JAN- 4--93 MON 15 :04 P. 02
SURFACE WATER CONTAMINATION
FROM NONPOINT SOURCES
by LEN KREMER
The 1972 amendments to the Federal Water Polution Control Act prohibit the
discharge of any pollutant to navigable waters from a point source unless the
discharge is authorized by a permit. Efforts to improve surface water quality
under the permit program established in the act have traditionally focused
primarily on reducing pollutants in discharges of industrial process wastewater
and municipal wastewater. This program emphasis has developed.for a number of:
reasons. Municipal wastewater outfalls and industrial process, discharges were
easily identifiable as responsible for poor, often drastically degraded water
quality conditions and represented pressing environmental problems. As
treatment and control of these discharges improved, it became, evident that more
diffuse sources of water pollution, such as agricultural and urban runoff were:
also major causes of water quality problems.
Since enactment of the 1972 amendments to the act, significant progress in
cleaning up water pollution has be&n made, particularly with regard to:
industrial process wastewater and municipal wastewater. Significant
0 expenditures at the Federal, State, and local level to construct and upgrade:
municipal wastewater treatment facilities have substantially increased the
population served by higher levels of treatment. Large industries have
developed sophisticated treatment processes to handle their process wastewater.
Industrial process wastewater discharges to municipally owned treatment works
are commonly retreated. Continued improvements are expected for these
discharges as the program continues to shift to toxic and water quality-based
Although assessments of water quality are extremely difficult to perform
and verify, the "National Water Quality Inventory, 1986 Report. to Congress"
provides a general assessment of water quality based on biennial reports
submitted by the States. The States were asked to indicate the fraction of the:
States' waters that were assessed, as well as the fraction of the States' waters
that were 'fully supporting, partly supporting, or not supporting designated
uses. The.States indicated that of the rivers, lakes, and estuaries that were
assessed (approximately one-fifth of stream miles, one-third of lake acres and
one-half of esturine waters), roughly 75 percent are supporting the uses for
which they are designated. States were asked to determine if the impairments'
to their waters were due to nonpoint (agricultural and urban runoff and other
sources), municipal wastewater, industrial wastewater, combined sewer
overflows, natural, and other sources. They were also asked to estimate the'
relative percentage of State waters affected by each source. The relative
importance of the various sources of pollution causing use impairments was
ON assessed and weighted national averages were calculated. Industrial process
wastewater were cited as the cause of impairment of 9 percent for rivers and
streams, 1 percent lakes, and 8 percent for estuaries. Municipal wastewater was
the cause of impairment of 17 percent of rivers and streams, 8 percent lakes,
and 22 percent estuaries. Nonpoint sources was the cause of impairment of
65 percent of rivers and streams, 76 percent of lakes, and 45 percent of
estuaries. :The Assessment concluded that pollution from diffuse sources such
as runoff from agricultural and urban areas is the leading cause of water
quality impairment: As discharges of industrial process wastewater and
municipal wastewater come increasingly under control, nonpoint source (NPS)
water pollution is increasingly recognized as the primary source of surface
water degradation. It is the cause for nonattainment of water quality goals in
6 out of 10 regions.4 NPS pollution is responsible for 73 percent of the oxygen
demanding loadings, 84 percent of nutrients, 98 percent'of bacteria counts, and
99 percent of suspended solids in the nation's waters.
To provide a better understanding of the nature of urban runoff from
commercial ind residential areas, the Environmental Protection Agency provided
funding and guidance to the Nationwide Urban Runoff Program (NURP) from 1978
through 1983. The NURP program included 28 projects across the Nation,
conducted separately at the local level but centrally reviewed, coordinated, and
One focus of the NURP program was to characterize the water quality of
discharges from separate storm sewers which drain residential, commercial, and
light industrial sites. The majority of samples collected in the study were
analyzed for eight conventional pollutants and three metals. Data collected in
NURP indicated that on an annual loading basis, suspended solids in discharges
from separate storm sewers draining runoff from residential, commercial and
light industrial area are almost an order of magnitude or more, greater than
effluent from wastewater treatment plants receiving secondary treatment. In
addition, the study indicated that annual loadings of chemical .pXygen demand
(COD) is comparable in magnitude to effluent from wastewater treatment plants,
receiving Sedondary treatment, When analyzing annual loadings associated with*
urban runoff, it i. important to recognize that discharges of urban runoff are
highly intermittent, and that the short-term loadings associated with individual
events will be high and may have shockloading effects on receiving water such
as sag in dissolved oxygen levels. NURP data also showed that fecal coliform
counts in Urban runoff are typically in the tens to hundreds of thousand per
100 ml of 4rnoff during warm weather conditions. Although NURP did pot evaluate:
oil and grease, other studies have demonstrated that urban runoff is an'
extremely important source of oil pollution to receiving waters, with'
hydrocarbon levels in urban runoff typically being reported at a range of 2 to!
