Chapter 15.55
FLOOD DAMAGE PREVENTION1
Sections:
15.55.010 Statutory authorization.
15.55.030 Statement of purpose.
15.55.040 Methods of reducing flood losses.
15.55.060 Lands to which this chapter applies.
15.55.070 Basis for establishing the areas of special flood hazard.
15.55.080 Penalties for noncompliance.
15.55.090 Abrogation and greater restrictions.
15.55.110 Warning and disclaimer of liability.
15.55.115 Development permitted when.
15.55.120 Development permits.
15.55.130 Local administrator – Designated.
15.55.140 Local administrator – Duties and responsibilities.
15.55.160 Conditions for variances.
15.55.200 Standards for shallow flooding areas (AO zones).
15.55.210 Coastal high hazard areas.
15.55.010 Statutory authorization.
The Legislature of the State of Washington has delegated the responsibility to local governmental units to adopt regulations designed to promote the public health, safety, and general welfare of its citizenry. Therefore, the city council of the city of Burien, Washington, does find as set forth in this chapter. [Ord. 250 § 1, 1999]
15.55.020 Findings of fact.
(1) The flood hazard areas of the city of Burien are subject to periodic inundation which results in loss of life and property, health, and safety hazards, disruption of commerce and governmental services, extraordinary public expenditures for flood protection and relief, and impairment of the tax base, all of which adversely affect the public health, safety, and general welfare.
(2) These flood losses are caused by the cumulative effect of obstructions in areas of special flood hazards which increase flood heights and velocities, and when inadequately anchored, damage uses in other areas. Uses that are inadequately flood-proofed, elevated, or otherwise protected from flood damage also contribute to the flood loss. [Ord. 741 § 1, 2020; Ord. 250 § 1, 1999]
15.55.030 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:
(1) To protect human life and health;
(2) To minimize expenditure of public money and costly flood control projects;
(3) To minimize the need for rescue and relief efforts associated with flooding and generally undertaken at the expense of the general public;
(4) To minimize prolonged business interruptions;
(5) 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;
(6) 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;
(7) To ensure that potential buyers are notified that property is in an area of special flood hazard; and
(8) To ensure that those who occupy the areas of special flood hazard assume responsibility for their actions.
(9) To participate in and maintain eligibility for flood insurance and disaster relief. [Ord. 741 § 2, 2020; Ord. 250 § 1, 1999]
15.55.040 Methods of reducing flood losses.
To accomplish its purposes, this chapter includes methods and provisions for:
(1) Restricting or prohibiting uses and development which are dangerous to health, safety, and property due to water or erosion hazards, or which result in damaging increases in erosion or flood heights or velocities;
(2) Requiring that uses and development vulnerable to floods, including facilities which serve such uses, be protected against flood damage at the time of initial construction;
(3) Controlling the alteration of natural floodplains, stream channels, and natural protective barriers, which help accommodate or channel floodwaters;
(4) Controlling filling, grading, dredging, and other development which may increase flood damage; and
(5) Preventing or regulating the construction of flood barriers that will unnaturally divert floodwaters or may increase flood hazards in other areas. [Ord. 741 § 3, 2020; Ord. 250 § 1, 1999]
15.55.050 Definitions.
Unless specifically defined below, words or phrases used in this chapter shall be interpreted to give them the meaning they have in common usage and to give this chapter its most reasonable application.
(1) “Alteration of watercourse” means any action that will change the location of the channel occupied by water within the banks of any portion of a riverine water body.
(2) “Appeal” means a request for a review of the city manager’s interpretation of any provision of this chapter or a request for a variance.
(3) “Area of shallow flooding” means designated AO or AH zones on the flood insurance rate map (FIRM). The base flood depths range from one to three feet, a clearly defined channel does not exist, the path of flooding is unpredictable and indeterminate, and velocity flow may be evident. AO is characterized as sheet flow and AH indicates ponding.
(4) “Area of special flood hazard” means the land in the floodplain within a community subject to a one percent or greater chance of flooding in any given year. It is shown on the flood insurance rate map (FIRM) as Zone A, AO, AH, A1-30, AE, A99, AR (V, VO, V1-30, VE). “Special flood hazard area” is synonymous in meaning with the phrase “area of special flood hazard”.
