Internal heat pump in the basement not possible due to groundwater?

Now I could no longer edit the old post, so here are my questions:

What exactly does the soil report say about the issue of unexploded ordnance? Something must be making the general contractor suspicious. Building on green, previously untouched meadow? Are there aerial photos at the municipality that could be reviewed? In which federal state is the construction supposed to take place?

Now I understand it a bit better. The heat pump does not have an outdoor unit at all and is therefore operated via very large shaft cross sections with supply and exhaust air. That also explains the air shafts on the outside – now a lot becomes clear to me. This is therefore a completely different issue than I had initially assumed. Through image search on the "www" I have looked at the device in its installed state and can now understand the general contractor a bit more.

Call the manufacturer and ask if there is a pressure-waterproof house penetration for this. The second option would be a pressure-waterproof air shaft outside (there are also pressure-waterproof light shafts) with forced drainage including a backflow preventer.

What does the soil report say about the groundwater level and which load case is present? Is the design water level of -1.75 m already loaded with a risk surcharge (usually 0.3 m)? What does the soil report recommend for sealing the basement? Presumably WU construction and pressure-waterproof light shafts and windows?

All in all, I see it positively that your general contractor immediately raises concerns here instead of just blindly getting to work.

"Before carrying out the civil engineering work, an explosive ordnance survey of the property must be carried out by a certified explosive ordnance detection service due to possible undiscovered explosives from World War II."

Statement from the municipality: "For the building plot, neither an abstract nor a concrete risk regarding explosives is known."
The property is an untouched meadow that was previously used for agricultural purposes and is in Bavaria