OSD Detention Volume & Module Estimator

Estimate detention volume and StormGrid module count from your council’s Site Storage Requirement. Indicative only — your engineer certifies the final figure.

Your site inputs

Impervious site area

Roof + paved area contributing runoff, in m².

Council Site Storage Requirement (SSR)

m³ per hectare. Parts of Sydney commonly use ~300–500 m³/ha — confirm your council’s DCP.

Module usable void

Void-adjusted storage delivered per module.

Indicative result

Detention volume required

21.0 m³

Estimated modules

89 modules

Approx. single-layer footprint

22 m² @ 0.5 m deep

Request a spec-sheet match for this volume →

Volume = site area (ha) × SSR rate. Module count = volume ÷ usable void, rounded up. Footprint assumes a single 0.5 m-deep layer; deeper stacks reduce area. This is a planning estimate, not a certified design — your project engineer applies your council’s exact SSR/PSD method to the subject site.