During the inground pool kit excavation process you never know what you will find underground that you will have to deal with in your pool installation process. In most cases, dirt and small rocks and roots are all that is encountered. Or, you may have to deal with water, large tree roots or boulders.
The most common issue is some degree of underground water problems. As all water problems are unique, so are the solutions. If you hit a high water table during the dig, what is usually done is to over-dig the side slopes and deep end bottom by a foot and put in ¾” gravel, covered by a barrier of landscape cloth or roofing paper.
In extreme cases you will need to install an underground pipe and pump into the gravel bed with a check valve or foot valve at the bottom of the line. The pipe is connected to a self-priming pump outside the pool area.
The dewatering pump would be running during the installation process to keep the pool bottom dry and when the pool is full of water, you can disconnect the pump. Mark where the pipe is on your plot plan, so down the road when you need to change the liner you can connect the pump back to the line if needed.
If you just have water slowly weeping in, you would not need a pipe and pump set-up. If it is not much at all - sometimes it will just stop on its own or you may have to put a gravel sink bed where the water is weeping into the pool.
For weepers, overdig the area where it's running out, and continue digging down to the pool floor. Fill with gravel and then put some tar paper over top. Add some topsoil, and your finished floor material over top. This usually will take care of weepers during pool excavation.
Drainage: Another thing to take into consideration is ground water or storm run off. You want your pool elevation to be at least 6" higher than the surrounding ground. Your entire construction area should be pitched away from the pool to allow good flow around the pool. This will allow water to run away form the pool and not towards it. If you have a hill behind one side of your pool you will want to cut in a swale and grade the land to divert the water around your pool.
Soil: Different soil conditions play a role in pool construction water problems. Clay holds water and is always wet, where other loamy soils or sandy soils tend to drain better.
Topography: The water table tends to follow the curve of the terrain. If your property is located in a very low, depressed area, topographically speaking, it will tend to have water table closer to the surface. The same may be said for pool locations that are very close to sea level elevation.
Large rocks that have to be removed are another problem. The biggest problem is having a machine big enough to remove the rock or bust up a stone ledge in the pool area. Boulders that are larger than the bucket can be strap lifted - but if they are too large, they may need to be broken first, which may require a jackhammer attachment.
After a very large boulder has been removed, clean fill dirt should be put in its place and compacted or tamped to bring the floor or walls back up to where they need to be. This can be a lot of work, so another option is to "shave" off large boulders. I have had rocks that were so big, when I only needed to dig another few inches, and it was easier to jack hammer the rock, or "shave it" than to remove the entire rock, and then backfill the crater.
Large roots are another issue you may have with inground pool construction. You want to remove them for sure; but better if you can see where they are coming from and cut them back a good 10 ft or so from your pool area. Cut the roots within the excavation area only, and you are leaving yourself wide open for them to grow back within a few years, and damage the pool.
If you saw my post about Trees around the Pool, you'll know that I am absolutely opposed to any trees within 10 or 20 feet of the pool. Large trees, and their roots can cause more problems later on - to your pool walls, floors, liner and surrounding pool deck. Plus, do you really want to be cleaning leaves out of the pool?
Most excavators will slice through large roots with ease, so that's not the real problem. The real problem are large roots that are cut off just a few feet from the pool walls and floors. Better to take out the tree, and poison the roots, or cut the roots back at least 10 feet from the pool walls.
How Can You Tell What's Underground? There are no Apps or Divining Rods to help you know if there is underground water or large rocks in your yard. You can do a little investigation on your own, however. Do any of your neighbors have an inground pool? Ask what they encountered underground, did they hit water or rock? Do you have a sump pump in a pit in your house, or basement water problems? You may already know if you have a high water table. Also consider the topography and drainage of the planned pool area.
Your local building department may have an area map that shows water elevations, or the building inspector should have an idea of what's generally expected to be underground in your area.
And of course, if you run into any of these problems with an SPP Pool Kit, we are here to help you every step of the way, like we were with Lloyd Brown's water problem during his very rainy pool construction week.
Remember that usually - there is nothing underground but tierra firma, with small rocks and surface roots. Large scale inground pool construction problems with rocks, roots and water are rare, and most situations are solved quickly and cheaply.
SPP Pool Expert