C.R. O'Neill Co. Construction works the granite-boned rise of Chelmsford, where the Merrimack Valley opens out and the wind comes across the fields with nothing to slow it down. Snow gathers here the way it always has — banked along the stone walls, drifted against every north-facing drive between Heart Pond and the Lowell line — and the answer to it is a plow blade moving before the streetlights give up. There is a plain satisfaction in the work: black pavement reappearing in one long pass, the turnaround squared off at the corners, the walk cut wide enough for two. They clear snow for Chelmsford and out through the greater Boston area, so the first person out the door in the morning simply finds the way open.