ARCHIVED REPORTS_DRAFT - PHASE I REMEDIAL INVESTIGATION REPORT

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Kennedy/Jenks Consultants Section 4: Quality Assurance/Quality Control 4.1 Field Quality Assurance/Quality Control In addition to equipment decontamination between samples and sampling locations, quality assurance/quality control (QA/QC) measures employed during the field work included collecting and analyzing duplicate reconnaissance groundwater samples. Duplicate groundwater samples were collected from Borings OU5-AO110-S12 and OU5-AO110-S15. The analytical results from the duplicate samples were comparable with the results from the primary samples. In addition, equipment blanks were collected each day from decontaminated soil and groundwater sampling equipment. Soil equipment blanks were collected by pouring distilled water over and through a cleaned sample barrel and liner. Groundwater equipment blanks were collected by pouring the distilled water over the decontaminated steel check valve. The blank ' samples were contained in appropriate sample containers and submitted for the same analyses as the soil and groundwater samples collected that day. Analytes were detected at concentrations exceeding analytical reporting limits in four of the 15 equipment blank samples, as described below. • OU5-AO19-GW-3-EB. TPHd was detected at a concentration of 52 pg/I in this sample collected from the groundwater sampling equipment. This sample was collected after completing borings OU5-AO19-S26, OU5-AO19-S27, and OU5-AO19-S28. TPHd was reported in groundwater samples from these borings at concentrations of 130 pg/l, 67 pg/I, ' and 77 pg/l, respectively. OU5-AOI10-S-6-EB. TPHd was detected at 51 pg/I in this sample collected from the soil sampling equipment. TPHd concentrations in soil samples collected that day ranged from less than the analytical reporting limit to 190 mg/kg, and when detected, TPHd was usually accompanied by TPHmo. • OU2-AO17-S-13-EB. Zinc was detected at 0.075 mg/I in this sample collected from the soil sampling equipment. In soil samples collected that day, zinc was detected at concentrations ranging from 37 mg/kg to 360 mg/kg. • OU4-S-14-EB. TPHd was detected at 52 pg/I and nickel was detected at 0.0085 mg/I in this sample collected from the soil sampling equipment. TPHd concentrations in soil samples collected that day ranged from less than reporting limit to 3,900 mg/kg, and when detected, TPHd was usually accompanied by TPHmo. Nickel concentrations in soil samples collected that day range from 16 mg/kg to 43 mg/kg. The TPHd detected in one of the groundwater equipment blanks does not significantly affect the findings or conclusions of the investigation. Even if the 52 pg/I TPHd detected in the equipment blank was subtracted from the TPHd concentrations detected in the three groundwater samples collected that day, the interpreted TPHd distribution, discussed in detail in the following sections, would not change appreciably. DRAFT Phase 1 Remedial Investigation Report Page 19 Former Tracy Railyard, Tracy, California g:1is-groupladminjo610510565777.18_uprr109-reportsVi rptAeddoc