Chapter 16.21 FLOODPLAIN MANAGEMENT

The Legislature of the state of Washington has delegated the responsibility to local government units to adopt regulations designed to promote the public health, safety and general welfare of its citizenry. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.020 Findings of fact.

A. The flood hazard areas of the city of Centralia 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 hazard which increase flood heights and velocities, and when inadequately anchored, damage uses in other areas. Uses that are inadequately floodproofed, elevated or otherwise protected from flood damage also contribute to the flood loss. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.030 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. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.035 Methods of reducing flood losses.

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

A. Restricting or prohibiting uses which are 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 uses 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 floodplains, 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;

E. Preventing or regulating the construction of flood barriers which will unnaturally divert floodwaters or may increase flood hazards in other areas; and

F. A floodplain overlay area shall be created to protect health, safety and property in the most flood prone areas of the city.

All new lots created in the floodplain shall show that they have five thousand square feet of buildable area outside the zero-rise floodway. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.040 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.

“Appeal” means a request for a review of the community development director’s interpretation of any provision of this chapter or a request for a variance.

“Area of shallow flooding” means a designated AO or AH zone 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.

“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 on maps always includes the letter A or V.

“Base flood” means the flood having a one percent chance of being equaled or exceeded in any given year. Base flood also refers to the “one-hundred-year flood.” Designation on maps always includes the letter A or V.

“Base flood elevation” is also known and shown as BFE. The BFE means the elevation, expressed in feet above mean sea level, to which flooding can be expected to occur on a frequency of once in every one hundred years, or which is subject to a one percent or greater chance of flooding in any given year.

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

“Below-grade crawlspace” means a crawlspace meeting the requirement of 44 CFR 60.3(a)(3) and 60.3(c)(2) and (c)(5) of the NFIP regulations. The crawl area is an enclosed area below the BFE.

“Breakaway wall” means a wall that is not part of the structural support of the building and is intended through its design and construction to collapse under specific lateral loading forces, without causing damage to the elevated portion of the building or supporting foundation system.

“Critical facilities” means facilities that are critical to the health and welfare of the population and that are especially important during and after a hazard event. 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 or storage of equipment or materials 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 level by foundation walls, shear walls, post, piers, pilings, or columns.

“Elevation certificate” means the official form (FEMA Form 81-31) used to track development, provide elevation information necessary to ensure compliance with community floodplain management ordinances, and determine the proper insurance premium rate with Section B completed by community officials.

“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 adopted floodplain management regulations.

“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).

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

1. The overflow of inland or tidal waters; and/or

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

“Flood insurance rate map (FIRM)” means the official map on which the Federal Insurance Administration has delineated both the areas of special flood hazards and the risk premium zones applicable to the community.

“Flood insurance study” means the official report provided by the Federal Insurance Administration that includes flood profiles, the flood insurance rate maps, and the water surface elevation of the base flood.

“Floodplain” means any land area susceptible to being inundated by water from any source. For the purposes of this chapter, the floodplain is the area identified by the Federal Emergency Management Agency in the one-hundred-year floodplain as the floodway fringe.

“Floodproofing” means any combination of structural and nonstructural additions, changes, or adjustments to structures that reduce or eliminate flood damage to real estate or improved real property, water and sanitary facilities, structures, and their contents.

“Floodway” means the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than one foot.

“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 CMC 16.21.180.

“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 attached 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 one hundred eighty consecutive days. For insurance purposes the term “manufactured home” does not include park trailers, travel trailers and other similar recreational vehicles.

“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.

“New construction” means structures for which the “start of construction” commenced on or after the effective date of the ordinance codified in this chapter.

“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 the ordinance codified in this chapter.

“One-hundred-year flood” means the flood having a one percent chance of being equaled or exceeded in magnitude in any given year. Contrary to popular belief, it is not a flood occurring once every one hundred years.

“One-hundred-year floodplain” means the area adjoining a river, stream, or watercourse covered by water in the event of a one-hundred-year flood.

