In the world of landfills, the transition from active to closed status is much like the transition from feast to bed. When a community is done “feeding” the landfill, i.e., finished actively adding waste to it, owners pull a cover from the toe to the crown of these giants and allow the necessary digestive processes to take place. The digestive process in this analogy equates to solid waste degrading over time until the landfill can move into a “post-closure” care step and, eventually, into productively reusing the land.
Often, the landfill flare – which is a controlled flame that burns off excess landfill gas – is the most conspicuous sign of the digestive process. Flares, in tandem with a landfill’s post-closure slumber, may go for several decades during which time owners diligently keep watch. Some landfills sleep soundly, while others may suffer indigestion – often in the manner of excess landfill methane and other contaminants impacting landfill area groundwater, soil, and gas -- and require special attention.
When the flare or “Night Light” goes out, landfill owners and operators can move on from active to passive landfill gas treatment, which means one step closer to post-closure finalization and closing the landfill.
After Nearly 30 Years, Jefferson County Celebrates a Rare Landfill Milestone
The flare at the Jefferson County landfill has run since 1993, until this year when owners, regulators, and Aspect partnered to turn it off – a rare milestone in the lifecycle of closed landfill operations.
Those responsible for watching and caring for these sleeping giants rarely see true milestone moments as the years roll on. Aspect has supported the team at Jefferson County for over 10 years with monitoring and reporting post-closure care at their landfill just outside Pt. Townsend. Over the last year, Aspect has guided the Jefferson County team toward ending post-closure care. As one of the final milestones, they finally turned off the flare installed in 1993, nearly 30 years ago, effectively turning out the “night light.”
Closed landfills don’t get new waste but still have active engineering controls and monitoring to ensure digestive byproducts, like gas and leachate, don’t impact air quality or groundwater quality. At enormous landfills, like the Cedar Hills Regional Landfill Facility in King County, landfill gas is often used as an alternative energy source. At smaller landfills, like the Jefferson County landfill, flares have been used to treat landfill gas to control odor, prevent air pollution, and reduce greenhouse gas emissions. Over time, the digestive processes slow down and less gas is created. Eventually, there is not enough landfill gas to directly fuel a flare, and supplemental fuel (like propane) may be used to keep the flare going—which erodes the value of using a flare for landfill gas treatment.
Switching Off the Night Light in Favor of 14 Biofilters
It takes a coordinated effort to turn off a flare. After years of operating the flare with supplemental fuel, Aspect coordinated with Jefferson County and regulatory agencies to help move to a better solution. The regional air quality authority, ORCAA, confirmed air quality would be protected without the flare. Jefferson County Public Health approved removing flare treatment from the closed landfill permit. The Jefferson County Public Works team built and installed 14 new biofilters and is now monitoring them to ensure they effectively do their job.
Landfill gas flares – like this one at the Port Angeles landfill, which Aspect also consults on — require both considerable operation and maintenance and constant care as landfill gas – i.e., their fuel – runs out.
Biofilters are increasingly used to treat landfill gas during the final stages of digestion and gas generation because they provide “polishing” treatment with little monitoring or maintenance. Landfill gas is directed from horizontal collectors below the cover system through perforated pipe, which is buried by wood mulch. Naturally occurring microbial communities break down landfill gas as it passes through. Barometric pressure changes will allow the landfill to breathe, inhaling atmospheric air during increasing pressure and exhaling landfill gas during decreasing pressure.
Safely Reducing Monitoring Costs and Seeing the End Goal
Turning off the flare brings the Jefferson County team one step closer to ending post-closure monitoring at the landfill. The next steps include showing:
There is little to no landfill gas generation. No subsurface landfill gas migration has been observed recently under intermittent operation of the flare. Compliance gas probes near the property boundary will be monitored during passive landfill gas collection to ensure explosive gases remain in very good control.
The cover system has good integrity with little to no settlement and is resilient to erosion. The cover system prevents rainfall from infiltrating through the landfill and creating leachate. Settlement surveys have begun, and the vegetated surface is in very good shape.
There is little to no leachate generation. Like most older landfills, the Jefferson County landfill started receiving waste before bottom liners were required. So, any leachate that is generated due to infiltration or during digestion will reach groundwater. A network of groundwater monitoring wells is being sampled for a wide range of potential contaminants and results look favorable.
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