New York shut what had been the world’s largest landfill in 2001 after more than 150 million tons of waste had been buried at Fresh Kills — and the 2,200-acre site is now being transformed into a park almost three times the size of Central Park while methane is still collected from beneath the capped, grass-covered mounds

Roughly 150 million tons of household garbage sit under the grass on the western edge of Staten Island. NYC Parks records that the four mounds hold roughly 150 million tons of solid waste.

Not was there. Is there. The trash New York City produced for more than half a century did not go away when the trucks and barges stopped coming. It got buried, sealed, and shaped into rolling hills, and it is now the ground beneath a park.

That park is Freshkills, and how it came to be raises a few obvious questions. What is under the grass? Why is methane still being pumped out from beneath it? And how do you turn a dump into public parkland without pretending the dump was ever really gone?

What got buried at Fresh Kills, and how much

The landfill opened in 1948 on former tidal marsh, and it grew fast. By the mid-1950s it was the largest landfill in the world, taking household trash from all five boroughs. At its 1986-87 peak, the site took in as much as 29,000 tons of garbage a day. That went on, in one form or another, for decades.

A state law forced the closure, and Fresh Kills accepted its last barge of garbage on March 22, 2001. It briefly reopened after September 11 to sort debris from the World Trade Center. What it left behind was four enormous mounds holding roughly 150 million tons of solid waste. Those mounds are the raw material of the park. Nobody dug the trash back out. The plan was always to cover it and keep it covered.

What is actually under the grass now

The mounds you’d walk on are not just piles of dirt over garbage. They are built in layers, designed to keep the waste sealed off from the air, the water, and the people up top. According to Freshkills Park, “these layers stabilize landfilled waste, separate the waste from the environment and park visitors and prevent the release of landfill gas to the atmosphere.” That is the design goal. Whether it holds perfectly forever comes down to maintenance, which is rather the point of this piece.

The full cap runs between 3 and 12 feet deep. It includes a soil barrier at least two feet thick and, on top, a final layer of clean planting soil at least six inches deep, seeded with native plants. The grass you see is doing structural work, its roots holding the surface together.

The hills are also slowly shrinking. As the buried material breaks down, the mounds settle. Freshkills Park notes the height can drop by 10 to 15 percent over time, and that settling continues for at least 20 years after the last waste is placed, with about half of it in the first five to ten years.

Why methane is still being pulled from underneath

Buried food and other organic waste doesn’t just sit there. As it rots without oxygen, it gives off gas, mostly methane and carbon dioxide. Left alone, that gas would seep upward. So the mounds are laced with a network of pipes to collect it. As Freshkills Park describes it, “below the cap, a network of wells, pipes and blowers collect landfill gas from the capped landfill mounds and send it to an onsite purification plant.”

For years, that gas was more than a hazard to manage. It was a product. The recovered methane gets sold to the utility. Back in 2012, Freshkills Park reported that “this methane, enough to heat approximately 22,000 homes, is sold to National Grid and the city generates approximately $12 million in annual revenue from the sale of that gas.” Gas production drops off as the waste finishes breaking down, and the numbers today are probably lower.

How long does this go on? The 2012 plan was fairly clear. Recovery and sale were expected to continue “until the amount of gas produced by the landfill is minimal enough as to no longer be economically viable, at which point it will be burned off at flare stations onsite.”

The plan has since shifted. The park’s more recent engineering page describes the collection system being wound down rather than run forever: “the systems will be decommissioned once monitoring data collected by DSNY and reviewed by DEC shows that they are no longer needed.” The gas gets watched, the sanitation department runs the numbers, the state reviews them, and only then does the hardware come out. A decades-long process. The city’s planners put the useful window at at least 30 years.

What a park almost three times Central Park becomes

Central Park is 843 acres. Freshkills is 2,200. NYC Parks puts it plainly: “at 2,200 acres, Freshkills Park will be almost three times the size of Central Park and the largest park developed in New York City in over 100 years.”

It is opening in pieces, not all at once, which is why most New Yorkers still haven’t set foot on the mounds. The capping itself ran in phases over years, and the finished park is expected around 2036. Sections have already opened with trails, creeks, and grassland that draws grassland birds you don’t easily find elsewhere in the city. The rest arrives slowly, one section at a time, as the ground beneath each mound is judged ready.

The tidy version of this story is redemption: the world’s biggest dump becomes a park, and everyone feels better. The truer version is more interesting and less finished. There is still a working piece of sanitation infrastructure under the grass, gas wells and pipes and monitoring equipment that the state has to sign off on before anyone can retire them. The waste didn’t leave. It got engineered into place, and keeping it in place is a job the site will carry long after the last trail opens.