Landform Design Research Articles

Field Testing of Geomorphic Landform Design Features in Central Appalachia

Reclamation Highlights: We assessed construction methods for the application of geomorphic landforming and the use of paper mill sludge as a soil amendment for coarse coal refuse. The cap and cover system included a growth layer and low-permeability layer over coarse refuse. Coarse coal refuse and paper mill sludge blend can sustain vegetation.

Sustainable design of tailings dams using geotechnical and geomorphic analysis

ABSTRACT Geomorphic landform design for mine waste structures has been proposed as a sustainable alternative to traditional design approaches for decades. Over this time, the focus on mine closure and related sustainability approaches has grown steadily. Many geotechnical engineers and responsible mining companies understand the obligation to design and construct structures that will perform well in the long term. Concepts and tools are provided in this paper that will assist engineers in achieving their long-term goals. This research evaluates four tailings dam designs in terms of their geotechnical stability and long-term geomorphology: two traditional designs (uniform slope and platform-bank) and two geomorphic-inspired designs (catena and horseshoe). All four designs were subjected to two- and three-dimensional (3D) stability analysis, as well as 3D landscape evolution modeling (geomorphic analysis). Results indicated that the horseshoe-style geomorphic tailings dam design performed better than the others for each of the analyses completed. The horseshoe design consisted of interspersed catena slopes and uniform slopes, which resulted in a type of buttressing effect that enhanced the geotechnical stability of the dam while also reducing and focusing surface erosion.

A Somolinos quarry land stewardship history: From ancient and recent land degradation to sensitive geomorphic-ecological restoration and its monitoring

This research documents the successful application of a novel holistic approach to return land degraded over thousands of years of use to full ecological function. The surroundings of the Somolinos hamlet in Central Spain illustrate a millennial history of land transformation and degradation by agrarian and extractive activities exacerbated at the second half of the 20th century by mechanized mining. This land stewardship history was culminated by a recent intervention of geomorphic-based ecological restoration and its monitoring.Historic anthropogenic processes which triggered gully erosion were intense deforestation for agriculture and grazing, and construction materials quarrying. From 1963 to 2006 mechanized quarrying operated over ancient extractive landforms. In 2007, a conventional rehabilitation mitigated risks but failed at controlling erosion and promoting soil and vegetation reestablishment. A geomorphic-based ecological restoration was accomplished since 2011. The GeoFluv-Natural Regrade CAD software was used for geomorphic landform design, and construction was completed with a carbonatic colluvium topdressing supplemented with a manure-amended soil, that was seeded with grasses. The whole process was a truly complete application of ecological engineering.One of the main purposes of this research was to carefully scrutinize the completed project, to evaluate its effectiveness and, if any deficiencies were found, to analyze their causes, so that they could be avoided in the future. Therefore, the landscape evolution and erosional behaviour of the restored area has been monitored from 2011 to 2020 through a time-lapse sequence of several oblique aerial photos, and by comparing topographies through Digital Elevation Models (DEMs) of Difference (DoDs). Those topographies were surveyed with differential GPS (DGPS) and with Structure from Motion (SfM) combined with Unmanned Aerial Vehicles (UAVs). This monitoring revealed: (a) landscape healing and diversification of the vegetation community composition and structure, as a result of the environmental heterogeneity of the geomorphic design; and (b) absence of hillslope and channel erosion for 99.8% of the area with limited surface erosion zones in 0.2% of the restored area.Our analysis attributed those limited erosion zones to a combination of: (a) minor design oversights; (b) slight construction deviation from the design grade; and (c) excessive runoff entering the repaired area that exceeded the design discharge. These erosion zones started to stabilize five years after initial restoration and achieved steady-state stability at nine years.The main lesson learnt from these minor deficiencies is that such erosion zones can be avoided at the design phase within GeoFluv-Natural Regrade by checking proper convex-concave slopes and concave channel profiles and by carefully considering any adjacent runoff entering the designed areas, which influence the channel's tractive forces. The use of Landscape Evolution Models, such as SIBERIA, can also identify design anomalies subject to erosion. Then, after rigorously inspecting the design, it is imperative that the construction is completed true to the design by defining and following construction tolerances.

