ARCHIVED REPORTS XR0011668 - Laserfiche WebLink

Home Browse Search

• umsH�u•M��NOFs, n+c. Ll • Based on procedures and recommendations established in the LUFT Manual , the Weber Point property has a leaching potential analysis score which indicates that due to the site specific hydrogeologic conditions, if residual petroleum hydrocarbon constituents are left in the soil , there is a high potential for these residuals to migrate and impact the groundwater resources in the area. The LUFT Manual , however, assumes naturally compacted soil with no cover; the Weber Point property is completely covered with asphalt or concrete, greatly reducing the natural leaching potential . For the conservative case of no ground cover, the LUFT Manual recommends that the TPH as gasoline concentration which can be left in place without posing a threat to the groundwater resources is 10 ppm or less. According to the LUFT Manual , at this low TPH level , BTX&E levels are not 1 applicable. The recommended maximum allowable residual levels from the LUFT Manual evaluation are also presented at the bottom of Table 2. The LUFT Manual evaluation tables which characterize the leaching potential are included in Appendix F. The second analysis in the LUFT Manual , the general risk appraisal , relies on generalized environmental fate, chemistry data, and some site-specific information. However, because of the results from the leaching potential analysis, the general risk appraisal is not applicable for this site. Soil borings S83 and SB4 contained detectable levels of TPH as gasoline above recommended LUFT Manual maximum allowable concentration levels to depths less than 5 feet above the potentiometric groundwater surface. These soils are a • r potential continuing source of groundwater contamination and cannot be left in place and must be remediated. 5.2 EVALUATION OF GROUNDWATER The LUFT Manual does not specify maximum allowable petroleum hydrocarbon concentrations in groundwater. Therefore, for illustrative purposes only, LH will compare the analytical results from the monitoring wells to established California drinking water standards. DOHS has established maximum contaminant levels (MCL's) for specific organic and inorganic chemicals {Title 22, Section 64444.5 of the California Code of Regulations. Three gasoline constituents are on the list of regulated chemicals: Constt�nt M fin DDb) Benzene I Xylene 1750 Ethylbenzene 680 An MCL is a legally enforceable maximum level ; therefore, water to be provided j for public consumption cannot contain contamination levels in excess of the established MCL. 24 1