Coal Waste Impoundments Risks, Responses, and Alternatives (2002) / Chapter Skim
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8 Conclusions and Recommendations
8 Conclusions and Recommendations
Pages 165-174
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From page 165... ...
Second, the committee was charged with evaluating the accuracy of mine maps and exploring ways to improve surveying and mapping for underground coal mines with the goal of delineating more accurately how underground mines relate to current or planned slurry impoundments. The third committee task was to evaluate alternative technologies that could reduce the amount of coal waste generated or allow productive use of the waste.
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From page 166... ...
Hence, the committee recommends that MSHA review its current practice and develop guidelines for the design of bulkheads intended to withstand hydraulic heads associated with slurry impoundments. While the embankments designed and constructed under the current regulatory system have generally performed according to design, the committee believes that prudence requires that MSHA and OSM continue to evaluate worldwide experience with impounding structures, and to stay abreast of lessons learned from failures experienced in other mining applications so that their design criteria reflect the latest experience in all the mine sectors.
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From page 167... ...
The committee recommends that MSHA and OSM consider requiring additional continuous monitoring in specific instances and evaluate automation of monitoring instruments. SITE CHARACTERIZATION The committee examined two parts of the question of site characterization, the accuracy of mine maps and the use of geophysical techniques to delineate the extent of underground mine workings In situations where maps do not exist or may not be sufficiently accurate.
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From page 168... ...
on the mine map, · Adding a qualifying statement to accompany any coordinate transformation that is based upon the alignment of surface features, Improving and maintaining the location of surface controls, · Determining which mine permit documents should be retained, in what form, and for how long, · Avoiding the use of coal seam names as the sole basis for determining the vertical location of an abandoned mine. In situations where no mine maps are available or there is reason to doubt the accuracy of maps that do exist, additional investigation of the relative location of underground mine workings with respect to an existing or proposed impoundment is warranted.
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From page 169... ...
The opportunities for reducing slurry volume include mining alternatives and coal processing alternatives. However, modem methods of surface and underground coal mining offer only a limited possibility for quality control during mining.
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From page 170... ...
Further research is needed on the use of fine coal waste slurries as feeds; incentives may be needed if these technologies are to be utilized widely for fine coal waste combustion. While coal combustion wastes from power plants are already being used for a number of purposes, the issue of the safe handling of coal combustion waste from these advanced combustion technologies should be studied further.
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From page 171... ...
Profitable remitting may be possible if impoundments contain at least 1 million tons of in-situ slurry material, at an expected recovery rate of a marketable fine coal product of not less than 30 percent. The committee concludes that, as advances are made in the use of low value coal or coal water slurry, remitting of slurry impoundments can be an attractive source of fuel.
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From page 172... ...
Proposed new impoundments should also be assigned to risk categories, based on a combination of hazards and consequences, as was suggested for existing impoundments. To maximize the potential for risk reduction, the committee recommends that all impoundment designs be accompanied by a risk analysis utilizing qualitative methods.
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From page 173... ...
SUMMARY The conclusions and recommendations offered above reflect the committee's judgments concerning ways to improve the design process for coal waste impoundments, ways to improve mapping of mines and the characterization of sites of existing and future impoundments, and ways to improve the assessment and mitigation of risks associated with impoundments. The committee believes that implementation of those recommendations will substantially reduce the potential for uncontrolled release of coal slurry from impoundments, particularly through the mechanism of breakthrough into nearby underground Nine workings.
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From page 174... ...
The relatively clean flue gas goes on to the heat exchanger. This approach theoretically simplifies feed design, extends the contact between sorbent and flue gas, reduces likelihood of heat exchanger tube erosion, and improves SO2 capture and combustion efficiency (DOE, 2001~.
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