An improved method of inserting reactive material in the ground for treating groundwater contaminated with chlorinated solvents has been devised. An older method involves the removal of a significant portion of soil overlying the treatment volume, and consequently the expensive off-site disposal of the large amount of removed soil (some or all of which is contaminated). In the improved method, only a relatively small amount of soil need be removed.
The first step in the improved method is to remove approximately the first 4 ft (1.2 m) of soil from above the water table where the reactive material is to be placed. Hollow casings are inserted in the ground surface over the treatment site, then hammered down to the required placement depth. [The placement depth in the original application at Kennedy Space Center was 40 ft (12 m).]
Once each casing reaches the required depth, a gravity-fed hopper is used to fill the casing with the reactive material plus, if needed, bulking material to increase permeability. The casing is then removed, leaving behind a column of treatment material. In this manner, several such columns are positioned throughout the treatment volume.
An in situ deep-soil-mixing rig is then used to mix the reactive columns with the adjacent soil. Thorough mixing is achieved by up-and-down motion of the rig. The rig includes paddles, the turning of which acts in combination with the up-and-down motion to help increase the permeability of the soil.
This work was done by Jacqueline Quinn of Kennedy Space Center and Debra R. Reinhart, Christian A. Clausen III, Manoj B. Chopra, and Cherie L. Geiger of the University of Central Florida.
This invention has been patented by NASA (U.S. Patent No. 6,207,114). Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Technology Commercialization Office, Kennedy Space Center, (321) 867- 8130. Refer to KSC-11957.