“Recreational vehicle” means a vehicle which is:

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, 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 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 foundations 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 anything erected, the use of which has fixed location on or in the ground, or attachment to something having fixed location on the land, including but not limited to buildings, fences, signs, and walls.

“Substantial damage” means damage of any origin sustained by a structure whereby the cost of restoring the structure to its before-damaged condition would be equal to or exceed fifty percent of the market value of the structure before the damage occurred.

“Substantial improvement” means any reconstruction, rehabilitation, addition, or other 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 over a ten-year period. 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 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

2. Any alterations 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 which cannot exist in any other location and is dependent on the water by reason of the intrinsic nature of its operations. (Ord. 2338 § 1, 2014: Ord. 2232 § 9 (Exh. A), 2009).

16.21.050 Lands to which this chapter applies.

This chapter shall apply to all areas of special flood hazard and to areas that have a history of inundation during a flood event within the jurisdiction of the city of Centralia. (Ord. 2532 § 1, 2023; Ord. 2232 § 9 (Exh. A), 2009).

16.21.060 Basis for establishing areas of special flood hazard.

The areas of special flood hazard identified by the Federal Insurance Administration in a scientific and engineering report entitled the Flood Insurance Study for the city of Centralia dated December 1, 1981, and any revisions thereto and the flood insurance rate map (FIRM) dated June 1, 1982, and any revisions thereto are adopted by reference and declared to be a part of this chapter. The Flood Insurance Study and the FIRM are on file at the community development department, City Hall, Centralia, Washington. The best available information for flood hazard area identification shall be the basis for regulation until a new FIRM is issued that incorporates data utilized under CMC 16.21.140(B). Properties that are outside of the Centralia city limits but within its urban growth boundary shall meet the adopted flood insurance rate map (FIRM) and any revisions thereto by Lewis County. (Ord. 2338 § 2, 2014: Ord. 2232 § 9 (Exh. A), 2009).

16.21.070 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 five thousand dollars for each violation, and in addition shall pay all costs and expenses involved in the case. Nothing herein contained shall prevent the city of Centralia from taking such other lawful action as is necessary to prevent or remedy any violation. Each person violating any provision of this chapter shall be deemed guilty of a separate offense for each day during which such violation continues. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.080 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. 2232 § 9 (Exh. A), 2009).

16.21.090 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; and

C. Deemed neither to limit nor repeal any other powers granted under state statutes. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.100 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 of Centralia, 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 lawfully made hereunder. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.110 Floodplain development permit required.

A floodplain development permit shall be obtained before construction or development begins within any area of special flood hazard established in CMC 16.21.060. The permit shall be for all structures including manufactured homes, as set forth in CMC 16.21.040, Definitions, and for all development including fill and other activities, also as set forth in CMC 16.21.040. A fee of fifty dollars shall be collected from the applicant at the time of the application. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.120 Application for floodplain development permits.

Application for a floodplain development permit shall be made on forms furnished by the community development department 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 floodproofed;

C. Certification by a registered professional engineer or architect that the floodproofing methods for any nonresidential structure meet the floodproofing criteria in CMC 16.21.180; and

D. Description of the extent to which a watercourse will be altered or relocated as a result of proposed development. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.130 Designation of the community development director.

The community development director or designee is appointed to administer and implement this chapter by granting or denying development permit applications in accordance with its provisions. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.140 Duties and responsibilities of the community development director.

Duties of the community development director shall include, but not be limited to:

A. Permit Review.

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

2. Review all development permits to determine that all necessary permits have been obtained from those federal, state or local governmental agencies from which prior approval is required;

3. Review all development permits to determine if the proposed development is located in the floodway. If located in the floodway, assure that the provisions of CMC 16.21.190 are met.

B. Use of Other Base Flood Data. When base flood elevation data has not been provided in accordance with CMC 16.21.060, the community development director shall obtain, review and reasonably utilize any base flood evaluation and floodway data available from a federal, state or other source, in order to administer CMC 16.21.180 and 16.21.190.

