In cooperation with the National Park Service Assessment of Characteristics and Remedial Alternatives for Abandoned Mine Drainage: Case Study at Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Cambria County, Pennsylvania, 2004 By Charles A. Cravotta, III Open-File Report 2005-1283 U.S. Department of the Interior U.S. Geological Survey Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 2. REPORT TYPE 3. DATES COVERED 2005 N/A - 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Assessment of Characteristics and Remedial Alternatives for Abandoned Mine Draingage: Case Study at Staple Bend Tunnel Unit of Allegheny 5b. GRANT NUMBER Portage Railroad National Historic Site, Cambria County, Pennsylvania, 2004 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. 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Patrick Leahy, Acting Director U.S. Geological Survey, Reston, Virginia: 2005 For sale by U.S. Geological Survey, Information Services Box 25286, Denver Federal Center Denver, CO 80225 For more information about the USGS or its products: Telephone: 1-888-ASK-USGS World Wide Web: http://www.usgs.gov Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured by the individual copyright owners to reproduce any copyrighted materials contained in the report. ii Contents Abstract ................................................................................................................................................................................................1 Introduction ..........................................................................................................................................................................................2 Selection of a Test Site ..............................................................................................................................................................3 Purpose and Scope.....................................................................................................................................................................4 Data Collection and Evaluation .........................................................................................................................................................5 Field Methods ..............................................................................................................................................................................5 Laboratory Methods ...................................................................................................................................................................6 Data Evaluation and Computational Methods ........................................................................................................................7 Characteristics of Abandoned Mine Drainage.............................................................................................................................10 Abandoned Mine Drainage Flow Rates and Chemistry......................................................................................................10 Pond-Water Volume and Chemistry.......................................................................................................................................12 Mineralogy and Chemistry of Pond Sediments ....................................................................................................................14 Considerations for Remediation of the Abandoned Mine Drainage at the ALPO-SBTU Test Site ......................................14 Mineralogy and Chemistry of Limestone and Steel Slag for Cubitainer Tests ...............................................................15 Cubitainer Tests of Short-Term Reaction Rates ..................................................................................................................18 Cubitainer Estimates of Long-Term Performance ...............................................................................................................21 Identification of Remediation Strategies at the ALPO-SBTU Test Site............................................................................21 Summary and Conclusions ..............................................................................................................................................................23 Acknowledgments.............................................................................................................................................................................24 References Cited ...............................................................................................................................................................................25 iii Figures 1. Color aerial photograph of the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania, showing locations of water-quality sampling sites..................................................................32 2. Flow chart for selection of passive treatment alternatives .......................................................................................33 3. Graphs showing flow rate and chemistry of abandoned mine drainage, April 7 and 27, 2004, Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania .................................................34 4. Graphs showing trace-element concentrations in abandoned mine drainage, April 7 and 27, 200, Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania.......................................36 5. Graphs showing rate of change in pH, alkalinity, and calcium concentrations of effluent from sites 1 and Fe at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania, during cubitainer tests .....................................................................................................................................................38 6. Graphs showing measured and simulated effect of detention time on limestone or steel-slag treatment of abandoned mine drainage from sites 1 and Fe at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania, on the basis of cubitainer tests ....................................................39 7. Graphs showing simulation of long-term performance of limestone-or steel-slag substrates for treatment of abandoned mine drainage from site 1 at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania, on the basis of cubitainer test data and corresponding first-order or second-order rate