500 Million years ago, the area surrounding the Great Lakes was an ancient salt water body. 100 million years following that time, the sea dried up due to volcanic activity, creating the Silurian, or salt formation. Movement of glaciers in the region covered the 100 foot thick layer of salt. This highly useful material that we define as rock salt was discovered in the latter half of the 1950s by a test drilling company hired by International Salt Co.
At that time, it was determined by International Salt that production could reach 1.5 million tons of the material per year, and the deposit itself could hold 170 million tons, and they were granted a lease by the State of Ohio to mine the material under the lake. A peninsula known as Whiskey Island in Cleveland, Ohio was set as the location for operation, and construction of the mine began in 1958.
Upon the completion of construction in 1961, the depth of the mine reached 1,800 feet, or two-and-a-half times the height of the Terminal Tower. An elevator shuttled men and machinery down the mine’s shaft to corridor dubbed “main street,” or the main drag of the mine. International Salt used the ‘room and pillar’ method to extract the salt. 50% of the salt is left behind in the form of columns 100 feet in diameter to support the ground and Lake Erie above. This is done by drilling into the salt and pumping it full of an explosive, called ammonium nitrate. Rooms measuring 30’ by 40’ and 16’ high are left behind, along with roads connecting the rooms measuring 40’ feet wide.
Due to the physical characteristics of the mine, and the fact that it stretches over two miles out from the shoreline, people have called it an “underground city.” International Salt’s underground city has been a major industry for the city of Cleveland, which offered over 200 jobs to run the mine. The union-based job offered year-long employment because the mine was kept at a constant temperature of 75 degrees.
Mining was interrupted in 1981 when the United States Department of Energy requested use of the mine for an experiment involving nuclear waste. The DOE proposed experiment would determine if the mine could safely house nuclear waste. Even though the DOE promised that the mine would not become an N-waste dump, Clevelanders and officials were outraged, and protests followed. The DOE refused to drop plans of the tests, despite bitter objections from leading protester, Representative Mary Rose Oakar, who claimed that the DOE was lying about the true intentions of the tests. Finally, in February 1982, Cleveland City Council passed an ordinance to restrict the testing, which resulted in the surrender of the DOE to press forward.
The mine is still in operation today, owned and operated by one of the world’s largest producers of rock salt, Cargill Incorporated. The mine does not offer tours, leaving media as the only means for the public to experience it.
Photograph Courtesy of Cleveland State University, Michael Schwartz Library, Special Collections, Cleveland Press Collection, James Thomas, 7/13/1962
This photograph, taken in 1962 is a picture of what International Salt Co. workers deemed “Main Street.” It was given the name due to its utility as the main corridor for entering and exiting the mine. At 1,800 feet below the surface this particular street was 40 feet wide and 30 feet high, making it an ideal location to reassemble heavy machinery that was sent down the elevator shaft to extract rock salt under Lake Erie.
Photo courtesy of http://www.ishouldabeenastripper.com/2010/01/c-cleveland_30.html
The room and pillar photograph shows the hollowed Salina salt formation after salt extraction. The method of mining used is called “room and pillar,” where explosives are used to blast rooms roughly 40 feet in diameter, and 16 feet high, while 100 foot sections are left to support the ground above. The salt is loaded onto an elevator where it is transported to the surface. A vast network of rooms like this extend about three miles out under Lake Erie.
Photo courtesy of Cleveland State University, Michael Schwartz Library, Special Collections, Cleveland Press Collection, James Thomas, 3/18/1960
This arial photgraph taken in 1960 shows the size of the mine’s facility. Notice the large barges towards the top of the picture. The facility was able to transport rock salt to the Cuyahoga River which empties into Lake Erie. The facility was also in proximity to railroads making the site of the mine an excellent location to transport its product.
Photo courtesy of Cleveland Public Library, Cleveland Plain Dealer, 12/7/1958
This advertisement was published to attract business owners to buy International Salt’s deicing salt. In this context, a slip hazard was threatening to business owners for various reasons. The cartoon depicts total chaos at Sam’s storefront. This advertisement was published before the mine was in production.