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' These samples will be collected prior to excavation to allow for completion of disposal profiling ' prior to mobilization. This will allow for better management of stockpiles and direct loading as feasible based on truck availability. 4.2.2 Excavation Confirmation Sampling Following removal of soil to the limits presented in Geocon's October 2015 Site Investigation Report, a XRF will be used' to screen for lead levels in the field. If the XRF indicates that lead ' concentrations are below cleanup goals, then confirmation soil samples will be collected as discussed below. ' Soil samples will be collected at discrete locations approximately every 25-linear feet along the length of the excavation sidewalls. The outside perimeter of the proposed excavation limits is approximately 614 feet; therefore, it is anticipated that a total of 25 sidewall samples will be ' collected for analysis. Sidewall samples will be collected at the surface to a depth of three inches 4. Discrete excavation floor confirmation soil samples will be collected for every 25 foot by 25 foot ' area (every 625 square feet). Based on the assumed excavation area of 16,604 W, a total of 27 bottom samples will be collected for analysis. Samples will be collected from areas of visual staining or other indications of impacts if observed. ' Confirmation samples (52 samples total) will be analyzed by Asset Laboratories' for total lead by EPA Method 6010B. A total of 25% of the confirmation samples (13 samples)will also be analyzed for CAM Metals by EPA Method 6010B/747IA and polynuclear aromatic hydrocarbons PAHs by EPA Method 8270C/SIM. The following table summarizes RSLs and laboratory Method Detection Limits (MDLs) and Practical Quantitation Limits (PQLs): Analyte RSL(mg/kg) MDL (mg/kg) PQL (mg/kg) tAntimony 31 0.213 2 ' Arsenic 126 0.103 1 Copper 3,100 0.107 2 Lead 80 0.116 1 Tin 47,000 0.0085 15 s Geocon has indicated that they will be performing the proposed XRF screening during field activities. 4 Sidewall samples are typically collected at the mid-point depth; however, surficial sampling is proposed as the majority of the observed contamination is surficial. 'Asset Laboratories is certified by the State of California's Department of Public Health Environmental Laboratory Accreditation Program (ELAP)and the National Environmental Laboratory Program(VELA) for the proposed metals with the exception of tin in soil for which there is not certification in California. ' e D[T�SSC-Schools Program screening value. +` yPACIFIC EDGE ENGINEERING 8 SREW_Manteca_draft.docx ' (949)470-1937;(949)470-0943(FAX)