View File - Development Services - City of Oxnard

1.0 IntroductionThis Technical Report evaluates potential impacts on groundwater resources within aquifersunderlying the Oxnard Plain and Pleasant Valley areas (project area) resulting from the Cityof Oxnard (City) Groundwater Recovery Enhancement and Treatment (GREAT) Program(proposed project). This evaluation was performed using the numerical groundwater flowmodel of the Santa Clara-Calleguas Basin that was developed by the United SatesGeological Survey (USGS) (USGS, 2003) in the 1990s and recently updated by theUnited Water Conservation District (UWCD) (UWCD, 2003).The City of Oxnard GREAT Program would be located in the area of western VenturaCounty known as the Oxnard Plain, which includes the urban and suburban areas of theCity and adjacent communities (for example, Port Hueneme, Nyeland Acres, and El Rio). Italso includes agricultural areas of Ventura County, including the Pleasant Valley area. TheOxnard Plain is located approximately 60 miles northwest of downtown Los Angeles and35 miles south of Santa Barbara (see Figure 1-1).1.1 Project PurposeThe GREAT Program is a water resources project that would combine wastewater recyclingand reuse; groundwater injection, storage, and recovery; and groundwater desalination toprovide regional water supply solutions to water users within the Oxnard Plain andPleasant Valley areas. This technical report evaluates those elements of the GREAT Programthat will have a cumulative (year-to-year) regional effect on groundwater elevations withinthe aquifers underlying the Oxnard Plain and Pleasant Valley areas. Certain GREATProgram elements would create new sources of water supply by reusing City waste watertreatment plant effluent (WWTP) that is currently being treated to secondary standards anddischarged to a deep ocean outfall. Potential new water supplies would include thefollowing.• In Lieu Groundwater Recharge using Recycled Water. A portion of the currentsecondary effluent from the City WWTP would be treated to meet regulatory standardsfor direct nonpotable reuse (primarily irrigation) using a new tertiary treatment facility(TTF). This tertiary treated wastewater effluent would then be treated using a newadvanced water treatment facility (AWTF) to meet agricultural irrigation water qualitycriteria. This recycled water would be provided to growers on the south Oxnard Plainand Pleasant Valley in lieu of pumping groundwater for irrigation, where effects ofcurrent overdraft conditions are most severe. New pipeline conveyance systems wouldbe constructed to deliver the recycled water for irrigation. This would allowgroundwater pumping for irrigation to be reduced; and groundwater levels and theeffects of overdraft would recover using this in-lieu groundwater recharge technique.• Direct Injection Groundwater Recharge using Recycled Water. During winter monthswhen agricultural irrigation demand is low, a portion of the tertiary treated wastewatereffluent would be treated to meet regulatory standards using the new AWTF for directW112003002SCO LW1458.DOC/ 033390002 1