Lawmakers are continuing close oversight of Guam’s response to dieldrin detected in the island’s water system. At the latest joint hearing, agencies laid out what’s been done so far to contain the contamination, identify its source, and improve how the public is kept informed.

Since dieldrin was first detected last year, the Guam Waterworks Authority says its immediate focus has been stopping exposure and stabilizing the system. GWA assistant general manager Brett Railey reports that interim treatment systems are now in place at affected wells, including Well Y-15 in Yigo, and that since installation, water entering the distribution system has remained non-detect for dieldrin.

The agency continues monthly monitoring of wells that exceed 50% of the interim action level, while more than 300 households have requested point-of-entry treatment systems. He adds that permanent treatment systems are now on-island and will be installed once construction pads are completed.

Installations for wells D-17, M-4, and Y-15 remain on schedule for completion by summer.

And the Guam Environmental Protection Agency has been leading efforts to identify where the contamination may have come from, as administrator Michelle Lastimoza says it has identified a possible sources of dieldrin on Andersen Air Force Base, and, alongside the US EPA, has formally requested an investigation by Joint Region Marianas.

“In partnership with USEPA, we did provide a joint letter to Joint Region Marianas to initiate investigation of a dieldrin source on Andersen Air Force Base," said Lastimoza. She says decades-old data indicating potential dieldrin hotspots on the base helped justify their request.

At the same time, Guam EPA senior science advisor Captain Elizabeth Degrange is expanding its risk evaluations beyond drinking water, including Tumon Bay and possible impacts to the food chain. She explained, “The levels in the water there are 100 times lower than what we saw in Y-15. We are fairly certain there is no additional risk to the community through dermal exposure. Our bigger concern is consumption of larger fish.”

EPA has also requested additional testing of crops and soil in Northern Guam and a Public Health assessment to determine whether further action is needed. As agencies coordinate mitigation and investigation, officials acknowledge communication gaps with the public.

Environmental health specialist for the island's Safe Drinking Water Program Juliana Mendoza said, "We made assumptions that we did public outreach in these past two years, but it’s not enough and we are hearing the public. With that said, moving forward we’ll do more public outreach and be more proactive with public education.”

As oversight continues, agencies say coordination, accountability, and timely public information remain key to rebuilding trust and ensuring Guam’s water remains safe.