Attachment 1 Chapter 9.10 Final1
Planning Commission Draft
Chapter 9.10
AREAS OF SPECIAL FLOOD HAZARD AREA
9.10.010. Purpose.
9.10.020. Definitions.
9.10.030. Applicability.
9.10.040. General Provisions.
9.10.050. National Flood Insurance Program General Standards.
9.10.060. No Net Loss Standards.
9.10.0760. Violations.
§ 9.10.010. Purpose.
The purpose of this chapter is to promote public health, safety, and general welfare, and to minimize public
and private losses due to flooding in special flood hazard areas by provisions designed to:
A. Protect human life and health;
B. Minimize expenditure of public money for costly flood control projects;
C. Preserve natural and beneficial floodplain functions;
CD. Minimize the need for rescue and relief efforts associated with flooding and generally undertaken at
the expense of the general public;
DE. Minimize prolonged business interruptions;
EF. Minimize damage to public facilities and utilities such as water and gas mains; electric, telephone
and sewer lines; and streets and bridges located in areas of special flood hazard areas;
FG. Help maintain a stable tax base by providing for the sound use and development of flood hazard areas
so as to minimize blight areas caused by flooding;
GH. Notify potential buyers that the property is in an area of special flood hazard area;
HI. Notify those who occupy areas of special flood hazard area that they assume responsibility for their
actions; and
IJ. Participate in and maintain eligibility for flood insurance and disaster relief.
9.10.020. Definitions.
Unless specifically defined below, words or phrases used in this chapter shall be interpreted so as to give
them the meaning they have in common usage. These definitions are only applicable to this chapter and
Tigard Community Development Code (TCDC) Chapt er 18.510, Sensitive Lands.
"Appeal" means a request for a review of the interpretation of any provision of this chapter or a request for
a variance.
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"Area of shallow flooding" means a designated Zone AO, AH, AR/AO or AR/AH (or VO) on the city's
Flood Insurance Rate Map (FIRM) with a one percent or greater annual chance of flooding to an average
depth of one to three feet where a clearly defined channel does not exist, where the path of flooding is
unpredictable, and where velocity flow may be evident. Such flooding is characterized by ponding or sheet
flow.
"Area of special flood hazard" means the land in the floodplain within the city subject to a one percent or
greater chance of flooding in any given year. It is shown on the Flood Insurance Rate Map (FIRM) as Zone
A, AO, AH, A1-30, AE, A99, AR. "Special flood hazard area" is synonymous in meaning and definition
with the phrase "area of special flood hazard."
"Base flood" means a flood having a one percent chance of being equaled or exceeded in any given year.
"Base flood elevation (BFE)" means the elevation to which floodwater is anticipated to rise during the base
flood.
"Basement" means any area of the building having its floor subgrade (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; new and replacement bridges; hospitals;
police, fire, and emergency response in stallations; and installations that produce, use, or store hazardous
materials or hazardous waste.
"Development" means any man-made change to improved or unimproved real estate, including, but not
limited to, buildings or other structures, mining, dredging, filling, grading, paving, excavation or drilling
operations or storage of equipment or materials.
“Fill” means placement of any materials such as soil, gravel, crushed stone, or other materials that
change the elevation of the floodplain. Placement of fill is considered “development”.
“Fish accessible space” means the volumetric space available to fish to access.
“Fish egress-able space” mean the volumetric space available to fish to exit or leave from.
"Flood" or "flooding" means:
1. A general and temporary condition of partial or complete inundation of normally dry land areas
from:
a. The overflow of inland or tidal waters;
b. The unusual and rapid accumulation or runoff of surface waters from any source;
c. Mudslides (i.e., mudflows) which are proximately caused by flooding as defined in
subsection 1.b of this definition and are akin to a river of liquid and flowing mud on the
surfaces of normally dry land areas, as when earth is carried by a current of water and
deposited along the path of the current.
2. The collapse or subsidence of land along the shore of a lake or other body of water as a result of
erosion or undermining caused by waves or currents of water exceeding anticipated cyclical
levels or suddenly caused by an unusually high water level in a natural body of water,
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accompanied by a severe storm, or by an unanticipated force of nature, such as flash flood or an
abnormal tidal surge, or by some similarly unusual and unforeseeable event which results in
flooding as defined in subsection 1.a of this definition.
Flood Elevation Study. See "Flood Insurance Study."
"Flood Insurance Rate Map (FIRM)" means the official map of the city, on which the Federal Insurance
Administrator has delineated both the special hazard areas and the risk premium zones applicable to the
city. A FIRM that has been made available digitally is called a Digital Flood Insurance Rate Map (DFIRM).
"Flood Insurance Study (FIS)" means an examination, evaluation and determination of flood hazards and,
if appropriate, corresponding water surface elevations, or an examination, evaluation and determination of
mudslide (i.e., mudflow) or flood-related erosion hazards.
"Flood proofing" means any combination of structural and nonstructural additions, changes, or adjustments
to structures which reduce or eliminate risk of flood damage to real estate or improved real property, water
and sanitary facilities, structures, and their contents.
“Floodplain functions” mean flood storage, water quality, and riparian vegetation conditions .
"Floodway" means the channel of a river or other watercourse and the adjacent land areas that must be
reserved in order to discharge the base flood without cumulatively increasing the water surface elevation
more than one foot. Also referred to as "regulat ory floodway."
"Functionally dependent use" means a use which cannot perform its intended purpose unless it is located
or carried out in close proximity to water. The term includes only docking facilities, port facilities that are
necessary for the loading and unloading of cargo or passengers, and ship building and ship repair facilities,
and does not include long term storage or related manufacturing facilities.
“Green infrastructure” means the use of natural or human-made hydrologic features to manage water
and provide environmental and community benefits. Green infrastructure uses management approaches
and technologies that use, enhance, or mimic the natural hydrologic cycle processes of infiltration,
evapotranspiration, and reuse. At a large scale, it is an interconnected network of green space that
conserves natural systems and provides assorted benefits to human populations. At a local scale, it
manages stormwater by infiltrating it into the ground where it is generated using vegetation or porous
surfaces, or by capturing it for later reuse. Green infrastructure practices can be used to achieve no net
loss of pervious surface by creating infiltration of stormwater in an amount equal to or greater than the
infiltration lost by the placement of new impervious surface.
