Evaluation of the Potential for Beneficial Use of Contaminated Water in a Flooded Mine Shaft in Butte,Montana

The mines of Butte, Montana include over 16,000 km of abandoned underground workings, most of which are now filled with water. The feasibility of using the flooded mine workings as a source of irrigation water was investigated. The geochemistry and stable isotopic composition of water produced during a 59 day pumping test of the flooded Belmont Mine workings are described. Although static water in the pumping well initially met proposed irrigation standards, the quality deteriorated during pumping as water from deeper in the mine complex was drawn into the well. Stable isotopes show that this lower-quality water was not sourced from the nearby Berkeley Pit lake, but most likely came from the mine shaft itself. At steady state, the water pumped to the surface had pH 5.5–6.0 with high concentrations (in mg/L) of dissolved SO₄ (1,600), Fe (160), Mn (19), Zn (15), and As (1.8). Despite substantial bicarbonate alkalinity (≈150 mg/L as CaCO₃), the water became strongly acidic after equilibration with air due to oxidation and hydrolysis of Fe²⁺. Benchtop experiments were performed to test different strategies for low-cost chemical treatment prior to irrigation. The most feasible alternative involved aeration (to remove large quantities of dissolved CO₂) prior to pH adjustment to >9 with lime or NaOH. Further work is needed to see if such treatment is economically viable compared to the cost of using municipal water. Another concern is whether irrigation of grass with high TDS, high sulfate water is sustainable. The mine water reached a steady-state temperature of 19°C during pumping, and therefore the possibility of using this water to help heat nearby buildings should also be explored.     

Quality Assessment of Mine Water in the Raniganj Coalfield Area,India

In a qualitative assessment of mine water from the Raniganj coalfield, 77 mine water samples were analyzed to assess water quality and suitability for domestic, industrial, and irrigation uses. The pH of the mine water ranged from 6.5 to 8.8. Total dissolved solids (TDS) ranged from 171 to 1,626 mg L⁻¹; spatial differences between the TDS values reflect variations in lithology, activities, and prevailing hydrological regime. The anion chemistry was dominated by HCO₃ ⁻ and SO₄ ²⁻. On average, Cl⁻ contributes 10 and 19% of the total anionic balance, respectively, in the Barakar and Raniganj Formation mine water. F⁻ and NO₃ ⁻ contribute <2% to the total anions. The cation chemistry is dominated by Mg²⁺ and Ca²⁺ in the mine water of the Barakar Formation and Na⁺ in the Raniganj Formation mines. Much of the mine water, especially of the Barakar Formation area, has high TDS, total hardness, and SO₄ concentrations. Concentrations of some trace metals (i.e. Fe, Cr, Ni) were found to be above the levels recommended for drinking water. However, the mine water can be used for irrigation, except at some sites, especially in the Raniganj Formation area, where high salinity, sodium adsorption ratio, %Na, residual sodium carbonate, and excess Mg restrict its suitability for agricultural uses.     

Development of the Sleeper Pit Lake

Abstract.  The Sleeper open pit gold mine operated from the mid-1980s through the mid-1990s. Operations were mostly sub-water table and extensive dewatering was required to lower groundwater levels by 180 m. Dewatering flows peaked at 930 L/s, with most flow contributed from an alluvial aquifer. After completion of mining, the pit was rapidly filled with water pumped from the alluvial aquifer to reduce the exposure time of sulfide wall rocks and waste rocks in the ultimate pit. The pumped alluvial groundwater provided a large volume of low total dissolved solids (TDS), high alkalinity water that controlled the early chemistry. The rising lake waters were amended with lime to buffer excess acidity contributed to the lake from reactive pit wall rocks during submergence. The pore water contained in submerged waste rock at the base of the pit was elevated in TDS and subsequently of higher density that the lake water. The density contrast and waste rock location limited contributions of waste rock pore water to the main body of the lake. Some stratification of the early lake occurred, with shallow water characterized by higher pH, low dissolved metals, and sulfate; deeper water had lower pH and higher dissolved metals and sulfate. The reservoir of alkalinity in the shallow layer mixed with the deeper waters and created a stabilized lake with a homogenized column that exceeded water quality expectations. Current water quality meets all Nevada primary drinking water standards with the exception of sulfate, TDS, and manganese, which are slightly elevated, as predicted. Chemistry has remained stable since development of the initial lake.     

