I had a church with 2 stairwells years ago. They were a pain to do. That year, we happen to get a 30" blizard, and like Snoworks said "What stairwells?". They drifted right over.
My laborer shovel a path down into the well, then drove the snowblower down the stairs. Luckily, no one was out in this storm. With him and a helper, they positioned the blower at the bottom of the stairs, one guy ran the blower, and the other shoveled snow into the augers. It took them a long time, but they got ALL the snow out. We used a rope and my truck to slowly pull the blower up out of the well, backwards.
On lighter snowfalls we left piles in the corners at the bottom. Luckily, it doesn't melt fast in stairwells below grade. There was only a tiny 4" drain at the bottom. We also made it a point to shovel out snow from prior snowfalls when we were there for a 2 or 3" storm. I was worried about the freeze thaw cycle, especially at a church that didn't want any salt.... It was in the contract so I was most likely "covered" but I didn't want to take chances.
I will also say those wells doubled the price of the walks. Between the wells and the main road frontage (it was on a corner) the walks almost cost as much as plowing the lot.
~Chuck