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immune effects, thyroid effects, and cholesterol changes. PFOA, PFOS, and other PFAS are primarily introduced into the body by the ingestion of contaminated food or liquid (including water). PFOA and PFOS were found in the blood of nearly all people tested in several national surveys but have steadily decreased since 2000. The major sources of PFAS are fire training /fire response sites (such as airports), industrial sites, landfills, and wastewater treatment plants. Groundwater contamination with PFAS has typically been associated with these sources. PFAS are very stable in the environment and are resistant to breaking down. Once in groundwater they can easily be transported large distances and can contaminate drinking water wells. Regulatory Timeline Below provides a regulatory timeline of events relating to PFOA and PFOS in drinking water: • 2013 — 2015: US EPA conducted UCMR3 program which included testing for PFOA and PFOS. Note that the detection limits at that time were 20 ppt and 40 ppt, respectively. Zone 7 and City testing were non-detect for PFOA and PFOS. • May 2016: EPA issued a combined Health Advisory Level of 70 ppt for PFOA and PFOS. Currently, the US EPA has not set health advisory levels for other PFAS chemicals. • July 2018: DDW issued a Notification Level of 14 ppt for PFOA, a Notification Level of 13 ppt for PFOS, and a Response Level of 70 ppt for PFOA and PFOS combined. • March 2019: DDW issued orders to over 600 water system sites (including City of Pleasanton and Zone 7 groundwater wells) and nearly 250 potential source type locations such as landfills and airports with fire training and response areas. For water system sites, the order requires testing for PFAS chemicals including PFOA and PFOS on a quarterly basis. DDW indicated additional testing orders will occur at industrial sites and wastewater treatment plants. Note that detection limits at this time are now approximately 2 ppt. • August 2019: DDW issued revised Notification Levels of 5.1 ppt for PFOA and 6.5 ppt for PFOS. The revised levels were consistent with updated health recommendations by the OEHHA. DDW also announced that it requested OEHHA to develop a PHG for both PFOA and PFOS, the next step in the process of establishing a future regulatory standard/MCL. • By end of 2019: DDW plans to revise the Response Levels for PFOA and PFOS. Zone 7 Testing and Follow-up Actions Zone 7 began voluntary testing for PFOA and PFOS in late 2018, followed by full testing as part of the DDW order in April of 2019. Table 2 provides a summary of their test results to date. Note that Zone 7 has indicated that their surface water supplies, and Hopyard Wellfields have been non-detectable for PFOA and PFOS. Page 7 of 13