South32 still isn't saying how much coal waste sludge was washed down a creek in Figtree from its Dendrobium mine almost three weeks ago, but says it has contracted out clean-up works on the waterway.
The Environment Protection Authority, which regulates pollution incidents, will rely on the miner's assessment for more details, but estimated about 10 megalitres of liquid - containing coal fines - was washed downstream in heavy storms over the weekend of August 8.
The EPA said water samples were still being analysed.
South32 was required by the EPA to file an incident report early in the week of August 16, and a full environmental assessment by August 31.
A South32 spokesman said it had engaged an environmental clean-up specialist to do the work on Brandy and Water Creek, and American Creek.
"Clean-up activities to date have involved the removal of coal fines found in the two creeks," he said.
"We have been conducting a detailed assessment of the incident and this is expected to conclude soon."
The investigation has not satisfied Wollongong Greens councillor Cath Blakey, who wants the city council to write to Environment Minister Matt Kean and seek a more robust inquiry.
Cr Blakey will ask council to "appeal for a robust and comprehensive investigation of the breach of the Dendrobium water discharge licence, including a comprehensive clean-up of the pollution residue, and public and transparent reporting on the quantity and quality of the pollutants, and what actions are being undertaken to prevent further pollution incidents".
An EPA spokesman estimated the spill at 10 megalitres but said the EPA was waiting for more detailed information from the miner about what the liquid contained and its impact.
"EPA officers attended the site immediately when notified by South32 of the incident and collected water samples from the creek for laboratory analysis that are currently being assessed," he said.
"The EPA is awaiting an Environment Impact Report on the incident from South32 to ensure well-informed further clean-up and monitoring actions that are likely to be required. This report is due Monday 31 August."
Cr Blakey also wants assurances from the NSW Treasurer that the EPA is "sufficiently resourced to ensure robust and comprehensive regulation of pollution controls".