v>EPA
United States
Environmental Protection
Agency
Office of Water
Washington, D.C.
EPA 832-F-99-022
September 1999
Storm Water
Management Fact Sheet
Non-Storm Water Discharges to Storm Sewers
DESCRIPTION
Identifying and eliminating non-storm water
discharges to storm sewers is an important and very
cost-effective Best Management Practice (BMP) for
improving runoff water quality. Non-storm water
discharges can include discharges of process water,
air conditioner condensate, non-contact cooling
water, vehicle wash water, or sanitary wastes, and
are typically the result of unauthorized connections
of sanitary or process wastewater drains to storm
sewers. These connections are common, yet often
go undetected. Typically these discharges are
significant sources of pollutants, and, unless
regulated by an NPDES permit, they are also illegal.
Environmental impact evaluations have shown that
the elimination of non-storm water discharges is an
effective BMP, because such discharges may
contain a significant loading of pollutants.
Several studies exist on the contents of non-storm
water discharges. Pitt and Shawley (1982) reported
that non-storm water discharges were found to
contribute substantial quantities of a variety of
pollutants, even though the individual
concentrations of each pollutant were not high.
During extended periods of base flow conditions,
the lower concentration was offset, leading to a
substantial loading of pollutants. Gartner, Lee and
Associates, Ltd. (1983) conducted an extensive
survey of non-storm water discharges in the Humber
River watershed (Toronto). Out of 625 outfalls,
about 10 percent were considered significant
pollutant sources. Further investigations identified
many industrial and sanitary non-storm water
discharges into the storm drainage system.
Sources found in industrial areas included liquid
dripping from animal hides stored in tannery yards,
and washdowns of storage yards at meat packing
facilities. Therefore, it is anticipated that elimination
of non-storm water discharges will be a highly
effective BMP.
Identifying and eliminating non-storm water
discharges has rarely been done at industrial
facilities. Part of the problem is education: many
facility operators are unaware of what constitutes a
non-storm water discharge and what the potential
environmental impacts of these discharges are.
Compliance with NPDES permit requirements for
the presence of non-storm water discharges will
greatly improve the implementation of this BMP.
APPLICABILITY
Almost every industrial facility that has not been
tested or evaluated for the presence of potential
non-storm water discharges should be so evaluated.
Typically NPDES permit certification includes:
• Identification of potential non-storm water
discharges.
Results of a site evaluation for the presence
of non-storm water discharges.
• The evaluation criteria or test method used.
• The date of testing and/or evaluation.
• The on-site drainage points that were
directly observed during the test and/or
evaluation.
This certification must be signed in accordance for
the facility's NPDES storm water permit. A sample
certification form is shown in Figure 1.
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ADVANTAGES AND DISADVANTAGES
Identifying and eliminating non-storm water
discharges can be an easy and cost-effective method
for preventing runoff contamination and pollution of
receiving water bodies. However, identifying these
discharges may be problematic. Possible problems
in identifying non-storm water discharges include:
A non-storm water discharge may not occur
on the date of the test or evaluation.
• The method used to test or evaluate the
discharge may not be applicable to the
situation.
• A lack of available data on the location of
storm drains and sanitary sewers, especially
in older industrial facilities, may make
identifying an illicit connection difficult.
KEY PROGRAM COMPONENTS
Key program criteria include identifying and
locating non-storm water entries into storm drainage
and investigating their sources.
For any effective investigation of pollution within a
storm water system, all pollutant sources must be
included. For many pollutants, storm water may
contribute the smaller portion of the total pollutant
mass discharge from a storm drainage system. In
addition to conventional storm water runoff
associated with rainfall, pollutant sources may
include dry-weather entries occurring during both
warm and cold months and snowmelt runoff.
Consequently, much less pollution reduction benefit
will occur if only storm water is considered in a
control plan for controlling storm drainage
discharges.
The investigations may also identify illicit point
source outfalls that do not carry storm water.
Obviously, these outfalls also need to be controlled
and permitted. Figure 1 can be used as a sample
worksheet to report non-storm water discharges.
There are four primary methods for investigating
non-storm water discharges.
