The Stormwater Experts

Evaluation and implementation of street drainage gully “INNOLET”


Besides overflow, deterioration of urban water quality and the high cost of water treatment; are issues facing current cities.

Many publications and investigations tend to promote the concepts of separate systems and decentralization for urban drainage systems. However; even when separate storm water networks are installed, runoff could be sometimes loaded with undesirable pollutants prior of water entry into the gullies.

Along its path surface water can pick up and carry many toxic substances resulting in numerous costs to the public and to wildlife.

For this reason, preventing or reducing pollution load prior of its entry into the network is much more affordable than cleaning polluted water.

The city of “Hagen” proposed the use of road drain filters “INNOLET” to treat streets runoff. The built inn filter of “INNOLET” is suitable for retrofitting inlets and for treatment of the effluent rainwater.


The main challenge was to treat the highly polluted water resulting from street runoff before it is mixed with the less loaded surface water generated from roofs and yards.

For pollution reduction INNOLET® filter cartridges was accommodated in the road gullies. The attachment dimensions of the grating consisted of: 500x500 and 300x500 mm.

This research program included installation, measurement, operation and quality monitoring of the proposed measure whereas the final deliverable consisted of an assessment report evaluating and quantifying the treatment level of resulting surface runoff.

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Dr.-Ing. Harald Sommer
+49 3342 3595-16
Stadtentwässerung Hagen SEH