Route 22 runs the length of the Harlem Valley, and in Patterson it carries the first traffic of the day past dark fields and colder air sliding down off the ridges. Allied Pollution Control Inc turns out into that hour all winter, plowing lots and drives, cutting the banks back, laying salt and sand so the pavement is honest underfoot. Snow in this valley can come fine and dry on a northwest wind or heavy and wet off the coast, and each kind wants a different pass with the blade. What matters is the same either way — a clean surface, square corners, room to turn a vehicle around without a second thought. By the time the valley goes gray with daylight, the work is already behind them.