Manhole precast vaults filling with water

[David Ryder]

Hey, gang. I found this forum as a result of a google search for the topic in question. There was an old thread that pertained, but was closed, so I'm opening a new one.

My building has redundant 13kV feeds coming in underground. The feeds both pass through 3 dedicated underground precast vaults on their way from the substation across the street to our building (please see the attached pdf). I presume these vaults are solid bottom, as they fill to the brim with water several times throughout the year. The problem is that the last vault is higher in elevation than the conduit opening in my building, so when it fills completely, water enters my building through the conduit. I'm looking for solutions. Installing a sump pump is problematic, since I can't have anything above ground...our landscapers are legendary in their ability to hit anything that sticks up out of the ground. And the pump would need to throw the water quite a distance, otherwise it would just enter the water table again and come back into the vaults soon after.

I'm wondering if there's any precedence for running a drainage pipe from the electrical vault to a sewer or stormwater vault (there are some nearby in the same area). If I put that penetration lower than the level of the conduits in my building, the vault would (in theory) never rise above that point. Comments?

 

[dkidd]

I have installed a drain to stormwater before. You would not be allowed to drain to sanitary sewer.

 

[Sunny_92]

How about sealing the conduits where they enter the building?

 

[brantmacga]

Could you possibly run drain tile out below the elevation of the building conduit entry? If so maybe you could route a sump pump to that line and keep it dry in there.

Or run a pop-up drain somewhere?


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[MAC702]

Is it possible to add a floor to the vaults that would have drainage but greatly decrease the incoming volume from groundwater?

 

[petersonra]

sump inside the building where the water is coming in collect it and pump it out

 

[Cow]

I would use this:

https://www.google.com/url?sa=t&rct...alant-video/&usg=AOvVaw0GmKS6SQqCE9cf1xdj2EPO

or this:

https://www.polywater.com/product/polywater-fst-foam-duct-sealant/

 

[drktmplr12]

i would first seal the conduits where the water is entering the building.

running a pipe to storm drain-you might need to check with local permit requirements-or you could just do it and not worry about that.

although you say you can't due to landscapers, i would still install a sump pump. replace sod with rocks, up to 2' in all directions to keep the landscapers clear. If they are still hitting it, a bollard or two will stop them. or consider a more robust pipe like ductile iron.

 

[LarryFine]

I would think that preventing the filling of the vaults would be vastly superior to sealing the conduit, albeit more involved, but the combination would be best.

 

[David Ryder]

How about sealing the conduits where they enter the building?

It was tried. Back at the vault conduit penetration. Unsuccessfully. I think they sprayed in some kind of expanding foam, which slowed the process, but didn't stop it. Water always finds a way, if gravity is on its side.

 

[David Ryder]

Is it possible to add a floor to the vaults that would have drainage but greatly decrease the incoming volume from groundwater?

Not at this stage. This is a data center, so now that those feeds are in place, there'll be no mucking around at the bottom of those vaults. To say nothing of what might happen if a contractor was down there and nicked one of those 13kV lines...

 

[David Ryder]

sump inside the building where the water is coming in collect it and pump it out

The drawing I provided is pretty accurate; the top of the conduits only come out of the floor about 2", so there's already a 'sump', in that the water spills over into the switchgear rack, then comes out onto the floor. Not a desirable situation. I suppose I could chop a groove in my floor and then dig a sump elsewhere in the room, but that seems pretty hokey.

 

[David Ryder]

I would think that preventing the filling of the vaults would be vastly superior to sealing the conduit, albeit more involved, but the combination would be best.

That's where I'm at. Getting near the ends of the conduits where they penetrate into the building means being within 24" of live 13kV terminals, which can't be de-energized. And I'm not overly confident in any of the sealing tech mentioned, because I believe that's what the original electrical contractor did 6 years ago when we complained about this. As I said, it didn't stop the water ingress...all it did was slow it down, and now, when I pump out the vaults, it takes that much longer for the water in my building to recede, since it has to flow BACK through their seals.

The ratio of cable diameter to conduit is quite a bit different from what's shown in those product demo videos, so stuffing that foam around the cables isn't going to work as well for us, even if we wanted to be that close to those terminals.

I originally mentioned the idea of a passive drainage system because, as we all know, sump pumps eventually all fail. dkidd mentioned he'd done that once himself....did you just excavate down to a point alongside the vault, then punch through and then trench to another stormwater vault, dkidd?

 

[Sierrasparky]

You have 13kv terminating inside your building.
It must be a huge building.

