Wisconsin Natural Attenuation Study
To reduce cleanup costs and decrease the backlog of contaminated sites, Wisconsin changed its rules regarding cleanup approvals and case closures. In 1996 Wisconsin began to accept natural attenuation as a tool to achieve case closure. Closure may be granted if there is a source control and a stable or receding contaminate plume. It is assumed that ground water standards can be achieved within a reasonable time through natural attenuation. Once it is determined that natural attenuation is working the sites are closed and monitoring is discontinued.
In October 2003, Wisconsin received a grant to evaluate their procedures for closing a site using natural attenuation. The Wisconsin Departments of Natural Resources and Commerce along with the University of Wisconsin at Madison, are interested in determining if the presumptions made about natural attenuation at the time of closure were accurate and if sites continued to remediate without continued sampling or oversight. If the study shows contaminate plumes are stable or receding then it can be concluded Wisconsin's methodologies were correct.
In most states once natural attenuation is chosen as the remedy at a LUST site, a facility is required to continue sampling to "monitor" the progress of natural attenuation. This study will examine whether long-term monitoring is beneficial or necessary for site closure. If the study shows that continued sampling is not providing necessary or valuable information, then sites could be "closed" sooner and save state fund money from annual sampling events. Other states can use the data from this study to re-evaluate their closure protocols and determine the relevancy of continued oversight. Reducing the overall time spent on natural attenuation oversight should help reduce cleanup costs and decrease the backlog of open contaminated sites.
For more information contact:
Wisconsin Department of Natural Resources
Theresa A Evanson
Wisconsin Department of Commerce