RE-EVALUATED: A REGIONAL DATA EVALUATION OF ILLICIT DISCHARGE, DETECTION, AND ELIMINATION (IDDE) RECORDS IN WESTERN WASHINGTON

Item

Identifier
Thesis_MES_2022Su_SpechtS
Title
RE-EVALUATED: A REGIONAL DATA EVALUATION OF ILLICIT DISCHARGE, DETECTION, AND ELIMINATION (IDDE) RECORDS IN WESTERN WASHINGTON
Date
August 2022
Creator
Specht, Skyler
extracted text
RE-EVALUATED: A REGIONAL DATA EVALUATION OF ILLICIT DISCHARGE,
DETECTION, AND ELIMINATION (IDDE) RECORDS IN WESTERN WASHINGTON.

by
Skyler Specht

A Thesis
Submitted in partial fulfillment
Of the requirements for the degree
Master of Environmental Studies
The Evergreen State College
August 2022

©2022 by Skyler Specht. All rights reserved.

This Thesis for the Master of Environmental Studies Degree
by
Skyler Specht

has been approved for
The Evergreen State College
by

_______________________________
Ralph Murphy, Ph.D.
Member of Faculty

_______________________________
Date

ABSTRACT
Re-evaluated: A Regional Data Evaluation of Illicit Discharge, Detection, and Elimination
(IDDE) Records in Western Washington.
Skyler Specht
In 2017, Stormwater Action Monitoring (SAM) published the Illicit Discharge Detection and
Elimination (IDDE) Regional Data Evaluation for Western Washington, a regional monitoring
study that evaluated IDDE records from the 2014 permit reports submitted from municipal
stormwater permittees as part of their annual reporting requirements. Through the efforts of this
study, a standardized reporting format was created to help facilitate the ease of data collection
and analysis among permittees that began rollout starting in 2020. In this thesis, IDDE records
submitted through the new standardized reporting format in the first year of its utilization in
2020 were collected to perform a similar type of analysis using methodology modified from the
original regional data evaluation.

Table of Contents
List of Figures ................................................................................................................................ vi
List of Tables ................................................................................................................................ vii
Acronyms ..................................................................................................................................... viii
Acknowledgements ........................................................................................................................ ix
Positionality Statement ................................................................................................................... x
Introduction ..................................................................................................................................... 1
Chapter 1. Literature Review .......................................................................................................... 4
Introduction ................................................................................................................................. 4
Federal Stormwater Regulation and its Origins .......................................................................... 4
Federal Water Pollution Control Act of 1948 ......................................................................... 4
Environmental Awareness in the 1960’s and 1970’s .............................................................. 5
Clean Water Act of 1972 ......................................................................................................... 8
Federal Municipal NPDES Program ..................................................................................... 10
Washington State Stormwater Regulations and Monitoring Efforts ......................................... 11
Washington State Municipal NPDES Program ..................................................................... 11
Illicit Discharge Detection, and Elimination (IDDE) ............................................................ 12
Stormwater Work Group (SWG) ........................................................................................... 14
Stormwater Action Monitoring (SAM) ................................................................................. 16
SAM Source Identification Study: Regional Data Evaluation .............................................. 17
Conclusion................................................................................................................................. 22
Chapter 2. Methods ....................................................................................................................... 24
Introduction ............................................................................................................................... 24
Data Acquisition ........................................................................................................................ 24
Descriptive Analysis ................................................................................................................. 25
Statistical analysis ..................................................................................................................... 26
Conclusion................................................................................................................................. 28
Chapter 3. Results ......................................................................................................................... 29
Introduction ............................................................................................................................... 29
Descriptive Analysis ................................................................................................................. 29
Data Represented ................................................................................................................... 29
MS4 Discharge ...................................................................................................................... 30
Pollutant Types ...................................................................................................................... 33
iv

Pollutant Sources ................................................................................................................... 36
Source Tracing Methods ........................................................................................................ 40
Correction and Elimination Methods .................................................................................... 42
Discovery Methods ................................................................................................................ 44
Statistical Analysis .................................................................................................................... 46
Pollutant Type vs. Phase Type .............................................................................................. 46
Pollutant Type vs. Pollutant Source ...................................................................................... 46
Pollutant Type vs. Correction and Elimination Method ........................................................ 47
Pollutant Type vs. Discovery Method ................................................................................... 47
Pollutant Type vs. Tracing Method ....................................................................................... 48
Conclusion................................................................................................................................. 48
Chapter 4. Discussion ................................................................................................................... 50
Introduction ............................................................................................................................... 50
Distribution of Data ................................................................................................................... 50
Pollutant Types and Pollutant Sources ...................................................................................... 51
Source Tracing Methods ........................................................................................................... 52
Discovery Methods ................................................................................................................... 53
Correction and Elimination Methods ........................................................................................ 53
Reporting standardization ......................................................................................................... 54
Limitations and Recommendations ........................................................................................... 56
Conclusion................................................................................................................................. 56
Chapter 5. Conclusion ................................................................................................................... 58
References ..................................................................................................................................... 60
Appendix A: Contingency Tables and Maximum Likelihood Chi-Squared Analysis ................. 65
Appendix B: Permittees Represented ........................................................................................... 70

v

List of Figures
Figure 1 Number of Records Submitted by Permittee Type ......................................................... 30
Figure 2 MS4 Discharge by Permittee Phase Type ..................................................................... 31
Figure 3 MS4 Discharge by Permittee Phase Type, Expanded ................................................... 32
Figure 4 Phase I Pollutants.......................................................................................................... 33
Figure 5 Phase I Pollutants with MS4 Discharge, Ranked by Frequency ................................... 34
Figure 6 Phase II Pollutants ........................................................................................................ 35
Figure 7 Phase II Pollutants With MS4 Discharge, Ranked by Frequency ................................. 36
Figure 8 Phase I Pollutant Sources ............................................................................................. 37
Figure 9 Phase I Pollutant Sources with MS4 Discharge, Ranked by Frequency ....................... 38
Figure 10 Phase II Pollutant Sources .......................................................................................... 39
Figure 11 Phase II Pollutant Sources with MS4 Discharge, Ranked by Frequency ................... 40
Figure 12 Phase I Source Tracing Methods ................................................................................ 41
Figure 13 Phase II Source Tracing Methods ............................................................................... 42
Figure 14 Phase I Correction and Elimination Methods ............................................................. 43
Figure 15 Phase II Correction and Elimination Methods ........................................................... 44
Figure 16 Phase I Discovery Methods ......................................................................................... 45
Figure 17 Phase II Discovery Methods ........................................................................................ 45
Figure 18 Permittee Names and Frequencies of Records Submitted ........................................... 70

vi

List of Tables
Table 1
Table 2
Table 3
Table 4
Table 5
Table 6
Table 7

Clean Water Act Amendments .......................................................................................... 9
MS4 Discharge Fields and Combined Categories ......................................................... 26
Observed Frequencies and Residuals for Pollutant Type by Phase Type ...................... 65
Observed Frequencies and Residuals for Pollutant Type by Pollutant Source .............. 66
Observed Frequencies and Residuals for Pollutant Type by Correction Method .......... 67
Observed Frequencies and Residuals for Pollutant Type by Discovery Method ........... 68
Observed Frequencies and Residuals for Pollutant Type by Tracing Method ............... 69

vii

Acronyms
BMPs

Best management practices

EPA

Environmental Protection Agency

ERTS

Environmental Response Tracking System

IDDE

Illicit Discharge Detection and Elimination

MS4

Municipal Separate Storm Sewer System

NEPA

National Environmental Policy Act

NPDES

National Pollution Discharge Elimination System

PARIS

Permit and Reporting Information System

PRO-C

Pooled Resources Oversight Committee

RSMP

Regional Stormwater Monitoring Program

SAM

Stormwater Action Monitoring

SWG

Stormwater Work Group

SWMP

Stormwater Management Program

viii

Acknowledgements
I would like to express my sincere gratitude to my thesis reader and MES Faculty Ralph
Murphy, who provided consistent support and a myriad of his time in guiding me through this
research. I also want to thank MES Faculty Shawn Hazboun, who provided oversight to me
during the beginning stages of my thesis research. Averi Azar, Assistant Director of MES, also
deserves recognition for her assistance and guidance throughout the thesis process. The 2017
SAM Source ID study, the Illicit Discharge Detection and Elimination (IDDE) Regional Data
Evaluation for Western Washington, must also be referenced as it is a foundational element of
this analysis. I would also be remiss without mentioning my work colleagues for their comments
and suggestions regarding my thesis research. Finally, I want to acknowledge my fiancé and my
family for their unwavering support and belief in me. I would not have been able to complete this
thesis without their encouragement throughout these past few years.

ix

Positionality Statement
To provide transparency to my role as a researcher, I am a stormwater inspector for a
Phase II municipal stormwater permittee in Western Washington doing thesis research
independent of said organization to fulfill the requirements of this degree. My job duties
primarily relate to the operation and maintenance of private stormwater facilities, however for
this thesis I have decided to focus on the Illicit Discharge Detection and Elimination component
of the municipal stormwater permit. As stormwater has been a part of my daily life for a better
part of the last three years, I have built an understanding of the municipal stormwater permit and
stormwater management in Washington State, however much of my knowledge and expertise
relates to operations and maintenance of stormwater facilities, not necessarily on Illicit
Discharge Detection and Elimination. To provide clarity to the reader, I rely on primary sources
and not my first-hand experience throughout this analysis.

x

Introduction
To meet stormwater monitoring needs of municipal separate stormwater sewer systems
(MS4s) for municipalities, a preliminary study was conducted to evaluate Illicit Discharge
Detection and Elimination (IDDE) using records from municipalities in Western Washington
from self-reported permit submissions in 2014 (SAM, 2017). This research seeks to further
evaluate regional spill data using data from 2020 to look for new or existing trends in the spill
data. Furthermore, it is an attempt to further the conversation that was started regarding regional
IDDE Evaluation in Western Washington. This chapter will provide context to the origins of the
initial study, its findings and significance, and the purpose and objective of continuing of this
research.
Municipalities in urbanized areas in the United States are required under the National
Pollutant Discharge Elimination System (NPDES) enacted under the Clean Water Act to obtain a
municipal stormwater permit from the Department of Ecology. In Western Washington, there are
6 Phase I municipalities (cities and counties with a population over 100,000) and 88 Phase II
permittees (urbanized growth areas with a population less than 100,000). The permit requires the
establishment of a Stormwater Management Program (SWMP) which requires, among many
components, an Illicit Discharge Detection and Elimination (IDDE) program designed to deter
pollutants from entering stormwater and surface waters, and to detect and eliminate illicit
connections to the MS4. An illicit connection is an unpermitted or undesired connection to the
MS4 such as a sewer pipe, floor drain, or other pipe inlet or outlet. An illicit discharge is any
discharge to the MS4 that is not entirely stormwater, or allowable non-stormwater discharges as
allowed by the permit (Herrera Environmental Consultants & Aspect Consulting, 2020) As part
of this program to eliminate illicit connections and track and reduce illicit discharges, permittees

