This is a User's Guide and Tool developed under ESTCP project, "Development of a Quantitative Framework for Evaluating Natural Attenuation of 1,1,1-TCA, 1,1-DCA, 1,1-DCE, and 1,4-Dioxane in Groundwater." The tool is intended to help users follow OSWER directive 9200.4-17P on MNA of chlorinated ethenes. While the USEPA has yet to develop a similar directive for chlorinated ethanes and 1,4-dioxane, the tool follows a very similar technical approach in evaluating MNA for these compounds.