United States Office of Research and EPA/600/R-92/238
Environmental Protection Development January! 993
Agency Washington, DC 20460
&EPA Investigation of
Inappropriate
Pollutant
Entries into Storm
Drainage Systems
A User's Guide
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EPA/600/R-92/238
January 1993
INVESTIGATION OF INAPPROPRIATE
POLLUTANT ENTRIES INTO STORM DRAINAGE SYSTEMS
A User's Guide
by
Robert Pitt and Melinda Lalor
Department of Civil Engineering
The University of Alabama at Birmingham
Birmingham, Alabama 35294
Donald Dean Adrian
Civil Engineering Department
Louisiana State University
Baton Rouge, Louisiana 70803
Richard Field
Storm and Combined Sewer Program
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Edison, New Jersey 08837
Donald Barbe'
Department of Civil Engineering
The University of New Orleans
New Orleans, Louisiana 70148
Contract Number 68-C9-0033 and Cooperative Agreement Number CR-816862
Project Officer
Richard Field, Chief
Storm and Combined Sewer Control Program
Risk Reduction Engineering Laboratory
Edison, New Jersey 08837
This report was conducted in cooperation with the
Center of Environmental Research Information
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
and
The Urban Waste Management and Research Center
The University of New Orleans
New Orleans, Louisiana 70148
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
Printed on Recycled Paper
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NOTICE
The information in this document has been funded wholly or in part by the United States
Environmental Protection Agency under contracts 68-03-3255 and 68-C9-0033 for Foster-Wheeler
Enviresponse, Inc. and under cooperative agreement CR-816862 for the Urban Waste Management
and Research Center of the University of New Orleans. Although it has been subjected to the Agency's
peer and administrative review and has been approved for publication as an EPA document, it does not
necessarily reflect the views of the Agency and no official endorsement should be inferred. Also, the
mention of trade names or commercial products does not imply endorsement by the United States
government.
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FOREWORD
Today's rapidly developing and changing technologies and industrial products and practices
frequently carry with them the increased generation of materials that, if improperly dealt with, can
threaten both public health and the environment. The U.S. Environmental Protection Agency is charged
by Congress with protecting the Nation's land, air, and water resources. Under a mandate of national
environmental laws, the Agency strives to formulate and implement actions leading to a compatible
balance between human activities and the ability of natural systems to support and nurture life. These
laws direct the EPA to perform research to define our environmental problems, measure the impacts,
and search for solutions.
The Risk Reduction Engineering Laboratory is responsible for planning, implementing, and
managing research, development, and demonstration programs to provide an authoritative, defensive
engineering basis in support of the policies, programs, and regulations of the EPA with respect to
drinking water, wastewater, pesticides, toxic substances, solid and hazardous wastes, and
Superfund-related activities. This publication is one of the products of that research and provides a vital
communication link between the researcher and the user community.
The purpose of this User's Guide is to provide guidance to municipalities for investigating
non-stormwater entries into storm drainage systems. Contaminated non-stormwater entries into storm
drainage systems have been shown to contribute substantial levels of contaminants to the Nation's
waterways. These entries may originate from many diverse sources including sanitary wastewaters
from leaky or directly connected sanitary sewerage and from poorly operating septic tank systems,
washwaters from laundries and vehicle service facilities, and many types of industrial wastewaters that
are discharged to floor drains leading to the storm drainage or from direct industrial wastewater
connections to the storm drainage system. Conventional pollution control programs may be ineffective
if these pollutant sources are not identified and corrected.
This User's Guide will be useful to municipalities in conducting required studies as part of their
stormwater discharge permit activities, in addition to other interested users. It will enable users to
identify the type and to estimate the magnitude of non-stormwater pollutant entries into storm drainage
systems and to design needed pollution control activities. An associated demonstration project (Pitt
and Lalor publication pending) describes the development and testing of the procedures presented in
this User's Guide.
E. Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
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ABSTRACT
This User's Guide is the result of a series of EPA sponsored research tasks to develop a
procedure to investigate non-stormwater entries into storm drainage systems. A number of past
projects have found that dry-weather flows discharging from storm drainage systems can contribute
significant pollutant loadings to receiving waters. If these loadings are ignored (e.g., by only
considering wet-weather stormwater runoff), little improvement in receiving water conditions may
occur with many stormwater control programs. These dry-weather flows may originate from many
sources, the most important sources may include sanitary wastewater or industrial and commercial
pollutant entries, failing septic tank systems, and vehicle maintenance activities. After identification
of the outfalls that contain polluted dry-weather flows, additional survey activities are needed to locate
and correct the non-stormwater entries into the storm drainage systems.
This User's Guide contains information to allow the design and conduct of local investigations
to identify the types and to estimate the magnitudes of these non-stormwater entries.
This report was submitted in partial fulfillment of contracts numbered 68-03-3255 and
68-C9-0033 and cooperative agreement CR-816862 under the sponsorship of the U.S. Environmental
Protection Agency. This report covers a period from October 1, 1990 to September 30, 1992, and
work was completed as of September 30, 1992. This report was prepared under subcontract to
Foster-Wheeler Enviresponse, Inc. of Edison, New Jersey, and the Urban Waste Management and
Research Center of the University of New Orleans.
(iv)
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CONTENTS
Foreword iii
Abstract iv
Figures vii
Tables ' viii
Acknowledgment ix
1. Introduction 1
Role of dry-weather flows in urban stormwater runoff analyses 1
Current legislation 2
2. Overview 4
Potential dry-weather discharge sources 4
Residential and commercial sources 4
Industrial sources 6
Intermittent sources 6
Direct connections to storm drains 7
Infiltration to storm drains 7
Investigative methodology 8
Recommendations 11
3. Mapping and Preliminary Watershed Evaluation 12
Purpose 12
Mapping 12
Receiving waters and storm sewer outfalls 12
Drainage area for each outfall 13
Land uses for each outfall drainage area 13
Other relevant information and features 16
Preliminary watershed evaluation 16
4. Selection of tracer parameters 18
Introduction 18
Candidate parameters 19
Physical inspection 19
Chemical parameters 21
Toxicity screening tests 25
Tracer characteristics of source flows 25
Determining number of observations needed 28
Selection of analytical methods 30
Detection limit requirements 30
Required sample analytical precision 35
Recommended analytical methodology 37
(v)
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5. Initial Field Screening Sampling Activities 41
Sampling strategy 41
Field data collection 41
Outfall locations 43
Field survey 43
Irregular flows 50
6. Data Analysis to Identify Problem Outfalls and Flow Components 51
Indicators of contamination 52
Simple checklist for major flow component Identification 53
Treated potable water 53
Sanitary wastewaters 58
Flow-weighted mixing calculations 59
Example calculations 59
Matrix algebra solution of simultaneous equations 64
Matrix algebra considering probability distributions of library data 65
7. Watershed Surveys to Confirm and Locate Inappropriate
Pollutant Entries to the Storm Drainage System 66
Using tracer parameters in the drainage system 66
Review industrial user surveys or reports 66
Follow-up drainage area and on-site investigations 66
Flow mass balances, dye studies, and smoke tests 67
Locating an industrial source 67
8. Corrective Techniques 74
Public education 74
Commercial and industrial disconnections of non-stormwater sources . . 76
Failing septic tank systems 76
Direct sanitary sewerage connections 78
Rehabilitating storm or sanitary sewers to abate contaminated
water infiltration 78
Zoning and ordinances 79
Widespread sanitary sewerage failure 80
Glossary 81
References 86
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FIGURES
Number Page
1 Outline of major topics presented in this User's Guide 9
2 Flow chart for investigative procedures 10
3 Required number of samples for allowable error and COV 29
4 Required detection limits for low COV mixture components
having means differing by 1.3 times 33
5 Required detection limits for low COV mixture components
having means differing by 5 times ." 33
6 Required detection limits for low COV mixture components
having means differing by 20 times 34
7 Required detection limits for low COV mixture components
having means differing by 75 times 34
8 Analysis precision needed for detection of one percent
contamination at ninety percent confidence 36
9 Outfall characteristics for Birmingham, Alabama,
demonstration project 42
10 Flow chart to identify residential area non-stormwater
flow sources 57
11 Industrial inventory field sheet 68
12 Flowsheet for industrial case example 1 70
13 Flowsheet for industrial case example 2 71
14 Flowsheet for industrial case example 73
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TABLES
Number Page
1 Potential inappropriate entries into storm drainage systems 5
2 Sources of industrial non-stormwater pollutant entries into
storm drainage systems 14
3 Significant chemicals in industrial wastewaters 24
4 Field survey parameters and associated non-stormwater
flow sources categories 26
5 Tracer concentrations found in Birmingham, Alabama, waters 27
6 Detection limit requirements for tracer concentrations found in
Birmingham, Alabama waters 32
7 Sample analyses lab sheet 38
8 Field equipment list 44
9 Sample evaluation sheet 47
10 Interpretations of physical observation parameters and
likely associated flow sources 48
11 Chemical and physical properties of industrial non-stormwater
entries into storm drainage systems 54
12 Assumed source flow quality 60
13 Characteristics of source groupings 61
14 Mixture calculations to identify source flow components 62
(viii)
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ACKNOWLEDGMENT
This User's Guide contains information that has been developed and tested in a number of
separate research reports investigating inappropriate pollutant entries into storm drainage systems.
Many case studies were reviewed during early parts of this research to identify the most appropriate
methods of investigation. Information that was obtained from these cities is gratefully acknowledged.
Valuable technical assistance concerning industrial dry-weather discharges was provided by
Mark Miller and Tom Meinholtz (Triad Engineering, Inc.) who were supported by Kevin Weiss of the
NPDES Branch, Permits Division, Office of Water, of the EPA through the Cadmus Group, Inc. Early
report guidance was also provided by Gene Driscoll (Woodward Clyde Consultants), also supported by
the Permits Division, Office of Water, of the EPA. Dan Murray, of the Center of Environmental
Research Information, Cincinnati, Ohio, EPA, also provided support for the publication of this Guide.
Richard Field, Chief of the Storm and Combined Sewer Pollution Control Program, EPA, was
the Project Officer for this project and provided much valued direction during this research. Michael
Brown and Marie O'Shea of his staff, along with Ramjee Raghavan at Foster Wheeler Enviresponse,
Inc., also provided important project assistance. Darwin Wright of the Office of Research and
Development, EPA is gratefully acknowledged for his suggestion to work with the University of New
Orleans, Urban Waste Management and Research Center to conduct EPA stormwater research
activities. Helpful comments from the report reviewers are also gratefully acknowledged.
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SECTION 1
INTRODUCTION
Current interest in illicit or inappropriate connections to storm drainage systems is an outgrowth
of investigations into the larger problem of determining the role urban stormwater runoff plays as a
contributor to receiving water quality problems. Urban stormwater runoff is traditionally defined as that
portion of precipitation which drains from city surfaces exposed to precipitation and flows via natural
or man-made drainage systems into receiving waters. An urban stormwater drainage system also
conveys waters and wastes from many other sources. For example, Montoya (1987) found that slightly
less than half the water discharged from Sacramento's stormwater drainage system was not directly
attributable to precipitation. Sources of some of this water can be identified and accounted for by
examining current NPDES (National Pollutant Discharge Elimination System) permit records, for
permitted industrial wastewaters that can be discharged to the storm drainage system. However, most
of the water comes from other sources, including illicit and/or inappropriate entries to the storm
drainage system. These entries can account for a significant amount of the pollutants discharged from
storm drainage systems (Pitt and McLean 1986).
The U. S. Environmental Protection Agency's (EPA's) Office of Research and Development's Storm
and Combined Sewer Pollution Control Program and the Office of Water's NPDES Program Branch have
supported the development of this User's Guide for the investigation of inappropriate entries to storm
drainage systems. This User's Guide is designed to provide information and guidance to local agencies
by meeting the following objectives of:
1. Identifying and describing the most significant pronounced sources of non-stormwater pollutant
entries into storm drainage systems.
2. Describing an investigative procedure that will allow for the determination of whether
significant non-stormwater entries are present in a storm drainage system, and then to identify
the particular source, as an aid to the ultimate location of the source.
The background study prepared in conjunction with this User's Guide (Pitt and Lalor publication
pending) examined three categories of non-stormwater outfall discharges: pathogenic/toxicant,
nuisance and aquatic life threatening, and clean water. The most important category is outfall
discharges containing pathogenic or toxic pollutants. The most likely sources for this category are
sanitary or industrial wastewaters. The outfall analysis procedure described in this User's Guide has
a high probability of identifying all of the outfalls in this most critical category. High probabilities of
detection of other contaminated outfalls are also likely when using these procedures. After
identification of the contaminated outfalls, their associated drainage areas are then subjected to a
detailed source identification investigation. The identified pollutant sources are then corrected.
ROLE OF DRY-WEATHER FLOWS IN URBAN STORMWATER RUNOFF ANALYSES
The EPA's Nationwide Urban Runoff Program (NURP) highlighted the significance of pollutants
from illicit entries into urban storm drainage (EPA 1983). Such entries may be evidenced by flow from
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storm drain outfalls following and during 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 (e.g., leaky sanitary
sewerage contributions through infiltration). Many of these dry-weather flows are continuous and
would therefore also occur during rain induced runoff periods. Pollutant contributions from the
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.
Dry-weather flows 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 (TAWMSS) monitored and characterized both stormwater and
baseflows (Pitt and McLean 1986). This project involved intensive monitoring in two test areas (one
a mixed residential and commercial area, and the other an industrial area) during both warm and cold
weather and during both wet and dry weather. The annual mass discharges of many pollutants were
found to be dominated by dry-weather processes.
During the mid-1980s, several individual municipalities and urban counties initiated studies to
identify and correct illicit connections to their storm drain systems. This action was usually taken in
response to receiving water quality problems or information noted during individual NURP projects.
Data from these studies indicate the magnitude of the cross-connection problem in many urban areas.
From 1984 to 1986, Washtenaw County, Michigan dye-tested 160 businesses in an effort to locate
direct illicit connections to the County stormwater drainage. Of the businesses tested, 61 (38 percent)
were found to have improper storm drain connections (Schmidt and Spencer 1986). In 1987, the
Huron River Pollution Abatement Program dye-tested 1067 commercial, industrial, and tax exempt
businesses and buildings. A total of 154 (14 percent) were found to have improper connections to
storm drainage (Washtenaw Co. 1988). Commercial car washes and other automobile related
businesses were responsible for the majority of the illicit connections in both studies. Discharges from
commercial laundries were also noted. An investigation of outfalls from the separate storm drain
system in Toronto, Canada revealed 59 percent with dry-weather flows. Of these, 84 (14 percent of
the total outfalls) were identified as grossly polluted based on the results of a battery of chemical tests
(GLA 1983). In 1987, an inspection of the 90 urban stormwater outfalls draining into Inner Grays
Harbor in Washington revealed 29 (32 percent) flowing during dry weather (Pelletier and Determan
1988). A total of 19 outfalls (21 percent) were described as suspect based on visual observation
and/or anomalous pollutant levels as compared to those expected in typical urban stormwater runoff
characterized by the EPA 1983 NURP report.
CURRENT LEGISLATION
With additional data now available, the Clean Water Act of 1987 contained provisions specifically
addressing 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-stormwater discharges into the
storm drains, and
iii. Shall require controls to reduce the discharge of pollutants to the maximum extent
practicable, including management practices, control techniques and system design and
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engineering methods, and such other provisions as the Administrator or the State
determines appropriate for the control of such pollutants.
In response to these provisions, the EPA issued a final rule to begin implementation of section
402(p) of the Clean Water Act on November 16, 1990 (40 CFR parts 122, 123, and 124 National
Pollutant Discharge Elimination System Permit Regulations for Storm Water Discharges, Federal
Register, Vol. 55, No. 222). A screening approach which includes chemical testing of outfalls or storm
drainage with dry-weather flow (defined by a 72-hour antecedent dry period), was adopted. The
parameters to be tested are a combination of several pollutants of concern and "tracers" that may be
used to help identify contaminated outfalls and predict the source of illicit discharges.
Section 122.26 (d) (1) (iv) (D) of the rule applies specifically to this User's Guide. The EPA
requires an initial screening program to provide a means of detecting high levels of pollutants in storm
sewerage. The protocol of this User's Guide seeks to determine whether or not non-stormwater flows
are causing problems (e.g. pathogenic, toxic, aquatic life threatening, nuisance), and to provide
additional detail with respect to the source. It accomplishes this by outlining an effective screening
methodology to identify storm drainage system outfalls contaminated by illicit or inappropriate
discharges and to determine specifically how the likely sources can be identified. This protocol is
supported by a research report (Pitt and Lalor publication pending) containing the results of a
demonstration project using these procedures and much more detailed information.
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SECTION 2
OVERVIEW
POTENTIAL DRY-WEATHER DISCHARGE SOURCES
This User's Guide is directed to the identification and location of non-stormwater entries into storm
drainage systems. It is important to note that for any effective investigation of pollution within a
stormwater system, all pollutant sources must be included. Prior research has shown, that for many
pollutants, stormwater may contribute the smaller portion of the total pollutant mass discharged from
a storm drainage system. Significant pollutant sources may include dry-weather entries occurring
during both warm and cold months and snowmelt runoff, in addition to conventional stormwater
associated with rainfall. Consequently, much less pollution reduction benefit will occur if only
stormwater is considered in a control plan for controlling storm drainage discharges. This User's Guide
contains a protocol to identify sources of inappropriate entries to storm drainage systems. The
investigations presented in this User's Guide may also identify illicit point source outfalls that do not
carry stormwater. Obviously, these outfalls also need to be controlled and permitted.
Table 1 summarizes the potential sources of contaminated entries into storm drainage systems,
along with their likely flow characteristics. The following subsections summarize these sources.
Residential and Commercial Sources
The most common potential non-stormwater entries, which have been identified by a review of
documented case studies for commercial and residential areas are:
• Sanitary wastewater sources:
- sanitary wastewater (usually untreated) from improper sewerage connections, exfiltration, or
leakage
- effluent from improperly operating, or improperly designed, nearby septic tanks
• Automobile maintenance and operation sources:
- car wash wastewaters
- radiator flushing wastewater
- engine de-greasing wastes
- improper oil disposal
- leaky underground storage tanks
• Irrigation sources:
- lawn runoff from over-watering
- direct spraying of impervious surfaces
• Relatively clean sources:
- infiltrating groundwater
- water routed from pre-existing springs or streams
- infiltrating potable water from leaking water mains
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TABLE 1. POTENTIAL INAPPROPRIATE ENTRIES INTO STORM DRAINAGE SYSTEMS
Potential
Source:
Residential Areas:
Sanitary Wastewater
Septic tank effluent
Household chemicals
Laundry wastewater
Excess landscaping
watering
Leaking potable water
pipes
Commercial Areas:
Gasoline filling station
Vehicle
maintenance/repair
Laundry wastewater
Construction site
de-watering
Sanitary wastewater
Industrial Areas:
Leaking tanks and pipes
Miscellaneous process
waters111
Storm Drain
Entry
Direct Indirect
X x
X
x X
X
X
X
X x
X x
X
X
X x
x X
X x
Flow
Characteristics
Conti- Inter-
nous mittent
X x
X x
X
X
X
X
X
X
X x
X x
X
X x
X x
Contamination Category
Patho- Nu
genie/ an
Toxic
is- Clear
ce
X x
X x
X
X
x x X
X
X
X
x X
X
X
X
X x x
Note: X: most likely condition
x: may occur
blank: not very likely
see Table 2 for industrial examples
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• Other sources:
- laundry wastewaters
- non-contact cooling water
- metal plating baths
- dewatering of construction sites
- washing of concrete ready-mix trucks
- sump pump discharges
- improper disposal of household toxic substances
- spills from roadway and other accidents
- chemical, hazardous materials, garbage, sanitary sludge landfills and disposal sites
From the above list, sanitary wastewater is the most significant source of bacteria and oxygen
demanding substances, while automobile maintenance and plating baths are the most significant
sources of toxicants. Waste discharges associated with the improper disposal of oil and household
toxicants tend to be intermittent and low volume. These wastes may therefore not reach the
stormwater outfalls unless carried by higher flows from another source, or by stormwater during rains.
Industrial Sources
There are several types of industrial dry-weather entries to storm drainage systems. Common
examples include the discharge of cooling water, rinse water, other process wastewater, and sanitary
wastewater. Industrial pollutant sources tend to be related to the raw materials used, final product,
and the waste or byproducts created. Guidance on typical discharge characteristics associated with
common industries is given in Sections 4, 5, and 6.
There is also a high potential for unauthorized connections within older industries. One reason for
this is that at the time of an industry's development, sanitary sewers may not have been in existence,
since early storm drains preceded the development of many sanitary sewer systems. Also a lack of
accurate maps of sanitary and storm drain lines may lead to confusion as to their proper identification.
In addition, when the activities within an industry change or expand, there is a possibility for illicit or
inadvertent connections, e.g., floor drains and other storm drain connections receiving industrial
discharges which should be treated before disposal. Finally, industries processing large volumes of
water may find sanitary sewer flow-carrying capacity inadequate or sanitary sewers located too far
away, leading to improper removal of excess water through the storm drain system.
Continuous processes, e.g., industrial manufacturing, are important potential sources because any
waste streams produced are likely to be constantly flowing. Detection of dry-weather discharges from
these sources is therefore made easier, because the continuous and probably undiluted nature of these
discharges is more discernable, e.g., odors produced will be stronger and colors more intense along
with their tracer constituents being more concentrated and more readily detected by sampling.
Intermittent Sources
The presence of regular, but intermittent, flows will usually be a good indication of contaminated
entries to the storm drains, and can usually be distinguished from groundwater infiltration flows.
However, as drainage areas increase in size, many intermittent flows will combine to create a
continuous composite flow. Examples of possible situations or activities that can produce intermittent
dry-weather flows are:
• Wash-up operations at the end of a work shift, or job activity.
• Wash-down following irregular accidents and spills.
• Disposal of process batches or rinse water baths.
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• Over-irrigation of lawns.
• Vehicle maintenance, e.g., washing, radiator flushing, and engine de-greasing.
Industries that operate on a seasonal basis, e.g., fruit canning and tourism can be a source of
longer duration intermittent discharges.
Direct Connections to Storm Drains
Direct connections are defined in this Guide as physical connections of sanitary, commercial, or
industrial piping (or channels) carrying untreated or partially treated wastewaters to a separate storm
drainage system. These connections are usually unauthorized. They may be intentional or may be
accidental due to mistaken identification of sanitary sewerlines. They represent the most common
source of entries to storm drains by industry.
Direct connections can result in continual or intermittent dry-weather entries of contaminants into
the storm drain. Some common situations are:
• Sanitary sewerlines that tie into a storm drain.
• Foundation drains or residential sump-pump discharges that are frequently connected to storm
drains. While this practice may be quite appropriate in many cases, it can be a source of
contamination when the local groundwater is contaminated, as for example by septic tank
failures.
• Commercial laundries and car wash establishments that may route process wastewaters to
storm drains rather than sanitary sewers.
Infiltration to Storm Drains
Infiltration into storm drains most commonly occurs through leaking pipe joints and poor
connections to catch basins and manhole chimneys but can also be due to other causes, such as
damaged pipes and subsidence.
Storm drains, as well as natural drainage channels, can therefore intercept and convey subsurface
groundwater and percolating waters. In many cases, these waters will be uncontaminated and have
variable flows due to fluctuations in the level of the water table and percolation from rainfall events.
Underground potable water main breaks are another potential clean water source to storm drains.
While such occurrences are not a direct pollution source, they should obviously be corrected.
