Abstract
At the completion of a regulating pond in the land developed for an industrial complex, the water near the bed of the pond was found to be highly acidic. As a result of investigations, it was found that high acidity was attributable to the formation of sulphuric ion due to pyrite (FeS2) contained in the mudstone layer (sedimentary mudstone layer in the Neogene period) exposed on the bed. In order to correct the situation, the costruction of a cover on the bed was proposed. The VE method was used for selecting a countermeasure. A method was finally selected to remove the soil surface which had turned acidic, and then costruct in its place a cover of improved soil, which is a mixture of the quality soil produced in the site and soil stabilizer. The validity of the countermeasure was verified through pilot construction, and the specification for implementation was determined based on the data obtained. The regulating pond was filled after the implementation of the countermeasure. It was confirmed that the pH of water started to stabilize in more than five months and gradually became close to 7.
