The last phase of the ER-1552 project further expanded the project scope by enhancing the usability of the project outcomes from Phases I and II. The objectives were 1 to investigate the potential repartitioning of contaminants in sediment following the removal of AC after stabilization treatment, 2 to standardize field monitoring methods using polyethylene passive samplers, and 3 to develop a user-friendly, standalone program for HOC mass transfer model to predict sequestration and pore water concentrations. The experimental results showed that when sorbent is selectively lost from the sorbent-treated sediment by winnowing, the repartitioning of contaminants may occur to some degree, but the repartitioning process is neither prolonged nor substantial to cause significant loss of the treatment effectiveness. Our close examination on the PRC-based PE sampling method indicated that the PRC method can provide reliable predictions at certain conditions, but more studies are needed to further investigate the PRC method for varying conditions. A standalone HOC mass transfer model was successfully developed, which is equipped with an IO excel file, GUI, and detailed user manual, so to enhance its user-friendliness in a great extend. A separate standalone program for sediment desorption kinetic model and the modeling case study booklet will also enhance the usability and accessibility of the HOC mass transfer model to DoD users.