Although it is set in the US, Netflix's new thriller starring Tom Hardy was filmed across Wales.
Experts believe slag heaps are a largely untapped resource in preserving Wales' rarest plant species.
The fire service had earlier warned about the dangers of previous arson attacks at the site.
People nearby were advised to close doors and windows when a liquid gas tanker started leaking.
The new arrivals will help fill the shortage left by retirements and staff leaving for a new career.
People struggling to afford to heat their home can head to libraries and churches to keep warm.
Holes were drilled into the trunks and an undiluted herbicide poured in, officials say.
Welsh ministers accused their UK counterparts of failing to help after spending the cash.
The man was arrested after a director of his own firm was found with a serious knife wound.