Groundwater may be contaminated, either in localized areas or on a relatively widespread basis.
In cases where infiltration into the storm drains occurs, it can be a source of excessive contaminant
levels in the storm drains. Potential sources of groundwater contamination include, but are not limited
to:
Failing or nearby septic tank systems.
Exfiltration from sanitary sewers in poor repair.
Leaking underground (and above-ground) storage tanks (LUST) and pipes.
Landfill seepage.
Hazardous waste disposal sites.
Naturally occurring toxicants and pollutants due to surrounding geological or natural
environment.
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Leaks from underground and above-ground storage tanks and pipes are a common source of soil
and groundwater pollution and may lead to continuously contaminated dry-weather entries. These
situations are usually found in commercial operations such as gasoline service stations, or industries
involving the piped transfer of process liquids over long distances and the storage of large quantities
of fuel, e.g., petroleum refineries.
INVESTIGATION METHODOLOGY
Applying the methodology presented in this User's Guide will determine if a storm drain outfall
(and drainage system) is affected by pronounced non-stormwater entries. In many cases, the
information to be collected by using this methodology will also result in a description of the most likely
sources of these discharges.
Several aspects of this methodology were derived from the experience of many municipalities that
have previously investigated inappropriate entries into storm drainage systems.
The methodology establishes priorities to identify the areas with the highest potential for causing
problems. The investigative procedures then separate the storm drain outfalls into three general
categories (with a known level of confidence) to identify which outfalls (and drainage areas) need
further analyses and investigations. These categories are outfalls affected by non-stormwater entries
from: (1) pathogenic or toxic pollutant sources, (2) nuisance and aquatic life threatening pollutant
sources, and (3) unpolluted water sources.
The pathogenic and toxic pollutant source category should be considered the most severe because
it can cause illness upon water contact or consumption and significant water treatment problems for
downstream consumers, especially if the pollutants are soluble metal and organic toxicants. These
pollutants may originate from sanitary, commercial, and industrial wastewater non-stormwater entries.
Other residential area sources (besides sanitary wastewater), e.g., inappropriate household toxicant
disposal, automobile engine de-greasing, and excessive use of chemicals (fertilizers and pesticides) may
also be considered in this most critical category.
Nuisance and aquatic life threatening pollutant sources can originate from residential areas and
aside from raw sanitary wastewaters may include laundry wastewaters, lawn irrigation runoff,
automobile washwaters, construction site dewatering, and washing of concrete ready-mix trucks.
These pollutants can cause excessive dissolved oxygen depletions, and algal growths, tastes and odors
in downstream water supplies, offensive coarse solids and floatables, and noticeably colored, turbid
or odorous waters.
Clean water discharged through stormwater outfalls can originate from natural springs feeding
urban creeks that have been converted to storm drains, infiltrating groundwater, infiltration from
potable waterline leaks, etc.
Figure 1 is an outline of the major topics presented in this User's Guide, and Figure 2 is a
simplified flow chart for the detailed methodology. The initial phase of the investigative protocol
includes the initial mapping and field surveys. These activities require minimal effort and result in little
chance of missing a seriously contaminated outfall. The initial activities are followed by more detailed
watershed surveys to locate and correct the sources of the contamination in the identified problem
areas. After corrective action has been taken, repeated outfall field surveys are required to ensure that
the outfalls remain uncontaminated. Receiving water monitoring should also be conducted to analyze
water quality improvements. If expected improvements are not noted, then additional contaminant
sources are likely present and additional outfall and watershed surveys are needed.
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MAPPING & PRELIMINARY WATERSHED EVALUATION (SECTION 3)
1) Identify receiving waters.
2) Locate all outfalls and associated drainage areas.
3) Compile data on land uses within drainage areas.
SELECTION OF TRACER PARAMETERS (SECTION 4)
1) Select physical and chemical parameters to measure.
2) Determine suitable analysis techniques and number of samples
required.
3) Develop library of potential local source flow characteristics.
INITIAL FIELD SCREENING SAMPLING ACTIVITIES (SECTION 5)
1) Conduct outfall screening survey for intermittent and continuous
flows.
DATA ANALYSIS TO IDENTIFY PROBLEM OUTFALLS
AND FLOW COMPONENTS (SECTION 6)
1) Simple procedures using checklists for typical major flow
components.
2) More detailed analyses utilizing library of data on potential source
flows will quantify flow components.
WATERSHED SURVEYS TO CONFIRM AND LOCATE INAPPROPRIATE
POLLUTANT ENTRIES TO THE STORM DRAINAGE SYSTEM (SECTION 7)
1) Conduct drainage surveys using tracer parameters in critical
watersheds.
2) Use flow mass balances, dye studies, smoke tests, and T.V. surveys
in isolated drainage areas.
CORRECTIVE TECHNIQUES (SECTION 8)
1) Educate public/industry and enforce with ordinances, zoning, etc.
2) Disconnect illicit direct connections.
3) Wide spread entries may require regional solutions or designation of
storm drainage system as a CSO.
Figure 1. Outline of major topics presented in this User's Guide
9
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/
Prepare A/ea Map.
/ \
-/ Prioritize Areas: y
Figure 2. Flow chart for investigation procedures.
10
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RECOMMENDATIONS
This User's Guide should be used as part of a comprehensive stormwater management plan which
addresses all sources of stormwater pollution. Correction of pollutant entries identified by use of only
this User's Guide is unlikely to achieve a significant improvement in the quality of stormwater
discharges or receiving waters.
A municipality will need to plan their investigation of inappropriate entries to a storm drainage
system to suit local conditions. This User's Guide describes the issues in sufficient depth and provides
examples to enable the design of a local investigation. Greater detail and the results of a
comprehensive demonstration of these procedures will be given in a supporting research report by Pitt
and Lalor (publication pending).
The full use of all of the applicable procedures described in this User's Guide is likely to be required
for successful identification of pollutant sources. Attempting to reduce costs, for example by only
examining a certain class of outfalls, or using inappropriate testing procedures, will significantly reduce
the utility of the testing program and result in inaccurate data. Also cursory data analyses is likely to
result in inaccurate conclusions.
During investigations of non-stormwater entries to storm drainage systems, consideration should
be given to any economic and practical advantages of designating the storm drainage system as a
combined sewer systems and applying end-of-pipe combined sewer overflow (CSO) control-treatment.
It is also recommended that the methodology (appropriately modified) be applied to other types
of sewerage systems, such as combined and separate sanitary sewerage systems, to locate
inappropriate entries, e.g., untreated or toxic industrial wastewaters/wastes or infiltration/inflow (I/I)
in separate sanitary sewers.
It is recommended that this User's Guide be updated and refined by incorporating experience
gained in its application. Incorporation of information from a wide variety of test locations (e.g., lake
and large river receiving waters, tidal receiving waters, areas experiencing long dry periods, areas
having short summers, areas having unusual groundwater characteristics, etc.) will improve the testing
and data analyses protocols described.
11
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SECTION 3
MAPPING AND PRELIMINARY WATERSHED EVALUATION
PURPOSE
An investigation of non-stormwater entries into a storm drainage system needs to proceed along
a systematic path of action, which investigates areas from high to low potential for causing problems,
and focuses in from general outfall screening to pin-pointing pollutant sources.
A mapping and evaluation methodology, as detailed in this section, is required to identify the areas
to investigate and to provide a basis to prioritize the areas by potential to contribute non-stormwater
entries into the storm drainage system.
The data collected in this phase is important as it forms the basis for the rest of the more detailed
investigations, described in the subsequent sections of this User's Guide.
MAPPING
To make this exercise as economical and productive as possible, full advantage should be taken
of any existing and available information. Data gained from existing sources will need to be
supplemented with information obtained by field investigations. The following summarizes the
information required, likely data sources, and how to obtain the information.
Receiving Waters and Storm Sewer Outfalls
The receiving waters and stormwater drainage outfalls must be identified and accurately located
on appropriate maps. However records of all outfalls are hard to locate, and even for those that can
be found, the locations of the outfalls may not be accurate. It is therefore important that the field
survey described in Section 5 be used to supplement the data collected during this initial stage. As
noted in Section 5, it can take three visits to a drainage area to find all (or almost all) outfalls.
Possible sources of documented information include:
City records, drainage maps, and storm drain maps.
Previous surveys, e.g., sanitary sewer infiltration/inflow (I/I) and sewer system evaluation
survey (SSES) studies.
Topographic maps.
Existing GIS (Geographic Information System) data.
Pre-development stream locations.
Drainage department personnel having knowledge of the area.
Aerial surveys.
12
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Drainage Area for Each Outfall
The drainage area for each outfall must be determined and marked on the map. This will enable
known potential pollutant source locations to be assigned to the correct outfall. Sources for this
information are storm drain maps and topographical maps. These should be at least 1" = 200' scale and
have no greater than 5 ft contour intervals (depending on the steepness of the area).
Land Uses for Each Outfall Drainage Area
Local planning departments should have detailed zoning maps of the area. These maps should
designate residential, commercial, and industrial land uses in each of the outfall drainage areas. In
addition, local revenue departments should have lists of business licenses for the entire municipality,
but they may not be usefully sorted. The public health department should know where septic tanks
are used. Aerial photographs can provide useful information to identify and/or confirm land use areas.
Historical land uses, especially landfills and industrial areas, should also be noted.
An effective way to obtain this information is to examine the municipality's zoning maps and to
drive to the critical areas to conduct inspections. The land uses of most interest are all industrial, most
commercial, and some municipal activities. The activities in the commercial areas of most concern
include vehicle related activities (sales, parts, service, or repair), laundry or dry cleaning (including
hospitals and hotels), and restaurants. The municipal activities of most concern include but are not
limited to: landfills, bus barns, airports, and sanitary wastewater treatment facilities.
Table 2 can be used to identify the local industries in each drainage area most likely to contribute
non-stormwater entries into the storm drainage system. The categories considered in this table include
loading and unloading of dry bulk or liquid materials, outdoor storage or processing, water usage
(cooling and process waters), dust or particulate generating processes, and illicit or inadvertent
industrial connections. The likelihood of an industry producing dry-weather or wet-weather discharges
in each of these categories was rated on the basis of high, moderate, or low potential and not
applicable if there was no relationship evident.
The industrial categories listed in Table 2 were defined according to the 1987 Standard Industrial
Classification Manual codes (SIC code). The industries were classified according to six main categories.
The category for "Primary Industries" includes facilities involved in the production of food products and
other basic goods. The category of "Material Manufacturing" includes those industries producing
materials such as lumber, paper, glass, and leather. Similarly, the "Chemical Manufacturing" category
includes those industries making products such as plastics, paints, detergents, fertilizers, pesticides,
and other related substances. "Transportation and Construction" primarily concerns the discharge of
contaminants from building or other types of outdoor development. The "Retail" category includes
establishments engaged in the selling of merchandise or offering merchandise related services. Finally,
all other industries which did not fit into any of the above classifications were placed into a "General"
category. Those industries which are not specifically listed should have characteristics resembling the
industries of the major groups with which they are classified by SIC code.
Investigators should take care to include any area where the land use has a potential to contribute
pollutant sources to a storm drainage system. As stated above, these land uses may not be covered
by Table 2. Some common examples of land use areas to be included are given below:
• Landfill areas can be a source of leachate and polluted runoff.
• Airports have a high potential for fuel spillage. Aircraft deicing agents, and other maintenance
operations, produce wastewaters that may be discharged into the storm drainage system.
13
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TABLE 2. SOURCES OF INDUSTRIAL NON-STORMWATER ENTRIES INTO STORM DRAINAGE SYSTEMS
Industrial Categories
Major Classifications
SIC Group Numbers
Loading/Unloading
Dry Bulk Liquids
Outdoor
Storage/
Processing
Water Usage
Cooling Process
Particle Illicit/
Generating Inadvertent
Process Connections
Primary Industries
20
201
202
203
204
205
206
207
208
21
22
23
Food & Kindred Products
Meat Products
Dairy Products Processing Industry
Canned & Preserved Fruits
& Vegetables
Grain Mill Products
Bakary Products
Sugar & Confectionary Products
Fats & Oils
Beverages
Tobacco Manufactures
Textile Mill Products
Apparel & Other Finished Products
Made from Fabrics
& Similar Materials
H
H
H
H
H
H
H
H
H
H
H
L
H
H
H
M
M
H
H
M
L
L
H
NA
H
L
NA
NA
NA
NA
NA
NA
NA
H
H
H
H
NA
L
M
H
NA
H
NA
H
H
H
H
H
M
H
H
M
H
M
L
NA
M
H
M
H
NA
M
H
M
M
H
H
H
H
L
L
M
L
M
H
L
Material Manufacture
24
25
26
27
31
32
33
34
37
Lumber & Food Products
Furniture & Fixtures
Paper & Allied Products
Printing, Publishing, & Allied Industries
Leather & Leather Products
Stone, Clay, Glass, &
Concrete Products
Primary Metal Industries
Fabricated Metal Products
Transporation Equipment
H
H
H
H
H
H
H
H
L
L
M
H
M
H
M
M
H
H
H
NA
H
NA
L
H
H
L
L
NA
NA
H
NA
L
L
H
H
H
M
L
H
M
H
H
H
H
H
H
M
H
H
H
H
H
H
L
(continued)
L
L
H
L
H
L
H
H
H
-------
TABLE 2. (continued)
Industrial Categories
Major Classifications
SIC Group Numbers
Outdoor
Loading/Unloading Storage/
Dry Bulk Liquids Processing
Particle
Water Usage Generating
Cooling Process Process
Illicit/
Inadvertent
Connections
Chemical Manufacture
28 Chemicals & Allied Products
281
282
283
284
285
286
287
Industrial Inorganic Chemicals
Plastic Materials & Synthetics
Drugs
Soap, Detergents, & Cleaning
Preparations
Paints, Varnishes, Lacquers
Enamels & Allied Products
Industrial Organic Chemicals
Agricultural Chemicals
H
H
L
H
H
H
L
H
H
L
H
H
H
L
NA
L
NA
NA
NA
NA
NA
H
H
H
H
L
H
H
H
M
M
H
H
H
L
H
L
L
H
H
H
L
H
H
L
H
L
M
L
29 Petroleum Refining & Related Industries
291
296
30
Transportation
16
16
Retail
62
63
64
55
66
67
58
Other
NOTE:
Petroleum Refining
Paving & Roofing Materials
Rubber & Misc. Plastic Products
& Construction
Building Construction
Heavy Construction
Building Materials, Hardware
Garden Supply, &
Mobile Home Dealers
General Merchandise Stores
Food Stores
Automotive Dealers &
Gasoline Service Stations
Apparel & Accessory Stores
Home Furniture, Furnishings
and Equipment Stores
Eating & Drinking Places
Coal Steam Electric Power
Nuclear Steam Electric Power
H: High potential M
L
H
H
M
M
H
H
H
H
H
H
H
H
NA
Medium potential
H
H
H
L
L
L
M
H
H
L
L
M
L
L
L
H
H
NA
H
H
H
L
NA
H
NA
L
NA
H
NA
Low potential
H
NA
H
NA
NA
NA
NA
NA
NA
NA
NA
NA
H
H
NA:
L
M
H
L
L
L
L
M
M
L
L
M
L
L
Not applicable
NA
M
H
H
H
NA
NA
L
L
NA
NA
NA
H
NA
H
L
M
L
L
L
L
L
M
L
L
M
L
NA
CJI
-------
• Government facilities, such as military bases, may store or use polluting materials and have
large vehicle maintenance facilities.
• Agricultural impacts are likely to be greater for wet-weather flows, but practices such as
irrigation and drainage tiles may also produce dry-weather flows.
Finally, it is necessary to identify and locate existing permitted discharges to streams and storm
drainage. The National Pollutant Discharge Elimination System (NPDES) permits, administered by most
states or, if not, by the EPA Regional Offices, contain this information for the facilities currently having
discharge permits. Only a small fraction of all industries have NPDES permits, as most have no direct
wastewater discharges to waters of the United States. Pretreatment programs for municipal sewage
treatment plants would also contain additional industrial information.
Other Relevant Information and Features
It is important that investigators be aware of any relevant features or information which may be
specific to their drainage area and not included specifically in the above subsections of this User's
Guide. Examples of some items that need to be included are discussed in this subsection.
Information on pre-development streams and springs, which may have been routed into the storm
drainage system, will aid in the identification of natural uncontaminated or contaminated dry-weather
flows.
Information regarding depth to the water table will be helpful. If the water table is well below the
storm drain invert at all times, then groundwater infiltration may be less important as a potential source
of dry-weather flow. However, the accumulation of percolating shallow groundwater will still occur in
storm drainage fill material and be a potential source of some infiltration water. Groundwater conditions
for the study area may be available from special studies conducted by the USGS (U.S. Geological
Survey), the state water agency, or other sources. Utility construction and repair crews and earth
moving companies should know of areas having shallow groundwater. Local I/I and SSES studies also
include information concerning shallow groundwater. Well log data collected during drilling of water
supply wells, and information from geotechnical investigations, may also be useful.
Areas serviced by sanitary sewerage and areas serviced by septic tanks should be determined in
order to identify the areas most likely to have direct connections and infiltration sources, respectively.
Either local health, sewerage, utility, environmental, or public works departments should have
information on the location of these areas.
Older residential areas with failing infrastructure (especially sanitary sewerage in poor condition),
and high density residential areas with septic tanks, should be designated as areas with a high potential
for pollutant entries into the storm drainage system.
PRELIMINARY WATERSHED EVALUATION
The above activities should produce maps with complete descriptions of the drainage areas,
including outfall locations, NPDES permittees, critical land uses, drainage boundaries for each outfall,
city limits, major streets, streams, etc. The investigators need to classify drainage areas by their
potential for causing non-stormwater entries. This mapping information, together with the information
to be obtained as described in Sections 4 and 5 and analyzed as described in Section 6, will form the
basis to rank the drainage areas in order of priority for further detailed drainage area investigations
(Sections 7 and 8).
16
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The investigation of non-stormwater entries will have a cost associated with it, which will increase
with the drainage system size and complexity, and with the number of sources being investigated. All
pollutant sources, including both wet- and dry-weather pollutant entries, will need to be controlled to
have an effective improvement in the quality of the stormwater system discharge. Pitt and McLean
(1986) noted that even with the removal of directly connected non-stormwater entries, stormwater
originating from industrial and commercial land uses has a high probability of having unacceptable
pollutant loads. It would therefore be prudent, at an early stage in the investigation, to review the
costs of the investigation and corrective action versus the cost for treatment of the stormwater system
discharge. The classification of the storm drainage system as a combined sewer, and subsequent
treatment of the flow, may prove to be a more economical and practical alternative. An appropriate
time for such a review would be after the mapping and field screening activities to avoid complex,
costly, and time consuming drainage system investigations into inappropriate non-stormwater entries,
and instead direct resources to pollution control.
17
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SECTION 4
SELECTION OF TRACER PARAMETERS
INTRODUCTION
The detection and identification of inappropriate entries requires the quantification of specific
characteristics of the observed outfall baseflow. The characteristics of most interest should be
relatively unique for each potential flow source. This will enable the presence of each flow source to
be noted, based on the presence (or absence) of these unique characteristics. The selected
characteristics are termed tracers, because they have been selected to enable the identification of the
sources of these waters.
One approach presented in this User's Guide is based on the identification and quantification of
clean baseflow and contaminated components. If the relative amounts of potential components are
known, then the importance of the baseflow can be determined. As an example, if a baseflow is
mostly uncontaminated groundwater, but contains 5 percent raw sanitary wastewater, it would be a
likely important source of pathogenic bacteria. Typical raw sanitary wastewater parameters (e.g., BOD6
or suspended solids) would be in low concentrations and the sanitary wastewater source would be
difficult to detect. Fecal coliform bacteria measurements would not help much because they originate
from many possible sources. Expensive specific pathogen measurements would be needed to detect
the problem directly.
The ideal tracer should have the following characteristics:
• Significant difference in concentrations between possible pollutant sources;
• Small variations in concentrations within each likely pollutant source category; •
• A conservative behavior (i.e., no significant concentration change due to physical, chemical
or biological processes); and,
• Ease of measurement with adequate detection limits, good sensitivity, and repeatability.
In order to identify tracers meeting the above criteria, literature characterizing potential
inappropriate entries into storm drainage systems was examined. Several case studies which identified
procedures used by individual municipalities or regional agencies were also examined. Though most
of the investigations resorted to expensive and time consuming smoke or dye testing to locate
individual illicit pollutant entries, a few provided information regarding test parameters or tracers. These
screening tests were proven useful in identifying drainage systems with problems before the smoke
and dye tests were used. The case studies also revealed the types of illicit pollutant entries most
commonly found in storm drainage systems.
This list of potential illicit sources (see Section 2) led to a search for information regarding the
chemical and physical characteristics of these specific flows. This search yielded typical characteristics
for sanitary wastewater, septic tank effluent, coin-operated laundries and car wash effluents as well
as potable water and "natural waters". This information, along with specifics obtained from case
studies, provided the basis for selecting parameters for further study. Specific analyses will be needed
to identify the characteristics of local potential inappropriate entries and uncontaminated water
18
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sources, as described in this section.
CANDIDATE PARAMETERS
Many different candidate parameters were evaluated before the suggested list was developed (Pitt
and Lalor publication pending). It is recommended that the initial field screening effort (in the absence
of known commercial and industrial activities in the watershed) include at least:
• Placement of outfall identification number.
• Outfall discharge flow estimate.
• Floatables, coarse solids, color, turbidity, oil sheen, and odor characteristics of discharge and/or
receiving nearfield water.
• Other outfall area characteristics, e.g., stains, debris, damage to concrete, corrosion, unusual
plant growth, or absence of plants.
• Water temperature.
• Specific conductivity.
• Fluoride and/or hardness concentrations.
• Ammonia and/or potassium concentrations.
• Surfactant concentration and/or fluorescence.
• Chlorine concentration and pH.
If commercial or industrial activities occur in the drainage area, then it is important to add additional
parameters (e.g., a toxicity screening procedure and specific metallic and organic toxicant analyses)
to the above list.
Most of the screening effort items listed above can be obtained at the outfall location using field
procedures. It is much easier, more cost-effective, and much more accurate to collect samples in the
field for later laboratory analyses. Analyzing multiple samples for the same parameter is much more
efficient than trying to analyze a single sample for many parameters, especially under adverse field
conditions.
The selection of the analysis procedures and equipment will depend on many conditions, most
notably the expected concentrations in the uncontaminated baseflows and in the potential
non-stormwater discharge flows, along with the needed probabilities of detection at the minimum
contamination level. A description of the techniques developed as part of this study to help in the
selection of the analytical procedures is given later in this section. Other factors affecting procedure
selection include ease of use, analytical interferences, cost of equipment, training requirements, and
time requirements to conduct the analyses.
Physical Inspection
Estimates of outfall flow rates, and noting the presence of oil sheens, floatables, coarse solids,
color, odors, etc. will probably be the most useful indicators of outfall problems. Physical observations
of outfall conditions have been noted in case studies to be very useful in determining the significance
of contaminated dry-weather flows. There has been a good correlation between storm drains judged
contaminated after physical inspection and those judged contaminated after chemical tests at several
case studies (e.g., Inner Grays Harbor, Washington, Beyer, et al. 1979 and Pelletier and Determan
1988; Fort Worth, Texas, Falkenbury 1987 and 1988 and Moore and Hoffpauir 1988; and Toronto,
Ontario, GLA 1983).
