A. General Standards: In all special flood hazard areas the following standards are required:
1. Developments Outside The Floodway:
a. Developments, including fill, new construction and substantial improvements, shall require certification from a registered professional engineer that such developments shall not result in an increase in base flood elevations greater than one foot (1').
b. The cumulative impacts of such proposed developments when combined with all other existing and anticipated development, will not increase the water surface of the base flood more than one foot (1') at any point within the floodplain within the city of Stanley community.
c. For the purposes of administering this subsection, anticipated development shall mean only developments for which an application or applications are currently under review for permit approval by the administrator. The administrator shall collect and separately maintain records for pending and approved developments within the floodplain areas and make such records available for use by the applicants for use in performing the one foot (1') rise analysis.
d. Applicants for proposed projects that increased the base flood elevation more than a foot shall obtain from FEMA a conditional letter of map revision before the project may be permitted.
e. Engineering certification as described in subsection A1a of this section shall not be required for substantial improvements to structures that have suffered substantial damage if the substantial improvement is a reconstruction of a structure previously certified as required in subsection A1a of this section, without any significant changes in structural design.
2. Anchoring:
a. All new construction and substantial improvements shall be securely anchored on pilings, columns, or foundation walls oriented to the axis of the flow path to prevent flotation, collapse, or lateral movement of the structure. Such supports shall be certified by a registered professional engineer as capable of withstanding all applied loads of the base flood, with a reasonable margin of safety.
b. All manufactured homes shall be anchored to resist flotation, collapse or lateral movement, and shall be installed using methods and practices that minimize flood damage. Methods of anchoring may include, but are not to be 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.
3. AH Zone Drainage: Adequate drainage paths are required around structures on slopes to guide floodwaters around and away from proposed structures.
4. Construction Materials And Methods:
a. All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.
b. All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage.
c. All electrical, heating, ventilation, plumbing and air conditioning equipment and other service facilities shall be elevated to or above the flood protection elevation or be floodproofed so that floodwaters cannot enter and accumulate within the system components during a flood.
5. Utilities:
a. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system.
b. Water wells shall be located on high ground that is not in the floodway, and comply with setbacks from the floodway as required by the Idaho department of environmental quality.
c. New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters into the systems and discharge from the systems into floodwaters.
d. On site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
e. Buried utility transmission lines transporting hazardous substances (e.g., electrical, gas) that are located in a floodway shall be buried at a minimum depth of four feet (4') below the maximum depth of scour for the base flood, as predicted by a registered professional engineer.
6. Subdivision Standards:
a. All subdivision proposals shall be consistent with the need to minimize flood damage.
b. All subdivision preliminary plats/development plans shall include the mapped flood hazard zones from the effective FIRM.
c. All subdivision proposals shall have public utilities and facilities, such as sewer, gas, electrical, and water systems located and constructed to minimize or eliminate flood damage.
d. All subdivision proposals shall have adequate drainage provided to reduce exposure to flood damage.
e. Approval of preliminary and final subdivision plats shall be conditioned upon compliance with all applicable requirements of this chapter, and upon demonstration that potential future development of lots and structures upon such lots can potentially comply with all of the requirements of this chapter.
f. All new subdivision proposals and other proposed developments (including proposals for new manufactured home parks and manufactured home subdivisions) greater than fifty (50) lots or five (5) acres, whichever is the lesser, shall include within such proposals flood protection elevation data.
7. Fill:
a. Fill shall be placed using good engineering practices to ensure that it is reasonably safe from flooding. Fill areas may be protected by retaining walls, pursuant to subsection A1 of this section. The height of retaining walls shall not exceed the height of the fill. Retaining walls shall be constructed of durable or permanent materials, which are attractive earth tone or natural colored material, and screened to blend with the floodplain vegetation. Retaining walls shall be constructed and reinforced according to the preengineered design standards and for the retaining wall system used or, if not preengineered, shall require some reinforcement for walls above two feet (2') in height and, if greater than four feet (4') in height, shall require structural design parameters capable of resisting hydrostatic and hydrodynamic loads and the effect of buoyancy, as certified by a registered professional engineer. Retaining walls may not be built in areas that have not been filled.
8. Preexisting Nonconforming Developments: A development that predates the adoption of this chapter, but which is not in conformity with the provisions of this chapter may be continued subject to the following conditions:
a. No such use or structure shall be expanded, enlarged, or altered in any way which increases its nonconformity unless a flood hazard development permit variance is approved.
b. If any nonconforming use or structure is substantially damaged it shall not be reconstructed except in conformity with the provisions of this chapter.
c. Uses which are or become nuisances as defined in title 8 of this code shall not be permitted to continue as nonconforming uses.
d. Owners of properties with nonconforming structures or other developments may be required to mitigate the off property erosion and channelization impacts of changes in floodways that can be directly attributed to the nonconforming use of such structures or developments.
B. Specific Standards: In all special flood hazard areas where base flood elevation data have been provided as set forth in subsection 15.08.030B, "Basis For Establishing Areas Of Special Flood Hazard", or in subsection 15.08.040B1d of this chapter, use of other and floodway data, the following standards are required for all development:
1. Residential Construction:
a. All new construction and substantial improvements, including a structure that has been substantially damaged, shall be constructed with materials resistant to flood damage and constructed using methods and practices that minimize flood damage.
b. The lowest floor, including basement, of new construction or substantial improvement of any structure shall be elevated to or above the flood protection elevation.
c. Fully enclosed areas below the lowest floor such as crawl spaces, vehicle parking areas, building access, and storage areas, that are subject to flooding during the base flood, are prohibited unless designed to automatically equalize hydrostatic forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for automatically equalizing hydrostatic forces on exterior walls during floods must either be certified by a registered professional engineer or architect or must meet the following criteria:
(1) 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.