Visual Inspection
The simplest method for detecting non-storm water
connections in the storm water collection system is
to observe all discharge points during periods of dry
weather. Key parameters to look for are the
presence of stains, smudges, odors, and other
abnormal conditions.
Sanitary and Storm Sewer Map Review
A review of a plant schematic is another simple way
to determine if there are any unauthorized
connections to the storm water collection system.
A sanitary or storm sewer map, or plant schematic,
is a map of pipes and drainage systems used to carry
NON-STORM WATER DISCHARGE
ASSESSMENT AND CERTIFICATION
Date of Test or
Evaluation
Outfall Directly
Observed During
the Test (Identify as
indicated on the site
map)
Method Used to
Test or Evaluate
Discharge
Worksheet Comple
Title:
ted By:
Date:
Signature:
Describe Results
from Test for the
Presence of Non-
Storm Water
Discharge
Identify Potential
Significant Sources
Name of Person
Who Conducted
the Test or
Evaluation
Source: U. S. EPA, 1992.
FIGURE 1 SAMPLE WORKSHEET FOR RECORDING NON-STORM WATER DISCHARGES
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process wastewater, non-contact cooling water, and
sanitary wastes. These maps (especially as-built
plans) should be reviewed to verify that there are no
unauthorized connections. However, a common
problem at many sites is that they often do not have
accurate or current schematics.
Dye Testing
Another method for detecting improper connections
to the storm water collection system is dye testing.
A dye test can be performed by simply releasing a
dye (either pellet or powder) into either the sanitary
or process wastewater system. Discharge points
from the storm water collection system are then
examined for color change.
Sampling and Chemical Analysis
Sewer mapping and visual inspection are also
helpful in identifying locations for sampling.
Chemical tests are needed to supplement the visual
or physical inspections. Chemical tests can help
quantify the approximate components of the
discharge mixture at the outfall or discharge point.
Samples should be collected, stored, and analyzed in
accordance with standard quality assurance and
quality control (QA/QC) procedures. Statistical
analysis of the chemical test results can be used to
estimate the relative magnitudes of the various flow
sources. In most cases, non-storm water discharges
are made up of many separate sources of flow, such
as leaking domestic water systems, sanitary
discharges, ground water infiltration, automobile
washwater, etc. Key parameters that can be helpful
in identifying the source of the non-storm water
flows include biochemical oxygen demand (BOD),
chemical oxygen demand (COD), total organic
carbon (TOC), specific conductivity, temperature,
fluoride, hardness, ammonia, ammonium, potassium,
surfactant fluorescence, pH, total available chlorine,
and toxicity screening. It may be possible to
identify the source of the non-storm water discharge
by examining the flow for specific chemicals.
Just as high levels of pathogenic bacteria are usually
associated with a discharge from a sanitary waste
water source, the presence of certain chemicals is
generally associated with specific industries. Table
1, includes a listing of various chemicals that may
be associated with a variety of activities.
IMPLEMENTATION
Identification of non-storm water discharges should
be part of every facility's maintenance program.
Facilities should conduct annual inspections for
non-storm water discharges, even if previous tests
have found no such discharges. New processes,
building additions, or other plant changes may have
brought about unauthorized connections to the
storm water conveyance system.
COSTS
The above methods are mostly time-intensive;
therefore, the cost is dependent on the level of effort
employed, and on the level of expertise. Visual
inspections are the least expensive of the three. Dye
testing may be more cost effective for buildings that
do not have current schematics of their sanitary and
storm sewer systems. The cost of disconnecting
illicit discharges from the storm water system will
vary depending on the type and location of the
connection.
The full use of all of the applicable procedures is
most likely necessary to identify all pollutant
sources. For example, attempting to reduce costs
by examining only a certain class of outfalls, or
using inappropriate testing procedures, will
significantly reduce the utility of the testing
program and result in inaccurate conclusions.
REFERENCES
1. California Environmental Protection
Agency, Draft, 1992. Staff Proposal for
Modification to Water Quality Order No.
91-13D WQ Waste Discharge Requirements
for Discharges of Storm Water Associated
with Industrial Activities.
