Chapter 18.87 FLOOD DAMAGE PREVENTION

The Legislature of the state has in Chapter 86.16 RCW delegated the responsibility to local governmental units to adopt floodplain management regulations designed to promote the public health, safety and general welfare of its citizenry. Therefore, the city council of the city of Prosser, Washington, does ordain the provisions set out in this chapter. (Ord. 3186 § 2, 2022; Ord. 1917 § 1 (part), 1997).

18.87.020 Findings of fact.

A. The flood hazard areas of the city 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.

B. 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 floodproofed, elevated or otherwise unprotected from flood damage also contribute to the flood loss. (Ord. 3186 § 3, 2022; Ord. 1917 § 1 (part), 1997).

18.87.030 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:

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;

I. To participate in and maintain eligibility for flood insurance and disaster relief. (Ord. 3186 § 4, 2022; Ord. 1917 § 1 (part), 1997).

18.87.040 Methods of reducing flood losses.

In order to accomplish its purposes, this chapter includes methods and provisions for:

A. Restricting or prohibiting development that is dangerous to health, safety and property due to water or erosion hazards or which result in damaging increases in erosion or in flood heights or velocities;

B. Requiring that development vulnerable to floods, including facilities which serve such uses, be protected against flood damage at the time of initial construction;

C. Controlling the alteration of natural floodplain, stream channels, and natural protective barriers, which help accommodate or channel floodwaters;

D. Controlling filling, grading, dredging and other development which may increase flood damage; and

E. Preventing or regulating the construction of flood barriers which will unnaturally divert flood waters or may increase flood hazards in other areas. (Ord. 3186 § 5, 2022; Ord. 1917 § 1 (part), 1997).

18.87.050 Lands to which this chapter applies.

The ordinance codified in this chapter shall apply to all areas of special flood hazards within the jurisdiction of the city. (Ord. 3186 § 6, 2022; Ord. 1917 § 1 (part), 1997).

18.87.060 Basis for establishing the areas of special flood hazard.

The special flood hazard areas identified by the Federal Insurance Administrator in the flood insurance rate map (FIRM) for the city of Prosser, Washington, dated October 13, 1981, and any revisions thereto, and the special flood hazard areas identified by the Federal Insurance Administrator in a scientific and engineering report entitled “The Flood Insurance Study (FIS) for Benton County, Washington Unincorporated Areas” dated June 15, 1994, and any revisions thereto, with accompanying flood insurance rate maps (FIRMs) dated July 19, 1982, and any revisions thereto are hereby adopted by reference and declared to be a part of this chapter. The FIS and the FIRMs are on file at City Hall, as defined in Section 1.04.015. (Ord. 3186 § 7, 2022; Ord. 1917 § 1 (part), 1997).

18.87.070 Abrogation and greater restrictions.

The ordinance codified in this chapter is not intended to repeal, abrogate, impair any existing easements, covenants, or deed restrictions. However, where the ordinance codified in this chapter and any other ordinance, easement, covenant or deed restriction conflict or overlap, whichever imposes the more stringent restrictions shall prevail. (Ord. 3186 § 8, 2022; Ord. 1917 § 1 (part), 1997).

18.87.075 Compliance.

All development within special flood hazard areas is subject to the terms of this chapter and other applicable regulations. (Ord. 3186 § 9, 2022).

18.87.080 Interpretation.

In the interpretation and application of this chapter, all provisions shall be:

A. Considered as minimum requirements;

B. Liberally construed in favor of the governing body;

C. Deemed neither to limit nor repeal any other powers granted under state statutes. (Ord. 3186 § 10, 2022; Ord. 1917 § 1 (part), 1997).

18.87.090 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 rare 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, any officer or employee thereof, or the Federal Insurance Administrator, for any flood damages that result from reliance on this chapter or any administrative decision lawfully made hereunder. (Ord. 3186 § 11, 2022; Ord. 1917 § 1 (part), 1997).

18.87.100 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.

“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.

“Appeal” means a request for a review of the interpretation of any provision of this chapter or a request for a variance.

“Area of shallow flooding” means a designated AO, AH, AR/AO or AR/AH zone on a community’s flood insurance rate map (FIRM) with a one percent or greater chance of flooding to an average depth range from one to three feet where 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.

“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. Designation is shown on the flood insurance rate map (FIRM) as zone A, AO, AH, A1-30, AE, A99, AR. “Special flood hazard area” (SFHA) is synonymous in meaning with the phrase “area of special flood hazard.”