19
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Odor-
The odor of a discharge can vary widely and sometimes directly reflects the source of
contamination. Industrial dry-weather discharges will often cause the flow to smell like a particular
spoiled product, oil, gasoline, specific chemical, or solvent. As an example, for many industries, the
decomposition of organic wastes in the discharge will release sulfide compounds into the air above the
flow in the sewer, creating an intense smell of rotten eggs. In particular, industries involved in the
production of meats, dairy products, and the preservation of vegetables or fruits, are commonly found
to discharge organic materials into storm drains. As these organic materials spoil and decay, the sulfide
production creates this highly apparent and unpleasant smell. Significant sanitary wastewater
contributions to a dry-weather flow will also cause pronounced and distinctive odors.
Color--
Color is another important indicator of inappropriate discharges, especially from industrial sources.
Industrial dry-weather discharges can have various colors. Dark colors, such as brown, gray, or black,
are most common. For instance, the color contributed by meat processing industries is usually a deep
reddish-brown. Paper mill wastes are also brown. In contrast, textile wastes are varied. Other intense
colors, such as plating-mill wastes, are often yellow. Washing of work areas in cement and stone
working plants can cause cloudy dry-weather discharges. Potential dry-weather sources causing
various colored contaminated waters from industrial areas include process waters (slug or continuous
discharges), equipment and work area cleaning water discharged to floor drains, and spills during
loading operations (and subsequent washing of the material into the storm drains).
Turbidity--
Turbidity of water is often affected by the degree of gross contamination. Dry-weather industrial
flows with moderate turbidity can be cloudy, while highly turbid flows can be opaque. High turbidity
is often a characteristic of undiluted dry-weather industrial discharges, such as those coming from
some continual flow sources, or some intermittent spills. Sanitary wastewater is also often cloudy in
nature.
Temperature-
Temperature measurements may be useful in situations where the screening activities are
conducted during cold months, or in areas having industrial activity. It may be possible to identify an
outfall that is grossly contaminated with sanitary wastewater or cooling water during cold weather and
possibly to conduct a rough heat balance. Both sanitary wastewater and cooling water could
substantially increase outfall discharge temperatures. Elevated baseflow temperatures (compared to
baseflows at other outfalls being screened) could be an indicator of substantial contamination by these
warmer source flows.
Floatable Matter-
A contaminated flow may also contain floatables (floating solids or liquids). Evaluation of floatables
often leads to the identity of the source of industrial or sanitary wastewater pollution, since these
substances are usually direct products or byproducts of the manufacturing process, or distinctive of
sanitary wastewater. Floatables of industrial origin may include substances such as animal fats, spoiled
food products, oils, plant parts, solvents, sawdust, foams, packing materials, or fuel; whereas
floatables in sanitary wastewater include fecal matter, sanitary napkins, and condoms.
Deposits and Stains--
Deposits and stains (residue) refer to any type of coating which remains after a non-stormwater
discharge has ceased. They will cover the area surrounding the outfall and are usually of a dark color.
Deposits and stains often will contain fragments of floatable substances and, at times, take the form
of a crystalline or amorphous powder. These situations are illustrated by the grayish-black deposits that
contain fragments of animal flesh and hair which often are produced by leather tanneries, or the white
20
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crystalline powder which commonly coats sewer outfalls due to nitrogenous fertilizer wastes.
Vegetation--
Vegetation surrounding an outfall may show the effects of intermittent or random non-stormwater
discharges. Industrial pollutants will often cause a substantial alteration in the chemical composition
and pH of the discharge. This alteration will affect plant growth, even when the source of
contamination is intermittent. For example, decaying organic materials coming from various food
product wastes could cause an increase in plant life. In contrast, the discharge of chemical dyes and
inorganic pigments from textile mills could noticeably stunt plant growth, as these dry-weather
discharges are often acidic. In either case, when the industrial pollution constituent in the flow ceases,
the vegetation surrounding the outfall will continue to show the effects of the contamination.
In order to accurately judge if the vegetation surrounding an outfall is normal, the observer must
take into account the current weather conditions, as well as the time of year in the area. Thus,
flourishing or inhibited plant growth, as well as dead and decaying plant life, are all signs of pollution
or scouring flows when the condition of the vegetation beyond the outfall contrasts with the plant
conditions near the outfall. It is important not to confuse the adverse effects of high storm-induced
flows on vegetation with highly toxic dry-weather intermittent flows. Poor plant growth could be
associated with scouring flows occurring during storms.
Damage to Sewerage/Outfall Structure--
Sewerage structural damage is another readily visible indication of both continual and intermittent
industrial dry-weather discharge contamination. Cracking, deterioration, and spading of concrete or
peeling of surface paint, occurring at an outfall are usually caused by severely contaminated
discharges, usually of industrial origin. These contaminants are usually very acidic or basic in nature.
For instance, primary metal industries have a strong potential for causing sewerage structural damage
because their batch dumps are highly acidic. However confusion is possible due to the effects poor
construction, hydraulic scour, and old age may have had on the condition of the outfall structure or
sewerage system.
Chemical Parameters
Chemical tests are needed to supplement the above described physical inspection parameters.
Chemical tests are needed to quantify the approximate components of a mixture at the outfall. In most
cases, dry-weather discharges are made up of many separate source flows (e.g., potable water,
groundwaters, sanitary wastewater, and automobile washwaters). Statistical analyses of the chemical
test results can be used to estimate the relative magnitudes of the various flow sources (as described
in Section 6 of this Guide).
Specific Conductivity-
Specific conductivity can be used as an indicator of dissolved solids. Specific conductivity
measurements can be conducted with relative ease in the field, while dissolved solids measurements
must be made in a laboratory.
The literature indicates that variation in specific conductivity measurements between water and
wastewater sources could be substantial enough to indicate the source of dry-weather flow in the
storm drainage system. Specific conductance was judged to be a reliable and quick field indicator of
general outfall contamination in Toronto (GLA 1983). Observed levels ranged from 25 to 100,000
fjS/cm (microSiemens per cm). Specific conductivity levels less than 1000 /jS/cm indicated significant
levels of rainwater in the drainage. Specific conductivity can be measured quickly, easily and cheaply.
For these reasons, it was selected as a parameter for further study.
21
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Fluoride--
Fluoride concentration should be a reliable indicator of potable water where fluoride levels in the
raw water supply are adjusted to consistent levels and where groundwater has low to non-measurable
natural fluoride levels. It is common practice for communities to add fluoride to municipal waters to
improve dental health. Concentrations of total fluoride in fluoride treated potable waters are usually
in the range of 1.0 to 2.5 mg/L.
Fluoride measurements have often been used to distinguish treated waters from natural waters.
During the Allen Creek drainage study (Schmidt and Spencer 1986), the fluoride concentrations of
dry-weather flows at outfalls were undetectable after most of the known improper connections to
storm drains were eliminated. Very few of these improper connections were of sanitary wastewater
to the storm drainage. Apparently, most of the non-stormwater discharges were treated potable water.
Hardness--
Hardness may also be useful in distinguishing between natural and treated waters (like fluoride),
as well as between clean treated waters and waters that have been subjected to domestic use.
The hardness of waters varies considerably from place to place, with groundwaters generally being
harder than surface waters. Natural sources of hardness are limestones which are dissolved by
percolating rainwater made acid by dissolved carbon dioxide. Information regarding the average
hardness of potable water as well as local groundwater and surface waters should be readily available
wherever a public water supply system exists.
Ammonia/Ammonium--
As part of the nitrogen cycle, ammonia is produced by the decay of organic nitrogen compounds.
Ammonia may then be broken down, forming nitrites and nitrates. The presence or absence of
ammonia (NH3), or ammonium ion (NH4 + ), has been commonly used as a chemical indicator for
prioritizing sanitary wastewater cross-connection drainage problems. Correlations between elimination
of improper sanitary wastewater cross-connections into storm drainage and reduced numbers of storm
drainage outfalls with ammonia present were noted in Fort Worth (Falkenbury 1987 and 1988; Moore
and Hoffpauir 1988). During studies in Toronto (GLA 1983), more "problem" storm drain outfalls had
high ammonia concentrations (>1 mg/L) than any other single parameter, except TKN. During the
Huron River (Michigan) study (Washtenaw Co. 1987 and 1988; Murray 1985), ammonia levels were
found to be greater at all "problem" storm drain outfalls than at control locations. However, the Allen
Creek (Michigan) Drainage study (Schmidt and Spencer 1986) reported that with 92 percent of the
improper non-stormwater entries to storm drains eliminated, the ammonia concentrations did not
change significantly (all were about 0.44 mg/L). However, very few of these cross-connection
eliminations were for sanitary wastewater. Ammonia should be useful in identifying sanitary wastes
and distinguishing them from commercial water usage.
Potassium--
Large increases of potassium concentrations have been noted for sanitary wastewater compared
to potable water during studies in California (Evans 1968), Virginia (Hypes, et al. 1975), and Brussels,
Belgium (Verbanck, et al. 1990). These potassium increases following domestic water usage suggest
its potential as a tracer parameter.
Surfactants and Fluorescence-
Surfactants are discharged from household and industrial laundering and other cleaning operations.
In the United States, anionic surfactants are commonly used in detergents and account for
approximately two thirds of the total surfactants used. Anionic surfactants are commonly measured
as Methylene Blue Active Substances (MBAS). In raw sanitary wastewaters, surfactants generally
range from 1 to 20 mg/L, while natural waters usually have surfactant concentrations below 0.1 mg/L.
22
-------
Large concentrations of surfactants are found in sanitary wastewater, but some researchers
(Alhajjar, et al. 1989) have reported that they are not found in septic tank effluent. Surfactants can
be totally degraded in the septic tanks. During the Allen Creek drainage study (Schmidt and Spencer
1986; Washtenaw County Drain Commissioner 1984; and Washtenaw County Statutory Drainage
Board 1987), surfactants (as MBAS) decreased significantly after most of the improper non-stormwater
entries to storm drains were eliminated. Surfactants can be used to identify sanitary or laundry
wastewater cross-contamination in storm drainage systems. They may also be of use in distinguishing
between infiltrating septic tank effluent and other washwaters from domestic or commercial cleaning
operations.
Water fluorescence is also an indicator of detergent residue in waters. Most detergents contain
fabric whiteners which cause substantial fluorescence. Fluorescent indicators remain after sanitary
wastewater treatment in septic tanks. Fluorescence in contrast to MBAS may be useful in
distinguishing between sanitary wastewater contamination and septic tank effluent.
pH-
The pH of most uncontaminated baseflows, as well as sanitary wastewater, is usually quite close
to neutral (pH of 7). Therefore, Ph will probably not serve as an indicator of sanitary cross connections.
However, pH values may be extreme in certain inappropriate commercial and industrial flows or where
groundwaters contain dissolved minerals. If unusual pH values are observed, then the drainage system
needs to be carefully evaluated. Very few of the stormwater outfalls tested during dry-weather in Fort
Worth (Falkenbury 1987 and 1988; Moore and Hoffpauir 1988) had pH values either below 6 or above
9. None of the Toronto (GLA 1983) "problem" outfalls were reported to have extreme pH values.
Chemicals (acidic and alkaline) released into storm drains by chemically-oriented industries are
frequently the cause of pH fluctuations which can range from 3 to 12.
Industries that commonly release low pH (acidic) dry-weather discharges include (but are not
limited to) textile mills, pharmaceutical manufacturers, metal finishers/fabricators, as well as companies
producing resins, fertilizers and pesticides. Wastes containing sulfuric, hydrochloric, or nitric acids are
common industrial sources of low pH discharges.
Many industrial wastes contain high pH (alkaline) chemicals such as cyanide, sodium sulfide, and
sodium hydroxide. High concentrations of these contaminants are found in discharges from soap
manufacturers, textile mills, metal plating industries, steel mills, and producers of rubber or plastic.
Total Available Chlorine--
Chlorine can be present in water as free available chlorine and as combined available chlorine
(usually as chloramines). Both types can exist in the same water and be determined together as the
total available chlorine. Chlorine is not stable in water, especially in the presence of organic
compounds. Tests of clean potable water during the demonstration project (Pitt and Lalor publication
pending) found that total available chlorine only decreased by about 25 percent in 24-hours during an
aerated bench-scale test. However, the chlorine demand of contaminated water can be very large, with
chlorine concentrations decreasing to very small values after short periods of time. Chlorine therefore
cannot be used to quantify flow sources because of its instability, but the presence of chlorine in
baseflow waters (very unlikely) could indicate a significant and very close potable water flow source.
Other Chemicals Indicative of Manufacturing Industrial Activities-
Table 3 is a listing of various chemicals that may be associated with a variety of different
industrial activities. If the industrial activities in an outfall watershed are known, it may be possible to
examine the non-stormwater outfall flow for specific chemicals (e.g., listed in Table 3) to identify
which industrial activities may be responsible for the dry-weather flow.
23
-------
TABLE 3. SIGNIFICANT CHEMICALS IN INDUSTRIAL WASTEWATERS
Chemical:
Acetic acid
Alkalies
Ammonia
Arsenic
Chlorine
Chromium
Cadmium
Citric acid
Copper
Cyanides
Fats, oils
Fluorides
Formalin
Hydrocarbons
Hydrogen peroxide
Lead
Mercaptans
Mineral acids
Nickel
Nitro compounds
Organic acids
Phenols
Silver
Starch
Sugars
Sulfides
Sulfites
Tannic acid
Tartaric acid
Zinc
Industry.
Acetate rayon, pickle and beetroot manufacture.
Cotton and straw kiering, cotton manufacture, mercerizing,
wool scouring, and laundries.
Gas, coke, and chemical manufacture.
Sheep-dipping, and felt mongering.
Laundries, paper mills, and textile bleaching.
Plating, chrome tanning, and aluminum anodizing.
Plating.
Soft drinks and citrus fruit processing.
Plating, pickling, and rayon manufacture.
Plating, metal cleaning, case-hardening, and gas
manufacture.
Wool scouring, laundries, textiles,and oil refineries.
Gas, coke, and chemical manufacture, fertilizer plants,
transistor manufacture, metal refining, ceramic plants, and
glass etching.
Manufacture of synthetic resins and penicillin.
Petrochemical and rubber factories.
Textile bleaching, and rocket motor testing.
Battery manufacture, lead mining, paint manufacture, and
gasoline manufacture.
Oil refining, and pulp mills.
Chemical manufacture, mines, Fe and Cu pickling, brewing,
textiles, photo-engraving, and battery manufacture.
Plating.
Explosives and chemical works.
Distilleries and fermentation plants.
Gas and coke manufacture, synthetic resin manufacture,
textiles, tanneries, tar, chemical, and dye manufacture and
sheep-dipping.
Plating, and photography.
Food, textile, and wallpaper manufacture.
Dairies, foods, sugar refining, and preserves.
Textiles, tanneries, gas manufacture, and rayon
manufacture.
Wood process, viscose manufacture, and bleaching.
Tanning, and sawmills.
Dyeing, wine, leather, and chemical manufacture.
Galvanizing, plating, viscose manufacture, and rubber
process.
Source: Van der Leeden, et al. 1990.
24
-------
Toxicitv Screening Tests
In addition to the parameters described above, relative toxicity can be an important outfall
screening parameter. Short-term toxicity tests, such as the Microtox™ test (from Microbics) are
valuable for quickly and cheaply assessing the relative toxicity (to a selected test organism) of different
storm drain baseflows. These tests can be used to identify outfalls that contain flows in the most
serious (toxic) category and that require immediate investigation. These tests are also very useful in
identifying likely sources of toxicants to the drainage system by utilizing a toxicity reduction evaluation
(TRE) procedure in the drainage system. If an outfall contains a highly toxic flow, then specific metallic
and organic toxicants can be analyzed to support source identification.
TRACER CHARACTERISTICS OF SOURCE FLOWS
Table 4 summarizes the relative concentrations of tracer parameters in source flows. The unique
"fingerprints" of each flow category shown can be used to identify the flow components, as shown
in Section 6. This table also contains redundancies, (e.g., potassium and ammonia) to help identify
sanitary wastewater and septic tank effluent. Fluoride and hardness are similarly used to identify
treated potable water and surfactant (MBAS) and fluorescent measurements are used to identify
washwaters.
Table 5 is a summary of the tracer parameter concentrations found in Birmingham, Alabama, from
April 1991 to September 1992. This table is a summary of the "library" that describes the tracer
conditions for each potential source category. The important information shown on this table includes
the median and coefficient of variation (COV) values for each tracer parameter for each source
category. The COV is the ratio of the standard deviation to the mean. A low COV value indicates a
smaller spread of data compared to a data set having a large COV value. It is apparent that some of
the abstracted and generalized relationships shown on Table 4 did not exist during the demonstration
project. This stresses the need for obtaining local data describing likely source flows.
The fluorescence values shown on Table 5 are direct measurements from the Turner™ (Model
111) fluorometer having general purpose filters and lamps and at the least sensitive setting (number
1 aperture). The toxicity screening test results are expressed as the toxicity response noted after 25
minutes of exposure. The Microtox™ unit measures the light output from phosphorescent algae. The
I2B value is the percentage light output decrease observed after 25 minutes of exposure to the sample.
If an outfall sample has a very high light reduction value, it is typically subjected to additional organic
and metallic toxicant tests. Fresh potable water has a relatively high response because of the chlorine
levels present. Aged, or dechlorinated, potable water has much smaller toxicity responses.
Appropriate tracers are characterized by having significantly different concentrations in flow
source categories requiring identification. In addition, effective tracers also need low COV values within
each flow category. Table 4 indicates the expected changes in concentrations per category and Table
5 indicates how these expectations compared with the results of an extensive local sampling effort.
The study indicated that the COV values were quite low for each category, with the exception of
chlorine, which had much greater COV values. The high chlorine COV values reinforce what was
previously indicated (under Total Available Chlorine), that chlorine is not recommended as a
quantitative tracer to estimate the flow components. Similar data must be collected in each community
where these procedures are to be used. The following subsection discusses how the number of
samples needed per category can be estimated.
25
-------
TABLE 4. FIELD SURVEY PARAMETERS AND ASSOCIATED NON-STORMWATER FLOW SOURCE CATEGORIES
Parameter
Fluorides
Hardness Change
Surfactants
Fluorescence
Potassium
Ammonia
Odor
Color
Clarity
Floatables
Deposits/Stains
Vegetation Change
Structural Damage
Conductivity
Temperature Change
pH
Natural
Water
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
Potable
Water
+
+ /-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
Sanitary
Wastewater
+
+
+
+
+
+
+
-
+
+
+
+
-
+
+ /-
-
Septic
Tank
Effluent
+
+
-
+
+
+
+
-
+
-
-
+
-
+
-
-
Indus.
Water
+ /-
+ /-
-
-
-
-
+
+
+
+
+
+
+
+
+
+
Wash-
Water
+
+
+
+
-
-
+ /-
-
+
+ /-
+ /-
+ /-
-
+ /-
+ /-
-
Rinse
Water
+
+
-
-
-
-
-
-
+ /-
+ /-
+ /-
-
-
+
+ /-
-
Irrig.
Water
+
-
-
-
-
-
-
-
-
-
+
-
+
-
-
0)
NOTE:
implies relatively low concentration
+ implies relatively high concentration
+ /- implies variable conditions
-------
TABLE 5. TRACER CONCENTRATION FOUND IN BIRMINGHAM, ALABAMA WATERS
(MEAN, STANDARD DEVIATION AND COEFFICIENT OF VARIATION. COV)
Fluorescence
(% scale)
Potassium
(mg/L)
Ammonia
(mg/L)
Fluoride
(mg/L)
Toxicity
(% light
decrease
after 25 min.,
I25)
Surfactants
(mg/L as
MBAS)
Hardness
(mg/L)
PH
(pH units)
Color
(color units)
Chlorine
(mg/L)
Spec.
Conduct.
(jjS/cm)
Number of
Samples
Spring
Water
6.8
2.9
0.43
0.73
0.070
0.10
0.009
0.016
1.7
0.031
0.027
0.87
<5
n/a
n/a
<0.5
n/a
n/a
240
7.8
0.03
7.0
0.05
0.01
<1
n/a
n/a
0.003
0.005
1.6
300
12
0.04
10
Treated
Potable
Water
4.6
0.35
0.08
1.6
0.059
0.04
0.028
0.006
0.23
0.97
0.014
0.02
47
20
0.44
<0.5
n/a
n/a
49
1.4
0.03
6.9
0.29
0.04
<1
n/a
n/a
0.88
0.60
0.68
110
1.1
0.01
10
Laundry
Waste-
water
1020
125
0.12
3.5
0.38
0.11
0.82
0.12
0.14
33
13
0.38
99.9
<1
n/a
27
6.7
0.25
14
8.0
0.57
9.1
0.35
0.04
47
12
0.27
0.40
0.10
0.26
560
120
0.21
10
Sanitary
Waste-
water
250
50
0.20
6.0
1.4
0.23
10
3.3
0.34
0.77
0.17
0.23
43
26
0.59
1.5
1.2
0.82
140
15
0.11
7.1
0.13
0.02
38
21
0.55
0.014
0.020
1.4
420
55
0.13
36
Septic
Tank
Effl.
430
100
0.23
20
9.5
0.47
90
40
0.44
0.99
0.33
0.33
99.9
<1
n/a
3.1
4.8
1.5
235
150
0.64
6.8
0.34
0.05
59
25
0.41
0.013
0.013
1.0
430
311
0.72
9
Car
Wash-
water
1200
130
0.11
43
16
0.37
0.24
0.066
0.28
12
2.4
0.20
99.9
<1
n/a
49
5.1
0.11
160
9.2
0.06
6.7
0.22
0.03
220
78
0.35
0.070
0.080
1.1
485
29
0.06
10
Radiator
Flush
Water
22,000
950
0.04
2800
375
0.13
0.03
0.01
0.3
150
24
0.16
99.9
<1
n/a
15
1.6
0.11
50
1.5
0.03
7.0
0.39
0.06
3000
44
0.02
0.03
0.016
0.52
3300
700
0.22
10
27
-------
Determining Number of Observations Needed
It is very important to determine the number of observations needed for each tracer parameter for
each source category in order to build a useful data library for analyzing the outfall data. This
determination is a function of the tolerable error level in the data means and the standard deviations.
The following paragraphs briefly describe a method that can be used to estimate the sampling effort
needed to develop a useful library of source characteristic data.
Estimating Errors--
One equation that can be used to calculate the number of analyses needed, based on the
allowable error is (Cochran 1963):
Number of samples = 4(standard deviation)2/(allowable error)2
With a 95 percent level of confidence, this relationship determines the number of samples needed to
obtain a value within the range of the sample mean, plus and minus the error. Similarly, this equation
can be used to predict the 95 percent confidence interval, based on the measured (or estimated)
standard deviation and number of samples obtained:
Error = 2(standard deviation)/(number of samples)0 5
where the confidence interval is the mean plus and minus the calculated error value.
Example of Log10 Transformation-
These equations assume a normal distribution of the data. However, most water quality data
needs to be log 10 transformed before a normal distribution is obtained. As an example, consider a tracer
having a COV of 0.23 and a median value of 0.14. The resulting Iog10 transformed standard deviation
would be about 0.12. For ten samples, the resulting 95 percent confidence range of the median
observation (0.14 mg/L) is:
Error = 2(0.12)/(10)05 = 0.076 in Iog10 space
The confidence interval is therefore loglo(0.14) +/- 0.076, which is -0.778 to -0.930 in Iog10 space.
This results in a conventional 95 percent confidence range of 10~°-930 (= 0.12) to 10~°-778 (= 0.17). The
error in the estimate of the median value is therefore between 14 and 21 % for ten samples. If the
original untransformed data were used, the error associated with 10 samples is 15%, within the range
of the estimate after log transformations. These results are close because of the low COV value (0.23).