C. Information to Be Obtained and Maintained.

1. Where base flood elevation data is provided through the Flood Insurance Study (FIS) or required as in subsection (B) 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;

2. For all new or substantially improved floodproof structures where base flood elevation data is provided through the FIS, FIRM, or as required:

a. Verify and record the actual elevation (in relation to mean sea level); and

b. Maintain the floodproofing certifications required in CMC 16.21.120;

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

D. Alteration of Watercourses.

1. 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. Generally, stream relocations will only be allowed if the primary function of the action is to restore ecological function;

2. Require that maintenance is provided within the altered or relocated portion of said watercourse so that the flood-carrying capacity is not diminished;

3. Alterations and relocations, including stabilization projects, shall not degrade fish habitat or the physical processes that create and maintain habitat, or cause increased flood hazard or erosion to other properties and shall be subject to the following provisions:

a. Bridges shall be used instead of culverts on all Type 1 streams, and shall meet fish habitat requirements of the State Department of Fish and Wildlife.

b. Any culverts that are used on fish-bearing streams must be arch/bottomless culverts or provide comparable fish protection, and must meet fish habitat requirements of the State Department of Fish and Wildlife Design Manual for Culverts, or more restrictive local standards.

c. Bridges or other crossings must allow for uninterrupted downstream movement of wood and gravel, must be as close to perpendicular to the stream as possible, be designed to minimize fill and to pass one-hundred-year flood flows.

d. Wherever feasible as part of an alteration, culverts that do not meet fish habitat requirements must be removed or replaced as part of the project.

e. Alteration projects shall not result in blockage of side channels. If at the time of alteration there are known barriers to fish passage into side channels, they shall be removed.

f. For any alteration of a salmonid-bearing stream whose channel is subject to migration, bioengineered (“soft”) armoring of stream banks is required. For alteration of other fish-bearing streams, soft armoring of stream banks is required wherever possible, in order to allow for woody debris recruitment, gravels for spawning and creation of side channels.

E. Interpretation of FIRM Boundaries. Make interpretations where needed, as to exact location of the boundaries of the areas of special flood hazards (for example, where there appears to be a conflict between a mapped boundary and actual field conditions). The person contesting the location of the boundary shall be given a reasonable opportunity to appeal the interpretation as provided in this chapter.

F. The director shall have the authority to serve a person a stop work order if an action is being undertaken in violation of this chapter. If a portion of a project is in violation of this chapter, the director may issue a stop work order for the entire project. Failure to comply with the terms of a stop work order shall result in enforcement actions described in CMC 16.21.070. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.150 Appeals.

A. The hearing examiner shall hear and decide appeals and requests for variances from the requirements of this chapter.

B. The hearing examiner shall hear and decide appeals when it is alleged there is an error in any requirement, decision or determination made by the community development director in the enforcement of administration of this chapter; provided, however, such appeal must be in writing and filed within ten days of the community development director’s decision being appealed from.

C. Those aggrieved by the decision of the hearing examiner, or any taxpayer, may appeal such decision to the Lewis County superior court but such appeal must be made within twenty-one days of the decision being appealed from.

D. 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:

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 after 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 facts of subsection (D) 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.

F. The community development director shall maintain the records of all appeal actions and report any variances to the Federal Insurance Administration upon request. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.160 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 CMC 16.21.150(D)(1) through (11) have been fully considered. As the lot size increases beyond the one-half acre, 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. A 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 CMC 16.21.150(D), or conflict with existing local laws or ordinances.

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 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 it 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 CMC 16.21.170(A) and (B).

H. 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 floor 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. 2232 § 9 (Exh. A), 2009).

16.21.165 Zero-rise floodplain overlay.

The intent of this section is to preserve areas of the floodplain most prone to flooding and has no physical protection during flooding. To best protect human life, health and property, the following restrictions are placed on development within this area known as the zero-rise floodplain overlay.

