Project : Screenings Chamber Modification – PARR Alliance, for Sydney Water Corporation (2008)
Project Date : 2008
Project Location : Sydney, Australia
Project Client : PARR Alliance, for Sydney Water Corporation
The Screenings Chamber Modification at the North Head Sewerage Treatment Plant (STP) was awarded to Silver Raven following the successful completion of the complex Wet Well Modification undertaken earlier in 2008. The Screenings Chamber Modification required Silver Raven to work closely with Sydney Water plant managers. As the modification works required the establishment of a work site within the treatment plant, adjacent to active screenings infrastructure, extensive coordination with Sydney Water personnel ensured that the plant infrastructure, employees and productivity were not affected by the modification works.
The Screenings Chamber Modification at the North Head Sewerage Treatment Plant (STP) was awarded to Silver Raven following the successful completion of the complex Wet Well Modification undertaken earlier in 2008. The Screenings Chamber Modification required Silver Raven to work closely with Sydney Water plant managers. As themodification works required the establishment of a work site within the treatment plant, adjacent to active screenings infrastructure, extensive coordination with Sydney Water personnel ensured that the plant infrastructure, employees and productivity were not affected by the modification works.
The Screenings Chamber Modification required the following sequence of works:
- Excavate an access tunnel through a sandstone pillar. Maintaining the structural integrity of the pillar was essential. Silver Raven utilised excavation techniques that guaranteed the rock adjacent to the excavation would not be compromised by the works. Ultra high pressure hydro-blasting was employed to remove the shotcrete, allowing an inspection of the underlying rock prior to commencing the excavation. A combination of wire sawing and hydraulic rock splitting was utilised to excavate the rock material ensuring the surrounding rock remained completely unaffected by the excavation.
- Construct a large dust curtain and utilise dust suppression methods to contain dust within the confines of the construction site.
- Modify and maintain adequate ventilation for the work site without adversely affecting the ventilation of the STP.
- Increase the dimensions of the main Screenings Chamber access tunnel. This aspect of the project required Silver Raven to adhere to a strict excavation and support programme. Working in sections along the tunnel, we were required to excavate each section and place stress bars and rock bolts as per the designers specifications before moving on to the next section. The excavation involved the removal of shotcrete with a road header: Cuts were then placed with a rock saw to control the sections excavated. An excavator with a hammer was then used to remove the section of isolated rock. Extensometer measurements were recorded daily by Silver Raven, monitoring the tunnel and ensuring that any movement would be detected immediately.
- Construct the supporting walls for a large roller door installed by others. This construction required the excavation of the footing and drainage for the door, placing of steel reinforcement, installation of roller door frame, construction of formwork and concrete pour.
- Excavation of Screenings Chamber drainage. This excavation included coring through sandstone to provide drainage into existing live flow channels. A portion of these works were performed in a confined space.
- Demolition of redundant Screenings Chamber roller door and supporting structure
- Shotcreting of the modified tunnel and access tunnel