Just because they're bringing in pollen doesn't mean they're bringing in nectar. Not all plants provide both, in fact, many only provide on or the other. However, I don't have the slightest clue as to what grows in Utah, or is flowering. All I can say is that if they are storing up nectar past 1/4-1/3 of the frames (not including the ones on the outer edge of the brood nest), then feeding probably isn't necessary.