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woo>aaRo &CURRAN 5. SUFFICIENCY DETERMINATION 5.1 Supply and Demand Comparison The total water demand anticipated for the Project is 3,798 AFY at buildout, as shown previously in Table 13. Of this total buildout demand, 760 AFY is anticipated to be met by recycled water. Projected water supply and demand for the entire City of Lathrop service area is presented in Table 23.As shown, the City's current and planned water supply is sufficient to meet all demands, including those proposed for the Project, in normal water years. The 2019 WSMP shows insufficient supply to meet total demand under normal year conditions in 2035 and at buildout. The updated projections below include revised demand estimates for the River Islands project area,and now show the supplies as sufficient to meet total demands. Table 23: City of Lathrop Water Demand (including River Islands)versus Normal Year Water Supply Water Use Category 2020 2025 2030 2035 2040 Buildout Potable Water Supply(AFY)1,2 11,480 11,531 11,583 11,607 15,391 Demand (AFY) 5,573 7,632 9,157 10,266 11,732 Sufficient Supply? Yes Yes Yes Yes Yes Recycled Water Supply(AFY)3 1,159 2,103 3,061 3,775 4,479 Demand AFY 1,159 2,103 3,061 3,775 4,479 Sufficient Supply?4 Yes Yes Yes Yes Yes Notes: 1. Source:City of Lathrop 2019 WSMP(EKI,2019),Table 5-8.Assumes both Well 21 and Well 9 remain offline. 2. Groundwater supply assumes that there will be no curtailments or limitations under the GSP currently being developed for the Tracy Subbasin. 3. Source:2015 UWMP(EKI,2017).Consistent with the 2015 UWMP,projected recycled water demands are estimated to be equal to the volume of treated effluent available(volumes presented previously in Table 8). River Islands will have the ability to supplement City recycled water supplies with lake and river water.These supplemental sources can be used to meet up to 100%of River Islands non- potable demands if recycled water supplies are unavailable. 4. Based on discussions between the River Islands developer Califia and the City of Lathrop, it is anticipated that there will be sufficient recycled water supplies to meet the new recycled water demands of River Islands. 5.2 Supply and Demand Comparison in Dry Years The assessment below considers available supply under single-dry and multiple-dry water year conditions to evaluate the potential for shortfalls in supply under such hydrologic conditions. Per the City's 2015 UWMP, the City's Water Shortage Contingency Plan includes demand reduction measures that would be implemented to eliminate any supply shortfall. A summary of the City's dry year demands with the Project is included in Table 24. A comparison of the projected supplies and demands under single-dry and multiple-dry year conditions is presented in Table 25.As shown in the table, the City's supply is sufficient to meet total projected demands (the City's planned and future uses and the Project) in all years in multiple-dry year conditions. In single-dry years conditions, there is an anticipated supply shortage in 2035 of 4 percent before accounting for the implementation of the City of Lathrop's Water Shortage Contingency Plan, which is discussed further in Section 5.2.1. If the supply is not sufficient, the City will enact conservation and demand management measures to ensure demand does not exceed supply. For the purpose of this analysis, City water supplies at buildout are assumed to be consistent with 2040 supplies, which makes this a conservative estimate. In addition, per the 2015 UWMP, the City has planned for water shortages and would enact more stringent water conservation measures and/or the appropriate stage of the Water Shortage Contingency Plan Califia(0011533.00) 40 Woodard&Curran, Inc. River Islands Phase 2 Development Water Supply Assessment September 2020