French Drain
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French Drain?

This is an aerial photograph of an abandoned gold mine refinery site near Phillipsburg, Montana. The waste rock pile at the site was mainly composed of pebble to boulder size crushed clean granite. The original creek channel had been diverted as the rock was dumped at the site, shifting it to the south.

 

A developer used most of the rock to build roads on the property and had excavated to nearly the original ground level to build the pond shown here.  While excavating the pond a spring was uncovered which proved to be a real gusher. The situation developed into a legal issue of importance and it became necessary to locate the source of the water without doing any further excavation.

Our hydrologic review of the sight suggested that the source could be the old creek channel suggested above (Paleochannel).  Another view was that the developer had installed a French drain from the existing creek location without the proper permits or water rights.

ECHOTECH conducted two resistivity profiles; one along the present creek embankment (Line 1), and the other across the entire drainage and both proposed sources (Line 2).


 

The first profile showed the presence of the paleochannel as predicted.  Profile 2 showed the paleochannel again, but also showed the presence of water at the location of the suspected French drain.  The size of this feature, however, was much larger than expected.



We concluded from this that a French drain had not been constructed recently, but that the entire waste rock pile was a huge rock drain capable of channeling water through the porous matrix. 

 

Last modified: 04/27/05             Copyright 2003-2005, ECHOTECH GEOPHYSICAL, INC.  All Rights Reserved.                Hit Counter