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PROVEN TECHNOLOGIES AND REMEDIES GUIDANCE—REMEDIATION OF METALS IN SOIL <br /> Table 6. Recommended Fill Material Sampling <br /> EXTENT OF INDIVIDUAL NUMBER OF SAMPLES <br /> BORROW AREA <br /> 2 acres or less Minimum of 4 samples <br /> 2 to 4 acres Minimum of 1 sample for every 0.5 acres <br /> 4 to 10 acres Minimum of 8 samples <br /> Greater than 10 acres Minimum of 8 locations with 4 subsam les per location <br /> VOLUME OF BORROW NO. OF SAMPLES <br /> AREA STOCKPILE <br /> Up to 1,000 cubic yards 1 sample per 250 cubic yards <br /> 1,000 to 5,000 cubic yards 4 samples for first 1,000 cubic yards; <br /> 1 sample per each additional 500 cubic yards <br /> Greater than 5,000 cubic yards 12 samples for first 5,000 cubic yards; <br /> 1 sample per each additional 1,000 cubic yards. <br /> From DTSC Information Advisory, Clean Imported Fill(DTSC, 2001). <br /> Composite sampling for fill characterization may or may not be appropriate, depending <br /> on the quality and homogeneity of the source/borrow area and the potential <br /> contaminants. The DTSC Information Advisory, Clean Imported Fill(DTSC, 2001) <br /> provides further discussion on the use of composite samples for certain contaminant <br /> groups. <br /> 7.7 QUALITY CONTROL / QUALITY ASSURANCE <br /> The workplan should address the quality assurance and quality control (QA/QC) <br /> procedures that will be followed. If a quality assurance project plan (QAPP) was <br /> prepared during the characterization phase, the plan may be amended to address the <br /> pertinent changes for the excavation plan. <br /> Excavation is selected as the remedy of choice when removal of the top layers of <br /> contaminated soil will prevent the direct contact and exposure to receptors. Soil <br /> samples from the outer limits of the excavation are typically collected to ensure that the <br /> clean up objectives have been met. The approximate locations, sampling frequency, <br /> number of samples, and the associated detection limits for confirmation samples should <br /> be identified (see annotated outline for soil confirmation sampling plan in Appendix D3). <br /> The documentation of activities should be included, ensuring site activities were <br /> conducted in accordance with the approved workplan. <br /> 36 <br />