Every modular tank looks alike on a brochure. These are the nine engineering criteria that separate them on a Saudi site, plus a one-page checklist for your drainage submittal.
Every modular geocellular system is a plastic box with a high void ratio. On a brochure they are interchangeable. On a Saudi site — 50 °C surface temperature, sulphate ground, dust-laden runoff, a Balady reviewer asking for structural proof — they separate quickly. This guide gives consultants and contractors the nine criteria NGS applies when specifying a system, so that the comparison happens on engineering rather than price per module.
Storage per cubic metre. Above 95% means the excavation is a third of a gravel soakaway; anything lower costs you dig, disposal and land.
30 t for landscape, 45 t for car parks, 60 t for roads and HGV yards — with the minimum and maximum cover depth stated for each. Ask for the CIRIA C737 structural calculation, not a brochure figure.
A 50-year design life is meaningful only with long-term creep data for the polymer at Saudi ground temperatures. Insist on the test report.
Internal channels for CCTV and jetting, and access chambers at inlet and outlet. A tank that cannot be inspected will not be maintained — and Balady reviewers know it.
Can it be built shallow and wide around services, or stepped? Urban Saudi plots rarely offer a clean rectangle.
Silt traps and catchpits sized for dust-laden Saudi runoff. The tank is only as good as what keeps the fines out of it.
Permeable geotextile for infiltration, welded geomembrane for attenuation — with the geotextile grade and membrane thickness specified, not left to the contractor.
Has the system been approved through a Saudi municipal submission and prequalified on a giga-project? Reviewers accept faster what they have accepted before.
Who sizes it, prepares the submittal, and supervises the first panels on site? A tank is a product; a working drainage system is a service.
NGS supplies the FloodFort range against every line of this checklist — with datasheets for each load class on the Stormwater & SuDS page — and prepares the submittal package for your consultant. Read the specification clause and the geocellular vs concrete comparison.
What void ratio should a geocellular system have?
At least 95%. This is what makes the excavation a third of the size of a gravel soakaway and is the single biggest driver of installed cost.
Which load class do I need?
Landscape and pedestrian areas typically 30 t; car parks 45 t; roads, fire-access routes and HGV yards 60 t. The cover depth range for each class must be stated and checked to CIRIA C737.
How do I know a 50-year design life claim is real?
Ask for long-term creep test data for the polymer at elevated temperature. Without it the claim is a brochure statement, not an engineering one.
Can geocellular systems be cleaned?
Well-designed ones can: internal inspection channels allow CCTV survey and jetting, and access chambers at inlet and outlet allow silt removal. Specify these explicitly.
Does Balady have a preferred system?
Balady approves designs, not brands. Systems with a track record of Saudi municipal approvals and giga-project prequalification move through review faster because the supporting documentation already exists.