If the COV value is large, the need for log transformations increases. Figure 3 (Pitt 1979) shows the
approximate sample size needed to obtain different allowable errors for different COV values (using
nontransformed data).
The COV value in the above example (0.23) was close to the median COV value for all of the
source categories and tracer parameters shown on Table 5. Therefore, about 10 samples per source
flow category should generally result in less than a 25 percent error for the median values obtained.
As shown in a later section, narrow confidence intervals are needed in order to estimate the
relative mixes of the non-stormwater sources as measured at the outfall. Therefore, much care needs
to be taken in order to estimate the characteristics of the potential non-stormwater flow sources,
especially the COV values and medians.
28
-------
10.0
CO
1
.0
.2
CO
t)
o
is
0)
i
0)
8.
I
0.1
0.05
(5%)
0.1
(10%)
0.25
(25%)
Allowable error as a fraction of the mean
Figure 3. Required number of samples for allowable error and COV
Source: Pitt 1979
29
-------
Understanding the mechanisms affecting the non-stormwater sources (e.g., time of day, season,
area of town, type and magnitude of land use activities, etc.) and obtaining a relatively large data base
library for the source flow tracer concentrations is very important and should be a significant portion
of a dry-weather flow source identification project.
SELECTION OF ANALYTICAL METHODS
The selection of the analytical procedure to be used is dependent on a number of factors, including
(in order of importance):
appropriate detection limits
freedom from interferences
good analytical precision (repeatability)
low cost and good durability
minimal operator training required
The following sub-sections discuss these requirements and present the recommended analytical
procedures. Tracer characteristics in potential local source flows affect most of these requirements.
Therefore, the suggested analytical procedures may not be the most cost-effective for all areas.
Detection Limit Requirements
In order to identify potential non-stormwater sources, it is necessary to have a basic knowledge
about each potential source flow. As shown earlier, a significant sampling and analysis effort is needed
to develop a library of source flow tracer concentrations. The COVs and means of the tracer
concentrations are needed to estimate the detection limits required by the analytical procedures.
There are a number of different types of detection limits defined for laboratory use. Most
instrument manufactures present a minimum readable value as the instrument detection limit (IDL) in
their specifications for simple test kits. The usual definition of IDL, however, is a concentration that
produces a signal to noise ratio of five. The method detection limit (MDL) is a more conservative value
and is established for the complete preparation and analysis procedure. The practical quantification limit
(PQL) is higher yet and is defined as a routinely achievable detection limit with a relatively good
certainty that any reported value is reliable. Standard Methods (APHA, et al. 1989) estimates that the
relationship between these detection limits is approximately: IDL:MDL:PQL = 1:4:20. Therefore, the
detection limit shown in much of the manufacturer's literature is much less than what would be used
by most analytical laboratories.
Because of the screening nature of the outfall field surveys, the instrument detection capabilities
are appropriate for the methodology described in this Users' Guide. The larger uncontrollable errors
associated with obtaining representative outfall samples and in the variations of the tracer
concentrations in the potential source flows would tend to diminish the significance of errors
associated with reading concentration values from the instrument that are lower than the PQL.
A quick (and conservative) estimate of the needed detection limit can be made by only knowing
the median concentration and the concentration variation of the tracer in the least contaminated
component flow. Any amount of another component having a greater tracer concentration will increase
the tracer concentration of the mixture. By ignoring this increase, minimum detection limits can be
estimated based on the numerous probability calculations presented in the background demonstration
project report (Pitt and Lalor publication pending):
30
-------
COV value: Multiplier for detection limit:
<0.5 (low) 0.8
0.5 to 1.25 (medium) 0.23
>1.25 (high) 0.12
As an example, if the baseflow tracer has a low COV «0.5), then the estimated required detection
limit is about 0.8 times the median tracer concentration.
More than 80 percent of the library categories (source flows and tracers) examined in Birmingham,
Alabama during the demonstration of these procedures (shown on Table 5) had low COV values. About
15 percent had medium COV values, and about 5 percent had high COV values. Free available chlorine
had medium or high COV values for almost all source categories. This is a major reason why chlorine
is not used quantitatively to identify source flow components in outfall samples. Chlorine is used in a
similar manner as an aesthetic parameter (e.g., turbidity or odor). If high chlorine concentrations are
found at the outfall (greater than about 0.5 mg/L), then a major treated potable water leak is likely
associated with the dry-weather flow.
Table 6 lists the detection limit requirements for the tracer parameter concentrations found during
the Birmingham, Alabama, demonstration project. The recommended analytical methods satisfy most
of the required detection limits, except for ammonia and surfactants in spring water and surfactants
in potable water. The spring water ammonia concentrations were about equal to the detection limit,
but because the variation in the ammonia concentrations were so large, a much lower detection limit
would be preferable.
Figures 4 through 7 are probability plots showing the required analytical detection limits for
mixtures of two source area flows both having low COV values (similar to the majority of expected
conditions). Pitt and Lalor (publication pending) present similar plots for all possible combinations of
COV values. These figures show four curves corresponding to four mixtures. PER100 is for a 100
percent solution of the flow having the higher tracer concentration, PER50 is for a solution having 50
percent each of two components, PER15 is for a solution of 15 percent of the component having the
higher tracer concentration and 85 percent of the component having the lower tracer concentration,
while PERO is a solution only made of the component having the lower tracer concentration. Figure 4
is for two components that have mean concentrations differing by 1.33 times, Figure 5 is for a mixture
where the component mean concentrations differ by five times, Figure 6 is for two components with
mean concentrations differing by 20 times, and Figure 7 is for two components with mean
concentrations differing by 75 times. Each figure shows the detection limits, relative to the lower base
concentrations, for different probability of detection values. The detection limits required are reduced
significantly as the means of the tracer components differ by greater amounts, especially for low
probabilities of detection.
For example, if the two tracer mean concentrations vary by about five times (e.g., treated potable
water and sanitary wastewater potassium concentrations from Table 5) and a mixture of 15 percent
sanitary wastewater and 85 percent potable water needs to be identified with a 90 percent probability
of detection, the required detection limit would be about:
1.4 [factor from Fig.5] x 1.6mg/l [potassium in treated potable water Table 5] = 2.2 mg/L
The more conservative approach stated above would result in a minimum detection limit of:
0.8 [factor for COV < 0.5] x 1.6mg/l = 1.2 mg/L.
31
-------
TABLE 6. DETECTION LIMIT REQUIREMENTS FOR TRACER CONCENTRATIONS FOUND IN
BIRMINGHAM, ALABAMA WATERS
Tracer Parameter
and
Units
Fluorescence
% of full scale
Potassium
mg/L
Ammonia
mg/L
Fluoride
mg/L
Surfactants
mg/L as MBAS
Hardness
mg/L as CaC03
Color
HACH™ color
units
Specific
Conductivity
/vS/crn
Median Cone. (mg/L) of Least
Contaminated
Sources: median (COV)
Potable water: 4.6 (0.08)
Spring water: 6.8 (0.43)
Spring water: 0.73 (0.10)
Potable water: 1 .6 (0.04)
Spring water: 0.01 (1.7)
Potable and Radiator water:
0.03 (0.23)
Spring water: 0.031 (0.87)
Sanitary wastewater: 0.77
(0.23)
Spring and potable water: < 1
Sanitary wastewater: 1.5
(0.82)
Laundry water: 14 (0.57)
Potable and radiator water:
49 (0.03)
Spring and potable water: < 1
Sanitary wastewater: 38
(0.55)
Potable water: 110 (0.01)
Spring water: 300 (0.04)
Required
Detection Limit
3.7
5.4
0.58
1.3
0.001
0.024
0.01
0.62
0.35
3.2
39
8.7
88
240
Available
Detection
limit111
0.1
0.01
0.01
0.01
0.01
1
1
10
(1) From anlaytical methods discussed under: "Recommended Analytical Methodology"
32
-------
o 2.5
o
CJ
o5
% 2.0
1
o 1-5
o
* 1.0
0.5
rS °-°
PERO
PER15
0
20 40 60
Probability of Detection
80
100
Figure 4. Required detection limits for low COV mixture
components having means differing by 1.3 times.
o
8
o
o3
o
05
I
o
CO
_o
"o
CB
§
8
7
6
5
4
3
2
1
0
PERtoo
PER50
PER 15
PERO
0
20 40 60
Probability of Detection
80
Figure 5. Required detection limits for low COV mixture
components having means differing by 5 times.
100
33
-------
o
o
CD
o
CO
o
co
.o
"o
CD
"CD
Q
o
03
3
o
CO
o
"o
CD
"CD
Q
40
30
20
5 10
0
.PER50
PER15
PERO
0
20 40 60 80
Probability of Detection
100
Figure 6. Required detection limits for low COV mixture
components having means differing by 20 times.
150
100
50
0
PER50
PER15
PERO ,
0
20
40
60
80
100
Probability of Detection
Figure 7. Required detection limits for low COV mixture
components having means differing by 75 times.
34
-------
Even with the above analytical requirements satisfied, it may still be difficult to precisely estimate
the degree of contamination, especially for low contamination levels and for high COVs. The ratio of
the tracer concentration in the contaminating source flow to the tracer concentration in the cleaner
baseflow must increase as the desire to detect smaller contaminating source flows is required. Listed
below, for 90 percent confidence levels and low COV values, are percentages of source flow in the
baseflow and the corresponding minimum concentration ratios (source to clean baseflow tracer
concentrations) required for the detection of the source flow contamination of the baseflow.
Percent of Source Flow Required concentration ratios
Contamination in Baseflow: (low COV values):
1% 50
5% 10
10% 7
25% 3
35% 1.5
50% 1.2
As an example, the median tracer concentration in the contaminating source flow must be about
10 times greater than the median tracer concentration in the cleaner baseflow to detect a five percent
source flow contamination of the baseflow. If the tracer COV values are "medium" or "high", then the
required concentration differences are much greater (up to 250 times difference in concentrations may
be required).
Therefore, the differences in tracer concentrations must be quite large, and the COVs quite small,
in order to have confident estimates of low levels (percentages) of contaminating source flows. Few
tracers exhibit such a wide range in characteristics between source flow and baseflow categories. This
is the main reason why the use of multiple tracers for source flow identification is important. Some
tracers may not uniformly produce good estimates of contaminating source flow levels, but the use
of redundant tracers for the same decision (e.g., ammonia and potassium to identify sanitary
wastewater; fluorides and hardness to identify treated potable water; and surfactants and fluorescence
to identify wash waters) and good estimates of local contaminant characteristics, will minimize these
errors.
The actual minimum level of contaminating source flow that will be detectable will be dependent
on the analytical precision, as discussed next.
Required Sample Analytical Precision
The repeatability of the analytical method is an important consideration in its selection. Precision,
as defined in Standard Methods (APHA, et al. 1989), is a measure of the closeness with which multiple
analyses of a given sample agree with each other. It is determined by repeated analyses of a stable
standard, conducting replicate analyses on the samples, or by analyzing known standard additions to
samples. Precision is expressed as the standard deviation of the multiple analysis results.
Figure 8 is a summary of the probability plots from Pitt and Lalor (publication pending) and
indicates the needed analytical precision (repeatability) as a fraction of the median tracer concentration
(i.e., the flow with the lower tracer concentration) to resolve one percent contamination of the
baseflow by the source flow, at a 90 percent confidence level. This figure was developed for COV
values of the tracer parameters in the contaminating flows ranging from 0.16 to 1.67.
35
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Figure 8. Analysis precision needed for detection of one percent contamination
at ninety percent confidence.
-------
If the available analytical precision is worse than these required values, then small contaminating
flow levels may not be detected. Therefore, even with adequate analytical detection limits, poor
analytical precision may not allow adequate identification of low levels of contaminating flow. In many
cases, it is expected that a contaminating flow level of just a few percent can cause significant toxic
and pathogenic problems. Examples include gasoline spills, direct connections of raw sanitary
wastewater, and metal plating bath wastewaters.
If the tracer concentrations of the flow components are close in value and the variation of the
concentrations are high, then it will be very difficult to adequately discern flow components. In
contrast, if the tracer concentrations of the flow components are widely different and have low
variabilities, then much smaller levels of contaminating flows could be detected. As an example, if the
median contaminant tracer concentrations differ by a factor of 10 in two flow components, but have
high concentration variations (high COV values), a precision of between 0.015 to 0.03 of the lower
baseflow median tracer concentration is needed, for each percent of contaminating flow that needs
to be detected. If the median tracer concentration in the cleaner baseflow is 0.15 mg/L (with a
corresponding tracer median concentration of 10 times this amount, or 1.5 mg/L, in the contaminating
source flow), then the required analytical precision is about 0.015 x 0.15 = 0.002 mg/L to 0.03 x
0.15 = 0.005 mg/L per one percent of contaminating flow to be detected. If at least five percent of
contaminating flow is needed to be detected, then the minimum precision would have to be 5 x 0.002
= 0.01 mg/L.
The conservative method noted previously can be used to estimate the detection limit
requirements for the above example:
low COV in the cleaner baseflow: 0.8 x 0.15 mg/L = 0.12 mg/L
medium COV in the cleaner baseflow: 0.23 x 0.15 mg/L = 0.035 mg/L
high COV in the cleaner baseflow: 0.12 x 0.15 mg/L = 0.018 mg/L.
The required analytical precision would therefore be about one-half of the lowest detection limit
needed, and about 1/12 of the largest estimated required detection limit.
Recommended Analytical Methodology
An important part of the development of these investigation procedures and the demonstration
project (Pitt and Lalor publication pending) was the laboratory and field testing of alternative analytical
methods. Dry-weather outfall samples were subjected to different tests which compared several
analytical methods for each of the major tracer parameters of interest. Tests were conducted to enable
comparison of the results of alternative tests with standard procedures and to identify which methods
had suitable detection limits, based on real samples. In addition, representative samples were further
examined using standard addition methods (known amounts of standards added to the sample and
results compared to unaltered samples) in order to identify matrix interferences. Matrix interferences
are generally caused by contaminants in the samples interfering with the analysis of interest. Many of
the analysis methods were also tested against a series of standard solutions to identify analytical
precision (repeatability), linearity, and detection limits. The following paragraphs (and Table 7)
summarize the recommended analytical procedures.
Most of the recommended analyses are conducted using small "field-type" instruments. However,
despite their portability, the use of these instruments in the field can introduce many errors.
Temperature and specific conductivity are the only analyses that are recommended for field analyses.
For the other analyses, samples are collected at the site, iced, and taken back to the laboratory for
analyses. The recommended analytical procedures can be easily conducted in a temporary laboratory;
all that is needed is a work space and adequate ventilation. Access to power and water would be
37
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TABLE 7. SAMPLE ANALYSES LAB SHEET
Sample number:.
Date:
Location:
Outfall #:_
Specific conductivity YSI™ SCT meter (field).
Temperature YSI™ SCT meter (field)
pH pH meter (lab)
Ammonia Direct Nesslerization (lab)_
Color HACH™ color kit (lab)
Fluoride HACH DR/2000™ spect. with AccuVacs™ (lab).
Hardness HACH™ field titration kit (lab)
Surfactants HACH™ detergent field kit (lab).
Fluorescence Turner™ fluorometer (lab)
Potassium HACH DR/2000™ spect. (lab).
Turbidity HACH™ Nephelometer (lab)
Chlorine HACH DR/2000™ spect. with AccuVacs™ (lab).
Toxicitv Microtox™ 100% sample screen (lab)
38
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helpful, but all of the equipment can be operated with batteries. At each outfall, a (2 L) sample of
dry-weather discharge needs to be collected and stored in a polyethylene container. Another (500 mL)
sample can also be collected in a glass container having a Teflon-lined lid for toxicity screening and
selected toxicant analyses. All samples must be analyzed (or extracted) within accepted time limits.
Descriptions of the procedures and parameters recommended for the analysis and identification
of dry-weather outfall samples are:
Water color-
Determine in the laboratory using a simple comparative colormetric (color wheel) field test kit from
the HACH Company. Apparent color (unfiltered samples), expressed in HACH color units.
pH-
pH is measured in the laboratory using a standard laboratory pH meter after accurate calibration
using at least two buffer solutions bracketing the expected sample pH value. (pH measurements using
pH test paper have been found to be generally within one unit of the laboratory meter. However, this
difference is too large and is not recommended. Small "pen" pH meters most suitable for field use can
easily be off by a 0.5 pH unit and are relatively hard to calibrate. They accordingly must be used with
care.)
Specific conductivity and temperature-
These parameters are quickly and easily measured in the field using a multi-parameter SCT meter
from YSI model 33. Both specific conductivity and temperature must be calibrated against standard
specific conductivity solutions and a standard thermometer. Specific conductivity should also be
corrected to standard values obtained at 25°C (APHA, et al. 1989):
K = (KmC)/[1 +0.0191(1-25)]
where K = specific conductivity at 25°C
Km = measured specific conductivity at temperature t°C
and C = cell constant
The cell constant is a correction factor determined by measuring a 0.01 M KCI solution at 25°C, after
three rinses, compared to 1413 //S/cm, the expected value. This equation results in about a 2%
change in specific conductivity for every degree in temperature difference from 25°C. The International
System of Units (Systeme International d' Unites, SI) specific conductivity unit of measurement is the
fjS/cm which is numerically equivalent to the U.S. Customary unit, ^mhos/cm.
Fluoride-
Easily analyzed in the laboratory using a field spectrophotometer and evacuated reagent and
sample vessels (HACH DR/2000™ and AccuVac™ ampules using SPADNS reagent, without
distillation). The AccuVac™ procedure works well for sample concentrations less than 2.5 mg/L;
however, in rare instances of higher concentrations, sample dilution is required because of non-linear
instrument responses. The samples should be filtered through a 0.45 jj membrane filter (e.g.,
Millipore™ filter) before analysis to minimize color interference. (Specific-ion probes were also
evaluated, but the technique proved to be too inconsistent, especially for personnel having little
training.)
39
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Ammonia--
Easily measured in the laboratory using a direct Nesslerization procedure and spectrophotometer
(HACH DR/2000™ Nessler method, but without sample distillation). The samples should be filtered
through a 0.45 fj membrane filter before analysis to minimize color interference. (The use of various
indicator test papers and simple field test kits for ammonia determination gave poor results.
Specific-ion probes were also tested. Typical problems encountered for these procedures, (except for
the direct Nesslerization procedure), were color interferences, long analysis times, inconsistent results,
and poor performance when standard solutions were analyzed.)
Potassium--
Measured in the laboratory either using a spectrophotometer (HACH DR/2000™ Tetraphenylborate
method), or a flame atomic absorption spectrophotometer (if available). The samples should be filtered
through a 0.45 fj membrane filter before spectrophotometric analysis to minimize color interference.
(Specific-ion probes were also evaluated and indicated the same poor results found for fluorides and
ammonia.)
Surfactants--
Measured in the laboratory using a simple comparative colormetric (color wheel) method (from the
HACH Company). The samples should be filtered through a 0.45 p membrane filter before analysis to
minimize color interference. This procedure should be carried out under a laboratory fume hood.
(Specific-ion probe titrations for surfactants were not successful because of poor detection limits.)
Fluorescence--
Analyzed using a laboratory fluorometer (Turner model 111). The fluorometer had general purpose
filters and lamps and was operated at the most sensitive setting (number one aperture).
Hardness--
Determined in the laboratory using a field-titrimetric kit (HACH Digital Titrator Model 16900). The
samples should be filtered through a 0.45 fj membrane filter before analysis to minimize color
interference. (A number of simple field test kits were tested but the direct reading titration method
proved most convenient and accurate. However, hardness test paper can be used to estimate the
titration end point.)
Turbidity-
naity-
Determined using a HACH Nephelometer in the laboratory.
Chlorine-
Total available chlorine was determined with the DPD (N, N-diethyl-p-phenylenediamine) method
using a HACH DR/2000™ spectrometer with AccuVac™ ampules.
Toxicity-screening-
Toxicity screening tests have been found to be very useful as indicators of contamination of storm
drains. The Microtox™ (from Microbics) toxicity screening test can be used for relative toxicity values.
The 100 percent screening test was most commonly used. If the light output decrease after 25
minutes (the I25 value) was greater than 50 percent, then the standard Microtox test was used to
determine the sample dilution required for a 50 percent light decrease (the EC50 value). If a sample
results in a large toxic response, then specific toxicant analyses (organics and metals) could be
performed to better identify the toxicant source. In general, the Microtox™ screening test was found
to be an efficient method for toxicity analysis, particularly for identifying samples requiring further
analyses. (A number of simple test kits were used for specific heavy metal analyses, but with very poor
results. High-detection limits and interferences make these methods impractical, unless an outfall is
grossly contaminated with a concentrated source, such as raw plating bath wastewater.)
40
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SECTION 5
INITIAL FIELD SCREENING SAMPLING ACTIVITIES
SAMPLING STRATEGY
The importance of sampling all outfalls, regardless of size, should be stressed. Figure 9 shows the
distribution of outfalls for the Birmingham, Alabama area surveyed for the city's stormwater discharge
permit application. The median equivalent diameter of the 566 outfalls that had drainage area estimates
available was 36 in. About 20 percent of the outfalls were greater than 60 in. in diameter and about
20 percent were less than 20 in. in diameter. Most of the largest outfalls were actually drainage
ditches. There was an average of about 70 acres draining to each outfall, but the drainage areas
ranged from much less than one acre to over 1500 acres. About 40 percent of the outfalls were
affected by either commercial or industrial land uses and would therefore be considered as critical
drainage areas for both dry-weather flows and stormwater runoff.
The Birmingham, Alabama demonstration project that tested this protocol covered a residential
and commercial drainage area having approx. 70 outfalls. The median outfall size of the outfalls in this
study area was 16 in., and more than 75 percent of the outfalls were less than 36 in. in diameter.
Examination of the outfalls during seven separate sampling occasions found that while some of the
dry-weather flows occurred intermittently, most were continuous. About 25 percent of the outfalls
were found to be consistently flowing during dry weather, with about two-thirds of the flows
discharging from pipes that were less than 36 in. in diameter. About five percent of the outfalls
exhibited dry-weather flows which were extremely toxic or were raw, undiluted, sanitary wastewater.
Each of these contaminated outfalls were 20 in., or less, in diameter. Some of the worst dry-weather
flow discharge problems were associated with very small (4 in. diameter) pipes draining automobile
service areas adjacent to the receiving water. It was found that small outfalls can contribute significant
pollutant loads to receiving waters and should not be neglected if receiving water improvement is a
serious goal.
FIELD DATA COLLECTION
Before the field data can be collected, preliminary mapping and land use evaluation work is
needed. Section 3 described the preliminary work and the likely data sources for the information that
is needed before the field investigations can begin. The most important preliminary information required
is:
• outfall locations,
• outfall drainage areas,
• commercial and industrial activities in each drainage area, and
• locations of septic tanks in the individual drainage areas.
41
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42
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Outfall Locations
Frequently, city maps of known outfall locations are inadequate. Many outfalls are not located on
city drainage maps because of infrequent or improper updating, or unauthorized installations. Because
it is very difficult for communities to maintain up-to-date maps of drainage facilities, actual stream
surveys are needed to verify and update existing information. Illicit outfalls will not usually be shown
on maps, and field surveys will be required to detect these as well. Most newer developments do have
accurate drainage and outfall maps, but the outfall locations may not have been transferred to an
overall city map. A few cities have Geographic Information Systems (GIS) in place and are including
the storm drainage systems on appropriate data overlays. It is important to identify all outfalls because
present data indicates no relationship between the most significant sources of non-stormwater
discharges and the largest drainage areas, or the largest diameter outfalls.
