ᐅ Excavation/Foundation Construction in High Groundwater Areas – Experiences?

Dear community,

We are facing a challenge as our earthworks were actually supposed to start since this/last week. However, our plot is located in a high groundwater area, and the earthworks are complicating things. I haven’t received clear statements from our earthworks contractor, so I would like to hear about your experiences.

Situation:
- Basement floor slab with overhangs needs to be poured
- Groundwater is currently about 1.85 m (6 feet) below the plot surface
- Excavation for the basement floor slab must reach 3.55 m (12 feet) deep → thus, the earthworks will be 1.70 m (5.5 feet) below the groundwater level
- Planned earthworks measures: 3 boreholes for dewatering; pipeline route to sewer 470 m (1,540 feet), diameter of sewer pipe into which we can discharge: 40 cm (16 inches)
- Additionally: We have installed a soakaway well on the property, reaching a depth of 8 m (26 feet), theoretically allowing further water discharge
- Weather forecast for the next two weeks looks rather positive (2-3 rainy days, otherwise mostly dry); on dry days, the water level drops about 1-2 cm (0.4–0.8 inches) per day

Further info: At the very beginning, sheet piling was considered. However, no clear necessity was explained to me, so I decided against it—mainly due to the risks of damaging neighboring houses.

Currently, our earthworks contractor is installing the pipes and planned to start pumping from Friday.

Now my main question to you: How do you see the situation? How optimistic can I be that it will work out, on a scale from 0 (very pessimistic) to 10 (very optimistic)?

Thank you all.

Best regards