Geomorphic landscape design integrated with progressive mine restoration in clay quarries of Catalonia

ABSTRACT Geomorphic-based mine restoration of clay quarries in Tortosa (Catalonia) was co-funded by the European Union’s LIFE programme. The landform design was made with GeoFluv-Natural Regrade. Their building was performed with existing machinery pool and operators. The main constraint was the impossibility of setback regrading of pre-existing-benched highwalls. Progressive geomorphic mine restoration neither reduced mineral production nor changed the operations. The approach has resulted in higher landscape functionality and integration. Monitoring showed localised erosion due to poorly planned discharge of road runoff and sporadic tunnel erosion. Sediment movement at the designed drainage network is similar to the local fluvial dynamics.

Use of Remote Sensing Tools to Measure a Fluvial Geomorphic Design-Input Parameter for Land Reclamation

Fluvial geomorphic approaches for reclamation landform design have been applied since 2000, mostly in mined lands, as an alternative to conventional landform design methods. Those approaches aim to reconstruct mature landforms and drainage networks that would develop within a natural catchment, after thousands of years of work performed by geomorphic processes. Some fluvial geomorphic design methods take specific measurements from natural and stable reference areas for initial input values for reclamation design. Valid reference areas can be difficult to find, can be in highly anthropized environments, or may be difficult to access. This paper evaluates the use of remote sensing tools to measure morphometric parameters in upper sections of agricultural land catchments considered for use as reference areas. The ridge to head of channel distance (Xrh) was the parameter of interest. We used land surface profiles developed from LiDAR (Laser Imaging Detection and Ranging) data and planimetric measurements from orthoimages to estimate Xrh. The results obtained by the two methods were encouraging but showed a significant difference. Ground truthing showed that ploughing obliterated between 19.5 and 22.4 m (on average) of the headwater section of first-order channels, reducing the channel length by 15.1 to 32.4%. Using a greater Xrh value than appropriate for near steady-state conditions as a design input for a geomorphic reclamation project would be expected to result in active erosion processes in the constructed reclamation to regain their missing channel length. We recognize the advantages and limitations of remote sensing methods for measuring the morphometric parameters of the landform relief design inputs. We show how these tools may be used to help select and prioritize reference areas, and warn about the use of disturbed landscapes as reference areas to assure the geomorphic stability of the constructed reclamation designs.

Sustainable Decommission of Mining Lands: Landform Design for Eaton Tuner Shaft (ETS) Area, Obuasi, Ghana

Ghana is the first country in the Sub-Sahara African region to reform its mining sector and has become the poster child for such change in the developing world. Obuasi is the hub of gold mining in Ghana. The Obuasi mine is currently operated by AngloGold Ashanti (AGA), and contributes immensely to the Gross Domestic Product (GDP) of Ghana. Mining is however, an activity that causes disturbance to the natural habitat and threatens biodiversity. Mining of mineral resources results in extensive soil damage, altering microbial communities and affecting vegetation leading to destruction of vast amounts of land which needs to be reclaimed and restored. Reclamation is the process to restore the ecological integrity of these disturbed mine land areas. Mining at the Eaton Tuner Shaft (ETS) area has been decommissioned and this paper seeks to explain processes leading to the sustainable design of a safe and suitable landform for the ETS as part of closure plan by reclaiming the vast land currently in the heart of Obuasi town. This is an exploratory study employing survey methods, geotechnical profiling and topographical survey to obtain data for the landform design and ultimate land reclamation. The study revealed that the soils at the ETS area have an upper stratum of sandy Gravels underlain by strata of silts or sands with average plasticity index of 14.46% and can be used as fill material with mean allowable bearing capacity between 781KPa and 1,413KPa. For a sustainable landform design, the study recommends a gentle slope transitions of about 2.5% and 1:2 for embankments. Keywords: Reclamation, Mining lands, Sustainable decommissioning, Landform design, Obuasi DOI : 10.7176/JEES/9-12-07 Publication date: December 31 st 2019

