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<br />Housing Constraints City of Pleasanton | C-47 <br />conservative assumptions, including assumed buildout of sites at their maximum zoned density, <br />development of as many as 26 locations preliminarily studied as potential housing sites (versus <br />the 19 re-zone sites ultimately selected for inclusion in the Housing Element), and assuming new <br />housing would be in addition to, rather than replace, any existing non-residential uses on site. As <br />such, the minor exceedance of demand compared to the UWMP was determined not to be <br />significant. However, the WSA noted that it is possible that additional water supply sources may <br />be necessary to accommodate the Housing Element Update combined with additional growth, <br />under the conservative demand forecast. Zone 7 has committed to work to increase water supply <br />sources for the City and surrounding areas to account for increasing population and climate <br />changes. <br />Not reflected in the 2020 UWMP, but acknowledged in the WSA for the Housing Element update, <br />are supply deficiencies due to the recently-emerging issue of contamination by per- and <br />polyfluoroalkyl substances (PFAS, chemicals that can contaminate drinking water supplies) in <br />local groundwater supplies. The City’s water supply comes from two sources: approximately 80 <br />percent is supplied by the Zone 7 Water Agency (Zone 7), while the remaining 20 percent comes <br />from three City owned groundwater wells: Wells 5, 6, and 8. Test results from 2019 and 2020 <br />showed elevated levels of per- and polyfluoroalkyl substances (PFAS, chemicals that can <br />contaminate drinking water supplies) at Well 8, which is now inoperative.8 <br />TheWell 8 was placed in “Standby Service” with the Division of Drinking Water (DDW) in June <br />2019 due to PFAS concentrations being significantly above response levels at the time of its <br />issuance. The well has not operated since June 2019. Well 5 and 6 are still “In Service” with DDW <br />but have not operated since November 2022. This is a precautionary decision made based on <br />test results being near response levels. When regulatory maximum contaminant levels (MCLs) <br />are established (estimated to occur late 2023 / early 2024), the City anticipates all three wells will <br />be above the MCLs. A supply deficiency would remain until the groundwater supply wells have <br />PFAS treatment added or alternative water supplies are found. <br />As a result, the City is actively exploring several alternative water supply options while the PFAS <br />contamination is being addressed. In September 2020, the City began considering a PFAS <br />Treatment and Groundwater Wells Rehabilitation Project to address PFAS contamination and <br />extend the life of the existing groundwater supply by 30 years. This project would <br />rehabilitate/replace existing well facilities, construct a new well facility, and construct a Centralized <br />Treatment Facility for disinfection and PFAS treatment of groundwater before distribution. The <br />preliminary cost estimate of the project is $46 million. Given project cost and other considerations, <br />in September 2022, the City Council authorized staff to proceed with performing a Water Supply <br /> <br /> <br />8 Upon receipt of the test results, the City placed Well 8 on Emergency Standby Status. Well 8 has not operated since <br />the beginning of June 2019 and the City has determined that all groundwater supply wells may be taken out of <br />commission no later than the first quarter of 2023.