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it TABLE 1 First Quarter 1993 Monitor Well Physical Parameter Data Summary ' San Joaquin County Human Services Building Site Sample Date: April 15 and 16, 1993 ' Well ID Well Depth to Groundwater Temperature' pH' Electrical Elevation' Groundwater' Elevation' (°F) Conductivity' ' (feet) (feet) (feet) (umhos) MW-4 13 46 5050 -3704 669 80 1341 ' MW-5 12 83 4863 -35 8 700 74 876 MW-6 13 17 4874 -3557 679 7 1 1738 ' MW-7 13 14 5150 -38 36 65 3 76 1719 MW-8 I3 76 51 87 -38 11 671 2 7 5 1418 1 EIevations are given in feet relative to Mean Sea Level (MSL) and are based upon measurements from top of ' PVC casing (TOC) 2 Measured from TOC ' 3 Measured at end of purge 4 MW-2 and MW-3 were dry 2.2 Chemical Analysis Summary Concurrent with the measurement of the physical parameters, groundwater samples were collected and analyzed for the following parameters by the methods referenced • Benzene, toluene, ethylbenzene and xylene (BTEX), EPA Method 602 • Total petroleum hydrocarbons as gasoline (TPH-G), Method 8015M • Total petroleum hydrocarbons as diesel (TPH-D), Method 8015M • Ethylene dibromide (EDB) (also known as 1,2-dibromoethane), EPA Method 504 • Total lead, EPA Method 239 2 Per agreement with the EHD, the analyses for TPH-D, EDB and Total Lead will be deleted from the analytical suite if these constituents are not detected after two quarters of sampling The chemical analysis results for the 1st quarter 1993 monitoring event are summarized in Table 2 while the complete analytical report is presented in Appendix B With regard to the quality control samples, analysis of the primary well sample MW-7 and the blind duplicate (labeled MW-10) both produced analytical results of 1 7µg/L for benzene and non-detectable for toluene, ethylbenzene and xylene indicating good repeatability of the laboratory analyses Analysis of the field decontamination sample, which was collected after sampling MW-7, showed a trace of toluene (1 3 Mcg/L) Since the primary MW-7 sample contained no detectable toluene, the trace of toluene in the decontamination sample may be from a source other than the sample bailer, such as air emissions or another unspecified source Since MW-7 was the last well sampled in the first quarter program, the trace of toluene in the bailer had no impact on any subsequent analytical results STKIRPTS18Jr IST WP 4 05118/93 I