Stabilization by geomorphic reclamation of a rotational landslide in an abandoned mine next to the Alto Tajo Natural Park

Two abandoned kaolin mines, surrounding one of the most outstanding natural parks of Spain, the Alto Tajo, have caused frequent environmental impacts. Within these are unstable areas prone to extensive mass movements that influence off-site sediment dynamics over the fluvial system. A waste dump in the Nuria mine obstructing a stream in the center of a valley experienced a rotational landslide. Mass movement between 2012 and 2014 was 0.025–0.026 m day−1. To mitigate the high risk of an earthflow, a novel stabilizing surface drainage technique was implemented. Two remedial valleys designed with fluvial channels were constructed surrounding the landslide main body using natural landform design and regrading, with no need for artificial materials such as concrete or piles. This novel remediation process is generically termed geomorphic reclamation. The specific method applied to this site was GeoFluv with Natural Regrade software. Before (2014) and after geomorphic stabilization (2015–2017), the landslide was monitored using Digital Elevation Models (DEMs) of Difference (DODs) obtained by a Geomorphic Change Detection (GCD) tool. Two modern techniques, Terrestrial Laser Scanning (TLS), and, Structure from Motion photogrammetry combined with an Unmanned Aerial Vehicle (SfM-UAV), were used to acquire High-Resolution Topographies (HRTs) from which DEMs were derived. Data analysis and field monitoring results demonstrate that: i) the Nuria mine transformed almost 50% of the upper part of a natural catchment; ii) a waste dump active landslide with a surface rupture <15m posed a high-risk hazard due to its continuous advance; iii) geomorphic reclamation succeeded in stabilizing the landslide during the monitoring period; iv) SfM-UAV-based topographies offer better accuracy and higher resolution, are cheaper and are obtained faster than TLS for mine areas.

Evaluating How Landform Design and Soil Covers Influence Groundwater Recharge in a Reclaimed Watershed

AbstractLandscape‐scale reconstruction and prescription of soil cover systems following oil sands mining is challenging due to the quality of available reclamation materials and the subhumid climate of the Boreal Plains of Canada. In an experimental reclaimed watershed (Sandhill Fen Watershed), basin‐scale upland landforms (i.e., hummocks) were designed to provide groundwater to adjacent lowlands, necessitating adequate recharge following establishment of forest vegetation. Volumetric water contents, soil water pressure heads, and groundwater levels were monitored for four years throughout the watershed and used to calibrate and verify numerical models in HYDRUS. Using a variably saturated two‐dimensional domain, we identified a threshold‐like relationship between recharge (or upflux) and upland hummock height, where upland hummocks not tall enough to limit root water uptake from the saturated zone decreased recharge or resulted in net upflux. Recharge varied with soil cover texture (higher in coarser‐textured) and associated soil hydraulic parameters. Furthermore, scenario tests indicated the importance and relative influence that maximum rooting depths, forest floor placement thicknesses, and leaf area indices (all associated with forest development) had on recharge. Simulations utilizing a historical climate record indicated that interannual climatic variability was as influential as variation in soil cover texture in determining recharge. Reclamation practitioners should recognize that the water balances of reconstructed landscapes are largely influenced by the trade‐off between optimizing forest productivity and sourcing water to downgradient landscape positions.

Predicting erosion at valley fills with two reclamation techniques in mountainous terrain

ABSTRACT Minimising erosion resulting from mining is important to improve of reclamation and management. Geomorphic landform design (GLD) is a reclamation technique that attempts to replicate a long-term erosionally stable condition. Erosion was evaluated using the Revised Universal Soil Loss Equation (RUSLE) comparing two reclamation scenarios (conventional and GLD) to the undisturbed condition. Soil loss rates were highest during the post-mining, pre-vegetation condition (conventional: 123.2 t ha−1 yr−1; GLD: 204.3 t ha−1 yr−1). Long-term erosion rates showed little difference between valley fills reclaimed with GLD and conventional methods; however, erosion was concentrated along the conventional fill face and distributed over the GLD landform.

