Former Galmoy Mines Tailings Restoration Project
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Former Galmoy Mines tailings restoration Cora Devoy1, Linda Wrong1, Kevin Collins2 1Environmental Manager, Lundin Mining Corporation, [email protected] 1Director of Sustainability and Regulatory A airs, Lundin Mining Corporation, [email protected] 2Bird Watch Ireland - Tipperary Branch, [email protected] Abstract Galmoy Mines completed the restoration of a tailings management facility (TMF), in- corporating an engineered wetland, returning the site to a land use compatible with the surrounding countryside, while e ciently treating surface water runo and creating an enhanced environment for local and migratory bird species. Increased breeding density of Curlews (IUCN Red List), in addition to nesting Little Ringed Plover and a Glossy Ibis were observed, demonstrating biodiversity support. e wetland system improved post-closure water quality. Ammonia in the revegetated caps of the TMF has stabilised and reductions in the sulphate were noted as the TMF remediation matures. Keywords: Mine Closure, Wetland, Biodiversity, Little Ringed Plover, Ammonia, Sul- phate Introduction of the progressive rehabilitation of Phase 1 Galmoy Mines zinc-lead deposit, located in (9.36 Ha) and Phase 2 (14.02 Ha) of the TMF south-central Ireland, discovered in 1986 was completed during mine operation. TMF (Doyle 2016), was owned and operated by drainage design allowed for the safe discharge the Lundin Mining Corporation since 2005. of water during the operational and post-clo- Most of the underground mine workings sure stage. e three main sources of water were between 100 m and 160 m below sur- identi ed were seepage water from the inter- face, hosted in extensively dolomitized and nal drainage within the cells (potentially con- brecciated basal Waulsortian (Lower Carbon- taminated), tailings surface water discharged iferous) “Reef” mudbank limestones Produc- from the TMF (potentially contaminated), tion of concentrates at Galmoy commenced and clean surface water reporting to the pe- in early 1997, with mine production carried rimeter drains (Golder 2011). out by room-and-pillar and bench-and- ll e mine operated under an Integrated methods as reported by Lowther et al. (2003). Pollution Control Licence, Planning Permis- During the operational phase, the excess sions, and State Mining Licences [Environ- non-acid generating tailings from process- mental Protection Agency (EPA) 2002; Local ing ore were disposed of in the TMF, with Authorities (Kilkenny County Council) 1994; drainage reclaim water pumped to the mine Department of Communications, Climate site, treated and discharged to the licensed Change, & Environment (DCCAE) SML 1, discharge point (River Goul). e surface 6, 8-10 (1994–2005)]. All licenses and per- area of the TMF measures 33.64 Ha and is missions referred to the rehabilitation of the an engineered double HDPE lined ring dam TMF as an integral part of the Mine Closure built from local glacial materials with chim- Plan (MCP). In the MCP 1992, the preferred ney and nger drains of sand (Derham 1999). option for rehabilitation was the develop- While the original concept of three adjoining ment of a “general amenity/wildlife sanctu- cells remained constant; the numbering, size, ary”, with interim and nal drainage schemes and sequence of construction changed due incorporated into the post-closure periods to revisions of the life of mine and discovery using a combination of wet/dry landscapes of new orebodies, a ecting the underlying on the surface of the TMF. At that time, the principles behind the original design. Most long-term maintenance requirements were Wolkersdorfer, Ch.; Sartz, L.; Weber, A.; Burgess, J.; Tremblay, G. (Editors) 9 01_Mining for closure BOOK.indb 9 9/3/18 10:20 AM 11th ICARD | IMWA | MWD Conference – “Risk to Opportunity” envisaged to be minimal and a “walk-away” mum concentrations are below the upper end-point would not pose a threat to the threshold of the concentration ranges that environment. However, modern legislation, could be considered excessive in leaf tissue. regulators, and Galmoy Mines recognised Perkins et al. (2015) suggest low translocation the retention of water below the crest of the factors, noted at Galmoy TMF, indicate the dam wall did not o er a “walk-away” solu- positive potential future use of remediated tion. e Second Interim Mine Closure Plan TMFs for uses including pastoral agriculture, (2005) envisaged a wetland located externally even where the soil layer is very thin. to the southwest of the TMF, however at the Successful sheep grazing trials in 2008 announcement of unplanned early closure in and subsequent cattle trials in 2011 and 2012 2009 Phase 3 of the TMF remained partially were conducted on Phase 1 to con rm the ag- un lled and the closure design of the TMF ronomic value of the rehabilitated cap. Analy- required modi cation. sis was conducted on the grass; the animals’ liver, kidney and muscle