ORD 2009-13 SURFACE STORMWATER MANAGEMENT
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ORDINANCE NO. 2009-13
AN ORDINANCE of the City. of.
Bainbri~ge 'Island, relating to Surface and.
Stormwater ' Management; ., amending
Chapter 15.20 of the Bainbridge Island.
Municipal Code.
WHEREAS, the City. Council wishes to amend standards for surface and
stormwater management consistent with Department of Ecology guidelines; and
WHEREAS, the City Council, in amending the standards, complies with the
condition of the city's Municipal Stormwater Discharge Permit, S5.C4.a; and
WHEREAS, the City Council adopted Chapter 15.20 to Title 15 of the City.of
Bainbridge Islan.d Municipal Code on February 4, 1999 and amended it on November 22,
2005; and
WHEREAS, the City desires to amend the following sections of Chapter 15.20;
now, therefore,
THE CITY COUNCIL OF THE CITY .OF. BAINBRIDGE. ISLAND,.
WASHINGTON, DO ORDAIN AS FOLLOWS:
Section 1.
follows:
Section 15~20.010 of the Bainbridge Island Municipal Code is amended as
"15.20.010 Purpose
The provisions of this chapter are intended to establish regulation for all
new development, ef redevelopment or construction activities within the
city that will or may impact surface or storm waters. The provisions of this
chapter establish the minimum requirements that must be met to. permit a
property to be developed, ef rede.veloped or ..proceed with construction
activities within.,the city~ The purpose of this chapter is to:
A. Preserve and .enhance the suitability of waters for contact recreation,
fishing, and other beneficial uses;
B.. Minimize water quality degradation and sedimentation in streams,
ponds, lakes, wetlands and other water bodies;
c~ Minimize the impact of increased runoff, erosion and sedimentation
caused by land development and poor .maintenance practices;
D~ Maintain and protect ground water resources;
E. Minimize .adverse impacts from projects on ground and. surface water
quantities, locations and flow patterns;
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F. Decrease potential landslide, flood and erosion damage to public and
private property;
G~ Promote site planriing and construction pr~ctices that are consistent
with natural topographical, vegetational and hydrological conditions;
H. Maintain and protect the city stonn-water management. infrastructure
and downstream systems and properties;
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Section 2. Section 15.20.020 .of the Bainbridge Island Municipal Co.de is amended to
read as follows:
"15.20.020 Definitions
1. "Approval" means the proposed work or completed work conforms to
this chapter in the opinion of the director.
2. "As-graded" means the extent of surface conditions on completion. of
grading~
3. "Basin plan" means a plan and all implementing regulations and
procedures including but not limited to land use management adopted by
ordinance for managing surface and stonn-water .management facilities
and features within individual sub-basins~
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4. ".Bedrock" means the more or less solid rock in place either on or
beneath the surface of the earth~ It may be soft, medium, or hard and have
a smooth or irregular surface.
5.. "Bench" means ..a relatively level step excavated into earth material on
which fill is to be placed.
6. "Best management practice (BMP)". means physical, structural, and/or.
managerial practices that,-when used singly or in.combination, prevent or
reduce pollution of water. BMPs are listed and described in the manual.
79 "Certified Erosion and Sediment Control Lead (CESCL)" - means an
individual who has current certification through an approved erosion and
sediment control training program that meets the minimum training
standards established. by the Department of Ecology (see BMP C160 in the
manual)~ A CESCL is knowledgeable in the principles and practices of
erosion and se~iment controL The CESCL must have the skills to assess
site conditions and construction activities that could impact the quality of
stormwater and, the effectiveness of erosion . and sediment control
measures used to control the quality of stormwater discharges.
Certification is obtained through an Ecology-approved erosion and
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sediment c.o'ntrol course. Course listings are provided online at Ecology's
web site~
8. "City" shall mean the city of Bainbridge Island.
9. "Civil engineer" means a professional engineer licensed in the state of
Washington in civil engineering who is experienced and knowledgeable in.
the practice.
10. "Civil engineering" means the application of the knowledge of the
forces of nature, principles of mechanics and the properties of materials
and to the evaluation, design and construction of civil works~
11. "Clearing" means the destruction and removal of vegetation by
manual, mechanical, or chemical methods.
12. "Commercial' .agriculture" means those activities conducted on lands
defined in RCW 84.34.020(2), and activities involved in the production of
crops or livestock for wholesale trade~ An activity ceases to be considered
commercial agriculture when the area on which it is conducted is proposed
for conversion to a nonagricultural use or has been idle for more than five
years, unless. the idle land is registered in a federal or state soils
conservation program, or unless the activity is maintenance of irrigation
ditches, laterals, canals, or drainage ditches related to an existing and
ongoing agricultural activity.
13 ~ "Compaction" means densification of a fill by mechanical means.
14. "Critical areas" means, at a minimum, areas which include wetlands,
areas with a critical recharging effect on aquifers used for potable water,
fish and wildlife habitat conservation areas, frequently flooded areas,
geologically hazardous areas, including unstable slopes, and associated
areas and ecosystems~ Reference Chapter 16.20 BIMC.
15. ."Design storm" means a prescribed hyetograph and total precipitation
amount (for a specific duration recurrence frequency) used. to estimate
runoff for a hypothetical storm for the purposes of analyzing existing
drainage, designing new drainage facilities or assessing other impacts of a
proposed project on the flow of surface water~ (A hyetograph is a graph of
. percentages of total precipitation for a series of time steps representing the
total time during which the precipitation occurs.)
