Winmalee Sewage Treatment Plant Modifications

Project Description:

Abergeldie carried out modifications to the existing STP to increase capacity and enhance environmental performance. The scope of work included supply and construction of chlorine tanks, a new pump station and grit dewatering system, structural strengthening of the sequencing batch reactors and digesters, and installation of a third tertiary filter feed pump access platform. A new 1800mm pipe line was installed to take effluent from the old CCT to the new CCT.

Complex Challenges:

The plant had to be kept live throughout all stages of the modifications, requiring extreme caution has been exercised throughout all stages of the work. As the Winmalee regional plant services several townships, it was imperative not to obstruct the flow into the plant. Some of the more technically complex modifications to the plant were therefore undertaken during the night when inflows to the plant were at lowest volume.

The inlet works construction was particularly complex. Into this section raw sewage enters from several nearby townships and the flow can change in strength and level quite swiftly. Detailed risk assessment was carried out and safety measures put in place, including having a spotter on duty whenever works were being carried out to visually monitor upstream changes in influent level. A level sensor with an alarm was also installed to warn of any significant rise in level of the influent.

It was noted that some older existing pipes showed evidence of movement and cracking due to soil instability. Abergeldie therefore initiated a design review and verification process to determine the most reliable method for installation of the new 1800 mm pipeline to minimise risk of the pipe cracking and leaking in the future.

Business unit:

Water

Client:

Sydney Water Corporation

Current status:

Complete

Start date:

December 2008

Completion period:

December 2010

Contract type:

Lump sum

Value:

$10.5 million