The collapsed edge of the Ballpark stope
The “Ballpark” stope in reality is a host of smaller stopes that were developed on a single large orebody. This orebody was known as the new southwest orebody, first discovered in 1918 by 5-15 drift on the 5th level of the southwest mine. By the end of 1928 it had yielded nearly 1,000,000 tons of oxidized ore averaging 9.5% copper. After this time lessors continued to mine the edges of the orebody cleaning up the small amounts of the remaining ore left by Phelps Dodge. Ore had been mined from just below the 5th level to just below the 7th level, some 200 ± vertical feet, with a curved length of nearly 2,000 feet.
Early in 1932 the removal of pillars and edges by the much ore hungry leases took its toll as the huge stope began to collapse. Even though much of the open area had been gobbed during mining, the large area could not support its self.