A. General Standards: In all areas of special flood hazards, the following standards are required:
1. Anchoring:
a. All new construction including manufactured housing and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure.
b. All manufactured homes must likewise be anchored to prevent flotation, collapse or lateral movement, and shall be installed using methods and practices that minimize flood damage. Anchoring methods may include, but are not limited to, use of over the top or frame ties to ground anchors (reference FEMA's "Manufactured Home Installation In Flood Hazard Areas" guidebook for additional techniques).
2. 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. Electrical, heating, ventilation, plumbing, and air conditioning equipment and other service facilities shall be designed and/or otherwise elevated or located at least one (1) foot above the base flood elevation.
3. 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;
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; and
d. On site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding. A habitat impact assessment shall be conducted in accordance with subsection 14-1-7B5 of this chapter as a condition of approval of an on site waste disposal system to be located in the regulatory floodplain.
4. Subdivision Proposals 1 : This section applies to all subdivision proposals, short subdivisions, short plats, planned developments, and new and expansions to manufactured housing parks.
a. All subdivision proposals shall be consistent with the need to minimize flood damage;
b. All subdivision proposals shall have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage;
c. All subdivision proposals shall have adequate drainage provided to reduce exposure to flood damage;
d. Where base flood elevation data has not been provided or is not available from another authoritative source, it shall be generated for subdivision proposals and other proposed developments which contain at least fifty (50) lots or five (5) acres (whichever is less);
e. The proposed subdivision should have one or more new lots in the regulatory floodplain set aside for open space use through deed restriction, easement, subdivision covenant, or donation to a public agency. The density of the development in the portion of the development outside the regulatory floodplain may be increased to compensate for the amount of land in the regulatory floodplain preserved as open space in accordance with Orting development regulations. Optionally, the city may choose to accept a mitigation contribution in lieu of dedicated open space; and
f. The final recorded subdivision plat shall include a notice that part of the property is in the SFHA, riparian habitat zone and/or channel migration area, as appropriate.
5. Review Of Building Permits: Where elevation data is not available either through the flood insurance study, FIRM, or from another authoritative source, applications for building permits shall be reviewed to assure that proposed construction will be reasonably safe from flooding. The test of reasonableness is a local judgment and includes use of historical data, high water marks, photographs of past flooding, etc., where available. Failure to elevate at least two feet (2') above the highest adjacent grade in these zones may result in higher insurance rates.
6. Shoreline Modifications:
a. The proposed project must be designed and located so that new structural flood protection is not needed.
b. Bank stabilization measures must be minimized to the maximum extent possible. If bank stabilization measures are necessary, bioengineered armoring of stream banks must be used per the "Integrated Streambank Protection Guidelines" 2003.
7. Hazardous Materials: No new development shall create a threat to public health, public safety, or water quality. Chemicals, explosives, gasoline, propane, buoyant materials, animal wastes, fertilizers, flammable liquids, pollutants, or other materials that are hazardous, toxic, or a threat to water quality are prohibited from the regulatory floodplain. This prohibition does not apply to small quantities of these materials kept for normal household use. This prohibition does not apply to the continued operations of existing facilities and structures, reuse of existing facilities and structures, or functionally dependent facilities or structures. If the proposed project cannot meet these requirements, then a habitat assessment must be conducted in accordance with section 14-1-7 of this chapter.
B. Specific Standards: In all areas of special flood hazards where base flood elevation data have been provided as set forth in subsection 14-1-6B of this chapter, the following provisions are required:
1. Residential Construction:
a. New construction, substantial improvements and/or reconstruction due to substantial damage of any residential structure, including machinery and equipment shall have the lowest floor, including basement, elevated one foot (1') or more above base flood elevation.
b. Fully enclosed areas below the lowest floor shall be used solely for parking of vehicles, building access, or storage. These enclosed areas shall be designed and constructed to allow for the entry and exit of floodwaters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or must meet or exceed the following minimum 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.
