Adjacent Mine Research Articles

Hydrologic Characteristics of a 35-Year-Old Underground Mine Pool

The hydrology of a 14,672 acre (5,940 ha) coal mine complex in Cambria County, Pennsylvania, USA, was characterized. This flooded mine complex was evaluated to determine the potential of using the mine water for downstream agricultural purposes in an adjoining watershed. The hydrologic characteristics of the mine complex dictate the amounts and rates of mine water discharge that are available. The original coal extraction rate was known to be 63%, but post-mining subsidence has reduced the effective porosity to a mean of 11%. Thus, the mine stores considerably less mine water than was anticipated, a priori. The mine receives vertical recharge averaging 0.27 gallons (gal) per minute per acre (24.6 L/s per ha), which is equivalent to 11.6% of the mean precipitation. The recharge rate fluctuates about the mean by ±22%. The low storage capacity combined with the moderately low recharge rates allow the large mine complex to be rapidly drawn down when the pumping rate is raised from 4.68 to 9.36 × 106 gal (17.7–35.4 × 106 L/day). Conversely, the mine refills rapidly, up to 0.8 ft (0.24 m) or spatially 33 acres (13.4 ha) per day, once the pumping rate is reduced back to 4.68 × 106 gal/day (17.7 × 106 L/day), which is well below the total recharge rate. In addition to vertical recharge, 6.3–40.4% of the inflow into the mine pool complex occurs from coal barrier seepage from an adjacent flooded mine. The seepage rates are relatively constant and are estimated to be insensitive to changes in head up to 50 ft (15.2 m).

Pilar-barreira entre painéis de lavra para a mina de carvão

A função de um pilar-barreira é proteger o painel de lavra em operação contra a transferência de pressões imposta pelos painéis de lavra adjacentes nos quais os pilares foram recuperados. No caso das minas de carvão em Santa Catarina, o pilar-barreira tem função de proteger o eixo da mina e os painéis em atividade contra a ruptura de pilares inesperada dos painéis de lavra antigos que já encerraram sua operação. O objetivo desse trabalho é verificar a validade do método empírico para o dimensionamento de pilar-barreira apresentado em Peng (1986) por meio da simulação numérica de uma geometria de lavra-padrão, que é aplicada para minas de carvão. Modelos numéricos em duas dimensões foram construídos obedecendo à geometria dos pilares do eixo e do painel de lavra para diferentes profundidades da camada Bonito. Foram consideradas as propriedades das materiais que formam o sistema piso-pilar-teto. Os resultados mostram que o método empírico é válido para a geometria projetada, onde os pilares do eixo não sofrem sobrecarga devido à lavra do painel e nem o teto sofre ruptura devido à redistribuição das tensões.

English

Major proposed changes in drainage control from a large underground mine pool required a detailed assessment of the hydrology, geochemistry, and impacts on the receiving streams. Proposed changes entail relocation of the withdrawal and treatment facilities to an adjoining, but separate watershed and increasing the pumping rate by 35%. Fifteen major and numerous smaller mines in two coal seams comprise the mine pool system. Degree of interconnection between mines ranges from horizontal and vertical seepage through natural fractures, subsidence-induced fractures, and coal cleat to open pass-throughs, slopes, and shafts. Water levels of several mines rise and fall in a mirrored fashion with only a few meters of head difference. An adjacent mine pool with 59.7 meters of head and an intact barrier ranging from 9.4 to 457 meters thick contributes at least 28% to the discharge rate. Mine storage capacity (5.38 billion liters) equates to a porosity of about 11%, a significant reduction from the original extraction volume of 63%. Mean ground water yield of the complex is 28 million liters per day. Recharge rate of 0.41 liters per minute per hectare is less than expected due to the thick overburden over much of the mine complex. The mine complex responds sharply to large precipitation events and large-volume pumping due to the relatively low storage volume and large aerial extent of the mine complex. Water levels respond to large precipitation events within three days and rises exceeding one meter have been recorded. Conversely, current maximum pumping at 35.6 million liters per day will draw the pool down an average of 0.09 meters per day. The proposed pumping of 37.9 million liters per day will, over the long term, exceed ground- water recharge and will dewater large portions of the mine complex. This will adversely impact the water quality, may induce additional subsidence, and could dewater some domestic water wells. Addition of water from an adjacent mine would allow the discharge of 37.9 million liters per day.

