title: Mine drainage and surface mine reclamation : proceedings of a conference
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'bv 1 .i?*V * ^ * v ^ IC 9183 Bureau of Mines Information Circular/1988 AP R Mine Drainage and Surface Mine Reclamation Proceedings of a conference sponsored by The American Society for Surface Mining and Reclamation, The Bureau of Mines, and The Office of Surface Mining Reclamation and Enforcement. The conference was held in Pittsburgh, Pennsylvania on April 19-21, 1988. Volume I: Mine Water and Mine Waste. UNITED STATES DEPARTMENT OF THE INTERIOR Information Circular 9183 Mine Drainage and Surface Mine Reclamation Proceedings of a conference sponsored by The American Society for Surface Mining and Reclamation, The Bureau of Mines, and The Office of Surface Mining Reclamation and Enforcement. The conference was held in Pittsburgh, Pennsylvania on April 19-21, 1988. Volume I: Mine Water and Mine Waste. *'*c'TT* Volume II: Mine Reclamation, Abandoned Mine Lands and Policy Issues, is also available from The Bureau of Mines as Information Circular 9184. UNITED STATES DEPARTMENT OF THE INTERIOR Donald Paul Hodel, Secretary BUREAU OF MINES David S. Brown, Acting Director ^ QS-£ol7i3 UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT With Factors for Conversion to U.S. Customary Units and the International System of Units (SI)'' Abbreviation Unit of measure To convert to — Multiply by — or unit acre acre hectares 0.405 bar bar NA bu bushel NA C coulomb NA cm centimeter inches 0.3937 eV electron volt NA ft foot meters 0.3048 ft2 square foot square centimeter 929.0 ft3 cubic foot cubic meters 0.028 ft/s foot per second centimeters per second 30.48 g gram ounces 0.0353 gal gallon liters 3.785 gal/h gallon per hour liters per hour 3.785 gal/min gallon per minute liters per minute 3.785 h hour NA ha hectare acres 2.471 in inch centimeters 2.54 K kelvin NA kg kilogram pounds 2.205 L liter cubic inches 61 .025 lb pound kilograms 0.4536 lb/min pounds per minute kilograms per minute 0.4536 L/min liter per minute gallons per minute 0.2642 m meter feet 3.28 M mole per liter M mega NA m3 cubic meter cubic yards 1.308 m3/s cubic meter per second gallons per second 264.2 mil mil inch 0.001 inch mile mile kilometers 1.609 mg milligram grains 0.0154 mg/L milligram per liter NA mg/(L-h) milligram per liter per hour NA min minute NA mL milliliter cubic inches 0.061 mm millimeter inches 0.0394 mmho/m millimho per meter NA mol .. mol/L mv ym iifi?sv t liter micrometer inches 3.94 x 10"5 ohm ohm NA pet percent NA psi pound per square inch grams per square centimeter 70.307 std ft3/min standard cubic foot per NA minute NA ton ton metric tons 0.907 yr year NA NA Not applicable. 1 0wing to the preference of individual authors, U.S. customary and SI units have both been used in this report. Conversion factors are provided for the assistance of the reader. TABLE OF CONTENTS Acid Mine Drainage: Prediction Page Use of Acid-Base Accounts in Premining Prediction of Acid Drainage Potential: A New Approach from Northern West Virginia 2 R. S. diPretoro and H. W. Rauch Evaluation of Overburden Analytical Methods as Means to Predict Post-Mining Coal Mine Drainage Quality.. 11 P. M. Erickson and R. S. Hedin Relationships Between the Initial Geochemistry and Leachate Chemistry of Weathering Overburden Samples.. 21 R. S. Hedin and P. M. Erickson Application of Acid-Base Analysis to Wastes From Base Metal and Precious Metal Mines 29 S. D. Miller and G. S. Murray A Study of Mine Drainage Quality and Prediction Using Overburden Analysis and Paleoenvironmental Reconstructions, Fayette County, Pennsylvania 33 K. B. C. Brady, J. R. Shaulis and V. W. Skema Acid Mine Drainage: Field Applications Phosphatic Clay Slurries for Reducing Acid Mine Drainage From Reclaimed Mines Sites 44 E. D. Chiado, J. J. Bowders and J. C. Sencindiver Laboratory and Field Testing of a Salt-Supplemented Clay Cap as an Impermeable Seal Over Pyritic Slates. 52 E. W. Murray, S. P. Goudey, R. G. L. McCready, and J. Salley The Partitioning of Flow Components of Acidic Seeps From Surface Coal Mines and the Identification of Acid Producing Horizons within the Backfill 59 D. T. Snyder and F. T. Caruccio The Use of Phosphate Materials as Ameliorants for Acid Mine Drainage 67 J. J. Renton, A. H. Stiller and T. E. Rymer A Computer Simulation Probability Model for Geochemical Parameters Associated with Coal Mining Operations 76 T. E. Rymer, II, J. J. Renton and A. H. Stiller Chemical Stability of Manganese and Other Metals in Acid Mine Drainage Sludge 83 G. R. Watzlaf Acid Mine Drainage: General Treatments to Combat Pyrite Oxidation in Coal Mine Spoil 91 C. A. Backes, I. D. Pulford and H. J. Duncan A Growth Inhibition Model for Thiobacillus Ferrooxidans 97 K. L. Shuttleworth and R. F. Unz Rehabilitation of Waste Rock Dumps at the Rum Jungle Mine Site 104 J. W. Bennett, J. R. Harries and A. I. M. Ritchie Chemical Inhibition of Iron-Oxidizing Bacteria in Waste Rock and Sulfide Tailings and Effect on Water Qual i ty 109 G. R. Watzlaf Mapping Buried Tipple Refuse - Is the Magnetometer Better Than Terrain Conductivity? 