Mill Brook still runs under Arlington, mostly out of sight, on its way from the reservoir down toward the Mystic — a town built over water it rarely looks at. Nick's Irrigation Service works above it, mowing, edging and trimming lawns from the side streets near the center out to the reservoir's grassy shoulder. Late August is the real test, with heat sitting on the pavement and lawns going pale, so the cut goes high to keep roots in shade. Spring and autumn bring the cleanups: beds cleared, leaves off, edges reset for the season ahead. The satisfaction is a lawn that holds its color into September, when the heat finally lets go.