25C - AGMT - OCWD CENTENNIAL PARK

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Section 5 IMPACT HW Q-2: Would the project substantially deplete groundwater supplies or interfere substantially with groundwater recharge such that there would be a net deficit in aquifer volume or a lowering of the tonal groundwater table? Alternative 1: No Federal Action /No Project Under Alternative 1, the project would not be implemented. The injection wells within Centennial Park would not be constructed and there would not be any increase in groundwater recharge capacity within the project area. Alternative 2: Proposed Project Groundwater Supply Within Centennial Park groundwater was identified to occur at 13 feet to 23 feet below the ground surface. Depending on the depth of excavation for the underground vaults and where the construction would be conducted, groundwater could be encountered and groundwater dewatering activities could be required. The groundwater would be discharged into a local storm drain and then into the Greenville Banning Channel. The amount of ground water discharged from the dewatering activities would be minimal compared to the overall amount of water in the groundwater basin and would have a less than significant impacts on groundwater supplies. The Mid Basin Centennial Park Injection Well Project would add an estimated 12 MGD of additional groundwater recharge capacity into the Orange County Groundwater Basin. Additionally, the operation of the Mid Basin Centennial Park Injection Wells Project would free up capacity in other OCWD recharge facilities to allow for the capture of additional amounts of storm flow for groundwater recharge. Implementation of the Proposed Project would', have a beneficial impact on groundwater supplies. Demonstration Mid -Basin Injection JCWD's Demonstration Mid -Basin Injection (DMBI) Project infrastructure includes one full -scale injection well (MB1 -1) equipped with a dedicated back flushing pump; associated pipelines and appurtenances for GW RS injection water supply and back flush discharge; and two, multi -zone, nested, down gradient groundwater monitoring wells (SAR -10 and SAR -11). Injection operations at well MBI -1 began in April 2015. The injection flow rate has varied from approximately 1.5 to 2 million gallons per day (MGD). Backwash events are conducted to maintain the injection performance and occur for an approximate duration of 40 minutes of continuous pumping at a flow rate of 3,000 gallons per minute. Backwash events are currently conducted with MBI -1 approximately three times per week. k Mid Basin Centennial Park 9iP97A Project Final E I R 5 -111