Are you sure they are wasps? Perhaps they are hornets? Yellowjackets? It is important to know what you are battling.
Paper wasps are generally harmless, the only time I have been stung was when I accidentally knocked some of them down the back of my shirt - I cannot blame them for being unhappy about that.
I have no
experience with hornets, but they also make a (usually large) paper nest above ground. I believe they are more aggressive than paper wasps.
Yellowjackets nest
underground, and are aggressive when disturbed. I disturbed a yellowjacket nest once and got stung by 10 of them.
If you must knock down a wasp or hornet nest, do so when the weather is cold, and preferably at night. They will be sluggish and thus unlikely to sting you.
I would imagine that you could pour a bubbly
soap solution into a yellowjacket nest. But I shudder to think what might happen if you missed the hole or something.
If you know where their nest is, keep everyone away from it. Also don't leave attractants laying around (anything that is like meat or rotting fruit - i.e. meat, sugary drinks). Ensure that your garbage can lid fits tightly. These guys have an important role to play in your
yard (e.g. eating pest insects), if possible you should try to coexist with them. But that means you need to understand what they are and what they want.