Like dug wells, driven("driven point" or "sand point") wells pull water from the water-saturated zone above the bedrock. If properly located and constructed, and taking into consideration the land use in the immediate area, driven-point wells can offer protection from most types of contaminants, especially biological contaminants like bacteria.
Sandy soils alone will not guarantee successful installation of a driven-point well. If the water table is deep, it may not be physically possible to drive the well point deep enough to reach it. Large boulders or layers of tightly compacted soil like clay or “hardpan” may be encountered that effectively stop the driving process. Further, though clay can hold a lot of water, the clay particles are too closely packed to allow water to ﬂow through it into a well. Depth to the water table is another very important consideration when installing a driven-point well.
Driven wells can be deeper than dug wells. They are typically 30 to 50 feet deep and are usually located in areas with thick sand and gravel deposits where the ground water table is within 15 feet of the ground’s surface. In the proper geologic setting, driven wells can be easy and relatively inexpensive to install. Although deeper than dug wells, driven wells are still relatively shallow and have a moderate-to-high risk of contamination from nearby land activities.
Usually, lengths of two to three inches diameter metal pipes(sometimes smaller) are assembled using threaded couplings. The pipes are then driven into the ground. A screened “well" or "drive" point located at the end of the pipe helps drive the pipe through the sand and gravel. The screen is usually 2 to 3 feet long with the hardened steel tip or “drive-point” at the bottom. The screen allows water to enter the well and filters out sediment. Water can then be pumped up through the pipe to the surface.
The pipe and drive-point resemble a long spear. Installation of a driven-point well begins by driving the point and a single length of pipe into the ground. A special ﬁtting called a drive cap is threaded onto the top of the initial pipe to protect the pipe threads while driving and to prevent contaminants from entering the pipe. Sometimes a shallow “starter hole” is dug or augured at the ground surface to accommodate the pipe lengths and facilitate the starting of the driving process. Sections of steel pipe are added as the pipe is driven deeper into the ground. This is continued until a sufficient depth below the water table is reached.
Dig A Well Using A Hand Auger
An auger is a metal "bit" similar to a drill bit, that's attached to a rod that's attached to a handle. A hand auger is used to manually dig holes in the ground. The auger is turned back and forth while soil collects in the middle. It is then lifted out of the hole and emptied. The process is repeated, and extensions can be added, until the hole reaches the desired depth.
With the right ground conditions this method can be a good choice for tapping into groundwater. On the other hand, if you run into rocks or clay, it can cause a lot of headaches. One problem with using an auger to dig a well is that once you hit the watertable, lifting it up through the water tends to wash away the load of dirt you've accumulated before you can get it top-side again. Since your aim is to get as deep below the water table as possible, this method of well-digging can require some ingenuity and patience.
Installing Pipe(or "Casing") Into The Well
Once you've dug your well, in most soil conditions you will need to line the hole to prevent the sides of the well from collapsing. Schedule 40 PVC pipe is perfect for lining a driven well or a well dug with an auger. Cap the bottom end of the pipe, and cut slits or drill holes four feet up from the bottom. The slits allow water to pass into the pipe, where it will be pumped up a smaller pipe to the surface. Once you have lowered the pipe into the well, pea gravel should be poured around the outside of the casing to help keep the holes clear of debris and to filter out larger particles.
Installing A Pump
Different pumps and pumping equipment are available and they vary in their ability to draw water from various depths. A shallow well pump or pitcher pump can only draw water from a maximum depth of about 20’ - 25', and for these shallow water table depths, 1-1/4” diameter well pipe is generally sufficient. These pumps can be installed in any of the three well types above.
*Note - When you consider how you will be accessing your well water, consider this. Pumps will eventually fail. If you're handy you might be able to construct a home-made pump out of spare parts. (see the video at top of page for an example) If you found yourself in a position where pump replacement or repair isn't possible, then you might want to consider constructing the larger dug well so that when necessary, water could easily be accessed with the old, "rope and bucket".
Finishing Your Well
Create an apron or install a concrete slab and drain to prevent ponding of
water at the top of your well. This will not only help to keep water from penetrating the well from above, but it will also help protect the earth around the well from washing away.
Credit For Content:
Department of Geosciences,Texas A & M University
Texas Academy of Science