Dieldrin Testing Data - April 8, 2026

On March 25, 2026 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 25 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.