Prelocation tunnel 300

The planning of infiltration ditches/tanks

The GRAF Infiltration Tunnel is a system which has been particularly designed for the infiltration of rainwater and retention respectively. The structure of the modules allows a space-saving installation close to the surface, even under footprints used by cars. The calculation according to ATV - A 138 (german standard) or corresponding, country-specific technical regulations in force must be followed for larger projects. In order to avoid silt accumulation a infiltration filter must be installed.

Choice of position
The distance of the ditch to adjacent buildings for non-sealed up cellars has to be at least 6 metres. The GRAF Infiltration Tunnel has to be installed with
at least 39.4 inches space to the groundwater.
The distance to existing or planned tree population must correspond at least to the (expected) diameter of the crown.

Installation of the feed pipes and deaeration pipes:
The feed pipes will be connected at the front of the end plates. For this purpose the accordingly perforated and labelled circular cut-outs will be detached. The feed pipes must extend into the tunnel modules approximately 20 cm. For assuring that the water enters into the modules in a steady way, it is essential in case of extensive module laying that every infiltration line is equipped with its own inlet pipe. Use the connection on the upper side of the module or the deaeration / inspection end (1 deaeration/inspection end per line).
 
Installation of the GRAF Infiltration Tunnel
The horizontal, flat footprint of the excavation first has to be filled with a layer of gravel (approx. 10 cm, grain size 8/16) which serves as granular sub-grade course. The infiltration tunnels are put on the gravel pit and connected with each other in lines (lengthwise). In order to protect the infiltration tunnel from silt etc. they are wrapped round by filter fleece and thus being separated from the filling material. The filter fleece should overlap the end of the modules by at least 30 cm. Afterwards the excavation will be filled steadily and in layers.