Characteristics of compression fracture of “three soft” coal bed by perfusion and gas sucking technique

Against the particularity of stratum-structure in “three soft” mine areas, according to rock indoor test and on-site sucking experiment, discussed the characteristics of argillization, compression fracture and sucking technique of soft coal with low permeability. It is clearly pointed out that the gas can be highly effectively sucked only by compression fracture along the occurrence of the coal seam, creating inter-seams crack belt because of the difference of bulgy deformation. After the flooding experiment in the 24080 workface of Pingdingshan No.10 mine, the average single-bore volume of gas increases from 77 m³ to 7 893 m³, while decay cycle extended from 7 days to 80∼90 days. Also, the single-bore extracting rate of gas increases to 33%.     

Hydrogeochemistry,Elemental Flux,and Quality Assessment of Mine Water in the Pootkee-Balihari Mining Area,Jharia Coalfield,India

Ninety nine mine water discharge samples were collected and analyzed for pH, electrical conductivity (EC), major cations, anions, and trace metals in the Pootkee-Balihari coal mining area of the Jharia coalfield. The mines of the area annually discharge 34.80 × 10⁶ m³ of mine water and 39,099 t of solute loads. The pH of the analyzed mine waters ranged from 6.97 to 8.62. EC values ranged from 711 μS cm⁻¹ to 1862 μS cm⁻¹, and reflect variations in lithology, geochemical processes, and hydrological regimes in the mines. The cation and anion chemistry indicate the general ionic abundance as: Mg²⁺ > Ca²⁺ > Na⁺ > K⁺ and HCO₃ ⁻ > SO₄ ²⁻ > Cl⁻ > NO₃ ⁻ > F⁻, respectively. Elevated SO₄ ²⁻ concentrations in the Gopalichuck, Kendwadih, and Kachhi-Balihari mine waters are attributed to pyrite weathering. The water quality assessment indicated that TDS, hardness, Mg²⁺, and SO₄ ²⁻ are the major parameters of concern in the study area. Except for Fe, all of the measured metals in the mine water were well within the levels recommended for drinking water. With only a few exceptions, the mine water is of good to permissible quality and suitable for irrigation.     

An In-lake Reactor to Treat an Acidic Lake: the Effect of Substrate Overdosage

An “in-lake” reactor system was developed to treat acidic mining lakes. The reactor uses the microbial processes of sulfate reduction and iron reduction followed by precipitation of iron sulfides to remove acidity, sulfur, and iron from the lake water. The basic reactor design is a straw-filled tube, which was vertically installed in the water column of an enclosure in the lake. Bottom water was pumped through the reactor, and ethanol was continuously fed as substrate for the microbial processes. Microbial sulfate reduction and iron reduction took place inside the reactor, even under acidic conditions. Overdosage of substrate led to the accumulation of the potentially toxic intermediates H₂S and acetate. Leakage of ethanol led to anoxic conditions in the entire enclosure, followed by accumulation of H₂S in the water column. Sulfides were not precipitated because the pH was never above 3.8. Mixing of the water column in autumn introduced oxygen into the system and led to reoxidation of the H₂S. Future designs of in situ reactors to treat acidic mine drainage should consider that the limiting step is not the microbial formation of alkalinity but the fixation of the alkalinity gain as pyrite.     

