Cost-optimal contaminant plume management with a combination of pump-and-treat and physical barrier systems

The economic potential of combining hydraulic barriers and pump-and-treat systems to manage contaminant plumes is investigated by means of a comparative cost analysis. The analysis is based on a preceding study on the hydraulic performance of barrier-supported and conventional pump-and-treat systems, which revealed the efficiency of accurately positioned barriers in reducing pumping rates for contaminant plume capture. In the present paper, we examine whether the application of physical barriers like slurry walls or sheet piles also leads to economic benefits, i.e., whether the reduction of the operational costs outweighs the capital costs associated with the construction of the barriers. An economic model is presented that quantifies remediation costs by the use of cost functions relating costs to site-specific and system-specific parameters. The model is applied to a hypothetical remediation scenario. The results clearly demonstrate that physical barriers may yield significant savings in the total costs, particularly if unit costs for on-site treatment are high. Furthermore, as barriers tend to reduce the uncertainty about the pumping rate required to capture a plume, they smooth the trade-off curves between total remediation costs and system reliability.