Hidden underground danger: North Jersey's 600 abandoned mines

NEW JERSEY — An unstable crater in the forest floor is just another reminder of the state's rich mining history and the many tunnels left behind and hiding just under the surface.

Timothy Rack stands beside the flooded 15-foot wide crater. A swath of black plastic netting separates human from hole.

“It looks like a little bit of soil subsidence on one side, some rocks sliding in,” Rack, safety manager for the Morris County Parks Commission said in 2018. “It’s kind of hard to tell whether it’s a big deal or not a big deal.”

The ovoid depression is one of many pits, shafts, and tunnels carved into the rolling hills of North Jersey by iron miners more than a century ago.

Dark-gray gneiss speckled with gleaming quartz surrounds the pit's edge. Similar depressions are nearby. In the distance, stacked-stone foundations are camouflaged by leaves. School buses rumble past.

"The pit is losing water," Rack says.

Usually, the various features comprising the region’s hard rock mines stay relatively stable. When the features change, Rack acts to address a potential collapse.

"The concern is: It's going to fall in," Rack says, gesturing to the surrounding rocks and soil. "I think it stabilized itself, but it's hard to tell. If somebody walks on that and falls in with in, they may end up infinitely lower than we are right now," he said pointing to a rock pile.

The 600 mines of northern New Jersey region represent just a fraction of the nation's 500,000 abandoned ones, according to the the Bureau of Land Management. Still, area officials and experts remain concerned about the condition of partially-hidden shafts and tunnels left behind by three centuries of activity.

Hard to find, often poorly mapped and easy to forget, these underground tunnels can be deep, narrow and prone to collapse.

Some shafts and tunnels have only been discovered after sinkholes appeared and swallowed porches, roads, and backyards in the last 50 years.

Rack installed the black plastic in the Morris County reservation at the end of February as a temporary barrier in case a hiker strays from the trails to explore the pock-marked terrain.

Further inspections from New Jersey Department of Labor's Mine Safety Compliance Unit will be needed to determine whether or not the fenced crater — part of the Dodge Mine — is a candidate for a more permanent solution.

Filling the shaft with expanding concrete is an option, Rack said. Chain-link fencing is a more likely, cost-effective solution, he added. Another flooded depression sits unguarded just feet away.

The Dodge Mine opened in 1868 and closed 16 years later, state records show. The multi-shaft mine - probably three of four, Rack said - dipped more than 130 feet into the ground as miners traced two veins of magnetic ore containing 50 percent iron.

Approximately 12 feet in width, the veins ran a half-mile northeast to the Ford and Schofield mines near the highest peak in Morris County, renowned mining expert William Bayley wrote in a 1910 report for the Geological Survey of New Jersey.

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Bayley surmised that the mines were likely swells on a single snaking vein topped by green granite spotted with lichen.

The Dodge Mine already contains one stone-walled shaft surrounded by a small square of chain link — "probably a well," Rack said. The records are spotty. The Weldon group of mines ceased operations in 1896.

Long before strip malls, petrochemical tanks, and office buildings, such bands of iron mines dotted New Jersey's northern Highlands and fueled the economy.

The scars remain.

In North Arlington, the Schuyler copper mine underlies post-war housing. In Mine Hill, tunnels snake under busy streets and into surrounding towns. And in Ringwood, iron mines bookend a neighborhood where Ford Motor Company left a toxic legacy consisting of industrial waste and sinkholes that are now part of life.

"To me it was just normal," said Wayne Mann, who grew up in Ringwood's mining district. "We played around the holes, and I really didn't think twice about it."

The abandoned mines were Mann's "playground."

Ringwood's mining district once contained 42 working mines. The largest, most famous, and now the most polluted is Peters Mine. Covered by a pond filled with pumpkin-colored water, the mine dips more than 1,800 feet beneath the surface and serves as the focus of a 500-acre Superfund site.

Peters Mine opened to provide shot for the Revolutionary War and was rehabilitated in 1942 for brief use during World War II.

