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.
305er schrieb:
Evolith, where are you building? Sounds like our development area In Marl. [emoji4]
There are some differences depending on the municipality. Rainwater that cannot infiltrate into the ground due to sealed (or partially sealed) surfaces must be:
a.) infiltrated on the property using infiltration systems (e.g., soakaways, swales, or shafts)
b.) discharged into the municipal stormwater drainage system (if available)
or
c.) discharged into the regular sewer system
In our case, rainwater from all (partially) sealed surfaces (roof, terrace, yard/driveway/parking space) should preferably infiltrate on site. Discharging it would have been possible here as well, but it probably wouldn’t have saved any money and would have meant additional drainage fees.
We had the infiltration system calculated by our civil engineer, and the result was 13 Intewa boxes measuring 80×80×36 cm (32×32×14 inches) with a total volume of 2.78 m³ (98.2 cubic feet).
According to our soil report, we have a kf value of 5×10^-5. The groundwater level on the day of the investigation was between 1.9 m and 1.7 m (6.2 ft and 5.6 ft). The report also mentioned a design groundwater level of 0.4 m (1.3 ft) below the reference point. Is that our worst-case scenario?
a.) infiltrated on the property using infiltration systems (e.g., soakaways, swales, or shafts)
b.) discharged into the municipal stormwater drainage system (if available)
or
c.) discharged into the regular sewer system
In our case, rainwater from all (partially) sealed surfaces (roof, terrace, yard/driveway/parking space) should preferably infiltrate on site. Discharging it would have been possible here as well, but it probably wouldn’t have saved any money and would have meant additional drainage fees.
We had the infiltration system calculated by our civil engineer, and the result was 13 Intewa boxes measuring 80×80×36 cm (32×32×14 inches) with a total volume of 2.78 m³ (98.2 cubic feet).
According to our soil report, we have a kf value of 5×10^-5. The groundwater level on the day of the investigation was between 1.9 m and 1.7 m (6.2 ft and 5.6 ft). The report also mentioned a design groundwater level of 0.4 m (1.3 ft) below the reference point. Is that our worst-case scenario?
Wow... I have only one question: according to the installation instructions, the infiltration trenches must be at least 1 meter (3.3 feet) above the highest expected groundwater level. With 1.7 meters (5.6 feet), the cover is already tight; with 0.4 meters (1.3 feet), it’s impossible. How is this supposed to be achieved?
B
bierkuh8323 Mar 2017 15:26Evolith schrieb:
Well, I have to disappoint you. We do not need to include paved areas (as long as they are not sealed with asphalt) in the calculations. As long as classic paving is installed with a slope towards the street, it is considered acceptable. Only the roofs are subject to review.You’re not disappointing me with that... That’s great. Your municipality is probably happy that the sewers get properly flushed since the pipes are so large that otherwise there would hardly be a sufficient flow rate...
In the end, it’s a matter of personal calculation and decision whether someone wants or is allowed to discharge or prefers infiltration...
Next, someone will come along wanting to wash their laundry with the rainwater or water mom’s tulips...
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