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Structural Stormwater Controls Science Review and Synthesis Project Final White Paper

Summary: Structural Stormwater Controls Science Review and Synthesis Project, SSC Science Review, literature review of structural stormwater controls, science to inform future policy discussions, key findings

Structural Stormwater Controls | Science Review & Synthesis Project
Structural Stormwater Controls
Science Review and Synthesis Project
Final White Paper
Prepared for:
Washington State Department of Ecology
Prepared by:
Aimee S. Navickis‐Brasch, PhD, PE
Osborn Consulting, Inc.
Maria Peraki, PhD, EIT
Osborn Consulting, Inc.
James Packman
Aspect Consulting
Paul Fendt, PE
Parametrix
Christian Nilsen, PE
Geosyntec Consultants
Taylor Hoffman‐Ballard, PE
Osborn Consulting, Inc.
Mark Maurer, PE, PLA
Osborn Consulting, Inc.
Structural Stormwater Controls | Science Review & Synthesis Project
iii
Table of Contents
Executive Summary …………………………………………………………………………………………………………………………………………….. 1
Introduction …………………………………………………………………………………………………………………………………………. 1‐1
1.1
Chapter Purpose and Contents ………………………………………………………………………………………………………… 1‐1
1.2
Overview of Work Completed …………………………………………………………………………………………………………. 1‐1
1.3
Project Purpose ……………………………………………………………………………………………………………………………… 1‐1
1.3.1
Project Background and Goals ………………………………………………………………………………………………….. 1‐1
1.3.2
Additional Goals ……………………………………………………………………………………………………………………… 1‐2
1.3.3
TAC Project Vision …………………………………………………………………………………………………………………… 1‐4
1.4
TAC and Consultant Team Role ………………………………………………………………………………………………………… 1‐5
1.5
White Paper Contents and Organization …………………………………………………………………………………………… 1‐6
1.5.1
Chapter 1. Introduction ……………………………………………………………………………………………………………. 1‐6
1.5.2
Chapter 2. Define Requirements ………………………………………………………………………………………………. 1‐6
1.5.3
Chapter 3. Benefit Questions ……………………………………………………………………………………………………. 1‐6
1.5.4
Chapter 4. Application Questions ……………………………………………………………………………………………… 1‐7
1.5.5
Chapter 5. Conclusion ……………………………………………………………………………………………………………… 1‐7
1.6
Appendices ……………………………………………………………………………………………………………………………………. 1‐8
1.6.1
Appendix 1‐1 TAC Comments and Consultant Responses …………………………………………………………….. 1‐9
Define Requirements, Goals, and Vision …………………………………………………………………………………………………… 2‐1
2.1
Chapter Purpose and Contents ………………………………………………………………………………………………………… 2‐1
2.2
Overview of Work Completed …………………………………………………………………………………………………………. 2‐1
2.3
Relevant Requirements …………………………………………………………………………………………………………………… 2‐1
2.4
Reasoning for Permit Language ……………………………………………………………………………………………………….. 2‐7
2.5
Overview of Jurisdictions SSC Programs ………………………………………………………………………………………….. 2‐10
2.6
References ………………………………………………………………………………………………………………………………….. 2‐17
2.7
Appendices ………………………………………………………………………………………………………………………………….. 2‐21
2.7.1
Appendix 2‐1 – Phase II Screening Questions and Responses ……………………………………………………… 2‐22
2.7.2
Appendix 2‐2 – Interview Questions ………………………………………………………………………………………… 2‐27
2.7.3
Appendix 2‐3 – Interview Responses: Phase I and Phase II …………………………………………………………. 2‐34
2.7.4
Appendix 2‐4 – TAC Comments and Responses to Comments …………………………………………………… 2‐130
Benefit Questions ………………………………………………………………………………………………………………………………….. 3‐1
3.1
Chapter Purpose and Contents ………………………………………………………………………………………………………… 3‐1
3.2
Overview of Work Completed …………………………………………………………………………………………………………. 3‐1
3.3
Literature Search ……………………………………………………………………………………………………………………………. 3‐1
