What is a plume irregularity factor” and why is it needed?
A “plume irregularity factor” is referred to in Appendix 2 of ERCB Directive 001 and is a multiplier to adjust preliminary soil volume estimates to account for the irregular and curvilinear nature of plume boundaries (plume fingers). The extrapolation techniques used to define the boundaries of the plume result in a polyhedron with smooth edges connecting the data points; however, contaminant plumes rarely, if ever, have straight edges as contaminants migrate irregularly and follow preferential flow pathways. The plume irregularity factor compensates for the underestimated plume volume resulting from using a straight edged figure.
