Solid Waste & Recycling


High Soil-to-Waste Ratios

Solutions from automated alternative daily cover systemsRealizing that past landfill practices have wasted a lot of space, a number of Canadian municipalities have recently embarked on landfill reclam...

Solutions from automated alternative daily cover systems

Realizing that past landfill practices have wasted a lot of space, a number of Canadian municipalities have recently embarked on landfill reclamation projects. Soil accounts for as much as 60 to 80 per cent of the total landfill volume reclaimed. This high soil-to-waste ratio has stimulated a reassessment of current practices, renewing interest in automated alternative daily cover systems. Automated systems allow equipment operators to cover waste with minimal labour using existing equipment. Common wisdom has held that these were only practical for large landfill sites. However, the City of Quesnel in British Columbia found an automated alternative daily cover system solved the problem of the high soil-to-waste ratio at its relatively small landfill site.

Located in central B.C., Quesnel (population 8,000) is surrounded by the Central Caribou Regional District (population 12,000). Combined, they landfill 14,000 tonnes of waste per year. Past operations called for spreading six inches of daily soil cover over the waste. According to Jack Marsh, director of public works and engineering, the city was burying as much soil as garbage. In order to reduce the ratio, Marsh initiated a search for a cover material that would save air space, meet daily cover requirements, be automated, and operate in most weather conditions.

The search led to the Enviro landfill cover system developed by Environmental Products Inc. (EPI) of Conroe, Texas. The system consists of two components: degradable polyethylene film (available in 2, 3, or 5 mm thickness) and the “landfill rover” machine that attaches to the blade of existing equipment. The landfill rover dispenses the degradable film from a 16-foot-wide roll below two ballast-holding hoppers. The hoppers contain one cubic yard of ballast soil. An auger system (operated by electronic remote control from the operator’s cab) feeds the ballast material from four exit ports in windrows on the film. The hydraulic augers are powered by a gas or diesel engine mounted in the centre of the machine.

After assessing the District of Chilliwack landfill-which had already had the system in place for two years-Marsh decided to enter into an “evaluation agreement” with EPI’s Canadian distributor, Technicoat Ltd. from September 1997 to March 1998.

The results were significant. Where Quesnel had previously used 28 cubic yards of daily cover soil, the new system used a small amount of 2 mm degradable plastic film and about half a cubic yard of gravel. In addition, the

city realized equipment rental savings of over $2,000 per week (the cost of trucking soil from the local gravel pit). Once deployed and ballasted, the plastic film, at 6-cents per square foot, cost approximately $90 per day to cover the waste.

The plastic film completely covered and sealed the waste; odour, vector, litter, and water infiltration were effectively controlled. Unlike the gravel cover, birds were not able to scavenge because of the opaque brown appearance, slippery surface, and film strength.

The system is also user-friendly. After receiving training in the maintenance and operation of the landfill rover, the operator was able to cover the waste after just three passes. No additional staff or time were required with the application.

Weather conditions were not a problem. The system was continually used throughout the winter. (Operators have found that it’s a good idea to empty the hopper each night in sub-zero conditions to prevent ballast material from freezing.) Relatively dry material was found to work better in cold temperatures.

Other small landfill sites have experienced similar results. For example, Heather Chowen manages the waste management facility, in East Prince, Prince Edward Island. “The traditional six inches of daily cover was using up a phenomenal amount of valuable landfill air space,” she says. “We were filling up our $700,000, three-acre landfill cell with soil. Using the landfill rover, one operator can easily cover the waste in a matter of minutes.”

This type of system has been proven to save both money and air space, but political views must change before many landfills solve the problem of high soil-to-waste ratios.

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