A. General Standards: In all areas of special flood hazards the following provisions are required for all new construction and substantial improvements:
1. All new construction or substantial improvements shall be designed (or modified) and adequately anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy;
2. All new construction or substantial improvements shall be constructed by methods and practices that minimize flood damage;
3. All new construction or substantial improvements shall be constructed with materials resistant to flood damage;
4. All new construction or substantial improvements shall be constructed with electrical, heating, ventilation, plumbing, and air conditioning equipment and other service facilities that are designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding;
5. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system;
6. New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters into the system and discharge from the systems into floodwaters; and
7. On site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
B. Specific Standards: In all areas of special flood hazards where base flood elevation data has been provided the following provisions are required:
1. Residential Construction: New construction and substantial improvement of any residential structure shall have the lowest floor (including basement), elevated to one foot (1') above the base flood elevation. A registered professional engineer, architect, or land surveyor shall submit a certification to the floodplain administrator that the standards of this chapter are satisfied.
2. Nonresidential Construction: New construction and substantial improvements of any commercial, industrial or other nonresidential structure shall either have the lowest floor (including basement) elevated to one foot (1') above the base flood level or together with attendant utility and sanitary facilities, be designed so that below the base flood level the structure is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. A registered professional engineer or architect shall develop and/or review structural design, specifications, and plans for the construction, and shall certify that the design and methods of construction are in accordance with accepted standards of practice as outlined in this subsection. A record of such certification which includes the specific elevation (in relation to mean sea level) to which such structures are floodproofed shall be maintained by the floodplain administrator.
3. Enclosures: New construction and substantial improvements, with fully enclosed areas below the lowest floor that are usable solely for parking of vehicles, building access or storage in an area other than a basement and which are subject to flooding shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or meet or exceed the following minimum criteria:
a. A minimum of two (2) openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided.
b. The bottom of all openings shall be no higher than one foot (1') above grade.
c. Openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters.
4. Manufactured Homes:
a. Require that all manufactured homes to be placed within zone A on a community's FHBM or FIRM shall be installed using methods and practices which minimize flood damage. For the purposes of this requirement, manufactured homes must be elevated and anchored to resist flotation, collapse, or lateral movement. Methods of anchoring may include, but are not limited to, use of over the top or frame ties to ground anchors. This requirement is in addition to applicable state and local anchoring requirements for resisting wind forces.
b. Require that manufactured homes that are placed or substantially improved within zones A1-30, AH, and AE on the community's FIRM on sites: 1) outside of a manufactured home park or subdivision, 2) in a new manufactured home park or subdivision, 3) in an expansion to an existing manufactured home park or subdivision, or 4) in an existing manufactured home park or subdivision on which a manufactured home has incurred "substantial damage" as a result of a flood, be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated to or above the base flood elevation and be securely anchored to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.
c. In A1-30, AH, and AE zones, require that manufactured homes to be placed or substantially improved in an existing manufactured home park to be elevated so that the lowest floor is at or above the base flood elevation; or the chassis is supported by reinforced piers no less than thirty six inches (36") in height above grade and securely anchored.
5. Recreational Vehicles: Require that recreational vehicles placed on sites within zones A1-30, AH, and AE on the community's FIRM either:
a. Be on the site for fewer than one hundred eighty (180) consecutive days,
b. Be fully licensed and ready for highway use, or
c. Meet the permit requirements of subsection 12-1-4C of this chapter and the elevation and anchoring requirements for "manufactured homes" of this section. A recreational vehicle is ready for highway use if it is on its wheels or jacking system, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions.
C. Standards For Subdivision Proposals:
1. All subdivision proposals including the placement of manufactured home parks and subdivisions shall be consistent with the provisions of this chapter.
2. All proposals for the development of subdivisions including the placement of manufactured home parks and subdivisions shall meet development permit requirements of this chapter.
