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Feb 24

Making a landfill live longer

Posted on February 24, 2017 at 11:38 AM by Becky Robinson

As someone who has spent a fair amount of time in the glamorous world of solid waste, I am enthralled by the idea of digging into closed landfills. What would you find? The possibilities are perturbing and endless.

2017-02-16 Landfill Cell Excavation_2The SWA recently undertook a project that included re-opening a closed part of the landfill, and thankfully for everyone, the only thing we found was an opportunity to extend the life of the landfill.

Like all modern landfills, the SWA landfills at Renewable Energy Park in West Palm Beach are constructed in cells. Two of these cells, filled with municipal solid waste, wastewater sludge, construction debris, ash from our Renewable Energy Facility, etc. were closed in September of 2007. They had reached the height permitted by law, and were therefore capped with layers of plastic cover (geosynthetic), dirt and then grass.

But the story of those cells wasn’t over. As time passed, the waste inside settled as much as 20 feet in some parts, making the cells shorter than the maximum landfill height. That created storm water management problems and presented an opportunity to place more waste in the space. Landfill air space is a valuable commodity - even relatively minor differences in elevation between the surface of a mature landfill and the permitted elevation can in some cases be recovered and provide economic value.

The SWA, in conjunction with our Landfill consultant CDM Smith, asked the Florida Department of Environmental Protection for permission to remove the geosynthetic cap in the settled cells and refill them back to the maximum permitted landfill height with ash from our Renewable Energy facilities. With the go-ahead from the state, we began work last month.

2017-02-16 Landfill Cell Excavation_1The geosynthetic cap system is being excavated and carefully removed in relatively small sections during the dry season to make sure a minimal amount of water enters the cell. While the SWA landfill has a system to deal with leachate, or garbage juice, the less of it, the better. We began the process of refilling these cells in mid-January.

The SWA work crews are following a detailed road map to bring these areas back up to the new permitted height and to make sure they provide a smooth transition to neighboring cells. When this work is completed, the life of the landfill will be extended by about 12 months.

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