Abstracts For
Urban Stormwater
and
Combined Sewer Overflow
Impact on Receiving Water Bodies
November 26-28, 1979
Holiday Inn
6515 International Drive
Orlando, Florida 32809
Sponsored By:
U.S. Environmental Protection Agency
luniclpal Environmental Research Laboratory
Storm and Combined Sewer Program
rican Society of Civil Engineers - Florida Section
ersitf of Central Florida, College of Engineering
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Abstracts For
Urban Stormwater
and
Combined Sewer Overflow
Impact on Receiving Water Bodies
November 26-28, 1979
Holiday Inn
6515 International Drive
Orlando, Florida 32809
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SESSION ONE
Monday, November 26, 1979
9:00 - 10:00
URBAN RUNOFF RECEIVING WATER IMPACTS:
PROGRAM OVERVIEW AND RESEARCH NEEDS
by
Richard Field and Robert Turkeltaub
Environmental Protection Agency
Edison, New Jersey
ABSTRACT
Receiving water impacts are a major national concern. We are spending
huge sums of money on secondary treatment plants, meanwhile major culprits,
stormwater and combined sewer overflows, are still uncontrolled. To attain
the goals set forth in PL 92-500 and PL 95-217 of abating pollution and
achieving water quality standards in an economical and efficient manner those
analyzing, planning and designing controls must have a thorough understanding
of the impact of pollutants on receiving waters. Receiving water impacts are
the bottom line justification for funding countermeasure campaigns and the
passage of abatement legislation. This conference will provide a forum for
the attendees to acquire first hand knowledge of the state-of-the-art and to
consider ongoing and recently completed research.
Data on the environmental impacts of urban stormwater and combined sewer
overflow are being gathered by projects of the Storm and Combined Sewer Pro-
gram (SCSP) of the Municipal Environmental Research Laboratory (MERL) as a
first step in developing control needs and a methodology to quantify pollutant
stress and evaluate the impact in relation to receiving water standards and
desired uses. This paper will contain a brief history of our receiving water
impact projects, an overview of recently completed and ongoing projects. The
projects will be briefly described including project objectives and an out-
line of significant results to date. Also, future Program needs will be
discussed and areas in which we anticipate concentrating our efforts will be
outlined.
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SESSION TWO
Monday, November 26, 1979
10:30 - 12 noon
AN ASSESSMENT OF THE IMPACT OF URBAN DRAINAGE ON
EUTHROPHICATION-RELATED WATER QUALITY IN URBAN LAKES
by
G. Fred Lee and R. Anne Jones
Department of Civil Engineering
Colorado State University
Fort Collins, CO 80523
ABSTRACT
The conversion of rural lands to urban area is often accompanied by a
significant increase in the total amount of phosphorus and nitrogen derived
per unit area of a waterbody's watershed. For rural lands phosphorus without
livestock, export coefficients typically range from 0.005 to 0.5 g P/m^/yr,
while in urban areas the typical export coefficient is 0.1 g P/m /yr. A
significant part of this difference is due to the much greater water yield per
unit area of watershed in urban areas compared to rural areas.
Urban runoff typically contains appreciable quantities of both soluble
ortho P and particulate forms of P. Studies have been conducted .to evaluate
the amounts of available forms of phosphorus present in typical urban storm-
water drainage for several municipalities located across the U.S. It has
been found that on the order of 10 to 30 percent of the particulate phosphorus
present in urban stormwater drainage would likely become available to affect
algal growth in a lake or stream. As a result of these findings, the focal
point of the control of nitrogen and phosporus from urban stormwater sources
should be directed toward the soluble orthophosphate component. Most storm-
water drainage control programs are directed toward control of particuiate
matter. Such programs are likely to have limited impact on eutrophication-
related water quality in urban lakes, since only a small part of the
particulate phosphorus will likely become available to stimulate aquatic
plant growth in the waterbody.
The OECD — (JS£$a&±zLa£d&XLjEQ,1L^]i£^^ eutro-
phication modeling study which included about 40 water-bodies across the
U.S. and 200 waterbodies in Western Europe, North America, Japan, Australia,
etc., has shown that the phosphorus load normalized by waterbody mean depth
and hydraulic retention time is correlated to the planktonic algal chloro-
phyll concentration, planktonic algal-related water clarity and hypolimnetic
oxygen depletion rate. The results of the OECD study provide the tools
necessary to quantitatively assess what water quality improvement can be
achieved as the result of various nutrient control efforts.
