6.3.1 General Sample Processing Considerations

Other than Appendix A of USEPA SW-846 Method 8330B, there are no reviewed, published SOPs for laboratory processing of ISM samples. Therefore, on a sample- and contaminant-specific basis, the possible effects of ISM sample processing should be considered. Possible contaminant interference, interaction with, and/or contribution from all equipment used in ISM sample processing should be evaluated during systematic planning and discussed with the laboratory prior to ISM processing and analysis.

Drying, even at ambient room temperature, may contribute to the loss of more volatile and/or photosensitive contaminants. Drying at elevated temperatures is not recommended unless it is documented that the analyte of concern is thermally stable at that temperature. Additionally, ambient drying is not in accordance with accepted methodology of retaining samples cooled or refrigerated (e.g., 4 ± 2oC) until extraction. Excessive drying periods for high-moisture soils may contribute to increased biodegradation of contaminants. Finally, increased ISM drying and processing periods should also be considered in regard to method-specific holding times. Holding time violations may result in estimated or rejected data.

Most contaminant concentrations are reported on a dry-weight basis; thus, a subsample for percent moisture determination should be collected using the same techniques as for the contaminant. Subsampling and percent moisture determination should be performed on the as-received ISM bulk sample prior to any processing in the lab and on any moisture-modified samples (intentionally dried or wet, see Section 6.2.2.4), depending on the sample processing decisions made to achieve the ISM project DQOs by the project team during the initial project planning phase. The original sample moisture content can be determined for informational purposes by using the 2-D Japanese slabcake subsampling process to collect a subsample of the as-received bulk ISM sample for percent moisture analysis.