Retsof Salt Mine, New York

In 1994, this was the largest salt mine in North America, and the second largest in the world. 300 people worked within the 6,000 acres of excavated space, a thousand feet below ground, extracting salt from a natural deposit for use as road salt, table salt, and in industry. In March of1994, however, the ceiling in one of the large underground chambers collapsed, the first of a series of effects caused by groundwater entering the salt deposit, which had been dry for all of the 110 previous years of mining at the site. Over the next 21 months, the mine cavities collapsed and filled with water. Mining operations scrambled to work the accessible areas before the spreading flood, until operations were suspend when the mine was fully saturated with water, in 1995. The effect of filling all this space sank the aquifer, leaving many drinking water wells dry, and led to surface subsidence, even sinkholes 200 feet wide, damaging structures and highways. 8 or 9 feet of additional subsidence is expected to take place over the next century. In 2000 a new mine, the Hampton Corners mine, opened 10 miles away, a new vertical shaft accessing the large salt deposits of the area, possibly beginning a new era New York salt mining.