A. “Development” means any alteration by grading or filling of the ground surface, or by construction of any improvement or other impervious surface area that affects the hydraulic properties of any parcel of land.

B. “Impervious surface” means those hard surfaced areas which either prevent or retard the entry of water into the soil in the manner that such water entered the soil under natural conditions preexisting any development on the property, and/or those hard surfaced areas which cause water to run off the surface in greater quantities or at an increased rate of flow from that present under natural conditions preexisting any development on the property, including, but not limited to, such surfaces as rooftops, asphalt or concrete sidewalks, paving, driveways, parking lots, walkways, patio areas, storage areas, and gravel, oiled macadam, or other surfaces which similarly affect the natural infiltration or runoff patterns existing prior to development.

C. “Impervious unit” means a configuration or conglomeration of impervious surface estimated to contribute an amount of runoff to the City’s storm water management system which is approximately equal to that created by the average single-family residential parcel. One impervious unit (IU) is equivalent to two thousand square feet of impervious surface area. For purposes of computation of the charges provided for in this chapter, impervious units are truncated (rounded down) to the nearest tenth.

D. “Regional storm water facilities” or “regional system” means public conveyance, detention, infiltration, and/or water quality facilities designed to manage storm water runoff from specific areas of the City to meet the City’s water quality goals, and to support new development in a cost effective manner. Properties being developed may have the option to or be required to participate in the financing of the facilities, and in return requirements for onsite controls are eliminated or reduced. Proposed facilities are shown on the Proposed Regional Storm Water Facilities Map in the Clearing, Grading, and Storm Water Management Technical Notebook. (Ord. 2921 § 2 (part), 2018: Ord. 2566 § 2 (part), 2010: Ord. 2464 § 4 (part), 2009: Ord. 2306 § 2, 2006; Ord. 2041 § 1 (part), 1999).