Concepts and Results in the Uranium Mill Tailings Remedial Action Ground Water Project

Abstract

The U. S. Dept of Energy is responsible for bringing 22 former uranium millsites into compliance with ground water standards determined by the U. S. Environmental Protection Agency. These standards require that contaminants in the ground water not cause an unacceptable risk to human health and the environment. One of three compliance strategies is selected for each site; no further action, passive (natural flushing) remediation, or active-engineered remediation. Selection is based on site characteristics and conditions. Initially, target strategies are proposed using a limited data set, matching the site conditions to the provisions in the standards. More than one strategy may be targeted based on knowledge of the site. Data gaps are identified, and additional site data are collected. The targeted strategy(ies) is (are) then confirmed or reselected. With this process, additional site characterization activities are focused on a particular remediation strategy(ies), thus avoiding the tendency to keep studying the site. This process also helps to avoid the tendency to focus on just one remedial action alternative too early, prior to having enough characterization data. Lessons learned from applying this process to initial sites include: (1) risks associated with using limited characterization data sets are typically manifested during the remedial construction phase; (2) targeting more than one strategy offsets the risk of a compliance strategy not suceeding; (3) different contaminants may require different compliance strategies; (4) the process requires built-in flexibility because each site is generally unique and parameters vary in degrees of freedom between sites, resulting in unique solutions; and (5) early stakeholder involvement is essential to gain buy-in of the final solution. Lessons learned are continually updated to incorporate experience and efficiencies.