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Jimco Truck Plaza <br /> Page 3 of 3 <br /> vertically delineate chemicals of concern (COC) in groundwater. EHD approves the <br /> advancement for the three CPT borings; however, EHD believes at least one of three CPT <br /> borings should be advanced to approximately 100 feet bgs instead of the proposed 80- <br /> foot depth. Soil lithology for the two deepest soil borings, B-17 and B-18, indicates that <br /> soil tends to be primarily sand and silt with low sorption capacity between approximately <br /> 40 and 55 feet bsg. Grab groundwater samples collected at 55 to 60 feet bgs from B-18 <br /> demonstrate high concentrations of petroleum hydrocarbon contamination. • There is a <br /> significant possibility that COC may have descended through the subsurface to deeper <br /> permeable intervals, and a boring advanced to approximately 100 feet bgs near the source <br /> area may delineate the vertical extent of dissolved petroleum hydrocarbon contamination <br /> at this site. <br /> Although the work plan indicates that soil samples will be analyzed for COC, the only <br /> criteria stated for collecting soil samples were "near the water table and at lithologic <br /> changes." Please indicate whether soil samples will be collected from each borehole for <br /> analysis, and approximately what number of soil samples will be analyzed. <br /> Also,: in addition to analyzing the soil and groundwater samples for total petroleum <br /> hydrocarbons as gasoline (TPH-g), total extractable petroleum hydrocarbons as diesel <br /> (TEPH-d), TEPH as motor oil (TEPH-mo), benzene, _toluene, ethylbenzene, and total <br /> xylenes (BTEX), and methyl tertiary-butyl ether (MTBE), EHD believes that tertiary <br /> butyl alcohol (TBA) should be added to the analytical list since TBA has consistently <br /> been detected in groundwater samples at this site. <br /> Please submit an addendum to this work plan-to EHD by September 29, 2006, that will <br /> address the proposals presented by EHD. <br /> If you have any questions please contact Vicki McCartney at (209) 468-3456 or by <br /> electronic mail at vmccartney@sjcelhd.com. <br /> Donna Heran, REHS, Director <br /> Environmental Health Department <br /> Victoria L. McCartney, Senior REHS Ma�ggorio, REHS <br /> LOP/Unit IV/Site Mitigation Program Coordinator Unit IV <br /> c: Brandon S. Wilken,PG - Cambria <br /> James L.L. Barton, PG- CVRWQCB <br />