ABSTRACT:

This paper reports a case study of site investigation and remediation of a soil contaminated with Trichloroethylene (TCE) at a factory site still in operation. Early investigation indicated contamination of the ground surrounding a warehouse building. This soil was excavated and treated on-site by soil vapor extraction. Meanwhile, the degree of contamination of the soil under the warehouse building was determined by several borings in horizontal direction from outside the building. The locations of the borings were designed such as to serve later as wells for the vacuum extraction.

GEOLOGICAL FEATURES OF INVESTIGATION AREA

The factory site is located on a terrace that is part of a fan deposit derived from colluvial volcanic deposits and debris flow. The surface has a gradient of 4/100 (Figure 1). The geology of the terrace is dominated by gravel, sand, mud and volcanic breccia (andesite). The surface stratum is loam of aeolian deposits, with a thickness of about 10 m. The factory was built on leveled ground, which had been achieved by excavating soil uphill and backfilling downhill. Groundwater level is from 12 m to 14 m below ground, and its flow direction is roughly identical to the gradient of the natural ground surface. Also flow direction of water in surface layer and groundwater are alike.

INVESTIGATION OF CONTAMINATED SOILS WITH TCE

The factory had been using Trichloroethylene (TCE) as a solvent for cleaning of electronic devices. But that practice was abandoned at several years ago to follow legal restrictions. The investigation pursued two goals. One was to confirm whether or not the ground underneath pipe fittings of the storage tanks had been contaminated with TCE. A second goal consisted of carrying out a general investigation for the whole factory ground according to a national guideline.

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