“ASCE 24” means the most recently published version of ASCE 24, Flood Resistant Design and Construction, published by the American Society of Civil Engineers.

“Base flood” means the flood having a one percent chance of being equaled or exceeded in any given year. Also referred to as the “one-hundred-year flood.”

“Base flood elevation” (BFE) means the elevation to which floodwater is anticipated to rise during the base flood.

“Basement” means any area of the building having its floor sub-grade (below ground level) on all sides.

Building. See “Structure.”

“Building code” means the currently effective versions of the International Building Code and the International Residential Code adopted by the city of Prosser under Chapter 15.04.

“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 which produce, use, or store hazardous materials or hazardous waste.

“Development” means any manmade 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.

“Elevated building” means, for insurance purposes, a nonbasement building that has its lowest elevated floor raised above ground by foundation walls, shear walls, posts, piers, pilings, or columns.

“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).

“Essential facility” has the same meaning as “essential facility” defined in ASCE 24. Table 1-1 in ASCE 24-14 further identifies building occupancies that are essential facilities.

“Existing manufactured home park or subdivision” means a manufactured home park or subdivision for which the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including, at a minimum, the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads) is completed before the effective date of the floodplain management regulations adopted by the community.

“Expansion to an existing manufactured home park or subdivision” means the preparation of additional sites by the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads).

“Farmhouse” means single-family dwelling located on a farm site where resulting agricultural products are not produced for the primary consumption or use by the occupants and the farm owner.

“Flood” or “flooding” means a general and temporary condition of partial or complete inundation of normally dry land areas from:

1. a. The overflow of inland or tidal water; and/or

b. The unusual and rapid accumulation of runoff or surface waters from any source.

c. 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.

2. 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.

“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).

“Flood insurance rate map (FIRM)” means the official map on which the Federal Insurance Administrator has delineated both the areas of special flood hazards and the risk premium zones applicable to the community. A FIRM that has been made available digitally is called a digital flood insurance rate map (DFIRM).

“Floodplain or flood-prone area” means any land area susceptible to being inundated by water from any source. See “Flood or flooding.”

“Floodplain administrator” means the community official designated by title to administer and enforce the floodplain management regulations.

“Floodplain management regulations” means zoning ordinances, subdivision regulations, building codes, health regulations, special purpose ordinances (such as floodplain ordinance, grading ordinance and erosion control ordinance) and other application of police power. The term describes such state or local regulations, in any combination thereof, which provide standards for the purpose of flood damage prevention and reduction.

“Floodproofing” means any combination of structural and nonstructural additions, changes, or adjustments to structures which reduce or eliminate risk of flood damage to real estate or improved real property, water and sanitary facilities, structures, and their contents. Floodproofed structures are those that have the structural integrity and design to be impervious to floodwater below the base flood elevation.

“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 a designated height. Also referred to as “regulatory floodway.”

“Functionally dependent use” means a use which cannot perform its intended purpose unless it is located or carried out in close proximity to water. The term includes only docking facilities, port facilities that are necessary for the loading and unloading of cargo or passengers, and ship building and ship repair facilities, and does not include long-term storage or related manufacturing facilities.

“Highest adjacent grade” means the highest natural elevation of the ground surface prior to construction next to the proposed walls of a structure.

“Historic structure” means any structure that is:

1. Listed individually in the National Register of Historic Places (a listing maintained by the Department of the Interior) or preliminarily determined by the Secretary of the Interior as meeting the requirements for individual listing on the National Register;

2. Certified or preliminarily determined by the Secretary of the Interior as contributing to the historical significance of a registered historic district or a district preliminarily determined by the Secretary to qualify as a registered historic district;

3. Individually listed on a state inventory of historic places in states with historic preservation programs which have been approved by the Secretary of the Interior; or

4. Individually listed on a local inventory of historic places in communities with historic preservation programs that have been certified either:

a. By an approved state program as determined by the Secretary of the Interior, or

b. Directly by the Secretary of the Interior in states without approved programs.

“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 nonelevation design requirements of this chapter found at Section 18.87.290(B).

“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. The term “manufactured home” does not include a “recreational vehicle.”

“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.

“Mean sea level” means, for purposes of the National Flood Insurance Program, the vertical datum to which base flood elevations shown on a community's flood insurance rate map are referenced.

