GWA Provides Fourth Mitigation Update to Sen. Lujan – May 1, 2026

On May 1, 2026, the Guam Waterworks Authority (GWA) provided a followup to the the Authority's March 25 update on GWA's dieldrin mitigation efforts following the conclusion of a joint oversight hearing held by the 38th Guam Legislature.

GWA is pleased to report that post-storm assessments performed on well Y-15 and the interim granular activated carbon (GAC) treatment system confirm that the well, GAC vessels, plumbing and valving were not damaged by Super Typhoon Sinlaku and are operating normally.

This update is provided to you and your colleagues as a follow up to our second dieldrin mitigation effort update transmitted to your office on March 23, 2026:

Point-of-Entry (POE) Program:

• American Watertek plans to begin installing POE units on May 19, 2026. GWA customer care representatives will be contacting applicants to schedule installations. American Watertek received a partial shipment of POE units and hardware on April 6, and informs GWA that the remaining order is expected to arrive on island on May 6.

  
  

• SBS Guam informs GWA that additional POE units and hardware are expected to arrive on island on May 18. A planning meeting with SBS Guam to execute installations is forthcoming and an update will be provided in May.

• As of April 3, 2026, GWA has received 355 applications for POE provision and installation. Nine applications were cancelled at the request of the customers.

• Thirty (30) home assessments are pending scheduling. GWA customer care representatives are experiencing difficulty in contacting these remaining 30 customers and will continue attempts to contact them.

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 then, GWA POE applications will 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 April 6, GWA filed a petition with the Public Utilities Commission (PUC) to request PUC approval to increase GWA’s existing contract with A & R Pacific-Garney Federal JV for GAC treatment system construction at wells D-17, M-4 and Y-15. This petition with the PUC follows the Consolidated Commission on Utilities (CCU) adoption of GWA resolution 14-FY2026. The increase in funding will benefit customers and afford GWA the opportunity to:

  
  

  • Add BMPs to address endangered species (Samoana Fragilis) found at well M-4.

  • Modify construction work at well Y-15 to build a 4-vessel system in place of the 2-vessel design originally planned as the permanent treatment system.

  • Add treatment to well M-3 by installing a transmission line linking this well to well M-4’s GAC treatment system.

  • Procure three (3) additional GAC treatment systems to increase GWA’s treatment capacity and response to dieldrin and other emerging contaminants.

  • Procure GAC media, GAC system storage and GAC media storage

  
  

• Well Y-15’s interim treatment system will remain online until the permanent GAC treatment system is installed and is tested to yield non-detect levels of dieldrin for four (4) consecutive weeks.

• 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.

• 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 April 8, 2026:

• In our March 23 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 March 23 reporting with analytical data from samples collected on April 8, 2026:

Dieldrin Sampling Results - Running Annual Average (RAA) – 124 SAMPLE LOCATIONS
Wells	RAA	Remarks
30	Non-Detect (ND)	• No detections for dieldrin
86	0.01 ppb to 0.09 ppb	• 86 locations are less than 0.1 ppb or 50% of the IAL
5	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. • D-17 offline since 7/31/25; treatment under construction. Result for samples taken on 3/10/26 is 0.1 ppb. RAA remains at 0.09 ppb.
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 4/8/26 is 0.17 ppb; RAA is 0.16 ppb; M-3 was placed offline on 01/26/26. • EX-11 remains online and has not had a RAA over the IAL; Result for samples taken on 4/8/26 is 0.14 ppb; RAA is 0.15 ppb.

The Guam Environmental Protection Agency’s (GEPA) current IAL requires that all entry points (wells) in a public water system must be tested for dieldrin on a quarterly basis. 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 May 6, 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.