Chapter 12.40
FLOOD DAMAGE PREVENTION
Sections:
12.40.010 Statement of purpose.
12.40.020 Definitions.
12.40.030 Lands to which this chapter applies.
12.40.040 Basis for establishing the areas of special flood hazard.
12.40.050 Development permit required.
12.40.060 Designation of the Administrator.
12.40.070 Duties and responsibilities of the Administrator.
12.40.080 General standards for flood hazard reduction.
12.40.090 Specific standards for flood hazard reduction.
12.40.100 Floodways.
12.40.010 Statement of purpose.
It is the purpose of this chapter to promote the public health, safety, and general welfare, and to minimize public and private losses due to flood conditions in specific areas by provisions designed:
A. To protect human life and health;
B. To minimize expenditure of public money and costly flood control projects;
C. To minimize the need for rescue and relief efforts associated with flooding and generally undertaken at the expense of the general public;
D. To minimize prolonged business interruptions;
E. To minimize damage to public facilities and utilities such as water and gas mains, electric, telephone and sewer lines, streets and bridges located in areas of special flood hazard;
F. To help maintain a stable tax base by providing for the sound use and development of areas of special flood hazard so as to minimize future flood blight areas;
G. To ensure that potential buyers are notified that property is in an area of special flood hazard; and
H. To ensure that those who occupy the areas of special flood hazard assume responsibility for their actions. (Ord. 93-1022 § 1)
12.40.020 Definitions.
Unless specifically defined below, words or phrases used in this chapter shall be interpreted so as to give them the meaning they have in common usage and to give this chapter its most reasonable application.
A. “Area of special flood hazard” means the land in the flood plain within a community subject to a one percent or greater chance of flooding in any given year. Designation on maps always includes the letters A or V.
B. “Base flood” means the flood having a one percent chance of being equalled or exceeded in any given year. Also referred to as the “100-year flood.” Designation on maps always includes the letters A or V.
C. “Development” means any man-made change to improved or unimproved real estate, including but not limited to buildings or other structures, mining, dredging, filling, grading, paving, excavation or drilling operations located within the area of special flood hazard.
D. “Flood” or “flooding” means a general and temporary condition of partial or complete inundation of normally dry land areas from:
1. The overflow of inland or tidal waters; and/or
2. The unusual and rapid accumulation of runoff of surface waters from any source.
E. “Flood Insurance Rate Map (FIRM)” means the official map on which the Federal Insurance Administration has delineated both the areas of special flood hazards and the risk premium zones applicable to the community.
F. “Flood Insurance Study” means the official report provided by the Federal Insurance Administration that includes flood profiles, the Flood Boundary-Floodway Map, and the water surface elevation of the base flood.
G. “Floodway” means the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than one foot.
H. “Lowest floor” means the lowest floor of the lowest enclosed area (including basement). An unfinished or flood-resistant enclosure, usable solely for parking of vehicles, building access or storage, in an area other than a basement area is not considered a building’s lowest floor, provided that such enclosure is not built so as to render the structure in violation of the applicable non-elevation design requirements of Section 12.40.090A of this code.
I. “Manufactured home” means a structure, transportable in one or more sections, which is built on a permanent chassis and is designed for use with or without a permanent foundation when connected to the required utilities. For flood plain management purposes the term “manufactured home” also includes park trailers, travel trailers, and other similar vehicles placed on a site for greater than 180 consecutive days. For insurance, purposes the term “manufactured home” does not include park trailers, travel trailers, and other similar vehicles.
J. “New construction” means structures for which the “start of construction” commenced on or after the effective date of this chapter.
K. “Start of construction” includes substantial improvement, and means the date the building permit was issued, provided the actual start of construction, repair, reconstruction, placement or other improvement was within 180 days of the permit date. The actual start means either the first placement of permanent construction of a structure on a site, such as the pouring of slab or footings, the installation of piles, the construction of columns, or any work beyond the stage of excavation; or the placement of a manufactured home on a foundation. Permanent construction does not include land preparation, such as clearing, grading and filling; nor does it include the installation of streets and/or walkways; nor does it include excavation for a basement, footings, piers, or foundation or the erection of temporary forms; nor does it include the installation on the property of accessory buildings, such as garages or sheds not occupied as dwelling units or not part of the main structure.
