OSD Tanks: Important Facts You Should Know

In urban development, managing stormwater effectively is crucial to preventing flooding, protecting infrastructure, and maintaining environmental balance. 

An On-Site Detention (OSD) tank plays a key role in modern stormwater management. This system helps prevent overwhelming public drainage networks. It reduces the risk of flash flooding and erosion.

This blog covers what you need to know about how OSD tanks work and their importance for effective stormwater management.

Why Are OSD Tanks Required?

An on-site detention tank is a stormwater management system designed to temporarily store excess rainwater before gradually discharging it into the public drainage network. Unlike retention tanks, which permanently hold water for reuse, OSD tanks focus on controlled outflow to prevent sudden surges in stormwater systems.

Councils across Australia enforce on-site detention system requirements to manage stormwater runoff from residential, commercial, and industrial properties. 

Urban developments increase hard surfaces that prevent water from soaking into the ground. As a result, the ground’s ability to absorb rainwater is reduced. Without proper detention, water quickly flows into drains, increasing the risk of floods. OSD tanks mitigate this issue by regulating stormwater discharge.

How Does an OSD System Work?

An OSD system operates through an effective mechanism:

• Stormwater Collection: Rainwater from roofs, driveways, and other impervious surfaces is directed into the on-site detention tank.
• Temporary Storage: The tank holds excess water, preventing immediate runoff into the stormwater network.
• Controlled Discharge: A calibrated outlet releases water at a regulated rate, preventing an overload of public drainage systems.
• Overflow Mechanism: In extreme rainfall events, an emergency overflow system ensures water can bypass the tank safely.

Key Benefits of OSD Tanks

• Prevents Flooding: By regulating stormwater discharge, OSD tanks help prevent flash floods in urban areas.
• Reduces Soil Erosion: Uncontrolled stormwater runoff can erode soil and damage landscapes. OSD systems slow the flow, minimising erosion risks.
• Protects Infrastructure: Stormwater surges can overwhelm public drains and lead to costly damage. An OSD tank construction ensures gradual water release, protecting drainage infrastructure.
• Ensures Council Compliance: Most councils in Australia mandate on-site detention system installations for new developments to manage urban stormwater effectively.
• Supports Sustainable Water Management: By controlling stormwater at the source, OSD tanks help regulate the urban water cycle, easing pressure on natural waterways.

Types of On-Site Detention Systems

• Above-Ground OSD Tanks: Made from polyethylene or steel, these tanks are easy to install and maintain. They are integrated into landscaping or car parks to save space.
• Underground OSD Tanks: Installed beneath driveways or gardens, these tanks help maximise space while managing stormwater. They are typically made from concrete, plastic, or fibreglass. They require excavation and precise engineering.
• Combined OSD and Retention Systems: These systems store water for both detention and reuse. This helps with stormwater control and water conservation. They allow property owners to reuse water for irrigation or other non-potable uses.

OSD System Regulations and Compliance in Australia

Regulated components include:

• Minimum Storage Capacity: The required tank size is based on rainfall intensity, property size, and the non-absorbent surfaces.
• Construction Standards: OSD tanks must comply with Australian Building Codes and Hydraulic Engineering Standards to ensure durability and safety.
• Overflow Management: An OSD system must include an emergency overflow mechanism to safely direct excess water without causing structural damage or uncontrolled runoff.
• Integration with Site Design: The OSD system must be designed to fit within the development layout, considering available space, accessibility for maintenance, and compliance with local stormwater discharge policies.
• Maintenance Requirements: Regular inspections and debris removal keep the OSD system functioning properly. This prevents blockages and ensures smooth water flow.

Conclusion

Understanding the importance of an OSD system is crucial for compliance and environmental responsibility.

At Buildaroo, we specialise in OSD tank construction and stormwater management solutions. Our team provides expert guidance and top-quality installations to help you manage stormwater.

If you need a reliable on-site detention system, get in touch with us today. Call 0421 841 919 or fill out our online form for a consultation. Let’s make your stormwater management seamless and compliant.

Frequently Asked Questions

• Do All New Developments Require an OSD Tank?

Most urban developments require an on-site detention system, but small residential builds may be exempt. Always check with your local council’s requirements.

• How Long Do OSD Tanks Last?

The lifespan depends on the material and maintenance. Concrete tanks can last over 50 years, while polyethylene tanks typically last 20-30 years.

• How often should an OSD tank be maintained?

Routine maintenance should be performed every 6 to 12 months. This includes debris removal, sediment checks, and inspections of outlet control mechanisms to ensure proper function.