Geological and environmental pre-conditions for utilisation of the Maardu granite deposit, northern Estonia

Abstract

Efficient use of natural resources is a global goal. A specific way of improving resource productivity in Estonia is utilisation of Maardu granite deposit as a joint goal for producing granite aggregates and construction in the caverns of the granite mine and a pumped hydroaccumulation plant. The environmental impact assessment in connection with construction of a Maardu deep granite mine was accepted by the Estonian Ministry of Environment in 2009. The most challenging engineering task, causing also the biggest environmental risks, is safe penetration of aquifers and aquitards during construction of vertical and/or inclined tunnels for granite mine and/or pumped hydroaccumulation plant. A major problem is also the high radiation level in the Maardu area and in the planned deep mine. High radon concentrations up to 10 000 Bq/m3 have been recorded on the outcrops of alum shale in the mine area and they can be dangerous to human health. Based on the hydrogeological modelling it was found, that under normal circumstances the construction and operation of the Maardu deep granite mine is environmentally safe. The territory of the former Maardu phosphorite opencast is highly polluted and damaged and therefore the foundation of the granite mine with overground buildings is the best way for the environmental improving of the area.