"Water had to be flowing constantly into the borehole to keep the drill running smoothly." What is a borehole?
a deep, narrow hole made in the ground, especially to locate water or oil
"If that didn't work, he would talk to them earnestly and try to persuade them." What does it mean to do something earnestly?
Very seriously and sincerely
"The din of machinery and hard work could be heard for miles." What does din mean?
A loud, unpleasant, prolonged noise