Republic Services has discovered a more efficient way to process 3,200 tons (2,903 t) of waste delivered daily on average to the Sycamore Landfill in Santee, Calif.

A pair of Cat D7E track-type tractors push municipal solid waste at the tipping face, move soil for daily cover, and help maintain the 491-acre site. “The machines are being utilized 100 percent of the time,” said Gabe Gonzales, operations manager. “The machines keep the material moving, and there’s no loss in power because they are electronic.”

The D7E’s unique diesel-electric powertrain burns considerably less fuel than traditional systems. The electric generator, power inverter, and propulsion module in the electric drive system replace traditional mechanical components to improve power and efficiency.

“Based on the fuel economy and torque of the machine, we’re able to process the same amount of material at a lower cost,” said Gonzales. “Our operators use direct drive at all times.”

To keep pace with 23-ton (21 t) truckloads of material, the landfill uses both of the D7Es to spread municipal solid waste at the tipping face during the hours of peak activity.

The flexibility of having two machines for peak hours and separating them at other times has proven to be very beneficial in meeting a variety of dozing requirements throughout the day. Each D7E burns 6.6 gal. (25 L) of fuel per hour compared to 13 gal. (49 L) per hour for the larger track-type tractor they replaced. The ability to perform different dozing tasks in different locations has actually increased productivity and overall efficiency.

Operators are easily able to handle the peak hours each day, and keep pace with waste flow at other times using only one machine.

When not working at the tipping face, the D7Es place the daily cover, and provide maintenance throughout the site.

Another benefit of the electric drive motor, the D7E meets Tier IV Interim emission standards. This helps the landfill reduce its carbon footprint.

Operator Favorites

The new machines — one of which was purchased in 2012 and the other earlier this year — are quickly becoming operator favorites. They especially like the ergonomics of the cab and controls, quiet operation, and ability to set the hydraulic feed to their own specifications. “The user screen is very friendly,” Gonzales said. “Overall, it’s an easy machine to operate.”

To help the machines with the heavy workload at the landfill, Hawthorne CAT installed a specialized guarding for the undercarriage and windows.

A 3-ft. (.9 m) high screen was added to prevent waste from spilling over the blade. Hawthorne CAT employees also helped landfill staff become acquainted with the new machines through walk-arounds and reviewing the D7E’s new technologies and performance features. The professionals at Hawthorne CAT are available to answer questions about the D7Es or any of the other Cat machines in the fleet. “They’re a phone call away,” said Gonzales. It all adds up to increased efficiency at the landfill, and an improved bottom line for Republic Services, according to the company.

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