117 J. H. Schueck The Use of Pre-Aeration to Reduce the Cost of Neutralizing Acid Mine Drainage 131 T. C. Jageman, R. A. Yokley and G. W. Heunisch Mine Geochemistry Methods for Determining Fundamental Chemical Differences Between Iron Disulfides From Different Geologic Provenances 136 R. W. Hammack, R. W. Lai and R. J. Diehl Page Interpretation of Isotoplc Compositions of Dissolved Sulfates in Add Mine Drainage 147 R. 0. van Everdingen and H. R. Krouse Geochemistry of Abandoned Lignite Mine Spoil in Texas 157 J. K. Horbaczewski and F. Van Ryn The Rate of Oxidation of Pyrites From Coal and Ore Sources - An AC Impedance Study 164 S. Chander and A. Briceno A Quantitative Assessment of the Natural Abatement of Acid Mine Drainage by Interaction with Allegheny Group Lithologies 170 A. D. Stahl and R. R. Pan'zek Mine Waste Characterization Prediction of Add Mine Drainage From Duluth Complex Mining Wastes in Northeastern Minnesota 180 K. Lapakko Acid Mine Drainage and Management of Eastern Oil Shale Resources and Associated Waste Products 191 P. J. Sullivan and J. L. Yelton Evaluation of the TCLP Method for Two Mill Tailings 200 J. C. Franklin and E. G. Zahl A Comparison of Results From Acid-Base Accounting Versus Potential Acidity Measured by the Peroxide Oxidation of Weathered and Unweathered Soils Containing Pyrite 206 J. T. Ammons and P. A. Shelton The Interrelationship of Factors Influencing the Dissolution of Metals in Columns of Mine Tailings 210 R. D. Doepker Improved Rock Durability Testing Techniques for Appalachian Valley Fills 220 R. A. Welsh, Jr. and M. K. Robinson Mine Hydrology Acid Mine Drainage Research: Hydrology's Critical Role and Unifying Theme 228 F. T. Caruccio Stream Sealing to Reduce Surface Water Infiltration into Underground Mines 232 T. E. Ackman and J. R. Jones Unsaturated Fluid Flow in Mine Spoil: Investigative Methods Leading to a Quantitative Characterization. 240 D. M. Diodato and R. R. Parizek Forecasting the Effect of Mine Site Rehabilitation Works on Local Ground Water Quality 248 D. K. Gibson and G. Pantelis Photo-Linear Characterization, Lithologic Variability, and the Effects of Mining Activity by Fracture Studies and In Situ, Air-Injection, Permeability Testing 253 C. A. Shuman and R. R. Parizek Modeling Sulfate Retention in a Lake Receiving Acid Mine Drainage 261 A. T. Herlihy, A. L. Mills and W. Lung Pennsylvania's Approach to Cumulative Hydrologic Impact Assessment of Coal Mining Activities 269 L. E. Langer Biological Mine Water Treatment Biological Metal Removal From Mine Drainage 274 K. Wetland Systems for Mine Water Treatment - Process & Design Effects of Cattails ( Typha ) on Metal Removal From Mine Drainage 359 J. C. Sencindiver and D. K. Bhumbla Water and Soil Parameters Affecting Growth of Cattails: Pilot Studies in West Virginia Mines 369 D. E. Samuel, J. C. Sencindiver and H. W. Rauch Determining the Capacity for Metal Retention in Man-made Wetlands Constructed for Treatment of Coal Mine Drainage 375 R. K. Wieder Implications of Sul fate-Reduction and Pyrite Formation Processes For Water Quality in a Constructed Wetland: Preliminary Observation 382 R. S. Hedin, P. M. Hyman and R. W. Hammack An Evaluation of Substrate Types in Constructed Wetlands Acid Drainage Treatment Systems 389 G. A. Brodie, D. A. Hammer and D. A. Tomljanovich Poster Session Abstracts Isolation and Culture of a Manganese-Oxidizing Bacterium from a Man-made Cattail Wetland 399 W. J. Vail, S. Wilson and R. K. Riley Screening of Mosses and Algae in Greenhouse Experiments for Their Ability to Remove Iron from Water 399 H. J. Webster, L. R. Stark and S. E. Stevens, Jr. Ecological Engineering and Biological Polishing: Its Application in Close-out of Acid Generating Waste Management Areas 399 M. Kalin Wetlands and Mine Drainage - An Ecotechnology Approach 400 W. J. Mitsch, M. S. Fennessy, M. A. Cardamone, and D. Palmieri Peat Blanket to Lock Acid Mine Spoils in a Self-Sustaining Ecosystem 400 A. Brown, S. p. Mathur and D. J. Kushner Wetland/Riparian Reconstruction Following Surface Mining: Part III. Recommendation on Channel Morphology to Support a Wet Meadow 400 R. E. Behling A Staged Wetland Treatment System for Mine Water with Low pH and High Metal Concentrations 401 T. M. Demko and B. G. Pesavento Construction of a Wetland Demonstration Site for a Metal-Mine Drainage 401 T. R. Wildeman, L. S. Laudon and E. A. Howard Page Response of Thiobacillus ferrooxidans to Organic Compounds: Leakage of Cellular Material and Inh1 bltlon of Growth 401 M. Bhatnagar and G. Singh Iron Monosulfide and Pyn'te Formation In Sediments of Lakes that Receive Acid Mine Drainage 402 C. M. Wicks, J. S. Herman, A. L. Mills, and J. P. Schubert Hydrology and Geochemistry of Surface Coal Mine Lakes 402 J. P. Schubert Water Resource Development Engineering and Acid Mine Drainage in the Upper Ohio River Basin 402 M. Koryak Aeration Efficiency in the In-Line Aeration and Neutralization System 403 T. E. Ackman and C. . C. Hustwit Treatment of Acidic Coal Refuse by Addition of Crushed-Stone Pond Screenings 403 S. J. Stokowski, Jr. and R. R. Gilbert X-ray Diffraction Evaluation of Coal Overburden Neutralization Potential 403 T. L. Despard Stream Sealing Over an Active Longwall Panel 404 T. E. Ackman and C. C. Hustwit Micromap — A Database Retrieval and Display Manager for Microcomputers 404 T. E. Rymer, II, J. J. Renton and A. H. Stiller Installation and Stability of Inverted Pyramid-Shaped Plugs for Closing Abandoned Mine Shafts Galena, KS Demonstration Project 405 J. S. Volosin MINE DRAINAGE AND SURFACE MINE RECLAMATION Proceedings of a Conference jointly sponsored by the Bureau of Mines, the Office of Surface Mining Reclamation and Enforcement, and the American Society of Surface Mining and Reclamation. ABSTRACT Mine waste and mine reclamation are topics of major interest to the mining industry, the government and the general public. This publication and its companion volume are the proceedings of a conference held in Pittsburgh, April 19-21, 1988. There were nine sessions (50 papers) that dealt with the geochemistry, hydrology and problems of mine waste and mine water, especially acid mine drainage. These comprise Volume 1. The nine sessions (43 papers) that dealt with reclamation and restoration of disturbed lands, as well as related policy issues, are included in volume 2. Volume 2 also contains