Case Study: Appraisal of Four Soil-Based Metrics in the Establishment of Sustainable Upland Grassland at a Mine Site in South Wales, United Kingdom

Abstract

In the United Kingdom, rehabilitated mineral workings are subject to a statutory minimum 5-year period of aftercare management to ensure that the rehabilitated land is of a 'standard' that enables the intended after-use to be "beneficial and sustainable." Aftercare begins on the completion of overburden backfilling, placement of soils, and the required sowing/planting. The current devolved Welsh Government guidance acknowledges that specific standards are difficult to define, so there is reliance on certain management activities having been undertaken, rather than specifying the outcome of evaluative methods. We appraise the application of four soil-based metrics (comprising the description of soil profile physical characteristics, grassland soil physical condition, soil fertiliser requirement, and a measurement of soil health) under operational circumstances at a rehabilitated mine site in South Wales. Here, the aim is to establish a sustainable upland acidic grassland ecosystem and to facilitate release of monies from the financial bond. It is concluded that evaluation of the upland grassland is more realistically and reliably based on determining the physical characteristics of the soil profile than the other three metrics deployed; although there is merit in the use of a more rapid visual assessment method for soil physical condition (VESS) for screening purposes and/or for increasing site coverage at a lower cost, as well as the determination of levels of organic matter and nitrogen mineralisation. The use of the soil profile characteristics metric enabled the planning authority to release the rehabilitated land from the financial bond.

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“…Concurrently, much of the applied state-of-the art, concerning measures in soil reclamation for planning and design purposes, is reflected in a recent article by Humphries et al, examining soil metrics in Wales, United Kingdom, stressing the importance of vegetation-related assessments as opposed to soil measurements [27]. The emphasis remains on evaluating the capacity of the soil quickly and efficiently for bond release.…”