Attenuation tanks have historically been situated under the car park, or within the access road on high volume residential developments.
Within metropolitan areas planning and environmental conditions are reducing the space for tanks, whilst imposing structures within the build area preventing standard rectangular structures being designed and installed.
Planners are reducing car parking spaces within city developments to encourage the use of public transport thereby limiting parking space, whilst incorporating features such as tree pits within the car park and road areas. The nett effect is less space for the footprint of the tank, which needs installing in a complex shape between crane pads, tree pits etc.
Hewitech have many years experience designing and installing such structures.
Variobox products are available in 100mm increments of height – 100,200,300,400,600mm, that enable the engineer to design the tank to the optimum soffit level allowed by the flood level within the drainage system , maximising storage within the available space.
When installing the tank it is critical that the seals between sheets of membrane are robust and tested for integrity. This becomes more difficult when the tank has internal corners as the tank cannot be constructed from one piece of membrane.h V sections needing to be infilled within the internal corners. This is done using an extrusion welder that places a bead of plastic along the joint forming a continuous seal.
CIRIA 753 The SUDS Manual states – Impermeable geomembranes
“It is essential to seal the joints between adjacent sheets of impermeable geomembrane correctly. Geomembranes designed to be impermeable should be seamed using proprietary welding techniques”
CIRIA 768 Site handbook for the construction of SUDS states –
“All storage tanks should be fully sealed in accordance with waterproofing standards,
i.e. Welded joints rather than adhesive tape, and the integrity of the seal checked through non-destructive testing, to ensure it is leak-proof”
Site installer will require a tank drawing detailing each individual crate to ensure correct initial setting out, whilst leaving sufficient working space to install the internal corners. Hewitech can provide this in a dwg format for the client and Hewitech installation team.
Hewitech provide a full service from design, materials production, to site installation that is covered by a 30 year warranty to cover the full life cycle of the system.
If you want to know more about our systems – get in touch