“New construction,” for purposes of determining insurance rates, means structures for which the “start of construction” commenced on or after the effective date of an initial flood insurance rate map or after December 31, 1974, whichever is later, and includes any subsequent improvements for such structures. For floodplain management purposes, “new construction” means structures for which the “start of construction” commenced on or after the effective date of a floodplain management regulation adopted by a community and includes any subsequent improvements to such structures.

“New manufactured home park or subdivision” means a manufactured home park or subdivision for which the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including at a minimum, the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads) is completed on or after the effective date of adopted floodplain management regulations adopted by the community.

One-Hundred Year Flood or 100-Year Flood. See “Base flood.”

“Reasonably safe from flooding” means development that is designed and built to be safe from flooding based on consideration of current flood elevation studies, historical data, high water marks and other reliable data known to the community. In unnumbered A zones where flood elevation information is not available and cannot be obtained by practicable means, reasonably safe from flooding means that the lowest floor is at least two feet above the highest adjacent grade.

“Recreational vehicle” means a vehicle:

1. Built on a single chassis;

2. Four hundred square feet or less when measured at the largest horizontal projection;

3. Designed to be self-propelled or permanently towable by a light duty truck; and

4. Designed primarily not for use as a permanent dwelling but as temporary living quarters for recreational, camping, travel, or seasonal use.

“Start of construction” includes substantial improvement, and means the date the building permit was issued; provided, the actual start of construction, repair, reconstruction, rehabilitation, addition, placement or other improvement was within one hundred eighty days of the permit date. The “actual start” means either the first placement of permanent construction or 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 part of a building, whether or not that alteration affects the external dimensions of the building.

“Structure” means a walled and roofed building including a gas or liquid storage tank that is principally above ground, as well as a manufactured home.

“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 fifty percent of the market value of the structure before the damage occurred.

“Substantial improvement” means any repair, reconstruction, addition, or improvement of a structure, the cost of which equals or exceeds fifty percent of the market value of the structure before the “start of construction” of the improvement. This term includes structures which have incurred “substantial damage,” regardless of the actual repair work performed.

The term does not, however, include either:

1. Any project for improvement of a structure to correct previously identified existing violations of state or local health, sanitary or safety code specifications that have been identified by the local code enforcement official and that are the minimum necessary to assure safe living conditions; or

2. Any alteration of a “historic structure”; provided, that the alteration will not preclude the structure’s continued designation as a “historic structure.”

“Variance” means a grant of relief from the requirements of this chapter which permits construction in a manner that would otherwise be prohibited by this chapter.

“Water dependent” means a structure for commerce or industry that cannot exist in any other location and is dependent on the water by reason of the intrinsic nature of its operation.

“Water surface elevation” means the height, in relation to the vertical datum utilized in the applicable flood insurance study of floods of various magnitudes and frequencies in the floodplains of coastal or riverine areas. (Ord. 3186 § 12, 2022; Ord. 1917 § 1 (part), 1997).

18.87.110 Development permit required.

A development permit shall be obtained before construction or development begins within any area of special flood hazard established in Section 18.87.060. The permit shall be for all structures including manufactured homes, as defined in Section 18.87.100, and for all development including fill and other activities, also as defined in Section 18.87.100. (Ord. 3186 § 13, 2022; Ord. 1917 § 1 (part), 1997).

18.87.120 Application for development permit.

Application for a development permit shall be made on forms furnished by the floodplain administrator and may include but not be limited to: plans in duplicate drawn to scale showing the nature, location, dimensions and elevation 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 recorded on a current elevation certificate with Section B completed by the floodplain administrator;

B. Elevation in relation to mean sea level to which any structure has been floodproofed;

C. Certification by a registered professional engineer or architect that the floodproofing methods for any nonresidential structure meet the floodproofing criteria in Section 18.87.300;

D. Description of the extent to which a watercourse will be altered or relocated as a result of proposed development;

E. Where development is proposed in a floodway, an engineering analysis indicating no rise of the base flood elevation; and

F. Any other information that may be reasonably required by the floodplain administrator in order to review the application. (Ord. 3186 § 14, 2022; Ord. 1917 § 1 (part), 1997).

18.87.130 Designation of the floodplain administrator.

The community development director is appointed to administer and implement this chapter by granting or denying development permit application in accordance with its provisions. The floodplain administrator may delegate authority to implement these provisions. (Ord. 3186 § 15, 2022; Ord. 1917 § 1 (part), 1997).

