Chrissy Harris

Tests show dredging not harmful

A NEW round of water quality sampling in Port Curtis shows no evidence that water quality is affecting fish health or that dredging in Gladstone Harbour is causing environmental harm.

The report by the Department of Environment and Resource Management (DERM) was released on Wednesday. 

DERM Director-General Jim Reeves today released a peer-reviewed report of tests taken in late October and data from further independent testing conducted late November.

"The sampling shows no clear pattern in the water quality results taken across the Port Curtis region to suggest that dredging was having any obvious impact on water quality," Mr Reeves said.

"What we are seeing is a natural month to month variation across all testing zones. 

"There was no evidence that turbidity, pH, oxygen levels, salinity or temperature had any negative impact on water quality in Port Curtis harbour or its estuaries, or fish health concerns.

"Neither was there any clear pattern in the number of exceedances of dissolved metals guidelines for aluminium and copper.

"Turbidity levels in November were generally higher than in October but lower than in September. 

"There were high levels of turbidity and nutrient levels, especially nitrogen, found at Boat Creek. 

"This is a considerable distance from the dredging, and the localised nature suggests high turbidity can occur naturally in some areas within Port Curtis.

"With the exception of aluminium, generally the concentrations of metals and metalloids were lower in October and November compared with the first round of sampling in September.

"Dissolved aluminium was found at 18 sites surveyed throughout Port Curtis area, compared with one site in October and six sites in September, indicating the dynamic and highly variable nature of Port Curtis.

"The November data found no dissolved chromium at any sites, and levels of total zinc were within guidelines at all sites other than at Boat Creek which may be related to the elevated turbidity at that site.

"From the data available, there is no clear connection between fish health and the results of the monitoring that has been undertaken to date.

"Monthly sampling will continue and the results will be made public."

The latest test results are available at

DERM is investigating water quality in Port Curtis as part of the Queensland Government response to concerns about fish health in Port Curtis during the latter half of 2011.

DERM's independent water quality sampling is in addition to the monitoring conducted by Gladstone Ports Corporation at 16 sites around the harbour, offshore and in a nearby bay.

In addition, water quality monitoring at 170 sties across the harbour has as been undertaken as part of the Port Curtis Integrated Monitoring Program since 2005 and published in the Port Curtis Ecosystem Health Report Card.

The latest report card was published in November 2011.

DERM's investigation is looking into whether there have been changes in water quality in Port Curtis during 2011 which could cause or contribute to fish ill-health.

It is also looking for any pattern in water quality which could be explained by dredging.

Water quality testing is being carried out in three zones - zone 1 being the closest to current dredging and associated activities and Zone 3 being the furthest away.

On 5 October 2011 a report was released which collated and compared current and historical water quality data which included monthly monitoring of water quality in the Boyne and Calliope estuaries carried out by the Department of Environment and Resource Management since 1994.

It concluded that the water quality was consistent with historical trends, apart from the impacts of the significant rainfall events in late 2010 and 2011 which occurred throughout the State.

This report noted that a limitation of the existing metal concentration data was that only total concentration data were available and that these have little biological relevance.

On 4 November a report summarising the results of the first round of sampling undertaken in September 2011 concluded "that none of the water quality properties measured were of significant environmental concern".

On 22 November, preliminary results drawn from the data second round of sampling undertaken in October 2011 indicated that there was no clear pattern to suggest that dredging was having any obvious impact on water quality and no evidence that could directly link water quality with ongoing concerns with fish health.