ROCK SALT. Cleveland generates massive amounts of salt from below ground annually, but few outside academia or the salt industry may know that the area s halite deposits were discovered generations before the
Of over 14,000 applications of salt since roughly 1980, about 19 percent are household and the other 58 percent chemical and industrial. International Salt Company used 10-ton forces to compress 50-pound salt blocks for stockmen and farmers to give to cattle as feed supplements. Similar blocks provide home water softeners the ability to remove ionic compounds from well and other untreated hard waters. The chemical industry demands sodium chloride as solid halite for the production of elemental sodium, sodium sulfate, hydrogen, hydrochloric acid, chlorine gas, soda ash, and caustic soda. Construction of roads since the 1950 s has led to a greater demand for highway salt. By 1979, Cleveland provided over 500,000 tons of salt to Ohio and other Great Lakes states at a value of 28 million dollars a year. Viscose yarn production of rayon, cellulose fabrics, and other synthetic fabrics requires salt in the form of caustic soda. Products dependent on the addition of salt compounds include explosives, detergents, soap, fertilizers, plastics, and synthetic versions of natural materials like rubber.
The Salina Formation is the source of salt beneath Cleveland. It is located at the bottom of a 1500-foot thick section of limestone called the "Big Lime" by drillers and other workers in the mining industry. In the eleven counties near Lake Erie, the Salina Formation is less than 300 feet below ground. Individual beds of salt can be less than 50 feet thick or greater than 100 feet thick. Units dip down to the southeast about thirty to fifty feet every horizontal mile on the surface. This evaporate was deposited under natural conditions without a modern analog for comparison, because deposits of this size do not occur in supratidal zones or in locally barred shallow lagoons.
Salt is recovered from subsurface deposits either by injecting fresh water down to the rock unit, and then pumping the brine mixture back to the surface for processing, or by mining the hard rock formation to get to the halite deposits.
A geologist named Landes proposed a nomenclature in 1945 to distinguish various units of the subsurface geology beneath Ohio and other connecting states. Use of this nomenclature has simplified communication among researchers and private companies, especially salt companies in Cuyahoga, Lake, Geauga, and Ashtabula counties in Ohio. Researchers who used Landes work as a platform to further our knowledge of sedimentary geology include James Pepper, who published in 1947 the first study on Ohio salt to be considered valid by the scientific community. Alling and Briggs conducted a study from 1958 to 1961 on the evaporate facieses and stratigraphic sedimentary units, including the paleography of basins that contributed to the deposition of the Salina group. Also in 1961, Addison Cate produced cross-section illustrations of western Pennsylvania and surrounding areas of rocks from the Devonian and Silurian times of deposition. All of these and other works dependent on Landes nomenclature have helped to target the F2 unit of salt beds currently mined in northwestern Ohio as deposits sourced from the Chatham Sag section of the Michigan Basin.
The first discoverers of salt deposits were animals, which left signs of geophagy, which means literally, "the eating of earth." Geophagy involved the excavation as well as consumption of earth materials. Animals ate the soils to get nutrients and elements in the source rock formation not available in the diet temporarily or seasonally in necessary amounts. Animals typically accessed the formation through digging, using body parts as tools, and the repeated licking of surfaces. By following and observing animals such as deer and buffalo, early peoples and later settlers learned of the contents within rock formations containing minerals, especially salt.
Mining of rock salt by native peoples of North America has been deduced through modern archeology. However, little is known about salt usage by the
Early attempts to remove impurities from brine salt before drying and evaporation processing suggest that peoples without formal education had some working knowledge of the chemistry involved. To clean the brine, settlers added egg whites to pick up acids, and bovine blood, tallow, or heavy alcohols like beer to concentrate the impurities. In time, a scum developed on top of the brine that could be skimmed off, removing the salt impurities with the additives.
