Data Series 766
AbstractPrevious investigations indicate that concentrations of chlorinated volatile organic compounds are substantial in groundwater beneath the 9-acre former landfill at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington. The U.S. Geological Survey has continued to monitor groundwater geochemistry to ensure that conditions remain favorable for contaminant biodegradation as specified in the Record of Decision for the site. This report presents groundwater geochemical and selected chlorinated volatile organic compound data collected at Operable Unit 1 by the U.S. Geological Survey during June and October 2012, in support of long-term monitoring for natural attenuation. Groundwater samples were collected from 13 wells and 9 piezometers, as well as from 10 shallow groundwater passive-diffusion sampling sites in the nearby marsh. Samples from all wells and piezometers were analyzed for oxidation-reduction (redox) sensitive constituents and dissolved gases. Samples from all piezometers also were analyzed for chlorinated volatile organic compounds, as were all samples from the passive-diffusion sampling sites. In 2012, concentrations of redox-sensitive constituents measured at all wells and piezometers were consistent with those measured in previous years, with dissolved oxygen concentrations all at 0.4 milligram per liter or less; little to no detectable nitrate; abundant dissolved manganese, iron, and methane; and commonly detected sulfide. In the upper aquifer of the northern plantation in 2012, chlorinated volatile organic compound (CVOC) concentrations at all piezometers were similar to those measured in previous years, and concentrations of the reductive dechlorination byproducts ethane and ethene were slightly higher or the same as concentrations measured in 2011. In the upper aquifer of the southern plantation, CVOC concentrations measured in piezometers during 2012 continued to be extremely variable as in previous years, and often very high, and reductive dechlorination byproducts were detected in two of the four wells and in all piezometers. Beneath the marsh adjacent to the southern plantation, chloroethene concentrations measured in 2012 continued to vary spatially and temporarily, and also were very high. Additionally, CVOC concentrations measured in samplers deployed in access tubes were about two to four times less than those measured in the two samplers buried nearby, beneath the marsh stream. Total CVOC concentration, at what has been historically the most contaminated passive-diffusion sampler site (S-4), continued an increasing trend. For the intermediate aquifer in 2012, concentrations of reductive dechlorination byproducts ethane and ethene were consistent with those measured in previous years. |
First posted April 19, 2013 For additional information contact: Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge. |
Huffman, R.L., 2013, Groundwater geochemical and selected volatile organic compound data, Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington, June and October 2012: U.S. Geological Survey Data Series 766, 44 p.
Abstract
Introduction
Sample Collection and Analysis
Selected Monitoring Data
Summary
References Cited
Appendix A. Quality Assurance and Control of U.S. Geological Survey 2012 Geochemical Sampling