The application of natural landform analogy and geology‐based spoil classification to improve surface stability of elevated spoil landforms in the Bowen Basin, Australia—A review

AbstractLarge‐scale open cut mining has occurred within the Bowen Basin for over 4 decades, transitioning from shallow mining depths and limited spoil elevation to increased mining depths, prestripping and increasingly elevated mesa‐like landforms.As a result of this evolution, the stabilisation of modern constructed landforms is no longer assured through the establishment of vegetation alone. The selection of resilient fragmental spoil types for the construction of final landform surfaces, and as cladding for stabilising steep erosive batters, is a practical methodology that has the potential to significantly improve rehabilitation outcomes, by increasing surface rock cover, roughness, and infiltration and reducing erodibility. An understanding of the properties and behaviour of individual spoil materials disturbed during mining is required.Relevant information from published literature on the geological origins, lithology, and weathering characteristics of individual strata within the Bowen Basin Coal Measures (and younger overlying weathered strata) has been reviewed, related to natural landforms and applied to the surface stability of major strata types when disturbed by mining.A spoil classification derived from geological characteristics and weathering behaviour of identifiable lithologic components has been reviewed and refined, demonstrating the application of use of geological information.This classification system is a tool for the allocation of spoil types and use of categories that have application in premine feasibility investigations, landform design, and material selection and placement. The logic of classifying materials based on their stability in the natural landscape has wider relevance to other mining areas where elevated landforms of sedimentary material are constructed.

Use of shrub willows (Salix spp.) to develop soil communities during coal mine restoration

Afforestation or reforestation in highly degraded environments (e.g., surface mines) is often complicated by the total removal of vegetation and severe soil degradation that occurs during mining operations, necessitating revegetation to be undertaken in tandem with the re-establishment of soil developmental processes. Shrub willows (Salix spp.) are effective as colonizer species initiating revegetation dynamics; however, it is unclear if they also serve as nurse plants facilitating the establishment of soil communities such as those of nematodes. We established a study in a former coal mine site in New Brunswick, Canada, to assess whether the presence of willows on otherwise bare, poorly developed soil contributed to nematode community development and to what degree landform design (e.g., slope) may influence these dynamics. Our results demonstrate that willows can facilitate nematode communities at this site, but that slope strongly influences these effects, likely as a consequence of hydrology and overland water flow. These results confirm the beneficial role that willows can play in reforestation of highly degraded environments both for revegetation and for the re-initiation of soil ecosystem processes.

Soil erosion predictions from a landscape evolution model – An assessment of a post-mining landform using spatial climate change analogues

Landscape Evolution Modelling (LEM) technologies provide a means by which it is possible to simulate the long-term geomorphic stability of a conceptual rehabilitated landform. However, simulations rarely consider the potential effects of anthropogenic climate change and consequently risk not accounting for the range of rainfall variability that might be expected in both the near and far future. One issue is that high resolution (both spatial and temporal) rainfall projections incorporating the potential effects of greenhouse forcing are required as input. However, projections of rainfall change are still highly uncertain for many regions, particularly at sub annual/seasonal scales. This is the case for northern Australia, where a decrease or an increase in rainfall post 2030 is considered equally likely based on climate model simulations. The aim of this study is therefore to investigate a spatial analogue approach to develop point scale hourly rainfall scenarios to be used as input to the CAESAR - Lisflood LEM to test the sensitivity of the geomorphic stability of a conceptual rehabilitated landform to potential changes in climate. Importantly, the scenarios incorporate the range of projected potential increase/decrease in rainfall for northern Australia and capture the expected envelope of erosion rates and erosion patterns (i.e. where erosion and deposition occurs) over a 100year modelled period. We show that all rainfall scenarios produce sediment output and gullying greater than that of the surrounding natural system, however a ‘wetter’ future climate produces the highest output. Importantly, incorporating analogue rainfall scenarios into LEM has the capacity to both improve landform design and enhance the modelling software. Further, the method can be easily transferred to other sites (both nationally and internationally) where rainfall variability is significant and climate change impacts are uncertain.

