14.22.150 - General standards.

In all areas of special flood hazards as shown on the Flood Insurance Rate Maps (FIRM) and as defined in Section 14.22.040, the following standards are required:

(1)

Anchoring.

(A)

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

(B)

All manufactured homes must likewise be anchored to prevent flotation, collapse, or lateral movement, and shall be installed using methods and practices that minimize flood damage. Anchoring methods may include, but are not limited to, use of over-the-top or frame ties to ground anchors. (Reference "FEMA 85—Manufactured Home Installation in Flood Hazard Areas" guidebook for additional techniques.)

(2)

Construction Materials and Methods.

(A)

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

(B)

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

(C)

Electrical, heating, ventilation, plumbing, and air conditioning equipment and other service facilities shall be designed and/or otherwise elevated or located so as to prevent water from entering or accumulating within the components during conditions of flooding.

(3)

Utilities.

(A)

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

(B)

The proposed water well shall be located on high ground that is not in the floodway. It shall be protected from a one hundred-year flood and from any surface or subsurface drainage capable of impairing the quality of the ground water supply (WAC 173-160-171).

(C)

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.

(D)

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

(4)

Subdivision Proposals.

(A)

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

(B)

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

(C)

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

(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).

(E)

Proposals for subdivisions or boundary line adjustments shall not result in any lot which is nonconforming to the provisions of this chapter.

(F)

Subdivisions located entirely within a floodplain shall not be allowed increased density through a performance or clustered subdivision as described in Title 16. A performance subdivision may be used for parcels located partially within a floodplain provided all allowed building areas are located outside the floodplain, and all other regulatory provisions are met. When feasible, lots shall be designed to locate building sites outside the floodplain.

(G)

No parcel shall be created that would require a reasonable use exception or variance before new residential or commercial construction would be allowed.

(5)

Review of Building Permits. Where elevation data is not available either through the Flood Insurance Study or from another authoritative source (Section 14.22.130(2)), applications for building permits shall be reviewed to assure that proposed construction will be reasonably safe from flooding. The test of reasonableness is a local judgement and includes use of historical data, high water marks, photographs of past flooding, etc., where available. Failure to elevate at least two feet above the highest adjacent grade in these zones may result in higher insurance rates.

(Ord. 87-08 Attach. A (part), § 5.1, 2008: Ord. 81-07, Attach. A, § 5.1, 2007: Ord. 9-03, Attach. B8, § 5.1, 2003: Ord. 10-02, Attach. B, § 5.1, 2002: Ord. 16-00, Attach. B, § 5.1, 2000: Ord. 59-91, § 5.1, 1991).

14.22.160 - Specific standards.

In all areas of special flood hazards and special flood risk zones where base flood elevation data has been provided as set forth in Section 14.22.060, Basis for establishing the areas of special flood hazard or Section 14.22.130(b), Use of other base flood data, the following provisions are required:

(1)

Residential Construction.

(A)

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

(B)

Fully enclosed areas below the lowest floor that are subject to flooding are prohibited, or shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or must meet or exceed the following minimum criteria:

(i)

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

(ii)

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

(iii)

Openings may be equipped with screens, louvers, or other coverings or devices provided that they permit the automatic entry an exit of floodwaters.

(C)

If crawlspaces are used and have enclosed areas or floors below the base flood elevation, then the following requirements apply:

(i)

The building must be designed and adequately anchored to resist flotation, collapse, and lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy. Hydrostatic loads and the effects of buoyancy can usually be addressed though the required openings discussed in the next bullet. Because of hydrodynamic loads, crawlspace construction is not recommended in areas with flood velocities greater than five feet per second unless the design is reviewed by a qualified design professional, such as a registered architect or professional engineer. Other types of foundations are recommended for these areas.

(ii)

The crawlspace is an enclosed area below the BFE and, as such, must have openings that equalize hydrostatic pressures by allowing for the automatic entry and exit of floodwaters. The bottom of each flood vent opening can be no more than one foot above the lowest adjacent exterior grade. For guidance on flood openings, see FEMA Technical Bulletin 1-93, Openings in Foundation Walls.

(iii)

Crawlspace construction is not permitted in V zones. Open pile or column foundations that withstand storm surge and wave forces are required in V zones.

