ᐅ Permeable paving, clay soil, general water management

Our development plan requires permeable paving for the driveway and parking spaces. In principle, there's nothing wrong with that, but the problem is that the soil underneath is very clayey and hardly suitable for allowing water to simply drain away. Even days after the last rain, a layer of mud several centimeters thick sticks to boots, and the infrastructure work was probably delayed because every hole filled up during this wonderful summer. During heavy rain, a stream often runs through the neighbors’ gardens in the first construction phase as well.

I just reviewed the soil survey again; it states loess-bearing fluvial clay with a kf value of 9.5*10^-8 m/s (approximately ~10^-7). According to Wikipedia, soil with a permeability of 10^-6 or less is considered impermeable.

Now the question is how to deal with this situation. I see the following problems here:
- Originally, I planned to use the same paving for the path from the driveway to the front door, but now I worry that this could direct water underneath the foundation.
- An additional problem is that the road is located almost at the highest point of the property, and with a connected substructure, the water will likely follow the path of least resistance.
- Where should the water that seeps through the paving go? Probably less of an issue with light rain, but heavy rain could cause significant ponding.
- How to handle frost? The subsoil itself is classified as F3 and is already somewhat problematic, and having trapped water on top sounds like a recipe for problems. Our property is at 666 meters (The Number of the Beast... 😉 ), so we can expect significant frost.
- The neighbors to the east and northeast are at higher elevations, and depending on their construction, heavy rain could flow toward our front door. That’s exactly why permeable paving in front of the house was appealing.

Of course, I have already considered possible solutions:
- For the path to the house and the terrace, maybe avoid permeable paving so that rainwater flows away from the house on the surface and is directed by a slight slope into the lawn?
- Some sort of water barrier within the substructure using deep edge restraints between the driveway and the path so that each substructure is reasonably separated? The paths need much less sub-base than the driveway anyway.
- Or simply use permeable paving all the way up to the house but excavate extra deep under the driveway so that all water drains and infiltrates there? The driveway will be about 30cm (12 inches) higher than the ground floor level, so that would indeed mean excavating quite deep and probably extra cost.
- Or is diverting all this water unnecessary, and would a standard 30cm (12 inches) base layer plus 30cm (12 inches) frost protection under permeable paving be sufficient?
- Does it make a difference whether porous stones are used or if infiltration happens through the joints? I’m not really a fan of wide joints because they always seem to become completely covered with moss.