Australia: Cutter Suction Dredging in Gladstone Harbour Suspended

Turbidity levels in the Western Basin of Gladstone harbour have been increasing in recent days.

Water quality monitoring systems have recorded levels at QE4 (at the northern end of the bund wall) above the limits set out in the project approvals.

This has meant a temporary suspension of cutter suction dredging has been put in place by the Queensland Department of Environment and Resource Management (DERM).

GPC will comply fully with the decision to reduce dredging in the Western Basin this week and continue to assist water conditions return to normal as soon as possible.

GPC’s implementation of the Turbidity Management Plan during the Spring tides late last year has been largely successful in mitigating turbidity increases seen during the large tidal ranges.

As part of our adaptive approach we have voluntarily suspended cutter suction dredging on previous occasions.

Backhoe and grab dredges will continue to operate.

Turbidity levels are an important measurement of water quality to ensure the health of the seagrasses throughout the harbour. Seagrass beds are continuing to recover from the extreme weather events of 2010-2011.

Cutter suction dredging is expected to resume when turbidity levels at all water quality monitoring sites have fallen under and remained below the limit for a period of more than 24 hours.

Turbidity levels at QE4 have exceeded the approval limit of 34NTUs for a period of longer than 48 hours. QE4 turbidity levels have ranged from 0 to over 100NTUs during normal summer weather.

Inner harbour turbidity is typically between 10-35NTUs, however, during heavy rains turbidity can typically reach 100NTUs, and last summer’s floods caused turbidity over 250NTUs.

The limit of each water quality monitoring site was established by the DERM based on background turbidity levels recorded prior to dredging.

GPC is committed to carrying out the Western Basin Dredging and Disposal Project with care and respect for our environment.

“We are committed to ensuring the protection of the local environment, and the Western Basin Dredging project is being managed under world’s best practice for dredging, informed by the Dredging Technical Reference Panel,” CEO Leo Zussino said.

 “GPC is working with the authorities to enable dredging to continue in order to ensure Gladstone’s economic growth and future prosperity.”

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Dredging Today Staff, January 11, 2012; Image: westernbasinportdevelopment