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Pilkington North America, Inc. - 3 - 16 March 2015 <br /> 3. Page 3 of the Work Plan also propose to collect two soil samples from the deep <br /> zone of each of the proposed continuous core soil borings. Soil samples will be <br /> selected for analyses based on field observations and photoionization detector <br /> (PID) measurements. Samples with highest PID readings, or other indicators of <br /> possible contamination such as staining, shall be considered for analyses over <br /> samples with lower readings or fewerindications of contamination. Please <br /> include field notes regarding selection of soil samples for analyses in the final <br /> report for the investigation. <br /> 4. The First Quarter 2014 (Semi-Annual) Groundwater Monitoring Report shows the <br /> presence of motor oil at concentrations of 1,320 and 518 ug/L in SW-Sump and <br /> MW-2, respectively. In Figure 2 of the Work Plan, SW-Sump and MW-2 are <br /> depicted as located at opposite ends of the historical range of gradients provided <br /> in Figure 2. Motor oil was not reportedly part of the original diesel release in <br /> 1996 indicating that there is likely an additional source of pollution being released <br /> to groundwater at the site. <br /> Staff of the Regional Water Board find that the Work Plan is incomplete as discussed in the <br /> comments above. By 24 April 2015, please submit a revised Work Plan that addresses all <br /> comments discussed above and describe the actions taken to implement the following staff <br /> recommendations: <br /> 1. Please specify when the deep zone sampling at all locations will occur. <br /> 2. Please show the locations of the four sumps and soil core sampling locations in <br /> Figure 2. <br /> 3. Please include a minimum of one down-gradient boring. At a minimum, two <br /> selected soil samples from each of the continuous core soil samples should be <br /> submitted for analyses. <br /> 4. Samples with the highest PID readings, or other indicators of possible <br /> contamination like staining, shall be chosen for analyses over samples with lower <br /> readings or fewer indications of contamination. Please include field notes <br /> regarding selection of soil samples for analyses in the final report for the <br /> investigation. <br /> 5. Please analyze a soil or groundwater sample containing diesel or motor oil for <br /> methyl tertiary butyl ethylene (MTBE), if testing for MTBE has not been <br /> completed already. Please include results if an MTBE analysis has already been <br /> conducted for this site. <br /> 6. Regional Water Board staff requests construction and operations details for the <br /> four sumps located in the interior, including what materials are historically and <br /> currently discharged to the sumps, be included in the final report for this <br /> investigation. <br />