Centennial Mills in the north Pearl District area has been an iconic landmark since the Great Depression. A project to clean up the graffiti on the water tower will begin soon, June 12, 2013 (KOIN 6 News/Ellen Hansen)

Graffiti tarnishes Centennial Mills tower

Since the Great Depression, Centennial Mills has been part of Portland’s history and is even seen on paintings of the city’s skyline. But wi…