The community advocacy group has demanded a developer be ordered to pay compensation for what it termed "environmental destruction" of wetlands.
The Goluburn Group's letter to the council comes at the same time as a clean-up notice and fine issued to the developer of a 28-lot Torrens title residential subdivision in the NSW Southern Tablelands city.
It followed torrential rainfall on Friday night that washed heavily silted soil from the cleared block below Rocky Hill, into the Goulburn wetlands off May Street. It was third time such occurrence since November, sparking frustration and "distress" among wetland volunteers due to infrastructure and ecological damage.
The council's environment and planning director, Scott Martin, said a November stop-work order was still "in play." No work can resume until further stormwater and drainage measures are implemented on site, to the council's satisfaction.
"To date we have not been satisfied. The last two rainfall events have further demonstrated to us that (the controls) are underdone," he said.
Now, The Goulburn Group (TGG), which initiated the wetlands project, has added its voice to what it described as "major damage" to the swamplands resulting from "irresponsible clearing" of the May Street land. Paths and vegetation had been destroyed and water pollution would likely kill fish, reptiles and other species, president Urs Walterlin wrote.
"It was the worst of a series of such incidents that have occurred over recent months," the letter stated.
"This was an environmental disaster waiting to happen, given the indiscriminate clearing of trees and other vegetation on a steep hill."
"We are dismayed that, despite objections and warnings on multiple occasions, inadequate action was taken to prevent what has occurred. The wetlands are a major asset for our city, initiated by TGG, supported by the council and created through the tireless efforts over many years of volunteers at Friends of Goulburn Swamplands, the Goulburn Field Naturalists Society and the Australian Plant Society as well as many individuals.
"Our members are devastated by the extent of the destruction. We demand that the developer be required to pay compensation and conduct remediation work after an expert assessment of the damage has been completed. As well, we are asking the council to ensure that further work is undertaken on the development site to ensure that this cannot occur again."
Mr Walterlin said the group had started the wetland just over 10 years ago, transforming it from a brick and rubbish pit into a thriving community asset.
The developer has not responded to requests for comment.
Mr Martin said in addition to the clean-up order, which carried a fine, his officers were "keeping a close eye" on how this was done.
"We're concerned about how they'll go about it. We want to know the methodology first because we don't want further damage," he said.
The proponent had built detention dams onsite and pumped them out ahead of heavy rainfall. Some drainage measures have also been implemented but Mr Martin said more could be done. This included clean-water diversions to stop heavily silted flow downhill and rock dams to slow velocity and settle sediment.
The developers have repaired damage to neighbouring backyards and structures such as retaining walls destroyed by the deluge. They have also cleaned up the wetlands. But FROGS volunteers were unhappy that excess silted water had been pumped into stormwater drains flowing to the wetland.
Mr Martin said Monday was the first time the owner had a recognised stormwater consultant onsite but recommendations for action "could be a few weeks away."
The developer had also been previously fined for alleged non-compliance with consent conditions surrounding vegetation clearing. Mr Martin said controls should have been in place before vegetation was "stripped."
"Instead it was done back to front and they are now trying to deal with an unmanageable site," he said.
The development was approved in 2008 but was still 'live' due to effective commencement. Mr Martin previously told The Goulburn Postthe extent of clearing would not necessarily be accepted today, due to changed attitudes to nature conservation.
"The consent we have permitted clearing but unfortunately the way it was done hasn't assisted," he said.
"Hindsight is a wonderful thing and I think the developer realises now that a staged approach to clearing would have been better."
Despite the amount of topsoil lost from successive flooding, Mr Martin said the council wasn't concerned about the ground's structural stability for housing construction.
Meantime, a real estate agent removed a sign advertising the subdivision, known as The View, on Wednesday morning. It's understood all lots are sold.