Moment Tensor Inversion of Ground Motion from Mining-Induced Earthquakes, Trail Mountain, Utah

A seismic network was operated in the vicinity of the Trail Mountain mine, central Utah, from the summer of 2000 to the spring of 2001 to investigate the seismic hazard to a local dam from mining-induced events that we expect to be triggered by future coal mining in this area. In support of efforts to develop ground-motion prediction relations for this situation, we inverted ground-motion recordings for six mining-induced events to determine seismic moment tensors and then to estimate moment magnitudes M for comparison with the network coda magnitudes M c. Six components of the tensor were determined, for an assumed point source, following the inversion method of McGarr (1992a), which uses key measurements of amplitude from obvious features of the displacement waveforms. When the resulting moment tensors were decomposed into implosive and deviatoric components, we found that four of the six events showed a substantial volume reduction, presumably due to coseismic closure of the adjacent mine openings. For these four events, the volume reduction ranges from 27% to 55% of the shear component (fault area times average slip). Radiated seismic energy, computed from attenuation-corrected body-wave spectra, ranged from 2.4 × 105 to 2.4 × 106 J for events with M from 1.3 to 1.8, yielding apparent stresses from 0.02 to 0.06 MPa. The energy released for each event, approximated as the product of volume reduction and overburden stress, when compared with the corresponding seismic energies, revealed seismic efficiencies ranging from 0.5% to 7%. The low apparent stresses are consistent with the shallow focal depths of 0.2 to 0.6 km and rupture in a low stress/low strength regime compared with typical earthquake source regions at midcrustal depths.

Changes in avian species composition following surface mining and reclamation along a riparian forest corridor in southern Indiana

Data on the response of bird communities to surface mining and habitat modification are limited, with virtually no data examining the effects of mining on bird communities in and along riparian forest corridors. Bird community composition was examined using line transects from 1994 to 2000 at eight sites within and along a riparian forest corridor in southwestern Indiana that was impacted by an adjacent surface mining operation. Three habitats were sampled: closed canopy, riparian forest with no open water; fragmented canopy, riparian forest with flood plain oxbows; and reclaimed mined land with constructed ponds. Despite shifts in species composition, overall bird species richness, measured as the mean number of bird species recorded/transect route, did not differ among habitats and remained unchanged across years. More species were recorded solely on mined land than in either closed forest or forested oxbow habitats. Mined land provided stopover habitat for shorebirds and waterfowl not recorded in other habitats, and supported an assemblage of grassland-associated bird species weakly represented in the area prior to mining. A variety of wood warblers and other migrants were recorded in the forest corridor throughout the survey period, suggesting that, although surface mining reduced the width of the forest corridor, the corridor was still important habitat for movement of forest-dependent birds and non-resident bird species in migration. We suggest that surface mining and reclamation practices can be implemented near riparian forest and still provide for a diverse assemblage of bird species. These data indicate that even narrow (0.4 km wide) riparian corridors are potentially valuable in a landscape context as stopover habitats and routes of dispersal and movement of forest-dependent and migratory bird species.