1

must submit their IDDE records annually to the Department of Ecology (Washington State
Department of Ecology, 2019d, 2019c). Each IDDE record represents a specific discharge event
that was discovered by or reported to the municipality, whether it be an illicit connection to the
MS4 or a spill of any kind of pollutant that may discharge to the MS4.
In 2017, Stormwater Action Monitoring (SAM), a permittee-funded regional monitoring
program in Western Washington, funded and published the Illicit Discharge Detection and
Elimination (IDDE) Regional Data Evaluation for Western Washington (Aspect Consulting,
2017). This study evaluated IDDE records submitted in 2014 from 78 total municipalities in
Western Washington as part of the annual reporting requirements of the municipal stormwater
permit. This first SAM Source Identification (Source ID) project helped further the goal of the
subgroup to provide information on successful illicit discharge detection and elimination
methods and strategies to reduce the discharge of pollutants to stormwater. The report indicated a
wide variety of reporting formats and the obvious necessity for a standardized reporting format
due to the of preliminary task the team overtook in transcribing the data to fit within a common
schema (Aspect Consulting, 2017). In addition, the study identified the most common pollutants,
source tracing methods, methods of reporting, correction and elimination methods, and incident
response times. Directly following this study, the Source ID subgroup worked with the
Department of Ecology to come up with a standardized data reporting format that is now
required to be used in the most recent iteration of the permit, starting 2020 (Washington State
Department of Ecology, 2019a).
With the first Source ID data evaluation complete and a new data schema in place to
facilitate standardization of IDDE reporting, 2020 would be the first year that permittees would
use the new reporting format that would utilize Ecology’s Water Quality Permitting and
2

Reporting Information System (PARIS). The standardized reporting format would allow for
direct comparison between individual IDDE records between permittees without the previously
required coding element to compare between the various reporting formats that were previously
accepted. This also enabled Ecology to compile IDDE records from municipal stormwater
permittees into an online database that enabled a much more feasible method of data collection,
as the previous method required the collection of each individual permittee’s IDDE report via
Ecology’s “Document Search” database.
The purpose of this thesis is to perform a regional data evaluation of the 2020 IDDE
report data, the first year of available annual IDDE reporting data collected using the new
standardized reporting format via Ecology’s online PARIS IDDE Report database. This extends
the research of the previous regional data evaluation which performed analysis on 2014 data
prior to the establishment of the standardized reporting format. To set up the foundation for this
research, the literature review will first review stormwater regulation and specifically municipal
stormwater regulation in the United States and more locally in Washington State. The next
section will focus on the IDDE element of the municipal stormwater permit including regional
monitoring efforts and groups associated with such efforts including SAM, and then review the
Illicit Discharge Detection and Elimination (IDDE) Regional Data Evaluation for Western
Washington which provides the foundation for this analysis.

3

Chapter 1. Literature Review
Introduction
To establish context to this study, it is necessary to review key background information
regarding the establishment of stormwater regulation in the United States and highlight the
previous study which is foundational to this research. This chapter will start with a review of the
origins of federal water quality regulation, then cover the growing environmental movement in
the 1960’s and 1970’s. This will lead to the 1972 introduction of the Clean Water Act and focus
on point source pollution, and the subsequent addition of the Municipal National Pollutant
Discharge Elimination System (NPDES) Program focused on reducing non-point source
pollution. The next section will move more locally to Western Washington to review municipal
NPDES stormwater regulation in Washington State and stormwater work groups associated with
said regulation that are relevant to this research. The last elements of this chapter will focus on
the Illicit Discharge Detection and Elimination (IDDE) component of the municipal stormwater
permit and the Illicit Discharge Detection and Elimination (IDDE) Regional Data Evaluation for
Western Washington (2017) that serves as the basis for this research.
Federal Stormwater Regulation and its Origins
Federal Water Pollution Control Act of 1948
Much of the federal stormwater regulation within the United States receives its origin
from a federal statute commonly referred to as the Clean Water Act, originally known as the
Federal Water Pollution Control Act of 1948 prior to sweeping amendments made in 1972. The
1948 law was the first major law passed by Congress regarding the federal regulation of water
pollution in the United States, as previous regulation had largely focused on water transportation
and quantity, not quality (Hunter & Waterman, 1996). The Rivers and Harbors Appropriation
4

Act of 1899 was technically the first federal law regarding water quality as it established federal
oversight of navigable waters within the United States and controlled river and harbor
improvements (EPA, n.d.-b). The 1948 law was a good first attempt to establish widespread
regulation, but the enforcement mechanisms established were flawed in that it was very difficult
to establish a link between an impaired waterway to a particular discharger. In addition, direct
federal involvement in enforcement was limited to interstate matters, so much of the oversight
authority was delegated to the states (Copeland, 2014). Because many states did not have the
financial capacity or lacked the commitment to implement the programs outlined in the act,
implementation was scattered and ineffective (Hunter & Waterman, 1996). By the 1960’s, the
overall perception of water quality regulation in the United States was poor, as frustration
loomed over the slow response to cleaning up impaired waterways, in addition to the timeconsuming nature of the enforcement process of the current legislation (Copeland, 2016).
Environmental Awareness in the 1960’s and 1970’s
By the late 1960’s, public attention for the health of the nation’s waterways was at an alltime high. In January 1969, a massive oil spill off the coast of Santa Barbara killed an
indescribable amount of fish, seabirds and other aquatic life, and impacted nearly eight hundred
miles of beaches (Clarke & Hemphill, 2002). In their 2002 retrospective of the oil spill events,
Clarke and Hemphill describe the damage as so extensive that people of all age groups and
political affiliations immediately came together to help begin cleanup, and a grassroots
movement began that would quickly pick up steam. In June of 1969 when the Cuyahoga River
caught fire in Cleveland, public attention turned to public outroar. The river had just caught on
fire for the 10th time since 1868 and for the first time since 1952, when public sentiment towards
industrial pollution was mostly indifferent: the river had been used for industrial discharge of a

5

wide variety of solvents, oils, and industrial pollutants for generations (Blakemore, 2019).
Beyond Cleveland, where the complacent belief at the time was that the fires were simply , the
nation would become outraged at the events that would unfold on their TV screens and in their
newsprint media: it was simply becoming too much (Blakemore, 2019). In 1971, Ralph Nader
formed a task force that would subsequently release Water Wasteland, a report providing
anecdotal evidence of the horrific state of U.S. waterways. This report documented findings of
multiple studies, including mercury-contaminated drinking water, DDT levels in fish nearly ten
times the legal limit, unsafe swimming areas due to bacterial contamination, and multiple record
fish kills including the single largest fish kill event to date – 26.5 million fish due to discharges
from food processing plants in Lake Thonotosassa, Florida (Adler et al., 1993; Zwick et al.,
1971). The report, confirmed by governmental sources to be legitimate, pushed the issue of water
pollution even further into the limelight of media attention (Adler et al., 1993).
The nation could no longer wait for water pollution regulation. This was the generation of
Rachel Carson’s Silent Spring, whose book inspired millions of Americans to open their eyes to
the impact of DDT and other contaminants in nature and is often associated as a piece of
foundational media leading up to the implementation of the CWA. Carson’s book was just one
small example of the growing movement of environmentally focused media, from books,
articles, scientific literature, to nature shows and songs heard on the radio (Stradling, 2013). But
there were other pressing social and political concerns at hand at the same time in the United
States. Author David Stradling in his book The Environmental Movement, describes the social
context of concentrated urban poverty, racism, and the callousness of the Vietnam War and how
it created a situation where “civilization itself appeared to be threatened” (2013, p. 6). Stradling

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(2013) proceeds to address the anxiety much of the nation felt by referencing Allan Temko’s
1963 New York Times article which perfectly captures the sentiment of the era:
Confronted by an environmental crisis of now almost incredible gravity, as traditional
urban civilization disintegrates without a coherent order of technological civilization to
take its place, our supposedly affluent and inventive society finds itself strangely
powerless to establish rational patterns of growth (p. 6).
With public awareness of environmental problems and water quality issues at an all-time
high during the late 1960’s, the pathway was paved for change in the 1970s. In Robert Adler’s
1993 book The Clean Water Act 20 Years Later, he portrays the Clean Water Act as an example
of the “new social regulation of the seventies”, describing its origin as the product of swift action
from Congress due in response to demands from “newly empowered mass movements and
interest groups” (Adler et al., 1993, p. 198). Adler also suggests that such activism and
environmental values helped establish a political climate that encouraged politicians to “push the
limits on such legislation” (pg. 198). It was clear by the 1970’s that the nation was ready for
water quality regulations at a federal level. Early on in his presidency, Richard Nixon declared
that the 1970’s must be an era reclaiming the purity of the nation’s waterways, air, and
environment, and to own up to the mistakes of the past. On January 1, 1970, Nixon signed the
National Environmental Policy Act (NEPA), the first major environmental law in the United
States requiring federal agencies to assess the environmental implications of their proposed
actions prior to making any decisions. (EPA, n.d.-d; Nepa.gov, n.d.) This would eventually lead
to the establishment of the Environmental Protection Agency later that year (Clarke & Hemphill,
2002). In April of 1970, the first Earth Day took place, which clearly demonstrated the nation’s
concern for the environment through public education and action (Stradling, 2013).
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In the late 1960’s and early 1970’s, politicians were playing catch-up with this newly
emerging national concern for the environment. In December of 1970, President Richard Nixon
signed an executive order creating the Environmental Protection Agency (EPA), which
combined several pollution programs into one agency. The EPA was the first and only regulatory
agency in the United States that does not sit within the legislative government and is overseen by
an administrator whose term runs concurrent with the president. This allows for the president to
select an administrator of the EPA, although the selection must be confirmed by the Senate
(Hunter & Waterman, 1996). Later in 1970, the Clean Air Act was signed, aimed at reducing air
pollution and controlling air quality throughout the nation. The foundation was set for Congress
to make big changes to the Federal Water Pollution Control Act, and it would come in the form
of the Clean Water Act of 1972.
Clean Water Act of 1972
Between 1948 and 1972, five amendments to the Federal Water Pollution Control Act
were made (see Table 1) (Copeland, 2014). The Water Pollution Control Act of 1956
strengthened enforcement provisions (EPA, n.d.-b); the 1961 Federal Water Pollution Control
Act Amendments extended federal oversight to all navigable waters and coastal waters in the
United States (Cohen & Sonosky, 1962); the Water Quality Act of 1965 established water
quality standards for surface waters (EPA, n.d.-b); the Clean Water Restoration Act of 1966
which gave provisions to help guide the 1965 law (United States Senate, n.d.); and the Water
Quality Improvement Act of 1970 which again expanded federal oversight of marine polluters
(EPA, 2016). However, despite the many improvements since the introductory legislation in
1948 law, the resulting framework was a combination of ineffective water quality acts and

8

change was needed to be able to effectively administrate and enforce water quality standards
(EPA, n.d.-b).
Table 1
Clean Water Act Amendments
Year
1948
1956
1961
1965
1966
1970
1972
1977
1987

Act
Federal Water Pollution Control Act
Water Pollution Control Act of 1956
Federal Water Pollution Control Act
Amendments
Water Quality Act of 1965
Clean Water Restoration Act
Water Quality Improvement Act of 1970
Federal Water Pollution Control Act
Amendments
Clean Water Act of 1977
Water Quality Act of 1987

Note. This table includes the major amendments of the Clean Water Act. Modified from
Copeland, 2014 for this study.
Congress began to draft the 1972 amendments to the Federal Water Pollution Control Act
of 1948, completely rewriting the bill and shifting the focus from maintaining ambient water
quality to increasing attention on individual dischargers (Hunter & Waterman, 1996). These
sweeping amendments would be commonly referred to as the Clean Water Act. These
amendments established a framework for regulating pollutant discharge from industrial point
sources, mandated protection of the nation’s surface waters, and delegated the Environmental
Protection Agency the authority to delegate the provisions of the CWA. The act would set
ambitious goals: the elimination of all pollution discharges into navigable waters of the United

9

States by 1985, and another goal to restore water quality to provide “…’fishable’ and
‘swimmable’ waters…” to all navigable waters by 1983 (Copeland, 2014, p. 30).
With the establishment of the CWA, anyone who would discharge pollutants through a
point source into a water of the United States would be required to obtain a National Pollutant
Discharge Elimination System (NPDES) permit. The permit included constraints on what could
be discharged, monitoring requirements, and other provisions to ensure the protection of United
States waterways (EPA, n.d.-c). In addition, many technology-driven statutes were included to
enforce industries to enforce best practicable control technology (BPT) to clean up industrial
pollution (Copeland, 2014).
Federal Municipal NPDES Program
In 1977, the Clean Water Act was signed to provide initial fine-tuning to the 1972
amendments and further clarification of the legislature (Hall, 1978). The Water Quality Act of
1987 established the NPDES program for municipalities, requiring municipalities to develop
nonpoint pollution control programs (Copeland, 2014). Prior to the amendments in 1987,
regulation was directed towards point source pollution coming from discrete, identifiable
industrial and municipal sources and had little focus on non-point pollution that comes from
stormwater runoff picking up pollutants as it conveys to a waterway (Copeland, 2014). The EPA
established the first phase of these requirements in 1990, requiring municipalities with a
population of 100,000 or more (based on the 1990 census) to implement a Stormwater
Management Program (SWMP) that would address outlined stormwater control components in
the permit.