18.87.140 Duties and responsibilities of the floodplain administrator.

Duties of the floodplain administrator shall include, but not be limited to, those described in Sections 18.87.150 through 18.87.190. (Ord. 3186 § 16, 2022; Ord. 1917 § 1 (part), 1997).

18.87.150 Permit review.

The floodplain administrator shall:

A. Review all development permits to determine that the permit requirements of this chapter have been satisfied;

B. Review all 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;

C. 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 18.87.320(A) are met;

D. Notify FEMA when annexations occur in the special flood hazard area;

E. Notify FEMA of changes to the base flood elevation within six months of when technical information of such changes becomes available. (Ord. 3186 § 17, 2022; Ord. 1917 § 1 (part), 1997).

18.87.160 Use of other base flood data.

When base flood elevation data has not been provided (in A zones) in accordance with Section 18.87.060, the floodplain administrator 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 Sections 18.87.280 through 18.87.320. (Ord. 3186 § 18, 2022; Ord. 1917 § 1 (part), 1997).

18.87.170 Information to be obtained and maintained.

A. Where base flood elevation data is provided through the flood insurance study, FIRM, or required as in Section 18.87.160, obtain and maintain a record of 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 floodproofed nonresidential structures where base flood elevation data is provided through the FIS, FIRM, or as required in Section 18.87.160:

1. Obtain and maintain a record of the elevation (in relation to mean sea level) to which the structure was floodproofed; and

2. Maintain the floodproofing certifications required in Section 18.87.120(C).

C. Maintain for public inspection all records pertaining to the provisions of this chapter.

D. Certification required by Section 18.87.320(A)(1) (floodway encroachments).

E. Records of all variance actions, including justification for their issuance.

F. Improvement and damage calculations. (Ord. 3186 § 19, 2022; Ord. 1917 § 1 (part), 1997).

18.87.180 Alteration of watercourses.

The floodplain administrator shall:

A. Notify adjacent communities and the Department of Ecology (DOE) prior to any alteration or relocation of a watercourse, and submit evidence of such notification to the Federal Insurance Administrator through appropriate means; and

B. Require that maintenance is provided within the altered or relocated portion of the watercourse so that the flood-carrying capacity is not diminished. (Ord. 3186 § 20, 2022; Ord. 1917 § 1 (part), 1997).

18.87.190 Interpretation of FIRM boundaries.

The floodplain administrator shall make interpretations where needed, as to the 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 Section 18.87.200. (Ord. 3186 § 21, 2022; Ord. 1917 § 1 (part), 1997).

18.87.200 Appeal board.

A. The city council as established by Prosser, Washington, shall hear and decide appeals and requests for variances from the requirements of this chapter.

B. The city council shall hear and decide appeals when it is alleged there is an error in any requirements, decisions or determination made by the floodplain administrator in the enforcement or administration of this chapter.

C. Those aggrieved by the decision of the city council, or any taxpayer, may appeal such decision to the superior court, as provided in all applicable statutes.

D. In passing upon such applications, the city council shall consider all technical evaluations, all relevant factors, standards specified in other sections of this chapter, and:

1. The danger that materials may be swept onto other lands to the injury of others;

2. The danger to life and property due to flooding or erosion damage;

3. The susceptibility of the proposed facility and its contents to flood damage and the effect of such damage on the individual owner;

4. The importance of the services provided by the proposed facility to the community;

5. The necessity to the facility of a waterfront location, where applicable;

6. The availability of alternative locations for the proposed use which are not subject to flooding or erosion damage;

7. The compatibility of the proposed use with existing and anticipated development;

8. The relationship of the proposed use to the comprehensive plan and floodplain management program for that area;

9. The safety of access to the property in times of flood for ordinary and emergency vehicles;

10. 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

11. The costs of providing governmental services during and steer flood conditions, including maintenance and repair of public utilities and facilities such as sewer, gas, electrical and water systems, and streets and bridges.

E. Upon consideration of the factors of subsection D of this section and the purposes of this chapter, the city council may attach such conditions to the granting of variances as it deems necessary to further the purposes of this chapter.

F. The floodplain administrator shall maintain the records of all appeal actions and report any variances to the Federal Insurance Administrator upon request. (Ord. 3186 § 22, 2022; Ord. 1917 § 1 (part), 1997).

