Closure Planning on a Large Scale – Approach to Optimising PFS Closure Designs for the Western and Central Development Areas at a site in Central Laos

Author(s): 
John Chapman, Claire Linklater, Daryl Hockley, Justin Rowntree, Donna Noonan
Date: 
Tuesday, September 4, 2018
First presented: 
Mine Closure 2018
Type: 
Article
Category: 
Mining
 
 
Closure plans for an extensive mine site located in central Laos are currently being developed. The mining area includes more than 40 pits, some of which have been backfilled, and 13 waste rock dumps.
 
In support of the development of the closure strategy, technical studies have been completed which included development of a site-wide water and load balance, assessment of the geotechnical stability of pit walls and dumps, and geochemical characterisation to understand the distribution of ongoing sources of solute production around the site. Specific issues associated with the site include proximity of local communities and accessibility of the site, stability of the pit high walls and exposure of acid forming rock on the high walls, positive water balances for the pit lakes and the large distance across which the site is spread.
 
Future water quality predictions were combined with the site-wide water balance to develop an integrated closure strategy for the site, identifying optimal closure measures to mitigate water quality impacts to downstream receptors (drinking water resources) and ensure public safety. Conceptual closure designs for WRDs and pits were developed incorporating both passive and active water management infrastructure. Two companion papers describe the development of the water balance and the water quality predictions. This paper presents the practical implications of the outcomes and the overall closure strategy that was developed for the site.

Feature Author

John Chapman

John Chapman has more than 26 years of relevant experience and has developed multi-disciplinary skills relating to mining environmental impacts assessment and environmental controls.  He is a recognised expert in ARD assessment and prediction, mine waste characterisation and management, and mine closure with recent project experience in Australia, South East Asia, Canada, USA and Europe.  John has facilitated enterprise-wide risk assessment workshops, undertaken due diligence and environmental risk assessments for a wide range of mining projects.  Recent projects include detailed geochemical assessment of the tailings properties for the Olympic Dam Project in SA, design and development of the geochemical characterisation program for the Cannington Life Extension project in QLD as well as for the Yeelirrie Project in WA.

Principal Consultant (Geochemistry and Environment)
MSc (Chemical Engineering), P Eng (British Columbia), P.Eng (Yukon Territory)
SRK Brisbane
Claire Linklater

Claire Linklater has 22 years’ experience in interpretation of geochemical data, building conceptual models of processes which control in situ geochemical behaviour and the application of geochemical modelling codes.  Her early career was focused on management of radioactive wastes; understanding and quantifying the geochemical behaviour and mobility of radionuclides in the ‘geosphere’ surrounding a proposed underground repository and assessing the long-term stability of engineered and natural barriers.  More recently, she has focused on sulfidic materials management: acid/alkaline rock drainage (ARD) assessment and prediction; water quality and pollutant mobility from waste rock dumps, tailings storage facilities, underground workings and pit walls; assessing the effectiveness of potential mine closure strategies.

Principal Consultant (Geochemistry)
PhD (Geology), FGS, FAusIMM
SRK Sydney
SRK Africa