Derivation of a Liquid-to-Soild Ratio for ASTM Method D3987-85 for Soils Containing Chromite Ore Processing Residue Using Selected Unsaturated Zone Models

While most health-based cleanup levels for hexavalent chromium [Cr(VI)] in soil are established to protect the general population against cancer, the New Jersey Department of Environmental Protection (NJDEP) has established a Cr(VI) soil cleanup criterion to protect Cr(VI)-sensitive individuals against allergic contact dermatitis (ACD). For this criterion, exposure is assumed to occur when a Cr(VI)-sensitized individual contacts a puddle in which rainfall has dissolved Cr(VI) from the associated surface soils. To simulate the movement of Cr(VI) from surface soil into puddle water after rainfall events, this soil cleanup criterion requires that the Cr(VI) concentration extracted from soil using ASTM Method D3987-85 at a 2:1 liquid-to-solid ratio (LSR) be less than 25 mg/L. However, this LSR is based on several simplifying assumptions that may not be appropriate for many soil types. In this article, three unsaturated zone transport models—Chemflo, SWIM, and HYDROGEOCHEM—are evaluated for developing LSRs for...