Natural attenuation is increasingly relied upon for the passive remediation of contaminated soils and groundwater. Fully a quarter of the Superfund sites closed in 1995 relied to some extent on natural attenuation. More recently, CERCLA reauthorization efforts have called for consideration of natural attenuation at a majority of sites. Despite the apparent shift in remediation focus from active remediation techniques to passive ones, including monitored natural attenuation (MNA), there is no mutually agreed upon set of guidelines for implementing natural attenuation.
EPAís Office of Solid Waste and Emergency
Response (OSWER) recently issued interim guidelines for relying
on monitored natural attenuation at Superfund, RCRA Corrective
Action and Underground Storage Tank sites (see: http://www.epa.gov/swerust1/directiv/9200_417.html).
EPA views MNA as a remedial alternative that should be evaluated
during the site characterization and remedial selection phase.
Concurrently, the use of monitored natural attenuation should
be supported by site specific information that demonstrates the
efficacy of the method much like any other remedial approach.
Nevertheless, the OSWER directive addresses natural attenuation
as a whole and does not provide data or evaluation criteria for
specific contaminants. A step-by-step guidance document that
addresses individual contaminants is needed to satisfy the larger
picture guidelines outlined by the OSWER Directive. Sandia National
Laboratories, Pacific Northwest National Laboratories, and Oak
Ridge National Laboratories have been tasked by DOE headquarters
to develop for the DOE complex a step-by-step protocol for:
The guidance document and site-screening protocol
is also set up as a web-based decision support tool to assist
US Department of Energy (DOE) site environmental managers and
their staff and contractors in evaluating and implementing MNA
consistent with EPA guidelines on site characterization, conceptual
model development, and long-term monitoring. The site-screening
software and documentation will be released in draft form in the
Spring of 1998. The guidance document will be finished in draft
form by September of 1998.
Points of Contact:
Patrick V. Brady, Robert D. Waters, and David
J. Borns
Sandia National Laboratories
P.O. Box 5800, MS 0750
Albuquerque, NM 87185
Office: 505-844-7146; Fax: 505-844-7354
Email to: P. Brady
Kenneth M. Krupka
Pacific Northwest National Laboratory
P.O. Box 999, MS K6-81
Richland, WA 99352
Brian P. Spalding
Oak Ridge National Laboratory
2597 B ¾ Road
Grand Junction, CO 81503