Publisher Summary This chapter reviews the issues and current progress with regard to regulatory acceptance and the cost data currently available for permeable reactive barriers (PRBs). The most important properties of the contaminants are their speciation and geochemical behavior, particularly their mobility under different redox and pH conditions. Active groundwater remediation methods should be applied if the pollutant concentration is high and decontamination measures must be taken immediately. Passive remediation technologies, such as PRBs, tend to work over longer periods of time, and can be used if long treatment times are acceptable. The main decision-making tool when selecting a groundwater remediation technique is an economic evaluation of all viable techniques. During the planning stage of any kind of remediation scheme the costs and effectiveness of the different techniques have to be compared. It is very important that long-term remediation costs are factored into these comparisons, although these are difficult to estimate. In general, the costs of remedial activities are classified as capital investment costs that stem from the construction of the remediation system and operation and maintenance costs that arise continuously or periodically during operation of the system.