The Basics of Illicit DischargesChapter 1: The Basics of Illicit Discharges
Chapter 1: The Basics of Illicit Discharges
An understanding of the nature of illicit
discharges in urban watersheds is essential
to find, fix and prevent them. This chapter
begins by defining the terms used to
describe illicit discharges, and then reviews
the water quality problems they cause. Next,
the chapter presents the regulatory context
for controlling illicit discharges, and reviews
the experience local communities have
gained in detecting and eliminating them.
1.1 Important Terminology
and Key Concepts
This Manual uses several important terms
throughout the text that merit upfront
explanation. This section defines the
terminology to help program managers
perform important illicit discharge detective
work in their communities. Key concepts
are presented to classify illicit discharges,
generating sites and control techniques.
Illicit Discharge
The term "illicit discharge" has many
meanings in regulation' and practice, but we
use a four -part definition in this manual.
Illicit discharges are defined as a storm
drain that has measurable flow during
dry weather containing pollutants
and /or pathogens. A storm drain
with measurable flow but containing
no pollutants is simply considered a
discharge.
140 CFR 122.26(b)(2) defines an illicit discharge as any
discharge to an MS4 that is not composed entirely of storm
water, except allowable discharges pursuant to an NPDES
permit, including those resulting from fire fighting activities.
2. Each illicit discharge has a unique
frequency, composition and mode of
entry in the storm drain system.
Illicit discharges are frequently caused
when the sewage disposal system
interacts with the storm drain system. A
variety of monitoring techniques is used
to locate and eliminate illegal sewage
connections. These techniques trace
sewage flows from the stream or outfall,
and go back up the pipes or conveyances
to reach the problem connection.
4. Illicit discharges of other pollutants are
produced from specific source areas
and operations known as "generating
sites." Knowledge about these generating
sites can be helpful to locate and
prevent non - sewage illicit discharges.
Depending on the regulatory status of
specific "generating sites," education,
enforcement and other pollution
prevention techniques can be used to
manage this class of illicit discharges.
Communities need to define illicit
discharges as part of an illicit discharge
ordinance. Some non -storm water discharges
to the MS4 may be allowable, such as
discharges resulting from fire fighting
activities and air conditioning condensate.
Chapter 4 provides more detail on ordinance
development.
Illicit Discharge Detection and Elimination: A Guidance Manual 5
Chapter 1: The Basics of Illicit Discharges
Storm Drain
A storm drain can be either an enclosed
pipe or an open channel. From a regulatory
standpoint, major storm drains are defined
as enclosed storm drain pipes with a diameter
of 36 inches, or greater or open channels that
drain more than 50 acres. For industrial land
uses, major drains are defined as enclosed
storm drain pipes 12 inches or greater in
diameter and open channels that drain more
than two acres. Minor storm drains are
smaller than these thresholds. Both major and
minor storm drains can be a source of illicit
discharges, and both merit investigation.
Some "pipes" found in urban areas may
look like storm drains but actually serve
other purposes. Examples include foundation
drains, weep holes, culverts, etc. These pipes
are generally not considered storm drains
from a regulatory or practical standpoint.
Small diameter "straight pipes," however,
are a common source of illicit discharges
in many communities and should be
investigated to determine if they are a
pollutant source.
Not all dry weather storm drain flow
contains pollutants or pathogens. Indeed,
many communities find that storm drains
with dry weather flow are, in fact, relatively
clean. Flow in these drains may be derived
from springs, groundwater seepage, or leaks
from water distribution pipes. Consequently,
field testing and /or water quality sampling
are needed to confirm whether pollutants are
actually present in dry weather flow, in order
to classify them as an illicit discharge.
Discharge Frequency
The frequency of dry weather discharges
in storm drains is important, and can be
classified as continuous, intermittent or
transitory.
Continuous discharges occur most or all
of the time, are usually easier to detect,
and typically produce the greatest pollutant
load. Intermittent discharges occur over
a shorter period of time (e.g., a few hours
per day or a few days per year). Because
they are infrequent, intermittent discharges
are hard to detect, but can still represent a
serious water quality problem, depending on
their flow type. Transitory discharges occur
rarely, usually in response to a singular
event such as an industrial spill, ruptured
tank, sewer break, transport accident or
illegal dumping episode. These discharges
are extremely hard to detect with routine
monitoring, but under the right conditions,
can exert severe water quality problems on
downstream receiving waters.
Discharge Flow Types
Dry weather discharges are composed of one
or more possible flow types:
• Sewage and septage flows are produced
from sewer pipes and septic systems.
• Washwater flows are generated from a
wide variety of activities and operations.
Examples include discharges of gray
water (laundry) from homes, commercial
carwash wastewater, fleet washing,
commercial laundry wastewater, and
floor washing to shop drains.
