Aquavoid-Traffic and Aquavoid-Plus
The Naylor Aquavoid range of storage tanks provides an economic versatile storage system for general (Traffic) and heavy duty use (Plus). The Aquavoid has been designed specifically to meet the needs of sustainable construction as advocated by the UK Government and provides the means for rainwater, collected from roofs and pavements, to be infiltrated into the soil. The sewage system is relieved of additional loads and drying out of the sub-surface can be prevented.
Aquavoid used as a soakaway: the rainwater collected through pipes from the roof and/or road can be slowly infiltrated into the soil. By infiltrating relatively clean water into the soil, the drainage system is relieved and drying out of the sub-surface can be prevented. Infiltration of rainwater is part of sustainable construction as advocated by the UK Government.
Aquavoid used as an attenuation system: when the normal drainage systems cannot cope with the volume of surface water this is diverted into the Naylor Aquavoid storage system and released slowly after the storm has passed avoiding localised flooding.
When creating a soakaway, these underground storage units are wrapped in a heavy duty non-woven, needle punched geotextile to allow water discharge to the subsurface, but prevent any soil or sand particles to go through.
The construction of an attenuated structure is almost identical to that of a soakaway with the exception of the structure being wrapped within a geomembrane as well as a geotextile to create a sealed system allowing temporary storage of the stormwater until the storm has passed.
CIRIA C737 Guidance: The new CIRIA C737 guidance for the structural design of such systems was published in 2016 and details far more stringent testing regimes for the crates compared to its predecessor.
As a result we are delighted to announce that the Aquavoid-Plus system has already been tested by the independent German DIBt certification body to an equivalent set of DIN standards to those in the new regime, and can therefore be specified with confidence when designing structures requiring up to 50 years lifespan. We are able to offer 2 versions to the market – a standard Aquavoid-Traffic version, with a short term compressive load rating of 400kN/m2, and a heavy duty Aquavoid-Plus version, with a load rating of 700kN/m2 (when tested in accordance with the previous CIRIA C680 guidance) – and sales of these systems are starting to rapidly increase. Furthermore, both Aquavoid systems can be assembled in 100mm depth intervals, or are available as 400mm high modules from stock, and the ability to create a silt route right through the structures enhances their compliance with the new guidance.
Advantages & Benefits of Naylor Aquavoid:
- High Bearing Capacity, sufficient for pedestrian, traffic and HGV use
- Large Storage Capacity, 95% voids
- Economic to install & maintain
- Prevents extreme peak flows to main drainage and water purification systems
- Rainwater is “cleaned” by geotextile surround
- Decreases flooding during heavy rain falls
- Promotes the balance in the groundwater position
- Decreases environmental problems caused by development
- Flexible – can easily be expanded in all directions
- Suitable for high and low groundwater situations
- Inlets/Outlets: 110, 160, 200, 225 & 300mm dia pipes
- Car Parks
- Landscaped Areas
- Recreational Areas
- Amenity Areas
- Caravan Sites
- Commercial Sites
Overview of System:
Aquavoid-Traffic – Vertical Strength 400kN/m2 Lateral Strength 100kN/m2
Aquavoid-Plus – Vertical Strength 700kN/m2 Lateral Strength 200kN/m
Crate size (both systems): 600mm x 600mm x 400mm depth Void ratio 95% (6.944 units/m3) – effective capacity 137 litres.
N.B. the 400mm deep units are held in stock but units are available in 100mm depth intervals to suit local conditions.
- Connecting butterfly clips (2 per unit) – supplied FOC
- Shear connectors for multi-layer systems (1 per unit) – supplied FOC
- Top Hats 110mm – 300mm
- Flange Connectors 110 – 300mm
- Inspection & Control Units (600x600x600mm) to allow multiple diameter connections
- Geotextiles for soakaways & attenuation systems
- Geomembranes for attenuation
- Vortex Flow Controls – to restrict flows
- Smart silt traps (retaining both silt and hydrocarbon
Inspection & Control units – These 600 x 600 x 600 units not only provide the facility to connect multiple diameter connections but also a 500 x 500 clear route right through the structure for both access and maintenance.
A major concern amongst designers is long term functionality of the structures when subject to siltation over a period of many years. This has led to the creation of units with a clear opening through the systems, which although this allows a visual check on the silt build up, it doesn’t actually retain the silt so it can be cleaned out simply. At best, it’s possible to clear the immediate area adjacent to the maintenance route with a jet cleaner, but at worse it just spreads this silt over a larger area of the structure.
However, this problem has been addressed with the Aquavoid Inspection & Control Units. When creating a clear route through the system, if a high strength geotextile is wrapped around the line of Control Boxes then the silt is retained within the route itself and can actually be simply flushed out as intended with a jet wash, leaving the whole system free of silt as originally designed.
Structural Testing – to the internationally recognised DiTB standards.
The Naylor Aquavoid systems have been subjected to extensive testing by an independent accredited testing laboratory and have been certified by the German DiBT standards. This testing was carried out to determine the structural performance of the Aquavoid to enable structural calculations for loading to be carried out under all conditions. Under the new guidance within CIRIA document C737 (replacing C680) the use of a 300mm plate for testing is reserved purely as a reference for consistency and testing should now be carried out under full plate conditions as stated within the DiBT standards above.
Compressive tests were carried out to establish deflection under load and ultimate compressive strength at failure in both a vertical and lateral plane. These tests were carried out using a full plate covering the whole unit to duplicate in-situ conditions.
Aquavoid-Traffic (400 kN/m2) is sufficient for most situations and is the usual choose for landscape areas up to car parking area when dealing with “normal” conditions. The high strength Aquavoid-Plus (700kN/m2) is normally used for extreme depths, where the surrounding soil is very week or where extra ordinary loads such as HGVs are present.
Minimum cover over the structure:
Landscape areas: 500mm
Car Parks (restricted): 600mm
HGV Areas: 800mm
For lesser cover a detailed design is necessary, please contact Naylor technical department
Maximum Burial Depth:
A detailed design in accordance with CIRIA C680/C737 “Structural design of modular geo-cellular drainage tanks” to take into account live and dead loads imposed and soil conditions should be carried out.
For assistance with calculations to define the design loads, please contact Naylor technical department who have software compliant with C680 calculations. For Guidance the following approximate depths can be used (Depends on shear angle of soil):
Aquavoid – Traffic: 3.7m Aquavoid – Plus: 4.5m
Further technical and installation details together with structural guidance are available from Naylor Environmental on request.