Recycling and transfer station keeps clean with inside-out design approach
The Bow Lake Recycling and Transfer Station in Tukwila, Wash., is the newest facility in the King County waste handling system. King County, which encompasses the metropolitan Seattle region, is the largest county in the state of Washington with a land area and population larger than Delaware. The new station and its innovative design can handle 2,400 tons per day of solid waste.
It was constructed on the site of a smaller, outmoded station that was built in the 1960s. An extensive on-site roadway system can accommodate heavy mixed traffic of private vehicles, commercial haulers and 53-foot semi-trailer transfer trailers. Traffic through four independent vehicle scales is handled by a computer-controlled Automated Traffic Management System; the first application of this technology to a high-volume transfer station.
Though solid waste transfer stations may appear to be relatively simple, they are highly specialized facilities that have to satisfy many stringent and often conflicting requirements. They must be designed for the efficient “throughput” of large amounts of solid waste and recyclables while providing a high level of safety for customers and staff. “This includes being able to accommodate a large variety of traffic from private cars to 53-foot solid waste transfer tractor trailer rigs and everything in between,” says Charles A. Conway, project manager at Seattle-based KPG Inc., the firm responsible for the architectural design. “These facilities must also be designed with longevity in mind. More than 50 years is not an uncommon life span for transfer stations, and the facilities must be robust to withstand extensive wear and tear.”
In addition to these functional requirements, King County set ambitious goals when designing the transfer station, including:
- Maximizing the use of recycled and recyclable materials in the construction.
- Maximizing the durability of key construction elements.
- Minimizing facility energy consumption.
- Minimizing off-site traffic impacts.
- Mitigating off-site environmental impacts like noise, dust and odor.
- Providing a healthy interior environment for customers and employees.
The facility’s design also needed to meet a new objective: recover as many resources from the waste stream as possible. To do this, the Bow Lake facility has two distinct recycling facilities: a yard waste and recyclables drop-off facility for public use, and a material recovery facility within the transfer building that allows recyclables to be extracted from the solid waste stream so they can be sorted, baled and loaded into trailers for transfer to recycling facilities.
The transfer building
The heart of the station is the 100,000-square foot transfer building where waste is tipped onto a receiving floor and loaded into two large hydraulic compacters that compress the waste into truck-sized bales and eject it into waiting transfer trailers. The transfer building incorporates many energy-saving and sustainability measures including dust- and odor-control misting systems, sophisticated daylighting and lighting control systems, dust collection and filtration systems, rainwater collection systems (which provide water for wash-down activities), hydraulic oil waste heat collection systems (for domestic heating) and photovoltaic electric generation.
Photovoltaic panels from Scottsdale, Ariz.- based Kyocera Solar Inc. were installed to generate electricity on-site. “The south-facing roof was the natural choice for installation because it allowed for maximum sunlight exposure while showcasing the panels to customers and drivers on the adjacent Interstate 5 freeway,” says Tom Creegan, project manager at Seattle-based King County Solid Waste Division. “The completed solar array has a peak generation capacity of 16.4 kilowatts.”
Metal’s use
To ensure a long life span while being robust enough to withstand heavy use 24 hours a day, seven days a week with minimum maintenance and repair, metal was chosen as the facility’s primary structure and building envelope. “Careful attention to design, surface preparation and application of an epoxy/urethane high-performance coating to the steel structural system yielded a durable, easily cleaned structural frame that is very economical on a life cycle cost basis,” says Creegan. “High-performance fluoropolymer coatings were specified for all exposed interior and exterior surfaces of the wall and roof cladding to ensure long life and low maintenance for the building envelope as well.”
Metal also permitted an innovative inside-out design approach that placed structural and mechanical components on the building’s exterior. It has a distinctive architectural theme with massive columns and seismic braces of the long-span steel frames exposed on the exterior façade.
“Coupled with careful attention to the details of bracing and connections, this approach yielded a very ‘clean’ interior with minimum of places for dirt and debris to collect or birds to perch,” Creegan says. “The roof structure was further simplified by a continuous metal deck from ASC Steel Deck, West Sacramento, Calif. in place of a more typical purlin system. Rigid insulation from Portland, Mainebased Hunter Panels between the steel deck and the metal roofing contributes to the longevity of the structure by eliminating condensation.”