10 mg/l. Th~se hydrocarbons tend to accumulate in bottom sediments where they:
may persist for long periods of time, and exert adverse impacts on benthic.
A portion of the NURP program involved monitoring 120 priority pollutants.
in stormwater discharges from lands used for residential, commercial and light
industrial activities. Seventy-seven priority pollutants were detected in'
samples of stormiwater discharges from residential, commercial and light;
industrial lands taken during the NURP study, including 14 inorganic and 63:
organic pollutants. Table 1 shows the priority pollutants which wore detected
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JAN-- 4--93 MON 15: 05
in at least 10 percent of the discharge samples which were sampled for priority
(' pollutants.: '
The 14 inorganic pollutants, 13 metals plus cyanides, were the most
prevalent group of priority pollutants in the samples. All 14 were found at
least once and il were found in at least 10 percent of the samples. The most
frequently found inorganic pollutants were copper, lead, and zinc; all occurring
in at least 91 preaent of the samples. Comparisons of individual constituent :
results to EPA water quality criteria and drinking water standards showed that:
lead exceeded its drinking water standard in 73 percent of the runoff samples;
that lead and coperb':often exceeded freshwater acute criteria; and that lead,
copper, zinc,' and dadmium regularly exceeded freshwater chronic criteria.
The NURP study provides insight on what can be considered background levels
of pollutants for urban runoff, as the study focused primarily on monitoring-
runoff from residential, commercial and light industrial areas; However, NURP
concluded that'the quality of urban runoff can be adversely impacted by several .
sources of'pollutants that were not directly evaluated in the study and are,
generally hot reflected in the NURP data, including illicit connections,
construction site.'unoff,'industrial site runoff, and illegal dumping.
Other studies have shown that many storm sewers contain illicit discharges
of non-stormwater, and that large amounts of wastes, particularly used oils, are
improperly. dispoSed in storm sewers. Removal of these discharges present
opportunities for dramatic improvements in the quality of stormwater discharges.,
Stormwater discharges from'industrial facilities may contain, in addition to
f4 illicit connections and improperly disposed wastes, toxics and conventional;
pollutants'when material management practices allow exposure to stormwater.
Table 2 lists heavy metals associated with various industrial activities.
Construction Site Runoff
Intensive construction activities may result in severe localized impacts:
on water quality because of high unit loads of pollutants, primarily sediments. ,.
Construction sites'can also generate other pollutants such as phosphorus and
nitrogen from fertilizer, pesticides, petroleum products, construction'
chemicals, and sold wastes. These materials can be toxic to aquatic organisms
and degrade water' tor drinking and water-contact recreation-, Sediment runoff
rates from construction sites are typically 10 to 20 times that of agricultural
lands, with runoff rates as high as 100 times that of agricultural lands, and
typically 1,000 to 2,000 times that of forest lands. Even a small amount of
construction may have a significant negative impact on water quality in.
localized 4reas. .Over a short period of time, construction sites can contribute
more sediment:to streams than was previously deposited over several decades.
In agricultural areas, the major nonpoint source pollutants are sediment,
nutrients, pesticides, bacteria, and oxygen-demanding substances.
Sediment is'made up of tiny soil particles that are washed or blown into
lakes and streams. Sediment is considered to be one of the most damaging'
pollutants in agricultural areas and is the major pollutant by volume in surface
JAN-- 4-93 MON 15:06
waters. Sediment 'can fill in lakes, streams, rivers, wetlands, and road
( ditches, and can affect aquatic life by smothering fish larvae and eggs.
Suspended soil particles make water look cloudy or turbid. Excessive turbidity
decreases light penetration needed for aquatic plant growth, increases water
temperature by absorbing solar radiation, and can significantly increase
drinking water treatment costs.
Although the6s problems are visible and easy to understand, other pollution
problems associated. ith sediment are less obvious. Nutrients .and pesticides
can become strongly bound to sediment, especially fine soil particles, and can
be carried with it to surface and ground waters.
