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Manteca Quarterly Groundwater Monttonng Page4 The analytical groundwater parameters include volatile hydrocarbons, benzene, toluene, ethylbenzene, and xylene (BTEX) (EPA Methods 50301801518020),and total lead (EPA Method 7421) The analytical groundwater samples were placed in a cooler containing additional frozen blue ice packets, and shipped following chain-of-custody procedures to North Creek Analytical for analysis Ethylenebromide (EDB)was not included in the suite on analytes, because EDB degrades in soil I very rapidly(EDB is converted almost completely within 2 months to ethylene) and also in water, where it hydrolyzes to ethyleneglycol and bromoethanol (under neutral conditions and ambient temperature the half-life of the reaction is 5-10 days) SRK requested further guidance and ' justification from Ms Margaret Lagono, Senior REHS, San Joaquin County PHS/EHD, prior to the April 1992 sampling event, however, no response was received by SRK from the PHS/EHD during or after the sampling event r 5 0 ANALYTICAL DATA Organic analyses were performed by North Creek Analytical (California FLAP # 1267), and the inorganic analyses were performed by Sequoia Analytical (California FLAP # 1210) It should be noted that North Creek Analytical and Sequoia Analytical are jointly owned Copies of the analytical data and chain-of-custody are provided in Appendix C The chain-of-custody states that the groundwater samples were received by the laboratory in good condition at 4°C The chain-of- custody clearly documents that the samples were shipped from California to Washington The I chain-of-custody includes the sample location in the Project Name "Diamond Lumber-Manteca", and in the Sample Identification, "SRK-MWI-MAN' The top of the chain-of-custody form clearly states the name and address of North Creek Analytical in Bothell, Washington The constituents of BTEX or volatile hydrocarbons were not detected in groundwater samples SRK-MWI-MAN and SRK-MW3-MAN Analyses of sample SRK-MW2-MAN detected volatile hydrocarbons at 1,800 ppb, benzene at 220 ppb, and xylenes at 120 ppb Lead concentrations were detected in each of the monitoring wells, including 26 ppb in sample SRK-MW1-MAN, 57 ppb in sample SRK-MW2-MAN, and 27 ppb in sample SRK-MW3-MAN Table 2 contains analytical groundwater data from both the November 1991 and April 1992 1 sampling events The constituents of volatile hydrocarbons and BTEX were not detected in monitoring wells SRK-MW1 and SRK-MW3 during either the November 1991 or April 1992 sampling events The November 1991 analyses of samples from monitoring well SRK-MW2 detected benzene at 16 ppb, and xylenes at 0 90 ppb, while the April analyses from this monitoring well detected volatile hydrocarbons at 1,800 ppb, benzene at 220 ppb, and xylenes at 120 ppb Table 1 contains static water level information during both sampling events The static water levels were measured from the top of the 2-inch diameter PVC casing using a Solinst Water Level Indicator Copies of the Field Groundwater Purging/Sampling Logs from the November 1991 and 32S.22%oru1rcv 21 Steffen Robertson and Kirsten