Guam Water Authority outlines response after dieldrin detected in Jigo well; interim treatment due in October

Guam Water Authority General Manager Miguel Bergadio told the Mayor’s Council of Guam on Tuesday that the pesticide dieldrin has been found in multiple source wells across the island and that one large producing well serving the Jigo area (Y15) exceeded Guam Environmental Protection Agency’s interim action level of 0.2 parts per billion.

Bergadio said GWA has allocated more than $7 million for design and construction of permanent granular-activated-carbon (GAC) treatment systems at three affected wells and received legal approval to award a construction contract on Sept. 11, 2025. The single bid for the three-site project was $7.14 million, above the engineer’s estimate; GWA secured additional funding and the contractor is scheduled to complete permanent systems in 2026. In the near term, Bergadio said an interim flow‑reduction and two‑vessel treatment system is being built and GWA expects it to be operational by mid‑October, after which GWA will collect repeat samples; Guam EPA has agreed to lift the public advisory for the Jigo area after four consecutive non‑detect sampling events.

Why it matters: Dieldrin is a pesticide that was widely used decades ago as a termiticide and was banned nationally in 1987. Because the chemical persists in soils and groundwater, regulators and the water utility must balance public‑health protection with the immediate need to maintain water supply from a large producing well. Bergadio told mayors that shutting Y15 without…