SOURCES OF SALINITY AND WATER IN A SPRING AND NATURAL OIL/TAR SEEP SYSTEM IN THE SANTA SUSANA MOUNTAINS, NEWHALL, CALIFORNIA.

The purpose of this study is to identify the source(s) of salinity and water of naturally occurring springs and oil/tar seeps which have been identified as contributing fluids to the north flowing streams of Towsley and Wiley canyons of Newhall, California. To date, a combined total of 33 springs and natural oil/tar seeps have been identified through geologic mapping of this project area which is located within a local conservation park of Los Angeles County. The waters discharging from these sources were evaluated over a period of one year by testing pH, dissolved oxygen, electrical conductivity, and elemental composition. Preliminary salinity testing of these waters had results of total dissolved solids (TDS) ranging from 900 to 5300 mg/L and chloride values in excess of 10,000 ppm which far exceeds the Environmental Protection Agency’s (EPA) National Secondary and Primary Drinking Water Standards and California’s Secondary Maximum Contaminant Levels for water quality. Geochemical analyses coupled with geologic mapping have revealed a dynamic fluid flow system of which thrust faulting and contacts of the steeply dipping Modelo and Towsley formations, Miocene to early Pliocene in age, appear to control the migratory paths for fluid flow within the northwest trending Pico Anticline along the southern boundary of the Upper Santa Clara River Groundwater Basin, east subbasin of the Santa Clarita valley. Chloride values exceeding the State of California’s water quality standards (250 ppm, an upper limit of 500 ppm, and a short term limit of 600 ppm) has been a prolonged problem for this groundwater basin and for the Ventura basin which is downgradient to the Santa Clarita valley (CH2MHill, 2005; Watersheds Coalition of Ventura County, 2006). This project indicates that the waters discharging from springs and oil/tar seeps in the Santa Susana Mountains may also be contributing to the high chloride content of groundwater in the basins north of the project area.