Because of the likelihood of poor data concerning the outfall locations, it will probably be
necessary to "walk" the creeks and actively look for outfalls. In most cases, it requires several trips
(about three) to locate all outfalls. The initial outfall surveys should be conducted during times when
riparian vegetation is minimal. Whenever an outfall is located, it needs to be marked (coded using spray
paint or by other means).
If the receiving water is a small creek, it can be waded in a downstream direction. If the receiving
water body cannot be waded, a small boat or canoe can be used to look for outfalls above the water.
Submerged outfalls are more difficult to find and require more careful inspections for storm drain
manholes along the shore. In flood or estuary tidal areas, surveys should be conducted during low tides
when more outfalls are likely to be exposed. In many cities, streets parallel the banks of creeks or
drainage canals that contain outfalls. It may be possible to carefully search the opposite bank from a
moving automobile. It may also be cost-effective to use light aircraft (including helicopters) to search
for outfalls. Submerged outfalls could be easier to identify from the air than from the water in cases
where discharge plumes are visible.
Obviously, outfall characterizations should be conducted during these surveys, if possible. In all
cases, at least two people are needed to look for outfalls, especially if wading a creek. Another person
can drive a shuttle car to a convenient downstream location for crew rotation.
Field Survey
The main elements of the field sampling plan are the collection of necessary information and
equipment, and preliminary screening of outfalls.
Collect necessary information and equipment-
Maps-Maps are the most important part of the field equipment. Adequate field maps can be
prepared by enlarging standard USGS 7-1/2 minute quadrangle maps to appropriate scales. In addition,
detailed street maps are also needed to locate specific street crossings and to identify locations of
outfalls in the field.
Field sampling and analysis equipment-Table 8 lists the equipment that is needed for a field
survey. In no case should personnel conduct the field surveys alone, wade streams without wearing
waders, or be in boats without wearing life preservers. Heavy duty waders (heavy Cordura™ nylon)
are preferred. Urban streams contain appreciable debris (broken bottles, etc.). In addition, urban
43
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TABLE 8. FIELD EQUIPMENT LIST
Temperature and specific conductivity meter.
Field notebook containing maps and non-stormwater flow evaluation field sheets.
Waterproof marker/pen.
Camera and film.
Spray paint.
Tape measures (both 3m and 30m).
Flashlight.
Watch (with second hand).
Glass sample containers with waterproof labels (500 ml).
Plastic sample containers with waterproof labels (1 to 2 L).
Ice boxes with ice (left in vehicle).
Backpack.
Grab water sampler (dipper on long pole).
Hand operated vacuum pump sampler for shallow flows.
Waders and walking stick.
First aid kit and pocket knife.
Self protection pepper spray.
Two-way radios for communication between field crew and van driver.
Hand held GPS (global positioning satellite) system receiver (only capable of locating
positions within about 100 to 350 feet).
44
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streams are isolated wildlife areas which tend to concentrate certain wildlife species that live in close
proximity to man (including cottonmouths, water moccasins, copperheads, and rattlesnakes), plus
contain lush growths of poison ivy or oak. The self protection pepper spray may be especially handy
in case of harassing dogs.
This equipment would supplement needed boating equipment, if boats are used. Some of this
equipment (ice coolers and ice, along with extra bottles) would be kept in the vehicle. In most cases,
the vehicle should be moved in about 1/2 mile increments. This length would typically contain up to
ten outfalls, with relatively few flowing outfalls to sample. The collected samples would therefore be
iced within about 1/2 hour of collection. It is possible that the vehicle driver could conduct critical
analyses (chlorine, pH and ammonia) while waiting. It is suggested that a three person crew rotate,
with a new driver at each new shuttle location.
Arrange for lab testing and other support equipment-Before the field crew goes into the field to
collect samples, the laboratory needs to be notified and ready to analyze the samples soon after they
are available. As shown in the next section, the laboratory testing procedures for the basic tracer
parameters are all simple and can be conducted in an unsophisticated laboratory. It may be feasible
for the field crew to conduct the sample analyses in the afternoon of the day when they are collected.
Preliminary screening of outfalls-
Location of outfalls-Outfall locations need to be transferred to field maps and the daily activities
planned. The number of outfalls that can be visited and sampled in a single day is highly dependent
on outfall accessibility and mobility along the receiving water. The initial survey requires the longest
time, after which repeated surveys require much less effort. In a small creek having shallow and slow
water with numerous road crossings, about three miles of creek can be walked (with about 40 outfalls
visited and ten outfall samples obtained) in a half-day of field activity with a crew of three people.
Most other conditions would require additional labor for the same sampling effort. In all cases, careful
planning, especially having an idea of where the outfalls are located, would greatly reduce the labor
involved.
Scheduling field surveys-It is important to schedule the field surveys during low water levels
(during low tides or low flows) because outfalls could be submerged and concealed during high water
conditions. It is also best not to conduct the field surveys during periods of high flow in the receiving
waters because of safety concerns.
Field surveys which are timed (diurnally, or seasonally) to coincide with periods with a greater
potential for non-stormwater entries, are likely to reveal more dry-weather discharges. As examples,
morning periods (or in areas of tourism, during the tourist season) usually experience the greatest
sanitary wastewater flows. Scheduling sampling during these morning hours would be most successful
in identifying sanitary wastewater contamination of the storm drainage system. Many inappropriate
industrial entries to the storm drainage system also occur on a scheduled basis, e.g., cleaning up work
areas between work shifts, or increased wastewater flows during periods of the year when the specific
industry is especially busy. Again, investigating potentially affected storm drain outfalls during these
critical periods would result in better data.
The field survey schedule will need to be flexible to avoid sampling during and immediately after
a storm event, to ensure only dry-weather flows are recorded. In most urban areas storm runoff
drainage flows will cease within 12 hours following the storm event, but this will need to be reviewed
for each watershed area. The time to flow through the upstream drainage system and any detention
and subsequent release of the storm water could extend this 12 hour period. This subject is discussed
45
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further under Section 5, Irregular Flows.
Sampling techniques-After an outfall is located, it is labeled with paint or marked by other means
and the form shown on Table 9 is completed in the field. Table 10 describes the physical observation
choices, previously discussed in Section 4. The use of field sheets and laboratory record keeping is
very important because of the large number of outfalls that will likely be surveyed in each municipality.
Table 9 is a field sheet that can be used to record the observations and analytical results for the
outfall survey. The top of the sheet includes basic outfall descriptive and weather information, a flow
rate estimate, and an indication if industrial or commercial activities are known to occur in the area.
The physical observation data section requires simple circling of the most appropriate value, or writing
in another response. Samples should be obtained of floatable and staining materials for further
laboratory microscopic analyses. If unusual vegetative conditions or damage to structures are found,
then the extent and appearance of the damage should be described. In all cases, several photographs
need to be taken of outfall conditions for each site visit. The analyses results are written on the form,
along with a short descriptions of the equipment used.
Flows are estimated and visually characterized for each outfall visit. Field temperature and specific
conductivity measurements are made in the field, and dry-weather discharge water samples are
collected for later (same day) laboratory analyses. A single water sample (1 to 2 L) is sufficient for
almost all analyses that may be conducted on the sample. This sample can be collected in a
polyethylene collapsible container. In addition, another (500 mL) sample can be collected in a glass
bottle (having a Teflon lined lid) if a toxicity screening procedure (like Microtox™) and selected organic
tracers are to be analyzed. Specific sample volume requirements need to be determined in conjunction
with the laboratory personnel. Excess samples should be placed in smaller polyethylene bottles and
frozen for potential future analyses (e.g., heavy metals and major ions).
Sample preservation-Usually icing of samples after collection and same-day laboratory analyses
is adequate. Ammonia, chlorine, and pH are susceptible to change with time and special tests may be
needed to determine the tolerable delay before laboratory analyses. As noted previously, it is not
efficient to analyze the samples in the field, especially after each sample is collected.
Field tests-The only tests recommended for field analyses are temperature and specific
conductivity. If a multi-purpose temperature/specific conductivity meter is being used for the
temperature analyses, then both can be easily determined in the field.
Record keeping, sample preservation, and analyses-As noted above, the collected water samples
need to be analyzed soon after collection. A central laboratory is much more effective than trying to
analyze each sample in the field as it is collected. Section 4 presents the recommended laboratory
procedures.
Data analyses-
Identification of contaminated outfalls-Section 6 describes several methods to identify the likely
components in each flowing outfall. This information is then used to identify the contaminated
dry-weather flows.
Isolation and correction of contaminating flow sources-After the problem outfalls are identified,
drainage system surveys are used to find the sources of the contaminating flows. These procedures
are briefly discussed later in this User's Guide.
46
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TABLE 9. SAMPLE EVALUATION SHEET
Outfall # Photograph # Date:
Location:
Weather: air temp.: °C rain: Y N sunny cloudy
Outfall flow rate estimate: L/sec
Known industrial or commercial uses in drainage area? Y N
describe:
PHYSICAL OBSERVATIONS:
Odor: none sewage sulfide oil gas rancid-sour other:.
Color: none yellow brown green red gray other:
Turbidity: none cloudy opaque
Floatables: none petroleum sheen sewage other: (collect sample)
Deposits/stains: none sediment oily describe: (collect sample)
Vegetation conditions: normal excessive growth inhibited growth
extent:
Damage to outfall structures:
identify structure:
damage: none / concrete cracking / concrete spelling / peeling paint / metal
corrosion
other damage:
extent:
ANALYSES: EQUIPMENT USED:
Specific conductivity: /vS/cm
Temperature: °C
Fluoride: mg/L
Hardness: mg/L
Surfactants: mg/L
Florescence: % of scale
Potassium: mg/L
Ammonia: mg/L as N
pH:
47
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TABLE 10. INTERPRETATIONS OF PHYSICAL OBSERVATION PARAMETERS
AND LIKELY ASSOCIATED FLOW SOURCES
Odor - Most strong odors, especially gasoline, oils, and solvents, are likely associated with high
responses to the toxicity screening test. Typical obvious odors include: gasoline, oil, sanitary
wastewater, industrial chemicals, decomposing organic wastes, etc.
sewage: smell associated with stale sanitary wastewater, especially in pools near outfall.
sulfide ("rotten eggs"): industries, e.g., meat packers, canneries, dairies, etc; and
stale sanitary wastewater.
oil and gas: petroleum refineries or facilities associated with vehicle maintenance and
operation or petroleum product storage.
rancid-sour: food preparation facilities (restaurants, hotels, etc.).
Color - Important indicator of inappropriate industrial sources. Industrial dry-weather discharges
may be of various colors, but dark colors, such as brown, gray, or black, are most common.
yellow: chemical, textile, and tanning plants.
brown: meat packers, printing plants, metal works, stone and concrete works, fertilizer
application, and petroleum refining facilities.
green: chemical plants, and textile facilities.
red: meat packers.
gray: dairies.
Turbidity - Often affected by the degree of gross contamination. Dry-weather industrial flows
with moderate turbidity can be cloudy, while highly turbid flows can be opaque. High turbidity is
often a characteristic of undiluted dry-weather industrial discharges.
cloudy: sanitary wastewater, concrete or stone operations, fertilizer facilities, and
automotive dealers.
opaque: food processors, lumber mills, metal operations, and pigment plants.
Floatable Matter - A contaminated flow may contain floating solids or liquids directly related to
industrial or sanitary wastewater pollution. Floatables of industrial origin may include animal fats,
spoiled food, oils, solvents, sawdust, foams, packing materials, or fuel.
oil sheen: petroleum refineries or storage facilities and vehicle service facilities.
sewage: sanitary wastewater.
(continued)
48
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TABLE 10. (continued)
Deposits and Stains - Refer to any type of coating near the outfall and are usually of a dark
color. Deposits and stains often will contain fragments of floatable substances. These situations
are illustrated by the grayish-black deposits that contain fragments of animal flesh and hair
which often are produced by leather tanneries, or the white crystalline powder which commonly
coats outfalls due to nitrogenous fertilizer wastes.
sediment: construction site erosion.
oily: petroleum refineries or storage facilities and vehicle service facilities.
Vegetation - Vegetation surrounding an outfall may show the effects of industrial pollutants.
Decaying organic materials coming from various food product wastes would cause an increase in
plant life, while the discharge of chemical dyes and inorganic pigments from textile mills could
noticeably decrease vegetation. It is important not to confuse the adverse scouring effects of
high stormwater flows on vegetation with highly toxic dry-weather intermittent flows.
excessive growth: food product facilities.
inhibited growth: high stormwater flows, beverage facilities, printing plants, metal product
facilities, drug manufacturing, petroleum facilities, vehicle service facilities
and automobile dealers.
Damage to Outfall Structures - Another readily visible indication of industrial contamination.
Cracking, deterioration, and spalling of concrete or peeling of surface paint, occurring at an
outfall are usually caused by severely contaminated discharges, usually of industrial origin. These
contaminants are usually very acidic or basic in nature. Primary metal industries have a strong
potential for causing outfall structural damage because their batch dumps are highly acidic. Poor
construction, hydraulic scour, and old age may also adversely affect the condition of the outfall
structure which are not indications of upstream contaminating entries.
concrete cracking: industrial flows
concrete spalling: industrial flows
peeling paint: industrial flows
metal corrosion: industrial flows
49
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Irregular Flows
Irregular flows pose a special problem during the field surveys. Outfall apparent "dry-weather"
flows can be intermittent in nature, only flowing soon after rains and then remaining dry, or may flow
when inappropriate water sources enter the storm drainage system. If irregular flows are associated
with rains, outfall surveys should be postponed until sufficient time has lapsed since the last major rain.
For most urban areas, storm runoff drainage ends several hours (but usually less than 12) after the rain
stops. Extended, but decreasing flows, after rains could be associated with high groundwater or
percolating rain water infiltrating into the drainage system. In this case, most outfall surveys should
be further delayed. However, some pollutant sources may be associated with these after storm flows,
especially contaminated groundwaters (septic tank problems, leaky underground storage tanks, etc.).
Therefore, it may be important to sample these flows, especially if these contaminant sources
potentially exist.
Basic field indicators, such as the presence of residual stains or deposits, oil sheens, coarse solids,
floatables, color, odors, etc., in the absence of a flow, indicate the likelihood of intermittent
dry-weather flows. These observations will be enhanced by installing simple "tell-tale" devices, e.g.,
a terry-cloth (strain the discharge) or small caulk dam in the drain. Outfalls exhibiting these signs of
non-continuous discharges should be visited several times to increase the probability of observing and
sampling a dry-weather discharge. Analyzing pooled water immediately below the outfall or collected
between visits in small, constructed dams within the storm drain can greatly assist in identifying
non-continuous discharges. Coarse solids and/or floatables can be captured through the erection of
coarse screens and/or booms at a manhole site, the mouth of the outfall, or in the receiving stream.
It may be necessary to visit suspect outfalls frequently. However, it is virtually impossible to capture
an isolated short-term intermittent flow (e.g., from the illegal dumping of wastes into the storm
drainage system) from outfall visits.
Simple outfall area characteristics, noted above, are the most reliable indicator of a potential
intermittent source at an outfall. In addition to using a dam, or other indicator device (e.g., a small
screen to capture particulate debris), it may be desirable to use an automatic water sampler at
especially important outfalls. Automatic samplers would be unreasonable and expensive to use at many
outfalls in an area and test locations would need to be carefully selected. A sampler located in a
close-by manhole and set to sample every fifteen minutes (with four samples placed in each bottle) can
monitor for intermittent flows for a period of 24 hours. Automatic samplers can also be used to
characterize variable quality flows. This information can be valuable in identifying possible discharge
sources.
50
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SECTION 6
DATA ANALYSIS TO IDENTIFY PROBLEM OUTFALLS
AND FLOW COMPONENTS
The field screening surveys are to be used as an initial effort to identify the outfalls needing more
detailed drainage area investigations which would identify specific pollutant sources and control
options. These field screening surveys, discussed in Sections 4 and 5, include physical, chemical, and
relative toxicity evaluations of outfall and/or discharge conditions.
The purpose of the procedures presented in this User's Guide is to separate storm drain outfalls
into general categories (with a known level of confidence) and to identify which outfalls (and drainage
areas) need further analyses and investigations. The categories used in this Guide are outfalls affected
by non-stormwater entries from: (1) pathogenic or toxic pollutant sources, (2) nuisance and aquatic
life threatening pollutant sources, and (3) unpolluted water sources.
The pathogenic and toxic pollutant source category should be considered the most severe because
it could cause disease upon water contact or consumption and cause significant impacts on receiving
water organisms. They may also cause significant water treatment problems for downstream
consumers, especially if they contain soluble metal and organic toxicants. These pollutants may
originate from sanitary, commercial, and industrial wastewater non-stormwater entries. Other important
residential area activities that may also be considered in this most critical category (in addition to
sanitary wastewater) include inappropriate household toxicant disposal, automobile engine de-greasing,
vehicle accident clean-up, and irrigation runoff from landscaped areas excessively treated with
chemicals (fertilizers and pesticides).
Nuisance and aquatic life threatening pollutant sources can originate from residential areas and
can include laundry wastewater, landscaped area irrigation runoff, automobile washing, construction
site dewatering, and washing of concrete mixing trucks. These pollutants can cause excessive algal
growths, depressed dissolved oxygen concentrations, tastes and odors in downstream water supplies,
offensive coarse solids and floatables, and highly colored, turbid or odorous waters.
Relatively clean or unpolluted water discharged through stormwater outfalls can originate from
natural springs feeding urban creeks that have been converted to storm drains, infiltrating groundwater,
and infiltrating potable water from water line leaks.
A method must be used to compare data from individual outfall dry-weather samples to the library
of dry-weather source flow data to identify which outfalls belong in which general category of
contamination listed above. This comparison should result, at the very least, in the identification of the
outfalls that are considered as major pollutant sources for immediate remediation. The degree of detail
which can be identified for an outfall will depend on the extent of the local data collected to describe
the likely source flows.
The procedures that can be used to identify outfall flow components may begin with simple
yes/no checks. For example, if no surfactants are measured in an outfall sample, then sanitary
wastewater is unlikely to be a contributor to the outfall flow. If no fluoride is measured, then fluoride
51
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treated potable water sources could be ruled out as contributors. The probability that remaining
contenders are present alone or in a mixture may be determined using a combination of matrix algebra
and the selecting of random values from within specified ranges using a Monte Carlo process and many
iterations.
Most contaminated outfalls will require correction before the receiving water quality recovers to
acceptable levels. However, ranking the outfalls allows the most serious outfalls to be recognized and
enables corrective action to be initially concentrated in the most cost-effective manner. In some of the
case studies investigated, correcting only problems at the most critical outfalls resulted in insufficient
receiving water quality improvements. It may be important to eventually correct all non-stormwater
discharge problems throughout a city, not just the most severe problems. The field screening program
should therefore be considered as an initial effort that needs to be followed-up with more detailed
watershed drainage surveys in most of the areas having observed dry-weather flows. The follow-up
watershed surveys are to identify and correct inappropriate pollutant entries into storm drainage
systems, as discussed in Sections 7 and 8.
The identification of flow components of the dry-weather storm drain flow can be used to
determine which outfalls have the greatest pollution potential. As an example, if an outfall contains
sanitary wastewater, it could be a significant source of pathogenic microorganisms. Similarly, if an
outfall contains plating bath water from a metal finisher, it could be a significant source of toxicants.
These outfalls would be grouped into the most critical category of toxicants/pathogens. If an outfall
contains washwaters from a commercial laundry or car wash, the wastewater could be a major source
of nutrients and foaming material. These outfalls would be grouped into an intermediate category of
nuisance and aquatic life threatening. Finally, if an outfall only contains unpolluted groundwater or
water from leaky potable water mains, the water would be non-polluting and the outfall would be
grouped into the last category of unpolluted water sources.
The five methods of data analyses presented in the following discussions present a hierarchy of
methods, ranging from relatively simple reviews of the outfall characteristics to more sophisticated
methods requiring computer modeling for evaluation. It is suggested that as many of the procedures
be used as possible in evaluating the data, as each method provides some unique insights into the
problems. Pitt and Lalor (publication pending) contains a more through discussion of these analysis
procedures, including evaluation of the Birmingham, Alabama, demonstration project data.
INDICATORS OF CONTAMINATION
Indicators of contamination (negative indicators) are clearly apparent visual or physical parameters
indicating obvious problems and are readily observable at the outfall during the field screening
activities. These observations are very important during the field survey because they are the simplest
method of identifying grossly contaminated dry-weather outfall flows. The direct examination of outfall
characteristics for unusual conditions of flow, odor, color, turbidity, floatables, deposits/stains,
vegetation conditions, and damage to drainage structures is therefore an important part of these
investigations. Table 10 in Section 5 presented a summary of these indicators, along with narratives
of the descriptors to be selected in the field.
This method does not allow quantifiable estimates of the flow components and if used alone will
likely result in many incorrect determinations (missing outfalls that have important levels of
contamination). These simple characteristics, discussed further below, are most useful for identifying
gross contamination. Only the most significant outfalls and drainage areas would therefore be
recognized from this method. The other methods, requiring chemical determinations, can be used to
52
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quantify the flow contributions and to identify the less obviously contaminated outfalls.
Indications of intermittent flows (especially stains or damage to the structure of the outfall) could
indicate serious illegal toxic pollutant entries into the storm drainage system that will be very difficult
to detect and correct. Highly irregular dry-weather outfall flow rates or chemical characteristics could
indicate industrial or commercial inappropriate entries into the storm drain system.
During the demonstration phase of this research project (Pitt and Lalor publication pending), odors
and high turbidity were found to be the most useful physical indicators of severely contaminated outfall
flows. High turbidity correlated well with high levels of surfactants and toxicity. Noticeable odors also
correlated well with elevated toxicity. Color was not a very useful indicator of gross contamination and
elevated toxicity, unless the color exceed 65 HACH color units.
Gross industrial wastewater contamination may be indicated by the presence and nature of
floatable material and deposits near the outfall. Table 11 summarizes possible chemical and physical
characteristics of non-stormwater discharges which could come from various industries. The properties
considered are pH, total dissolved solids, odor, color, turbidity, floatable materials, vegetation, and
damage to outfall structure. The descriptions in each of these categories contain the most likely
conditions for a non-stormwater discharge coming from a particular industry. It should be noted that
outfalls are likely to be affected by several industrial sources simultaneously, especially if draining
industrial parks. The initial watershed analysis, discussed previously, which needs to describe the
industrial and commercial facilities that are operating in each outfall's watershed, will be of great
assistance in identifying which industries may be contributing dry-weather entries into the storm
drainage system.
SIMPLE CHECKLIST FOR MAJOR FLOW COMPONENT IDENTIFICATION
Figure 10 is a flow chart describing the analysis strategy to identify the major non-stormwater
discharge sources in residential areas. The first indicator is the presence or absence of flow. If no
dry-weather flow exists at an outfall, then indications of intermittent flows must be investigated.
Specifically, stains, deposits, odors, unusual stream-side vegetation conditions, and damage to outfall
structures can all indicate intermittent non-stormwater flows. However, frequent visits to outfalls over
long time periods are needed to confirm that only stormwater flows occur. The other points on the
flow chart (Figure 10) serve to indicate if major contaminating sources are present, or if the water is
uncontaminated water. The other methods discussed later are needed to quantify the component
contributions.
