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Planned coal mine subsidence in Illinois — a public information booklet
EXCAVATIONS:SUBSIDENCE operation involved the use of a floating bucket-ladder dredge with an integrated, gravity-based treatment plant to extract free particulate gold from the seabed gravels. Three-quarters of the throughput was disposed of at 1.5 m below sea level through two pipes, each of 0.51-m diameter. The system's design resulted from considerable trial and error and modeling studies to achieve regulated seawater conditions. The mining permit specified waste discharge controls and environmental impact limits for topics of local concern: the dredge's effluents, the red king crab population (an important fishery resource), seawater turbidity, and bioaccumulation of trace metals, especially mercury (a remnant of prior beach mining). (from Authors)
966358 Review of 23 years of STD: Island Copper Mine, Canada D. V. Ellis, T. F. Pedersen, G. W. Poling, C. Pelletier & I. Home, Marine Georesources & Geotechnology, 13(1-2), 1995, pp 59-99. The submarine tailings disposal (STD) system at Island Copper Mine has been subjected to a comprehensive cnviroumental monitoring program initiated in 1970, some 20 months before the mill started processing ore. The program has been extended and modified as new factors became relevant or it became clear that particular factors were not of concern at this site. The major environmental issues have concerned: 1) tailings resuspension and upwelling, 2) smothering of benthos, and 3) trace metal contaminant from acid rock drainage (ARE)). The results of the monitoring are described. (from Authors) 966359 Effects of changing environmental rules: Kitsault molybdenum mine, Canada T. F. Pedersen, D. V. Ellis, G. W. Poling & C. Pelletier, Marine Georesources & Geotechnology, 13(1-2), 1995, pp 119-133. Initial oceanographic assessments showed that a submarine tailings disposal (STD) system would function to produce a tailings density current that would deposit on the fjord bed. There was substantial community interest and action during the final years of the development at a time when new pollution controls were being developed in Canada. The STD system essentially met its design criteria, but new oceanographic instrumentation at the time showed some contribution of tailings at the outfall discharge point to a naturally present mid-water turbidity layer. The first intensive postclosure monitoring of ecosystem rehabilitation following STD use anywhere in the world was undertaken between 1983 and 1989. Soon after closure in 1983, pore waters in the submerged deposited tailings were observed to be enriched in molybdenum, which must have supported an efflux of the metal to the overlying water. The indicated flux would have been too small to have had a measurable effect on the Mo inventory in the deep waters and, furthermore, was predicted to diminish with time. (from Authors) 966360 Deep water STD at the Misima gold and silver mine, Papua, New Guinea S. G. Jones & D. V. Ellis, Marine Georesources & Geotechnology, 13(1-2), 1995, pp 183-200. The Misima Mine is the pioneer of deep-water submarine tailings disposal (STD) and discharges at 112-m depth, well below the zone of major biological productivity (euphotic zone), onto a steep seafloor slope that leads directly to a deep ocean basin. The system discharges approximately 18 000 tonnes of tailings solids per day and has a mix tank with seawater intake from 82-m depth. Two validation surveys have shown that the system complies with regulatory conditions and meets ambient standards for contaminants well within a submerged mixing zone that extends to 1200-m radius from the mix tank location. Video records obtained by remotely operated vehicle (ROV) show the tailings slurry descending the steep slope as a coherent bottom-attached density current. Geophysical survey and ocean floor sediment
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sampling has confirmed that accumulation of tailings solids are confined to the gently sloping floor of a deep basin. The ocean at Misima is permanently stratified, and it was predicted that tailings would not rise to the surface providing the outfali was deeper than 100 m. After 5 years of continuous operation, no tailings material has ever been observed in the surface waters. (from Authors)
