To assist in the design of enhanced reductive dechlorination systems for in situ remediation of chlorinated solvent source zones, the software BUCHLORAC (BUffering of deCHLORination ACidity) was developed to predict the amount of buffer required to maintain the groundwater pH in a DNAPL treatment zone within the optimal range for dechlorinating bacteria. Reductive dechlorination is an acidforming process with hydrochloric acid and organic acids typically building up in the treatment zone. Remediation of source zones is associated with such extensive localized dechlorination that it may be common for the soils’ natural buffering capacity to be exceeded. As groundwater acidification may inhibit the activity of dechlorinating microorganisms and thus slow or stall the remediation process, sufficient alkalinity must be present to maintain a near-neutral pH. BUCHLORAC is a Windows Graphical Interface based on an abiotic geochemical model that is implemented through the program PHREEQC. BUCHLORAC allows users to estimate the buffer requirements for their specific operating and design conditions including, for example, site water chemistry, mineralogy, amount of chlorinated solvent to be degraded, design inhibition pH, and type of organic substrate and buffering additive.