2. Gartner, Lee and Associates, Ltd., 1983.
Toronto Area Watershed Management
Strategy Study, Technical Report No. 1,
Number River and Tributary Dry Weather
Outfall Study. Ontario Ministry of the
Environment, Toronto, Ontario.
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TABLE 1 CHEMICALS COMMONLY FOUND IN INDUSTRIAL DISCHARGES
Chemical
Acetic Acid
Alkalis
Ammonia
Arsenic
Chlorine
Chromium
Cadmium
Citric Acid
Copper
Cyanides
Fats, Oils
Fluorides
Formalin
Hydrocarbons
Hydrogen Peroxide
Lead
Metcaptins
Mineral Acids
Nickel
Nitro Compounds
Organic Acids
Phenols
Silver
Starch
Sugars
Sulfides
Sulfites
Tannic Acid
Tartaric Acid
Zinc
Industries
Acetate rayon, pickle and beetroot manufacture
Cotton and straw kiering, cotton manufacture
Gas and coke manufacture, chemical manufacture
Sheep-dipping, felt mongering
Laundries, paper mills, textile bleaching
Plating, chrome tanning, aluminum anodizing
Plating
Soft drinks and citrus fruit processing
Plating, pickling, rayon manufacture
Plating, metal cleaning, case-hardening, gas manufacture
Wool scouring, laundries, textiles, old refineries
Gas and coke manufacture, chemical manufacture, fertilizer plants,
Manufacture of synthetic resins and penicillin
Petrochemical and rubber factories
Textile bleaching, rocket motor testing
Battery manufacture, lead mining, paint manufacture, gasoline
Oil refining, pulp mills
Chemical manufacture, mines, iron and copper pickling, brewing, textiles
Plating
Explosives and chemical works
Distilleries and fermentation plants
Gas and coke manufacture, synthetic resin manufacture, textiles,
Plating and photography
Food, textile, wallpaper manufacture
Dairies, foods, sugar refining, preserves, wood process
Textiles, tanneries, gas manufacture, rayon manufacture
Wood process, vicose manufacture, bleaching
Tanning, sawmills
Dyeing, wine, leather, and chemical manufacture
Galvanizing, plating, viscose manufacture, rubber process
Source: Pitt et a/., 1992.
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7.
Pitt, R. and G. Shawley, 1982. A
Demonstration of Non-Point Pollution
Management on Castro Valley Creek,
Alameda County Flood Control District
(Hayward, California) and U.S. EPA,
Washington, DC.
Pitt, R., D. Barbe, D. Adrian, and R. Field,
1992. Investigation of Inappropriate
Pollution Entries Into Storm Drainage
Systems - A Users Guide, U.S. EPA,
Edison, New Jersey.
Pitt, R., and R. Field, 1992. Non-Storm
Water Discharges into Storm Drainage
Systems. NTIS Report No. PB92-158559.
U.S. EPA, 1992. Storm Water
Management For Industrial Activities:
Developing Pollution Prevention Plans and
Best Management Practice. EPA 833-R-
92-006.
Washington State Department of Ecology,
February, 1992. Storm Water Management
Manual for the Puget Sound Basin.
Northern Virginia Planning District Commission
David Bulova
7535 Little River Turnpike, Suite 100
Annandale, VA 22003
Southeastern Wisconsin Regional Planning
Commission
Bob Biebel
916 N. East Avenue, P.O. Box 1607
Waukesha, WI53187
The mention of trade names or commercial products
does not constitute endorsement or recommendation
for the use by the U.S. Environmental Protection
Agency.
ADDITIONAL INFORMATION
Center for Watershed Protection
Tom Schueler
8391 Main Street
Ellicott City, MD21043
King County, Washington
Dave Hancock
Department of Natural Resources, Water and Land
Resources Division, Drainage Services Section
700 5th Avenue, Suite 2200
Seattle, WA 98104
State of Minnesota
Lou Flynn
Minnesota Pollution Control Agency
520 Lafayette Road North
St. Paul, MN 55155
For more information contact:
Municipal Technology Branch
U.S. EPA
Mail Code 4204
401 M St., S.W.
Washington, DC, 20460
IMTB
Exceience fh compliance through optftnal technical sotrtroru:
MUNICIPAL TECHNOLOGY
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