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Joint Tri-Valley Potable Reuse Technical Feasibility Study I ESI TRI-VALLEY WATER AGENCIES r.,Lay cb.>'rrrr A -`k 1.. Stacktor. r. as �UAW,' A• 7A• :1tN r mo Des Zane>s..,b.Arm tars hair Qw..Un loom sats 0.W Mtir sorvc.0.0 Qty or wumo..+war sorra ,. tip of w....rrn Mar Sera. oq y(K (''want}. V CGMa+w New Soma coat.* S n .'. ,_ xnwndwatrr hunky Figure ES.1 Tn-Valley Water Agencies and Service Areas Range of Water Supply Yield The 2016 WSE Update evaluated a number of water supply portfolios including a combination of the following potential new supplies:California WaterFix,desalination,and potable reuse.Los Vaqueros was also included as a potential new storage location.Desalination and potable reuse were assumed to have yields of 5,600 acre-feet per year(AFY)and 7,800 AFY,respectively.For the purposes of this study,an upper bookend of 10,000 AFY was assumed for potable reuse, which was also consistent with projected wastewater availability,as discussed further below.A lower bookend of 5,500 AFY was used. Existing Facilities and Regulations Zone 7 supplies water to the Tri-Valley using raw imported water(State Water Project),local water(Arroyo Valle),and groundwater.Raw water is treated at either the Patterson Pass Water Treatment Plant(PPWTP)or the Del Valle Water Treatment Plant(DVWTP)before distribution (locations shown in Figure ES.2).Zone 7's wells are primarily located in the western portion of the service area.Some groundwater in the Mocho Wellfield area with high total dissolved solids (TDS)is treated through a demineralization plant before distribution.Additional Zone 7 water facilities include the Chain of Lakes(COL),a series of existing or former gravel quarries that are in the process of reclamation or have been reclaimed as water storage and/or recharge lakes (Figure ES.2).Zone 7 currently owns Cope Lake and Lake I,with the rest of the ten lakes due to be transferred to Zone 7 in the future.Lake H is expected to be transferred for Zone 7's use over the next few years.Zone 7 will use the COL for a variety of water resource management activities. C FINAL I MAY 2018 3