A. Permitted Uses.

1. Single-family dwellings;

2. Wildlife preserves;

3. Agricultural structures and uses;

4. Private and public parks, greenbelts and open space for active or passive recreation or enjoyment. (Note: Whenever a park or open space is created as an integral part of a subdivision or development, such park or open space shall be designated an open space/public facilities district on the official zoning map);

5. Flood damage reduction facilities, such as levees, revetments and pumping stations;

6. Stream bank stabilization structures, aquatic areas, and wetland restoration projects;

7. Municipal facilities required for local service;

8. Roads, highways and streets, both established and new;

9. Maintenance of roads, highways and streets;

10. Bridge piers and abutments;

11. Boat launches and related recreation structures; and

12. Other unlisted, similar or related uses, and criteria for determination of similarity or relatedness, as follows:

a. Uses similar to, or related to, those listed in this subsection (A) are permitted upon a finding of the enforcing officer and/or the site plan review committee that a particular unlisted use does not conflict with the intent of this chapter or the policies of the Centralia comprehensive plan;

b. The criteria for such finding of similarity shall include, but not be limited to, the following:

i. That the proposed use is appropriate in this district;

ii. That the development standards for permitted uses can be met by the proposed use; and

iii. That the public need is served by the proposed use.

B. Prohibited Uses. Uses other than those identified or described in subsection (A) of this section are prohibited.

C. Filling and Grading. Development shall not reduce the effective base flood storage volume of the zero-rise floodplain overlay.

1. Grading or other activity in the zero-rise floodplain overlay which would reduce the effective storage volume must be mitigated by creating compensatory mitigation. When development is permitted under this subsection, it shall be designed to meet the compensatory mitigation requirements in CMC 16.21.170(F).

2. Any fills over five hundred cubic yards require a zero-rise analysis.

3. Excavation shall not be counted as compensating for fill if such areas will be filled with water in nonstorm winter conditions.

D. The following uses and activities are not subject to the requirements of subsection (C) of this section:

1. Excavation and fill necessary to plant new trees or vegetation.

2. Excavation and fill required for the construction of public detention facilities or structures, and other facilities specifically designed to reduce or mitigate flood impacts. Such facilities shall not be used to create new buildable lands.

3. New culverts, stream crossings, and transportation projects may be permitted only if designed as balanced cut and fill projects or designed to not raise the base flood elevation.

E. Zero-Rise Floodplain Overlay General Requirements.

1. The provisions of this section apply to lands located within the zero-rise floodplain overlay depicted on the zero-rise floodplain overlay map, adopted May 12, 2009. Development requirements in this section shall be in addition to those of the underlying zone and, where explicitly noted, supersede the underlying zoning. If implementation of this section conflicts with the other provisions of the Centralia Municipal Code, state or federal law, the more restrictive requirement applies.

2. Development activity must not reduce the effective storage volume of the floodplain.

3. Development proposals, including permitted new construction or reconstruction, must not cause an increase in the one-hundred-year flood elevation.

4. All temporary structures or materials hazardous to public health and safety must be removed or secured during the flood season, from September 30th to May 1st.

F. Construction/Building.

1. The designated construction period is May 1st to September 30th. Any construction preformed outside this period, during the flood season, must be permitted by the community development director dependent upon weather conditions. These renewable permits will be issued at ten-day increments throughout the flood season. There shall be no limit to the number of temporary flood season building permits issued for any single project.

2. Agricultural Structures. The lowest floor in an agricultural structure may be located at the base flood elevation or higher; provided, that the structure is 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 professional engineer in the state of Washington or must meet or exceed the following minimum criteria:

a. A minimum of two openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided;

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

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

3. New residential or nonresidential structures shall be constructed at least three feet above the BFE.

G. Zero-Rise Analysis.

1. When it is determined that a proposed project is located within a zero-rise floodplain overlay area, a zero-rise analysis shall be required to determine that no increase in base flood elevation, displacement of flood volume, or flow conveyance reduction will occur as a result of the development or fill. A zero-rise analysis may be waived at the discretion of the director if it can be found that impacts from a project will not contribute to an overall rise to the zero-rise floodplain overlay area.

2. The zero-rise analysis shall be conducted utilizing HEC-RAS modeling methodology or other alternative methodology approved by the city. The proposed development may need to be reduced or specially engineered (such as utilizing piers or pilings) to achieve zero rise.

