16 July 2024 Finishing Up my OB Pool

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AQUA~HOLICS said:
I advise customers that this is the only part of the process that is a complete Crud-shoot as to who will walk into the backyard and how that person will react to what they see.

My experience is if they start to get a little bit out of hand I will pick up the steel engineering plans and ask them to explain a specific part to see what how they answer, that typically puts both feet back on the ground.
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Good advice Aqua, thanks. One of the good things about owner building the house first is I got to know the inspectors and plan reviewers pretty well. I think I had 28 inspections on the house. I found them all to be very professional and easy to work with and never waited more than 24 hours for an inspector. They're pretty high-tech and if needed can approve electronically using their phone. I considered them part of my QA plan and they did find some things that got me a better house. Never failed me but they did give me provisional on several so I didn't have to stop work. I've heard horror stories from others in this development which make me thing there were some people trying to cut corners. Or I might have been lucky. Either way I hope it goes the same way on the pool! I'm only slated for 6 inspections for the pool permit.

Chris
 
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21 Feb 2024 The Big Dig

The day of the big dig is finally here. Pretty soon all the dimensions and elevations will get "cast in concrete (and steel)" so while I wait for the crews to start I've been double-checking all the dimensions, volumes, and elevations. Basin calculations on this pool are new to me and when I have wait time anxiousness it helps to run through the numbers:
  • Didn't realize it at the time but many infinity edge pools have very little fat in the basin size. If 10 average adults jump in all at once, that's about 180 gallons of water that needs to spill over almost instantaneously. My basin is ~1800 gal so 180 gal only moves the level about 10% of the depth. For 3' depth that's about 4". So we're good.
  • Another check is to assume all the pipe running back to the the equipment pad drain back to the pool during a power failure or something. Assuming 16-2.5" lines 100' each the volume is about 400 gal. That's about 8". So we should be good on this as well.
OK, I'm relaxed now.

Chris
 
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Most common problems are spillway flow evenness and under sized catch basins.

Are the calculations for determining the catch basin size and depth, free board, water in transit, bather surge and evaporation all being accounted for?

Do you have an overflow and auto fill system built into the catch basin?

Spillway cap will also have a calculation on width of catch basin.

18 gallons of water per person for bather surge seems on the low side.
 
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A 200 pound person will displace 24 gallons of water.

(8) 200 pound people will displace 192 gallons, which will require about a 3/8" lift in a 20 x 40 pool

When they jump in, they will create a wave that can surge over the infinity edge.

The wave can displace a lot more than 24 gallons, but this is temporary.

The catch basin should be big enough to handle as many people as will be in the pool as well as surges from waves.

The catch basin can be made wider or deeper if necessary.

The number of main drains helps reduce the suction on each, so the water can get lower without sucking in air.

The bigger pump can increase the lift if necessary to 1/2", which gives you 250 gallons of extra water in the pool as long as the catch basin is big enough.
 
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21 Feb 2024 update 2

We've got all the sod cut and removed. A few details for OB around productivity for the dig in our sandy soils:
  • Safety First for construction. Working in confined space below grade always has safety risks. I like to make sure there's one person in charge in the hole and he communicates clearly what the plan is for cave-ins. Also, nobody in the hole without his prior approval. Language barrier needs to be addressed so everybody positively understands.
  • We need to balance trip time, trip length etc early to make excavation as cost effective as possible. The excavation contractor has a dump site close by and near the rock supplier. Also, we found another OB house project right in the neighborhood that will take most of our soil diggings. Ideally we want the excavator digging and piling up with the skid steer hauling his piles to the truck and keeping up so no or very little wait time for the excavator. We use a contract that pays $/linear ft of perimeter.
  • In Florida and many places in the south water table is high. I estimated we'd see water at 51/2' and turns out it's about 61/2'. Most pool jobs I've seen in the area keep a pump running on a well that's dug at the bottom to de-water and it works fine. Trick is to get plastic and rock in the bottom to prevent cave-ins from the shallower parts of the pool and that's the plan here. Worst case we dig a couple more well points around the pool but looks for now that won't be needed.
  • Right now we're waiting on rock so the forming crew is setting up walls in the spa. Forming crew is incentivized with their contract as well. So I didn't have to push them to make progress.
Chris

Spa end at depth.
1708530568235.jpeg
 
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AQUA~HOLICS said:
Most common problems are spillway flow evenness and under sized catch basins.

Are the calculations for determining the catch basin size and depth, free board, water in transit, bather surge and evaporation all being accounted for?

