In one application for containing and remediating contaminants in sediments, employing a geocomposite eliminates the need for a thick cap or removal and subsequent ex situ treatment of the sediment. A geocomposite with at least one layer of reactive material is placed over the area to be remediated. A layer of available surcharge materials such as sand, gravel, or riprap covers the geocomposite. The weight of the surcharge materials causes pore water to flow from the sediment through the reactive layer or layers. Contaminants may be trapped in this reactive layer or layers. A top or bottom layer, or both a top and bottom layer, may be provided to inhibit incursion from outside the sediment layer, while permitting appropriate flow direction of pore water into the reactive layer or layers.