(5) “Base flood” means the flood having a one percent chance of being equaled or exceeded in any given year (also referred to as the “100-year flood”).
(6) “Base flood elevation” (BFE) means the elevation to which floodwater is anticipated to rise during the base flood.
(7) “Basement” means any area of the building having its floor subgrade (below ground level) on all sides.
(8) “Critical facility” means a facility for which even a slight chance of flooding might be too great. Critical facilities include, but are not limited to, schools, nursing homes, hospitals, police, fire and emergency response installations, and installations that produce, use, or store hazardous materials or hazardous waste.
(9) “Development” means any manmade changes to improved or unimproved real estate, including but not limited to buildings or other structures, mining, dredging, filling, grading, paving, excavation or drilling operations or storage of equipment or materials located within the area of special flood hazard.
(10) “Elevation certificate” means an administrative tool of the National Flood Insurance Program (NFIP) that can be used to provide elevation information, to determine the proper insurance premium rate, and to support a request for a Letter of Map Amendment (LOMA) or Letter of Map Revision based on fill (LOMR-F).
(11) “Flood” or “flooding” means:
(a) A general and temporary condition of partial or complete inundation of normally dry land areas from:
(i) The overflow of inland or tidal waters.
(ii) The unusual and rapid accumulation of runoff of surface waters from any source.
(iii) Mudslides (i.e., mudflows) which are proximately caused by flooding as defined in subsection (1)(b) of this definition and are akin to a river of liquid and flowing mud on the surfaces of normally dry land areas, as when earth is carried by a current of water and deposited along the path of the current.
(b) The collapse or subsidence of land along the shore of a lake or other body of water as a result of erosion or undermining caused by waves or currents of water exceeding anticipated cyclical levels or suddenly caused by an unusually high water level in a natural body of water, accompanied by a severe storm, or by an unanticipated force of nature, such as flash flood or an abnormal tidal surge, or by some similarly unusual and unforeseeable event which results in flooding as defined in subsection (1)(a) of this definition.
(12) “Flood elevation study” means an examination, evaluation, and determination of flood hazards and, if appropriate, corresponding water surface elevations, or an examination, evaluation and determination of mudslide (i.e., mudflow) and/or flood-related erosion hazards. Also known as a flood insurance study (FIS).
(13) “Flood insurance rate map (FIRM)” means the official map on which the Federal Insurance Administration has delineated both the areas of special flood hazard and the risk premium zones applicable to the community.
(14) “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.
(15) “Floodplain or flood-prone area” means any land area susceptible to be inundated by water from any source. See “Flood” or “flooding.”
(16) “Floodplain administrator” means the community official designated by title to administer and enforce floodplain management regulations.
(17) “Flood proofing” means any combination of structural and nonstructural additions, changes, or adjustments to structures which reduce or eliminate the risk of flood damage to real estate or improved real property, water and sanitary facilities, structures, and their contents. Flood-proofed structures are those that have the structural integrity and design to be impervious to floodwater below the base flood elevation.
(18) “Floodway” means the channel of a river or other watercourse and the adjacent land areas that must be reserved to discharge the base flood without cumulatively increasing the water surface elevation more than one foot.
(19) “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 to render the structure in violation of the applicable nonelevation design requirements of this chapter found at BMC 15.55.180(1)(b).
(20) “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 floodplain 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.
(21) “Manufactured home park or subdivision” means a parcel (or contiguous parcels) of land divided into two or more manufactured home lots for rent or sale.
(22) “New construction” means structures for which the “start of construction” commenced on or after the effective date of the ordinance codified in this chapter.
(23) “Recreational vehicle” means a vehicle:
(a) Built on a single chassis;
(b) Four hundred square feet or less when measured at the largest horizontal projection;
(c) Designed to be self-propelled or permanently towable by a light-duty truck; and
(d) Designed primarily not for use as a permanent dwelling but as temporary living quarters for recreational, camping, travel or seasonal use.
