During Questions from the Public at last week's council meeting, Southern Highlands Coal Action Group president Peter Martin accused Boral of breaching its Environment Protection License (EPL) by pumping wastewater into the river.

Mr Martin said the company, in its reports, admitted the wastewater contained elements such as Manganese, Nickel, Zinc and salts.

He said the levels of the elements were in excess of "trigger levels".

"These substances are potentially toxic to aquatic species particularly at low water levels and can accumulate over time in sediments on the river-bed," Mr Martin said.

Boral has denied the claims and was recently granted approval from the state government's Planning and Assessment Committee to increase production at the mine.

Cr Graham McLaughlin, also a Boral employee, said he had proof that the water was not toxic to fish, pointing to a fish pond on a property at Medway which contained water pumped directly from the mine.

"Either Peter Martin is wrong or these fish don't know that they should be dead," Cr McLaughlin said.

"It's simply a beat up by people who are using Boral's expansion as a test case for the much larger proposed coal mine from Hume Coal."

Owner of the fishpond, Les Talbert, who is the father to one of Cr McLaughlin's work colleagues at Boral, said the 11 fish in the 20-year-old pond had been there for up to four years.

He also said they used the mine water to feed the dogs and horses on the property and have done so for years.

"I've been living here for 56 years and this mine has actually helped us in times of drought," Mr Talbert said.

Mr Martin urged the council to contact the Chairman of Boral and request that it "halt any expansion plans and immediately put in place remedial measures to clean the wastewater of identified toxicants to well below trigger levels before it is pumped into the Wingecarribee River".

He asked the council to contact the EPA and request an explanation as to how long they have known of these "breaches" and ask for an explanation as to why the EPL hasn't been enforced.

He also asked the council to support an application to the Land and Environment Court for a review of the PAC decision regarding the expansion.

Goulburn MP Pru Goward said, on 2ST, that once the PAC had made a decision, there was no appeals mechanism and that was the end of the process.

She added that if there was still unhappiness about the expansion of the colliery then the only other avenue was to take it to the Land and Environment Court.

"There's a couple of grounds, such as factual grounds, and I think there's a judicial cut path. It just depends on whether the case can be made that the law hasn't been applied properly," she said.

The council took Mr Martin's questions on notice.