Dewatering method
Dewatering method
(OP)
Hello,
My company has been engaged in this project in NYC, we are going to prepare SOE for exist. building vertical and horizontal extension. They are deepening the existing cellar - new foundation will be 4-5' lower than exist. The ground water table is around 11' below the sidewalk elevation which means we will be around 5' under ground water table..There are 2 adjacent masonry buildings..all buildings around 100 years old. I've done recently SOE for the same scenario at nearby property where I did sheet piles and now my boss is trying to "Design" a custom made hydraulic press to press sheet piles in - but as you can imagine, I am not sure if that's gonna work so I don't want to rely on this. That's why I would like to look for an alternative. Can I dewater the site without causing any damages to the adjacent properties and then do a typical underpinning ? Or is it too risky? I know secant piles is the option but it might be too expensive.Any reference materials would be very helpful.Thank you for any advice.
Best,
Heldbaum
My company has been engaged in this project in NYC, we are going to prepare SOE for exist. building vertical and horizontal extension. They are deepening the existing cellar - new foundation will be 4-5' lower than exist. The ground water table is around 11' below the sidewalk elevation which means we will be around 5' under ground water table..There are 2 adjacent masonry buildings..all buildings around 100 years old. I've done recently SOE for the same scenario at nearby property where I did sheet piles and now my boss is trying to "Design" a custom made hydraulic press to press sheet piles in - but as you can imagine, I am not sure if that's gonna work so I don't want to rely on this. That's why I would like to look for an alternative. Can I dewater the site without causing any damages to the adjacent properties and then do a typical underpinning ? Or is it too risky? I know secant piles is the option but it might be too expensive.Any reference materials would be very helpful.Thank you for any advice.
Best,
Heldbaum





RE: Dewatering method
Unconfined dewatering (say, with well points) is too risky, IMHO. The dewatering zone of influence will potentially (probably) affect the soil under the adjacent masonry buildings (on shallow foundations, I assume). Suggest getting a geotechnical engineer involved, if you pursue this type approach.
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RE: Dewatering method
RE: Dewatering method
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RE: Dewatering method
So I visited the site today. Attached are two pictures from the cellar that is going to be deepen. The existing cellar is no more than 7' high. They want to make it deeper to have around 12' height. So we would have to go around 6-7' under existing slab level to build the footings. According to the geotechnical report, water table is expected to be around 1' below existing slab which means we are going to be around 5-6' in the water.
All exterior walls, including front facade, stay as they are. It's a landmark building. One extra floor ( penthouse) will be added. What would you do for SOE over there? There are adjacent buildings from both sides. We can't neither use any heavy machinery nor cause any vibration. I wold appreciate any thoughts on that subject. Thank you!
Heldbaum
RE: Dewatering method
RE: Dewatering method
www.PeirceEngineering.com
RE: Dewatering method
Thanks!
RE: Dewatering method
This idea is probably a bit far fetched but you could look to freeze the existing ground, then excavate and try install an L shaped retaining wall. It is potentially feasible but too expensive maybe!!
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RE: Dewatering method
RE: Dewatering method
www.PeirceEngineering.com
RE: Dewatering method
RE: Dewatering method
www.PeirceEngineering.com
RE: Dewatering method