Dieldrin IAL Update Release No. 4: FOR THE THIRD WEEK IN A ROW, TEST RESULTS SHOW NO DETECTION OF DIELDRIN AT WELL Y-15, TREATMENT SOLUTION SUCCESSFUL

No dieldrin has been detected at well Y-15 in Yigo after treatment, according to confirmed laboratory analysis after three rounds of testing.  The results of “non-detect” continues to affirm the Guam Waterworks Authority’s (GWA) interim treatment system at well Y-15 has successfully removed dieldrin levels. This system, completed on Oct. 10, uses granular activated carbon (GAC) filtration, an EPA-approved and proven technology used to remove contaminants like dieldrin and PFAS from drinking water.

Dieldrin analysis is performed by Eurofins Eaton Analytical, an EPA-certified laboratory in California.  GWA continues conducting weekly sampling at Y-15 at the request of Guam EPA to ensure the system’s efficacy to comply with the interim action level (IAL) for dieldrin. After one more consecutive week of satisfactory laboratory results, GWA will confer with Guam EPA to lift the “Do Not Drink without Treatment” advisory issued to affected GWA customers in the Yigo/Santa Rosa area.

GWA will continue to operate the interim GAC treatment system at well Y-15 until the permanent treatment system is completed, performing monthly sampling and analysis for dieldrin after the initial four consecutive weeks of sampling is complete. Results will be shared with the public and will be available for review by visiting guamwatersafety.com. Additionally, GWA will provide timely updates on progress toward the 2026 permanent treatment system.

DIELDRIN LEVELS BELOW INTERIM ACTION LEVELS AT MOST WELLS

In addition to well Y-15, only one other well showed running annual averages above Guam EPA’s IAL for dieldrin: D-17 in Dededo which was taken offline July 31, 2025. The table below provides additional information about dieldrin levels in all of GWA’s entry points as of Oct. 21, 2025:

DIELDRIN INFORMATION HOTLINE HOURS ADJUSTED

GWA customer service call center has returned to normal hours of Monday through Friday from 7:30 a.m. to 6 p.m. and Saturday from 8 a.m. to noon. Customers can reach the call center at 671-647-7800 / 7803. Additionally, customers may submit 

questions and service requests to the online customer portal at gwa.custhelp.com at their convenience.

The return to normal hours comes after GWA previously offered extended call center hours for customer questions regarding the recent dieldrin IAL announcement at well Y-15 in the Yigo/Santa Rosa area. Residents with questions about their water service or quality are encouraged to visit guamwatersafety.com for the latest news and updates.

The Guam EPA has also established a hotline at 671-888-4342 for customers who have health risk or water safety questions, available Monday through Friday 8 a.m. to 5 p.m.

Visit guamwatersafety.com to stay up-to-date on GWA’s latest action to fight legacy contaminants in Guam’s groundwater. 

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