The kablan said he's coming tomorrow to - in his words - "hermetically seal" everything. He said that he's doing that not just for the dust - but for the water from the drill as well. Apparently, they will be cutting three strips to make the hole. The slabs of concrete will then fall directly into a "pool" which will be resting on tires to absorb the impact.
The hole will be just past the door to AMG's room, and the stairs will slope down from there towards the back of the house. In other words, when ascending the stairs, one will be facing the front of the house.
Here is what the spot where the hole will be looks like now:
Tomorrow night, the kablan will drill a few holes in the ceiling so that the guys will know where to make the hole when they I"YH arrive on Tuesday morning. According to the kablan, he's getting a "bochur yeshiva" to come clean everything up by Tuesday evening.
The stairs guy is scheduled to come on Wednesday.
Meanwhile, after clearing out the bathroom, we discovered that the bathroom sink is not a berez perach after all, but the kablan said it isn't a problem to switch it. Here's what it looks like now: