Chapter 15.48
FLOOD DAMAGE PREVENTION
Sections:
15.48.010 Statutory authorization—Findings of fact —Purpose and objectives.
15.48.050 Provisions for flood hazard reduction.
15.48.060 Critical facilities.
15.48.010 Statutory authorization—Findings of fact—Purpose and objectives.
A. Statutory Authorization. The Legislature of the state has in RCW 36.32.120(7) delegated the responsibility to local governmental units to adopt regulations designed to promote the public health, safety, and general welfare of its citizenry. Chapter 36.70A RCW also requires general purpose local governments planning under that chapter to adopt regulations for frequently flooded areas.
B. Findings of Fact.
1. The flood hazard areas of the county 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 welfare.
2. These flood losses are caused by the cumulative effect of obstructions in areas of flood hazard that increase flood heights and velocities, and, when inadequately anchored, damage uses on other areas. Uses that are inadequately floodproofed, elevated, or otherwise protected from flood damage also contribute to the flood loss.
C. Statement of Purpose. It is the purpose of this chapter to promote the public health, safety, and general welfare, to comply with applicable state law and to minimize public and private losses due to flood conditions in specific areas by provisions designed to:
1. Protect human life and health;
2. Minimize expenditure of public money and costly flood control projects;
3. Minimize the need for rescue and relief efforts associated with flooding and generally undertaken at the expense of the general public;
4. Minimize prolonged business interruptions;
5. Minimize damage to public facilities and utilities such as water and gas mains, electric, telephone and sewer lines, roads and bridges located in areas of flood hazard;
6. Help maintain a stable tax base by providing for sound use and development in areas of flood hazard so as to minimize future flood blight areas;
7. Provide a means by which potential purchasers of property can determine if that property is in an area of flood hazard; and
8. Ensure that those who occupy the areas of flood hazard assume responsibility for their actions.
D. Methods of Reducing Flood Losses. In order to accomplish its purposes, this chapter includes methods and provisions for:
1. 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;
2. Requiring that uses vulnerable to floods, including facilities that serve such uses, be protected against flood damage at the time of initial construction;
3. Controlling the alteration of natural floodplains, stream channels, and natural protective barriers, which help accommodate or channel floodwaters;
4. Controlling filling, grading, dredging, and other development, which may increase flood damage;
5. Preventing or regulating the construction of flood barriers which will unnaturally divert floodwaters or which may increase flood hazards in other areas. (Ord. TLS 09-07-38B Exh. A (part): Ord. TLS 02-01-07B Exh. A (part): Ord. TLS 01-02-06B Exh. A(part): Ord. TLS 97-10-71B Exh. C (part))
15.48.020 Definitions.
Words, terms and phrases used in this chapter are defined in DCC Chapter 14.98 as supplemented herein. Unless specifically defined, 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 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 subject to a one percent or greater chance of flooding in any given year. Designation on maps always includes the letter A.
“Basement” means any area of a building or structure having a floor that is subgrade, or below ground level, on all sides.
“Critical facility” means a facility for which even a slight chance of flooding might be too great. Critical facilities include, but are not limited to, schools, nursing homes, convalescent homes, hospitals, police facilities, fire protection facilities, emergency response facilities, and installations which produce, use or store hazardous materials and/or hazardous waste.
“Development” means any manmade use or change to improved or unimproved real estate including, without limitation: the construction, reconstruction, conversion, structural alteration, relocation or enlargement of any buildings or other structures; mining; dredging; drilling; filling; stockpiling; grading and excavation; the storage of equipment or materials; and divisions of land.
“Elevated building” means, for insurance purposes, a nonbasement building which has its lowest elevated floor raised above ground level by foundation walls, shear walls, posts, piers, pilings, or columns.
“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 July 13, 1987 (effective date of Ordinance 87-5).
“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).
“Lowest floor” means the lowest floor or 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 DCC Section 15.48.050(B)(1)(b).
