City Council Agenda
Memo to: Manteca City Council
From: George Montross, Director of Utilities
Date: November 17, 2026
Subject: PFAS Chemical Detections at City Wells
title
Approve a resolution acknowledging that the Manteca City Council was notified by staff that various Per- and Polyfluoroalkyl Substances, chemicals commonly used in a wide range of industrial processes, were detected in raw groundwater from several City Wells at levels exceeding the State Water Board’s Division of Drinking Water (DDW) Notification Level and authorize staff to forward the resolution to the DDW.
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Background:
On April 10, 2024, the United States Environmental Protection Agency announced the final National Primary Drinking Water Regulations for several Per- and Polyfluoroalkyl Substances (PFAS) chemicals, see table below. As part of the regulation, all public water systems were required to conduct initial monitoring for these PFAS chemicals. The City of Manteca completed the initial monitoring and several groundwater wells had PFAS chemical detections. These detections were reported to City Council on October 21, 2025. The City continues to monitor our groundwater wells for these PFAS chemicals and during 2026 we had Perflouorooctanoic Acid (PFOA) and Perfluorohexane Aulfonic Acid (PFHxS) detections, requiring new notifications.
Additionally, on October 29, 2025, the State of California updated their Notification Level (NL) and Response Levels (RL). Several PFAS chemical NL and RL concentrations were lowered and one chemical was added to the list, see table below:
|
Chemical Name |
Abbreviation |
Notification Level (NL) |
Response Level (RL) |
What Changed? |
|
Perflouorooctanoic Acid |
PFOA |
4.0 ppt |
10 ppt |
Lowered NL from 5.1 ppt |
|
Perfluorooctane Sulfonic Acid |
PFOS |
4.0 ppt |
40 ppt |
Lowered NL from 6.5 ppt |
|
Perfluorobutane Sulfonic Acid |
PFBS |
500 ppt |
5,000 ppt |
No Change |
|
Perfluorohexane Aulfonic Acid |
PFHxS |
3.0 ppt |
10 ppt |
Lowered RL from 20 ppt |
|
Perfluoroheptanoic Acid |
PFHxA |
1.0 ppb |
10 ppb |
New Addition |
|
Perfluorononanoic Acid |
PFNA |
NA |
NA |
No Change |
Notification Levels are advisory levels and not enforceable standards, DDW requires public water systems to notify their governing body and to include the detections in the annual Consumer Confidence Report (CCR). Both notifications need to include the health based risks associated with these chemicals. For PFOA, exposure has resulted in increased liver weight and cancer in laboratory animals and PFHxS exposure has resulted in decreased total thyroid hormone in male rats. The Utilities Department has included this information in our prior annual CCRs and will include it in future CCRs.
It is important to note that the PFAS detections are in the City’s raw groundwater supply. The City treats the majority of its groundwater, so nearly all the raw detections were treated and the concentrations were removed or reduced before being distributed to our customers, see the Average Treated Concentration column in the table below.
Of the detections, see table below, all the levels are reduced below the NL, except for two wells. Well 22, located at 364 Victory Avenue, is blended with surface water to reduce arsenic concentrations below the allowable limit. The volume of surface water used for blending isn’t enough to reduce the PFAS level below the NL. The Engineering Department has completed design of a treatment system to remove PFAS and they are currently moving into the construction phase. Well 17, located at 658 Pestana Avenue, is the latest well with a PFAS detection. This well doesn’t have any treatment, the Engineering Department is working on design of a PFAS treatment system. In the meantime, Well 17 will be used as little as possible.
Below is a table listing the type of PFAS chemical detected, the impacted well, the average raw water concentration, the type of treatment present, the average treated concentration level and the notification level:
|
PFAS Chemical Detected |
Well Number |
Average Raw Concentration |
Type of Treatment |
Average Treated Concentration |
Notification Level Concentration |
|
PFOA |
|
|
|
|
|
|
|
17 |
4.2 ppt |
None |
4.2 ppt |
4.0 ppt |
|
|
19 |
6.2 ppt |
Carbon |
0.0 ppt |
4.0 ppt |
|
|
21 |
32.0 ppt |
Carbon |
0.0 ppt |
4.0 ppt |
|
|
22 |
7.0 ppt |
Blending |
2.6 ppt |
4.0 ppt |
|
PFHxS |
|
|
|
|
|
|
|
12 |
3.2 ppt |
Blending |
2.0 ppt |
3.0 ppt |
|
|
16 |
3.4 ppt |
Blending |
2.0 ppt |
3.0 ppt |
|
|
19 |
8.4 ppt |
Carbon |
0.0 ppt |
3.0 ppt |
|
|
21 |
27.0 ppt |
Carbon |
0.0 ppt |
3.0 ppt |
|
|
22 |
21.0 ppt |
Blending |
8.2 ppt |
3.0 ppt |
Fiscal Impact:
There is no fiscal impact associated with this notification.
Documents Attached:
Attachment 1 - Resolution