January in the hills above the Sprain: hemlocks holding their load of snow, the parkway hissing below, and every driveway in Yonkers a small emergency until somebody clears it. Five Brothers Enterprises, Inc works those nights — plowing drives and lots, shoveling out steps and walkways, salting the slick patches that form where meltwater runs downhill and freezes again. In a city of grades the ice never sits still; it travels. Getting ahead of it means going back, and going back is most of the job. The payoff is black pavement at seven in the morning and nobody's tires spinning at the curb.