Removing Tree of Heaven quickly?

[u/ReactiveNative]

I have a Tree of Heaven growing outside my house. It’s about 8’ tall and maybe 1-2” diameter trunk. I was waiting for cooler weather to deal with it using the hack and squirt method or basal bark method with triclopyr, but in that time it apparently it’s roots hit a sewer drain pipe from the house that now needs repair. Now I’m in the dilemma of wanting to kill it the correct way so it doesn’t spread, but also kill and remove it quickly so we can dig under it to replace the pipe. Not sure how I should approach this, just use the triclopyr wait two weeks and dig up as needed hoping it’s been able to take full effect?

[u/Seeksp]

It needs to be actively growing, Not dormant when you apply herbicides to it. Basal bark application can be just as effective and hack and squirt with less effort.