3. The zero-rise analysis shall be prepared, signed, and dated by a professional engineer.

4. When structures are elevated by piers or pilings and no fill is placed in the zero-rise floodplain overlay area, the requirement to submit a zero-rise analysis may be waived at the director’s discretion. (Ord. 2338 § 3, 2014: Ord. 2269 § 1, 2011: Ord. 2232 § 9 (Exh. A), 2009).

16.21.170 General standards.

In all areas of special flood hazard, the following standards are required:

A. Anchoring.

1. All new construction and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure.

2. All manufactured homes shall 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, the use of over-the-top or frame ties to ground anchors. (Reference FEMA’s Manufactured Home Installation in Flood Hazard Areas guidebook for additional techniques).

B. Construction Materials and Methods.

1. All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.

2. All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage.

3. Electrical, heating, ventilation, plumbing, and air-conditioning equipment and other service facilities shall be elevated to a minimum of one foot above the base flood elevation.

C. Utilities.

1. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system;

2. Water wells shall be located on high ground that is not in the floodway;

3. 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

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

D. Subdivision Proposals.

1. All subdivision proposals shall be consistent with the need to minimize flood damage;

2. All subdivision proposals shall have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage;

3. All subdivision proposals shall have adequate drainage provided to reduce exposure to flood damage;

4. Where base flood elevation and floodway delineation (if applicable) 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 twenty-five lots or five acres (whichever is less); and

5. Substantial improvement to existing residential structures shall be permitted in the zero-rise floodplain outside the FEMA floodway where the footprint will not be increased.

E. Review of Building Permits. Where elevation data is not available either through the Flood Insurance Study, FIRM, or another authoritative source, applications for building permits shall be reviewed to assure that proposed construction will be reasonably safe from flooding. The test of reasonableness is a local judgment and includes the use of historical data, high water marks, photographs of past flooding, and any other relevant studies, data, or information that may be required by the director to make a determination that the proposed construction will be reasonably safe from flooding. Failure to elevate at least three feet for residential structures and one foot for nonresidential structures above the highest adjacent grade in these zones may result in higher insurance rates.

F. Compensatory Mitigation (Fill in the Floodplain).

1. The amount of compensatory mitigation required within the floodplain is determined by the following:

a. Zero to five hundred cubic yards of fill: No mitigation is required.

b. Five hundred one plus cubic yards of fill: Mitigation is required which is a zero-rise or a minimum of a one-to-one ratio, which means for filling and grading new excavated storage volume shall be equivalent to the flood storage capacity eliminated by filling or grading. “Equivalent” shall mean that the storage removed shall be replaced by equal live storage volume.

2. Mitigation storage may be located off site, but it shall be located within the city of Centralia jurisdictional boundaries unless the director approves other alternatives if they are within the same drainage areas.

3. All off-site storage shall be documented by a legally binding contract that maintains the storage in perpetuity. This document shall be recorded with the Lewis County assessor’s office.

4. Fees in lieu of compensatory mitigation for any fills over five hundred one cubic yards of fill may be permitted through the city’s SEPA process. The collected funds shall be used for an established flood protection enhancement program or mitigation project as listed in the city’s adopted comprehensive floodplain management plan. The fee shall be set at ten dollars per cubic yard of fill material that will be located within the floodplain and shall be calculated based on the total amount of fill per the entire project. All enhancement programs or mitigation projects shall decrease flooding damage to businesses and residential properties within the city of Centralia or its urban growth area. At the discretion of the director through the SEPA process, the mitigation fee may be reduced if mitigation techniques or a project is demonstrated to reduce flooding in the city or its urban growth area. (Ord. 2532 § 2, 2023; Ord. 2508 § 1, 2022; Ord. 2269 § 2, 2011: Ord. 2232 § 9 (Exh. A), 2009).

