Since the Enhanced Monitored Natural Recovery material is assumed to mix with the existing surface sediment (during placement, by bioturbation, and by deposition and mixing of newly deposited sediment), it appears reasonable to use of a replacement value greater than natural background (i.e., dioxin/furans in Puget Sound natural background is 4 ppt) or the use of a dilution factor as the concentration in the upper 10 cm of sediment at time t=0 post construction. Does anyone have suggestion for this replacement value and do you have any examples of site where this has been done? Thank you, Pete