16. "Detention" means the release of storm-water runoff from a specific
site at a slower rate than it is collected by the storm-water facility system,
the difference being held in temporary storage~
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17. "Detention facility" means an above or below ground facility, such as
a pond .or tank, that temporarily stores storm-water runoff and
subsequently releases it at a slower rate than it is collected by the drainage
facility system. There is little or no .infiltration of stored storm-water.
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18. "Drainage basin" means a geographic. and hydrologic subunit of a
watershed~ Further clarification is located in the .drainage reconnaissance
study or basin assessment
19~ "Earth . material" means any rock, natural soil or fill. and/or any
combination thereof.
20. "Engineering geologist" means a geologist experienced and
knowledgeable in engineering geology.
21.. "Engineering geology" means the application of geologic knowledge
and principles in the investigation and evaluation of naturally occurring
rock and soil for use in the design of civil works.
22~ "Erosion" means the wearing away of the land surface by rurming
water, wind, ice, or other geological agents, including. such processes as
gravitational creep, or the detaclunent and movement of soil or rock
fragments by water, wind, ice, or gravity.
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23 ~ "Excavation" means the mechanical removal of earth material.
24. "Experimental BMP" means a BMP that has not been tested, .evaluated
and approved for general use by the Department of Ecology in
collaboration with local governments and technical experts~ These include
BMPs known as emerging technologies~
25. "Fill" means a deposit of earth material placed by artificial means~
26. "Forest practice" means any activity conducted on or directly
pertaining to forest land and relating to growing, harvesting, or processing
timber, as defined by RCW 76~09.050.
27. "Frequently ,flooded areas" means the IOO-year floodplain
designations of the Federal Emergency Management Agency and the
National Flood Insurance Program. Reference Chapter 15.16 BIMC~
28. "Geologically hazardous areas" means areas susceptible to erosion,
sliding, earthquakes, or other geological events. They pose a threat to the
health and safety of citizens when used as sites for commercial, residential
or industrial development. Reference Chapter 16~20 BIMC~
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29. "Grade'.' means the slope .of a road, channel, or natural ground, the
finished surface of a canal b.e.d, roadbed, top of embankment, or bottom of
excavation or any .surface .prepared for.the support of construction such as .
paving or the laying of a conduit.
a. "Existing grade" means the grade prior to grading.
b~ "Rough grade" means. the stage at which the grade approximately
conforms to the approved plan.
c~ "Finish grade" me'ans the final grade of the site which conforms to the
approved plan. .
30. "Grade, to" ("to grade") means to finish the surface of a canal bed,
roadbed, top of embankment or bottom of excavation.
31. "Gradient terrace" means an earth embankment or a ridge-and-channel
constructed with suitable spacing and an acceptable grade to reduce
erosion damage by intercepting surface runoff and conducting it to a stable
outlet at a stable non...erosive .velocity.
32. "Ground water" means water in a saturated zone. or stratum beneath
the surface of land or a surface water body.
33~ "Hydroperiod" means the seasonal occurrence of flooding and/or soil
saturation; it encompasses depth, frequency, duration, and seasonal pattern
of inundation.
34. "Illicit discharge" and "illegal connections" are as defined In
Bainbridge Island Municipal Code 9hapter 15.22.020.
35~ "Impervious surface" means a hard surface area which either prevents
or retards the entry of water . into the soil mantle as under natural
conditions prior to development and/or a hard surface area which causes
water to run off the surface in greater quantities or at an increased rate of
flow from the flow present under n'atural conditions prior to development.
Common impervious surfaces include, but are not limited to, roof tops,
walkways, patios, driveways, parking lots Of, storage areas, concrete or
asphalt paving,. gravel roads, packed earthen materials, and oiled,
macadam or other surfaces which similarly impede the natural infiltration
of storm-water. Open, uncovered retention/detention facilities shall.not be
considered as impervious surfaces for purposes of determining whether
the thresholds for application. of minimum requirements are exceeded~
Open, uncovered retention/detention facilities shall be considered
impervious surfaces for purposes of runoff modeling.
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36~ "Interflow" means that portion of rainfall that infiltrates into the soil
and moves. laterally through the upper soil horizons until intercepted by a
stream channel or until it returns to the surface; for example, in a wetland,
sprIng or seep.
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3 7. "Land disturbing activity" means any activity that results in movement
of earth, or a change in the existing soil cover (both vegetative and non-
. vegetative) and/or the existing soil topography. Land disturbing activities
include, but are not limited to clearing, grading, filling and excavation.
Compaction that is associated with stabilization of structures and road
construction shall also be considered a land disturbing activity.
Vegetation maintenance practices are not considered land-disturbing
acti vi ty.
38. "Mitigation" means, in the following order of preference:
a. Avoiding the impact altogether .by not taking a certain action or part of
an action;
b~ Minimizing impacts by limiting the degree or magnitude of the action
and its implementation, by using appropriate technology, or by taking
affirmative steps to avoid or reduce impacts;
c. Rectifying the impact by repairing, rehabilitating or restoring the
affected envirorunent;
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d~ Reducing or eliminating the impact over time by preservation and
maintenance operations during the life of the action.
39~ "Natural location" means the location of those channels, swales, and
other non-manniade conveyance systems as defined by the first
documented topographic contours existing for the subject property, either
from maps or photographs, or such other means as appropriate.