16.21.175 Erosion and sediment control.

All new development and redevelopment that includes land disturbing activities equal to or greater than one-half acre shall comply with erosion and sediment control requirements, subsections (A)(1) through (14) of this section. All new development or redevelopment that includes land disturbing activities less than one-half acre shall comply with subsection (B) of this section. Compliance with the erosion and sediment control requirements shall be demonstrated through implementation of an approved erosion and sediment control plan. The following erosion and sediment control requirements shall be met:

A. Sites Equal to or Greater Than One-Half Acre in Size.

1. All exposed and unworked soils shall be stabilized by suitable application of BMPs. From October 1st to April 30th, no soils shall remain unstabilized for more than two days. From May 1st to September 30th, no soils shall remain unstabilized for more than seven days. Prior to leaving the site, stormwater runoff shall pass through a sediment pond or sediment trap, or other appropriate BMPs.

2. In the field, mark clearing limits and/or easements, setbacks, sensitive/critical areas and their buffers, trees and drainage courses.

3. Properties adjacent to the project site shall be protected from sediment deposition through the deployment of silt fencing or other approved appropriate BMPs.

4. Sediment ponds and traps, perimeter dikes, sediment barriers, and other BMPs intended to trap sediment on site shall be constructed as a first step in grading. These BMPs shall be functional before land disturbing activities take place. Earthen structures such as dams, dikes, and diversions shall be seeded and mulched according to the timing indicated in subsection (A)(1) of this section.

5. Cut and fill slopes shall be designed and constructed in a manner that will minimize erosion. In addition, slopes shall be stabilized in accordance with the erosion and sediment control requirement indicated in subsection (A)(1) of this section.

6. Properties and waterways downstream from development sites shall be protected from erosion due to increases in volume, velocity, and peak flow rate of stormwater runoff from the project site.

7. All temporary on-site conveyance channels shall be designed, constructed and stabilized to prevent erosion from the expected velocity of flow from a two-year, twenty-four-hour frequency storm for the developed condition. Stabilization adequate to prevent erosion of outlets, adjacent stream banks, slopes and downstream reaches shall be provided at all outlets of all conveyance systems.

8. All storm drain inlets made operable during construction shall be protected so that stormwater runoff shall not enter the conveyance system without first being filtered or otherwise treated to remove sediment.

9. The construction of underground utility lines shall be subject to the following criteria:

a. Where feasible, no more than five hundred feet of trench shall be opened at a time.

b. Where consistent with safety and space considerations, excavated material shall be placed on the uphill side of trenches.

c. Trench dewatering devices shall discharge into a sediment trap or sediment pond.

10. Wherever construction vehicle access routes intersect paved roads, provisions must be made to minimize the transport of sediment (mud) onto the paved road. If sediment is transported onto a road surface, the roads shall be cleaned thoroughly at the end of each day. Sediment shall be removed from roads by shoveling or sweeping and be transported to a controlled sediment disposal area. Street washing shall be allowed only after sediment is removed in this manner.

11. All temporary erosion and sediment control BMPs shall be removed within thirty days after final site stabilization is achieved or after temporary BMPs are no longer needed. Trapped sediment shall be removed and stabilized on site. Disturbed soil areas resulting from removal shall be permanently stabilized.

12. Dewatering devices shall discharge into a sediment trap or sediment pond.

13. All pollutants other than sediment that occur on site during construction shall be handled and disposed of in a manner that does not cause contamination of stormwater.

14. All temporary and permanent erosion and sediment BMPs shall be maintained and repaired as needed to assure continued performance of their intended function. All maintenance and repair shall be conducted in accordance with all state and local regulations.

B. Sites Less Than One-Half Acre in Size.

1. Construction vehicle access shall be, whenever possible, limited to one route. Access points shall be stabilized with quarry spall or crushed rock to minimize the tracking of sediment onto public roads.

2. All exposed soils shall be stabilized by suitable application of BMPs, including but not limited to sod or other vegetation, plastic covering, mulching, or application of ground base on areas to be paved. All BMPs shall be selected, designed and maintained in accordance with an approved manual. From October 1st to April 30th, no soils shall remain unstabilized for more than two days. From May 1st to September 30th, no soils shall remain unstabilized for more than seven days.

3. Adjacent properties shall be protected from sediment deposition by appropriate use of vegetation buffer strips, sediment barriers or filters, dikes or mulching, or by a combination of these measures and other appropriate BMPs.

