Modifying Coal Bin

I need advice.
First, my back is to the detached garage. The chimney and stove is at the other end of the house. At least we have a walk in basement. Not asking for sympathy, we are young and strong. The coal bin is in the back of the detached garage. We climb up the ladder and shovel the coal into buckets. It's a 4x4x8 bin. This doesn't show it very well but the left wall is slightly blown out in the back corner. I need to repair that too. So, I need a better way to get the coal out. I don't know if the coal is on the concrete or if there is a wood floor. I have two ideas: I cut the plywood in the second void, where the level is. I then build a rail system so I can remove a panel at a time.
Or in the same void make a doghouse at the bottom. I don't know anything about this, how big it should be for nut coal.

Either way I can't get all the way to the bottom, assuming it is on the concrete. Does the doghouse easily keep the coal in when it is full?

Any ideas?

Having grown up on a farm & on a farm most of my life I would do like is done with corn cribs.Put //// vertically up the 2x4,s & then slide 1x 6 in each / , not really a slot just an angle / under each / 1 x 6 , you can then pull the bottom board to let enough out & shove in back in on it's /, these // are steeper than they need to be but I do not know how to tilt them on here,but do know how to in the real life project.

Hmmmm. I take a shot at it. First I would disassemble the existing bin. Then rebuild it with a slanted floor.
The slant does not have to be on a 45° degree angle as you can pull the coal to the door with a rake or hoe.
Build the front wall with heavier framing than the side walls, as the slant does load the front wall heavier than the side walls will.
Use these on the corners. To reinforce them.
http://www.homedepot.com/p/Simpson-Strong-Tie-14- ... 5yc1vZaqta
Have a door that you can open and shovel the coal out of and into your buckets.
If you can find a couple pallet protector sheets you could attach them to the floor of the bin to get the coal to slide easier.
Or you could build a vacuum loader system and just repair the bin.
Dan.