Slope stability and landform design in a coarse coal refuse reclamation.

Restoration of abandoned mine lands is on-going in Appalachia and across the United States. One potential technique to reclaim these areas is through the use of geomorphic landforming combined with paper mill residuals used as a soil amendment. The geomorphic approach attempts to approximate the long-term, steady state landform condition, leading to reduced erosional adjustment as compared to standard engineered fill designs. This study analyzed regraded mine refuse slopes for safety and erosion sustainability under a 100-year storm event for the Royal Scot refuse pile located near Anjean, WV. The project involved the design and evaluation of a cap and cover system composed of two layers. The first layer is a 60 cm. compacted barrier layer (hydraulic barrier) and second is a 30cm vegetative growth layer. The focus of the analysis was the effectiveness of the hydraulic barrier layer and the final slope stability of the system. A reclamation design was prepared and 3D finite element modeling was performed to assess ground surface terrain profiles considering weather and material strength. Results from the modeling indicate that for a 100-year storm event, the slope remains stable with a factor of safety ranging from 1.3 to 1.9 for different slope profiles. After the 100-year storm event, the hydraulic barrier reached a 20% degree of saturation proving its effectiveness with minimizing infiltration into the reclamation fill.

Simulating the hydrologic response when streams are incorporated in valley-fill design

The geomorphic landform design (GLD) approach has the potential to incorporate stream networks into valley-fill reclamation. This work modelled the potential hydrologic response of GLD by evaluating storm response as well as flooding of the receiving reach of one West Virginia valley fill in several construction phases (i.e. pre-mining, conventional design and GLD). The GLD during construction condition resulted in peak flowrates that were more than twice the undisturbed pre-mining condition, but peak flowrates reduce to pre-mining conditions over time. A GLD that included surface ponds was presented to offer on-site streamflow. A retrofit example was presented to improve bond failing sites.

Geomorphic landform design alternatives for an existing valley fill in central Appalachia, USA: Quantifying the key issues

The goal of the geomorphic approach to reclamation is to reconstruct landforms that reduce the effect of natural geomorphic processes, replicating a mature landform that is stable and in erosive equilibrium. The geomorphic approach is becoming widely accepted as an alternative method for reclaiming disturbed landforms, with the success of geomorphic reclamation being acclaimed in the southwestern United States at surface mine sites. The following potential challenges, however, exist when applying geomorphic design principles to surface mine reclamation in the central Appalachian region of the United States: (i) geomorphic design criteria must be measured locally; (ii) constructing artificial landforms that naturally blend into the steep slopes of the surrounding environment may not ensure stability; and (iii) shallower, more stable slopes of geomorphic landforms could create greater stream burial to maintain fill volumes. This research established geomorphic design criteria specific to central Appalachia and completed a series of alternative geomorphic landform designs for an existing valley fill in southern West Virginia, United States using the GeoFluv™ method to investigate and quantify these issues. Designs investigated geotechnical stability and channel design on reclaimed landforms while considering permitted and expanded impact areas. Based on field data and spatial analysis, the geomorphic design criteria of mean drainage length and mean drainage density were calculated as 124m (408ft) and 4.7km−1 (61.7ft/ac), respectively. Conceptual designs confirmed that the issues associated with steep slope topography, landform stability, and channel stability are valid, especially if minimizing the area of impact is a priority. Creating a stable geomorphic design as an alternative to a conventional valley fill in central Appalachia is possible, although it does not comply with current regulations and policies governing excess spoil placement. Additional issues with respect to constructability must be investigated and further studies on quantifying the benefits of geomorphic reclamation with respect to erosion and water/contaminant management should be completed to fully assess the practicality of implementing geomorphic reclamation in central Appalachia.

