NATURALLY OCCURRING CONCENTRATIONS OF SEVENTEEN METALS IN THE BAY POINT FORMATION, SAN DIEGO, CALIFORNIA

The natural variability of metals in the native formations of San Diego County is poorly understood. Specific formation studies are critical in identifying the spatial variability of metals and concentrations that are anthropogenic and what may be naturally occurring. Few studies of the concentrations of metals within the native sediments of San Diego County exist. The existing studies are regional in nature and formation specific studies in the San Diego Embayment are not readily available. The concentrations of metals in soils is a fundamental criteria regarding remediation and potential disposal options for soils removed from contaminated or potentially contaminated properties in San Diego County.

We present the results of distinct geogenic soil samples representing the in-situ Bay Point Formation (upper and lower facies) of San Diego, California. The location for this project is in downtown San Diego and consists of an area of approximately 1.3 square miles (3.34 km). All of the soil samples collected were analyzed by a California Certified Analytical Laboratory for various metals following Environmental Protection Agency 6000 / 7000 Series Methods on a ICP Mass Spectrometer.

The naturally occurring Arsenic concentrations detected during this study exceed commonly used health risk soil screening levels and other risked-based corrective action guidelines utilized by many regulatory agencies on contaminated sites in California. The other metals concentrations do not exceed any such published criteria. Additional research is needed to assess the bio-availability of the Arsenic, the potential impact to human health and the environment, and the impact these results may have on current regulatory thresholds for assessing soils on residential and commercial properties.

Ultimately, this project will include the uploading of all raw analytical data to a central database for public use. Further research is currently underway to identify the range of concentrations of metals in additional formations throughout the San Diego Embayment (e.g. San Diego Formation, Torrey Sandstone, Mission Valley Formation). Additional data will be collected from specific locations so that a comprehensive study of the concentration of naturally occurring metals in San Diego County sediments can be published.