Technical information describing the numerical method BUGS Scratchpad implements is available in the on-line version of A Two Dimensional Numerical Model for Simulating the Movement and Biodegradation of Contaminants in a Saturated Aquifer, a Master's Thesis by Jason E. Fabritz, (1995). This document presents a discussion of the subsurface processes modeled by the program; develops the numerical methodology; evaluates model performance in a general sense; and provides an example remedial design. Detailed calculations and other information can also be found in the appendices.