A PROJECT to remediate services protection on the bed of the Yarra River downstream of the West Gate Bridge will see shipping movements organised to provide an uninterrupted 6-hour window for works.
In an industry briefing the Port of Melbourne noted protection structures were designed and installed to protect underlying services – Melbourne Water’s Hobsons Bay Main Sewer, APA’s Gas Pipeline, and the Western Port Altona Geelong oil pipeline – from anchor drop, drag and scour from passing shipping vessels.
The grouted rock protection assets consist of rock layers strengthened by engineered grout to reduce the risk of uplift and movement of the rock layers. The most recent condition surveys have identified localised areas of grout erosion and rock displacement attributed to natural current flows and shipping impacts.
Rectification will be undertaken in three phrases, beginning next Monday 16 September and are expected to take 6-8 months. The phases are (1) dredging works above the Yarra services protection structure to clear sediments allowing for further investigation and remediation works; (2) installation of physical grid markers to increase repair efficiency, and potential pre-survey to record defects of significance; and (3) visual survey of the grouted rock protection structure to inform defects, and remediation of deteriorated grouted rock protecting the oil and gas pipelines.
Port of Melbourne notes it has worked closely with Ports Victoria to establish a set of protocols that provide maximum flexibility while facilitating these essential works:
▪ Works require an uninterrupted 6-hour window to allow inspections, installation of grout and curing.
▪ Works must be conducted during daylight hours Monday – Saturday.
▪ The 6-hour window can slide left or right to accommodate shipping movements, which see a start time between 07:00 – 10:00.
▪ Should there be no scheduled shipping movements, the works window can extend out to 8 hours to expedite works without additional impacts to shipping.
▪ Should Ports Victoria or the Harbour Master identify periods of significantly higher shipping movements, they have discretion to suspend or cancel works to reduce the number of workdays to as low as 4 days per week. This would however result in a longer duration of the overall works program.
“While these works have direct impacts on shipping proceeding upriver, there are secondary effects to other shipping movements across the port. This is a result of the shipping schedule becoming compressed around the operational diving windows and increasing pressure on port service providers (tugs, pilots & mooring crews), the PoM said.
“To address this, the following priority protocols have been established in conjunction with Ports Victoria:
1. 3 hours prior to and following the daily 6 hour works window, shipping proceeding to/from upriver berths will have priority;
2. While daily works are underway, shipping downriver will have priority;
3. Cruise shipping will retain priority as per current arrangements.”
During the works an exclusion zone will be in place.
