5 story basement, 30' below water table
5 story basement, 30' below water table
(OP)
We're designing a building with a 5 story basement, and the lowest level will be roughly 30 feet below the water table. There is a permanent dewatering system for the project including an underground drainage system.
The footprint of this building is huge (about 320'x320'), and the levels below grade are only parking levels. I was thinking it would be prudent to specify "pop-up valves" or hydrostatic relief valves in case the dewatering system failed to let it flood the basement rather than fail the slab on grade that is not designed to take the pressure. I know these valves are installed in pools, but I cannot find any information on these valves for "building application". An alternative would be to provide breakaway sections of the slabs, but that would likely be more costly.
Does anyone have any experience with this or a resource?
Thanks!
The footprint of this building is huge (about 320'x320'), and the levels below grade are only parking levels. I was thinking it would be prudent to specify "pop-up valves" or hydrostatic relief valves in case the dewatering system failed to let it flood the basement rather than fail the slab on grade that is not designed to take the pressure. I know these valves are installed in pools, but I cannot find any information on these valves for "building application". An alternative would be to provide breakaway sections of the slabs, but that would likely be more costly.
Does anyone have any experience with this or a resource?
Thanks!






RE: 5 story basement, 30' below water table
Can you anchor the building on piles or piers to resist uplift?
RE: 5 story basement, 30' below water table
We're looking for something relatively cheap as a prudent precaution. The building is square in plan and nothing inhibits water intrusion (in the event that the dewatering system fails) around the perimeter since there is a gap between the earth retention system and the edge of slab on grade - thus we are more concerned with the interior portions of the floor plate.
Maybe we don't even need the secondary system to relieve water pressure...
RE: 5 story basement, 30' below water table
You might want to install sump pumps and alarms in the basement.
RE: 5 story basement, 30' below water table
I think steel plate cladded design will keep the seepage out. But you should design it for whole uplift.
Ciao.
RE: 5 story basement, 30' below water table
I've heard of jobs using the relief valves, but have not heard of any results if they actually worked. They were all installed as "just in case", and apparently havent been needed yet.
RE: 5 story basement, 30' below water table
Simple is beautiful...
RE: 5 story basement, 30' below water table
Thanks to JedClampett above, we're considering the Trumbal relief valves - these things open at about 9 inches head of water, and retract when the water retreats. They're only $57 apiece (4" diameter and 9" long) and they extend into the gravel drainage layer below the slab. We're going to install them at around 40' O.C. in both directions. It's a cheap safeguard that is hopefully never needed.
Thanks to all for your input.
RE: 5 story basement, 30' below water table
RE: 5 story basement, 30' below water table
RE: 5 story basement, 30' below water table
In addition to BigH's question on soil stratigraphy and thickness, I would be curious if the water level reported was determined from single standpipes slotted all the way or from standpipes or piezometers placed at various levels.
Very often standpipe information can be misleading depending on the installation technique used. I am not saying that this is the case on your project as I presume that your geotech consultant would be very experienced for a project of this nature.
If there are any buildings with basements around what was their experience.
RE: 5 story basement, 30' below water table
dicksewerrat: The dewatering system has an alarm in case it fails. Not sure about the electrical cutouts on the elevators.
VAD: Water table drawdown effects on existing adjacent structures has been studied in depth.
Thanks all for your comments....huge help.