For 15 years, the graffiti wall at the East End Wastewater Treatment Facility in Portland has served as a welcoming canvas for artists and others searching for a place to express their creative impulses. But now there is a movement afoot to banish the Portland Water District’s so-called graffiti wall. The district’s Board of Trustees is scheduled to discuss the future of the controversial wall at a workshop Monday night. The agenda states, “A discussion will begin regarding continued use of the wall at the treatment plant for graffiti art purposes.” The topic was added to the agenda after Jay York, a Bayside resident and photographer, asked the board at its Nov.