Scientific Investigations Report 2006-5030
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2006-5030
Shallow ground water is contaminated with the chloroethenes—trichloroethene (TCE), cis-1,2-dichloroethene (cis-DCE), and vinyl chloride (VC)—beneath the former Building 957 drum storage area at the Naval Undersea Warfare Center, Division Keyport, Washington. Chloroethene concentrations, monitored by the U.S. Navy since 1991, generally have decreased. To better understand the decrease in concentrations, the U.S. Geological Survey collected, analyzed, and evaluated water level, geochemical, and chloroethene data from eight monitoring wells at the site during June and August 2003 for evidence of chloroethene biodegradation.
The geochemical and chloroethene data clearly indicated that much of the TCE and VC, and some cis-DCE was biodegraded in ground water as it flowed beneath and slightly beyond the former Building 957 drum storage area. No apparent TCE biodegradation through any mechanism was indicated at the upgradient margin of the former drum storage area where aerobic ground water was indicated. Substantial reductive dechlorination of TCE and cis-DCE was indicated in the downgradient anaerobic ground water. Reductive dechlorination was definitively indicated by the presence of daughter products cis-DCE and VC in the downgradient wells. Ground-water redox conditions were favorable for biodegradation through microbial oxidation of VC (and cis-DCE to a lesser extent) in downgradient wells, and measured increases in the cis-DCE to VC ratio over time at those wells provided strong evidence for microbial oxidation of VC. All chloroethene concentrations detected in ground water at the former Building 957 drum storage area were less than 20 µg/L. In three wells where the 2003 TCE or VC concentrations exceeded remediation goals, concentrations consistently decreased over time.
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U.S. Department of the Interior |
U.S. Geological Survey
Persistent URL: https://pubs.water.usgs.gov/sir20065030
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