API PUBL 4730:2003

This guide provides strategies for focusing remediation efforts on 1) the change in contaminant mass flux(footnote 1)in different subsurface transport compartments (e.g. the vadose zone, smear zone or a zone within an aquifer of interest) and 2) the change in remediation timeframe. In this approach, groundwater flow and contaminant concentration data are combined to estimate the rate of contaminant mass transfer past user-selected transects across a contaminant plume. The method provides the user with a means to estimate the baseline mass flux and remediation timeframe for various transport compartments and then evaluate how different remedies reduce the mass flux and the remediation timeframe in each transport compartment. Results from one or more transects can be used to evaluate: -- Potential water quality impacts on downgradient water supply wells. -- The natural attenuation of the contaminant mass with distance downgradient of the source. -- The relative benefits of remedies based on their anticipated reductions in mass flux from the source to the receptor. In addition to step-by-step instructions for the strategies, several utilities are provided including: -- Worksheets for estimating baseline mass flux and remediation timeframe and evaluating potential remedies. -- Tools for calculating mass flux. -- Resources on estimating remediation lifetime and evaluating remedy flux reduction / mass removal factors. -- Tools for evaluating how long it takes for an upgradient remedial action to affect a downgradient groundwater transect zone. Footnote 1 - Strictly speaking, mass discharge