9.05.060 Permit issuance or denial – Floodplain district

9.05.060 Permit issuance or denial – Floodplain district.

A. Floodways. Located within areas of special flood hazard established in the FIRM are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of flood waters which carry debris, potential projectiles, and erosion potential, the following provisions apply:

1. Prohibit encroachments, including fill, new construction, substantial improvements, and other development, unless certification by a registered professional engineer or architect is provided demonstrating that encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge.

2. If subsection (A)(1) of this section is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this section.

3. For property within the floodway fringe of Beaverton Creek (main stem) from Murray Boulevard upstream to State Highway 8 (Canyon Road), fill that facilitates development may be placed without regard for the holding capacity of the property in question; provided, that the fill is shown not to raise the base flood elevation or create additional flooding inside and outside the established flood hazard area of tributaries to Beaverton Creek that cross the floodway fringe and converge with Beaverton Creek within those boundaries.

1. In addition to the grounds for denial contained in BC 9.05.055, the city engineer shall also deny a permit for development in an area of special flood hazard if the city engineer finds that any of the following circumstances exist:

a. The proposed development will diminish the flood carrying capacity of the water course;

b. The proposed development does not maintain the holding capacity of the site;

c. The proposed development will significantly raise the flood surface elevations up or down stream from or adjacent to the site;

d. The proposed development will endanger life or property on or off the site;

e. Where elevation data is not available either through the flood insurance study or from another authoritative source, proposed construction will not be reasonably safe from flooding. The test of reasonableness is a local judgment and includes use of historical data, high water marks, photographs of past flooding, etc., where available. Failure to elevate at least two feet above grade in these zones may result in higher insurance rates;

f. All necessary permits have not been obtained from those Federal, State or local governmental agencies from which prior approval is required.

2. In lieu of denial, the city engineer may grant the permit with any conditions necessary to assure that the provisions of this section will be met.

C. General Standards. In all areas of special flood hazards, the following standards are required:

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).

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.

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

b. New and replacement sanitary sewer systems shall be designed to minimize or eliminate infiltration of flood waters into the systems and discharge from the systems into flood waters; and

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

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; and

d. Where base flood elevation data has not been provided or is not available from another authoritative source, and the city engineer determines base flood elevation data to be necessary to properly administer regulations within an area of special flood hazard, base flood elevation data shall be generated.

5. Review of Building Permits. Where elevation data is not available either through the flood insurance study 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 judgment and includes use of historical data, highwater 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.

D. Specific Standards. In all areas of special flood hazards where base flood elevation data has been provided as set forth in the flood insurance rate map (FIRM), the following provisions are required:

a. In new construction or the substantial improvement of any residential structure the lowest floor, including the basement, shall be elevated to not less than one foot above the base flood elevation. If within the special flood hazard area of Beaverton Creek (main stem) from Murray Boulevard upstream to State Highway 8 (Canyon Road), the lowest floor, including the basement, shall be elevated to not less than two feet above 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 flood waters. 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 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 one foot above the level of the base flood elevation and, if within the special flood hazard area of Beaverton Creek (main stem) from Murray Boulevard upstream to State Highway 8 (Canyon Road), be elevated to not less than two feet above the base flood elevation; or together with attendant utility and sanitary facilities, shall:

a. Be floodproofed to an elevation one foot above the base flood level and, if within the special flood hazard area of Beaverton Creek (main stem) between Murray Boulevard upstream to State Highway 8 (Canyon Road), be floodproofed two feet above the base flood elevation so that the structure is watertight and 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 building official as set forth in BC 9.05.035(F);

d. Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in subsection (D)(1) 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 floodproofed level (e.g., a building floodproofed to the base flood level will be rated as one foot below).

a. All manufactured homes to be placed or substantially improved within Zones A1-30 and AE shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is at least one foot above the base flood elevation and be securely anchored to an adequately anchored foundation system in accordance with the provisions of subsection (C)(1) of this section;

b. For new manufactured home parks and subdivisions; for expansions to existing manufactured home parks and subdivisions; for existing manufactured home parks and subdivisions where the repair, reconstruction or improvement of the street, utilities and pads equals or exceeds 50 percent of the value of the streets, utilities and pads before the repair, reconstruction or improvement has commenced; and for manufactured homes not placed in a manufactured home park or subdivision, it is required that:

i. Stands or lots are elevated on compacted fill or on pilings so that the lowest floor of the manufactured home will be at or above the base flood level;

ii. Adequate surface drainage and access for a hauler are provided; and

iii. In the instance of elevation on pilings, that:

(A) Lots are large enough to permit steps,

(B) Piling foundations are placed in stable soil no more than 10 feet apart, and

4. Floodways. Located within areas of special flood hazard established in the FIRM are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of flood waters which carry debris, potential projectiles, and erosion potential, the following provisions apply:

a. Prohibit encroachments, including fill, new construction, substantial improvements, and other development unless certification by a registered professional engineer 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.

b. If the requirements of subsection (D)(4)(a) of this section are satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of subsection C of this section. [BC 9.05.060, amended by Ordinance No. 3400, 9/10/84; amended by Ordinances No. 3487, 1/14/86, Ordinance No. 3564, 5/5/87, Ordinance No. 3887, 3/21/94, Ordinance No. 3984, 6/9/97, Ordinance No. 4078, 11/8/99, Ordinance No. 4107, 5/1/00, Ordinance No. 4249, 4/7/03, Ordinance No. 4744, 10/17/18]