• Liquid wastes refers to a wide variety
of flows, such as oil, paint, and process
water (radiator flushing water, plating
bath wastewater, etc.) that enter the
storm drain system.
• Tap water flows are derived from
leaks and losses that occur during
the distribution of drinking water in
the water supply system. Tap water
discharges in the storm drain system
may be more prevalent in communities
6 Illicit Discharge Detection and Elimination: A Guidance Manual
with high loss rates (i.e., greater than
15 %) in their potable water distribution
system. (source of 15% is from National
Drinking Water Clearinghouse http://
www.nesc.wvu.edu /ndwe /articles /OT/
FA02 /Economics_Water.html)
Landscape irrigation flows occur when
excess potable water used for residential
or commercial irrigation ends up in the
storm drain system.
• Groundwater and spring water flows
occur when the local water table rises
above the bottom elevation of the storm
drain (known as the invert) and enters
the storm drain either through cracks
and joints, or where open channels or
pipes associated with the MS4 may
intercept seeps and springs.
Water quality testing is used to conclusively
identify flow types found in storm drains.
Testing can distinguish illicit flow types
(sewage /septage, washwater and liquid
wastes) from cleaner discharges (tap water,
landscape irrigation and ground water).
Each flow type has a distinct chemical
fingerprint. Table 1 compares the pollutant
fingerprint for different flow types in
Alabama. The chemical fingerprint for each
flow type can differ regionally, so it is a
good idea to develop your own "fingerprint"
library by sampling each local flow type.
In practice, many storm drain discharges
represent a blend of several flow types,
particularly at larger outfalls that drain
larger catchments. For example, groundwater
flows often dilute sewage thereby masking
its presence. Chapter 12 presents several
techniques to help isolate illicit discharges
that are blended with cleaner discharges.
Illicit discharges are also masked by high
volumes of storm water runoff making it
Chapter 1: The Basics of Illicit Discharges
difficult and frequently impossible to detect
them during wet weather periods.
Mode of Entry
Illicit discharges can be further classified
based on how they enter the storm drain
system. The mode of entry can either be
direct or indirect. Direct entry means that
the discharge is directly connected to the
storm drain pipe through a sewage pipe,
shop drain, or other kind of pipe. Direct
entry usually produces discharges that are
continuous or intermittent. Direct entry
usually occurs when two different kinds of
"plumbing" are improperly connected. The
three main situations where this occurs are:
Sewage cross- connections: A sewer pipe that
is improperly connected to the storm drain
system produces a continuous discharge of
raw sewage to the pipe (Figure 1). Sewage
cross - connections can occur in catchments
where combined sewers or septic systems
are converted to a separate sewer system,
and a few pipes get "crossed."
Straight pipe: This term refers to relatively
small diameter pipes that intentionally
bypass the sanitary connection or septic
drain fields, producing a direct discharge
into open channels or streams as shown in
Figure 2.
Figure 1: Sewer Pipe Discharging to
the Storm Drain System
Illicit Discharge Detection and Elimination: A Guidance Manual
Chapter 1: The Basics of Illicit Discharges
Table
1: Comparative
Flow Type
Hardness NH3 Potassium Conductivity Fluoride
(mg /L as
Detergents
CaCO3) (mg /L) (mg /L) (PS/cm) (mg /L)
(mg /L)
Sewage
50 (0.26)*
25 (0.53)*
12 (0.21)*
1215 (0.45)*
0.7(0.1)-
9.7 (0.17)*
Septage**
57(0.36)
87(0.4)
19 (0.42)
502 (0.42)
0.93 (0.39)
3.3(l.33)
Laundry Washwater
45 (0.33)
3.2 (0.89)
6.5 (0.78)
463.5 (0.88)
0.85 (0.4)
758 (0.27)
Car Washwater
71 (0.27)
0.9 (1.4)
3.6 (0.67)
274 (0.45)
1.2(l.56)
140 (0.2)
Plating Bath (Liquid
Industrial Waste * *)
1430 (0.32)
66 (0.66)
1009(l.24)
10352 (0.45)
5.1 (0.47)
6.8 (0.68)
Radiator Flushing
(Liquid Industrial
Waste * *)
5.6(l.88)
26 (0.89)
2801 (0.13)
3280 (0.21)
149 (0.16)
15 (0.11)
Tap Water
52 (0.27)
<0.06 (0.55)
1.3 (0.37)
140 (0.07)
0.94 (0.07)
0 (NA)
Groundwater
38 (0.19)
0.06 (1.35)
3.1 (0.55)
149 (0.24)
0.13 (0.93)
0 (NA)
Landscape Irrigation
53 (0.13)
1.3 (1.12)
5.6 (0.5)
180 (0.1)
0.61 (0.35)
0 (NA)
* The number in parentheses after each concentration is the Coefficient of Variation; NA = Not Applicable
** All values are from Tuscaloosa, AL monitoring except liquid wastes and septage, which are from Birmingham, AL.
Sources: Pitt (project support material) and Pitt et al. (1993)
Figure 2: Direct Discharge
from a Straight Pipe
Industrial and commercial cross -
connections: These occur when a drain
pipe is improperly connected to the storm
drain system producing a discharge of wash
water, process water or other inappropriate
flows into the storm drain pipe. A floor
Sewage has the greatest potential to
produce direct illicit discharges within
any urban subwatershed, regardless of
the diverse land uses that it comprises.
