Service structures shall be screened in all zoning districts. Service structures shall include but not be limited to: loading docks, propane tanks, dumpsters, electrical transformers, utility vaults and other equipment or elements providing service to a building or a site. Structures may be grouped together; however, screening height shall be based upon the tallest of the structures. A continuous planting of evergreen, fence, wall or earthen mound must enclose any service structure on all sides, unless such structure must be frequently moved or accessed, in which case screening material shall be established on three sides and shall be at least one foot taller than the height of the enclosed structure, but shall not be required to exceed ten feet in height in any case. If the fourth side is visible from the public right-of-way, it shall be gated and screened. Plant material used to screen a service structure shall be an evergreen species that retains its needles throughout the year. Deciduous plant material cannot be used to fulfill this screening requirement. The height of the evergreen plant material at installation must be equal to, or greater than, two-thirds of the height of the service structure(s) and meet the height and one hundred percent (100%) opacity requirement within four years. All plant material shall be nursery grown, installed, and maintained in accordance with good horticultural practices. Plant material shall meet current standards set by the American Association of Nurserymen and shall be freshly dug, have outstanding form and be free of disease, insects and/or damage. Alternatives to these materials that can be shown to meet both the intent and requirements of this Zoning Code may be approved if adequate evidence is presented that alternative means of screening will be equally effective.