Whiskey Island mine

The mine taps under Lake Erie into the F₁ unit of the Salina Formation, which is more than 70 feet (21 m) high in the area.^[4][5] According to mine manager Bob Supko, it is unusual for a salt mine to be located in an urban area (downtown Cleveland), but it keeps supply close to Cargill's business.^[6] The location is leased from the State of Ohio,^[7][8] and royalties are paid to the state and the City of Cleveland per amount of salt mined.^[5]

Access to the mine is on the shore of Lake Erie on Whiskey Island, where the above-ground facilities are located.^[9] The mine dives through limestone to a depth of 1,793 feet (547 m),^[5] a four-minute trip by elevator,^[10] before expanding horizontally under the lake, which is only 56 feet (17 m) deep here.^[11][9] The mine has grown significantly over the years, from 4 square miles (10 km²) in 2013^[9] to 12 sq mi (31 km²) in 2016^[11] to 16 sq mi (41 km²) as of 2023^[update].^[10] The temperature inside remains around 70 °F (21 °C) year-round.^[6][10]

Mining takes place using the room and pillar system.^[8] Salt is removed by drilling holes filled with ammonium nitrate, an explosive,^[10][6][9] then transported by conveyor belt and cut before it is lifted to the surface.^[6] Pillars are left behind for support and allowed to flex in a technique called "yielding pillar".^[8] There are hundreds of rooms in the mine, and each room has a height of about 25 ft (7.6 m) and an area of about 45 sq ft (4.2 m²).^[12] They branch off east and west from a 4-mile (6.4 km) primary tunnel extending to the north.^[10] According to engineer David Harris, "it’s surprisingly similar to how it was mined 50 years ago".^[10]

As of 2023^[update], there were 223 workers at the mine.^[10] The miners are members of the union Teamsters Local 436.^[9] Equipment is transported down the mine in pieces and, once assembled, remains underground forever.^[6][13] Maintenance is also performed underground.^[13] The low humidity prevents the machinery from quickly rusting.^[10]

The average yield is 12,000 short tons (11,000 t) per day.^[10] According to engineering manager Bob Nelson, demand for salt is relatively stable compared to other parts of the mining industry.^[10] Superintendent Nick Newsome claims that "about 80 percent of our production goes to de-icing control".^[6] Salt is also used in the manufacture of a wide variety of materials.^[5] The mine supplies salt across the Snow Belt and was the largest supplier for Ohio in 2012.^[9] Shipping by boat takes place from April to the end of the year.^[10]

As of 2013^[update], reserves are expected to last for another 100 years.^[6]

For most of the 19th century, Cleveland relied on salt from Youngstown or out-of-state.^[5] The present deposit was discovered accidentally in 1886 when drilling for natural gas.^[5] Construction of the mine began in 1958 by the International Salt Company.^[7] Production began in 1962,^[4][7] and the company would be renamed Akzo Nobel Salt following an acquisition.^[7] The mine was acquired by Cargill in 1997.^[9] The company launched a $13.8 million expansion of operations in 2010.^[9]

In 2012, Cargill, along with Morton, its only competitor in the state,^[14] were the target of an antitrust lawsuit filed by the Ohio Attorney General.^[9] The suit alleged price fixing in rock salt sold to state and local governments.^[15] In 2015, the case settled for $11.5 million.^[16][14][17]

On August 19, 2013, the mine was shut down indefinitely after the discovery of a potential cave-in threat.^[9][1] Sensors had detected a convergence, or narrowing between the floor and ceiling, measuring fractions of an inch.^[8] Local geologists suspected that it was caused by weight sagging above and predicted that the closure would not be permanent.^[8] Below-ground workers were given paid leave^[1][9] while the company brought in consultants from the Ohio Department of Natural Resources (ODNR) and the Mine Safety and Health Administration (MSHA).^[18] Above ground operations, including shipping, were not affected.^[9] Operations gradually resumed starting ten days later after determining that the affected area was isolated.^[12][18]