(iv)

Portions of the building below the BFE must 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. The recommended construction practice is to elevate the bottom of joists and all insulation above BFE. Insulation is not a flood-resistant material. When insulation becomes saturated with floodwater, the additional weight often pulls it away from the joists and flooring. Ductwork or other utility systems located below the insulation may also pull away from their supports. See the section Flood-Resistant Materials, on page 8 of FEMA Technical Bulletin 1-93. For more detailed guidance on flood-resistant materials see FEMA Technical Bulletin 2-93, Flood-Resistant Materials Requirements.

(v)

Any building utility systems within the crawlspace must be elevated above BFE or designed so that floodwaters cannot enter or accumulate within the system components during flood conditions. Ductwork, in particular, must either be placed above the BFE or sealed from floodwaters. For further guidance on the placement of building utility systems in crawlspaces, see FEMA 348, Protecting Building Utilities from Flood Damage.

(vi)

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 1.

(vii)

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 1) at any point. The height limitation is the maximum allowable unsupported wall height according to the engineering analyses and building code requirements for flood hazard areas (see the section Guidance for Pre-Engineered Crawlspaces, on page 7 of FEMA Technical Bulletin 1-93). This limitation will also prevent these crawlspaces from being converted into habitable spaces.

(viii)

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

Figure 1. Requirements regarding below-grade crawlspace construction.

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.

(ix)

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.

(x)

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

(2)

Nonresidential Construction. New construction and substantial improvement of any commercial, industrial or other nonresidential structure, except those defined as an accessory structure, shall either have the lowest floor, including basement, elevated one foot or more above the level of the base flood elevation; or, together with attendant utility and sanitary facilities, shall:

(A)

Be flood proofed so that below one foot above the base flood level, the structure is watertight with walls substantially impermeable to the passage of water;

(B)

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

(C)

Be certified by a registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting provisions of this subsection based on their development and/or review of the structural design, specifications and plans. Such certifications shall be provided to the official as set forth in Section 14.22.130(3)(B);

(D)

Nonresidential structures that are elevated, not flood proofed, must meet the same standards for space below the lowest floor as described in subsection (1)(B) of this section;

(e)

Applicants floodproofing nonresidential buildings shall be notified that flood insurance premiums will be based on rates that are one foot below the flood proofed level (e.g., a building flood proofed to one foot above the base flood level will be rated as at the base flood level).

(3)

Accessory Structures. Construction or substantial improvement of accessory structures, as defined in Section 14.22.040, shall either have the lowest floor elevated one foot or more above the level of the base flood elevation; or must meet the following criteria:

(A)

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

(B)

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

(C)

Openings may be equipped with screens, louvers, or other coverings provided they may permit the automatic entry and exit of floodwaters.

(D)

Structures shall not be designed for human habitation.

(E)

Structures shall be firmly anchored to prevent flotation which may result in damage to other structures.

(F)

Service facilities such as electrical and heating equipment shall be elevated or flood proofed.

(4)

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. Flood proofing and sealing measures must be taken to ensure that toxic substances will not be displaced by or released into floodwaters. Access routes elevated to or above the level of the base floodplain shall be provided to all critical facilities to the extent possible.

(5)

Manufactured Homes. All manufactured homes to be placed or substantially improved within Zones A1-30, AH, and AE on the community's FIRM shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is one foot or more above the base flood elevation; and is securely anchored to an adequately anchored foundation system in accordance with the provisions of Section 14.22.150(1)(B). In unnumbered A zones, all manufactured homes shall be elevated such that their lowest floor is at least two feet above the highest adjacent elevation.

(6)

Recreational Vehicles. Recreational vehicles placed on sites within Zones A1-30, AH, and AE on the community's FIRM shall either:

(A)

Be on site for fewer than one hundred eighty consecutive days;

(B)

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

(Ord. 87-08 Attach. A (part), § 5.2, 2008: Ord. 81-07, Attach. A, § 5.2, 2007: Ord. 9-03, Attach. B8, § 5.2, 2003: Ord. 10-02, Attach. B, § 5.2, 2002: Ord. 16-00, Attach. B, § 5.2, 2000: Ord. 59-91, § 5.2, 1991).

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

In areas with base flood elevations (but 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. 87-08 Attach. A (part), § 5.3, 2008: Ord. 81-07, Attach. A, § 5.3, 2007).

14.22.180 - 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)

Encroachments are prohibited 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 analysis performed in accordance with standard engineering practice that the proposed encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge.

(2)

Construction or reconstruction of residential structures is prohibited within designated floodways, except for repairs, reconstruction, or improvements to a structures which do not increase the ground floor area; and (ii) 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 which have been identified by the local code enforcement official and which are the minimum necessary to assure safe living conditions or on structures identified as historic places shall not be included in the fifty percent determination.

