Life in a Desert City like Scottsdale, Ariz., is all about conservation. A shortage of water — particularly in light of a drought that is approaching the one-decade mark — has forced residents to cut back on unnecessary water use. Low-flow showerheads and toilets are the rule rather than the exception. Roof-mounted “swamp coolers” use the evaporative process to aid in cooling, saving electricity and keeping electric bills down.
So when the city built its first waste transfer station in 1996, it approached the facility with that same sense of frugality. Today, the City of Scottsdale Solid Waste Transfer Station handles more than 107,000 tons of waste annually, has dramatically reduced vehicle mileage and wear, and cleanly and efficiently maximizes loads heading out the door.
James Livingston, systems coordinator for the city's Solid Waste Management Department, says Scottsdale's transfer station was built to shorten the routes of collection vehicles that were serving the burgeoning neighborhoods north of the city and having to haul their waste across town to the Salt River Landfill. “The result of that move has been tremendous,” Livingston says. “By bringing waste to this site and transferring it to larger trucks — each trailer can hold two and a half collection vehicles' worth of trash — we save approximately 450,000 miles a year.”
By shortening the trips, the city also saves on fuel, a boon given the dramatic rise in gas prices of late. Even with a conservative mileage estimate of six miles per gallon (mpg), that calculates to 75,000 fewer gallons of fuel used each year. At an equally conservative price estimate of $2.60 per gallon, the city can save nearly $195,000. In addition, the shorter trips mean the trucks last longer and operators can get back out onto their routes much faster.
“The transfer station has been the right answer on so many levels,” Livingston says.
Putting Safety on a Pedestal
In designing the station, the city looked at a number of different methods to optimize the loading of waste into the trailer trucks as they pass beneath the tipping floor.
“We felt a pedestal-type boom material handler was the best answer for us,” Livingston says. “First of all — and for us, this is actually of paramount concern — there is the safety issue. If a machine is not traveling back and forth, the risk of injury to a worker on the tipping floor is effectively eliminated. Because the unit we chose is an electric-hydraulic machine, there are no diesel fumes for the workers to deal with; it's a much cleaner operating unit.
“Secondly, there are fewer moving parts than a traditional wheeled or track crane, so that helps eliminate many maintenance concerns,” says Livingston, adding that the material handler installed in 1996 was recently replaced with a newer model.
Livingston's crew uses the handler to tamp down trash in the 48-foot-long trailers, eliminating wasted space and maximizing payloads for the 40-mile round trip to and from the landfill. According to David Florez, the unit's operator, the machine's impact is particularly noticeable on days in which recyclables, rather than municipal solid waste (MSW), are being loaded.
“Regular MSW is a lot heavier and settles into the trailer easily,” Florez says. “We only have to make sure branches and longer pieces are pushed down. On Thursdays and Fridays, however, we take in recyclable material headed to the [material recovery facility], which is also located at the landfill site. That material is much lighter and really has to be tamped down to get the weights we need.”
“We have the handler fitted with a trash grapple, which has a square profile when closed. That works very well for getting it all down where we need it,” says Florez, estimating that the facility loads between 24 and 28 trucks per day, on average.
Planning for the Future
While the transfer facility is currently meeting Scottsdale's daily needs, continued growth in the area will generate additional volumes of waste, taxing the limits of the site. “We are just about at maximum capacity here right now, doing upwards of 450 to 500 tons per day, five days a week,” Livingston says. “Set up the way we are now, we couldn't really handle the huge increase in volumes based on our projected growth.”
Fortunately, the city anticipated the need for more capacity and next year plans to build an identical facility adjacent to the current one that will double the city's waste handling capacity and streamline the sorting of recyclables.
“Growth in this area shows no sign of letting up so we have no choice but to meet it head on,” Livingston says.
— Larry Trojak is president of Trojak Communications, a Ham Lake, Minn.-based marketing communications firm. He has written extensively for the solid waste, construction, recycling, demolition, scrap and aggregate processing markets.