The Margin - The Margin

What officials knew
What the public knew
2008
2021
2023
2025
2026
Oct. 13, 2008

Dieldrin measured at 1.7 µg/L in Well Y-15, roughly eight and a half times the standard Guam would eventually adopt.

Oct. 2008–June 2021

No sampling at Y-15. Thirteen years with the well absent from the monitoring record.

June 27, 2021

Y-15 peaks at 1.9 µg/L, the highest reading ever recorded there.

Oct. 20, 2023

EPA threatens federal enforcement against GWA over dieldrin.

July 16, 2025

Contractor writes a brief notification letter, addressed to Guam EPA, that contaminated soil will be encapsulated.

Sept. 12, 2025

GWA sends some Yigo residents a letter advising them not to drink the tap water without treatment due to the presence of dieldrin in the groundwater.

Oct. 27–28, 2025

Guam EPA receives the 2024 soil management plans, thirteen months after they were written and only after asking military contractors.

Dec. 23, 2025

Guam EPA and U.S. EPA formally asked Joint Region Marianas to investigate potential sources of dieldrin contamination on the base.

June 15, 2026

Guam EPA senior science advisor tells U.S. EPA “there’s rumors that maybe JRM isn’t sharing all of the data that they already have.”