(24) “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. For a substantial improvement, the “actual start of construction” means the first alteration of any wall, ceiling, floor, or other structural parts of a building, whether or not that alteration affects the external dimensions of the building.
(25) “Structure” means a walled and roofed building including a gas or liquid storage tank that is principally above ground.
(26) “Substantial damage” means damage of any origin sustained by a structure whereby the cost of restoring the structure to its before-damaged condition would equal or exceed 50 percent of the market value of the structure before the damage occurred.
(27) “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:
(a) Before the improvement or repair is started; or
(b) If the structure has been damaged and is being restored before the damage occurred.
For this definition “substantial improvement” is considered to occur when the first alteration of any wall, ceiling, floor, or other structural parts of the building commences, whether or not that alteration affects the external dimensions of the structure.
The term can exclude:
(a) Any project for improvement of a structure to correct pre-cited existing violations of state or local health, sanitary, or safety code specifications which have been previously identified by the local code enforcement official and which are the minimum necessary to assure safe living conditions; or
(b) Any alteration of a structure listed on the National Register of Historic Places or a state inventory of historic places.
(28) “Variance” means a grant of relief from the requirements of this chapter that permits construction in a manner that would otherwise be prohibited by this chapter.
(29) “Water dependent” means a structure for commerce or industry that cannot exist in any other location and is dependent on the water because of the intrinsic nature of its operations. [Ord. 741 § 4, 2020; Ord. 685 § 1 (Exh. A), 2018; Ord. 417 § 1, 2004; Ord. 250 § 1, 1999]
15.55.060 Lands to which this chapter applies.
This chapter shall apply to all areas of special flood hazards within the jurisdiction of the city of Burien. [Ord. 250 § 1, 1999]
15.55.070 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 titled “The Floor Insurance Study for King County, Washington, and Incorporated Areas,” dated August 19, 2020, and any revisions thereto, with accompanying flood insurance rate maps (FIRMs) dated August 19, 2020, and any revisions thereto, are hereby adopted by reference and declared to be a part of this chapter. The flood insurance study and the FIRM are on file at Burien City Hall. The best available information for flood hazard area identification as outlined in BMC 15.55.140(2) shall be the basis for regulation until a new FIRM is issued that incorporates data utilized under BMC 15.55.140(2). [Ord. 741 § 5, 2020; Ord. 685 § 1 (Exh. A), 2018; Ord. 417 § 1, 2004; Ord. 250 § 1, 1999]
15.55.080 Penalties for noncompliance.
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 more than $1,000 or imprisoned for not more than 90 days, or both, for each violation, and in addition shall pay all costs and expenses involved in the case. Nothing contained in this chapter shall prevent the city of Burien from taking such other lawful action as is necessary to prevent or remedy any violation. [Ord. 250 § 1, 1999]
15.55.090 Abrogation and greater restrictions.
This chapter is not intended to repeal, abrogate, or impair any existing easements, covenants, or deed restrictions. However, where this chapter and another ordinance, easement, covenant, or deed restriction conflict or overlap, whichever imposes the more stringent restrictions shall prevail. [Ord. 250 § 1, 1999]
15.55.100 Interpretation.
In the interpretation and application of this chapter, all provisions shall be:
(1) Considered as minimum requirements;
(2) Liberally construed in favor of the governing body; and
(3) Deemed neither to limit nor repeal any other powers granted under state statutes. [Ord. 250 § 1, 1999]
15.55.110 Warning and disclaimer of liability.
The degree of flood protection required by this chapter is considered reasonable for regulatory purposes and is based on scientific and engineering considerations. Larger floods can and will occur on occasions. Flood heights may be increased by manmade or natural causes. This chapter does not imply that land outside the areas of special flood hazards or uses permitted within such areas will be free from flooding or flood damages. This chapter shall not create liability on the part of the city of Burien, any officer, or employee thereof, or the Federal Insurance Administration, for any flood damages that result from reliance on this chapter or any administrative decision made hereunder. [Ord. 250 § 1, 1999]
15.55.115 Development permitted when.
(1) No development shall be permitted within any area of special flood hazard except:
(a) Where it can be shown that such development will cause no displacement or diversion of floodwaters; or
(b) When provision has been made on the subject property to balance the capacity to store floodwaters and accommodate potential surface flow in an amount equal to the amount of floodwater likely to be displaced or diverted by such development.
