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The Dubbo STP Major Upgrade represented the third joint venture project built by CCB Envico and Cockram, the upgrade ensured Dubbo has adequate facilities in place to service the needs of an estimated population of up to 55,000 people in 2035.


The project augmented the existing STP with a new biological nutrient removal plant which includes but is not limited to the following:


  • Provision of two 6 ML/day bioreactor trains with a total of 12ML per day capacity;

  • Two 31m diameter secondary clarifiers for solids separation as well as chemical dosing and storage facilities and an in-channel UV unit;


Challenging elements of construction included:


  • Swift mass excavation of over 50,000m3 for the in-ground bioreactor tanks.

  • UP to 1500m3 concrete pours commencing in some cases at 10pm and conducted throughout the night due to very high day time temperatures.

  • Installation and testing large diameter 7-meter-deep pipework beneath the clarifier structures.

  • 7-meter-deep shielded excavation through a 60degree batter for the inlet feed pipe, in very close proximity to adjacent operating STP.

The Dubbo STP is the third water treatment infrastructure project undertaken using the Cockram Envico Joint Venture, specifically established to undertake projects of this nature, the STP upgrade and associated inlet works odour control project at over $25m represent the biggest single capital works project ever carried out by the Dubbo City Council.   


Both the client and superintendent evaluated the contractor performance withhigh and improving scores on communication, time, cost, quality, safety, and issue resolution and contract relations.  Dubbo Sewage Treatment Plant was completed in 2015 within the head contract program and with a comparatively low level of cost variations, the majority of which being client initiated.

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