3. Base flood elevation data shall be generated for subdivision proposals and other proposed development including the placement of manufactured home parks and subdivisions which is greater than fifty (50) lots or five (5) acres, whichever is lesser.
4. All subdivision proposals including the placement of manufactured home parks and subdivisions shall have adequate drainage provided to reduce exposure to flood hazards.
5 All subdivision proposals including the placement of manufactured home parks and subdivisions shall have public utilities and facilities such as sewer, gas, electrical and water systems located and constructed to minimize or eliminate flood damage.
D. Standards For Areas Of Shallow Flooding (AO/AH Zones): Located within the areas of special flood hazard established in subsection 12-1-3B of this chapter, are areas designated as shallow flooding. These areas have special flood hazards associated with base flood depths of one to three feet (3') where a clearly defined channel does not exist and where the path of flooding is unpredictable and where velocity flow may be evident. Such flooding is characterized by ponding or sheet flow; therefore, the following provisions apply:
1. All new construction and substantial improvements of residential structures have the lowest floor (including basement) elevated above the highest adjacent grade at least as high as the depth number specified in feet on the community's FIRM (at least 2 feet if no depth number is specified).
2. All new construction and substantial improvements of nonresidential structures:
a. Have the lowest floor (including basement) elevated above the highest adjacent grade at least as high as the depth number specified in feet on the community's FIRM (at least 2 feet if no depth number is specified), or
b. Together with attendant utility and sanitary facilities be designed so that below the base flood level the structure is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads of effects of buoyancy.
3. A registered professional engineer or architect shall submit a certification to the floodplain administrator that the standards of this section, as proposed in subsection 12-1-4C1a of this chapter, are satisfied.
4. Require within zones AH or AO adequate drainage paths around structures on slopes, to guide floodwaters around and away from proposed structures.
E. Floodways: Floodways located within areas of special flood hazard established in section 12-1-3 of this chapter, are extremely hazardous areas due to the velocity of floodwaters which carry debris, potential projectiles and erosion potential, the following provisions shall apply:
1. Designate a regulatory floodway which will not increase the base flood level more than one foot (1').
2. Encroachments are prohibited, including fill, new construction, substantial improvements and other development within the adopted regulatory floodway unless it has been demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment would not result in any increase in flood levels within the community during the occurrence of the base flood discharge.
3. All new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this section.
4. Under the provisions of 44 CFR chapter 1, section 65.12, of the national flood insurance regulations, a community may permit encroachments within the adopted regulatory floodway that would result in an increase in base flood elevations, provided that the community first applies for a conditional FIRM and floodway revision through FEMA.
F. Penalties For Noncompliance: In accordance with section 59.2(b) of CFR 44, chapter 1, of the national flood insurance program (NFIP) regulation, to qualify for the sale of federally subsidized flood insurance, a community must adopt floodplain management regulations that meets or exceeds the minimum standards of section 60. "These regulations must include effective enforcement provisions." In accordance with section 60.1(b) of CFR 44, chapter 1, of the NFIP regulations, "These regulations must be legally enforceable, applied uniformly throughout the community to all privately and publicly owned land within flood prone (i.e., mudflow) or flood related erosion areas, and the community must provide that the regulations take precedence over less restrictive conflicting local laws, ordinances or codes."
No structure or land shall hereafter be constructed, located, extended, converted, or altered without full compliance with the terms of this chapter and other applicable regulations. Violation of the provisions of this chapter by failure to comply with any of its requirements (including violations of conditions and safeguards established in connection with conditions) shall constitute a misdemeanor. Any person who violates this chapter or fails to comply with any of its requirements shall upon conviction thereof be fined not to exceed the current maximum penalty for conviction of a class 2 misdemeanor from time to time in effect under South Dakota code or imprisoned for not more than thirty (30) days, or both, for each violation, and in addition shall pay all costs and expenses involved in the case. Nothing herein contained shall prevent the city of Mitchell from taking such other lawful action as is necessary to prevent or remedy any violation. (Ord. 2342, 9-20-2010)
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