Waterproofing

[mfrisbie]

I am building a pit to hold some huge, uncommon, expensive machinary that is very interesting to discuss but of little importance to my question, so I will omit that info.
Pit dimensions:

• 12-20 ft deep
• 50' x 32' L x W
• wall thickness 16"
• Slab depth 2'9"

The project is located in the East bay area and has a water table depth of 40' according to the soils report. We are soil-nailing for shoring purposes and shotcrete-ing the walls to finished thickness. We would like to do this in one pass but will not be able to waterproof with traditional polyurethane membranes due to the soil nails. The only water mitigation will be a corrugated backing placed behing the shotcrete down full depth into a 12" layer of base rock.

My question is does anyone have any thoughts about how risky this would be to simply not waterproof other than the backing. And, does anyone know how well sodium bentonite or Integral crystalline waterproofing methods work?

 

[stout1]

Huh?

 

[mfrisbie]

My main question is: Does anyone have experience with Sodium Bentonite or ICW as a waterproofing method? And secondly, does anyone know the risks of not waterproofing other than a corrugated backing?

 

[cvorkian]

I have done a considerable amount of construction.

To answer your question is nearly impossible unles you give me a soils study, ground water charts, and a size of the vault.

I will say, ANYONE using the materials you are, in a manner that you are, should just consult an engineer, geologist, or engineering construction firm...

Paying now will save in the long run. Do it right, do it once.

BTW, depending on the size of your hole...vault or WHATEVER you are doing... it may be considered a confined space and require specific safety considerations for occupancy, even if temporary.

ALSO, confined spaces do not have to be full enclosed to be deadly... hydrogen sulfide and CO linger....

Just my 2 cents worth.

 

[mfrisbie]

Thank you for your input I really appreciate your time. I should explain myself better. I'm trying to be brief.

I have a soils report. The pertinent info boils down to: the water table is 25' below excavation of the sump pit (deepest part of pit). Soil consists primarily of fine grained units consisting of silts clay to clayey. Low potential for liquefaction. Less than 5' excavation will stand verticle with little shoring.

We are soil nailing specifically for safety as far as shoring goes. Shotcreteing as we excavate. This system will be designed by a registered PE.

It is definately considered a confined space and the OSHA standards are being employed.

We are definitely "paying now" with a 6.5 million dollar project construction cost.

My main question was in regards to Sodium Bentonite as waterproofing. We are trying to shotcrete to finished wall thickness and if this procedure is used a polyurethane membrane will not be an option due to the soil nails. I've heard of a fiber additive to the mix to decrease shrinkage and hence cracking. Any experience with these methods?

 

[Will67]

Sorry only used it as an additive to drilling mud or slurry walls or in grout of water well annular seal. I would use the sodium bentonite vs calcium bentonite for sure!

 

[theoldwizard1]

Not an expert.

Is there anyway to install drainage around the hole to a pump pit ?