How do I use separate dock for each monitor? I have three monitors. I'd like to use a dock on each monitor that displays the apps / windows open on that monitor. Is this possible?

Thanks!
Unfortunately, OS X does not support multiple docks running on multiple monitors simultaneously.
According to Apple's support article:

When the Dock is configured to appear at the bottom of your screen, it's available on whichever screen you’re working on. Just move your pointer to the bottom of either display. When the Dock is configured for the left or right position, it appears on the leftmost or rightmost display edge.
Tip: If you don't see your dock because it's set to hidden or there's a full screen app on the display, move your pointer to the location of the Dock. If the Dock still doesn't appear, swipe your pointer towards the Dock again to unhide it.