Vibrating Beam Slurry Wall, Organoclay Containing Slurry, Repairs Leaking Landfill Liners
Leaking landfill liners cause the groundwater to be contaminated by various organic compounds and heavy metals. Groundwater below storage tanks and yards of chemical storage sites, at military bases and other sites, is often contaminated with plumes of DNAPL and other organic compounds. There are numerous methods available to treat such groundwater, such as the “pump and treat method”, bioslurpers, in situ methods, and others.
In many situations, if the contaminant plume has not progressed too far, a sorption barrier can be dug into the ground down to the nearest clay layer. Now the contaminants are held up by the sorption barrier, and will pile up near the barrier. The groundwater can be cleaned up by the above-mentioned methods. The ingredients of the sorption barrier can adsorb any contaminants that might invade the barrier.
A type of sorption barrier would be a slurry wall. Because a standard slurry wall is 3 feet wide, the sorption ingredients are too expensive due to the need for a large volume. A more suitable type slurry trench is the one constructed with the “vibrating beam” method, which is only 10 inches in diameter, and thus affordable.
The key slurry ingredients for effective sorption are organically modified clay, Type F fly ash, cement, and bentonite. The organically modified clay and, to a small degree, the fly ash, sorb the organics, and the bentonite traps heavy metals by ion exchange.
The slurry material, which the vibrated beam method encompasses, consists generally of either cement and bentonite, or IMPERMIX ®, a combination of attapulgite clay and slag cement. Organoclays for the removal of organic compounds, and zeolites to extend the bentonites life can easily be included into the slurry mix. The addition of Organoclay and/or zeolite is well established in the soil and waste stabilization industry.
Utilizing a vibrated beam slurry wall, which is very economical, allows for the formation of a wall around an existing or abandoned landfill, and, if need be, for a second one farther away, i.e. two parallel slurry walls. Obviously, wells could be drilled between the two slurry walls, and a pump and treat system installed to maintain the integrity of the outer slurry wall. In situ methods could also be used, such as oxidation or biological methods, as in the case of large DNPL plumes.
