Earthworks/basement construction in high groundwater areas – any experiences?

Dear community,

we are facing the challenge that our earthworks should have actually started since this/last week. However, our plot is located in a groundwater high area, and the earthworks are throwing a wrench in our plans. I am not receiving a clear statement from our earthworks contractor, so I would like to understand your experiences.

Situation:
- Basement floor slab with overhangs must be poured
- The groundwater level is currently about -1.85m below the plot line
- Excavation for the basement floor slab must go down to -3.55m -> Thus, the earthworks are 1.70m in the groundwater
- The following earthworks measures are planned: 3 earth drills for water retention; pipeline path to the sewer 470m, diameter of the sewer pipe we can discharge into: 40cm
- Additionally: We have installed a swallow well on the plot that goes down to 8m and into which further water can theoretically be discharged
- The weather for the next 2 weeks looks rather positive (2-3 rainy days, otherwise apparently dry); on dry days the level drops by 1-2cm per day

Further info: Very early on, sheet piles were considered. However, I was not told the real necessity and therefore refrained from it - especially due to the risks of damage to neighboring houses.

Currently, our earthworks contractor is building the pipelines and wanted to start pumping on Friday.

Now my key question to you: How do you see the situation? How optimistic can I be that it will work out from 0 (highly pessimistic) to 10 (highly optimistic)?

Thank you.

Best regards

I'm calling in , he also built on groundwater...

An open water drainage was sufficient for me. I had one pump at the cistern excavation and one pump in the basement. We waited until the groundwater level was very low. Time pressure is rather counterproductive. It should work well with lowering wells. What did the geologist suggest?

Thank you. How much did you have to reduce in the end with the measures? The geologist was basically relaxed. The problem is not the possibility itself. We were just not told at the beginning that the channel would be the limiting factor, as it was originally assumed that we could pump into a small stream. Now I am standing perplexed in front of the problem and want to weigh how realistic it will be with our conditions to lower the water sufficiently.

we are facing the challenge that our earthworks should have actually started since this/last week. However, our plot is located in a groundwater high area and the earthworks are throwing a wrench in the works.

Oh! – aren't you the Munich guy with the expensive architect? – to me that smells like a serious oversight in performance phase 1 if there is anything surprising about the complained situation. is probably right, not to trust the architect breed ...

Yes. I want to postpone the topic of "guilt" for now and revisit it later. Right now, I am more in fight mode to better assess the situation.