Chapter 17.22 FREQUENTLY FLOODED AREAS – FLOOD HAZARD ZONE (FHZ)

A. The flood hazard areas of Chehalis are subject to periodic inundation which may result 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 climatic conditions and the cumulative effect of natural and manmade obstructions in areas of special flood hazards which increase flood heights and velocities, and may damage uses in other areas. Uses that are inadequately floodproofed, elevated or otherwise protected from flood damage also contribute to the flood loss. [Ord. 849B § 3, 2009.]

17.22.020 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 to:

A. Protect human life and health;

B. Minimize expenditure of public money and costly flood control projects;

C. Minimize the need for rescue and relief efforts associated with flooding and generally undertaken at the expense of the general public;

D. Minimize prolonged business interruptions;

E. 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. 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. Ensure that potential buyers are notified that property is in an area of special flood hazard; and

H. Ensure that those who occupy the areas of special flood hazard assume responsibility for their actions. [Ord. 849B § 3, 2009.]

17.22.030 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; and

E. Preventing or regulating the construction of flood barriers which will unnaturally divert floodwaters or which may increase flood hazards in other areas. [Ord. 849B § 3, 2009.]

17.22.035 Zero-rise policy.

A. A “zero-rise policy” means any project in a floodplain must be reviewed to determine to not increase flood heights.

B. Any fill material over 500 cubic yards cumulatively placed within a floodplain shall require compensatory excavation necessary to achieve zero net rise.

C. Any fill greater than 500 cubic yards as measured cumulatively within the 100-year floodplain shall require a P.E. stamped engineering report identifying the findings on the impact of the BFE in terms of impacting the height of the BFE based on the proposed fill project. The engineer will evaluate the impact referencing the latest HEC-RAS hydraulic modeling or other available modeling consistent with current hydraulic modeling.

D. If an engineering report shows a rise in the BFE, the applicant shall provide compensatory excavation. The compensatory site must remain as a compensatory site in perpetuity. However, if the fill site is behind the airport levee, the compensatory site must function as such, or until the levee is raised utilizing NGVD29 with a BFE of 182 feet. It shall be the applicant’s responsibility to obtain a compensatory fill site and secure such site prior to commencing fill.

E. The compensatory fill site shall be recorded as such with the Lewis County auditor.

F. The requirement of compensatory fill is waived if an engineering report is provided from a professional engineer stating there will be no rise in the BFE due to the proposed fill. The report shall be stamped by the P.E.

G. If the engineering report shows a rise in the base flood elevation (BFE) due to the proposed fill, in lieu of compensatory excavation, the applicant may contribute funds for flood storage mitigation and aquatic species enhancement projects within the Chehalis River floodplain. Said fee will be calculated per cubic yard of material, utilizing prevailing wage rates. Said fee will need to be periodically updated to meet future prevailing wage rates or other costs that may fluctuate. Said fees shall be deposited into the city’s compensatory excavation mitigation fund, which will be utilized solely for capital projects that provide flood storage and habitat enhancement that are on the Chehalis River and its associated floodplain within the city of Chehalis limits. Said fee shall be added to the city’s fee schedule. [Ord. 982B § 1, 2017; Ord. 958B § 2, 2016.]

17.22.040 Flood hazard zone created.

The areas of special flood hazard identified by the Federal Insurance Administration in a scientific and engineering report entitled “The Flood Insurance Study for Chehalis,” dated July 17, 2006, (Appendix Chapter W), with associated flood insurance rate maps (FIRMs), is hereby adopted by reference and declared to be a part of this chapter. The FIRMs are on file at the Community Development Department, 1321 S. Market Boulevard. The city of Chehalis shall also be empowered to create special flood hazard zones. Best available information shall also be used to determine the flood hazard zone based on elevation data, topographic information and flood-of-record data. [Ord. 858B § 10, 2010; Ord. 849B § 3, 2009.]