40. "New development" land disturbing activities, including Class IV -
general forest practices that are conyersions from timber land to other
uses; structural development, including construction or installation of ~
building or other structure; creation of impervious surfaces; and
subdivision,.. s~ort subdivision and binding site. plans, as defined and
applied in. Chapter 58.17 RCW. Projects meeting the definition of
redevelopment shall not be considered new development~
41. "Pollution" shall be construed to means such contamination or other
alteration of the physical, chemical, or biological properties, of waters of
the state, including change in temperature, taste, color, turbidity, or odor
of the waters, or such discharge of any liquids, gaseous, solid, radioactive
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or other substance into any waters of the state as will or is likely to create
a nuisance or render such waters harmful, detrimental or injurious to the.
public health, safety or welfare, or to domestic, conunercial, industrial,
agricultural, recreational, or other legitimate beneficial uses, or to
livestock, wild animals, birds, fish or other aquatic life; as defined in
RCW 90~48..020 as now existing or hereafter amended.
42. "Redevelopment" means--on a site that is already substantially
developed (i.e~,. .has 350/0 or more of existing impervious surface
coverage), the creation or addition of impervious surfaces; the expansion
of a building footprint or addition or replacement of a structure; structural
development including. construction,. installation or expansion of a
building or other structure;; replacement of impervious surface that is not
part of a routine maintenance activity; and land disturbing activities.
43. "Regional retention/detention system" means a storm-water quantity
control structure designed to correct existing excess .surface water runoff
problems of a basin or sub-basin for two or more . properties. The area.
downstream has been previously identified as having existing or predicted
significant and regional flooding and/or erosion problems. This term is
also used when a detention facility is used -to detain storm-water runoff
from a number of different businesses, developments or areas within a
catchment.
44~ "Retention/detention. facility (RID)" means a type of drainage facility
designed either to hold water for a considerable length of time and then
release it by evaporation, plant transpiration, and/or infiltration into the
ground; or to hold surface and storm-water runoff for a short period of
time and then reh;~ase it to the surface and storm-water management
system~
45. "Site" means-the area defined by the legal boundaries of a parcel or
parcels of land that. is (are) subject to new development or redevelopment..
For road projects, the length of the project site and the right-of-way
boundaries define the site.
46. "Slope" means the degree of deviation of a surface from the
horizontal, . measured as a numerical ratio, percent, or in degrees.
Expressed as a ratio, the first number is the horizontal distance (run) and
the second is the vertical distance (rise), as 2: 1.. A 2: 1 slope is a 50 percent
slope. Expressed in degrees, the slope is the angle from the horizontal
plane, with a 90 degree slope being vertical (maximum) and 45 degrees
being a 1: 1 or 100 percent slope.
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47. "Soil" means the unconsolidated .mineral and organic material on the
immediate surface of the. earth that serves as a natural medium. for the
growth of land plants.
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48. "Source control BMP" means a structure or operation that is intended
to prevent pollutants from coming into contact with stonnwater through
physical separation of areas or careful management of activities that are
sources of pollutants. .The manual separates source control BMPs into two
types. Structural Source Control BMPs are physical, structural, or
mechanical devices, or facilities that are intended to. prevent pollutants
from entering stormwater~ Operational BMPs are non~structural practices
that prevent or reduce pollutants from entering stormwater. See Volume
IV of the manual for details~
49. "Storm-water" means that portion of precipitation that does not
naturally percolate into the ground or evaporate, but flows via overland, ,
interflow, channels or pipes into a defined surface water challl1el, or a
constructed. -intil trati on facility.
50. "Storm-water drainage system" means constructed and natural features
which function together as a system to collect, convey, channel, hold,
inhibit, retain, detain, infiltrate, divert, treat or filter stonn-water.
51. "Stonn-water facility'~ means a constructed component of a storm
water drainage system, designed or constructed to perform a particular
function, or multiple functions, including but not limited to, pipes, swales,
ditches, culverts,. street gutters, detention basins,. retention basins,
constructed . wetlands, infiltration devices, catch basins, oil/water
separators, sediment basins and modular pavement
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52. "Storm-water management manual" or "(manual)" means the
Stormwater Management Manual for Western Washington adopted by
reference and .prepared by .Washington State Department of Ecology,
dated February 2005 Publieation Numbers 05-10-029 through 05-10-033
including subsequent publications which contains BMPs to prevent or
reduce poIlution~
53. "Toe of slope" . means a point or line of slope in an excavation or cut
where the lower surface changes to horizontal or meets.the exiting ground
slope.
-S4~ "Top of slope" means a point or line on the upper surface of a slope
where it changes to horizontal or meets the original surface.
55. "Unstable slopes" means those sloping areas of land which have
exhibited past and present history of mass movement of earth.
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56~ "Vegetation'~ means all organic.plant life growing on the surface of the
earth. Reference Chapter 16~24 BIMC.
57. "Watershed" means a geographic region within which water drains
into a particular river, stream,_ or body of water as identified. and numbered
by the state of Washington Water Resource Inventory Areas (WRIAs) as
defined in Chapter 173-500 W AC~
58. "Wetlands" means those areas that are inundated or saturated by
surface or ground water at a frequency and duration sufficient to support,
(and under normal circumstances do support), a prevalence of vegetation
typically adapted for life in saturated soil conditions, such as swamps,
marshes, bogs~ and other similar areas. This definition includes wetlands
created, restored or enhanced as part of.a mitigation .procedure; it does not
include constructed wetlands or the following surface waters of the state
intentionally constructed from sites that are not wetlands: irrigation and.
drainage ditches, grass-lined swales, canals, agricultural detention
facilities, farm ponds, and' landscape amenities. Reference Chapter 16.20
BIMC~"
Section 3. Section 15.20..040 of the Bainbridge Island Municipal Code is amended to
read as follows.
