Pitkin County work group seeks more data, funding to address Lincoln Creek contamination

Pitkin County officials and outside contractors told the Board of County Commissioners on March 18 that sampling shows elevated metals and acidic water in Lincoln Creek and that the county-led Lincoln Creek Work Group is moving to a phase‑2 plan to better characterize sources and possible mitigations.

The work group formed after visual discoloration and a fish kill in Grizzly Reservoir prompted Colorado Parks and Wildlife and the EPA to investigate. Lisa Tasker of the Pitkin County Healthy Rivers Program said the EPA labeled parts of Lincoln Creek “toxic to aquatic life” based on its 2022 sampling and assessment, and that EPA found a mineralized tributary several hundred yards from the old Ruby Mine that appears to be the primary source of dissolved metals.

Why it matters: Lincoln Creek drains into the Roaring Fork River and into downstream water users; county staff and contractors said uncertainty about seasonal variation and climate impacts makes it important to collect consistent data before deciding whether and how to intervene.

Chip Fisher, an engineer with LRE Water who led a site visit and produced a phase‑1 memo for the work group, described the field observations and initial samples. Fisher said crews saw a clear change where the mineralized tributary entered Lincoln Creek, with “very acidic, low pH, and really high specific conductivity” and colored precipitates that indicate aluminum, iron and copper precipitating out of solution. He added, “the flow in this mineralized tributary is quite low…the concentration of metals…there’s a ton of capacity for dissolving metal and carrying it downstream, and that’s what we’re seeing.”

County and contractor findings so far - EPA sampling and a 2022 assessment found elevated iron, aluminum and copper and identified a mineralized tributary close to the Ruby Mine as the dominant source; the mine itself may contribute a smaller share. (Work group presentations referenced EPA sampling and report.) - Field pH measurements reported by LRE Water showed values in parts of Lincoln Creek in the roughly 3.5–4.5 range after the mineralized tributary joins; the mineralized tributary itself produced even lower pH values in some spots (the memo cited pH near ~2.9 in local pockets). - LRE Water’s memo and mapping showed high specific conductivity and metal loading from the upper watershed downstream through Grizzly Reservoir; some dissolved material can settle in reservoir sediments.

Work done and near-term plan - Phase 1: The county and partners hired a contractor to conduct a rapid site visit and to review last year’s sampling plan; Tasker said phase‑1 work cost about $16,000 and was paid by the Independence Pass Foundation and Pitkin County’s Healthy Rivers Program. - Phase 2 (proposed): LRE Water has submitted a scope of work to develop a targeted sampling and analysis plan, measure streamflow and hydrology, and build a mass‑balance model identifying inputs and potential reductions. County staff said the goal is a multi‑year, focused sampling program (water, benthic insects and fish tissue where appropriate) that enables evaluation of feasible mitigation options and their expected downstream benefit.

Scientific and monitoring items - University of Colorado researchers brought a core sampler to the reservoir to collect sediments; Tasker said the CU team intends to analyze sediment layers to see whether metals are increasing over time and whether a climate signal can be detected. Tasker said CU would likely seek funding through the Healthy Rivers program to support that work. - Colorado Parks and Wildlife’s RiverWatch lab processed the county’s water samples; county staff said CPW is also reviewing fish‑tissue questions related to stocking and human consumption.

Funding and next steps County staff said they are pursuing small, targeted funding to start phase‑2 work and to cover modeling and additional sampling this summer; Tasker and staff said a Basin Roundtable grant application for roughly $150,000 was being presented to the roundtable the week after the meeting and that the work group would present to the basin group. The county has also begun a contract process with LRE Water to start the phase‑2 scope if funding is secured.

Possible mitigation options described by contractors ranged from low‑maintenance passive treatments in sensitive locations to more active engineered treatment systems — but LRE Water and the county emphasized they will not recommend major interventions until the targeted monitoring and hydrologic analysis better define sources, flows, and the expected effectiveness of any remedy.

No formal policy decision was made at the March 18 work session. The county’s immediate next steps are to finalize contracting for the phase‑2 scope if funding is available, await final RiverWatch laboratory results, coordinate sediment analyses with the CU team if CU obtains funding, and continue the work group’s multi‑agency coordination.

Ending: County staff asked partners and the public to await the phase‑2 sampling plan and model results before debating specific mitigation measures; work group members said the additional data will inform whether the effort focuses on passive, low‑footprint approaches or more intensive treatment.