3.3.1
Define Key Terms ……………………………………………………………………………………………………………………. 3‐1
3.3.2
Approach ……………………………………………………………………………………………………………………………….. 3‐3
Structural Stormwater Controls | Science Review & Synthesis Project
3.3.3
Summary of Literature Findings ………………………………………………………………………………………………… 3‐6
3.3.4
Summary of Research Gaps ……………………………………………………………………………………………………… 3‐6
3.4
Responses to Benefit Questions ………………………………………………………………………………………………………. 3‐7
3.4.1
Benefit Question 1 ………………………………………………………………………………………………………………….. 3‐8
3.4.2
Benefit Question 1a ………………………………………………………………………………………………………………. 3‐17
3.4.3
Benefit Question 2 ………………………………………………………………………………………………………………… 3‐18
3.4.4
Benefit Question 2a ………………………………………………………………………………………………………………. 3‐22
3.4.5
Benefit Question 2b ………………………………………………………………………………………………………………. 3‐23
3.4.6
Benefit Question 2c ……………………………………………………………………………………………………………….. 3‐23
3.4.7
Benefit Question 2d ………………………………………………………………………………………………………………. 3‐24
3.5
Conclusion …………………………………………………………………………………………………………………………………… 3‐26
3.6
References ………………………………………………………………………………………………………………………………….. 3‐27
3.7
Appendices ………………………………………………………………………………………………………………………………….. 3‐31
3.7.1
Appendix 3‐1 SSC Literature Search Template ………………………………………………………………………….. 3‐32
3.7.2
Appendix 3‐2 SSC Performance Indicator Matrices ……………………………………………………………………. 3‐34
3.7.3
Appendix 3‐3 TAC Comments and Responses to Comments ……………………………………………………….. 3‐40
Application Questions ……………………………………………………………………………………………………………………………. 4‐1
4.1
Chapter Purpose and Contents ………………………………………………………………………………………………………… 4‐1
4.2
Overview of Work Completed …………………………………………………………………………………………………………. 4‐1
4.3
Approach to Answer Application Questions ………………………………………………………………………………………. 4‐1
4.4
Responses to Application Questions …………………………………………………………………………………………………. 4‐4
4.4.1
Application Question 1 …………………………………………………………………………………………………………….. 4‐4
4.4.2
Application Question 1a …………………………………………………………………………………………………………… 4‐6
4.4.3
Application Question 2. ………………………………………………………………………………………………………….. 4‐10
4.4.4
Application Question 2a. ………………………………………………………………………………………………………… 4‐13
4.4.5
Application Question 2b. ………………………………………………………………………………………………………… 4‐15
4.4.6
Application Question 3. ………………………………………………………………………………………………………….. 4‐17
4.5
Conclusion …………………………………………………………………………………………………………………………………… 4‐17
4.6
References ………………………………………………………………………………………………………………………………….. 4‐19
4.7
Appendices ………………………………………………………………………………………………………………………………….. 4‐21
4.7.1
Appendix 4‐1 Updated Matrices of SSC BMP Performance Indictors ……………………………………………. 4‐22
4.7.2
Appendix 4‐2 – TAC Comments and Responses to TAC Comments ……………………………………………… 4‐24
Conclusion ……………………………………………………………………………………………………………………………………………. 5‐1
5.1
Chapter Purpose and Contents ………………………………………………………………………………………………………… 5‐1
5.2
Overview of Work Completed …………………………………………………………………………………………………………. 5‐1
5.3
Overview of Study and Data Gaps ……………………………………………………………………………………………………. 5‐1
Structural Stormwater Controls | Science Review & Synthesis Project
5.3.1
Chapter 2 Define Requirements, Goals, and Vision ……………………………………………………………………… 5‐1
5.3.2
Chapter 3 Benefit Questions …………………………………………………………………………………………………….. 5‐2
5.3.3
Chapter 4 Application Questions ………………………………………………………………………………………………. 5‐3
5.4
Future Research Considerations ………………………………………………………………………………………………………. 5‐3
5.4.1
SSC Performance Limitations ……………………………………………………………………………………………………. 5‐4
5.4.2
Impact Factors ………………………………………………………………………………………………………………………… 5‐4
