geosciences Review Using Geomembrane Liners to Reduce Seepage through the Base of Tailings Ponds—A Review and a Framework for Design Guidelines Anne Tuomela 1,* , Anna-Kaisa Ronkanen 2 , Pekka M. Rossi 2, Anssi Rauhala 1 , Harri Haapasalo 3 and Kauko Kujala 2 1 Structures and Construction Technology, University of Oulu, P.O. Box 4300, 90014 Oulu, Finland; anssi.rauhala@oulu.fi 2 Water, Energy and Environmental Engineering, University of Oulu, P.O. Box 4300, 90014 Oulu, Finland; anna-kaisa.ronkanen@oulu.fi (A.-K.R.); pekka.rossi@oulu.fi (P.M.R.); [email protected].fi (K.K.) 3 Industrial Engineering and Management, University of Oulu, P.O. Box 4300, 90014 Oulu, Finland; harri.haapasalo@oulu.fi * Correspondence: anne.tuomela@oulu.fi; Tel.: +358-50342-6151 Abstract: Geomembranes are used worldwide as basin liners in tailings ponds to decrease the permeability of the foundation and prevent further transportation of harmful contaminants and contaminated water. However, leakage into the environment and damage to the geomembrane have been reported. This paper reviews available literature and recommendations on geomembrane structures for use as a basal liner in tailings ponds, and presents a framework to achieve early Citation: Tuomela, A.; Ronkanen, involvement and an integrated approach to geomembrane structure design. Cohesive planning A.-K.; Rossi, P.M.; Rauhala, A.; guidelines or legislative directions for such structures are currently lacking in many countries, which Haapasalo, H.; Kujala, K. Using often means that the structure guidelines for groundwater protection or landfill are applied when Geomembrane Liners to Reduce designing tailings storage facilities (TSF). Basin structure is generally unique to each mine but, based Seepage through the Base of Tailings on the literature, in the majority of cases the structure has a single-composite liner. The type of Ponds—A Review and a Framework liner system used depends mainly on the material to be used on top of the structure, local hydraulic for Design Guidelines. Geosciences 2021, 11, 93. https://doi.org/ pressure gradient, and climate conditions. More practical information and scientific knowledge 10.3390/geosciences11020093 on the use of base liners in various cases are needed. A sustainable approach could be risk-based design, where the life cycle of the basin is taken into consideration. To this end, this paper proposes Academic Editors: geomembrane-lined tailings pond to be assessed as a stakeholder. Emphasis on this, early enough, Jesus Martinez-Frias and can ensure critical factors for tailings ponds to be considered from the outset in the design of mines Michael Campbell and reduces the environmental footprint of the mining industry. More holistic project management and early involvement and integration are recommended to improve construction quality during Received: 21 November 2020 the entire life cycle of the pond. In the long term, use of dry stacking or other alternative methods Accepted: 12 February 2021 should be encouraged, despite the higher costs for operators. Published: 17 February 2021 Keywords: geomembrane; tailings pond; basin liner; mine environment; site characterization; early Publisher’s Note: MDPI stays neutral involvement and integration with regard to jurisdictional claims in published maps and institutional affil- iations. 1. Introduction The use of geosynthetics in industrial applications has become common since the 1970s [1]. There is huge potential to use these in different mine-related applications, Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. e.g., as geomembranes, plastic pipes, geotextiles, geosynthetic clay liners (GCLs) and This article is an open access article reinforcements. The first major mining application was for lining process ponds and as distributed under the terms and partly impermeable basal structures for solar ponds at the Tenneco Minerals mines in Utah, conditions of the Creative Commons USA, and at a Sociedada Quimica y Minera mine in Northern Chile at the beginning of the Attribution (CC BY) license (https:// 1970s [2]. By the late 1970s, geomembranes were in general use in the basal structures of creativecommons.org/licenses/by/ heap leach pads, but they have only become widely been used in the basal liner structures 4.0/). of tailings ponds and waste rock dumps during the past 20 years [2–5]. Geosciences 2021, 11, 93. https://doi.org/10.3390/geosciences11020093 https://www.mdpi.com/journal/geosciences Geosciences 2021, 11, x FOR PEER REVIEW 2 of 23 Geosciences 2021, 11, 93 2 of 22 of heap leach pads, but they have only become widely been used in the basal liner struc- tures of tailings ponds and waste rock dumps during the past 20 years [2–5]. ImpoundmentImpoundment of of tailings tailings generally