To mine or not to mine waste? That is the question.

How do you take 80-acres of unlined, relatively flat landfill footprint which generates leachate at a rate faster than an operating landfill footprint and reduce leachate generation? During the spring rain and snow melt season, leachate generation rates skyrocket – overwhelming the on-site leachate pretreatment facility and requiring almost continuous leachate hauling.

By evaluating the landfill design, our team theorized that the gas venting layer was likely collecting percolation through the flat soil cap section. In addition, the perimeter leachate collection piping, located below the stormwater swale between the landfill and the perimeter access road, was likely collecting stormwater and treating it as leachate.

The County needed an approach that the regulatory authorities could support and permit that would modify the existing unlined municipal solid waste (MSW) landfill while decreasing leachate generation, reducing downgradient environmental impacts and simplifying ongoing operations. This solution needed to be completed expeditiously, as there was a pending need for additional landfill airspace.  

We proposed a unique solution involving waste mining and reclaiming 40-acres of the unlined landfill footprint to focus on what was believed to be the most likely source of stormwater being collected and treated as leachate.

The waste in a 40-acre section of unlined landfill footprint would be excavated and placed on the remaining 40-acres of relatively flat, unlined landfill to steepen the slopes in an effort to reduce leachate generation and to simplify landfill operations. The work was proposed over three separate phases.

The 40-acres of recently reclaimed footprint would be used to create a new, state-of-the-art lined landfill facility to address pending airspace needs. The 40-acres of now consolidated MSW would be capped at steeper slopes with a new geomembrane and capping system meeting current regulations. Both the steeper slopes and the geomembrane should reduce percolation into the existing waste and further reduce downgradient impacts, which would continue to be evaluated over time.

The landfill reclamation work was completed under a modification to an existing consent order to expedite the process. Permitting of a landfill expansion within the soon-to-be created footprint was completed concurrently to address the need for airspace. 

The unique approach led to one of the largest landfill reclamation projects in New York State. The first phase of reclamation in 2022 required the relocation of over one million cubic yards of waste, opened about 18-acres of footprint and required approximately one year to complete. The resulting subgrade was tested to meet the required clean-up standards and impacted soil was also excavated while adhering to limit volumes. The original landfill cap was excavated and stockpiled for use in future closure activities.

The year following the first phase of reclamation was used to prepare the subgrade for the future Section V Cell 1 Landfill Expansion. That expansion work is being completed in 2024.

The leachate generation from the old landfill footprint was reduced from about 21 million gallons in 2021 to 13.8 million gallons in 2022 and 9.4 million gallons in 2023 – an impressive 55% reduction in leachate generation. Remarkably, the landfill expansion was permitted without the need for additional leachate storage capacity… but most importantly, the County has not hauled leachate since May 2023 and has even shut down the leachate pretreatment plant on occasion due to a lack of leachate.