Nutrients such as phosphorus, nitrogen, and potassium are an essential part
of agrcultire Theiy are normally added to the soil in the form of fertilizer,
manure, or decaying Vegetation. Nutrients may also be added to the soil by
nitrogen-fixing plants or they may be present in soil organic matter. In
agricultural areas, these nutrients -- particularly phosphorus and nitrogen --
can become pollutants when they are transported to surface and ground waters in
runoff or are leached below the root zone.
In many surface waters, phosphorus is the nutrient of greatest concern
because it'usually controls the growth of plants in lakes. Aquatic plants are
essential to a well balanced healthy lake, but excessive growth of aquatic
plants and.algae can be harmful. As phosphorus levels increase, algal blooms
may occur and aquatic plants become more evident. Water clarity may be reduced,
and the lake can shrink in size as shoreline areas accumulate decaying plants.
As the 'plants:die and decay, oxygen is consumed. This can cause a serious
decline in the dissolved oxygen levels in a lake, Fish populations become
dominated by species tolerant of these conditions, often rough fish.
Nitrogen is another nutrient that can cause severe water quality problems.
Nationwide, the use of inorganic nitrogen fertilizer doubled between 196$5and
1984, greatly increasing the amounts that can be lost to lakes, streams, and
groundwater. Nitrogen is found in several forms in the environment. Animal!
wastes and fertilizers are common nonpoint sources of ammonium nitrogen, a form
of nitrogen that is very toxic to fish. The ammonium can be converted"'to the
nitrate an4 nitrite forms in a process called nitrification, which consumes
large amounts of oxygen and can kill fish by lowering dissolved oxygen levels
Nitrate nitrogen is naturally found in water at low levels, When nitrogen
is applied to cropland in excess of crop needs or at a time when it will not be'
used by'crops,.nitrates can leach below the root zone, eventually reaching'
groundwater, Studies have shown an association between nitrogen fertilizer
application and nitrates in groundwater.
Pesticide is a term that covers a wide range of chemicals such as"
herbicides, insecticides, and fungicides. The use of these chemicals helps
farmers produce high yields; however, crop and field application of these
substances also provide a pathway for toxic pollutants to enter surface and
groundwatefs. The pesticides wash off crops and fields into lakes and streams
where they may be toxic to fish and other aquatic organisms. Table 3 lists
common agricultural chemicals and their characteristics.
JTN-_ 4-93 MON 1! : 07
Fecal coliform bacteria are prolific in the intestines of warm-blooded
1 animals, including humans. Although these bacteria are not necessarily harmful,
they are often associated with disease-producing organisms, or pathogens, that
can cause diarrheal diseases, infectious hepatitis, parasites, and cholera.
Common sources of bacteria are runoff or seepage from feedlots and failing
Aquatic life depends on dissolved oxygen in the water to survive. The
oxygen consumed by aquatic life is naturally replenished through photosynthesis
by aquatic plants, and through aeration, when air comes in contact with oxygen-
depleted water. When'oxygen-demanding pollutants enter a lake or stream, they
can upset the delicate balance between oxygen-consuming organisms and the
oxygen-replenishing process. Pollutants such as inadequately treated manure,
crop residues, and decaying organic matter such as leaves create an oxygen
demand on .a lake or stream. If oxygen is consumed faster than it is
replenished, the oxygen content can fall below the level needed to support
Aauatic Fate of Toxic OrLanic Substances
Technological change has resulted in the generation of enormous quantities :
of chemicals as products for production, consumption and as waste. As the.
volume and number 'of chemicals has increased, numerous unintended adverse
effects of these chemicals have been observed in the environment. Because of.
the potential hazard that exposure to these compounds poses to biota, the levels
of toxic and carcinogenic substances in the environment have become important'l
criteria for evaluating environmental quality.
The level, or concentration, of a toxic compound in the environment depends
on the quantity added to the environment and the processes which influence its
fate. "Transport" processes tend to distribute chemicals between the
atmospheric, aquatic, and soil environments depending on the affinity of the
compound for .each. phase. "Transformation" processes within each phase
chemically alter pollutants to forms of lesser, equivalent, or sometimes greater
toxicity. 'These processes occur at rates which are specific to each chemical'
and to each environmental compartment. The sum of these processes and their:
interactions determines the environmental fate and consequent exposure of biota
to a toxic'pollutant.
Comparison of Convyntional and Toxic Pollutants
Toxic substances frequently exhibit properties which are quite different.
from.the properties of conventional aquatic pollutants. It is worthwhile to
compare these differences in order to better appreciate the problems of.
analyzing impacts of toxicants in surface water systems. Table 4 shows some of
the more important differences.