“Habitat restoration activities” mean activities with the sole purpose of restoring habitats that have only
temporary impacts and long -term benefits to habitat. Such projects cannot include ancillary structures
such as a storage shed for maintenance equipment, must demonstrate that no rise in the BFE would
occur as a result of the project, obtain a CLOMR and LOMR, and have obtained any other required
permits (e.g., CWA Section 404 permit).
“Hazard trees” mean standing dead, dying, or diseased tree or ones with a structural defect that makes
it likely to fail in whole or in part and that present a potential hazard to a structure o r as defined in Title
8, Urban Forestry.
"Highest adjacent grade" means the highest natural elevation of the ground surface prior to construction
next to the proposed walls of a structure.
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"Historic structure" means any structure that is:
1. Listed individually in the National Register of Historic Places (a listing maintained by the
Department of the Interior) or preliminarily determined by the Secretary of the Interior as meeting
the requirements for individual listing on the National Register;
2. Certified or preliminarily determined by the Secretary of the Interior as contributing to the
historical significance of a registered historic district or a district preliminarily determined by the
Secretary to qualify as a registered historic district;
3. Individually listed on a state inventory of historic places in states with historic preservation
programs which have been approved by the Secretary of the Interior; or
4. Individually listed on a City of Tigard Historic Resources list acknowledged by the Secretary of
the Interior.
“Hydraulically equivalent elevation” means a location (e.g., a site where “no net loss” standards are
implemented) that is approximately equivalent to another (e.g., the impacted site) relative to the same
100-year water surface elevation contour or base flood elevation. This may be estimated based on a point
that is along the same approxima te line perpendicular to the direction of flow.
“Hydrologically connected” means the interconnection of groundwater and surface water such that they
constitute one water supply and use of either results in an impact to both.
“Impervious surface” means a surface that cannot be penetrated by water and thereby prevents
infiltration and increases the amount and rate of surface water runoff, leading to erosion of stream
banks, degradation of habitat, and increased sediment loads in streams. Such surfaces can accumulate
large amounts of pollutants that are then “flushed” into local water bodies during storms and can also
interfere with recharge of groundwater and the base flows to water bodies.
“Low impact development (LID)” means an approach to land development (or redevelopment) that works
with nature to manage stormwater as close to its source as possible. It employs principles such as
preserving and recreating natural landscape features and minimizing effective imperviousness to create
functional and appealing site drainage that treats stormwater as a resource rather than a waste product.
Low impact development refers to designing and implementing practices that can be employed at the site
level to control stormwater and help replicate the predevelopment hydrology of the site. Low impact
development helps achieve no net loss of pervious surface by infiltrating stormwater in an amount equal
to or greater than the infiltration lost by the placeme nt of new impervious surface. LID is a subset of
green infrastructure.
"Lowest floor" means the lowest floor of the lowest enclosed area (including basement). An unfinished or
flood resistant enclosure, usable solely for parking of vehicles, building access or storage in an area other
than a basement area is not considered a building's lowest floor, provided that such enclosure is not built so
as to render the structure in violation of the applicable non -elevation design requirements of this chapter.
"Manufactured dwelling" means a structure, transportable in one or more sections, which is built on a
permanent chassis and is designed for use with or without a permanent foundation when attached to the
required utilities. The term "manufactured dwelling" does not include a "recreational vehicle" and is
synonymous with "manufactured home."
"Manufactured dwelling park or subdivision" means a parcel (or contiguous parcels) of land divided into
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two or more manufactured dwelling lots for rent or sale.
“Mean higher-high water” means the average of the higher-high water height of each tidal day observed
over the National Tidal Datum Epoch.
"Mean sea level" means, for purposes of the National Flood Insurance Program, the National Geodetic
Vertical Datum (NGVD) of 1929 or other datum, to which base flood elevations shown on the city's Flood
Insurance Rate Map are referenced.
"New construction" means, for floodplain management purposes, structures for which the "start of
construction" commenced on or after the effective date of a floodplain management regulation adopted by
City of Tigard and includes any subsequent improvements to such structures.
“No net loss” means a standard where adverse impacts must be avoided or offset through adherence to
certain requirements so that there is no net change in the function from the existing condition when a
development application is submitted to the state, tr ibal, or local jurisdiction. The floodplain functions
of floodplain storage, water quality, and vegetation must be maintained .
“Offsite” means mitigation occurring outside of the project area.
“Onsite” means mitigation occurring within the project area.
“Ordinary High Water Mark” means the line on the shore established by the fluctuations of water and
indicated by physical characteristics such as a clear, natural line impressed on the bank; shelving;
changes in the character of soil; destruction of terrestrial vegetation; the presence of litter and debris;
or other appropriate means that consider the characteristics of the surrounding areas.
“Qualified Professional” means a person who has a minimum of a bachelor’s degree in wildlife or
fisheries habitat biology, or a related degree in a biological field from an accredited college or university
with a minimum of four years’ experience as a practicing fish or wildlife habitat biologist; or is listed on
the Oregon Department of Transportation’s official list of consultants qualified to provide Endangered
Species Act Documentation.
“Reach” means a section of a stream or river along which similar hydrologic conditions exist, such as
discharge, depth, area, and slope. It can also be the length of a stream or river (with varying conditions)
between major tributaries or two stream gages, or a length of river for which the characteristics are well
described by readings at a single stream gage.
"Recreational vehicle" means a vehicle which is:
1. Built on a single chassis;
2. 400 square feet or less when measured at the largest horizontal projection;
3. Designed to be self-propelled or permanently towable by a light duty truck; and
4. Designed primarily not for use as a permanent dwelling but as temporary living quarters for
recreational, camping, travel, or seasonal use.
“Riparian” means of, adjacent to, or living on, the bank of a river, lake, pond, or other water body.
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“Riparian buffer zone (RBZ)” means the outer boundary of the riparian buffer zone is measured from
the ordinary high water line of a fresh waterbody (lake; pond; ephemeral, intermittent, or perennial
stream) or mean higher-high water line of a marine shore line or tidally influenced river reach to 170
feet horizontally on each side of the stream or 170 feet inland from the MHHW. The riparian buffer
zone includes the area between these outer boundaries on each side of the stream, including the stream
channel. Where the RBZ is larger than the special flood hazard area, the “no net loss” standards shall
only apply to the area within the special flood hazard area.
