FINAL DRAFT REPORT PASSIVE AND SEMI-ACTIVE TREATMENT OF ACID ROCK DRAINAGE FROM METAL MINES - STATE OF THE PRACTICE Prepared for U.S. Army Corps of Engineers 696 Virginia Road Concord, Massachusetts 01742 April 2, 2003 URS Corporation 477 Congress Street Annex, Suite 3A Portland, Maine 04101 TABLE OF CONTENTS 1. Section 1 Introduction ................................................................................................... 1-1 1.1 Limitations of Available Information ...................................................... 1-1 2. Section 2 State of the Practice...................................................................................... 2-1 2.1 Passive Treatment History ....................................................................... 2-1 2.2 Currently Available Passive Treatment Components.............................. 2-2 2.2.1 Aerobic Wetlands......................................................................... 2-3 2.2.2 Anoxic Limestone Drains ............................................................ 2-4 2.2.3 Open Limestone Channels ........................................................... 2-5 2.2.4 Settling Ponds .............................................................................. 2-5 2.2.5 Successive Alkalinity Producing System (SAPS) ....................... 2-5 2.2.6 Solid-Reactant Anaerobic or Sulfate Reducing Bacteria (SRB) Bioreactors........................................................................ 2-6 2.2.7 Liquid-Reactant (Semi-active) Bioreactors ................................. 2-9 3. Section 3 Case Studies.................................................................................................. 3-1 3.1 Burleigh Tunnel Pilot Cells ..................................................................... 3-1 3.2 Brewer Pad 5 Pilot Cell............................................................................ 3-1 3.3 Ferris-Haggerty Mine/Osceola Tunnel .................................................... 3-2 3.4 Doe Run Mine.......................................................................................... 3-2 3.5 Leviathan Mine ........................................................................................ 3-3 4. Section 4 Acid Rock Drainages at the Elizabeth Mine................................................ 4-1 4.1 GEOLOGY AND MINE FEATURES .................................................... 4-1 4.2 GEOCHEMISTRY OF ACID ROCK DRAINAGE ............................... 4-1 5. Section 5 Conceptual Design Approach for the Elizabeth Mine ................................ 5-1 5.1 Conceptual Design ................................................................................... 5-1 5.2 Feasibility Level Cost Estimate ............................................................... 5-2 6. Section 6 References..................................................................................................... 6-1 P:\project\13846\066\passive treatment\ARD_StateOfArt-Review REV2.doc 04/02/03(3:04 PM) i TABLE OF CONTENTS Tables Table 1 Feasibility Level Capital Cost Estimate Table 2 Feasibility Level Operation and Maintenance Cost Estimate Figures Figure 1 Flowchart for Selecting a Passive Acid Rock Drainage Treatment System Based on Water Chemistry and Flow Figure 2 Anoxic Limestone Drain Plan Profile and Section Figure 3 Typical Cross-Section View of a Successive Alkalinity Producing System (SAPS) Treatment Component Figure 4 Schematic Cross Section of Upflow and Downflow Sulfate Reducing Bacteria Anaerobic Bioreactor Appendices Appendix A Bibliography Appendix B Overview Papers Appendix C Manganese Removal Papers Appendix D Papers by Jim Gusek et al. on Solid-Reactant SRB Bioreactors Appendix E Papers by Tim Tsukamoto et al. on Liquid-Reactant SRB Bioreactors P:\project\13846\066\passive treatment\ARD_StateOfArt-Review REV2.doc 04/02/03(3:04 PM) ii SECTIONONE Introduction 1. Section 1 ONE Introduction This document presents an overview of current state-of-the-practice applications for passive and semi-active treatment systems to treat acid rock drainage (ARD) associated with metal mines. Acid rock drainage is a common effluent of metal mining and one of the major environmental impacts resulting from mining activities. It is caused by the natural weathering of pyrite and other metal sulfides in the mineral deposit, or through the accelerated weathering of waste products generated by the mining process. The sulfide minerals react with oxygen in air or pore water and produce sulfuric acid. Acid rock drainage is thus low-pH water with elevated concentrations of iron, sulfate, and heavy metals and metalloids of varying composition dependant upon the originating mineral deposit type. The purpose of this document is to identify passive and semi-active treatment technologies that could potentially be used at the Elizabeth Mine Site (herein after referred to as the Site), present general capital, operation and maintenance costs for specific treatment technologies, and discuss the relative success of these treatment technologies at other sites. Technologies reviewed are inclusive of the passive treatment methods of aerobic wetlands, anoxic limestone drains (ALD), open limestone channels (OLC), settling ponds, successive alkalinity-producing systems (SAPS), and solid-reactant anaerobic sulfate-reducing bacteria (SRB) bioreactors, and the semi-active method of liquid-reactant SRB bioreactors. 