THE State Government has created a loophole in the monitoring of dredging in Gladstone Harbour which allows potentially disease-causing conditions to be ignored.

The standard of monitoring is a key issue in the harbour's massive expansion which is feared linked to diseases in fish and water quality issues.

Greens spokesman Andrew Jeremijenko said yesterday the Environment Department and Gladstone Ports Corporation agreed before dredging for gas industry expansion began that water quality would be deemed to have been impacted if turbidity levels were exceeded over a 48-hour period.

A "natural variation" clause was added to cover flood or cyclone periods but this was now being used as a loophole.

When muddy conditions occurred, the corporation explained it away as a natural variation caused by high and low tides.

"They have continued to dredge except for one or two days during this time of high turbidity," Dr Jeremijenko said. "This highly turbid water contains high levels of heavy metals, in particular aluminium.

"DERM also is provided with the turbidity data and did not ask the port to take action."

Environment Minister Vicki Darling said recent instances of high turbidity had coincided with high spring tides.

She said tests showed turbidity levels were higher than normal around dredge sites and dredging was suspended.

If a further review indicated a need for DERM to amend the dredging approval conditions, the department would take immediate action, the minister said.

Great Barrier Reef Marine Park Authority chairman Russell Reichelt has also told the ABC's Four Corners that he warned federal Environment Minister Tony Burke that major dredging associated with the building of four coal seam gas processing plants at Gladstone would have an unacceptable impact.

Mr Burke imposed water quality guidelines, with Mr Reichelt then agreeing harbour expansion could go ahead.

In July, UNESCO admonished the state and federal governments for allowing gas processing on the reef doorstep, with Premier Anna Bligh replying that appropriate environmental protections were in place.

Dr Jeremijenko said high turbidity levels had occurred for more than two weeks in the past two months.

This confirmed water quality was affected by dredging in contrast to a departmental report on the issue.

Originally published as Dredging loophole risks harbour water