(3)

If subsection (1) of this section is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this article, Provisions for Flood Hazard Reduction.

(Ord. 87-08 Attach. A (part), § 5.4, 2008: Ord. 81-07, Attach. A, § 5.4, 2007: Ord. 9-03, Attach. B8, § 5.3, 2003: Ord. 10-02, Attach. B, § 5.3, 2002: Ord. 16-00, Attach. B, § 5.3, 2000: Ord. 59-91, § 5.3, 1991).

14.22.190 - Special flood risk zone—Floodplain of the Skokomish River, Vance Creek and tributaries.

(a)

Special Flood Risk Zone. A special flood risk zone is established for the Zones A and A2 floodplain of the Skokomish River, Vance Creek and tributaries, and is illustrated on FIRM map Community Panels #530115-0175D and # 530115-0180D, (both December 1998). The special flood risk zone is designated as a floodway and the entire floodway is designated an avulsion risk area. Construction of a new structure or an expansion of the square foot area of an existing structure is prohibited in this designated floodway. For purposes of this subsection, the term structure shall not include a gas or liquid storage tank.

(b)

Dikes, Levees and Other Water Flow Modification Structures.

(1)

Areas where floodwater releases and overflows from the main Skokomish River channel shall not be modified, meaning levied or diked, in any manner which would result in increased stream flow in the main channel.

(2)

Maintenance to existing legally established (constructed by past permits or historically occurring) levees, dikes, and other water flow modification structures shall be permitted with appropriate approvals from all affected agencies, provided that the maintenance does not result in increased stream flow within the main channel (as verified by a hydraulic engineer), and the maintenance is consistent with provisions and recommendations of the adopted Skokomish River Comprehensive Flood Hazard Management Plan. Emergency alterations to dikes and levees necessary for the protection of human life and property shall be permitted as provided for within the applicable regulatory permit processes.

(3)

If the public works director finds an imminent flood threat to the public health, safety, and welfare exists based on:

(A)

A flow capacity of seventy percent of the one hundred-year flood stage for the specific river or creek, or

(B)

A rainfall within the last forty-eight hours in excess of four inches, or

(C)

Issuance of a flood warning by the National Weather Service for the specific area, or

(D)

A significant isolated blockage occurs such as a log jam or slide, that impacts the geography or water velocity such that an overflow bank path has or is likely to occur;
then the public works director may recommend to the board of commissioners that they declare an emergency flood condition, which shall then authorize the county to make on-site inspections on private property of dikes and other impediments as necessary, and to direct or design immediate or subsequent improvement, repair, removal, or modification to said dikes, levees, or other impediments, as subject to other regulations; and shall maintain a record of the condition and structure of said dikes.

(4)

Alterations to dikes and levees, and bank stabilization efforts that would prevent legitimate potential emergency situations shall be permitted, provided that all affected agencies have been notified and appropriate permits have been acquired.

(5)

Activities related to the repair, maintenance or construction of bank stabilization, dikes, levees or other related development are a permit required activity under Section 14.22.110, are subject to all provisions for development standards within this chapter, and shall provide for appropriate inspections during and following construction and/or repair. Construction shall meet NRCS standards, as recommended within the Skokomish River Comprehensive Flood Hazard Management Plan, or as revised.

(6)

Projects proposed by government agencies under this section as recommended within the Skokomish River Comprehensive Flood Hazard Management Plan shall be evaluated on a case-by-case basis. The administrator shall include the following considerations in making an evaluation:

(A)

Recommendations of applicable study;

(B)

Provisions of this chapter;

(C)

Project-specific engineering;

(D)

Public benefit;

(E)

All applicable regulations.

(7)

All approved permits shall require the monitoring of performance which shall include, at a minimum, a post-construction inspection for compliance with the conditions of approval. Additional inspections may be required when recommended by the engineering report or the county engineer. Monitoring shall be established as a condition of approval.

(8)

Dike Monitoring Program. Information on the condition of levees, dikes, or other structures ascertained from successive on-site inspections shall be maintained by the county for the purpose of updating and cataloging existing conditions as part of their ongoing flood and dike management program. Dikes shall be monitored for safety purposes. Dikes shall be inspected by the public works director at least biennially.