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THE EFFECT OF URBAN STORMWATER RUNOFF
ON THE WATER QUALITY OF LAKE JACKSON, FLORIDA
by
Chris Byrne , C, R. Donahue and W. C. Burnett
Department of Oceanography
Florida State University
Tallahassee, Florida 32301
ABSTRACT
Lake Jackson, Leon County, Florida, a depression of approximately 4800
acres, is a north Florida lake of conflicting water quality. In contrast to
the northern portions of the lake, which have been found to possess excellent
water quality, the southern portions are consistently characterized by sig-
nificantly poorer water quality. Investigations into this problem have dis-
covered that the reduction in the water quality in the southern sections is
a direct result of increased "urbanization" in that area. Extensive field
research and data analysis of the water quality of the southern watersheds of
Lake Jackson, in particular the urban watershed of Meginniss Arm, have con-
cluded that the magnitude of the pollutional loading of that area was due to
stormwater runoff. Analyses of the runoff of Meginniss Arm have revealed
high concentrations of suspended solids, dissolved nutrients, heavy metal
particulates, and petro-chemicals. In response to the serious state of water
quality in this area of the lake, the Florida Department of Environmental
Regulations in association with the United States Environmental Protection
Agency have prop£s^ed_t^Q_cQn.s_truct and maintain a bio-filtration system in
the urban watershed of Meginniss Arm to resTzritrt the poTTutiT5n"H™T5~ading.
One of the pollutants mentioned in the analyses of the urban stormwater
runoff was petro-chemicals. Lake Jackson affords an area for a very in-
teresting study of the loading of hydrocarbons into the lake. There are two
watersheds in Lake Jackson, which are similar in size, topography, and
geology (Ox-Bottom Creek in the northern section and Meginniss Arm in the
southern section). These two watersheds are very dissimilar in land usage:
Ox-Bottom Creek is primarily f orested-agricultural with little mechanical
activity; Meginniss Arm, in contrast, is highly urbanized with
_
The analyses of the stormwater runoff from these two areas will enable
comparisons of the concentrations and possible sources of hydrocarbons, both
biogenic and anthrog^genis,,^ that enter Lake Jackson. Rainfall, dust, sed-
TmSnt, and lake water samples will be examined to determine other possible
sources and sinks for hydrocarbons in the lake.
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A COMPARISON OF STORM-RELATED MATERIALS LOADING TO TWO
GLACIAL LAKES FROM URBAN, WETLAND, AND AGRICULTURAL SOURCES
by
R. P. Glandon, F. C. Payne, C. D. McNabb, and T. R. Batterson
Department of Fisheries and Wildlife
Michigan State University
East Lansing, Michigan 48824
ABSTRACT
Comprehensive watershed and in-lake studies have been conducted for two
glacial lakes located in the Lake Michigan drainage system. These studies
have shown tha,t^J27|;__gj^thj^a£^^ received by these
lakes annually 'in runoff is discharged during 10-12 weeks in thej3pjring_.
During that interval, large differences in s torm-relat^niuTjj^&l^.Xaadlng- were
measured f rom,u-:&b.an, ^wetland^ and agricultural watersheds. Separating runoff
due to melt of the snow pack from that dulTTfcTTFain events , it was found that
storm-related discharge from the xirban__ar_ea_studied was 0_J_Z85~kg._tp_tal_-P___and,,
Rain induced runoff from .marshes, in the
__
amedrainage^a s Tn~transp~o r t ed J]M)]L9_kg__ to tal^P and 0.545 kg total-N ,
of catchment. Rainfall in the same amount caused runoff
land_oj£ £_.jmiJs£_J^£aJU^E^n^ A1 ga.e jofToth lakes
were phosphorus limited; nitrogen was present in excess. Using constants
from Nicholls-Dillon relationships in the literature regarding phosphorus,
phytoplankton biomass, and secchi disk transparencies,
phjDsphorushar^of drainage was sufficient to bring 0^
__
to ^ unders^able^alg^alblofljn j^aE-11^ , Similarly , marshingu^'^a^'-would bring
an es timated 0 . 03 ha-m into bloom. By the same calculation, storm-related
agr_iculturai ru'n''o'tlrllllwouTa~*result in 0 $ 14 hagB o f lake water becoming under-
sirab"^**r^^naTrn~iaTfae . Knowing the number of hectares in these types of
catchment and the volume available in a particular lake for phytoplankton
production, decisions regarding cost-effective treatment of storm-related
discharge can be made.
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SESSION THREE
Monday, November 2,6, 1979
1:30 - 3:00'
IMPACT OF STORMWATER RUNOFF ON A FLORIDA LAKE ECOSYSTEM:
EFFECTS ON WATER QUALITY AND BIOTA
by
Eldon C. Blancher II
Department of Environmental Engineering Sciences
University of Florida
Gainesville, Florida 32611
ABSTRACT
' ,A study of external nutrient loadings to the Lake Conway ecosystem, an
interconnected series of three lakes located in Orange County, Florida,
showed that both nitrogen (2.6g-N/m -yr) and phosphorus (0.22 gP/m^-yr)
inputs were within the range of loadings that leads to mesc'-.rophic conditions.
