|Ellie - The Droughts||Cash, Red Chest, Buttplug Pistol (Optional Objective)||4|
Once you've started the mission Cult Following, Ellie will have a Side Mission waiting for you. Head back to her garage and interact with the bounty board to accept the Dump on Dumptruck Side Mission.
Kill The Holy Dumptruck / Shoot ’em in the Ass (Optional Objective)
With the mission accepted head over to the waypoint on the map where there will be a group of enemies waiting for you, take them all out and make your way up to the top of the building. Once you've reached the top, the Holy Dumptruck will come out of his room.
In order for you to complete this Optional Objective you're going to need to shoot him in the ass when he's shaking it at you. This shouldn't too much of a problem as you'll need to stand back and wait for him to turn around due to his shield blocking your bullets.
Open Trap Door
Now that The Holy Dumptruck has been dealt with you're going to need to restore power to the trap door in order to gain access. Shoot the bullseye up above to your left to release the water onto the pipes, which will open the trap door.
Head around the corner and drop down into the trap door where you'll find a Red Chest waiting for you.