tissues; and blood Methods samples at the end of each trial. e practical TMF rehabilitation at Galmoy Mines began experience and analytical information from in 2001 with a pilot-scale tailings dam con- the grazing trials demonstrated the ability structed to mimic the conditions in the TMF of the grassed cap to support livestock that, at closure. Pilot trial cells were established at slaughter, complied with all the relevant in compliance with planning permission re- regulatory requirements for animals to safely quirements. e trial cells were subdivided, enter the food chain. and a variety of grass species and depth of A variety of organic materials and gla- substrate were investigated with a mixture cial till substrates were approved for use by of topsoil and compost assessed. Nine cul- the EPA throughout progressive remediation tivars were selected on the basis of a litera- of Phase 1 and 2 (Figure 1), including black ture search and the experience gained at Tara spent grains, limed sewage sludge, kieselguhr Mines, Navan Ireland (Brady 1993). Vegeta- (a form of diatomaceous earth used in various tion trials demonstrated that the grasses se- manufacturing and laboratory processes), ef- lected for the large-scale TMF remediation uent screenings, sludge from BulmersTM ci- (Festuca rubra cv. Merlin, Agrostis castellana der production, topsoil from the borrow area, cv. Heriot and Agrostis capillaris cv. Hyland) and composted products. e aim was to pro- were based on genetic or physiological toler- vide a sustainable growing medium to sup- ance to metals, low uptake of lead and zinc port a natural and vibrant vegetation cover, to allow for the possibility of grazing animals, however, the organic material cover on Phase and good surface coverage and sustainability 1 and 2 generated e uent with high levels of vegetation density. of BOD, COD, ammonia, nitrate, phospho- Based on these trials, capping and reveg- rus and potassium, during the early stages of etation of TMF Phase 1 began in 2001, with remediation which would likely require pas- subsequent monitoring of the performance of sive treatment presenting a challenge to long- the cover through the collection and analy- term discharge compliance, due to elevated sis of soil and vegetation samples. Calcula- ammonia concentrations in particular, in the tion of a bioconcentration factor by Perkins interstitial layer of the vegetation cap. et al. (2015) suggests no accumulation of the A wetland trial was designed by Vesi En- As, Cd, and Pb studied in the roots of grass vironmental Ltd., in 2009 whereby two cells growing on the Galmoy TMF. e data would were constructed adjacent to the TMF. Both suggest that grass species growing on the Gal- cells were planted with four types of wetland moy TMF are relatively successful in exclud- species (Glyceria maxima (main species), ing metals, taken up by the roots, from trans- Carex riparia, Cladium mariscus and Alisma ferring to the remainder of the plant. Recent plantago-aquatica) and irrigated using water studies by Perkins et al. (2015) have shown from the TMF spillway and surface runo , to that the maximum As, Cd, and Pb in herbage assess the impact on the wetland plants of the on Phase 1 and the trial cells are within the parameters of interest. normal ranges for plants and that all maxi- 10 Wolkersdorfer, Ch.; Sartz, L.; Weber, A.; Burgess, J.; Tremblay, G. (Editors) 01_Mining for closure BOOK.indb 10 9/3/18 10:20 AM 11th ICARD | IMWA | MWD Conference – “Risk to Opportunity” Figure 1 Final layout and design of TMF, wetland, and attenuation to licensed discharge (oriented North) e remediation of partially lled Phase considered doming their tailings facility to 3 (8.29 Ha) presented an additional challenge eliminate the long-term risks associated with in the closure process. Approval was received containment and spillage of surplus water. from the authorities to redesign TMF Phase Following the passive treatment of Phase 1 3 and develop an integrated constructed wet- and 2 surface waters in the ICW, P4 discharge land (ICW) on the surface area of the partially directed towards the attenuation pond lo- lled Phase 3 (Figure 1). e innovative loca- cated northwest of Phase 2 is polished, prior tion of the ICW within Phase 3, was designed to discharge through the post-closure outfall to reduce the footprint of the tailings runo to Glasha stream(Figure1). e surface area area and remediate Phase 3 simultaneously. of the attenuation pond is approximately 2.4 e deposited tails in Phase 3 required resur- Ha, with a capacity of 50,000m3 and varies facing before the ICW could be constructed in depth due to the undulating nature of the on the capped surface. Designed by Golder limestone bedrock. Construction of the ICW Associates (2011), Phase 3 was capped with commenced within the boundary of Phase glacial till and HDPE liner derived from the 3 of the TMF in 2013, providing an HDPE reduction in the height of the dam wall of the lined area in which to locate the ICW.