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DO YOU KNOW WHAT IT TAKES TO BUILD A WELL?

by New Reader Media

JULY 2021

Behind the celebratory moment when water come gushing out of the ground is the labor of service to gift a community with access to safe water. In this piece, I will show you a glimpse of the process in creating a well once the receiving community’s site is chosen.

 

First, it helps to know where to drill. 

           I mentioned in my previous blog that a geological survey is always conducted before starting to drill a well. This is important, not only in terms of practicality but also because this evaluation is required by federal law in Kenya.  The field survey consists of inserting rods into the ground—in an ever-widening grid pattern—and sending an electrical pulse between the rods. Then, the geologist returns to his office where he evaluates the results and prepares a report of his findings. In his report, he will typically select the two best sites within the property and recommend one that is most suited.   He will also provide his estimate for the depth to drill and the potential for encountering water at various depths.

 

           Only after reviewing the report and sometimes, speaking with a geologist, will we mobilize our equipment and team to the site and prepare to start drilling. 

           Even with this basic understanding of what lies beneath the ground, we still encounter surprises on nearly every borehole. And therein lies the mystery of good drilling.  Years ago, in a discussion I was having with a 40-year veteran well driller, he told me, “You can never really know what to expect when you screw a pipe deep into the Earth!”  Needless to say, that statement has stuck with me throughout my short drilling career.

           For us and our small drill rig, the two things that cause the most difficulty in drilling are very hard rocks or underground caves. Hard rocks are difficult for us to penetrate, even with our diamond matrix drill bit.  And when we encounter underground caves, we quickly lose circulation, causing all of our drilling mud to disappear. Without the drilling mud to bring the cuttings to the surface, we cannot continue drilling without the risk of getting our drill bit stuck, sometimes deep in the ground. If this happens, we would not only lose the borehole, but we would also lose our treasured drill bit, as well as all of our drilling pipes down to the bit. Trust me, I know. This happened to us on more than one occasion!

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           Eventually, we do always complete the well and often encounter significant amounts of water along the way. So what comes next, one might ask? Good question. We can't just leave an open hole in the ground. We have to begin installing well casing almost immediately upon completing the drilling and removing the drill pipes. If not, water will begin seeping in at an increasing rate, with the most likely outcome - the borehole will cave in, causing us to have to re-drill it!

 

           To begin the casing process, we first remove the drill rig from beside the borehole and install a heavy steel pipe tripod in its place.   The casing pipes are generally either 4"- or 6"-diameter PVC pipe sections 10' in length with threads on both ends.  We use a 4" casing for hand pumps and a 6" casing for submersible pumps, either electric or solar. During the drilling process, we keep a log of the material encountered and the location of groundwater flowing into the well. This is important to know because it defines where we will insert the good screens so that the water can penetrate the casing and be lifted to the surface by the pump. Screens are similar to casing pipes except they containfor its very thin slits cut in the sides in a geometric pattern throughout the length. Typically, we insert between three and five of these screen sections into a well of depth 150 to 250 ft. Once the casing and screen sections are screwed together and dropped, one by one, to the bottom of the borehole, we then insert filter gravel in the space between the soil and the casing wall. We stopped the gravel pack about 10' below the surface so that to that space with concrete grout, to protect the well from surface contamination runoff.

 

           At the surface, we install either a small concrete or metal vault for a submersible pump or a concrete pad and pedestal for supporting a hand pump. The submersible pump vault will contain the pump discharge pipe and the electrical cable connections to the ground distribution pipes and electrical power and control panel, respectively.

 

           Two tasks remain before the well can be considered complete. These tasks are, too often, improperly performed which causes the greatest problem in maintaining the pumps, whether hand or electric. The first task is called development. It merely means the removal of all the cuttings left from the drilling process. This is typically performed using an air compressor but can also be as simple as a hand bailer on a long rope, dropped to the bottom, and then lifted back up with the dirty water and cuttings inside. This muddy water is then poured out, and the bailer dropped back down the well - over and over again until the water comes clean.

 

           The final task is flushing of the well either by inserting a hose to the bottom and pumping water from the surface, pushing the dirty water remaining out, or by connecting a water hose to the top of the good casing and pumping water down the well and out through the gravel – 10 ft. below the surface. Once the flushing is complete, the concrete sealing of the top 10 feet above the gravel can now be done.

 

           And there you have it - a completed well. That wasn’t so difficult, now was it?