Treated Potable Water
A number of tracer parameters may be useful for distinguishing treated potable water from natural
waters:
• Major ions or other chemical/physical characteristics of the flow components can vary
substantially depending upon whether the water supply sources are groundwater or surface
water, and whether the sources are treated or not. Specific conductance may also serve as a
rough indicator of the major water source.
• Fluoride can often be used to separate treated potable water from untreated water sources.
Untreated water sources can include local springs, groundwater, regional surface flows or
non-potable industrial waters. If the treated water has no fluoride added, or if the natural water
has fluoride concentrations close to potable water fluoride concentrations, then fluoride may
53
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TABLE 11. CHEMICAL AND PHYSICAL PROPERTIES OF INDUSTRIAL NON-STORMWATER ENTRIES INTO STORM DRAINAGE SYSTEMS
Industrial Categories
Major Classifications
SIC Group Numbers
Odor
Color
Turbidity
Floatables
Debris &
Stains
Damage to
Outfall
Structures
Vegetation
pH
Total
Dissolved
Solids
Primary Industries
20
201
202
203
204
205
206
207
208
21
22
23
Food and Kindred Products
Meat Products
Dairy Products
Canned & Preserved
Fruits & Vegetables
Grain Mill Products
Bakery Products
Sugar and
Confectionery Products
Fats and Oils
Beverages
Tobacco Manufactures
Textile Mill Products
Apparel and Other Finished
Products
Spoiled Meats
Rotten Eggs and Flesh
Spoiled Milk
Rancid Butter
Decaying Products
Compost Pile
Slightly Sweet & Musty
Grainy
Sweet and or Spoiled
NA
Spoiled Meats,
Lard or Grease
Rat Soda, Beer or
Wine, Alcohol, Yeast
Dried Tobacco,
Cigars, Cigarettes
Wet Burlap, Bleach,
Soap, Detergents
NA
Brown to
Reddish Brown
Gray to White
Various
Brown to
Reddish Brown
Brown to Black
NA
Brown to Black
Various
Brown to Black
Various
Various
High
High
High
High
High
Low
High
Moderate
Low
High
Low
Animal Fats, Byproducts
Pieces of Processed
Meats
Animal FatB
Spoiled Milk Products
Vegetable Waxes,
Seeds,
Skins, Cores, Leaves
Grain Hulls and Skins
Straw & Plant Fragments
Cooking Oils, Lard,
Flour, Sugar
Low Potential
Animal Fats, Lard
Grains & Hops, Broken
Glass, Discarded
Canning Items
Tobacco Stems &
Leaves
Papers and Fillers
Fibers, Oils, Grease
Some Fabric Particles
Brown to
Black
Gray to
Light Brown
Brown
Light Brown
Gray to Light
Brown
White Crystals
Gray to Light
Brown
Light Brown
Brown
Gray to Black
NA
High
High
Low
Low
Low
Low
Low
High
Low
Low
Low
Flourish
Flourish
Normal
Normal
Normal
Normal
Normal
Inhibited
Normal
Inhibited
Normal
Normal
Acidic
Wide
Range
Normal
Normal
Normal
Normal
Wide
Range
Normal
Basic
Normal
High
High
High
High
High
High
High
High
Low
High
Low
Material Manufacture
24
25
26
27
31
33
34
32
Lumber & Wood Products
Furniture & Fixtures
Paper & Allied Products
Printing, Publishing, and
Allied Industries
Leather & Leather Products
Primary Metal Industries
Fabricated Metal Products
Stone, Clay, Glass, and
Concrete Products
NA
Various
Bleach, Various Chemicals
Ink, Solvents
Leather, Bleach
Rotten Eggs or Flesh
Various
Detergents,
Rotten Eggs
Wet Clay, Mud
Detergents
NA
Various
Various
Brown to Black
Various
Brown to Black
Brown to Black
Brown to
Reddish-Brown
Low
Low
Moderate
Moderate
High
Moderate
High
Moderate
Some Sawdust
Some Sawdust, Solvents
Sawdust, Pulp Paper
Waxas, Oils
Paper Dust, Solvents
Animal Flash & Hair
Oils & Grease
Ore, Coke, Limestone
Millscale, Oils
Dirt, Grease. Oils
Sand, Clay Dust
Glass Particles
Dust from Clay or Stone
Light Brown
Light Brown
Light Brown
Gray to
Light Brown
Gray to Black
Salt Crystals
Gray to Black
Gray to Black
Gray to
Light Brown
Low
Low
Low
Low
High
High
Low
Low
Normal
Normal
Normal
Inhibited
Highly
Inhibited
Inhibited
Inhibited
Normal
Normal
Normal
Wide
Range
Normal
Wide
Range
Acidic
Wide
Range
Basic
(continued)
Low
Low
Low
High
High
High
High
Low
01
-------
TABLE 11. (continued)
en
en
Industrial Categories
Major Classifications
SIC Group Numbers
Odor
Color
Turbidity
Floatables
Debris &
Stains
Damage to
Outfall
Structures Vegetation
PH
Total
Dissolved
Solids
Chemical Manufacture
28
281
2
281
6
282
283
284
285
286
286
1
286
5
287
287
3
287
4
287
6
29
291
30
Chemicals & Allied Products
Alkalis and Chlorine
Inorganic Pigments
Plastic Materials and
Synthetics
Drugs
Soap, Detergents, &
Cleaning Preparations
Paints, Varnishes, Lacquers,
Enamels and Allied Products
(SB-Solvent Base)
Industrial Organic Chemicals
Gum and Wood Chemicals
Cyclic Crude), & Cyclic
Intermediates, Dyes, &
Organic Pigments
Agricultural Chemicals
Nitrogenous Fertilizers
Ptiosphatlc Fertilizers
Fertilizers, Mixing Only
Petroleux Refining and
Related Industries
Petroleum Refining
Rubber & Miscellaneous
Plastic Products
Strong Halogen or
Chlorine
Pungent, Burning
NA
Pungent, Fishy
NA
Sweet or Flowery
Latex- Ammonia
SB-Dependent upon Solvent
(Paint Thinner, Mineral Spirits)
Pine Spirits
Sweet Organic Smell
NA
Pungent Sweet
Various
Rotten Eggs
Kerosene, Gasoline
Rotten Eggs
Chlorine, Peroxide
Alkalis - NA
Chlorine - Yellow
to Green
Various
Various
Various
Various
Various
Brown to Black
NA
NA
Milky White
Brown to Black
Brown to Black
Brown to Black
Moderate
High
High
High
High
High
High
Low
Low
High
High
High
Moderate
Glass Particles
Dust from Clay or Stone
Low Potential
Plastic Fragments,
Pieces of Synthetic
Products
Gelatin Byproducts for
Capsulatlng Drugs
Oils, Grease
Latex - NA
SB-All Solvents
Rosins and Pine Tars
Translucent Sheen
NA
NA
Pelletlzed Fertilizers
Any Crude or Processed
Fuel
Shredded Rubber
Pieces of Fabric or Metal
Gray to
Light Brown
Various
Various
Various
Gray to Black
Gray to Black
Gray to Black
NA
White
Crystalline
Powder
White
Emorphous
Powder
Brown
Emorphous
Powder
Black
Salt Crystals
Gray to Black
Highly Normal
Inhibited
Low Highly
Inhibited
Low Inhibited
Low Highly
Inhibited
Low Inhibited
Low Inhibited
Low Inhibited
Low Highly
Inhibited
High Inhibited
High Inhibited
Low Normal
Low Inhibited
Low Inhibited
Basic
Wide
Range
Wide
Range
Normal
Basic
Latex-
Basic
SB-
Normal
Acidic
Normal
Acidic
Acidic
Normal
Wide
Range
Wide
Range
Low
High
High
High
High
High
High
Low
High
High
High
High
High
(continued)
-------
TABLE 11. (continued)
Industrial Categories
Major Classifications
SIC Group Numbers Odor
Transportation & Construction
1 5 Building Construction Various
1 6 Haavy Construction Various
Re rail
52 Building Materials, NA
Hardware, Garden Supply,
and
Mobile Home Dealers
53 Gen. Merchandise Stores NA
54 Food Stores Spoiled Produce
Rancid, Sour
65 Automotive Dealers & Oil or Gasoline
Gasoline Service Stations
56 Apparel & Accessory Stores NA
57 Home Furniture, Furnishings, NA
& Equipment Stores
58 Eating & Drinking Places Spoiled Foods
Oil & Grease
Coal Steam Electric Power NA
Nuclear steam Electric Power NA
Debris &
Color Turbldrty Floatable* Stains
Brown to Black High Oils, Grease, Fuels Gray to Black
Brown to Black High Oils, Grease, Fuels Gray to Black
Diluted Asphalt or
Cement
Brown to Black Low Some Seeds, Plant Parts, Light Brown
Dirt, Sawdust, or Oil
NA NA NA NA
Various Low Fragments of Food Light Brown
Decaying Produce
Brown to Black Moderate Oil or Gasoline Brown
NA Low NA NA
NA Low NA NA
Brown to Black Low Spoiled or Leftover Brown
Foods
Brown to Black High Coal Dust Black
Emorphous
Powder
Light Brown Low Oils, Lubricants Light Brown
Damage to Total
Outfall Dissolved
Structures Vegetation pH Solids
Low Normal Normal High
Low Normal Normal High
•
Low Normal Normal Low
Low Normal Normal Low
Low Flourish Normal Low
Low Inhibited Normal Low
Low Normal Normal Low
Low Normal Normal Low
Low Normal Normal Low
Low Normal Slightl Low
y
Acidic
Low Normal Normal Low
Ul
en
-------
(Jl
-vl
igh potassiunv^ Yes
or ammonia?
Untrealod natural
water.
Probably not a
contaminated
Tion-stormwater source.
\ \ Likely washwater \
A \ •»«* \
Figure 10. Flow chart to identify residential area non-stormwater flow sources.
-------
not be an appropriate indicator.
• Hardness can also be used as an indicator if the potable water source and the baseflow are
from different water sources. An example would be if the baseflow is from hard groundwater,
and the potable water is from softer surface supplies.
• If the concentration of chlorine is high, then a major leak of disinfected potable water is likely
to be close to the outfall. Because of the rapid dissipation of chlorine in water (especially if
some organic contamination is present) it is not a good parameter for quantifying the amount
of treated potable water observed at the outfall.
Water from potable water supplies (that test positive for fluorides, or other suitable tracers) can be
relatively uncontaminated, e.g., potable waterline leakage or irrigation runoff, or heavily contaminated,
e.g., sanitary wastewater.
Sanitary Wastewaters
In areas containing no industrial or commercial sources, sanitary wastewater is probably the most
severe dry-weather contaminating source of storm drain flows. The following parameters can be used
for quantifying the sanitary wastewater components of the treated potable water portion:
• Surfactant analyses may be useful in determining the presence of sanitary wastewaters.
However, surfactants present in water originating from potable water sources could indicate
sanitary wastewaters, laundry wastewaters, car washing wastewater, or any other waters
containing surfactants. If surfactants (or fluorescence) are not present, then the potable water
could be relatively uncontaminated (potable waterline leaks or irrigation runoff).
• The presence of fabric whiteners (as measured by fluorescence using a fluorometer in the
laboratory or in the field) can also be used in distinguishing laundry and sanitary wastewaters.
• Sanitary wastewaters often exhibit predictable trends during the day in flow and quality. In
order to maximize the ability to detect direct sanitary wastewater connections into the storm
drainage system, it would be best to survey the outfalls during periods of highest sanitary
wastewater flows (mid to late morning hours).
• The ratio of surfactants to ammonio or potassium concentrations may be an effective indicator
of the presence of sanitary wastewaters or septic tank effluents. If the surfactant
concentrations are high, but the ammonia and potassium concentrations are low, then the
contaminated source may be laundry wastewaters. Conversely, if ammonia, potassium, and
surfactant concentrations are all high, then sanitary wastewater is the likely source. Some
researchers have reported low surfactants in septic tank effluents. Therefore, if surfactants are
low, but potassium and ammonia are both high, septic tank effluent may be present. However,
Pitt and Lalor (publication pending) found high surfactant concentrations in septic tank effluent
during the Birmingham, Alabama demonstration project. This further stresses the need to
obtain local site specific characterization data for potential contaminating sources.
• Obviously, odor and other physical characteristics, e.g., turbidity, coarse and floating "tell-tale"
solids, foaming, color, and temperature would also be very useful in distinguishing sanitary
wastewater from wash water or laundry wastewater sources. However, these indicators may
not be very obvious for small levels of sanitary wastewater contamination.
58
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FLOW-WEIGHTED MIXING CALCULATIONS
Before any flow-weighted mixing calculations can be made, the characteristics of potential
contaminating sources must be identified. Table 12 summarizes hypothetical concentration medians
and COVs for tracers that have been recommended to be used in the investigation of non-stormwater
entries into storm drainage systems in residential areas. This method is an extension of the
checklistmethod described above and attempts to quantify the likely source flow components at the
outfall during dry weather.
Two general groupings of flow sources can usually be recognized for each of these tracers, a high
concentration group and a low concentration group. Table 13 describes these groups, along with their
composite tracer concentration ranges, variations, and medians. The outfall flow can be split between
the two general groupings by simple algebra. This method can result in substantial errors if the tracer
concentrations cannot be separated into distinct source groupings. The next two methods, using matrix
algebra to solve simultaneous equations, do not require this simplifying assumption.
Example Calculations
The drainage area for a sampled outfall had no septic tanks or commercial and industrial land uses.
The likely flow sources had source flow characteristics as described in Table 12. The required detection
limits and precision for outfall characterizations must be determined, as previously described, for these
source flow characteristics and desired study results. This outfall had the following tracer
concentrations in a dry-weather sample:
Fluoride: 0.6 mg/L
Hardness: 200 mg/L as CaC03
Surfactants: 0.6 mg/L as MBAS
Potassium: 3 mg/L
Ammonia: 3 mg/L
The water had a slight septic odor, with some floatables of apparent sanitary wastewater origin. In
addition, dry-weather flow was observed at the outfall during all visits.
It is apparent that this outfall has a direct connection(s) of raw sanitary wastewater. This method
can determine the approximate mix of sanitary wastewater in the outfall flow and identify the other
flow components. Table 14 summarizes the example calculations used in this analysis. The list below
indicates the approximate expected source components at this outfall from this analysis:
Raw sanitary wastewater: 5%
Laundry wastewater: 5%
Groundwater: 70%
Remainder (most likely potable water, but may also contain irrigation water): 20%
This analysis did not consider the potential ranges in observed tracer concentrations and the
59
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TABLE 12. ASSUMED SOURCE FLOW QUALITY
(All Cone, in mg/L)
Source
Surface median
Waters COV
Ground- median
waters COV
Septic Tank median
Effluent COV
Raw median
Sanitary COV
Wastewater
Laundry median
Wastewater COV
Irrigation median
Water COV
Fluoride
0.14
0.23
0.29
0.23
1.3
0.14
1.3
0.14
1.3
0.14
1.3
0.14
Hardness
(as Ca Co3)
39
0.20
250
0.14
39
0.20
39
0.20
39
0.20
39
0.20
Surfactants
(as MBAS)
0.35
0.13
0.05
0.13
0.05
0.13
4.6
2.2
4.6
2.2
0.35
0.13
Potassium
0.72
0.23
1.7
0.40
21
0.91
21
0.91
5.3
0.57
0.72
0.23
Ammonia
(N as NH3)
0.76
1.1
0.22
0.63
47
1.5
22
0.63
0.31
0.91
0.38
1.1
60
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TABLE 13. CHARACTERISTICS OF SOURCE GROUPINGS
Fluorides
surface & groundwaters
overall range:
COV:
median:
Concentration ratio
of medians:
0.1-0.4 mg/L
0.54
0.20 mg/L
6.5
all other categories
1-1.5 mg/L
0.14
1.3 mg/L
Hardness
groundwaters
overall range:
COV:
median:
Concentration ratio
of medians:
200-300 mg/L
0.14
250 mg/L
6.4
all other categories
30-50 mg/L
0.20
39 mg/L
Surfactants
raw sanitary wastewater
& laundry wastewater
overall range:
COV:
median:
Concentration ratio
of medians:
0.2-100 mg/L
2.2
4.6 mg/L
33
all other categories
0.04-0.4 mg/L
0.83
0.14 mg/L
Potassium
septic tank effluent &
raw sanitary wastewater
overall range:
COV:
median:
Concentration ratio
of medians:
10-100 mg/L
0.91
21 mg/L
9.1
all other categories
0.5-11 mg/L
1.2
2.3 mg/L
Ammonia
septic tank effluent &
raw sanitary wastewater
overall range:
COV:
median:
Concentration ratio
of medians:
6-380 mg/L
1.5
47 mg/L
107
all other categories
0.1-3 mg/L
1.3
0.44 mg/L
61
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TABLE 14. MIXTURE CALCULATIONS TO IDENTIFY SOURCE FLOW COMPONENTS
Fluorides: 0.6 mg/L observed at outfall
x = fraction of surface & groundwater
with concentration of 0.2 mg/L
y = fraction of treated water (all other sources)
with concentration of 1.3 mg/L
(x & y fraction concentrations taken from Table 13)
x(0.2) + yd.3) = 0.6 (for a unit volume of outfall water)
x + y = 1 (for no other sources of fluorides)
x = 0.63 (surface & groundwater)
y = 0.37 (all other sources)
Hardness 200 mg/L as CaCO3 observed at outfall
x = fraction of groundwater
with concentration of 250 mg/L as CaC03
y = fraction of all other sources
with concentration of 39 mg/L as CaC03
x(250) + y(39) = 200
x = 0.76 (groundwater)
y = 0.24 (all other sources)
From Fluorides and Hardness Data:
Groundwater & Surface water = 0.63
Groundwater alone = 0.76
Surface water alone = -0.13-»0
Therefore:
Groundwater fraction = (0.63 + 0.761/2 = 0.7
Surfactants: 0.6 mg/L as MBAS observed at outfall
x = fraction of sanitary & laundry wastewater
with a concentration of 4.6 mg/L as MBAS
y = fraction of all other sources
with a concentration of 0.14 mg/L as MBAS
x(4.6) + y(0.14) = 0.6
x = 0.10 (sanitary & laundry wastewater)
y = 0.90 (all other sources)
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TABLE 14. (continued)
Potassium: 3 mg/L observed at outfall
x = fraction of sanitary wastewater
with a concentration of 21 mg/L
y = fraction of all other sources
with a concentration of 2.3 mg/L
x(21) + y(2.3) = 3
x = 0.04 (sanitary wastewater)
y = 0.96 (all other sources)
Ammonia: 3 mg/L observed at outfall
x = fraction of sanitary wastewater
with a concentration of 47 mg/L
y = fraction of all other sources
with a concentration of 0.44 mg/L
x(47) + y(0.44) = 3
x = 0.06 (sanitary wastewater)
y = 0.94 (all other sources)
From Surfactants, Potassium, and Ammonia Data:
Sanitary wastewater = (0.04 + 0.06)/2 = 0.05
Laundry wastewater = 0.1 - 0.05 = 0.05
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resulting errors that may be associated with the above mixture portions. The following procedures are
better suited for error analyses.
MATRIX ALGEBRA SOLUTION OF SIMULTANEOUS EQUATIONS
It is possible to estimate the outfall source flow components using a set of simultaneous
equations. The number of unknowns should equal the number of equations available, resulting in a
square matrix. If there are eleven likely source categories, then there should be eleven tracer
parameters used. If there are only four possible sources, then only four tracer parameters should be
used.
Further statistical analyses may therefore be needed to rank the usefulness of the tracers for
distinguishing different flow sources. Pitt and Lalor (publication pending) show examples of how cluster
and principal component analyses can be used to identify redundancy and other problems in the data
library. As an example, chlorine is not useful for these analyses because the concentration variability
within many source categories is high (it is also not a conservative parameter). Chlorine may still be
a useful parameter, but only to identify possible large potable waterline leaks. It cannot be used to
quantify the flow components. Another parameter having problems for most situations is pH. The
variation of pH between sources is very low (they are all very similar). However, pH may still be useful
to identify industrial wastewater problems, but it cannot be used to quantify flow components. pH is
also not linearly affected by mass balance mixtures (a solution of 50 percent/50 percent of two
components would not result in a pH value that is the average of the two individual pH values).
These equations are structured on a mass balance basis, like the previous procedure, but they can
be used to distinguish all source categories simultaneously. A simplified example is shown in the
following discussion considering just four possible flow components and four tracer parameters (P1,
P2, P3, P4). This would result in the following set of equations for each outfall sample:
tracer
parameter:
possible sources:
2 3
outfall
quality
P1: (A1MC11) + (A2)(C21) + (A3HC31) + (A4)(C41) = ml
P2: (A1)(C12) + (A2)(C22) + (A3HC32) + (A4)(C42) = m2
P3: (A1MC13) + (A2)(C23) + (A3HC33) + (A4)(C43) = m3
P4: (A1HC14) + (A2)(C24) + (A3)(C34) + (A4)(C44) = m4
A1 through A4 represent the fraction of flow contributed from each possible flow source. The "C"
terms represent concentrations from the source flow library for each particular parameter (P)
within each flow source(1-4). The "m" terms represent the concentration of P actually measured
in the outfall sample.
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The following is an example for an outfall dry-weather sample:
possible sources:
tracer potable ground sanitary laundry outfall
parameter: water water wastewater wastewater quality
fluoride: (A1H0.97 mg/L) + (A2M0.031 mg/L) + (A3H0.77 mg/L) + (A4)(33 mg/L) = 3.8 mg/L
hardness: (A1)(49mg/L) + (A2)(240 mg/L) + (A3)(140 mg/L) + (A4)(14 mg/L) =126 mg/L
surfactants:(A1)(0 mg/L) + (A2)(0 mg/L) + (A3M1.5 mg/L) + (A4H27 mg/L) = 3.0 mg/L
potassium: (A1)(1.6 mg/L) + (A2K0.73 mg/L) + (A3M6.0 mg/L) + (A4)(3.5 mg/L) = 2.2 mg/L
This simple 4x4 matrix can be solved using available scientific calculators or math programs for
personal computers, or by hand. For this example, the following are the approximate flow
components (rounded to the nearest 5 percent):
• treated potable water (A1): 30%
• groundwater (A2): 35%
• sanitary wastewater (A3): 20%
• laundry wastewater (A4): 10%
These component contributions do not all add up to 100 percent. A number of errors, especially
variations in source area characteristics and other sources present that were not considered, tend to
result in component sums that are not 100 percent. The following method is similar, but considers
uncertainty in source area characteristics and results in a range of likely component contributions.
MATRIX ALGEBRA CONSIDERING PROBABILITY DISTRIBUTIONS OF LIBRARY DATA
A stochastic version of the above procedure enables the variation in the library values to be
considered. The matrix is set up in the same way, but instead of using a single value representing the
parameter concentration for each likely source flow, a Monte Carlo simulation is used to randomly
select values. A large number of analyses (from a few hundred to many thousands) are conducted and
the percentage contributions for each component source are presented as a probability distribution
instead of a single value.
It is therefore necessary to describe the distribution of source flow characteristics. In most cases,
the tracer parameters can be represented using log-normal distributions. Some parameters, however,
are adequately described with normal distributions. Again, local source flow monitoring is necessary
to obtain this information. Pitt and Lalor (publication pending) contains examples using this method,
including the code for the necessary computer program.