In 1809, much of the salt used in Cleveland came from Onandaga, New York, or Pittsburg, Pennsylvania, for twenty dollars a barrel, or from salt springs nine miles west of Youngstown, Ohio, because other, local brine well production sites could not meet Cleveland s demands. Partly in response to this demand for salt,
Natural gas and anthracite coal exploration led to the accidental discovery of salt along the Lake Erie shoreline in the later half of the 19th Century. Private citizens had searched for oil since the Civil War. They were thrilled with the 1863 discovery of salt in Ohio that quickly made it the third greatest salt-producing state in the Union. Prominent west-side residents had been occasionally successful in attempts to finding natural gas when drilling in their privately-owned wells, but salt deposits were generally unknown until the
By the late 19th century,
In Northeastern Ohio, five salt companies popped up during this period. It is now known that approximately half of the total 1,470 feet of Silurian deposits of the Salina group are under northeastern part of the state of Ohio. Since the nearest natural outcroppings of rocks of the Silurian age to the city of Cleveland are located in Port Clinton, Ohio, the local access to brine wells within the city provided an important convenience for industry and private consumers.
Sterling Morton and Clarence Foster from Sterling Salt Company near Buffalo, New York, took an interest in this salt revolution occurring at a time when the last local coal deposits were being emptied. Foster examined records of discoveries from
In 1957, International Salt Company acquired Whiskey Island, the peninsula in the Cuyahoga River about 1.5 miles from downtown Cleveland. Whiskey Island is the surface entrance to a large rock-mining establishment beneath the city. 9000 acres have been mined by several companies at the site located about 1765 feet below the surface, obtained on a royalty basis from the City of Cleveland and the State of Ohio. The mine has two elevator shafts, one for entering and the other for exiting, which extend down 1793 feet to the mining floor. The personnel elevator ride takes over four minutes in a cage that can hold up to thirty people in one trip. When salt production began in 1961, International Salt Company employed over 200 workers. Rooms sizes are 45 feet wide and 18-20 feet tall, separated by safety pillars of 105 feet square a roof of salt at least 2.5 feet thick before changing strata units. About half of the salt in each unit is mined and removed to the surface, and the other half of the salt volume remains in the pillars. These pillars support more than 350 vertical feet of deposits above the galleries currently excavating the bed called F2-B. The rock salt removed after blasting one room can be up to 650 tons in weight.
Crushing larger blocks makes it easier to physically move the salt in the rooms, and to remove impurities from the rocks. At the earliest stages, waste deposits separated from the desired rock salt are replaced back into rooms that have been completely mined. This simplifies disposal by recycling space with natural resource byproducts and helps to channel fresh air to ventilate the rooms where mining is currently underway.
Cutting away masses of rock within a short period of time can lead to structural change in the mine or accentuate natural structural inconsistencies. There is some structural deformation in the area of the Salina beneath Whiskey Island, although it is difficult to discern how much of this deformation results from the loss of weight of salt being removed rather than merely representing natural variations in the rock unit s composition. Only two faults currently run through the mine. One fault is displaced only four feet and six inches at most, while another is fifty-seven feet in displacement. Because salt is relatively mobile sedimentary rock, displacement can occur as the spilling and misshaping of pillars between rooms, the roof slouching or breaking into slabs along lines of cleavage, and the floor heaving. Any displacement that has occurred in large amounts other than the presence of these two faults has not been revealed by the public relations of the International Salt Company.
