Guam EPA revises Y‑15 well risk assessment; plans public comment and press release as testing regime is clarified

Guam Environmental Protection Agency staff presented proposed updates Nov. 13 to the agency’s interim action level (IAL) risk assessment for the Y‑15 well and other water systems affected by PFAS. The changes add specific monitoring and mitigation requirements staff say will make it clearer when treatment can be deemed effective and a public advisory could be lifted.

"We want at least four weekly samples for consecutive weekly samples to verify that the treatment that is in place is non‑detect or less than half of the interim action level," Shannon, the presenting agency staffer, told the board, explaining that weekly testing would be followed by monthly checks for a minimum of 12 months to detect possible breakthrough and to ensure the treatment is being maintained.

Shannon said the draft updates were informed by recent input from U.S. EPA and include clearer criteria for when the agency can reduce monitoring and when it should increase it. The revised language would also require a mitigation plan when an exceedance occurs and set out how a public water system would supply safe drinking water while returning to compliance.

Public process and communications: Agency staff said they would send corrected draft language to the board by close of business the next day and planned to post the draft for public comment — likely starting the coming Friday — for two to three consecutive weeks. Acting Guam Water Authority General Manager Chris Budassy asked Guam EPA to allow GWA to tell the public that treated water from Y‑15 is safe after treatment.

"I just wanna request for [GWA] to go out and make a public statement that the water coming out of the Y‑15 well after treatment is safe," Budassy said, citing anxiety among affected customers. Shannon and other Guam EPA staff said they would prepare a press release and are finalizing a formal letter and regulatory steps that must be completed before any advisory is lifted.

Next steps: Guam EPA staff said they expect to return to the board after the public comment period with responses to comments and a recommended final document, with the aim of having the item ready for the December meeting. Staff also noted ongoing coordination with U.S. EPA, ATSDR and local health officials on sampling, source investigation and possible epidemiological work.

What remains open: The board did not approve the revised risk assessment on Nov. 13; the draft will go out for comment and staff will return with agency responses and a recommended action. The timing of any change to public advisories depends on the monitoring results and completion of the agency’s regulatory signoffs.