966361 Issues in assessing the long-term stability of engineered landforms at Ranger Uranium Mine, Northern Territory, Australia S. J. Riley, Journal & Proceedings - Royal Society o f New South Wales, 128(3-4), 1995, pp 67-78. Assessment of the long-term stability of engineered landforms of rehabilitated uranium mines and uranium mill tailings containment structures is primarily a geomorphic issue. It involves consideration of site stability, containment stability and the dispersion of the products of weathering and erosion and hence relies on models of the hydrogeomorphic environment. For Ranger Uranium Mine geomorphic assessment has defined areas with the least risk of instability and the erosional stability of uranium mill tailings containment structures has been modelled using the geomorphie model SIBERIA. Assessment of the dispersion of products throughout the receiving fluvial system is critical in setting the guidelines for acceptable levels of erosion and risk to the environment of failure of the containment structure. (from Author) 966362 Mineralogic constraints on the bioavailability of arsenic in smelter-impacted soils A. Davis, M. V. Ruby, M. Bloom, g. Schoof, G. Freeman & P. D. Bergstrom, Environmental Science & Technology, 30(2), 1996, pp 392-399. Supcrfund risk assessments and the resulting soil arsenic cleanup levels selected for mining sites are currently based on the toxicity of soluble As in drinking water. However, Anaconda soils and house dusts contain less soluble smelter-related As phases, consisting primarily of metalarsenic oxides and phosphates. If accidentally ingested, As bioaccessibility is restricted by the sparingly soluble nature of As-bearing phases, the prevalence of authigenic carbonate and silicate rinds, the kinetic hindrance to dissolution, and the inaccessibility of encapsulated As. These limitations to As disolution explain the lower bioavailability factors observed for Anaconda As-bearing soils. (Authors)
Subsidence, caving and rockbursts 966363 The effects of pulsed pumping on land subsidence in the Santa Clara Valley, California A. M. Wilson & S. Gorclick, Journal of Hydrology, 174(3-4), 1996, pp 375-396. Pulsed pumping has the potential to 'concentrate' subsidence around the pumping well. For all simulations, pulsed pumping caused greater subsidence near the test well than constant pumping. Under some conditions a transition point was reached, beyond which pulsed pumping caused less subsidence than steady pumping. The distance from the test well to the transition point decreases for: l) decreasing aquifer transmissivity, 2) decreasing ratio of pumping period to recovery period, and 3) increasing pulsing interval length. The concentration of subsidence was reduced considerably when delay in release of water from storage in compressible aquitards was neglected, indicating the importance of including delay effects in subsidence studies. All pulsed pumping strategies caused a greater total volume of subsidence than steady pumping. (from Authors)
966358 Review of 23 years of STD: Island Copper Mine, Canada D. V. Ellis, T. F. Pedersen, G. W. Poling, C. Pelletier & I. Home, Marine Georesources & Geotechnology, 13(1-2), 1995, pp 59-99. The submarine tailings disposal (STD) system at Island Copper Mine has been subjected to a comprehensive cnviroumental monitoring program initiated in 1970, some 20 months before the mill started processing ore. The program has been extended and modified as new factors became relevant or it became clear that particular factors were not of concern at this site. The major environmental issues have concerned: 1) tailings resuspension and upwelling, 2) smothering of benthos, and 3) trace metal contaminant from acid rock drainage (ARE)). The results of the monitoring are described. (from Authors) 966359 Effects of changing environmental rules: Kitsault molybdenum mine, Canada T. F. Pedersen, D. V. Ellis, G. W. Poling & C. Pelletier, Marine Georesources & Geotechnology, 13(1-2), 1995, pp 119-133. Initial oceanographic assessments showed that a submarine tailings disposal (STD) system would function to produce a tailings density current that would deposit on the fjord bed. There was substantial community interest and action during the final years of the development at a time when new pollution controls were being developed in Canada. The STD system essentially met its design criteria, but new oceanographic instrumentation at the time showed some contribution of tailings at the outfall discharge point to a naturally present mid-water turbidity layer. The first intensive postclosure monitoring of ecosystem rehabilitation following STD use anywhere in the world was undertaken between 1983 and 1989. Soon after closure in 1983, pore waters in the submerged deposited tailings were observed to be enriched in molybdenum, which must have supported an