Department of Ecology
October 2022
Introduction and problem statement
During summer 2020, the Washington State Department of Ecology’s (Ecology’s) Environmental Assessment Program initiated Phase 1 of a field study to address potential sources of per- and polyfluoroalkyl substances (PFAS) contamination in resident fish from Lake Washington, King County (Furl and Meredith 2010, Mathieu and McCall 2017, Mathieu 2022).
During Phase 1, we assessed concentrations of PFAS in Lake Washington and in potential contaminant pathways to the lake. The Phase 1 study design included characterization of PFAS concentrations in the lake and its direct tributaries, groundwater discharges, stormwater discharges, bridge runoff, and bulk atmospheric deposition (Wong and Mathieu 2021, Escobedo 2021).
This Quality Assurance Project Plan (QAPP) addendum describes the Phase 2 study design. In Phase 2, we will sample in areas of the Lake Washington watershed where we detected some of the highest PFAS concentrations and potential PFAS loading sources among the samples collected in Phase 1. The findings from this study will help us determine the sources and pathways of PFAS entering Lake Washington that may also be applicable to other urban watersheds.