 

[petersonra]

The drawing I provided is pretty accurate; the top of the conduits only come out of the floor about 2", so there's already a 'sump', in that the water spills over into the switchgear rack, then comes out onto the floor. Not a desirable situation. I suppose I could chop a groove in my floor and then dig a sump elsewhere in the room, but that seems pretty hokey.

it is not all that hard to put a tench in an existing floor. it is probably not something you can do yourself but cutting the trench, installing an insert, and then the grating is done all the time.

 

[rambojoe]

to be clear, (to the best of your knowledge)... is the water from seepage within the vaults (cracks), from the manhole covers, the pipes (bad glueing) or the sub staion? (which always has some kick butt drainage and gravel..) and are you a good back hoe operator? i just finished a french drain to move water away from my home- works great if you can keep it dirt and debris free. the last vault is higher but are others in a retention? a really good excavating company could give you the best advice in this topic..

 

[David Ryder]

You have 13kv terminating inside your building.
It must be a huge building.

We actually have two 13kv feeds, from two different utility grids. As I mentioned earlier, this is a data center. We come directly off the 132kv high lines into our own substation, which is on our property and external to the building. But the services coming into the building from that substation are both 13kv. There are seven 13.2kv/480 subs inside the building.

it is not all that hard to put a trench in an existing floor. it is probably not something you can do yourself but cutting the trench, installing an insert, and then the grating is done all the time.

I'm not concerned with the difficulty, but I'm not sure the powers that be would be pleased with me cutting up and digging holes in the floor. Still, it's an option, I suppose...

to be clear, (to the best of your knowledge)... is the water from seepage within the vaults (cracks), from the manhole covers, the pipes (bad glueing) or the sub staion? (which always has some kick butt drainage and gravel..) and are you a good back hoe operator? i just finished a french drain to move water away from my home- works great if you can keep it dirt and debris free. the last vault is higher but are others in a retention? a really good excavating company could give you the best advice in this topic..

I really don't know where the water's coming from, Rambojoe. It seems unlikely to me that the entirety of it could be coming in from around the manhole cover. And it's not like we stand around staring down into the hole when it's raining. Actually, the manhole covers weigh over 300lbs, so years ago I holesawed 3" holes in them (which we plug) so we could pump the water out without removing them (after becoming the first work-related injury on the site when one of my guys dropped his half of a cover on my foot....) I built a 20-ft long PVC 'straw' that we hook up to a cart-mounted trash pump with a 50-ft fire hose on the output. So we actually never open those vaults anymore. Unfortunately, the only way we know when it's time to go out and pump manholes is when we come in and there's water all over the floor of that switchgear room.

As for my skills with a backhoe, I'll be contracting out any solution.

 

[JoeyD74]

You need to find out if it’s ground water rising up into the man holes or if it’s run off entering from the covers.

 

[GoldDigger]

You need to find out if it’s ground water rising up into the man holes or if it’s run off entering from the covers.

Not rising up if floor is solid. Possibly coming through joints and duct penetrations?

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[Fulthrotl]

Hey, gang. I found this forum as a result of a google search for the topic in question. There was an old thread that pertained, but was closed, so I'm opening a new one.

My building has redundant 13kV feeds coming in underground. The feeds both pass through 3 dedicated underground precast vaults on their way from the substation across the street to our building (please see the attached pdf). I presume these vaults are solid bottom, as they fill to the brim with water several times throughout the year. The problem is that the last vault is higher in elevation than the conduit opening in my building, so when it fills completely, water enters my building through the conduit. I'm looking for solutions. Installing a sump pump is problematic, since I can't have anything above ground...our landscapers are legendary in their ability to hit anything that sticks up out of the ground. And the pump would need to throw the water quite a distance, otherwise it would just enter the water table again and come back into the vaults soon after.

I'm wondering if there's any precedence for running a drainage pipe from the electrical vault to a sewer or stormwater vault (there are some nearby in the same area). If I put that penetration lower than the level of the conduits in my building, the vault would (in theory) never rise above that point. Comments?

with all regard to the departed iwire, as he shared this info, this stuff
is flat awesome. you can seal up the conduits, and they will withstand
a 20' head of water.

i included a 1/2" piece of vinyl hose with a stop cock on the end of it,
so i could drain the pipe and see if there was water in it. i did it once.
the customer never used it again. it's been there 11 years now, with
no leak.

i would not even consider using anything else.

american polywater 250 sealant.

https://youtu.be/H94MBHdXduw