Typically, one to two dozen pollutants and water quality parameters are
classified as "conventional". Until the past several years, these parameters
(e.g..BOD, nutrients) have received most of the attention of water quality
planners. In contrast to the small number of conventional pollutants there are
Thousands of toxicants and many more synthetic chemicals are continually being
developed. Potentially, any of these toxicants could enter the environment.
J f N -+ =P 11 I- .. -.
Even though there are relatively few types of conventional pollutants,
numerous sources combine to routinely discharge large quantities. However,
because many surface water bodies have a capacity to assimilate conventional
pollutants (e.g. BOD) without apparent adverse effects, .this practice is
acceptable within limits. Toxic substances, oh the other hand, can cause
adverse effects even at low discharge rates.
Concentrations of conventional pollutants are most often expressed in unite
of parts per million (ppm or mg/1). Because of the small quantities of
toxicants which are typically released, concentrations are often expressed in:
the parts per billion (ppb or Ig/1) range, or in even smaller. units. This
represents at least a' thousand fold difference relative to concentrations of
conventional pollutants. However, because toxic substances. present in small
amounts can adverse impact the environment, these small concentrations cannot
always be ignored..
Many toxic chemicals strongly adhere to suspended and bedded .seiments and
consequently dan .become a part of the immobile sediments in the bed. The
residence time of such chemicals can be on the order of years; Therefore,
depending oh the properties of the toxicant the period if impact can greatly
exceed the period of discharge. Consequently, the recovery period of a system
can be years;
water Qualitv Criteria
As previously indicated, toxicants are present in the environment in'
quantities which are often measured in the ppb range. Such small concentrations
are often foreign to.many workers in the field. When data or model predictions.
contain confentrations in the ppb range, the significance of the toxicant level,
is not always obvious (i.e., there is no "feel" as to whether the concentration
is large or small). Proposed criteria for toxic substances can serve as a basis
to gauge the significancee of observed or predicted levels. .Table 5 shows
proposed criteria for toxicants found in NURP samples. Since proposed criteria:
evolve ovet time, the criteria shown in the table are not necessarily the most
current. Nelertheless, their function remains: to provide a comparison with
levels observed or predicted in real systems. The data in this table comes from
the "R'd Book": (U.S.EPA, 1976), the Federal Register, March 15, 1979; July 25,
1979; October 1, 1979; and November 28, 1980 and Minnesota Rules, chapter 7050,'
1990, Criteria, ':designed to protect human health, for levels of toxicants in,
domestic water supplies, are also available from these sources.
Most States have adopted surface water standards for toxic substances. In
Minnesdta, the standards Were established to prevent discharge of municipal
wastewater, industrial wastewater, or other wastes from point or non-point :'
sources to surface waters in amounts that might impair the quality of the waters
of the state or the aquatic community, or in any manner render the aquatic'
community unsuitable or objectionable for fishing, fish culture, or recreational
The standards are intended to protect the aquatic community from the toxic'
effects of substances means the protection of no less than 95 percent of all the'
* species in any aquatic community. The standards are also intended to protect
JAN- 4--93 MON 15: 08
human consumers of fish, other edible aquatic organisms, and water for drinking
C from surface waters from exposure to both noncarcinogenic and carcinogenic
chemicals. The standards provide for protection of wildlife that eat aquatic
organisms by protecting the most sensitive wildlife species or populations.
Control of Nonpoiht Source Contamination
Where there hai been a sufficient economic incentive to do so, industry'
generally has improved the efficiency of manufacturing processes and prevented
pollution. B:'ut' oly recently have government and industry turned their
attention to preveiiing pollution in the name of environmental protection as an
alternative to disposing waste once it has been generated.
Those who promote pollution prevention advocate a hierarchy of alternatives
whereby source control or reducing the generation of waste would take precedence:
over recycling or rousing waste once generated. Recycling and reuse would take'
precedence over waste treatment. Only after these options are exhausted would'
the remaining residuals be disposed of as wastes. Our challenge is to better
understand the impediments standing in the way of pollution prevention and to;
promote adoption 6f this hierarchy in ways that are technologically acceptable ;
and economically feasible.