the ten papers that pertained to control of subsidence and mine fires at abandoned mines. Poster session presentations are, in general, represented by abstracts; these have been placed in the back of both volumes. Reference to companies and specific products in these papers does not imply endorsement by the Bureau of Mines. USE of acid-base accounts in premining prediction of acid DRAINAGE POTENTIAL: A NEW APPROACH FROM NORTHERN WEST VIRGINIA o Richard S. diPretoro and Henry W. Rauch Abs trac t. --Premining prediction of postmining drainage quality is required by law, but the method most often used, in- volving acid-base accounting, was never intended to predict mine drainage quality and as used in the past has proven unreliable. In this study, postmining drainage chemistry was measured at base flow in a one-time sampling program for 75 surface coal mines in Monongalia and Preston Counties in West Virginia. The drainage chemistry was then compared to available acid-base account parameters to identify reliable premining predictors, if any, of drainage quality. Sampling locations included seeps, springs, first order streams, and inflows to ponds if they primarily contained mine drainage. Each sampling location was paired with the closest available acid-base account log, which was mathematically adjusted to yield the volume percentage of each geochemical unit in the mined coal overburden, plus one foot of pavement. Both total and net neutralization potentials (NP) of overburden are significantly and directly related to net alkalinity (alkalinity minus acidity) of mine drainage. Every sampled mine is producing drainage with positive net alkalinity if it has greater than 40 tons of CaCO^ equivalent of total NP per thousand tons of overburden, or greater than 30 tons of CaCOo equivalent of net NP per thousand tons of overburden. Conversely, every mine with less than 20 tons per thousand tons of total NP or less than 10 tons per thousand tons of net NP is producing drainage with negative net alkalinity. Total sulfur content and hence maximum potential acidity (MPA) in overburden bears very little relation to mine drainage quality. All mines in this study with very low (<0.2%) sulfur content in overburden produce acid drainage. The ratio of NP to MPA is significantly and directly related to net alkalinity of mine drainage. Every sampled mine is producing drainage with negative net alkalinity if it has an NP to MPA rati'o of less than 2.4. INTRODUCTION Public Law 95~87 (Surface Mining Con- trol and Reclamation Act 1977) requires premining planning. The law states that surface coal mining permits are not to be issued where required reclamation is not feasible or cannot be accomplished by the plan submitted. Acceptable drainage quali- Paper presented at the 1988 Annual Mine Drainage and Surface Mine Reclamation Conference sponsored by the American So- ciety for Surface Mining and Reclamation and the U. S. Department of the Interior (Bureau of Mines and Office of Surface Mining Reclamation and Enforcement), April 17-22 1988, Pittsburgh, PA. Richard S. diPretoro is a Consulting Geologist in Morgantown, WV and Henry W. Rauch is a Professor of Geology at West Virginia University, Morgantown, WV. ty is one of the components of required reclamation and such quality is to be in- sured in part by pre-iden t i f y ing acid- producing materials so as to avoid acid drainage. Thus, the Federal government has produced a legal requirement that acid- producing materials in coal overburden and pavement be identified in advance of mi- ning. To aid operators and state agencies in ^re-identifying acid-producing ma- terials, the U.S. Environmental Protection Agency (EPA) published a method developed at West Virginia University known as the acid-base account method (Sobek et al. 1978). The method was intended to aid revegetation by identifying the best choices for topsoil substitute material. Although it was not intended by its authors to be used to predict postmining drainage quality, acid-base accounting has been used for that purpose and has produced mixed results (Renton 1985). This study attempted to identify re- liable premining predictors of acid drainage potential. This paper reports on reliability of acid-base account parameters for the premining prediction of acid post- mining drainage. Description of the Study Area The area of study for this project comprises all or part of the areas shown on thirteen 7.5 _ minute topographic quadrangles of the U.S. Geological Survey in northern Preston and eastern Monongalia Counties, WV (fig. 1). The coal-bearing rocks are middle Pennsylvanian to Permian in age and consist primarily of sandstone and shale with les- ser amounts of limestone and coal. The structures are low-lying open folds tren- ding northeast-southwest. The climate of the study area is of the humid, continental type characterized by mild summers and cold winters. Rainfall ranges from 42 to 52 inches (Herb et al. 1981). All ground water that is eventually discharged from the study area is generated by the infiltration of precipitation except for minor amounts being flushed from deep saline aquifers. U. S. Geological Survey 7.5 Minute Quadrangles 1 Osage 2 Morgantown North 3 Lake Lynn 4 Bruceton Mills 5 Brandonville 6 Rivesville 7 Morgantown South 8 Ma son town 9 Valley Point 10 Cuzzart 11 Gladesville 12 Newburg 13 Kingwood Location of Study Area Figure 1. --Location map of the study area. METHODS OF INVESTIGATION Sampl ing Seventy-five surface water sites were selected for a one-time sampling program designed to indicate in a broad sense the quality of drainage from reclaimed surface coal mine sites. The mine sites were selec- ted based on pre-de t erm ined criteria dis- cussed below