Ms Stuart said the repeated pollution incidents from the Peabody mine at Helensburgh last year had not been properly addressed.

"I have always been clear in my opposition to expansion of mining under our water catchment areas," she told the Mercury.

"Water security is paramount to all of us who rely on the water supply.

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"If elected, I will advocate for protecting the environment, every living thing and the workforce, my hope is that a new coal mine in this location will not be required."

"After the serious and unacceptable pollution incident last year, the NSW Government said it would act. It hasn't."

If Labor forms government after the state election, however, voters should not expect Ms Stuart's position to be implemented.

Labor policy supports mining in the catchment when approved by proper planning authorities. Labor policy is for mining to be allowed with environmental protections in approval conditions, so coking coal can continue to supply steelmaking in the Illawarra.

Liberal Member for Heathcote Lee Evans' position is a continuation of the status quo.

"Mining in the Special Areas has substantial economic benefits as it supplies coking coal to the steel industry in Port Kembla and Whyalla, which creates direct and indirect jobs," he said.

"The Department of Planning and Environment (DPE) has been implementing recommendations of the Independent Expert Panel for Mining in the Catchment to improve the regulation of mining.

"Mining beneath Woronora Reservoir was approved subject to strict conditions. These require the mining company to have a negligible impact on the reservoir and to comply with comprehensive monitoring and management requirements."

Two other Heathcote candidates, the Greens' Cooper Riach and the Animal Justice Party's Arielle Perkett, are both firmly against mining in the catchment.

Mr Riach said the Greens' policy was to shut down the Metropolitan Colliery by revoking its pollution licence.

"If elected I will work to phase out these mines as soon as possible to ensure the future health and security of the Illawarra/Greater Sydney water catchment," he said.

"It is Greens policy to shutdown the Peabody Metropolitan Colliery. Given the size and location of this mine it is impossible for it to comply with any Environmental Protection Licence.

"We will support the affected workforce with ready access to training and financial security."

Ms Perkett said restrictions should be tightened on catchment area miners.

"Mining ruins ecosystems and heritage sites while also impacting ecosystems and habitats for animals," Ms Perkett said.

"Animal Justice Party does not support fossil fuels on grounds of the environmental damage that extraction causes."

Mr Evans faces a tough fight to retain his seat after its boundaries were redrawn to include northern Wollongong suburbs as far south as Bulli. These are suburbs where the environmental and Greens vote has traditionally been higher than average.