"15.20.040 Regulated activities and allowed activities.
A. Regulated Activities. Consistent with the minimum requirements
contained in the manual, the administrator shall approve or disapprove the
following a.ctivities.
1. New Development.
a. Land disturbing activities;
b~ Structural development, including construction, installation or
expansion of an existing building or other structure;
c~ Creation of new impervious surfaces greater than 800 square feet;
d~ Class IV general forest practices that are conversions from timber land
to other uses; and
e. Subdivision,. short subdivision and binding site plans, as defined in
RCW 58.17~020_
2~ Redevelopment. On an already developed site, the creation or addition
of impervious surfaces greater than 800 square feet; structural
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development including constructi~n, installatipn. or expansion of . . a
building or other structure; any land disturbing . activity, andlor
replacement of impervious surface (that is not part of a routine
maintenance activity); and. land disturbing activities associated. with
structural_or imp.ervious redevelopment."-
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Section 4. Section 15.20.050 of the Bainbridge Island Municipal Code is amended to
read as follows:
"15.20.050 General Requirements.
A. Stonnwater Management Manual Adopted. The February 2005 Edition
of Washington State Department of Ecology's Stormwater Management.
Manual for Western Washington. is hereby. adopted by reference and is
hereinafter. referred to as the manual; provided, that certain provisions of
the manual are amended as stated in BIMC 15.20.060~
B. Illicit discharges: and illegal connections to the. stormwater drainage
system are prohibited by Bainbridge Island Municipal Code Chapter
15.22.
c. Low impact development manual adopted. The 2009 edition of the
Low Impact Development (LID) Guidance Manual - A Practical Guide to
LID Implementation in Kitsap County is hereby adopted by reference and ..
is hereinafter referred to as the LID Manual for use in meeting the relevant
sections of the manual."
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Section 5. Section 15.20.060 of the Bainbridge Island Municipal Code IS
amended to read as follows:
"15.20.060 Approval Standards.
A. In V olurne I, Section 2.3 of the manual, Definitions Related to
Minimum Requirements, the definition of "threshold discharge. area" is
not adopted.
B~ In Volume I, Section 2.5.6 of the manual, Minimum Requirement No.6.
Runoff Treatment, and Section 2.5.7, Minimum Requirement No.7 Flow
Control and Section. 4.2, . BMP and Facility Selection Process, references
to "threshold discharge area" are deleted.
c. In Volume I, Section 2~4.1 of the manual, New Development is
amended to read as follows:
All new development that shall be required to comply with
Minimum Requirement No.2. -In addition, new development
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that exceeds certain thresholds shall be required to comply .
with additional Minimum Requirements as follows4 The
following new development shall .comply. with Minimum
Requirements No.. 1 through .No. 5:
1 ~ Creates or adds 800 square. feet, or greater, of .new,
replaced, or new pluS replaced impervious surface area, or
2~ Has land disturbing activity of 7,000 square feet or greater.
The following new development shall comply with Minimum
Requirements No. 1 through 10:
1. Creates or adds 5,000 square feet, or more,. of new
impervious surface area, or
2. Converts '3/4 acres, .or more, of native vegetation to lawn.
or landscaped areas, or
3t Converts 2.5 acres, or more, of. native vegetation to
pasture.
D. In Volume I, Section 2.4.2 of the manual, Redevelopment, is amended
to read as follows:.
All redevelopment shall be required to comply with
Minimum Requirement No~ 2. In addition, all redevelopment
that excee.ds certain thresholds shall be required to comply
with additional Minimum Requirements as follows.
The following redevelopment shall comply with Minimum
Requirements No.1 through No.5 for the new and replaced
impervious surfaceS and the land disturbed:
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1. The new, replaced, or total of new plus replaced
impervious surfaces is 800. square feet or more, or
2.7,000 square feet or more of land disturbing activities.
The following redevelopment shall comply with Minimum
Requirements No. 1 through 10 for the new impervious
surfaces and converted pervious areas:, .
1. Adds 5,000 square feet or more of new impervious
surfaces, or
2. Converts 3/4 acres, or more, of native vegetation to lawn
or landscaped areas, or
3~ Converts 2.5 acres, or more, of native vegetation to
pasture~
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If the runoff from the new impervious surfaces and conv~rted
pervious surfaces is not separated from runoff from other
surfaces on. the project. site, the 'stormwater treatment
facilities must be sized for the entire flow that is directed to
them.
The administrator may allow the Minimum Requirements to
be met for an equivalent (flow and pollution characteristics)
area within the same site. For public roads projects, the
equivalent area does not have to be within the project limits,
but must drain to the sam.e receiving water. ' . .
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Additional Requirements for the Project Site
For road-related projects, runoff from the replaced and. new
. impervious surfaces (including pavement, shoulders, curbs,
and sidewalks) shall meet all the Minimum Requirements if
the new impervious surfaces total 5,000 square feet or more
and total 50% or more of the existing impervious surfaces
within the project limits. The project limits shall be defined
by the length of the project and the width of the right-of-way.
