Minimize risk of localized breakthrough through the more uniform treatment layer
Relatively long residance/contact time between contaminant and adsorptive or reactive material
Lower quantity of adsorptive material required meaning lower cost
Can be used on a slope or bank to address groundwater to surface water discharge
A primary challenge in the use of amendment or treatment materials for an active (reactive) cap is addressing the issue of non-uniform movement or upwelling of contamination through the sediments and, therefore, the cap. This creates a situation where isolated breakthrough of a cap can take place where contaminant concentrations are high (e.g. isolated seep zones) or where pore water velocity may be higher than the surrounding area.
The funnel and gate concept, as applied to treatment of contaminated sediment, is similar in approach to groundwater remediation. The goal is to use a low-permeability layer of AquaBlok® (e.g. the funnel) to direct groundwater and contaminants to a permeable treatment zone consisting of AquaGate®+ materials (e.g. the gate). The AquaBlok layer is designed to control the directional flow of the impacted groundwater, while the AquaGate+ layer adsorbs or treats contaminants as the groundwater passes through. The AquaGate+ materials consists of adsorptive materials, such as powdered activated carbon (PAC), organoclay, and others (e.g. ZVI, RemBind, etc.) that chemically react to neutralize contaminants. The primary objective of the funnel & gate approach is to minimize the potential for contaminant breakthrough of the active treatment material at a much lower cost than alternative ex-situ “pump and treat” approaches.