Not under threat at all, just you will be able to see the mine from town. The mine does pay tax and pours money into the local community, most of the Bulga community have or do work at said mine.
The mine is visible from Bulga now and is moving closer.
The mine owner is Yancol which is Chinese owned and pay virtually no tax in Australia, they run at a fake loss and yet have enough money to buy $2.5B worth of Rio Tinto coal mines in Australia. Yancol use their fake loss to not pay tax. Yancol also ship uncovered coal trains through Newcastle to the port and cause many serious health issues for people who live along the rail line.
http://www.yancoal.com.au/page/assets/mine-sites/mount-thorley-warkworth/
You are wrong about Bulga not under threat from the a tax avoiding foreign (Chinese) owned mine, the locals have run a campaign to #savebulga for several years.
Have a read of the Bluga declaration and then have a good look at their web site.
https://www.savebulga.org.au/bulga-declaration/
The mine has recently closed the Wakeworth Road and has moved closer to the town in the last year. The mine wants to demolish the town and destroy the local cemetery so it can expand. I have ancestors (Eather family) buried in that cemetery, who were among the first white settlers in the Hunter Region and find the mines disregard for the locals and history about what one would expect from destructive open cut coal miners.
https://www.savebulga.org.au/yancoal-stakeholder-update/
The people of Bulga have twice won court cases against the mine expanding, the NSW Gov changed the law twice in favour of the foreign owned mine and once again the town is under threat. A few people in Bulga area do work in the mine, but most residents would like to keep their homes and farms.
Coal mining is destroying Australian farms and homes in one of the most productive agricultural areas of Australia.The mines in the Hunter do not have to level the waste (spoil) piles and fill holes (voids) they make. The open cut mines are already destroying the water table in the Hunter. Once they stop coal mining and the voids will fill and become toxic acidic lakes which will almost certainly end agriculture along the Hunter River. Coal mining is very short term, for a few temporary jobs we loose a beautiful productive well watered agricultural area that could provide food and jobs for many more centuries.
The beautiful Hunter Valley has just under 200 years of farming and jobs, which soon may stop because of open cut coal mines. There is no future in coal these big companies will just sell up and move away and leave the mess for Australian taxpayers to fix.