||National Risk Management Research Lab., Ada, OK. ;Air Force Center for Environmental Excellence, Brooks AFB, TX. ;Parsons Engineering Science, Inc., Denver, CO.
A major initiative to evaluate monitored natural attenuation (MNA) of ground-water contaminated with fuel hydrocarbons began in June 1993 and continued through September 1999. The main emphasis was to evaluate natural degradation mechanisms to reduce dissolved fuel components of benzene, toluene, ethylbenzene, and xylenes (BTEX). The results are summarized in this report for the six-year study. During this time, site characterization studies were conducted at 28 spill sites on Air Force bases within all 10 USEPA regions. All sites were evaluated for natural attenuation trends according to the procedures outlined in the technical protocol document (Wiedemeier, et al. 1995). This research report has not been subjected to U.S. EPA review and official endorsement of conclusions made should not be inferred. Monitored natural attenuation refers to the use of naturally occurring attenuation processes to decrease ground-water contaminants by physical, chemical, and biological processes.