Drilling water wells might seem like a simple task. After all, humans have been doing it for thousands of years. But making sure your well is a safe, reliable water source is a lot harder than just putting a hole in the ground.
Before you remove the first cuttings on, for instance, a remote water well project in a developing country, there are lots of items on the checklist to verify, like making sure you have the right drill rig for the project. If you are working at a remote site, it’s important to gather your materials. It’s also a good idea to make sure your portable well drilling rig is ready for operation by, for instance, setting up the mud pump for mud rotary drilling. When you’re eager to get started, these steps can seem tedious but, by taking your time, you will be more successful and efficient when it’s finally time to start the dirty work and drill a water well.
First Contact – The Pilot Hole
Despite your efforts to select an appropriate site, there is no guarantee you will hit water with every bore on these types of projects. That’s why most drilling projects should start with a pilot hole. Use the small pilot bit to bore a 4-inch diameter hole. Depending on your well drilling equipment and site conditions, the time for this process will vary. Carefully collect and record the cutting samples from this exploratory hole to develop a bore log, which will help you design your well if the site pans out.
As you advance your borehole, watch out for signs that you’ve reached an aquifer:
- Thinner mud
- “Streams” of clear water in the drilling mud as it exits the borehole
- Mud temperature changes
- Rapid increase or decrease in mud level in the suction pit
- Sand or gravel in cuttings
- Clay chips that are moist inside when broken apart
Once you’ve found an aquifer, use the information from your cuttings to determine the best depth for the well screen. Cut the necessary amount of well screen with a hacksaw and set aside until you prepare your casing.
Go Big or Go Home
You’ve found water and determined well depth. Now it’s time to get serious. Using the reaming bit, increase the hole diameter to 6 inches. To avoid borehole collapse, complete reaming, casing installation and gravel pack in a continuous operation. Make sure you have enough fuel, drilling fluid and time before you start this step. Reaming creates a lot more cuttings than the pilot hole and will require frequent clearing of mud pits.
Once the designated depth is reached, remove the drill pipe swiftly and install the casing.
Then, it’s time to flush out drilling mud. Certain drill rigs, like the LS200, include a casing flushing tool to make this job easier. If your rig does not include this feature, slowly pump clear water down the well casing to force drilling mud out the borehole. This might require multiple drums of water, so be sure to have extra readily available.
With a very low flow of clear flushing water, gradually add the gravel pack to the hole by hand. Use clean, round gravel — like that produced from streams, rivers and beach deposits — approximately .125- to .25-inches (3- to 6-millimeters) in diameter. Never use crushed rock, as grains will lock together over time and reduce the flow of water into the well. You will need to have enough gravel on hand to bring gravel up to a point 3 feet (1 meter) above the top of the well screen.
At this point, the danger of collapse has passed, and it is safe to leave the site. Cover the borehole and put away all tools before leaving.
Don’t Be Afraid of Commitment
If you’ve chosen your site wisely and managed to avoid hole collapse by reaming, installing casing and placing gravel all in one go, you’re about to find out if your hard work has paid off. It’s time to test your well yield.
After measuring the initial water level, use a bailer to draw out as much water as you can in 10 minutes and pour it into a bucket for further measurements. Once you are done bailing, check the water level a second time. If you are able to bale around 2.6 gallons (10 liters) per minute with little or no drop in water level, congratulations! Your well is likely to produce enough water to supply a hand pump. If the well went dry in just 10 minutes, though, don’t panic. It’s not unusual for an undeveloped well to produce very little water. Repeat the process for 2 to 4 days. If the well is still dry with a brief bailing at that point, there is probably not sufficient flow to support a well.
After confirming sufficient flow, you should perform a water quality field test. There are several kits available. Use the one you are most comfortable with, since accurate results are important.
Depending on the results of your tests, you have a decision to make. Do you develop the well and install a pump, or start over at a new site? Poor water quality can affect the health and safety of people, plants and animals relying on the well, so use the parameters outlined by the test kit to determine if you move forward with development. Additionally, if your well isn’t producing at least 2 to 4 gallons per minute, it won’t be able to keep up with a hand pump, and you’re better off trying again.
Quitting Time … Not Quite
Once you’ve reached a decision, there is still a lot of work to be done. If the well has potential, it is important to protect it from surface contamination by sealing, developing and sanitizing it. If, on the other hand, you chose to look for a new location, be sure to seal the borehole to prevent injury or cross contamination.
Digging water wells isn’t always easy, but a rush of cool, clear, thirst-quenching water at the end of the day makes it all worthwhile.