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 one foot (1') or more above the level of the base flood elevation; or, together with attendant utility and sanitary facilities, shall:
a. Be floodproofed so that below one foot (1') above the base flood level the structure is watertight with walls substantially impermeable to the passage of water;
b. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy;
c. Be certified by a registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting provisions of this subsection based on their development and/or review of the structural design, specifications and plans. Such certifications shall be provided to the official;
d. Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in subsection B1b of this section; and
e. Applicants floodproofing nonresidential buildings shall be notified that flood insurance premiums will be based on rates that are one foot (1') below the floodproofed level (e.g., a building floodproofed to 1 foot above the base flood level will be rated as at the base flood level).
3. Critical Facility: Construction of new critical facilities shall be, to the extent possible, located outside the limits of the SFHA. Construction of new critical facilities shall be permissible within the SFHA if no feasible alternative site is available. Critical facilities constructed within the SFHA shall have the lowest floor elevated to three feet (3') or more above the level of the base flood elevation at the site. Floodproofing and sealing measures must be taken to ensure that toxic substances will not be displaced by or released into floodwaters. Access routes elevated to or above the level of the base flood elevation shall be provided to all critical facilities to the maximum extent possible.
4. Manufactured Homes: All manufactured homes to be placed or substantially improved within zones A1-30, AH, and AE on the community's FIRM shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is one foot (1') or more above the base flood elevation; and be securely anchored to an adequately anchored foundation system in accordance with the provisions of subsection A.1.b. of this section.
5. Site Design:.
a. Structures and other development shall be located to avoid flood damage.
(1) If a lot has a buildable site out of the regulatory floodplain, all new structures shall be located in that area, when possible.
(2) The structure shall be aligned parallel with the direction of flood flows where practicable.
(3) If a lot does not have a buildable site out of the regulatory floodplain, all new structures, pavement, and other development must be sited in the location that has the least impact on habitat by locating the structures as far from the water body as possible or placing the structures on the highest land on the lot.
(4) A minimum setback of fifteen feet (15') from the protected area shall be required for all structures.
b. All new development shall be designed and located to minimize the impact on flood flows, flood storage, water quality, and habitat.
(1) Stormwater and drainage features shall incorporate LID BMPs in accordance with section 9-5A-9D of this code unless, based on the Stormwater Management Manual, LID BMPs are infeasible.
(2) If the proposed project will create new impervious surfaces where no more than ten percent (10%) of the lot in the regulatory floodplain is covered by impervious surface, it must comply with title 9, chapter 5, "Stormwater Regulations", of this code, and mitigate adverse impacts as provided by this chapter.
(3) Construction or reconstruction of residential structures is prohibited within designated floodways, except for: a) repairs, reconstruction, or improvements to a structure which do not increase the ground floor area, and b) repairs, reconstruction, or improvements which do not exceed fifty percent (50%) of the market value of the structure as specified in Washington administrative code 173-158-070.
C. Floodways: Located within areas of special flood hazard established in subsection 14-1-6B of this chapter are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of floodwaters which carry debris, potential projectiles, and erosion potential, the following provisions apply:
1. Prohibit encroachments, including fill, new construction, substantial improvements, and other development unless certification by a registered professional engineer or architect is provided demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practices that encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge.
2. Construction or reconstruction of residential structures is prohibited within designated floodways, except for: a) repairs, reconstruction, or improvements to a structure which do not increase the ground floor area; and b) repairs, reconstruction or improvements to a structure, the cost of which does not exceed fifty percent (50%) of the market value of the structure either: 1) before the repair, reconstruction, or improvement is started, or 2) if the structure has been damaged, and is being restored, before the damage occurred. Any project for improvement of a structure to correct existing violations of state or local health, sanitary, or safety code specifications which have been identified by the local code enforcement official and which are the minimum necessary to assure safe living conditions, or to structures identified as historic places shall not be included in the fifty percent (50%).
3. If subsection B of this section is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this section.
D. Wetlands Management: To the maximum extent possible avoid the short and long term adverse impacts associated with the destruction or modification of wetlands, especially those activities that limit or disrupt the ability of the wetland to alleviate flooding impacts. The following process should be implemented:
1. Review proposals for development within base floodplains for their possible impacts on wetlands located within the floodplain.
2. Ensure that development activities in or around wetlands do not negatively affect public safety, health, and welfare by disrupting the wetlands' ability to reduce flood and storm drainage.