“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 July 13, 1987 (effective date of Ordinance 87-5).
“Recreational vehicle” means a vehicular unit primarily designed as temporary living quarters for recreational, camping, or travel use and that is certified as a recreational vehicle (RV) by the Department of Labor and Industries.
“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 roads and/or walkways; nor does it include excavation for a basement, footings, piers, or foundation or the erection of temporary forms; nor does it include the installation on the property of accessory buildings such as garages or sheds not occupied as dwelling units or not part of the main structure.
“Structure” means a walled and roofed building including a gas or liquid storage tank or manufactured home that is principally aboveground.
“Substantial damage” means damage of any origin, including intentional and unintentional demolition, sustained by a structure whereby the cost of restoring the structure exceeds fifty percent of its value before damage as determined by using the most recent ICC building valuation data tables.
“Substantial improvement” means:
A. Any repair, reconstruction, or improvement of a structure, the cost of which equals or exceeds fifty percent of the value of the structure, as determined by using the most recent ICC building valuation data tables, either:
1. Before the improvement or repair is started, or
2. If the structure has been damaged and is being restored, before the damage occurred. For the purposes of this definition, “substantial improvement” is considered to occur when the first alteration of any wall, ceiling, floor, or other structural part of the building commences, whether or not that alteration affects the external dimension of the structure.
B. The term “substantial improvement” does not, however, include either:
1. Any project for the improvement of a structure to comply with existing state or local health, sanitary, or safety code specifications which have been previously identified by the local code enforcement official responsible for administration of those code specifications, and which are solely necessary to assure safe living conditions; or
2. Any alteration of a structure listed on the National Register of Historic Places or a state inventory of historic places.
“Water dependent” means a structure for commerce or industry that cannot exist in any other location and is dependent on the water by reason of the intrinsic nature of its operations. (Ord. TLS 09-07-38B Exh. A (part): Ord. TLS 02-01-07B Exh. A (part): Ord. TLS 01-02-06B Exh. A(part): Ord. TLS 97-10-71B Exh. C (part))
15.48.030 General provisions.
A. Lands to Which This Chapter Applies. This chapter shall apply to all flood hazard areas within the unincorporated areas of the county.
B. Basis for Establishing the Areas of Flood Hazard. The areas of flood hazard identified by the Federal Insurance Administration in a scientific and engineering report entitled “The Flood Insurance Study for the Unincorporated Areas” dated July 17, 1978, and as revised on May 17, 1982, and any subsequent revisions thereto, with accompanying flood insurance rate maps, and any subsequent revisions thereto, is adopted by reference and declared to be a part of this chapter. The flood insurance study is on file at the offices of the Douglas County department of transportation and land services. Flood hazard areas also include those areas not designated in the flood insurance study but that have a historical pattern of flooding and mudslides. The best available information for flood hazard area identification as outlined in DCC Section 15.48.040(D)(2) shall be the basis for regulation until a new FIRM is issued which incorporates the data utilized under that section.
C. Reference Datum. Certifications of the elevations of sites, structures and base flood levels shall use a reference datum that is consistent with the applicable Flood Insurance Rate Map (FIRM).
D. Compliance. 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.
E. 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.
F. Interpretation. In the interpretation and application of this chapter, all provisions shall be:
1. Considered as minimum requirements;
2. Liberally construed in favor of the board of commissioners and the review authority; and
3. Deemed neither to limit nor repeal any other power.
G. 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 flood hazard or uses permitted in such areas will be free from flooding or flood damages. This chapter shall not create liability on the part of the county, any officer or employee thereof, for any flood damages that result from reliance on this chapter, any administrative decision lawfully made thereunder, or unauthorized actions by others. (Ord. TLS 21-06-19B Exh. B; Ord. TLS 09-07-38B Exh. A (part): Ord. TLS 02-01-07B Exh. A (part): Ord. TLS 01-02-06B Exh. A(part): Ord. TLS 97-10-71B Exh. C (part))
15.48.040 Administration.
A. Establishment of Development Permit. A development permit shall be obtained before construction or development begins within any area of flood hazard established in DCC Section 15.48.030(B). The permit shall be for all buildings and structures including manufactured homes, as defined in DCC Chapter 14.98 and DCC Section 15.48.020, and for all other development, including fill and other activities, also defined in DCC Chapter 14.98 and DCC Section 15.48.020.
