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Section 1: Introduction and Background Kennedy/Jenks Consultants (Kennedy/Jenks) prepared this Additional Soil and Groundwater Sampling Work Plan (Work Plan) on behalf of the BNSF Railway Company (BNSF) for the BNSF Mormon Yard in Stockton, California (Site), shown on Figure 1. The objective of the Work Plan is to describe the soil and groundwater sampling that will be conducted to address comments in the Review of High Resolution Site Characterization Report, BNSF Railway Company Mormon Yard, 801 Diamond Street, San Joaquin County letter from the Central Valley Regional Water Quality Control Board (RWQCB) to BNSF dated 19 March 2018. In this letter, the RWQCB reviewed the High Resolution Site Characterization Report, BNSF Mormon Yard, Stockton, California, submitted by Kennedy/Jenks on 15 September 2017 (Kennedy/Jenks 2017), describing the results of a laser-induced fluorescence (LIF) boring program conducted at the Site in May and June 2017. 1.1 2015 Soil and Groundwater Sampling The 2017 high resolution site characterization (HRSC) program followed a 2015 program in which Kennedy/Jenks conducted soil and groundwater sampling to assess whether there were residual impacts at the Site due to a 2011 surface fuel spill located near the mechanic's shop. The 2015 work was conducted after San Joaquin County Environmental Health Department (SJCEHD) contacted BNSF in May 2013 regarding the confirmation sample results collected after the spill was remediated. In 2015, SJCEHD requested the RWQCB provide oversight for the soil investigation. Based on a call with the RWQCB on 18 February 2015, Kennedy/Jenks submitted the Soil Investigation Work Plan, BNSF Mormon Yard, Stockton, California (Kennedy/Jenks 2015a) on 27 March 2015. The RWQCB issued a Conditional Concurrence with the Soil Investigation Work Plan, BNSF Railway Company Mormon Yard, 801 Diamond Street, San Joaquin County on 23 April 2015 (RWQCB 2015a), reducing the number of borings but increasing the depth to collect groundwater samples. The 2015 soil and groundwater sampling results were presented in the Soil Investigation Report, BNSF Mormon Yard, Stockton, California dated 24 August 2015 (Kennedy/Jenks 2015). Total petroleum hydrocarbons as diesel (TPHd) was detected in shallow soil but not detected or detected at very low concentrations in deeper soil, indicating that the surface fuel spill had not migrated downward. However, TPHd was detected in groundwater and appeared to be unrelated to the 2011 diesel release due to the vertical separation of unimpacted vadose zone soil between the impacted vadose zone soil and the groundwater table. In a 6 January 2016 meeting of BNSF, Kennedy/Jenks, and the RWQCB to discuss the findings, the RWQCB agreed that the distribution of diesel fuel in soil suggests that the 2011 diesel release was not the source of diesel in groundwater. The RWQCB also agreed that biological degradation of diesel appears to be occurring in both soil and groundwater. However, the RWQCB expressed concern at the presence of diesel in groundwater and requested that BNSF evaluate the source and extent of diesel in groundwater. Additional Soil and Groundwater Sampling Work Plan, BNSF Mormon Yard, Stockton CA Page 1 11fwybnsf2\bnsfwp \wpl201811899020.00_mormon_yardlwork_plan_id \2018 mormon yard sampling wp_mwm doc