after examining over 400 per- mit applications for surface coal mines and other water and overburden data at the U.S. Office of Surface Mining Reclamation and Enforcement (OSM) in Morgantown, WVa. All reclaimed surface coal mines in Monongalia and Preston Counties in the Waynesburg, Upper and Lower Freeport, and Upper, Middle, and Lower Kittanning Coal Seams were selected for sampling where the mines couid be reached on the ground and had observable drainage. Seventy-five such sites were sampled. Mine drainage sampling locations in- cluded seeps and springs located in and near the mine backfill, both undeveloped and developed for domestic or livestock uses. First order streams and inflows to ponds were also sampled if they primarily contained mine drainage. The selected water sampling sites were usually near vegetated mine backfills that usually had been reclaimed for 2 or more years. They were mostly chosen on the downdip side from the mine drainage source with the highest flow rate. Where possible, they were estab- lished at or below the original level of the coal near the center of the mine to increase the chances of discerning any mining effects and to decrease the chances of dilution by unaffected ground water or of complicating effects from other nearby mines. Previously mined areas (before recent mining) were generally avoided, as were mines which had disposed tipple refuse or treatment residues. The field sites were sampled during base flow (at least 3 days after the last measurable rain), in the spring of 1985. Base flow is not subject to wide fluctua- tions and is indicative of shallow aquifer ground-water characteristics (Hem 1970, Todd 1980, Helsel 1983). The sampling sites were all located in heavily dissected upland areas not subject to any regional ground-water discharge. Temperature, spe- cific conductance, Eh, pH, and flow rate v/ere measured. Three water samples were collected and treated (as appropriate) for laboratory analysis at each site. Hot total acidity (HTA), alkalinity, sulfate, total and dissolved iron, and dis- solved manganese were determined (for each set of water samples) in the Hydrogeology Laboratory in the Department of Geology and Geography at West Virginia University. After the drainage sites had been sampled, acid-base accounts from OSM permit files were chosen to be paired where possi- ble with each water sampling point for later comparison. Such logs were taken from the same mine or a mine working the same coal seam within 2 km of the watershed draining to the sampling point. In most cases, logs fell within 1 km of the sam- pling point watershed as per recommenda- tions of the Suggested Guidelines (Surface Mine Drainage Task Force 1979). Such pairs were created for 30 out of the 75 mines s tudied. Adjustment of Core Log Data for Volume Core logs record the thickness and type of each rock lithology over an area that is so small compared to the area to be mined that they can be considered lines in cross-section. Mined overburden in the field area is not rectangular in cross- section, as it is in Illinois for example, but is more nearly triangular in cross- section because of the notable terrain slopes. Therefore, the volumes of each lithology represented by the core log are not in fact in the same volume proportion to each other in the mined overburden as they are in the linear record of the log. Those near the top are over-represented and those near the bottom are under-represented by an unadjusted log. Volumetric adjustment is in order if better predictions are to be made of the combined effects that the different over- burden rocks will have on water after mine reclamation, assuming that water quality is related to the mass of certain constituents in the rocks. The ideal solution would be to have a closely spaced grid of cores that would be s tratigraphically correlated, al- lowing the strata to be projected to their crop lines according to the dip and strike. The average area of each lithologic unit would then be measured by planimeter and multiplied by its average thickness to arrive at a total volume for each rock lithology. Tonnages would be computed if necessary, based on estimated (or measured) rock densities. An effort similar to that just des- cribed was successfully carried out and described in the literature by Caruccio and Geidel (1981). Such efforts were also carried out for some West Virginia surface mine reclamation permit applications for a brief time in 1981 (diPretoro 1986). The reason for such calculations in permit applications was to compute the amount of limestone that is supposed to be needed to compensate for deficiencies identified by acid-base accounting. For this study, a simpler volumetric adjustment was designed that could be ap- plied quickly to limited core log data. This volumetric adjustment was conceived by the senior author and carried out by means of a computer program written by Mr. Paul Sutter, systems analyst for the West Vir- ginia University Department of Geology and Geography. The volumetric adjustment yields the approximate percentage of the total over- burden volume occupied by each rock unit and requires knowing only the total thickness of the s tra t igraphic overburden column, the thickness of the individual rock units, and their relative positions. It starts with the recognition that every mined tract in the field area is part of a slope, hill, or mountain. It assumes that the shape of a mined hill can be approxi- mated as one of a number of three-dimen- sional shapes, each of which is a triangle in cross-section. These include shapes similar to those for contour mines and area or mountaintop removal mining operations where the top of the mountain is cone or prism shaped (fig. 2). The core log's top is usually located at the highest point of the triangle, and the coal or pavement forms the triangle's base leg which is roughly perpendicular to the core log. Symmetry about the core (vertical axis) is not required on conical shapes, and trian- gular cross-sections need not be isosceles. (In this study, some logs represented more, or less, overburden than was present at the mine producing the drainage samples. Where the log represented more overburden, the extra amount was removed from the calcula- tions. Where the log represented less CONTOUR HILLSIDE STRAIGHT HILLSIDE MOUNTAINTOP OR KNOB Figure 2 .