Killing Salal, bamboo & cascade barberry, permanently!
Thank you for your questions. Since they involve a multitude of issues, I suggest you contact the real experts for help: http://npic.orst.edu/contactus.html Good luck!
PS - NPIC - National Pesticide Information Center - has pesticide experts who can talk you through the appropriate use and protective steps for pretty much any pesticide.
They can also discuss how long these herbicides stick around in the soil and could potentially impact new plantings. Good luck!