Other types of redevelopment projects shall comply with all
the Minimum Requirements for the new and replaced
impervious surfaces if the total of new plus replaced
impervious surfaces, ~s 5,000 square feet or more, and the
valuation of proposed improvements - including interior.
improvements ~ exceeds 50% of the assessed value .of the
existing site improvements.
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E. In Volume I, Section 2~5.1 0 of the Mmanual, ."Minimum Requirement
#10: Operation and Maintenance", is amended to read as follows: An
operation and maintenance manual that is consistent with BIMC 15~21 and
the provisions in Volume V of this manual shall be provided for all
proposed private stormwater facilities and BMPs, and the party (or parties)
responsible for maintenance and operation shall be identified. For private
facilities, a copy of the. manual shall be provided to the city prior to
occupancy and a copy retained onsite or within reasonable access to the
site, and shall be transferred with the property to subsequent owners. The
copy of the manual shall be: retained in the Public Works Department. A
log of maintenance activity that indicates .what actions were taken shall be
kept and be available for inspection by the Administrator.
F.. In Volume I, Section 2.6.1 pf the manual, Financial Liability/Bonding,
is not adopted.
G. In Volume I, Section 2.6.2 of the manual, Optional Guidance No.2:
Off Site Analysis and Mitigation, and V olwne I, Section 3.1 ~3, Perform an
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Offsite Analysis, are adopted by reference and established for. projects
creating 5,000 square feet-or more of impervious area~
I-I. In Volume I, Section 2.6.2 of the-, manual, Optional Guidance No.2: .
Off Site Analysis and Mitigation Development, is amended to read as .
follows:
Development projects that discharge stormwater off-site shall
submit an off~site analysis report that assesses the potential
off-site water quality, erosion, slope stability, and drainage
impacts associated with the project and. that proposes
appropriate mitigation of those impacts. An initial qualitative
analysis shall extend downstream for the entire flow- path-
from the project site to the receiving water or up to one mile,
whichever is less.
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If a receiving. water is within one..quarter mile, the analysis
shall extend within the receiving water - to one-quarter mile
from the project site. The analysis shall extend one-quarter.
mile beyond any. improve~ents proposed as mitigation. The
analysis must extend upstream to a point where any.
backwater effects created by the project cease. Upon review
of the qualitative, analysis,. the local. administrator may
require that a quantitative analysis be performed~
The existing. or potential impacts to be evaluated and
mitigated shall include:
1 ~ Conveyance system capacity problems;
2. Localized flooding;
3. Upland erosion impacts, including landslide hazards;
4. Stream channel erosion at the outfall location;
5. Violations of surface water quality standards as identified
in a Basin Plan or a TMDL (Water Clean-up Plan); or
violations of ground water standards in a wellhead protection
area~
Projects shall be required to initially submit, with the permit
application, a qualitative analysis of each downstream system
leaving a site. The analysis should accomplish four tasks:
Task 1 - Define and map the study area.
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Submission of ' . a site map .. showing property lines; a
topographic map (at R: minimum a USGS - 1 :24000
Quadrangle Topographic map) showing site boundaries,
study area boundaries,. downstream, flowpath, and
potential/existing problems~
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Task 2 - Review all available information on the study area.
This should include all available basin plans, ground water
management area. plans, drainage studies,
floodplain/floodway FEMA maps, wetlands. inventory maps,
Critical Areas maps,. stream. habitat reports, salmon -
distribution reports, etc.
Task 3 - Field inspect the study area.
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The design engineer. should physically. -inspect the existing
on- and off-site drainage systems of the study area for each.
discharge location. for existing or potential problems. and
drainage features~ An initial inspection and investigation
should include:
1. Investigate problems reported or observed during. the
resource review;
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2. Locate existing/potential constrictions or capacity
deficiencies in the drainage system;
3. Identify existing/potential flooding pto.blems;
4~ Identify. existing/potential overtopping, scouring, bank
sloughing, or sedimentation;
5. Identify significant destruction of aquatic habitat (e.g.,
siltation, stream incision);
6. Collect qualitative data on features such as land use,
impervious surface,. topography,. soils, presence of streams,
wetlands;
7. Collect information on pipe sizes, channel characteristics,
drainage structures;
8. Verify tributary drainage areas identified in Task 1;
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9. Contact the local .government.office with. drainage review.
authority, neighboring p.roperty owners, and residents about
drainage problems; and
10. Note date and weather at time of inspection.
Task 4. - Describe the drainage. system, and.. its existing and
predicted problems.
For each .drain~ge system component (e.g., pipe, culvert,
bridges, outfalls, ponds, vaults) the following should be
covered in the analysis: location, physical description,
problems, and field observations. All existing or potential
problems (e.g., ponding water, erosion) identified in t.asks 2
and 3 above should be described~ The descriptions should be
used to determine whether adequate mitigation can be
identified, or whether more detailed quantitative analysis is
necessary. The following information should be provided for
each existing or potential problem:
1. Magnitude of or damage caused by the problem.;
2. General frequency and duration;
3. Return frequency of storm or flow when the problem
occurs (may require quantitative analysis);
4. Water elevation when the problem .occurs;
5. Names and concerns of parties involved;
6. Current mitigation of the problem;
7. Possible cause of the ptoblem; and
8. Whether the project is likely to aggravate the problem or
create a new one~
Upon review of this analysis, the administrator may require
mitigation measures deemed adequate for the problems, or a
quantitative analysis, depending upon the presence of
existing or predicted flooding, erosion, or water quality
problems, and on the proposed design of the onsite drainage
facilities. The analysis should repeat Tasks 3 and 4. above,
using quantitative field data including profiles and cross-
sections.
