Storm Water

Overview

Storm water management is a critical component in almost every new build projects. Continuing urban development has led to a decrease in the natural drainage areas for rain water to return to streams and rivers, often leading to localised flash floods. These artificial surfaces can also lead to the water quality of natural watercourses being contaminated.

Attenuation Tanks
The high technology solution to excess storm water.

Attenuation tanks act as storage for excess run-off water, storing the water beneath the ground and controlling when and at what rate the water is released into streams and rivers. From individual housing soakaways to large scale storage lagoons beneath car parks, attenuation tanks prevent flash floods and the damage they can cause, often aiding planning applications as a result.

Advantages of Precast Attenuation Tanks:
• Suitable for Water storage tanks, attenuation tanks, aeration tanks. etc
• Wall panels and floor slabs are constructed off-site regardless of weather conditions and are rapidly assembled on    site.
• Tanks can be designed to required capacity

Construction and Installation
1. All Reinforcement Steel for Floor is delivered to Site.
2. Steel Fixer ties Reinforcement are placed in position. Starter Bars are fixed into there respective positions.
3. The Floor is then poured with whatever profile is specified by the design.
4. The Walls are erected in sequence .
5. The Operative hooks lifting hooks into the two lifting eyes on each Pre-cast wall. Lifting eyes are checked before unit is lifted.
6. Operative signals to driver either by hand signal or two-way radio that wall is ready to be lifted.
7. A strip of Waterbar is attached to the underside of each Wall before it is placed on the Floor.
8. A Waterbar Strip is also placed on the Walls at each Joint.
9. 10-15mm of Mortar is placed on the floor where Wall is to be fitted.
10. Driver lifts the wall to its position. Operative guides the wall to its final position.
11. Shims are used under the Wall to ensure that they are placed level.
12. If the Walls are landed in Floor recess, the wall has to cover a minimum of 40mm into the recess.
13. Push - Pull Props are then connected to the Wall (Anchors are cast into Wall during the manufacturing process).
      One end of Prop is connected to Wall and the other is connected to the Floor by appropriate bolts.
14. When this process is complete, operatives will then place the next Wall and continue until all Walls have
      been fitted.
15. The Tubes in the Wall are then grouted. The areas where Walls meet each other are shuttered and grouted.
      All Grout operations are to be made using non-shrink grout. The joints are closed properly and the surface
      is made smooth along the joints.
16. The Walls of the Tank are then sealed along all joints. This will be carried out by a third Party. The Walls can be
      sealed before the floors are placed or alternatively after, as there are manholes in the floor slabs.
17. The Floor Slabs are erected in position.
18. Operative hooks chains into the four lifting hooks on each slab. Hooks are checked before unit is lifted.
19. Operative signals to crane driver either by hand signal or by two-way radio that slab is ready to be lifted.
20. Crane driver slings slab to its position. Slab foreman guides the slab to its final position, ensuring correct bearing
      is achieved.
21. The Rebars protruding out of the top of the Walls are Bent over the Floor Slabs.
22. The Reinforcement steel A252 Mesh is then placed on top of floor slabs.
23. The Screed is then poured to height as required by the particular design.
24. The Screed is then Power-Floated.
25. The Push-Pull Props are removed after screed on floor is cured.

How attenuation tanks work
Perforated polypropylene units with 95% void space are fully encapsulated with an impermeable geomembrane, with welded and tested joints. The geomembrane is protected by an outer layer of geotextile, nominally 300g/m2. The unit is then connected to a series of inlet and outlet pipes, all fully sealed and tested by trained personnel.


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