5.4.3
Performance Indicators ……………………………………………………………………………………………………………. 5‐4
5.5
Appendices ……………………………………………………………………………………………………………………………………. 5‐8
5.5.1
Appendix 5‐1 TAC Comments and Consultant Responses …………………………………………………………….. 5‐9
Structural Stormwater Controls | Science Review & Synthesis Project
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Acronyms
Structural Stormwater Controls | Science Review & Synthesis Project
viii
ACRONYMS
AKART
All Known, Available, and Reasonable Methods of Prevention, Control, and Treatment
BMP
Best Management Practice
DNR
Department of Natural Resources
Ecology
Washington State Department of Ecology
EIA
Effective Impervious Area
EPA
Environmental Protection Agency
ISBD
International Stormwater BMP Database
LID
Low Impact Development
MEP
Maximum Extent Practicable
MS4
Municipal Separate Stormwater Sewer System
NPDES
National Pollutant Discharge Elimination System
O&M
Operations and Maintenance
OCI
Osborn Consulting, Inc.
OHWM
Ordinary High‐Water Mark
PCHB
Pollution Control Hearings Board
ROW
Right of Way
SSC
Structural Stormwater Controls
SWMP
Stormwater Management Program
SWMMWW
Stormwater Management Manual for Western Washington
TAC
Technical Advisory Committy
TMDL
Total Maximum Daily Load
WAC
Washington Administrative Code
WEC
Washington Environmental Council
WSDOT
Washington State Department of Transportation
Structural Stormwater Controls
Executive Summary
Science Review & Synthesis Project
June 30, 2021
Page | 1
BACKGROUND AND PURPOSE
Executive Summary
In 2018, municipal stormwater (MS4) permittees in Western Washington requested a stakeholder group work on policy
and technical issues related to future Structural Stormwater Control (SSC) requirements. In response to this request, the
Washington State Department of Ecology (Ecology) in 2020 requested proposals to collect and summarize existing
scientific findings on SSCs and selected the City of Tacoma’s consultant team. The consultant team was…

Municipal Stormwater Permit Extract – special condition S5.C.1

Summary: WW Phase II Permit extract for stormwater planning

S5.C.1
Western Washington Phase II Municipal
Page 11 of 56
Stormwater Permit – August 1, 2019
The SWMP shall be designed to reduce the discharge of pollutants from regulated small MS4s
to the MEP, meet state AKART requirements, and protect water quality.
The SWMP shall include the components listed below. To the extent allowable under state or
federal law, all components are mandatory for city, town, or county Permittees covered
under this Permit.
Stormwater planning
Each Permittee shall implement a Stormwater Planning program to inform and assist in
the development of policies and strategies as water quality management tools to protect
receiving waters.
The minimum performance measures are:
a. By August 1, 2020, each Permittee shall convene an inter-disciplinary team to inform
and assist in the development, progress, and influence of this program.
b. Coordination with long-range plan updates.
Each Permittee shall describe how stormwater management needs and
protection/improvement of receiving water health are (or are not) informing the
planning update processes and influencing policies and implementation strategies
in their jurisdiction. The report shall describe the water quality and watershed
protection policies, strategies, codes, and other measures intended to protect
and improve local receiving water health through planning, or taking into account
stormwater management needs or limitations.
