Monitored Natural Attenuation (MNA)

In Monitored Natural Attenuation (MNA), you'll learn ...

• Initial and detailed evaluation to determine viability of MNA for soil and groundwater cleanup
• Physical and biological processes that affect MNA performance
• Hydro-geologic and contaminant properties that affect MNA performance
• Long-term performance monitoring for soil and groundwater

Overview

Credit: 4 PDH

Length: 82 pages

EPA confirmed over 7,300 new releases from underground storage tanks (USTs) during fiscal year 2008, bringing the cumulative total to 480,000 releases. Of these, about 103,000 are still in cleanup status. (Source: EPA, FY 2008 End of Year Activity Report, 11/22/2008.) These UST leaks pose a grave threat to human health and the environment by contaminating groundwater and soil.

Depending on the presence of free product and stability of the contaminant plume, MNA can serve as a follow-up or standalone method for soil and groundwater remediation.

MNA is considered passive because, aside from placement of monitoring wells, there is negligible disturbance of the subsurface. MNA does not use pumped wells for injection or extraction of air or water, as do bioventing or soil vapor extraction. Instead, MNA relies on physical and chemical activity in the natural subsurface to attenuate contaminants. Due to longer remediation time frames, contaminant migration, and other uncertainties, performance monitoring is much more critical for MNA than other strategies. MNA seems attractive as a “do-nothing” approach; however, in order to use MNA exclusively, you must be certain that 1) the contaminant source is eliminated and 2) the plume is contracting. Otherwise, a more active strategy is necessary.

This course is intended for environmental engineers who wish to expand their knowledge of alternative methods of site remediation.