Morrisville Unified Development Ordinance - February 2021.2

Article 5: Development Standards Section 5.6. Floodplain Management 5.6.5. Standards for Special Flood Hazard Areas with Flood Elevation Data

3. The time frame before the flood event for removal of the temporary structure (e.g., a minimum of 72 hours before landfall of a hurricane or immediately upon flood warning notification); 4. A copy of the contract or other suitable instrument with the entity responsible for physical removal of the temporary structure; and 5. Documented designation of a location outside the Special Flood Hazard Area or Future Conditions Flood Hazard Areas to which the temporary structure will be moved. H. Accessory Structures 1. The following standards shall apply to accessory structures (sheds, detached garages, etc.) placed within a Special Flood Hazard Area or Future Conditions Flood Hazard Area: a. The accessory structure shall not be used for human habitation (including working, sleeping, living, cooking or restroom areas). b. The accessory structures shall not be temperature-controlled. c. The accessory structures shall be designed to have low flood damage potential. d. The accessory structures shall be constructed and placed on the building site so as to offer the minimum resistance to the flow of floodwaters. e. The accessory structures shall be firmly anchored in accordance with Section 5.6.4.A. f. All service facilities such as electrical shall be installed in accordance with Section 5.6.4, General Standards for All Special Flood Hazard Areas. g. Flood openings to facilitate automatic equalization of hydrostatic flood forces shall be provided below the regulatory flood protection elevation in accordance with subsection D.3 above. 2. An accessory structure that has a footprint less than 150 square feet, or represents a minimal investment of $3,000 or less, and satisfies the standards in subsection 1 above shall not require an elevation or floodproofing certificate. Elevation or floodproofing certifications are required for all other accessory structures in accordance with 5.6.2, Required Certificates. I. Tanks The following standards shall apply when gas and liquid storage tanks are placed within a Special Flood Hazard Area: 1. Underground Tanks Underground tanks in flood hazard areas shall be anchored to prevent flotation, collapse or lateral movement resulting from hydrodynamic and hydrostatic loads during conditions of the design flood, including the effects of buoyancy assuming the tank is empty. 2. Elevated Above-Ground Tanks Above-ground tanks in flood hazard areas shall be attached to and elevated to or above the design flood elevation on a supporting structure that is designed to prevent flotation, collapse, or lateral movement during conditions of the design flood. Tank-supporting structures shall meet the foundation requirements of the applicable flood hazard area. 3. Non-Elevated Above-Ground Tanks Above-ground tanks that do not meet the elevation requirements of Section 5.6.5.B, Nonresidential Construction, shall be permitted in flood hazard areas provided the tanks are anchored or otherwise designed and constructed to prevent flotation, collapse, or lateral movement resulting from hydrodynamic and hydrostatic loads during conditions of the design flood, including the effects of buoyancy assuming the tank is empty and the effects of flood-borne debris.

Morrisville, NC

February 1, 2021

Unified Development Ordinance

Page 5-27