Column: Mine Study Seeks to Prevent Collapses, It Should Also Preserve Highlands History

Having a giant sinkhole open in your backyard is a scary thing.

Believe it or not, it happens on average twice a year in North Jersey.

That’s because the Highlands region in particular is rich in iron ore, leading to the creation of hundreds of mines throughout Morris, Sussex, Warren, Passaic and Hunterdon counties. In fact, 95 percent of New Jersey’s 600 known mines are located in the Highlands. The mines were a major reason the region developed and prospered until the discovery of ore in the Mesabi range that was cheaper to mine. The mines closed and homes were built atop them.

Empty cavities of land sometimes cave in.

So it’s important that the state Department of Environmental Protection is about to embark on a $350,000 study of ground instability and subsidence, or surface depressions, occurring in areas with abandoned mines.

The DEP’s New Jersey Geological Survey got a grant from the Federal Emergency Management Agency that it is matching with state funds to more accurately map mines using GPS locations and create a database of scientific information to determine where future collapses are most likely to occur.

Having this kind of data would be very important to at least make property owners and officials alert to, and possibly prevent, future sinkholes. State officials said 77 mine collapses have occurred in the last 30 years.

Rockaway Township, the home of a number of mines, has had numerous collapses in various locations. Most recently, the township had to fill in two sinkholes atop the former White Meadow Mine, in 2005 and 2007. The cost was more than $500,000.

In Morris County, Jefferson, Pequannock, Washington Township, Wharton, Mount Arlington, Mount Olive, the Chesters and, of course, Mine Hill, have abandoned mines.

When the land was mined in the region back in the 1700s, 1800s and even early 1900s, there were few people around besides the miners and their families. Eventually, small communities rose up to serve the mines. As time passed and mining moved west, the mines were closed and buildings grew up atop them.

It’s not just homeowners who have to worry. Schools, churches and businesses are built over or near abandoned mines. There are also mines under parkland and roads—Weldon Road parallels the old Weldon Mine in Jefferson.

Because these are old mines, they typically were supported by wooden beams. But over time, the wood rots. Many of the mines also flood and the forces of rain and freezing and thawing, not to mention gravity, bring on collapses.

The state geologist said the potential for mine collapses is great in many communities.

Some towns have passed ordinances that require a certification that an abandoned mine does not pose a danger before issuing a building permit for a site. Most, however, do not.

DEP Commissioner Bob Martin said the study will also help officials determine where it’s safe to develop and redevelop lands in the region.

Prohibiting construction atop potentially unstable mines is critical. But when the DEP finds mine sites to be stable and not likely to collapse, that should not necessarily give developers a green light to start building.

Even if a site is deemed safe (and is any abandoned tunnel really going to be able to withstand the power of flood waters forever?) there’s the historical significance of the mines to consider.

For instance, the Mount Hope Mine in Rockaway Township is believed to be one of the oldest and largest iron mines in the country. Opened in 1710, it operated for more than 250 years and yielded millions of tons of iron ore.

The State Historic Preservation Office has indicated that Weldon Mine in Jefferson and the iron mines in Montville are eligible for listing as historic sites.

Even non-mining sites like Speedwell Village in Morristown were related to the iron industry, as was the Morris Canal, which ran from Phillipsburg through Morris County to Jersey City.

Places like Speedwell, Waterloo Village and the Sterling Hill Mining Museum in Ogdensburg are known historic places. Almost all of the canal is gone, but signs throughout the region mark its former route. Many of the mines in the Highlands, however, are not even signed.

DEP officials will be reviewing historic documents relating to the mines, some of which are original maps. Hopefully that will convince them that many of these sites need to be preserved, not just so they don’t collapse, but also to keep the past alive.

Click here to see old maps and drawings of mines.

Colleen O'Dea is a writer, editor, researcher, data analyst, web page designer and mapper with almost three decades in the news business. Her column appears Mondays.