Passive aerobic treatment of net-alkaline,iron-laden drainage from a flooded underground anthracite mine,Pennsylvania, USA

This report evaluates the results of a continuous 4.5-day laboratory aeration experiment and the first year of passive, aerobic treatment of abandoned mine drainage (AMD) from a typical flooded underground anthracite mine in eastern Pennsylvania, USA. During 1991–2006, the AMD source, locally known as the Otto Discharge, had flows from 20 to 270 L/s (median 92 L/s) and water quality that was consistently suboxic (median 0.9 mg/L O₂) and circumneutral (pH ≈ 6.0; net alkalinity >10) with moderate concentrations of dissolved iron and manganese and low concentrations of dissolved aluminum (medians of 11, 2.2, and <0.2 mg/L, respectively). In 2001, the laboratory aeration experiment demonstrated rapid oxidation of ferrous iron (Fe²⁺) without supplemental alkalinity; the initial Fe²⁺ concentration of 16.4 mg/L decreased to less than 0.5 mg/L within 24 h; pH values increased rapidly from 5.8 to 7.2, ultimately attaining a steady-state value of 7.5. The increased pH coincided with a rapid decrease in the partial pressure of carbon dioxide (PCO₂) from an initial value of 10^−1.1 atm to a steady-state value of 10^−3.1 atm. From these results, a staged aerobic treatment system was conceptualized consisting of a 2 m deep pond with innovative aeration and recirculation to promote rapid oxidation of Fe²⁺, two 0.3 m deep wetlands to facilitate iron solids removal, and a supplemental oxic limestone drain for dissolved manganese and trace-metal removal. The system was constructed, but without the aeration mechanism, and began operation in June 2005. During the first 12 months of operation, estimated detention times in the treatment system ranged from 9 to 38 h. However, in contrast with 80–100% removal of Fe²⁺ over similar elapsed times during the laboratory aeration experiment, the treatment system typically removed less than 35% of the influent Fe²⁺. Although concentrations of dissolved CO₂ decreased progressively within the treatment system, the PCO₂ values for treated effluent remained elevated (10^−2.4 to 10^−1.7 atm). The elevated PCO₂ maintained the pH within the system at values less than 7 and hence slowed the rate of Fe²⁺ oxidation compared to the aeration experiment. Kinetic models of Fe²⁺ oxidation that consider effects of pH and dissolved O₂ were incorporated in the geochemical computer program PHREEQC to evaluate the effects of detention time, pH, and other variables on Fe²⁺ oxidation and removal rates. These models and the laboratory aeration experiment indicate that performance of this and other aerobic wetlands for treatment of net-alkaline AMD could be improved by aggressive, continuous aeration in the initial stage to decrease PCO₂, increase pH, and accelerate Fe²⁺ oxidation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Groundwater Source Discrimination and Proportion Determination of Mine Inflow Using Ion Analyses: A Case Study from the Longmen Coal Mine,Henan Province,China

Complex hydrogeological conditions in China’s coal mines have contributed to frequent mine water disasters. A simple and effective method to determine water inflow sources and paths is therefore essential. The Longmen Mine, located in Henan Province, in central China was used as a case study. A Piper diagram and cluster analysis were used to screen the characteristic values of 18 water samples from potential aquifers. A comprehensive fuzzy evaluation of the groundwater ions was carried out to determine the main source of the total mine inflow. Then, based on conservation of ionic masses, a matrix function was established to calculate the groundwater recharge composition. Finally, using measured water inflows for the Cambrian limestone aquifer, the calculated and observed results were compared. The results showed that the Carboniferous Taiyuan Formation limestone aquifer (the L₇ limestone aquifer) accounts for 60.8% of the total mine inflow, while the Cambrian limestone and roof sandstone aquifers account for 34.8 and 4.4% of the inflow, respectively. The normal mine inflow totals about 19,200 m³/day, of which 6,840 m³/day is from the Cambrian limestone aquifer. This agrees well with the calculated value of 6,720 m³/day. Thus, the method is feasible and reliable.     

The Use of Measured and Calculated Acidity Values to Improve the Quality of Mine Drainage Datasets

