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.
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.
Evolith schrieb:
@305er: Sorry if I missed it. How many liters do you need to infiltrate, and what is your roof area? According to the chart, with our 265m² (2852 sq ft), it seems to be over 10,000 liters (24 boxes of 420 liters each). Does that sound right? That seems like a really large volume to me.I can only recommend double-checking the calculations and, if necessary, calling Graf again. In our case, the trainee did the calculations and unfortunately made a mistake.
B
bierkuh8323 Mar 2017 13:38Just to illustrate, directly below the topsoil on our site there is a 6m (20 feet) thick clay layer, with the highest groundwater level about 1.5m (5 feet) below the surface of the plot. Infiltration is impossible, so option a) was chosen. I would have preferred infiltration, but it’s not feasible. It always costs money, either a higher mortgage payment or an annual fee. The fee tends to increase over time, while the mortgage payment eventually ends...
The driveway is made with permeable interlocking paving sloped towards the house. At the house, runoff is directed via a collection channel to a gravel lawn area... Therefore, only the sealed surfaces of the roof and carport are subject to fees...
The driveway is made with permeable interlocking paving sloped towards the house. At the house, runoff is directed via a collection channel to a gravel lawn area... Therefore, only the sealed surfaces of the roof and carport are subject to fees...
bierkuh83 schrieb:
To illustrate, directly beneath the topsoil at our site there is a 6m (20 feet) thick clay layer, with the highest groundwater level 1.5m (5 feet) below the surface. Infiltration is impossible here, so option a) applies. I would have preferred infiltration, but it’s not possible. Nice idea, if the municipality agrees. Here we have a clear directive: "Soil replacement until infiltration is possible."
So, you can’t generalize.
B
bierkuh8323 Mar 2017 14:18Then they probably dropped the ball during network planning... Hopefully, this is an isolated case. I would have considered a pre-filter and a natural swimming pond [emoji4]
bierkuh83 schrieb:
Hopefully, this is an isolated case I believe that in the future it will more likely become standard practice that no rainwater may be discharged.
And this has nothing to do with negligence.
bierkuh83 schrieb:
Folks, this isn’t that hard to understand. The local authority is primarily concerned with what you allow to infiltrate from your property into the public sewer system. There are basically two possibilities:
a) permitted – subject to an annual fee based on the sealed surface area that drains into the sewer system
b) prohibited
If b), then all water must be absorbed on your own property, including paved areas and similar surfaces.
In that case, you should have a slope away from public paths or channel the water via a catchment channel to an infiltration system on your property...
Regarding the calculation... You could submit the manufacturer’s specifications related to the sealed surface to the local water authority. It should be acceptable if everything is clearly documented. They usually know the soil and groundwater level quite well. What is the concern exactly? You could also consult your geotechnical engineer or geologist about the calculations. It may cost a bit...Well, I have to disappoint you. We do not have to include paved surfaces (as long as they are not sealed with asphalt) in the calculation. As long as classic paving is installed with a slope towards the street, it is assumed to be acceptable. Only roofs are considered in this regard.
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