10

Now that the Clean Water Act and general water quality requirements have been
introduced, this next section will focus specifically on non-point stormwater pollution and
NPDES implementation in Washington State.
Washington State Stormwater Regulations and Monitoring Efforts
Washington State Municipal NPDES Program
The EPA allows states and tribes to oversee the implementation of NPDES programs and
in Washington State, the Washington State Department of Ecology (Ecology) is the delegated
authority that writes the permit and oversees its operation. Ecology published the first five-year
cycle of the Phase I Municipal Stormwater Permit in 1990 (to begin in 1995) for cities and
counties with a population greater than 100,000 based on the 1990 census. By 1999, the Phase II
of the permit was published (to begin in 2003) for cities and counties with a population less than
100,000 in census-defined urban areas. In Washington State there are two Phase II permits based
on region: the Phase II Municipal Stormwater Permit for Western Washington covers 80 cities
and five counties; the Phase II Municipal Stormwater Permit for Eastern Washington covers 19
cities and portions of six counties (Washington State Department of Ecology, 2019b, 2019d).
The five-year permit cycle process is designed to be adaptive so that the permit can evolve as our
understanding of various pollutants and the methods and technology we use to eliminate them
develop. Throughout each permit cycle, Ecology maintains a timeline for rollout of the next
five-year cycle of the permit that includes several opportunities for permittees to provide
comments to Ecology on existing and upcoming elements of the permit. With each iteration of
the permit cycle, new permit elements for the permittees to establish are along with a specified
timeline for rollout, along with any modifications of the existing sections of the permit based on
feedback from municipal stormwater permittees.
11

Phase I and Phase II municipalities are required to submit an annual report that outlines
each element of the permit in a questionnaire format that the permittee can fill out and submit
online. The questions are designed to indicate whether the permittee has completed the outlined
elements of each permit section and ask specified information regarding each permittee’s SWMP
and the actions they have taken to implement the components of the permit. The data from this
analysis comes from a portion of this annual report that permittees are required to submit
regarding spill records that the municipality has logged throughout the year. This will be
explained in greater detail in the next section.
Illicit Discharge Detection, and Elimination (IDDE)
Now that an overview has been provided of the origins of federal municipal stormwater
regulation and how federal regulation is implemented in Washington State, the component of the
Municipal Stormwater Permit that pertains most to the topic of this analysis can be explored. As
previously described Phase I and Phase II municipalities are required to implement a Stormwater
Management Program (SWMP) that has outlined components that each permittee much include.
In the current cycle of the Phase I Municipal Stormwater Permit, there are 11 SWMP
components, including: Legal Authority; MS4 Mapping and Documentation; Coordination;
Public Involvement and Participation; Controlling Runoff from New Development;
Redevelopment and Construction Sites; Stormwater Planning; Structural Stormwater Controls;
Source Control Program for Existing Development; Illicit Connections and Illicit Discharges
Detection and Elimination; Operation and Maintenance Program; Education and Outreach
Program. In the current cycle for both Phase II Municipal Stormwater Permits, there are 9
SWMP components, including: Stormwater Planning; Public Education and Outreach; Public
Involvement and Participation; MS4 Mapping and Documentation; Illicit Discharge Detection

12

and Elimination; Controlling Runoff from New Development, Redevelopment and Construction
Sites, Operations and Maintenance, Source Control Program for Existing Development.
The analysis in this study focuses on the Illicit Connections and Illicit Discharges
Detection and Elimination component of the Phase I and Phase II municipal stormwater permit.
For this component of the SWMP, permittees must implement a program that includes multiple
elements: eliminate non-stormwater discharges and illicit connections to the municipal separate
stormwater system (MS4); implement an ordinance that prohibits non-stormwater discharges into
the permittee’s MS4; list a public hotline for public reporting of spills and other discharges; train
staff responsible for responding to illicit discharges and illicit connections; and track and
maintain records of all activities under this section. For the annual reporting requirements of this
section of the permit, permittees are required to submit data for the illicit discharges, spills, and
illicit connections that the permittee found, investigated, or were reported to. This analysis
evaluates spill data that was submitted by municipal stormwater permittees for this permit
obligation in 2020 for permittees in Western Washington. It is a continuation of previous
regionally funded monitoring efforts in Western Washington which analyzed spill data for the
2014 calendar year.
The next section will review the Stormwater Work Group (SWG) and Stormwater
Action Monitoring (SAM), two regional stormwater groups that are associated with the
implementing monitoring associated with the municipal stormwater permit. SWG is responsible
for oversight and implementation of SAM projects related to stormwater monitoring, which will
be discussed in further detail.

13

Stormwater Work Group (SWG)
As Ecology describes on their Stormwater Work Group (SWG) webpage, most NPDES
permits require some form of compliance monitoring. This presents a unique challenge for the
municipal stormwater permit which applies to both point sources and non-point sources. As
referenced earlier in this literature review, point sources are discernable conveyances including
pipes, ditches, or other channels that are designed to convey specific discharges (EPA, n.d.-a).
Non-point sources largely involve pollution coming from stormwater runoff as it picks up
pollutants that exist over a broad landscape. These pollutants include fertilizers, oils and greases,
sediment, bacteria, and other products from a variety of commercial, industrial, and residential
sources (EPA, n.d.-a). The largest pollution concern comes from non-point pollution sources that
are not a discrete, controlled source like the end of a pipe as they are difficult to track over a
continuous landscape. Due to this, permittees came to Ecology to request an alternative to the
traditional compliance monitoring that would be difficult, if not impossible to obtain
(Washington State Department of Ecology, n.d.-e). Thus, in 2008, the Stormwater Work Group
(SWG) formed to help guide a regional effort in understanding stormwater pollution and how to
better manage it (Stormwater Work Group, n.d.-a). Participating stakeholders in the group
include representatives of local, state, and federal governments, public ports, environmental and
business organizations, and other various stormwater stakeholders in Puget Sound. In the first
few years of the work group, hundreds of participants came together to develop a regional
monitoring program for Western Washington (Washington State Department of Ecology, n.d.-e).
Within SWG, there are multiple subgroups that are designed to tackle specific issues
within stormwater management, including the Effectiveness Studies Subgroup, The Source
Identification Subgroup which we will discuss later in this section, and the most recently formed

14

6PPD Subgroup. This new subgroup formed to discuss and tackle 6PPD-quinone, a contaminant
found in tire wear particles, that was recently linked to a widely documented phenomenon
known as coho pre-spawn mortality in Puget Sound streams by researchers at UW Tacoma (Tian
et al., 2022). Though it is not the core focus of this analysis, coho pre-spawn mortality rests
within the core of stormwater literature in Puget Sound and must be referenced in the discussion
of regional monitoring efforts. Recurrent die-offs of coho salmon returning to spawn in urban
streams in the Seattle area were first documented in 1999 and 2000 during early monitoring
efforts of newly accessible urban stream segments after a series of stream restoration projects in
the 1990s (Scholz et al., 2011). This discovery led to a series of studies linking this phenomenon
to toxic contaminants in stormwater from urbanized watersheds through spatial analyses of land
use and coho mortality (Feist et al., 2011) and laboratory studies exposing coho salmon to
untreated stormwater runoff (Scholz et al., 2011). Later studies provided evidence that simple
biofiltration techniques are sufficient to eliminate the toxic effects of stormwater runoff to coho
salmon (McIntyre et al., 2014, 2015, 2016), leading to a push to understand how biofiltration
stormwater management techniques may mitigate against pre-spawn coho mortality.
Of the various subgroups within SWG, the Source Identification (Source ID) subgroup is
most relevant subgroup to this study as it is responsible for the oversight and implementation of
the Stormwater Action Monitoring (SAM) Source Identification projects. This includes oversight
of the key study that will be covered in the next section, the Illicit Discharge Detection and
Elimination (IDDE) Regional Data Evaluation for Western Washington. The Source ID
subgroup formed in 2011 to help build tools to guide permittees in implementing the illicit
discharge, detection, and elimination component of their SWMP (Stormwater Work Group, n.d.-

15

a). It will be discussed further in the next section when SAM Source Identification projects are
covered.
Stormwater Action Monitoring (SAM)
Beginning with the launch of the 2014 permit cycle, Stormwater Action Monitoring
(SAM) formed as a regional stormwater monitoring program funded by more than 90 municipal
stormwater permittees in Western Washington. The overall goal of the group is to “improve
stormwater management, reduce pollution, improve water quality, and reduce flooding”
(Washington State Department of Ecology, n.d.-d) through targeted, collaborative studies. This
program is the only example in the state where permit-driven monitoring efforts are defined and
funded by the permittees themselves, allowing for the permittees to guide much of the overall
process.
To explain how the relationship between this program and SWG, Washington State
Department of Ecology (Ecology) serves as the administrator of SAM, overseeing the collection
of the funds for the group and executing contracts for the projects. As a formal stakeholder group
of SAM, SWG provides leadership, expertise, and general oversight of SAM projects. The
Pooled Resources Oversight Committee (PRO-C) of SWG, the formal committee which oversees
the pooled resources funding account, is responsible for overseeing Ecology’s implementation of
SAM and the administration of SAM’s pooled resources (Stormwater Work Group, n.d.-b). The
SAM coordinator works with PRO-C to review general administrative functions and discuss
current projects. PRO-C provides consent for the SAM coordinator to execute contracts, gives
general oversight, and reports back to SWG to discuss any issues that may need to be discussed
further in subgroups, technical advisory committees, or with other various stakeholders
(Stormwater Work Group, n.d.-c).
16

SAM studies focus on three broad categories related to stormwater management:
effectiveness studies, status and trends studies, and source identification projects, the latter of
which will be described in detail. SAM has published 14 effectiveness studies which focus on
evaluating the viability of required or innovative stormwater management practices (Washington
State Department of Ecology, n.d.-a). The status and trends studies focus on monitoring of
Washington streams and nearshore waters in relation to stormwater management (Washington
State Department of Ecology, n.d.-c). SAM’s Source Identification studies are the most relevant
to this thesis. These projects focus on discovering the best methods of preventing and eliminating
illicit discharges, and detecting and reducing pollutants to stormwater (Washington State
Department of Ecology, n.d.-b). The Source Identification subgroup of SWG oversees the
implementation of SAM Source Identification projects. To date, three SAM source identification
studies have been completed: the Regional Spill Hotline Feasibility Study, the Illicit Connection
and Illicit Discharge Field Screening Manual, and the Illicit Discharge, Detection, and
Elimination (IDDE) Regional Data Evaluation for Western Washington (Washington State
Department of Ecology, n.d.-b). This next section will cover the regional data evaluation in detail
as it serves as a foundation for the thesis.
SAM Source Identification Study: Regional Data Evaluation
In 2017, SAM completed the first Source Identification study, the Illicit Discharge
Detection and Elimination (IDDE) Regional Data Evaluation for Western Washington. This
study compiled IDDE incidents from the 2014 calendar year submitted by Western Washington
municipal stormwater permittees as part of their annual permit reporting requirements. The
identified goal of the study was to “…provide information on source identification and
elimination methods and identify opportunities for regional solutions to common stormwater

