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We are designing an U/G car parking

We are designing an U/G car parking

We are designing an U/G car parking

(OP)
We are designing an U/G car parking garage of 16,000.00 S.F. My question how we estimate hoe many Area Drain, spacing and best location ? Thanks for you help and or advise any referrence or books to use.

RE: We are designing an U/G car parking

About like you design roof drains on a flat roof.
At entries and exits are typically located trench drains.
Bear in mind you will have people walking about so will want to plan slopes to drain away from main walking paths.
Have it go through an oil-water separator.

RE: We are designing an U/G car parking

(OP)
Thank you very mush.
for flat roof rain water, we have the S.T and the denisty of the rain fall.
But in U/G parking we don't have this one.
Please advise

RE: We are designing an U/G car parking

Actually, you do have that.
Key difference is that it is only going to apply to the perimeter where water is going to make its way in. If there is a building on top of the garage, don't forget to account for rain hitting the sides of the building and coming down the sides.
What is happening to the rain on the roof?
One major source of water I can think of is at the entry/exit(s). Rain on any ramps or swells is going to flow in toward the garage.
I don't know the details of the garage's design, so it is up to up to evaluate all potential means for water to enter the garage and design the drainage system accordingly. I would expect a lot of drains around the perimeter with few if any in the middle.

Are you in a flood zone? Does the jurisdiction you are building in have any special flood zone requirements?

RE: We are designing an U/G car parking

Just design it like you would a surface car park with slopes and long gully drains. The practicality of trying to slope a floor into just a few discrete drains is just too hard.

Water will drip off cars and be carried in with cars, wind, tyres etc so you can't just ignore it.

The worst case you will have is probably fire sprinklers assuming you have them so use that as sizing for your drains which should be a lot less than exposed car park drainage.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: We are designing an U/G car parking

You should engage the services of a qualified geotechnical engineer to provide an evaluation of the underground water conditions.

RE: We are designing an U/G car parking

Talk to your AHJ.

Depending on where you are located, only the drains on the top (if exposed to elements) will be allowed to go to the storm system (and drains at the base of any ramp leading to the top. A lot of AHJ do not want excess water from storm events going to the storm system. The other interior located drains will not be allowed to go to the storm system since they are not directly open to the elements. They have to go to the sanitary system. The drains that might receive wind driven rain may or may not have to go to the storm system. If they go to the sanitary, I would recommend upsizing them to accommodate extra flow. The drains that receive water from vertical elements of the building should go to the storm.

If the garage is not heated and in areas subject to freezing, do not put traps on the drains since they will freeze. We have been able to send these drains to a master trap (sand/oil interceptor) which is vented. We do not vent the drains (no traps).

RE: We are designing an U/G car parking

Another point no one has mentioned is to select heel-proof drains. That is, drain openings smaller than 1/2" (I think) for women's high heels. If they step on a drain and the heel goes through an opening and causes an injury, guess what? Lawsuit ! The drains have now become a lot bigger because of the smaller openings. Check local codes, especially if you are signing and sealing the drawings.

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