A descriptive and quantitative approach regarding erosion and development of landforms on abandoned mine tailings: New insights and environmental implications from SE Spain

The San Cristóbal–Perules mining site in Mazarrón in southeast Spain was subjected to about a hundred years of intense mining activity for lead, silver, and zinc. Metallurgical operations (smelting, calcination, gravity concentration) carried out during the late nineteenth century–early twentieth century induced significant land transformation, and the most conspicuous wastes of this period consist of a chaotic piling of ‘old’ tailing deposits. Later on, during the mid-twentieth century, ‘modern’ tailings resulting from froth flotation were accumulated filling small valleys; these latter valley-fill tailings rose sequentially according to the upstream construction method, progressively raising the level of the dam during the process. Once abandoned, both types of tailing deposits underwent severe erosion, resulting in a mosaic of erosional and sedimentary landforms developed upon (e.g., gully formation) and within them (e.g., piping). We made an inventory and classification of these landforms. Our study shows the geomorphic work to reestablish a new steady state between the tailings deposits and the local erosive conditions. This scenario implies several hazards related to the extremely high heavy metal contents of these tailings and the geomorphic instability of the deposits. We also quantified the tailings tonnage and erosion that occurred at one of the tailings dams (El Roble). As shown by an oblique aerial photograph taken in 1968, this dam had a terraced topography, whereas in 2013 this morphology had evolved into a badland-type relief with deep parallel gullies. By recognizing and surveying specific, remnant points along the benches and outslopes of the older terraced topography, we were able to build up a first digital elevation model (DEM1) reflecting the initial topography. A second DEM, this time showing the present topography, allowed quantification of erosion via Material Loss=DEM1−DEM2. This yields an erosion rate (1968–2009) of 151.8Mg (MT)ha−1y−1, which matches well typical values for erosion of mined areas, commonly above 100Mg (MT)ha−1y−1. Abandoned mine tailing deposits are extremely common in the semiarid scenarios of the SW USA, Australia, Chile, and Peru. Given the similarities of these scenarios with SE Spain, the example from Mazarrón may provide useful new insights regarding the erosion and geomorphic evolution of such tailing deposits. These matters should be addressed in key environmental actions such as mine closure plans and land reclamation projects. A solution may come via restoration of these deposits through landform design involving the building up of stable mature landscapes, which in turn can withstand erosion much more easily.

Evolution of landform design concepts

Over the last 10 years, Landloch Pty Ltd has developed and applied a distinctive approach to the design of final waste dump shapes and the management of their rehabilitation. Various elements of that approach have been recommended and/or adopted by both industry and regulators to greater or lesser degrees, and with varying levels of both commitment and success. This paper briefly outlines the approach applied, and discusses its limitations and successes, using examples from a number of mine sites. It then considers alternative approaches to landform design that have been advanced, including use of generic guidelines, attempts to mimic natural landscapes, and attempts to simply mimic advanced design methodologies. Conceptual weaknesses of those alternative approaches are reviewed, and potential for further refinement is discussed, again, using data from various sites.

Restoring earth surface processes through landform design. A 13‐year monitoring of a geomorphic reclamation model for quarries on slopes

