This level has quite a large amount of hidden weapons, and also a large trigger network leading up to the boss. There aren't a lot of C4HDs here, but the ones that are there are something to watch out for. There is an Earthshaker in this level, and because of the boss, you may need it, or any that you've stockpiled earlier. Be sure to leave most for the next boss, though.
First you must destroy a control panel and pick up a hostage, then you will be in sight of the blue key. You can't get it straight away, because there is a forcefield blocking your path, which can be disabled by blasting the trigger on the other side of the room and knocking out the other one behind the Blue Key, and a secret door.
With the blue key, you can blast another trigger in the blue door, which will allow you to reach a mini-reactor. When this is destroyed, and the trigger behind it, you can blow another trigger, then one more Mini-Reactor, and acquire the red key. At the point you are able to destroy the boss.