6 To evaluate remedial options and forecast future river conditions with confidence, EPA developed a computer model to simulate and compare the results of various dredging scenarios, ranging from no dredging to extensive dredging. What the model found was that the assumption that more dredging was better was not necessarily true. Indeed, it showed that significantly more dredging in the Upper Hudson would not be significantly more protective, but that strategic dredging of sediments with elevated PCB concentrations would deliver nearly the same risk-reduction benefit (see Figure 1). This was the basis for EPA’s choice of remedy. Rather than setting a simple requirement for removal of a set volume of PCBs, EPA required removal of PCBs that exceeded specified criteria in three sections of the Upper River. This approach ensured that the greatest mass and the highest concentrations of PCBs would be removed, and that the remedy could be scaled up if more PCBs were discovered. Indeed, more PCBs were found during the pre-dredging sampling program, and more PCBs were removed than originally anticipated. The project EPA chose led to the removal of the vast majority of PCBs through a combination of very extensive dredging in parts of the Upper Hudson near Fort Edward, and selective dredging downstream. EPA made clear from the outset that the remedy would not remove all of the PCBs but would – over time – achieve the Agency’s mandate of protecting public health and the environment, EPA determined significantly more dredging in the Upper Hudson would not be significantly more protective, but that strategic dredging of sediments with elevated PCB concentrations would deliver nearly the same risk-reduction benefit. Dredging activities near Fort Edward, NY.