Treatment Area Dimensions: 1,200 CY of soil up to 19 feet deep
Description of Work:
As a part of an Area Requiring Environmental Evaluation (AREE), volatile organic compounds (VOCs) were found in the clayey soils and groundwater at this former Army Base. The concentrations of chlorinated solvents and VOCs on this site ranged from 250 – 10,000 µg/kg. In-Situ Chemical Reduction (ISCR) technology was selected to remediate the site. Based on studies by Colorado State University, a mixture of 2% ZVI (zero valent iron), bentonite clay and a very small amount of emulsified vegetable oil was selected for mixing with the site soils to reduce the VOCs and stimulate biological degradation of the contaminates.
Geo-Solutions was contracted to provide the Soil Mixing machine, slurry mixing and pumping equipment, and specialty operators for the ISCR work. Geo-Solutions mobilized and made equipment ready for soil mixing work in about two days.
Thirty-five soil mix treatment columns, eight foot in diameter and up to 19 feet deep were installed. ZVI was added to the top of the columns while a slurry of bentonite and oil was injected through the hollow Kelly bar of soil mixing machine to blend and distribute the ISCR treatment into the depths of the columns. The entire soil mixing proportion of the work, including mobilization and demobilization was completed in three weeks.
Geo-Solutions also demonstrated new methods to inject the ZVI through the hollow Kelly bar, but this method was not fully utilized due to the shallow treatment depths of this project. This application of ISCR by Geo-Solutions demonstrated the success of the technology and the economics of using newer, modern Soil Mixing equipment to perform the work. The reduction of VOCs on the site ranged from 92% to 99.4% and averaged 97.6%.