Using a Water Balance to Determine the Source of Water in the Flooding Underground Mine Workings of Butte

Abstract.  Nearly 10,000 miles (16,000 km) of underground mine workings began flooding on April 22, 1982 when the large pumps used to dewater the mines of Butte, Montana were shut off. In the first few months, water levels in the workings rose hundreds of meters. Flooding continues to this day at a slower rate, nearly 25 years later. An early evaluation of the water chemistry in the flooding mines suggested that the initially poor water quality was the result of flushing of a reservoir of stored acidity and metals. However, a detailed water balance for the Berkeley pit, underground workings, and associated mining features suggests an alternative explanation. During the early period of mine flooding, acidic surface water from the deactivated heap leach operations and nearby acid rock drainage were routed into the empty Berkeley Pit, and thence drained downward and outward into the underground mine workings, causing widespread degradation of water quality in the underlying workings. After 21 months, the hydraulic gradients in the system reversed, causing a change in the direction of ground water flow and a gradual improvement in water quality of the mine shafts.     

The Comprehensive Realistic Yearly Pit Transient Infilling Code (CRYPTIC): A Novel Pit Lake Analytical Solution

Abstract.  Permitting of open pit mines that intersect the groundwater table necessitates the use of sophisticated numerical models to determine the temporal impact of pit lake hydraulics. However, while mine feasibility and the potential environmental influences of open-pit dewatering can be estimated using conventional screening-level methods, to date there have been few published transient analytical solutions to estimate the pit lake recovery duration and inflow rates. The Comprehensive Realistic Yearly Pit Transient Infilling Code (CRYPTIC) described here is based on the Jacob-Lohman equation, modified to include the pit geometry and effects of precipitation and evaporation from the pit lake surface as well as the input/output of external flows. It assumes that the aquifer is homogeneous and isotropic with laterally extensive horizontal flow but differs from other methods in that it includes transient inflows. CRYPTIC was used to successfully model the Berkeley Pit Lake (Butte, Montana) recovery data and its predictions also compared favorably with results from the Pipeline Pit (north-central Nevada) numerical model. However, while this analytical approach provides useful hydraulic insights at the feasibility stage of mine planning, more detailed analysis is required to determine critical mine permitting requirements. For example, the lateral extent of the drawdown cone, time to maximum extent of dewatering, and temporal effects on springs and seeps require deployment of a full numerical code and substantially more data.     

Using Helicopter Electromagnetic Surveys to Identify Environmental Problems at Coal Mines

Abstract.  Helicopter-mounted electromagnetic (HEM) surveys have been used to delimit conductive mine pools and groundwater features at various areas in the eastern United States that contain abandoned surface and underground coal mines. HEM was used to delineate the source areas and flow paths for acidic, metal-containing groundwater. This will aid remediation efforts. A recent HEM survey of Kettle Creek Watershed, Clinton County, Pennsylvania, using a 6-frequency electromagnetic data acquisition system, is presented. The survey accurately located conductive pools within underground mines, acidgenerating mine spoil at surface mines, and areas of groundwater recharge and discharge.     

Long Term Changes in the Limnology and Geochemistry of the Berkeley Pit Lake, Butte, Montana

Abstract.  The Berkeley pit lake in Butte, Montana is one of the largest accumulations of acid mine drainage in the world. The pit lake began filling in 1983, and continues to fill at a rate of roughly 10 million liters d^-1. This paper details how changes in mining activities have led to changes in the rate of filling of the pit lake, as well as changes in its limnology and geochemistry. As of 2005, the Berkeley pit lake is meromictic, with lower conductivity water resting on top of higher conductivity water. This permanent stratification was set up by diversion of surface water—the so-called Horseshoe Bend Spring—into the pit during the period 2000 to 2003. However, the lake may have been holomictic prior to 2000, with seasonal top-to-bottom turnover events. The present mining company is pumping water from below the chemocline to a copper precipitation plant, after which time the Cu-depleted and Fe-enriched water is returned to the pit. Continued operation of this facility may eventually change the density gradient of the lake, with a return to holomictic conditions. A conceptual model illustrating some of the various physical, chemical, and microbial processes responsible for the unusually poor water quality of the Berkeley pit lake is presented.     

Evaluation of Hydrogeological Parameters Associated with Limestone Mining: A Case Study from Chandrapur,India

Abstract.  Hydrogeological study of the Manikgarh and Naokari limestone mining areas, located in the Chandrapur region of central India, indicate that the mining operations should not cause environmental problems. Conversion of hill mining to pit mining at the Manikgarh Limestone Mine should be feasible and safe. At the Naokari Limestone Mine, a partial diversion of a seasonal stream, the Bop Nala, has been proposed to simplify mining and maximize production; this can be done without significantly altering the natural drainage pattern of the area and is not expected to have any adverse effects on the hydrological regime of area.     

