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LNAPL detected in LIF#4 is associated with that UST or associated piping, which was removed <br />in 1990 (see documentation in Kennedy/Jenks [2016]). <br />As shown on Figure 2, borings LIF#6 and LIF#7 were drilled west and east respectively, of <br />LIF#4. LIF#3 is located (upgradient) of LIF#4. Boring LIF#15 was located approximately <br />160 feet northwest (downgradient) of LIF#4. The LIF did not detect the presence of LNAPL in <br />any of these borings, limiting the southern, eastern, and western extent of the LNAPL around <br />LIF#4, and the downgradient extent in the direction of LIF#15. <br />The LIF investigation did not identify any remaining residual or free phase LNAPL in the vicinity <br />of the former 10,000-gallon wastewater UST or the associated wastewater lines. No LNAPL was <br />identified in the area of the 2011 diesel release. <br />Based on removal of the diesel UST in 1990, the significant soil excavation activities that <br />followed, and the limited extent of LNAPL identified during this investigation, Kennedy/Jenks <br />(2017) concluded that the Site was a candidate for the Low-Threat Underground Storage Tank <br />Case Closure Policy and recommended that the Site be evaluated for low-threat closure. <br />1.2.3 RWQCB Response to HRSC <br />The RWQCB responded to Kennedy/Jenks (2017) in the Review of High Resolution Site <br />Characterization Report, BNSF Railway Company Mormon Yard, 801 Diamond Street, San <br />Joaquin County letter to BNSF dated 19 March 2018 (RWQCB 2018). In this letter, RWQCB <br />directed soil and groundwater sample collection at LIF#4 to identify the product detected with <br />the LIF, soil and groundwater sample collection beneath the 26,000-gallon excavation between <br />the LIF transects (the deeper portion of the UST excavation), as well as hydraulically upgradient <br />and downgradient. <br />1.2.4 Proposed Sample Locations <br />BNSF proposes two soil borings to address the extent of remaining LNAPL: one boring near <br />LIF#4, and one boring in the 26,000-gallon excavation between the LIF transects (the deeper <br />portion of the UST excavation). These locations are shown on Figure 2. The boring at LIF#4 and <br />under the former UST will be advanced to evaluate the extent of the hydrocarbon impacts in soil <br />and groundwater. <br />As described above and in Kennedy/Jenks 2017, numerous LIF borings were advanced <br />upgradient, downgradient, and laterally from LIF#4 and near the other former USTs. No <br />indication of hydrocarbon impacts was detected in four upgradient and one downgradient LIF <br />locations or in any of the other LIF locations. <br />Based on no hydrocarbon responses found upgradient and downgradient of LIF#4, additional <br />sampling upgradient and downgradient of LIF#4 does not appear to be warranted, and therefore <br />this work plan does not include sampling these areas. <br />The proposed soil borings will be advanced to a depth where visual indications of hydrocarbon <br />impact (staining, sheen, odor, headspace reading) are not observable, first-encountered <br />Additional Soil and Groundwater Sampling Work Plan, <br />BNSF Mormon Yard, Stockton CA Page 3 <br />Shiyybnsf2 tonsfyip yyp1201811899020 00_mormon_yard \work_plan_id12018 mormon yard sampling wp_mwm.doc