The Wallkill leaves Hamburg heading north, which is not what rivers are supposed to do, and the town has never seemed troubled by it. A A Fence LLC keeps lawns along that valley floor — mowing, edging, string trimming, and the seasonal cleanups that bookend a Sussex County year. Grass here comes up fast off the wet bottomland in May and asks for attention right through the humid weeks of August. The reward is the plain, satisfying sight of a cut lawn at dusk, its borders drawn clean, the river light going gold behind it. It is unglamorous work, and it makes a whole street look cared for.