Page 15 of24
The quantitative analysis should provide information on .the
severity and frequency .of an existing problem or the
likelihood of. creating a new problem~ It should evaluate.
proposed mitigation intended to avoid aggravation of the
existing problem and to avoid.creation of a new problem.
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I. In Volume I,. Section 2.7 ,of the manual, '~'Adjustments",-is not adopted.
J. In Volume III, Section 3.1.2 of the manual, Downspou~ Dispersion
Systems, is modified for use with additional standard details as .prescribed
by the city.
K. In Volume III, Section 3.1.3 of the manual, Perforated Stub-out
Connections, is. mo.dified for use with. additional standard details as
prescribed by the city..
L. In Volume III,. Section 3.2 of the manual, Figure 3.12, "Pond Signage,"
is amended to include the. following language:
Developers shall provide the required signage for constructed
ponds as a part of the project.
M. In Volume V: Section 4.3 "Setbacks, slopes and embankments", is
amended to include the following language: -
-J
All stormwater facilities and infiltration systems constructed
within 200 feet of a geologically hazardous area shall have
the concurrence of a Geotechnical Engineer..
N. In Volume V, Section 5.3.1 of the manual, -BMP T 5.10 Downspout
Dispersion, is modified for use with additional standard details as
prescribed by the city.
o. In Volume V, Section 5..3.2 of the manual, BMP T 5.21 Better Site
Design: Build Narrower Streets, is amended to include the following
language:
Streets and roadways must, however, comply with city of
Bainbridge Island Design and Construction Standards and
Specifications unless an exception is granted in writing by
the administrator.
P. In Volume V, Section 5~3.3 of the manual, BMP T 5.30 Full Dispersion,
is modified for use with additional standard details as prescribed by the
city.
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Page 16 of24
Q. In Volume V of the manual, Chapter 12, Emerging Technologies, is not
adopted.
R8~ In Volume I, Section 2.5~2 of the manual, "Minimum Requirement #2:
Construction Stormwater Pollution Prevention (SWPP), the following
language replaces or amends the language found in. Section 2.5.2 of the
manual:
All new development. and redevelopment .projects. are
responsible for preventing erosion and discharge of sediment
and other pollutants into receiving waters.
Sediment and erosion control BMPs shall be consistent with
the BMPs contained "in Chapters 3. and 4 of Volume II of the
manual.
The SWppp shall include a narrative and drawings. All
BMP's shall be clearly referenced in the narrative and
marked on the drawings~ The S.Wppp narrative shall. include
documentation to explain and justify the pollution prevention
decisions made for the project~
1. Volume I, Section 2.5.2 of the manual, "Minimum
Requirement #2: Construction Stormwater Pollution
Prevention Plan (SWPPP) Elements: The following language
replaces or amends the language found in the .Elements
Section 2.5~2 of the manual:
Element. 2.c.: .Wheel.. wash or tire baths shall be
located on site, if the stabilized construction
entrance is not effective in preventing sediment
from being tracked .onto public roads.
Element .6.c~ Temporary pipe slope drains shall
handle the e.xpected peak J O-minute flow velocity
from a type lA, lO-year, 24-hour frequency storm
for the developed condition.
The hydrologic analysis shall use the existing land
cover . condition for predicting flow rates .from.
tributary areas outside. the project limits~ For
tributary areas on the project site, the analysis shall
use the temporary or permanent project land cover
condition, whichever will produce the highest flow
rates. If using the Western Washington Hydrology
Page 17 of24
model to predict flows, bare soil areas should be
modeled as "landscaped area."
.'-...]
i .-...-
Element 7 ~ Protect Drain Inlets.
"All sediment and street wash water shall not be
allowed to enter storm drains without prior and
adequate treatment unless treatment is provided
before the stonn drain .discharges to waters of the
State."
Element 9. Control Pollutants
Permittees shall require .construction site operators
obtain written approval from the Department prior
to using chemical treatment other than C02 or dry
ice to adjust pH.
s. Volume I, Section 2.5.6 .of the manual, "Minimum Requirement #6
Runoff Treatment:
The following language replaces the language found in Section 2~5..6 of
the manuaL
Project Thresholds
The following require construction of stonnwater treatment
facilities (see Table below):
· Projects in which the total of effective, pollution-generating
impervious surface (POlS) is 5,000 square feet or more in a
threshold discharge area of the project, or
~::]
· Projects in which the total of pollution-generating pervious
surfaces (PGPS) is three-quarters (3/4) of an acre or more in
a threshold discharge area, and from which there is a surface
discharge in a natural or. man-made conveyance system from
the site.
