SITE INFORMATION AND CORRESPONDENCE_1988-1991

Home Browse Search

Ms. Barbara Marcotte • Page 2 pathway is not considered in the risk assessment given the nature of the chemicals identified, the projected land use patterns, and the lack of use of groundwater for irrigation. SPECIFIC COMMENTS Hazard Identification: Three types of potential contaminants have been examined baed on historical land use and known contamination at SHAD - vo atile organic compounds (VOC's) , pesticides, and arsenic. No pest.cides were detected in any soil samples and are not considered fu ther. VOC's were detected in all media and are considered th main contaminants of concern. Arsenic was detected in all soil s mples and for reasons discussed below was omitted from subsequent risk consideration. Arsenic, a known carcinogen, is present in Valley Haven soil at concentrations which occur naturally resulting from both natural and man made sources. Background levels of arsenic in soil nationwide and in San Joaquin valley soils are generally about 5 ppm. The four "background" samples collected about five miles north of the site are also consistent with naturally occuring levels. Although inhalation of arsenic, even at naturally occuring background levels, may pose an increased risk of lung cancer, the primary risk from arsenic generally comes from diet including drinking water (Toxicological Profile for Arsenic, Agency for Toxic Substances and Disease Registry, U.S. Public Health Service, 1988) . In addition, the air monitoring data for arsenic collected at SHAD reports values that are typical of urban background levels (2-10 ng/m3) . Although there are some rather high values for arsenic i soil samples at SHAD, these samples generally come from subsurface samples which would not contribute to airborne arsenic 1 vels. Arsenic contamination of groundwater is a possibility, but as long as no groundwater is being used at Valley Haven, arsenic which may have been used or generated at SHAD cannot be shown to contribute to the levels of arsenic measured at Valley Haven. It is thus reasonable to omit arsenic from further consideration in the risk assessment which is being reviewed for a borde� zone determination. The hazard identification appropriately identifies inhalation of Valley Haven soil VOC emissions, SHAD soil VOC emissions, and emissions from the SHAD air stripping tower currently in operation as the pathways to be considered for exposure evaluation. Inhalation of these VOC' s are assumed to be of ambient air. These VOC's may potentially accumulate in subsurface structures such as basements or foundations at concentrations