Opponents to the Bligh Government's Traveston Crossing Dam were making sure their message was being heard and read after delivering more than 30,000 letters to state and federal politicians.

With a decision on the fate of the dam due on November 18, although federal Environment Minister Peter Garrett can ask for a deadline extension, Save The Mary River (STMR) president Glenda Pickersill said they remained hopeful of a positive outcome.

The STMR group have specifically targeted Prime Minister Kevin Rudd, Environment Minister Garrett, Queensland Premier Anna Bligh and her Environment Minister Kate Jones with their mail campaign.

"We've sent more than 30,000 letters and countless emails on behalf of people protesting against the dam," Ms Pickersill told AAP on Saturday.

"We've sent letters to Kevin Rudd, Anna Bligh, Peter Garrett and Kate Jones but the most have been sent to Garrett.

"We hope it's made an impact."

She said the number of letters and emails that have been sent should indicate to the politicians the enormous support for their cause in saving the Mary River and preventing the Traveston Crossing Dam.

"Our support is not only local. The large number of Brisbane addresses on these letters shows the extent to which people in Anna Bligh's backyard disapprove of the project," she said.

Earlier this week, the Queensland opposition teamed up with wildlife conservationist Bob Irwin in its fight to stop the Traveston Crossing Dam.

The controversial $1.8 billion project was approved last month by the state's coordinator-general, subject to 1,200 conditions.

Mr Irwin said last Sunday that allowing the project would be "environmental vandalism" as he appealed to Mr Garrett to listen to the people.

"At 1.3 times the size of Sydney harbour, the proposed Traveston Dam would block one of the last free flowing rivers on the east coast of Australia," he said in a statement.