FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

Appendix A:Previous Environmental Activities to correspond to on-site water-supply well W-1,but could not be confirmed because the street address listed in the DWR Water Well Drillers report no longer exists. SAIC 2012 HUMAN HEALTH SCREENING EVALUATION/ECOLOGICAL SCREENING EVALUATION19 SAIC evaluated cancer risks and non-cancer hazards from exposure to COPCs in soil and groundwater in a residential land-use scenario. SAIC also evaluated the potential for exposure of sensitive ecological receptors to COPCs at the Site. SAIC developed the HHSE using approaches and methodology consistent with those presented in the Preliminary Endangerment Assessment(PEA)Guidance Manual(California Environmental Protection Agency[Cal/EPA] Department of Toxic Substances Control [DTSC])20. SAIC quantitatively evaluated the exposure routes of incidental ingestion of soil and dermal contact with soil; inhalation of wind-blown dust for non-volatile constituents; inhalation of chemical vapors from soils for volatile constituents; and inhalation of chemical vapors from subsurface vapor intrusion to indoor air for volatile constituents detected in groundwater. Shallow groundwater is unlikely to be used as a drinking-water source at the Site; therefore, exposure to groundwater was not evaluated quantitatively in the HHSE. All analytes detected in soil in at least one sample between 0 and 10 feet bgs(or approximately 3 meters)were considered COPCs. Metals are not typically considered critical constituents of crude oil at former OVP and TAOC sites; therefore, soil samples from the Site were not analyzed for metals. BTEX and PAHs were detected in soil and therefore considered to be COPCs for the Site and were evaluated quantitatively in the HHSE. SAIC estimated total potential cancer risk to a hypothetical resident from oral, dermal, and inhalation exposures to on-site soils to be 2E-06. This level of risk is within the lower end of the risk management range of 1E-06 to 1E-04 established by Cal/EPA and DTSC. This is a conservative estimate of risk, and actual risks are believed to be significantly lower. SAIC estimated the total potential non-cancer hazard index from oral, dermal, and inhalation exposures to on-site soils to be 0.02. This level of hazard is far less than a hazard index of 1, and therefore indicates an acceptable non-cancer health hazard for exposures to on-site soils for a hypothetical resident. SAIC queried the California Natural Diversity Database to search for threatened, endangered, or sensitive species in the vicinity of the Site 21. The database report identified six threatened or endangered species in the surrounding vicinity of the Site: the San Joaquin kit fox, Swainson's hawk, western yellow-billed cuckoo, delta button-celery, riparian(San Joaquin Valley) woodrat, and the riparian brush rabbit. Of the identified species, there were no occurrences within 1 mile of the Site. The closest occurrence was a Swainson's hawk identified in 2003, approximately 1.6 miles northwest of the Site. This assessment indicates that a threat to sensitive ecological receptors does not appear to exist. 19.SAIC,2012. Human Health Screening Evaluation, US Can—Welty Road,35275 Welty Road, Vernalis,San Joaquin County, California.March 22. 20.DTSC and Cal/EPA, 1999. Preliminary Endangerment Assessment Guidance Manual,Department of Toxic Substances Control.June. 21. California Department of Fish and Game,2011. California Natural Diversity Database.June. A-8 SAIE