have busted cast iron drainage (services kitchen sink, dishwasher and bar sink. Have located area that is broken in wall behind bar sink but and not able to remove/replace pipe myself as the break is in the area that immediately goes under slab/foundation of house. Anyone have ANY suggestions?
Plumbing – Broken/busted main cast iron drain line
plumbing
Related Solutions
No, there should not ever be two traps on a single drain line.
The point of the trap is to create a water barrier which prevents sewer gasses from coming up the empty pipe and into the house.
When you have two traps on the same line, you end up creating a kind of vapor block in the line which prevents it from draining properly.
What do you do?
Get yourself some 1 1/2" PVC (not CPVC, which is yellow, PVC which is white) with a 90 deg elbow, and also get two Fernco couplings (black plastic couplings with straps on each end that can be tightened) that will fit the pvc and iron drain pipe.
Use a metal blade on a sawz-all and cut out the p-trap in your basement. (Have a bucket handy!) Leave room to connect the Fernco coupling on both sides. I'd cut the right hand side out just past the coupling.
Measure and cut the PVC so that with the 90 elbow the ends line up with the newly cut drain lines. Glue the PVC together and confirm the fit, then connect to the old drains with the Fernco.
Viola - a proper drain line that will drain smoothly w/ no vapor lock.
One of these ironic things? ("American" Valve - Made in Taiwan...)
You should probably try to smooth the pipe out more - a lot can be done with a narrow strip of coarse sandpaper, 
wrapped around the pipe so you can "saw" it back and forth. You can also try really cranking on the hose clamps - if you're only using a screwdriver, you haven't really hit what they can do (but you have to maintain some sense of proportion once you switch to using a socket and ratchet on them, or you'll find the breaking point.)
For sheer desperation, I'm not sure if silicone or beeswax (from a toilet seal ring, of course) would be the better desperation move. With kitchen waste it could get too hot for beeswax.
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Best Answer
As others have suggested, it might be a good time to call a pro, but if you are going to handle it yourself, here is what you should do:
see if you have enough space above the slab to fit a rubber collar of the cast iron/pvc adapter. If this is the case, you should secure the cast iron pipe and cut it. Replace the section with PVC and put rubber adapters on both sides.
If you are not lucky and you don't have enough room, you have to break the slab (usually 4" max) and get to the sand/gravel layer. The main stack should make a 90 degree turn. You should place your cast iron to PVC adapter there. It is just as much work as it sounds like, but it can be done.