English

Numerous underground coal mines in the Pittsburgh coal basin of West Virginia and Pennsylvania have closed in the period 1980-2003. Of an estimated 1000+ once-active mines, only 11 are currently active, most relatively deep in the basin. These closures have caused flooding of mines and caused new discharges of mine water, of which all are either currently flooding or pumped and treated by mine operators or state agencies. This newly-created aquifer is a series of semi-interconnected compartments formed by mines separated by barrier pillars of 25->400 feet thickness. The leakage rate through barrier pillars is quite variable spatially and may be either very high (with hydrologically open conditions between adjacent mines) or very low (creating relatively isolated “pools” of one or more mines). Due to this fact and to the various closure dates of mines, the flooding history is complex with mines at a wide variety of water levels and flooding extents. However, experience shows that most mines near the Monongahela River flood within 10 years or less, and thus a new “equilibrium state” is expected to be attained by about 2015. At this time, flooding of most mines will be complete and an estimated 53,000 gpm (85,479 acre-ft/year) of mine discharge – both treated and untreated – will flow into the Monongahela watershed from below-drainage mines. This is in addition to an additional 8000 gpm estimated from abovedrainage free-draining mines. At this time, the flooded Pittsburgh coal will become the largest spatially-continuous high-yield aquifer exclusive of CambroOrdovician karst aquifers in the Northern Appalachian region. The locations of discharge from mines are known for 2003, subject to limitations of data availability, and may be speculatively projected for year 2015, subject to numerous assumptions and future circumstances. It is expected that all of the new discharges will require active treatment for metals removal to prevent discharge to the Monongahela and Ohio river watersheds. This resource of treated water may be utilized for other purposes, such as commercial development and aquaculture. Additional

English

Water quantity and quality conditions are described for a mine-pool aquifer in a fully flooded complex of underground mines in northern West Virginia. Abandoned mines in the Pittsburgh coal bed are contiguous, and separated by coal barrier pillars ranging from as little as 9 to about 60 meters thick. Barrier pillars are transmissive enough to circulate significant quantities of water between mines, yet they control head distribution and flow direction within the aquifer. The mine-pool acts as a partly confined to confined aquifer, and recharge is approximately balanced by withdrawal of about 5700 Liters/minute, leakage to adjacent mines, and unquantified outflow to unmined areas. Resulting drawdown prevents the mine-pool from discharging directly into overlying streams. A centrally located subgroup of mines within the aquifer currently acts as a ground-water sink, but water levels are slowly increasing in the sink, and in some outflow areas. Mine waters are highly reduced, with circumneutral pH, and variable Fe concentrations from 5 to over 100 mg/L. Total alkalinity averages about 200 mg/L with a mixed Ca-Na-HCO3-SO4 composition in recharge areas. End of flow path waters contain up to 600 mg/L alkalinity, and are Na-SO4 type waters with higher dissolved solids and metals concentrations. The shift from Ca to Na dominated waters is attributed mainly to cation exchange. Potentiometric head is increasing in the aquifer, and mine-pool withdrawal may have to be increased to prevent discharge to the surface. Mine-pool quality remains poor, and has shown slow improvement in 6 years of monitoring.

Estimation of Hydraulic Conductivity of Coal Mine Barriers, Pittsburgh Coal, Northern West Virginia, 1992-2000

Unmined coal barriers separate adjacent coal mines and restrict horizontal leakage between mines. Understanding the leakage rate across such barriers is important in planning mine closure and strongly affects recharge calculations for post-mining flooding. This study presents maximum estimates for intact (non-compromised) barrier hydraulic conductivity (K) in two closed mines at moderate depth (100-350 meters) in the Pittsburgh coal basin. The estimates are based on pumping rates from these mines 1992-2000 associated with leakage across common barriers from upgradient flooded mines. Both the pumped mines were maintained nearly dry, and so had dry seepage faces downdip from flooded mines, allowing accurate estimates of hydraulic gradient. The two mines do not approach the outcrop and are sufficiently deep that vertical infiltration is thought to be negligible. Similarly, there are no wetted barriers facing on other mines, and therefore pumping is the only discharge. The length of barriers totals 24 kilometers for the two mines, generally ranging in thickness from 15 to 50 m, and so the K test was large-scale. These test conditions are ideally suited to K estimation. K values from the test ranged from 0.03 m/d to 0.15 m/d using an isotropic model, and 0.05 to 0.27 (face cleat Kf) and from 0.03 to 0.15 m/d (butt cleat Kb) using an anisotropic model.

