ᐅ Lowering of Groundwater According to Geotechnical Report – Your Experiences?
Created on: 8 Apr 2022 14:42
A
Allthewayup
Hello everyone,
according to the soil report, groundwater lowering is necessary during the basement construction, and it can only be discharged into the sewer system. During the boreholes, groundwater was encountered at a depth of 2.5m (8 feet). The Danube River flows approximately 500m (1,640 feet) away in a straight line, so we had already anticipated this. Over the past few months, we have contacted numerous companies regarding water management. Despite follow-ups, we have never received a response. Either there is no interest in such small projects, or we were told to get in touch again just before the start of construction in autumn. Based on the soil report and the neighbor’s references, we have fairly reliable estimates of the volume of water to be pumped. We have set aside €30,000 for this scope of work but remain uncertain about reliable estimates from the company to be hired. The neighbor had to handle this independently because they did not commission a soil report, and the water only emerged after they had already begun the foundation slab. So it was a chaotic situation that ended after 5 days.
My question to users here with experience on this topic:
What costs did you incur for your water management, and how was it carried out? (open, closed, vacuum systems)
What difficulties did you encounter during implementation?
What would you do differently if you were in the same situation again?
To avoid discussions about “omitting the basement,” it must be said that we absolutely need the space, and on a 300sqm (3,230 sq ft) lot, it would not be possible to build it close to ground level.
according to the soil report, groundwater lowering is necessary during the basement construction, and it can only be discharged into the sewer system. During the boreholes, groundwater was encountered at a depth of 2.5m (8 feet). The Danube River flows approximately 500m (1,640 feet) away in a straight line, so we had already anticipated this. Over the past few months, we have contacted numerous companies regarding water management. Despite follow-ups, we have never received a response. Either there is no interest in such small projects, or we were told to get in touch again just before the start of construction in autumn. Based on the soil report and the neighbor’s references, we have fairly reliable estimates of the volume of water to be pumped. We have set aside €30,000 for this scope of work but remain uncertain about reliable estimates from the company to be hired. The neighbor had to handle this independently because they did not commission a soil report, and the water only emerged after they had already begun the foundation slab. So it was a chaotic situation that ended after 5 days.
My question to users here with experience on this topic:
What costs did you incur for your water management, and how was it carried out? (open, closed, vacuum systems)
What difficulties did you encounter during implementation?
What would you do differently if you were in the same situation again?
To avoid discussions about “omitting the basement,” it must be said that we absolutely need the space, and on a 300sqm (3,230 sq ft) lot, it would not be possible to build it close to ground level.
A
Allthewayup5 May 2022 12:18*EDIT*
Of course, it’s always wise to have a plan B ready in case you misjudge the situation or if the groundwater level rises significantly due to an unusually rainy summer. In our case, this means having an additional set of plans submitted for approval, where the house is raised about 32cm (13 inches) above the ground. While this would disrupt accessibility and landscaping plans, there is nothing worse on a construction site than unexpected issues that become very costly and cause delays because you were unprepared.
Of course, it’s always wise to have a plan B ready in case you misjudge the situation or if the groundwater level rises significantly due to an unusually rainy summer. In our case, this means having an additional set of plans submitted for approval, where the house is raised about 32cm (13 inches) above the ground. While this would disrupt accessibility and landscaping plans, there is nothing worse on a construction site than unexpected issues that become very costly and cause delays because you were unprepared.
A
Allthewayup5 May 2022 12:37TmMike_2 schrieb:
@Allthewayup
Old Finn. I would install a water flow meter for 500€ (about $540)!!!
I just can’t imagine that volume.
There’s always theory and practice!The neighbor pumped 44.45 m³/h (49.04 yd³/h) of water in 2013. My calculation came to 44.58 m³/h (49.15 yd³/h). And yes, I couldn’t imagine it either, but the helpful city official gave me many reference construction sites that I also visited. When you see the actual volumes flowing, you’re speechless at first.
We even planned two dry-run water meters DN100 after the grit chamber to be able to measure the volumes at all. These water meters have diameters you can put your arm through. We had to get used to those dimensions for quite some time.
The amounts aren’t that big. There are construction sites with millions of cubic meters of water; what we’re doing is just puddle splashing by comparison :-D
@Allthewayup Using the neighbor as a reference is of course a different matter. I was not aware of that.
I just can’t imagine that the drainage system carries 40 m³/h (about 1765 ft³/h), which equals over 10 liters per second (about 2.64 gallons per second).
But please keep us updated nonetheless.
I just can’t imagine that the drainage system carries 40 m³/h (about 1765 ft³/h), which equals over 10 liters per second (about 2.64 gallons per second).
But please keep us updated nonetheless.
A
Allthewayup5 May 2022 13:34@TmMike_2
We initially thought the drainage pipes couldn’t handle it either. In total, about 60 meters (200 feet) of drainage pipes are installed in a special pattern, and the two infiltration wells with a diameter of 400 mm (16 inches) are also coarsely perforated. The slope of the drainage system is significantly steeper than that of "standard" drainage to channel the water more quickly to the nearby discharge points. Discovering this was part of the hydraulic calculation. It is also possible to stack the drainage pipes vertically, but that would only have a positive effect at the start of pumping operations. Once the drawdown cone has formed and the water column in the surrounding area decreases, the water pressure and the associated inflow also decline.
We initially thought the drainage pipes couldn’t handle it either. In total, about 60 meters (200 feet) of drainage pipes are installed in a special pattern, and the two infiltration wells with a diameter of 400 mm (16 inches) are also coarsely perforated. The slope of the drainage system is significantly steeper than that of "standard" drainage to channel the water more quickly to the nearby discharge points. Discovering this was part of the hydraulic calculation. It is also possible to stack the drainage pipes vertically, but that would only have a positive effect at the start of pumping operations. Once the drawdown cone has formed and the water column in the surrounding area decreases, the water pressure and the associated inflow also decline.
G
Grobmutant5 May 2022 13:51About 22,000 cubic meters (777,000 cubic feet) were pumped out over the course of 3 weeks at our site. So your 29,000 cubic meters (1,024,000 cubic feet) seem realistic.