Best way of Killing Ants in the crawl space in cellar?

[compact]

So not exactly the garden, but in the cellar / crawl space I have some 2inch holes in the earth.
I have found streams of ants going out to the garden and also noticed them in the house (luckily I am renovating)

So what is the best way to kill

I was thinking, put some ant killer in the holes.
Wait a week, then dig them out.

Questions
1)What's the best ant killer
2) Any idea how deep I'll have to dig? (I'm thinking about 20 gorilla tubs of earth might be my limit in such a small crawl space)

Cheers

 

[foxhole]

Ant powder work well, gets transferred to food store and kills all.