B. Application for Development Permit. Application for a development permit shall be made on forms furnished by the review authority. The information to be submitted with the application shall be submitted in addition to that information necessary to obtain other permits, as well as for those developments and substantial improvements which require no other permit approvals, and may include, but not be limited to:
1. The nature, location, dimensions, and elevations of the project site;
2. Typical cross sections disclosing both existing ground elevations, proposed ground elevations, height of existing structures, and height of proposed structures;
3. Proposed land contours, where appropriate, if development involves grading, filling, cutting, or other alterations of land contours. When required, contours shall be at two-foot intervals for land with a slope of ten percent or less and five-foot intervals for land with a slope greater than ten percent;
4. Dimensions and locations of existing structures to be maintained;
5. Dimensions and locations of proposed structures;
6. The source, composition and volume of fill materials;
7. The composition and volume of any excavated materials and the identification of the proposed disposal site;
8. The location of existing and proposed utilities such as water, sanitary sewer, stormwater drainage, septic tanks and drainfields, gas and electricity;
9. The elevation in relation to mean sea level of the lowest floor (including basement) of all structures as certified by an engineer, surveyor or architect;
10. The elevation in relation to mean sea level to which any structure has been floodproofed as certified by an engineer or surveyor;
11. Certification by an engineer or architect that the floodproofing methods for any nonresidential structure meet the floodproofing criteria in DCC Section 15.48.050(B)(2);
12. Description of the extent to which any watercourse will be altered or relocated as a result of proposed development; and
13. Certification by an engineer demonstrating that any alteration or encroachments shall not result in any increase in flood levels during the occurrence of a base flood discharge.
C. Designation of the Review Authority. The director is appointed to administer and implement this chapter by granting or denying development permit applications in accordance with its provisions.
D. Duties and Responsibilities of the Review Authority. Duties of the review authority shall include, but not be limited to:
1. Permit Review.
a. Review all development permits to determine the permit requirements of this chapter have been satisfied;
b. Refer development permit applications to federal, state, or local governmental agencies as appropriate in order for those agencies to determine applicability of their permit requirements to the development and enable them to contact the applicant directly regarding those requirements;
c. Review all development permits to determine if the proposed development is located in the floodway. If located in the floodway, assure that the encroachment provisions of DCC Section 15.48.050(D)(1) are met.
2. Use of Other Base Flood Data. When base flood elevation data have not been provided in accordance with DCC Section 15.48.030(B), the review authority may obtain, review and reasonably utilize any base flood elevation and floodway data available from a federal, state or other source, in order to administer DCC Section 15.48.050(B) and (D).
3. Information to Be Obtained and Maintained.
a. Where base flood elevation data are provided through the flood insurance study, flood insurance rate map (FIRM) or required as in subsection (D)(2) of this section, obtain and record the certifications of the actual elevation (in relation to mean sea level) of the base flood elevation and the lowest habitable floor (including basement) of all new or substantially improved structures, and whether or not the structure contains a basement.
b. For all new or substantially improved floodproofed nonresidential structures where base flood elevation data are provided through the flood insurance study, flood insurance rate map or as required by subsection (D)(2) of this section:
i. Obtain and maintain the certifications of the actual elevation (in relation to mean sea level) to which the nonresidential structure was floodproofed; and
ii. Maintain the floodproofing certifications required in subsection (B)(11) of this section.
