Following the discovery by the Arizona Department of Environmental Quality (ADEQ) of two PFAS chemicals, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in two City wells in the airport area in early July, which were immediately turned off, the City requested that ADEQ sample the additional City production wells located in Chino Valley. At the same time, the City employed an independent lab to test all City water production wells. Those results have come back, resulting in barely detectable levels of PFOA in three of four operational Chino Valley wells and detectable levels of PFOS and PFOA in Airport Well No. 5. PFAS were not detected in Chino Valley Well No. 4, Airport Well No. 2, and Airport Well No. 3. Consequently, Airport Well No. 5 will remain off-line. Since Airport Well No. 3 came back as non-detectable for the chemicals, it will be placed back into service.
Since PFAS were detected for the first time in 3 of 4 Chino Valley wells, City staff will make operational changes to minimize levels of PFAS in city potable water supplies by turning off Well Nos. 3 and 5 and blending water from Well Nos. 2 and 4 before sending it to customers. It is expected that this blending plan will result in non-detectable levels of PFAS in city potable water supplies.
The most recent City test results are shown in the table below:
| Well | PFOS (ppt) | PFOA (ppt) | Detection Limit |
| Chino 2 | ND | 2.84 | <1.89 |
| Chino 3 | ND | 3.06 | <1.80 |
| Chino 4 | ND | ND | <1.67 |
| Chino 5 | ND | 2.21 | <1.72 |
| Airport 2 | ND | ND | <1.76 |
| Airport 3 (raw) | ND | ND | <1.82 |
| Airport 3 (treated) | ND | ND | <1.84 |
| Airport 5 | 8.1 | 12.4 | <1.85 |
ppt=parts per trillion
As a reference point, one part per trillion is equal to ¾ of a teaspoon in Watson Lake, so these test results show extremely low levels of PFAS in four City potable water supply wells.
The City will regularly test for PFAS in its potable water supply to continue to maintain adequate quantities of safe, clean drinking water. As test results are received, City staff will immediately inform the public and quickly make operational changes to minimize the introduction of PFAS into City potable water supplies.
PFAS have been extensively produced and used since the 1940s. Some firefighting foams used to extinguish oil and gas fires contain PFAS. These chemicals have also been used in a number of industrial processes and to make carpets, cosmetics, clothing, fabrics for furniture, paper packaging for food, cookware, etc., that are resistant to water, grease and stains. Because these chemicals have been used in many consumer products, most people have been exposed to them. While consumer products and food are the largest source of exposure to these chemicals for most people, drinking water can be an additional source of exposure in communities where these chemicals have contaminated water supplies. This is an emerging issue that is affecting nearly 3,000 sites in 50 states and 2 US territories as of June 2022. As we learn more, the City of Prescott is committed to be at the forefront of efforts to protect our citizens.
Currently, the US Environmental Protection Agency (EPA) is developing guidance referred to as Health Advisory Levels (HALs). As the EPA continues to research the chemicals, they have continued to lower the minimum level in their guidelines. While Prescott’s wells were far below the previous HAL of 70 parts per trillion (ppt), in June 2022, the EPA announced a lower HAL of 0.02 ppt for PFOS and 0.004 ppt for PFOA. Please note that HALs are only recommendations; they are not yet regulatory requirements. Therefore, the City of Prescott remains in compliance with all applicable potable water quality regulations established by the EPA and ADEQ.
If you are concerned about PFOA/PFAS, you can get more information from the EPA. PFAS Explained | US EPA. If you have young children and/or members of a sensitive subgroup, you should speak to your doctor. For older children and adults (not in a sensitive subgroup), the HAL is applicable to a lifetime of consuming contaminated water. For these groups, shorter duration exposures present less risk. However, if you are concerned about your exposure while steps are being taken to assess and lower the PFAS concentration in the drinking water, use of PFAS-free bottled water could reduce your exposure.
Use of home water treatment systems that are certified to remove PFAS by an independent testing group such as NSF, UL, or the Water Quality Association may be effective in treating the water. These may include point of entry systems, which treat all the water entering a home, or point of use devices, which treat water where it is used, such as at a faucet.
Please direct questions or concerns to the City’s Public Works Department at 928-777-1118.
Original source can be found here.
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