Supervisors back pilot to inventory abandoned mines, protect water and plan mitigation

Nevada County supervisors discussed a broad initiative to identify and mitigate risks from abandoned and legacy mines after hearing a presentation from Chair Hall on environmental and public‑health concerns posed by old mine workings.

Chair Hall told the board that the county does not know the number or condition of many historic mines and that mercury, arsenic and other heavy metals can seep into creeks and drinking-water supplies. The presentation cited recent examples — including ongoing acid‑mine drainage concerns tied to sites such as Lava Cap and engineered drains at Empire Mine State Park — to illustrate long‑running contamination and the perpetual treatment systems already required.

Why it matters: Presenters and supervisors said the main public‑safety threat is drinking‑water contamination and the physical danger of unmarked shafts. They argued that early assessment and targeted mitigation would be cheaper and more effective than reactive cleanup after a failure.

What the board asked staff to do: Chair Hall asked staff to pilot a multiyear program beginning with a focused assessment: compile available lists of mines, evaluate which sites pose immediate threats to water or public safety, and develop short‑ and mid‑term options for mitigation and funding. He recommended establishing relationships with state and federal agencies (EPA, DTSC, Department of Conservation) so the county can act quickly if a hazard emerges. Several supervisors raised concerns about property‑rights implications and the county’s role on private land; presenters said the county’s early role would be primarily informational — education, referral and resource navigation for property owners.

Timeline and next steps: Supervisors directed staff to work with Chair Hall and Supervisor Tucker and return with a plan within roughly six months that lays out the scope, likely staffing or consultant needs and any recommended budget requests. The board did not authorize immediate funding but asked staff to identify options, including a possible pilot and whether some workload could be covered within existing resources.

Ending: Supervisors agreed that protecting drinking water and avoiding future costly cleanups merit attention; staff will return with a project plan and options for board consideration.