“Riparian buffer zone fringe” means the area outside of the RBZ and floodway but still within the SFHA.
“Silviculture” means the art and science of controlling the establishment, growth, composition, health,
and quality of forests and woodlands.
Special Flood Hazard Area. See "Area of special flood hazard" for this definition .
"Start of construction" includes substantial improvement and means the date the building permit was issued,
provided the actual start of construction, repair, reconstruction, rehabilitation, addition, placement, or other
improvement was within 180 days from the date of the permit. 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 dwelling on a foundation. Permanent construction does not include land
preparation, such as clearing, grading, and filling; nor does it include the insta llation of streets and/or
walkways; nor does it include excavation for a basement, footings, piers, or foundations or the erection of
temporary forms; nor does it include the installation on the property of accessory buildings, such as garages
or sheds not occupied as dwelling units or not part of the main structure. For a substantial improvement,
the actual start of construction means the first alteration of any wall, ceiling, floor, or other structural part
of a building, whether or not that alteration affects the external dimensions of the building.
"Structure" means, for floodplain management purposes, a walled and roofed building, including a gas or
liquid storage tank, that is principally above ground, as well as a manufactured dwelling.
"Substantial damage" means damage of any origin sustained by a structure whereby the cost of restoring
the structure to its before damaged condition would equal or exceed 50% of the market value of the structure
before the damage occurred.
"Substantial improvement" means any reconstruction, rehabilitation, addition, or other improvement of a
structure, the cost of which equals or exceeds 50% of the market value of the structure before the "start of
construction" of the improvement. This term includes structures which have incurred "substantial damage,"
regardless of the actual repair work performed. The term does not, however, include either:
1. Any project for improvement of a structure to correct existing violations of state or local health,
sanitary, or safety code specifications which have been identified by the local code enforcement
official and which are the minimum necessary to assure safe living conditions; or
2. Any alteration of a "historic structure," provided that the alteration will not preclude the
structure's continued designation as a "historic structure."
“Undeveloped Space” means the volume of flood capacity and fish-accessible/egress-able habitat from
the existing ground to the Base Flood Elevation that is undeveloped. Any form of development including,
but not limited to, the addition of fill, structures, concrete structures (vaults or tanks), pilings, levees and
dikes, or any other development that reduces flood storage volume and fish accessible/egress -able habitat
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must achieve the “no net loss” standards.
"Violation" means the failure of a structure or other development to be fully compliant with the city's
floodplain management regulations. A structure or other development without the elevation certificate,
other certifications, or other evidence of compli ance required in this chapter is presumed to be in violation
until such time as that documentation is provided.
9.10.030. Applicability.
A. All development within areas of special flood hazard areas is subject to the terms of this chapter and
is required to comply with its provisions and all other applicable regulations including, but not limited
to, TCDC Chapter 18.510, Sensitive Lands.
B. The areas of special flood hazard areas identified by FEMA in a scientific and engineering report
entitled "The Flood Insurance Study for Washington County, Oregon and Incorporated Areas
effective October 19, 2018" with accompanying Flood Insurance Map (FIRM Panels: 41067C0529F,
41067C0533E, 41067C0534E, 41067C0541E through 41067C0544E, and 41067C0563E) is hereby
adopted by reference and declared to be a part of this chapter.
9.10.040. General Provisions.
A. Coordination with State of Oregon Specialty Codes. Pursuant to the requirement established in ORS
455 that the City of Tigard administers and enforces the State of Oregon Specialty Codes, the City of
Tigard does hereby acknowledge that the Oregon Specialty Codes contain certain provisions that
apply to the design and construction of buildings and structures located in areas of special flood
hazard areas. Therefore, this chapter is intended to be administered and enforced in conjunction with
the Oregon Specialty Codes.
B. Warning. 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 man-made or natural causes. This
chapter does not imply that land outside the areas of special flood hazards or uses permitted within
such areas will be free from flooding or flood damages.
C. Permit Review. The duties of the Floodplain Administrator, or their designee, shall include, but not be
limited to, review all development permits to determine that:
1. Determine that theThe permit requirements of this ordinance have been satisfied;
2. Determine that allAll other required local, state, and federal permits have been obtained and
approved;
3. Review all development permits to d Determine if the proposed development is located in a
floodway.
a. If located in the floodway , assure that the floodway provisions are met;
b.4. Review all development permits to dDetermine if the proposed development is located in an
area where base flood elevation data is available either through the Flood Insurance Study or
from another authoritative source. If base flood elevation data is not available then ensure
compliance with the provisions of Section 9.10.050.J; and
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c.5. Provide to building officials the base flood elevation applicable to any building requiring a
development permit;
4. 6.Review all development permit applications to dDetermine if the proposed development qualifies
as a substantial improvement as defined by Section 9.10.020;
5.7. Review all development permits to dDetermine if the proposed development activity is a
watercourse alteration. If a watercourse alteration is proposed, ensure compliance with the
provisions in Section 9.10.050.C; and
6. 8.Review all development permits to dDetermine if the proposed development activity includes the
placement of fill or excavation ; and.
7. Determine whether the proposed development activity complies with the “no net loss”
standards in Section 9.10.060.
D. Information to be Obtained and Maintained. The following information shall be obtained and
maintained and shall be made available for public inspection as needed:
1. Obtain, record, and maintain the actual elevation (in relation to mean sea level) of the lowest floor
(including basements) and all attendant utilities of all new or substantially improved structures
where base flood elevation data is provided through the Flood Insurance Study, Flood Insurance
Rate Map, or obtained in accordance with Section 9.10.050.J.
2. Obtain and record the elevation (in relation to mean sea level) of the natural grade of the building
site for a structure prior to the start of construction and the placement of any fill and ensure that
the requirements of Section 9.10.050.N are adhered to and all other required local, state, and
federal permits have been obtained and approved.
3. Upon placement of the lowest floor of a structure (including basement) but prior to further
vertical construction, obtain documentation, prepared and sealed by a professional licensed
surveyor or engineer, certifying the elevation (in relation to mean sea level) of the lowest floor
(including basement).
4. Where base flood elevation data are utilized, obtain record drawing certification of the elevation
(in relation to mean sea level) of the lowest floor (including basement) prepared and sealed by a
professional licensed surveyor or engineer, prior to the final inspection.
