OCWD staff recently prepared two geologic cross sections that take present day information and adjust it with historic evidence for an even more accurate picture of where injected water is going to ensure proper protection of the basin from seawater intrusion.

One is oriented along Ellis Avenue based on the data from over 30 Talbert Seawater Barrier injection and monitoring wells. The second cross section is oriented north/south along the Santa Ana River from Ellis Avenue to the Pacific Ocean and includes the four southeastern Talbert Barrier injection wells along the Santa Ana River and several monitoring wells. These two cross sections intersect each other on the east end of the barrier at injection well I26.

Although staff has studied the aquifers in the Talbert Gap for decades and has made refinements to the California Department of Water Resources' earlier geologic interpretations, these are the first detailed cross sections along the barrier alignment that accurately depict the depths and screened intervals of the injection wells with the multiple aquifers that are being recharged and protected against seawater intrusion.

Seawater intrusion occurs when ocean water seeps into fresh groundwater in aquifers along the coast, contaminating the freshwater. OCWD injects Groundwater Replenishment System highly purified recycled water into a series of barrier wells and pushes the dense saltwater back, while also replenishing the groundwater basin.