Browsing by Author "Conolly, Carol L."

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Coal Reserve Assessment and Database Development of the Danville and Springfield Coal Members in Indiana: Final Report
(Indiana Geological Survey, 2001-01) Conolly, Carol L.; Rupp, John A.
This study assesses the coal resources of the Danville and Springfield Coal Members (Dugger and Petersburg Formations, respectively) in Indiana and provides new estimates of the tonnage of coal in the following categories as of January 1, 2000: original resources in place, resources remaining after mining, identified resources, demonstrated reserve base, accessible reserve base, and estimated recoverable reserves. In addition, the sulfur, heat, and ash content of the Danville and Springfield Coals were mapped in order to allocate indicated reserves, demonstrated reserve base, accessible reserve base, and estimated recoverable reserves according to specified categories of sulfur, heat, and ash content. The resources and reserves categories are defined based upon criteria for minimum coal thickness, overburden thickness, and reliability category. Three reliability categories are used to express the relative degree of geologic assurance or reliability of the resource estimate based upon the density of coal thickness data points that are used to derive the resource estimate. The reliability categories are: measured (0-0.5 miles from the data point), indicated (0.5-2.0 miles), and inferred (2.0-4.0 miles). The geologic and land use factors which limit the mining of the Danville and Springfield Coal were identified through interviews with geologists and mining engineers from companies mining these coals in Indiana and Illinois. These factors were mapped and then applied to the tonnage of demonstrated reserve base in order to calculate the tonnage of accessible reserve base. Recovery-rate factors for surface and underground mining (80% and 50%, respectively) were estimated using proprietary mine recovery rate data from mines operating in the Danville and Springfield Coals during the 1980s and 1990s. Estimated recoverable reserves were calculated by multiplying the accessible reserve base by these recovery-rate factors. The tonnage of original identified resources of Danville and Springfield Coal in Indiana is calculated to be 18.8 billion short tons (tonnage by coal bed is also provided in this report). Of the 18.8 billion short tons, 1.8 billion short tons have been removed by mining or lost in the mining process, thus leaving 17.0 billion short tons of remaining Danville and Springfield resources. Of the remaining resources, 16.4 billion short tons are demonstrated reserve base. Technological and land use restrictions remove 9.2 billion short tons of demonstrated reserve base from potential mining, thus leaving 7.2 billion short tons (38.2% of the original resources or 42.3% of the remaining resources) of accessible reserve base. Of the 7.2 billion short tons of accessible reserve base, 0.9 billion short tons (4.7% of the original resources or 12.3% of the total accessible reserve base) are estimated to be recoverable by surface mining, while 3.1 billion short tons (16.4% of the original resources or 43% of the total accessible reserve base) are estimated to be recoverable by underground mining.
The Availibility of the Danville Coal Member for Mining in Indiana
(Indiana Geological Survey, 2000-06) Conolly, Carol L.; Zlotin, Alex
This study assesses the resources of the Danville Coal Member in Indiana and identifies those resources that have the most favorable geologic and land use characteristics for mining. The tonnage of original coal in place, remaining coal after mining, coal unlikely to be mined due to geologic and land use factors, and available coal resources were calculated for the Danville Coal in Indiana. The geologic and land use factors which restrict the mining of the Danville Coal were identified through interviews with geologists and mining engineers mining the Danville Coal in Indiana and Illinois. These restrictions were applied to the tonnage of remaining Danville Coal resources in order to calculate the tonnage of available resources. The original, remaining, and available coal resources are reported in terms of potential method of mining, "surface" or "underground," coal thickness, "14-28 inches," "28-42 inches," or "greater than 42 inches," and overburden thickness, "0-200 feet," and "greater than 100 feet." Coal that lies between depths of 100 and 200 feet is considered minable by both surface and underground methods. Additionally, the resources are categorized by three levels of geologic assurance or reliability. The reliability categories express the degree of reliability of the resource estimate based on the density of coal thickness data points that are used to derive the resource estimate. The three reliability categories are: measured (0-0.5 miles from the data point), indicated (0.5-2.0 miles), and inferred (2.0-4.0 miles). The total volume of original Danville Coal resources in Indiana is calculated to be 6.55 billion short tons. Of the 6.55 billion short tons, 0.36 billion short tons have been removed by mining or lost in the mining process, thus leaving 6.19 billion short tons of remaining Danville resources. Technological and land use restrictions remove 5.36 billion short tons from potential mining, leaving 0.83 billion short tons (13% of the original resources or 13% of the remaining resources) available for mining in Indiana. Of the 0.83 billion short tons of total available resources, 0.52 billion tons (8% of the original resources or 63% of the total available resources) are available for underground mining, while 0.31 billion short tons (5% of the original resources or 37% of the total available resources) are available for surface mining.