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LFR Inc. Notes: mg/kg = milligrams per kilogram; TTLC = Total Threshold Limit Concentration; rPRGs = residential Preliminary Remediation Goals. ND = not detected above the laboratory reporting limit. Ca = California Modified. Metal concentrations detected in the soil samples, with the exception of arsenic, were below the U.S. Environmental Protection Agency's (U.S. EPA) Region 9 Preliminary Remediation Goals (PRG) established for residential soil. The concentrations of arsenic detected in Sample Nos. Id, 2d, and 3d were above the rPRG soil screening level of 0.39 mg/kg. Arsenic occurs naturally at varying background concentrations. Several reports document background concentrations measured in samples collected throughout California from a variety of geologic units and soils. In Professional Paper 1270, "Element Concentrations in Soils and Other Surficial Materials of the Coterminous United States" (USGS 1984), the United States Geological Survey cites an average arsenic concentration in California soils at 7.2 mg/kg. The University of California, Riverside, cites a range of concentrations between 0.6 mg/kg to 11 mg/kg in their March 1996 study "Background Concentrations of Trace and Major Elements in California Soils." Lawrence Berkeley National Laboratory published the document "Analysis of Background Distributions of Metals in the Soil at Lawrence Berkeley National Laboratory" dated June 2002 and based upon results published in this report arsenic was detected in samples collected in the East Bay at concentrations ranging from 4.7 mg/kg to 14 mg/kg, depending on geological formation. The range of arsenic detected in soils at the Site is consistent with the expected background range for California. Therefore, the arsenic in soil at the Site is considered background. Additional characterization and evaluation activities are not required with respect to arsenic at this Site. Soil sample locations are depicted on Figure 2. A copy of the chemical laboratory report is presented in Appendix F. 11.0 FINDINGS This section identifies known or suspect recognized environmental conditions (RECs), historical RECs, and de minimis conditions obtained during the ESA. 11.1 Known or Suspect RECs This assessment has revealed evidence of the following recognized environmental condition (REQ in connection with the Site: • Numerous soil stockpiles reportedly illegally disposed of at the Site represents a 1 1 recognized environmental condition to the Site because of the unknown source of the stockpiles. 003-09246-00_UwerSac n(oRoad_JLHomes_Ph=I FSA:dh Page 28