GWA Provides Third Mitigation Update to Sen. Lujan – Mar. 25, 2026

On March 25, 2026, the Guam Waterworks Authority (GWA) provided a followup to the the Authority's February 25 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:

• As of March 20, 2026, GWA has received 352 applications for POE provision and installation. Nine applications were cancelled at the request of the customer.

• Since January 28, 2026, GWA has completed 276 home assessments. As of March 20,

  34 home assessments are pending completion. GWA customer care representatives

  continue contacting POE applicants to schedule all remaining home assessments.

• POE treatment systems are en route to Guam, and assessed customers will be contacted to schedule final installations once systems arrive in Guam.

  
  

  • American Watertek informs GWA that 80 POE units are expected to arrive in

    Guam by the end of this month. American Watertek further informs GWA that the

    remaining units are anticipated to ship from the manufacturer in two weeks.

  • SBS Guam informs GWA that POE units are expected to arrive in Guam in late

    May 2026.

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 March 17, 2026, the Consolidated Commission on Utilities (CCU) unanimously passed and adopted GWA Resolution 14-FY2026, relative to the approval to increase funding for deep wells Y-15, D-17 and M-4 GAC systems for dieldrin treatment. The

  resolution increases the project funding by an additional $5.27M. The increase in funding will benefit customers and afford GWA the opportunity to:

  
  

  • Install BMPs to address endangered species (Samoana Fragilis) found onsite at

    well M-4.

  • Modifications to construction work at well Y-15 to accommodate a 4-vessel

    system in place of the 2-vessel design originally planned as the permanent

    treatment system.

  • Adding 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 has demonstrated 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 is anticipated as follows:

  
  

  • Well D-17: By or before September 30, 2026

  • Wells M-4 and Y-15: By or before June 30, 2026

Dieldrin Testing Data from Samples Collected March 10, 2026:

• In our February 25 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 February 25, 2026 reporting with analytical data from samples collected on March 10, 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
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 0.014 and neither has had RAA over the IAL.
4	0.15 ppb to 0.19 ppb	• M-4 offline since 10/3/25; RAA is 0.16 ppb; treatment under construction • M-3 is was placed on standby on 10/19/25; placed online intermittently only if needed operationally to meet customer demand; Result for samples taken on 3/10/26 is 0.15 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 3/10/26 is 0.15 ppb; RAA is 0.15 ppb. • 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.

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 April 9, 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.