by Louis Panagopoulos on June 15, 2018

Often referred to as on-site detention tanks, (OSD) is now not only compulsory for large scale developments, but also residential builds, renovation construction and developments.

Most councils now require new property owners to provide a system that captures rainwater that falls on their property and release it at a slower rate than it would normally do.

The reason for this is to improve and reduce flooding problems which occur in protentional flooding areas.

So How Does On-Site Detention Work?

In urban and developed areas, surfaces such as pavements and roofs prevent precipitation from naturally soaking into the ground. Instead, water runs rapidly into storm drains, sewer systems and drainage ditches causing flooding, erosion, muddiness, and infrastructure damage.

However, with a good stormwater on-site detention plan it can capture and reuse stormwater to maintain or restore natural hydrology.

Providing temporary storage of storm water run-off ensures the run off rate and volume be easily controlled to reduce the risk of overload. Put simply, on-site stormwater detention is a means of detaining the stormwater from your site to ensure all development areas can be safely controlled.

With new developments and the removal of natural landscapes we run the risk of nowhere for rainwater to collect. Along with advancements in construction and hard surfaces like pavements, roofs and site drainage, there is an increase in volume and speed of stormwater run-off.

Case Study: Aurrum Nursing Home

The Civil Engineering works included external overland flow path, carpark entry and drainage, on-site stormwater detention, and visitor carparking facilities.

Strategy

LP Consulting’s Civil Engineers worked within council development application requirements for flooding, water reuse and stormwater detention. This strategy provided an integrated solution for access to the computer carpark, access over the floodway and the provision of smooth grade new driveways and pedestrian accessway. The civil works commuter carpark was carefully constructed over the existing detention tanks and the retaining walls.

Solution

The overland flow strategy (see photos above) was integrated with pedestrian bridge works to link the commuter carpark and the building pedestrian entries.

The commuter carpark is accessible via multiple tiered pedestrian ramps and was planned to fit around the footprint of the existing and proposed on-site detention tank.

The other components of the infrastructure included rainwater ruse tanks, back of house carparking, new concrete pavements in a selection of colour and multi- tiered landscaped retaining walls along the site frontage.

When Does A Property Need An On-Site Stormwater Detention?

Commercial, industrial and special use buildings or structures
Town houses, villas, units or other strata subdivisions (these may use a single OSD system for the total site area as long as it’s located on common property and the body corporate is responsible for maintenance).
Dual occupancy lots (each lot within the dual occupancy must have its own OSD system with individual owners responsible for maintenance)
Sporting facilities

You May Be Exempt From An OSD System If:

Single residential dwelling
Site area is under 250 m2
The development site is at the lower section of the catchment
Renovating an existing building but maintaining the existing drainage system

Stormwater On-site Detention

Good water management outcomes can be achieved through civil and water engineering solutions.

When it comes to complex building and infrastructure development, LP Consulting is an industry leader in civil engineer consulting, providing a range of specialist design and consulting services for local and state government and the private sector.