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GeosMtec'' <br /> consultants <br /> The potential presence of naphthalene in the soil from 0 to 5 feet bgs could not be <br /> evaluated because the chemical was not analyzed in previous investigations.Naphthalene <br /> will be analyzed to fill the data gap. <br /> RWQCB staff recommend the Port of Stockton also collect groundwater samples from <br /> monitoring wells 917-3,917-4,and 917-10 simultaneously with soil sampling to evaluate <br /> concentrations of TPH and benzene in groundwater (RWQCB, 2018a). However, these <br /> wells are sampled as part of the RRI Groundwater Sampling Program. Geosyntec will <br /> evaluate the June 2018 or more recent data as it's collected in conjunction with the soil <br /> data that will be collected as part of the UST Data Gaps investigation. <br /> 1.2.4 UST Site 916B <br /> Building 916B housed pumps and piping associated with two 4,000-gallon USTs used to <br /> supply diesel fuel for railroad locomotives. The tanks were installed in 1945 and removed <br /> in 1997. Associated piping and pumps, as well as contaminated sediments beneath the <br /> building, were removed when Building 916B was demolished in 2002. Following <br /> demolition, one soil investigation and one groundwater monitoring event have been <br /> conducted to characterize the extent of residual contamination in the area (ERS, 2008b). <br /> Per the RWQCB's analysis, the site meets general and media-specific criteria for closure <br /> under the LTCP program, apart from TPH, which exceeded the media-specific criteria <br /> for closure under the LTCP program (RWQCB, 2018a). <br /> Soil and groundwater samples and chemical test data from two soil borings adjacent to <br /> the previous highest area of detection (soil borings 916-05 and 916-C6;3 Figure 5) are <br /> required to fill the data gap (RWQCB, 2018a and 2018b). TPHd was detected in soil <br /> sample 916-05 (collected from 5 to 8 feet bgs) and soil sample 916-C-6 (collected at 5 <br /> feet bgs) at concentrations of 790,000 mg/kg and 2,000 mg/kg, respectively. <br /> Due to limited access in the vicinity of former UST916B, one boring will be drilled at the <br /> location shown in Figure 5. A soil and grab groundwater sample will be collected from <br /> this boring.The soil sample will be collected from depth of 5 feet bgs and will be analyzed <br /> for TPHg and TPHd to address LTCP media-specific criteria for petroleum vapor <br /> intrusion to indoor air (RWQCB, 2018a). TPHd and total petroleum hydrocarbons as <br /> motor oil (560 mg/kg) were the only constituents analyzed in 2008 at location 916-C6 <br /> s Boring location also referred as C-5 and C-6 by ERS(2008b)and RWQCB(2018a). <br /> 20190122- FINAL UST Data Gap Work Plan 4 22.01.2019 <br />