Treatment-Type Thresholds
1 ~ Oil Control:
Treatment to achieve Oil Control applies to projects that have
"high-use sites." - High-use sites are those that typically
generate high concentrations of oil due to high traffic
turnover or the frequent transfer of oil. High-use sites
include:
a. An area of a commercial or industrial site subject to
an expected average daily traffic (ADT) count equal to or
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Page 18 of24
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greater than 100 vehicles per 1,OOOsquare feet of gross
building area;
b. An area of a commercial or industrial site subject to
petroleum storage and transfer in excess of 1,500 gallons per
year, not including routinely delivered heating oil;
c. An area of a commercial or industrial site subject to
parking, storage or maintenance of 25 or more vehicles that
are over 10 tons gross weight (trucks, buses, trains, heavy
equipment, etc.);
Treatment Requirements by Threshold Discharge A.rea
< % acres of > % acres < 5,000 sf >. S,O~O sf
PGfS PGPS PGIS PGIS
Treatment t,/ "
F acil ities
- Onsite Stonnwater v \/. . v .,
BMPs
PGPS ;;::: pollution-generating pervious surfaces
PGIS = pollution-generating impervious surfaces
sf;:::: square feet
~-' "]
d~ A road intersection with a measured ADT count of
25,000 vehicles or more on the main roadway and 15,000
vehicles or more .on any -intersecting roadway, excluding
projects proposing. primarily pedestrian or bicycle use
improvements.
2. Phosphorus Treatment:
The requirement' to provide phosphorous control is
determined by the local government with jurisdiction (e.g.,
through a lake management plan), or the Department of
Ecology (e~g, through a waste load allocation)~ The local
government may have developed a management plan and
implementing ordinances or regulations for control of
phosphorus from new/redevelopment for the receiving
water(s) of the stormwater drainage. The local government
can use the following sources. of information for pursuing
plans and implementing ordinances and/or regulations:
a. Those waterbodies reported under section 305(b) of
the Clean Water Act, and. designated as not supporting
beneficial uses due to phosphorous;
b. Those listed in Washington Staters Nonpoint
Source Assessment required under section 319(a) of the
Clean Water Act due to nutrients.
Page 19 of24
3. Enhanced Treatment:
Enhanced treatment for . reduction in dissolved metals is
required for the following project sites that discharge to fish-
bearing streams, lakes, or to waters or conveyance systems
tributary to fish-bearing streams or lakes:
Industrial project sites,
Commercial project sites,
Multi-family project sites, and
High AADT roads as follows:
Within Urban :Growth Management Areas:
· Fully controlled .and partially controlled limited access
highways with Annual Average Daily Traffic (AADT) counts
of 15,000 or more
· All other roads with an AADT of7,500 or greater
Outside of Urban Growth Management Areas:
· Roads with an - AADT of 15,000 or greater unless
discharging to a 4th Strahler order stream or larger;
· Roads with an AADT of 30,000 or greater if dischargi~g to
a 4th Strahler order stream or larger (as determined using
1 :24,000 scale maps to delineate stream order).
-..J
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However, such sites listed above that discharge directly (or,
indirectly tluough.a municipal storm sewer system) to Basic
Treatment Receiving Waters (Appendix I-C .of the manual),
and areas of the abo_ve-listed project sites that are identified
as subject to Basic Treatment requirements, are also not
subject to Enhanced Treatment requirements. For
developments with a mix of land use types, the Enhanced
Treatment requirement shall apply when the runoff from the
areas subject to the Enhanced Treatment requirement
comprise 50% or more of the total runoff within a threshold
discharge area~
U}
4. Basic Treatment:
Basic Treatment generally applies to:
· Project sites that..discharge to the ground, UNLESS:
1) The soil suitability criteria for infiltration treatment are
met; (see Chapter 3 of Volume III of the manual for soil
suitability criteria) or
2) The project. uses infiltration strictly for flow control - not
treatment - and the discharge is within 'i4-mile of a
phosphorus sensitive lake (use a Phosphorus Treatment
facility), or within 'l4 mile of a fish-bearing stream, or a lake
(use an Enhanced Treatment facility).
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Page 20 of24
· Residential projects not. otherwise needing phosphorus
control as designated by USEP A, the Department of Ecology,
or by the Permittee; and
· Project sites discharging directly to salt . waters,. river
segments, and lakes listed in Appendix I-C of the. manual;
and
· Project sites that drain to streams that are not fish-b.earing,
or to waters not tributary to fish-b.earing streams;
· Landscaped areas of industrial, commercial, and multi-
family project sites, and parking lots of industrial - and
commercial project sites that do not involve pollution-
generating sources (e.g., industrial activities, customer
parking, storage of erodible or leachable material, wastes or
chemicals) other than parking of employees' private vehicles.
For developments with a mix of land use types, the Basic
Treatment requirement shall apply when the runoff from the
areas subject to the Basic Treatment requirement comprise
50% or more of the total runoff within a threshold discharge
area.
Treatment Facility Sizing
Water Quality Design Storm Volume: The volume of runoff
predicted from a 24-hour storm with a 6-month return
frequency (a.k.a~, 6-month, 24-hour storm). Wetpool
facilities are. sized based upon the volume of runoff predicted
through use of the Natural Resource Conservation Service
curve nuniber equations ion Chapter 2 of Volume III of the
manual, for the 6-month, 24-hour storm. Alternatively, the
91 st percentile, 24-hour runoff volume indicated by an
approved continuous runoff model may be used~
Water Quality Design Flow Rate
1. Preceding Detention Facilities or when Detention Facilities
are not required:
The flow rate at or below which 91 % of the runoff volume,
as estimated by an .approved continuous runoff model, will be
treated.. I?esign .criteria for treatment facilities are assigned to
achieye the applicable performance goal at the water quality
design flow rate (e.g., 80% TSS removal)~
2. Downstream of Detention Facilities:
The water quality design flow rate must be the full 2-year
release rate f~o:m the ,detention faci.lity. r\ltemative methods
may be used. if they identify volumes and flow rates that are.
at least equivalent That portion of any development project
in which the above PGIS or PGPS thresholds are not
exceeded in a threshold discharge area shall apply On-site
Page 21 of24
Stormwater -Management. BMPs. In. accorda11-ce with
Minimum Requirement #5.
