Design of a backyard swimming pool in an area with a high water table 1

[Lindseyr]

Hey everyone,

I'm planning on building a swimming pool in my backyard, and I'm facing some challenges due to the high water table in the area. The geotechnical assessment cautions that the hydrostatic pressure from the water table could harm the pool's walls and floor despite the fact that the pool will be 25 feet long, 12 feet wide, and 6 feet deep. I'm thinking about backfilling the pool with a certain kind of soil, but I'm curious if anyone has any other recommendations for addressing the hydrostatic pressure issue.

I'm also using design tables and software to calculate the forces on the pool, but I'm still confused of what to do. There isn't enough area for pressure release valves, which I had contemplated using.

Any advice or recommendations would be greatly appreciated!

 

[hokie66]

The problems all arise when the pool is empty, or before it is filled. Design the walls and floor accordingly, with full water pressure plus buoyant soil pressure on the outside, and sufficient mass or anchorage to tie it down. Not sure what you mean about pressure relief valves, as they are small and located in the floor. But they are not very reliable, so I wouldn't count on them saving you from uplift.

 

[Tomfh]

The hydrostatic pressure is more fundamental than localised damage to walls/floor. At worst the entire pool can float out of the ground, aka a popped pool.

What sort of structure is it? Concrete?

 

[Canuck65]

I see two options:
Option 1 - Dewater during construction (). Structurally design floor and walls of pool so that it can resist the hydrostatic pressures and resist buoyancy when the pool is empty (very thick, heavy construction). This will likely require lots of concrete for ballast (thicker floor, thicker walls). Once construction is finished, backfill and turn off the dewatering. Then you can fill and use the pool. Future draining of the pool for maintenance will not be a problem.
Option 2 - Dewater during construction (). Design more like a regular pool, (but a bit more robust). Maintain dewatering until construction is finished and pool has been filled. Any future draining of the pool for maintenance will require dewatering be in place before pool is drained.

Type of soil used for backfill will not alter the hydrostaic pressure of a water table.

Almost forgot Option 3 - the cheapest of them all ... build a pond instead of a pool!!

 

[phamENG]

Quite common here. Water table is roughly 8" below the surface at the moment. If I pull two shovels of dirt out of the ground, there will be water in the hole within an hour. In-ground pools are also pretty common.

General procedure as I understand it (I don't have a pool, but know some people that do):

1) Install well, connect pump, turn it on for a few days.
2) Start digging.
3) If hole fills with water, let the pump run a while longer or bring in bigger pump or more wells
4) backfill as required and shape the pool
5) install flexible liner
6) fill with water
7) cap well but leave it in place and accessible - ever need to drain or work on your pool? you'll have to pump down the ground water. In the winter, you pump the pool down to roughly match ground water and leave it at that. When summer comes again, you just have to shock it back to a usable chemistry.

 

[JoshPlumSE]

I don't see how this is a whole lot different than any pool design. The governing load case is ALWAYS when the pool is empty and the water table is at its max. That affects the types of failures that others have likely mentioned.

Now, I think there are likely construction issues that may occur for this site. Maybe you want to build in some french drains that lead to a sump pump or something for whenever you have the pool empty.

 

[Tomfh]

I don't see how this is a whole lot different than any pool design.

The reality is most pools aren't designed for it, and rely upon the water table never getting that high when the pool is empty.

 

[MotorCity]

I would design for the two worst cases (which are the same).....keep the water out (high water table) or keep the water in (free standing pool)

 

[jerseyshore]

Around here, many houses on or near the water/ lagoon have helical piles that connect directly to the underside of the pool since the water table is high in most of these shore towns.