Derivation of summary measures from water monitoring data
The Washington State Department of Health provided water monitoring data for 24,856 drinking water sources throughout the state. These included wells (95%), springs (3%) and surface water sources (2%). Most (86%) were community sources, either monitored under the SDWA (26%) or only under state regulations (fewer than 25 people and 15 connections, 60%). The remainder were non-community sources (e.g. non-residential sources of water consumed by the public). Nearly all (93%) were permanent sources, not emergency or seasonal sources. We included all sources to maximize geographic coverage.