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Surface Resistivity Testing
As the Little Sioux River winds through the O’Brien County, it passes through a narrow valley with a shallow alluviale aquifer where Osceola County Rural Water has drawn water for years. The depths and quality of sands and gravels is highly variable throughout this valley. OCRWS rapid growth in water demands had pushed their existing wells to the limit, and it was now time to start looking for additional water supply.
The river valley in this area is very narrow, but potential well sites were limited by the size of the floodway and land owners in the valley who were less than cooperative. OCRWS was eventually able to secure an option to purchase on nearly 2 quarter sections of ground, but with so much land to cover, traditional exploration methods using a drilling rig would be expensive and possibly miss highly productive areas.
DGR Engineering partnered with WSP to perform 4 days of surface resistivity testing to give multiple cross section “snap shots” of the aquifer thicknesses in the area. With field results available in the field instantaneously, we were able to quickly dismiss large sections of the exploration areas and focus on areas of high potential. We were even able to access public access state land at the last minute to expand our search. We were able to do this without any permits, due to the non-evasive nature of the testing.
In the end, our team located 2 new well sites in the original search area. We were also able to identify a 70’ deep vein of gravel on State owned ground, nearly double what we found anywhere else in the search. Physical drilling in these locations confirmed the results, and now we are in the final stages of the necessary state permits to drill two new wells on State ground, which will be the most productive wells OCRWS has in the valley.