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Page 3 <br /> West Lauffer Road <br /> February 29,2008 <br /> RESULTS AND DISCUSSION <br /> The results our site observations and the soil sampling/analysis are favorable. As shown on <br /> Table I and the attached laboratory report, the tested soil samples did not contain BTEX <br /> compounds at concentrations above the laboratory reporting limits. The soil samples <br /> collected from the final horizontal and vertical limits of the remedial excavation contained <br /> non-detect or very low concentrations of diesel-range petroleum hydrocarbons. <br /> To evaluate the very low concentrations of residual diesel-range petroleum hydrocarbons <br /> detected in some of the clearance soil samples, we have considered Environmental <br /> Screening Levels (ESLs) established by the California Regional Water Quality Control <br /> Board (CRWQCB)3 The CRWQCB has published ESLs for common contaminants; <br /> development of the ESLs involved consideration of protection of human health, drinking <br /> water resources, vapor intrusion into buildings, aquatic habitats and terrestrial biota. The <br /> referenced screening levels generally are considered to be conservative; additional <br /> investigation and remediation is generally not considered necessary when the screening <br /> values are not exceeded. The ESL for gasoline and middle distillate (diesel) range <br /> petroleum hydrocarbons is 83 milligrams per kilograms; this value is considered a <br /> conservative target clean-up value for use at the subject site. Because none of the final <br /> clearance soil samples contained diesel-range petroleum hydrocarbons at concentrations <br /> above 78 milligrams per kilogram, the remedial soil removal appears to have been <br /> successful. Based on our site observations and the laboratory data, further remedial soil <br /> excavation within the area of the former above-ground diesel tank does not appear to be <br /> necessary. <br /> If you have any questions or require further information, please contact the undersigned at <br /> (916)371-0434. <br /> Sincerely, <br /> RANEY GEOTECHNICAL,INC. <br /> Je Brusca <br /> C rtified Engineering Geologist No. 1948 <br /> Attachments: Plate 1- Vicinity Map <br /> Plate 2- Plot Plan <br /> Table 1, Summary of Soil Analytical Data <br /> Laboratory Report and Chain-of-Custody Documentation <br /> JBJb <br /> (2)addressee <br /> 3 CRWQCB, San Francisco Bay Region; "Screening for Environmental Concerns at Sites with Contaminated <br /> Soil and Groundwater,Volume 1:Summary Tier 1 Lookup Tables';November 2007. <br />