Question 1

When is on-site detention (OSD) required?

Accepted Answer

OSD is typically required when the proposed impervious area for a development exceeds the council's stormwater policy threshold. Smaller projects may discharge directly to the kerb by gravity.

Question 2

Can stormwater discharge by gravity to the street?

Accepted Answer

If the site has sufficient natural fall to the kerb and the impervious area is below the OSD trigger, gravity discharge through a uPVC pipe network is generally acceptable.

Question 3

What is WSUD?

Accepted Answer

Water Sensitive Urban Design — drainage that incorporates water quality treatment (rain gardens, swales, permeable pavements) in addition to flow management.