The pollution of surface/ground water caused by the inflow of acid water in which heavy metals are enriched poses a serious environmental problem around excavation sites where sulfide minerals such as pyrite chemically decomposes. To establish a method to evaluate the exudation of acid water from rock, we examined the exudation feature and geochemical characteristics of the rock distributed in the Hakkoda tunnel. As a result, it became clear that it was possible to evaluate the exudation of acid water from rock by the following three indices: (1) the pH value one hour after the batch-leaching test; (2) the sulfur contents of rock; and (3) the S/Ca mole ratio of rock in the case of only mudstones.

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