Faro Mine GSC Closure
CLIENT: Government of Yukon
LOCATION: Central Yukon Territory, Canada
The Faro Mine Complex (FMC) in central Yukon was once the largest open-pit lead-zinc mine in the world. The FMC produced lead, zinc, silver and gold from the 1960s through to 1998, and sulphide-bearing waste from these historic mining operations is stored in several waste rock dumps (WRDs) and the Rose Creek Tailings Area (RCTA). Seepage from the storage of sulphidic waste in the Faro WRDs has variably impacted groundwater and surface water reporting to the North Fork Rose Creek (NFRC) channel.
BGC has been involved with various work scopes at the FMC over the past two decades. Beginning in 2016, Crown-Indigenous Relations and Northern Affairs Canada (CIRNAC) retained BGC to complete “Urgent Works” projects. The Urgent Works included the NFRC Realignment Project, of which the primary objective is to “keep clean water clean” through separation of non-contact surface water (within the NFRC watershed) from contact water (originating from the adjacent WRDs). The NFRC Realignment Project was divided into two components, the non-contact water (NCW) Diversion Channel, and the contact water collection and conveyance system (CW System). The BGC Geochemistry Team was involved on both components along with geotechnical, civil engineering, permafrost engineering, geology, hydrogeology and hydrotechnical services. The work involved numerous site investigations with multidisciplinary scopes as well as significant (office-based) technical work to build on site learnings and advance construction designs.
NCW Diversion Channel
Construction of the NCW Diversion Channel commenced in September 2019 and it was commissioned on October 24, 2020. The NCW Diversion Channel is approximately 1.9 km long and, together with the inlet dam and outlet works, diverts the NFRC into a hydraulically isolated channel on the opposite side of the NFRC valley from the WRDs.
The BGC Geochemistry Team provided support for the design of the NCW Diversion Channel through the following services:
- Field investigations which included monitoring well installation, well development, groundwater and surface water sampling, surface water flow monitoring, and geochemical sampling
- Evaluation of metal leaching and acid rock drainage (MLARD) potential of construction materials from borrow sources and quarries
- Development of water quality models to estimate impacts to the NCW Diversion Channel from construction activities and materials
In 2018, BGC advanced conceptual design of the CW System to collect contact (impacted) water migrating from the WRDs towards the NFRC and within the NFRC Valley. While 2019 was focused on contingency planning, in Spring 2020, BGC progressed the design of an initial CW System (referred to as the CW Interim Measure) in response to changing site conditions, the progress of the NCW Diversion Channel construction, and feedback received from independent project review panel experts and stakeholders. Construction of the CW Interim Measure commenced in November 2020 and was commissioned on April 15, 2021.
The BGC Geochemistry Team provided support for the design of the CW System through the following scopes:
- Development of a CW Monitoring Program to monitor changes in groundwater quality prior to and following diversion of the NFRC. The data from the monitoring program were also used to develop inputs for water quality modelling
- Conceptual site model development and plume mapping of sulphate and zinc (the primary contaminant of concern) to identify contaminant carrying hydrostratigraphic units
- Development of a water quality model to support options assessments and conceptual design of the CW System and detailed design of the CW Interim Measure
- Design of a performance monitoring network for the CW Interim Measure and an associated field investigation which included monitoring well installation for performance monitoring, well development, slug testing and groundwater sampling
- Annual reporting for the CW monitoring program and the performance monitoring of the CW Interim Measure.