18.87.210 Conditions for variances.

A. 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, providing items (1) through (11) in Section 18.87.200(D) have been fully considered. As the lot size increases, the technical justification required for issuing the variance increases.

B. 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.

C. Variances shall not be issued within a designated floodway if any increase in flood levels during the base flood discharge would result.

D. Variances shall only be issued upon a determination that the variance is the minimum necessary, considering the flood hazard, to afford relief.

E. Variances shall only be issued upon:

1. Showing of good and sufficient cause;

2. A determination that failure to grant the variance would result in exceptional hardship to the applicant;

3. 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 or victimization of the public as identified in Section 18.87.200(D), or conflict with existing local laws or ordinances;

4. A showing that the use cannot perform its intended purpose unless it is located or carried out in close proximity to water. This includes only facilities defined in Section 18.87.100.

F. 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 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. As such, variances from the flood elevations should be quite rare.

G. Variances may be issued for nonresidential buildings in very limited circumstances to allow a lesser degree of floodproofing than watertight or dry floodproofing, where in can be determined that such action will have low damage potential, complies with all other variance criteria except subsection (A) of this section, and otherwise complies with Sections 18.87.230 and 18.87.240.

H. Any applicant to whom a variance is granted shall be given written notice over the signature of the floodplain administrator that the structure will be permitted to be built with a lowest floor elevation below the base flood elevation which will result in increased premium rates for flood insurance up to amounts as high as twenty-five dollars for one hundred dollars of insurance coverage, and such construction below the BFE increases risks to life and property. The floodplain administrator shall maintain a record of all variance actions, including justification for their issuance. The floodplain administrator shall condition the variance as needed to ensure that the requirements and criteria of this chapter are met. (Ord. 3186 § 23, 2022; Ord. 1917 § 1 (part), 1997).

18.87.220 General standards.

In all areas of special flood hazards, the following standards in Sections 18.87.230 through 18.87.270 are required. (Ord. 3186 § 24, 2022; Ord. 1917 § 1 (part), 1997).

18.87.230 Anchoring.

A. All new construction and substantial improvements, including those related to manufactured homes, shall be anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads including the effects of buoyancy.

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). (Ord. 3186 § 25, 2022; Ord. 1917 § 1 (part), 1997).

18.87.240 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. (Ord. 3186 § 26, 2022; Ord. 1917 § 1 (part), 1997).

18.87.245 Storage of materials and equipment.

A. The storage or processing of materials that could be injurious to human, animal, or plant life if released due to damage from flooding is prohibited in special flood hazard areas.

B. Storage of other material or equipment may be allowed if not subject to damage by floods and if firmly anchored to prevent flotation, or if readily removable from the area within the time available after flood warning. (Ord. 3186 § 27, 2022).

18.87.250 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.

C. On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.

D. Water wells shall be located on high ground that is not in the floodway. (Ord. 3186 § 28, 2022; Ord. 1917 § 1 (part), 1997).

18.87.260 Subdivision proposals and development.

A. All subdivision proposals as well as new development shall be consistent with the need to minimize flood damage.

B. All subdivision proposals as well as new development shall have public utilities and facilities such as sewer, gas, electrical and water systems located and constructed to minimize or eliminate flood damage.

C. All subdivision proposals as well as new development 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 lots or five acres, whichever is less. (Ord. 3186 § 29, 2022; Ord. 1917 § 1 (part), 1997).

18.87.270 Review of building permits.

Where elevation data is not available either through the flood insurance study, FIRM, or from another authoritative source (Section 18.87.160), applications for floodplain development 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. 3186 § 30, 2022; Ord. 1917 § 1 (part), 1997).

18.87.280 Specific standards.

In all areas of special flood hazards where base flood elevation data has been provided as set forth in Section 18.87.060 or Section 18.87.160, the following provisions in Sections 18.87.290 through 18.87.310 are required. (Ord. 3186 § 31, 2022; Ord. 1917 § 1 (part), 1997).

18.87.290 Residential construction.

A. In AE and A1-30 zones or other A zoned areas where the BFE has been determined or can be reasonably obtained, 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. Mechanical equipment and utilities shall be waterproofed or elevated at least one foot above the BFE.

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:

1. 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;

2. The bottom of all openings shall be no higher than one foot 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;

4. A garage attached to a residential structure, constructed with the garage floor slab below the BFE, must be designed to allow for the automatic entry and exit of floodwaters.

