Fill Existing Pool and Build Over the Top

[ridgeline]

Client is looking to fill and existing pool and build a small garage in its place. Any experience on the best approach? Core the bottom for drainage and backfill with gravel?

 

[Ron]

Swiss cheese the bottom, fill with gravel first 12 to 18 inches. Put filter fabric over the gravel, fill with structural fill.

Remove the upper 12 inches or so of the perimeter wall and backfill over it so as not to create "hard spot" in the bearing soils.

 

[paddingtongreen]

Some township code guys will make you break up the slab completely, or they used to. I know Philadelphia insisted on this.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

 

[oldestguy]

Hey: You are passing up a good thing. Many a home mechanic would trade with him, since that would make a good greasing pit. No excavating. How about a storage place for junk to keep the garage clear? Some structural work needed however.

 

[CELinOttawa]

Lol... Beat me to it Oldestguy; My first thought was "Nearly free basement".

 

[EireChch]

Hi Ron, what would be the need for the filter fabric between the gravels and structural fill? Is the gravel layer intended to be a sub fill drainage layer or something? Why not just fill the entire pool with structural fill e.g well graded sandy gravel? Or for piece of mind just romove the concrete slab base and walls and just have an open excavation and fill as normal.

Also good point regarding reducing the height of perimeter walls to avoid hard spots beneath the foundation.

Thanks from a Irish graduate engineer working in NZ

 

[CELinOttawa]

Hey Eire: I take it you're in ChCh.... Worked and met my wife in Christchurch. What firm, and did they ever reopen Café Roma? You have to try Cafe Abundance (1/10 Acheron Dr, Riccarton, Christchurch, +64 3-341 8818). Rhonda and Bryan's old café (with the cheeky name "The Next Best Cafe" was a welcome home away from home when I moved down there...

As to the op's question, I still think removal will be more expensive than adapting.

 

[Ron]

Reason for the filter fabric is so that structural fill will not drift into the gravel and create loss of density/settlement of the structural fill. Gravel is only to enhance drainage. Might not be necessary depending on soil below the pool bottom. If free draining, delete the gravel and fill with structural fill.

 

[EireChch]

Fair point Ron, thanks for replying. If that was your concern it could be an option to use a 150-200mm layer of smaller size strcutral fill like AP40 (max size 40mm) then construct compacted layers of GAP65 (max size 65mm). Sorry for the metric, and local aggregate terms. I am learning my trade here so it all I know.

Hi CELinOttawa, unfortunitely I am not in Christchurch anymore, left almost a year ago. When I was there though Cafe Roma was not open!! and i dont think it is now!I have moved to Auckland now. I am still heavily involved in the Christchurch Rebuild though and make the odd trip down to Christchurch, I will have to check out the cafe your recommend.

 

[civeng80]

Why not just backfill with compacted crushed rock ?