Delineation of Discharge Areas of Two Contaminant Plumes by Use of Diffusion Samplers, Johns Pond, Cape Cod, Massachusetts, 1998
Water-Resources Investigations Report 00-4017
By Jennifer G. Savoie, Denis R. LeBlanc, Dann S. Blackwood, Timothy D. McCobb, Richard R. Rendigs, and Scott Clifford
Diffusion samplers were installed in the bottom of Johns Pond, Cape Cod, Massachusetts, to confirm that volatile organic compounds from the Storm Drain-5 (SD-5) plume emanating from the Massachusetts Military Reservation (MMR) were discharging into the pond. An array of 134 vapor-diffusion samplers was buried by divers about 0.5 feet below the pond bottom in the presumed discharge area of the SD-5 plume and left in place for about 2 weeks to equilibrate.
Two areas of high concentrations of volatile organic compounds (VOCs) were identified. Samples from the first area contained trichloroethene (TCE) and tetrachloroethene with concentrations in vapor as high as 890 and 667 parts per billion by volume, respectively. This discharge area is about 1,000 feet wide, extends from 100 to 350 feet offshore, and is interpreted to be the discharge area of the SD-5 plume. Samples from the second area were located closer to shore than the discharge area of the SD-5 plume and contained unexpectedly high vapor concentrations of TCE (more than 40,000 parts per billion by volume). Ground-water samples collected with a drive-point sampler near the second area had aqueous TCE concentrations as high as 1,100 micrograms per liter. Subsequently, a more closely spaced array of 110 vapor-diffusion samplers was installed to map the area of elevated TCE concentrations . The discharge area detected with the samplers is about 75 feet wide and extends from about 25 to 200 feet offshore . TCE vapor concentrations in this area were as high as 42,800 parts per billion by volume.
TCE concentrations in micrograms per liter in water-diffusion samples from 15 selected sites in the two discharge areas were about 35 times lower than the TCE concentrations in parts per billion by volume in corresponding vapor-diffusion samples. The difference in values is due to the volatile nature of TCE and the different units of measure. TCE was detected in diffusion samplers set in the pond water column above the plume discharge areas, but the TCE concentrations were 20 to 30 times lower than the corresponding levels in diffusion samplers buried in the pond bottom.
Principles of Operation and Construction of Diffusion Samplers
Deployment and Retrieval Schedule
Installation and Retrieval Methods
Collection of Water Samples with the Drive-Point Sampler
Analysis of Vapor and Water Samples
Discharge Areas of Two Contaminant Plumes at Johns Pond
Storm Drain-5 Plume Discharge Area
Trichloroethene Plume Discharge Area
Results from Water-Diffusion Samplers
Results from Water-Column Samplers
1. Map showing location of study area, the Storm Drain-5 plume, Johns Pond, and altitude of water table, Cape Cod, Massachusetts
2. Longitudinal section showing vertical path of Storm Drain-5 plume in ground water along section AA', Johns Pond, Cape Cod, Massachusetts
3-9. Maps showing:
3. Location of Storm Drain-5 plume and diffusion samplers collected in April 1998 to delineate the Storm Drain-5 plume discharge area
4. Location of Storm Drain-5 plume and diffusion samplers collected in August 1998 to delineate the Storm Drain-5 plume discharge area
5. Location of drive-point water samples collected in September 1998 from discharge area of the previously unidentified trichloroethene plume
6. Location of diffusion samplers collected in December 1998 to delineate the discharge area of the trichloroethene plume
7. Discharge areas of Storm Drain-5 plume and the previously unidentified trichloroethene plume based on concentrations in vapor-diffusion samples, August 1998
8. Discharge area of the trichloroethene plume based on concentrations in vapor-diffusion samples, December 1998
9. Discharge areas and plume paths of the Storm Drain-5 and trichloroethene plumes, August and December 1998
10. Graph showing relation between trichloroethene concentrations in vapor- and water-diffusion samples collected in December 1998
1. Results of analyses for volatile organic compounds in vapor-diffusion samples collected from pore water in pond-bottom sediments near the Storm Drain-5 plume, Johns Pond, Cape Cod, Massachusetts, April 1998
2. Results of analyses for volatile organic compounds, specific conductance, dissolved oxygen, and selected inorganic constituents in drive-point water samples collected near the trichloroethene plume, September 1998
3. Results of analyses for volatile organic compounds in vapor-diffusion samples collected from pore water in pond-bottom sediments near the trichloroethene plume, December 1998
4. Results of analyses for volatile organic compounds in water-diffusion and adjacent vapor-diffusion samples collected from pore water in pond-bottom sediments, August and December 1998
5. Results of analyses for volatile organic compounds in diffusion samples collected from the pond-water column and adjacent pond-bottom sediments, August and December 1998
6. Results of analyses for volatile organic compounds in vapor-diffusion samples collected from pore water in pond-bottom sediments near the Storm Drain-5 plume, August 1998
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The citation for this report, in USGS format, is as follows:
Savoie, J.G., LeBlanc, D.R., Blackwood, D.S., McCobb, T.D., Rendigs, R.R., and Scott Clifford, 2000, Delineation of Discharge Areas of Two Contaminant Plumes by Use of Diffusion Samplers, Johns Pond, Cape Cod, Massachusetts, 1998: U.S. Geological Survey Water-Resources Investigations Report 00-4017, 30 p.
For more information about USGS activities in Massachusetts-Rhode Island District, visit the USGS Massachusetts-Rhode Island Home Page.
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