2014
Rainwater management – cleverly planned and thus avoiding costly sewer connections
“The conditions for the infiltration of rainwater are bad …”
“The water table is too high …”
“The seepage passage of one meter (required by DWA-A 1381.) cannot be maintained …”
“Why do you want to seep away the rainwater? There is a canal in the street …!
We received these and more answers from the responsible authorities and the municipal utility company when we came up with our idea of rainwater management for the new construction of a production hall, including of the outdoor facilities (in the industrial area Mitte) in Dessau-Roßlau presented to the licensing authority.
Especially the last statement (question), which every economically active company could have answered immediately in order to save costs, in our case not inconsiderable rainwater fees, made us look for new ways for the rainwater to solve the drainage problem.
The exemption of our client from the annual discharge fees and the periodic price increases of the wastewater company was very important to us.
After all, the rainwater charges projected over the medium term were around EUR 15,000. An amount that must first be earned on the free market. And that only for the drainage of the valuable protected asset (rain) water.
Now that it was explained to us in detail how it does not work, probably also because of our own economic interests (municipal sewage carriers), economic solutions had to be found in order to cancel the high groundwater level in planning and the one meter percolation distance required by worksheet DWA-A 1381.) to reach.
Because this (seepage passage of one meter) lay between us and the long-awaited water law permit for internal seepage, and thus the lifting of the cost-intensive compulsory use of the public sewage system (rainwater sewer).
As a result of the cost calculations, the elevation (filling) of the area in the area of the infiltration systems emerged as an economic partial solution in order to achieve the required distance of one meter from the groundwater level. The required earth mass could be made available from the excavation areas of the production hall and the traffic areas.
Positive side effect:
The costs for soil disposal and excavation work have been reduced significantly.
Due to the favorable soil permeability (kf value), lawn troughs were planned as the most cost-effective system type for infiltration. The water is supplied above the ground from the outside downpipes of the production hall via open paving gutters or directly via the transverse slope of the traffic systems to the troughs in the lawn.
The connection of the internal drainage of the building to the troughs was more problematic, as the ground pipes landed below the troughs if they were laid in accordance with the norms at a depth of frost (ie pipe apex 0.8 m below the terrain + height loss due to the performance gradient).
The new factual question was now “How do you get the rainwater up without technical aids?”
The technical solution to this is as simple as it is old.
According to the principle of communicating tubes.
In vessels that are open at the top but connected at the bottom, a homogeneous liquid is at the same level because the force of gravity and the air pressure are constant (hydrostatic paradox).
This is how the ancient Romans built their aqueducts.
It is now possible thanks to the hydrostatic pressure resulting from the roof height
to feed the troughs in the lawn with rainwater via the underground pipes below.
The water is distributed in the troughs in the turf using specially designed spring pots made from KG molded pieces.
Drainage concept
Conclusion:
It pays to think, first check the feasibility of rainwater infiltration and then build.
The result of the cost calculations made it clear that in addition to saving rainwater charges (around EUR 3,000 per year), the construction costs can also be reduced compared to a conventional drainage solution (sewer connection) through a sophisticated rainwater management system.
In the present project, this is explained by the elimination of many cost-intensive underground drainage facilities (underground pipes and manhole structures) and the favorable soil permeability at the site, which made it possible to create more cost-effective infiltration troughs here.
1.) Worksheet DWA-A 138 “Planning, construction and operation of systems for infiltration of rainwater” is the relevant set of rules for the planning and approval of systems for infiltration of rainwater.
Rainwater management – economically planned and saved high rainwater charges
With new investments and the expansion of industrially operated plants, approval according to the Federal Immission Control Act, better known as BIm SchG, is usually required.
What is less well known is that evidence of the proper disposal of the accumulating rainwater must also be provided for the existing systems.
Our practical experience shows that there is generally no water law permit for existing properties, as this (water law permit) was not required at the time of initial commissioning.
The fact is:
The protection of existing property for the existing property is canceled by the new approval procedure under water law. Evidence of the disposal of the accumulating rainwater in accordance with the permit must be provided for all areas (whether old or newly planned).
This is how it came about for a Dessau waste disposal company to expand its demolition business on the site of a disused industrial area.
In the course of the BIm Sch procedure, the proper disposal of the accumulating rainwater had to be proven for the entire company premises, either through the connection to the public sewage network or the decentralized infiltration on the own property.
With regard to the high degree of sealing of the industrial area (Au = 10,605 m2 impermeable area) and the resulting discharge fees of around 13,000 EUR / year (medium-term around 65,000 EUR), the decision was not difficult for the management.
She favored the internal infiltration of the accumulating rainwater.
In order not to destroy the existing structure of traffic, storage and outdoor areas, troughs were planned at the low points and in the side areas of the paved areas.
They represent the most cost-effective infiltration option.
Drainage concept
Redesign of the play areas in Polling Park Dessau completed
With the acceptance of the football field in December 2013, the overall construction project “Play areas in the polling park” was brought to a successful conclusion, to the delight of all children and those involved in the project.
In addition to the football field, which was equipped with basketball stands and streetball goals and produced with a floor covering, a terrain model was created in the park center with a combination play area, multiple swings and cable car.
A little away from it, under shady trees, a sand play area with a mud table was created for the toddlers.
The new play areas are under high pressure to use and, to our delight, are very well received by the children.
The following is the planning and some photos for all those interested in the project.
For those who know how to plan:
Some photos from the implementation phase
Production of the tennis ceiling (picture left and center), combination play system (picture right)
