Traverse City is built on old glacial hills, and the driveways that climb them are the ones that turn interesting in a storm. Denali Services takes on that winter work — plowing, shoveling and ice control on the steep approaches above town, where a half inch of glaze matters more than a foot of powder. Up near the sled hills the snow lands deeper and stays later than it does down by the water. A cleared, gritted slope at the top of a hill is a genuinely good thing to leave behind you. That is the reward, storm after storm, from the first November squall to the last gasp of April.