This post will describe one of our projects this year on our property. We have water there through a deep drilled well, but we really wanted an auxiliary source of water. The answer came when we found a spot we thought would be suitable for a dug well.
What Kinds Of Wells Are There?
There are several different kinds of wells, but there’s only three that are commonly used.
When you picture an old fashioned well with a little roof over it, a bucket suspended from a crank, that’s a dug well.
Whether dug by hand and shovels or with power tools, they are usually shallow and are relatively inexpensive. They should be lined with something impermeable. Historically this was often stone or brick,, but nowadays concrete is often used.
The theory behind a dug well is to dig below the water level of a shallow aquifer, allowing the hole to fill from the bottom of the hole. The hole fills up with water, giving you a source of water.
A drilled well is usually a deep and narrow shaft that is usually drilled with a machine, though occasionally hand drilling methods can be used.
At the surface, a drilled well resembles a pipe sticking out of the ground a few feet. The hole itself can be up to 3,000 feet or so.
Typically you’ll be getting water from one or more aquifers that are deeper than the top aquifer. Basically, you usually ignore the first aquifer you hit, and try to find deeper aquifers that have a better flow.
Most wells nowadays are drilled.
A driven well is basically a perforated pipe that is pounded into the ground until it hits water. You may use more than one pipe section. You use a solid drive point at the bottom of the pipe to prevent it from filling up with dirt and rock.
These aren’t very common, but are certainly an option!
Locating A Spot For A Dug Well
First, we waited until the driest part of the year. In our case this was the September/October time frame.
Second, we looked for spots that still had green grasses as opposed to the yellowed dried out grasses that were prevalent in the rest of the pasture. This is a key indicator of water.
Third, we chose the most likely three locations and decided to give them a good test.
Digging A Test Well
It was pretty straight forward to dig test wells at each location. We simply called a friend who has a small backhoe and used it to go down about eight feet. We then watched to see how deep we had to go to hit water, and how fast the water flowed in.
We ended up with water in all three holes, with two of the three yielding a quick fill rate of approximately 12 gallons per minute. The third was in a dramatically different location and filled much slower. We didn’t get a good calculation on the fill rate for the third hole.
The first two holes were tapping the same aquifer, just in different locations. One hole was about six feet higher in elevation than the other. This turned out to be the deciding difference.
While initially we were planning to use the lower well, which would yield us a greater holding capacity given the same depth, we decided after a bit of consideration to use the higher hole. The main reason was to avoid any potential flooding of the area that the well was in. If water levels rise above the rim of the well, you’ll get contaminated water and you have to sanitize your well before using it.
Digging and Installing The Final Well
Once we had the well site selected, it was a simple matter of bringing the backhoe back and digging the final well. By first digging out a ‘shelf’ for the backhoe to operate on, we were able to dig down about 16′.
We then lowered a pre-cast concrete pipe into the center of the hole on a bed of gravel. The hole itself was dug about 4′ wider than the pipe itself. Once the pipe was set, we filled in around it with large size gravel.
After the gravel was about 1 foot above the water table, we covered the gravel with dirt from the excavation. Our well was mostly done, the only other thing to do was to cap it off and let it fill.
Final Well Preparation
The last thing to do with any well is to pump it dry, let it refill, and repeat that process a couple times to get all of the impurities out. Then test the water. We’re working on that right now. We don’t know for sure that the water will be fine, but we’re pretty confident.
Increasing Well Capacity
We are pretty sure that the fill rate for this well will be more than adequate. However, if we need to add more capacity we can dig feeder trenches. The concept is pretty straight forward:
First, dig one or more trenches that radiate from the edge of the gravel surrounding the main well. You want the trench to be about 1′ deeper than the water table at minimum.
Then fill the trench with gravel about a foot above the water table, then fill it back in with dirt.
This allows more water to flow into the trench and subsequently into the gravel around the main well. Since water flows through the gravel faster than dirt, you get a faster fill rate for your main well.
I’ll be documenting our water distribution system and how we plan to become our own water utility company in a future post, so stay tuned!