By Dave Trumm, CRL Energy Ltd., ,

Acid Mine Drainage in New Zealand Figure 3. AMD at the abandoned BlackBall mine near Greymouth. Flow rates vary between 30 and 100 L/s.

Introduction problem in New Zealand over the last few relatively low, however, in recent years (AMD) associ- decades, and efforts to curb the pollution with low levels of water in hydroelectric ated with has been a difficult have begun. This article provides a brief lakes, coal has been increasingly used to problem to solve in much of the world. background on the extent and impor- meet growing energy requirements. Per- Although research and application of re- tance of coal and mitting for a new coal-fired power plant mediation systems has been ongoing for a short review of research and remedia- has recently begun for the West Coast on over 40 years in the eastern USA (Ziem- tion efforts which have aimed to solve the the . Although coal use is kiewicz et al. 2003; Sengupta 1994), oth- AMD problem downunder. prominent in New Zealand, the majority er places in the world have not been so of the high quality coking coal is exported lucky. This can be for various reasons, in- Extent of Coal Mining in to steel mills in . cluding: little money available for research New Zealand In New Zealand, coal is mined using and remediation, minimal or no regula- New Zealand agriculture, cement, tim- two basic extraction methods: surface min- tions for AMD discharge to river systems, ber, and general industrial processing all ing (open cast) and underground mining or possibly no recognition that it is even rely on coal to power their plants. Coal use (hydromining and bord and pillar meth- a problem. AMD has become a serious for electricity generation has always been ods). Most of the historic mining was un-

ISSUE 1 • 2007 • reclamation matters 23 derground, while most of the current min- ing today is by open cast techniques. Most of the economic coal resources of New Zealand are restricted to the north- ern and western regions of both the North Island and the South Island. The seven coal regions of the country are: North- land, , , Nelson, West Coast, Canterbury, , and Southland (Figure 1). Large lignite resources occur in Central Otago and Eastern Southland, whereas sub-bituminous coal is located in the Waikato Coal Region, the Taranaki Coal Region, and in Western Southland. Bituminous are located primarily in the West Coast Region. Quality values for typical bituminous coal are: 13,000 Btu/ lb, 58 percent carbon, 7 percent moisture, 0.8 percent to 4 percent ash, and 0.2 per- cent to 1.6 percent sulfur. For sub-bitumi- nous coal, typical values are: 9,300 Btu/lb, 38 percent carbon, 23 percent moisture, 2 percent to 11 percent ash, and 0.1 percent to 3 percent sulfur (Barry et al. 1994). The Waikato Region in the North Is- land and the West Coast Region in the South Island are the biggest suppliers of coal and the majority of the high-quality bituminous coal comes from the Buller Coalfield in the West Coast Region (Fig- ure 1). Within the Buller Coalfield, the Denniston and Stockton areas have been the most extensively mined using both underground and open cast methods. The Stockton Plateau contains the location of the biggest coal mine in New Zealand (Stockton No. 2). The mines on this pla- teau are currently operated by Solid En- ergy New Zealand Limited (SENZ). Ap- proximately 40 million tons of coal was mined in New Zealand in 2005, with 60 Figure 2. Typical West Coast topography. percent being exported and the rest going to domestic uses for heating (10 percent), manufacturing and other industrial do- mestic uses (30 percent). ferences in depositional environments and , whereas the Brunner Coal was diagenetic processes between these two enriched with pyrite from overlying ma- Occurrence of AMD formations result in a generally greater oc- rine sediments. Therefore, the absence of As would be expected, the majority currence of AMD from the Brunner Coal carbonate rocks and enrichment with py- of AMD coincides with the major coal- Measures. The Paparoa Coal Measures rite results in a greater occurrence of AMD producing region in New Zealand, the were deposited in a fluvial to lacustrine from the Brunner Coal Measures. West Coast of the South Island. Within environment, where rapid accumulation AMD from open cast mines hosted in this region, however, lithologic variation of sediments preserved co-deposited car- the Brunner Coal Measures typically has a and mining techniques influence the oc- bonate rocks, whereas the Brunner Coal higher aluminum to iron ratio than AMD currence and chemistry of AMD (Pope, Measures were deposited in an estuarine from underground mines (Pope, New- Newman and Craw 2006). environment, in which reworking of sedi- man and Craw 2006). The Al:Fe ratio Coal dominantly occurs on the West ments was unfavorable for the preservation is typically greater than two in open cast Coast within the Brunner Coal Measures of carbonate- bearing rocks (Pope, New- mines and less than four in underground (mostly to the north) and the Paparoa man and Craw 2006). Post deposition, the mines. It is hypothesized that the reaction Coal Measures (mostly to the south). Dif- Paparoa Coal was enriched with carbonate between H2SO4 (produced by pyrite

