U.S. Environmental Protction Agency, Robert S. Kerr Environmental Reserch Laboratory, P.O. Box 1198, 919 Kerr Research Drive, Ada, Oklahoma 74820

A -- FORCES AND FACTORS GOVERNING COLLOID MOBILIZATION IN SUBSURFACE SYSTEMS Sol. RFA-95-2. Due 042195. Contact Point, Stephen Kovash, (405) 436-8708. The USEPA, Robert S. Kerr Environmental Research Laboratory, in Ada, Oklahoma, is seeking assistance by cooperative agreement with non-profit organizations (minimum of 5% cost sharing required) or by interagency agreement with Federal Agencies qualified to conduct research in the area of colloid mobilization in subsurface systems. Colloidal transport in subsurface systems has only recently been recognized as a potential mechanism of contaiminant transport. Additional research is sought to address detailed surface and aqueous chemical effects and hydrologic factors which are responsible for colloid mobilization, stability and transport in natural subsurface systems (in particular, groundwater) and their significance in terms of risk assessment. Factors to be considered include, but are not limited to, the following: ground-warter flow velocity effects on particle shear and transport, flow path tortuosity and pore size effects, colloid surface charge, and the influence of particle coatings (organic and oxide) on colloid stability and transport. Information on these factors is of significance not only for prediction and quantification of this containment transport mechanism, but also for remediation optimization strategies and the choice of ground-water eampling protcols. Experimental designs which utilize ``natural'' materials will be given preference as will those which incorporate a field experimental component. While the focus of the research is colloid mobilization phenomena under natural gradient flow there is also interest in obtaining information concerning colloid mobilization under induced increases in flow (e.g. caused by pumping of wells) and the development of sampling methodologies which are capable of differentiating between ``naturally suspended'' and ``artifactually suspended'' colloids in ground water. The project is anticipated as a two-year project with the total budget not to exceed $200,000 for the two-year period, pending availability of funds. Interested sources must request a solicitation package containing a scope of work, evaluation criteria, and additional instructions in writing before the response date of April 21, 1995. FAX requests may be directed to (405) 436-8597. Telephone requests for the solicitation package or technical information will not be accepted. (079)

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