The objective of this Statement of Need was to develop a better understanding of relatively minor components of common groundwater contaminant mixtures in terms of their degradation kinetics and attenuation in the environment. Of particular interest was their behavior at environmentally relevant concentrations (often <100 ppb) in both natural systems and in engineered systems designed for treatment of the more common groundwater contaminants found at Department of Defense (DoD) sites. The following research objectives were of interest:

• Assess the natural attenuation mechanisms and degradation kinetics of chemicals of interest in groundwater at environmentally relevant concentrations.
• Determine the fate and transport of chemicals of interest during implementation of common groundwater treatment scenarios for primary contaminants such as chlorinated solvents or petroleum hydrocarbons.
• Evaluate whether minor modifications can be made to common groundwater treatment scenarios for improved treatment of low concentrations of chemicals of interest.

Proposals should have addressed one or more of the objectives listed. The chemical of greatest interest was 1,4-dioxane as it frequently co-occurs at low concentrations with chlorinated solvents. Other chemicals of interest included 1,1-dichloroethane (1,1-DCA) and 1,2-dichloroethane (1,2-DCA). Other chemicals were considered but must have met the criteria of co-occurrence with common groundwater contaminants within chlorinated solvent or petroleum hydrocarbon plumes at DoD sites; the rationale for inclusion of other chemicals must have been clearly defined. Proposed efforts must have been conducted at environmentally relevant concentrations to be considered.

Research and development activities at laboratory-, bench-, and field-scale were considered, but work did not necessarily have to culminate in a field-scale effort. Technologies and approaches should have been applicable to a variety of hydrogeologic settings.

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