Head to the garbage dump and prepare to infiltrate it. Approach the garbage dump from the northern side of the road. There’s a small room there with a guard with his back against you so you can easily kill him. There’s a small stack of cash as well and a fuse.
Now make your way to the upper catwalk and take out the sentries there. Make your way into the building and you'll find two more roving guards. Time your attack to take them out silently, then head to the office where you’ll find a whole lot of cash and a Vargas painting.
Now exit through the catwalk that leads to the disposal site and kill the lone guard there. Plant the explosives and leave the area to complete the mission. After sabotaging the dump, you’ll have to Interrogate the extortionists next.