County-funded study finds PFAS in La Cienega wells; investigators identify data gaps and short-term steps

Santa Fe County-funded investigators told the Board of County Commissioners on Sept. 30 that per- and polyfluoroalkyl substances (PFAS) have been detected in private wells in the La Cieneguilla and La Cienega communities and that the higher concentrations are concentrated in La Cieneguilla.

The findings were presented by Entera Incorporated staff, who said the work was supported by the New Mexico Environment Department and included about 90 samples from private wells, surface water and publicly collected effluent or monitoring results. "Each sample represents a snapshot in time," Karen Flores, a project manager and geologist with Entera, told the commission.

Why it matters: PFAS are long‑lasting chemicals associated with some health risks at elevated levels; the U.S. Environmental Protection Agency has issued drinking‑water maximum contaminant levels for several PFAS compounds that the Entera team used to judge exceedances. The county and state officials said the work is an early step intended to guide mitigation and to identify likely sources.

What the study found - Total PFAS heat maps developed by Entera showed substantially higher total PFAS concentrations in the La Cieneguilla subdivision than in La Cienega. - Samples taken by Entera and provided by other entities indicate multiple exceedances of EPA drinking‑water maximum contaminant levels in wells within the study area. Flores said 169 parcels sampled had MCL exceedances; about 650 parcels had detectable PFAS in sampled wells (figures reported by presenters as summaries of their dataset). - Entera and its technical lead, Joe Gallimore, described a hydrogeologic picture where a shallow, more permeable unit (the Ancha formation) supplies well water in the area and where a perched clay layer near the Army Aviation Support Facility traps very high PFAS concentrations in perched groundwater.

Potential sources and remaining questions Entera identified several possible sources of PFAS in the area where contamination was highest: the Army National Guard Aviation Support Facility (where aqueous film‑forming foam, AFFF, historically used in firefighting, has been documented), the Paseo Real Water Reclamation Facility (effluent and biosolids/leachate), local septic systems and the Santa Fe Regional Airport. Presenters said the three documented sources (guard facility, Paseo Real and biosolids) are collocated in the same general area, complicating source attribution.

"We have not identified one particular source," said Joe Gallimore, Entera technical lead. He said fingerprinting and composition comparisons show similarities among sources but also contradictions — for example, PFOS (a legacy PFAS) appears in some domestic wells but was not present in the guard‑site monitoring samples Entera showed.

Data gaps and next steps Presenters told the board the investigation requires additional, targeted work before regulators or the county can select a long‑term remedy. Key gaps they identified include: - Discrete, depth‑specific (screened) monitoring wells in the La Cieneguilla subdivision so vertical extent of contamination can be determined. - Additional sampling in a southwest portion of La Cieneguilla where limited data exist. - Additional sampling along the Santa Fe River and on the Santa Fe Regional Airport property, where few data exist. - Sampling of septic leach fields and leachate from biosolids to estimate contribution from those sources.

Short‑term mitigation and state support County officials said the state has provided funding to support ongoing work. "We received about $1.5 million from NMED," County Manager Greg Schaeffer told commissioners during the meeting; he and Entera also said the state has offered additional support for remediation planning. Entera representatives said point‑of‑use filters and reverse osmosis devices can reduce household exposures now but require frequent replacement and produce waste streams that must be managed.

What the county is doing The county has funded Entera’s work and amended the consultant agreement to add samples from Amigos Bravos, a nonprofit that contributed funds for additional analysis. Commissioners and staff said the county is coordinating with NMED and the City of Santa Fe. County staff said they will continue outreach, send household results to well owners, and discuss potential reimbursement or financial support for households that purchased treatment systems; officials said that potential reimbursement had been raised with the state but had not yet been finalized.

Where this goes next Entera and county staff recommended targeted additional testing to close the data gaps that limit source attribution and that will be required to design a long‑term remedy. Commissioners pressed for clarity on the additional investigation schedule and costs; county and state staff said they would return with a proposed work plan and budget as funding details are clarified.

Ending: County and state officials said they regard the contamination as a serious community issue and urged residents to use tested drinking sources until results and mitigation plans are finalized.