Manholes and underground vaults

[mshields]

I'm designing a 5kV underground distribution system which will include manholes of course as well as vaults under pad mounted switchgear. It seems to me that the norm is to use open bottom and that while this surrenders the idea of keeping them dry, it at least assured if done properly that they will drain.

A colleague is urging me to use closed bottom structures. I assume you'd still have to have some kind of a sump at the bottom. Frankly, I'm not sure how that would work.

Would be interested in your feedback.

Thanks,

Mike

 

[Nom Deplume]

They will fill with water with a closed bottom. There is no stopping it.
I have installed a few two piece precast solid bottom manholes.

They all had a sump for pumping with a portable pump.
some of the precast companies have designs for the precast manholes.

Try Old Castle Precast in Rehoboth.
http://www.oldcastleprecast.com/

 

[GoldDigger]

I'm designing a 5kV underground distribution system which will include manholes of course as well as vaults under pad mounted switchgear. It seems to me that the norm is to use open bottom and that while this surrenders the idea of keeping them dry, it at least assured if done properly that they will drain.

A colleague is urging me to use closed bottom structures. I assume you'd still have to have some kind of a sump at the bottom. Frankly, I'm not sure how that would work.

Critical question: What is the ground water level? At which season?
If you are above the water level, have soil with good drainage, and limit the water coming in via manhole and ducts, then an open bottom might be OK.
If you are below the water level, you will have to pump whatever you do.