-- Idea 1 i ze d shapes of hills having triangular cross-sections when mined. overburden, the missing amount could not be evaluated. The program takes the thickness of each layer of rock and calculates the per- centage of the area of the whole cross- sectional triangle occupied by that layer. The areas of the triangle and its parts are proportional to the volumes of the cor- responding parts of the overburden as a whole (fig. 3). Because the coal is, for the most part, gone after reclamation, its contribu- tion is removed and the relative percen- tages of each remaining layer are recalcu- lated. (Bottom coal, partings and other wastes are often left on the pavement but in the interests of simplicity are ignored in this study.) The percentage for each layer is then multiplied as a decimal frac- tion by the acid-base NP or MPA for that layer to arrive at its contribution to the total for each parameter. The adjusted NP and MPA for each layer is then summed to produce an adjusted NP and MPA for the entire column. Totals of unadjusted NP and MPA are physically meaningless because layer thickness and volume have not been taken into account. This right triangular method incor- porates simplifying assumptions. The core does not always represent all the overbur- den. The dip is ignored, but the maximum dip is low in the study area, rarely ap- proaching 10 percent. Cross-sections are not exactly triangular, but are slightly elliptical. Lithologic units are usually laterally discontinuous and may thicken, thin or pinch out altogether away from the core hole. Despite its shortcomings, how- ever, the volumetric adjustment technique used in this study is an adequate first approximation and is an improvement over an assumption of a linear relationship between percentage of a certain lithologic unit in a core log and its volume in the mine backfill. Characterization of Post-Mining Drainage For the purposes of this study, the legal definition of acid mine drainage (AMD) was used as a basis for characteriza- tion of postmining drainage. AMD is legal- ly defined as water discharged from an active, inactive, or abandoned mine and from areas affected by surface mining with a pH of less than 6.0 in which total acidi- ty exceeds total alkalinity (Code of Fed- eral Regulations 1986). The legal defi- nition of acid mine drainage creates an operational parameter to characterize water quality, herein called "net alkalinity," which is calculated by subtracting the acidity from the alkalinity of a drainage water sample with both measured in the same units (mg/L as CaCOo). Net alkalinity can be positive (when alkalinity exceeds acidi- ty) or negative (when acidity exceeds alka- linity). In this study, most drainage samples had only acidity or alkalinity. In the samples that had both acidity and alka- P = \ of Overburden Occupied by Stratum = i^fl£^2 x100 Area WXYZ figure 3. — Triangular cross-sections of idealized hill used in the volumetric adjustment program. showing variables linity, one outweighed the other by a fac- tor of at least 10 in most cases. Net alkalinity for the sampled drain- age sites was compared by use of graphical data plots and statistical analyses with values for the geochemical parameters eva- luated. All the raw data were reported by diPretoro (1936); diPretoro and Rauch (1987) reported other results of the same study having to do with lithologic parameters. RESULTS AND DISCUSSION In spite of their shortcomings, acid- base accounts were used in this study be- cause they are available in large quantity and they do give some useful information on the geochemical nature of the individual strata. Neutralization Potential (NP) and Net NP Figure 4 compares net alkalinity of mine drainage to the acid-base account parameter of net NP in overburden, with each plotted point representing a sampled mine site. The statistically significant regression line depicts the average rise of net alkalinity of drainage with increasing net NP. Figure 4 also shows that all sites having net NP of less than 10 tons of calcium carbonate equivalent per thousand tons of overburden had drainage with nega- tive net alkalinity, while all sites having net NP of greater than 30 tons per thousand had drainage with positive net alkalinity. Note that the acid-base account method defines potentially toxic material in indi- vidual strata as that having a net NP of less than -5 (Sobek et al. 1978). This study indicates that the threshold level of concern for net NP for the overburden as a whole must be set higher. A similar trend (with a slightly lower R value that is statistically significant at 0.05 alpha) was also observed for total NP. All sites with total NP greater than 40 tons per thousand tons had drainage with positive net alkalinity while all sites with less than 20 tons per thousand tons had drainage with negative net alkalinity. Maximum Potential Acidity (MPA) MPA, calculated by multiplying total sulfur content as a decimal fraction by 31.25 (Sobek et al. 1978, p. 55), was found to have no statistically significant rela- tionship (at 0.05 alpha) to net alkalinity of mine drainage. As shown in