More than 400 Southern Highlands residents have attended a seminar organised by a group opposed to Hume Coal's proposed Sutton Forest mine.
During the event, held at the Moss Vale RSL, Southern Highlands Coal Action Group (SHCAG) members presented a peer reviewed report, which suggested the groundwater level in the area of the mine could fall by up to 120 metres if the project went ahead.
SHCAG convener Peter Martin said attendees had been interested in what the group had to say.
"We kept the emotion out of it, we kept criticism out of it.
"It was intentionally scientific, people were very intent on learning about it," he said.
The battle over the proposed mine has been raging for close to three years.
Early designs from the company suggested the mine would produce 4.1 million tonnes of coal a year once operational, however a final mine plan is yet to be publicly released.
Mr Martin said the report presented at the meeting was modelled on a "conservative" prediction of what the mine might look like.
He said the issue that would cause the "dewatering" of the aquifer was to do with underground geology, not the type of mine.
"[The study] finds that the unique geology of the Southern Highlands, where the sandstone aquifer sits right on top of the coal seam means that the impact on the groundwater of the proposed mine will be substantial," Mr Martin said.
Hume Coal project director Greig Duncan said the study was "hypothetical" and was "open to a high margin of error".
"While the study has been the subject of a lot of discussion, it doesn't provide a lot of new information or insights," he said.