(2) The provisions of this section do not apply to the body of water known as Puget Sound, which is designated on flood insurance rate maps as an area of special flood hazard. [Ord. 328 § 1, 2001]
15.55.120 Development permits.
(1) Required. A development permit shall be obtained before construction or development begins within any area of special flood hazard established in BMC 15.55.070. The permit shall be for all structures including manufactured homes, as set forth in BMC 15.55.050, and for all development including fill and other activities, also as set forth in BMC 15.55.050.
(2) Application. Application for a development permit shall be made on forms furnished by the city of Burien and may include but not be limited to plans in duplicate drawn to scale showing the nature, location, dimensions, and elevations of the area in question; existing or proposed structures, fill, storage of materials, drainage facilities, and the location of the foregoing. Specifically, the following information is required:
(a) Elevation in relation to mean sea level of the lowest floor (including basement) of all structures;
(b) Elevation in relation to mean sea level to which any structure has been flood-proofed;
(c) Certification by a registered professional engineer or architect that the flood-proofing methods for any nonresidential structure meet the flood-proofing criteria in BMC 15.55.180(2); and
(d) Description of the extent to which a watercourse will be altered or relocated as a result of a proposed development.
(e) Where a structure is proposed in a V, V1-30, or VE zone, a V-zone design certificate;
(f) Where development is proposed in a floodway, an engineering analysis indicating no rise of the base flood elevation; and
(g) Any other such information that may be reasonably required by the floodplain administrator to review the application. [Ord. 741 § 6, 2020; Ord. 250 § 1, 1999]
15.55.130 Local administrator – Designated.
The building official or his designee shall administer and implement this chapter by granting or denying development permit applications in accordance with its provisions. [Ord. 250 § 1, 1999]
15.55.140 Local administrator – Duties and responsibilities.
Duties of the building official or his designee shall include, but not be limited to:
(1) Permit Review.
(a) Review all building development permits to determine that the permit requirements of this chapter have been satisfied;
(b) Review all building development permits to determine that all necessary permits have been obtained from those federal, state, or local governmental agencies from which prior approval is required; and
(c) Review all development permits to determine if the proposed development is located in the floodway. If located in the floodway, assure that the provisions of BMC 15.55.190 are met.
(2) Use of Other Base Flood Data. When base flood elevation data has not been provided in accordance with BMC 15.55.070, Basis for establishing the areas of special flood hazard, the city manager or his designee shall obtain, review, and reasonably utilize any base flood elevation and floodway data available from a federal, state or other source, in order to administer BMC 15.55.180, Specific standards, and 15.55.190, Floodways.
(3) Information to Be Obtained and Maintained.
(a) Where base flood elevation data is provided through the flood insurance study, FIRM, or required as in subsection (2) of this section, obtain and record the actual (as-built) 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.
(b) For all new or substantially improved flood-proofed structures:
(i) Verify and record the actual elevation (in relation to mean sea level) to which the structure was flood-proofed; and
(ii) Maintain the flood-proofing certifications required in BMC 15.55.120(2)(c).
(c) Maintain for public inspection all records pertaining to the provisions of this chapter.
(4) Alteration of Watercourses.
(a) Notify adjacent communities and the Washington State Department of Ecology prior to any alteration or relocation of a watercourse, and submit evidence of such notification to the Federal Insurance Administration.
(b) Require that maintenance is provided within the altered or relocated portion of the watercourse so that the flood-carrying capacity is not diminished.
(5) 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 as provided in BMC 15.55.150 and 15.55.160. [Ord. 741 § 7, 2020; Ord. 685 § 1 (Exh. A), 2018; Ord. 250 § 1, 1999]
15.55.150 Appeal board.
(1) The hearing examiner and/or the building code board of appeals shall hear and decide appeals and requests for variances from the requirements of this chapter.
(2) The hearing examiner and/or the building code board of appeals shall hear and decide appeals when it is alleged there is an error in any requirements, decision, or determination made by the city in the enforcement or administration of this chapter.