17

pollution problems related to illicit discharges and illicit connections” (Aspect Consulting, 2017,
pg. 4).
In total 2,913 data records were compiled from 78 jurisdictions, including seven Phase I
and 71 Phase II Permittees. At the time of the study, Ecology had an online submittal option with
a standardized set of data fields available for permittee usage, however only 7 of the 78 reporting
jurisdictions used this method as it was not part of the 2014 annual permittee submission
requirements. Most of the records were thus obtained via Ecology’s Permit and Reporting
Information System (PARIS) designed for permittees to submit annual permit reporting data.
The next step of the compilation phase required the team to organize the data records into a
standardized database so that records could be compared. Because of this requirement, the
authors included a set of recommendations in the study to “…reduce time-constraining data entry
for future IDDE data collection…” (Aspect Consulting, 2017, pg. 11). As this analysis seeks to
extend the research of this initial IDDE data evaluation, it serves as a representation of what the
authors reference here and will be expanded on later in detail.
The standardized database included fields representing the type of incident (whether it
was an allowable or illicit discharge), pollutant type, pollutant source, correction and elimination
methods, how the incident was reported, and additional explanatory fields including the location,
date, and the amount of time it took to resolve the incident. After the records were compiled into
a standardized database, the records were evaluated by comparing counts of record types and
incident characteristics primarily using graphical analysis. Statistical analysis was also
performed to compare the records and to test for logical associations, (i.e., sediment pollution
comes from a logical source such as a construction site, where sediment-exposing activity
typically occurs).
18

In the discussion of this study, the authors reference five discussion topics relevant to the
Source ID component of SAM, including the distribution of data among permittees, pollutants
and their sources, source tracing and indicator testing methods, notification methods and
response times, and correction and elimination methods. A modified version of these five
discussion topics will be used in the discussion section to review the results. Thus, it is necessary
to review the key findings from this study as the thesis will explore similar topics and trends.
These findings are presented in the format of the five discussion topics below.
Distribution of Data. A total of 1,269 Phase I records and 1,644 Phase II records were
obtained from 2014 annual IDDE permit submission reports. Data was weighted towards two
cities in particular: one Phase I municipality contributed two thirds (59%) of the total IDDE
records, and one Phase II contributed one fifth (19%) of the total IDDE records. The authors
highlight that a low number of records from some jurisdictions, especially some of the larger
Phase I entities with robust stormwater management programs, could represent room for
improvement in terms of fulfilling the IDDE reporting requirements. However, as the authors
indicate, this presumes that a high number of IDDE records represents a “good” implementation
of the IDDE component (pg. 45). This is a valid critique as the number of records a municipality
submits may be some indication of the level of effort the municipality places in tracking and
recording IDDE incidents. Nevertheless, the number of records by itself is not a direct reflection
of the quality of a municipality’s stormwater management program, as the quality of each record
entry is also important.
Pollutants and Pollutant Sources. A total of 53 pollutants and 58 pollutant sources were
grouped into eight pollutant categories and 7 pollutant sources categories during the data
standardization process. Pollutant sources had to be manually interpreted through record notes.
19

The most common pollutants found were petroleum hydrocarbons from accidents and auto
activities, sediment from construction sites, chemicals from industrial activities, and sewage
from illicit connections. Statistical analysis confirmed logical association of pollutants to
pollutant sources that expose said type of pollutant. These included sediment from construction
sites, chemicals from industrial activities, and hydrocarbons from spills and dumping.
Source Tracing and Indicator Testing. To distinguish between the two, source tracing
methods are the specific methods used to track a discharge. Indicator testing is a broad range of a
visual, chemical, or odorous indicators that can be documented when tracing a spill. Source
tracing methods were grouped into three categories from 10 reported methods during the data
standardization process. These categories include in-pipe testing (i.e., dye testing, pressure
testing, smoke testing, video testing), visual and empirical methods (i.e., visual reconnaissance,
mapping), and an “other” category including methods such as canine detection. Visual and
empirical methods were the most common source tracing methods, with the next-most frequent
category including records that were left blank. Four categories of indicator testing methods were
created from 18 reported methods during the data standardization process. These categories
include chemical testing indicators, odor/pH/fecals, visual indicators such as turbidity
(cloudiness of a liquid), and an “other” category for all other indicator tracing methods. Visual
indicators were the most common category, suggesting that visual methods are most used for
both source tracing and indicator testing. Statistical analysis confirmed the logical association of
indicator types to pollutant types associated with said indicator. These included including
chemical testing methods associated with in-pipe source tracing.
Notification Methods and Response Times. During the data standardization process, 19
reported notification methods were transformed into three notification categories. These include
20

hotline calls and other reports directly to the jurisdiction, inspection or observation by staff, or
referral from another agency. Hotline calls and other methods of direct reporting to staff were the
most common methods of incident reporting, followed by inspections from field staff performing
construction inspections, business inspections, or other field-related activities. Average response
times ranged from within seven days for all incidents to within 21 days for illicit connections,
with most responses occurring between one and three days.
Correction and Elimination Methods. From 13 reported correction and elimination
methods, five categories were created during the data standardization process. These include
enforcement, BMPs or cleanup, referral to another agency, no action needed, and an “other”
category for all other methods. Discharges were corrected primarily with cleanup or
implementation of Best Management Practices (BMPS). Enforcement was utilized to correct a
discharge in a similar frequency for both Phase I and Phase II municipalities, although Phase I
municipalities had a higher overall proportion of enforcement records.
Concluding Remarks. As referenced in the beginning of this section, the authors of this
study indicated that the collection and standardization process was time-consuming in nature and
could greatly benefit from a standardized data collection process. Due to these recommendations,
the Source ID subgroup created an updated list of incident fields based on the optional data
standardization schema from Ecology. Since then, the incident fields have gone through
revisions and are now in a standardized schema that is required for usage by all municipal
stormwater permittees as of 2021 (Washington State Department of Ecology, 2019a).
This regional data evaluation serves as key reference to how municipalities in Western
Washington respond to illicit discharges and illicit connections. By examining common
pollutants and their sources along with the common methods of correcting and eliminating said
21

pollutants, municipal stormwater permittees can be better informed on how to guide their
stormwater management programs in response. The authors indicate a myriad of uses these types
of data evaluations can serve, including fostering inter-jurisdictional coordination, targeting
public outreach efforts, tracking temporal and spatial trends, focusing municipal inspection
efforts on common pollutants, among many others. Regional data evaluations are an effective
tool to help guide municipal stormwater permittees in implementing the monitoring component
of the permit and revisiting this type of data evaluation would be a practical exploration. Thus,
analysis that follows serves as an extension of this original data evaluation which used annual
reporting data from the 2014 calendar year. This analysis uses data collected from the 2020
calendar year and explores how changes to the IDDE reporting form have facilitated the
collection of IDDE data since the implementation of the standardized reporting format.
Conclusion
This section started with an introduction to how water federal quality and stormwater
regulation became established in the United States starting with the Federal Water Pollution
Control Act of 1948. This first attempt of introducing federal water quality legislation proved
ineffective, leading to a surge of environmental awareness and public engagement in the 1960’s
and 1970’s surrounding numerous environmental catastrophes. With public support in full and
after numerous attempts to amend the bill in its current state, Congress published sweeping
amendments to the Federal Water Pollution Control Act of 1948 that would be commonly known
as the Clean Water Act. This paved the way for the introduction of the Environmental Protection
Agency (EPA) and the National Pollutant Discharge Elimination System (NPDES) permit
including the municipal NPDES permit.

22

After covering the establishment of federal stormwater regulations, this literature review
covered municipal stormwater regulations and current monitoring work performed specifically in
Washington State. This started with an overview of the municipal NPDES permit in Washington
State and the Illicit Discharge Detection and Elimination (IDDE) component of the permit. The
regional stormwater groups and subgroups associated with monitoring efforts related to the
municipal stormwater permit were next introduced as they are related to the first regional IDDE
evaluation performed in Western Washington. Stormwater Work Group (SWG) and specifically
the Source Identification subgroup led the oversight of the Stormwater Action Monitoring
(SAM) Source Identification project, the Illicit Discharge Detection and Elimination (IDDE)
Regional Data Evaluation for Western Washington. This study was covered in detail in the final
part of the literature review. Key findings were outlined that will provide additional context to
the findings presented in this analysis. In addition to these findings, this section referenced key
discussion points raised by the authors, including the need for a standardized reporting format for
municipal stormwater permittees to facilitate future regional data evaluations like the thesis that
will now be presented. This next chapter will cover the methodology performed in this study,
which evaluates IDDE submission data from the 2020 calendar year. This analysis serves to
provide an extension of the research performed in the original SAM Source Identification
regional data evaluation, which evaluated records from the 2014 calendar year prior to the
implementation of the standardized data format.

23

Chapter 2. Methods
Introduction
This chapter describes the methods of data acquisition and data analysis. This includes
both descriptive analysis in the form of graphical comparisons between data fields, and statistical
analysis through chi-square contingency tests.
Data Acquisition
A total of 541 Phase I records and 1340 Phase II records were obtained from the
Washington State Department of Ecology’s (Ecology) Water Quality Permitting and Reporting
Information System (PARIS) IDDE Report webpage. Using the fields on the PARIS webpage,
records for filtered for the

I Municipal Stormwater Permit and Phase II Municipal Stormwater Permit for Western
Washington for the 2020 annual report submission year. Since the focus of this study was Phase
I and Phase II municipalities in Western Washington, data from the Phase II Municipal
Stormwater Permit for Eastern Washington was excluded. The records contained in PARIS only
contain records that were submitted by permittees through Ecology’s WQWebIDE portal or
through their own system that uses an XML IDDE schema provided by Ecology. As mentioned
in the literature review, a new reporting schema was developed through the efforts of the SAM
Source ID regional data evaluation. Permittees could begin using the new form and reporting
method for the 2020 annual submission (Appendix 12) using either a zipped .xml file following
the schema or another spreadsheet that follows the same schema (Washington State Department
of Ecology, 2019a). By 2022, permittees are required to utilize the new standardized reporting
using the zipped .xml format.
24

Each IDDE record contains the jurisdiction name and permit number; date the incident
was discovered or reported date of beginning response; date of end of response; how the incident
was discovered or reported; whether there was a discharge to the MS4; the incident location;
pollutants identified; source or cause; source tracing approaches; correction/elimination methods;
and a field for field notes, explanations, or other comments.
Descriptive Analysis
In the first phase of the analysis, a database was created to make frequency counts of six
categories using a spreadsheet of the collected IDDE data, including: MS4 discharge; pollutant
types; pollutant source; source tracing methods; correction and elimination methods; and
discovery methods.
For the MS4 discharge analysis, MS4 discharge field responses were compared by phase
type. For the five other categories besides MS4 discharge, the ten MS4 discharge field responses
were combined to three categories: yes, no, and inconclusive for ease of analysis. “Yes” MS4
Discharge responses were combined from four responses: yes, allowable discharge; yes, no
notice required; yes, notified Ecology; yes, notified Health. “No” MS4 Discharge responses were
combined from the following responses: no, cleaned up; no, discharged to UIC (Underground
Injection Control); no, none found. “Inconclusive” MS4 responses from the Phase II program
were combined from three fields: other, unknown, and blank records (see Table 2).

