Abstract
The problems of geological engineering surveys and evaluations for improvement of final disposal sites have been noticed from the view of environmental conservation. Waste containing mercury exceeding the standard was landfilled in the Itoigawa final disposal site. To improve this final disposal site, we carried out several geological-engineering surveys, including geophysical prospecting and numerical analysis of groundwater.
The results of surveys and numerical analysis showed that internal water containing arsenic and other harmful heavy metals might leak from the landfill site with heavy rain. Therefore, if drainage wells are provided in landfill sites, they would not only act as an effective countermeasure for environmental conservation as water barriers, according to the results of our numerical analysis, but they would also effectively contribute to the mechanical stability of the landfill. This water barrier countermeasure uses a method in which the hydraulic potential of the internal water in the landfill is lower than that of the groundwater in natural ground around the landfill. For an example, there are several drainage wells (with drainage bore holes) and water treatment facilities. This countermeasure is inexpensive with good workability.