(a)
On or before March 31, 2021, the Permittee shall respond to the series of
Stormwater Planning Annual Report questions to describe how anticipated
stormwater impacts on water quality were addressed, if at all, during the
2013-2019 permit term in updates to the Comprehensive Plan (or
equivalent) and in other locally initiated or state-mandated, long-range land
use plans that are used to accommodate growth or transportation.
(b)
On or before January 1, 2023, the Permittee shall submit a report
responding to the same questions included in (a), above, to describe how
water quality is being addressed, if at all, during this permit term in updates
to the Comprehensive Plan (or equivalent) and in other locally initiated or
state-mandated, long-range land use plans that are used to accommodate
growth or transportation.
c. Low impact development code-related requirements.
Permittees shall continue to require LID Principles and LID BMPs when updating,
revising, and developing new local development-related codes, rules, standards,
or other enforceable documents, as needed.
The intent shall be to make LID the preferred and commonly-used approach to
site development. The local development-related codes, rules, standards, or
other enforceable documents shall be designed to minimize impervious surfaces,
native vegetation loss, and stormwater runoff in all types of development
situations, where feasible.
S5.C.1
Western Washington Phase II Municipal
Page 12 of 56
Stormwater Permit – August 1, 2019
(a)
Annually, each Permittee shall assess and document any newly identified
administrative or regulatory barriers to implementation of LID Principles or
LID BMPs since local codes were updated in accordance with the 2013
Permit, and the measures developed to address the barriers. If applicable,
the report shall describe mechanisms adopted to encourage or require
implementation of LID principles or LID BMPs.
By December 31, 2023, New Permittees shall review, revise, and make effective
their local development-related codes, rules, standards, or other enforceable
documents to incorporate and require LID principles and LID BMPs. New
Permittees shall conduct a similar review and revision process, and consider the
range of issues, outlined in the following document: Integrating LID into Local
Codes: A Guidebook for Local Governments (Puget Sound Partnership, 2012).
New Permittees shall submit a summary of the results of the review and revision
process with the annual report due no later than March 31, 2024. This summary
shall be in the required format described in Appendix 5 and include, at a
minimum, a list of the participants (job title, brief job description, and
department represented), the codes, rules, standards, and other enforceable
documents reviewed, and the revisions made to those documents which
incorporate and require LID principles and LID BMPs. The summary shall include
existing requirements for LID principles and LID BMPs in development-related
codes. The summary must be organized as follows:
(a)
Measures to minimize impervious surfaces.
(b)
Measures to minimize loss of native vegetation.
(c)
Other measures to minimize stormwater runoff.
d. Stormwater Management Action Planning3 (SMAP). Permittees shall conduct a similar
process and consider the range of issues outlined in the Stormwater Management
Action Planning Guidance (Ecology, 2019; Publication 19-10-010). Permittees may rely
on another jurisdiction to meet all or part of SMAP requirements at a watershed-
scale, provided a SMAP is completed for at least one priority catchment located
within the Permittee’s jurisdiction.
Receiving Water Assessment. Permittees shall document and assess existing
information related to their local receiving waters and contributing area
conditions to identify which receiving waters are most likely to benefit from
stormwater management planning.
By March 31, 2022, Permittees shall submit a watershed inventory and include a
brief description of the relative conditions of the receiving waters and the
contributing areas. The watershed inventory shall be submitted as a table with
each receiving water name, its total watershed area, the percent of the total
watershed area that is in the Permittee’s jurisdiction, and the findings of the
stormwater management influence assessment for each basin. Indicate which
3 New Permittees are exempt from S5.C.1.d. for this permit term.
S5.C.1
Western Washington Phase II Municipal
Page 13 of 56
Stormwater Permit – August 1, 2019
receiving waters will be included in the S5.C.1.d.ii prioritization process. Include a
map of the delineated basins with references to the watershed inventory table.
(a)
Identify which basins are expected to have a relatively low Stormwater
Management Influence for SMAP. See the guidance document for definition
and description of this assessment.