25

Table 2
MS4 Discharge Fields and Combined Categories
Yes
Yes, Allowable Discharge
Yes, No Notice Required
Yes, Notified Ecology
Yes, Notified Health

No
No, Cleaned up
No, Discharged to UIC
No, None found

Inconclusive
Other
Unknown
Blank

Note. The ten MS4 discharge fields and the three combined categories are described. This figure
was derived from the analysis of this study.
Each of the five other categories (besides MS4 discharge) compared the respective
category to MS4 discharge, using the combined MS4 discharge categories as described
previously. This allowed for analysis of different spill incidents by the incident type, as will be
explored in the results section. When performing the graphical analysis, separate spreadsheets
and graphs were created to differentiate between Phase I and Phase II records.
Statistical analysis
Since the data in this study was largely categorical, chi-square analysis was performed to
determine the relationship between individual variables and test for logical associations between
the data. Chi-square analysis tests for differences between the observed and expected frequencies
where the expected frequencies represent a random distribution of records. A statistically
significant result indicates that the distribution of records is not random. As explained in the
literature review, these tests can confirm logical associations such as sediment coming a
construction site, or sewage from an illicit connection. This method was also used in the SAM
Source Identification regional data evaluation using 2014 data.

26

This study performed analysis of the 2020 calendar year IDDE records from Phase I and
Phase II permittees. Pollutant type categories were compared to five other category types: phase
type categories, pollutant source categories, correction and elimination method categories,
discovery method categories, and tracing method categories. Contingency tables were manually
created using an excel spreadsheet for each test. For the statistical analysis portion of this study,
chi-square analysis was performed using only IDDE records that had discharged to the MS4.
This analysis included the four “yes” MS4 discharge responses record responses in the analysis
(see Table 1). The reason for doing so was to perform analysis only on the data records that
contributed a discharge to the permittee’s MS4. Phase I and Phase II records were also combined
for ease of analysis.
The two assumptions of the chi-square test are that no more than 20% of the cells can
have an expected frequency of less than five, and no cell can have an expected frequency less
than one. To meet these assumptions for each of the five statistical tests, categories were
combined when necessary and where possible. In some circumstances, the assumptions could not
be met without transforming the data substantially. In these situations, best judgement was used
and if the assumptions were close to being met, the assumptions were deemed to have been met
for the purposes of this study. Since the chi-square test is a relatively simple test that tests for
associations between two or more categorical variables and is used primarily to test for logical
associations and should be sufficient for this analysis.
A statistically significant result was determined by calculating a maximum likelihood
chi-squared statistic for each of the tests and comparing to a critical value obtained using the chisquared distribution the chi-squared with the associated significance level and degrees of
freedom. A significance level of 0.05 (95 percent confidence level) and 0.001 (99.9 percent
27

confidence level) were used to calculate the critical value that was then compared to the
calculated maximum likelihood chi-squared statistics for each test.
When analyzing the contingency tables to examine for relationships between the data, if
the residual (observed-expected) frequencies were greater than 10, an association between the
two variables was assumed. If the residual was greater than 40, a high degree of association was
assumed. The same could be said in the negative direction, with residual frequencies less than
-10 considered an association, and residual frequencies less than -40 considered a high degree of
association. These values were selected based on visual interpretation of the contingency tables.
Since these contingency tables were manually calculated and statistical significance was only
tested for the individual tests and not for these specific relationships, these associations are not
confirmed to be statistically significant, but rather are to point out logical associations. However,
a relatively high degree of confidence in the results was placed when with high (>50) or low (<50) residuals. Using this type of analysis helps evaluate the relationship between the categorical
variables.
Conclusion
This chapter described the data acquisition process of compiling IDDE records from the
2020 calendar year from municipal stormwater permittees. The process of how the descriptive
analysis was performed was presented, demonstrating how the data was analyzed graphically by
for each of the six IDDE field categories chosen to study in greater detail. Finally, the statistical
analysis performed in this study was reviewed for the five chi-square categorical tests performed
in this study. This next section will present the results of this analysis.

28

Chapter 3. Results
Introduction
This chapter covers the descriptive analysis and statistical analysis performed in this
study. First, the descriptive analysis elements will be covered. This will start with a section
highlighting the data represented, followed an in-depth analysis of the six IDDE field categories
examined in the descriptive analysis phase. The following section will cover the statistical
analysis portion of the study.
Descriptive Analysis
Data Represented
A total of 1340 Phase I and 543 Phase II records were submitted in a format that was
compatible with Ecology’s PARIS reporting system from 3 Phase I municipalities and 40 Phase
II municipalities (see Figure 1 and Appendix B, Figure 18). City of Tacoma (396 records) and
City of Seattle (136 records) contributed 98 percent of the total Phase I spill records, with Port of
Seattle contributing 9 additional records. For Phase II municipalities, the top 5 contributing
municipalities submit 100 or more IDDE records each, contributing nearly 60 percent of the total
records (City of Kirkland, 266; City of Redmond, 156; City of Bothell, 127; City of Gig Harbor,
127; Kitsap County; 108).

29

Figure 1
Number of Records Submitted by Permittee Type

543

1340

Phase I

Phase II

Note. This graph represents the total number of Phase I and Phase II permittees captured in this
study. This figure was derived from the analysis of this study.
MS4 Discharge
Roughly half of the submitted IDDE records discharged to the permittee’s municipal
separate stormwater system (MS4), which constitutes an MS4 Discharge. For Phase I, 249
records were coded as yes and 293 as no. For Phase II, 519 records were coded as yes, 604 as no,
and 217 as other, unknown, or blank (grouped as “inconclusive”) (see Figure 2). A yes response
indicates that the spill discharged to the permittee’s MS4.

30

Figure 2
MS4 Discharge by Permittee Phase Type
Phase I

Phase II

217
519

249
293
604

MS4 Discharge
yes no

MS4 Discharge
yes no Inconclusive

Note. These graphs demonstrate the frequency of records that discharged to the MS4 (municipal
separate storm sewer system) for Phase I and Phase II jurisdictions. This figure was derived
from the analysis of this study.
The other, unknown and blank MS4 discharge records constituted just over 16 percent of
the total Phase II records. Of these records, 93 were reported as “other” where the permittee
could write in a text response to provide further clarification to the impact of the spill to the MS4
(see Figure 3). Some of the responses referenced that the spill was outside of the permittee’s
jurisdiction, a non-stormwater issue, dried on the surface, or referenced an Environmental Report
Tracking System (ERTS) number that is provided when a spill is reported via Ecology’s
statewide environmental incident report form. City of Sammamish records often contained
responses such as “other: Republic notified” to indicate that the report was referred to their waste
disposal agency Republic Services. Within the field notes and comments section, the permittee
included additional notes regarding where spill occurred including the impact to the MS4.
31

Forty-five records were reported as having unknown MS4 Discharge by Phase II
permittees (see Figure 3). Of these records, many of the responses within the field notes and
comments field indicated that the permittee had performed some type of response and could not
determine if there was a discharge to the MS4 or the report was referred the report to another
agency. Of the 79 Phase II records with the MS4 discharge field left blank, 76 records came from
the City of Kirkland. Within the field notes and comments field for these records, most of the
responses either were left blank, indicated there was no IDDE found, or included a short
response to the nature of the report.
Figure 3
MS4 Discharge by Permittee Phase Type, Expanded
450
403

387

400
350

Phase I

Phase II

# of Records

300
250
200
188

200

186

150
105

101

93

100
48
50
5

1

45

16

10 15

0
No, cleaned
No,
up
Discharged
to UIC

No, none
found

Yes,
Allowable
Discharge

Yes, No
Notice
Required

Yes,
Notified
Ecology

Yes,
Notified
Health

Other

Unknown

MS4 Discharge

Note. MS4 Discharge types are shown for Phase I and Phase II permittee types showing all
possible field responses. This figure was derived from the analysis of this study.

32

Pollutant Types
Phase I. For Phase I permittees, the pollutant category was skewed by whether there was
a discharge to the MS4, likely because Ecology does not require permittees to answer all the
questions for an individual IDDE record if the discharge does not occur to the MS4 For records
that did not discharge to the MS4 (Washington State Department of Ecology, 2019a). 291 of 293
of the records reported the pollutants identified as “unconfirmed, unspecified, or not identified”
(see Figure 4). All but one of these records were from the City of Tacoma, and upon examining
the spill records from City of Tacoma that did discharge to the MS4, all the records included the
specific pollutant type. This indicates that the City of Tacoma does not indicate the pollutant type
when the spill does not contribute a discharge to the permittee’s MS4.
Figure 4
Phase I Pollutants

Pollutant Type

0
Firefighting foam
Food-related oil/grease
Fuel and/or vehicle related fluids
Other
Paint
Sediment/soil
Sewage/septage/pet waste/human waste
Soap or cleaning chemicals
Solid waste/trash
Unconfirmed, unspecified, or not identified

100

# of Records
200
300
MS4 Discharge
Yes No

Note. The Phase I pollutants are portrayed in this stacked bar graph which distinguishes the
records by MS4 Discharge. This figure was derived from the analysis of this study.

33

400

When only examining Phase I records that have discharged to the permittee’s MS4, the
top three contributing pollutant categories were fuel and/or vehicle related fluids,
sewage/septage/pet waste/human waste, and the “other” write in category, contributing to 78
percent of the total records (see Figure 5). The next three top contributing pollutant categories,
sediment/soil, soap or cleaning chemicals, and food-related oil/grease contributed 17 percent of
the overall records. The least observed pollutants categories that discharged to the MS4 for Phase
I permittees were food-related oil/grease, firefighting foam, solid waste/trash, paint, and
unconfirmed, unspecified, or not identified.
Figure 5
Phase I Pollutants with MS4 Discharge, Ranked by Frequency

Pollutant Type

0

20

# of Records
40
60

80

100

Fuel and/or vehicle related fluids
Sewage/septage/pet waste/human waste
Other
Sediment/soil
Soap or cleaning chemicals
Food-related oil/grease
Firefighting foam
Solid waste/trash
Paint
Unconfirmed, unspecified, or not identified

Note. This figure ranks the most common Phase I pollutants that have discharged to the MS4.
This figure was derived from the analysis of this study.

34

Phase II. When examining the Phase II pollutant types for all discharge types, it appears
that even records that were coded as “no” and “inconslusive” for MS4 discharge still had a
pollutant type associated, even though a full record is not required for IDDE records that do not
constitute a discharge to the permittee’s MS4 (see Figure 6). The top three contributing pollutant
categories without distinguishing between MS4 discharge were fuel and/or vehicle related fluids,
sediment/soil, and unconfirmed, unspecified, or not identified. The fuel and/or vehicle related
fluids category constituted 36 percent of the overall records, with sediment/soil and unconfirmed,
unspecified, or not identified at 17 percent and 10 percent, respectively.
Figure 6
Phase II Pollutants
0

Pollutant Type

Firefighting foam
Food-related oil/grease
Fuel and/or vehicle related fluids
Paint
Sediment/soil
Sewage/septage/pet waste/human waste
Soap or cleaning chemicals
Solid waste/trash
Other
Unconfirmed, unspecified, or not identified
Blank

# of Records
200
400

600

MS4 Discharge
Yes
No
Inconclusive

Note. The Phase II pollutants are portrayed in this stacked bar graph which distinguishes the
records by MS4 Discharge. This figure was derived from the analysis of this study.