5. Maintain all elevation certificates submitted to the City of Tigard.
6. Obtain, record, and maintain the elevation (in relation to mean sea level) to which the structure
and all attendant utilities were floodproofed for all new or substantially improved floodproofed
structures where allowed under this chapter and where base flood elevation data is provided
through the FIS, FIRM, or obtained in accordance with Section 9.10.050.J.
7. Maintain all floodproofing certificates required under this chapter.
8. Record and maintain all variance actions, including justification for their issuance.
9. Obtain and maintain all hydrologic and hydraulic analyses performed as required under Section
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9.10.050.N.
10. Record and maintain all substantial improvement and substantial damage calculations and
determinations as required under subsSection 9.10.040.H.
11. Documentation of how the “no net loss” standards have been met (see Section 9.10.060).
1211 . Maintain for public inspection all records pertaining to the provisions of this chapter.
E. City Boundary Alterations. The Floodplain Administrator shall notify the Federal Insurance
Administrator in writing whenever the boundaries of the city have been modified by annexation or the
city has otherwise assumed authority or no longer has authority to adopt and enforce floodplain
management regulations for a particular area, to ensure that all Flood Hazard Boundary Maps and
Flood Insurance Rate Maps accurately represent the city's boundaries. The notification will include a
copy of a map of the city suitable for reproduction, clearly delineating the new corpora te limits or
new area for which the city has assumed or relinquished floodplain management regulatory authority.
F. Watercourse Alterations. The Floodplain Administrator shall notify adjacent communities, the
Department of Land Conservation and Development, and other appropriate state and federal agencies,
prior to any alteration or relocation of a watercourse, and submit evidence of such notification to the
Federal Insurance Administration. This notification shall be provided by the applicant to the Federal
Insurance Administration as a Letter of Map Revision along with either a proposed maintenance plan
to assure the flood carrying capacity within the altered or relocated portion of the watercourse is
maintained; or certification by a registered professional engineer that the project has been designed to
retain its flood carrying capacity without periodic maintenance. The applicant shall be required to
submit a Conditional Letter of Map Revision when required under subsectionSection 9.10.040.G to
ensure compliance with all applicable requirements in subsectionSections 9.10.040.G and Section
9.10.050.C.
G. Requirement to Submit New Technical Data. The city's base flood elevations may increase or
decrease resulting from physical changes affecting flooding conditions. As soon as practicable, but
not later than six months after the date such information becomes available, the city must notify the
Federal Insurance Administrator of the changes by submitting technical or scientific data in
accordance with Title 44 of the Code of Federal Regulations (CFR), Section 65.3. The city may
require the applicant to submit such data and review fees required for compliance with this section
through the applicable FEMA Letter of Map Change process. The Floodplain Administrator shall
require a Conditional Letter of Map Revision prior to the issuance of a floodplain development permit
for proposed floodway encroachments that increase the base flood elevation and proposed
development which increases the base flood elevation by more than one foot in areas where FEMA
has provided base flood elevations but no floodway. An applican t shall notify FEMA within six
months of project completion when an applicant has obtained a Conditional Letter of Map Revision
from FEMA. This notification to FEMA shall be provided as a Letter of Map Revision.
H. Substantial Improvement and Substantial Damage Assessments and Determinations. The Floodplain
Administrator shall:
1. Conduct substantial improvement (as defined in Section 9.10.020) reviews for all structural
development proposal applications and maintain a record of Substantial Improvement
calculations within permit files in accordance with subsectionSection 9.10.040.D.
2. Conduct substantial damage assessments when structures are damaged due to a natural hazard
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event or other causes.
2. Make substantial damage determinations whenever structures within the area of special flood
hazard area (as established in Section 9.10.030.B) are damaged to the extent that the cost of
restoring the structure to its before damaged condition would equal or exceed 50% of the market
value of the structure before the damage occurred.
I. Floodplain Development Permit Required. A development permit shall be obtained before
construction or development begins within any area horizontally within the area of special flood
hazard area established in Section 9.10.030.B. The development permit shall be required for all
structures, including manufactured dwellings, and for all other development, as defined in Section
9.10.020, including fill and other development activities.
J. Application for Development Permit. Application for a development permit may be made on forms
furnished by the Floodplain Administrator and may include, but not be limited to, plans in duplicate
drawn to scale showing the nature, location, dimensions, and elevations of the area in question;
existing or proposed structures, fill, storage of materials, drainage facilities; and the location of the
foregoing. Specifically, the following information is required:
1. In riverine flood zones, the proposed elevation (in relation to mean sea level), of the lowest floor
(including basement) and all attendant utilities of all new and substantially improved structures;
in accordance with the requirements of subsectionSection 9.10.040.D;
2. Proposed elevation in relation to mean sea level to which any nonresidential structure will be
floodproofed;
3. Certification by a registered professional engineer or architect licensed in the State of Oregon that
the floodproofing methods proposed for any nonresidential structure meet the floodproofing
criteria for nonresidential structures in Section 9.10.050.M.3;
4. Description of the extent to which any watercourse will be altered or relocated;
5. Base flood elevation data for subdivision proposals or other development when required by this
chapter;
6. Substantial improvement calculation for any improvement, addition, reconstruction, renovation,
or rehabilitation of an existing structure; and
7. The amount and location of any fill or excavation activities proposed.
K. No Net Loss. Adherent to the NMFS 2016 Biological Opinion, mitigation is necessary to ensure no
net loss in floodplain functions. FEMA’s 2024 Draft Oregon Implementation Plan identifies
proxies that provide measurable actions that can prevent the net loss of the parent floodplain
functions. These proxies include undeveloped space, pervious surfaces, and trees to account for no
net loss in respective floodplain functions of floodplain storage, water quality, and vegetation.
Mitigation of these proxies must be completed to ensure compliance with “no net loss” standards.
“No net loss” standards apply to the net change in floodplain functions as compared to existing
conditions at the time of proposed development and mitigation must be addressed to the floodplain
function that is receiving the detrimental impact. The standards described below apply to a ll special
flood hazard areas as defined in Section 19.10.020.
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LK. Severability. This chapter and the various parts thereof are hereby declared to be severable. If any
section clause, sentence, or phrase of this chapter is held to be invalid or unconstitutional by any court
of competent jurisdiction, then said holding sha ll in no way effect the validity of the remaining
portions of this chapter.
