Would the solder joint be able to handle that (I assume that on the triac side has to be soldered since it's the standard TO-xx packaging)?
If the leads of the package can handle it then the solder joint certainly should.
I would lay down wide PCB traces and cover them with solder, all the way from the triac to the 10 AWG wire connector. That should handle 30A, though you may want to check the cross-sectional area of that solder blob against the cross-sectional area of 10AWG wire.
Finally, the conductivity of solder is not as good as that of copper. This chart shows percent conductivity (relative to annealed copper, known as IACS) of various solders....most have less than 10% the conductivity of copper:
http://www.microwaves101.com/encyclopedia/SolderChart.cfm
So....it's a tough question is what I'm saying 
Put down big, wide tracks, cover with solder, then slowly start turning up the current and see how hot it gets. That's what I'd do....
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