17-5-4 Standards and Submittal Requirements for Subdivisions.
A. All new subdivision proposals and other proposed development (including proposals for manufactured home parks and subdivisions), greater than fifty (50) lots or five (5) acres, whichever is the lesser, shall:
1. Identify the regulatory floodplain area and the elevation of the base flood; and
2. Identify on the final plans the elevation(s) of the proposed structure(s) and pads. If the site is filled above the base flood elevation, the final lowest floor and grade elevations shall be certified by an Arizona registered professional engineer or Arizona registered professional land surveyor and provided to the Floodplain Administrator.
B. All subdivision proposals shall be consistent with the need to minimize flood damage.
C. All subdivision proposals (also referred to as a final site plan) shall have all public utilities and facilities, including but not limited to sewer, gas, electrical, and water systems, located and constructed to minimize flood damage.
D. All subdivisions shall provide adequate drainage to reduce exposure to flood hazards (see adopted drainage criteria manual).
E. Suitability of the Land. Land that has been found by the Floodplain Board to be unsuitable for development with permanent structures based on hydrological and engineering studies of flooding can be platted and used only for open space and greenbelt uses such as those identified in Section 17-5-7(B)(1). This includes land which is:
1. Physically unsuitable because of flooding, poor drainage, and other features which may endanger health, life, or property, aggravate erosion, increase the flood hazard, or increase the burden imposed on the community, its governmental units, and its citizens;
2. Subject to flooding because of its proximity to the stream or watercourse; or because of low elevation. In applying this provision, the Floodplain Board, with technical support and recommendations from the Town Engineer, shall consider:
a. Land subject to flooding by the base flood shall not be platted for residential occupancy, or building sites, or for any other uses that may increase the flood hazard or endanger health, life, or property, unless each lot contains a building site that meets requirements set forth below, in subsections (G) and (H) of this section, and within other pertinent sections of this chapter;
b. Fill shall not be used to raise land within the regulatory floodway. In other areas subject to flooding by the base flood, fill may be used; provided, that the proposed fill does not restrict the flow of water and increase flood heights or velocities in the regulatory floodway, according to the same standards established in Section 17-5-8; and provided, that compensatory flood storage is provided.
F. Flood Situation to Be Shown on Plat. Plats submitted shall show the following:
1. Conceptual site development plans (plats) shall show the location, by survey, of watercourses, channels, irrigation laterals, private ditches, culverts, lakes, or other water features, including direction of flow, water level elevations, and the location and extent of areas subject to frequent inundation;
2. All preliminary subdivision proposals shall identify the special flood hazard areas, regulatory floodplain, the elevation of the base flood, pre- and post-development water surface elevations, and pre- and post-development floodplain limits;
3. All conceptual and final subdivision plans will provide the elevation(s) of proposed structure(s) and pads. If the site is filled above the base flood elevation, the final lowest floor and pad elevation shall be certified by an Arizona registered professional engineer or an Arizona registered professional land surveyor and provided to the Floodplain Administrator and the Town Building Official;
4. Final plats shall show the limits of the regulatory floodplain and the regulatory floodway, as well as the corresponding one hundred (100) year flood peaks, and their contributing drainage areas, entering and exiting the development;
5. Conceptual and final site plans shall show proposed improvements for areas subject to flooding and/or for areas which contain extremely poor drainage facilities such that the proposed improvements make the areas safe from flooding for the respective type of occupancy.
G. Street Elevations.
1. Refer to the Town’s adopted drainage criteria manual and subdivision street standards for additional information and requirements.
2. Fill used for the streets in areas subject to flooding shall not increase flood heights more than a designated amount as defined in Section 17-5-8(A)(1)(b).
3. The developer shall provide pre- and post-developed water surface elevation for streets proposed for placement in or adjacent to areas subject to flooding. Headwater ponding limits and water surface elevations shall be shown upstream of all culvert crossings.
H. Building Site.
1. Residential lots shall contain a building site, either natural or manmade, which is not subject to flooding by the base flood.
2. In areas subject to flooding by the base flood, where no fill is proposed, the building line shall be located no closer to the watercourse or channel than the edge of the area subject to flooding by the base flood. In areas where fill is used to raise the elevation of the building site, no fill shall be placed in the regulatory floodway. Further, where fill is used, the erosion setback shall not be less than twenty-five (25) feet from an unprotected bank, and not less than fifteen (15) feet for protected banks.
I. Setback from Channels. Along reaches of all regulated watercourses, erosion setback requirements from banks of washes shall be established in accordance with the Town’s adopted drainage criteria manual or standards accepted by the Town Engineer.
J. Easements for Drainage. Whenever any watercourse is located in the area being subdivided, an easement or common area encompassing each side of the watercourse shall be provided for the purpose of protecting and/or maintaining the watercourse for flood and drainage purposes, and such further width for construction of bank protection, physical access for maintenance, or for allowing for natural meander of the stream or watercourse that may be reasonably expected, or for all these as will be adequate for the purpose, as determined by the Town Engineer.
K. Detention/Retention Systems. See Town’s adopted drainage criteria manual for requirements pertaining to detention/retention systems by visiting the administrative offices of the Town of Oro Valley. ((O)21-06, 11/17/2021; (O)17-04, 04/05/2017; (O)05-35, 10/05/2005)