My house is surrounded by rocks (wraps all the way around the house and in places is 10 feet wide) that my father-in-law put in 20+ years ago, way before my wife and I bought his house. Those rocks grow lots and lots of weeds and the reason they grow lots and lots of weeds is because there is a lot of dirt in the rocks. 

There is black plastic underneath the rocks, but I'd imagine that either, much of it is damaged, or enough organic material decomposed on top of the rocks to give everything a nice layer of sediment in which to grow weeds (and there are lots of bushes that were ripped out without ever repairing the plastic.

So, this isn't really back breaking labor since it's impossible to shovel these rocks in any meaningful way, it just takes me a million years to sit and sift out the dirt and replace the plastic.

What's the easiest way to repair (remove the dirt and weeds) rock garden landscaping so it's good for another 10-15 years or so?