1.1 LIMITATIONS OF AVAILABLE INFORMATION The evaluation of passive treatment systems has involved numerous discussions with system designers and operators. Numerous examples of failed systems have been identified. In the majority of these cases, evaluations to determine how and why systems failed were not generally performed, or this information was not otherwise made available to URS. It was found that the owners were unwilling to invest additional money to evaluate the failure cause without financial benefit. Therefore, detailed information on system failures is somewhat limited. Additionally, as many treatment technology applications have been research-based, for proprietary reasons developers have been guarded in discussing details of either processes or applications with URS. P:\project\13846\066\passive treatment\ARD_StateOfArt-Review REV2.doc 1-1 SECTIONTWO State of the Practice 2. Section 2 TWO State of the Practice This section describes the generalized history of passive treatment systems and currently available passive treatment system components. The overview is based on application experience combined with information provided by several well-known experts in the field, an extensive literature search, and review of recent technical publications. Appendix A presents a bibliography of reviewed publications, arranged by topic. Appendix B includes several overview papers useful in defining the technologies and applications history. Significant recent publications outlining case studies of individual applications are included as Appendices C, D, and E. Information provided and case studies reviewed include those associated with publicly available records. Information on systems developed and/or operating under confidentiality agreements are not included. 2.1 PASSIVE TREATMENT HISTORY The cost of potentially perpetual treatment of ARD using traditional active lime treatment technology has caused the mining and regulatory communities to search for less expensive alternative treatment solutions. In the late 1970s and early 1980s, evidence from coal mine drainages suggested that wetlands, with their complex mix of biological, chemical, and physical processes, could potentially treat ARD. In the 1980s, the use of constructed wetlands was attempted to mimic natural wetlands and treat ARD. Researchers developed hypotheses as to which wetland processes (e.g., plant uptake, adsorption, microbial reactions) were most important in the treatment of ARD. Early research in the field of passive wetland treatment focused on maximizing these processes. In the late 1980s and early 1990s, a practical understanding of the biological and chemical processes was developed and several authors (i.e., Brodie 1992; and Hedin, Nairn, and Kleinmann 1994) published guidelines for designing treatment systems (e.g., aerobic constructed wetlands) based on the influent water chemistry (Figure 1). In one early investigation of a treatment wetland (Brodie 1992), ARD emanating from the base of a coal debris pond flowed under an old roadbed made of limestone rubble. The limestone from the roadbed was found to add alkalinity to the anoxic subsurface flow, which in turn allowed iron to precipitate when it became oxidized in the adjacent wetland. From this research originated the ALD concept. Open limestone channels were also used to add alkalinity to ARD before it enters a constructed wetland. Much of the early work focused on passive treatment of ARD at eastern U.S. coal mine sites. These techniques were then applied to hard-rock drainages. Investigators found that typical hard-rock ARD had lower pH (i.e., <4) and higher concentrations of heavy metals (e.g., copper, zinc) that could not be treated as effectively with aerobic surface-flow constructed wetlands (Day, Filipek, and Papp 1986). In response, researchers attempted to employ subsurface processes of natural wetlands, mainly bacterially mediated anaerobic sulfate reduction systems (e.g., SRB systems). The sulfide produced by this process was found to bind with iron and most heavy metals, re-forming the same minerals that had originally