35

However, when distinguishing between records that have only discharged to the
permittee’s MS4, the top three pollutant categories were sediment/soil, fuel and/or vehicle
related fluids, and the “other” write in category, contributing to 33 percent, 24 percent, and 15
percent of the overall records, respectively (see Figure 7). The next three contributing pollutant
categories were sewage/septage/pet waste/human waste, unconfirmed, unspecified, or not
identified, and paint, contributing to 22 percent of the overall records combined. The four leastcontributing pollutant categories that discharged to the MS4 for Phase II permittees were soap or
cleaning chemicals, food-related oil/grease, solid waste/trash, and firefighting foam, contributing
to just 6 percent of the overall records.
Figure 7
Phase II Pollutants With MS4 Discharge, Ranked by Frequency

Pollutant Type

0

50

# of Records
100

150

200

Sediment/soil
Fuel and/or vehicle related fluids
Other
Sewage/septage/pet waste/human waste
Unconfirmed, unspecified, or not identified
Paint
Soap or cleaning chemicals
Food-related oil/grease
Solid waste/trash
Firefighting foam

Note. This figure ranks the most common Phase II pollutants that have discharged to the MS4.
This figure was derived from the analysis of this study.
Pollutant Sources
Phase I. For Phase I permittees, the Pollutant Source category was often marked as
“unconfirmed” when there was no discharge to the permittee’s MS4, as again only a partial
36

IDDE record is required for discharges that do not reach the permittee’s MS4 (see Figure 8).
However, for 10 of these records, the pollutants were confirmed to have reached the permittee’s
MS4 and constituted a discharge, even though the spill source was not confirmed.
Figure 8
Phase I Pollutant Sources

Source or Cause

0

100

Construction activity
Food-related business
Illicit connection
Intentional dumping
Landscape-related business
Other accident/spill
Other commercial/industrial activity
Other:
Vehicle collision
Vehicle-related business
Unconfirmed

# of Records
200

300

400

MS4 Discharge

yes

no

Note. Represented in this figure are the frequencies of pollutant sources found in Phase I
municipal stormwater permit records, distinguished by MS4 discharge. This figure was derived
from the analysis of this study.
For Phase I permittee MS4 discharge IDDE records, the top three pollutant source
categories were other accident/spill, the “other” write-in category, and construction activity,
contributing to 25 percent, 18 percent, and 16 percent of the overall records (figure 9). When
examining the field notes and comments field of the other accident/spill records, comments
ranged from vehicle-related incidents such as fuel, oil, antifreeze, and hydraulic fluid spills, to
leaking grease traps, paint spills, turbid discharge, sewer overflows, and a sewer cross
connection into the storm system. For the “other” category, permittees could write in their own

37

description for a record that may not exactly fit within the description of any of the designated
responses. Among these responses were reports of vehicle-related incidents such as fuel leaks
and vehicle/RV fires requiring fire-fighter response, to broken water mains, pump failures,
sanitary sewer failures, pollutant sheens and soapy water discharging into catch basins.
Figure 9
Phase I Pollutant Sources with MS4 Discharge, Ranked by Frequency

Source or Cause

0

10

20

# of Records
30
40

50

60

70

Other accident/spill
Other:
Construction activity
Vehicle-related business
Intentional dumping
Vehicle collision
Other commercial/industrial activity
Unconfirmed
Illicit connection
Food-related business

Note. This graph depicts the most common pollutant source types for Phase I permittees for
incidents that have discharged to the MS4. This figure was derived from the analysis of this
study.
Phase II. The unconfirmed pollutant source category contained the largest number of
records for Phase II municipalities for all types of MS4 discharge, suggesting that although
Phase II municipalities appeared to populate the pollutant type category, permittees were either
unsure or did not desire to populate the pollutant source field (see Figure 10). In addition, there
were over 100 blank records in for this category for the “no” MS4 discharge responses. For all

38

types of MS4 discharge, the top contributing pollutant sources were the “unconfirmed” category
followed by construction activity and vehicle-related business.
Figure 10
Phase II Pollutant Sources
# of Records

Source or Cause

0

100

Construction activity
Food-related business
Illicit connection
Intentional dumping
Landscape-related business
Mobile business
Other accident/spill
Other commercial/industrial activity
Other:
Vehicle collision
Vehicle-related business
Unconfirmed
Blank

200

yes

300

MS4 Discharge
no
inconclusive

Note. Represented in this figure are the frequencies of pollutant sources found in Phase I
municipal stormwater permit records, distinguished by MS4 discharge. This figure was derived
from the analysis of this study.
When only examining the Phase II records that discharged to the MS4, construction
activity, unconfirmed, and the “other” category were the top contributing pollutant source
categories with 32 percent, 19 percent, and 11 percent of the overall records, respectively (see
Figure 11). Of the unconfirmed records, most of all the records were cleaned up or
education/technical assistance was provided. Some of the records contained field notes in
comments field, with responses ranging from illegal or unconfirmed dumping of fluids, to

39

reports of power washing fluid discharges, water main breaks, and cloudy water reports where
the police were called in to assist the scene. For the “other” pollutant category where the
permittee could write in their own response, some of the pollutant types included concrete
washout, hydraulic fluid, potable water, and yard waste.
Figure 11
Phase II Pollutant Sources with MS4 Discharge, Ranked by Frequency

Source or Cause

0

50

# of Records
100

150

200

Construction activity
Unconfirmed
Other:
Vehicle-related business
Other accident/spill
Other commercial/industrial activity
Vehicle collision
Mobile business
Intentional dumping
Food-related business
Illicit connection

Note. This graph depicts the most common pollutant source types for Phase II permittees for
IDDE incidents that have discharged to the MS4. This figure was derived from the analysis of
this study.
Source Tracing Methods
As mentioned in the literature review, source tracing methods are the methods used to
find the source of an illicit discharge or illicit connection. For Phase I permittees, the most
common response for the source tracing method was not applicable, with 77 percent of the
overall records. The next common response was the observation category, with 19 percent of the

40

overall records. The analytical laboratory indicators, map analysis, and the “other” categories
constituted just 3 percent of the overall records (see Figure 12).

Figure 12
Phase I Source Tracing Methods

Source Tracing Methods

0

100

# of Records
200
300

400

500

Not applicable
Observation

MS4 Discharge
Yes
No

Analytical laboratory indicators
Map analysis
Other

Note. Phase I source tracing methods are portrayed in this figure, ranked by frequency and
distinguished by MS4 discharge. This figure was derived from the analysis of this study.
For Phase II source tracing methods, the observation category was the most common
response with 72 percent of the overall records (see Figure 13). The next top categories were the
not applicable category and records that were left blank.

41

Figure 13
Phase II Source Tracing Methods
0

200

# of Records
400
600

800

1000

Source Tracing Methods

Observation
Not applicable
Blank
yes

Other

MS4 Discharge
no
Inconclusive

Map analysis

Analytical laboratory indicators
Field indicator measurements
Dye, smoke, or pressure testing

Note. Phase II source tracing methods are portrayed in this figure, ranked by frequency, and
distinguished by MS4 discharge. This figure was derived from the analysis of this study.
Correction and Elimination Methods
Correction and elimination methods used to resolve a discharge ranged from cleanup,
education and outreach, or the implementation of Best Management Practices (BMPs) including
operational, structural, and treatment BMPs (although rare in usage for both Phase I and Phase II
permittees). For Phase I permittees, cleanup was the most common correction and elimination
method, followed by the “other” category and the education/technical assistance categories (see
Figure 14). Cleanup was also the most prevalent method for Phase II permittees, followed by
education/technical assistance and the category including blank records (see Figure 15).

42

Figure 14
Phase I Correction and Elimination Methods

Correction/Elimination Methods

0

100

# of Records
200
300

400

500

Clean-up
Other
Education/technical assistance

MS4 Discharge

yes

Add/modify operational BMP

no

Add/modify structural BMP
Add/modify treatment BMP
Enforcement
Referred to other agency

Note. Phase I correction and elimination methods are portrayed in this figure, ranked by
frequency, and distinguished by MS4 discharge. This figure was derived from the analysis of this
study.

43

Figure 15
Phase II Correction and Elimination Methods
0

200

# of Records
400
600

800

1000

Correction/Elimination Method

Clean-up
Education/technical assistance
Blank
MS4 Discharge

Other

yes

no

Inconclusive

Refferred to other agency
Add/modify operational BMP
Enforcement
Add/modify structural BMP
Add/modify treatment BMP

Note. Phase II correction and elimination methods are portrayed in this figure, ranked by
frequency and distinguished by MS4 discharge. This figure was derived from the analysis of this
study.
Discovery Methods
Discovery methods include the method the jurisdiction receives an IDDE report, ranging
from the pollution hotline and staff referrals to ERTS (Environmental Report Tracking System)
referrals through Department of Ecology’s online portal, and field inspections. For both Phase I
and Phase II jurisdictions, the pollution hotline was the most frequent discovery method for
incidents. For Phase I jurisdictions, the next-most frequent discovery methods were direct reports
to your staff, and staff referrals (see Figure 16). For Phase II jurisdictions, staff referrals and
ERTS were the next-most common discovery methods (see Figure 17).

44

Figure 16
Phase I Discovery Methods

Discovery Method

0

50

100

Pollution hotline
Direct report to your staff
Staff referral
ERTS referral
MS4 inspection or screening
Business inspection
Other
Other agency referral
Construction inspection

# of Records
150
200

250

300

MS4 Discharge

yes

no

Note. Phase I discovery methods are portrayed in this figure, ranked by frequency, and
distinguished by MS4 discharge. This figure was derived from the analysis of this study.
Figure 17
Phase II Discovery Methods

Discovery Method

0

100

Pollution hotline
Staff referral
ERTS referral
Direct report to your staff
Other agency referral
Other
MS4 inspection or screening
Construction inspection
Business inspection
Blanks

# of Records
200
300

400

500

MS4 Discharge

yes

no

inconclusive

Note. Phase II discovery methods are portrayed in this figure, ranked by frequency, and
distinguished by MS4 discharge. This figure was derived from the analysis of this study.

45

Statistical Analysis
Statistical analysis performed on each of the five chi-square contingency tests was
statistically significant, indicating that the relationship between each of the categorical variables
represented a distribution that was not random (see Appendix A). As referenced in the methods
section, these tests compared pollutant type categories to: phase type categories, pollutant source
categories, correction and elimination method categories, discovery method categories, and
tracing method categories. By examining each of the contingency tests, relationships can be
gleaned between the variables, and logical associations confirmed. This section will describe
these results in detail.
Pollutant Type vs. Phase Type
When comparing pollutant type categories to phase type categories, Phase I jurisdictions
had more fuel and/or vehicle related fluids and sewage/septage/pet waste/human waste records
than expected compared to Phase II jurisdictions (see Appendix A, table 3). Phase I jurisdictions
received less sediment/soil and unconfirmed, unspecified, or not identified pollutant records than
expected compared to Phase II jurisdictions.
Phase II jurisdictions had more sediment/soil records than expected compared to Phase I
jurisdictions. Phase II jurisdictions received less fuel and/or vehicle related fluids and
sewage/septage/pet waste/human waste pollutant records than expected compared to Phase II
jurisdictions.
Pollutant Type vs. Pollutant Source
When comparing pollutant type categories to pollutant source categories, several logical
associations are confirmed by the observed counts compared to the residuals. Construction
activity was highly associated with sediment/soil pollutants, and not highly associated with fuel
46

and/or vehicle related fluids (see Appendix A, table 4). Construction activity was also not
associate with sewage/septage/pet waste/human waste and the unconfirmed, unspecified, or not
identified pollutant category. Illicit connections were associated with sewage/septage/pet
waste/human waste and was not associated with sediment/soil pollutants. Other accidents were
associated with fuel and/or related fluids and sewage/septage/pet waste/human waste, and not
associated with sediment/soil pollutants. The unconfirmed pollutant source category was not
associated with sediment/soil pollutants. Vehicle collisions were highly associated with fuel
and/or vehicle related fluids, and not associated with sediment/soil and sewage/septage/pet
waste/human waste.
Pollutant Type vs. Correction and Elimination Method
When comparing pollutant type categories to correction and elimination method
categories, Best Management Practices (BMPs) were associated with sediment/soil pollutants
and not associated with fuel and/or vehicle related fluids (see Appendix A, table 5). Cleanup was
highly associated with fuel and/or vehicle related fluids, and highly not associated with
sediment/soil. Education/technical assistance was associated with soap or cleaning chemicals and
was not associated with fuel and/or vehicle related fluids.
Pollutant Type vs. Discovery Method
When comparing pollutant type categories to discovery method categories, inspection
discovery methods were not associated with fuel and/or vehicle related fluids (see Appendix A,
table 6). Hotline calls were associated with fuel and/or vehicle related fluids and the
unconfirmed, unspecified, or not identified category, and were not associated with sediment/soil
pollutants. Intra-or interagency referrals were associated with sediment/soil, and not associated
with the unconfirmed, unspecified, or not identified pollutant category.
47

