Here's an interesting diagram. It's a cross section showing some of the shafts on WEM. Note at the bottom is the Sinker, with a shaft rising from the tunnel towards the Golden Chariot and Ida Elmore. Supposedly it's only 150 feet or so from the Golden Chariot, which will be the ventilation/escape shaft. This is from Asher's report (link), which has a clearer image online than the original in Piper and Laney. Sorry about the oversize, but I didn't want to reduce it with the print so small already.