Speak to Macha near the entrance to the Zhu's Hope colony. This can be done at any time after speaking with Fai Dan for the first time, and subsequently eliminating the geth that interrupt your conversation. Alternatively, this assignment can be acquired by reactivating one of the water valves before talking to Macha.
Head towards the elevator to the skyway, and continue down the stairs beyond it. Once down in the tunnels several geth will need to be fought, if not encountered already. After crossing the first bridge and entering a small corridor, there will be a white panel to the right. Activate it, the next one in the same corridor, and the last one in the next corridor. They are hard to miss because they are nearly the only white objects that are in the tunnels. When all three valves have been opened, leave the tunnels and return to Macha Doyle for the reward.
- If you killed Macha during the main Feros mission you can still acquire, but not complete, this assignment.