The mine contains 17 levels that root off horizontally under state parkland and Mann's old neighborhood. That mine, the nearby Cannon Mine, and a municipally-sanctioned landfill in between the two also contain pollution from paint sludge and other industrial waste dumped by Ford Motor Company with the approval of borough officials in the 1960s and '70s

"Dumping was like a normal, everyday thing there," said Mann.

Researchers from New York University and others are studying the relationship between the pollution and reported spikes in cancer and early death among local residents. Still, Mann said the pollution is far from the only concern for residents.

The neighborhood off Peters Mine Road has seen a portion of Sheehan Drive lost to a sinkhole in 2007, a 15-foot deep pit open up off Cablehouse Road in 2005, and a 60-foot-long chasm open up near Van Dunk Lane in late 2016.

In 1963, when Mann was just a boy, Harry Van Dunk fell into a collapsing mine shaft while playing with friends in the woods surrounding the neighborhood. Van Dunk was 15. He was never seen again.

"We were running around mines and pits that we really didn't know," Mann said.

Mann said he did not start to truly understand the danger lurking below his old neighborhood until 2005 when the ground started to give near two homes on Van Dunk Lane. The following year, that subsidence near the polluted Cannon Mine forced the homeowners to vacate.

"It's a grave concern, because you don't know whose yard could be next," Mann said.

Only about 0.12 percent of the roughly 500,000 abandoned mine sites in the nation are in northern New Jersey, according to estimates from the federal Government Accountability Office.

Built into hard rock, namely gneiss and granite, the area's mines suffer from isolated subsidence in comparison to those in coal country, federal reports show.

The surround rock is preventing collapse and preserving the danger associated with the region's 4,000 mine shafts, said Ronald Mishkin, a retired miner, mining historian and geologist.

A change in shape could hint at a forming sinkhole or tunnel collapse, Rack said. Old mine shafts were often held open by timbers that have collapsed, become entangled, and collected enough debris to appear not as deep pits but innocent depressions in solid ground, Mishkin said.

"It's almost like you to have to wait until there's a problem to say, 'Gee whiz, there's a shaft over there,' " Mishkin said.

A spurt of mine prospecting around the 1880s also left behind a variety of unnamed and unmapped pits and shafts from operations that tapped into small blobs or narrow veins of ore that soon pinched out, Mishkin said.

The shafts that remain can be deep, narrow and deadly, Mishkin said. Adits, which cut horizontally into a hillside, have both provided shelter from aggressive black bear and swallowed lives whole.

The adits fall "off into nothing most of the time,” Mishkin said.

For the most part, to Rack's relief, North Jersey's mines are difficult to find. Piles of fractured granite, flooded trenches, and the occasional threaded rod provide hints, however, said Dan Lopez, a hobbyist mine explorer.

Bayley's maps from 1910 helped Lopez locate most of the area's lost mines. Many of them Lopez said, likely look the same below the surface as they did when they were closed decades if not centuries ago.

"We used to think they were caved, but one day we took a shovel and we started digging one and we actually opened up the mine portal," Lopez said.

Voyaging into these often-cramped chasms is strictly prohibited by the state of New Jersey, which regulates several dozen mines. Lopez said he nevertheless found ways to explore roughly 50 hard rock mines in a four-year period.

Some are just small pits.

Many have flooded, "and they pretty much look like little ponds," Lopez said.

Often murky and decisively uninviting, the ponds provide both a mask and a deterrent for what would otherwise be dangers in need of fencing or filling, Rack said.

Up the sandy bed of the old Ogden Mine Railroad from the angular foundations marking the Dodge Mine lies the fully-flooded Ford Mine. The flooded trench is mirrored by the Schofield Mine just a few dozen steps uphill, where a relatively lower water table reveals a deep trench strewn with trash.

Farther south, along the railway-turned-hiking trail, are the Weldon mines where timbers lie preserved in water.

"We put a fence up to keep people from walking into the mines while looking at their cell phones," Rack said. "Thankfully, no one wants to swim in them."

New Jersey has 2,700 locations where mining or prospecting occurred, according to a 2014 state report. There are about six on Morris County parkland that Rack said are particularly concerning.