The most commonly reported sewage -
related direct discharges are broken
sanitary sewer lines (81% of survey
respondents), cross - connections (71%
of survey respondents), and straight
pipe discharges (38% of survey
respondents). (CWP, 2002).
Older industrial areas tend to have a higher
potential for illicit cross - connections.
Indirect entry means that flows generated
outside the storm drain system enter through
storm drain inlets or by infiltrating through
the joints of the pipe. Generally, indirect
modes of entry produce intermittent or
transitory discharges, with the exception of
groundwater seepage. The five main modes
of indirect entry for discharges include:
shop drain that is illicitly connected to the Groundwater seepage into the storm drain
storm drain system is illustrated in Figure 3. pipe: Seepage frequently occurs in storm
8 Illicit Discharge Detection and Elimination: A Guidance Manual
drains after long periods of above average
rainfall. Seepage discharges can be either
continuous or intermittent, depending on
the depth of the water table and the season.
Groundwater seepage usually consists of
relatively clean water that is not an illicit
discharge by itself, but can mask other illicit
discharges. If storm drains are located close
to sanitary sewers, groundwater seepage
may intermingle with diluted sewage.
Spills that enter the storm drain system at
an inlet: These transitory discharges occur
when a spill travels across an impervious
surface and enters a storm drain inlet. Spills
can occur at many industrial, commercial
and transport - related sites. A very common
example is an oil or gas spill from an
accident that then travels across the road and
into the storm drain system (Figure 4).
Dumping a liquid into a storm drain inlet:
This type of transitory discharge is created
when liquid wastes such as oil, grease, paint,
solvents, and various automotive fluids are
dumped into the storm drain (Figure 5).
Liquid dumping occurs intermittently at
sites that improperly dispose of rinse water
and wash water during maintenance and
Figure 3: A common industrial cross
connection is a floor drain that is illicitly
connected to a storm drain
Chapter 1: The Basics of Illicit Discharges
cleanup operations. A common example is
cleaning deep fryers in the parking lot of
fast food operations.
Outdoor washing activities that create flow
to a storm drain inlet: Outdoor washing may
or may not be an illicit discharge, depending
on the nature of the generating site that
produces the wash water. For example,
hosing off individual sidewalks and
driveways may not generate significant flows
or pollutant loads. On the other hand, routine
washing of fueling areas, outdoor storage
areas, and parking lots (power washing), and
construction equipment cleanouts may result
in unacceptable pollutant loads (Figure 6).
Non - target irrigation from landscaping
or lawns that reaches the storm drain
system: Irrigation can produce intermittent
discharges from over - watering or
misdirected sprinklers that send tap water
over impervious areas (Figure 7). In some
instances, non - target irrigation can produce
unacceptable loads of nutrients, organic
matter or pesticides. The most common
example is a discharge from commercial
landscaping areas adjacent to parking lots
connected to the storm drain system.
Figure 4: Accident spills are significant
sources of illicit discharges to the storm
drain system
Illicit Discharge Detection and Elimination: A Guidance Manual 9
Chapter 1: The Basics of Illicit Discharges
r.
«`
y'
Figure 5: Dumping at a storm drain inlet
Rte,
2'
Figure 6: Routine outdoor washing and
rinsing can cause illicit discharges
Figure 7: Non - target landscaping
irrigation water
Land Use and Potential Generating
Sites
Land use can predict the potential for
indirect discharges, which are often
intermittent or transitory. Many indirect
discharges can be identified and prevented
using the concept of "generating sites,"
which are sites where common operations
can generate indirect discharges in a
community. Both research and program
experience indicate that a small subset of
generating sites within a broader land use
category can produce most of the indirect
discharges. Consequently, the density
of potential generating sites within a
subwatershed may be a good indicator of the
severity of local illicit discharge problems.
Some common generating sites within major
land use categories are listed in Table 2, and
described below.
Residential Generating Sites: Failing
septic systems were the most common
residential discharge reported in 33% of
IDDE programs surveyed (CWP, 2002). In
addition, indirect residential discharges were
10 Illicit Discharge Detection and Elimination: A Guidance Manual
also frequently detected in 20% of the IDDE
programs surveyed, which consisted of oil
dumping, irrigation overflows, swimming
pool discharges, and car washing. Many
indirect discharges are caused by common
residential behaviors and may not be
classified as "illicit" even though they can
contribute to water quality problems. With
the exception of failing septic systems and
oil dumping, most communities have chosen
education rather than enforcement as the
primary tool to prevent illicit discharges
from residential areas.
