Guam EPA reports PFAS and pesticide detections at several public water systems; GWA, US EPA and governor move to provide temporary treatment

At its Oct. 2 meeting the Guam Environmental Protection Agency reported results from recent sampling that found per- and polyfluoroalkyl substances (PFAS) and pesticide detections in multiple public water systems and described short-term response measures to reduce exposure for affected households.

“On September 12, GWA issued a tier 1 advisory notification to those affected customers that get water from distribution well Y‑15,” Administrator Michelle told the board, reporting that 1,112 customers received the Sept. 12 notice because a running annual average at Y‑15 exceeded the action level previously approved by the board. Following that notification, the acting governor declared a state of emergency and allocated $250,000 to the Guam Water Authority to procure whole‑house point‑of‑entry (POE) filters for affected households.

Michelle briefed the board on short‑ and medium‑term responses. She said GWA is installing two smaller DACC systems moved from other wells to Y‑15; installation was expected by the day after the meeting. She also described a GWA reimbursement plan that would reimburse affected customers who purchase or install whole‑house systems; Michelle said the whole‑house POE systems are estimated at about $2,700 per unit, exclusive of installation and pre‑piping costs.

US EPA Region 9 conducted a sampling effort funded through the American Rescue Plan Act of 2021 and presented results to Guam EPA staff. Nicole Dearest (presenting the EPA deliverable) summarized the sampling: four public water systems were sampled (GWA North, airport, GRMC and Grand Plaza), producing 72 PFAS samples in total with nine analytes per sample. The sampling detected multiple PFAS compounds. Notable values discussed at the meeting included PFOS up to about 62 nanograms per liter (ng/L), PFOA up to about 14.5 ng/L, and PFHxS up to about 30.8 ng/L in single-sample results; a combined hazard-index metric exceeded 1.0 at several sample points (the highest hazard-index value presented was about 3.08), indicating the mixture exceeded the interim benchmark used for that index in the Region 9 deliverable.

Pesticides were sampled at GWA North (53 pesticide samples); two results exceeded the interim action levels the board used for screening (the deliverable cited interim action levels of 0.2 and 0.5 parts per billion). The maximum pesticide sample result presented was 1.5 ppb.

Michelle also reported a child-lead investigation: after a child with elevated blood lead was reported, staff used XRF screening and found floor tiles with lead concentrations above 5,000 parts per million; water samples were not collected because the residence lacked running water on the scheduled sampling day. The agency is following up.

On potential long-term cleanup, Guam EPA staff said the U.S. Army Corps’ Area 101 site (Anau/Santa Rosa) is moving into the remedial-investigation/feasibility-study (RI/FS) phase, with field work expected in February 2026; Parsons Corporation has been contracted for RI/FS work through 2030.

Agency staff emphasized that some regulatory benchmarks (for example, state or federal maximum contaminant levels) are not yet established for all PFAS compounds and that the board and partners are using interim action levels and a hazard-index approach for screening and immediate response. US EPA Region 9 indicated it would provide funding flexibility through existing State Revolving Fund allocations, technical assistance for treatment selection and help procuring short‑term and permanent treatment options.

Next steps: GWA will continue to install DACC systems at Y‑15, complete distribution modifications to remove a portion of customers from that distribution zone where possible, implement the reimbursement plan for POE/POU units, and coordinate with Guam EPA, DOH/DHSS and US EPA on further sampling and site‑specific response planning.