Over 9 million Mg of waste foundry sands (WFS) are produced annually in the United States as a by-product of the metal casting industry. The majority of WFS are deposited in restricted or sanitary waste landfills. Considerable savings is available to the metal casting industry through the development of reuse applications for their WFS and generators are often willing to provide WFS to a job site at no cost to the end user. Laboratory investigations have indicated that WFS from ferrous foundries can provide the necessary engineering properties for a highway embankment and that the MicrotoxTM bioassay test can be used to screen the “toxicity” of WFS to prevent a negative environmental impact. In 1996, the Indiana Department of Transportation (INDOT) and Purdue University constructed a demonstration embankment using WFS. WFS and control embankments were instrumented to monitor geotechnical and environmental performance. Stockpile and job site “grab” WFS samples were also tested. Detailed geotechnical results are presented in a companion report by Fox and Mast (1998). In general, results indicate that WFS can perform well as a structural fill with strength and deformation characteristics comparable to natural sand, but cannot be considered as freely draining. Environmental testing consisted of MicrotoxTM and Nitrotox bioassays, ion chromatography, and inductively coupled plasma testing for metals. Bioassay results indicate the WFS have not resulted in inhibitions (toxicity) higher than those expected from natural sands. Ion migration from the WFS into the foundry sand lysimeter was found, supporting bioassay data, but at concentrations below reuse regulatory criteria. Metal concentrations were generally below Indiana regulatory criteria, exceedences appeared in both up- and down-gradient wells suggesting background metal concentrations as opposed to significant leaching from WFS. The WFS did not result in a negative environmental impact on the site. State environmental regulatory agencies were the most frequently identified source of barriers to the beneficial reuse of WFS and reuse is further compounded by the lack of decision-based scientific tools such as life-cycle or risk-based analysis methods. The resultant liability exposure from state and federal regulations was the prevailing concern expressed by Departments of Transportation (DOTs) when considering using a regulated waste such as WFS. Furthermore, foundries often lack an organizational commitment to the reuse of its WFS as evidenced by the lack of both product quality control and a marketing strategy. To facilitate the use of WFS by INDOT, an Acceptance Criteria protocol based on the MicrotoxTM bioassay test was developed as part of this project. Additionally, a proposed “Recurring Special Provision” for the use of WFS in embankment construction and a WFS stockpile random sampling protocol were developed. The necessary decision tools for incorporating WFS into transportation construction, primarily embankment construction, appear to be available to the Indiana DOT and other DOTs) as products of this research.

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waste foundry sand, highway embankments, bioassay, Microtox, environmental quality, regulatory issues, liability, cost savings, SPR-2136

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Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, IN

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