Location 1: Bounty Board (White Chest)
There is a white chest on the bounty board building. To get up there, head right and towards the arrow above Shotz Bar, jumping up the containers. Once at the roof of Shotz Bar (where there is a cash box and ammo chest), turn around and jump onto the roof of the bounty board building. The chest is around the corner, beneath the red tarp.
Location 2: Boat (Red Chest)
At Zed's roundabout, there are two boat cranes - the boat hanging from the one on the right holds a red chest. Simply drop down for it, but you will need to get out the hard way: killing yourself, quitting the game or, in co-op, having your teammates travel out of T-Bone Junction.
Location 3: Meat Popsicle (Red Chest)
At the right side of the building east of Scooter's garage is another network of walkways. Keep heading down and at a fork in the path, take the structure on the right with the arrows. The right arrow shows the path to the red chest. (Above the chest is the button to unlock the Meat Popsicle door, to which the left arrow leads.)
Location 4: Below Vulcana (White Chest)
Coming up the road from the junction, turn into the first Lance Assassin pod area (where you meet Vulcana), which should be on your left. With reference to the curved ledge, again on your left, you can drop off the first or second support beam onto the roof of a hut below, on which the white chest sits. Taking visual reference is advised before making the drop.