That was the defiant stance the project delivery director of a proposed gold mine in the region's south took after an at-times heated line of questioning centred around water during the final hearing of the parliamentary inquiry into the impact of mining on health.

Wayne Taylor, the project delivery director for the Regis Resources McPhillamys project was one of the witnesses during the final hearing at Sydney in October.

Mr Taylor was being pressed about the proposed mine's looming impact on water in the Blayney shire by Greens MLC Cate Faehrmann.

Ms Faehrmann was questioning the mine's proposed location for a tailings dam, which is likely to be built near the Belubula River.

"I understand there are 24 or so springs that will be plugged for the tailings dam to essentially be built right on top of the springs at the headwaters of Belubula River. Is that actually what your company is going to do?" she said.

Mr Taylor replied by saying the springs have been studied in a "huge amount of detail".

He said the springs Ms Faehrmann was referring to in that area don't run all the time.

"With the development of the site, we actually don't take the water out of the ground," Mr Taylor said.

"If we were to cover one of these wet areas, the water stays in the ground and it continues to move through the ground and it will come out at the next point of weakness, which would be further - let's call it downstream, and effectively feed back into the Belubula anyway.

"We're not actually taking any water out of the system."

"What happens if the tailings dam wall falls?" Ms Faehrmann then questioned.

Which led to this exchange, which included interjections for a number of the sitting panel, including the chair Dr Amanda Cohen.

Mr Taylor: "I can assure you that it will not fail. With the design of it ..."

Ms Faehrmann: "I'm sure Cadia said the same thing about their tailings dam."

Bronnie Taylor: "Point of order: I think the witness is answering the question, and you're using ..."

Emily Suvaal: "It's a bit like adverse mention as well."

Bronnie Taylor: "Yes. You're using ..."

Ms Faehrmann: "What is adverse mention?"

Emily Suvaal: "You're accusing Cadia ..."

Ms Faehrmann: "How is it adverse mention saying Cadia dam would have said the same thing. For goodness' sake."

The Chair: "I think there may have been a bit of argument in the question. Can you perhaps restate the question as a question?"

Ms Faehrmann: "The question is you can't say that it's not going to fail. Even in terms of extreme weather events, we've seen ..."

Bronnie Taylor: "Point of order: You cannot say to someone that they can't say something. Mr Taylor is here in his own time coming to give evidence. He's given the evidence. Accept his evidence, but you can't tell him what to say. You can't say that."

The Chair: "There's been a fair bit of commentary with questions, like 'Isn't that the case?' today. I think the member needs to phrase it as a question and I'll allow it."

Ms Faehrmann: "Climate change and extreme weather events-have you factored in the one-in-100-year extreme rain events that we're seeing? How can you guarantee that a tailings dam won't fail? Because they do and they do all over the world, and we saw it at Cadia. Wouldn't you agree?"

Mr Taylor: "I'm familiar with the basic design principles of the Cadia dam. Our dam is not constructed in the same manner. Our dam is constructed to handle a one-in-10,000-year rainfall event, so I think it's a pretty high level of design criteria. It is the best in the world.

Ms Faehrmann: "Some 10 per cent of tailings dams fail, as I understand, around the world. You're saying that yours won't be one of those?"

Mr Taylor: "Ours is a downstream construction methodology, which is the safest dam wall that you'll get."

Ms Faehrmann: "Say it did fail, because we've seen extraordinary scenes, haven't we, in terms of extreme weather around the world in the last few years beyond anything we have imagined possible- just say it did fail, what happens?

Mr Taylor: "It's not going to fail."

The inquiry into current and potential impacts of gold, silver, lead and zinc in mining on human health, land, air and water quality in New South Wales held four hearings. They were in Orange, Mudgee and two in Sydney.

The above exchange was heard during the fourth hearing at the Macquarie Room, Parliament House, Sydney on October 27.

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