Preserving landfill capacity is a foremost objective for today’s landfill operators thanks to increasing complications with both permitting of new sites and expansion of existing ones.
In an effort to maximize the capacity at its 300-acre landfill in Manchester, New Jersey, Ocean County Landfill Corp. began to look at options in the mid-2000s for preserving space at the site.
The company first looked at redeveloping an older, unlined portion of its landfill built between 1972 and 1985, which comprised around 60 acres. The original goal was to expand capacity and extend the lifespan without requiring a horizontal or vertical expansion beyond what the landfill was presently permitted for.
“The footprint of the landfill is pretty well-established, and we don’t really have the luxury of going out any farther without encroaching on neighborhoods and wetlands and things like that,” explains Martin Ryan, vice president of engineering at Ocean County Landfill Corp. “So, as we were looking at the lifespan of our facility and trying to figure out ways to squeeze a little more time out of it, we thought that certainly a vertical expansion was something that was a possibility, but that’s not a definite thing that will get approved by the regulators. Also, I think there’s some sensitivity to the surrounding community, as well. You don’t want to have this huge mountain of garbage sticking up out of the pine trees [that surround the landfill], so we had kind of settled on our final elevation with some sensitivity to the surrounding community.”
Ryan says the company first discussed an overliner design where new waste could be placed on top of the existing capped areas within the vertical limits the site was approved for. In order to assess the viability of this, Ocean County Landfill Corp. had waste composition tests performed. The primary goals were to gauge the thickness of cover soils and to obtain waste characterization, condition and stage of decomposition data.
“The firm we hired did a biomethane potential (BMP) test, which basically said that the waste was largely ‘cooked,’ for lack of a better word,” Ryan says. “This meant it was largely decomposed. The testing also found the mass should be stable and not prone to a lot of settlement, while simultaneously showing that there was quite a bit of cover soil there.”
Ryan says, at the time, the landfill was importing almost every yard of soil it was using for cover and capping construction. Between the desire to minimize the height of waste at the landfill and the ample supply of cover soil that would eliminate the need to outsource from third parties, Ocean County Landfill Corp. decided that landfill mining, not installing an overliner, was the best course of action.
Ryan says that, at the time, no landfill mining project of the scale the company was proposing had been undertaken in New Jersey. This necessitated both ample planning and time needed to secure permitting.
“We were looking at mining basically all of the waste that’s in that old, 60-acre part of the landfill, but we looked at it as a win-win because we would be keeping our construction crews busy with mining during times in between building baseliners and caps, we would create a lot of cover soil for us to help offset the need to then import all that soil, and then we’d also develop a new area for future landfilling, which we hope will allow us to operate until around 2036 or 2037, [beyond the original estimated close date of 2024],” Ryan says.
Mining for opportunity
After going through all the regulatory hurdles to be approved by the state, Ryan says that they began screening operations in 2014. They developed a plan for phased excavation and base liner construction that constituted three phases, which would stretch out over approximately 15 years.
Lawrence Kiesel, vice president of construction at Ocean County Landfill, says before commencing operations, the company evaluated several different types of screens for the project. The company demoed both shaker deck-type screens where waste was placed in the top and fines and dirt filtered out the bottom as well as trommel screens that spun to accomplish the same goal.
Ocean County ultimately settled on a Doppstadt SM720K trommel screen since the circular rotation was able to better separate the dirt from the waste. Kiesel notes that the company uses an excavator to dig to a depth of around 40 to 45 feet. The excavator then transfers the waste to an off-road end-dump truck so the material can be moved from the area that is being mined to a separate screening station, where another excavator feeds the hopper of the trommel screen. A wheel loader is then used to load the resulting material into off-road end-dump trucks, which transport the 2-inch-minus cover soil and over 2-inch waste materials, respectively, back to the site’s active landfill cell.
Kiesel notes that while their process has become synchronized over time, there has been some trial and error to find the best method to effectively mine the material. He says they originally attempted to load material from the landfill directly into the trommel screen via an excavator, but found that, instead, first loading this waste into a truck to be screened in another location yielded greater efficiencies without exposing the trommel to damage from bulky materials like engine blocks, tree stumps and other sizable debris.
According to Ryan, Ocean County’s landfill mining work is conducted in spurts throughout the year so that they’re ensuring that cells are available for waste placement while at the same time they’re economically “minimizing the impacts to the facility’s funding requirements for routine landfill construction and closure/post-closure care.”
To meet regulatory approval, crews at the Ocean County Landfill are required to comply with rigorous safety standards to protect both operators and neighboring citizens.
Workers conduct hydrogen sulfide tests to ensure emissions from C&D wallboard landfilled at the site aren’t being generated as waste is uncovered. Air monitoring for other emissions is also part of the process.
Kiesel says workers are required to don appropriate PPE including hard hats, safety vests and eye protection. The company also works to limit personnel around the trommel screen while in operation due to particulate matter in the air. Finally, third-party certified labs routine test the soil coming off the screen to make sure that it’s in compliance with criteria outlined by the New Jersey Department of Environmental Protection for the site’s cover soil acceptance plan.
A purposeful plan
Kiesel notes that in the six-plus years they have been mining at the site, they’ve made some adjustments to maximize production and efficiency, but haven’t encountered any major difficulties or setbacks. When all is said and done, Ocean County Landfill Corp. will be excavating and screening approximately 4 million cubic yards of material from the 60-acre parcel.
This project is estimated to create an additional 6 million cubic yards of new capacity, allow placement of waste in the existing landfill cross section with modern landfill techniques and compaction, and recover approximately 2 million cubic yards of cover soil.
"It’s an expensive project, but I think if you look at the cost versus the benefits, there is no doubt it is well worth the effort,” –Martin Ryan, vice president of engineering, Ocean County Landfill Corp.
While landfill mining is a strategy that has been used for years to free up airspace, uncover commodities of value, reconstruct a site or remove potentially problematic wastes, it isn’t a strategy that is as commonly deployed in the U.S. as it is overseas.
Ryan says that the suitability of landfill mining is very site-specific, and depends on the following: timing of need for additional airspace; the value of the airspace, reclaimed soil and possible recyclables; the age of the waste; environmental and permitting issues governing the site; and financial considerations determined by a cost/benefit analysis.
Ryan says that although landfill mining is a process that requires commitments including manpower, time, equipment investment, dealing with permitting obstacles, and dedication to avoiding environmental issues and complaints from neighboring citizens, the process is one Ocean County Landfill Corp. has fully embraced.
“We’re the only privately owned and operated landfill left in the state of New Jersey, and we’re the only landfill facility that’s located in the county of Ocean—we’re basically written in the county’s solid waste management plan as the lone disposal site,” Ryan says. “From the perspective of trying to keep this facility open, to serve the needs of the county that we’re in, obviously that comes with responsibility of trying to do what we can to serve the needs of the residents as long as we can. And without taking on this landfill mining project, we certainly would be closing up shop a lot sooner. It’s an expensive project, but I think if you look at the cost versus the benefits, there’s no doubt it’s well worth the effort.
“We are pleased with the results and progress to date. We believe extending the lifespan of our facility to continue to meet the waste disposal needs of Ocean County for an additional 10-plus years is well worth the effort and expense.”