The accident would have been avoided had the EPA team checked on water levels inside the abandoned mine before digging into its collapsed and leaking entrance, says document.
The world's largest equipment maker not only reported lower quarterly profits, but also cut its 2015 earnings forecast and warned its revenue would fall even further next year.
The environmental group is after Vattenfall's lignite business in eastern Germany, in a bid to scale back the operations put up for sale by the Swedish state-owned energy giant.
The rough-diamond miner extracted about 11.6 million carats in Q3, or 20% more than in the same period last year. However, it could only sell 4.9 million carats.
The worker who developed leukemia was exposed to less radiation than many, said authorities, which suggests that the number of compensation cases could spike.