RES 2024025 - Laserfiche WebLink

28 established a notification level (NL) and response level (RL) for PFHxS. This is the fourth PFAS constituent to have an established NL and RL; the other three constituents (PFOS, PFOA, and PFBS) had NLs and RLs established between 2019 and 2021. As defined by DDW: • NL is the concentration level of a contaminant in drinking water delivered for human consumption that DDW has determined, based on available scientific information, does not pose a significant health risk but warrants 30-day notification to the governing body and annual notification to the public via the consumer confidence report. • RL is the concentration of a contaminant in drinking water delivered for human consumption at which the water system, in the case of PFAS, must either (1) take the source out of service immediately; (2) utilize treatment or blending; or (3) provide immediate public notification of the exceedance if the source remains active. The table below indicates the NL and RL for each of the four PFAS chemicals as established by DDW: The table below indicates the NL and RL for each of the four PFAS chemicals as established by DDW: DDW Advisory Levels for PFAS (ng/L) PFAS Notification Level Response Level Perfluorooctanesulfonic acid (PFOS) 6.5 40 Perfluorooctanoic acid (PFOA) 5.1 10 Perfluorobutanesulfonic acid (PFBS) 500.0 5,000 Perfluorohexanesulfonic acid (PFHxS) 3.0 20 In 2023, the three City-owned wells exceeded the NL established by the DDW for PFOS and PFHxS. Well 8 equals the RL established by the DDW for PFHxS and remains out of service (it was placed in “Standby” with DDW in June 2019 for being above the RL for PFOS at that time of issuance and has not operated since). Wells 5 and 6 remain “in service” with DDW, they have been turned off since November 2022 for being above NL for PFOS and have not operated since. As a water provider, Zone 7 similarly is required to conduct quarterly testing on its water sources. Zone 7’s surface water supply at both treatment plants were ‘non-detect’ when tested for the PFAS constituents. For Zone 7’s groundwater supply, the Stoneridge well and Chain of Lakes 1 and 2 wells have not operated since fall/winter 2022 and are currently under construction to add PFAS treatment systems. Zone 7’s Mocho 2 and 3 wells are currently being treated at the Mocho Groundwater Demineralization Plant and blended with Mocho 4 well water to ensure the water is below the RL (but not the NL) before being supplied to the City. The agency’s Hopyard wells were ‘non-detect’ when tested for the PFAS constituents. As Zone 7 operates a connected treatment and distribution network, the water provided by Zone 7 to any of its water retailers may come from any of these sources. General. The City is not aware of any environmental or regulatory issues that would adversely impact its ability to deliver water. Water Quality. The applicable drinking water standards for the Water System are provided in the California Domestic Water Quality and Monitoring Regulations, Title 22 of the