Unlike the swamped mines in Jefferson, the mines 10 miles away in Mount Hope's historic mining district are among the driest and deepest, Lopez said.

"You’re talking hundreds of feet. They scare me to death," he said.

Dating to 1710, the Mount Hope mines are among about 80 major iron mines of the more than 500 that existed in the region, Mishkin said. The mines are also some of the oldest and most productive in the state, he added.

Hikers frequent the site today to walk well-maintained trails that are purposely kept at a distance from subsidence pits, shafts, and adits, Rack said.

Those large mines are generally the safest today, simply because they were productive, Mishkin said. The more important the mine, the more likely it was well-mapped and either fenced in or capped by large rocks or steel bars and several feet of concrete, he added.

"The danger is these small, prospect holes," Mishkin said.

Mishkin said too much improvisation in early mining resulted in smaller or prospect mines becoming either poorly mapped or not mapped at all.

"The state’s susceptibility to subsidence is due in part to the number of abandoned mines throughout New Jersey," according to a 2014 state report on geologic hazards. "One problem is that the mapped locations of some of the abandoned mines are not accurate."

The abandoned iron mine entrance that swallowed Andrew Kauff's backyard in Mine Hill was supposed to be 65 feet from his home. He found out otherwise two years ago as he stood staring that the hole, 19 feet deep and 20 by 30 feet, just 15 from his home. Kauff said things could have been much worse.

"It's funny because that same night I was laying in bed and I heard a thud," Kauff said. "I looked out the window and another section of my yard had dropped into the hole."

The cave-ins in Kauff's backyard swallowed roughly 15 truckloads of soil from the yard, said Sam Morris, Mine Hill's mayor. The shaft dated back to the late 1800s, he said.

Kauff said he shudders at the thought of what may have happened if the tunnel was just a few feet closer to his home.

"My son and his girlfriend were living in the basement at the time," he said. "It would have been a disaster."

Roughly 200 feet away from Kauff's home is Xenia Court, a residential street well known for its sinkholes. Cave-ins there as recently as 2014 have helped bring the total number in Mine Hill to seven since 2012, Morris said.

In the 30 years prior, there were 77 collapses in or around abandoned mines throughout North Jersey, state records show. Collapses in 2005 and 2007 near Rockaway's White Meadow Mine, cost more than $500,000 to manage.

Of the state's abandoned mine sites, approximately 220 have been rated as “high” risk, said Lawrence Hajna, a spokesman for the state Department of Environmental Protection. Those mines had cave-ins or feature subterranean shafts, adits, or significantly-sized surface openings, he said.

The mine entrances, generally square cuts of four to seven, are fairly well marked and accurately mapped, Morris said. Still, to monitor Mine Hill's abandoned mines, government officials are using drone and 3D-mapping technologies to determine miner changes in elevation.

To ward off disaster, the town also implements strict regulations on building in former mining areas that requires the use of ground penetrating radar. Records are kept for those applying for development permits or buying new homes in the area.

Radar was also used in Ringwood near a 16-acre municipal property containing as many as four old iron mine pits dating to the 1700s that was fenced in last winter.

North Arlington spent about $250,000 to shore up its modern mining community. Comprising five streets, roughly 75 homes, and more than 40 mine shafts, the neighborhood was built in the 1940s atop one of the state's oldest mines.

The Schuyler Copper Mine opened in the 1710s and closed its shafts in the early 1900s. Yet, porches, roads, and backyards have been swallowed in the last 50 years. Some involved the reopening of loosely-filled shafts. Others were the result of collapsed tunnels once cleared of groundwater by the nation's first steam engine, Mishkin said.

Today, the area is monitored for settling that could denote a potential for collapse, said Brian Intindola of Neglia Engineering Associations who consults for the town. Thankfully, the measurements have remained mostly unchanged over the last decade, Intindola said.

Officials in Mine Hill are hoping to see similar results when the drone returns to capture comparison images next summer, Morris said. The threat of sinkholes seems to be subsiding, he said.

"There may be one or two that open up in the woods some place, but as far as people's real estate I don't see it," Morris said.

Staff writer Jai Agnish contributed to this article.