TALES FROM THE FIELD
retrieve the data logger we would call him so he could coax us to continue trying. On the drive to the study site we formulated a plan of action and decided that the open casing well would be our best shot at a successful retrieval due to its accessibility when we compared it to the irrigation well.
Upon our arrival at the well in the middle of a recently plowed
field, we set to work unloading our retrieval tools: a reel of fish- ing line, hooks and weights to create a length of fishing line with a treble hook and a weight similar to what one would use for catfish. After dragging the hook on the gravel approximately 60 feet down at the bottom of the casing the line weighted, and I pulled it up. With a failed first attempt, and the sun rising higher in the humid Central Texas sky, Elena and I felt the heat as the temperature rose to 95°F. The lack of shade made this task particularly grueling, and since we could only deploy one line at a time, lest we hook ourselves, Elena was primarily relegated to a safety partner and moral support. After a few hours, we had suc- cessfully retrieved several pounds of what used to be well casing which was now pieces of porous rusted iron.
At that point, we
concluded that despite our best efforts we had to admit defeat. I asked Elena to call Dr. Yelderman so we could request permission to end our fishing expedition and when she put him on speaker, I decided to give it one last shot and dropped the line. After a few more attempts something weighted the line, and I carefully pulled it up while talking with my advisor on the phone. To our shock I had hooked the top of the data logger!
While the exact cause of the cable failure has not been posi-
tively determined, it seems likely that there was a biogeochemical reaction. The aquifer has relatively low dissolved oxygen, moderate pH and high salinity. Many farmers in the area also commonly lubricate their irrigation wells with oil that gets into the casing and provides a source of organic carbon. Due to these conditions, it is possible that bacteria feed off this source of organic carbon for cellular respiration using first the minimal dissolved oxygen, then the nitrates from fertilizer before utilizing dissolved iron, accelerating the dissolution of any solid iron, such as steel cables and well casing.
For the remainder of the study, I utilized a chemically resistant cord made of Kevlar which held up in the local aquifer condi- tions. Considering the biogeochemistry of the conditions that your equipment may need to tolerate is vital for successful research and would have saved us thousands of dollars and arguably, more importantly, avoided data gaps. From this experience there are lessons in biogeochemistry that could be explored, discussions about proper materials for anoxic conditions, but most importantly, a lesson about perseverance in the field. Mistakes will be made, issues will be encountered, and if we learn to share them, we can all become better.
Figure 3. The successful retrieval of the data logger from the bottom of the open casing.
With the logger in hand and after several excited yells, we
retrieved the data and even saw the moment in the data when the water level rose three feet within one sample interval when the cable broke and were able to adjust for it going forward.
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