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DSAC members raise groundwater and PFAS monitoring questions; request hydrology review
Summary
Committee members and public commenters flagged potential problems with the landfill monitoring network, well construction and interpretation of leachate/PFAS data. DSAC asked staff to pursue a hydrologist briefing and to collect spatial context for groundwater results.
Disposal Site Advisory Committee members and public commenters raised questions about the validity of Coffin Butte monitoring wells, the design of the monitoring network and the interpretation of leachate and PFAS results.
DSAC member David Hoffman described anomalies in the monitoring data for “Well 26,” noting a hydrograph that does not show expected seasonal rise and fall and corresponding chemical data that remain essentially flat. Hoffman said the construction of some older monitoring wells — nested wells from the 1970s — can allow interconnection of multiple aquifers and that well construction standards have changed since then. He asked the committee to seek clarity from the Oregon Department of Environmental Quality (DEQ) about well design and whether older wells remain reliable compliance points.
Public commenter Debbie Palmer and others drew attention to concerns about PFAS in landfill leachate and to the history of inspections and reporting. Committee members agreed that groundwater questions require spatial context; a single well’s trend cannot be interpreted without comparing nearby background wells and regional water‑quality baselines. Several members requested a technical briefing from a hydrologist or groundwater consultant (committee staff indicated they would contact a retired hydrologist known to the county) and asked Republic’s consultants to review monitoring network design.
DSAC voted to prioritize hydrology/groundwater (one of the committee’s top priorities for 2025) and to collect a short list of specific sampling and design questions for the consultant or hydrologist to address.
Ending: DSAC tasked staff to request a hydrology briefing and to compile a short, prioritized set of technical questions about well construction, spatial context and PFAS/leachate interpretation for consultants and county reviewers.
