Each tunnel is 1220mm long, 800mm wide, 500mm high and has an approximate 300 litre capacity.
They are specially designed to allow infiltration of storm water into the ground around them. The tunnels join together to create a very large capacity, shallow void in the ground. This void can then fill up in heavy rainfall conditions and soak away slowly over a period of hours or days.
Extensive use of this type of system has helped relieve pressure on conventional surface water drainage systems. This is in line with the Sustainable Urban Drainage Systems (SUDS) program.
Sustainable Urban Drainage is an environmentally friendly way of dealing with surface water runoff which avoids the problems associated with conventional drainage practice. Conventional drainage exacerbates flooding, causes pollution and is generally more expensive to install and to maintain than Sustainable urban Drainage schemes. The Environment Agency in the UK advocates Sustainable Urban Drainage schemes because they do not contribute to flooding, they encourage wildlife and reduce pollution.
For more information, please visit the Environment Agency website.