(2) The bottom of all openings shall be no higher than one foot (1') above grade.
(3) Openings may be equipped with screens, louvers, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters. Standard foundation vents as required by the international building code do not meet this standard.
(4) Crawl spaces below the lowest adjacent grade (LAG) are prohibited at sites where the velocity of floodwaters exceeds five feet (5') per second.
(5) The interior grade of a crawl space below the base flood elevation must not be more than two feet (2') below the LAG and the height of the below grade crawl space measured from the interior grade of the crawl space to the top of the crawl space foundation wall must not exceed four feet (4') at any point.
(6) There must be an adequate drainage system that removes floodwaters from the interior area of the crawl space within seventy two (72) hours after floodwaters are no longer entering the crawl space.
(7) Crawl spaces below the LAG constructed in accordance with the requirements listed in this subsection shall not be considered basements.
(8) Unfinished or flood resistant enclosures below the LAG shall only be used for parking of vehicles, limited storage of maintenance equipment, or building access.
(9) The interior portion of such enclosed area shall not be partitioned or finished into separate rooms.
d. Any chemicals or other toxic materials that could cause contamination of surface waters or groundwater, or that could be injurious to public health, safety, and welfare shall be located at or above the flood protection elevation and stored in a manner that prevents their release in the event of a flood.
2. Nonresidential Construction: New construction or the substantial improvement of any nonresidential structure located in zones A1-30, AE, or AH must be floodproofed if the new construction or improvement is not elevated. The structure and attendant utility and sanitary facilities must be designated to be watertight to the flood protection elevation with the walls substantially impermeable to the passage of water, and structural components having the capability of resisting hydrostatic and hydrodynamic loads and the effect of buoyancy. A licensed professional engineer or architect must certify that the design and methods of construction are in accordance with accepted standards of practice for meeting these provisions, and shall provide certification to the floodplain program administrator.
3. Accessory Structures: Accessory structures as defined in section 15.08.020 of this chapter shall comply with all provisions of subsection A, "General Standards", of this section and this subsection B, except for subsections B1b and B2 of this section.
4. Manufactured Homes: All manufactured homes to be placed or substantially improved in special flood hazard areas shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated to or above the flood protection elevation and must meet the requirements of subsection A, "General Standards", of this section and this subsection B.
5. Recreational Vehicles: Recreation vehicles placed within flood hazard areas are required to:
a. Be on site for fewer than one hundred eighty (180) consecutive days, and
b. Be fully licensed and ready for highway use, on wheels or jacking system, attached to the site only by quick disconnect type utilities and security devices, and have no permanently attached additions, or
c. The recreation vehicle must meet all the requirements for "new construction", including the anchoring and elevation requirements.
6. Critical Facilities: Construction of new critical facilities shall be, to the extent possible, located outside the limits of special flood hazard areas. Construction of such facilities shall be permissible within an SFHA if no feasible alternative site is available. Critical facilities constructed within SFHAs shall have the lowest floor elevated three feet (3') above the FPE or to the height of the 500-year flood, whichever is higher. The applicant shall be responsible for determining, with certification by a registered professional engineer, the height of the 500-year flood. Access routes to and from such facilities also shall be protected to the elevation standard of the facility, to the extent feasible. Floodproofing and sealing measures must be taken to ensure that toxic substances will not be displaced by or released into floodwaters.
C. Special Flood Hazard Areas With Base Flood Elevations But No Designated Regulatory Floodways:
1. In SFHAs with base flood elevations, but where a regulatory floodway has not been designated, no new construction, substantial improvements, or other development (including fill) shall be permitted within zones A1-30 and AE on a community's FIRM unless it is demonstrated that the cumulative effect of the proposed development, when combined with all other existing and anticipated development, will not increase water surface of the base flood more than one foot (1') at any point within the floodplain within the city of Stanley.
2. For the purposes of administering this subsection, anticipated development shall mean only developments for which an application or applications are currently under review for permit approval by the administrator. The administrator shall collect and separately maintain records for pending and approved developments within the floodplain areas without mapped floodway boundaries and make such records available for use by the applicants for use in performing the one foot (1') rise analysis.
3. Applicants for proposed projects that increased the base flood elevation more than a foot shall obtain from FEMA a conditional letter of map revision before the project may be permitted.
D. Floodways: Since the floodway comprises the main channel of a watercourse during a flood, it is an extremely hazardous area due to the velocity of floodwaters which carry debris, potential projectiles, and erosion potential.
1. All development, including fill, new construction, substantial improvements, and other developments are prohibited unless certification by a registered professional engineer is provided demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed development will not result in any increase in flood levels within the floodplain within the city of Stanley during the occurrence of the base flood discharge.
2. If subsection D1 of this section is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard provisions of this section.
3. Floodway bridge construction standards found in the Idaho transportation department (ITD) "Bridge Design LRFD Manual" and the ITD "Roadway Design Manual" are adopted by reference, unless they conflict with other provisions of this chapter.
E. Requirement To Submit New Technical Data:
1. For all development proposals that impact floodway delineations or base flood elevations, the community shall ensure that technical data reflecting such changes be submitted to FEMA within six (6) months of the date such information becomes available. These development proposals include:
a. Floodway encroachments that increase or decrease base flood elevations or alter floodway boundaries;
b. Fill sites to be used for the placement of proposed structures where the applicant desires to remove the site from the special flood hazard area;
c. Alteration of watercourses that result in a relocation or elimination of the special flood hazard area, including the placement of culverts;
2. It is the responsibility of the applicant to have technical data prepared in a format required for a conditional letter of map revision or letter of map revision and submitted to FEMA. Submittal and processing fees for these map revisions shall be the responsibility of the applicant. (Ord. 182, 5-13-2010)