05: The Raven

#1. After escaping the sewers and making it outside, find a ramp leading to an overturned container van to the left to find a dog tag there.
Container Dog Tag

#2. After successfully establishing the comm link, continue forth and follow Oneal. Fight your way through a few more xenos until you reach a closed hatch ahead. Check the floor in front of that door to get the second dog tag of the mission.
Hatch Dog Tag

#3. After reaching the vehicle bay/garage, check the floor behind the crate under the stairwell ahead. You should find the last dog tag of the mission there.
Stairs Dog Tag