Regardless of daily tonnage intake or the number of years left in a landfill’s life, the No. 1 issue on the minds of many managers at solid waste agencies is airspace management.
This holds true for two North Carolina solid waste professionals.
“We are in the business of selling airspace. The tighter we compact the material, the more waste we fit in the same space and the longer life we get from this site,” says Gene Walters, solid waste director for Roberson County Solid Waste.
“Airspace is my primary concern,” echoes Keith Cain, solid waste superintendent for the Hanes Mill Landfill in Winston-Salem.
While Hanes Mill and Roberson County have similar waste streams—primarily composed of municipal solid waste (MSW) and construction and demolition (C&D) material—that is where the parallels end. Hanes Mill receives up to 1,200 tons per day (TPD) from a population of nearly 600,000. The operation has a mid-range expected site life extending to 2035.
Roberson County, on the other hand, takes in roughly half the daily tonnage from a county population about a quarter the size. It also has the luxury of time on its side. “We have 59 years left at the existing site,” Walters says.
With such a variation in daily intake, the expectation might be for operators at both sites to rely on landfill compactors of different sizes to meet their compaction needs. However, both landfills have used monstrous machines that weigh nearly 115,000 pounds to maximize their compaction densities.
“The compactors previously working at Roberson County weighed 115,000 and 75,000 pounds, respectively, and had wheels that were configured in a triangular pattern, while Hanes Mill’s two compactors were modified wheel loaders weighing approximately 120,000 pounds each,” explains Barry Neal, governmental sales representative for James River Equipment. James River is an authorized landfill compaction equipment dealer for Columbia, South Carolina-based BOMAG.
These heavier compactors help deliver tight densities, even during periods of elevated material flow, such as during hurricane cleanup efforts. Roberson County and Hanes Mill landfills receive densities close to 1,400 pounds per square yard and 1,500 pounds per square yard, respectively.
Looking to duplicate the compaction capabilities achieved by the sites’ compactors, teams at Roberson County and Hanes Mill landfills made the decision to stick with heavier equipment when they recently replaced their existing equipment.
Hanes Mill transitioned to a new BOMAG BC 1172 RB-4 purchased from James River in mid-2017.
The roughly 123,000-pound machine includes a wheel design with more than twice the compaction teeth per wheel than the model it replaced, which is designed to help improve material shredding prior to compaction.
The BOMAG landfill compactor at Hanes Mill sees high utilization rates, logging about 3,000 hours per year. The compactor’s weekday starts at 6:30 a.m. when the cover is rolled off the landfill cells and doesn’t end until 5 p.m. after the cells are re-covered. On Saturdays, the compactor runs from 7:30 a.m. to noon.
To keep the machines operational, upkeep is key. That’s why both teams rely on regular service.
“With their high utilization, Hanes Mill has been able to take advantage of a warranty that covers the entire machine for five years. They bring the machine into James River for routine maintenance at the prescribed intervals,” Neal says.
Cain adds, “We’ve experienced high uptime availability with the machine over the past year.”
Since Hanes Mill’s new compactor is designed specifically for landfill compaction, its frame differs slightly from the operation’s previous machines. “The frame has a single sealed-tub design to keep the engine compartment clean,” says Jerry Fitch, territory manager for BOMAG.
This frame configuration creates a smooth underside on the compactor.
“It does not get the buildup in the belly since there are no belly pans,” Cain says.
When the compactor was delivered in September 2017, one difference Cain noticed from Hanes Mill’s previous equipment was the compactor’s oscillating center articulation joint. The BC 1172 RB-4 offers a 40-degree steering angle to help with machine maneuverability, plus 15 degrees of oscillation to help keep the wheels in contact with the material.
“When the machine runs into a dip, one wheel doesn’t go up in the air like our previous compactor,” Cain says. “All four wheels maintain contact to keep compacting.”
Neal explains that with the new compactor, machine weight is only one part of the equation for achieving high densities.
“The other crucial part is how the force is applied through the wheels to penetrate the material,” he says.
The BC 1172 RB-4’s four 55.1-inch-wide wheels consist of 72 polygonal disc teeth, positioned in rows to create the confinement that is designed to aid in material shredding.
“We need to break up the C&D material [especially] to increase compaction, and the weight and wheel design of the new compactor do a good job of this,” Cain says. “Our compaction rate is great with the BC 1172 RB-4.”
He notes that at last flyover, compaction densities at the landfill have increased to nearly 1,600 pounds per square yard with the new compactor.
Keeping it clean
Roberson County Solid Waste began its new compactor bid process shortly after Hanes Mill put its BC 1172 RB-4 to use. Walters says he took the opportunity to visit the landfill on a wet and muddy day and see the compactor at work before making a decision.
“The first thing that impressed me was how clean the wheels were,” Walters says. “There was no waste buildup on the wheels. Cleat penetration equals compaction.”
Walters credits the compactor’s wheel design, which includes adjustable wheel scrapers that fit between the rows, for helping to prevent material accumulation.
Impressed by the machine’s performance during the visit, Walters was able to piggyback on the Hanes Mill Landfill’s bid, and Roberson County purchased the same size compactor from James River. Walters explains that it’s not imperative for his landfill to have a machine this size to keep up with material intake, “but the compaction we are getting out of the heavier machine is better.”
Robertson County took delivery of its new compactor in July 2018 and has already noticed a difference.
“The biggest compliment I receive from the operators is that it’s quiet and user-friendly,” Walters says. “The forward/reverse lever is mounted on the joystick controls, so the operator doesn’t have to take his hands off of the joystick to switch travel directions.”
The machine’s air intake and cooling systems were designed specifically for landfills, which Fitch says helps with operations.
“The sealed tub design draws clean cooling air from the machine’s highest point, flows it across the engine and has it exit the rear and sides of the compactor,” he says. “Plus, we include standard reversing fans for the radiator to keep it clean.”
After several months of operation, Walters says he is impressed with the design. “We checked the inside air filter at the 500-hour service interval, and it looked brand new,” he says.
Workers are also noticing a difference in compaction compared to the landfill’s old 115,000-pound machine. Although Roberson County has kept its older compactors to run them as backup machines when the new machine receives routine maintenance, Walters says there is a noticeable difference.
“The material was fluffy and not tight, and we could tell a huge difference when we put the BC 1172 RB-4 back to work. The waste was flat and tight again,” says Walters.
With the new compactor at his disposal, Walters says he is confident the next flyover in the summer of 2019 will show increased densities similar to Hanes Mill, helping the site achieve its primary goal—making the most of its airspace for years to come.