Ordinance No. 2022-11 Revising Chaper 15.20 BIMC re Stormwater Mgmt Revised (Adopted 061422)Page 1 of 7
ORDINANCE NO. 2022-11
AN ORDINANCE of the City of Bainbridge Island,
Washington, relating to amending Chapter 15.20 and other
provisions of the Bainbridge Island Municipal Code to adopt
and incorporate the 2019 Stormwater Management Manual
for Western Washington and remain in compliance with the
City’s NPDES permit; providing for severability; and
establishing an effective date of June 30, 2022.
WHEREAS, the City Council adopted Chapter 15.20 to Title 15 of the
Bainbridge Island Municipal Code (“BIMC”) on February 4, 1999, and amended it on
November 22, 2005, August 12, 2013, and December 12, 2016; and
WHEREAS, the City Council adopted Ordinance No. 2016-28, which
incorporated the 2012 Department of Ecology Stormwater Management Manual for
Western Washington; and
WHEREAS, the Department of Ecology updated the Stormwater Management
Manual for Western Washington in 2019 (“2019 Stormwater Management Manual”); and
WHEREAS, the City Council desires to amend the BIMC to update the standards
for surface and stormwater management to be consistent with Department of Ecology
guidelines as provided in the 2019 Stormwater Management Manual; and
WHEREAS, the City Council also desires to amend the standards for surface and
stormwater management to comply with the City’s National Pollutant Discharge
Elimination System (“NPDES”) Municipal Stormwater Discharge Permit (see, e.g.,
S5.C6); and
WHEREAS, on June 14, 2022, the City Council held a public hearing on this
Ordinance No. 2022-11 related to adoption of the 2019 Stormwater Management Manual
in order to receive public comment regarding the updates to stormwater regulations; and
WHEREAS, after considering public testimony and other public comment
received regarding this Ordinance No. 2022-11 related to updating the BIMC to
incorporate the 2019 Stormwater Management Manual, the City Council determined on
June 14, 2022 to adopt the 2019 Stormwater Management Manual, and to amend and
update related provisions in the BIMC.
NOW, THEREFORE, THE CITY COUNCIL OF THE CITY OF
BAINBRIDGE ISLAND, WASHINGTON, DOES ORDAIN AS FOLLOWS:
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Section 1. Adoption of Findings. The recitals set forth above are hereby adopted
as part of the Bainbridge Island City Council’s findings justifying the revisions to the
Bainbridge Island Municipal Code adopted by this ordinance.
Section 2. Adoption of 2019 Stormwater Management Manual for Western
Washington.
A. The City hereby adopts the 2019 Stormwater Management Manual for
Western Washington as published by the Washington State Department of Ecology
(“2019 Stormwater Management Manual”).
B. In addition to the revisions to Chapter 15.20 of the Bainbridge Island
Municipal Code (“BIMC”) set forth below, this ordinance hereby amends, updates, and
supersedes each and every reference in the BIMC to the Washington State Department of
Ecology Stormwater Management Manual for Western Washington, as so stated or as
reasonably inferred from the text and the context (e.g., if the full title of the Stormwater
Manual is not so described) to mean the 2019 Stormwater Management Manual. The
intent of this ordinance is to ensure that the City is implementing and enforcing
stormwater regulations consistent with, and as required by, the Federal Water Pollution
Control Act (also known as the Clean Water Act), 33 U.S.C. §§ 1251 et seq., and the
National Pollutant Discharge Elimination System (“NPDES”) permitting program
established by the Act. The State of Washington has directed the City and other local
governments to implement these stormwater regulations to comply with the NPDES
permitting program, and such regulations are mandatory state regulations, rather than
discretionary local regulations.
Section 3. Section 15.20.050 of the Bainbridge Island Municipal Code is hereby
amended to read as follows:
15.20.050 General requirements.
A. Stormwater Management Manual Adopted. The Washington State Department of
Ecology’s 20122019 Stormwater Management Manual for Western Washington, as
amended in 2014, is hereby adopted by reference and is hereinafter referred to as the
stormwater manual; provided, that certain provisions of the stormwater manual are
amended as stated in BIMC 15.20.060.
B. Illegal discharges and illegal connections to the stormwater drainage system are
prohibited by Chapter 15.22 BIMC.
C. Low Impact Development Manual Adopted. The 2012 Low Impact Development
(LID) Technical Guidance Manual for Puget Sound is hereby adopted by reference and is
hereinafter referred to as the LID manual.
Section 4. Section 15.20.060 of the Bainbridge Island Municipal Code is hereby
amended to read as follows:
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15.20.060 Approval standards.
