This web based guidance document provides a format that is easy to navigate through an in-depth analysis and overview of Biochemical Reactors (BCRs) for mining influenced water (MIW). The guidance uses a decision tree to understand the applicability given a number of site and influent parameters, testing, design, construction and monitoring. BCRs can be designed to address a wide range of flows, acidity, and metals loading and also can be designed to operate in gravity flow or available powered mode. The decision tree presents the basic factors used to evaluate the efficacy and applicability of BCR treatment for a particular MIW, while several case studies also included in the document present a clear evaluation of diverse site conditions and detailed analysis and evaluation of several different chemical mixtures.