The Battle 4 Berrima Group believes a decision not to include the Wingecarribee River in an investigation into the effects of underground coal mining in the Sydney Water Catchment is a missed opportunity.
The investigation will be carried out by a panel of five experts, which will be chaired by the NSW Chief Scientist.
Spokesperson Michael Verberkt says they'll be asking for the terms of reference to be expanded.
He believes the investigation should include all areas.
A study conducted by Dr. Ian Wright found large amounts of pollution entering the Wingecarribee River from the disused Medway mine.