Leave a 1 Block space between quaries, This is so you can make a staircase to the Ore you didnt mine. Its not effiecient on energy to mine this one column. make a recycler for the cobble stone. when all is done cover the top. get a jetpac and rubber boots and make floors. so long as you leave a hole, its a perfect mob farm,,, Gotta do it with the blue torches to get each side to the end of the water