2024 Municipal Stormwater Permit Ad-Hoc Advisory Process
Illicit Discharge Detection and Elimination and Source Control Group
White Paper
February 2022
Authors
Bob Bernard, King County
Mark Joyner, City of Bellingham
David Kangiser, City of Tumwater
Rod Swanson, Clark County
Reviewed by
Bob Bernard, King County
Aaron Burkhart, City of Bellingham
Matthew Geiger, City of Mukilteo
Kristina Lowthian, City of Renton
Rod Swanson, Clark County
Ryean-Marie Tuomisto, City of Kirkland
Kenneth Waldo, City of Redmond
Lisa Werre, City of Sammamish
Editor
Mark Joyner, City of Bellingham
Introduction
The Department of Ecology (Ecology) is the National Pollutant Discharge and Elimination
System (NPDES) delegated authority in Washington State. The NPDES program was created
under the Federal Water Pollution Control Act, better known as the Clean Water Act. Ecology is
delegated by the Environmental Protection Agency to regulate additions of point-source
pollutants, such as municipal stormwater and wastewater outfalls, into Waters of the United
States. Ecology also enforces state water quality standards which protect a broader than
federally required collection of surface water bodies known as Waters of the State. To meet its
obligations under federal and state law, Ecology issues stormwater permits to municipal and
county governments with urbanized watersheds, large construction sites, and individual
industrial facilities.
In November of 2021, Ecology requested help from the Washington Stormwater Center with
convening an “ad-hoc advisory process” to gather recommendations for Ecology’s re-issuance
of the 2024 municipal stormwater permit. Permittees, non-governmental organizations, and
other interested parties, volunteered to provide feedback to Ecology through the creation of a
series of topic-driven white papers.
This ad-hoc advisory group was assigned to clarify the relationship between the 2019 municipal
stormwater permit (Permit) required Illicit Discharge Detection Elimination (IDDE) and Source
Control programs. In addition, this group elected to provide recommendations and feedback to
Ecology pertaining to the IDDE and Source Control programs.
Overview of Illicit Discharge, Detection, and Elimination and
Source Control
The Permit required Source Control Program and IDDE Program have commonalities in their
goals but operate with unique approaches. Awareness of these similarities and differences can
help permittees to implement their Stormwater Management Programs through leveraging
existing resources and identifying gaps in services to achieve Permit compliance. The IDDE
Program maintains procedures for identifying sources of pollution after they are observed in
the stormwater collection system or in the receiving water. The Source Control Program
maintains procedures for implementing best management practices (BMP) to prevent potential
pollutants from contacting stormwater.
Similarities between the programs
The IDDE Program and Source Control Programs can work in tandem: Illicit discharges may be
discovered during routine source control inspections and illicit discharge investigations can
often identify source control BMPs which can be employed by property owners and business
managers. Other environmental regulation violations, such as improper hazardous waste
storage and disposal and omitted industrial or construction stormwater general permit
coverage, may also be discovered during the operation of the two programs.
Educational material generated from existing IDDE Program efforts partially align with
messaging for Source Control Program goals and efforts. Messaging for the IDDE Program
mainly focuses on a reactive approach of spill awareness, reporting, and clean up. The Source
Control Program builds on this outreach with an added proactive approach of distributing
materials which intend to aid in the prevention of pollutants from mixing with stormwater.
Conducting outreach for both Programs requires good communication and interpersonal skills
and requires materials to be translated into multiple languages. A regional approach to
creating educational material would benefit many jurisdictions, particularly jurisdictions with
limited staff. For example, a collection of jurisdictions in Southwest Washington created a
partnership called Stormwater Partners to facilitate the sharing of educational materials.
Proficient understanding of municipal code, and the division of labor between departments, is
required for representatives of both the IDDE and Source Control programs. Education and
technical assistance are the preferred approaches for both programs, with enforcement actions
as a last resort. When enforcement actions are required, typically both IDDE Program Code
Enforcement and Source Control Program Code Enforcement normally follow the same return
to compliance method.
