attendant is present, the gates and lights for scales 2 and 3 can be operated by the respective Traffic Control Module instead of by foot switches.

Scale house 1, located between scales 2 and 3, is double-sided with transaction windows and equipment on both sides. During peak periods, two attendants will work within this building.

Scale house 2 is located between scales 3 and 4 and is essentially identical in arrangement to scale house 1. During less busy times, scale house 2 is unattended, with commercial-account customers having unknown tare weight scaling out with an automated transaction on scale 4. The remaining commercial and self-haul customers weigh out on scale 3 with an attendant transaction from scale house 1. Commercial customers with known tare weight and minimum-fee customers may bypass the scale facility when exiting.

On weekends, self-haul customers predominate, with possible peak traffic counts of more than 1,000 vehicles on a busy day. During these periods, scale 1 can be operated as an attended self-haul scale since it includes a small but well-equipped booth. This provides a total of three attended inbound scales (scales 1, 2, and 3), each with a dedicated attendant. If necessary, all exiting customers use scale 4 and are processed by a second attendant in scale house 2. As on weekdays, a bypass exit lane is provided for minimum-fee customers and those billed with known tare weights, which do not need to weigh out.

Natural Lighting: Seeing Is Believing

The facility siting adjacent to an airport necessitated a fully enclosed transfer building to avoid becoming a bird attractant. The resulting enclosed building is very large, with a receiving floor measuring nearly 203 ft. from sidewall to sidewall and 275 ft. from end to end, with 35 ft. of unobstructed clearance required above the floor.

Concerns about light escaping from overhead skylights distracting pilots and about contrasting light levels disorienting drivers when vehicles transition from outdoor to indoor operating areas led to the use of extensive, translucent sidewall panels to naturally balance brightness levels.

The daylighting design is complemented by electric lighting, with a total of 88 400-W high-bay, metal halide luminaires that augment natural lighting levels to maintain 30 foot-candles at floor level to ensure safe and efficient operation in the driving and receiving areas. The proportion of natural and artificial lighting is electronically and automatically tuned to coordinate changes in the natural light source, resulting in energy savings by avoiding unnecessary electrical lighting. This Wide-Lite system also will compensate automatically for the change in light output as the fixtures age and lenses become dirty between cleanings.

The following three variable-level lighting systems were evaluated to determine the most appropriate one for balancing the artificial and natural lighting levels:

1. Turning on and off certain luminaires. This method was not very desirable due to the resulting large variation in lighting levels and the long warm-up time of metal halide lamps. This also would shorten the lamp life.
2. Stepping the lighting levels, using two or three steps. This method actually would adjust the light output in definite steps with corresponding reduction in energy consumption. This method also was not very desirable since it appeared that this type of lighting control is intended for the reduction of lighting levels when the space is not occupied and since it results in a rather large variation in lighting levels (steps). It was felt that this was too drastic of a change to be comfortable to the staff.
3. Continuously variable lighting level. This system uses dimming ballasts and a dimming control system to continuously change the light output of the high-intensity discharge luminaires as required to maintain the set lighting level. This system appeared to be the most desirable.

The building was divided into three zones - north, south, and center, with photoelectric sensing to determine the lighting level of each zone - and three separate dimming-system zone controllers. This arrangement permits each zone to respond to and complement the varying amount of natural lighting available for the different zones.

Economic evaluations were made for these systems to determine if the expense of installing adjustable lighting was justifiable. The study indicated an annual energy savings of $1,500, not including the savings resulting from greatly extended lamp life, and a payback of approximately 15 years for the continuously variable light-level system. Based on this analysis, the design team proceeded with this option.

Another potential effect of sunlight that was less welcomed involved concerns from the nearby Federal Aviation Administration (FAA) air-traffic controllers regarding glare. During the design process, the FAA voiced a concern that sunlight reflected from the roof of the main building might result in glare that would interfere with viewing aircraft. Building designers addressed this concern by specifying a low-reflectivity finish on the metal roof and preparing an easy-to-visualize, computerized glare study. The study used a computerized mockup of the transfer station building and the sun's location throughout the year and was packaged in a CD-ROM for presentation to the FAA. The two-part strategy of low-reflectivity materials - Morin Corporation's steel panel with PPG Industries' Duranar fluoropolymer low-gloss coating and portable, easy-to-understand graphic analysis - has been adopted as the standard for other facilities under design at this airport.

Dust and Odor: A Breath of Fresh Air

Dust and odor control systems combine with multiple gas-detection systems to provide a healthy atmosphere. The health and welfare of the employees and customers were given a high priority by the station designers, especially within the waste-handling areas of the transfer building where dust, odors, and potentially harmful gases (carbon monoxide and nitrogen dioxide from vehicle exhaust and chlorine from spills) are a constant threat.

Three separate systems are employed to protect this area.

The first system is a NuTech Environmental Corp. five-zone, water-based dust/odor control misting system installed in the main waste-handling areas. This system uses atomized water droplets to help capture and settle airborne dust and can include odor-neutralizing agents. The system is split into two high-pressure, low-volume zones near the ceiling above the most active floor areas and three medium-pressure zones above the throats of the two waste compactor chutes and in the throat of the topload hopper that normally will be used for loading yardwaste and hard-to-handle waste (e.g., stumps, large pieces of concrete, or loads of dirt) that would be better handled this way than by being processed through the compactors. Each zone is separately remote-controlled by the operating staff using hand-held wireless controllers.

The second system is a ducted dust-extraction system with intake grills above and behind each of the two Shredding Systems Inc. compactor chutes. The areas immediately above the chutes are very dusty due to the waste dropping 12 ft. to the floor of the compactor. Each compactor chute has its own MAC Equipment Inc. dust-extraction system consisting of a 15,000-cfm cartridge-filter dust collector with automatic pulse-jet air cleaning. The filtered exhaust air is discharged from a stack above the roofline. The two dust-collection systems are designed to operate completely independently of each other since the compactors might not be running simultaneously. With the system controls in the "Auto" position, these systems operate on demand from the same hand-held wireless controllers used for the misting systems. The dust-extraction system controls are interlocked with those of the medium-pressure misting systems via a programmable logic controller to prevent moisture-laden dust from being extracted and blinding the dust filter bags.

A Mine Safety Appliances Company gas detection and alarm system provides the third protective measure for the transfer building. This system consists of multiple carbon monoxide, nitrogen dioxide, and chlorine detectors with both audible and visual alarms inside and at the entrances to the transfer building. Since chlorine would most likely enter the building in a liquid container in the wastestream, the sensor for this gas is located on the mobile floor loader close to where a broken container would be. The input from this sensor is transmitted by wireless radio signal back to the central monitor and recording system in the electrical room. Similar gas-detection equipment is located in other areas of the facility, including in the compactor level of the transfer building, in the employee building, and in the scale houses.

The success achieved in these three areas of the facility design reflect the excellence that the county's consultant team obtained throughout the facility and is largely a result of the county's ability to fully integrate its operations staff into the planning and design process.

Karl Hufnagel is a senior project manager with R.W. Beck Inc. in Seattle, WA. Mark Westenskow is the Airport Road Recycling and Transfer Station project manager for the Snohomish Count (WA) Solid Waste Management Division.

MSW - March/April 2004