News & Information

Weather and Dredging Triggers Turbidity Response

Wednesday, July 9, 2008

After more than 150 days of dredging turbidity levels continue to remain below the environmental limits, despite a response level being triggered by a monitoring meter located in the south of Port Phillip Bay.

Environmental Monitor, Mick Bourke said an elevated turbidity reading was recorded for a short period around midnight on 3 July 2008.

“Response Level 1 - a trigger level set out in the Environmental Management Plan (EMP) - was activated by a conformance meter located near the south east Dredged Material Ground,” Mr Bourke said.

“The turbidity limit set to protect seabirds in that area is 17 nephelometric turbidity units (NTUs). Turbidity peaked at nine NTUs, which triggered Response Level 1, but no further response levels were activated.

“The Office notes that the turbidity level had returned below the trigger level by 6am that morning.

“Despite the rise in turbidity, there was no breach of the environmental limit that was put in place to protect sensitive marine plants and animals in that area.

“This incident shows the Office and the community that the trigger system in place to provide the Port of Melbourne Corporation (PoMC) with an early warning of any unusual turbidity readings is working.

“The Office is satisfied PoMC responded to the localised short-term event appropriately and notified the Office as is required in the EMP or rulebook,” Mr Bourke said.

Mr Bourke said the rise in turbidity was caused by a combination of wild weather conditions and nearby dredging activity.

“Rainfall and choppy conditions in the Bay as well as dredging in the South Channel East by the Queen of the Netherlands contributed to the spike in turbidity.

“Elsewhere around the Bay turbidity levels also fluctuated. During the week (30 June to 7 July 2008) turbidity levels recorded at Lonsdale Bight near Point Lonsdale went up and down several times as the tide rose and fell.

“The combined effects of more than 25 millimetres of rainfall in the Geelong region and inflows into the Bay from the Barwon River, as well as strong winds and heavy swells increased turbidity in this area,” Mr Bourke said.

The Office provides an around-the-clock independent and transparent view on the environmental performance of the Channel Deepening Project.

Links

To view the latest turbidity monitoring results visit http://www.oem.vic.gov.au/Turbiditymonitoring.

Source: Media release from the Office of the Environmental Monitor