View File - Development Services - City of Oxnard

WATER RESOURCES TECHNICAL REPORTtwo UAS wells (Nos. 22 and 23), and three UAS wells. Water levels decreased up to20 feet in the UAS and up to 10 feet in the LAS in the vicinity of the water yard. Thesewater level decreases will result in the following:−−In the UAS, these small to moderate decreases, combined with the declines from theUWCD El Rio wellfield extractions, will increase the potential to induce brief periodsof coastal landward flow during extended, drier climatic periods (see Scenario 2chydrograph for coastal well 05G02, which twice briefly drops below sea level forsimulation period [Figure 6-27]).In the LAS, these moderate decreases will increase the moderate potential forlandward flow that exists, particularly during drier years and in the fall when waterlevels are seasonally low.• Moderate to large decline in groundwater elevations in the Forebay area as a result ofextracting 15,429 AFY (80 percent) of the 19,286 AFY of in-lieu recharge from the UWCDEl Rio wellfield. Water levels decreased up to 30 feet in the UAS and up to 10 feet in theLAS. The water level decline in the LAS is mostly due to interference from drawdown atthe City Water Yard. These water level decreases will result in the following:−−In the UAS, these moderate to large declines may interfere with pumping operationsat the Forebay spreading grounds. Combined with the declines from City WaterYard extractions, these declines will contribute to the increased potential to inducebrief periods of coastal landward flow during extended, drier climatic periods (seeScenario 2b hydrograph for coastal well 05G02, which twice briefly drops below sealevel for simulation period [Figure 6-27]).In the LAS, these small declines are attributed mostly to drawdown from theextractions at the City Water Yard and, consequently, will have no significant effect.These changes will result in the following reductions in overdraft:• For the UAS, the average height above the coastal water level goal will remainapproximately the same, 5.6 feet for Scenario 2b compared to 5.7 feet for the Base Case.• For the LAS, the reduction in overdraft will be 32 percent compared to the Base Case.Scenario 2cScenario 2c results in the following changes relative to the Base Case:• Very large rise in groundwater elevations at the coastal injection wells (seawaterintrusion barrier) as a result of injecting 6,172 AFY in this area and a large rise overbroad areas across the southern Oxnard Plain and Pleasant Valley areas. This occursmostly in the LAS, as a result of delivering 19,286 AFY of recycled water to growers(Ocean View pipeline, PTP system, PVCWD system) in lieu of those growers pumpinggroundwater. Water levels increased up to 80 feet in the LAS along the injection wellsand up to 30 feet in the UAS across the southern Oxnard Plain and Pleasant Valley areas.Figures 6-23 and 6-24 show UAS and LAS groundwater elevations, respectively, for thefirst quarter 2020 (winter period) when water levels will be highest from injectionactivities (i.e., injection quarter). These water level increases will result in the following:W112003002SCO LW1458.DOC/ 033390002 91