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SECTION 7
WATERSHED SURVEYS TO CONFIRM AND LOCATE INAPPROPRIATE POLLUTANT
ENTRIES TO THE STORM DRAINAGE SYSTEM
After initial outfall surveys have indicated the presence of contamination, further detailed analyses
are needed to identify and locate the specific contaminant source(s) (e.g., residential, commercial,
and/or industrial) in the drainage area. For source identification and location, upstream survey
techniques should be used in conjunction with an in-depth watershed evaluation. Information on
watershed activities can be obtained from aerial photography and/or zoning maps, while upstream
survey techniques will include the analysis of the dry-weather flow at several manhole points along the
storm drainage system to narrow the location of the contaminating source; tests for specific pollutants
or ions associated with known activities within the outfall catchment area; and the measurement of
water flow rate and temperature, visual and T.V. inspections, and smoke and dye tests.
USING TRACER PARAMETERS IN THE DRAINAGE SYSTEM
In order to identify the specific contaminant sources in the drainage system, further detailed
watershed analyses are needed. These may include:
• drainage system surveys (tests for specific pollutants, visual inspections, T.V. drainage pipe
inspections, and smoke and dye tests),
• in-depth watershed evaluation (including aerial photographs), and
• industrial and commercial site studies.
Review Industrial User Surveys or Reports
This will require the submission of a questionnaire to industries to determine which industries or
commercial locations are discharging to a storm drainage system. However site inspections will still
be required because questionnaires may not be returned or may give incorrect details (either
deliberately or unknowingly).
Follow-up Drainage Area and On-Site Investigations.
Further drainage area investigations upstream of identified problem outfalls would be conducted
after the outfall studies have indicated dry-weather discharge problems. In order to be cost-effective,
only a sub-sample of manholes located in a drainage area identified as having significant
non-stormwater sources should be tested for the tracers. As an example, the main storm drain trunk
sewer could be divided into tenths and the manholes closest to these subdivisions would be sampled.
This would identify the upper limit of the drainage area above which the major sources are not located.
A location may also be identified where the downstream manhole tracer mass yields (concentration
times flow rate) are the same. This would mark the downstream limit of the contributing area for the
tracers of concern. After the main trunk drainage reach is identified that contains the major
non-stormwater sources, the branch storm drain lines can be similarly subdivided (but into fewer
sections each, perhaps about three) and evaluated. Depending on the drainage area and complexity
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of the storm drainage system, this scheme could be suitably modified to enable the identification of
relatively small areas responsible for the non-stormwater pollutant entries into the storm drainage
system. These small areas would then be subject to the more intensive on-site investigations by smoke
tests, dye studies, and T.V. inspections.
The above drainage system analysis procedure may find that the drainage system is contaminated
by widespread sanitary wastewater entries, possibly due to sanitary and storm drainage systems in
extremely poor condition. This situation may require that the drainage system undergo extensive and
costly repairs. It may be more appropriate to consider the storm drainage system as a combined sewer
and examine control alternatives that have been developed for combined sewer systems. This would
also save further detailed drainage system analyses costs.
These drainage system surveys would be followed by industrial and commercial on-site
investigations (e.g., dye and smoke studies and T.V. inspections) to locate specific sources of
non-stormwater pollutant entries into the drainage system. Additionally, aerial photography can be very
useful during later phases of non-stormwater discharge control projects. As an example, aerial
photography can help identify areas having failing septic systems located in residential areas served
by storm drainage systems. Aerial photography can also be used to identify continuous discharges to
surface drainage systems, such as sump discharges, and to identify storage areas that may be
contributing significant amounts of pollutants during rains. For example, the Tennessee Valley
Authority (TVA), among other agencies, has extensively used aerial photography (stereo color infrared)
to identify pollution sources, especially from failing septic tanks (Perchalski and Higgins 1988). The
TVA's flights are made in early spring when investigating septic tank failures, to be able to identify
unusual grass conditions, with minimal interference from trees. The flights are made at 6,000 feet,
with resulting image scales of 1 inch to 1,000 feet. Their photography costs have been about $40 to
$150 per square mile.
FLOW MASS BALANCES, DYE STUDIES, AND SMOKE TESTS
Industrial areas are known to contribute significantly polluted wet-weather stormwater discharges,
along with contaminated dry-weather entries into the storm drainage system. Additional industrial site
investigations are therefore needed to identify activities that apparently contribute these contaminants
to the storm drainage system. Figure 11 is an industrial site survey form prepared by the Non-Point
Source and Land Management Section of the Wisconsin Department of Natural Resources (R.
Bannerman, personal communication). This form has been used to help identify industrial activities that
contribute significantly polluted, indirectly connected dry- and wet-weather non-stormwater entries into
the storm drainage system.
This form only considers outside sources that would affect the storm drainage system by entering
through inlets or through sheetflow runoff into drainage channels. It does not include any information
concerning indoor activities, or direct plumbing connections to the storm drainage system. However,
the information included on this form can be very helpful in devising runoff control programs for
industrial areas. This information most likely affects wet-weather discharges much more than
dry-weather discharges. Obvious dry-weather leaching or spillage problems are also noted on the form.
Locating An Industrial Source
Hypothetical examples have been created to demonstrate how dry-weather discharges can be
characterized so that their likely industrial sources can be identified. These examples show how
observations of outfall conditions and simple chemical analyses, combined with a basic knowledge of
wastewater characteristics of industrial and commercial operations located in the drainage area, can
67
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City: 'Industry Name:_
Site Number: Photo #
Street Address: Roll
Type of industry:.
Instructions: Fill in blanks or circle best answer in following:
Material/waste Storage Areas
1. Type of material/waste:
2. Method of storage: pile tank dumpster other
3. Area occupied by material/waste (acres):
4. Type of surface under material/waste: paved unpaved
5. Material/waste is disturbed: often sometimes never unsure
6. Description of spills (material, quantity & frequency):
7. Nearest drainage (feet) and drainage type:
8. Control practice: berm tarp buffer none other
9. Tributary drainage area, including roofs (acres)
10. Does storage area drain to parking lot: yes no unsure
Heavy equipment storage
1. Type of equipment:
2. Area covered by equipment (acres):
3. Type of surface under equipment: paved unpaved
4. . Nearest drainage (feet) and drainage type:
5. Control practice: berm tarp buffer none other
6. Tributary drainage area, including roofs (acres)
7. Does storage area drain to parking lot: yes no unsure
Air pollution
1. Description of setteable air pollutants (types & quantities):
2. Description of particulate air pollutant controls;
Railroad yard
1. Size of yard (number of tracks):
2. General condition of yard:
3. Description of spills in yard (material, quantity & frequency):
4. Type of surface in yard: paved unpaved
5. Nearest drainage (feet) and drainage type:
6. Type of control practice: berm buffer other
7. Does yard drain to parking lot: yes no unsure
8. Tributary drainage area, including roofs (acres):
Loading Docks
1. Number of truck bays:
2. Type of surface: paved unpaved
3. Description of spills in yard (material, quantity & frequency):
4. Nearest drainage (feet) and drainage type:
5. Type of control practice: berm buffer other
6. Does loading area drain to parking lot: yes no unsure
7. Tributary drainage area, including roofs (acres):
Source: From Wisconsin Dept. of Natural Resources (R. Bannerman, Personal communication)
Figure 11. Industrial Inventory Field Sheet. (Use other sheets for multiple
areas on same site)
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be used to identify the possible pollutant sources. The initial activities include pollutant analyses of
outfalls being investigated. This requires the characterization of the non-stormwater flows, the
identification of the likely industries responsible for the observed discharges, and finally, locating the
possible specific sources in the watershed.
Hypothetical Conditions-
The hypothetical industries which were identified as being located in a stormwater drainage area
(from the watershed analysis) included a vegetable cannery, general food store, fast food restaurant,
cheese factory, used car dealer, cardboard box producer, and a wood treatment company. The
methods used to determine the most likely industrial source of the dry-weather discharges are
considered for three hypothetical situations of outfall contamination.
Case Example One--The hypothetical results of the pollutant analysis for the first situation found
constant dry-weather flow at the outfall. The measurements indicated a normal pH (6) and low total
dissolved solids concentrations (300 mg/L). Other outfall characteristics included a strong odor of
bleach, no distinguishing color, moderate turbidity, sawdust floatables, a small amount of structural
corrosion, and normal vegetation.
The significant characteristic in this situation is the sawdust floatables (see Figure 12). The
industries which could produce sawdust and have dry-weather flow drainage to this pipe are the
cardboard box company and the wood treatment company. According to SIC code, the cardboard box
company would fall under the category of "Paper Products" (SIC# 26) while the wood treatment
company would be under that of "Lumber and Wood" products (SIC# 24). Looking up these two
industries by their corresponding SIC group numbers in Table 11 and comparing the listed properties,
indicates that the paper industry has a strong potential for the odor of bleach. Wood products does
not indicate any particular smell.
Based upon this data, the most likely industrial source of the industrial non-stormwater discharge
would be the cardboard box company. Table 2 under SIC# 26 indicates that there is a high potential
for direct connections in paper industries under the categories of water usage and illicit or inadvertent
connections. At this point, further testing should be conducted at the cardboard box company to find
if the constant source of contamination is coming from cooling waters, process waters, or direct piping
connections (process waters are the most likely source given the bleach and sawdust characteristics).
Case Example 2-The results of the pollutant analysis for the second situation found intermittent
dry-weather discharges at the outfall. The test measurements indicated a low pH (3) and high total
dissolved solids concentrations (approximately 6,000 mg/L). Other characteristics included a
rancid-sour odor, grayish color, high turbidity, gray deposits containing white gelatin-like floatable
material, structural damage in the form of spelling concrete, and an unusually large amount of plant
life.
The rancid-sour smell and the presence of floatable substances at this outfall indicates that some
type of food product is probably spoiling. This narrows the possible suspect industries to the fast food
restaurant, cheese factory, vegetable cannery, and food store (see Figure 13). The corresponding SIC
categories for each of these industries are "Eating and Drinking Places" (SIC# 58), "Dairy Products"
(SIC# 202), "Canned and Preserved Fruits arid Vegetables" (SIC# 203), and "Food Stores" (SIC# 54).
Comparison of the properties listed in Table 11 for these SIC numbers indicates that elevated plant life
is common to industrial wastes for the "Dairy Products" and "Food Stores" categories. However, the
deciding factor is the low pH, which is only listed for "Dairy Products". Thus, the white gelatin-like
floatables are most likely spoiled cheese byproducts which are also the probable cause of the
sour-rancid smell.
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(1)
POLLUTANT
ANALYSIS
OF
SUSPECT
OUTFALL
(2)
FLOATABLES
SAWDUST
Table 11
CARDBOARD
BOX
COMPANY
SIC # 26
WOOD
TREATMENT
COMPANY
SIC # 24
(1) Characterization of non-stormwater discharge.
(2) Identification of industry.
(3) Possible sources.
(2)
ODOR
BLEACH
Table 11
CARDBOARD
BOX
COMPANY
(3)
1
DISCHARGE
CONTINUAL
Table 2
DIRECT
WATER USAGE
AND
\ PIPING
\ CONNECTIONS
Figure 12. Flowsheet for Industrial Case 1.
-------
1
(1)
POLLUTANT
(2)
ODOR
(2)
FLOATABLES
(2)
VEGETATION
(2)
£H
(3)
DISCHARGE
i
ANALYSIS
OF
SUSPECT
OUTFALL
RANCID-
SOUR
WHITE
GRANULES
Table 11
FAST FOOD
RESTAURANT
SIC # 58
CHEESE
FACTORY
SIC # 202
VEGETABLE
CANNERY
SIC # 203
FOOD
STORE
SIC # 54
ELEVATED
Table 11
CHEESE
FACTORY
FOOD
STORE
(1) Characterization of non-stormwater discharge.
(2) Identification of industry.
(3) Possible sources.
ACIDIC
\ DRY/
I INTERMITTENT
Table 11
Table 2
CHEESE
FACTORY
I l
I INDIRECT !
I I
LOADING/ | j
UNLOADING
DIRECT
WATER USAGE
AND
PIPING
CONNECTIONS
Figure 13. Flowsheet for Industrial Case Example 2.
-------
Since the dry-weather entry to the storm drainage system occurs intermittently, the flow could
be caused by either a direct or indirect connection. To locate the ultimate source of this discharge
coming from the cheese factory, both direct and indirect industrial situations are considered under the
category of "Dairy Products" in Table 2. Thus, further examination of the loading dock procedures,
water usage, and direct piping connections should be conducted since these categories all exhibit high
potential for pollution in dairy production.
Case Example 3- The results of the test measurements for the final situation found a normal pH
(6) and low total dissolved solids (about 500 mg/L). Signs of contaminated discharges were found at
the outfall only during and immediately following rainfalls. Other outfall properties observed included
an odor of oil, deep brown to black color, a floating oil film, no structural damage, and inhibited plant
growth (see Figure 14).
According to Table 11, the fast food restaurant and the used car dealer are the only two industrial
sources in this area with high potential for causing oily discharges. Their respective SIC categories are
"Eating and Drinking Places" (SIC# 58) and "Automotive Dealers" (SIC# 55). Comparison of the
properties shown on Table 11 indicates inhibited vegetation only for the second category. Thus, the
most likely source of the discharge is the used car dealer.
Furthermore, the source of contamination must likely be indirect, since the discharge occurs only
during wet weather. Reference to Table 2, under the category of "Automotive Dealers", indicates a
high potential for contamination due to outdoor storage. This fact, plus the knowledge that most used
cars are displayed outdoors, makes it fairly clear that surface runoff is probably carrying spilled car oil
into the storm drain during rains.
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GO
i
i i i !
! (1) | (2) (2) ' (2)
POLLUTANT ODOR FLOATABLES VEGETATION
| ANALYSIS jg>g> j
OF OIL OILY i | INHIBITED
SUSPECT FILM \
OUTFALL j
i
|
Table 1 1 Table 1 1
i i
i
FAST FOOD USED CAR USED CAR
(3)
DISCHARGE
WET
WEATHER
FLOW
Table 2
INDIRECT
RESTAURANT DEALER DEALER
SIC # 58 SIC # 55
i
(1) Characterization of non-stormwater discharge.
(2) Identification of industry.
(3) Possible sources.
OUTDOOR
STORAGE
Figure 14. Flowsheet for Industrial Case Example 3.
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SECTION 8
CORRECTIVE TECHNIQUES
In addition to identifying problems of unauthorized or inappropriate entries to stormwater systems,
it is even more important to prevent problems from developing at all, and to provide an environment
in which future problems will be avoided. Thus, a combined approach of identifying and correcting
existing problems and avoiding future problems has considerable merit. In this section, the focus is on
discussing ways in which future problems can be avoided. However it should be noted that this is not
an in depth review, but has been included to provide the reader with suggestions that could be
incorporated into a pollution prevention program.
There are also situations in which the sanitary system is so connected to the stormwater system
that good intentions, vigilance, and reasonable remedial actions will not be sufficient to solve the
problems. In an extreme case, it may be that while it was thought that a community had a separate
sanitary sewer system and a separate storm drainage system, in reality the storm drainage system is
acting as a combined sewer system. When recognized for what it really is, the alternatives for the
future become clearer: undertake the considerable investment and commitment to rebuild the system
as a truly separate system, or recognize the system as a combined sewer system, and operate it as
such, without the disillusionment that it is a problem-plagued storm drainage system which can be
rehabilitated.
Less extreme than designating a polluted stormwater drainage system a combined sewer system,
is the action of focusing on pollution prevention by:
• public education,
• an organized systematic program of disconnecting commercial and industrial non-stormwater
entries into the storm drainage system,
• tackling the problem of widespread septic system failure,
• disconnecting direct sanitary sewerage connections,
• rehabilitating storm or sanitary sewers to abate contaminated water infiltration, and
• developing zoning and ordinances.
In this section, the above items will be discussed, together with a section on treatment of wide spread
sanitary sewerage failure.
PUBLIC EDUCATION
One can argue that an ill informed and apathetic public has condoned the past actions of private
citizens, commercial entities, industrial concerns, and public officials which led to some of the past and
present problems with unauthorized entries to storm drainage systems. One also knows the power of
an aroused, concerned public in altering behavior at all levels. Thus, public education has a role to play.
It can be effective in altering the behavior of an individual who had assumed that the inlet on the curb
was the place to discharge used crankcase oil. It can be effective when organized groups lobby for the
return of a stream or a reservoir to a clean and attractive condition.
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Public education carries with it the implicit assumption that an educated public will make the
"right" decisions, the educated public will be concerned about the "right" problems, and it will
encourage private and public organizations to develop solutions to the "right" problems. Fortunately,
most of the problems, issues, and corrective measures are clear cut with respect to unauthorized
entries to the stormwater system. Public education is a communication art associated with significant
changes when successful, and imperceptible change when unsuccessful. As with all education, it does
not end, but is a continuing process. The following paragraphs describe some of the ways in which
public officials can help to educate the public. The "public" has been subdivided into categories which
are representative of the problem areas with respect to unauthorized entries to storm drainage
systems. The subcategories of the public are:
• industrial
• commercial
• residential
• governmental
Industrial decision makers can be educated by public officials through direct contact when they
seek information, by education of the consultants from whom industry seeks advice, and by education
of trade associations. Indirect educational opportunities are provided by speaking to meetings of
professional organizations and by writing in professional newsletters and journals. Industrial decision
makers are a small group which is likely to respond as they recognize that they have to address the
problem of unauthorized entries to the stormwater system.
Commercial storm drainage system users are a larger group to educate. The educational process
will have to focus on both proprietors and their employees. It will have to recognize the state of both
groups, new businesses opening; existing businesses moving, expanding, and closing; and employees
entering the work force and changing jobs. Education will have to be focused in the local community.
The role of trade and professional associations will be less than was the case with industrial groups.
News announcements in the local press will play a role as well as mailed news items. Individual contact
between a public official and the proprietor of a commercial establishment will play a larger role. Follow
up and repeated contact may be necessary to answer questions and cope with employee turnover.
Public education can also benefit from failures. For example, certain violations of discharge practices
may be so serious, or flagrant, that a citation or fine results. The local press, if informed, may find such
an incident newsworthy. The general public, or other potential offenders, may benefit from this
educational procedure.
An informed public willing to act on their convictions is the product sought from public education.
The public educator focuses on large groups, as one-on-one contact is unlikely to be either time or cost
effective. Long range educational goals may be tackled through school programs, while shorter range
educational goals may focus on community groups. Public education will have to focus on broader
environmental issues than inappropriate entries to storm drains. Subgroups in the community may play
important roles in public education. For example, scouts may undertake community improvement
projects including placing signs on curbside storm drains informing the public that the drain is for
stormwater only, and not for discharge of wastes. Thus, public education must take advantage of
opportunities presented by groups looking for community improvement projects, the opportunities that
are available in working with the school system, and opportunities arising from the news media being
supplied with newsworthy items.
The final group that public officials should address in public education is other public officials and
governmental institutions. Some small governmental units may not know about precautions to be taken
with discharges to storm drainage systems unless they are properly informed. Such subgroups may
include road departments, sanitation workers, and workers at public institutions such as hospitals and
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prisons. A multilevel, multitarget public education program can help to avoid problems.
COMMERCIAL AND INDUSTRIAL SITE DISCONNECTIONS OF NON-STORMWATER SOURCES
Out of convenience and out of ignorance, commercial and industrial sites may impose an
increasing load on the storm drainage system. This may be through direct discharges to the storm
drainage system, or it may be through diffuse and indirect sources in which the site grounds are
contaminated by spills and discharges which are then washed off by storm runoff to the storm drain
during rainfall events or by washwater during wash-down operations. The problem is compounded by
the vast array of sizes of commercial and industrial enterprises. A single person enterprise has little
opportunity to build expertise on the subject of stormwater pollution, while a large industrial enterprise
may have an environmental division. To the uninformed person, any curb opening may be thought to
be part of a comprehensive sanitary wastewater treatment system and the proper entrance point for
polluted water discharges or other debris.
Corrective measures for improper uses of storm drains have to be developed recognizing the
differences in knowledge and sophistication of the client. Industrial users are relatively few in number
but are expected to have the most complex problems. If industrial users are aware, or made aware,
of existing and or new federal, state, or local regulations to prevent pollution of stormwater drainage
systems, they will usually comply with the regulation. If not, these regulations provide the authority
and communication means to instigate corrective action.
Commercial groups are heterogeneous. An appropriate way of working with them to institute
changes in their use of storm drainage systems, may be to work with one category of commercial
groups at a time. For example, consider gasoline filling stations as a single category. It is possible to
focus on correcting similar problems at many facilities that exist in this category. The flushing of
radiators may be seasonally common. A typical practice is to let radiator flushing waters (including
coolants) to drain to an inlet to the storm drainage system. Education followed by assurance that there
will be strict enforcement of discharge regulations or ordinances may be effective. However, a group
such as gasoline filling stations cannot be expected to have a long institutional memory as new
operators take over and others drop out. Thus, vigilance and follow-up are important to insure that
there is not a gradual diminution of appropriate practices.
For both small commercial and large industrial enterprises, willful and knowledgeable violation of
the regulations limiting entries to storm drainage systems have to be dealt with firmly and promptly
or the enforcement program runs the chance of becoming ineffective. Thus the governmental unit
undertaking responsibility for improving the practices regarding entries to storm drainage systems must
have an enforcement plan ready.
FAILING SEPTIC TANK SYSTEMS
Failing septic tank systems can have an impact on an otherwise well functioning storm drainage
system. Before discussing corrective measures, it is important to identify the relationship that may
develop between a septic tank system and a storm drainage system.
A septic tank system consists of two major components: a septic tank and a leaching field (a
waste spreading or soil absorption system). In addition, of course, there is piping associated with the
system. Sanitary wastewaters are piped directly to the septic tank. The septic tank typically is made
of concrete, is rectangular in shape, is usually divided into two compartments, and has a capacity of
one to several thousand gallons. The septic tank serves as an anaerobic digestion, floatation and
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settling unit in which biological action converts the biodegradable liquid and solid waste particles into
stable end products. Gravity separates a significant portion of both biodegradable and
non-biodegradable particulate matter to the tank bottom or top (depending on whether the particles
sink or rise, respectively). Some of the products of this partial treatment process are carbon dioxide,
methane, hydrogen sulfide and other odor producing gases, digested and refractory or relatively
non-biodegradable sludge, and floating scum. Because the septic tank remains full, it must discharge
a volume of wastewater each time a volume of wastewater is discharged into it. This discharged water
enters a leaching field where some additional treatment occurs and the final effluent is discharged to
the ground.
A septic tank may be a low maintenance treatment unit, but it is not entirely maintenance free.
As the septic tank continues to be loaded, the scum and sludge layers build up so that the remaining
volume available for treatment is reduced. Thus, some of the partially digested or undigested solids,
scum, and sludge may be carried from the septic tank to the leaching field where the soil void space
may become clogged. As the soil voids become clogged, the ability of the leaching field to handle the
liquid portion of the waste is reduced, and surface ponding of the wastewater may result. Of course,
ponding could have been prevented by having the septic tank serviced; that is, by having the septic
tank pumped. Pumping removes the sludge, scum, and other contents of the septic tank so that its
storage and treatment capacity is restored. Pumping frequency varies depending on the size of the
septic tank and its loading rate. Residential septic tanks may need to be pumped every two to five
years. Commercial and institutional septic tanks may need more frequent pumping.
Failed septic tank systems have the potential to pollute stormwater because the leaching field will
saturate the ground, and possibly form ponded water on the ground surface. The ponded water may
run off and enter a storm drain inlet or drainage ditch, or infiltrate the ground in another area which
is intercepted by a storm drain through infiltration. When it rains, any remaining ponded water may be
washed off with the runoff to the storm drainage system. Depending on the severity of the septic tank
failure, the ponded water can have the characteristics of partially treated sanitary wastewater or nearly
untreated sanitary wastewater. Thus, septic tank failures can contaminate the stormwater drainage
system during both wet and dry weather.