3. Request technical assistance from the department of ecology in identifying wetland areas. Existing wetland map information from the national wetlands inventory (NWI) can be used in conjunction with the community's FIRM to prepare an overlay zone indicating critical wetland areas deserving special attention.
E. Native Vegetation: The site plan required in section 14-1-8 of this chapter shall show existing native vegetation.
1. In the riparian habitat zone, native vegetation shall be left undisturbed, except as provided in sections 7.1 and 7.2.C.
2. Outside the riparian habitat zone, removal of native vegetation shall not exceed thirty five percent (35%) of the surface area of the portion of the site in the regulatory floodplain. Native vegetation in the riparian habitat zone portion of the property can be counted toward this requirement.
3. If the proposed project does not meet the criteria of sections 7.4.A and B, a habitat impact assessment shall be conducted pursuant to section 7.7 and, if necessary, a habitat mitigation plan shall be prepared and implemented pursuant to section 7.8.
F. Compensatory Storage: New development shall not reduce the effective flood storage volume of the regulatory floodplain. A development proposal shall provide compensatory storage if grading or other activity eliminates any effective flood storage volume. Compensatory storage shall:
1. Provide equivalent volume at equivalent elevations to that being displaced. For this purpose, "equivalent elevation" means having similar relationship to ordinary high water and to the best available 10-year, 50-year and 100-year water surface profiles;
2. Be hydraulically connected to the source of flooding;
3. Provide compensatory storage in the same construction season as when the displacement of flood storage volume occurs and before the flood season begins; and
4. The newly created storage area shall be graded and vegetated to allow fish access during flood events without creating fish stranding sites.
G. Additional Standards; Crawl Space Construction For Buildings Located In Special Flood Hazard Areas:
1. The interior grade of a crawl space below the BFE must not be more than two feet (2') below the lowest adjacent exterior grade (LAG), shown as D in figure 3 of this section.
2. 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') (shown as L in figure 3 of this section) at any point. The height limitation is the maximum allowable unsupported wall height according to the engineering analyses and building code requirements for flood hazard areas.
3. There must be an adequate drainage system that removes floodwaters from the interior area of the crawl space. The enclosed area should be drained within a reasonable time after a flood event. The type of drainage system will vary because of the site gradient and other drainage characteristics, such as soil types. Possible options include natural drainage through porous, well drained soils and drainage systems such as perforated pipes, drainage tiles, or gravel or crushed stone drainage by gravity or mechanical means.
4. The velocity of floodwaters at the site should not exceed five feet (5') per second for any crawl space. For velocities in excess of five feet (5') per second, other foundation types should be used.
5. Any building utility systems within the crawl space must be elevated above BFE or designed so that floodwaters cannot enter or accumulate within the system components during flood conditions. Ductwork, in particular, must either be placed above the BFE or sealed from floodwaters.
6. Portions of the building below the BFE must be constructed with materials resistant to flood damage. This includes not only the foundation walls of the crawl space used to elevate the building, but also any joists, insulation, or other materials that extend below the BFE.
7. Below grade crawl space construction in accordance with the requirements listed above will not be considered basements.
H. Critical Facilities:
1. Construction of new critical facilities shall be, to the extent possible, located outside the limits of the regulatory floodplain (SFHA). Floodproofing and sealing measures must be taken to ensure that toxic substances will not be displaced by or released into floodwaters. Access routes elevated to or above the level of the base flood elevation shall be provided to all critical facilities to the maximum extent possible.
2. Construction of new critical facilities in the regulatory floodplain shall be permissible if no feasible alternative site is available, provided:
a. Critical facilities shall have the lowest floor elevated three feet (3') above the base flood elevation or to the height of the 500-year flood, whichever is higher. If there is no available data on the 500-year flood, the permit applicants shall develop the needed data in accordance with FEMA mapping guidelines.
b. Access to and from the critical facility shall be protected to the elevation of the 500-year flood.
(Ord. 913, 9-28-2011; amd. 2017-1006, 2-22-2017; Ord. 2019-1057, 1-8-2020; Ord. 2021-1072, 1-27-2021)
Notes
| 1 | 1. See title 12 of this code. |