How do you permanently delete iPhoto pictures in OS X 10.9?

A few months ago we upgraded our 2010 Macbook Pro to the latest software. We moved a bunch of stuff to an external harddrive, reinstalled the disks, and upgraded it. When we deleted pictures off of it then, you went to the pictures folder and deleted everything. Well, my computer is getting full again and I'm trying to make some space. I moved 80gb of photos to my external hard drive. When I deleted those pictures from iPhoto (and iPhoto trash), they're still on the computer somewhere. I can't find them, but I have no more space on my computer. I tried finding my iPhoto cache in my iPhoto folder but couldn't seem to locate it the way it was explained online. All I want to do is delete these pictures.