The client and civil engineer will begin with the relevant city or planning authority to determine the requirements surrounding detention, retention and infiltration systems, as this may affect choice of product.
These authorities can approve ACO StormBrixx® systems where appropriate.
To design and install ACO StormBrixx®, specifiers need to consider three factors:
- Hydraulic Design (catchment & volume)
- Structural Design advice (loadings)
- Flow from tank where applicable
Hydraulic design deals with surface runoff as well as the temporary storage of water in storm events. The objective is to reduce the volume, speed, and frequency of surface water runoff. Factors will be site specific and calculations for hydraulic design may be undertaken using locally accepted and approved methods.
No current building code / standard covers the testing and use of geocellular system in North America.
The English CIRIA C697 offers design guidelines. Construction Industry Research and Information Association (CIRIA) is a non-profit body that provides guidance on the planning, design, construction and maintenance of Sustainable Drainage Systems to assist with effective implementation within developments.
Structural design considers the load bearing capacity of the ACO StormBrixx® system to ensure it can safely carry the loads it will be subjected to. The initial decision must be made on the type of system required ‑ retention, detention or infiltration and then the design parameters shown below should be considered.
- Soil type
- Vertical loading (including site traffic movement)
- Groundwater (water table)
- Depth of cover and total installation depth
- Surface finish
- Horizontal loading
Consideration must be given to the maximum surface deflection allowable for the pavement above the tank. Although excessive deflections may not lead to tank failure, they will cause local pavement deterioration. ACO can provide structural deflection results for specific live loads. Creep (long term deflections under permanent dead loads) should also be investigated to ensure the durability of the tank.
Structural calculations should be carried out using methodology detailed in CIRIA C680 – “Structural design of modular geocellular drainage tanks”. For further advice please contact ACO Technical Services.
ACO will provide general installation drawings, addressing key requirements.
The frequency of a maintenance procedure for the tank will be determined by the inspection cycles. A recommendation is no less than twice-yearly inspections, and during the first year after every significant storm event.
In order to minimise silt build-up, ACO recommends the use of pretreatment systems upstream of the retention/detention system.
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