L. “Structure” means a walled and roofed building including a gas or liquid storage tank that is principally above ground.
M. “Substantial improvement” means any repair, reconstruction, or improvement of a structure, the cost of which equals or exceeds 50 percent of the market value of the structure either:
1. Before the improvement or repair is started; or
2. If the structure has been damaged and is being restored, before the damage occurred. For the purposes of this definition “substantial improvement” is considered to occur when the first alteration of any wall, ceiling, floor, or other structural part of the building commences, whether or not that alteration affects the external dimensions of the structure. (Ord. 93-1022 § 1)
12.40.030 Lands to which this chapter applies.
This chapter shall apply to all areas of special flood hazards within the jurisdiction of the City of SeaTac. (Ord. 93-1022 § 1)
12.40.040 Basis for establishing the areas of special flood hazard.
The areas of special flood hazard identified by the Federal Insurance Administration in a scientific and engineering report entitled “The Flood Insurance Study for the City of SeaTac,” dated February 26, 1993, and as it may be amended or updated thereafter, with accompanying Flood Insurance Maps is adopted by reference and declared to be a part of this chapter. The Flood Insurance Study is on file at SeaTac City Hall, SeaTac, State of Washington. (Ord. 94-1031 § 1; Ord. 93-1022 § 1)
12.40.050 Development permit required.
A development permit shall be obtained before construction or development begins within any area of special flood hazard established in Section 12.40.040 of this code. The permit shall be for all structures including manufactured homes, as set forth in the “Definitions” in Section 12.40.020 of this code, and for all development including fill and other activities, also as set forth in the “Definitions”. (Ord. 93-1022 § 1)
12.40.060 Designation of the Administrator.
The City Manager or designee is appointed, as Administrator, to administer and implement this chapter by granting or denying development permit applications in accordance with its provisions. (Ord. 93-1022 § 1)
12.40.070 Duties and responsibilities of the Administrator.
Duties of the Administrator shall include, but not be limited to:
A. Permit Review.
1. Review all development permits to determine that the permit requirements of this chapter have been satisfied.
2. Review all development permits to determine that all necessary permits have been obtained from those federal, State, or local government agencies from which prior approval is required.
3. Review all development permits to determine if the proposed development is located in the floodway. If located in the floodway, assure that the encroachment provisions of Section 12.40.100(A) are met.
B. Use of Other Base Flood Data. When base flood elevation data has not been provided in accordance with Section 12.40.040 of this code, Basis for Establishing the Areas of Special Flood Hazard, obtain, review, and reasonably utilize any base flood elevation and floodway data available from a federal, State or other source, in order to administer Sections 12.40.090, Specific Standards, and 12.40.100, Floodways.
C. Information to be Obtained and Maintained.
1. Where base flood elevation data is provided through the Flood Insurance Study or required as in subsection B of this section, obtain and record the actual elevation (in relation to mean sea level) of the lowest floor (including basement) of all new or substantially improved structures, and whether or not the structure contains a basement.
2. For all new or substantially improved floodproof structures:
a. Verify and record the actual elevation (in relation to mean sea level); and
b. Maintain the floodproofing certifications by this chapter.
3. Maintain for public inspection all records pertaining to the provisions of this chapter.
D. Alteration of Watercourses.
1. Notify adjacent communities and the appropriate department of the State of Washington prior to any alteration or relocation of a watercourse, and submit evidence of such notification to the Federal Insurance Administration.
2. Require that maintenance is provided within the altered or relocated portion of said watercourse so that the flood-carrying capacity is not diminished.
