If they are actually inside the iron scrap and not the walls mining out the pile will do one of 2 things. Break the draugr archer out of the scrap where you can hit it or push it into the wall where you can't.

Which gets you to the strategy that Scrambled onions recommends (you can also half mine the scrap pile so that nothing can pass through except arrows and use an aetgir or your bow through the opening on the body pile).

Once the body pile is dealt with you can fully mine the scrap heap and deal with the stuck archer that is now freed or if it is stuck in the wall grab the loot and move on past it.

The draugr maintains a steady pace of firing arrows you can dodge or block them or you can use the terrain (by going around a corner) to avoid them.