Boliden – Tara Mine In-Rush Event Assessment

On 20 November 2021, an incident occurred at a drill site within PLA 4502. This incident was an in-rush of water into an exploration tunnel (Tara Deep Exploration Drive) constructed from the South West Extension (SWEX) area of Tara Boliden’s Navan mine. The flow rate increased over the next few days, flooding the tunnel and underground workings. The in-rush was stopped on 2 December 2021.

In January 2022, the Geoscience Regulation Office (GSRO), the Environmental Protection Agency (EPA) and Meath County Council commissioned Wardell Armstrong International (WAI) to undertake an independent hydrogeological review of the Boliden Tara Deep Deposit and surrounding area.

The objectives of this review were to:

• Review and appraise the conceptual hydrogeological model of the mine for the Tara Deep Area
• Assess the monitoring regime being undertaken for the Tara Deep Area
• Review the most likely causes of the November 2021 in-rush of water into the mine
• Try and determine whether there was a linkage or not between the mining activities and the drop in groundwater levels in the nearby Robinstown - Shambo area. Reduced water levels were recorded since at least early summer 2021. Conversely, the assessment also needed to consider if there is a natural explanation for this or some other ‘hydrological’ reason

Data reviewed to support this assessment has been provided primarily by Boliden Tara Mines DAC. Data was also provided by Meath County Council, the EPA, Residents of Robinstown – Shambo area and the Department of the Environment, Climate and Communications (DECC) via the GSRO.