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Permeable Reactive Barrier Walls
Permeable Reactive Barrier Wall Illustration
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A permeable reactive barrier wall is a newer technology that remediates contaminated groundwater and soil without mass excavation, disposal or conventional “pump and treat” methods. Usually, a treatment media, or reactive barrier, is buried in a narrow trench beneath the ground surface so that contaminated groundwater passes through the media, and it emerges ‘clean’ because contaminates are treated and/or removed by the reactive barrier. Typical treatment media used as a permeable reactive barrier wall include granular iron, activated carbon, engineered bacteria, chemicals, and special clays.
The Funnel and Gate Method
Often, slurry walls are used to funnel the groundwater toward a reactive media gate; this type of installation is called a “funnel and gate”. Special construction considerations are needed for installing reactive barrier walls to ensure the design life of the media and to be cost-effective. Since any permeable reactive barrier wall must be buried deep underground and below the groundwater table, geotechnical methods are quite useful in minimizing excavation volumes, eliminating dewatering, and reducing costs.
Save Money with Slurry Trenches
Placing Iron Fillings Mixed with Sand
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In most cases, the least expensive method for installing funnel and gate is a slurry trench method. A slurry wall can provide the funnel to direct groundwater toward the reactive barrier materials. A Bio-Polymer slurry trench drain can provide the gate of the permeable reactive barrier wall for the installation of the reactive media. The savings from this combination of methods are considerable including savings in excavation volumes, disposals costs, mobilization, and construction time. Slurry trenching methods have been proven to permit the installation of reactive iron (ZVI), engineered bacteria, compost, carbon and other materials without significantly affecting the reactive potential of the reactive barrier walls. In some cases, i.e. bio-treatment schemes, the Bio-Polymer slurry can actually promote the reactivity of the media. The installation of the reactive iron using the bio-polymer slurry method requires special equipment, materials and methods that have been developed, in part, by Geo-Solutions.
When In Situ Soil Mixing may be Best Used in Conjunction with Permeable Reactive Barrier Walls
On some sites, the reactive media can be applied directly to the contamination instead of through a funnel and gate. Usually, these sites have lower groundwater flows and the contamination is less mobile. For these sites, In Situ Soil Mixing provides an ideal method for applying the reactive materials directly without excavation or dewatering. In-situ treatment using soil mixing is usually much less expensive than off-site disposal and completely avoids excavation and transportation costs.
Excavation and Backfilling under Slurry
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Geo-Solutions’ Experience with Permeable Reactive Barrier Wall Construction
The management of Geo-Solutions has been involved in the development of reactive barrier wall technology since the late 1980’s. Vice Presidents Steve Day and Bob Schindler have been involved in a number of pioneering reactive media projects that used soil mixing methods to inject granular iron, potassium permanganate, heated air and proprietary admixtures into the ground to treat contamination. Mr. Day and Mr. Schindler consulted with the Department of Energy contractors on the first-ever, granular iron-filled trench to use the Bio-Polymer trench installation method.
Why Use Geo-Solutions for Your Reactive Barrier Needs
Geo-Solutions remains active in the advancement of reactive barrier technology. We maintain close working relationships with the inventors, scientists, and engineers who study and design reactive barrier installations. Geo-Solutions’ expertise with slurry walls, grouting, and soil mixing provides the perfect background for planning and building new permeable reactive barrier walls that are more easily constructed, less costly and more effective.
Permeable Reactive Barrier Wall Project Examples
Recent permeable reactive barrier wall projects include:
A design mix study for the application of ZVI-clay to a former dry cleaners site in North Carolina
Technical assistance for the installation of activated carbon on a 1,500 sq. ft. Superfund site in upstate New York
Technical assistance for the installation of ZVI on a munitions site in West Virginia
Technical assistance for the installation of sulfate eating bacteria media on a site in Vancouver, BC, Canada
Learn More about Reactive Barriers
Geo-Solutions has authored several papers on reactive barrier walls, including those used in conjunction with Bio-Polymer slurry trenches and In Situ Soil Mixing.
View our library to read and download several papers and abstracts about permeable reactive barrier walls.
Call Us Today
For help with passive and permeable reactive barrier walls, call us at 724-335-7273.
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