Concerns have been raised about a planned sand mine in the New South Wales Southern Highlands.

The proposed Sutton Forest sandstone quarry and processing plant would include an extraction area, processing and stockpiling area on 64 hectares just off the Hume Highway.

Water scientist Ian Wright says the damage on the ecosystem could be irreversible.

Dr Wright has been testing local waterways for contamination for 20 years, and says the ecosystem that feeds into Sydney's water catchment to supply 5 million people could be irreparably damaged.

“The proposed mine does pose substantial and unquantified risks,” said Dr Wright.

“It's likely that it's going to change the hydrology of this area and it's likely to produce sediment-laden run-off with a whole series of contaminants.”

The quarry will be dug about 60 metres below the ground.

The environmental impact statement (EIS) for the project says risks include contaminating groundwater and reducing the water availability for agriculture and domestic use.

“We get a lot of intense rainfall here,” Dr Wright said.

“Any major human activity that involves clearing of vegetation [and] disturbance of soil and rock has the opportunity of creating soil erosion and transporting eroded material into waterways.

“These waterways are the lifeblood of the local ecosystems and the lifeblood of the Sydney [catchment] now and in the future, a catchment that currently supplies water for about 5 million people with more to come.”

Public submissions on the plans close on June 21.

The NSW Department of Planning says about 20 submissions have been received so far.

“Following the EIS exhibition, the proponent, Sutton Forest Quarries, will then prepare a Response to Submissions (RtS) report,” a department spokesperson said.

“The department is also planning to hold a community meeting to better understand concerns and address these in its assessment, which will also provide an opportunity for Sutton Forest Quarries to hear the community's concerns directly.”

The department’s assessment will take into account the EIS, community submissions, comments from local government and the RtS.

“If there are more than 25 public objections, then the department's assessment report and recommendations are sent to the Independent Planning Commission (IPC) for final consideration and a decision,” the spokesperson said.