APPLYING THE DISSOLVED OXYGEN ALTERATION METHOD WITH HYDRAULIC ISOLATION TO MEASURE WATER QUALITY IN INDIVIDUAL FRACTURES IN OPEN WELLBORES
This study demonstrates a method for assessing water quality in individual fractures in open crystalline bedrock wellbores utilizing naturally-occurring flow conditions in the well. The technique uses the dissolved oxygen alteration method (a borehole dilution technique), hydraulic isolation using a single control pump, and a simple sampling device. The method was demonstrated in two wells containing one and two transmissive inflowing fractures, and has been described conceptually for nine bedrock wells with varying flow conditions containing one, two, or three transmissive inflowing fractures. The method can provide preliminary information for long-term monitoring, and offers a low cost means of sampling discrete zones in wells where permanent or long-term multi-level sampler installation may not be feasible. Furthermore, the technique can identify fractures that may be an ideal candidate for sealing or long-term monitoring if contaminant concentrations are particularly high.