4. Alteration of Watercourses.
a. Notify adjacent communities and the Washington State Department of Ecology prior to any alteration or relocation of a watercourse, and submit evidence of such notification to the Federal Insurance Administration;
b. Require that maintenance be provided within the altered or relocated portion of the watercourse so that the flood-carrying capacity is not diminished.
5. Interpretation of FIRM Boundaries. Make interpretations, where needed, as to exact location of the boundaries of the areas of flood hazard (for example, where there appears to be a conflict between a mapped boundary and actual field conditions). (Ord. TLS 09-07-38B Exh. A (part): Ord. TLS 02-01-07B Exh. A (part): Ord. TLS 01-02-06B Exh. A(part): Ord. TLS 97-10-71B Exh. C (part))
15.48.045 Variance procedure.
A. The Douglas County hearing examiner shall hear and decide requests for variances from the requirements of this chapter and appeals of decisions made after full administrative review (DCC Section 14.10.030).
B. There shall be no administrative appeal of a decision of the hearing examiner. An appeal of a decision of the hearing examiner shall be timely filed as a judicial appeal in the superior court in accordance with DCC Section 14.12.020.
C. The hearing examiner shall consider all technical evaluations, all relevant factors, standards specified in other sections of this chapter, and the following:
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 that 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.
D. Upon consideration of the factors of subsection C of this section and the purposes of this chapter, the hearing examiner may attach such conditions to the granting of variances as deemed necessary to further the purposes of this chapter.
E. The review authority, or his/her designee, shall maintain the records of all appeal actions and report any variances to the Federal Insurance Administration upon request.
F. Criteria for variances:
1. Generally, the only condition under which a variance from the elevation standard may be issued is for new construction and substantial improvements to be erected on a lot of one-half acre or less in size contiguous to and surrounded by lots with existing structures constructed below the base flood level; provided, that subsections (C)(1) through (C)(11) of this section have been fully considered. As the lot size increases the technical justification required for issuing the variance increases.
2. Variances may be issued for the reconstruction, rehabilitation, or restoration of structures listed on the National Register of Historic Places or the State Inventory of Historic Places, without regard to the procedures set forth in this section.
3. Variances shall not be issued within a designated floodway if any increase in flood levels during the base flood discharge would result.
4. Variances shall only be issued upon a determination that the variance is the minimum necessary, considering the flood hazard, to afford relief.
5. Variances shall only be issued upon:
a. A showing of good and sufficient cause;
b. A determination that failure to grant the variance would result in exceptional hardship to the applicant;
c. A determination that the granting of a variance will not result in increased flood heights, additional threats to public safety, extraordinary public expense, create nuisances, cause fraud on or victimization of the public as identified in subsection C of this section or conflict with existing local laws or ordinances.
6. Variances as interpreted in the National Flood Insurance Program are based on the general zoning law principle that they pertain to a physical piece of property; they are not personal in nature and do not pertain to the structure, its inhabitants, economic or financial circumstances. They primarily address small lots in densely populated residential neighborhoods. As such, variances from the flood elevations should be quite rare.
7. 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 (F)(1) of this section, and otherwise complies with DCC Section 15.48.050(A)(1) (anchoring) and DCC Section 15.48.050(A)(2) (construction materials and methods).
8. Any applicant to whom a variance is granted shall be given written notice that the structure will be permitted to be built with a lowest 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. TLS 09-07-38B Exh. A (part): Ord. TLS 02-01-07B Exh. A (part): Ord. TLS 01-02-06B Exh. A(part): Ord. TLS 97-10-71B Exh. C (part))
15.48.050 Provisions for flood hazard reduction.
A. General Standards. In all areas of flood hazard the following standards are required:
1. Anchoring.
a. All new construction and substantial improvements shall be anchored to prevent flotation, collapse or lateral movement of the structure.
b. All manufactured homes must likewise be anchored to prevent flotation, collapse or lateral movement, and shall be installed using methods and practices that minimize flood damage. Anchoring methods may include, but are not limited to, use of over-the-top or frame ties to ground anchors (reference FEMA’s “Manufactured Home Installation in Flood Hazard Areas” guidebook for additional techniques).
