On-site sewage system (OSS) and social vulnerability GIS dashboard: using data to inform approaches for equitable wastewater…

Public Health - Seattle & King County created the On-site Sewage Systems (OSS) and social vulnerability GIS map and dashboard to evaluate if the distribution of aging on-site wastewater treatment systems (also known as septic systems) is correlated with demographics and social inequities. The dashboard combines King County OSS location and age data with the CDC Social vulnerability index at the census tract level, showing that urban OSS are more likely to be located in the most vulnerable census tracts. The map and dashboard provide a data-informed tool to help prioritize locations that have the greatest need for infrastructure planning to address systematic inequitable investments in public sewer infrastructure. It also helps identify locations where OSS provide sufficient treatment and can be the prioritized wastewater treatment option. This has implications for policy development and localized neighborhood scale project prioritization to reduce pollution sources and promote clean water. We will present the process used to create and validate the OSS data necessary for this tool, present the interactive map, and share a summary of the policy implications and examples of localized projects that resulted from using this tool.