figure 5, there appears to be a slight rise in average net alkalinity with rising sulfur content, and all sites with very low sulfur produce acid. This seeming anomaly relates to the NP/MPA ratio present. NP of over- burden rises as MPA rises, but NP rises at a faster rate. Very low MPA values are on average associated with proportionately less NP (and hence neutralizing capability) than are higher MPA values (above 5). The median value of NP/MPA ratio for sites in this study with MPA below 5 is 0.5. The median value of NP/MPA ratio for sites with MPA above 5 is 2.9. NP/MPA RATIO Caruccio et al. (1980) and Caruccio and Caruccio (1982) have found a strong relationship between drainage quality and carbonate to sulfur ratio. In this study, the ratio of NP to MPA (herein called RATIO) was assumed to approximate the ratio of carbonate to sulfur. The regression line showing the relationship of RATIO to net alkalinity in mine drainage had the 400 200 NET ALKALINITY e (mg/1 as CaC0 3 ) 1400 zero net alkalinity regression line KEY: • = data point 2,3 = multiple data points REGRESSION LINE DATA: net alkalinity = -232 + 6.93 x NET R = 0.423 n = 30 significant at 0.05 alpha 5 25 SO 75 iee 12 ACID-BASE NET NEUTRALIZATION POTENTIAL (tons CaCO-j equivalent per thousand tons of material) Figure 4. — Net alkalinity in mine drainage versus acid-base net neutra- lization potential in coal overburden. greatest degree of statistical significance of those for the acid-base account para- meters tested in this study. Figure 6 shows that all of 15 sites having a RATIO of less than about 2.4 had drainage with negative net alkalinity, while 11 of 14 sites having RATIOS greater than about 2.4 had drainage with positive net alkalinity. Note that the presently used acid-base account method would place the critical RATIO boundary below 1.0 (or even below zero) because geologic units having net NP greater than -5 are considered not poten- tially toxic (Sobek et al. 1978, Surface Mine Drainage Task Force 1979, Erickson et al. 1985). For example, one acid-base account in this study has an NP of 0.3 and an MPA of 4.6, producing a RATIO of 0.1. Strict application of acid-base account guidelines would result in this overburden being considered by some persons not poten- tially toxic because 0.3 minus 4.6 is greater than -5.0. The drainage from the two sampling locations within 2 km of this acid-base account, however, is highly acid. CONCLUSIONS This investigation of reclaimed sur- face coal mine sites in the northern West Virginia study area has led to four conclu- sions about the study results and a fifth general conclusion about acid-base accounting : 1) After adjusting acid-base account core logs for volume, all sites with acid- base neutralization potential (NP) greater than 40 tons per thousand tons of overbur- den equivalent calcium carbonate yield drainage having positive net alkalinity; all sites with NP less than 20 tons per thousand tons equivalent calcium carbonate yield drainage having negative net alkali- nity. 2) Acid-base maximum potential acidi- ty (MPA, calculated by multiplying percen- tage sulfur by 31.25) in premining coal overburden bears very little relation to net alkalinity of post-mining drainage in the study area except that below about 0.2 percent sulfur, reclaimed overburden is likely to produce acid drainage because of concomitant low neutralizing capacity. ■too NET ALKALINITY (mg/1 as CaC0 3 ) -698 . zero net alkalinity KEY: • = data point 2,3 = multiple data points n = 30 *— 5 MPA line ACID-BASE MAXIMUM POTENTIAL ACIDITY (MPA) (calculated by multiplying percentage of total sulfur by 31.25; expressed as tons CaC03 equivalent per thousand tons of material) Figure 5. — Net alkalinity in mine drainage versus acid-base maximum poten- tial acidity in coal overburden. 3) All sites with acid-base net NP (NP-MPA) greater than 30 tons per thousand tons of equivalent calcium carbonate (20 percent of sites in this study) yield drainage having positive net alkalinity; all sites with net NP less than 10 tons per thousand tons calcium carbonate equivalent (47 percent of sites in this study) yield drainage having negative net alkalinity. The original acid-base account application, which placed the threshold level of net NP for drainage having positive net alkalinity at -5 (same units), was obviously in error. 4) Acid-base NP divided by MPA yields a variable called RATIO. Sites with RATIO values greater than 2.4 are most likely to produce drainage having positive net alka- linity; sites with RATIO less than 2.4 are most likely to produce drainage having negative net alkalinity. The original acid-base account application which placed the threshold level of RATIO for drainage having positive net alkalinity at or below 1.0, was in error. 5) Despite its limitations, acid-base accounting can be used more effectively than it is currently being used to produce accurate premining assessments of post- mining drainage quality. Because of the complexity of coal mining and reclamation operations, professional judgement (taking into account lithology and history of drainage quality in a given area, as well as acid-base account parameters) will al- ways be required to arrive at a final determination. LITERATURE CITED Caruccio, F. T. and Caruccio, G. G. 1982. Method of Determining Weathering Char- acteristics of Rock Formations in Earth Moving Operations. United States Patent 4,328,001. 200 NET ALKALINITY (mg/1 as e CaC0 3 ) REGRESSION LINE DATA: net alkalinity = -427 + 138 x RATIO R = 0.486 n = 29 significant at 0.01 alpha 12 3 4 5 RATIO (Neutralization Potential/Maximum Potential Acidity) Figure b. -- Net alkalinity in mine drainage versus acid-base account RATIO (NP/MPA) in coal overburden. Caruccio, F. T., G. Geidel, and A. Pelle- tier. 1980. The Assessment of a Stra- tum's Capability to Produce Acidic Drainage. In: Proceedings of Sympo- sium on Surface Mining Hydrology, Sedimen tology and Reclamation. pp. 437-443. University of Kentucky, Lexington, KY. Caruccio, F. T. and G. Geidel. 