17.22.050 Compliance.

This chapter shall apply to all areas subject to a base flood and/or designated as an area of special flood hazard within the jurisdiction of the city. All development shall hereafter proceed in compliance with the terms of this chapter and other applicable regulations. [Ord. 849B § 3, 2009.]

17.22.060 Abrogation and greater restrictions.

This chapter is not intended to repeal, abrogate or impair any existing easements, covenants or deed restrictions which may be enforced by private action among the affected parties. This chapter establishes the standards for public action. [Ord. 849B § 3, 2009.]

17.22.070 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. 849B § 3, 2009.]

17.22.080 Criteria for land management and use.

The standards and definitions contained in this title shall be the minimum standards administered and enforced for flood damage reduction within the city and its UGA. [Ord. 849B § 3, 2009.]

17.22.090 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 unpredictable occasions. Flood heights may be increased by manmade or natural causes. This chapter does not warrant or imply that land outside the areas of special flood hazards or uses permitted within such areas will be free from flooding or flood damages. The city and/or any of its officers or employees shall not be responsible for the accuracy of materials submitted for review and do not guarantee that flood damage will not result from reliance on this chapter or any administrative decision lawfully made thereunder. [Ord. 849B § 3, 2009.]

17.22.100 Development permit required.

A. A development permit shall be obtained before any construction or development begins within any special flood hazard zone established in CMC 17.22.040. The permit shall be for all structures, including manufactured homes, as set forth in the definitions in Chapter 17.06 CMC and for all development including fill and other activities, also as set forth in the definitions in Chapter 17.06 CMC.

B. In addition to the standard development permit application, a JARPA application (see Appendix Chapter B) shall be required for any development or site work which is not constructed to the flood protection elevation within any flood hazard zone (the 100-year floodplain). If such application is not otherwise required to comply with Chapter 17.18 or 17.24 CMC, no fee shall be required for a JARPA form submitted only to satisfy the requirement in this section for such information. [Ord. 849B § 3, 2009.]

17.22.110 Use of other base flood data.

When base flood elevation data has not been provided on official maps, the administrator shall obtain, review, and reasonably utilize any base flood elevation and floodway data available from a federal, state, local, or other source, including topographic data, in order to administer this chapter, including application of such information to subdivisions and other proposed development. [Ord. 849B § 3, 2009.]

17.22.120 Information to be obtained and maintained.

A. Where base flood elevation is provided through the flood insurance study, the developer shall provide to the building official the actual elevation, certified by a licensed land surveyor (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. The building official shall maintain this elevation certificate in a permanent file.

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

1. The developer shall provide to the building official the actual elevation, certified by a licensed land surveyor. The building official shall obtain and record the elevation (in relation to mean sea level) to which the structure was floodproofed; and

2. The building official shall maintain such floodproofing certifications.

C. The building official shall maintain for public inspection all records pertaining to development within the flood hazard zone. [Ord. 849B § 3, 2009.]

17.22.130 Variance criteria (flood hazard zone).

A. Generally, a variance from the elevation standard may be issued by the hearing examiner for new construction, additions, and substantial improvements of habitable structures 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; and provided, that floodproofing is required as a condition of such a variance. As the lot size increases, the technical justification required for issuing the variance increases.

B. Generally, variance requests for habitable structures shall be heard and decided by the hearing examiner; however, the administrator may grant flood elevation variances under the following circumstances:

1. The examiner has previously granted a flood elevation variance for the subject property, and the conditions of record, if any, are incorporated into the conditions attached to the subject proposal;

2. The administrator finds that the proposal is consistent with the policies outlined in CMC 17.22.020, and with the development requirements of this section through CMC 17.22.190;

3. The methods of floodproofing are reasonable and afford maximum protection from flood damage, and are consistent with any conditions of record;

4. The applicant must attend a DRC meeting where the variance criteria and the notice to the applicant are made a matter of public record.

