Guam Waterworks Authority completes installation of dieldrin-treatment system at Yigo well

By Pacific Island Times News Staff

The Guam Waterworks Authority has installed its interim treatment system at a dieldrin-contaminated well in Yigo, completing the first step toward the eventual rescission of the “do not drink without treatment” advisory issued to 1,112 customers.

 “With the installation of this treatment system, our community can be assured that the water supply meets all federal and local drinking water standards while we continue working toward our long-term solution for Y-15,” said Miguel C. Bordallo, GWA general manager.

GWA issued a Tier 1 advisory for dieldrin on Sept. 12, affecting customers in the Santa Rosa area. Dieldrin is a federally unregulated, carcinogenic chemical used as an insecticide and termiticide from the 1950s until 1987.

The interim treatment system uses granular activated carbon filtration, GWA explained, adding that the EPA-approved technology has been proven effective in removing contaminants like dieldrin and PFAS from drinking water.

GWA said it will conduct weekly sampling at Y-15 at the request of the Guam Environmental Protection Agency to ensure the system’s efficacy to comply with the Interim Action Level for dieldrin.

 “Analysis will be expedited and performed by an EPA-certified laboratory in the U.S.,” GWA said.

“After four consecutive weeks of satisfactory laboratory results, GWA will confer with Guam EPA to lift the advisory that was issued to affected GWA customers in the Santa Rosa/Yigo area.”

GWA said the initiative on a full-scale treatment solution to address dieldrin and other potential contaminants across its system began in 2023. It is a multi-year project that is expected to be completed by summer 2026. 

“The investment made in the full-scale treatment facilities will provide a long-term safeguard to ensure drinking water remains safe and reliable for the community,” GWA said.

As part of coordinated efforts with Guam EPA and the Office of the Governor, GWA has implemented measures to assist affected customers, including bottled water distribution, which began on Oct. 2.

On Oct. 10, GWA initiated procedures for reimbursements of customer-purchased point-of-use and point-of-entry treatment systems.

Guam EPA has partnered with the Guam Department of Agriculture to inspect farms and develop a sampling and testing strategy to help GWA better assist with dieldrin contamination and related risks.

Online resources: Results of monthly sampling will be available for review on guamwatersafety.com. Additionally, GWA will provide timely updates on progress toward the 2026 permanent treatment system. Guam EPA has added a direct link to dieldrin-related information to their website’s homepage, available in the upper right-hand corner, and also at epa.guam.gov/dieldrin-information.

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