Commercial Generating Sites: Illicit
discharges from commercial sites were
reported as frequent in almost 20% of local
IDDE programs surveyed (CWP, 2002).
Chapter 1: The Basics of Illicit Discharges
Typical commercial discharge generators
included operations such as outdoor
washing; disposal of food wastes; car
fueling, repair, and washing; parking
lot power washing; and poor dumpster
management. Recreational areas, such
as marinas and campgrounds, were also
reported to be a notable source of sewage
discharges. It is important to note that
not all businesses within a generating
category actually produce illicit discharges;
generally only a relatively small fraction
do. Consequently, on -site inspections of
individual businesses are needed to confirm
whether a property is actually a generating
site.
Sewage can also be linked to significant indirect illicit discharges in the form of
sanitary sewer overflows (52% of survey respondents), sewage infiltration /inflow
(48% of survey respondents), and sewage dumping from recreational vehicles (33% of
survey respondents) (CWP, 2002).
Illicit Discharge Detection and Elimination: A Guidance Manual
Chapter 1: The Basics of Illicit Discharges
Table 2:
Land Uses, Generating Sites and Activities That Produce
Land Use
Generating Site Activity that Produces Discharge
Residential
• Apartments
• Car Washing
• Multi- family
• Driveway Cleaning
• Single Family Detached
• Dumping /Spills (e.g., leaf litter and RV /boat
holding tank effluent)
• Equipment Washdowns
• Lawn /Landscape Watering
• Septic System Maintenance
• Swimming Pool Discharges
Commercial
• Campgrounds /RV parks
• Building Maintenance (power washing)
• Car Dealers /Rental Car Companies
• Dumping /Spills
• Car Washes
• Landscaping /Grounds Care (irrigation)
• Commercial Laundry /Dry Cleaning
• Outdoor Fluid Storage
• Gas Stations /Auto Repair Shops
• Parking Lot Maintenance (power washing)
• Marinas
• Vehicle Fueling
• Nurseries and Garden Centers
• Vehicle Maintenance /Repair
• Oil Change Shops
• Vehicle Washing
• Restaurants
• Washdown of greasy equipment and grease
traps
• Swimming Pools
Industrial
• Auto recyclers
• All commercial activities
• Beverages and brewing
• Industrial process water or rinse water
• Construction vehicle washouts
• Loading and un- loading area washdowns
• Distribution centers
• Outdoor material storage (fluids)
• Food processing
• Garbage truck washouts
• Marinas, boat building and repair
• Metal plating operations
• Paper and wood products
• Petroleum storage and refining
• Printing
Institutional
• Cemeteries
• Building Maintenance (e.g., power washing)
• Churches
• Dumping /Spills
• Corporate Campuses
• Landscaping /Grounds Care (irrigation)
• Hospitals
• Parking Lot Maintenance (power washing)
• Schools and Universities
• Vehicle Washing
Municipal
• Airports
• Building Maintenance (power washing)
• Landfills
• Dumping /Spills
• Maintenance Depots
• Landscaping /Grounds Care (irrigation)
• Municipal Fleet Storage Areas
• Outdoor Fluid Storage
• Ports
• Parking Lot Maintenance (power washing)
• Public Works Yards
• Road Maintenance
• Streets and Highways
• Spill Prevention/ Response
• Vehicle Fueling
• Vehicle Maintenance /Repair
• Vehicle Washing
12 Illicit Discharge Detection and Elimination: A Guidance Manual
Industrial Generating Sites: Industrial sites
produce a wide range of flows that can
cause illicit discharges. The most common
continuous discharges are operations
involving the disposal of rinse water, process
water, wash water and contaminated, non -
contact cooling water. Spills and leaks,
ruptured pipes, and leaking underground
storage tanks are also a source of indirect
discharges. Illicit discharges from industry
were detected in nearly 25% of the local
IDDE programs surveyed (CWP, 2002).
Industries are classified according to
hundreds of different Standard Industrial
Classification (SIC) codes. The SIC
coding system also includes commercial,
institutional and municipal operations'.
Many industries are required to have storm
water pollution prevention and spill response
plans under EPA's Industrial Storm Water
NPDES Permit Program. A complete list of
the industries covered by the Storm Water
NPDES Permit Program can be found in
Appendix A. The appendix also rates each
industrial category based on its potential to
produce illicit discharges, based on analysis
by Pitt (2001).