Abstract:  The net acidity of a water sample can be measured directly by titration with a standardized base solution or calculated from the measured concentrations of the acidic and basic components. For coal mine drainage, the acidic components are primarily accounted for by free protons and dissolved Fe²⁺, Fe³⁺, Al³⁺, and Mn²⁺. The base component is primarily accounted for by bicarbonate. A standard way to calculate the acidity for coal mine drainage is: Acid^calc = 50*(2*Fe²⁺/56 + 3*Fe³⁺/56 + 3*Al/27 + 2*Mn/55 + 1000*10^-pH)—alkalinity, where acidity and alkalinity are measured as mg/L CaCO₃ and the metals are mg/L. Because such methods of estimating acidity are derived by independent laboratory procedures, their comparison can provide a valuable QA/QC for AMD datasets. The relationship between measured and calculated acidities was evaluated for 14 datasets of samples collected from mine drainage discharges, polluted receiving streams, or passive treatment systems, containing a total of 1,484 sample analyses. The datasets were variable in nature, ranging from watersheds where most of the discharges contained alkalinity to ones where all of the discharges were acidic. Good relationships were found to exist between measured and calculated acidities. The average acidity measurement was 239 mg/L CaCO₃ and the average acidity calculation was 226 mg/L CaCO₃. Linear regressions were calculated for individual datasets and for the entire dataset. The linear regression for the entire dataset was: Acid^calc = 0.98 * Acid^meas – 8, r² = 0.98. The good correlation between calculated and measured acidity is the basis for an easy and inexpensive QA/QC for AMD data. Substantial variation between measured and calculated acidities can be used to infer sampling or analytical problems.     

Environmental pollution from coal mining activities in the Enugu area Anambka state Nigeria

Hydrogeological studies of the Enugu coal mining area were carried out which included hydrogeochemical analyses of water samples. These analyses revealed high sulphate and iron content in the acid mine drainage water as well as high total dissolved solids’ (TDS) and low pH (acidity) values. The water issues from the Ajali Sandstone formation and the underlying carbonaceous Mamu Formation and is classified as hard water. As a consequence of under-mining this aquifer, huge volumes of (polluted) water has flooded the mines are channelled into some streams or rivers which in turn get chemically polluted. Remedial measures have been indicated which include the following:

1. the treatment of acid mine water before pumping into streams or river;
2. the disposal of mine spoil wastes in carefully prepared and designed disposal sites;
3. planned and detailed mapping of the fractures in the Manu Formation for more effective dewatering scheme and increased exploitation of the overlying Ajali Sandstone aquifer to reduce or limit the amount of water flooding the mines in the underlying Mamu Formation.

     

Geochemistry of Perched Water in an Abandoned Underground Mine, Butte, Montana

Abstract.  The Lexington tunnel is the last accessible underground mine working in the Butte, Montana mining district. Used as recently as 1993, the tunnel and adjacent workings have been abandoned for over 10 years. Although the Lexington tunnel is over 200 m above the regional water table, perched water is present over much of its extent. Mine water near the portal is moderately acidic (pH 4 to 5), with extremely high concentrations of metals, including Cu (up to 1000 mg/L) and Zn (up to 1400 mg/L). In the middle reaches of the tunnel, the quality of the water is much better, with near-neutral pH, high bicarbonate alkalinity, and lower concentrations of heavy metals. The low acidity and metal content is attributed to a lack of pyrite and other sulfides in this portion of the mine, as well as the presence of carbonate minerals, such as rhodochrosite (MnCO₃), in exposed veins. Sulfide minerals are more widespread further back in the tunnel, and are now oxidizing rapidly, leading to pockets of severe acid drainage (pH< 3, dissolved Zn up to 5000 mg/L). Geochemical modeling suggests that the near-neutral waters—the most voluminous type encountered in the Lexington tunnel—are close to equilibrium saturation with rhodochrosite and hydrous Zn-carbonate (ZnCO₃•H₂O). The Eh of these waters is most likely controlled by redox reactions involving dissolved Mn²⁺ and secondary, Zn-rich, hydrous Mn-oxides. In contrast, the Eh of the acidic waters appears to be controlled by reactions involving Fe²⁺ and Fe³⁺. Most of the acidic waters are saturated with K-jarosite, which forms delicate, straw-like dripstones at several localities. Decaying mine timbers could be an important renewable source of organic carbon for heterotrophic microorganisms, such as iron- and sulfate-reducing bacteria, especially deeper in the mine workings where the ground is saturated with anoxic ground water.     