Ground-Water Flow and Quality in A Fully Flooded Underground Complex

Water quantity and quality conditions are described for a mine-pool aquifer in a fully flooded complex of underground mines in northern West Virginia. Abandoned mines in the Pittsburgh coal bed are contiguous, and separated by coal barrier pillars ranging from as little as 9 to about 60 meters thick. Barrier pillars are transmissive enough to circulate significant quantities of water between mines, yet they control head distribution and flow direction within the aquifer. The mine-pool acts as a partly confined to confined aquifer, and recharge is approximately balanced by withdrawal of about 5700 Liters/minute, leakage to adjacent mines, and unquantified outflow to unmined areas. Resulting drawdown prevents the mine-pool from discharging directly into overlying streams. A centrally located subgroup of mines within the aquifer currently acts as a ground-water sink, but water levels are slowly increasing in the sink, and in some outflow areas. Mine waters are highly reduced, with circumneutral pH, and variable Fe concentrations from 5 to over 100 mg/L. Total alkalinity averages about 200 mg/L with a mixed Ca-Na-HCO3-SO4 composition in recharge areas. End of flow path waters contain up to 600 mg/L alkalinity, and are Na-SO4 type waters with higher dissolved solids and metals concentrations. The shift from Ca to Na dominated waters is attributed mainly to cation exchange. Potentiometric head is increasing in the aquifer, and mine-pool withdrawal may have to be increased to prevent discharge to the surface. Mine-pool quality remains poor, and has shown slow improvement in 6 years of monitoring.

The Loch Tay Fault: type section geometry and kinematics

Synopsis The Loch Tay Fault in the Central Highlands of Scotland is the easternmost of six major faults that transect the Dalradian. Examination of the limited exposure along the sub-vertical fault walls in the type area demonstrates that it has undergone a history of left-lateral strike-slip as well as dip-slip. Evidence from the displacement of formation boundaries and of fold traces shows that the fault has undergone a finite history of 6.5–7.5 km of left-lateral strike-slip and a dip-slip, down to the NW, of 750–1000 m in the SW and central area, diminishing to 200 m or less in the NE. A major fault lens to the NW of the main fault (the Braes of Foss Fault Complex) has similarly undergone dip-slip (but down to the SE) and left-lateral strike-slip; however, two fault lenses to the SE of the major fault (the Glen Goulandie Fault Complex and a smaller lens to its SW) and associated splays have undergone right-lateral displacement. Displacements on the Frenich Burn Fault, a minor fault to the east of the Loch Tay Fault, are again dominantly left-lateral with small displacements down to the NW, whereas faults in an adjacent mine pit illustrate that displacements in the country rock are dominantly dip-slip. By analogy with the Tyndrum Fault, the main left-lateral and dip-slip movements are considered to be pre-Devonian, whereas the right-lateral and late extensional movements are interpreted as Carboniferous.

Effects of Nickel Mining Activities on Water Quality

Acid Mine Drainage (AMD) originates from the sulphide mineral oxidation in the presence of water and oxygen, and to some extent bacteria, yielding sulphuric acid. The acid generated mobilizes some metals resulting in their increased bioavailabilities, creating a hazardous environment for aquatic animals and plants. The groundwater quality emanating from adjacent mine sites is a useful tool for measuring AMD. The purpose of this study was to determine extent of mine drainage from an active nickel mine and to develop mitigation. Major mining pollution sources were identified for constant monitoring. Recommendations for possible remediation and abatement of AMD were made. Several liquid samples were taken from selected sites along two streams, which flow out of the mining complex. Eight water samples were collected once a month from June to October. pH and conductivity were immediately measured followed by determination of Cu, Fe, Ni, sulphates, Total Suspended Solids (TSS) and Total Dissolved Solids (TDS). Elevated concentrations of sulphate, high conductivity and TDS were observed indicating the presence of AMD. An increase in sulphate concentration, TDS and Conductivity levels for the Community Rivers was observed. This was caused by the water flowing from the nickel mine. The quality of the natural river water was grossly affected. A passive treatment strategy would need to be developed. For the treatment process to succeed, a complete characterisation of the contaminated mine drainage is needed. Topsoiling and revegetation are other cheaper methods that can be used to reduce the extent of sulphide oxidation.

