Subsurface remediation research in support of DOE’s cleanup mission is the central focus of the ERSP. Many of DOE’s subsurface contamination problems have no practical remedy because the contamination is present at low concentrations, too widely dispersed in the subsurface or, present in extremely complex matrices. Excavation and/or pump and treat technologies for these contaminant scenarios can be prohibitively costly. The ERSP funds research of potentially novel methods to remove and/or immobilize/stabilize contaminants in the subsurface. This research encompasses the investigation of both active technologies (physical, chemical and biological processes) and passive technologies for intercepting and/or attenuating contaminant concentrations in situ (barrier systems, natural attenuation). ERSP seeks and funds projects of direct relevance to DOE in order to develop promising techniques for use in cleanup operations at DOE sites.