GWA Provides Fifth Mitigation Update to Sen. Lujan – May 27, 2026

On May 27, 2026, the Guam Waterworks Authority (GWA) provided a followup to the the Authority's May 1 update on GWA's dieldrin mitigation efforts following the conclusion of a joint oversight hearing held by the 38th Guam Legislature.

Point-of-Entry (POE) Program – INSTALLATIONS NOW IN PROGRESS:

• American Watertek began installing POE units on May 19, 2026 – with 39 installations completed as of this writing. SBS Guam began installing POE units on May 25, 2026 – with 16 installations completed as of this writing.

  
  

• 215 home assessments have been completed, with 141 home assessments pending. Pending assessments are the result of scheduling conflicts with the customer and our contractors, or non-responsiveness from the customer to confirm scheduling.

• GWA Customer Care Representatives continue to work with our contractors to coordinate installations and home assessments.

Although an interim granular activated carbon (GAC) treatment system was commissioned for well Y-15 in Yigo on October 12, 2025 and has been producing water without any detections of dieldrin since commissioning, GWA POE applications will be accepted from now and until within 30 days of date of GWA commissioning of the permanent GAC treatment system at well Y-15 in Yigo. The commissioning date for all three GAC treatment systems is forthcoming.

GAC Treatment System Construction:

• On May 7, the Public Utilities Commission (PUC) issued an order to approve GWA’s petition to increase the Authority’s existing contract with A & R Pacific-Garney Federal JV for GAC treatment system construction at wells D-17, M-4 and Y-15. As a result of the PUC’s approval, the contract was ratified to authorize an additional $5.2M to support change orders which strengthen GWA’s treatment system capacity – including treatment at well M-3.

• GAC vessels have been refurbished and relocated to Well M-4. Vessels have been mounted to concrete pads. Plumbing and valving work is in progress.

• Concrete pad construction to support four (4) GAC vessels at well Y-15 in progress. Once the pad is cured, vessel mounting, plumbing and valving work will begin.

• After Y-15’s permanent GAC treatment system results in four (4) consecutive weeks of non-detect levels of dieldrin, the interim treatment GAC vessels originally commissioned on October 12, 2025 will be refurbished and relocated for commissioning at Well D-17.

• Concrete pad construction at well D-17 was completed on April 18.

• At this time, construction competition for well D-17 is by or before September 30, 2026, and wells M-4 and Y-15 by or before June 30, 2026.

Dieldrin Testing Data from Samples Collected May 6, 2026:

In our May 1 update, GWA had previously reported the status of entry points that tested higher than, or equal to 50% of the IAL for dieldrin. The table below provides a status update to the May 1 report with analytical data from samples collected on May 6, 2026:

Dieldrin Sampling Results - Running Annual Average (RAA) – 124 SAMPLE LOCATIONS
Wells	RAA	Remarks
30	Non-Detect (ND)	• No detections for dieldrin
87	0.01 ppb to 0.09 ppb	• 86 locations are less than 0.1 ppb or 50% of the IAL • D-17 offline since 7/31/25; treatment under construction. Result for samples taken on 3/10/26 is 0.1 ppb. RAA is 0.09 ppb.
4	0.10 ppb to 0.14 ppb	• A-23 & A-25 offline for PFAS since 2016; treatment under construction • M-2 & D-18 remain online; RAAs for both are 0.14 and neither has had RAA over the IAL.
3	0.15 ppb to 0.19 ppb	• M-4 offline since 10/3/25; RAA is 0.16 ppb; treatment under construction • M-3 was placed on standby mode on 10/19/25 and will only be placed online intermittently if needed operationally to meet customer demand; Result for samples taken on 5/6/26 is 0.18 ppb; RAA is 0.17 ppb; M-3 was placed offline on 01/26/26, but was temporarily activated from 04/07/26 – 05/18/26 for Super Typhoon Sinlaku recovery and customer demand. • EX-11 remains online and has not had a RAA over the IAL; Result for samples taken on 5/6/26 is 0.15 ppb; RAA is 0.15 ppb.

On May 21, 2026, the Guam Environmental Protection Agency (GEPA) board of directors passed a resolution to amend the Risk Assessment Document (RAD) for dieldrin. GWA provided comments and feedback on the proposed amendments to the RAD in March. As you and your colleagues may recall, the RAD is GEPA’s official document which contains the established IAL for dieldrin, provides public notification requirements for all public water systems, and sets the monitoring frequency and reporting requirements for dieldrin in entry points within our distribution system.

The amended RAD will require GWA to increase dieldrin monitoring at wells with GAC treatment systems to a monthly basis. Most other wells within GWA’s distribution system will be subject to quarterly monitoring, or reduced monitoring for wells with minimal to non-detection levels of dieldrin.

However, in an ongoing effort to exercise due diligence, GWA has made the decision to increase the frequency of monitoring certain wells which show results at the “half-IAL,” or 50% of the IAL, as part of our mitigation efforts. The next monthly sampling for dieldrin is scheduled for June 2, 2026.

GWA will continue to provide timely and pertinent updates to the community as they become available. As a reminder, information about dieldrin mitigation may also be found on GWA’s microsite: guamwatersafety.com.