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Drinking Water Warning Do Not Drink without Treatment Advisory

  • GWA News
  • Sep 26
  • 3 min read

Updated: Oct 3

Originally released by GWA on September 8, 2025 (UPDATED: 09/29/2025)


The Santa Rosa Area of Northern Water System PWS ID# GU0000006 has high levels of dieldrin


This notification only affects the Santa Rosa service area identified in the map below.


Have more questions? Visit our FAQ page for more answers, or send us your questions via our contact page.
Have more questions? Visit our FAQ page for more answers, or send us your questions via our contact page.

Please share this information with all other people in the Santa Rosa area who drink this water, especially those who may not have received this notice directly (e.g. people in apartments, nursing homes, schools, and businesses).


This notice is being sent to you by: Guam Waterworks Authority PWS ID#: GU0000006 • Date distributed: Sept. 8, 2025 (reposted here on this website on 09-26-2025)


GWA has been proactively testing your drinking water for potential contaminants that are unregulated by U.S. EPA. On July 30, 2025, GWA received notice that the samples collected from December 19, 2024, to July 30, 2025 showed dieldrin levels of an average 1.75 micrograms per liter (μg/L = parts per billion = ppb) from one of the wells serving your area. This is above the dieldrin Interim Action Level (IAL) of 0.2 μg/L, established by Guam EPA and effective August 1, 2025. It also exceeds the IAL for the short-term, non-cancer health advisory concentration of 0.5 μg/L. Out of an abundance of caution, GWA is informing the affected customers of these findings.


WHAT DOES THIS MEAN?

Dieldrin is classified by the U.S. EPA as a probable human carcinogen. The Water supplied by this public water system in your area exceeds the dieldrin IAL and potentially represents an unacceptable long-term cancer risk. Lifetime consumption of water containing dieldrin above the IAL increases the likelihood of developing cancer. Drinking water containing dieldrin is also associated with a wide range of adverse, non-cancer health effects at concentrations of 0.5 micrograms per liter or more; it has been associated with an increased likelihood of adverse impacts on the liver and nervous system.


WHAT SHOULD I DO?

You should not drink or cook with water that contains dieldrin above the IAL without treatment. The most reliable form of treatment is granular activated carbon filters installed by your Public Water System (utility). Until a treatment system can be installed by your Public Water System, Guam EPA recommends that you obtain water for drinking and cooking from a Department of Public Health and Social Services-approved drinking water vendor, a GWA water tanker posted in your area, or a Point of Use (POU) device located at your home that includes granular activated carbon as part of its treatment process. A POU device is a treatment device installed at a single faucet or spigot for the purpose of reducing contaminants in drinking water at the source of installation. You should ensure that any POU device used in your home is certified by the National Sanitation Foundation (NSF) to meet the NSF-53 or 401 Standards. Also make sure you replace the granular activated carbon filter in accordance with the POU device manufacturer’s recommendations.


WHAT IS BEING DONE?

GWA has been working diligently to install an approved treatment system, at the affected well site. Funding for the multi-million-dollar improvements has been obtained, design work has been completed, and a construction contractor has been selected for the work. It will take approximately one (1) year for this work to be completed. With regard to the source of this pesticide in this limited area, the Guam Environmental Protection Agency has not identified the source of Dieldrin as of this time.



For more information about the issues of dieldrin, visit epa.guam.gov/sdw or contact Julie Mendoza, Guam EPA Environmental Health Specialist III at julie.mendoza@epa.guam.gov.


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You can also point your smartphone camera at the QR code above for information about dieldrin from Guam EPA.


NEW! For questions regarding health risks and water quality contact the Guam EPA hotline at 671-888-4342 7AM-9PM daily.


For more information on GWA’s water compliance requirements, contact Paul Kemp, Assistant General Manager for Compliance & Safety at compliance@guamwaterworks.org or by mail at Gloria B. Nelson Public Service Building, 688 Route 15, Mangilao, Guam 96913.


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