Institutional Generating Sites: Institutions
such as hospitals, corporate campuses,
colleges, churches, and cemeteries can be
generating sites if routine maintenance
practices /operations create discharges from
parking lots and other areas. Many large
institutional sites have their own areas for
fleet maintenance, fueling, outdoor storage,
and loading /unloading that can produce
indirect discharges.
'More recently, federal agencies including EPA, have adopted
the North American Industry Classification System ( NAICS,
pronounced "Nakes ") as the industry classification system.
For more information on the NAICS and how it correlates
with SIC, visit http: / /www.census.gov /epcd /www /naics.html.
Chapter 1: The Basics of Illicit Discharges
Municipal Generating Sites: Municipal
generating sites include operations that
handle solid waste, water, wastewater, street
and storm drain maintenance, fleet washing,
and yard waste disposal. Transport - related
areas such as streets and highways, airports,
rail yards, and ports can also generate
indirect discharges from spills, accidents and
dumping.
Finding, Fixing, and Preventing
Illicit Discharges
The purpose of an IDDE program is to find,
fix and prevent illicit discharges, and a series
of techniques exist to meet these objectives.
The remainder of the manual describes
the major tools used to build a local IDDE
program, but they are briefly introduced
below:
Finding Illicit Discharges
The highest priority in most programs is to
find any continuous and intermittent sewage
discharges to the storm drain system. A
range of monitoring techniques can be
used to find sewage discharges. In general,
monitoring techniques are used to find
problem areas and then trace the problem
back up the stream or pipe to identify the
ultimate generating site or connection.
Monitoring can sometimes pick up other
types of illicit discharge that occur on
a continuous or intermittent basis (e.g.,
wash water and liquid wastes). Monitoring
techniques are classified into three major
groups:
• Outfall Reconnaissance Inventory
• Indicator Monitoring at Storm Water
Outfalls and In- stream
• Tracking Discharges to their Source
Illicit Discharge Detection and Elimination: A Guidance Manual 13
Chapter 1: The Basics of Illicit Discharges
!!! Caution !!!
Using land use as an indicator for certain flow types such as sewage is often less
reliable than other factors in predicting the potential severity of sewage discharges.
More useful assessment factors for illicit sewage discharges include the age of the
sewer system, which helps define the physical integrity and capacity of the pipe
network, as well as age of development, which reveals the plumbing codes and practices
that existed when individual connections were made over time. Two particular critical
phases in the sewer history of a subwatershed are when sanitary sewers were
extended to replace existing septic systems, or when a combined sewer was separated.
The large number of new connections and /or disconnections during these phases
increases the probability of bad plumbing.
Fixing Illicit Discharges
Once sewage discharges or other
connections are discovered, they can be
fixed, repaired or eliminated through several
different mechanisms. Communities should
establish targeted education programs along
with legal authority to promote timely
corrections. A combination of carrots and
sticks should be available to deal with the
diversity of potential dischargers.
Preventing Illicit Discharges
The old adage "an ounce of prevention is
worth a pound of cure" certainly applies
to illicit discharges. Transitory discharges
from generating sites can be minimized
through pollution prevention practices
and well- executed spill management and
response plans. These plans should be
frequently practiced by local emergency
response agencies and /or trained workers at
generating sites. Other pollution prevention
practices are described in Chapter 9 and
explored in greater detail in Manual 8 of the
Urban Subwatershed Restoration Manual
Series (Schueler et al., 2004).
National Urban Runoff Project
EPA's National Urban Runoff Project (NURP) studies highlighted the significance of
pollutants from illicit entries into urban storm sewerage (EPA, 1983). Such entries may
be evidenced by flow from storm sewer outfalls following substantial dry periods. Such
flow, frequently referred to as "baseflow" or "dry weather flow ", could be the result of
direct "illicit connections" as mentioned in the NURP final report (EPA, 1983), or could
result from indirect connections (such as leaky sanitary sewer contributions through
infiltration). Many of these dry weather flows are continuous and would therefore
occur during rain induced runoff periods. Pollutant contributions from dry weather
flows in some storm drains have been shown to be high enough to significantly degrade
water quality because of their substantial contributions to the annual mass pollutant
loadings to receiving waters (project research).
14 Illicit Discharge Detection and Elimination: A Guidance Manual
1.2 The Importance of Illicit
Discharges in Urban Water
Quality
Dry and wet weather flows have been
monitored during several urban runoff
studies. These studies have found that
discharges observed at outfalls during dry
weather were significantly different from
wet weather discharges. Data collected
during the 1984 Toronto Area Watershed
Management Strategy Study monitored and
characterized both storm water flows and
baseflows (Pitt and McLean, 1986). This
project involved intensive monitoring in two
test areas (a mixed residential /commercial
area and an industrial area) during warm,
cold, wet, and dry weather. The annual mass
discharges of many pollutants were found to
be greater in dry weather flows than in wet
weather flows.
