"X57: Bring Down the Sky." Disable the three Fusion Torches by entering each Torch Facility and using the Torch Control inside. Then go to the Main Facility to the north and deal with Balak, the lead terroist. For "X57: Avoid the Blasting Caps," take out the Turrets from a distance with the Mako. Then park and walk up to the building. Kill the batarian guards outside and Disable the Blasting Caps. Then you can move the Mako in closer.
The southernmost one is X57 Radio. Loot the shack and turn on the radio, and every other shack you visit will be listening to the radio. The northern two: the southern construction site has some loot, and information on where the explosives are kept. Head to the northern site and loot the grenades.
"X57: Missing Engineers." The Transmission Tower up on the ridge just northwest from the first Torch will reveal the locations of the Engineers. Visit each site and Examine them to learn of their fates.
The map below shows the locations of all lootable objects in all three of the Torch Facilities.
