From the River Park Authority web site in Tulsa, Oklahoma.
"On the east bank of the river, there are a number of concrete block structures that are connected to the city's sewer system. Many of these structures have been painted by local artists. To receive permission to add a painting to one of the structures, the artist must submit a proposed design to the Authority. If the design is approved, the artist will receive a letter of permission to paint a specific block structure. The artist is responsible for all costs related to the painting."
