Ferguson, P, SeyedAli, M, Jones, D, Skoglund, J & Tebaibi, Z 2025, 'Closure and reclamation of the Bouchard-Hébert mine site, Rouyn-Noranda, Québec, Canada ', in S Knutsson, AB Fourie & M Tibbett (eds), Mine Closure 2025: Proceedings of the 18th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-14, https://doi.org/10.36487/ACG_repo/2515_20
(https://papers.acg.uwa.edu.au/p/2515_20_Ferguson/)
Abstract: The Bouchard-Hébert mine is a closed zinc operation located approximately 30 km northeast of the city of Rouyn-Noranda in the Abitibi region of Québec, Canada. The mine operated from 1987 to 2002 and was closed in 2005. In 2021 approximately 50,000 m3 of potentially acid generating (PAG) waste rock was relocated to the permanently flooded portion of the nearby open pit. This was done to both improve site aesthetics and reduce contaminant loads to groundwater downgradient and the site’s water treatment system. The waste rock is partially oxidised and has generated substantial acidity and metal-laden seepage due to acid rock drainage/metal leaching (ARD/ML) since it was deposited. An additional 18,700 m3 of waste rock was relocated to the pit in 2023 as part of ongoing reclamation activities.
Submerging PAG waste rock under water will eliminate future ARD/ML generation by these materials by preventing sulphide oxidation. This is best management practice for reactive, sulphide-bearing materials according to Mine Environment Neutral Drainage Program guidelines (MEND 2015) and other international guidelines, e.g. the Leading Practice Sustainable Development Program (LPSDP 2016). PAG waste rock relocated to the pit was amended with a neutralant (crushed limestone) to neutralise its existing acidity (titratable acidity plus jarosite acidity) content and thereby prevent the release of acidity and metals to groundwater once the waste rock is submerged. Waste rock that will not be submerged under water was amended with enough limestone to neutralise the total acidity content of the samples, i.e. acid generating potential and existing acidity. This paper describes how dosing rates were estimated and the process of mixing waste rock and limestone during relocation to the pit. The findings from recent sampling of the waste rock relocated in 2021 confirm that the jarosite in waste rock has decomposed. 

Keywords: mine closure, acid rock drainage, pit backfilling, limestone amendment