3.4 Establishing New Decision Units Based on Previous Results

In some situations it may be necessary to develop new DUs based on revised sampling objectives following the assessment of initial results. For example, a DU may have been initially established of such size that remediation of the entire DU is not practical. In this situation, it may be advantageous to resample by dividing the original DU into smaller DUs and sample each smaller DU to determine which have soils that do not meet cleanup goals and, therefore, should be remediated. Subdividing a source area DU designated for in situ treatment into smaller subunits can also help optimize the design of the remedial system based on a more accurate estimation of contaminant distribution within the DU.