Dear work neighbor,
Perhaps it has not been brought to your attention that when the snow melts, it reveals all the goodies your dog left all winter. Maybe it was unclear to you that many people park in the lot and have to walk by those large piles. I'm sure you didn't realize that if someone stepped in your dog's poop on a Monday morning, it would not be a good start to the week. I can tell the dog who was a puppy last year is growing into a large, hearty animal-congratulations!
Your work neigbhor
P.S. Did you know there is a park just across the street?