Both Programs require knowledge of the jurisdiction’s watersheds and municipal separate
storm and sewer systems. The Programs also require knowledge of material and potential
pollutant identification and how specific materials are transported through the built and
natural environment.
Differences between the programs
Many differences between the IDDE and Source Control Programs may be attributed to the
reactive and proactive nature of the programs, respectively. The IDDE Program detects and
eliminates ongoing discharges and is reactive to reports of spills. The Source Control Program is
proactive by preventing discharges to the storm sewer from occurring through the
identification of pollution generating activities and the application of pollutant source
controlling BMPs.
The public interactions vary between the two programs. The Source Control Program is
designed to address pollution sources at existing development. Contacts are usually made with
property owners and operators who may have a vested interest in the jurisdiction where their
property is located. The Source Control Program benefits from building relationships with
owners and operators and understanding motivations for requiring a business change their
practices. IDDE response can involve anyone from the public, including residential and
commercial property owners.
The number of Source Control Inspections compared to IDDE responses differs greatly.
Creating a streamlined process for data storage for tracking communications, responses,
photos, follow up visits, ownership, and contact information is essential to an efficient Source
Control Program. Creating notification templates or inspection report templates to use as
communication tools is important. IDDE investigations are often case specific, and notifications
and reports are usually customized to address the offender with discharge information and
BMPs to correct or clean up the discharge.
Training of staff is an ongoing Permit requirement for both programs. IDDE response
procedures are commonly known by members of several municipal departments; such as public
works, fire, police, parks, and planning. As such, IDDE Program training program is often
extensive and must occur in all involved departments. The Source Control Program is often
housed within a single department such as public works. Training for Source Control focuses on
inspection protocols and public interaction with a smaller group of inspectors or contractors.
Reporting requirements differ between the two programs. The IDDE Program reporting
requirements are extensive and include ongoing ERTS notification, annual reporting, and the
submission of data through the Ecology operated WQWebIDDE Portal. Source Control Program
data is required to be reported within the annual report in a table that includes NAICS codes
associated with the businesses.
Source Control inspections are conducted in all seasons but are often best administered during
wet periods when observations can be made about pollutant run off. Many pollutant
generating activities are not discovered until a Source Control inspector reviews business
practices during a site visit. Storm sewer outfall screening activities, a requirement for the IDDE
Program, are best investigated in the dry months when stormwater does not obscure possible
illicit connections. Other IDDE efforts, such as the identification of the source of a pollutant,
may be aided by an increase in rainfall and stormwater within the storm sewer system.
Skill sets differ for IDDE responders and Source Control inspectors. Both are trained in material
identification, spill response techniques and safety precautions. However, Source Control
Inspectors need additional skills to work with business owners and offer technical assistance to
solve potential pollution problems or BMP deficiencies.
IDDE Program Recommendations and Feedback
The IDDE Performance Standard
The phase I and phase II permit both include the requirement to on average, screen 12 percent
of the known MS4 each year. For permittees with large rural areas or large areas of suburban
residential development, the 12 percent yearly average requirement is unduly burdensome and
not a productive use of staff time. In rural areas, where traffic often travels at highway speeds,
screening ditches is hazardous. The Permit language should allow permittees to exclude areas
that are known not to or likely to not include illicit discharges from the 12 percent average
annual performance standard inventory.
IDDE in Urban Areas Served by Piped Conveyance Systems
The Permit should allow the permittee the use of source control visits as a primary means of
conducting IDDE screening of conveyance systems.
The primary source of illicit discharges in urbanized areas is outdoor activities at businesses.
Other sources such as improper sewage disposal by transient dwellings and failed septic
systems are not the focus of an illicit discharge detection screening program but must be
addressed by complaint response.
Outfall screening lacks effectiveness in suburban areas in Clark County, where the developed
urban area had its outfalls screened several times over the last 20 years. Very few illicit
connections or discharges were discovered during these previous screenings.
