The operation of any use established after the effective date hereof shall comply with the performance standards herein set forth for the zone in which such activity shall be located. No use already established on the effective date hereof shall be so altered or modified as to conflict with, or further conflict with, the performance standards herein established for the zone in which such use is located. A conforming use that is in compliance with existing zoning ordinances or a legal nonconforming use may be continued and maintained regardless of subsequent zoning changes on surrounding properties that otherwise would change the manner in which the requirements of this article apply to the preexisting use. (Ord. 3335 §4, 2008: Ord. 1691 §1(part), 1982)