Controlling acid mine drainage from the Ficher Mining District,Oklahoma, United States

The Picher Mining District, located principally in north-eastern Oklahoma, was one of the world's largest lead-zinc mining areas during its 55 year life. The field covers an area of approximately 72 square miles (186 km²); an estimated 1.22×10⁸ m³ of material worth in excess of one billion dollars, has been mined. Mining activities were typified by surface exploratory drilling indentifying ore distribution and extension of underground workings to the lead and zinc deposits outlined. Exploration holes were either left unplugged or plugged at the surface with a section of a telephone pole. Low grade ore and waste rock were discarded in mined out portions of drifts. These waste piles containing pyrite and marcasite were left underground and oxidised during the many years of active mining. Upon cessation of mining activities in the mid-1960s, the drifts and shafts of the abandoned workings began to flood as the cone of depression filled in, leading to the dissolution of the oxidised sulfides and the formation of large volumes of acid mine water in the mined out openings. The resulting poor quality water, with high concentrations of cadmium, iron, lead and zinc, began discharging at the surface in 1979. Contamination of the underlying aquifer supplying local residents was first detected on a localised scale in 1980. The present surface water and groundwater contamination have lead to the area being classified as one of the top ten hazardous waste sites in the U.S. by the EPA under the superfund program. To mitigate the current conditions we have proposed that acid mine water be collected where it currently discharges at identified springs and pumped from widely spaced wells in the workings. The water would then be treated at a 87.4 1/sec lime neutralisation/precipitation facility. Construction costs are estimated to be $3.7 million and $560,000/yr for 0 & M.     

Optimization of Water Pumping and Injection for Underground Coal Gasification in the Meiguiying Mine,China

The Meiguiying mine is a famous underground coal gasification (UCG) mine in China, but there has been a potential safety hazard since it began operating, that groundwater in the overlying aquifer might enter the mine and even extinguish the gasifier. A 3-D hydrogeological model was developed to explore the characteristics of the seepage field of the aquifer and determine an optimal water pumping and injection option for the UCG. The results indicate that more attention should be paid to control induced fractures of the roof due to the increasing water level of the aquifer, and that a pumping rate of 160 m³/day would decrease the water level to a reasonable elevation. Moreover, to maintain the groundwater table and mine safety, 120 m³/day was recommended as a reasonable and economical recharge (re-injection) rate in the study area.     

Technology of gas drainage and utilization in Huaibei mining area

With the characteristics of coal seam geology and gas occurrence, a “ground-underground” integrated gas drainage method was formed, which can relieve gas pressure and increase permeability by mining the protection seams in conditional regions. After coal seam gas drainage, high gas outburst seam was converted to low gas safety seam. In the coal face mining process, safety and high efficient coal mining were realized by the measure of gas-suction over mining. In addition to the drainage gas for civil gas and gas power generation, the Huaibei Mining Group has actively carried out research on the utilization technology of methane drainage by ventilation. On the one hand, it can save precious energy; on the other hand, it can protect the environment for people’s survival. In 2007, the amount of coal mine gas drainage was 120 hm³; the rate of coal mine gas drainage was 44%. Compared with the year 2002, the amount of coal mine gas drainage increased by two times. Meanwhile, the utilization rate of gas increased rapidly.     

Evaluation of drawdown curves derived from multiple well aquifer tests in heterogeneous environments

Aquifer coefficients derived from nonsteady-state, multiple well, aquifer tests in laterally heterogeneous environments often have uncertain meaning. Drawdown at observation wells reflects the removal of water from storage in the aquifer and transient refraction of ground water pathlines during the evolution of a non-symmetrical cone of depression. These effects are masked within observation well drawdown data such that “good” Theis (1935) type curve matches often result. Transmissivity and storativity values derived from independent drawdown curves plotted as drawdown versus time (t) or drawdown versus time/distance² (t/r²) usually differ from observation well to observation well. These aquifer coefficients often are considered to represent some type of average of the materials between and/or about the pumping well and the observation wells. Simulations of two multiple well aquifer tests with simple, arbitrary distributions of block heterogeneities suggest that transmissivity (T) and storativity values derived from independent drawdown curves by the Theis (1935) method generally increase with distance from the pumping well. This apparent scale effect is related to the force-fitting of earlytime drawdown data to the steep portion of the Theis type curve without sufficient late-time drawdown data to constrain vertical shifting of the drawdown data relative to the type curve. Log-log plots of drawdown versus t/r² for multiple well aquifer tests form families of curves that are characteristic of the distribution of observation wells and the degree of heterogeneity within the cone of depression. Separation between discrete drawdown curves within a family provides a qualitative measure of the degree of heterogeneity within the cone of depression. All of the drawdown curves within a family converge on a single curve at large values of t/r². A composite analysis of all of the drawdown data within the family yields an estimate of the average T within the cone of depression. Analysis of discrete drawdown curves as integral members of the family of curves provides a means to constrain type curve matches and minimizes force-fitting if drawdown data are defined for large values of t/r² for at least one well. The constrained type curve matches provide more reasonable estimates for T near individual observation wells than analysis of drawdown curves independently.     

