13.24.230 DESIGN STANDARDS: Storm Drainage and Floodplains

1. Drainage System. Complete drainage system for the entire subdivision area shall be designed by a professional engineer, licensed in the State of Utah and qualified to perform such work, and shall be shown graphically. All existing drainage features which are to be incorporated in the design shall be so identified. If the final plat is to be presented in sections, a general drainage plan for the entire subdivision shall be presented with the first section, and appropriate development stages for the drainage system for each section indicated. 2. Design. The drainage and floodplain systems shall be designed to: a. Permit the unimpeded flow of natural watercourses; b. Ensure adequate drainage of all low points; c. Ensure applications of the following regulations regarding development in designated floodplains: i. Construction of buildings shall not be permitted in a designated floodway with a return frequency more often than a one hundred (100) year storm. ii. Building construction may occur in that portion of the designed floodway where the return frequency is between a one hundred (100) years and a maximum probable storm provided all usable floor space is constructed above the designated maximum probable flood level. iii. Where floodway velocities are generally determined to be under five feet per second and maximum flood depth will not exceed three feet, such uses as cultivated agriculture, nurseries, parks and recreation facilities and accessory parking may be permitted. iv. Any use of land is prohibited where flooding would create a public health hazard or problem. This. includes shallow wells, uncased deep wells, sanitary landfills, septic tank and on-lot sewage disposal systems, not completely protected from inundation. v. Recreational vehicles and similar uses shall not be permitted in any designated floodway. vi. Any contemplated floodplain encroachment or channeling shall be thoroughly analyzed and its effect on steam flow determined before such encroachment is undertaken and must be approved by the Land Use Authority, before accomplishment. vii. No lot one (1) acre or less in area shall include floodlands. All lots more than one (1) acre shall contain not less than forty thousand (40,000) square feet of land which is at an elevation at least two feet (2’) above the elevation of the one hundred (100) year recurrence interval flood, or, where such data is not available, five feet (5’) above the elevation of the maximum flood of record. 3. Drainage System Plans. a. The drainage system shall be designed to consider the drainage basin as a whole and shall accommodate not only runoff for the subdivision area but also, where applicable, the system shall be designed to accommodate the runoff from those areas adjacent to and "upstream" from the subdivision itself, as well as its effects on land downstream. b. All proposed surface-drainage structures shall be indicated on the plans. c. All appropriate designs, details and dimensions needed to clearly explain proposed construction materials and elevations shall be included in the drainage plans.