E. Interpretation of FIRM Boundaries. Make interpretations where needed, as to exact location of the boundaries of the areas of special flood hazards (for example, where there appears to be a conflict between a mapped boundary and actual field conditions). The person contesting the location of the boundary shall be given a reasonable opportunity to appeal the interpretation. Such appeals shall be granted consistent with the standards of Section 60.6 of the rules and regulations of the National Flood Insurance Program (44 CFR 59-76). (Ord. 93-1022 § 1)
12.40.080 General standards for flood hazard reduction.
In all areas of special flood hazards, the following standards are required:
A. Anchoring.
1. All new construction and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure.
2. 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).
B. Construction Materials and Methods.
1. All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.
2. All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage.
3. Electrical, heating, ventilation, plumbing, and air-conditioning equipment and other service facilities shall be designed and/or otherwise elevated or located so as to prevent water from entering or accumulating within the components during conditions of flooding.
C. Utilities.
1. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of flood waters into the system;
2. New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of flood waters into the systems and discharge from the systems into flood waters; and
3. On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
D. Subdivision Proposals.
1. All subdivision proposals shall be consistent with the need to minimize flood damage;
2. All subdivision proposals shall have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage;
3. All subdivision proposals shall have adequate drainage provided to reduce exposure to flood damage; and
4. 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 50 lots or 5 acres (whichever is less).
E. Review of Building Permits. Where elevation data is not available either through the Flood Insurance Study or from another authoritative source (Section 12.40.070B), 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 above grade in these zones may result in higher insurance rates. (Ord. 93-1022 § 1)
12.40.090 Specific standards for flood hazard reduction.
In all areas of special flood hazards where base flood elevation data has been provided as set forth in Section 12.40.040, Basis for Establishing the Areas of Special Flood Hazard or Section 12.40.070(B), Use of Other Base Flood Data, the following provisions are required:
A. Residential Construction.
1. New construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated to or above base flood elevation.
2. Fully enclosed areas below the lowest floor that are subject to flooding are prohibited, or shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for entry and exit of floodwaters. Design for meeting this requirement must either be certified by a registered professional engineer or architect or must meet or exceed the following minimum criteria:
a. A minimum of two 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 above grade;
c. Openings may be equipped with screens, louvers, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters.
B. Nonresidential Construction. New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall either have the lowest floor, including basement, elevated to the level of the base flood elevation; or, together with attendant utility and sanitary facilities, shall:
1. Be floodproofed so that below the base flood level the structure is watertight with walls substantially impermeable to the passage of water;
2. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy;
3. 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 as set forth in Section 12.40.070C(2) of this code;
4. Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in Section 12.40.090A(2) of this code;
5. Applicants floodproofing nonresidential buildings shall be notified that flood insurance premiums will be based on rates that are one foot below the floodproofed level (e.g. a building constructed to the base flood level will be rated as one foot below that level).
C. Manufactured Homes. All manufactured homes to be placed or substantially improved within appropriate zones of the City shall be elevated on a permanent foundation such that the lowest floor of the manufactured homes is at or above the base flood elevation and be securely anchored to an adequately anchored foundation system in accordance with the provisions of Section 12.40.080A(2) of this code. (Ord. 93-1022 § 1)
12.40.100 Floodways.
Located within areas of special flood hazard established in Section 12.40.040 of this code are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of flood waters which carry debris, potential projectiles, and erosion potential, the following provisions apply:
A. Prohibit encroachments, including fill, new construction, substantial improvements, and other development unless certification by a registered professional engineer or architect is provided demonstrating that encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge.
B. Construction or reconstruction of residential structures is prohibited within designated floodways, except for (1) repairs, reconstruction, or improvements to a structure which do not increase the ground floor areas; and (2) repairs, reconstruction or improvements to a structure, the cost of which does not exceed 50 percent of the market value of the structure either, (a) before the repair, reconstruction, or repair is started, or (b) if the structure has been damaged, and is being restored, before the damage occurred. Work done on structures to comply with existing health, sanitary, or safety codes or to structures identified as historic places shall not be included in the 50 percent.
C. If subsection A of this section is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of Sections 12.40.080, 12.40.090, and 12.40.100 of this code. (Ord. 93-1022 § 1)