A. City-Specific Standards. The city amends the standards adopted as part of the
stormwater manual (summarized in subsection B of this section) as follows:
1. Instead of following the Better Site Design BMP (BMP T5.41) in Volume V,
Section 5.3.2 V-2 of the stormwater manual, conduct a site assessment following
the guidance in the LID manual adopted in BIMC 15.20.050. Comply with the city
of Bainbridge Island design and construction standards for streets and roadways
unless an exception is granted in writing by the administrator.
2. The hard surface threshold for triggering Minimum Requirements No. 1 through
5 for new development and redevelopment (Volume I, Section I-3.3) is reduced
from 2000 square feet to 800 square feet or greater of new plus replaced hard
surface area.
3. Projects that discharge directly, or indirectly through a stormwater drainage
system, to Puget Sound are required to implement the full list of on-site stormwater
management BMPs on List No. 1 or List No. 2 (see subsection B.2 of this section).
43. Optional Guidance No. 1 Volume I, Section 3.5.2 Additional Protective
Measure (“APM”) 1, Financial Liability, is not adopted.
54. Optional Guidance Volume I, Section 3.5.1 APM No. 2, Off Site Analysis and
Mitigation, and Volume I,III, Section 3.12.3, Perform an Offsite Analysis, is
required for new development and redevelopment projects creating 5,000 square
feet or more of hard surface area.
65. InVolume I, Section 2.73.6.1of the stormwater manual, Adjustments to the
MRs, is not adopted.
7. The use of threshold discharge areas, as defined by the stormwater manual, is not
adopted.
86. InVolume IIIV, Section 3.2 of the stormwater manual, Figure 3.2.4, Example of
Permanent Surface Water Control Pond Sign BMP D.1 Detention Ponds, Signage
section under Design Criteria, is amended to include the following language:
City of Bainbridge Island specific Ssignage for constructed ponds is required
to be provided by the developer as a part of the project. Contact the City
Stormwater Management Program Coordinator to obtain approved sign
specifications for a permanent surface water control pond, which will include
to determine the pond name, pond number, and telephone number to include
on the sign.
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97. InVolume V, Section 4.3.11.2, Setbacks, Slopes, and Embankments is amended
to add the following language after the first paragraph in the Setbacks section:
delete the current text and replace with the following language:
Chapter 16.20 BIMC defines “Zone of Influence” as it relates to moderate and
steep slopes. A Geotechnical Engineer is required to evaluate a project
stormwater site plan that proposes land disturbance, changes in land use, or
changes in site hydrology within the zone of influence of any geologically
hazardous area as defined in Chapter 16.20 BIMC.all stormwater facilities
and infiltration systems proposed within 200 feet of a geologically hazardous
area.
108. The City utilizes the Rain Garden Handbook for Western Washington: A
Guide for Design, Installation and Maintenance (Hinman et al., 2013). Volume V,
Section V-11 of the stormwater manual, BMP T5.14 Rain Gardens, is modified to
add the following text to the end of the first paragraph of the Design Guidelines
section:
The 2013 Rain Garden Handbook for Western Washington supplements the Rain
Garden (BMP T5.14A) design guidelines in the stormwater manual for projects
triggering Minimum Requirements No. 1 through 5. Use the “Good (80%)”
performance level for Rainfall Region 3 in the Rain Garden Sizing Chart in the
Rain Garden Handbook for Western Washington at a minimum. “Better (95%)”
performance level is preferred.
B. Stormwater Manual Standards. The stormwater manual adopted in BIMC 15.20.050
includes the following nine minimum requirements:
1. Minimum Requirement No. 1 – Preparation of Stormwater Site Plans.
2. Minimum Requirement No. 2 – Construction Stormwater Pollution Prevention.
3. Minimum Requirement No. 3 – Source Control of Pollution.
4. Minimum Requirement No. 4 – Preservation of Natural Drainage Systems and
Outfalls.
5. Minimum Requirement No. 5 – On-Site Stormwater Management.
6. Minimum Requirement No. 6 – Runoff Treatment.
7. Minimum Requirement No. 7 – Flow Control.
8. Minimum Requirement No. 8 – Wetlands Protection.
9. Minimum Requirement No. 9 – Operations and Maintenance.
The following is a summary of the general thresholds included in the stormwater manual
with modifications based on the city-specific standards provided in subsection A of this
section. Specific thresholds are also summarized for Minimum Requirements No. 5, 6,
and 7. The stormwater manual includes additional comprehensive guidance regarding
implementation of these thresholds.
1.Overall project thresholds include the following:
Applicable Requirements New Development Redevelopment
Minimum Requirement No. 2
(Construction Stormwater
Pollution Prevention)
All projects All projects
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Applicable Requirements New Development Redevelopment
Minimum Requirements Nos.
1 – 5
≥ 1,300 sf new plus
replaced hard surface
area1, or
≥ 7,000 sf land disturbing
activity, or
Land disturbing activity
covering ≥ 35% of the site
≥ 800 sf new plus replaced hard
surface area1, or
≥ 7,000 sf land disturbing activity, or
Land disturbing activity covering ≥
35% of the site
Minimum Requirements Nos.
