Designing for success: applying ecological criteria to restoration at BHP Beenup, Australia

Abstract

The former BHP Beenup titanium minerals operation is in the biodiverse Scott River region in southwest Western Australia and was closed prematurely in 1999 after only two years of operation. Significant modifications to the landscape (including deep dredging to 55 m, lime sand blending with the natural soils to mitigate acid generation) combined with limited previous knowledge of the recruitment biology of many of the plant species, created significant uncertainty as to the feasibility of restoring the site to near-natural communities. This paper covers two aspects of the closure process: (1) a novel planning approach undertaken for setting the end use and target ecosystems using a designed based philosophy informed by risk assessment, and (2) the assessment of restoration success using ecological completion criteria. In terms of planning and design, the geomorphic and biodiversity features of the regional landform types (dunes, plains, sumplands, damplands etc.) formed the basis of design of closure sites. These regional ecosystems were surveyed in detail to characterise the soils, hydrology and vegetation of each major feature, with these ecological relationships then used to develop rehabilitation design criteria. Artificial landforms (deep pools created by dredging) were modified into lakes via void infilling and the creation of extensive shallow shorelines to generate a more naturalistic final shape. The focus on ecosystem design enabled revegetation to be tailored to the specific vegetation communities that best matched the reconstructed landforms; this significantly reduced seed wastage and increased the probability of success. As far as we are aware, it is the first project of this scale in Australia that has successfully created a functional range of wetland types similar to the surrounding natural wetlands. In terms of performance assessment, a detailed and prescriptive set of restoration and completion criteria were developed to enable a greater certainty of outcomes and enabled quantitative measurements of restoration success. The incorporation of sustainability and resilience, which are global indices of success used in ecological restoration projects outside of mining, were applied here to guide both the approach to restoration (so as to enable the site to adapt to changing climates and unpredictable events) and to the measurement of success (completion criteria). This was one of the first instances globally to embed these ecological concepts as key success categories for rehabilitation. Fifteen years after restoration, 15 ecological communities and more than 251 plant species have been successfully restored, including many conservation-listed species. The project achieved regulatory sign off against rehabilitation completion criteria in 2018 and is one of the few 'ecologically designed' post-mining landscapes globally.

Mine completion criteria defined by best-practice: A global meta-analysis and Western Australian case studies

“…The use of multiple types of references to set completion criteria was the most common best-practice, appearing in 24 of 61 studies. It is recognized that in highly-altered mining landscapes, it can be unfeasible to restore pre-mining ecosystems (Lamb et al 2015), although this is still the most prevalent closure goal in Australia (Meney & Pantelic 2019;Rosa et al 2020) and elsewhere, e.g. the USA (Krzyszowska Waitkus 2018).…”

“…In highly disturbed mining landscapes, it is often not know if, when or how ecosystems will recover (Hernandez-Santin et al 2020;Meney & Pantelic 2019), or if they will do according to entrenched assumptions (Cristescu et al 2013). Such rehabilitation uncertainties make it difficult to define achievable criteria, particularly in early stages of the life-of-mine -as it is typically required by regulators (DMP & EPA 2015;Sánchez et al 2014;South African Government 2015).…”

“…Such rehabilitation uncertainties make it difficult to define achievable criteria, particularly in early stages of the life-of-mine -as it is typically required by regulators (DMP & EPA 2015;Sánchez et al 2014;South African Government 2015). At the same time, it is recognized that rehabilitation success is heavily dependent on the degree of understanding and its application to rehabilitation processes (Meney & Pantelic 2019), e.g. linking environmental variables and vegetation recovery (Burke 2018).…”

“…during the design or conceptual stages (Coppin 2013;Fawcett & Laurencont 2019;Jones et al 2008). Once defined, completion criteria should be used throughout the life-of-mine (Holmes et al 2015) to guide progressive rehabilitation and continuous improvement (Meney & Pantelic 2019;Morrison et al 2005). In Australia, it is advised that regulators require greater degree of progressive rehabilitation, which should be explicitly included into the business accounting practices (Lamb et al 2015).…”

Engaging stakeholders to achieve rehabilitation completion: a case study of the BHP Beenup Project

“…Building on BHP's mandate to do it once and do it well, the project, supported by a group of specialist consultants, undertook a process of rigorous materials characterisation, detailed planning of soil, water and engineering aspects, an ecosystem design based approach to revegetation (Meney & Pantelic 2019), comprehensive QA/QC processes during and after project execution, comprehensive and rigorous data collection and storage, regular data review, peer review and continuous improvement.…”