Potential Cap Technologies

Researchers will examine the effectiveness of the following alternative technologies in the Anacostia River capping demonstration:

AquaBlok^TM

This cap controls seepage and advective contaminant transport. It consists of a gravel/rock core covered by a clay layer that expands in water decreasing its permeability. It is applicable to seep locations such as Site 2 and may be useful as a funnel in a "funnel and gate reactive barrier design. A contract to demonstrate the technology is under negotiation with its owner, AquaBlok, Ltd.

Zero-valent iron

This capping technology encourages dechlorination and metal reduction. Forms of zero-valent iron under evaluation for the Anacostia demonstration include:

• Fe(0), Fe-S, Pd/Fe(0), which are subject to athodic reactions that yield hydrogen, driving biotic transformations, reductive declorination, and metal reduction. They also directly provide electrons for abiotic reduction.
• Chlorinated organic compounds (such as polychlorinated biphenyls) under evaluation by Carnegie Mellon University.
• Metals under evaluation by Rice University.

Apatite barriers

This phosphate mineral barrier encourages sorption and the reaction of metals. The evaluation of this technology is being conducted by Louisiana State University and the University of New Hampshire.

BioSoil^TM

This product encourages degradation of organic contaminants through enhancement of reductive dechlorination and anaerobic degradation of polyaromatic hydrocarbon (PAH) compounds. The soil is made from composting and has a high organic content that encourages sorption and retardation of transport. BioSoil is under evaluation at Louisiana State University.

OrganoClay Sorbent

This natural organic sorbent encourages sorption-related retardation (reduction in advective-diffusive transport). A candidate sorgent, Biomin EC-100, is an organo-modified clay with low permeability and high organic content. It encourages retention of both nonaqueous and dissolved constituents and has been evaluated for control of active hydrocarbon seeps in Thea Foss Waterway in Washington state.

Contract negotiations are underway for treatability testing with Hart-Crowser, which owns this sorbent.

Other Potential Cap Materials

An Ambersorb commercial sorbent and coal-based sorbents are undergoing initial review and feasibility evaluation.

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