Largely because many of our past efforts have addressed point sources,
controlling agricultural and urban runoff in the future is likely to be far more.
important to improved water quality than, say, removing the final 5 to 10'
percent of pollutants from domestic wastewater. Since most of the conventional.
e* pollutants have bcon removed from domestic and industrial wastewaters, runoff:
from urban And rural lands is the predominant cause of water quality .impairment
in more than half the nation's rivers and streams. Controlling runoff poses :
significant challenges to conventional pollution control strategies, given the
diversity of human activities on the land and the direct relationship between
land use and the contamination of. runoff. Agricultural runoff, which contains'
priority constituents and excess nutrients, is widely dispersed .over the'
landscape.' The practice of applying fertilizers and pesticides in amounts'
greater than the ecosystem can assimilate is a basic impediment to control.:
Developing and implementing land use management measures that prevent or reduce
impairment rather than mitigate it after it occurs is a major challenge.
We face major technological and economic challenges in preventing the
generation of toxic constituents in the first instance--both toxic wastes and'
products that may be.toxic in their own right. In addition, Iwe face challenges
in improving 'urret' end-of-pipe control technologies. The emphasis of today's
water quality problems center more on control of toxics, including metals,'
organic coApounds, and radioactive constituents than on conventional pollutants.
Whil6 guidelines limiting concentrations of toxics in point oaurces were put in'
place several years ago, control of toxic pollutants in NPS discharges has' only'
recently started.tb be addressed. water quality professionals are only just
beginning to seriously consider how to deal with locally contaminated sediments'
and the buildup of.toxic metals and other compounds from unchecked discharges
and runoff of past decades. Moreover, a significant source.of toxics in water'
. is atmospheric deposition. controlling these sources implies strengthened air'
toxics regulations, Compared to toxic released to water, toxic discharges to:
JAN- 4-93 MON 1!5:9
- 0 s
air have until recently been underregulated at the federal level and
S inconsistently regulated by individual states.
Given recent advances in our ability to detect toxic metals and organic
compounds in minute amounts, the policy challenge for future control of toxics
is a better understanding of the risks to health and ecosystems of toxics in
Many aquatic ecosystems have been degraded or destroyed by a broad range
of human activities. Although considerable knowledge of the local impacts of
human activities exists, documentation is not available on cumulative
degradation across legions. Ambient biological monitoring has been underused'
to assess the extent to which regulatory and other efforts have had the desired
effect in improving the quality of water resources. Our future challenge is to
prevent further degradation of aquatic habitat and find ways to restore losses
of past decades.
The 187 amendments to the Clean Water Act required the EPA to adopt
regulations establishing permit application requirements for stormwater;
discharges associated with certain industrial activities and discharges from;
municipal separate ptorm sewer systems serving populations o'f 160,000 or more.
The rules !'were adopted in November 1990 and are specifically aimed ati
controlling nonpoint runoff from urban areas. As part of .their permit;
applicatio'is; ''bth industries and municipalities are required to implement
controls or' Best Management Practices to reduce pollutant sources.
The wide range of costs associated with implementing 'the different BMP
S levels is significant. Best Management Practices for municipal stormwater'
management: programs can be classified into levels which reflect cost of
implementation as listed in Table 6. Therefore, BMPs must be selected carefully:
to provide the .highest value for the moneys spent. it will be necessary to
select the .BMPs as. part of the overall stormwater management program. This'
means prioritizing ithe water quality problems and identifying BMPS which will'
solve the local problems.
It algo'will be.necessary to continue to monitor the effectiveness of the ':
BMPs and proceed with a phased-approach based. Stormwater maAagement plans will.
be required to eliminate illicit discharges and include institutional controls'
to prevent pollutants from entering the stormwater, similar *MPs have been
identified for -industries and agricultural stormwater 'management. The
industries included in the current permit program will be required to develop'
stormwater' management plans considering BMPs. Although B MPs to manage,
agricultural runQff have been developed, their implementation to-4ate has been
largely vo uhtary and the agricultural runoff problem remains.unaddressed.
Therefore, 'it wii be important to evaluate future :chemical,. physical and
biological. water quality data to determine the extent 'of the. remaining
stormwater: pollution and the resultant effects on beheficial uses"'. Stringent
numerical limits and treatment standards may not be necessary throughout the ;
nation if the~majority of stormwater pollution problems can be" olved through
institutional iand $ource controls. .
JAN-- 4-913 MON 15:10
PRIORITY POLLUTANTS DETECTED IN AT LEAST 10% OF NURP SAMPLES
METALS AND INORGANICS
Copper : 91%
Methane, dichloro- 11%
PHENOLS AND CRESQLS
Phenol, pentachloro- 19%
Phenol, 4-nito 10%
Phthalate, bis(2-ethylhexyl) 22%
POLYCYCLIC ARQMATIC HYDROCARBONS