4. All erosion and sediment control BMPs shall be regularly inspected and maintained to ensure continued performance of their intended function.

5. As required by the director, other appropriate BMPs to mitigate the effects of increased runoff shall be applied. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.180 Specific standards.

In all areas of special flood hazards where base flood elevation data has been provided as set forth in CMC 16.21.060 or 16.21.140(B), the following provisions are required:

A. Residential Construction.

1. New construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated three feet or more above base flood elevation.

2. Fully enclosed areas below the lowest floor that are subject to flooding are allowed in the one-hundred-year floodplain provided they meet the design requirements of 44 CFR 60.3(a)(3) and 60.3(c)(2) and (c)(5) of the NFIP regulations. The structure shall be designed and adequately anchored to resist flotation, collapse, and lateral movement resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy. Hydrostatic loads and the effects of buoyancy may be addressed through the required openings discussed in subsection (A)(2)(a) of this section. Because of hydrodynamic loads, crawlspaces shall not be constructed in areas with flood velocities greater than five feet per second unless the design is reviewed and certified by a qualified design professional, such as a registered architect or professional engineer, or meets the following minimum criteria:

a. A minimum of two openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided;

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

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

3. Crawlspace Construction.

a. Portions of the building below the BFE shall be constructed with materials resistant to flood damage. This includes not only the foundation walls of the crawlspace used to elevate the building, but also any joists, insulation, or other materials that extend below the BFE.

b. Any building utility systems including equipment, ductwork, mechanical items, etc., shall be elevated one foot above BFE.

c. The interior grade of a crawlspace below the BFE shall not be more than two feet below the lowest adjacent exterior grade (LAG).

d. The height of the below-grade crawlspace, measured from the interior grade of the crawlspace to the top of the crawlspace foundation wall, shall not exceed four feet at any point.

e. The height limitation is the maximum allowable unsupported wall height according to the engineering analyses and building code requirements for flood hazard areas. This limitation also prevents these crawlspaces from being converted into habitable spaces.

f. There shall be an adequate drainage system that removes floodwaters from the interior area of the crawlspace. The enclosed area shall be drained within a reasonable time after a flood event. The type of drainage system may vary because of the site gradient and other drainage characteristics, such as soil types. Possible options include natural drainage through porous, well-drained soils and drainage systems such as perforated pipes, drainage tiles, or gravel or crushed stone drainage by gravity or mechanical means.

g. The velocity of floodwaters at the site shall not exceed five feet per second for any crawlspace. For velocities in excess of five feet per second, other foundation types shall be used.

h. Below-grade crawlspace construction in accordance with the requirements listed above shall not be considered basements.

B. Nonresidential Construction. New construction and substantial improvement of any commercial, industrial, or other nonresidential structure shall either have the lowest floor, including basement, elevated one foot (see subsection (B)(4) of this section) or more* above the level of the base flood elevation or, together with attendant utility and sanitary facilities, shall:

1. Be floodproofed in such a manner that all areas located one foot above the base flood elevation or lower on the structure are watertight with walls substantially impermeable to the passage of water;

2. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy;

3. Be certified by a registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting provisions of this subsection based on their development or review of the structural design, specifications, and plans. Such certifications shall be provided to the community development director; and

4. Nonresidential structures that are elevated, but not floodproofed, shall meet the same standards for space below the lowest floor as described in subsection (A)(2) of this section.

C. 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 at the site. Floodproofing and sealing measures shall 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 floodplain shall be provided to all critical facilities to the extent possible. No new construction of a critical facility shall be permitted within the zero-rise floodplain overlay.

D. Manufactured Homes.

1. All manufactured homes to be placed or substantially improved within special flood hazard areas on the community’s FIRM, on sites:

a. Outside of a manufactured home park or subdivision;

b. In a new manufactured home park or subdivision;

c. In an expansion to an existing manufactured home park or subdivision; or

d. In an existing manufactured home park or subdivision on which a manufactured home has incurred substantial damage as the result of a flood;

shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is three feet or more above the base flood elevation and shall be securely anchored to an adequately designed foundation system in accordance with the provisions of CMC 16.21.170(A).

2. Manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision within special flood hazard areas on the community’s FIRM that are not subject to the above manufactured home provisions shall be elevated so that the lowest floor of the manufactured home and all attendant utilities are elevated one foot above the base flood elevation.

E. Elevation or Floodproof Certificate Required. Prior to the issuance of an occupancy permit for any new construction or substantially improved structure in a special flood hazard area, an elevation certificate or floodproof certificate shall be required. Residential structures shall be elevated. Commercial structures have the option of elevating or floodproofing. Certificates shall be on the most recent form provided by the National Flood Insurance Program and shall be submitted to the community development department for approval. Certificates shall be prepared by a land surveyor, professional engineer, or architect authorized by law to certify elevation information. In order to properly certify new construction or substantial improvements, the individual or agency shall perform and document three separate elevation surveys, including:

1. Setting a benchmark and one-hundred-year flood elevation on the construction site prior to construction;

2. Checking the lowest floor grade at the time of foundation inspection prior to approval to pour concrete for elevation projects and prior to final inspection for floodproofing projects; and

3. The as-built lowest finished floor elevation or floodproof elevation. (Ord. 2532 § 3, 2023; Ord. 2508 § 1, 2022; Ord. 2453 § 2, 2020: Ord. 2338 § 4, 2014: Ord. 2232 § 9 (Exh. A), 2009).

*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 floodproofed to one foot above the base flood level will be rated as at the base flood level).

16.21.185 Recreational vehicles.

Recreational vehicles placed on sites within special flood hazard areas on the community’s FIRM shall either:

A. Be on the site for fewer than one hundred eighty consecutive days per calendar year; and

B. Be fully licensed and ready for highway use, on its 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 CMC 16.21.180 and the elevation and anchoring requirements for manufactured homes. (Ord. 2508 § 1, 2022; Ord. 2232 § 9 (Exh. A), 2009).

16.21.190 Floodways.

Located within areas of special flood hazard established in CMC 16.21.060 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:

A. Prohibit encroachments, including fill, new construction, substantial improvements, and other development unless certification by a registered professional engineer or architect is provided demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment shall not result in any increase in flood levels during the occurrence of the base flood discharge;

B. Construction or reconstruction of residential structures is prohibited within designated floodways, except for:

1. Repairs, reconstruction, or improvements to a structure which do not increase the ground floor area; and

2. Repairs, reconstruction or improvements to a structure, the cost of which does not exceed fifty percent of the market value of the structure either (a) before the repair, reconstruction, or repair is started, or (b) if the structure has been damaged, and is being restored, before the damage occurred. Work done on structures to comply with existing health, sanitary, or safety codes or to structures identified as historic places shall not be included in the fifty percent;

C. If subsection (A) of this section is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of CMC 16.21.170 through 16.21.210;

D. Any proposed fill or construction within the floodway must meet all applicable state and federal regulations. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.200 Wetlands management.

To the maximum extent possible, avoid the short- and long-term adverse impacts associated with the destruction or modification of wetlands, especially those activities which limit or disrupt the ability of the wetland to alleviate flooding impacts. The following process should be implemented:

A. Review proposals for development within base floodplains for their possible impacts on wetlands located within the floodplain in accordance with this chapter;

B. Ensure that development activities in or around wetlands do not negatively affect public safety, health and welfare by disrupting the wetlands’ ability to reduce flood and storm drainage;

C. Request technical assistance from the Department of Ecology in identifying wetland areas. Existing wetland map information from the National Wetlands Inventory (NWI) can be used in conjunction with the community’s FIRM to prepare an overlay zone indicating critical wetland areas deserving special attention. (Ord. 2232 § 9 (Exh. A), 2009).

16.21.210 Encroachments.

The cumulative effect of any proposed development, where combined with all other existing and anticipated development, shall not increase the water surface elevation of the base flood more than one foot at any point. (Ord. 2232 § 9 (Exh. A), 2009).