24 reclamation matters • ISSUE 1 • 2007 Figure 4. AMD at the abandoned Sullivan Mine north of Westport. Flow rate averages about 30 L/s and is considered a low-flow site. oxidation) and aluminum-bearing silicate AMD with very high flow rates, some- say, Kingsbury, and Pizey (2003), Hard- minerals in the coal measures – such as times coupled with rainfall events, in ing and Boothryd (2004), Hughes et al. clays and feldspars – proceed more rapidly locations with very limited space for re- (2004), Harding (2005), and Pope, New- and to a greater extent in open cast mines mediation (Figures 3, 4, 5, 6). The isola- man and Craw (2006). because coal measure sediments are more tion of mining sites, along with the low In contrast to assessment of AMD, very disturbed in mine pits compared to un- population on the West Coast, results little remediation has been accomplished derground mines. in an AMD legacy that is largely hidden in New Zealand. The majority of attempts from public view and does not impact on have consisted of small-scale pilot studies. Difference between AMD in New the clean-green image of New Zealand. It An early reference to AMD treatment is Zealand and Eastern USA is estimated, however, that approximately an active treatment system that was con- There are two major differences between 125 kilometers of streams are adversely af- structed at the Golden Cross Mine site the dominant AMD-producing region in fected by AMD (James 2003; Figure 7). to treat AMD with moderate pH levels the USA (Pennsylvania and West Virginia) (about 5) but high concentrations of iron and New Zealand, which affect the AMD: State of Assessment and Reme- and manganese (Goldstone and MacGil- topography and climate. The topography diation of AMD livray 2002). The treatment consisted of along the West Coast rises steeply from sea AMD in New Zealand has been stud- aeration followed by addition of calcium level to over 700 meters (2,300 feet), and is ied for many years. Most of these stud- oxide to raise the pH and promote re- mostly cloaked in thick, protected, native ies either focus on the geochemistry of moval of iron and manganese. A bioreac- rainforest (Figure 2). Mining sites are usu- AMD or the effects of the AMD on the tor was also constructed at the site, but re- ally situated in the higher reaches and are aquatic ecosystem, and the majority of sults to date show that the system was not often very remote. The dominant westerly the research is conducted by academics adequate for removal of manganese. Inter- winds off the Tasman Sea results in a high- from various universities in New Zealand. nal reports have been produced for SENZ rainfall climate with very low temperature A few non-governmental research orga- regarding installation and performance of seasonality. Rainfall on the Stockton Pla- nizations, such as CRL Energy Limited, an anoxic limestone drain (ALD) that was teau is, approximately, 7 meters (275 inch- also conduct AMD research. Some of the installed at the Bennydale Mine site, but es) per year. more significant publications on these no external publications on the success of This topography and climate results in subjects are Winterbourn (1998), Lind- this system are known. Periodic dosing

