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Thursday, November 13, 2014

#197 - Borehole and soil gas analysis- Part 2

A while back, we posted some information about analysis of boreholes at decommissioned mine sites. Here is Part 1 of the discussion.

At the time, we mentioned that we have frequently sold the Model 309 Portable O2 / CO2 analyzer for this application. Because some of the samples will be pulled up from deep into the borehole, we can install a heavy duty pump into the instrument. This solution has been great for this application.

One mining company recently contacted us requesting a solution to a problem they were having with water accumulation in their analyzers. In the standard instrument we supply to this company, we incorporate a bowl filter of some kind at the sample inlet to capture any water that may come up with the gas. This approach has usually been adequate for the brief period that they have sampled at each point. However, at some boreholes, water accumulation in the interstices between the back-fill material and the liner has been significant. The analyzer has to pull out a large volume of water from each of the tubes in the bundle before the gas analysis can begin.

To cope with this reality, we proposed a closed catch-pot arrangement that isolates the water while maintaining the extractive suction. In operation, the sample pump pulls on the borehole tube. The entrained water comes up first and simply falls to the bottom of the clear bowl. When the water is evacuated from the tube, the gas sample passes into the detectors for measurement.

This arrangement is nothing new; it’s an old trick that has been around for years. We just haven’t implemented it in such an overt style with a portable analyzer. If you are monitoring soil gas from a tube bundle in a mine tailings borehole, let us know. We can offer a solution.

For information on these and other gas analyzer systems, give Mike or Dave at Nova a call, or send us an e-mail.
sales at nova-gas dot com
websales at nova-gas dot com


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