Orange County North Basin. The Orange County Groundwater Basin is part of the 360-square-mile coastal plain of Orange County. The Santa Ana River, the primary surface water drainage feature in the area, is located east and southeast of the Study Area. The northern portion of the Basin, which includes the cities of Fullerton, Anaheim and Placentia, falls within the region known as the Forebay, the predominant area of basin recharge. In the Study Area, OCWD has identified three aquifers or aquifer systems: Shallow, Principal and Deep. The Principal Aquifer is the primary source of approximately 70 percent of the potable water supply in OCWD’s boundary. However, the Shallow Aquifer is also locally used for potable water supply. In portions of the Study Area, the boundary between the Shallow and Principal Aquifers is generally delineated by a fine-grained layer at a depth of approximately 200 to 250 feet; however, this fine-grained layer may be absent or discontinuous, particularly in the eastern part of the Study Area. OCWD is responsible for managing the Orange County Groundwater Basin, which supplies water to more than 20 cities and other water agencies, serving more than two million customers. OCWD has divided the aquifers into the three aforementioned primary aquifer systems based on the presence of regional aquitards, differences in potentiometric surfaces, and changes in water quality. In the Study Area, the Shallow Aquifer includes sediments extending to an average depth of approximately 200 feet below ground surface (bgs). The Principal Aquifer contains unconsolidated strata extending to an average depth of about 850 feet. The Deep Aquifer contains the unconsolidated aquifers below the Principal Aquifer, extending to an average depth of 1,300 feet bgs. Groundwater in these aquifers generally occurs under unconfined conditions in the North Basin and under semi-confined to confined conditions further west and south. The depth to groundwater in the Shallow Aquifer ranges from approximately 80 to 120 feet bgs. In the Shallow Aquifer, groundwater flow in the area is generally from east to west, but flow may change seasonally and year to year due to changes in groundwater pumping patterns and recharge Investigations of the North Basin, the area generally under the cities of Anaheim, Fullerton and Placentia, have revealed groundwater contamination from volatile organic compounds (VOCs) and other chemicals. Beginning in the 1950s, VOCs were used for industrial activities in this area. ...