The public works director and his designee is authorized to enter onto private or public land for the sole purpose of inspecting dikes for flood safety and for no other purpose. The inspections shall be done between the eight a.m. and four p.m. time period, with notice to the property owner sent by certified mail at least fourteen days in advance, unless there is a flood emergency.

The public works director shall report on the condition of the dikes to the board of county commissioners at the interval of once every two years. The report shall include an assessment of the condition and structure of the dikes; an analysis of whether any improvements needs to be done; a statement on the ability, or lack thereof, to inspect the dikes; and any other matter of importance to dike inspection and monitoring. The report shall also be based on the inspections and information gathered from dike monitoring. Existing dikes monitored shall be listed or be listed by reference to outside reports.

(c)

Bridges and Roadways.

(1)

Areas where floodwater releases and overflows from the main Skokomish River channel shall not be modified by construction or reconstruction of bridges or roadways, in any manner which would result in increased stream flows or flood elevations (as verified by a hydraulic engineer).

(2)

Maintenance to existing legally established (constructed by past permits or historically occurring) bridges and roadways shall be permitted with appropriate approvals from all affected agencies, provided that the maintenance does not result in increased stream flows or flood levels (as verified by a hydraulic engineer), and the maintenance is consistent with provisions and recommendations of the adopted Skokomish River Comprehensive Flood Hazard Management Plan. Emergency alterations to bridges and roadways necessary for the protection of human life and property shall be permitted as provided for within the applicable regulatory permit processes.

(3)

If the public works director finds an imminent flood threat to the public health, safety, and welfare exists based on:

(A)

A flow capacity of seventy percent of the one hundred-year flood stage for the specific river or creek, or

(B)

A rainfall within the last forty-eight hours in excess of four inches, or

(C)

Issuance of a flood warning by the National Weather Service for the specific area, or

(D)

A significant isolated blockage occurs such as a log jam or slide, that impacts the geography or water velocity such that an overflow bank path has or is likely to occur;
then the public works director may recommend to the board of commissioners that they declare an emergency flood condition, which shall then authorize the county to make on-site inspections on private property of bridges and roadways and other impediments as necessary, and to direct or design immediate or subsequent improvement, repair, removal, or modification to said impediments, as subject to other regulations; and shall maintain a record of such actions.

(4)

Alterations to bridges and roadways that would prevent legitimate potential emergency situations shall be permitted, provided that all affected agencies have been notified and appropriate permits have been acquired.

(5)

Activities related to the repair, maintenance or construction of bridges and roadways or other related development are a permit required activity under Section 14.22.110, are subject to all provisions for development standards within this chapter, and shall provide for appropriate inspections during and following construction and/or repair.

(6)

Projects proposed by government agencies under this section as recommended within the Skokomish River Comprehensive Flood Hazard Management Plan shall be evaluated on a case-by-case basis. The administrator shall include the following considerations in making an evaluation:

(A)

Recommendations of applicable study;

(B)

Provisions of this section;

(C)

Project-specific engineering;

(D)

Public benefit;

(E)

All applicable regulations.

(7)

All approved permits shall require the monitoring of performance which shall include, at a minimum, a post-construction inspection for compliance with the conditions of approval. Additional inspections may be required when recommended by the engineering report or the county engineer. Monitoring shall be established as a condition of approval.

Projects proposed by WSDOT under this section and receiving Federal Highway Administration funding shall be consistent with the recommendations within the Skokomish River Comprehensive Flood Hazard Management Plan and shall be evaluated on a case-by-case basis. The administrator shall include the following considerations in making an evaluation and issuing a permit:

(A)

Recommendations of project specific studies prepared by or on behalf of WSDOT;

(B)

All other provisions of this chapter do not apply;

(C)

Project specific engineering shall be completed in accordance with the WSDOT Design Manual;

(D)

Provide a public benefit;

(E)

Provide less than a cumulative one foot rise in the proposed one hundred-year flood fringe as determined by a step backwater analysis or higher. The cumulative total rise will consider projects that have been approved as well as projects that are planned to be approved.

(F)

Compliance with all applicable state and federal regulations.

(Ord. 87-08 Attach. A (part), § 5.5, 2008: Ord. 81-07, Attach. A, § 5.5, 2007: Ord. 86-05, § 1, 2005; Ord. 24-05, Attach. A, 2005; Ord. 9-03, Attach. B8, § 5.4, 2003: Ord. 10-02, Attach. B, § 5.4, 2002: Ord. 16-00, Attach. B, § 5.4, 2000: Ord. 59-91, § 5.4, 1991).