We are considering adding irrigation to a couple of fields this year. Last Monday we were able to get the well drilling rig into the fields. Over the course of a day and a half, they drilled two test holes for us on two farms.
Though we won’t know for sure what our gallon per minute rate is until they return to drill the actual well, the results were favorable. We are fortunate that the aquifer we live on is good and have not had draw down issues like some areas out west.
Doing advanced research
Some research can be done in advance. Indiana has a state well registry/database. You can do a map search of the area to get an idea of how deep the water is. It is better if you can find other high capacity wells, but even viewing records of residential wells in the area will give you an idea of how deep the well may be and maybe what formation lies below.
In general, records are vague, and each driller has their own definitions and descriptions. Additionally, nothing is guaranteed -- just because there is a water producing aquifer in one place doesn’t mean it is in the next. Thus the reason for a test well.
A test well is basically the same thing as a house well, except they don’t install the well casing or pump system. The driller is exploring the earth to find more information.
As they are drilling, the operator keeps a log of different formations and their depths. For example: one of our test wells went through topsoil, sand, clay, sand and gravel, hard clay, gravel, and hard clay again.
The driller also notes the depth or length of each formation. They will also collect samples to take back for a sieve analysis in order to properly size the screen for the well.
They could have continued drilling deeper, but they thought they found what they needed (which was consistent with other wells in the area). What they needed was to find a vein of a sand and or gravel formation long enough to support the desired water withdrawal.
In our area, 20-30 feet of a good formation will usually do it. Again, many factors go into whether a vein ends up being good and the driller is only providing their expertise and experience to make a prediction. Most of the time they are right, but sometimes they are not.
What happens next
In the next weeks they will return to drill the well. After boring a larger hole, they will first put in a 20’ section of screen and then weld well casing on in 20’ sections until they get to surface level. In our cases, the depth will be about 133’ and 145’. They will gravel pack around the casing and the use air and water to clean the well and develop it. At that time, they will have a pretty good idea of the well capacity.
After sizing the well pump and motor, they will return again to install the pump system. I’m hopeful all this goes smoothly and can be done before we start planting!