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kn KLEINFELDER 6.2 GROUNDWATER ASSESSMENT In general, concentrations of the analytes in the six samples tested ranged as follows. Where noted ' below ND indicates none detected at the laboratory reporting limits. • Fuel Fingerprint/Total Extractable Petroleum Hydrocarbons: ' • JP-4 [none detected] • JP-5 [none detected ] • Kerosene [none detected] • Diesel [none detected] • Lubricating Oil [none detected] • Unidentified Extractable Hydrocarbons [ND to 190,000 [tg/L] • CAM 17 Metals, none detected except: • Barium [0.080 to 0.70 mg/L] • Chromium [ND to 0.041 mg/L] • Volatile Organics by EPA Method 8260 [none detected], except: • Benzene [ND to 0.0024 mg/L] ' • Semi-Volatile Organics (Polynuclear Aromatic Hydrocarbons) by EPA Method 8270 [ND (for detection limits refer to lab reports)], except: • Phenanthrene [ND to 110 [ig/L] 6.3 GENERAL CONCLUSIONS AND RECOMMENDATIONS ' Based on the results of this assessment, Kleinfelder has the following conclusions and recommendations: 1. In the southwest portion of the site a concentration of 2.4 µg/L benzene was detected in groundwater from boring B6/HP-6. This concentration exceeds the Maximum Contaminant Level (MCL) listed in Title 22 of California Code of Regulations §64431. Unidentified Extractable Hydrocarbons (UEH) and phenanthrene (constituent of crude oil) were also detected in groundwater at concentrations of 190 mg/L and 110 µg/L, respectively, from boring B6/HP-6. Although Kleinfelder does not know of a MCL for petroleum hydrocarbons ranges, the UEH concentrations detected are relatively high. The source and extent of the impacted groundwater is unknown. 2. Toluene was detected in a soil sample obtained from boring 136/HP-6 at a depth of 10 feet at a concentration of 0.11 mg/kg. The concentration detected is very low. However, the concentration exists in soil near groundwater. The source and extent of the toluene in soil is unknown. 20-4054-01.E01/2018R299 Page 12 of 15 0 1998,Kleinfelder,Inc. May 8, 1998