Soil recycling at gas pipe construction site

At Tokyo gas, about 2 million tons of excavated soil is generated as a result of construction yearly. In the past it was largely disposed of as landfill and virgin materials (sand) were purchased to be used as backfill in its place. However the mining and transportation of sand results in environmental damage and emission of NO/sub x/. The cornerstone of their efforts to improve the situation consists of measures to restrict to the utmost the generation of excavated soil during pipeline construction (the trenchless method). They are also taking steps to reuse excavated soil, both as good quality soil (which can be backfilled as it is), and as improved soil. As a measure against the generation of excavated soil, soil recycling plants have already been constructed at two sites, but it is geographically infeasible for all of the construction sites in the company to use them. Hence, with the aim of covering other regions, they developed a small-sized, maneuverable, soil recycling vehicle. It can recycle soil into improved soil by a series of processes in a small space next to a gas construction site.