ESN recently completed a project in Deming, N.M. for D.B. Stephens & Associates and the New Mexico State Highway and Transportation Department to identify the source of ground water contamination by chlorinated solvents.
Conventional drilling at the site would have involved several thousand dollars per hole and risked missing the contaminants using interval soil sampling. The project design incorporated the deep pushing capability of the Heavy Duty Probe to 70-feetusing the 1.75" O.D., 1" I.D. drive pipe, gamma logging each hole from inside the pipe to identify zones of less permeable materials, and the setting as many as four permanent vapor implants just above these zones. At each selected depth, the aluminum implant was sand-packed; bentonite was installed between them to seal off each zone. All of this was done as the drive point was withdrawn. Each mulit-port well was finished with a flush mounted traffic cover.
Vapor sampling and analysis was conducted onsite in the ESN Mobile Lab. The results showed a clear pathway of contaminant migration extending vertically and horizontally several hundred feet from a formerly used septic tank to the area known to have ground water contamination. The maximum chlorinated vapor concentration observed was shown to decline in depth as distance from the septic tank increased, until it reached the area just above the maximum concentration in ground water. Methane was also measured in the soil vapor. Click here to view a cross-section of soil gas profiles.
Vertical profiling was instrumental in mapping contaminant distribution in three dimensions. In addition, the lithologic data was used directly in the design of a vapor extraction system. The gamma logging was a powerful tool for characterizing lithology, which would have been impossible to obtain otherwise, in a soil vapor project. The entire project, including 30 sampling locations and more than 100 vapor analyses, was conducted for less than the cost of 6 monitoring wells.