Your operation’s purpose is to put the excess rock created by excavating the coal seams into nearby valleys.
EPA: https://www.epa.gov/sc-mining/basic-information-about-surface-coal-mining-appalachia#impacts
Science X: https://phys.org/news/2017-07-mountaintop-coal-appalachian-rivers-saltier.html
Yale Environment 360: http://e360.yale.edu/features/mountaintop_mining_legacy_destroying_appalachian_streams
The Strip Mining Handbook (Scroll down to the sections on: Contour Mining, Mountaintop Removal Method, and Environmental Effects): https://sites.google.com/site/stripmininghandbook/chapter-2-1
The Dominion: http://www.dominionpaper.ca/articles/2093
Exploring the Environment: http://www.cotf.edu/ETE/modules/waterq/wqacidmine.html and for more details here: http://www.cotf.edu/ETE/modules/waterq/wqchemistry.html