C. Generally, a variance from the elevation standard may be issued by the administrator for nonhabitable accessory structures if:

1. The administrator finds that the proposal is consistent with the policies outlined in CMC 17.22.020, and with the development requirements of this section through CMC 17.22.190;

2. The methods of floodproofing are reasonable and afford maximum protection from flood damage, and are consistent with any conditions of record;

3. The applicant must attend a DRC meeting where the variance criteria and the notice to the applicant are made a matter of public record.

D. Variances may be issued by the administrator 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.

E. Variances shall not be issued within a designated floodway except for nonhabitable accessory structures designed by a licensed engineer to comply with all other applicable regulations in addition to this section.

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

G. 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; and

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 17.22.020, or conflict with existing local laws or ordinances.

H. 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.

I. Variances may be issued for nonresidential buildings in very limited circumstances to allow a lesser degree of floodproofing than watertight or dry-floodproofing (e.g., wet-floodproofing) where it can be determined that such action will have low damage potential, complies with all other applicable variance criteria, and otherwise complies with CMC 17.22.140 and 17.22.150.

J. 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. 849B § 3, 2009.]

17.22.140 Anchoring.

All structures, including manufactured homes, must likewise be anchored to prevent flotation, collapse, or lateral movement and shall be constructed or 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. Anchoring methods which are not described in the adopted edition of the uniform codes shall be engineered. [Ord. 849B § 3, 2009.]

17.22.150 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, ductwork, and air-conditioning equipment and other similar service facilities shall be elevated or otherwise located so as to prevent water from entering or accumulating within the components during conditions of flooding to the required flood protection elevation.

D. Additional Requirements for Below-Grade Crawlspaces (FEMA Technical Bulletin (TB) 11-01).

1. The interior grade of a crawlspace below the BFE must not be more than two feet below the lowest adjacent exterior grade (LAG), shown as D in Figure 3 of TB 11-01;

2. The height of the below-grade crawlspace, measured from the interior grade of the crawlspace to the top of the crawlspace foundation wall, must not exceed four feet (shown as L in Figure 3 of TB 11-01) at any point for unsupported wall height of plain masonry walls. The height limitation is the maximum allowable unsupported wall height of plain masonry walls according to the engineering analyses and International Building Code requirements for flood hazard areas;

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

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

5. Below-grade crawlspace construction in accordance with the requirements listed above will not be considered basements. [Ord. 849B § 3, 2009.]

17.22.160 Utilities.

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

B. New and replacement sanitary sewer 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. On-site water wells shall be located on high ground that is not in the floodway. [Ord. 849B § 3, 2009.]

17.22.170 Flood protection elevation.

A. Development within special flood hazard areas which requires elevation or floodproofing shall be elevated or floodproofed to or above the flood protection elevation (base flood elevation plus one foot or base flood elevation plus three feet for critical facilities), or to the flood of record elevation at the specific location as identified by the city, whichever minimum elevation is higher.

B. Where elevation data is not available either through the Flood Insurance Study, FIRM, or from another authoritative source, applications for building permits shall be reviewed to assure that proposed construction will be reasonably safe from flooding. The test of reasonableness is a local judgement and includes use of historical data, high water marks, photographs of past flooding, etc., where available. [Ord. 849B § 3, 2009.]

17.22.180 Residential construction.

A. New construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated to the flood protection elevation as described in CMC 17.22.170.

B. Fully enclosed areas below the lowest floor that are subject to flooding are prohibited, or shall be designed to automatically equalize hydrostatic 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 the lowest grade; and

3. Openings may be equipped with screens, louvers, or other coverings or devices; provided, that they permit the automatic entry and exit of floodwaters, and do not become obstructed during a flood event. [Ord. 849B § 3, 2009.]

