I do not have a good answer for you concerning economic impact of the sulphuric acid by-product, I was much more concerned about the handling of it due to environmental impact.  They seem to handle that well.  The site is inspected extensively by the Panama version of the EPA every 2 week.

I was concerned about the tailings being quite full but they are building new tailings in plenty of time to handle that.

I'll try to check.