ISSUE 1 • 2007 • reclamation matters 25 Why is there so Little AMD Reme- diation in New Zealand? There are several reasons. There is no remediation fund specifically for AMD. Therefore, any efforts toward remedia- tion are funded completely by the min- ing companies. Although New Zealand has a strong clean-green image overseas and has a strong green movement (the Green Party actually form part of the cur- rent government), regulations for AMD treatment and prevention are vague and Figure 7. Map of known streams impacted by AMD in the enforcement is lacking. West Coast Region. Environmental regulations are driven of low-flow, moderate pH AMD (pH 4) primarily by the Resource Management with calcium oxide has been reported at Act 1991 (RMA; New Zealand Govern- the Malvern Hills Coal Mine (Bell and ment, 1991) which does not specifically Seale, 2004). Small-scale trials of an ALD refer to AMD. Rather, the RMA states and limestone dosing system are currently that contaminants cannot be discharged underway at the site. to the environment unless the local re- Aside from the above-referenced work, gional environmental authority (a regional other remediation attempts include sev- council) has granted consent or unless the eral pilot studies and one full-scale system discharge is considered a permitted activ- by the author. Small-scale remediation ity under the regional plan of the regional systems consisting of an ALD, vertical council. Mines existing prior to publica- flow wetland (VFW), and an open lime- tion of the RMA have been allowed to stone channel (OLC) were constructed at continue to discharge AMD under their the abandoned Sullivan Mine (Figure 4) previous discharge agreement (if there with the goal of determining an optimum was any in the first place). The regional Figure 1. The coal regions of New Zealand. remediation strategy for full-scale imple- council for the dominant AMD-produc- mentation (Trumm, Black and Gordon, ing area in New Zealand, the West Coast propriate resource consents for new mines. 2003; Trumm et al. 2003; Trumm, et al. Regional Council (WCRC) has been in Aside from the obvious difficulties with 2005). The results of this work indicated negotiations with mines existing prior funding, regulations, and enforcement, that a VFW may be the best solution for to the RMA to help set limits for AMD. there are other, perhaps more important the Sullivan Mine, however construc- The process has encountered many diffi- reasons that the AMD situation in New tion of the full-scale system has not yet culties as both the mining companies and Zealand has not improved much over the begun. Laboratory experiments were the WCRC try to determine appropriate years. Coal mining is the backbone of the conducted suggesting that a limestone background levels for specific sites and ap- West Coast economy. Coal mining is the leaching bed may be successful in treat- propriate and achievable targets. largest employer in the region and has been ing AMD from the abandoned Blackball For mines started after publication of a respected industry for over 100 years. The Mine near Greymouth (Figure 3; Trumm the RMA, the WCRC typically sets dis- effects of coal mining (such as AMD) are and Gordon, 2004). Another small-scale charge limits based on various water qual- largely hidden from public view in a low- VFW was constructed at the Pike River ity targets. These targets are sometimes site population region and the effects of AMD Coal Mine adit and operated success- specific or are based on the Australian and in local watersheds are not commonly rec- fully for six months (Trumm, Watts and New Zealand Guidelines for Fresh and Ma- ognized as a problem. The source of AMD Gunn, 2005; Trumm, Watts, and Gunn, rine Water Quality (ANZECC, 2000). In- is typically in steep terrain surrounded by 2006). A full-scale VFW was constructed consistent guidelines for setting discharge protected native rainforests, which limits at the site in July 2006, however no pub- limits currently plague the industry and remediation options. Times, however, are lications have yet been produced on the the WCRC. A research program is current- changing. Current mining companies are success of the system. Finally, small-scale ly underway to help streamline this pro- volunteering to reduce impacts from ac- systems consisting of a limestone leaching cess (Black, Clemens and Trumm, 2004; tive mine sites and the regional council is bed (LLB), a VFW, an OLC, and a diver- Cavanagh et al. 2005). This program aims enforcing discharge limits for new mines. sion well were constructed at the Herbert to incorporate a database of known AMD Abandoned mines with AMD will likely be AMD site at the Stockton Mine in 2006. risk based on geology with threshold levels the next target. Both the VFW and the LLB performed that affect the aquatic ecosystem and with well and a full-scale LLB is currently be- known AMD treatment technologies. The References ing constructed at the site. database, along with the ecological work, Australian and New Zealand Environ- will provide a tool that can be used by the ment and Conservation Council (AN- mining industry and regulators to set ap- ZECC). 2000. Australian and New Zea-

26 reclamation matters • ISSUE 1 • 2007 AMD at the abandoned Bellvue Mine north of Greymouth. land Guidelines for Fresh and Marine 2005. Impacts of coal mining on water ding, D. Trumm (Eds.). Metal Contami- Water Quality 2000. Chapters 1-7. Aus- quality and metal mobilisation: case stud- nants in New Zealand: Sources and effects tralian and New Zealand Environment and ies from West Coast and Otago. p. 247- on health and ecology. Conservation Council and Agriculture and 260. In: Tim A. Moore, Amanda Black, Harding, J.S. and Boothryd, I. 2004. Resource Management Council of Jose A. Centeno, Jon S. Harding, Dave Impacts of mining. In: J. Harding, and New Zealand. A. Trumm (eds). Metal Contaminants in C. Pearson, B. Sorrell, and P. Mosley Barry, J.M., Duff, S.W., MacFarlan, New Zealand, Sources, Treatments, and (Eds.). Freshwaters of New Zealand. New D.A.B. 1994. Coal Resources of New Effects on Ecology and Human Health. Zealand Hydrological Society and New Zealand. Ministry of Commerce Energy Published by Resolutionz Press, a trading Zealand Limnological Society, Christ- and Resources Division. Resource Infor- arm of Resolutionz Consulting Limited, church. mation Report 16: 74 pp. 62 Richmond Hill Road, Sumner, Christ- Hughes, J., Lindsay, P., Peake, B., and Bell, D. and Seale, J. 2004. Settling church, New Zealand. Craw, D. 2004. An environmental evalu- pond design and performance – the Mal- Cavanagh, J., O’Halloran, K., Black, ation of the geochemical properties of vern Hills Coal Mine experience. p. 9-14. A., & Harding, J. 2005. Integration of Kaiata Mudstone and Brunner Coal Mea- In: The Australasian Institute of Mining aquatic toxicity data in a decision making sures, Cypress and Stockton Mines, West and Metallurgy New Zealand Branch framework for mining. Australian Society Coast, NZ. p. 41-50. In: The Australasian 37th Annual Conference “Looking Back for Ecotoxicity. Melbourne: Australian Institute of Mining and Metallurgy New – Looking Forward”, 29 August to 1 Sep- Society for Ecotoxicity Zealand Branch 37th Annual Conference tember 2004, Nelson, New Zealand. Goldstone, A. and MacGillivray, R. “Looking Back – Looking Forward”, 29 Black, A., Clemens, A., and Trumm, 2002. Closure of Golden Cross Mine. August to 1 September 2004, Nelson, D. 2004. A Collaborative Environmen- September 2002. Proceedings of the New New Zealand. tal Research Programme: Field studies Zealand Minerals and Mining Confer- Lindsay, P. Kingsbury, M. Pizey, M. contributing to the sustainability of New ence, . 2003. Impact of mining the Lower Zealand’s industry. p. 10. Ad- Harding, J. 2005. Impacts of metals Ngakawau River. The Australian Institute elaide:PACRIM and mining on stream communities. In: of Mining and Metallurgy, New Zealand Black, A., Trumm, D. and Lindsay, P. T.A. Moore, A. Black, J. Centeno, J. Har- Branch. 36th Annual Conference 3-5

