T he days of Brisbane's mighty meandering river as a muddy murky mire will end with the death of dredging next September, following an historic agreement forged on Friday.

The agreement - at a meeting which included two State Government ministers and three mayors, set September 30 as the deadline for dredging operators to cease all sand and gravel extraction from the river.

They are giants Pioneer Concrete (Qld) Pty Ltd, Boral Resources (Qld) Pty Ltd, and the much smaller Arnold Johnson Marine Services.

Pioneer already has announced it will end river dredging by March next year. However Boral wishes to continue. The intention of Arnold Johnson is unknown.

The historic agreement, forged at a four-hour Brisbane River Management Group meeting on Friday morning, followed a motion moved by Brisbane mayor Cr Jim Soorley.

Present were Cr Soorley, Group chairman Environment Minister Brian Littleproud, Natural Resources Minister Howard Hobbs, Ipswich Mayor John Nugent, Laidley Shire Major Graham Moon, Queensland Chamber of Industry and Commerce representative Robin Town, and the Queensland Conservation Council's Imogen Zethoven.

The agreement means that by September 30 next year, Boral will have to produced a report which shows that no alternative supplies of sand and gravel are available to it, and a full Environmental Impact Statement for any river dredging activities it wants to continue.

But it is believed unlikely that Boral will gain any extension beyond September 30, as Pioneer has found an alternative source for its sand and gravel needs.

Yesterday Cr Soorley hailed the decision as "a significant victory for Queensland". He said that for 100 years, the Brisbane River had been "treated as a sewer and a mine".

"No other capital cities in the world allow ugly dredges into the heart of their city to mine their river.

"It has been a hard and long battle to convince the State, who licence dredging, that these operations should cease.

"I am pleased that we were able to convince them that cleaning up the river requires hard decisions. The first has been taken."

Environment Minister Brian Littleproud said the decision was "very significant" and "a breakthrough", especially as the Brisbane River was governed by 28 pieces of legislation and, at one stage, 37 government authorities.

"The government has negotiated a major achievement in an area the previous government had neglected.

"They were all talk and no action when it came to the Brisbane River."

And Ms Zethoven said the agreement was "a major breakthrough for the rehabilitation of the river".

"Clearly dredging is way out of line with community attitudes."

But Mr Town, a committee member who also works for Boral, said the decision would lead to a huge alternative extractive sand industry in the Esk region, where over 200 truck-loads of sand were removed daily.

"Sixty percent of all sand for the south-east Queensland construction industry currently comes from the Brisbane River."

He said Boral would prepare an Environment Impact Statement and was planning to continue its river dredging operation.

"But we're happy to phase out dredging particularly sensitive areas, for example the CBD.

"We believe we can work with this decision. But we believe that a carefully planned phase-out is essential."

Since white settlement some 170 years ago, the Brisbane River has been subject to dumping, dredging, discharge, and damning.

Sand and gravel extraction began early this century, and by the mid 1980s over 26 million cubic metres of sand and gravel had been mined.

And the rewards for government were handsome - over $1 million in state government royalties annually in the late 1980s.

But there also has been an environmental downside. The erosion of riverbanks, and the deepening of the river has led to the conversion of what was once a short saltwater estuary to a tidal estuary over 60 km long, and salt-water mangroves once confined to Hamilton Reach have appeared as far upstream as Goodna.

Yesterday Cr Soorley moved to allay a long-held concern that an end to dredging would lead to algae blooms - because of the increased sunlight reacting with the high levels of sewerage nutrients in the river.

"Over the last five years, we have spent an extra $40 million upgrading sewerage, and all Brisbane sewerage treatment plants are at a secondary stage.

"But if the death of dredging means we now have another problem, so be it. That issue will then have to be solved."

He said Friday's agreement allowed for some dredging to continue, but only navigational dredging, and extractive dredging at the mouth of the river.

He said the public should not expect the river to appear less muddy overnight, "but over time I think the river will certainly clear up."

He said the end of cheap river sand would only slightly affect housing construction costs. A State Government analysis showed that the cost of a house might rise, but by no more than $105.