17.22.190 Nonresidential construction.

New construction and substantial improvement of any commercial, industrial, or other nonresidential structure shall either have the lowest floor, including basement, elevated to the flood protection elevation; or, together with attendant utility and sanitary facilities, shall:

A. Be floodproofed so that below the flood protection elevation the structure is watertight with walls substantially impermeable to the passage of water;

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

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

D. Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in CMC 17.22.180(B); and

E. 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. 849B § 3, 2009.]

17.22.200 Manufactured homes.

All manufactured homes to be placed or substantially improved within zones A1-30, AH, and AE shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is at the flood protection elevation as described in CMC 17.22.170 and be securely anchored to an adequately anchored foundation system (CMC 17.22.140). [Ord. 849B § 3, 2009.]

17.22.210 Critical facilities.

A. Critical facilities should be afforded additional flood protection due to their nature.

B. Construction of new critical facilities shall be, to the extent possible, located outside the limits of the 100-year floodplain as identified on the city’s FIRM. Construction of new critical facilities shall be permissible within the 100-year frequency floodplain if no feasible alternative site is available. Critical facilities constructed within the 100-year frequency floodplain shall have the lowest floor elevated to three feet or more above the level of the 100-year frequency floodplain. Floodproofing and sealing measures must be taken to ensure that toxic substances will not be displaced by or released into floodwaters.

C. Access routes elevated to or above the level of the 100-year frequency floodplain shall be provided to all critical facilities to the extent possible. [Ord. 849B § 3, 2009.]

17.22.220 Floodways.

Located within areas of special flood hazard 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. New development, substantial improvements and other development may be allowed only if certification by a registered professional engineer or architect is provided demonstrating, through hydrologic and hydraulic analysis performed in accordance with standard engineering practice, that the proposed encroachment would not result in any increase in flood levels during the occurrence of the base flood discharge; and

B. All new development and substantial improvements shall comply with all applicable flood hazard reduction provisions of this title and applicable state and federal regulations. [Ord. 849B § 3, 2009.]

17.22.225 Alteration of watercourses.

A. The city shall notify adjacent communities and the Department of Ecology prior to any alteration or relocation of a watercourse, and submit evidence of such notification to the Federal Insurance Administration.

B. Any approval of any alteration or relocation of any watercourse shall include a program of maintenance of such watercourse so that the flood- carrying capacity is not diminished. [Ord. 849B § 3, 2009.]

17.22.230 Special flood hazard areas with designated floodways.

When a regulatory floodway for a stream has been designated, the following shall apply:

A. Construction or reconstruction of residential structures shall be 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 50 percent of the market value of the structure either:

a. Before the repair, reconstruction, or improvement is started; or

b. If the structure has been damaged, and is being restored, before the damage occurred.

B. Work done on structures to comply with existing health, sanitary, or safety codes which have been identified by the local code enforcement official and which are the minimum necessary, or to structures identified as historic places, shall not be included in the 50 percent determination. [Ord. 849B § 3, 2009.]

17.22.240 Special flood hazard areas without designated floodways.

When a regulatory floodway or stream has not been designated, the following shall apply:

A. Applicants for new construction and substantial improvements shall reasonably utilize the best available information from a federal, state, and/or other source to:

1. Consider the cumulative effect of existing, proposed, and anticipated future development; and

2. Determine that the increase in water surface elevation of the base flood will not be more than one foot at any point in the community.

B. Building and development near streams without a designated floodway shall comply with the requirements of:

1. Title 44 Code of Federal Regulations; and

2. The National Flood Insurance Program regulations. [Ord. 849B § 3, 2009.]

17.22.250 Standards for shallow flood areas (AO zones).

Shallow flooding areas appear on FIRM as AO zones with depth designations. The base flood depths in these zones range from one to three feet 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) elevated to one foot above the highest adjacent grade of the building site, to one foot above the depth number specified in the FIRM (at least two feet if no depth number is specified);

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

1. Have the lowest floor (including basement) elevated to one foot above the highest adjacent grade of the building site, or one foot above the depth number specified in 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 the flood protection elevation 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;

C. Require adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures. [Ord. 849B § 3, 2009.]