Power Down (Destroyed the Power Facilities in EPS1 & EPS2) - ZOE 1
I believe this is story-based and unmissable.
1. Take out the tower at "City 1" using the SNIPER.
2. Find the underground tunnel in "EPS 1" marked by some >>>> symbols on the map and enter it. If you go straight without taking any turns, you'll arrive at the spot where you destroy the EPS generator.
3. Do the same thing in "EPS 2" except that you won't be able to proceed very far due to an energy field. After this, you'll need to find the Raptor control module. Exit the tunnel and obtain the passcode from a squad in EPS 2. The second part is found with a squad in TOWN 1. To get the control module, enter the tunnel in EPS 1 and follow the path that branches off to the right partway through it. You'll find the console.
4. Next you have to find an uncontrolled raptor. It's in TOWN 1 (or TOWN 2 per a comment posted -- need clarification on this to be sure). In an earlier cut-scene, it shows a spot where there are crashed mechs. They're kind of in a shallow ditch on the ground. Approach the Raptor to take control.
4. Next, you take the raptor through the tunnel in EPS 2. Keep moving ahead until you arrive at the spot where a path branches off to the right. Follow it and collect the detector mod from the console. Now return to the main path and go forward to the dead end. Attack the wall, drop down and destory the EPS generator same as the first one, and you will get the achievement.
Tip: While controlling the raptor, take out a few of the surface squads before entering the tunnel. There is a secret achievement, Benedict Arnold, earned for destroying 10 enemies with the Raptor.