You don't have to do this the first time, just make sure you have a save on or before
*** Spoiler - click to reveal ***Hospital (Underground)/Office - Head to the underground facility. You will have regained control of Jill and descended beneath the hospital, and will have just ridden a lift up to a door. The very next area after the save area is where you have to do this
so you can go back after.
Start off by bringing the MGL Grenade Launcher with Flame Rounds, M3 Shotgun, and .44 AE Lightning Hawk (magnum). You can bring Explosive Rounds if you want or have the space, and a grenade or two if you have them but I did not have any during my run. Bring a couple health kits if you are bad at dodging like me. Make sure you have at least 3 spaces available for the fuses. There are other items to pick up but for the sake of time you will be missing all of them. Of course sprint as often as you can through the area.
Equip the magnum, exit the save room, drop down and try to activate the lift ahead of you. You will see the fuse box explode. Move forward and activate the other lift while dodging the pale head and put at least two magnum rounds in him. Move the lift up, grab the fuse in front of you, and take the ladder to the left. Pull out the shotgun. You will see a short sequence where stuff falls from above and blocks you. Kill the two dogs that appear, move forward and see another short sequence of stuff dropping and blocking your way. Move forward to the left, take out the zombie and move through the narrow space. Make your way up the stairs, move across the one lift and raise another lift. Equip the grenade launcher with flame rounds, move across and drop down at the ladder. Move forward and watch the door fall, shoot a flame grenade and then IMMEDIATELY TURN AROUND. Another door will fall and a Hunter Gamma will appear. Put two flame rounds into him, turn around and equip the shotgun to clean up the zombies. Grab the next fuse and go back up the way you came down. Move back to the top of the stairs, equip the magnum and go through the door. Take out the pale head with the magnum and the zombies with the shotgun, move through the door to the left. Equip whatever weapons you think necessary to take out the hunter beta quickly (I just used flame rounds and shotgun), grab the fuse, and go back through the door you came in through. Unlock and go through the door on the left, you will be back in the save room, and head straight to where the fuse box is. You will fight a few nemesis zombies, a grenade or explosive rounds come in handy here. Once you get the fuses in and activate the lift the achievement will pop.