IWMS Year 1 - Passive Tree Irrigation

Stage 1 - AJ Steele Reserve


The first stage constructed as part of this contract saw Contek install an innovative passive tree irrigation system through a beautiful reserve in leafy Sandringham.

A diversion pit was constructed atop the existing stormwater system, funneling water into an Ecosol gross pollutant trap. Water then flowed through a complex system of PE bypass or into Stormtech arch tanks.

At the beginning and end of each tank, a pit was constructed and fitted with heavy-duty stainless steel diversion and water level weirs.

The tanks themselves were not sealed, with the aim of releasing water slowly to the trees that edged the reserve. Backfill was first a layer of 20mm aggregate, followed by a highly specified structural soil, then top soil.

"Soil fingers" emanated from the tanks towards the trees, made up of trenches filled with a layer of sand, geofabric and structural soil.

Upon completion of works, a rigorous soil amelioration scheme was carried out, prior to drill seeding of grass.

Main Scope:

• Diversion pit
• Ecosol GPT
• PE bypass pipework
• Stainless steel water controls
• Stormtech arch tanks

Client: Bayside City Council
Stage value: $330,000
Completion: September 2019

Stage 2 - North Road, Brighton


The second stage saw Contek install 14 passive tree irrigation pits along opulent North Road in Brighton.

The pits were providing irrigation to towering, heritage listed elm trees, which meant that all works had to be carefully managed under a rigid tree management plan. Specialist precast kerb and channel inlets were installed into the existing kerb, through which water flowed into PVC which filled tanks formed from ACO Stormbrixx cells.

Given the nature of the trees, hydro excavation was used to excavate the trench, and an exploratory trench around the tank excavation to identify any roots that would be affected. Once identified, arborist advice was sought. If no roots were identified, the tank excavation was then carried out mechanically.
The Stormbrixx were wrapped in geofabric, before being placed into the excavation and encased in sand.

Another challenging element came in the form of strict rigid VicRoads requirements, which very much limited the amount of working hours within the day. Contek was pleased to hand over a fantastic project to a satisfied client.

Main Scope:

• Hydroexcavation
• ACO Stormbrixx
• Precast Kerb Inlets


Stage value: $162,000
Completion: November 2019