Natural and man-made disasters can pose various threats to the environment and humans. Proper environmental monitoring, early alerts, and response planning and execution are essential. Most government organizations adhere to top-down planning operations, issuing instructions and setting rules and regulations for people to follow. In this chapter, the authors propose a participatory environmental planning platform where environmental planning is based on the data from sensors and “human sensors” to shift from a government-centric to a participatory environmental monitoring and planning paradigm. This platform incorporates intelligent technologies to enhance environmental situation awareness, to promote participatory governance, and to allow citizens to participate in the plan execution; participation is done through local data sharing as necessary to create situation awareness and through a resource sharing provided by citizen volunteers. The authors present a prototype system that provides shared services for the regional municipal governments’ environmental planning and response coordination.