efflux of the metal to the overlying water. The indicated flux would have been too small to have had a measurable effect on the Mo inventory in the deep waters and, furthermore, was predicted to diminish with time. (from Authors) 966360 Deep water STD at the Misima gold and silver mine, Papua, New Guinea S. G. Jones & D. V. Ellis, Marine Georesources & Geotechnology, 13(1-2), 1995, pp 183-200. The Misima Mine is the pioneer of deep-water submarine tailings disposal (STD) and discharges at 112-m depth, well below the zone of major biological productivity (euphotic zone), onto a steep seafloor slope that leads directly to a deep ocean basin. The system discharges approximately 18 000 tonnes of tailings solids per day and has a mix tank with seawater intake from 82-m depth. Two validation surveys have shown that the system complies with regulatory conditions and meets ambient standards for contaminants well within a submerged mixing zone that extends to 1200-m radius from the mix tank location. Video records obtained by remotely operated vehicle (ROV) show the tailings slurry descending the steep slope as a coherent bottom-attached density current. Geophysical survey and ocean floor sediment
285A
sampling has confirmed that accumulation of tailings solids are confined to the gently sloping floor of a deep basin. The ocean at Misima is permanently stratified, and it was predicted that tailings would not rise to the surface providing the outfali was deeper than 100 m. After 5 years of continuous operation, no tailings material has ever been observed in the surface waters. (from Authors)
966361 Issues in assessing the long-term stability of engineered landforms at Ranger Uranium Mine, Northern Territory, Australia S. J. Riley, Journal & Proceedings - Royal Society o f New South Wales, 128(3-4), 1995, pp 67-78. Assessment of the long-term stability of engineered landforms of rehabilitated uranium mines and uranium mill tailings containment structures is primarily a geomorphic issue. It involves consideration of site stability, containment stability and the dispersion of the products of weathering and erosion and hence relies on models of the hydrogeomorphic environment. For Ranger Uranium Mine geomorphic assessment has defined areas with the least risk of instability and the erosional stability of uranium mill tailings containment structures has been modelled using the geomorphie model SIBERIA. Assessment of the dispersion of products throughout the receiving fluvial system is critical in setting the guidelines for acceptable levels of erosion and risk to the environment of failure of the containment structure. (from Author) 966362 Mineralogic constraints on the bioavailability of arsenic in smelter-impacted soils A. Davis, M. V. Ruby, M. Bloom, g. Schoof, G. Freeman & P. D. Bergstrom, Environmental Science & Technology, 30(2), 1996, pp 392-399. Supcrfund risk assessments and the resulting soil arsenic cleanup levels selected for mining sites are currently based on the toxicity of soluble As in drinking water. However, Anaconda soils and house dusts contain less soluble smelter-related As phases, consisting primarily of metalarsenic oxides and phosphates. If accidentally ingested, As bioaccessibility is restricted by the sparingly soluble nature of As-bearing phases, the prevalence of authigenic carbonate and silicate rinds, the kinetic hindrance to dissolution, and the inaccessibility of encapsulated As. These limitations to As disolution explain the lower bioavailability factors observed for Anaconda As-bearing soils. (Authors)
Subsidence, caving and rockbursts 966363 The effects of pulsed pumping on land subsidence in the Santa Clara Valley, California A. M. Wilson & S. Gorclick, Journal of Hydrology, 174(3-4), 1996, pp 375-396. Pulsed pumping has the potential to 'concentrate' subsidence around the pumping well. For all simulations, pulsed pumping caused greater subsidence near the test well than constant pumping. Under some conditions a transition point was reached, beyond which pulsed pumping caused less subsidence than steady pumping. The distance from the test well to the transition point decreases for: l) decreasing aquifer transmissivity, 2) decreasing ratio of pumping period to recovery period, and 3) increasing pulsing interval length. The concentration of subsidence was reduced considerably when delay in release of water from storage in compressible aquitards was neglected, indicating the importance of including delay effects in subsidence studies. All pulsed pumping strategies caused a greater total volume of subsidence than steady pumping. (from Authors)