Triggered Seismicity in a Flooded Former Coal Mining Basin (Gardanne Area,France)

We studied the correlation between seismicity and the water table level in an abandoned coal mine (Bouches-du-Rhône, France), closed in 2003, where groundwater has been pumped out since 2010 to prevent underground flooding. Microseismicity was first felt by the population in 2010 and a strongly felt seismic swarm occurred in November 2012. The origin of the seismicity was therefore questioned, in relation to both the potential instability of old, shallow galleries that might generate damage at the surface and a local seismic hazard assessment. A temporary dense seismic network in the area allowed us to analyse the spatial distribution of the seismicity in detail. Most of the seismicity was clearly located under the mine workings, highlighting that an existing fault system crossing the mining operation was being hydraulically activated, in accordance with the known tectonic extension regime. Our analysis clearly shows a spatiotemporal relationship between seismic migration and the level of the mine aquifer between 2013 and 2017. Thus, seismicity will persist with oscillations of the mining aquifer, depending on the pumping capacities and effective rainfall. Continuous hydraulic and seismic monitoring is necessary to better understand these phenomena and assess the associated risks.

     

Safe production model for small mines

Presented a “safe production model” that can be adopted by small mine operators to achieve their production targets safely and efficiently. The model consists of eight elements ranging from management commitment and leadership to safety account-ability and communication. The model is developed considering the mine operators’ resource limitations and the workers’ training needs. The study concludes with a summary of a sample survey that is conducted to validate the model and estimate a parameter for each mine and determine its position in the safe production scale. Supported by the Research and Training Program on Hazard Identification and Risk Assessment for Small Mines in the Western US     

Reducing the Hardness of Mine Water Using Transformed Fly Ash

In the Jharia Coalfields, Dhanbad, India, huge quantities of water are pumped out of underground mines to make mining possible. The water contains high concentrations of total hardness, which makes it unsuitable for domestic use. Waste fly ash generated nearby from burning the coal in thermal power plants can be converted into a zeolitic mineral, and used to treat the mine water. The fly ash zeolite was determined to be effective in removing total hardness from the mine water. At a 40 g/L dose of fly ash zeolite, approximately 72% of the hardness was removed from the mine water. However, the mine water still requires additional treatment to further reduce total dissolved solids to make the mine water potable.     

侏罗纪煤田宝塔山砂岩含水层大流量大降深放水试验

为了在抽水试验的基础上进一步查明侏罗纪煤田宝塔山砂岩含水层的水文地质特征,开展了井下放水试验,单孔放水量平均值为237.91 m3/h,多孔放水量平均值为444.10 m3/h,宝塔山砂岩含水层地下水位下降最大值达310 m.通过大流量大降深放水试验,计算出含水层的渗透系数和单位涌水量,确定宝塔山砂岩含水层与白垩系、煤...     

Hazard identification for equipment-related fatal incidents in the U.S. underground coal mining

Based on the number of fatalities per year,a persistent area of concern in minesafety continues to be equipment related.Data from the period 1995 through 2007 werestudied in order to identify major hazards for underground mining equipment-related fatalincidents and to perform an analysis of those that occurred over the last 13 years.Reportson equipment-related fatal incidents were obtained from the Mine Safety and Health Administration(MSHA).The results show that underground mining equipment including c...