Concrete vaults

[ronjon322]

I have a question about concrete vaults.

I found a precast concrete vault online that will meet my application however now we are making modifications like a knockout and adding a sump. Are large concrete vaults (8'x 10') typically purchased as an off the shelf precast item and modified as needed in the field or are they typically designed by a precast company with all of the required features. My project only requires one of these units.

Ronnie

 

[msquared48]

Utility Vault Company, and others, have standard vault models for electrical and storm water applications that have knockout panels as needed.

Any special design vaults will be a higher cost.

I do not know your application, but would try to stick with off the shelf if possible.

Mike McCann, PE, SE (WA)

 

[bimr]

Will depend somewhat on the application which you have not specified.

 

[JedClampett]

My feeling after talking to some precast manufacturers is that while it's best if you stick to their standard models, their yard stock is pretty limited, so all vaults are custom made.

 

[darthsoilsguy2]

holes are commonly cored/sawed into vaults/manhole structures at the precast shop from stock pieces. A sump would be a major change and would require a custom casting. i'm assuming the sump is a lower elevation then the base floor of the vault like you see in an elevator pit.... It is common to just lower the entire floor of the precast structure to create a sump (i.e. catch basins) which lets you use standard pieces. sumps need to be detailed very well w/ respect to rebar continuity and crack control. Sumps tend to end up carrying a lot of the dead weight and stress concentrations because loads find the path of greatest resistance and the sump is usually bearing 2 ft lower than the rest of the slab. it is not uncommon in practice for the sump to end up bearing on rock or undisturbed soils while the remainder of the vault bears on the fill placed after the excavation, and that fill could see water during backfilling which could affect compaction.... or confined conditions which affect the compaction because the crew works better out of the hole and gets to use better equipment... etc. etc.

 

[77JQX]

I've had an extra layer of concrete floor poured in a precast vault to (1) create a sump while (2) adding ballast to prevent the vault floating during high groundwater. Usually field core for penetrations after consulting with manufacturer about appropriate locations.

 

[ronjon322]

Thanks for all of the input.

Ronnie

Measure twice, cut once.