estimates for limestone or steel slag dissolution and alkalinity production .........................40 8. Graphs showing simulation of long-term performance of limestone-or steel-slag substrates for treatment of abandoned mine drainage from site Fe at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania, on the basis of cubitainer test data and corresponding first-order or second-order rate estimates for limestone or steel slag dissolution and alkalinity production .........................41 iv Tables 1. Description of abandoned mine drainage and pond sites sampled in April 2004 for the assessment of the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania ..........................42 2. Flow rate, pH, net acidity, and concentrations of dissolved constituents for abandoned mine drainage and pond samples collected April 7 and 27, 2004, for assessment of water quality at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania .................................................43 3. Concentrations of dissolved trace elements in abandoned mine drainage and pond samples collected April 7 and 27, 2004, for assessment of water quality at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania..............................................................................................................44 4. Major mineralogical and chemical composition of pond sediment samples from the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania, and steel slag and limestone obtained from the vicinity and used in cubitainer tests..............................................................................................45 5. Trace-element composition of pond sediment samples from the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania, and steel slag and limestone obtained from the vicinity and used in cubitainer tests...............................................................................................................................46 6. Cubitainer test data for pH, alkalinity, and calcium concentrations in effluent from reaction between steel slag or limestone with abandoned mine drainage from Sites 1 and Fe at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania ...........................................................................47 7. Cubitainer test data for specific conductance, pH, alkalinity, computed acidity, and corresponding concentrations of dissolved major cations and anions in effluent from reaction between steel slag or limestone with abandoned mine drainage from Sites 1 and Fe at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania ...........................................................................48 8. Cubitainer test data for dissolved trace elements in effluent from reaction between steel slag or limestone with abandoned mine drainage from Sites 1 and Fe at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania..............................................................................................................49 9. Summary of cubitainer test conditions and results for rate of reaction between steel slag or limestone with abandoned mine drainage from Sites 1 and Fe at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania..............................................................................................................51 10. Rankings of pollutant loading and possible remedial alternatives for abandoned mine drainage at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania ..........................52 v Conversion Factors Inch/Pound to SI Multiply By To obtain Length inch (in.) 2.54 centimeter (cm) foot (ft) 0.3048 meter (m) mile (mi) 1.609 kilometer (km) Area square mile (mi2) 2.590 square kilometer (km2) Volume cubic foot (ft3) 0.02832 cubic meter (m3) Flow rate cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s) vi Abstract This report describes field, laboratory, and computational methods that could be used to assess remedial strategies for abandoned mine drainage (AMD). During April-June, 2004, the assessment process was applied to AMD from bituminous coal deposits at a test site in the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site (ALPO-SBTU) in Cambria County, Pennsylvania. The purpose of this study was (1) to characterize the AMD quantity and quality within the ALPO-SBTU test site; (2) to evaluate the efficacy of limestone or steel slag for neutralization of the AMD on the basis of reaction-rate measurements; and (3) to identify possible alternatives for passive or active treatment of the AMD. The data from this case study ultimately will be used by the National Park Service (NPS) to develop a site remediation plan. The approach used in this study could be applicable at other sites subject to drainage from abandoned coal or metal mines. During April 2004, AMD from 9 sources (sites1, 1Fe, Fe, 2, 3, 3B, 5, 6, and 7) at the ALPO-SBTU test site had a combined flow rate of 1,420 gallons per minute (gal/min) and flow-weighted averages for pH of 3.3, net acidity of 55 milligrams per liter (mg/L) as CaCO , and concentrations of dissolved sulfate, 3 aluminum, iron, and manganese of 694 mg/L, 4.4 mg/L, 0.74 mg/L, and 1.2 mg/L, respectively. These pH, net acidity, sulfate, and aluminum values exceed effluent criteria for active mines in Pennsylvania. During April-June 2004, limestone and steel slag that were locally available were tested in the laboratory for their composition, approximate surface area, and potential to neutralize samples of the AMD. Although the substrates had a similar particle-size distribution and identical calcium content (43 percent as calcium oxide), the limestone was composed of crystalline carbonates and the slag was composed of silicate glass and minerals. After a minimum of 8 hours contact between the AMD and limestone or steel slag in closed containers (cubitainers), near-neutral effluent was produced. With prolonged contact between the AMD and limestone or steel slag, the concentrations of iron, aluminum, and most dissolved trace elements in effluent from the cubitainers declined while pH was maintained greater than 6.0 and less than 9.0. The cubitainer testing demonstrated (1) lower alkalinity production but higher pH of AMD treated with steel slag compared to limestone, and (2) predictable relations between the effluent quality, detention time, and corresponding flow rate and bulk volume for a bed of crushed limestone or steel slag