8.5.4.4 Comparison of discrete samples and ISM samples

Many sites have historical discrete sampling data, and some have concurrent discrete sampling data taken in response to specific needs or regulatory requirements. Qualitative comparisons can be very instructive, but quantitative comparison of discrete and ISM data should be done only with caution. Comparison of ISM samples to discrete samples is discussed in Section 4.4.3.2. Key issues that should be considered whenever comparing ISM and discrete samples are sampling design, sample collection method, similar soil conditions, similar sample processing and analysis, and data quality being understood and appropriate for intended use.