Your house design leaves most of the foundation out of the ground so they did not have a tremendous amount of fill from the dig. Your pics do clearly show they stockpiled the loam in the pool area so unfortunately that area was probably already a bit low for the new grades so the loam just got left there. So as far as comparing your site the the rest of the development they could have much different site elevations so might not have had that much loam to deal with.
Try not to get too stressed out over all this. I would let the PB know you spoke with a soils engineer and he recommended not placing concrete on that much top soil and sod so you are not comfortable with there proposed approach. Ask him for a estimated cost to remove the organics and replace with structural fill in lifts. This will most likely involve brining a excavator to the site. If he refuses to help then let him finish the pool as he would have including bringing the elevations to a finish grade. Then if time permits this fall (or next spring) get a separate contractor to remove and replace the organics and prep for the concrete pad. If they can not remove all the organics because it cause too much stone to fall away from the pool then just remove the 2' and use the stabilization fabric.
You can also use the frost this winter to your advantage. If you place hay on the proposed dig areas a excavator can come in after a heavy frost and drive the trucks over the frost to make the job much easier. These contractors are very slow this time of year and are sometimes looking for work. Of course if we get a lot of snow than it can become counter productive, but you will be in good shape to get a early dig in the spring before the frost breaks.
Ok, let me play Devils Advocate here.
I did some quick calculations, right now the cheapest place i can find #57 is 26.50 a ton. It looks like (doing your plan) that It will take over 150 tons (6+ truckloads) to backfill the pool and the concrete area.
So Im looking at for arguments sake $3500.00 in material alone. Right now they are charging me 1K, extra just to backfill the pool alone with rock. So we are at $4500.00.
Im going to guess if I ask them how much to come back ant pull more dirt out it will be at least 2k. So we are at $6500.00 now. I hate to bring money into it but for the sake of this exercise, i am paying $8500.00 to install the concrete decking.
There has to be a compromise where this is cost effective.
My plan (thinking out loud):
Remove the sod layer where the concrete decking is.
Pull back the over dig topsoil and create a berm around the pool where the decking will be.
Backfill the pool with gravel
Fill the voids up to the berm where the decking will be with gravel, the berm will hold in any gravel so I can make a fairly flat surface.
Next year they install the concrete decking
Grade out the topsoil berm away from the concrete to create the finished grade (I assume this holds in some of the gravel under the decking so i would just need to be careful grading)?
I have to think that in my scenario, the decking 3ft around the pool including the coping will be completely solid.
In a perfect world I would love to do what you are recommending. Logistically I wouldn't know who to call, where to begin or justify the potential of spending close to 10k.
So lets talk failure rate
Percent that the decking fails in each scenario:
- Backfill with dirt and grade the topsoil around the pool and install deck next year?
- Backfill around the pool with gravel and then back fill with dirt, install decking next year?
- My Plan?
- Your plan?
Again im just talking out loud here, I need to go over all my options. If there is something else I can do in my plan, like maybe put down "stabilization fabric" (can someone send me a link on what this is) I am open.
I m not saying I wont pursue your plan, but I need a backup plan that makes sense for me.