> Is the environmental impact actually significant enough to warrant consideration in this circumstance?Abso-fucking-lutely! *Smack* The answer to that question is always a resounding yes when we're talking about massive industrial processes. The qualification "as long as a town isn't poisoned" is fantasy at these scales. Most mining facilities require tons of water so they're built near waterways and those are almost always populated downstream.
The tailing ponds contain very toxic waste that, if breached, will basically salt the earth around them and anything downstream. The tailings from a much less toxic processes like iron mining, for example, caused a massive ecological disaster in Brazil when the Mariana dam holding back millions of tons of mining waste broke [1]. It followed the Rio Doce to the Atlantic polluting over 600 kilometers of waterways along the way, affecting over a million people. Five years later people are still getting sick, fish stocks are way down, and farming along the river is crippled [2].
A few years later another dam in Brazil broke, once again contaminating hundreds of kilometers of waterways [3]. The Ok Tedi disaster in Papau New Guniea [4]. The Marcopper disaster in the Phillipines that still hasn't really been cleaned up decades later [5]. Aberfan in the UK [6]. History is full of these kinds of tailing disasters effecting millions of people, often the poorest with the least recourse.
Edit, forgot to add final point: Those Ganzhou tailing ponds are much more toxic than those above from lesser metals and coal. They're dangerous to approach without full PPE and much of the surrounding area has been polluted to the point where nothing will grow without remediation. Even assuming there's no accident, the environmental damage is already significant enough to cause political pressure in an authoritarian regime.
[1] https://en.wikipedia.org/wiki/Mariana_dam_disaster
[2] https://news.mongabay.com/2020/11/deadly-anniversary-rio-doc...
[3] https://en.wikipedia.org/wiki/Brumadinho_dam_disaster
[4] https://en.wikipedia.org/wiki/Ok_Tedi_environmental_disaster
[5] https://en.wikipedia.org/wiki/Marcopper_mining_disaster
[6] https://en.wikipedia.org/wiki/Aberfan_disaster