Groundwater is something to consider when building a new in-ground swimming pool. As the consumer you should know that no contractor can guarantee whether groundwater will be an issue just by looking at the lay of the land. More often than not you will need to rely on either their experience or a close by neighbor who may have recently had a swimming pool built for their property. This subject can also become a pre-determining reason as to whether or not you truly want to consider tackling a do-it-yourself project. Lacking experience in ground water control can turn a weekend project into a nightmare.
When excavating the foundation for a new swimming pool you may literally have less than an hour to get water under control. As you may be aware, water has carved canyons and it will certainly damage completed work in a matter of minutes. Lacking the skills to handle Mother Nature can do more than damage a freshly dug hole; the inexperienced can risk life and loss of equipment if not properly prepared. Due to this fact I will not detail every step to control ground water as it is seriously best left to the professionals commercial pool furniture. What I hope to help you understand is that this subject can damage existing swimming pools and wreak havoc on the contractor you may hire to build or repair your swimming pool.
Sandy soils are always assumed to be dry from top to bottom; this is especially true in the Virginia Beach area of Hampton Roads. The fact is that well water comes from sandy pockets of earth so don’t safely assume that you are out of the woods with a sandy lot. Chesapeake however seems to have the disadvantage of neighboring against the Dismal Swamp which is bordered by neighboring cities that have more clay like soils. Though no one can exactly pinpoint where the plentiful water supply comes from in Deep Creek or Western Branch this is certainly my opinion.
Preferably you will hope to hit ground water below four feet from the surface as this depth is beneath the bottom of your future swimming pool walls and footer. As long as water is beneath this level you have a good fighting chance to have a safe build. A professional pool builder will bring in between twelve and twenty tons of larger gravel known as 57 stone for the deep end of the pool before beginning the excavation. By over-digging the deep end or what is referred to as the hopper a builder can fill this area with stone to help collect the water. Typically the deep end is over dug by about two feet so that a well point can be installed as close to the bottom of the over dug area as possible. By doing this the water can be drained and help insure that the hole is mostly dry; or at least know that the water is nearly two feet beneath the future floor bottom. This well point line should be pulled back to at least the point of where your swimming pool equipment will be installed later in the build. You will hopefully not have a need for it once your pool is completed but if ever there is a need to service the pool by draining the water then you will be happy to have it accessible. The cost for controlling ground water at this level and in this fashion can cost the homeowner about an additional twelve hundred dollars over the cost of the original contract.
In those rare cases you find yourself dealing with water between two and four feet below the ground level surface your course of action is pretty limited. I have had to deal with this on just a handful of occasions and it was never pretty. Aside from the above mentioned over-dig the entire pool’s floor surface would also be scraped about four to six inches lower than normal. The only way to deal with the water was to line the entire pool floor and foundation where the future walls would sit with stone. Depending upon the size of your swimming pool this could add anywhere from two to three thousand dollars in stone cost alone and doesn’t include the additional unforeseen labor to handle the build.
Water can be handled up to a certain point but you must always exercise caution. Do not get a false sense of security just because the hole eventually dries out during groundwater management, there is still water in the earth you didn’t excavate that you can’t see. My closest near tragedy was a job in Virginia Beach; we had just finished the excavation and controlling the water. Seconds after the crew had walked out of the deep end and exited the new excavated area the hole collapsed inwards. A two foot wide section that ran the entire thirty-six foot length of the hole fell had fallen. The noise of the deadly thump drew our attention just as displaced air whooshed out of the hole. The deep end was seven feet and had anyone been standing in the middle of the pool during the collapse they would have been crushed by more than fifteen tons of sandy soil. Experienced or not, no one would have walked away from that accident unharmed but in this case it only cost us extra time to clean up.
Look for my newest article discussing how to build in clay.