ᐅ Infiltration of Rainwater: Which Method to Choose?

Created on: 20 Mar 2017 10:16
3
305er
Hi,

we’re about to start building soon, and the building permit-free process was not objected to.

However, on the advice of the construction manager, we informed the local authority that rainwater would be infiltrated via a soakaway basin in the garden.

The authority states:
Rainwater must be infiltrated; a calculation of the infiltration system according to ATV-DVWK A-138 is required and must be documented. An infiltration test or an equivalent laboratory test is necessary.

We have no expertise in this matter ourselves. I’ve tried to read up a bit, but the whole topic seems very complex.

As mentioned, we specified a soakaway basin, so the local authority was able to approve it directly and did not have to forward it to the lower water authority.

One neighbor in our new development installed a soakaway tank and prefers it over a basin because it doesn’t create a “wet biotope” in the garden.

Another neighbor who has already built (using the same earthworks company/gardening contractor as we are) installed a trench soakaway system.

Now I’m wondering which option is better or more cost-effective?
Attached is the offer, which also includes the trench soakaway.

The soakaway tank seems to be quite a bit cheaper??

I hope you can help me decide the best infiltration method.

Textdokument eines Bauangebots mit Tabellen und Preisen
RobsonMKK6 Apr 2017 15:43
In case of doubt, someone will come out during heavy rain to check whether the infiltration is working properly or if water is overflowing from the gutter.

But I’ve already told you that the garage and driveway need to be included. You could have had all of this calculated beforehand.
305er6 Apr 2017 16:06
Yes, but the driveway is made of a permeable surface. She wrote that you just need to make sure that the water does not run off onto my property, so simply having a lawn in front or something like that.
RobsonMKK6 Apr 2017 16:08
Hats off if you manage to get that done!
And it says there, even if it is a "permeable surface," we don’t care. The water somehow has to infiltrate your soil.
N
nms_hs
6 Apr 2017 18:37
In our case, they didn’t inspect themselves but requested photos of the installation and the completed state of the infiltration system.
No one cared anymore about the driveway/terrace…
You could ask them how you should document the system. They will probably tell you if they will come by or not.

Here in Schleswig-Holstein, terraces/drives have to be drained close to the surface and, in my opinion, cannot discharge directly into the soakaway (infiltration trench); so they should not be included in the calculations. That’s how the authority also stated it.
305er9 Apr 2017 18:06
I am still curious why, for the basin, only the roof area matters, but for the infiltration trench, everything has to be included.
L
Lumpi_LE
9 Apr 2017 19:00
Someone simply didn't pay attention before... In my opinion, everyone at the UWB is kind of out of touch anyway. Just submit a calculation for a soakaway drain that covers everything, and then build whatever you want...