For municipalities that do not operate sanitary sewage utilities, the great majority of illicit
discharges and connections are discovered during stormwater source control visits to
businesses.
In residential areas, common illicit discharges include the improper disposal of sewage and
refuse. These incidents are often reported to the Health Department or Code Enforcement by
neighbors. Outfall screening is ineffective at detecting these discharges. Low density
residential-area collection systems should not be required to be screened unless the collection
system includes potentially pollutant generating sites.
Rural Areas that are Served by Ditch Conveyance Systems
The primary sources of illicit discharges to the MS4 in zoned rural or undeveloped areas zoned
for urban land uses are businesses on rural lots. Failed septic systems are a likely source of
bacteria in streams but rarely discharge to MS4 roadside ditches. Many of the non-stormwater
discharges in the rural area do not enter the MS4, instead being discharged into the ground, a
natural drainageway or ditch not connected to the MS4.
While runoff to the rural MS4 ditches does originate from developed sites, most of the runoff is
from sheet flow from fields or woods, groundwater seeps and stormwater interflow.
Dry season roadside ditch and ditch outfall screening in rural areas is not an effective tool for
identifying illicit discharges from homes and businesses for several reasons. Ditches generally
have tall stands of grass that make the conveyance of illicit discharges and their detection
nearly impossible. Grassy ditches absorb any moisture available during the dry summer months.
Performing screening on foot in rural areas is extremely hazardous due to high-speed traffic
and a complete lack of shoulders. Ditches are generally very difficult to walk in due to
vegetation and the morphology of ditches. Rural roads in Western Washington are often on
right-of-way established in the 1800s and early 1900s when most travel was on narrow earthen
roads of the time. Consequently, the right-of-way is usually very narrow and lacking shoulders.
Recommendations from Clark County
1. Remove the outfall screening requirement for forested areas, rural ditches, and urban
residential areas and develop a viable tool for illicit discharge screening in these areas.
2. Rely on complaints to identify sources from failing septic systems or transient sources
such as trailers and motor homes.
3. Use a business source control approach as the primary tool in the rural area. The source
control approach should use an office screening to identify potential sources such as
home businesses parked heavy equipment, livestock areas, and plant nurseries. Use
targeted inspections of these sites to ensure there are no illicit discharges to the MS4. A
two-person crew could perform routine windshield surveys of rural county roads to
screen for potential illicit discharges and perform source control inspections.
Suggested permit language is in italics below:
[S5.C.9.c.i. Procedures for conducting investigations of the Permittees MS4, including field
screening and methods for identifying potential sources. These procedures may also include
source control inspections.]The Permittee shall implement a field screening methodology appropriate to the characteristics
of the MS4 and water quality concerns. Screening for illicit connections may be conducted using
the Illicit Connection and Illicit Discharge Field Screening and Source Tracing Guidance Manual
(Herrera Environmental Consultants, Inc., May 2013.); or another method of comparable or
improved effectiveness. The Permittee shall document the field screening methodology in the
Annual Report.]Permittees are not required to screen conveyance systems where land use is zoned residential,
rural or forest or is predominately residential. These conveyance systems may be removed from
the total screening inventory for the purpose calculating the annual percentage screened.
Permittees may use the source control program as the primary method to screen conveyance
systems if appropriate for local conditions.
IDDE Feedback from Ad-Hoc Group Meeting and White Paper Review
On November 4, 2021, a virtual meeting of Phase I and Phase II Western Washington
permittees was convened to discuss the Source Control and IDDE program requirements for the
2024 NPDES Municipal Stormwater Permits.
Feedback and recommendations made during the November 4th meeting and the review of this
white paper are listed below:
1. Discharges of stagnant and contaminated building fire sprinkler system during
maintenance are not clearly addressed in the permit. These discharges are known to
contain rust and corrosion inhibitors, oxidized metals, low dissolved oxygen, and cutting
oils. Some builders have been observed routing flushing lines…