Design, Construction and Performance Monitoring of the Large-Scale Waste Rock Cover System Field Trials at the Historic Mount Morgan Mine Site in Queensland, Australia

O’Kane, Michael; Meiers, Greg; McCombe, Chris

doi:10.36487/acg_repo/605_35

Cited by 2 publications

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“…The majority of research regarding the use of ROM overburden materials to construct evapotranspirative (ET) store-and-release soil covers has focused on field performance monitoring and numeric modelling related primarily to reduction of net percolation into underlying reactive mine wastes (INAP 2003, O'Kane et al 2006Shurniak et al 2012;Bonstrom et al 2012). The success of a store-and-release cover system to limit net percolation is largely reliant on the establishment and long-term functioning of a revegetated plant community appropriate for the life zone to remove soil moisture via transpiration (O'Kane & Ayers 2012;INAP 2017).…”

Section: Introductionmentioning

confidence: 99%

Successful revegetation of run-of-mine overburden soil covers without soil amendments: Copper mine closure studies in a semi-arid environment

Romig,

DeCastro,

Rabinowich

et al. 2023

Proceedings of the International Conference on Mine Closure

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Although most native plant species are well adapted to low fertility soil conditions, revegetation practitioners frequently recommend amending soil covers at considerable expense. But are soil amendments truly necessary for reclaiming semi-arid mine sites? Revegetation progress on unamended run-of-mine (ROM) overburden soil covers was monitored at three reclaimed sites for six to 12 years at two copper mines in New Mexico, USA. Monolithic, evapotranspiration (ET) soil covers (60 to 120 cm [2 to 4 ft] thick) were constructed using suitable overburden (leached cap) that was salvaged during pit development. Two sites were reclaimed using granite (GR) overburden and a third site was covered with a mixture of unmineralized rhyolite and leached granodiorite (RLG). Covers were placed over acid-generating waste and leach stockpiles. Cover construction primarily focused on material management of the ROM to reduce the rock content to approximately 50% by volume to improve seedbed conditions and water-holding capacity of the ET cover system. Both the GR and RLG soil covers are moderately coarse-textured sandy loams (USCS silty sands) with circumneutral to slightly alkaline pHs and are non-saline and non-acid generating (low sulfur). No soil amendments were used in the reclamation, though both ROM materials are considered infertile having low macronutrient (1-2 mg/kg nitrate) and organic matter content (<0.1% organic carbon). Sites were drill seeded with native seed mixes followed by mulching with long-stem grass hay. Periodic quantitative monitoring included assessment of the reclaimed site's canopy cover, shrub density and plant diversity compared to a native reference area.Each site has progressed steadily towards meeting or exceeding the native reference area canopy cover performance standard that is used for financial assurance release. All sites experienced significant growing season drought for at least two years during establishment. Total canopy cover at one GR site was 58% in Year 6 and 64% in Year 12, exceeding the total canopy cover of the native reference area in both years. The second GR site experienced significant drought during establishment but after six growing seasons still achieved 80% reference area canopy cover standard. Vegetation of RLG covers exceeded the reference area standard within eight years following seeding. Each site also recruited numerous desirable plant species, including several native legumes and other perennial forbs. Six years after seeding, the GR sites averaged 63 additional plant species beyond the original seed mix while the RLG site had 86 volunteer species after seven years.This work demonstrates that soil amendments are not always required to revegetate infertile ROM cover materials. Unamended overburden covers can support diverse and productive reclaimed plant communities that are resilient and capable of sustaining themselves under the adverse conditions typical of semi-arid environments.

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Section: Introductionmentioning

confidence: 99%

Successful revegetation of run-of-mine overburden soil covers without soil amendments: Copper mine closure studies in a semi-arid environment

Romig,

DeCastro,

Rabinowich

et al. 2023

Proceedings of the International Conference on Mine Closure

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“…This will result in variation in the storage capacity and hydraulic conductivity. Despite this, the performances of different cover designs have commonly been compared using single‐point measurements and it has been assumed that the trial covers are structurally homogeneous within any one design (Madalinski et al, 2003; O'Kane and Waters, 2003; Williams et al, 2003; O'Kane et al, 2006). Only recently, Meiers et al (2009) recognized the problem of heterogeneity in mine waste covers.…”

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confidence: 99%

Evaluation of the Heterogeneity of Constructed Landforms for Rehabilitation Using Lysimeters

Schneider

Baumgartl

Doley

2010

Vadose Zone Journal

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Rainfall ingress into sulfi dic rocks or tailings from metalliferous mining opera ons can result in acid mine drainage. Waste rock cover systems in semiarid areas are commonly designed to retain all precipitated water within benign material, from where it is removed by evapotranspira on. The long-term eff ec veness of covers is o en predicted from models that are based on data obtained from single trial plots assuming that the trials are homogeneous and representa ve of large areas. Two cover designs were tested in semiarid monsoonal northwest Queensland: (i) 1.5 m of unconsolidated waste rock overlying 0.5 m of consolidated waste rock; and (ii) 2.0 m of unconsolidated benign waste rock. Three idencal plots comprised each treatment in which water balance equa on parameters were es mated from meteorological measurements and ver cal arrays of soil suc on and moisture sensors and seepage collec on using a 3-m-deep lysimeter inserted in the waste rock. In a wet season with 900 mm of precipita on, water movement through the covers was followed through changes in moisture content, suc on, and seepage. Greater diff erences in these parameters occurred within than between cover treatments. Water reten on and water movement varied substan ally and seepage ranged from 2 to 80% of total rainfall. The internal heterogeneity of hydraulic proper es had more eff ect on cover performance than did the ini al cover design. Therefore, it is important to include internal heterogeneity in mine waste cover water balance models to improve their applicability.Abbrevia ons: ET, evapotranspira ve; NAF, non-acid-forming; PAF, poten ally acid forming; PSD, par cle size distribu on; WRC, water reten on curve.Mining can oft en result in hazardous or potentially hazardous byproducts such as waste rock from the extraction of the ore and fi ne-grained residues (tailings) from the processing of the ore. Th e exposure of potentially acid-forming (PAF) sulfi dic waste rock to O 2 and water can result in acidic or metal-contaminated drainage waters. Tailings can contain high concentrations of heavy metals or sulfi des and seepage from these systems can also be highly contaminated (Lottermoser, 2007). Infi ltration of precipitation into the waste material can result in the leaching of hazardous substances into adjacent environments. For mine lease relinquishment, mining companies are required to prevent any potential contamination of the surrounding environment.In semiarid environments, evapotranspirative covers (ET covers) have been proposed to prevent the ingress of water to hazardous mine wastes (Hauser et al., 2001; Mine Environment Neutral Drainage Program, 2004; Fourie and Tibbett, 2007). Th e aim of an ET cover system is to retain precipitation within the benign cover material, thus preventing it from either running off the surface or percolating through the base of the cover by deep drainage and reacting with the underlying hazardous waste. Stored rainwater is then removed from the cover through evaporation and transpiration (Mine Environme...

show abstract

Design, Construction and Performance Monitoring of the Large-Scale Waste Rock Cover System Field Trials at the Historic Mount Morgan Mine Site in Queensland, Australia

Cited by 2 publications

References 0 publications

Successful revegetation of run-of-mine overburden soil covers without soil amendments: Copper mine closure studies in a semi-arid environment

Successful revegetation of run-of-mine overburden soil covers without soil amendments: Copper mine closure studies in a semi-arid environment

Evaluation of the Heterogeneity of Constructed Landforms for Rehabilitation Using Lysimeters

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