14 ATTACHMENT 1 EXHIBIT A - Laserfiche WebLink

Chapter 6 Water Supply Characterization THE CITY OF PL£ASANTON augmentation") or directly into the water distribution system ("treated drinking water augmentation"). The State is currently developing standard criteria for DPR. Specifically, AB 574 requires the SWRCB to adopt uniform water recycling criteria for raw water augmentation on or before December 31, 2023. In 2018, the Tri -Valley Water Agencies completed the Joint Tri -Valley Potable Reuse Technical Feasibility Study' (Potable Reuse Study) with these goals: 1) to evaluate the feasibility of a wide range of potable reuse options for the Tri -Valley based on technical, financial, and regulatory considerations, and 2) assuming that potable reuse is found to be technically feasible, to recommend next steps for the agencies. The Potable Reuse Study also refined cost estimates for potable reuse. The Potable Reuse Study investigated three potential end uses for purified water in detail: 1) groundwater augmentation or recharge via injection wells, 2) groundwater recharge via Chain of Lakes surficial recharge, and 3) raw water augmentation to Zone 7's Del Valle Water Treatment Plant. Looking at annual yields ranging from 5,500 to 10,000 AFY, the Potable Reuse Study concluded that potable reuse is technically feasible for the Tri -Valley, with benefits to reliability and water quality. The lower yield would use only Livermore wastewater supply with year-round operations, while the higher yield would be achieved with seasonal availability of DSRSD wastewater supply. Water availability would increase over time as development occurs in the Tri -Valley and more wastewater is generated and collected. In other words, the maximum yield is expected to only be available after a certain point in the future; only a fraction of the maximum yield is available before buildout. In the 2019 WSE Update, raw water augmentation was modeled with the option for a two -phased project that initially produces a lower yield but increases to the maximum yield in 2035 (following a growth in available wastewater). Reflecting a more conservative estimate of future wastewater availability, the 2019 WSE Update used a reduced yield of 4,000 AFY starting in 2027 and 7,000 AFY after 2035. Conservation regulations have set low indoor water use targets for California, which are expected to reduce future wastewater flows. The estimates in the Potable Reuse Study had not incorporated the recently set statewide indoor water use targets. Future analyses will adjust estimates as necessary based on actual indoor water use trends and updated projections of wastewater availability for potable reuse. Zone 7 is completing a number of technical studies over the next few years that will support continued evaluation of potable reuse options and their costs and benefits. For planning purposes, the Zone 7's 2020 UWMP assumes 5,000 AFY of future supply from BARDP (discussed in Section 6.2.8.1) and/or potable reuse, with either or both systems online by 2030.10 9Tri-Valley Agencies and Carollo Engineers, 2018. Joint Tri -Valley Potable Reuse Technical Feasibility Study, htto://www.zone7water.com/library/reports-DlanninR-documents. 10 Pleasanton City Council voted not to participate in a regional potable reuse project at its February 21, 2021 City Council Meeting. WEST YOST N-680-60-20-04-WP-R-680-2020UWMP 6-29 City of Pleasanton 2020 Urban Water Management Plan May 2021