2. Construction Materials and Methods.
a. All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.
b. All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage.
c. Electrical, heating, ventilation, plumbing, and air conditioning equipment and other service facilities shall be designed and/or otherwise elevated or located so as to prevent water from entering or accumulating within the components during conditions of flooding.
3. Utilities.
a. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system. Water wells shall be located on high ground that is not in the floodway;
b. New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters into the systems and discharge from the systems into floodwaters; and
c. On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
4. Subdivisions, short subdivisions and binding site plans.
a. All subdivisions, short subdivisions and binding site plans shall be consistent with the need to minimize flood damage;
b. All subdivisions, short subdivisions and binding site plans shall have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage;
c. All subdivisions, short subdivisions and binding site plans shall have adequate drainage provided to reduce exposure to flood damage;
d. The base flood elevation shall be disclosed on the face of a final plat, final short plat or final binding site plan in a manner specified by the review authority. Where base flood elevation data have not been provided or are not available from another authoritative source, they shall be generated by the applicant for a subdivision, short subdivision, binding site plan or other proposed development; and
e. A disclosure statement shall be placed on the face of final plats, final short plats and final binding site plans advising property owners and potential purchasers of the potential flood hazard on the property, and that certain activities are subject to compliance with this chapter and other applicable provisions of the DCC.
5. Review of Building Permits. Where elevation data are not available, either through the flood insurance study or from another authoritative source (see DCC Section 15.48.040(D)(2)), applications for building permits shall be reviewed to assure that proposed construction will be reasonably safe from flooding. The test of reasonableness is a local judgment and includes certification by an engineer and use of historical data, high water marks, photographs of past flooding, etc., where available. Failure to elevate at least two feet above grade in these zones may result in higher insurance rates.
B. Specific Standards. In all areas of flood hazard where base flood elevation data have been provided as set forth in DCC Section 15.48.030(B) or 15.48.040(D)(2), 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 to or above one foot higher than the 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 be certified by an engineer or architect and must meet or exceed the following minimum criteria:
i. A minimum of two openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided;
ii. The bottom of all openings shall be no higher than one foot above grade;
iii. Openings may be equipped with screens, louvers, or other coverings or devices; provided, that they permit the automatic entry and exit of floodwaters.
2. Nonresidential Construction. New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall either have the lowest floor, including basement, elevated to or above one foot higher than the base flood elevation, or, together with attendant utility and sanitary facilities, shall:
a. Be floodproofed so that below one foot above the base flood 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 an engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting the 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 review authority;
d. Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in subsection (B)(1)(b) of this section;
e. Applicants that are 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 the base flood level will be rated as one foot below).
3. 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 elevated to or above one foot higher than the base flood elevation and be securely anchored to an adequately designed foundation system to resist flotation, collapse and lateral movement in accordance with the provisions of subsection (A)(1)(b) of this section.
C. Recreational Vehicles. Recreational vehicles placed on sites within Zones A, A1-30, and AE shall be on the site for fewer than one hundred eighty consecutive days unless parked at an occupied single-family residence, be fully licensed and ready for highway use, is on its wheels or a jacking system, is attached to the site only by quick disconnect type utility and security systems, and has no permanently attached additions.
D. Floodways. Located within areas of flood hazard established in DCC Section 15.48.030(B) are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of floodwaters, which carry debris, potential projectiles, and erosion potential, the following provisions apply:
1. Encroachments and obstructions, including fill, new construction, substantial improvements, and other uses, are prohibited unless certification by an engineer is provided demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge;
2. If subsection (D)(1) of this section is satisfied, all new nonresidential construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this chapter;
3. Construction or reconstruction of residential structures is prohibited within designated floodways except for repairs or improvements to a structure which do not increase the ground floor areas, the value of which in any twelve-month period does not exceed fifty percent of the value of the structure, as determined by using the current ICC building valuation data tables either (a) before the repair or improvement is started, or (b) if the structure has been damaged by any means or demolished to any extent, and is being restored, before damage occurred. Not included in the fifty percent value standard are repairs or improvements to buildings and structures to comply with existing health, sanitary, or safety codes that have been identified by the review authority and that are the minimum necessary to assure safe living conditions or repairs or improvements to buildings or structures identified as historic places.