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Treatment Facility ..Selection, Design, an.d Maintenance
Stormwater treatment facilities shall be:
· Selected in accordance with the process identified in
Chapter 4 of Volume l of the manual,
· Designed in accordance with the design criteria in Volume
V of the manual, and
· Maintained in accordance with the maintenance schedule in
Volume V of the manual"
Additional Requirements
The discharge of untreated- stormwater from pollution-
generating impervious surfaces to ground water is not
authorized, except for the discharge achieved by infiltration
or dispersion of runoff from residential sites through use of
On-site Stonnwater Matlagement BMPs~"
Section 6. Section 15.20~070 of the Bainbridge Island Municipal Code is amended to
read as follows:
"15.20.070 Administration.
~.J~]
"( -
~ .
i ._ -.
A. Administrator. The public works director or a designee shall administer
this chapter and shall be referred to as the administrator. The administrator
shall have the~ authority to develop and implement administrative
procedures to administer and enforce this chapter.
B. Review and Approval. The administrator may approve, conditionally
approve or deny an application for activities regulated by this chapter.
c. Enforcement Authority. The administrator shall enforce this chapter.
D. Inspection. All activities regulated by this ordinance, shall be inspected
by the Administrator. The Administrator shall inspect projects at various
stages of the work requiring approval to determine that adequate control is
being exercised. Stages of work requiring inspection include, but are not
limited to, preconstruction, installation of BMPs, land disturbing activities,
installation of utilities, permanent storm-water) control facilities,
landscaping, retaining walls and completion of project Whe~ required by
the Administrator, a special inspection and/or testing shall be performed."
Section 7.
follows:
Section 15..20.080 of the .Bainbridge Island Municipal Code is amended. as
:..J
P~ge 22 of24
"15.20.080. Enforcement.
A. Failure to Comply.
It is unlawful for any person'to violate . any provision or fail to' comply
with any of the. requirements of this chapter.
B. Emergency Access and Reparation.
In the event the violation.constitutes an immediate danger to public health
or safety, the administrator. is authorized to enter upon the .subject private
property, without giving prior notice, to take. any and all measures
necessary to abate the violation and/or restore the property. Anyexp.ense
related to such .remediation undertaken by the city shall be fully
reimbursed by the property owner and/or responsible party. Any relief
obtained under this section shall not prevent the city from seeking further
relief or applying other penalties as provided in this chapter~
c.. Civil Infraction.
Except as provided in subsection D of this section, conduct made unlawful
by this chapter shall constitute a. civil infraction and is subject. to
enforcement and fines as provided in BIMC 1.26.035. A civil infraction
under this section shall be processed in the manner set forth. in BIMC
Chapter 1.26. ..
D~ Misdemeanor. .
Any person who again violates this chapter within twelve (12) months
after having been found by the Bainbridge Island Municipal Court to be in
violation of this chapter, commits a misdemeanor and ~y person who is
convicted thereof shall be punished as provided in BIMC 1.24.01 O.A.
E~ Civil Penalty.
In addition to any civil infraction fine, criminal penalty, and/ or other
available sanction or remedial procedure, any person engaging in conduct
made unlawful by this chapter shall be subject to a cumulative civil
penalty in the amount of $1,000 per day for each violation from the date
set for compliance until the date of compliance~ Any such civil penalty
shall be collected in accordance with BIMC 1.26.090.
F.~ Additional Remedies.
1. In addition to any other remedy provided by this chapter or under
the Bainbridge Island Municipal Code, the city may initiate injunction or
Page 23 of 24
abatement proceedings or any other appropriate action in courts against
any person who violates or. fails to comply with any provision of this
chapter to prevent, enjoin, abate, and/or terminate viol~tions of this
chapter and/or to restore a condition which existed prior to the violation.
In any such proceeding, the. person violating and/or failing to comply with
any provisions of this chapter shall be liable., for the, costs and reasonable
attorneys' fees incurred by the city in bringing, maintaining and/or .
prosecuting such action.
2~ Any person who violates any provision of this chapter may also be
in violation of the. .Federal Clean . Water .Act, . NPDES Phase. II Permit,
and/or RCW Chapter 90.48 and may be subject to sanctions including.civil
and criminal penalties. Any enforcement action authorized. under. this
chapter shall. also include written notice to the violator of such potential
liability. "
<'-'''''''-)
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Section 8. Section.15.20~090 of the Bainbridge Island Municip.al Code is repealed in
its entirety.
Section 9. This ordinance shall be effective five .days after passage,. approval dnd
publication as required by law.
I,
PASSED by the City Council this 12th day of August, 2009.
APPROVED by the Mayor this lSthday OfAUgUS~ . .rE!.
Christopher Snow, Mayor
-'U'l
' 'j
ATTEST/AUTHENTICATE:
~\)\oJU:.nt'1 \} ~ lo..., ') D ~.
Rosalind D~ Lassoff, City Clerk
FILED WITH THE CITY CLERK:
PASSED BY TI-IE CITY. COUNCIL:
PUBLISHED:
EFFECTIVE DATE:
ORDINANCE NUMBER:
July 14, 2009
August 12, 2009
August 21, 2009
Aug.ust 26, 2009
2009-13
; 1
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Page 24 of 24