I'm thinking of building a large mobfarm (standard spawn on pressure plates, piston pushes the mob off, dies from fall damage and a waterflow collects the drops).
However, to maximize efficiency I want to build it at bedrock-level (due to lc values), meaning I need to clear out the area that I plan to build this on. Since mobs spawn within 128 blocks, this means I'll need to clear out a 128-radius circle from the collection point, which is a good few million blocks.
I realize the simplist option is to build it in the sky, but due to minecraft's lc value mechanics, the spawn rate will go down significantly and I want it to be as efficient as possible. I've tested with JL2579's mob farm design at bedrock compared to y=180, and the bedrock farm spawned about 2-3x faster.
I don't have any TNT right now (obtaining TNT being the purpose of making a mobfarm), so mining it all out by hand would probably take several weeks. Is there a good mining strategy to clear out large areas, or any better options? It's an SMP server, so no MCedit or world editing. Thanks!