Monitored natural attenuation (MNA) can be used to manage long-term obligations at contaminated sites. The objective of this project was to prepare a technically sound and concise guidance document answering frequently asked questions (FAQs) about MNA that will aid in the understanding and implementation of MNA.

The FAQ format has been used to develop technical overview documents for similar remediation topics, including chlorinated solvent releases (Frequently Asked Questions Regarding the Management of Chlorinated Solvents in Soil and Groundwater, published in 2008 as part of ESTCP project ER-200530). The document generated as part of this project was peer-reviewed by a panel of experts prior to release.

The FAQ format is characterized by a series of one-sentence "questions" followed by technical "answers" that cover one or two pages apiece. The intensive use of graphics provides a more effective and visually appealing means for conveying information. The answers provide links to other question/answer pairings within the FAQ document that deal with related topics, as well as references to other scientific publications that can provide further information. Because it compiles and references an extensive amount of source materials, this type of document represents an ideal starting point for readers who want to seek out additional information and serves as a valuable tool for project managers trying to assess the feasibility of using MNA at their sites.

This effort extends and complements existing work (e.g., Natural Attenuation of Chlorinated Solvents by Wiedemeier, Rifai, Newell, and Wilson, 1999); provides resources and key information about new MNA technology breakthroughs (e.g., compound-specific isotope analysis, molecular biological tools); presents new developments in how MNA is applied (e.g., source zone MNA); presents MNA solutions and approaches for a wide variety of constituents (e.g., inorganics, radionuclides); provides context for how emerging fate and transport processes (e.g., matrix diffusion) impact the application and attractiveness of MNA; and introduces new concepts about site management (e.g., "low-risk" site management).

The final product is publically available and distributed in electronic form.

The FAQ document provides a basis for the Department of Defense (DoD) to focus its remediation efforts and efficiently allocate environmental restoration funds. This is especially critical given the push to move DoD sites toward Response Complete. It is of potential benefit to all DoD sites, given that it will address MNA for a wide range of contaminants. The benefit is particularly targeted to those sites where a remedy is yet to be implemented or where there is some question about the long-term effectiveness of a technology that has already been implemented. It specifically addresses the need for approaches to manage risk at sites where persistent levels of contamination are expected following initial remedy implementation, given that monitoring post-treatment natural attenuation processes will be a necessity at these sites.