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Adikk Ah KLEINFELDER 2.3. CONFIRMATION SAMPLING Four soil samples were taken from Interim WMU F on December 29, 1999. The locations of these samples are shown on Plate 1. The base of the leachate impoundment was divided into 4 approximate equal areas for sampling. One soil sample was taken from the middle of each area with a drive sampler. Decontamination procedures were performed on the sampling equipment and brass collection tubes. Soil samples were obtained using a drive sampler to collect a 6" soil core from the base of the excavation. The soil sample was collected in brass tubes and capped with Teflon sheets and plastic end caps. The sample tubes were kept iced in coolers. 2.3.1. LABORATORY ANALYSIS The soil samples were relinquished in iced coolers along with the chain of custody to Sequoia Analytical on January 3, 2000. Sequoia is certified by the State of California Department of Toxic Substances Control for the analyses performed. The following analyses were performed by Sequoia Analytical on the soil samples as specified in sections of the Closure Plan and Construction Quality Assurance Manual: • EPA Method 8260 (Volatile Organic Compounds (VOCs)) • EPA Method 8270 (Semivolatile Organics) • EPA Method 8141 (Organophosphorous Compounds) • EPA Method 8150 (Chlorinated Herbicides) 2.3.2. LABORATORY RESULTS Laboratory results were received from Sequoia Analytical on January 21, 2000 and are included in Appendix A of this report. Detectable levels of two contaminants, chloroform and methylene chloride were noted in the results. Chloroform was also detected in the method blank, suggesting possible outside contamination. Kleinfelder contacted Sandra Hanson of Sequoia Analytical on February 4, 2000 and discussed the possibility of outside methylene chloride contamination in the samples. Ms. Hanson relayed that methylene chloride is a common solvent used in the laboratory and could have resulted in the detected levels of the contaminant in the analysis. 23-483849-1303/231 OR071 Page 4 of 7 April 11,2000 Copyright 2000 Kleinfelder,Inc.