It's not high enough for a mine. It only goes to +3. It needs to be +5 or so to qualify for placing a mine. I tried it with the standard vanilla mine, and Kid's Tiny/Mini Mine. Not high enough. Maybe someone can create a really small mine for coal and iron that would be able to use only a hill height of +3?
http://worldofbanished.com/index.php?action=downloads;sa=view;down=389
are you sure it isn't high enough but needs more land raised? the mines can be picky about placement. some even need totally flat land to the front. makes them very tuff to place cause you need a stgraight hill. the more curve to the base of the hill the less likely you can place a mine. very hard to see the red spaces that are bocked sometimes too.
save the game twice. then play around,flatten a 8 wide area and behind that raise about 6 long. experiment some so you have a better idea of how the mine fits or the spaces that need flattened or raised. then go back to the saved game. if you screw up you still have 1 save to work with. the terraform tools won't slope the ground very well.
what you need is a mine that has a ghosted mountain front that sits into a mountain slighty without flattening the mountain. we do have several options and some do work on flat ground.
yes, the front is flat. It's the back part that stays red. I used the +3 for a large area, with the front being flat. The back part stays red, even with a lot of room back there. So I can only conclude that +3 is not high enough.
it can be done. what happens is some spaces are not raised when using the terrarform tools,even thou they look like they were raised. the game still reads the space next to the 1 you raised at 0 height. tedious but you need to go back over the square and make sure you hit all the missed spaces. same thing happens when digging the ground out for RK dock farms,etc. hence it takes practice and trial and error with your main map saved.
i used terraform mod tool that gives different options but still is 3 spaces high. when i scroll back over with this tool it shows red,can't raise higher. it lights up on the missed spaces.