1981. Esti- mating the Minimum Acid Load that Can Be Expected from a Coal Strip Mine. In: Proceedings of Symposium on Sur- face Mining Hydrology, Sedimentology and Reclamation. pp. 117-133. Uni- versity of Kentucky, Lexington, KY. 1986. Chapter pp. Office of Code of Federal Regulations 30, Section 701.5. 622 the Federal Register, National Ar- chives and Records Administration, Washington, DC. diPretoro, R. S. 1986. Premining Prediction of Acid Drainage Potential for Surface Coal Mines in Northern West Virginia. 217 pp. Unpublished M.S. Thesis, De- partment of Geology and Geography, West Virginia University, Morgantown, WV diPretoro, R. S. and Rauch, H. W. 1987. Premining Prediction of Acid Drainage Potential for Surface Coal Mines in Northern West Virginia. J_n: Pro- ceedings of Symposium on Surface Mi- ning Hydrology, Sedimentology and Rec- lamation, pp. 395-404. University of Kentucky, Lexington, KY. Erickson, P. M., R. W. Hammack, R. L. P. Kleinmann. 1985. Prediction of Acid Drainage Potential in Advance of Mi- ning. I_n: Control of Acid Mine Drainage, Proceedings of a Technology Transfer Seminar. p.3~ll. Bureau of Mines IC 9027. Kelsel, D. R. 1983. Mine Drainage and Rock Type Influences on Eastern Ohio Stream Water Quality. Water Resources Bulle- tin 19:881-887. Hem, J. D. 1970. Study and Interpretation of the Chemical Characteristics of Natural Waters. Second Edition, 363 pp. Water Supply Paper 1473, U.S. Geo- logical Survey. Herb, W. J., L. C. Shaw, and D. E. Brown. 1981. Hydrology of Area 5, Eastern Coal Province, Pennsylvania, Maryland and West Virginia. 92 pp. Water Re- sources Investigation 81-538, U.S. Geological Survey, Harrisburg, PA. Renton, J. J. 1985. Evaluation of the Acid Producing Potential of Toxic Rock Materials. Mountain State Geology, pp. 7-12. West Virginia Geological and Economic Survey, Morgantown, WV. Sobek, A. A., W. A. Schuller, J. R. Free- man, and R. M. Smith. 1978. Field and Laboratory Methods Applicable to Overburdens and Minesoils. 203 pp. U.S. Environmental Protection Agency (EPA-oOO/2-78-054), Cincinnati, OH. Surface Mine Drainage Task Force. 1979. Suggested Guidelines for Method of Operation in Surface Mining of Areas with Potentially Acid-Producing Ma- terials. I_n: Symposium on Surface Coal Mining and Reclamation, pp. 177- 197. Louisville, KY. Surface Mining Control and Reclamation Act. 1986. Public Law 95"87, 30 USC 1201 et seq. 142 pp. An Unofficial OSMRE Compilation, U.S. Department of the Interior, Office of Surface Mining Reclamation and Enforcement. Todd, D. 535 NY. K. 1980. Groundwater Hydrology, pp. John Wiley and Sons, New York, 10 EVALUATION OF OVERBURDEN ANALYTICAL METHODS AS MEANS TO PREDICT POST-MINING COAL MINE DRAINAGE QUALITY 1 Patricia M. Erickson and Robert S. Hedin^ Abstract. --Prediction of the potential for acid drainage formation is required as part of the coal mine permitting process. Overburden analyses, by methods such as the acid-base account, are in common usage as part of this prediction despite the fact that a quantitative correlation between overburden properties and post-mining water quality had never been demonstrated adequately in the field. This study was designed to test the accuracy of predictions based solely on overburden analytical data. The study sites were selected to represent cases that have proven difficult to predict. Overburden samples were obtained from freshly exposed surfaces on highwalls or from cores preserved prior to mining. Post-mining drainage was analyzed at a reclaimed section of each site, paired to match the sampled overburden in terms of the presence and thickness of lithologic units. Overburden samples were analyzed by the acid- base account and a simulated weathering method. Overburden data were aggregated on thickness- and volume-weighted bases and water quality data were aggregated on a flow-weighted basis for each site. Drainage net alkalinity was correlated significantly (p<0.05) with the volume-weighted acid-base account parameters acid potential, neutralization potential, and net neutralization potential (r=0.358, 0.4197, 0.3799, respectively). However, when five sites having net neutralization potentials greater than 20 tons/1000 tons were excluded, these relationships became insignificant. Acid base account data showed boundaries useful in predicting the acid or alkaline character of post-mining drainage but no quantitative predictive equation could be developed. Simulated weathering test data correlated with actual sulfate concentrations in the post-mining seeps (r=0.4089, p=0.046), but the alkaline or acid nature of the seeps was not correlated with laboratory data (r=0.088, p=0.364). INTRODUCTION Ipaper presented at the annual meeting of the American Society for Surface Mining and Overburden analysis came into widespread use Reclamat 10 n, Apnl 17-22, 1988, Pittsburgh, PA. wUh pas$age of the ^^ Mining ^^ ^e 2p a tricia M Erickson is a Suoervisory Reclamation Act of 1977 (Public Law 95-87). The „ . P ? c "VK.JrJP Inu^nEmLnJfi ] aw requires, as part of the permitting process, Physical Scientist with the Environmental the identificatio f; of potentially acid producing Technology Group of the U.S. bureau of Mines, strata and determinatio P n of the J robabi ; nydrol ^ gic Pittsburgh Research Center Dr. Robert S. Hedin consequences of mining, including water resource is an Ecologist working with the Environmental degradation. Because little research had been Technology Group, Pittsburgh Research Center conducted on water quality prediction, the under a post-doctoral fellowship with Oak Ridge. regulatory authorities and industry initially had to adapt available methods to these purposes. 