Expert Witness & Custom OSD — Warehouse, Willoughby

Council — Willoughby City Council

Development — Industrial — warehouse and storage facility

Services — Stormwater Management Plan· Water Sensitive Urban Design· On-Site Detention · Hydrology Assessment· Expert Witness

Year — 2026

Outcome — Approved

Background

The development proposed demolishing an existing structure and building a new storage facility.

The problem

Three constraints at once. The site was tight on headroom, which limited conventional tank options. Council's permissible site discharge requirements and water quality targets weren't being met by the initial approach. And the matter proceeded to conciliation, requiring expert evidence on the building's form and function.

Our solution

MUSIC modelling combined with a proprietary treatment product installed within the OSD chamber met council's water quality targets without consuming additional site area.

For detention, we designed a custom two-chamber OSD tank. The configuration met council's permissible site discharge requirement and built in a safety factor should any part of the system fail — a design not available from a standard product catalogue.

At the section 34AA conciliation conference, mutual agreement was reached and the client was able to proceed to construction.

Was it approved? Yes

WSUD and OSD tank Detail