E. Grading and Filling. No fill, including fill for roads, and levees, grading, or excavating that unduly affects the efficiency or the capacity of the flood channel or floodway, or unduly decreases flood storage or increases flood heights, shall be permitted. Any proposed fill to be deposited in a flood hazard area shall not be contrary to the need for storage of floodwater nor shall the amount of fill be greater than is necessary to achieve the purpose for which the fill is intended. Fill materials shall be clean with a minimal potential for degrading water quality. All fill materials shall be protected against erosion with retaining walls or other mechanisms to deter erosion. If vegetative cover is chosen, the side slopes of the fill should not exceed two units of horizontal distance to one unit of vertical distance. All grading and fill activities shall be designed and certified by an engineer to conform to all applicable provisions of the DCC including, without limitation, DCC Titles 15, 19 and 20.
F. Shallow Flood Areas (AO Zones) with Depth Designations.
1. Shallow flooding areas appear on the FIRM as AO zones with depth designations. The base flood depth in these zones ranges 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 above the highest grade adjacent to the building, one foot or more above the depth number specified on the FIRM, and at least two feet if no depth number is specified.
b. New construction and substantial improvements of nonresidential structures within AO zones shall either:
i. Have the lowest floor (including basement) elevated above the highest grade adjacent to the building site, to or above the depth number specified on the FIRM and at least two feet if no depth number is specified; or
ii. Together with attendant utility and sanitary facilities, be completely floodproofed to or above that level so that any space below that level is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. An engineer or architect shall certify compliance as in subsection (B)(2)(c) of this section if this method is used.
c. Adequate drainage paths designed by an engineer shall be required around structures on slopes to guide floodwaters around and away from proposed structures.
d. Recreational vehicles placed on sites within an AO zone must either:
i. Be on the site for fewer than one hundred eighty consecutive days; or
ii. Be fully licensed and ready for highway use, on its wheels or jacking system, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions; or
iii. Meet the requirements of subsection F of this section and the elevation and anchoring requirements for manufactured homes.
2. Where hazardous velocities are noted on the FIRM, consideration shall be given to mitigating the effects of these velocities through proper design and construction techniques and methods.
G. Encroachments. The cumulative effort 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 as certified by an engineer. (Ord. TLS 09-07-38B Exh. A (part): Ord. TLS 02-01-07B Exh. A (part): Ord. TLS 01-02-06B Exh. A(part): Ord. TLS 97-10-71B Exh. C (part))
15.48.060 Critical facilities.
Construction of new critical facilities shall be, to the extent possible, located outside the limits of a flood hazard area. Construction of new critical facilities shall be permissible within a flood hazard area if no alternative feasible site is available. Critical facilities constructed within a flood hazard area shall have the lowest floor elevated three feet or more above the level of the base flood at the site. Floodproofing and sealing measures must be taken to ensure that toxic substances will not be displaced by or released into floodwaters. Access routes elevated to or above the level of the base flood elevation shall be provided to all critical facilities to the extent possible. The review authority shall require design and construction certifications prepared by an engineer, architect or surveyor, as appropriate to the aspect of the development, to assure compliance with this section and other applicable provisions of the DCC. (Ord. TLS 09-07-38B Exh. A (part): Ord. TLS 02-01-07B Exh. A (part): Ord. TLS 01-02-06B Exh. A(part): Ord. TLS 97-10-71B Exh. C (part))