Grosenheider, Kim E.

Mn/DOT engineers are increasingly looking to recycled materials as readily available and cost-effective substitutes for natural aggregate and to fly ash as a material that can be used in the stabilization of sub-base soils. These recycled wastes have the potential to contain unacceptably high levels of some chemicals. This project produced chemical data on wastes, non-surface background soils, and natural aggregates for use in a due diligence screening tool in current service by Mn/DOT and developed by the Office of Environmental Services (OES). These data will be used by OES for their internal Mn/DOT due diligence determinations using their streamlined hazard evaluation process. A future Local Road Research Board project will transform the OES streamlined hazard evaluation process into a CD-based product for use by the larger transportation community. Data developed by this current project will be used to populate the future CD-based product electronic database. This project will maintain consistency with the current in use Office of Environmental Services (OES) streamlined hazard evaluation process for waste recycling in Mn/DOT infrastructure projects.

The properties of soft fine grained soils sometimes require enhancement to facilitate road construction and increase long term road durability. One option for roadbed stabilization is to treat the soil with fly ash, which possesses several beneficial engineering properties. However, the concentrations of elements in fly ash may potentially pose an unacceptable risk to human health. The Screening Tool provides straightforward assessments of this hazard. This tool is intended to be used as part of the assessment of due diligence of these risks. The Screening Tool does not give permission for the use of fly ash and the screening tool was not designed to predict the effects on surface waters, which are regulated by the Minnesota Department of Natural Resources (DNR) and Minnesota Pollution Control Agency (MPCA). This computer program provides guidance to users, but users must make sure the proposed project complies with all applicable and relevant rules and regulations that govern use of fly ash. Details of the calculation and further discussion of the importance of site-specific data is included in this document.