Septic tank systems may fail even with good maintenance practices. Such failure can result when
the soil is simply not permeable enough for the leaching field, or when the soil absorbance capacity
is exceeded through long use. A tight clay soil may have such low permeability that the leaching
capacity is very limited. If a number of homes are built in close proximity, their septic tank leaching
fields may collectively exceed the soil's capacity, leading to a stormwater pollution problem. Even
properly operating septic tank systems are a potential pollutant source. Because the basic function of
the leaching field is to discharge partially treated effluent to the ground, this septic tank effluent can
infiltrate into nearby stormwater drainage systems.
Various corrective methods exist for failing septic tank systems that pollute stormwater. These
methods include: improve maintenance, institute preventative measures to avoid problems, and
abandon the septic tank system with connections made to a sanitary sewerage system. In some cases,
improved maintenance may be the answer. Some persons will not do any maintenance to their septic
tank system until it fails (they note ponded water in the leaching field area). Then they call for the
septic tank to be pumped. In many cases, this is not sufficient to correct the problem: it may be too
little action too late. The preventative action of having the septic tank pumped should have taken place
prior to failure of the system. Education may provide part of the remedy. The septic tank user may
respond to exhortations to have the septic tank pumped on a regular basis, before failure. Coercion
through ordinances may be another answer. Ordinances may require that the septic tank be pumped
at a specified frequency, with a public body monitoring the program to ensure that maintenance has
been carried out.
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It sometimes happens that soil conditions and population density rule out both voluntary or
involuntary maintenance. In this case, it may be necessary to consider abandoning the septic tank
system and installing a system consisting of sanitary sewers leading to a treatment plant. Another
option consists of abandoning the septic tank treatment method in favor of small package treatment
units that provide aerobic treatment of the sanitary wastewater which is then discharged to a regional
leaching field. This option may succeed where the septic tank system has failed, because wastes
treated in an aerobic unit may not have the leaching field clogging potential of wastes treated in an
anaerobic septic tank. However, experience has shown that these advantages are only obtained with
proper control and maintenance. Aerobic systems are more sensitive than conventional septic tank
systems to improper maintenance and may therefore not offer any real benefits.
DIRECT SANITARY SEWERAGE CONNECTIONS
Due to indifference, ignorance, poor enforcement of ordinances, or other reasons, a stormwater
drainage system may have sanitary wastewater sewerage direct connections. Obviously, the sanitary
wastewater entering the storm drain will not receive any treatment and will pollute a large flow of
stormwater, in addition to the receiving water. If the storm drain has a low dry-weather flow rate, the
presence of sanitary wastewater may be obvious due to toilet paper, feces, and odors. In cases of
high dry-weather flows, it may be more difficult to obviously detect raw sanitary wastewaters due to
the low percentage of sanitary wastewater in the mixture. Even though the sanitary wastewater
fraction may be low, the previously discussed field testing procedures (e.g., testing for surfactants,
ammonia, potassium, and fluorides) will assist in the detection and quantification of sanitary
wastewater contamination in the storm drainage system. Flow monitoring may show the variations in
the flow rate that are typical of sanitary wastewater.
Dye testing can be effective in finding specific sanitary wastewater connections between a house
and a storm drainage system. Dye, such as diluted rhodamine or fluorescein, is flushed down the toilet
of a house and the storm drain is monitored to determine whether the dye appears. Care has to be
exercised when using this method, as these dyes may stain fixtures that are being tested, and any
spillage in the house causes stains that are very difficult to remove.
Monitoring of the storm drainage system with television cameras can show the locations of breaks
in the storm drain where a sanitary wastewater sewer or house lateral was attached. Television
cameras may also show discharges taking place at these locations, demonstrating that the lines are
in active use.
Corrective measures involve undertaking a program of disconnecting the sanitary sewer
connections to the storm drainage system and reconnecting them to a proper sanitary wastewater
sewerage system. The storm drainage system then has to be repaired so that the holes left by the
disconnected sanitary sewer entrances do not become a location for dirt and groundwater to enter.
REHABILITATING STORM OR SANITARY SEWERS TO ABATE CONTAMINATED
WATER INFILTRATION
Infiltration of contaminated water into a stormwater drainage system can cause substantial
pollution of the system. This could occur where a sanitary sewer overlies and crosses (or parallels) a
storm drain, with sanitary wastewater exfiltrating from the sanitary sewer and percolating the storm
drain. Other instances would be in areas of polluted groundwater, where the storm drainage is below
the water table or intercepts infiltrating groundwater, or in areas having septic tank systems, as
discussed previously.
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It would be best to correct the sanitary sewer if only one drainage system can be corrected. This
would have the dual advantage of preventing infiltration of high or percolating groundwaters and
preventing pollution of stormwater with exfiltrating sanitary wastewater. Rehabilitation of the drainage
systems by use of inserted liners, or otherwise patching leaking areas, are possible corrective
measures. It is important that all drains with infiltration problems be corrected for this corrective action
to be effective. This would also include repairing house lateral sanitary wastewater lines, as well as
the main drainage runs. However, these corrective measures are more likely to be cost effective when
only a relatively small part of the complete drainage systems require rehabilitation.
ZONING AND ORDINANCES
Land use controls achieved by zoning have the potential to exacerbate problems or diminish them.
For example, in an area with soils that are ill suited for septic tanks and leaching fields, the potential
for future problems is increased if zoning allows small lots for single family residential development and
allows septic tank systems. As the area develops, septic tank failures will become common, resulting
in increased pollution of stormwater and groundwater. On the other hand, in areas having poor soils,
zoning can require correspondingly larger lot sizes and larger leaching fields, resulting in fewer future
problems. Ordinances may specify the results that have to be achieved by infiltration tests used to size
leaching fields. Also, ordinances can require that a responsible public official be present when the
infiltration test is run to decrease the likelihood of false or spurious results being reported. Certified
septic tank installers, also checked by public official inspectors, should also be required to increase the
likelihood of the system being installed correctly.
Zoning can also have a role to play in avoiding development of land that is subject to frequent
flooding. In such land, flooding and high groundwater conditions can result in the sanitary sewerage
system being gradually overloaded by infiltration so that cross flow to the storm drainage system can
occur.
Ordinances can help to control problems by putting the force of law and public policy behind
desirable practices. For example, ordinances can make mandatory practices such as septic tank
maintenance that otherwise would be voluntary. By making the practice mandatory, desirable practices
are performed on a regular schedule so that large problems have less opportunity to develop.
Ordinances can also regulate the persons doing the pumping of septic tanks so that they discharge the
septage to wastewater treatment plants where it can be properly treated rather than it being
discharged improperly where the pollution problem is just transferred from one location to another.
Ordinances can also help prevent and or control pollution from many other sources by restrictions
on: disposal of household toxic substances to storm drains, storage of chemicals by industry, disposal
of industrial wash down water, etc.
Zoning and ordinances represent important means for governing bodies to anticipate problems,
to avoid problems, and to manage problems, so that desirable ends are achieved and undesirable
consequences are avoided. Enactment of zoning and ordinances occurs in the public arena where
interested persons can participate and express their views and concerns. The public can become
educated in this process, but zoning and ordinances have the desirable characteristic of being
remembered and remaining enforceable long after an individual forgets, becomes disinterested, or
becomes recalcitrant.
Another important step that municipalities can take is the development of policies and procedures
for the management of spills from transportation (including both roadway and rail) and pipeline
accidents. Spills should not be merely washed into the storm drainage system, but should be collected
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for proper treatment and disposal.
WIDESPREAD SANITARY SEWERAGE FAILURE
Connections (whether directly by piping or indirectly by exfiltration or infiltration) of sanitary
sewers to the storm drainage system may be so widespread that the storm drainage system has to be
recognized as a combined sewer system. This could also be the case when the prevalence of septic
tank failures leads to widespread sanitary wastewater runoff to the storm drainage system. One usually
thinks of a combined sewer system as having all of the sanitary sewer connections to the same sewers
that carry stormwater, but the previous discussion suggests that there are degrees of a storm drainage
system becoming a combined sewer system. Previously, the recommendations have been made that
widespread failure of septic tank systems might necessitate the construction of a sanitary sewer to
replace the septic tanks. Also recommended was a program of identifying and disconnecting sanitary
sewers from the storm drainage system.
Prior to these actions taking place, the storm drainage system operates to some degree as a
combined sewer system. It may be that the sanitary sewerage system is not capable of handling the
load that would be imposed on it if a complete sewer separation program were undertaken. Or, in an
extreme case, no sanitary sewer system may exist. By recognizing that a combined sewer system does
in fact exist may help to focus attention on appropriate remedial measures. The resources may also
not be available to undertake construction of a separate sanitary wastewater drainage system.
One should then focus on how to manage the combined sewer system that is in place.
Management may require that end-of-pipe storage/treatment be investigated. Also, the combined sewer
system may be tied into other combined sewers so that more centralized treatment and storage can
be applied. Operation of a combined sewer system may be preferable to having the stormwater and
the large number of sanitary entries receive no treatment.
An early identification and decision to designate a storm drainage system a combined sewer
system, will prevent abortive time and costs being spent on further investigations. These resources can
then be more effectively used to treat the newly designated combined sewer system.
In essence, recognition of a system as being a combined sewer system provides a focus in the
regulatory community so that it may be possible to operate the system so as to minimize the damage
to the environment.
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GLOSSARY
Accuracy - The combination of bias and precision of an analytical procedure which reflects the
closeness of a measured value to a true value.
Baseflow - The dry-weather flow occurring in a drainage system, with no apparent source. Likely to
be mostly infiltrating groundwaters in a sanitary or storm drainage system, but can also be
contaminated with illicit wastewaters. See constant (or continual) dry-weather flow.
Batch dump - The disposal of a large volume of waste material during a short period of time. Usually
an industrial waste.
Bias - A consistent deviation of measured values from the true value, caused by systematic errors in
a procedure.
Coefficient of Variation (COV) - A measure of the spread of data (ratio of the standard deviation to the
mean).
Combined Sewer - A sewer designed for receiving surface (dry- and wet-weather) runoff, municipal
(sanitary and industrial) wastewater, and subsurface waters from infiltration. During dry weather, it
acts as a sanitary sewer, but it also carries stormwater from wet-weather runoff.
Combined sewer overflow (CSO) - Flow from an outfall (discharge conduit) of a combined sewer
collection system, in excess of the interceptor capacity or due to a malfunctioning or improperly set
flow regulator, that is discharged into a receiving water and/or an auxiliary CSO control
storage-treatment system.
Constant (or continual) dry-weather flow - Uninterrupted flow in a storm sewer or drainage ditch
occurring in the absence of rain. See baseflow.
Deposits and stains - Any type of coating or discoloration that remains at an outfall as result of
dry-weather discharges.
Detection limit - A number of different detection limits have been defined: IDL (instrument detection
limit), is the constituent concentration that produces a signal greater than five times the signal to noise
ratio of the instrument; MDL (method detection limit) is the constituent concentration that, when
processed through a complete method, produces a signal with a 99 percent probability that it is
different from a blank; PQL (practical quantification limit) is the lowest constituent concentration
achievable among laboratories within specified limits during routine laboratory operations. The ratios
of these limits are approximately: IDL:MDL:PQL = 1:4:20 (APHA, et al. 1989).
Direct (dry-weather) entries into the storm drainage system - Sources which enter a storm drainage
system directly, usually by direct piping connections between the wastewater conduit and the storm
drain.
Domestic sanitary wastewater - Sewage derived principally from human sources.
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Drainage area - The area of land from which a storm drainage system collects precipitation and storm
runoff and then delivers the resulting stormwater to a specific point.
Dry-weather flow - Flow in a storm sewer or drainage ditch occurring in the absence of storm flow.
But it is also a constituent of wet-weather flow. See baseflow.
Entries to storm drainage - Water (relatively clean or polluted) discharged into a stormwater drain from
sources such as, but not limited to, direct industrial or sanitary wastewater connections, roof leaders,
yard and area drains, cooling water connections, manhole covers, groundwater or subterraneous
stormwater infiltration, etc.
Floatables - Floating materials, (plastic containers, condoms, sanitary napkins, tissues, corks, paper
containers, wood, leaves, oil films, slimes, scum, etc.), that are either part of the inappropriate waste
streams discharged to a stormwater system, or collected by flows which enter a stormwater drainage
system.
Geographic Information System (GIS) - Computer software that maps land areas and produces images
and information relating to the land area, e.g., topography, drainage, public utilities, roads, buildings,
industry, land use, and demography.
Groundwater infiltration - Seepage of below water table groundwater and subterraneous stormwater
into stormwater, sanitary wastewater, or combined sewer drainage systems, through such means as
defective pipes, pipe joints, connections, or manhole walls.
Hardness - Caused by the presence of the divalent cations (principally calcium and magnesium) in
water. Causes an increased amount of soap usage before producing a lather and scale to form in hot
water pipes, boiler vessels, condensate return lines, cooling systems, kettles, etc.
House Lateral - A pipe connecting a house to a lateral or other sewerline. Also called a service
connection.
Indirect dry-weather entries into the storm drainage system - Non-stormwater sources which enter a
storm drainage system indirectly, usually by floor, areaway, and yard drains or inlets; and spills and
dumping.
Industrial dry-weather entries into the storm drainage system - Any solid or liquid waste coming from
industrial sources which enter storm drainage systems during periods of dry weather.
Infiltration - The process whereby water enters a drainage system underground through such means
as defective pipes, pipe joints, connections, manhole walls, etc.
Inflow - The process whereby water enters a sanitary wastewater drainage system from surface
locations, (e.g., through depressed manhole covers, yard and areaway inlets, roof leader setc.).
Intercepted stormwater/groundwater - The portion of surface runoff or groundwater moving through
the soil that enters a storm drainage, combined sewer, or sanitary sewer system.
Interceptor - A sewer that receives flows from a number of wastewater trunk lines.
Intermittent dry-weather flow - Irregular flow in a storm drainage system occurring in the absence of
storm flow.
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Lateral - A drain or sewer that has no other drains or sewers discharging into it, except for service
connections, or house laterals.
Leaching field - A system which facilitates the infiltration of a septic tank effluent into the soil. This
is typically done by a pipe and infiltrating trench system which takes the effluent from a septic tank
and distributes it through the leaching field, where additional treatment of the effluent occurs as it
percolates through the ground or soil column.
Monte Carlo probabilistic simulation - A statistical modeling approach used to determine the expected
frequency and magnitude of an output by running repetitive simulations using statistically selected
inputs for the model parameters.
Municipal sewage/wastewater - Sewage/wastewater from a community which may be composed of
domestic sewage/wastewater, industrial wastewater and/or commercial wastewater, together with
subsurface infiltration.
National Pollution Discharge Elimination System (NPDES) - A national system of permits issued to
industrial, commercial, and municipal dischargers to limit the amount of pollutants that can be
discharged to waters of the USA.
Non-contact cooling water - Water that decreases the temperature of an object, without ever physically
contacting the object.
Nonpoint pollution source- Any unconfined and nondiscrete conveyance from which pollutants are
discharged, or an urban drainage system not under the NPDES. These sources are usually from
agricultural, silvicultural, and rural land areas..
Outfall - In this User's Guide, an outfall refers to a point at which a stormwater drainage system
discharges to a receiving water. There is sometimes a concrete structure or retaining wall at this
location to protect the end of the discharge pipe and prevent erosion of the receiving water bank.
Pathogen -A disease-causing microorganism.
Point source -Any discernible, confined, and discrete conveyance from which pollutants are, or may
be, discharged. Under the NPDES it is an outfall discharge, or overflow of treated or untreated
sanitary, industrial, combined sewage, or stormwater (from a municipality greater than 100,000 in
population).
Pollutant - Any material in water or wastewater interfering with designated beneficial uses.
Potable water - Water that has been treated, or is naturally fit for drinking, i.e., the water has no
harmful contents to make it unsuitable for human consumption.
Precision - The measure of the degree of agreement among replicate analyses of a sample, usually
expressed as the standard deviation.
Pretreatment - The removal of material such as, gross solids, grit, grease, metals, toxicants, etc. or
treatment such as aeration, pH adjustment, etc. to improve the quality of a wastewater prior to
discharge to a municipal wastewater system. This is usually done by the industrial user of the water,
but can also refer to the initial treatment processes of a sewage treatment plant.
Process line discharge -The disposal of anything used in, or resulting from, a manufacturing process.
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Process water - Water used in industry to perform a variety of functions, or as an actual product
ingredient.
Receiving waters - Natural or man-made water systems into which stormwaters, or wastewaters, are
discharged.
Rinse water - Water that cleans or reduces the temperature of an object through actual physical
contact with the object.
Sanitary sewer - A sanitary wastewater drainage system intended to carry wastewaters from
residences, commercial buildings, industrial plants, and institutions together with minor quantities of
groundwater, stormwater and surface water that are not admitted intentionally [40 CFR 35.2005 (b)
(37)].
Sanitary wastewater - Wastewater of human origin.
Service Connection - See house lateral
Septic tank - A tank which receives sanitary wastewater direct from its source, (usually residential),
and permits settling of the heavy solids and floatation of greases and fats along with anaerobic
digestion. Septic tanks, typically need to meet minimum regulatory standards, e.g., minimum volume
and detention time.
Sewage - In this text the term "sewage" refers to sanitary wastewater or wastewaters generated from
commercial or industrial operations, it does not include stormwater.
Sewer -A pipe, conduit or drain generally closed, but normally not flowing full, for carrying sanitary,
industrial and commercial wastewater and storm-induced (combined wastewater and stormwater)
flows.
Sewerage - System of piping and appurtenances, with and without control-treatment facilities for
collecting and conveying wastewaters with or without pollution abatement from source to discharge.
Specific Conductivity - Expressed in microSiemens/cm (or micromhos/cm). It is an indication of the
dissolved solids (charged) concentration in a liquid.
Storm drainage discharge - Flow from a storm drain that is discharged to a receiving water.
Storm drain - A pipe, or natural or man-made channel, or ditch, that is designed to carry only
stormwater, surface runoff, street washwaters, and drainage from source to point of discharge [40
CFR 35.2005 (b) (47)].
Stormwater - Water resulting from precipitation which either infiltrates into the ground,
impounds/puddles, and/or runs freely from the surface, or is captured by storm drainage, a combined
sewer, and to a limited degree, by sanitary sewer facilities. See urban runoff and urban stormwater
runoff.
Surfactants - Surface-active agents and common components in detergents which affect the surface
tension of water and can cause foaming.
SIC - Standard Industrial Classification, a code used to describe an industry.
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Total solids - The entire quantity of solids in the liquid flow or volume including the dissolved and
paniculate (suspended, floatable, and settleable) fractions.
Toxicity - The degree to which a pollutant causes physiological harm to the health of an organism.
Tracer - In this User's Guide, a tracer is a distinct component, or combination of components
("fingerprint"), of a polluting source which is identified in order to confirm the entry of the polluting
source to a storm drainage system.
Trace Metals - Metals present in small concentrations. From a regulatory standpoint, this usually refers
to metal concentrations that can cause toxicity at trace concentrations.
Turbidity - The lack of clarity in the water usually caused by suspended particulate matter and
measured by interference to light penetration.
Urban runoff - Any runoff stormwater from an urban drainage area that reaches a receiving water body
or subsurface. During dry weather, it may be comprised of many baseflow components, both relatively
uncontaminated and contaminated. See stormwater and urban stormwater runoff.
Urban stormwater runoff - Stormwater from an urban drainage area that reaches a receiving water
body or subsurface caused by weather precipitation (rain, snow, etc.). See stormwater and urban
runoff.
Watershed - A geographic region (area of land) within which precipitation drains into a particular river,
drainage system or body of water that has one specific delivery point.
Wet-weather flow - Any flow resulting from precipitation (rain, snow, etc.) which may introduce
contaminants into storm drainage combined sewerage, or sanitary sewerage systems.
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REFERENCES
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Wastewater in Septic Tanks". Journal Water Pollution Control Federation, Volume 61, Number 5. May
1989.
APHA (American Public Health Association), American Water Works Association, and Water Pollution
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American Public Health Association. Washington, D.C. 1989.
Beyer, D.L., P.A. Kingsbury, and J.E. Butts. History and Current Status of Water Quality and Aquatic
Ecology Studies in the Lower Chehalis River and Grays Harbor, Washington. Prepared for Washington
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Cochran, William G. Sampling Techniques. Second edition. John Wiley and Sons, Inc. New York. 1 963.
Evans, R.L. "Addition of Common Ions from Domestic Use of Water." Journal American Water Works
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EPA (U.S. Environmental Protection Agency). Results of the Nationwide Urban Runoff Program, Water
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Falkenbury, John. Water Quality Standard Operating Procedures. City of Fort Worth Public Health
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GLA (Gartner Lee and Associates, Ltd.). Toronto Area Watershed Management Strategy Study,
Technical Report #1, Humber River and Tributary Dry-weather Outfall Study. Ontario Ministry of the
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Hypes, W.D., C.E. Batten, J.R. Wilkins. Processing of Combined Domestic Bath and Laundry Waste
Waters for Reuse as Commode Flushing Water. Technical Report NASA TN D-7937. National
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Montoya, Barry L. Urban Runoff Discharges From Sacramento, California. Prepared for the California
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Moore, A.H. and Dena Hoffpauir. Biotoxicitv Testing. Fort Worth Health Department, 1800 University
Drive, Fort Worth, Texas 76107. 1988.
Murray, James E., Washtenaw County Drain Commissioner. Statement To The Board Of
Commissioners. December 1985.
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Pelletier, G.J. and T.A. Determan. Urban Storm Drain Inventory Inner Gray Harbor. Prepared for
Washington State Department of Ecology, Water Quality Investigations Section, Olympia, Washington.
1988.
Pitt, Robert and Melinda Lalor. Birmingham, Alabama, Draft Final Report: Demonstration Project for the
Investigation of Inappropriate Pollutant Entries into Storm Drainage Systems. U.S. Environmental
Protection Agency. Storm and Combined Sewer Pollution Control Program. Edison, New Jersey.
Contract No: 68-C9-0033. Publication pending.
Pitt, Robert and James McLean. Toronto Area Watershed Management Strategy Studv: Number River
Pilot Watershed Project. Final Report. The Ontario Ministry Of The Environment. Toronto, Ontario.
1986.
Schmidt, Stacy D. and Douglas R. Spencer. "The Magnitude of Improper Waste Discharges in an Urban
Stormwater System", Journal Water Pollution Control Federation, Volume 58, Number 7. July 1986.
van der Leeden, Frits, Fred L. Troise and David Keith Todd. The Water Encyclopedia. Lewis Publishers.
Chelsea, Michigan. 1990.
Verbanck, Michel, Jean-Pierre Vanderborght, Roland Wollast. "Major Ion Content of Urban Wastewater:
Assessment of Per Capita Loading." Journal Water Pollution Control Federation. Volume 62, Number
1. January, 1990.
Washtenaw County Drain Commissioner and Washtenaw County Health Department. Allen Creek Drain
Water Quality Survey - Status Report. September 1984.
Washtenaw County Statutory Drainage Board. Huron River Pollution Abatement Program. September
1987.
Washtenaw County Drain Commissioner. Huron River Pollution Abatement Project, Summary. 1988.
Washtenaw County Statutory Drainage Board. Huron River Pollution Abatement Program. September
1987.
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