Here is the full list of all 16 Clandestinity of Elsie achievements.
Save your game for the first time.
Went to the Cunningham home.
Kill 10 Singed.
Kill an Alchy.
Activate the elevator at the Yorkshire Apartments.
Kill a Victim.
Kill a Thorn.
Find the pendant.
Escape the Singed ambush.
Gather medical supplies at the hospital.
Leave the sewage plant.
Enter the sewers (again).
Find the Blood Bag at the Troy Restaurant.
Return to Burnie's Garage.
You finally found Elsie.
Diverted the water flow.