Take a look inside the massive environmental cleanup preparing the site of High Falls State Park

Deep in the Genesee River gorge, just north of downtown, is a sprawling construction site mostly hidden from public view.

It’s the first of four major cleanups laying — or clearing — the foundation for a future High Falls State Park.

Excavators sit along the river’s edge, clawing at the embankment and the contaminated soils left behind by a gas manufacturing plant more than half a century ago. On this day, a distinct odor hangs in the air.

“That's the coal tar ... that's what you're picking up,” says Jeremy Wolf, project manager with Avangrid, which is handling the cleanup. “It's like a driveway sealer, is how I can describe it. Visually, it looks like a driveway sealer-type tar.”

The gas manufacturing process involved heating coal or petroleum products to produce gas for heating, cooking and lighting.

But a byproduct was a dense, oily liquid that now permeates the subsoil, extending deep into the riverbed.

“We're going to excavate all the way down the bedrock,” Wolf said, “as well as out into the river channel.”

A warehouse-sized tent sits at the edge of the site. Inside is where the most heavily contaminated material is separated and treated before it gets trucked off site. A worker in a hazmat suit with a respirator washes down the dump trucks that pass. And three industrial sized charcoal filters clean the air.

Sprayers also are used to douse the excavators and keep down the dust.

LISTEN: Turning High Falls into a tourist destination.

The worksite sits atop and among the old foundations of the gas plant and the coal-fired Beebee Station that came after. While the soil can be removed and replaced, parts of these structures remains and must be preserved, even strengthened — as is the case with an old river wall dating to 1913.

“(Beebee Station) was built right into the gorge wall,” Wolf said, looking over the ruins, including a section that seems fused with the gorge wall with a door still intact, halfway up. “So this is the footprint of of the power station … this was how it was designed, to be to be left, sort of looking like catacombs.”

It’s that mix of industrial remnants and untamed wilderness — in the heart of the city — that make the gorge such a unique place.

Local officials envision a day, maybe a decade from now, when you will walk along the water down in this space, or possibly zip line through the trees. There might be a small lodge or park shelter, an amphitheater perhaps. All in this place that harkens back to the city’s earliest days.

“That's what's so exciting about this,” said Vinnie Esposito, who heads up regional economic development efforts for New York state. "Most people don't know what's down there, because for over a century, most Rochesterians have not been able to get down there.”

WATCH: Learn more about the vision for High Falls State Park.

Rather, it has been a place to look down on from above, increasingly untouched by man, and reclaimed by nature.

“The wildlife has tended to leave us alone, now that we are here, occupying the footprint of this parcel,” Wolf said. “But we still occasionally do see deer. There are occasional turkey on the property as well. But I'm sure they'll come back when we are done.

The work here won’t be done until next December. This site spans more than 5 acres with an estimated project cost of $26 million.

“The estimate is 30,000 cubic yards,” Wolf said of how much contaminated soil has to be dug out of this site.

That’s upwards of sixty thousand tons. Or the equivalent of four thousand school buses.

“A lot of material,” he said. “But again, some of that is being reused. Some of that is being recycled, some of that goes to the landfill.”

An even larger clean up awaits RG&E and Avangrid downriver: an even older gas manufacturing plant, a total of 13 acres, and a price tag nearing $48 million. Plans and estimates for cleanup of an old city garbage incinerator and of a former Bausch & Lomb manufacturing site are still being developed.

Then comes the building of the park. And ultimately, the operation of it.

“One of the unique aspects about urban parks is they often have a huge economic advantage for the community they're in,” Esposito said. “It's not like, you know, a rural state park that wouldn't impact property values or economic activity other than some facet of tourism. Urban parks are different beasts.”

The city and state parks officials have been studying different models of revenue sharing that might capture some of that increased economic activity or property value to ensure the park has a revenue stream for maintenance and operations.

Elsewhere that has included sharing property taxes generated on increased values and development in the area. Or for the park to be self-sustaining through entry, program or event fees.

There are no plans for private development in the gorge itself, only recreational uses. But the park boundaries could include properties above the gorge, Esposito said, not for the state to own and lease but areas like High Falls Terrace Park, on the southeastern edge. The city owns it and intends for it to eventually become part of the state park.

Esposito is among those most passionate about the potential here, to create something spectacular that is also deeply rooted in history.

“If you go down there now, you see obviously the cliff walls and the rock formations, but then you see structures and foundations from different uses,” he said. “You get a sense that you're not only in a pretty serene place in the middle of the city with this incredibly beautiful waterfall, but you see the history of Rochester before you.”