(3) Those aggrieved by the decision of the hearing examiner may appeal such decision to the King County superior court, by writ of review, within 20 calendar days of the hearing examiner’s decision.
(4) In passing upon such applications, the hearing examiner shall consider all technical evaluations, all relevant factors, standards specified in other sections of this chapter; and:
(a) The danger that material may be swept onto other lands to the injury of others;
(b) The danger to life and property due to flooding or erosion damage;
(c) The susceptibility of the proposed facility and its contents to flood damage and the effect of such damage on the individual owner;
(d) The importance of the services provided by the proposed facility to the community;
(e) The necessity to the facility of a waterfront location, where applicable;
(f) The availability of alternative locations for the proposed use which are not subject to flooding or erosion damage;
(g) The compatibility of the proposed use with existing and anticipated development;
(h) The relationship of the proposed use to the comprehensive plan and floodplain management program for that area;
(i) The safety of access to the property in times of flood for ordinary and emergency vehicles;
(j) The expected heights, velocity, duration, rate of rise, and sediment transport of the floodwaters and the effects of wave action, if applicable, expected at the site; and
(k) The costs of providing governmental services during and after flood conditions, including maintenance and repair of public utilities and facilities such as sewer, gas, electrical, and water systems, and streets and bridges.
(5) Upon consideration of the factors of subsection (4) of this section and the purposes of this chapter, the hearing examiner may attach such conditions to the granting of variances as it deems necessary to further the purposes of this chapter.
(6) The building official shall maintain the records of all appeal actions and report any variances to the Federal Insurance Administration upon request. [Ord. 250 § 1, 1999]
15.55.160 Conditions for variances.
(1) Generally, the only condition under which a variance from the elevation standard may be issued is for new construction and substantial improvements to be erected on a lot of one-half acre or less in size contiguous to and surrounded by lots with existing structures constructed below the base flood level, provided BMC 15.55.150(4)(a) through (k) have been fully considered.
(2) Variances may be issued for the reconstruction, rehabilitation, or restoration of structures listed on the National Register of Historic Places or the State Inventory of Historic Places, without regard to the procedures set forth in this section.
(3) Variances shall not be issued within a designated floodway if any increase in flood levels during the base flood discharge would result.
(4) Variances shall only be issued upon a determination that the variance is the minimum necessary, considering the flood hazard, to afford relief.
(5) Variances shall only be issued upon:
(a) A showing of good and sufficient cause;
(b) A determination that failure to grant the variance would result in exceptional hardship to the applicant;
(c) A determination that the granting of a variance will not result in increased flood heights, additional threats to public safety, extraordinary public expense, create nuisances, cause fraud on the public, or conflict with existing local laws or ordinances.
(6) Variances as interpreted in the National Flood Insurance Program are based on the general zoning law principle that they pertain to a physical piece of property, they are not personal in nature and do not pertain to the structure, its inhabitants, economic or financial circumstances. They primarily address small lots in densely populated residential neighborhoods.
(7) Variances may be issued for nonresidential buildings in very limited circumstances to allow a lesser degree of flood proofing than watertight or dry flood proofing, where it can be determined that such action will have low damage potential, complies with all other variance criteria except subsection (1) of this section, and otherwise complies with BMC 15.55.170(1) and (2).
(8) Any applicant to whom a variance is granted shall be given written notice that the structure will be permitted to be built with a lowest flood elevation below the base flood elevation and that the cost of flood insurance will be commensurate with the increased risk resulting from the reduced lowest floor elevation. [Ord. 741 § 8, 2020; Ord. 250 § 1, 1999]
15.55.170 General standards.
In all areas of special flood hazards, the following standards are required:
(1) Anchoring.
(a) All new construction 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 so as to prevent water from entering or accumulating within the components during conditions of flooding.
(3) Utilities.
(a) All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system;
(b) 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
(c) On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
(d) Water wells should be located on high ground that is not in the floodway.
(4) Subdivision Proposals.
(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; and
(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 that contain at least 50 lots or five acres (whichever is less).