A California urban discharge study identified
commercial and residential discharges
of oil and other automobile - related fluids
as a common problem based on visual
observations (Montoya, 1987). In another
study, visual inspection of storm water pipes
discharging to the Rideau River in Ontario
found leakage from sanitary sewer joints or
broken pipes to be a major source of storm
drain contamination (Pitt, 1983).
Several urban communities conducted
studies to identify and correct illicit
connections to their storm drain systems
during the mid- 1980s. These studies were
usually taken in response to receiving water
quality problems or as part of individual
NURP research projects. The studies
indicated the magnitude and extent of
cross - connection problems in many urban
watersheds. For example, Washtenaw
County, Michigan tested businesses to locate
direct illicit connections to the county storm
Chapter 1: The Basics of Illicit Discharges
drain system. Of the 160 businesses tested,
38% were found to have illicit storm drain
connections (Schmidt and Spencer, 1986).
An investigation of the separate storm sewer
system in Toronto, Ontario revealed 59% of
outfalls had dry weather flows, while 14%
of the total outfalls were characterized as
"grossly polluted," based on a battery of
chemical tests (GLA, 1983). An inspection
of the 90 urban storm water outfalls draining
into Grays Harbor in Washington showed
that 32% had dry weather flows (Pelletier
and Determan, 1988). An additional 19
outfalls were considered suspect, based on
visual observation and /or elevated pollutant
levels compared to typical urban storm
water runoff.
The Huron River Pollution Abatement
Program ranks as one of the most thorough
and systematic early investigations of illicit
discharges (Washtenaw County, 1988). More
than a thousand businesses, homes and other
buildings located in the watershed were dye
tested. Illicit connections were found at 60%
of the automobile - related businesses tested,
which included service stations, automobile
dealerships, car washes, and auto body and
repair shops. All plating shops inspected were
found to have illicit storm drain connections.
Additionally, 67% of the manufacturers, 20%
of the private service agencies and 88% of the
wholesale /retail establishments tested were
found to have illicit storm sewer connections.
Of the 319 homes dye tested, 19 were found
to have direct sanitary connections to storm
drains. The direct discharge of rug- cleaning
wastes into storm drains by carpet cleaners
was also noted as a common problem.
Eliminating illicit discharges is a critical
component to restoring urban watersheds.
When bodies of water cannot meet
designated uses for drinking water, fishing,
or recreation, tourism and waterfront home
Illicit Discharge Detection and Elimination: A Guidance Manual 15
Chapter 1: The Basics of Illicit Discharges
values may fall; fishing and shellfish
harvesting can be restricted or halted; and
illicit discharges can close beaches,
primarily as a result of bacteria
contamination. In addition to the public
health and economic impacts associated with
illicit discharges, significant impacts to
aquatic life and wildlife are realized.
Numerous fish kills and other aquatic life
losses have occurred in watersheds as a
result of illicit or accidental dumping and
spills that have resulted in lethal pollutant
concentrations in receiving waters.
1.3 Regulatory Background
For Illicit Discharges
The history of illicit discharge regulations
is long and convoluted, reflecting an
ongoing debate as to whether they should be
classified as a point or nonpoint source of
pollution. The Clean Water Act amendments
of 1987 contained the first provisions to
specifically regulate discharges from storm
drainage systems. Section 402(p)(3)(B)
provides that "permits for such discharges:
(i) May be issued on a system or
jurisdiction -wide basis
(ii) Shall include a requirement to
effectively prohibit non -storm water
discharges into the storm sewers; and
(iii) Shall require controls to reduce the
discharge of pollutants to the maximum
extent practical including management
practices, control techniques and system
design and engineering methods, and
such provisions as the Administrator or
the State determines appropriate for the
control of such pollutants."
In the last 15 years, NPDES permits have
gradually been applied to a greater range of
communities. In 1990, EPA issued a final
rule, known as Phase I to implement section
402(p) of the Clean Water Act through the
NPDES permit system. The EPA effort
expanded in December 1999, when the
Phase II final rule was issued. A summary
of how both rules pertain to MS4s and illicit
discharge control is provided below.
Summary of NPDES Phase I
Requirements
The NPDES Phase I permit program
regulates municipal separate storm sewer
systems (MS4s) meeting the following
criteria:
• Storm sewer systems located in an
incorporated area with a population of
100,000 or more
• Storm sewer systems located in 47
counties identified by EPA as having
populations over 100,000 that were
unincorporated but considered urbanized
areas
• Other storm sewer systems that are
specially designated based on the
location of storm water discharges with
respect to waters of the United States,
the size of the discharge, the quantity
and nature of the pollutants discharged,
and the interrelationship to other
regulated storm sewer systems, among
other factors
An MS4 is defined as any conveyance or
system of conveyances that is owned or
operated by a state or local government
entity designed for collecting and conveying
storm water, which is not part of a Publicly
Owned Treatment Works. The total number
of permitted MS4s in the Phase I program is
1,059.
