Meiers, G, O'Kane, M & Mayich, D 2011, 'Evaluating the performance of a high density polyethylene lined cover system at the reclaimed Franklin Mine near Sydney, Canada', in AB Fourie, M Tibbett & A Beersing (eds), Mine Closure 2011: Proceedings of the Sixth International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 269-280, https://doi.org/10.36487/ACG_rep/1152_95_Meiers (https://papers.acg.uwa.edu.au/p/1152_95_Meiers/) Abstract: Enterprise Cape Breton Corporation (ECBC) has implemented a remediation programme for the Franklin coal mine located near Sydney, Nova Scotia, Canada. Waste rock generated from the Franklin mine and ten other mines in close proximity, all of which operated from 1885 to 1959, were consolidated into the Franklin waste rock pile (WRP). The waste rock is acid generating with the potential to continue to generate acid rock drainage (ARD). A cover system was constructed over the Franklin WRP in the fall of 2010 with the overall objective to minimise detrimental impacts of the mine waste on the receiving environment in the short term and facilitate recovery of the environment disturbed by mining over the long term. The Franklin WRP cover system consists of a geotextile fabric, engineered 60 mil high density polyethylene (HDPE) geomembrane, a geocomposite drainage layer, and 600 mm of glacial till. Instrumentation was installed during construction of the cover system to facilitate evaluation of its performance over time under site-specific climate conditions. The primary objective of the monitoring programme is to develop a database of cover system moisture and thermal field responses, as well as internal WRP dynamics and groundwater conditions within the WRP footprint, for eventual calibration of a soil-plant-atmosphere numerical model and groundwater flow and contaminant transport model. The modelling effort would ultimately be capable of developing predictions and further understanding of long-term cover performance in limiting impacts to the receiving environment. The WRP performance monitoring system is detailed within this paper along with preliminary performance of the cover system. This paper provides unique insight into developing an understanding for the change in waste rock pore-water chemistry and waste rock pile seepage quantity and quality as a result of placing a low permeability cover system over a full-scale waste rock pile in a seasonally humid environment. The challenges and solutions for developing a performance monitoring system for a full-scale cover system that incorporates a low permeability cover system are also discussed.