This is a guess, I would have to say pulling a tanker for the oil companies in North Dakota. Good money to be made working for the oil companies out there.
Water is sort of area dependent. In the Ross area you have Power Fuels, MBI, Braun and about a million mom and pops. Down south there is still MBI, Power Fuels, Cascade, Key. Every area has a company that has a bigger portion, I'd try to find out who was the big players in the area you want to be in before you hitch your wagon to anyone.