1 – 9
≥ 5,000 sf new plus
replaced hard surface
area, or
≥ 3/4 acre of vegetation
converted to lawn or
landscaped areas, or
≥ 2.5 acres of native
vegetation converted to
pasture
≥ 5,000 sf new hard surface area, or
≥ 3/4 acre of vegetation converted to
lawn or landscaped areas, or
≥ 2.5 acres of native vegetation
converted to pasture, or
≥ 5,000 sf of new plus replaced hard
surface
AND
New hard surface is ≥ 50% of the
existing hard surface within the
project limits (road-related projects),
or
Proposed improvements are > 50% of
the assessed value of the existing site
improvements
Optional Guidance No. 2:
Off-Site Analysis and
Mitigation
≥ 5,000 sf of hard surface
area2
≥ 5,000 sf of hard surface area2
1 – City-specific threshold for new development and redevelopment.
2 – City-specific threshold for off-site analysis and mitigation.
2.Thresholds related to Minimum Requirement No. 5 (Volume I, Section 2.5.5 of
the stormwater manual) include the following:
Applicable Requirements New Development and Redevelopment
List No. 1 Thresholds for Minimum Requirements No. 1 – 5 summarized in
BIMC 15.20.060.B.1
List No. 2 Thresholds for Minimum Requirements No. 1 – 9 summarized in
BIMC 15.20.060.B.1
LID Performance
Standard
Optional, but can be used instead of List No. 1 or List No. 2 as
specified above
BMP T5.13 (Post
Construction Soil Quality
and Depth)
Required for disturbed pervious areas
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Applicable Requirements New Development and Redevelopment
Direct Discharge to Puget
Sound
Projects discharging directly to, or indirectly through a stormwater
drainage system, to Puget Sound are required to evaluate the full list of
on-site stormwater management BMPs on List No. 1 or List No. 2 1
1 – City-specific requirement for direct discharges.
3. Thresholds related to Minimum Requirement No. 6 (Volume I, Section 2.5.6 of
the stormwater manual) include the following:
Applicable
Requirements New Development and Redevelopment
Stormwater Treatment
Facility
≥ 5,000 sf pollution-generating hard surfaces (PGHS), or
≥ 3/4 acre of pollution-generating pervious surfaces (PGPS)
Oil Control High-use sites
Phosphorus Treatment Not applicable at this time
Enhanced Treatment Industrial project sites, commercial project sites, multifamily project
sites, and high AADT roads1 that:
1) Discharge directly to fresh waters or conveyance systems tributary to
fresh waters designated for aquatic life use or that have an existing
aquatic life use; or
2) Use infiltration strictly for flow control – not treatment – and the
discharge is within 1/4 mile of a fresh water designated for aquatic life
use or that has an existing aquatic life use
Basic Treatment All sites meeting the stormwater treatment facility thresholds listed
above for PGHS or PGPS
1 – High AADT roads are designated as ≥ 15,000 (fully controlled and partially
controlled limited access highways) and ≥ 7,500 (all other roads).
4. Thresholds related to Minimum Requirement No. 7 (Volume I, Section 2.5.7 of
the stormwater manual) include the following:
Applicable Requirements New Development and Redevelopment
Flow Control Facility ≥ 10,000 sf effective impervious surface, or
≥ 3/4 acre of vegetation converted to lawn or landscaped areas, or
≥ 2.5 acres of native vegetation converted to pasture, or
≥ 0.15 cfs increase in the 100-year flow frequency (using a 15-minute
time step)
Direct Discharge
Exemption
Flow control facilities are not required for direct discharges, or
indirect discharges through a stormwater drainage system, to Puget
Sound
Section 5. Severability. Should any section, paragraph, sentence, clause, or phrase
of this ordinance, or its application to any person or circumstance, be declared
unconstitutional or otherwise invalid for any reason, or should any portion of this
ordinance be preempted by state or federal law or regulation, such decision or preemption
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shall not affect the validity of the remaining portions of this ordinance or its application
to other persons or circumstances.
Section 6. This ordinance shall take effect and be in force on June 30, 2022, after
its passage and publication as required by law.
PASSED by the City Council this 14th day of June, 2022.
APPROVED by the Mayor this 14th day of June, 2022.
Joe Deets, Mayor
ATTEST/AUTHENTICATE:
Christine Brown, MMC, City Clerk
FILED WITH THE CITY CLERK: May 20, 2022
PASSED BY THE CITY COUNCIL: June 14, 2022
PUBLISHED: June 24, 2022
EFFECTIVE DATE: June 30, 2022
ORDINANCE NUMBER: 2022-11