We have developed our original software system 'GERAS-3', a geo-environmental risk assessment system with detailed modeling, for the practical risk assessment of soil and groundwater contamination. The development was completed by the integration of various researches in geology, risk analysis, environmental engineering, and computer science. GERAS-3 has some features and advantages, in order to ensure the assessment of multiple contaminants, the 3-dimensional analysis of soil and groundwater, and the risk mitigation after treatment of contaminated soil. We also developed the databases for GERAS-3, such as on soil parameters, transport parameters of porosity and permeability, and various data for contaminants of oils, metals and VOCs. CD-ROMs of GERAS-3 have been distributed for free upon requests from companies and municipalities. We expect the system will be utilized much by a wider range of users including, local governments, factories, consultants, and educators, for self-governance activities and risk communication related to environmental risks from soil and groundwater contamination.