Geochemical and mineralogical controls on trace element release from the Penn Mine base-metal slag dump, California

Base-metal slag deposits at the Penn Mine in Calaveras County, California, are a source of environmental contamination through leaching of potentially toxic elements. Historical Cu smelting at Penn Mine (1865–1919) generated approximately 200,000 m 3 of slag. The slag deposits, which are flooded annually by a reservoir used for drinking water and irrigation, also may be in contact with acidic ground waters (pH<4) from the adjacent mine area. Slags vary from grey to black, are glassy to crystalline, and range in size from coarse sand to large (0.6×0.7×1.5 m), tub-shaped casts. Metals are hosted by a variety of minerals and two glass phases. On the basis of mineralogy, slags are characterized by 4 main types: fayalite-rich, glassy, willemite-rich, and sulfide-rich. The ranges in metal and metalloid concentrations of 17 slag samples are: As, 0.0004–0.92; Ba, 0.13–2.9; Cd, 0.0014–1.4; Cu, 0.18–6.4; Pb, 0.02–11; and Zn, 3.2–28 wt.%. Leachates from Toxicity Characteristic Leaching Procedure tests (acetic acid buffered at pH 4.93) on two willemite-rich slags contained Cd and Pb concentrations (up to 2.5 and 30 mg/l, respectively) in excess of US Environmental Protection Agency (USEPA) regulatory limits. Analyses of filtered (0.45 μm) water, collected within the flooded slag dump during reservoir drawdown, reveal concentrations of Cd (1.7 μg/l), Cu (35 μg/l), and Zn (250 μg/l) that exceed USEPA chronic toxicity guidelines for the protection of aquatic life. Data from field and laboratory studies were used to develop geochemical models with the program EQ3/6 that simulate irreversible mass-transfer between slag deposits and reservoir waters. These models include kinetic rate laws for abiotic sulfide oxidation and surface-controlled dissolution of silicates, oxides, and glass. Calculations demonstrate that the main processes controlling dissolved metal concentrations are (1) dissolution of fayalite, willemite, and glass; (2) sulfide oxidation; and (3) secondary phase precipitation. Close agreement between model results and measured concentrations of Al, Ba, Cu, Fe, SiO 2, and SO 4 in the slag dump pore waters suggests that the dissolved concentrations of these elements are controlled by solubility equilibrium with secondary phases. Differences between predicted and measured Cd and Pb concentrations imply that field weathering rates of glass and sulfides are approximately two orders of magnitude lower than laboratory rates. Overprediction of Pb release may also reflect other attenuation processes in the natural system, such as sorption or coprecipitation.

Ferrous Iron Treatment of Soils Contaminated with Arsenic-Containing Wood-Preserving Solution

This article discusses the results of efforts to reclaim As-contaminated soil from a former timber-treating plant. The study site, commonly referred to as the Rocker Timber Framing site, is located along Silver Bow Creek approximately 7 miles west of the Butte Mining District, MT, USA. The plant operations resulted in contamination of the soils with a highly caustic solution containing 5% As (III). Contaminated soil resulted in the groundwater plumes that contained up to 25 mg L−1 As, with As (V) being the predominant species. The objective of this study was to evaluate the effectiveness of Fe (II) treatment for remediation of As-contaminated soils.Laboratory-treatability studies were conducted on samples of saturated zone (AS1) and va-dose zone (AV1) soils. The AS1 soil was a mixture of coarse alluvium and potentially some mill tailings from adjacent mining operations. The AV1 soil consisted primarily of fill, including soil, construction debris, and timber fragments. Initial concentrations of total As in AS1 and AV1 soils were 683 and 4814 µg kg−1, respectively. Water-soluble As concentrations were 15.4 and 554 µg L−1, respectively, in a 20:1 solution to soil extract. Batch equilibration were performed by placing 10 g of soil into 20 vessels and adding increasing amounts of FeSO4.7H2O. Amendment increments were made as multiples of molar ratios of total As present in each soil. Treatability studies were run with and without a pH buffer of CaCO3 (added at a 2:1 molar ratio to the FeSO4.7H2O treatment). Solution concentrations of As in the AS1 and AV1 soils (without CaCO3) decreased from 554 to 15.4 µ L−1 and 3802 to 0.64 µ L−1, respectively, as the Fe:As molar ratios increased from 0 to 2, whereas for the AS1 soil the solution As concentration increased at the Fe:As molar ratios >2 and reverse trend was observed for the AV1 soils. The decrease in As solution concentration for the AS1 soil is attributable to the dramatic decrease in soil pH with increasing Fe:As molar ratios.In the case of soils treated with CaCO3, the solution concentrations decreased from 564 to 0.65 µg L−1 and 3790 to 0.79 µg L−1 for the AS1 and AV1 soils, respectively,as the Fe:As molar ratios increased from 0 to 50. Generally, in both the soils, the CaCO3-treated soil contained significantly more solution As compared with the non-CaCO3-treated soil at the comparable Fe:As molar ratios. This is attributable to higher solution pH on CaCO3 treatment.Our rapid engineering study indicates that treating both the soils with Fe:As molar ratio of 2 lowered the As water quality limit to <50 µL−1, whereas treating the AS1 and AV1 soils with Fe:As molar ratio of 2 and 3, respectively, lowered the As water quality limit to ≤15 µg L−1. The concentrations of the Cu and Zn were below the instrument detection limits for the AS1 and AV1 soils without CaCO3 treatment.Sequential extraction of Fe-treated soils illustrated that As was relatively stable. Less than 1% of the As was extractable using a modified TCLP approach and <70% of the As was extractable using a harsh acid modified hydroxylamine hydrochloride extraction.