For the roofing, 20-gauge, Kynar-coated, site-rollformed continuous panels from Bristol, Conn.- based Morin Corp., a Kingspan Group company, were used. For the siding, Morin’s 18- to 22-gauge, Kynar-coated, shop-formed metal panels in both exposed- fastener and concealed-fastener panels were used. The Morin roofing and siding panels were installed by Interstate Sheet Metal, Battle Ground, Wash. The color palette included dark green and dark gray for the wall panels, white for soffit panels and light gray for the roof panels. Orange was used for the gutters and downspouts as an accent.
The transfer building’s steel structural system permitted integrating large, continuous translucent polycarbonate skylights and wall panels from Lake Forest, Ill.-based CPI Daylighting Inc. into its roof and façade. It includes 16,500 square feet of skylights and 9,000 square feet of translucent wall panels. High-intensity fluorescent lights automatically dim and then extinguish as daylight levels increase. Because the major building components could be fabricated and finished off-site, steel allowed for relatively quick erection and completion of the building envelope. This helped maintain uninterrupted 24/7 operation of the existing facility throughout the construction process.
230-foot clear floor span
One crucial design goal with significant safety implications was to provide a clear-span roof for the transfer building with no vision-obstructing columns. Long-span structural steel fabricated by Western Fabrication of Kelso, Wash., and erected by JH Kelly, Longview, Wash., for the structural system was considered by the designers to be the only practical means of achieving this important goal.
Besides safety, the 230-foot building clear span also contributes to another important project goal: flexibility. “Solid waste handling and recycling are rapidly evolving, interrelated activities,” says Conway. “The large, unobstructed tipping floor will allow the county to increase the recycling and material recovery operations at the station as technology and public policy evolve over time.”
Earthquakes and neighbors
Earthquakes are a threat in the Pacific Northwest. The Bow Lake facility was designed to withstand a major earthquake safely and permit the immediate resumption of operations following the event. The strong, resilient nature of the steel structural frame and building cladding plays an essential role in assuring the facility will be functional when it is needed after an earthquake. In fact, two conference rooms in the office/crew area of the transfer building have been designed to function as auxiliary emergency command centers for King County emergency management personnel.
To ensure that the new stations are good neighbors, the fully enclosed structure controls dust, odor, noise and pests. While older stations were typically open-air designs that couldn’t always control dust, odor, noise or pests like rodents and birds, Conway says Bow Lake represents a new approach that manages these undesirable impacts by fully enclosing the transfer operations.
The facility opened on schedule in October 2013 after a three-year construction process. The $92 million facility was completed approximately 4 percent under budget. It has been honored with the Green Project of the Year Award by the Northwest Construction Consumer Council, the Silver Excellence Award by the Solid Waste Association of North America, the Silver Award for Engineering Excellence in Innovation by the American Council of Engineering Companies and LEED Platinum certification by the U.S. Green Building Council.
Sidebar: King County Solid Waste Station, Tukwila, Wash.
Completed: October 2013
Total square feet: 100,000 square feet
Building owner: King County Solid Waste Division, Seattle
Prime consultant/civil and structural engineering consultant: R.W. Beck/Leidos, Seattle
Architect/site planning/landscape architecture: KPG Inc., Seattle
Construction manager: KPFF Consulting Engineers, Seattle
General contractor: Lydig Construction, Spokane, Wash.
LEED consultant: Paladino and Co., Seattle
Structural steel engineer: MLA Engineering, Seattle
Structural steel fabricator: Western Fabrication, Kelso, Wash.
Structural steel erector: JH Kelly, Longview, Wash.
Metal installer: Interstate Sheet Metal, Battle Ground, Wash.
Metal deck: ASC Steel Deck, West Sacramento, Calif., www.ascsd.com
Metal roofing/wall panels: Morin Corp., a Kingspan Group company, Bristol, Conn., www.kingspanpanels.us
Photovoltaics: Kyocera Solar Inc., Scottsdale, Ariz., www.kyocerasolar.com
Rigid insulation: Hunter Panels, Portland, Maine,
www.hpanels.com
Skylights/translucent wall panels: CPI Daylighting Inc., Lake Forest, Ill., www.cpidaylighting.com