EPA On-line Tools for Site Assessment Calculation
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Investigative Techniques & Tools
In an investigation of this type it is useful to collect groundwater samples from temporary probe points, using push-probe equipment, in transects perpendicular to the long axis of the plume. The distance between the sampling points and the transects will vary depending on site conditions and accessibility. In this case two transects were completed at distances of about 250 and 450 feet from the source with a point-to-point spacing of approximately 25 to 30 feet. A portable GC was used to analyze the probe samples in the field to allow real time decisions and accelerate the delination process.
The results from the on-site analysis of the first transect indicated high (>10,000 ppb) levels of BTEX and MTBE in the samples collected at the water table. This changed to very low levels (<100 ppb) of both BTEX and MTBE in the second transect.
- Is this what you would expect?
- Is it likely that we have reached the extent of the dissolved component plumes?
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