A huge amount of dewatered cake is generated from water treatment processes in large-scaled construction work sites. Although the dewatered cake has been conventionally disposed as an industrial waste, its recycling becomes a big social concern, and the reuse of the dewatered cake is required. In this paper, we describe a past case in which the dewatered cake generated in the actual hydroelectric power plant expansion construction was recycled as a vegetative soil base. The dewatered cake, a single-grained structure of inorganic particles, was not suitable for the growth and development of vegetation. The improvement of physical and chemical properties of the dewatered cake was then required. The improvement of physical and chemical properties was achieved by mixing bark composts and fermented chicken manure composts with the dewatered cake and by aging them for 14 days. Mixing of such good organic composts improved directly soil in fertilizer aspect, served as a supply source of various microorganisms, expecting improvement effects to the physical properties by those metabolites. This improved soil caused neither germination disorder nor growth disorder to the vegetation, thus, it was shown that the dewatered cake was reusable as a vegetative soil base material with such a procedure.
