Rainwater infiltration

Our community also wants rainwater to infiltrate the ground on the property as much as possible (depending on the soil survey).

The community follows the principle that where rain falls, it should also stay or infiltrate. We have relatively sandy soil (the survey is still pending, but there are some natural "dunes" in the area), but I would also prefer to let it infiltrate. In terms of cost, it’s pretty much the same, right? Whether I bury a soakaway or lay a second sewer pipe (rainwater and wastewater are separated) doesn’t make a big difference, does it? Additionally, we have about 30m of connection path.

From an ecological perspective, I would think infiltration is better, right? At least if the soil is suitable....

I have just received an offer for the "Planungsleistungen" of the drainage.

I find the offer extremely high considering it only includes the planning. What do you think?

Cost: 1650 Euros

So, we now have our soil report and infiltration is possible. We have a varying thickness of topsoil (0.5m - 1.20m) followed by fine sand down to the borehole end (2.5m - 6m).

We already have the calculation for a trench infiltration from our BU and need a suitable infiltration system. The result of the calculation is a required storage volume of the trench of 2.78m³. The basis for the design by the BU is the system from DrainMax (Wabe).

Are there perhaps any tips or experiences regarding a trench infiltration? Which system would you recommend and why?

Where would you place the trench? Under the parking space or under the terrace? Or buried somewhere in the garden?

Tendentially, I would prefer to bury the trenches under the parking space/carport. However, this area is only about 13m x 5m in size and directly borders the neighbor.

How would you do it?

I would not let water seep under the parking space or the terrace, supposedly the soil can be moister at that spot (hearsay). Besides, you can only access it with much difficulty afterwards. Is a ventilation/control shaft required?
You are not allowed to build directly next to the neighbor, for example in our area, the minimum distance is specified by the city.
Are there differences in DrainMax regarding whether they are drivable by cars or trucks? Or even less?

We do not have DrainMax, but rather from Graf, but it seems to be the same principle. Calculation is free, installation can be done by yourself with these things. So far, it works flawlessly.

The graf infiltration system is designed to last forever and, of course, works flawlessly. we also have that. The infiltration system must be at least 3 meters away from the boundary, and normally you never have to access it again if you collect the dirt beforehand via an inspection shaft. We have a DN400 collection basin directly in front of the trenches, which is half a meter deeper than the pipe leading to the trench. In this hole, there is a perforated bucket, and all the water flushed in first falls into the hole, as do heavy things. Since there are currently no plants taller than a hundred meters in the vicinity, no leaves or similar fall onto our roof and thus nothing into the bucket. Under a paved area, you could certainly bury the trenches, after all, depending on the manufacturer, they are even fully drivable by trucks. But if something is wrong with it, it is naturally much more difficult to access. It is probably also a question of how deep you bury the parts. We buried ours under the lawn. It is easy to access and does not bother anyone there. You just can’t plant a large tree there.