ML. Abrogation. This chapter is not intended to repeal, abrogate, or impair any existing easements,
covenants, or deed restrictions. However, where this chapter and another provision, easement,
covenant, or deed restriction conflict or overlap, whichever imposes the more stringent restrictions
shall prevail.
9.10.050. National Flood Insurance Program General Standards.
In all areas of special flood hazard areas, the “no net loss” standards in Section 9.10.060 and the following
standards shall be adhered to:
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. Alteration of Watercourses. The Floodplain Administrator shall require that the flood carrying
capacity within the altered or relocated portion of said watercourse is maintained and that
maintenance is provided within the altered or relocated portion of said watercourse to ensure that the
flood carrying capacity is not diminished. Compliance with Sections 9.10.040.F and G.
D. Anchoring. All new construction and substantial improvements shall be anchored to prevent flotation,
collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads,
including the effects of buoyancy. All manufactured dwell ings shall be anchored in accordance with
subsection Section 9.10.050.M.4.
E. Water Supply, Sanitary Sewer, and On -Site Waste Disposal Systems.
1. All new and replacement water supply systems shall be designed to minimize or eliminate
infiltration of flood waters into the system.
2. New and replacement sanitary sewage systems shall be designed to minimize or eliminate
infiltration of flood waters into the systems and discharge from the systems into flood waters.
3. On -site waste disposal systems shall be located to avoid impairment to them or contamination
from them during flooding consistent with Oregon Department of Environmental Quality
regulations.
F. Electrical, Mechanical, Plumbing, and Other Equipment. Electrical, heating, ventilating, air -
conditioning, plumbing, duct systems, and other equipment and service facilities shall be elevated at
or above the base flood level or shall be designed and installed to prevent water fro m entering or
accumulating within the components and to resist hydrostatic and hydrodynamic loads and stresses,
including the effects of buoyancy, during conditions of flooding. In addition, electrical, heating,
ventilating, air-conditioning, plumbing, duct systems, and other equipment and service facilities shall,
if replaced as part of a substantial improvement, meet all the requirements of this section.
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G. Tanks. Underground tanks shall be anchored to prevent flotation, collapse and lateral movement
under conditions of the base flood. Above-ground tanks shall be installed at or above the base flood
level or shall be anchored to prevent flotation, collapse, and lateral movement under conditions of the
base flood.
H. Critical Facilities. Construction of new critical facilities must be, to the extent practicable, located
outside theareas of special flood hazard area.
1. Construction of new critical facilities, other than critical bridges, are allowed within theareas of
special flood hazard area if no feasible alternative site is available and the following applicable
criteria are met:
a. Critical facilities constructed within theareas of special flood hazard area must have the
lowest floor elevated three feet above base flood elevation or to the height of the 500 -year
flood, whichever is higher.
b. To the extent practicable, access to and from the critical facility should also be protected to
three feet above base flood elevation or to the height of the 500 -year flood, whichever is
higher.
c. Floodproofing and sealing measures must be taken to ensure that toxic substances will not be
displaced by or released into floodwaters.
2. All new and replacement critical bridges must have the lowest extension of the bridge
superstructure elevated three feet above base flood elevation or to the height of the 500 -year
flood, whichever is higher.
3. Where standard in subsSection 9.10.050.H.2 cannot be met, an analysis of alternative bridge
designs is required by a registered professional civil engineer. The proposed encroachment will
result in the least impact to base flood levels in the area of special flood hazard area of the
practicable alternative bridge designs — as demonstrated through hydrologic and hydraulic
analyses performed in accordance with standard engineering practice.
I. Subdivision Proposals.
1. All new subdivision proposals and other proposed new developments (including proposals for
manufactured dwelling parks and subdivisions) greater than 50 lots or five acres, whichever is the
lesser, shall include within such proposals, base flood elevation data.
2. All new subdivision proposals and other proposed new developments (including proposals for
manufactured dwelling parks and subdivisions) shall:
a. Be consistent with the need to minimize flood damage .;
b. Have public utilities and facilities such as sewer, gas, electrical, and water systems located
and constructed to minimize or eliminate flood damage .; and
c. Have adequate drainage provided to reduce exposure to flood hazards.
d. Comply with “no net loss” standards in Section 9.10.060.
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J. Use of Other Base Flood Data. When base flood elevation data has not been provided in accordance
with Section 9.10.030.B the local floodplain administrator shall obtain, review, and reasonably utilize
any base flood elevation data available from a federal, state, or other source, in order to administer
Section 9.10.050. All new subdivision proposals and other proposed new developments (including
proposals for manufactured dwelling parks and subdivisions) must meet the requirements of
subsectionSection9.10.050.I. Base flood elevations shall be determined for development proposals
that are five acres or more in size or are 50 lots or more, whichever is lesser in any A Zone that does
not have an established base flood elevation. Development proposals located withi n a riverine
unnumbered A Zone shall be reasonably safe from flooding; the test of reasonableness includes use of
historical data, high water marks, FEMA provided base level engineering data, and photographs of
past flooding, etc. When no base flood elevation data is available, the elevation requirement for
development proposals within a riverine unnumbered A Zone is a minimum of two feet above the
highest adjacent grade, to be reasonably safe from flooding. Failure to elevate at least two f eet above
grade in these zones may result in higher insurance rates.
K. Structures Located in Multiple or Partial Flood Zones. In coordination with the State of Oregon
Specialty Codes:
1. When a structure is located in multiple flood zones on the city's pertinent Flood Insurance Rate
Maps (FIRMs) the provisions for the more restrictive flood zone shall apply.
2. When a structure is partially located in thean area of special flood hazard area, the entire
structure shall meet the requirements for new construction and substantial improvements.
L. Specific Standards for Riverine (Including All Non -Coastal) Flood Zones. These specific standards
shall apply to all new construction and substantial improvements in addition to the general standards
contained in subsectionsSections 9.10.050.A through K and the “no net loss” standards in Section
9.10.060.