AbstractThe application of geomorphic principles to land reclamation after surface mining has been reported in the literature since the mid‐1990s, mostly from Australia, Canada and the USA. This paper discusses the reclamation problems of contour mining and quarries on slopes, where steep gradients are prone to both mass movement and water erosion. To address these problems simultaneously, a geomorphic model for reclaiming surface mined slopes is described. Called the ‘highwall–trench–concave slope’ model, it was first applied in the 1995 reclamation of a quarry on a slope (La Revilla) in Central Spain.The geomorphic model does not reproduce the original topography, but has two very different sectors and objectives: (i) the highwall–trench sector allows the former quarry face to evolve naturally by erosion, accommodating fallen debris by means of a trench constructed at the toe of the highwall; (ii) the concave‐slope base sector, mimicking the landforms of the surrounding undisturbed landscape, promotes soil formation and the establishment of self‐sustaining, functional ecosystems in the area protected from sedimentation by the trench. The model improves upon simple topographic reconstruction, because it rebuilds the surficial geology architecture and facilitates re‐establishment of equilibrium slopes through the management and control of geomorphic processes.Thirteen years of monitoring of the geomorphic and edaphic evolution of La Revilla reclaimed quarry confirms that the area is functioning as intended: the highwall is backwasting and material is accumulating at the trench, permitting the recovery of soils and vegetation on the concave slope. However, the trench is filling faster than planned, which may lead to run‐off and sedimentation on the concave slope once the trench is full. The lesson learned for other scenarios is that the model works well in a two‐dimensional scheme, but requires a three‐dimensional drainage management, breaking the reclaimed area into several watersheds with stream channels. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Physical dispersion of radioactive mine waste at the rehabilitated Radium Hill uranium mine site,South Australia

The Radium Hill uranium deposit, in semiarid eastern South Australia, was discovered in 1906 and mined for radium between 1906 and 1931 and for uranium between 1954 and 1961 (production of 969 300 t of davidite ore averaging 0.12% U3O8). Rehabilitation was limited to removal of mine facilities, sealing of underground workings and capping of selected waste repositories. In 2002, gamma-ray data and samples of tailings, uncrushed and crushed waste rock, stream sediment, topsoil and vegetation were collected to assist in examining the current environmental status of the mine site. The data indicate that capping of tailings storage facilities did not ensure the long-term containment of the low-level radioactive wastes due to the erosion of sides of the impoundments. Moreover, wind erosion of waste fines (phyllosilicates, ore minerals) from various, physically unstable waste repositories has caused increasing radiochemical (from a background dose of 35 – 70 nSv/h to max. 0.94 μSv/h) and geochemical (Ce, Cr, La, Lu, Rb, Sc, Th, U, V, Y, Yb) impacts on local soils. Plants (saltbush, pepper tree) growing on waste dumps display evidence of biological uptake of lithophile elements, with values being up to 1 – 2 orders of magnitude above values for plants of the same species at background sites. However, radiation doses associated with the mine and processing site average 0.67 μSv/h; hence, visitors to the Radium Hill site will not be exposed to excessive radiation levels. Although rehabilitation procedures have been partly successful in reducing dispersion of U and related elements into the surrounding environment, it is apparent that 20 years after rehabilitation, there is significant physical and limited chemical mobility, including transfer into plants. Additional capping and landform design of the crushed waste and tailings repositories are required in order to minimise erosion and impacts on surrounding soils and sediments.

Tree performance on minespoils in the South Wales coalfield

Summary 1. Variable growth of Larix leptolepis (Japanese larch) has been observed on restored opencast coal workings in South Wales. This has implications for the restoration of such sites. A study of the relationship of tree growth with minespoil chemical, nutritional, physical and hydrological factors was carried out. 2. Tree growth was positively related to nitrogen and phosphorus foliar concentrations, but negatively to those of magnesium. Seventy‐three per cent of the variation in tree growth was explained by variation in foliar chemistry. 3. Soil pH and extractable magnesium were negatively correlated with tree growth, with cation exchange capacity positively related to it. 4. Minespoils had bulk densities that commonly exceeded 1·7 g cm–3 below 0·2 m depth. Stone contents were high and typically 25% by volume. 5. Root systems of trees excavated were characterized by a high root density within 0·3 m of the minespoil surface. Restricted rooting was attributed to high bulk density and the incidence of shallow water tables. 6. Waterlogging during the spring and early summer, and the consequent presence of anaerobic soil conditions during periods of active growth, was found to be detrimental to tree growth. 7. The study suggests that landform design, selection of suitable soil or soil‐forming materials, spoil placement technique and appropriate species choice are central to the future success of forestry schemes on restored ground in South Wales.