Well you can fit 16 caches into a square garage 278,784 square yards big. That leaves the 17th cache. Does the garage have to be a square or rectangle in shape? Is so then it has to be 371,712 square yards. Or just have the smaller garage and have a small thin bit extending the 0.1 miles to put the 17th cache at the end of.
or thinking about it you could have a garage that is the width of a ammo box wide and 1.7 miles (0.1x17caches) long