1. Flood Openings. All new construction and substantial improvements with fully enclosed areas
below the lowest floor (excluding basements) are subject to the following requirements. Enclosed
areas below the base flood elevation, including crawl spaces shall:
a. Be designed to automatically equalize hydrostatic flood forces on walls by allowing for the
entry and exist of floodwaters;
b. Be used solely for parking, storage, or building access; and
c. Be certified by a registered professional engineer or architect or meet or exceed all of the
following minimum criteria:
i. A minimum of two openings,
ii. The total net area of non-engineered openings shall be not less than one square inch for
each square foot of enclosed area, where the enclosed area is measured on the exterior of
the enclosure walls,
iii. The bottom of all openings shall be no higher than one foot above grade,
iv. Openings may be equipped with screens, louvers, valves, or other coverings or devices
provided that they shall allow the automatic flow of floodwater into and out of the
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enclosed areas and shall be accounted for in the determination of the net open area, and
v. All additional higher standards for flood openings in the State of Oregon Residential
Specialty Codes Section R322.2.2 shall be complied with when applicable.
2. Garages. Attached garages may be constructed with the garage floor slab below the base flood
elevation in riverine flood zones, if the following requirements are met:
a. If located within a floodway the proposed garage must comply with the requirements of
subsection Section 9.10.050.N;
b. The floors are at or above grade on at least than one side;
c. The garage is used solely for parking, building access, and/or storage;
d. The garage is constructed with flood openings in compliance with subsectionSection
9.10.050.L.1 to equalize hydrostatic flood forces on exterior walls by allowing for the
automatic entry and exit of floodwater;
e. The portions of the garage constructed below the base flood elevation are constructed with
materials resistant to flood damage;
f. The garage is constructed in compliance with the general standards subsectionsSections
9.10.050.A through K; and
g. The garage is constructed with electrical, and other service facilities located and installed so
as to prevent water from entering or accumulating within the components during conditions
of the base flood.
3. Detached Garages. Detached garages must be constructed in compliance with the standards for
appurtenant structures in subsection Section 9.10.050.M.6 or nonresidential structures in
subsection Section 9.10.050.M.3 depending on the square footage of the garage.
M. For Riverine (Non-Coastal) Areas of Special Flood Hazard Areas with Base Flood Elevations. In
addition to the general standards in subsectionsSections 9.10.050.A through K, the following specific
standards shall apply in riverine (non -coastal) areas of special flood hazard areas with base flood
elevations: Zones A1-A30, AH, and AE:
1. Before Regulatory Floodway. In areas where a regulatory floodway has not been designated, no
new construction, substantial improvement, or other development (including fill) shall be
permitted within Zones A1 -30 and AE on the city's Flood Insurance Rate Map (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 at any point within the city and will not result in the net loss of flood storage volume.
When determined that structural elevation is not possible and where the placement of fil l
cannot meet the above standard, impacts to undeveloped space must adhere to the “no net loss”
standards in Section 9.10.060.
2. Residential Construction.
a. New construction, conversion to, and substantial improvement of any residential structure
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shall have the lowest floor, including basement, elevated at one foot above the base flood
elevation.
b. Enclosed areas below the lowest floor shall comply with the flood opening requirements in
subsection Section 9.10.050.L.1.
3. Nonresidential Construction.
a. New construction, conversion to, and substantial improvement of, any commercial, industrial,
or other nonresidential structure shall have the lowest floor, including basement, elevated at
one foot above the base flood elevation. Or, together with attendant utility and sanitary
facilities:
i. Be floodproofed so that below the base flood level the structure is watertight with walls
substantially impermeable to the passage of water;
ii. Have structural components capable of resisting hydrostatic and hydrodynamic loads and
effects of buoyancy; and
iii. 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 or review of the structural design,
specifications and plans. Such certifications shall be provided to the Floodplain
Administrator as set forth Section 9.10.040.D.
b. Nonresidential structures that are elevated, not floodproofed, shall comply with the standards
for enclosed areas below the lowest floor in subsection Section 9.10.050.L.1.
c. 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.
4. Manufactured Dwellings.
a. Manufactured dwellings to be placed (new or replacement) or substantially improved that are
supported on solid foundation walls shall be constructed with flood openings that comply
with subsection Section 9.10.050.L.1;
b. The bottom of the longitudinal chassis frame beam shall be at or above base flood elevation;
c. Manufactured dwellings to be placed (new or replacement) or substantially improved shall be
anchored to prevent flotation, collapse, and lateral movement during the base flood.
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); and
d. Electrical crossover connections shall be a minimum of 12 inches above base flood elevation
(BFE).
5. Recreational Vehicles. Recreational vehicles placed on sites are required to:
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a. Be on the site for fewer than 180 consecutive days; and
b. 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
c. Meet the requirements of subsection Section 9.10.050.M.4, including the anchoring and
elevation requirements for manufactured dwellings.
6. Appurtenant (Accessory) Structures. Relief from elevation or floodproofing requirements for
residential and nonresidential structures in Riverine (non -coastal) flood zones may be granted for
appurtenant structures that meet the following requirements:
a. Appurtenant structures located partially or entirely within the floodway must comply with
requirements for development within a floodway found in subsection Section 9.10.050.N;
b. Appurtenant structures must only be used for parking, access, or storage and shall not be used
for human habitation;
c. Appurtenant structures on properties are limited to one -story structures less than 600 square
feet in A zones and must meet applicable setbacks from property lines;
d. The portions of the appurtenant structure located below the base flood elevation must be built
using flood resistant materials;
e. The appurtenant structure must be adequately anchored to prevent flotation, collapse, and
lateral movement of the structure resulting from hydrodynamic and hydrostatic loads,
including the effects of buoyancy, during conditions of the base flood;
f. The appurtenant structure must be designed and constructed to equalize hydrostatic flood
forces on exterior walls and comply with the requirements for flood openings in subsection
Section 9.10.050.L.1;
g. Appurtenant structures shall be located and constructed to have low damage potential;
h. Appurtenant structures shall not be used to store toxic material, oil, or gasoline, or any
priority persistent pollutant identified by the Oregon Department of Environmental Quality
unless confined in a tank installed incompliance with subsection Section 9.10.050.G; and
i. Appurtenant structures shall be constructed with electrical, mechanical, and other service
facilities located and installed so as to prevent water from entering or accumulating within the
components during conditions of the base flood.
