In order to get to freshwater, a well must be dug through the overburden ground material and into the bedrock. This project is different for every piece of property, with every type of topsoil, and every type of terrain. And it’s not a project for beginners. Here’s why you should only trust a professional excavation crew to drill a water well.
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Reasons to Hire a Professional to Drill a Well
It’s important to hire a crew to drill the water well for a number of reasons. Here are some of the challenges.
- Permits are required before drilling a well.
- Ground-penetrating radar and other tools must be used to verify the best location for the well and to safely avoid hazards like underground utility lines and septic tanks.
- The overburden can be overwhelming. In some areas, it will require drilling hundreds of feet underground before hitting bedrock.
- Overburden isn’t just compact soil; it may include materials that are even more difficult to excavate, like gravel, rocks, boulder, silt, and clay.
- It is difficult to contain and handle the overburden without the proper machinery.
- Welding the casing is crucial to drilling successfully into the bedrock and should be done by a professional.
- There is also electrical work that is required to install the well pump which can be dangerous if you don’t know what you’re doing.
- Poorly dug wells are dangerous for anyone drinking the water and could taint the water table.
- In the end, it can actually be cheaper to hire a professional crew to dig the well because renting a drill is expensive and remediating any mistakes is a huge liability.
How Rotary Well Drilling Works
Mechanical drilling is the quickest, most accurate way to drill a water well. This involves using rotary drilling rig, which is a diesel-powered drill with a powerful hydraulic pump mounted on a truck. It works essentially like a giant hammer drill. The crew of technicians use this machinery to drill down and hammer the compacted ground material and rock below the surface.
When the equipment arrives on site to drill a well, first it extends its four feet to create a level and stable foundation to work from. This also makes it possible for the machine to drill straight down into the ground, rather than at an angle created by an uneven surface.
A support truck assists the rotary drilling machine. It is filled with a couple of thousand gallons of water that will be pressurized and used to help break through the ground material.
Then, the crew attaches the drill bit, a large, three-wheeled grinder on the main drilling rig. The grinders spin independently while high-pressure water and compressed air help to fracture and break up everything in its path.
Rotary drilling machines have a tall boom on the truck which is extended vertically on site. Before the machine goes to work, the drilling head attached travels down the vertical mast – about 20 feet. Then, the shaft is secured in place with a metal collar.
Drilling Through Topsoil & Overburden
Then, the rotary machine can start drilling. As it comes in contact with rock and soil, hydraulic power drives the drill head down and in a spinning motion. The drill bit proceeds down into the ground, the same 20-foot length of the drill shaft, and is then pulled back up to the top of the mast above the rig. This allows the crew to place another 20-foot length of pipe and thread it into the collar joint in order to extend the shaft length. The rig will continue to lock additional shaft pipes in place as the drill reaches deeper and deeper into the overburden material.
Drilling Through Bedrock
Once the drilling shaft hits bedrock, the crew will start adding steel casing pipes around the drilling shaft. This serves to contain the loose soil, sand, silt, or clay overburden and waste material, keep it out of the way of the drill bit and prevent the well shaft from caving in during the drilling process.
Similar to the drill shaft extensions, the 20-foot casing sections are threaded and screw into each other as the drilling progresses. Then, to make it even more resistant and secure, the casing sections are arc welded together. This ensures that the casing sections hold together as they drill down 40 to 80 feet, or in some cases 100 to 300 feet, to reach the bedrock. The casing has to endure a lot of friction as it twists against the overburden and can threaten the integrity of the connections. So, threading and welding the sections together serves to make it extra strong and able to complete the drilling job.
A thick steal drive shoe is attached to the first section that will go underground in this second phase. This component is designed to protect the drill casing. When the shaft and casing reach bedrock, the rig turns on the hydraulic hammer function, pounding the drive shoe into the bedrock.
Sealing the Well
The crew will need to drill about 8 to 20 feet into the bedrock to reach competent bedrock. During the entire drilling process, the crew works to ensure that the hole being drilled is about 1/2 – 1 inch in diameter larger than the steel casing. This margin will be used to fill in around the casing, sealing it into the bedrock and preventing surface water and contaminants from infiltrating the well water.
Grout used for sealing the well usually consists of neat cement or bentonite clay. It is poured into the margin between the drilled hole and the casing where it will mix with the moisture in the soil and harden. This provides a watertight seal around the well casing.
The drill will continue hammering into the bedrock through the bottom end of the casing until it produces water-bearing fractures. Again, this is usually another 8-20 feet deep into the bedrock.
Then, groundwater will fill the well to a level based on the geologic conditions of the site. The crew will turn off the compressed air and water that have been pumping into the well and assess the water flow to see if they have drilled deep enough. When the right depth has been reached to provide adequate water flow, the crew will drop down the submersible pump and install the wiring. The pump will bring water up to the surface so that it can be utilized.
Finally, the well casing will be trimmed so that it sits above the ground surface. A sanitary cap will be secured in place to protect the water from contamination.
Time to Hire a Professional Crew?
SoftDig works all around the country providing convenient underground utility locating, drilling, and excavation services. Contact us to find out how we can help you with your project.