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LABORATORY RESULTS The groundwater sample for the third round was submitted under chain-of-custody to Superior Precision Analytical in Martinez, California for the following analyses August 16, 1993 Sample #80283 ► Total Petroleum Hydrocarbon (TPH) extractable by EPA Method 8015M/3550 (diesel range) ► TPH purgeable by EPA Method 8015M/5030 (gasoline range) ► Benzene, Toluene, Ethylbenzene, and Xylenes (BTEX) by EPA Method 602 Superior is certified by the California Department of Toxic Substances Control (DTSC) for the requested analysis The laboratory data sheets and chain-of-custody forms are attached Total petroleum hydrocarbons as diesel were detected at 68 µg11, which is ,lust above the laboratory reporting limit of 50 pg/l. Benzene was detected at the reporting limit of 0 3 pg/1 Petroleum hydrocarbons were detected at similar low concentrations to the first (February 1993) and third (August 1993) samples rounds CONCLUSIONS • Petroleum hydrocarbons were not detected in the second round sample from the monitoring well MW-1 The benzene concentrations detected in two of the three rounds are below the maximum contaminant level (MCL) of 1 pg/l which is used as a drinking water standard Diesel contaminants detected in two of the three rounds are below the Suggested No Adverse Response Level of 100 pg/l Since the source of contamination (the tank) and affected soil have been removed, and detected petroleum hydrocarbon concentrations are below action levels, no additional groundwater assessment is not warranted at this time Kleinfelder recommends that Cal West Concrete Cutting, Inc request closure of the site from SJCPHS LUMTATIONS Kleinfelder performed this investigation in accordance with generally accepted standards of care which exist in Northern California at this time Conclusions in this report are based on the analytical results of three rounds of groundwater samples collected from MW-1 It should be recognized that definition and evaluation of environmental and geologic conditions is a difficult and inexact art Judgments leading to conclusions and recommendations are generally made with incomplete knowledge of the subsurface conditions present More extensive studies, including subsurface investigations, may be performed to reduce uncertainties If Cal West Concrete Cutting, Inc wishes to continue with this investigation, Kleinfelder should be notified for additional consultation No warranty, expressed or implied is made. 24-220172-AOo/DR4fi0(1993) Page 3 of 4 August 30, 193 Copynght 1993 Kleinfelder, Inc KLEINFELOER 3077 Fite Circle, Sacramento, CA 95827 (916) 366-1701