United States
Environmental Protection
Agency
Municipal Environmental Research '
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-025 Mar. 1981
Project Summary
Nationwide Assessment of
Receiving Water Impacts from
Urban Stormwater Pollution
Volume I. Summary
J. P. Heaney, W. C. Huber, and M. E. Lehman
Results of this nationwide search
for documented case studies of
impacts of urban runoff on receiving
waters indicate that well-documented
cases are scarce. Impacts previously
attributed to urban stormwater runoff
may be point-source impacts to dis-
guise, or they may be masked by
greater contributions from other
sources. In some cases they are offset
by hydrological, biological, or geolog-
ical attributes of the receiving water
body.
The lack of documentation and clear
definition of urban stormwater im-
pacts makes the task of assessing the
importance of this pollution source
even more difficult. Efforts to address
this aspect include relating sources of
pollutants and pollutant types to the
characteristics of the receiving water
and the effects on desired water uses.
Characteristics such as stream or lake
bed hydraulics, present and potential
water uses, established stream stand-
ards, ecological data, and water quali-
ty information have been summarized
for 248 urbanized areas. Results of
these analyses have been summarized
by the quantity of urban runoff, the
available dilution capacity in the pri-
mary receiving water, the number of
times the urban areas were cited as
having a "problem," the type of re-
ceiving waters, the impaired benefi-
cial uses, and the problem pollutants.
The results indicate that numerous
definitions of "problems" are being
used. Relatively little substantive data
to document impacts have been col-
lected. Impacts are most noticeable in
small receiving waters. Impacts from
urban runoff are difficult to isolate
from other sources such as municipal
and industrial wastes. Also, accidental
or deliberate discharges from point
sources under wet-weather condi-
tions are sometimes the primary cause
of wet-weather impacts. The findings
suggest the need to intensify monitor-
ing programs so that receiving water
impacts can be more realistically
evaluated. The present data base is
poor.
This Project Summary was devel-
oped by EPA's Municipal Environ-
mental Research Laboratory. Cincin-
nati, OH. to announce key findings of
the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at bach).
Introduction
Urban stormwater runoff has been
recognized as a potentially significant
source of pollution. Studies have shown
-------
urban stormwater runoff constituents
comparable in concentration to second-
arily treated sewage and often comprise
a majority of constituent loads to some
receiving waters. Nationwide estimates
of the cost of controlhlng urban storm-
water run into the billions of dollars.
The prohibitive costs of treating all
stormwater outflows have made it
necessary to take a more in-depth look
at the receiving waters on a case-by-
case basis. What are the impacts of
stormwater runoff?
Concentrations and loads are high,
but what actual impairments of benefi-
cial use occur? What documentation
exists? These questions have been the
impetus for undertaking this nationwide
assessment
A previous nationwide assessment
indicated urban runoff and combined
sewer overflows can be viewed as caus-
ing problems since, on a nationwide
average, the quantity (13.4 in./yr) is
approximately equal to the quantity of
sewage (12.8 in/yr), and the annual
BODsper acre from a sewagetreatment
plant with a removal efficiency of 90% is
59.4 Ib as compared to 43.6 Ib from
urban runoff and combined sewer over-
flows. Loads per acre from combined
sewer overflows are approximately four
times as large as loads per acre from
urban runoff. Furthermore, the cost of
controlling these wet-weather flows
appears to be competitive with the cost
of additional removal of pollutants in
sewage. If further reductions in pollu-
tant loads are needed, then wet-
weather controls as well as further
waste treatment should be evaluated
carefully The anticipated high price tag
for such control programs has prompted
decision makers to take a harder look at
the seriousness of the problem
Approach
This report represents the results of a
search through published and unpub-
lished literature, project documents
relating to sections 201 and 208 of the
Federal Water Pollution Control Act of
1972 (PL 92-500), EPA-furnished fish
kill data, Nationwide Urban Runoff
Program proposals and project mate-
rials, agency data and permit files, and
other miscellaneous data sources to
characterize urban wet-weather im-
pacts on receiving waters Information
is presented for each of the 248 urban-
ized areas in the United States.
