This talk is about the development of an Environmental Impact Assessments(EIA) data visualization system using FOSS4G. The system is being developed by Gaia3D utilizing several open source projects such as PostGIS, GeoServer, Cesium, and mago3D. Although EIA has played an important role for environmental decision-making and sustainable development, most EIA statements are published as a mix of text and tabular data that is not easily accessible to or understandable for the public. The system was designed to improve the public’s understanding of stakeholders before and after a construction project by providing visualization of key environmental elements. The final goal of the system is to improve the EIA process so that not only experts but also non-experts, citizens can participate in the EIA process and easily understand the meaning of the EIA statements with help from 3D GIS, Easy Finger real-time simulation technology. This system development is 5 years long project funded by Ministry of Environment(MOE-2020002990005), South Korea. This talk will focus on the research outcome of Phase I and future plans. The final system will be opened as an open source with permission from Ministry of Environment.