Hydrogeological and Hydrochemical Characteristics of the Partially Flooded Piaseczno Opencast Sulphur Mine in Southeastern Poland

Abstract.  The basic chemical properties of Tertiary (T) and Quaternary (Q) aquifers near the Piaseczno opencast sulphur mine and the water in the open pit, along with the stratigraphy and hydrogeology of the area, were characterized to assess the feasibility of inundating the mine with ground water. Ground water quality varied markedly in the opencast area. A distinct stratification was noted in the pit water; total dissolved solids, calcium, chloride, hardness, and hydrogen sulphide increased from the top water level to the bottom of the pit lake. The concentrations of SO₄^2- and Cl^- in the opencast water were very high, especially in the hypolimnion zone. Based on our preliminary analysis, it appears that an artificial lake formed in the Piaseczno open pit could be used in the future as a fish and wildlife habitat as well as for recreational purposes.     

Evaluation of Airborne Thermal Infrared Imagery for Locating Mine Drainage Sites in the Lower Youghiogheny River Basin,Pennsylvania, USA

Abstract.  Nighttime high-resolution airborne thermal infrared imagery (TIR) data were collected in the predawn hours during Feb 5-8 and March 11-12, 1999, from a helicopter platform for 72.4 km of the Youghiogheny River, from Connellsville to McKeesport, in southwestern Pennsylvania. The TIR data were used to identify sources of mine drainage from abandoned mines that discharge directly into the Youghiogheny River. Image-processing and geographic information systems (GIS) techniques were used to identify 70 sites within the study area as possible mine drainage sources. The combination of GIS datasets and the airborne TIR data provided a fast and accurate method to target the possible sources. After field reconnaissance, it was determined that 24 of the 70 sites were mine drainage. This paper summarizes: the procedures used to process the TIR data and extract potential mine-drainage sites; methods used for verification of the TIR data; a discussion of factors affecting the TIR data; and a brief summary of water quality.     

Evaluation of Airborne Thermal Infrared Imagery for Locating Mine Drainage Sites in the Lower Kettle Creek and Cooks Run Basins,Pennsylvania, USA

Abstract.  High-resolution airborne thermal infrared (TIR) imagery data were collected over 90.6 km² (35 mi²) of remote and rugged terrain in the Kettle Creek and Cooks Run Basins, tributaries of the West Branch of the Susquehanna River in north-central Pennsylvania. The purpose of this investigation was to evaluate the effectiveness of TIR for identifying sources of acid mine drainage (AMD) associated with abandoned coal mines. Coal mining from the late 1800s resulted in many AMD sources from abandoned mines in the area. However, very little detailed mine information was available, particularly on the source locations of AMD sites. Potential AMD sources were extracted from airborne TIR data employing custom image processing algorithms and GIS data analysis. Based on field reconnaissance of 103 TIR anomalies, 53 sites (51%) were classified as AMD. The AMD sources had low pH (<4) and elevated concentrations of iron and aluminum. Of the 53 sites, approximately 26 sites could be correlated with sites previously documented as AMD. The other 27 mine discharges identified in the TIR data were previously undocumented. This paper presents a summary of the procedures used to process the TIR data and extract potential mine drainage sites, methods used for field reconnaissance and verification of TIR data, and a brief summary of water-quality data.     

Evaluation of the Effluent Water Quality Produced at Phosphate Mines in Central Jordan

Abstract.   The effluent water produced by the washing process at the Al-Hisa and Al-Abyad phosphate mines in central Jordan was investigated in summer 2002. Twenty-four effluent and 10 ground water samples were collected and analyzed. There was a significant difference in water chemistry between input (groundwater) and output (effluent water) but, although the investigated area is highly fractured, the stable isotopic results indicated little or no mixing between the effluent water and groundwater in the area. This is attributed to the precipitation of clay-sized particles along the drainage channel. The quality of the effluent from the Al-Hisa mine was better than at the Al-Abyad mine, with electrical conductivity averaging 1474 µS/cm at Al-Hisa and 3250 µS/cm at Al-Abyad. The difference in effluent quality is attributed to slight lithological differences. At both mines, chloride was the predominant ion in the effluent water, with an average concentration of 669 ppm and 1299 ppm at the Al-Hisa and Al-Abyad mines respectively. The concentrations of heavy metals in the high-pH effluent water were very low, presumably due to precipitation and absorption onto suspended fine-grained particles. The effluent water from both mines was found to be relatively low in sodium and radiation, and suitable for the irrigation of salt tolerant plants.     

Surface Pre-grouting and Freezing for Shaft Sinking in Aquifer Formations

Abstract  Special techniques are used for shaft sinking in aquifer formations. In the unstable aquifer formations encountered in Chinese coal mines, freezing is always adopted for shaft constructions in an aquifer alluvium, while surface pre-grouting is generally adopted in bedrock formations. So far, freezing has been used to construct 500 vertical shafts, comprising a total length of 80 km, and surface pre-grouting has been used in more than 150 vertical shaft sinking projects. The maximum depth of freezing is about 700 m, while the maximum depth of surface pre-grouting exceeds 1000 m.