Use Diazinone or seven
Pouring a gallon of kerosene into the earth is lunacy as it will eventually end up in our water supply.
This from a prof exterminator: The way the powderd insecticides work with in ground nests is the adults go in and fan the nest to keep it cool
The fanning motion spreads the insecticide and will wipe out the entire nest in a matter of Hrs.
Be responsible in how you deal with this, if they are indeed Bumblebees, might wait a week or so, they are major pollinators, when the young leave the nest the problem will be over .
Bees are getting extinct, kill the bad guys (wasps, Hornets,yellowjackets)