C. New construction and substantial improvement of any residential structure in an AO zone shall meet the requirements in Section 18.87.330(A).

D. New construction and substantial improvement of any residential structure in an unnumbered A zone for which a BFE is not available and cannot be reasonably obtained shall be reasonably safe from flooding, but in all cases the lowest floor shall be at least two feet above the highest adjacent grade. (Ord. 3186 § 32, 2022; Ord. 1917 § 1 (part), 1997).

18.87.300 Nonresidential construction.

New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall meet the requirements of subsection A or B of this section:

A. New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall meet all of the following requirements:

1. In AE and A1-30 zones or other A zoned areas where the BFE has been determined or can be reasonably obtained:

New construction and substantial improvement of any commercial, industrial, or other nonresidential structure shall have the lowest floor, including basement, elevated one foot or more above the BFE, or elevated as required by ASCE 24, whichever is greater. Mechanical equipment and utilities shall be waterproofed or elevated at least one foot above the BFE, or as required by ASCE 24, whichever is greater.

2. If located in an AO zone, the structure shall meet the requirements in Section 18.87.330.

3. If located in an unnumbered A zone for which a BFE is not available and cannot be reasonably obtained, the structure shall be reasonably safe from flooding, but in all cases the lowest floor shall be at least two feet above the highest adjacent grade.

4. 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:

a. Have a minimum of two openings with a total net area of not less than one square inch for every square foot of enclosed area subject to flooding.

b. The bottom of all openings shall be no higher than one foot above grade.

c. Openings may be equipped with screens, louvers, valves, or other coverings or devices; provided, that they permit the automatic entry and exit of floodwater.

d. A garage attached to a residential structure, constructed with the garage floor slab below the BFE, must be designed to allow for the automatic entry and exit of floodwaters.

Alternatively, a registered engineer or architect may design and certify engineered openings.

B. If the requirements of subsection A of this section are not met, then new construction and substantial improvement of any commercial, industrial or other nonresidential structure shall meet all of the following requirements:

1. Be floodproofed so that below the base flood level the structure is watertight with walls substantially impermeable to the passage of water or dry floodproofed to the elevation required by ASCE 24, whichever is greater;

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 18.87.170(B);

4. Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in Section 18.87.290(B);

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). (Ord. 3186 § 33, 2022; Ord. 1917 § 1 (part), 1997).

18.87.305 Enclosed area below the lowest floor.

If buildings or manufactured homes are constructed or substantially improved with fully enclosed areas below the lowest floor, the areas shall be used solely for parking of vehicles, building access, or storage. (Ord. 3186 § 34, 2022).

18.87.310 Manufactured homes.

All manufactured homes to be placed or substantially improved on sites, shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated one foot or more above the base flood elevation and be securely anchored to an adequately anchored foundation system to resist flotation, collapse and lateral movement in accordance with the provisions of Section 18.87.230(A). (Ord. 3186 § 35, 2022; Ord. 1917 § 1 (part), 1997).

18.87.315 Recreational vehicles.

Recreational vehicles placed on sites are required to either:

A. Be on the site for fewer than one hundred eighty 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 Section 18.87.310. (Ord. 3186 § 36, 2022).

18.87.316 Appurtenant structures (detached garages and small storage structures).

For A zones (A, AE, A1-30, AH, AO):

A. Appurtenant structures used solely for parking of vehicles or limited storage may be constructed such that the floor is below the BFE, provided the structure is designed and constructed in accordance with the following requirements:

1. Use of the appurtenant structure must be limited to parking of vehicles or limited storage;

2. The portions of the appurtenant structure located below the BFE must be built using flood resistant materials;

3. The appurtenant structure must be adequately anchored to prevent flotation, collapse, and lateral movement;

4. Any machinery or equipment servicing the appurtenant structure must be elevated or floodproofed to or above the BFE;

5. The appurtenant structure must comply with floodway encroachment provisions in Section 18.87.320(A)(1);

6. The appurtenant structure must be designed to allow for the automatic entry and exit of floodwaters in accordance with Section 18.87.290(B);

7. The structure shall have low damage potential; and

8. If the structure is converted to another use, it must be brought into full compliance with the standards governing such use.

9. The structure shall not be used for human habitation.

B. Detached garages, storage structures, and other appurtenant structures not meeting the above standards must be constructed in accordance with all applicable standards in Section 18.87.290.