Basins having relatively low expected Stormwater Management Influence
for SMAP do not need to be included in S5.C.1.d.ii-iii.
Receiving Water Prioritization. Informed by the assessment of receiving water
conditions in (i), above, and other local and regional information, Permittees shall
develop and implement a prioritization method and process to determine which
receiving waters will receive the most benefit from implementation of
stormwater facility retrofits, tailored implementation of SWMP actions, and other
land/development management actions (different than the existing new and
redevelopment requirements). The retrofits and actions shall be designed to:
1) conserve, protect, or restore receiving waters through stormwater and land
management strategies that act as water quality management tools, 2) reduce
pollutant loading, and 3) address hydrologic impacts from existing development
as well as planned for and expected future buildout conditions.
No later than June 30, 2022, document the prioritized and ranked list of receiving
waters.
(a)
The Permittee shall document the priority ranking process used to identify
high priority receiving waters. The Permittee may reference existing local
watershed management plan(s) as source(s) of information or rationale for
the prioritization.
(b)
The ranking process shall include the identification of high priority
catchment area(s) for focus of the Stormwater Management Action Plan
(SMAP) in (iii), below.
Stormwater Management Action Plan (SMAP). No later than March 31, 2023,
Permittees shall develop a SMAP for at least one high priority catchment area
from (ii), above, that identifies all of the following:
(a)
A description of the stormwater facility retrofits needed for the area,
including the BMP types and preferred locations.
(b)
Land management/development strategies and/or actions identified for
water quality management.
(c)
Targeted, enhanced, or customized implementation of stormwater
management actions related to permit sections within S5, including:
IDDE field screening,
Prioritization of Source Control inspections,
O&M inspections or enhanced maintenance, or
Public Education and Outreach behavior change programs.
S5.C.2
Western Washington Phase II Municipal
Page 14 of 56
Stormwater Permit – August 1, 2019
Identified actions shall support other specifically identified stormwater
management strategies and actions for the basin overall, or for the
catchment area in particular.
(d)
If applicable, identification of changes needed to local long-range plans, to
address SMAP priorities.
(e)
A proposed implementation schedule and budget sources for:
Short-term actions (i.e., actions to be accomplished within six years),
and
Long-term actions (i.e., actions to be accomplished within seven to 20
years).
(f)
A process and schedule to provide future assessment and feedback to
improve the planning process and implementation of procedures or
projects.
Public Education and Outreach
The SWMP shall include an education and outreach program designed to:
Build general awareness about methods to address and reduce impacts from
stormwater runoff.
Effect behavior change to reduce or eliminate behaviors and practices that cause or
contribute to adverse stormwater impacts.
Create stewardship opportunities that encourages community engagement in
addressing the impacts from stormwater runoff.
Permittees may choose to meet these requirements individually or as a member of a
regional group. Regional collaboration on general awareness or behavior change
programs, or both, includes Permittees developing a consistent message, determining
best methods for communicating the message, and when appropriate, creating strategies
to effect behavior change. If a Permittee chooses to adopt one or more elements of a
regional program, the Permittee should participate in the regional group and shall
implement the adopted element(s) of the regional program in the local jurisdiction.
The minimum performance measures are:
a. Each Permittee shall implement an education and outreach program for the area
served by the MS4. The program design shall be based on local water quality
information and target audience characteristics to identify high priority target
audiences, subject areas, and/or BMPs. Based on the target audience’s demographic,
the Permittee shall consider delivering its selected messages in language(s) other
than English, as appropriate to the target audience. 4
General awareness. To build general awareness, Permittees shall annually select
at a minimum one target audience and one subject area from either (a) or (b):
(a)
Target audiences: General public (including overburdened communities, or
school age children) or businesses (including home-based, or mobile
businesses). Subject areas:
4 New Permittees shall begin implementing the requirements of S5.C.2 no later than August 1, 2021.