in an AMD passive-treatment system. The process for evaluating AMD remedial strategies at the ALPO-SBTU test site involved the computation and ranking of the metal loadings during April 2004 for each of the AMD sources and a comparison of the data on AMD flow and chemistry (alkalinity, acidity, dissolved oxygen, ferric iron, aluminum) with published criteria for selection of passive-treatment technology. Although neutralization Page 1 of the AMD by reaction with limestone was demonstrated with cubitainer tests, an anoxic limestone drain (ALD) was indicated as inappropriate for any AMD source at the test site because all had excessive concentrations of dissolved oxygen and (or) aluminum. One passive-treatment scenario that was identified for the individual or combined AMD sources involved an open limestone channel (OLC) to collect the AMD source(s), a vertical flow compost wetland (VFCW) to add alkalinity, and an aerobic wetland to facilitate iron and manganese oxidation and retention of precipitated solids. Innovative passive-system designs that direct flow upward through submerged layers of limestone and/or steel slag and that incorporate siphons for automatic flushing of solids to a pond also may warrant consideration. Alternatively, an active-treatment system with a hydraulic-powered lime doser could be employed instead of the VFCW or upflow system. Now, given these data on AMD flow and chemistry and identified remedial technologies, a resource manager can use a publicly available computer program such as “AMDTreat” to evaluate the potential sizes and costs of various remedial alternatives. Introduction Abandoned mine drainage (AMD) affects the quality and potential uses of water supplies in coal and metal mining regions worldwide (Herlihy et al., 1990; Nordstrom, 2000). AMD ranges widely in quality from mildly alkaline to strongly acidic and corrosive, with dissolved solids ranging from about 200 to 10,000 mg/L (Hyman and Watzlaf, 1997; Rose and Cravotta, 1998; Nordstrom and Alpers, 1999). AMD characteristically has elevated concentrations of dissolved sulfate, iron, and other metals. Dissolved metals and other constituents in AMD can be toxic to aquatic organisms and ultimately can precipitate forming ochreous encrustations that degrade the aquatic habitat (Winland et al., 1991; Bigham and Nordstrom, 2000). The pH and concentrations and loadings of alkalinity, acidity, and metals such as iron (Fe), aluminum (Al), and manganese (Mn) in mine effluent and receiving water bodies commonly are measured to identify potential for environmental effects (Commonwealth of Pennsylvania, 1998a, 1998b, 2002; U.S. Environmental Protection Agency, 2002a, 2002b). These parameters also are measured to identify appropriate treatment methods to remove the metals and maintain neutral pH (Hedin et al., 1994; Skousen et al., 1998). The pH of AMD is an important measure for evaluating chemical equilibrium, corrosiveness, and aquatic toxicity. The severity of toxicity or corrosion tends to be greater under low-pH conditions than under near-neutral conditions. For example, Al is soluble at low pH, and compared to Fe and Mn, relatively low concentrations of dissolved Al can be toxic (Elder, 1988; Bigham and Nordstrom, 2000). Accordingly, the U.S. Environmental Protection Agency (2000, 2002a, 2002b) recommends pH 6.5 to 8.5 for public drinking supplies and pH 6.5 to 9.0 for protection of freshwater aquatic life. Furthermore, the Page 2 Commonwealth of Pennsylvania (1998a, 1998b, 2002) stipulates that effluent discharged from active mines must have pH 6.0 to 9.0 and alkalinity greater than acidity. Recently, resource managers have gained access to the publicly available AMDTreat computer program for evaluation of the approximate construction and maintenance costs of active or passive systems for treatment of AMD (U.S. Office of Surface Mining Reclamation and Enforcement, 2002). Only the AMD flow rate and concentrations of acidity, alkalinity, iron, manganese, and aluminum are required as input data for this program. However, inappropriate comparisons of remedial strategies and poor decisions can result because the AMDTreat program does not consider if the selected AMD treatment technology meets recommended criteria for implementation. Different alternatives for treatment of AMD could be appropriate depending on the volume of the mine discharge, its alkalinity and acidity balance, its concentrations of dissolved oxygen and metals, and the available resources for construction and maintenance of a treatment system (Hedin et al., 1994; Skousen et al., 1998). If the effluent is “net alkaline,” the alkalinity exceeds the acidity and the pH will remain near neutral after complete oxidation of the effluent. In this case, systems that facilitate aeration of the effluent and retention of precipitated solids are indicated. On the other hand, if the effluent is “net acidic,” the acidity exceeds the alkalinity and the pH will decline to acidic values after complete oxidation and precipitation of the dissolved metals. In this case, systems that add alkalinity and that maintain or increase pH are indicated. Selection of a Test Site The Allegheny Portage Railroad in Cambria County, Pennsylvania, was constructed during 1831-1834 as a 36-mile-long inclined plane railroad over the Allegheny Mountains to connect canal segments along a 394-mile transportation route between Philadelphia and Pittsburgh, Pa. (Sellards & Grigg, Inc., 1991). Hailed as an engineering marvel in 1834, the canal and railroad reduced travel time between Philadelphia and Pittsburgh from three weeks by wagon to only four days (VisitPA.com, 2005). The 901-foot long Staple Bend Tunnel, excavated at the head of Plane 1 through a promontory that formed a bend in the Little Conemaugh River, was the first railroad tunnel to operate in the United States (Sellards & Grigg, Inc., 1991). Designated a National Historic Site in 1964 and acquired by the U.S. Department of Interior in 1991 from Bethlehem Steel Corporation, the present site is managed by the National Park Service (NPS) (Sellards & Grigg, Inc., 1991; National Park Service, 2005). The site covers 1,249 acres and includes various historical attractions plus hiking and biking trails. The site also includes remnants of abandoned coal mines and abuts the Cambria steel slag dump that postdate the 1833-1852 period of historical significance (Sellards & Grigg, Inc., 1991). Page 3