(5) Review of Building Permits. Where elevation data is not available either though the flood insurance study, FIRM, or from another authoritative source (BMC 15.55.140(2)), 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 the highest adjacent grade in these zones may result in higher insurance rates.
(6) Recreational vehicles placed on sites must either:
(a) Be on the site for fewer than 180 consecutive days; or
(b) Be fully licensed and ready for highway use, on their 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) Meet the requirements of BMC 15.55.200(1) and (3) and the anchoring requirements for manufactured homes (subsection (1)(b) of this section). [Ord. 685 § 1 (Exh. A), 2018; Ord. 250 § 1, 1999]
15.55.180 Specific standards.
In all areas of special flood hazards where base flood elevation data has been provided as set forth in BMC 15.55.070, Basis for establishing the areas of special flood hazard, or BMC 15.55.140(2), Use of other base flood data, the following provisions are required:
(1) Residential Construction.
(a) New construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated one foot or more above base flood elevation.
(b) 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 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:
(i) 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;
(ii) The bottom of all openings shall be no higher than one foot above grade;
(iii) Openings may be equipped with screens, louvers, or other coverings or devices; provided, that they permit the automatic entry and exist of floodwaters.
(2) Nonresidential Construction. New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall either have the lowest floor, including basement, elevated one foot or more above the level of the base flood elevation; or, together with attendant utility and sanitary facilities, shall:
(a) Be flood proofed so that below one foot 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, specification, and plans. Such certification shall be provided to the official as required in BMC 15.55.140(3)(b).
(d) Nonresidential structures that are elevated, not flood proofed, must meet the same standards for space below the lowest floor as described in subsection (1)(b) of this section.
(e) Applicants flood proofing nonresidential buildings shall be notified that flood insurance premiums will be based on rates that are one foot below the flood-proofed level (e.g., a building flood proofed to one 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 base floodplain. Construction of new critical facilities shall be permissible within the base floodplain if no feasible alternative site is available. Critical facilities constructed within the base floodplain shall have the lowest floor elevated to three feet or more above the level of the base flood elevation or to the height of the 500-year flood, whichever is higher. Access to and from the critical facility should also be protected to the height utilized above. Flood proofing 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 extent possible.
(4) Manufactured Homes. All manufactured homes to be substantially improved on sites shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is one foot or more above the base flood elevation, and be securely anchored to an adequately anchored foundation system in accordance with the provisions of BMC 15.55.170(1)(b).
(5) Recreational Vehicles. Recreational vehicles placed on sites are required to either:
(a) Be on the site for fewer than 180 consecutive days; or
(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) Meet the requirements of subsection (4) of this section and the elevation and anchoring requirements for manufactured homes.
Nothing in this section shall allow placement and use of recreational vehicles in violation of any other city codes and ordinances. [Ord. 741 § 9, 2020; Ord. 685 § 1 (Exh. A), 2018; Ord. 417 § 1, 2004; Ord. 250 § 1, 1999]
15.55.190 Floodways.
Located within areas of special flood hazard established in BMC 15.55.070 are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of floodwaters that 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 is provided demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practice 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 structures which do not increase the ground floor area; and (b) repairs, reconstruction, or improvements to a structure, the cost of which does not exceed 50 percent of the market value of the structure either (i) before the reconstruction or repair is started, or (ii) 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, may be excluded in the 50 percent.
(3) If subsection (1) of this section is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of BMC 15.55.170 through 15.55.210. [Ord. 685 § 1 (Exh. A), 2018; Ord. 417 § 1, 2004; Ord. 250 § 1, 1999]
15.55.200 Standards for shallow flooding areas (AO zones).
Shallow flooding areas appear on FIRMs as AO zones with depth designations. The base flood depths in these zones range from one to three feet above ground where a clearly defined channel does not exist, or where the path of flooding is unpredictable and where velocity flow may be evident. Such flooding is usually characterized as sheet flow. In these areas, the following provisions apply:
(1) New construction and substantial improvements of residential structures and manufactured homes within AO zones shall have the lowest floor (including basement) elevated above the highest grade adjacent to the building, one foot or more above the depth number specified on the FIRM (at least two feet if no depth number is specified).
