Three months later he was declared bankrupt, owing creditors more than $540 million, and a year or so after that he was banned from managing companies for three years and nine months.

But plans for Dartbrook, including re-opening the mine and extending its approval until 2027, are in their final stages after owner Australian Pacific Coal gave assurances about mine safety following concerns about the tragic history that stopped operations in 2006.

The company told the Department of Planning that gas in the previously-mined Wynn Seam was “not expected to occur” in its proposed Kayuga Seam operations and “real time” gas monitoring would ensure a safe workplace “at all times”. The Dartbrook mine was mothballed after three miners died in 12 years.

The risk of spontaneous combustion would also be managed by maintaining ventilation of all unsealed mine workings, Australian Pacific Coal said in a response to concerns raised by agencies. It plans to mine 1.5 million tonnes of coal per year and employ 99 workers using a bord and pillar underground method to shear coal from the seam and use “pillars” of remaining coal to maintain site stability, the company said.

It has sought approval to transport coal by trucks from one side of the mine site to another rather than use the approved Hunter Tunnel beneath the Hunter River, New England Highway and Main Northern Rail Line to transport coal on a conveyor belt. The variation would help meet the company’s objective of re-opening Dartbrook with “more cost effective mining and transportation methods”. 

But Muswellbrook Shire Council raised concerns about air pollution from the company’s plan to transport unwashed coal from the mine to Newcastle Port, the number of trucks, the potential for overloaded trucks to travel on council roads and the cumulative impact of open cut coal mines approved in the area since Dartbrook operations ceased 12 years ago.

Australian Pacific Coal said it would seal an internal dirt road after the council questioned the dust impact of an estimated 192 one-way B-double truck movements per day at the mine. The company also gave assurances trucks with 60-tonne loads, which would be classed as overloaded if using council roads, would not use the roads.

The council called on the NSW Government to fund a night-time air quality study of the Upper Hunter after raising concerns about the cumulative impact of many large open cut coal mines in the Singleton and Muswellbrook areas.

A 24-hour averaging period for monitoring air quality around the mines had the “unintended consequence of obscuring issues of elevated dust levels at night as a result of surface temperature inversions”, council general manager Fiona Plesman said in a submission to the Department of Planning on the Dartbrook proposal.

“Council submits that the result of these inversions is to trap dust emitted from this and other mining developments in the shire for sustained periods. This causes the level of dust in the air to increase substantially at night, which is in turn obscured by the lower levels of dust in the air during the day. Consequently, the average over a 24 hour period does not result in a technical exceedance,” she said.

The air quality issue was “beyond the responsibility of an individual mine entity”, Ms Plesman said.

“A number of matters raised by council relate to the NSW Government’s need to understand and analyse the cumulative impacts of mine development on infrastructure, the environment and the community, as various new proposals and modifications are submitted on an ongoing, ad hoc basis,” she said.

In a submission on the proposal the Hunter Thoroughbred Breeders Association said it was “disturbing that no-one (neither coal companies or the NSW Government) will take responsibility for the increasing dust deposition levels and ever decreasing air quality that mining is causing in the Upper Hunter”.

“What is worse, mining companies are admitting they will be exceeding safe air quality levels and yet their applications for modifications are still waived through,” the association said.

In its response Australian Pacific Coal said the mine would contribute $38 million in royalties, $14 million in NSW’s share of Australian company tax and $30 million in profits to shareholders. The proposed 1.5 million tonne per year haul was considerably lower than the approved 6 million tonnes per year and “is therefore expected to result in lower dust and noise emissions”, the company said.

The Department of Planning is assessing the proposal with a recommendation expected in the new year.

In December 2015 former Australian Coal Association chairman Ian Dunlop said the Dartbrook coal mine should stay mothballed because of issues including climate change.

Mr Tinkler is no longer an office holder in Australian Pacific Coal. Tinkler family members remained shareholders of the company when the Australian Stock Exchange was advised of the proposed Dartbrook re-opening plans in March.