A closed-loop system and method for heating of target contaminant zones having environmental contaminants of concern present in the groundwater and the soil by thermal conduction, and subsequent enhancements of physical, biological and chemical processes to attenuate, remove and degrade contaminants in the target contaminant treatment zones, is disclosed. The system and method collects solar or other heat and transfers the heat via a closed-loop and a set of borehole exchangers to subsurface soil in the proximity of and/or directly to the target contaminant treatment zones. The target contaminant treatment zone may comprise contaminated soil, contaminated groundwater in an aquifer, or industrial waste comprising water and/or solids. Solar collectors or heat exchangers capturing waste heat from industrial processes may be used as the heat source.