The results of the literature review
were analyzed and organized in terms of
the following characteristics of the
urban area as it related to types and
quantities of pollutants, characteristics
and types of receiving waters; uses of
receiving waters and water quality
standards; kind of impact whether eco-
logical or public health, characteristics
ot impact (e.g., short-term dissolved
oxygen sags versus longer term benthic
effects); and key pollutant or pollutants
causing the impact.
Data for each urban area were parti-
tioned into the following categories:
Demographic data
Hydrologic background
Waste sources
Receiving waters
Classification
Dilution ratio
Special studies
References to "Other studies"
category
1:500,000 USGS State Hydro-
logic Map for Urban Area and
environs
Ten years of monthly and an-
nual flow data for primary
receiving water(s).
An area was viewed as having an
actual or potential urban runoff
"problem" if any of the following condi-
tions applied'
1. The local or state 208 agency
viewed urban runoff as a priority
problem.
2. Runoff-related fish kills had been
reported during 1970-79
3. A runoff related beach closing was
reported.
4. It is a National Urban Runoff
Program (NURP) study area.
5 The urbanized area was identified
in EPA-funded projects as having
a potential dissolved oxygen
problem.
6. The urbanized area was listed m
the 1978 Report to Congress on
Control of Combined Sewer Over-
flow
7. The urbanized area was studied by
the National Commission on
Water Quality Studies
8. The urbanized area was men-
tioned m the National Eutrophica-
tion Survey.
9. The urbanized area was men-
tioned in the 1974 National Water
Quality Inventory.
10. The urbanized area was men-
tioned in the 1979 Congressional
Hearings.
11. The urbanized area has combined
sewers.
12. The urbanized area was men-
tioned in other studies.
Thus, any urbanized area may have a
"problem" as defined by these 1 2 condi-
tions some of which are interrelated.
Results
Major findings as a result of the litera-
ture search and assessment of wet-
weather impacts on receiving waters
are summarized below:
1. Impacts are not clearly defined.
Rather they are a composite of the
perspectives of professionals from
several branches of engineering
and science, environmental inter-
est groups, citizens committees,
etc The prevailing philosophical
definition of impacts during the
past decade was based on a broad-
based ecological framework.
However, the past year has wit-
nessed a shift back towards the
more traditional public health
perspective with more interest in
cost effectiveness. Against this
rather fuzzy backdrop, impacts
were tabulated in this report in
several ways as viewed by these
different groups. From a technical
point of view, impacts should be
more severe if the dilution capac-
ity of the receiving water is not too
large. Thus, dilution ratios were
calculated for each of the 248
urbanized areas in the United
States. Otherwise, "impacts"
were estimated by the number of
times the urbanized area was
cited in any of 12 categories of
special studies, e.g., the urbanized
-------
area listed urban runoff as a high
priority problem in its 208 plan-
ning study Admittedly, this
approach is subjective but it
appears to be reasonable due to
the paucity of available informa-
tion
2 Receiving waters are not well de-
fined. The literature contains
studies of receiving waters rang-
ing from the smallest ponds and
creeks to major rivers, estuaries,
and the ocean. Lacking a clear de-
finition of receiving waters,
1-500,000 USGS Hydrologic
Maps were used for all urbanized
areas. A dilution ratio calculation
was performed for the primary
receiving water(s) that is contigu-
ous to the urbanized area. In many
cases, receiving waters of noto-
riety in the literature, e.g , Lake
Eola in Orlando, Florida, do not
even appear on these maps
3 Almost 85% of the primary receiv-
ing waters contiguous to urban-
ized areas are rivers The majority
of these rivers have an average
flow of less than 10,000 cfs. Lakes
comprise 5% of the receiving
waters andthe remaining 10% are
estuaries or oceans.
4 Over 10,000 fish kill reports for
1970-1979 were reviewed Less
than 3% of these fish kills listed
urban runoff as the direct cause.
5. Water quality problems exist at
449 out of a total of 3521 beaches
throughout the United States Al-
though urban runoff was not listed
as a separate category in this
study, it may be a significant factor
since almost 50% of the closings
were due to undefined sewage
contamination or unknown
causes
6. Studies of continuous dissolved
oxygen (DO) records downstream
of urbanized areas indicate that
worst-case circumstances occur
after storms in approximately one-
third of the cases studied This
lowered DO is probably due to
combined sewer overflows, urban
runoff, and storm-caused resus-
pension of benthal materials.