(2) New construction and substantial improvements of nonresidential structures within AO zones shall either:
(a) Have the lowest floor (including basement) elevated above the highest adjacent grade of the building site, one foot or more above the depth number specified on the FIRM (at least two feet if no depth number is specified); or
(b) Together with attendant utility and sanitary facilities, be completely flood proofed to or above that level so that any space below that level 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. If this method is used, compliance shall be certified by a registered professional engineer or architect as in BMC 15.55.180(2)(c).
(3) Require adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures. [Ord. 741 § 10, 2020; Ord. 685 § 1 (Exh. A), 2018; Ord. 250 § 1, 1999]
15.55.210 Coastal high hazard areas.
Located within areas of special flood hazard established in BMC 15.55.070 are coastal high hazard areas, designated as zones V1-V30, VE and/or V. These areas have special flood hazards associated with high velocity waters from surges and, therefore, in addition to meeting all provisions in this chapter, the following provisions shall also apply:
(1) Due to the dynamic nature of coastal high hazard areas located along the Pacific Ocean, in areas with designated velocity zones (V zones) the following standards shall apply:
(a) Prohibit new or substantially improved construction in designated V zones; exceptions are for needed water-dependent structures or structures that facilitate public recreational access to the shore. Structures which require siting in the V zone should be sited landward of the primary dune if an active dune system is associated with the V zone.
(b) Prohibit any alteration of dunes in the above designated V zones which could increase potential flood damage; this restriction includes prohibiting any modifications or alteration or disturbance of vegetative cover associated with dunes located in designated V zones.
(2) All new allowable construction and substantial improvements in zones V1-V30 and VE (V if base flood elevation data is available) shall be elevated on pilings and columns so that:
(a) The bottom of the lowest horizontal structural member of the lowest floor (excluding the pilings or columns) is elevated one foot or more above the base flood level; and
(b) The pile or column foundation and structure attached thereto is anchored to resist flotation, collapse and lateral movement due to the effects of wind and water loads acting simultaneously on all building components. Wind and water loading values shall each have a one percent chance of being equaled or exceeded in any given year (100-year mean recurrence interval).
A registered professional engineer or architect shall develop or review the structural design, specifications and plans for the construction and shall certify that the design and methods of construction to be used are in accordance with accepted standards of practice for meeting the provisions of subsections (2)(a) and (b) of this section.
(3) Obtain the elevation (in relation to mean sea level) of the bottom of the lowest structural member of the lowest floor (excluding pilings and columns) of all new and substantially improved structures in zones V1-V30 and VE, and whether or not such structures contain a basement. The local administrator shall maintain a record of all such information.
(4) All new construction shall be located landward of the reach of mean high tide.
(5) Provide that all new construction and substantial improvements have the space below the lowest floor either free of obstruction or constructed with nonsupporting breakaway walls, open wood latticework, or insect screening intended to collapse under wind and water loads without causing collapse, displacement, or other structural damage to the elevated portion of the building or supporting foundation system. For the purpose of this section, a breakaway wall shall have a design safe loading resistance of not less than 10 and no more than 20 pounds per square foot. Use of breakaway walls which exceed a design safe loading resistance of 20 pounds per square foot (either by design or when so required by local or state codes) may be permitted only if a registered professional engineer or architect certifies that the design proposed meets the following conditions:
(a) Breakaway wall collapse shall result from a water load less than that which would occur during the base flood; and
(b) The elevated portion of the building and supporting foundation system shall not be subject to collapse, displacement, or other structural damage due to the effects of wind and water loads acting simultaneously on all building components (structural and nonstructural). Maximum wind and water loading values to be used in this determination shall each have a one percent chance of being equaled or exceeded in any given year (100-year mean recurrence interval).
(6) If breakaway walls are utilized, such enclosed space shall be usable solely for parking of vehicles, building access, or storage. Such space shall not be used for human habitation.
(7) Prohibit the use of fill for structural support of buildings.
(8) Prohibit manmade alteration of sand dunes that would increase potential flood damage. [Ord. 250 § 1, 1999]
Prior legislation: Ord. 82.