Faults and other porous features in rock mines can provide additional research opportunities aimed at future industrial application, or conversely, the exposure of risks. In his masters thesis, Michael J. Clifford analyzes the feasibility of injection pumps returning brine into rock units after rock salt mining in Cleveland. The International Salt Company penetrated the Salina Formation under Whiskey Island to a depth of 1,900 feet in 1972. Water leaking from the freshwater aquifer unit of the Oriskany Sandstone at a depth of 1,350 feet and let freshwater mix with the rock salt and create brine in the access wells. Initially, this brine was pumped up to the surface and discharged into the Cuyahoga River, which incited legal action against the International Salt Company. The company began considering other means of brine disposal, filed for a permit, and was granted one in June of 1971. With this permit, an observation well that had been drilled to the Oriskany Sandstone in 1959 was converted to a brine disposal well. The brine was pressure injected into the porous unit after filters and a pump were installed in May of 1972. Injection pressure is limited to fifteen gallons per minute into the unit at a pressure no more than fifty pascals per square inch. Since non-fresh water fluid injection is practiced in other units in Ohio as well, brine injection seems a minor threat to wells accessing the Oriskany Sandstone aquifer. Other wastes disposed by pressure injection are pickling liquors and phenols from steel productions, radioactive liquids, mixed organic such as plastics and insecticides, and other liquids which are expensive to treat in surface facilities, or for which no treatment is known with current technology.
One of the dangers not disclosed to the public is the possible impact on the stability of Cleveland s geographic structure of large amounts of freshwater or groundwater entering those interconnecting spaces in the International Salt mines which range three-fourths of a mile beneath the coast of Lake Erie, one and a half miles in the east-west direction, to a depth of six miles beneath Lake Erie s bottom. A model demonstrating the dynamics of cavernous dissolution under Cleveland s urban infrastructure has not been developed because of a lack of data. The shifting of overlying strata to an extent of between six to eight feet due to solution mixing at a Painesville artificial brine production site might provide some rough sense of what could happen to Cleveland. However, although as of the 1978 date of the study the strata had not ruptured, the spatial relationship of strata, dissolution cavities, and subsurface open spaces was completely unknown. So the Painesville site provides a poor comparison to the Whiskey Island mine.
The presence of two faults and the past formation of brine from freshwater leaks do not necessarily indicate significant danger to the city of Cleveland, however. At a horizontal extent of less than 2 miles and a vertical distance of twenty feet being mined out of over 1765 total feet of strata, the mine represents only a small fraction of the whole rock record beneath Cleveland. The odds of freshwater penetrating all of the overlying units and then dissolving halite in quantities to adequately displace above municipal structures are slim indeed.
The Silurian salt deposits are among the most economically important evaporate deposits in North America. The need to more precisely pinpoint the location and extent of salt and other mineral deposits was discussed as a high priority by Benjamin Tappan when he proposed the formation of a geological society to the Ohio at the State House of Representatives in late 1832. Although Ohio was one of the greatest salt-producing states during the Civil War, annual production decreased to less than 30,000 tons by 1890. Salina salt discoveries in Ontario in 1866, Michigan in 1881, and New York in 1878 provided alternative, more appealing sources of salt, with more concentrated brines and fewer impurities. It cost companies in Ohio three times as much to produce the same quality and quantity of salt as the firms in Canada and other states. In 1906, State of Ohio Geologist Edward Orton, seeking evidence of new opportunities for the local salt industry beyond those suggested in data taken in 1888, investigated and organized records available from private enterprise. Nevertheless, salt production in that year had multiplied by ten compared to decades earlier. Sales for The Union Salt Company during the three-month period ending on March 31, 1911, had a value totaling somewhere in the range of $10,061.12, although external accountants noted that this figure was not entirely reliable due to sloppy corporate bookkeeping. From 1931 to 1945, Ohio s annual salt production rose from 1,398,000 to 2,764,926 short tons, valuing at about $3,997,759. By 1945, Ohio was the third largest producer, and provided 18 percent of the nation s total salt output of 15,394,141 short tons. In 1945, 2,500,000 tons went towards the production of chemicals for the war effort, including applications in high-octane fuels and munitions. Engineers Gerald C. Gambs and George W. White, who were the contemporary recorders of these statistics, summarize the importance of Cleveland s rock salt in this period, "With its abundant supplies of salt and other vital raw materials Ohio can look forward to leading the way in the chemical industry for years to come."
Beverly R. Nordahl
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