ISSUE 1 • 2007 • reclamation matters 27 September 2003, Greymouth. March 26-30, 2006, St. Louis MO. R.I. of the Eastern United States. Sixth In- 1995. Re- Barnhisel (ed.) Published by the Ameri- ternational Conference on Acid Rock source Management Act 1991. , can Society of Mining and Reclamation Drainage, held on 12-18 July in Cairns, New Zealand; Published under the author- (ASMR), 3134 Montavesta Road, Lex- Queensland, Australia. ity of the New Zealand Government. ington, KY 40502. Pope, J., Newman, N., and Craw, D. Winterbourn MJ, 1998. Insect faunas 2006. Coal Mine Drainage Geochemis- of acidic coal mine drainages in Westland, try, West Coast, South Island – a Prelimi- New Zealand. New Zealand Entemolo- nary Water Quality Hazard Model. 39th gist, 1998, Vol. 21. annual AusIMM conference, held in Sep- Ziemkiewicz, P.F., Skousen, J.G., and tember 2006 in , New Zealand. Simmons, J.S. 2003. Long-term perfor- Sengupta, M. 1994. Environmental mance and cost benefit analysis of - pas impacts of mining: Monitoring, restora- sive acid mine drainage treatment systems tion and control. Lewis Publishers, Boca installed in the Appalachian coal region Raton, FL, pp. 121-164. Trumm, D., Black, A., Cavanagh, J., Harding, J., de Joux, A., Moore, T.A., O’Halloran, K., 2003. Developing as- sessment methods and remediation pro- BKS Environmental tocols for New Zealand sites impacted Associates, Inc. by Acid Mine Drainage (AMD). Sixth International Conference on Acid Rock • Reclamation Planning • Drainage, held on 12-18 July in Cairns, • Baseline Assessments • Environmental Monitoring Queensland, Australia, pp. 223-232. BRENDA SCHLADWEILER, Ph. D. Trumm, D., Black, A., Gordon, K., P.O. Box 3467 • Gillette, WY 82717-3467 • (307) 686-0800 • Fax (307) 686-0880 2003. Remediation strategies for acid mine P.O. Box Laramie, WY 82073-0574 e-mail: [email protected] drainage at Sullivan Mine, West Coast, www.bksenvironmental.com New Zealand. 36th annual AusIMM con- ference, held on 3-5 September 2003 in Greymouth, New Zealand, pp. 325-337. Trumm, D. and K. Gordon. 2004. So- lutions to Acid Mine Drainage at Black- ball and Sullivan Mines. p. 103-110. In: The Australasian Institute of Mining and Metallurgy New Zealand Branch 37th An- nual Conference “Looking Back – Look- ing Forward”, 29 August to 1 September 2004, Nelson, New Zealand. Trumm, D. Black, A. Gordon, K. Ca- vanagh, J. de Joux, A. 2005. Acid mine drainage assessment and remediation at an abandoned West Coast coal mine. In: T.A. Moore, A. Black, J. Centeno, J. Har- ding, D. Trumm (Eds.). Metal Contami- nants in New Zealand: Sources and effects on health and ecology. Trumm, D., Watts, M., and Gunn, P. 2005. Use of small-scale passive systems for treatment of acid mine drainage. 2005 New Zealand Minerals Conference, 13- 16 November 2005, Auckland, New Zea- land. Published by Crown Minerals and Australasian Institute of mining and Met- allurgy, New Zealand Branch. Trumm, D., Watts, M. and Gunn, P. 2006. AMD Treatment in New Zealand – Use of Small-scale Passive Systems. Pre- sented at the 7th International Confer- ence on Acid Rock Drainage (ICARD),

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