: We assumed a two man/dwarf crew in good physical shape. Tools were two pick axes, tweo square mouthed shovels, and an ore cart (I know that ore carts weren't mentioned, but we assumed that the dwarves would be smart enough to use even free ore carts, meaning no tracks laid) the cart would be standard meaning capable of moving one yard of material (that's about 3,000 pounds). We also assumed a work day of six to eight hours which was a typical shift for hardrock miners (working longer with hand tools wasn't practicle since you were more likely to serious injure or even kill you miners).

[snip]

One question that comes to mind is, where did they put the excavated rock? In The Black Gate Opens, Tolkien comments upon the two large 'slag mounds' piled by the Orcs through endless years of labor before the Gates of the Morannon. If the Dwarves excavated such large amounts of material, why were there no 'slag mounds' near the East or West Gates of Moria?

I suppose its possible that the excavated rock from the Western side could have been used in the construction of Ost-in-Edhil (doubtful, but possible), but there were no stone fortresses anywhere near the Eastern entrance. Unless, of course, the Dwarves simply dumped the extra stone down the naturally occuring shafts within the mountain.