7 Thirty cities are presently conduc-
ting intensive studies of urban
runoff under joint sponsorship of
the city and EPA's Nationwide
Urban Runoff Program. Several of
these studies will try to document
the deleterious receiving water
impacts that are caused by urban
runoff. There is little direct evi-
dence at this time to document
this cause-effect relationship.
8. The National Water Quality Inven-
tory studies indicated that 12 out
of 26 water quality constituents
have higher concentrations
during higher flow periods. These
studies were done for major
(>10,000 cfs) rivers that comprise
only 19% of the primary receiving
waters for urbanized areas.
9. Urban runoff was listed as a high
priority problem in 88 urbanized
areas. However, this prioritization
was done with relatively little
scientific/technical information.
10. The 1978 NEEDS Survey pro-
posed water quality criteria for
wet-weather flows and compared
these criteria to the results of
computer simulations However,
these criteria are admittedly arbi-
trary and the model does not
include the capability to incorpor-
ate the resuspension of benthal
deposits. Based on the evalua-
tions of DO data described in sum-
mary item 6, this factor is very
important
11. The 1979 Congressional Hearings
related to urban runoff discussed
the disturbing fact that existing
treatment plants are being oper-
ated poorly In many of these
cases, the results of plant break-
downs, spills, etc , are manifest as
urban runoff problems because
the discharges are made during
wet-weather periods.
12. A total of 120 urbanized areas
have combined sewers. Most of
these cities are located in the
eastern United States. In these
areas, the combined sewer over-
flow problem is more significant
than direct urban runoff.
13 The most popular theme of other
studies of urban runoff quality
was to predict water quality
changes in stormwater detention
ponds. The primary purpose of
these ponds is drainage control.
Concern exists that these ponds
may have serious water quality
problems and act as mosquito
breeding areas.
14. On the national level, about 150
million people live in urban areas
in the United States The average
annual precipitation in these
areas is 33 4 in The annual
volume of urban runoff is 4%
larger than the annual volume of
sewage. The median receiving
water has an annual flow of
approximately 15timesthesumof
the urban runoff and sewage. The
median number of the 12 condi-
tions that define this existence of
an urban runoff problem per
urbanized area is 1.6.
15. Unexpectedly, the number of
problem citations per urbanized
area increases as the dilution ratio
increases. One would expect the
opposite to occur since increased
dilution should reduce the number
of problem citations per urbanized
area. Overall, no obvious regional
trends in dilution ratio were
apparent.
16. Omitting those states not having
at least three urban areas, the
following seven states do not have
a dilution ratio greater than 10:
Connecticut (3.0)
North Carolina (3.5)
Colorado (3.5)
California (3.7)
Utah (5.1)
Massachusetts (6.2)
Ohio (7 2)
At the other extreme, the
following three states have dilu-
tion ratios greater than 1000:
Arkansas (1040)
West Virginia (1525)
Kentucky (2409)
17. The following 19 cities have four
to six problem citations:
Citations per
Urbanized Area
6
5
Urbanized
Area(s)
Philadelphia, PA
Boston, MA,
Chicago, IL,
1 US GOVERNMENT PRINTING OFFICE 1961 757-012/7061
-------
Detroit, Ml,
Lansing, Ml,
Milwaukee, Wl,
New York, NY,
Seattle, WA, and
Washington, DC
4 Atlanta, GA,
Baltimore, MD,
Cleveland, OH,
Denver, CO,
Des Momes, IA,
Mobile, AL,
Richmond, VA,
Savannah, GA,
Syracuse, NY, and
Youngstown, OH
This report was submitted in fulfill-
ment of Grant No. R805663 by the
University of Florida, Gainesville, FL,
under the sponsorship of the U S. Envi-
ronmental Protection Agency.
J. P. Heaney, W. C. Huber, and M. E. Lehman are with the University of Florida,
Gainesville, FL 32611.
John N. English is the EPA Project Officer (see below).
The complete report, entitled "Nationwide Assessment of Receiving Water
Impacts from Urban Stormwater Pollution: Volume I. Summary," (Order No.
PB 81-161 812; Cost: $14.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
r
L
00^3240
* Tn,uŁ
nr* v '"F
KKP
IT,
ST
------- |