ON 8/16/18, MINER REPORTED EXPERIENCING SEVERE BACK PAIN AFTER SITTING IN A CHAIR WHILE OPERATING THE DREDGE ON 8/14/18, FOLLOWED BY A 12 HR SHIFT PERFORMING MAINTENANCE ON 8/15/18. MINER INITIALLY REPORTED TO SUPERVISOR AND A GROUP OF MORE THAN FIVE OTHER MINERS THAT BACK PAIN WAS NOT RELATED TO WORK CONDITIONS.