This work package evaluates in situ bioprecipitation (ISBP) and selected physical-chemical processes and their engineering application for ISR of heavy metals at field-scale. The research will focus on fundamental processes (e.g. reaction mechanisms, rates, microbiological constraints, bioavailability, metal release, remobilization reactions) and the effect of environmental controls (e.g. carbon sources, reactant concentrations, toxicity, soil/aquifer properties, pH) on ISBP at the laboratory-scale, to develop performance criteria for the design of field-scale systems. An evaluation will be made of the ISBP concept for metals in controlled field experiments using a test cell at a mega-site, considering heterogeneity and up-scaling of processes on remediation performance. Novel molecular microbiological and stable isotope analysis, supported by mathematical modelling, will be used to interpret natural processes. The aim will be to devise design criteria for ISBP remediation systems and a technical basis for performance assessment.