Since 1998, a series of studies on geo-environment problems in waste disposal sites in coastal areas have been carried out. This report is writing on the development of high grade cutoff seawall structures, the field investigation technique for geo-environmental data and an environmental risk analysis method for waste disposal sites. The main conclusions are surmarized as follows:
1) A geo-environment monitoring cone was developed for the investigation of a large scale waste disposal sites in coastal areas.
2) When a part of cutoff sheet is broken, the equivalent permeability with consideration of the damage can be determined for a sheet-reserve soil system. By using the equivalent permeability and the probability of damage outbreak, it can be shown that the duble sheets - reserve soil system has a much better performance of cutoff systm than the single sheet,researve soil system. For the cutoff steel sheet piles, in the joints of which a small amount of leakage is taking place, the equibalent permeability can be determined for the analysis.
3) The mechanical properties of dredged slurry which is mixed with poor quantity of cement, were presented fas a low permeable geo-material used for a cutoff system of seawall.
4)The increase of horizontal permeability of clayey ground improved by SCP (sand compaction pile ) method will be 10 times the orizinal ground at most, when the construction work is carried out precisely. Practically, the SCP method is avairable for the ground improvement of seawll foundation.
5)The seawall structure of the duble PVC sheets and reserve soil system was constructed in Tachibana Port, Tokushima Prefecture, which was the first one after Ministry of Health and Welfare revised the technical standard of structures of waste disposal facility in 1998. Because most of the work had to be carried out below sea level, new techniques, which include on-ship heat bonding of PVC sheets and direct casting of cement treated clay, have been developed and used. This report introduces the design and construction method of a new type of seawall structure for waste landfill in coastal area.
6)The methods for analysy of ground water pollution and the environmental risk analysis are presented for waste disposal sites in coastal areas. Although the used model is in a primary stage, it can be used as an important tool for the construction and management of waste disposal site in coastal areas.