In August 2014 a catastrophic collapse of the Mount Polley Mining Corporation’s (MPMC) tailing storage facility released ~25 M cubic meters of contaminated water, tailings and scoured overburden from the local watershed delivering much of this material (~19 M m3) into Quesnel Lake, one of the largest (262 km2) and deepest (>500 m) lakes in British Columbia. To sustain production while a new tailings pond was being built MPMC received permission to discharge wastewater into Quesnel Lake via two diffuser pipes positioned at a depth of ~45 m, ~200 m offshore with effluent discharge beginning in December 2016. BC governmental regulations stipulated MPMC undertake physical, chemical and biological measurements at the edge of the Initial Dilution Zone (IDZ), a circular area with a diameter of 100 m. Nearly a decade later, the diffusion pipes continue to deliver wastewater to Quesnel Lake with government permits being reviewed, updated and renewed to address water quality and its impacts on aquatic biotic. In 2020 independent observations by UNBC’s Quesnel River Research Centre began in the IDZ region and this talk will present results of suspended sediment and water chemistry, as well as metal content of phytoplankton and zooplankton. Since 2022 data collected has been used to support the BC Biotic Ligand Model (BLM) to evaluate chronic copper guidelines for aquatic biota using Daphnia Magna to represent the lowest effect threshold of the most sensitive organism. Levels of copper in sediment and water have been found in excess of that suitable for aquatic life.