16 Illicit Discharge Detection and Elimination: A Guidance Manual
Chapter 1: The Basics of Illicit Discharges
PHASE I HIGHLIGHTS
Who must meet the requirements?
How many Phase I communities
exist nationally?
What are the requirements related
to illicit discharges?
Phase I MS4s were required to submit a
two -part application. The first part required
information regarding existing programs and
the capacity of the municipality to control
pollutants. Part 1 also required identification
of known "major" outfalls' discharging
to waters of the United States, and a field
screening analysis of representative major
outfalls to detect illicit connections. Part
2 of the application required identification
of additional major outfalls, limited
monitoring, and a proposed storm water
management plan (EPA, 1996).
Phase I communities were required to
develop programs to detect and remove
illicit discharges, and to control and prevent
improper disposal into the MS4 of materials
such as used oil or seepage from municipal
sanitary sewers. The illicit discharge
programs were required to include the
following elements:
• Implementation and enforcement of an
ordinance, orders or similar means to
prevent illicit discharges to the MS4
3A "major" outfall is defined as an MS4 outfall that dis-
charges from a single pipe with an inside diameter of at
least 36 inches, or discharges from a single conveyance
other than a circular pipe serving a drainage area of more
than 50 acres. An MS4 outfall with a contributing industrial
land use that discharges from a single pipe with an inside
diameter of 12 inches or more or discharges from a single
conveyance other than a circular pipe serving a drainage
area of more than two acres.
M54s with population in, AJOL
- 100,00
ARA•
1,059
Develop programs to prevent, detect and
remove illicit discharges
• Procedures to conduct ongoing field
screening activities during the life of the
permit
• Procedures to be followed to investigate
portions of the separate storm sewer
system that, based on the results of the
field screening required in Part 2 of
the application, indicate a reasonable
potential for containing illicit discharges
or other sources of non -storm water
• Procedures to prevent, contain, and
respond to spills that may discharge into
the MS4
• A program to promote, publicize, and
facilitate public reporting of the presence
of illicit discharges or water quality
impacts associated with discharges from
the MS4
• Educational activities, public information
activities, and other appropriate activities
to facilitate the proper management and
disposal of used oil and toxic materials
• Controls to limit infiltration of seepage
from municipal sanitary sewers to the
MS4
Illicit Discharge Detection and Elimination: A Guidance Manual 17
Chapter 1: The Basics of Illicit Discharges
Summary of NPDES Phase II
Requirements
The Phase II Final Rule, published in the
Federal Register regulates MS4s that meet
both of the following criteria:
Storm sewer systems that are not a
medium or large MS4 covered by
Phase I of the NPDES Program
Storm sewer systems that are located in
an Urbanized Area (UA) as defined by
the Bureau of the Census, or storm sewer
systems located outside of a UA that
are designated by NPDES permitting
authorities because of one of the
following reasons:
— The MS4's discharges cause, or have
the potential to cause, an adverse
impact on water quality
— The MS4 contributes substantially to
the pollutant loadings of a physically
interconnected MS4 regulated by the
NPDES storm water program
MS4s that meet the above criteria are
referred to as regulated small MS4s. Each
regulated small MS4 must satisfy six
minimum control measures:
1. Public education and outreach
2. Public participation /involvement
3. Illicit discharge detection and
elimination
4. Construction site runoff control
5. Post - construction runoff control
6. Pollution prevention /Good housekeeping
Under the third minimum measure, an illicit
discharge is defined as any discharge to an
MS4 that is not composed entirely of storm
water, except allowable discharges pursuant
to an NPDES permit, including those
resulting from fire fighting activities (40
CFR 122.26(b)(2)). To satisfy this minimum
measure, the regulated small MS4 must
include the following five components:
• Develop a storm sewer system map that
shows the location of all outfalls and the
names and locations of all waters of the
United States that receive discharges
from those outfalls
• Prohibit, through ordinance or other
regulatory mechanism, non -storm water
discharges into the storm sewer system
and implement appropriate enforcement
procedures and actions
• Develop and implement a plan to detect
and address illicit discharges to the MS4
• Educate public employees, businesses,
and the general public of hazards
associated with illicit discharges and
improper disposal of waste
• Identify the appropriate best
management practices and measurable
goals for this minimum measure
18 Illicit Discharge Detection and Elimination: A Guidance Manual
Chapter 1: The Basics of Illicit Discharges
PHASE II HIGHLIGHTS
Who must meet the requirements?
How many Phase II communities
exist nationally?
What are the requirements related
to illicit discharges?
What is the deadline for meeting
these requirements?
