A new spreadsheet-based tool helps site managers and consultants determine if matrix diffusion processes will cause “rebounding” of downgradient plume concentrations above remediation goals after plume remediation or isolation is complete. Having this information readily available before a remedy is implemented will assist stakeholders in selecting more appropriate remedies and improving effective risk communication. The tool was developed by GSI Environmental Inc. and Colorado State University with support from ESTCP. Matrix Diffusion Tool Kit