City Council Agenda
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Memo to: |
Manteca City Council |
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From: |
Jose Jasso, Assistant City Manager / Interim Director of Public Works |
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Prepared by: |
George Montross, Deputy Director of Public Works / Water Resources |
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Date: |
October 21, 2025 |
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Subject: |
Adopt a Resolution Acknowledging the Detection of Perfluorooctanoic Acid (PFOA) and Perfluorohexane Sulfonic Acid (PFHxS) at Wells 19 and 22 |
Recommendation:
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Adopt a resolution acknowledging that the Manteca City Council was notified by the Public Works Department that Perfluorooctanoic Acid (PFOA) and Perfluorohexane Sulfonic Acid (PFHxS), chemicals commonly used in a wide range of products and industrial processes, were detected in raw water source samples from Wells 19 and 22, at levels exceeding the State Water Board’s Division of Drinking Water (DDW) Notification Levels; and authorize the Public Works Department to forward the resolution to the DDW.
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Background:
Raw water samples collected from Wells 19, located at 290 South Powers Avenue, and 22, located at 376 Victory Avenue, had detections of Perfluorooctanoic Acid (PFOA) and Perfluorohexane Sulfonic Acid (PFHxS) above the State Water Resources Control Board’s Division of Drinking Water (DDW) Notification Levels.
Notification levels are nonregulatory, health based advisory levels and not enforceable standards. DDW requires notification of the City Council of exceedances, including to provide information on the health based risks associated with these chemicals. The health based risks associated with PFOA and PFHxS include problems with the liver, immune system, thyroid and may lead to an increased risk of certain cancers, including testicular and kidney cancers.
The highest detections are from the raw water supply, not from treated water which is distributed to customers. Treated water sample results from Well 19 are in compliance with DDW Notification Levels. Treated water sample results from Well 22 for PFOA are in compliance, however PFHxS levels were reduced, but not below the notification level.
Table A, below, shows the sample results and notification levels (NL):
Table A
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Date |
7/15/2025 |
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9/16/2025 |
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Average |
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NL |
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9/16/2025 |
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Type |
Raw |
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Raw |
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Raw |
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Treated |
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Well # |
19 |
22 |
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19 |
22 |
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19 |
22 |
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19 |
22 |
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PFOA (ppt) |
5.6 |
7.0 |
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5.7 |
5.9 |
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5.7 |
6.5 |
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5.1 |
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0 |
2.8 |
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PFHxS (ppt) |
7.3 |
18 |
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0 |
19 |
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3.6 |
19 |
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3 |
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0 |
7.5 |
The initial PFOA and PFHxS detections occurred on July 15, 2025, the DDW requires confirmation samples to be collected following a detection, which was done on September 16, 2025. The two samples are averaged in order to determine compliance. The averaged PFOS sample results for Wells 19 and 22 were 5.7 ppt and 6.5 ppt, respectively, which are above the DDW’s Notification Level of 5.1 ppt. The averaged PFHxS sample results for Wells 19 and 22 were 3.6 ppt and 19 ppt, respectively, which are above the DDW’s Notification Level of 3 ppt.
The treated sample results for Well 19 are non detect, as this water flows to an existing granular activated carbon (GAC) treatment system, which completely removes organics. At Well 22, the water is blended with surface water to reduce the concentration of arsenic. The treated water sample results for PFOS are reduced to 2.8 ppt, which is below the notification level of 5.1 ppt. For PFHxS, the treated water sample results were reduced to 7.5 ppt, which is above the Notification Level of 3 ppt.
Due to the inadequate treatment of PFHxS at Well 22, a treatment system with GAC is being designed to completely remove both PFOS and PFHxS.
DDW also recommends that water customers be notified in the annual Consumer Confidence Report. The Public Works Department will include these detections in our 2025 Consumer Confidence Report.
Protecting public health and ensuring our water is safe to drink remains the highest priority of the City’s Public Works Department. The water is safe to drink.
Fiscal Impact:
There is no fiscal impact associated with this acknowledgment.
Documents Attached:
1. Attachment 1 - Resolution