In the regulation, EPA recommends that the
plan to detect and address illicit discharges
include procedures for:
• Locating priority areas likely to have
illicit discharges (which may include
visually screening outfalls during dry
weather and conducting field tests of
selected pollutants)
• Tracing the source of an illicit discharge
• Removing the source of the discharge
• Program evaluation and assessment
1.4 Experience Gained in
Phase I
The Center for Watershed Protection
conducted a series of surveys and interviews
with Phase I communities to determine the
current state of the practices utilized in local
IDDE programs, and to identify the most
practical, low -cost, and effective techniques
to find, fix and prevent discharges. The
Selected small M54s
EPA estimates 5,000 -6,000
Develop programs to prevent, detect
and remove illicit discharges
Permits issued by March 10, 2003.
Programs must be fully implemented by
the end of first permit term (5 years)
detailed survey included 24 communities
from various geographic and climatic
regions in the United States. Some of the key
findings of the survey are presented below
(CWP, 2002)4.
• Lack of staff significantly hindered
implementation of a successful IDDE
program. Phase I communities rely
heavily on the expertise of their field
staff — practical expertise that has been
acquired over many years as programs
gradually developed. Methods or
approaches recommended for Phase II
communities should be less dependent
on professional judgment.
4 Survey results are based on responses from 24
jurisdictions from 16 states. Surveys were supplemented
by on -site interviews of staff of eight IDDE programs:
Baltimore City, MD; Baltimore County, MD; Boston Water
and Sewer Commission (BWSC), MA; Cambridge, MA;
Dayton, OH; Raleigh, NC; Wayne County, MI; and Fort
Worth, TX. Jurisdictions selected for the survey and
interviews represent a variety of geographic and climatic
regions. The EPA storm water coordinators for each region
of the country were contacted for recommendations on
jurisdictions to include in the survey. Also, a variety of
jurisdiction sizes in terms of population, IDDE program
service area, and land use was targeted.
Illicit Discharge Detection and Elimination: A Guidance Manual 19
Chapter 1: The Basics of Illicit Discharges
Clear and effective ordinance
language should be adopted by Phase
II communities to ensure that all
potential sources of illicit discharges
are prohibited, and that the community
has sufficient legal authority to
inspect private properties and enforce
corrections.
Many communities lacked up -to -date
mapping resources, and found that
mapping layers such as storm sewers,
open drainage channels, waters of
the U.S., outfalls, and land use were
particularly useful to conduct and
prioritize effective field investigations.
Outfall screening required the greatest
staff and equipment resources, and
did not always find problem outfalls.
Communities recommended a fast and
efficient sampling approach that utilizes
a limited number of indicator parameters
at each outfall to find problem outfalls.
• When purchasing equipment, Phase II
programs should communicate with
other jurisdictions to consider sharing
field equipment and laboratory costs.
• Use of some discharge tracers has proven
challenging and sometimes fruitless,
because of false or ambiguous results
and complex or hazardous analytical
methods. Accurate, cost - effective, and
safe monitoring methods are needed to
effectively use tracers.
• Municipal IDDE programs worked
best when they integrated illicit
discharge control in the wider context
of urban watershed restoration. Table 3
provides some examples of how greater
interagency cooperation can be achieved
by linking restoration program areas.
In summary, survey communities expressed
a strong need for relatively simple guidance
to perform illicit discharge investigations.
To address this need, the Manual has been
designed to make simple program and
technical recommendations for Phase II
communities to develop cost - effective IDDE
programs.
20 Illicit Discharge Detection and Elimination: A Guidance Manual
Chapter 1: The Basics of Illicit Discharges
Table 3: Linking Other
Municipal Programs to IDDE Program Needs
Watershed - Related Program
How Program Relates to IDDE Program Needs
Subwatershed Mapping and Analysis
• Mapping and aerial photography are critical tools needed for
illicit connection detection surveys. GIS tax map layers are
often useful to identify property ownership.
Rapid Assessment of Stream
• Observations from physical stream assessments are often
Corridors
useful in identifying problem areas, including dry weather flow
outfalls, illegal dumping, and failing infrastructure locations.
Watershed Monitoring and Reporting
• Compiled water quality and other indicator data can be useful in
targeting problem areas.
Stream Restoration Opportunities
• Stream restoration opportunities can often be coordinated with
sewer infrastructure upgrades and maintenance.
Watershed Education
• Educating the public about unwanted discharges can save
programs money by generating volunteer networks to report
and locate problem areas. Better awareness by the public can
also reduce the likelihood of unintentional cross - connections.
Pollution Prevention for Generating
• Providing incentives to businesses to inspect and correct
Sites
connections can save programs money.
Illicit Discharge Detection and Elimination: A Guidance Manual 21
Chapter 1: The Basics of Illicit Discharges
22 Illicit Discharge Detection and Elimination: A Guidance Manual