Pollutant Type vs. Tracing Method
When comparing pollutant type categories to tracing method categories, visual and
empirical tracing methods were associated with sediment/soil pollutants (see Appendix A, table
7). The combined in-pipe testing/not applicable category was associated with fuel and/or vehicle
related fluids and sewage/septage/pet waste/human waste, and not associated with sediment/soil.
Conclusion
This section presented the key findings from the descriptive and statistical analysis
performed in this study. For the descriptive analysis section, six IDDE field categories chosen to
study in greater detail were outlined. Of the 1340 records from 43 municipal stormwater
permittees in Western Washington, the majority came from two Phase I jurisdictions and five
phase II jurisdictions. Roughly half of the submitted records discharged to the permittee’s MS4.
Fuel and vehicle-related fluids spills were common among both Phase I and Phase II
jurisdictions. When pollutant sources were reported, construction activity, accidents and spills,
and the unconfirmed or other category were among the most commonly reported for both
permittee phase types. Source tracing methods were primarily observation, and clean-up was by
far the most common correction method. The pollution hotline was the most common reporting
method followed by referrals through staff or agency referrals, including ERTS (Statewide
Environmental Incident Report Form).
For the statistical analysis portion of the analysis, key findings from each of the five chisquare tests of the categorical comparisons were presented. This includes the confirmation of
logical associations between pollutant type categories and pollutant source categories, correction
and elimination methods, discovery methods, and tracing methods. For instance, the sediment
pollutant category was associated with construction sites, best management practices, intra or
48

inter-agency referrals, and visual tracing methods. In the discussion section, the implications of
these findings will be explored in further detail.

49

Chapter 4. Discussion
Introduction
This chapter will discuss the key findings from the results of this study using a modified
version of the five discussion topics used in the SAM Source Identification study. These include:
distribution of data; pollutant types and pollutant sources; source tracing methods; discovery
methods; correction and elimination methods. Next, several discussion topics will be presented,
including reporting standardization, and a section outlining limitations as well as future
recommendations.
Distribution of Data
Data evaluated from this study included records from a total of 43 Phase I and Phase II
jurisdictions in Western Washington. Data from the Phase I jurisdictions came from three
jurisdictions of the 15 total Phase I permittees and secondary permittees in Western Washington
(two cities, four counties, nine secondary permittees total). These records came from the City of
Seattle, City of Tacoma, and the Port of Seattle. Data was heavily weighted towards City of
Seattle and City of Tacoma, which contributed all but 6 of the IDDE records as indicated in the
results. Data from the Phase II jurisdictions came from 39 cities and one county, of the possible
118 Phase II permittees and secondary permittees in Western Washington (83 cities, five
counties, 30 secondary permittees). The top five contributing municipalities representing over 60
percent of the total number of records.
Since 2020 was the first year the standardized reporting format was available for use to
submit annual IDDE reporting data, the jurisdictions included in this study represent the first
wave of municipal stormwater permittees that have migrated to the new reporting format. The
benefit of this format is that little to no data standardization was needed to perform preliminary
50

analysis of the IDDE records. The reporting standardization discussion topic later on in this
chapter will explore this in detail.
Pollutant Types and Pollutant Sources
For Phase I municipalities, the most common pollutant types that contributed a discharge
to the permittee’s MS4 were fuel and vehicle related fluids and sewage/septage/pet waste/human
waste pollutants, followed by the “other” pollutant category with write-in responses. The most
common pollutant sources contributing a discharge to the MS4 were from the other accident/spill
category and “other” pollutant source category with write-in responses, followed by construction
activity.
For Phase II municipalities, the most common pollutant types that contributed a discharge
to the permittee’s MS4 were sediment/soil, and fuel and/or vehicle related fluids, followed by the
“other” pollutant category with write-in responses. The most common spill sources that
contributed a discharge to the permittee’s were construction activity, the “unconfirmed”
category, and the “other” pollutant source category with write-in responses.
For both Phase I and Phase II jurisdictions, fuel and vehicle related fluids, sediment, and
sewage were all common spill types. Spill sources were commonly coded using the
“unconfirmed” or “other” categories where permittees could write in their own responses,
however common pollutant sources also included construction activity, other accidents/spills and
vehicle related businesses.
Statistical analysis demonstrated logical associations between pollutant types and
pollutant sources. Sediment and soil were associated with construction sites, illicit connections

51

were associated with sewage and other waste, and vehicle collisions were associated with fuel or
vehicle related fluids.
Source Tracing Methods
For Phase I and especially Phase II municipalities, it appears that if the source tracing
method was not an observation, then it was likely either going to be left blank or checked as not
applicable. Very rarely did any Phase I or Phase II permittee use any other source tracing
method besides observation, suggesting that observation alone is the primary method of source
tracing for both permittees for the majority of IDDE records. In some circumstances when fecal
coliform or another type of human health hazard took place, analytical laboratory methods or
map analysis were conducted, however the records also indicate that permittees may also refer
the IDDE response to their Department of Health instead of performing analysis themselves.
Statistical analysis comparing pollutant type categories to source tracing categories
revealed the association that visual and empirical tracing methods were associated with
sediment/soil. This makes sense since turbidity, or the cloudiness of water due to soil
contamination, is a common indicator for soil pollution. Statistical analysis also revealed the
combined in/pipe testing/not applicable category was associated with fuel or vehicle related
fluids and the encompassing sewage category. This also makes sense because in pipe testing is a
logical source tracing method to trace illicit sewage connections, and specific source tracing
methods are often not used or necessary for fuel or vehicle related fluids where the spill may be
rather obvious. However, these interpretations can only be inferred since the category was
combined, which was necessary to meet the assumptions of the chi-square test for this specific
comparison (see page 27).

52

Discovery Methods
For both Phase I and Phase II municipalities, the pollution hotline was the most common
way that a discharge was identified or reported to the permittee. Direct referrals to staff, from
ERTS referrals, or from other agency referrals were also quite common. There were very few
records from both Phase I and Phase II permittees with MS4 inspection, construction inspection,
or business inspection as the indicated discovery method, suggesting inspections are typically not
when a discharge occurs. However, this could also indicate that there are only a small number of
MS4 inspections, construction inspections, or business inspections occurring. Regardless, it
appears that the pollution hotline is being utilized as it is the primary discovery method. This
result indicates that permittees should continue to utilize the use of their pollution hotlines and
create ways to inform the public on how they can utilize such a hotline.
Statistical analysis confirmed logical assumptions between the data. Hotline calls were
associated with fuel or vehicle related fluids, and the unspecified, unidentified, or not identified
category. This makes sense because fuel, oil, or vehicle related fluids are an easy substance to
spot, and spills and accidents are often called into the hotline. In addition, it would make sense
that calls coming in through the hotline would be associated with an unspecified or unidentified
pollutant category unless specific information regarding the spill was communicated through the
hotline report. Intra- or interagency referrals were associated with sediment/soil, which also
confirms logical assumptions because multiple agencies are often involved in sediment or
construction-related pollution-generating activities.
Correction and Elimination Methods
Cleanup was by far the most common response category for both Phase I and Phase II
permittees. There were only a few instances where an addition or a modification of a BMP were
53

required, and very few instances of enforcement among both permittee types. This indicates that
permittees may largely focus on the cleanup efforts of each IDDE record, but could also be the
most common response because cleanup of a discharge is typically necessary and it may be an
obligatory response from most permittees when populating an IDDE record.
Statistical analysis confirmed logical assumptions between correction and elimination
methods and pollutant types. Best Management Practices (BMPs) were associated with
sediment/soil pollutants, which makes sense because construction activities are often the source
of sediment or soil discharge due to inadequate or improperly installed BMPs. Cleanup was
highly associated with fuel or vehicle related fluids, which also makes sense because cleanup is
typically necessary when correcting a discharge of pollutants from a vehicle accident or fuel
spill.
Reporting standardization
Since the IDDE reporting data and format requirements were only recently implemented
and permittees were not required to submit their data in the format compatible with the online
database for the 2020 annual report, only a fraction of the total number of permittees and thus the
number of IDDE records were captured in this study. Thus, the results of this study represent
only a fraction of the total number of Phase I and Phase II municipal stormwater permittees in
Western Washington whereas the previous study manually compiled the individual reports
before standardizing the various reporting formats in a manner that would allow for comparison
between the records. Though this study only represents a sample of the total population, this
study proves that direct comparison between individual records is now possible with this new
standardized reporting format. However, the format does come with some nuances.

54

Permittees may write in a response in the “other” field when the record would have fit
just fine into one of the predetermined fields. For instance, hydraulic fluid was indicated in the
write-in “other” category when technically the pollutant source should have been logged as
fuel/and or vehicle related fluids. When combing through individual IDDE records, it becomes
clear each permittee populates an IDDE record slightly differently from small nuances and
variations in the way records are populated. Because of the recent rollout of the standardized
reporting format, it would be a great time for there to be a guidance document or short training
provided for permittees so that within the standardized reporting format, permittees themselves
have a standardized approach to populating an IDDE form. Granted, each jurisdiction has their
own management styles and techniques and regardless of any level of guidance documentation
or training provided, everyone may have their own interpretation of what an IDDE record should
look like. Thus, even with the standardized reporting format, some level of coding may be
necessary when conducting future regional data evaluations to ensure that the records submitted
truly capture the nature of each IDDE record.
Lastly, because the new IDDE reporting data has only recently been implemented and
was only required starting with the 2021 annual permit report, the data from this study which
evaluates 2020 annual permit reporting data is only a preliminary example of what a regional
data evaluation could look like with this new standardized reporting format. Only a small
fraction of permittees submitted data compatible with Ecology’s PARIS database for the 2020
permit reporting year. Hopefully in subsequent years all permittees are able to utilize the new
standardized reporting format to capture a more encompassing data spread in subsequent
regional data evaluations.

55

Limitations and Recommendations
If this study were to be replicated again, it would be recommended to distinguish between
records that constitute an illicit discharge instead of focusing solely on records that have
discharged to the MS4. To elaborate, the “yes, allowable discharge” MS4 discharge records
technically do not constitute an illicit discharge to the permittee’s MS4, as they are considered an
allowable discharge. In the results, the distinction was made to indicate that the results are for all
discharges to the permittees’ MS4, not just the records that were considered illicit discharges, as
was performed in the previous regional data evaluation. In future studies, the benefit between
indicating what is considered an illicit discharge, rather than all discharges to the permittees’
MS4 including allowable discharges.
Future studies should consider spending time performing some preliminary coding of the
data specifically in the field notes portion the amount of information that could be gleaned
specifically from the field notes field, and the “other” write-in category where municipalities
write in their own responses. Significant amount of time could be spent combing through these
records to see what typical responses are for this “other” category to try to come up with a
schema that encompasses these records. Through further research and evaluation, it could be
possible to amend the current schema to incorporate some of these records that are getting lost in
this “other” category. The results from this study are inspiring in that a limited amount of coding
was needed to be able to conduct a data evaluation and shows signs that the IDDE report
standardization was well worth the efforts.
Conclusion
This section further explored the key findings from this study, reviewing the five
modified discussion topics as was performed in the original SAM Source Identification regional
56

data evaluation. The success of the data reporting standardization was also discussed, followed
by a discussion of the limitations of this study including future recommendations. The final
chapter will offer concluding remarks on what has been covered in this study.