C. Upon completion of the structure, certification that the requirements of this section have been satisfied shall be provided to the floodplain administrator for verification. (Ord. 3186 § 37, 2022).

18.87.318 AE and A1-30 zones with base flood elevations but no floodways.

In areas with BFEs (when 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 the 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 the water surface elevation of the base flood more than one foot at any point within the community. (Ord. 3186 § 38, 2022).

18.87.320 Floodways.

A. Located within areas of special flood hazard established in Section 18.87.060 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 is provided demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachments would not result in any increase in flood levels during the occurrence of the base flood discharge. (Ord. 3186 § 39, 2022; Ord. 1917 § 1 (part), 1997).

18.87.325 Residential construction in floodways.

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 of the market value of the structure either (1) before the repair, or reconstruction 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, may be excluded from the fifty percent. (Ord. 3186 § 40, 2022).

18.87.327 All other building standards apply in the floodway.

If Section 18.87.320(A)(1) is satisfied or construction is allowed pursuant to Section 18.87.325, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions. (Ord. 3186 § 41, 2022).

18.87.328 General requirements for other development.

All development, including manmade changes to improved or unimproved real estate for which specific provisions are not specified in this chapter or the state building codes with adopted amendments and any city of Prosser amendments, shall:

A. Be located and constructed to minimize flood damage;

B. Meet the encroachment limitations of this chapter if located in a regulatory floodway;

C. Be anchored to prevent flotation, collapse, or lateral movement resulting from hydrostatic loads, including the effects of buoyancy, during conditions of the design flood;

D. Be constructed of flood damage-resistant materials;

E. Meet the flood opening requirements of Section 18.87.290(B); and

F. Have mechanical, plumbing, and electrical systems above the design flood elevation or meet the requirements of ASCE 24, except that minimum electric service required to address life safety and electric code requirements is permitted below the design flood elevation provided it conforms to the provisions of the electrical part of building code for wet locations. (Ord. 3186 § 42, 2022).

18.87.330 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:

A. New construction and substantial improvements of residential structures within AO zones shall have the lowest floor (including basement and mechanical equipment) 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).

B. New construction and substantial improvements of nonresidential structures within AO zones shall either:

1. 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

2. Together with attendant utility and sanitary facilities, be completely floodproofed 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 Section 18.87.300(B)(3).

C. Require adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures.

D. Recreational vehicles placed on sites within AO zones on the community’s FIRM either:

1. Be on the site for fewer than one hundred eighty consecutive days; or

2. Be fully licensed and ready for highway use, on its wheels or jacking system, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions; or

3. Meet the requirements of subsections A and C of this section and the anchoring requirements for manufactured homes (Section 18.87.230(B)). (Ord. 3186 § 43, 2022; Ord. 1917 § 1 (part), 1997).

18.87.335 Critical facility.

Construction of new critical facilities shall be, to the extent possible, located outside the limits of the SFHA (one-hundred-year floodplain). 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 three feet above BFE or to the height of the five-hundred-year flood, whichever is higher. Access to and from the critical facility should also be protected to the height utilized above. 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 BFE shall be provided to all critical facilities to the extent possible. (Ord. 3186 § 44, 2022).

18.87.337 Livestock sanctuary areas.

Elevated areas for the purpose of creating a flood sanctuary for livestock are allowed on farm units where livestock is allowed. Livestock flood sanctuaries shall be sized appropriately for the expected number of livestock and be elevated sufficiently to protect livestock. Proposals for livestock flood sanctuaries shall meet all procedural and substantive requirements of this chapter. (Ord. 3186 § 45, 2022).

18.87.340 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 gross 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 five thousand dollars or imprisoned for not more than three hundred sixty-four days or both, for each violation, and in addition shall pay all costs and expenses involved in the case. Nothing herein contained shall prevent the city from taking such other lawful action as is necessary to prevent or remedy any violation. (Ord. 3186 § 46, 2022; Ord. 1917 § 1 (part), 1997).

18.87.990 Severability.

If any section, subsection, sentence, clause, paragraph, phrase, or word of this chapter should be held to be invalid or unconstitutional by a court of competent jurisdiction, such invalidity or unconstitutionality thereof shall not affect the validity or constitutionality of any other section, subsection, sentence, clause, paragraph, phrase or word of this chapter. (Ord. 3186 § 47, 2022).