Abstract

Ongoing and intensive land development over several decades has led to increasing imperviousness of urban areas. This is specifically true for town and city centres. Precipitation cannot infiltrate into the underground and reduces groundwater renewal. Instead, storm water is conveyed by separate and combined sewer systems to the next treatment plant or receiving water, respectively.

Frequently, problems occur, when further development is planned in suburban areas to be connected to the main sewer system. According to traditional technology, existing parts of the sewer system become overloaded and must be replaced by larger diameters to convey additional sewerage and storm water.

In some cases even some of the existing treatment plants would become overloaded and must be rebuilt or modified to fulfil existing water quality standards. Investment costs for these modifications and extensions of the drainage system are distributed among the users connected to the system.

It is well known that onsite infiltration of storm water can contribute to considerably reduce storm water peaks and volumes.

Internationally a broad consensus exists that the re-routing of storm water into the natural water cycle is compulsory from the ecological and economical point of view. Several infiltration technologies have been developed for this purpose, such as drainage wells, gravel trenches and pervious pipes that include subsurface storage as well depression and reservoir infiltration including surface storage. The BIRCO Company in Baden-Baden has developed a new drainage system for such situations to infiltrate less or least polluted storm water. It is a combination of a surface collector flume cut into the impervious area connected to a subsurface gravel filled infiltration trench.

By means of this infiltration system it is possible to disconnect impervious sub areas from the main sewer system independent of surface cover. It can be effectively applied in those cases where an impervious soil cover is compulsory for architectural and technical reasons or when ditch trench systems cannot be applied due to space limitations.

The following fields of application can be emphasised

* Impervious yards of single family or semi-detached houses

* Roof runoff

* Drainage of sidewalks and bicycle lanes

* School yards and other public less polluted areas

* Pedestrian zones

* Parking areas with low or medium traffic frequencies in domestic or small to medium size industrial areas

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