Weather-induced changes in the tradeoff between SO 2 and NO x at large power plants

Mae Moh Power Plant generates 30% of Thailand's electricity by burning high sulfur content coal which comes from adjacent mines. The resulting sulfur dioxide emissions have been blamed for acid rains in the Mae Moh valley in 1991 and 1992. Mae Moh is now adding desulfurization plants to 60% of its 1994 generating capacity — the four largest units of an 11-unit facility. In 1995–1996, Mae Moh added two additional large units with desulfurization plants attached. The desulfurization plants should eliminate 95% of the sulfur dioxide produced by the generating units to which they are attached. In the past, abatement efforts have focused on sulfur dioxide. However, with the addition of the desulfurization plants and the expansion of Mae Moh's capacity, nitrogen oxides produced by Mae Moh's generation of electricity will become an increasingly important problem. This paper examines the tradeoff, and how climate affects it, between concentrations of sulfur dioxide and nitrogen oxides just prior to the addition of the desulfurization plants. Mae Moh can use knowledge of this tradeoff in its efforts to minimize the environmental damage from generating electricity.

Assessing geotechnical risk of instability between adjacent mining operations — a case study : Dunbavan, M; Boyd, G Proc 6th Australia-New Zealand Conference on Geomechanics, Christchurch, 3–7 February 1992P495–498. Publ New Zealand: New Zealand Geomechanics Society, 1992

Assessing geotechnical risk of instability between adjacent mining operations — a case study : Dunbavan, M; Boyd, G Proc 6th Australia-New Zealand Conference on Geomechanics, Christchurch, 3–7 February 1992P495–498. Publ New Zealand: New Zealand Geomechanics Society, 1992

Salt Mining and Associated Subsidence in Mid-Cheshire, England, and its Influence on Planning

