Evaluation of Rock Characteristics for Acid Water Drainage from Rock Muck

Surface/ground water pollution caused by the inflow of acid water enriched with heavy metals has become a serious environmental problem in the areas around mines [1,2]. This results from the sulfate discharge generated by the decomposition of pyrite contained in the altered rock in mining areas [3]. The same problem has arisen at engineering work excavation sites in recent years [4]. Therefore, if a tunnel is to be constructed in the vicinity of a mine area, the evaluation and prediction of the possibility of acid water drainage from rock muck and rock masses will be important environmental geology aspects. The 26,455m-long Hakkoda tunnel is currently under construction between Hachinohe and Shin-Aomori Stations on the Tohoku Shinkansen network in the northern part of Honshu, Japan. Because there are a number of mines around this tunnel, it is feared that the peripheral environment would be polluted by acid water and heavy metals percolating from the rock muck released by the tunnel's excavation. Therefore, we investigated the geochemical features of rock distributed around the Hakkoda tunnel to establish a method to evaluate the acid water drainage. This paper clarifies the geochemical characteristics of rock that discharges acid water. We also propose a method to evaluate acid water drainage from rock that was used in the construction of the Hakkoda tunnel.