Elevated Pool Flood Zone A 1

[vinpa]

I do a lot of work in a coastal community with an ever growing desire for private swimming pools. Most of the community is either Flood Zone AE or VE. We typically design wood cradle framed pool structures. Ideally the pool is elevated above the required design flood elevation for both zones. I have clients in Zone A that are looking to have pools installed where the entire pool is below flood and within the flood zone, fully elevated above grade. Again no wave action, so no need for breakaway. I have heard that a pool is classified the same as a deck, which is allowed to be below flood. Does anyone have experience with this? I have already seen several pools built below design flood in Zone AE, but that doesn't mean its acceptable per FEMA. Also, this is in NYS, which follows FEMA for flood.

 

[jerseyshore]

Everyone and their mother-in-law has a pool by me fully in the flood zone. Most pools have a few helical or timber piles attached to the bottom for uplift.

 

[vinpa]

Everyone and their mother-in-law has a pool by me fully in the flood zone. Most pools have a few helical or timber piles attached to the bottom for uplift.

I agree its being done everywhere. My opinion is that just because its being done doesn't mean it is compliant. My thought process causing my concern is that the volume of an elevated pool (above ground hanging from a deck) has the potential to displace flood water impacting the flood plain. I know people will argue the displaced volume is inconsequential, but if everyone offsets a micro amount of volume it will add up. NY does not adopt the International Swimming Pool and Spa Code, but they have the following section:

"R304.2.1 POOLS AND SPAS LOCATED IN DESIGNATED FLOODWAYS.
WHERE POOLS AND SPAS ARE LOCATED IN DESIGNATED FLOODWAYS, DOCUMENTATION SHALL BE SUBMITTED TO THE CODE OFFICIAL THAT DEMONSTRATES THAT THE CONSTRUCTION OF THE POOLS AND SPAS WILL NOT INCREASE THE DESIGN FLOOD ELEVATION AT ANY POINT WITHIN THE JURISDICTION."

FEMA tends to be conservative, so I would expect there to be something about pools in an AE Zone, but I cannot find anything.

 

[BrianApex]

I have done a few pools on the coast (Florida). ASCE24 walks through a lot of what is needed. Zone A is kind of weird because on the coast there is the LiMWA line. If the pool is seaward of this line than it is classified as Coastal A. In the ASCE24 it is divided into basically V zones, Coastal A Zones and everything else. V zone and coastal A is pretty much the same. Also check the FEMA insurance Map and see if they put in the LiMWA line.

ASCE chapter 9 talks about pools
For pools in the "other" area can be built like normal.
For pools in Coastal High Hazard Areas and Coastal A Zones, the pools have to be either; 1) entirely above the Design Flood Elevation, 2) completely breakaway, or 3) in the ground. AND if they are below DFE then it will need to be structurally independent.

For buoyancy I have always assumed the pool is empty and ground water table is to the grade. I think that is probably over doing it but it's a simple calc and it works and doesn't change too much. Like Jersey said, any pile should be good.

 

[jerseyshore]

I agree its being done everywhere. My opinion is that just because its being done doesn't mean it is compliant. My thought process causing my concern is that the volume of an elevated pool (above ground hanging from a deck) has the potential to displace flood water impacting the flood plain. I know people will argue the displaced volume is inconsequential, but if everyone offsets a micro amount of volume it will add up. NY does not adopt the International Swimming Pool and Spa Code, but they have the following section:

"R304.2.1 POOLS AND SPAS LOCATED IN DESIGNATED FLOODWAYS.
WHERE POOLS AND SPAS ARE LOCATED IN DESIGNATED FLOODWAYS, DOCUMENTATION SHALL BE SUBMITTED TO THE CODE OFFICIAL THAT DEMONSTRATES THAT THE CONSTRUCTION OF THE POOLS AND SPAS WILL NOT INCREASE THE DESIGN FLOOD ELEVATION AT ANY POINT WITHIN THE JURISDICTION."

FEMA tends to be conservative, so I would expect there to be something about pools in an AE Zone, but I cannot find anything.

Is the pool in a floodway? A flood zone is not a floodway.

 

[vinpa]

Is the pool in a floodway? A flood zone is not a floodway.

Good point. It is in a flood zone. It makes sense for zone A (outside of LIMWA and floodway) that an elevated pool is not an issue. The next step of this adventure is researching breakaway options for elevated pools in Zone VE with wave action...

 

[jerseyshore]

Good point. It is in a flood zone. It makes sense for zone A (outside of LIMWA and floodway) that an elevated pool is not an issue. The next step of this adventure is researching breakaway options for elevated pools in Zone VE with wave action...

I'd reach out to a local pool contractor. They probably know best what is and isn't allowed in that town. Like I said around here it seems like 50% of people have pools so the pool guys should know.

 

[jhnblgr]

Do you have to do a impact study to verify no flood elevation increase per NYS DEC standards?