generally poses poses on onee of of the the most most significant significant environmental environmental risksrisks associated associated with with mines mines [6], [6 ],with with the the risk risk closely closely linked linked to the to type the type and andquality quality of tail- of ings.tailings. Since Since each each mine mine is unique, is unique, the the physical physical and and chemical chemical quality quality of of the the tailings tailings varies. varies. TypicalTypical tailings tailings can can be be of of the the same same consistency consistency as as fine fine sand, sand, loamy loamy sand, sand, or or sandy sandy loam, loam, andand they they may may contain contain chemical chemical residues residues from from mineral mineral separation separation or or from from the the coagulants coagulants andand flocculants flocculants used used in inwater water separation, separation, e.g., e.g., [7]. [The7]. particle The particle properties properties differ differfrom those from ofthose natural of natural soils because soils because the grains the in grains tailings in tailings are jagged are jaggedin shape, in while shape, natural while naturalloam grains loam aregrains rounded. are rounded. High angularity, High angularity, grading grading characteristics characteristics and loose and loosedepositional depositional state stateof tail- of ingstailings have have direct direct effects effects on increasing on increasing compre compressibilityssibility compared compared with withnatural natural soils soils[8], but [8], alsobut alsoon susceptibility on susceptibility of liquefaction of liquefaction of tailings of tailings [9,10]. [9 ,10]. InIn conventional conventional disposal disposal systems, systems, tailings tailings are are dumped dumped in in ponds ponds as as a a slurry slurry with with a a solidssolids content content of of 20–40% 20–40% by by weight weight relative relative to to the the total total weight weight [11]. [11]. In In a a typical typical case, case, the the tailingstailings ponds ponds are locatedlocated withinwithin peatland peatland areas, areas, in in valleys, valleys, or onor on hillsides hillsides worldwide. worldwide. The Theobjective objective is to is utilizeto utilize natural natural soil soil layers layers with with low low water water permeability permeability (such(such as peat and and glacialglacial till) till) and locallocal soilsoil formationsformations to to reduce reduce the the risk risk of of pollution pollution to theto the environment. environment. The Themode mode of operation of operation of these of these ponds ponds is seepage is seepage of waterof water from from the the ponds ponds and and its its collection collection in ina nearbya nearby ditch ditch or or other other drainage drainage structure. structure. OneOne ofof the greatest environmental challenges challenges arisesarises with with tailings tailings that that create create an an acid acid environment environment [12,13]. [12,13]. Acid Acid is is formed formed through through the the oxidizationoxidization of of minerals minerals containing containing sulfur sulfur (e.g., (e.g., pyrite) pyrite) and and can can have have significant significant effects effects on on surfacesurface waters waters and and groundwater groundwater in in the the mine mine surroundings, surroundings, where where screening, screening, recovering recovering andand treating treating these these waters waters may may be be difficult difficult an andd expensive expensive [12]. [12]. Because Because releases releases of of acidic acidic minemine drainage drainage (AMD) (AMD) into into the the environment environment are are not not desirable, desirable, control control of of the the water water within within storedstored tailings tailings is is essential. essential. The The first first priority priority is is to to prevent prevent formation formation of of AMD AMD but but in in many many casescases an an impermeable impermeable basal basal layer layer may may need need to to be be constructed constructed (Figure (Figure 11).). FigureFigure 1. 1. AA conventional conventional way way of of disposing disposing of of mine mine tailings, tailings, as as a a slurry slurry in in a tailings pond. In In some some cases, cases, regulations regulations demanddemand use use of a geomembrane linerliner atat thethe pond pond base base to to achieve achieve low low permeability permeability and and keep keep seepage seepage waters waters away away from from the thesurrounding surrounding environment environment during during the the active active phase phase of disposal. of disposal. BecauseBecause awareness ofof environmentalenvironmental impacts impact hass has increased increased and and the legislationthe legislation on basal on basalstructures