N. Floodways. Located within the areas of special flood hazard areas established in Section 9.10.030.B
are areas designated as floodways. Because the floodway is an extremely hazardous area due to the
velocity of the floodwaters which carry debris, potential projectiles, and erosion potential, the
following provisions apply:
1. Prohibit encroachments, including fill, new construction, substantial improvements, and other
development within the adopted regulatory floodway unless:
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a. Certification by a registered professional civil engineer is provided demonstrating through
hydrologic and hydraulic analyses performed in accordance with standard engineering
practice that the proposed encroachment shall not result in any increase in floo d levels within
the city during the occurrence of the base flood discharge; or
b. A city may permit encroachments within the adopted regulatory floodway that would result in
an increase in base flood elevations, provided that a Cconditional Letter of Map Revision is
applied for and approved approval has been obtained by the Federal Insurance Administrator
through the Conditional Letter of Map Revision (CLOMR) application process, and the
requirements for such revision as all requirements established under Volume 44 of the Code
of Federal Regulations, Section 65.12 are fulfilled, and the encroachments comply with the
“no net loss” standards in Section 9.10.060.
2. If the requirements of subsection Section 9.10.050.N.1 are satisfied, all new construction,
substantial improvements, and other development shall comply with all other applicable flood
hazard reduction provisions of Section 9.10.050.
O. Standards for Shallow Flooding Areas. Shallow flooding areas appear on FIRMs as AO Zones with
depth designations or as AH Zones with base flood elevations. For AO Zones the base flood depths
range from one to three feet above ground 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. For both AO and AH Zones, adequate drainage paths are required
around structures on slopes to guide floodwaters around and away from proposed structures.
1. Standards for AH Zones. Development within AH Zones must comply with the standards in
subsection Section 9.10.050.A through O.
2. Standards for AO Zones. In AO zones, the following provisions apply in addition to the
requirements in subsection Section 9.10.050.A through K and O.
a. New construction, conversion to, and substantial improvement of residential structures and
manufactured dwellings within AO Zones shall have the lowest floor, including basement,
elevated above the highest grade adjacent to the building, at minimum to or a bove the depth
number specified on the Flood Insurance Rate Maps or at least two feet if no depth number is
specified. For manufactured dwellings the lowest floor is considered to be the bottom of the
longitudinal chassis frame beam.
b. New construction, conversion to, and substantial improvements of nonresidential structures
within AO Zones shall either:
i. Have the lowest floor (including basement) elevated above the highest adjacent grade of
the building site, at minimum to or above the depth number specified on the Flood
Insurance Rate Maps or 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 the depth number specified on the Flood Insurance Rate Map or a minimum of two
feet above the highest adjacent grade if no depth number is specified, so that an y 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 the effects of buoyancy. If this method is used , compliance shall
be certified by a registered professional engineer or architect as stated in subsection
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Planning Commission Draft
Section 9.10.050.M.3.a.iii.
c. Recreational vehicles placed on sites within AO Zones on the city's Flood Insurance Rate
Maps shall either:
i. Be on the site for fewer than 180 consecutive days; and
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 elevation requirements of subsection Section 9.10.050.O.2.a, and the anchoring
and other requirements for manufactured dwellings of subsection Section 9.10.050.M.4.
d. In AO Zones, new and substantially improved appurtenant structures must comply with the
standards in subsection Section 9.10.050.M.6.
e. In AO zones, enclosed areas beneath elevated structures shall comply with the requirements
in subsection Section 9.10.050.L.1.
9.10.060. No Net Loss Standards.
A. General Provisions.
1. No net loss of the proxies for the floodplain functions is required for development in the special
flood hazard area that would reduce undeveloped space, increase impervious surface, or result
in a loss of trees that are 6 -inches dbh or greater. “No net loss” standards can be achieved by
first avoiding negative effects to floodplain functions to the degree possible, then minimizing
remaining effects, then replacing and/or otherwise compensating for, offsetting, or rectifying the
residual adverse effects to the three floodplain functions.
2. Compliance with “no net loss” standards for undeveloped space or impervious surface is
preferred to occur prior to the loss of habitat function but, at a minimum, shall occur concurrent
with the loss.
3. Mitigations that meet “no net loss” standards must be provided within, in order of preference:
1) the lot or parcel that floodplain functions were removed from, 2) the same reach of the
waterbody where the development is proposed, or 3) the special flood hazard area within the
same hydrologically connected area as the proposed development. Table 9.10 presents the no net
loss mitigation ratios, which increase based on the preferences listed above .
B. Undeveloped space. Development proposals shall not reduce the fish-accessible and egress-able
habitat and flood storage volume created by undeveloped space within the special flood hazard
area. A development proposal with an activity that would impact undeveloped space shall achieve
no net loss of fish-accessible and egress-able space and flood storage volume. Lost undeveloped
space must be replaced with fish-accessible and egress-able compensatory volume based on the
ratio in Table 1; must be hydrologically connected to the waterbody that is the flooding source ; and
must be designed so that there is no increase in velocity .
C. Impervious surfaces. Impervious surface mitigation shall be mitigated through any of the following
options:
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Planning Commission Draft
1. Development proposals shall not result in a net increase in impervious surface area within the
special flood hazard area through the use of ratios prescribed in Table 1, or
2. Use low impact development or green infrastructure to infiltrate and treat stormwater produced
by the new impervious surface, as documented by a registered professional engineer, or
3. If prior methods are not feasible and documented by registered professional engineer
stormwater retention is required to ensure no increase in peak volume or flow and to maximize
infiltration, and treatment is required to minimize pollutant loading. See Section 9.10.060.E.3
for stormwater retention specifications.
D. Trees. Development proposals shall result in no net loss of trees 6 -inches dbh or greater within the
special flood hazard area.
1. Trees of or exceeding 6-inches dbh that are removed from the RBZ, Floodway, or RBZ -fringe
must be replaced at the ratios in Table 1 and planted within the special flood hazard area.
2. Replacement trees must have a minimum caliper of 1.5 inches or equivalent in height and be
native species that would occur naturally in the Level III ecoregion of the impact area.
E. Stormwater Management. Any development proposal that cannot mitigate as specified in Sections
9.10.060.C.1 and 9.10.060.C.2 must include the following:
1. Water quality (pollution reduction) treatment for post -construction stormwater runoff from any
net increase in impervious area; and
2. Water quantity treatment (retention or detention facilities) unless the outfall discharges into the
ocean.
