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Superfund Innovative Technology Evaluation (SITE)


Note: EPA no longer updates this information, but it may be useful as a reference or resource.


International Waste Technologies/Geo-Con In Situ Stabilization/Solidification
August 1990

An evaluation was performed of the International Waste Technologies (IWT) HWT-20 additive and the Geo-Con, Inc. deep-soil-mixing equipment for an in situ stabilization/solidification process and its applicability as an on-site treatment method for waste site cleanup. The analysis of this technology is contained in two reports, the Technology Evaluation which describes the demonstration and this Applications Analysis which evaluates the technology based upon all available data.

A demonstration was held at a General Electric Co. electric service shop in Hialeah, Florida, which provided the bulk of the information for the technology evaluation. Operational data and sampling and analysis information, for this first field application of the IWT additive, were carefully monitored and controlled to establish a database against which other available IWT and Geo-Con data, and their claims for their technologies, could be compared and evaluated. Conclusions were reached concerning the technology's suitability for use in cleanups of various contaminants and at different locations.

The technical criteria used to evaluate the effectiveness of the in situ process were contaminant mobility (based on leaching and permeability tests), and the potential long-term integrity of the solidified soils (based on some physical tests and microstructural studies). The Geo-Con deep-soil-mixing system was also evaluated.

Since the most controlled sampling on the IWT additive was performed during the demonstration, much of the emphasis of the evaluation is based upon this data. Test samples were taken of the site material before treatment to characterize the site and of the solidified materials after curing for 5 weeks. Samples of treated and untreated material were analyzed to determine: physical properties (such as unconfined compressive strength and permeability) that along with the microstructural studies provides clues to long-term durability of the treated mass; chemical properties (such as soil composition and leachability1 that provide information on contaminant mobility.

This report evaluates the in situ process (based on the test results of the demonstration), other data provided by the technology developers, and the general capabilities of cement-based systems. It also discusses the probable applicability of the technology to sites other than the GE electric service shop.

The conclusions drawn from the available data are that: (1) immobilization of polychlorinated biphenyls (PCBs) appears likely, although due to low leachate concentrations for both the treated and untreated soils — a result of the low concentrations of PCBs in the soil encountered in most of the tests — it cannot be confirmed; (2) heavy metals can probably be immobilized; (3) volatile organics can bereduced to low concentrations in treated soil leachates, but the ability to immobilize is not clear; (4) a small volume increase on the order of magnitude of 5%–10% can be expected; (5) the solidified material shows satisfactory physical properties — with high unconfined compressive strengths, moderately low permeabilities, and satisfactory integrity for the wet/dry samples — but unsatisfactory integrity for the freeze/thaw samples; and (6) microstructural results show a dense, low-porosity, homogeneous mass — indicating a potential for long-term durability.

Risk Mangement Research | Air and Climate Change Research | Water Research | Ecosystems Restoration Research | Land Risk Management Research | Technology: Sustainable Technologies Research, Environmental Technology Verification Program (ETV), and Technology Assessments

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