57

Chapter 5. Conclusion
Stormwater regulation in the United States has come a long way since its beginnings in
the 20th century. The nation has gone from an era of direct dumping into its waterways into the
era of identifying discharges and eliminating them, where each spill deserves its own record.
This thesis started by presenting how stormwater regulation was conducted in the early 20th
century, leading up to a review of the current regulation federally and in Washington State,
before diving into the Illicit Discharge, Detection, and Elimination (IDDE) portion of the
municipal stormwater permit. Here, the regional stormwater groups associated with these efforts
were discussed, including Stormwater Work Group (SWG) and Stormwater Action Monitoring
(SAM), which both play a crucial role in stormwater monitoring in Western Washington. Next,
the SAM Source Identification study, the Illicit Discharge Detection and Elimination (IDDE)
Regional Data Evaluation for Western Washington was covered, which served as a foundational
starting point for this study. Finally, the core of the thesis was explored. Descriptive and
statistical analysis of 2020 annually submitted IDDE data was performed to present key findings
regarding illicit discharge and illicit connection response by municipal stormwater permittees in
Western Washington. This study represents a successful attempt to conduct a regional data
evaluation using standardized data collected through search results on Ecology’s PARIS
webpage. This by itself speaks volumes, as the previous regional data evaluation required a timeconsuming data standardization step that this thesis did not require. Future studies will benefit
from this standardized data format and can be rest assured that this time-consuming step may no
longer be required in future efforts.
To conclude, the following is a list of key findings from this study:

58



Roughly half of the submitted IDDE records discharged to the permittee’s municipal
separate stormwater system (MS4)



The top three contributing pollutant categories for Phase I permittees were fuel and/or
vehicle related fluids, sewage/septage/pet waste/human waste, and the “other” write in
category.



The top three contributing pollutant categories for Phase II permittees were fuel and/or
vehicle related fluids, sewage/septage/pet waste/human waste, and the “other” write in
category.



The top three pollutant source categories for Phase I permittees were other accident/spill,
the “other” write-in category, and construction activity.



The top three pollutant source categories for Phase II permittees were construction
activity, unconfirmed, and the “other” category.



For all jurisdictions, observation was by far the most common source tracing method.



Clean-up was the most common method of correction or elimination of an IDDE record.



The pollution hotline was the most common method of reporting among both Phase I and
Phase II jurisdictions.



Statistical analysis confirmed various logical associations that are seen in stormwater
management as was seen in the previous regional data evaluation. Pollutants were linked
to common spill sources and associated discovery methods, correction methods, and
tracing methods.

59

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64

Appendix A: Contingency Tables and Maximum Likelihood Chi-Squared Analysis
The appendix provides additional detail to the analysis in the results chapter. Appendix A
contains tables portraying the chi-squared contingency analysis performed. Appendix B contains
a figure of all permittees represented in this study.
Table 3
Observed Frequencies and Residuals for Pollutant Type by Phase Type
Observed
Observed - Expected
Factor
Phase I Phase II Row Total Phase I Phase II
Firefighting foam
4
3
7
2
-2
Food-related oil/grease
6
7
13
2
-2
Fuel and/or vehicle related fluids
87
127
214
13
-26
Other wastewater
7
10
17
1
-2
Paint
3
22
25
-6
4
Sediment/soil
26
169
195
-41
29
Sewage/septage/pet waste/human waste
57
53
110
19
-26
Soap or cleaning chemicals
10
16
26
1
-3
Solid waste/trash
4
4
8
1
-2
Unconfirmed, unspecified, or not identified
3
41
44
-12
9
Column Total
207
452
615

Note. This table shows the observed frequencies and the residuals for the chi-square contingency
table comparing pollutant types and phase types. This table was derived from the analysis of this
study.
(Maximum Likelihood Chi-Square = 79, df = 9, p<0.001).

65

Table 4
Observed Frequencies and Residuals for Pollutant Type by Pollutant Source
Observed

Observed - Expected

Factor

1

2

3

4

5

6

7

8 Row Total

Firefighting foam

0

0

0

0

3

1

0

1

5

Food-related oil/grease

0

7

1

0

2

1

1

0

12

10

0

6

8 42 10

5

1

0

0

2

2

5

0

5

1 13

148

0

2

5

5

0 26

Fuel and/or vehicle related fluids
Other wastewater
Paint
Sediment/soil
Sewage/septage/pet waste/human waste

14

36 87

1

2

-1.54 -0.08
-3.69

6.80

199 -51.23 -3.33
14

3

4

5

6

7

-0.39 -0.18

2.21

0.69

-0.87

0.17

0.06 -0.44

0.09

0.26

-1.09

-1.99

10.39 -2.31

1.39

54.06

0.77

-1.10 -0.52

-0.22

1.13

0.57

-1.32

-5.15 -0.55

2.41 -0.21

7.76

0.96

-0.74

-4.46

3

1

0.69

3

5

1

33

4

17

3

184

0 27

5

5

1

78 -10.00 -1.30

-9.64

0.68

8

91.38 -3.08 -12.46 -1.77 -24.23 -7.38 -15.00 -27.46
19.87 -2.87

14.61

0.17

-8.57 -11.91

Soap or cleaning chemicals

0

1

2

1

1

6

8

4

23

-7.08

0.62

0.19

0.15

-2.65

4.58

4.00

0.19

Solid waste/trash

1

1

3

0

0

1

0

0

6

-0.85

0.90

2.53 -0.22

-0.95

0.63

-1.04

-0.99

Unconfirmed, unspecified, or not identified

1

0

2

7

0

4

29

1

-6.99

1.28

21.35

-6.28

Column Total

184 10 47 22 95 37 104 99

44 -12.54 -0.74

-1.46

5.38

598

Note. This table shows the observed frequencies and the residuals for the chi-square contingency
table comparing pollutant types and pollutant sources. This table was derived from the analysis
of this study.
Factor key: 1 = construction activity; 2 =food-related business; 3 = Illicit connection and
intentional dumping categories combined; 4 = landscape-related business; 5 = other
accident/spill; 6 = other commercial/industrial activity; 7 = unconfirmed; 8 = vehicle collision.
(Maximum Likelihood Chi-Square = 904, df = 63, p<0.0001)

66

Table 5
Observed Frequencies and Residuals for Pollutant Type by Correction Method
Observed
Factor
1 2 3
Firefighting foam
0 6 0
Food-related oil/grease
1 7 0
Fuel and/or vehicle related fluids
1 200 5
Other wastewater
1 8 6
Paint
0 20 3
Sediment/soil
34 97 35
Sewage/septage/pet waste/human waste
2 77 7
Soap or cleaning chemicals
1 10 14
Solid waste/trash
0 7 0
Unconfirmed, unspecified, or not identified
1 26 14
Column Total
41 458 84

4 Row Total
0
6
3
11
0
206
1
16
1
24
18
184
4
90
0
25
0
7
0
41
27
610

Observed-Expected
1
2
3
-0.40 1.50 -0.83
0.26 -1.26 -1.51
-12.85 45.33 -23.37
-0.08 -4.01 3.80
-1.61 1.98 -0.30
21.63 -41.15 9.66
-4.05 9.43 -5.39
-0.68 -8.77 10.56
-0.47 1.74 -0.96
-1.76 -4.78 8.35

4
-0.27
2.51
-9.12
0.29
-0.06
9.86
0.02
-1.11
-0.31
-1.81

Note. This table shows the observed frequencies and the residuals for the chi-square contingency
table comparing pollutant types and correction methods. This table was derived from the analysis
of this study.
Factor key: 1 = BMP; 2 = cleanup; 3 = education/technical assistance; 4 = enforcement and
referral to another agency categories combined.
(Maximum Likelihood Chi-Square = 209, df = 27, p<0.0001)

67

Table 6
Observed Frequencies and Residuals for Pollutant Type by Discovery Method

Factor
Firefighting foam
Food-related oil/grease
Fuel and/or vehicle related fluids
Other wastewater
Paint
Sediment/soil
Sewage/septage/pet waste/human waste
Soap or cleaning chemicals
Solid waste/trash
Unconfirmed, unspecified, or not identified
Column Total

Observed
Observed-Expected
1 2 3 Row total
1
2
3
2 3 4
9 1.35 -0.61 -0.74
2 3 7
12 1.13 -1.82 0.69
1 107 101
209 -14.11 23.08 -8.97
1 4 11
16 -0.16 -2.42 2.58
2 10 12
24 0.26 0.36 -0.63
22 50 125
197 7.76 -29.10 21.35
11 44 55
110 3.05 -0.17 -2.88
2 9 10
21 0.48 0.57 -1.05
2 2 4
8 1.42 -1.21 -0.21
2 29 13
44 -1.18 11.33 -10.15
47 261 342
650

Note. This table shows the observed frequencies and the residuals for the chi-square contingency
table comparing pollutant types and discovery methods. This table was derived from the analysis
of this study.
Factor key: 1 = inspection methods; 2 = pollution hotline; 3 = intra or interagency referral.
(Maximum Likelihood Chi-Square = 64, df = 18, p<0.0001).

68

Table 7
Observed Frequencies and Residuals for Pollutant Type by Tracing Method
Factor
Firefighting foam
Food-related oil/grease
Fuel and/or vehicle related fluids
Other wastewater
Paint
Sediment/soil
Sewage/septage/pet waste/human waste
Soap or cleaning chemicals
Solid waste/trash
Unconfirmed, unspecified, or not identified
Column total

Observed
1
2
3
61
3
3
23
39
10
3
8
155

Observed-Expected
2 Row total
1
2
5
7
0.33
-0.33
9
12
0.14
-0.14
152
213
10.29 -10.29
14
17
-1.05
1.05
22
25
-2.95
2.95
169
192 -22.71
22.71
69
108
13.29 -13.29
16
26
3.81
-3.81
4
7
1.33
-1.33
36
44
-2.48
2.48
496
651

Note: This table shows the observed frequencies and the residuals for the chi-square contingency
table comparing pollutant types and tracing methods. This table was derived from the analysis of
this study.
Factor key: 1 = in pipe testing and not applicable categories combined; 2 = visual and empirical
methods
(Maximum Likelihood Chi Square = 34, df = 9, p<0.0001).

69

Appendix B: Permittees Represented
Figure 18

Phase I

City of Tacoma
City of Seattle
Port of Seattle

Phase II

Permittee Name and Phase Type

Permittee Names and Frequencies of Records Submitted

City of Kirkland
City of Redmond
City of Gig Harbor
City of Bothell
Kitsap County
City of Sammamish
City of Des Moines
City of Mountlake Terrace
City of Kenmore
City of Edmonds
City of Lynnwood
City of Bremerton
City of Anacortes
City of Enumclaw
City of Maple Valley
City of Port Orchard
City of Seatac
City of Auburn
City of Snoqualmie
City of Woodinville
City of Tukwila
City of Monroe
City of Camas
City of Mukilteo
City of Lakewood
City of Bainbridge Island
City of Mount Vernon
City of Vancouver
City of Washougal
City of Medina
City of Edgewood
City of Aberdeen
City of Normandy Park
City of Battle Ground
City of Sumner
City of Granity Falls
City of Black Diamond
City of University Place
City of Shelton
City of Brier

396
136
9
266
156
127
127
108
92
52
51
43
36
33
33
32
31
30
29
27
25
24
15
15
14
13
11
11
11
10
9
5
5
5
5
3
3
2
2
2
1
1
1

0

Number of Records Submitted
100
200
300
400

Note. This figure is a list of permittees derived from the analysis of this study.

70

500