Do you have an overflow and auto fill system built into the catch basin?

Spillway cap will also have a calculation on width of catch basin.

18 gallons of water per person for bather surge seems on the low side.
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Aqua,

Yep all good points. I've looked at a lot of cases and with our relatively large basin we're in good shape. Definitely have an overflow designed so it's controlled if everything else fails. I think you're right that 18 is a little light and that still works. I've gotten a lot of great help from you and other experts for this design. One really nice thing is the big 5 hp pump. Thanks @JamesW! Nothing like having the TFP brain trust to help out!

Thanks all.

Chris
 
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Folks,

Long day today, pretty much 7 am to 6 "in the dig". Good news is we're about half way done with the spa and all of the 7' deep end down. Our sand is definitely a challenge. We've controlled water intrusion with a single pump and 2" slotted pipe under rock. Tomorrow we'll get the vertical members up and be able to flash gunite to hold the soil to avoid cave ins before we get the soil back-filled and compacted around the sensitive areas under our load bearing columns. I've been pretty puckered with this and relied heavily on prayers from @kimkats. We removed a LOT of soil today, 5-16 yard loads so far. In the morning we start the slope up to our 4' shallow end. That's going to require some skilled excavation work along with fast spreads of rock to hold it in place. We may end up needing 4-8 yds more rock. So far we've had 16 yd delivered. Here's where we were at end of the day today:

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More 🙏 coming to you and the skilled workers! I can see why the worry as that IS close!

You know what I am going to say next LOL Make sure to measure to make sure it is long, wide, deep, etc enough.

I just thought of something else to help with rain and such especially by the house. I am thinking it might be a good idea to get some thick plastic to cover the grass into the the pool. I would even find a way to have it start on the porch. That way the ground in that area does not get soaked and even looser.I see the gutter on the house and that will help but you know my mommy gut..................I just see water soaking the grass between the pool hole and the porch and it letting go. I know it is going to get flashed so that will help. But will it be thick enough to hold wet dirt up?
 
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Also, fair warning about James. While his attention to detail is spectacular, it got me blacklisted from every contractor north of the Mason-Dixon line. If I ever need a plumber (etc) again, I'll have to fly them in from Geaorgia, because they won't know what they're walking into. (y)
 
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kimkats said:
More 🙏 coming to you and the skilled workers! I can see why the worry as that IS close!

You know what I am going to say next LOL Make sure to measure to make sure it is long, wide, deep, etc enough.

I just thought of something else to help with rain and such especially by the house. I am thinking it might be a good idea to get some thick plastic to cover the grass into the the pool. I would even find a way to have it start on the porch. That way the ground in that area does not get soaked and even looser.I see the gutter on the house and that will help but you know my mommy gut..................I just see water soaking the grass between the pool hole and the porch and it letting go. I know it is going to get flashed so that will help. But will it be thick enough to hold wet dirt up?
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Kim, Prayers are working so thanks much. Yes I think plastic is a good idea. The forming guy plans to wrap all around the house edge down into the hole. Idea is to not let it soak in or erode that edge. We use a lot of rock since it's used all around the bottom and heavier in the wet areas. After one more load we'll be at 24 yards and I think that should do it.

Chris
 
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Newdude said:
Also, fair warning about James. While his attention to detail is spectacular, it got me blacklisted from every contractor north of the Mason-Dixon line. If I ever need a plumber (etc) again, I'll have to fly them in from Geaorgia, because they won't know what they're walking into. (y)
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Too funny! My screen enclosure guy feels the same way about me. After the last job he said he's adding 20% if he every works for another engineer. Things like requiring the stamped drawing for my project instead of a "generic" that requires he interpret certain details. Fastener metallurgy drove him nuts. No open fastener boxes allowed to be brought on site... but we were the only pool with enclosure that didn't have a mess with rust spots every place a screw penetrated the aluminum frame. We're going to have the stamped drawing framed.
 
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Why no open fastener boxes?

To assure different fasteners we’re not mixed together?
 
ajw22 said:
Why no open fastener boxes?

To assure different fasteners we’re not mixed together?
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Aircraft aluminum alloys use aluminum fasteners that must be kept stored in dry ice so their temperature remains lower than the precipitation hardening temperature. Once set in place they warm up and the alloy composition transforms at room temperature depositing precipitates at the internal crystal boundaries which drastically increases the hardness and shear strength of the rivets …. @setsailsoon likes to get fancy with his screen enclosures … 😂
 
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