3. Retention and detention facilities must:
a. Limit discharge to match the pre-development peak discharge rate (i.e., the discharge rate
of the site based on its natural groundcover and grade before any development occurred)
for the 10-year peak flow using a continuous simulation for flows between 50 percent of
the 2-year event and the 10 -year flow event (annual series).
b. Treat stormwater to remove sediment and pollutants from impervious surfaces such that at
least 80 percent of the suspended solids are removed from the stormwater prior to
discharging to the receiving water body.
c. Be designed to not entrap fish.
d. Be certified by a registered professional engineer.
4. Detention facilities must be designed by a registered professional engineer and drain to the source
of flooding.
5. Stormwater treatment practices for multi -parcel facilities, including subdivisions, shall have an
enforceable operation and maintenance agreement to ensure the system functions as designed.
This agreement will include:
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Planning Commission Draft
a. Access to stormwater treatment facilities at the site by the City of Tigard for the purpose of
inspection and repair.
b. A legally binding document specifying the parties responsible for the proper maintenance of
the stormwater treatment facilities. The agreement will be recorded and bind subsequent
purchasers and sellers even if they were not party to the original agreement.
c. For stormwater controls that include vegetation and/or soil permeability, the operation and
maintenance manual must include maintenance of these elements to maintain the
functionality of the feature.
d. The responsible party for the operation and maintenance of the stormwater facility shall have
the operation and maintenance manual on site and available at all times. Records of the
maintenance and repairs shall be retained and made available for inspecti on by the City of
Tigard for five years.
F. Exempt Activities. The following activities are not subject to the “no net loss” standards; however,
they may not be exempt from floodplain development permit requirements.
1. Normal maintenance of structures, such as re-roofing and replacing siding, provided there is no
change in the footprint or expansion of the roof of the structure.
2. Normal street, sidewalk, and road maintenance, including filling potholes, repaving, and
installing signs and traffic signals, that does not alter contours, use, or alter culverts and is less
than six inches above grade. Activities exempt do not include expansion of paved areas.
3. Routine maintenance of landscaping that does not involve grading, excavation, or filling .
4. Routine agricultural practices such as tilling, plowing, harvesting, soil amendments, and ditch
cleaning that does not alter the ditch configuration provided the spoils are removed from special
flood hazard area or tilled into fields as a soil amendment.
5. Routine silviculture practices (harvesting of trees), including hazardous fuels reduction and
hazard tree removal as long as root balls are left in place.
6. Removal of noxious weeds and hazard trees, and replacement of non -native vegetation with
native vegetation.
7. Normal maintenance of above ground utilities and facilities, such as replacing downed power
lines and utility poles provided there is no net change in footprint.
8. Normal maintenance of a levee or other flood control facility prescribed in the operations and
maintenance plan for the levee or flood control facility. Normal maintenance does not include
repair from flood damage, expansion of the prism, expansion of the face or toe or addition of
protection on the face or toe with rock armor.
9. Habitat restoration activities.
10. Pre-emptive removal of documented susceptible trees to manage the spread of invasive species.
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11. Projects that are covered under separate consultations under Section 4(d), 7, or 10 of the
Endangered Species Act (ESA).
G. Riparian Buffer Zone (RBZ).
1. The Riparian Buffer Zone is measured from the ordinary high-water line of a fresh waterbody
(lake; pond; ephemeral, intermittent, or perennial stream) or mean higher -high water of a
marine shoreline or tidally influenced river reach to 170 feet horizonta lly on each side of the
stream or inland of the MHHW. The riparian buffer zone includes the area between these outer
boundaries on each side of the stream, including the stream channel.
2. Functionally dependent uses are only subject to the “no net loss” standards in Sections 9.10.060.A
through D for development in the RBZ. Ancillary features that are associated with but do not
directly impact the functionally dependent use in the RBZ (including manufacturing support
facilities and restrooms) are subject to the beneficial gain standard in addition to “no net loss”
standards.
3. Any other use of the RBZ requires a greater offset to achieve no net loss of floodplain functions,
on top of the “no net loss” standards described above, through the beneficial gain standard.
4. Under FEMA’s beneficial gain standard, an area within the same reach of the project and
equivalent to 5% of the total project area within the RBZ shall be planted with native herbaceous,
shrub and tree vegetation.
Table 9.10 “No Net Loss” Mitigation Standards
Basic Mitigate
Ratios
Undeveloped
Space (ft3)
Impervious
Surface (ft2)
Trees
(6”<dbh≤20”)
Trees
(20”<dbh≤39”)
Trees
(39”<dbh)
RBZ and Floodway 2:1 1:1 3:1 5:1 6:1
RBZ-Fringe 1.5:1 1:1 2:1 4:1 5:1
Mitigation Multipliers:
Mitigation onsite
to Mitigation
offsite, same reach
100% 100% 100% 100% 100%
Mitigation onsite
to Mitigation
offsite, different
reach, same
watershed (5th
field)
200% 200% 200% 200% 200%
Notes:
1. Mitigation multipliers of 100% result in the required mitigation occurring at the same value
described by the ratios above, while multipliers of 200% result in the required mitigation being
doubled. For example, if a development would create 1,000 square feet of new impervious
surface, then 1,000 square feet of new pervious surface would need to be created. However, if
only 500 square feet can be created within the same reach, the remaining 500 square feet created
within a different reach would need to be double the required amount because of the 200 percent
multiplier. In other words, another 1,000 square feet of pervious surface would need to be created
at the location in the different reach, in addition to the 500 square feet created within the same
reach.
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9.10.0760. Violations.
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, including, but not limited to,
TCDC Chapter 18.510, Sensitive Lands. Violations of the provisions of this chapter by failure to comply
with any of its requirements (including violations of conditions and safeguards established in connection
with conditions) shall constitute a Class 1 civil infraction, processed according to the procedures in the
civil infractions ordinance, set out in TMC Chapter 1.16. Each violation of a separate provision of this
chapter shall constitute a separate infraction, and each day that a violation of this chapter is committed or
permitted to continue shall constitute a se parate infraction. A finding of a violation of this chapter shall
not relieve the responsible party of the duty to abate the violation. The penalties imposed by this section
are in addition and not in lieu of any remedies available to the city. If a provis ion of this chapter is
violated by a firm or corporation, the officer or officers, or person or persons responsible for the violation
shall be subject to the penalties imposed by this chapter. Nothing contained herein shall prevent the City
of Tigard from taking such other lawful action as is necessary to prevent or remedy any violation.
Attachment 1