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ARROYO LAGO RESIDENTIAL PROJECT ADDENDUM 136 FCS Https://adecinnovations.sharepoint.com/sites/PublicationsSite/Shared Documents/Publications/Client (PN-JN)/2148/21480036/Addendum/21480036 Arroyo Lago Residential Project Addendum.docx b) Groundwater Would the project: Substantially decrease groundwater supplies or interfere substantially with groundwater recharge such that the project may impede sustainable groundwater management of the basin? Prior FEIR Conclusions The Prior FEIR determined that the project site is located within the Livermore Valley Groundwater Basin, managed under Zone 7’s Alternative Groundwater Sustainability Plan. The County Project would be served by the California Water Service (Cal Water) and would comply with all applicable groundwater management actions. No significant extraction or interference with recharge was identified, and the proposed WWTP would not adversely affect groundwater quality. The Prior FEIR concluded that the County Project would not result in groundwater depletion or degradation. The County Project would not involve on-site groundwater extraction and would be served by municipal water supplies consistent with the Zone 7 Alternative Groundwater Sustainability Plan. Recycled water would be applied at agronomic rates and treated using membrane bioreactor technology that removes nitrogen, thereby avoiding nitrate loading to groundwater. Project-related salt contributions would be de minimis and would be managed through Zone 7’s basin-wide salt and nutrient management programs. Accordingly, the Prior FEIR determined that the County Project would not contribute to chronic lowering of groundwater levels, degradation of groundwater quality, land subsidence, or adverse effects on interconnected surface waters. Therefore, the Prior FEIR concluded that impacts would be less than significant. (Draft EIR, pp. 3.9-27, 6-16; Final EIR, pp. 2- 37–2-51). Proposed Project Analysis and Conclusion During construction, similar to the County Project, the proposed project would comply with applicable stormwater requirements, including those found in Pleasanton Municipal Code Chapter 9.14 (Stormwater Management and Discharge Control) and would incorporate BMPs to address water quality and control runoff from the project site; therefore, construction runoff would not be absorbed into the groundwater supplies. While dewatering is not expected to be required during project construction, such actions, if required, would be temporary and would not substantially interfere with groundwater supplies, recharge, or management. Water services for the proposed project would be provided by the City, which receives its water supply from Zone 7. Similar to the County Project, the proposed project could lead to an increased demand for water, which could lead to an increase in demand for groundwater production. However, the water demand for the proposed project would be slightly reduced compared to the County Project due to the reduction in dwelling unit count. The City receives 100 percent of its water from Zone 7.35,36 35 City of Pleasanton. 2026. About our Water. Website: https://www.cityofpleasantonca.gov/our-government/pleasanton- water/about-our-water/. Accessed March 10, 2026. 36 While the City previously obtained a portion of its supply from City-owned groundwater wells, those wells are no longer in