Rock salt occurs in the Lower and Upper Keuper Saliferous Beds in Cheshire, the former being 190 m while the latter is 404 m in maximum thickness. Although most of the Triassic rocks in Cheshire are covered by thick superficial deposits, natural brine runs occur at the surface and salt was recovered from these springs as long ago as Roman times. Indeed, most salt was obtained in this way until the end of the seventeenth century. In 1670 salt was discovered at Marbury near Northwich, and the first mine was sunk in 1682. In the succeeding eighteenth and nineteenth centuries, the salt industry expanded enormously and many mines and brine pits were sunk. The mines frequently had a short life and poor mining practices often led to roof collapse and ingress of water. When water entered into a collapsed mine it attacked the pillars and walls and thereby penetrated into adjacent mines. As adjacent mines collapsed subsidence spread until sets of flooded mines formed large underground reservoirs. Associated “rock pit holes” occurred at the surface. In terms of salt production, wild brine pumping became increasingly more important and overtook mining in the nineteenth century. The most successful wild brine pumping occurred on the major pre-existing natural brine runs. Such abstraction accelerated the formation of solution channels and active subsidence was concentrated at the heads and sides of brine runs. Serious subsidences could occur at considerable distances from the point of abstraction (up to 8 km). Flashes, that is, water-filled linear hollows, are probably the most notable features produced by such subsidence. The most disastrous subsidences took place in the second half of the nineteenth century and were due to the development of bastard brine pumping, that is, pumping from abandoned mine workings. These subsidences occurred suddenly and were on a large scale, producing dramatic loss of property and even life. Bastard brine pumping also disturbed brine levels significantly which, in turn, gave rise to sudden local collapses. Because of the unpredictable nature of subsidence due to wild brine pumping, responsibility could not be attributed to any particular wild brine operator. Hence, two Compensation for Subsidence Acts (1891 and 1952) were passed which imposed levies on the operators in order to provide compensation funds for subsidence damage. The latter act primarily extended the compensation district. The number of wild brine pumpers declined throughout the twentieth century, and after 1968 the County Council withheld permission to extend pumping outside the demarcated areas and no permission was given to sink new wild brine wells. It was their intention to phase out wild brine pumping by the 19809s. This has very nearly been accomplished, controlled solution mining now producing 99 percent of the brine in Cheshire. It is alleged that this method of production has given rise to no subsidence.

Monopsony and federal coal leasing — a bargaining approach

The Department of the Interior awards federal coal leases by competitive bidding to adjacent mining operations having an emergency need for the coal. Previous studies indicate that negotiation between the government and the operator would be a more apropriate mechanism for awarding emergency coal leases. This paper develops a theoretical bargaining model within the context of emergency leasing, with the buyer (adjacent operator) and the seller (federal government) having various degrees of monopoly power depending on the type of emergency leasing situation. The model provides an analytical framework for evaluating alternative negotiation strategies for capturing and sharing economic rents.

Depositional environments and paleogeography in the Albian Moosebar Formation and adjacent fluvial Gladstone and Beaver Mines formations, Alberta

The marine Moosebar Formation (Albian) has a currently accepted southerly limit at Fall Creek (Ram River area). It consists of marine mudstones with some hummocky and swaley cross-stratified sandstones indicating a storm-dominated Moosebar (Clearwater) sea. We have traced a tongue of the Moosebar southward to the Elbow River area (150 km southeast of Fall Creek), where there is a brackish-water ostracod fauna. Paleoflow directions are essentially northwestward (vector mean 318°), roughly agreeing with turbidite sole marks (329°) in the Moosebar of northeastern British Columbia.The Moosebar sea transgressed southward over fluvial deposits of the Gladstone Formation. In the Gladstone, thick channel sands (4–8 m) are commonly multistorey (up to about 15 m), with well developed lateral accretion surfaces. The strike of the lateral accretion surfaces and the orientation of the walls of channels and scours indicate northwestward flow (various vector means in the range 307–339°). The Moosebar transgression was terminated by construction of the Beaver Mines floodplain, with thick, multistorey sand bodies up to about 35 m thick. Flow directions are variable, but various vector means roughly cluster in the north to northeast segment. This indicates a major change in dispersal direction from the Gladstone and Moosebar formations.A review of many Late Jurassic and Cretaceous units shows a dominant dispersal of sand parallel to regional strike. This flow is mostly north-northwestward (Passage beds, Cadomin, Gladstone, Moosebar, Gates, Chungo), with the southeasterly dispersal of the Cardium being the major exception. Only at times of maximum thickness of clastic input (Belly River and higher units, and possibly Kootenay but there are no published paleocurrent data) does the sediment disperse directly eastward or northeastward from the Cordillera toward the Plains.

