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x. • ' involved collecting soil and groundwater grab samples using sterile or decontaminated sampling ' containers The dnll ng and direct push equipment were decontaminated pnor to use on the project Decontamination of the continuous core sampler included washing in a detergent solution and rinsing with clean water The samples were appropriately labeled, and placed in baggies in an ice chest cooled to approximately 4 degrees centigrade and sent under ' chain-of-custody procedures to Curtis & Tompkins laboratory of Berkeley, California, a state certified laboratory ' One trip blank was sent in each cooler containing soil and groundwater samples to the ' laboratory The trip blank was analyzed for TPH-gasoline TPH-gasoline was not detected in the trip blanks above the reporting limit The chain of custody forms and the laboratory reports are provided in Appendix C Silica gel cleanup was performed for TPH-diesel and TPH-motor oil analyses on the shallow soil samples collected on the 541 Site in order to remove natural sources of hydrocarbons (e g vegetable and animal products) The existence of naturally occurring hydrocarbons was of ' concern due to vanous filling and grading operations on the northern portion of the property The silica gel cleanup method was not performed on deeper soil samples collected below the ' groundwater or on groundwater grab samples to be consistent with past AGE and Chevron ' Service Station analytical data One control soil sample, TR-9 at 6-foot depth, was analyzed with and without silica gel cleanup The results showed no reduction for TPH-diesel and ' approximately 50 percent reduction in concentration of TPH-motor oil with silica gel cleanup (Table 3) ' QA/QC measures taken to confirm the integrity of the laboratory data included method blanks, matrix spikes, and surrogate spike recoveries Method blanks are analyzed to assess the effect of ' the laboratory environment on the analytical results and are performed for each parameter ' analyzed Matrix spike recoveries determine whether the sample matrix was interfering with the laboratory analysis Matrix spike duplicates determine the reproducibility and precision of the ' analytical method Surrogate spikes are used to determine if the analytical instruments are Field Investigation Report 1 1 8 December 2003 ' TREADWELL&ROLLO,INC