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Gibraltar Pioneers Groundbreaking Biological Water Treatment Process

Since 2009, Gibraltar has discharged surplus water from its Tailings Storage Facility (TSF) to the nearby Fraser River under strict conditions enforced by the BC Ministry of Environment and Climate Change Strategy. Permit conditions address the quality, quantity and timing of water to be discharged each year.

Under the terms of its discharge permit and federal regulation, Gibraltar is obliged to undertake far-reaching studies to ensure surplus water releases do not affect downstream fish or fish habitat. Regular water quality monitoring, as well as sampling of river sediments, benthic organisms (those living in river sediments) and fish tissue, have consistently demonstrated no impairment to Fraser River water quality and no impacts to fish or fish habitat.

In 2022, however, Gibraltar curtailed its water discharges to the Fraser River due to elevated nitrate levels in tailings water. Nitrates are associated with the use of explosives in the mining process and can accumulate in tailings over time.

To address this concern and ensure that water stored in the TSF meets permit requirements prior to discharge, Taseko, Gibraltar and consultants initiated a project to determine if biological treatment could provide a low-impact, passive solution to elevated nitrate levels. Following an initial pilot test, baseline monitoring and 3D modeling, as well as engagement with Indigenous communities and provincial permitting, a novel in-situ biological water treatment process was implemented in the spring of 2023.

A first of its kind in British Columbia, the biological treatment initiative utilized naturally occurring microbes within the TSF water body to target and reduce nitrate concentrations through a single application of a food-grade organic carbon source. The application was strategically timed to take advantage of natural stratification and seasonal turnover within the tailings pond, in order to maximize treatment efficacy and achieve targeted water quality.

The in-situ biological treatment process proved to be a resounding success, lowering nitrate levels in Gibraltar tailings water to well below permit limits - without any waste by-products, adverse chemistry or unnecessary legacy infrastructure. As a result, the authorized discharge of surplus water from the Gibraltar TSF was resumed in the fall of 2023.