Duluth UDC (unnumbered, p.423: Definitions — U)

Understory. Those trees that grow beneath the overstory and will generally reach a mature height of less than 40 feet. Unhealthy tree. As determined by an independent certified Arborist, a tree demonstrating one or more signs of loss of vigor and decline, as indicated by atypical leaf color, recurring short annual shoot extension, or less than one-third live crown ratio, or severe insect or disease infestation, or with damage or structural defects that may include, but are not limited to: severed or damaged roots greater than two inches in diameter within the critical root zone; signs of previous topping or other improper pruning practices resulting in decay or a structural defect; longitudinal cracks in the trunk; wounds that encompass greater than one-third of the circumference of the trunk; trunk cavities equal to or greater than two-thirds of the trunk diameter at the point of the cavity; cracks, wounds, or cavities of one or more of the scaffold limbs resulting in a structural defect that cannot be corrected to ensure a safe or healthy condition; and any other defect that cannot be corrected through standard arboricultural practices. Use: 1. Any purpose for which, a building, structure, or a tract of land may be designed, arranged, intended, maintained, or occupied; or, 2. Any activity, occupation, business, or operation carried on, or intended to be carried on, in a building or other structure, or on a tract of land. Use, Nonresidential. A principal use that is a business engaged in the sale of goods or the provision of personal, professional, business, entertainment, or other services; an institutional or nonprofit organization; a business engaged in the fabrication, manufacture, or production of durable or non-durable goods; an activity for the administration or support of a business or organization; or a place of lodging for the travelling public, such as a hotel, motel, or bed and breakfast. Use, Residential. A principal use that is intended for occupancy by an owner or lessee as their permanent abode. Utility. A public or private water or sewer piping systems, water or sewer pumping stations, electric power lines, fuel pipelines, telephone lines, storm water systems, and railroads or other utilities identified by the Planning and Development Department. Utility Pole. A pole or similar structure that is used in whole or in part for the purpose of carrying electric distribution lines or cables or wires for telecommunications, cable or electric service, or for lighting, traffic control, signage, or a similar function regardless of ownership, including city-owned poles. Such term shall not include structures supporting only Wireless Facilities.