Lowering of groundwater according to soil report - Your experiences?

  • Erstellt am 2022-04-08 14:42:30

Grobmutant

2022-04-09 09:37:40
  • #1
We had to pump out quite a lot of groundwater with lances around the excavation pit for about 3 weeks. Costs: €9500 gross to the general contractor + approx. €2000 fees (Lower Saxony) + electricity costs (I don't have exact figures for that yet) Fortunately, we were able to let the water seep away on a pasture. Discharging it into the sewer would definitely have been even more expensive. I can't imagine that pumping with our own pumps would have worked here. Quite a few liters of water accumulated.
 

Allthewayup

2022-04-17 22:11:17
  • #2
Thanks for the info. We have now decided to try it ourselves first. We have a buffer of 6-8 weeks from demolition to actual start of construction. I will lay about 30m of drainage pipes at the base of the excavation pit that lead into a lower-lying shaft. There we’ll put a sewage submersible pump with a capacity of 15,000 L/h. We’ll do that for a few days and see what happens. The material for that doesn’t cost more than €1,000. If it still doesn’t work, we’ll call in the professionals.
 

Nida35a

2022-04-18 01:39:28
  • #3
Where do you pump the water to inexpensively? Is the distance there far, which hose diameter do you want to use?
 

Allthewayup

2022-04-18 08:05:37
  • #4

It won’t be cheap, we have to obtain a water law permit to be allowed to discharge the water into the sewer and we will also have to rent a sand trap container. The distance to the sewer (about 25m) runs through the parental property, so that is uncritical. I have chosen a pump with a 1 1/2 inch C-connection. The hose itself is 2 inches. I just don’t know yet if the drainage pipes allow enough water through in such a short time. I have never dealt with this before. I am attaching pictures of the items to be used, maybe someone will have an idea about them. We place the pump in the large shaft, it fits well there thanks to its outlet at the top. On the left and right, the yellow drainage pipes run in via reducers. At the front on the third opening we put a blind plug. We run the drainage pipe practically like a loop once around the excavation pit. Oh yes, a second pump then sits in the settling container to pump the water into the sewer.




 

Nida35a

2022-04-18 09:30:34
  • #5
We had an open trench around the base plate to avoid pumping up too much sand/clay. It depends on the soil. If there is too much of it, you can still wrap fleece around the drainage pipes, 1.5 layers. With the container, you can measure how much water is pumped. It will be fine.
 

Allthewayup

2022-04-18 10:18:08
  • #6
We have pretty gravelly, thus permeable soil at the foundation level, which probably results in larger amounts of water. The drainage pipe is covered with a "sock" to minimize clogging with sand. There is also a sand trap under the floor in the soakaway shaft. I am already considering installing a second shaft on the opposite side because a pump might not be able to handle it.
 

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