11 The acid-base account method of overburden analysis was developed in the early 1970' s for identification of strata that could be used as soil substitutes in revegetation of coal mines (Smith et al 1974). The method (described subsequently in this paper) is based on determining whether the capacity of a stratum to produce acid via pyrite oxidation is greater or less than the ability of the same stratum to neutralize strong acid. A neutral izer deficiency greater than 5 tons/1000 tons as calcium carbonate equivalent^, a figure common for natural soils in West Virginia, was the recommended standard for identifying strata unsuited for supporting vegetation. This method was adopted widely as the overburden analytical tool for identification of acid and toxic strata. The term "toxic" was meant to indicate toxic to plants by virtue of high acidity levels. While the purpose and application of the method was delineated clearly in the literature, its more recent use as an indicator of water quality is not clearly defined. Based on the acid-base account and predict wheth would comply with other overburden numerous alternat static or kinetic properties while rates of relevant tests are kinetic the laboratory th field setting. C have recently bee Erickson, 1987) real or perceived failure of the to identify acid-producing strata er or not post-mining discharges regulatory standards, interest in analysis methods has grown. The ive methods can be classified as ; the former rely on bulk rock the latter take into account the reactions. Simulated weathering methods that aim to accelerate in e reactions that take place in the ommon static and kinetic tests n reviewed (Ferguson and At the start of this study, none of these methods had been adequately evaluated by comparing the predicted water chemistry to actual drainage chemistry. That is, there was no procedure for interpreting the results to predict post-mining water quality or character with a known degree of accuracy. The purpose of this study was to define the predictive capability of overburden analytical methods by applying them to many mine sites. Post- mining water quality measurements were made at the discharge points from reclaimed mine sections. Pre-mim'ng overburden samples were collected from preserved cores or from fresh channels cut in extant highwalls. These samples were analyzed using the acid-base account method and a simulated weathering test. The results of both overburden tests were then compared with the water quality results to determine if significant correlations exist. ^The unit, tons/1000 tons, derives from agronomy where 1000 tons is the estimated weight of an acre-plow layer of soil. The unit is identical to parts per thousand. CaC.03 equivalent indicates the mass of calcium carbonate needed to yield a specific magnitude of electrical charge (CaC03 = 50 g/mol of charge). The unit is used so that terms of opposite charge, such as acidity and alkalinity, are additive. METHODS Technical Approach Thirty-two sites were selected for the study, each comprised of a pre-mining section and a post- mining reclaimed section, so that pre- and post- mining data could be gathered simultaneously. The general concept was developed at the Bureau of Mines while the detailed approach was developed by Engineers International in response to our request for proposals. The contractor and its subcontractor, Sturm Environmental Services, selected all sites, conducted all sample collection and performed all water and rock analyses. Bureau personnel conducted all data analysis following completion of the contract. Sites were selected to represent cases that are difficult to predict. Overburden columns completely dominated by either acidic or alkaline strata were eliminated from consideration. Sites that were backfilled or reclaimed using acid- mitigating methods, such as selective spoil placement or surface alkaline addition, were also excluded. To minimize effects of local geology, sites in Pennsylvania, West Virginia, Maryland, Illinois and Kentucky were included in the study. Sites in west-central and southwestern Pennsylvania comprised about half of the study sites, through a prevalence of suitable candidates rather than through design. Water Quality Sampling and Analysis Post-mining water quality data were collected from reclaimed spoil sections at 32 mine sites paired with overburden sampling sites. Water sampling and flow measurement were conducted at all discharge points identified during the initial visit to each site. The discharges that comprised the majority of the flow, usually two or three at each site, were sampled subsequently at least nine times over about a year. Primary measurement and analysis methods for parameters used in this report are shown in Table 1. Table 1. --Analytical methods for selected parameters (U.S. EPA 1983) Parameter Measurement Method Water flow Bucket and stopwatch, L/min pH Electrometric, standard units Acidity Titration (hot, peroxide) to pH 8.3, mg/L as CaC03 Alkalinity Titration (cold) to pH 4.5, mg/L as CaC.03 Net Alkalinity Alkalinity minus Acidity, mg/L Sulfate Col orimetric methyl thymol blue, mg/L 12 Data Aggregation Water quality data for each site were aggregated to produce a single value for each parameter by calculating a flow-weighted average: flow-weighted X = n Y (concentration of X)(flow) (1) (flow) where n is the total number of samples at the site for which flow and concentration of X were measured and X is the chemical quantity net alkalinity, sulfate, or iron in mg/L. 