Coseismic and other short-term strain changes recorded with Sacks-Evertson strainmeters in a deep mine, South Africa

Summary. During 1977 March and April, three Sacks-Evertson borehole dilatometers were installed at the ends of boreholes drilled into the sidewall of an experimental tunnel at a depth of 3.1 km in the ERPM gold mine near Johannesburg. In the following year coseismic strain changes ranging from 5 ± 10−10 to values exceeding 5 ± 10−6 were recorded for hundreds of mine tremors in the magnitude range -1 to 3.7 and at hypocentral distances of 50 m to about 2 km. Hypocentral coordinates and magnitudes were determined from seismograms recorded from an underground array of geophones. Amplitudes and polarities of the coseismic strain steps are generally in excellent agreement with theoretical expectations based on point-source dislocation theory; specifically, the strain steps are proportional to the seismic moment divided by the cube of hypocentral distance. At a strain level of 5 ± 10−9 or greater the tremors do not appear to be preceded by any short-term indications of instability even for tremors producing coseismic steps greater than 5 ± 10−6 and for which the strainmeters were within a source radius of the hypocentre. Continuous strain changes observed at the times when the mine excavation, at a distance of about 100 m, is extended are in good agreement with calculated changes based on the theory of elasticity. A similar calculation is consistent with post-seismic strain changes observed to follow some of the closer tremors. These post-seismic strains show a logarithmic dependence on time following the tremor and appear to be due to the interaction of a tremor with the adjacent mine excavation rather than to deformation within the actual seismic source region.

Preparation and Injection of Grout From Spent Shale for Stabilization of Abandoned In-Situ Oil Shale Retorts

Summary A procedure has been developed for stabilizing abandoned in-situ oil shale retorts by means of high-temperature treatment of surface-processed shale, followed by grinding, mixing with water, and injection underground. Laboratory results indicate that abandoned in-situ retorts can be made strong enough to prevent subsidence and sufficiently impermeable to reduce ground-water flow greatly. The underground injection also reduces the amount of spent-shale disposal on the surface. Introduction For several years. Lawrence Livermore Natl. Laboratory has been developing procedures for in-situ processing of oil shale. In the proposed process described here, a large underground retort is prepared. Typically, each horizontal dimension of the retort is 20 to 100 m, and the height is 100 to 300 m. The retort height may be limited to avoid intersection with major aquifers in a particular location. The retort is prepared by removing a small portion of shale to the surface, probably about 20%, and rubbling the remainder. The size of oil-shale particles in the retort varies from a minimum equivalent to dust to a maximum of about 1 m. Ideally, the mining and rubbling are done in such a way as to provide uniform size distribution and void fraction within the retort. After preparation, the retort is ignited at the top, and a combustion zone is forced downward by flow of oxygen containing gas. Oil is released ahead of (below) the combustion zone. Some of the oil collects at the bottom of the retort and is pumped to the surface; the remainder is carried out of the retort by the gas stream.The processing of oil shale by this procedure may result in some problems in the area after processing is complete.1. Compaction of the processed shale and collapse of the retort root could lead to subsidence at the surface above the retort.2. Disturbance of normal groundwater flow could result in water contamination. This could be caused by leaching of material from the processed shale by groundwater as the water flows through the abandoned retort, or it could be caused by transfer through the retort of saline water from one aquifer to pure water in a different aquifer.3. Toxic gases could be released from the retort to the surface or to adjacent underground mining operations.4. Disposal of the oil shale taken to the surface to provide the void space for gas flow in the retort would be required.A possible solution to these problems lies in making use of the shale taken to the surface. A portion of this shale can be processed to form a grout that then can be returned underground to fill the void space. After bring crushed, the shale is subjected to three heat-treatment steps. First, the shale is retorted in an oxygen-free atmosphere. Second, the carbonaceous residue, or char, is burned off the shale. Third, a higher temperature and different gas are used to cause a reaction between the carbonate and silicate minerals. The products of these reactions have properties similar to those of ordinary cement. A requirement of the process is that the first two steps, retorting and burning, Occur at a low enough temperature that most of the carbonate minerals do not decompose. At least one available process, the Lurgi-Ruhrgas process, satisfies this requirement. After heat treatment, the shale is ground to fine powder, water is added, and the grout is injected underground to fill the void space in a processed in-situ retort.To solve the problems listed, the grout must have certain characteristics. First, the freshly mixed grout must be sufficiently mobile to be pumped readily and to flow easily into the void space underground. JPT P. 1609^