On May 9th, 2006, the City of Seattle completed the first major update to environmentally critical areas (ECAs) regulations and policies since they were first adopted in 1990. ECAs include the City’s wetlands, areas important for fish and wildlife, riparian corridors (such as creeks), geologic hazard areas (such as landslide-prone, steep-slope and liquefaction-prone areas), flood-prone areas, and abandoned landfills. These regulations address how development on and adjacent to Seattle's ECAs should be regulated.
The ordinance adopting these regulations is available along with supporting documentation. This update process focused on providing opportunities for citizens to generate ideas and input on how to best update the regulations to protect environmentally critical areas while still respecting private property (see public comments).
In April of 2007, the City designated new Geologic Hazard Areas including the Seattle Fault Zone and areas of the city that are at risk from tsunamis, seiches, and lahars. Identifying these areas will help to inform citizens about the risk and hazards inherent to living and working in the city. There are no additional regulation of these new Environmentally Critical Areas as a result of these designations.