The major external sources of both elements were atmospheric inputs, storm-
water runoff and subsurface seepage. Experimental evidence indicated that
phosphorus became a limiting factor in the lakes briefly during the spring
and summer of 1977. A dynamic hydrologic-phosphorus model demonstrated the
relative magnitudes of nutrient loadings from external sources and those
from internal nutrient cycling by the macrophyte communities and sediments in
this subtropical lake ecosystem.
l|*I]ultivariate analysis of water quality data by discriminant analysis
showed differences among the three lakes of the Conway system. Seasonal
trends in several water quality indicators varied""concomitantTy with changes
in external nutrient loadings, especially with those from residental storm-
water runoff. Those lakes that had a proportionately larger share of
phosphorus loadings from stormwater runoff showed a degradation in water
quality. Sj^rong linear relationships were found between watershed__ar-ea__tO-
,lake,area_ratio and stormwater phosphorus loadings (r2=0.9£); stormwater
phosphorus loadings and- Secchi^ disksjyransparenc.y (r2=0.98) and chloropjiyj.!^
_and_ total. zooplankton n:uinb*ers^~Trr^=0.96 ) . TEesef indings indicafe^adirect
impact of stormwater runoff on water quality and subsequently on changes in
the lakes biota.
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THE DISTRIBUTION OF SEDIMENTS AND PARTICULATE
CONTAMINANTS FROM COMBINED SEWER AND STORM DRAIN
OVERFLOWS IN SEATTLE'S NEARSHORE WATERS
by
R. D. Tomlinson*, B. N. Bebee*, S. Lazoff**,
R. G. Swartz*, and D. E. Spyridakis**
* Muncipality of Metropolitan Seattle, Seattle, WA 98104
** Department of Civil Engineering, University of Washington, Seattle
ABSTRACT
The distributions of particulates and the associated contaminants
emanating from combined sewar outfalls and storm drains in Lake Washington
were examined. In a preliminary study sediment samples were collected by
SCUBA divers from the area of greatest apparent contamination at each of
29 outfalls. The sample content of organics, heavy metals, oils and greases,
and pesticides was used to select stations for more intensive study. At
each of those sites quality and quantity analyses of the overflows provided
loading estimates for the wastewater particulates entering the nearshore
waters. Light transmissions measurements of storm-induced wastewater plumes
helped to define the nature of plume^disjDersion and its area of significant
influence. Org~air±c carbon and heavy metals analyses of settling particulates
and surface sediments near the outfalls supplied further detail arid con-
firmation of the fate of the wastewater particulates. Later in the program,
Dr. Thorn will discuss the response of infaunal communities to seasonal vari-
ations in wastewater discharge.
THE ECOLOGICAL EFFECTS OF URBAN RUNOFF ON STREAM COMMUNITIES
by
Donald B. Parcella
Tetra Tech Incorporated
Lafayette, California
ABSTRACT
A'literature review of the ecological effects of urban runoff on
streams indicates a dearth of principles for evaluating the impact of urban
runoff or any pollutant on streams and a serious lack of studies that de-
termine urban runoff impacts on communities of stream ecosystems. The_
uniqueness of urban runoff impacts results from the nature of pollutant input
t^TsJ^^^^-^SlSSTTO^ljff^ffe'^'ra^iOT^^^^'dcEast'ic occur rehce7~M6s"tf~sto rmwater
research has been directed towards determining runoff quantity and quality
including the fates of specific pollutants such as heavy metals, nutrients,
salts, toxic substances, and bacteria. Demonstration of the impacts of these
materials on stream communities is necessary to justify costs of managing
stormwater effects.
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Several approaches for analyzing ecosystems are suggested, such as
stream community analysis and biogeochemical cycling of elements (carbon,
nitrogen, phosphorus). Three published case studes of stream ecological
impacts typify the effects of urban runoff inputs resulting in a hypothesis
that large scale variations and instabilities of stream pollutant input and
concentration would result in greater impact to stream communities than steady
inputs. This concept is discussed and applied to urban runoff analysis and
management.
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SESSION FOUR
Monday, November 26, 1979
3:30 - 5:30
ANALYSIS OF RECEIVING STREAM IMPACTS
ON THE MILWAUKEE RIVER
by
Thomas L. Meinholz
EcolSciences, Inc.
Milwaukee, WI 53202
ABSTRACT
The Milwaukee Metropolitan area contains approximately 15,000 acres of
combined sewers which discharge to the three rivers of the area or directly
to Lake Michigan. As part of the Facilities Planning efforts of the
Milwaukee Metropolitan Sewerage District and research for EPA's Storm and
Combined Sewer Section, extensive monitoring and modeling efforts were per-
formed to quantify the receiving water impacts of the combined sewers.
Over 100 overflow points within the combined system were modeled
using the EPA SWMM model and Corps of Engineers STORM model. The output of
these models was used to load Harper's receiving water model. Major diffi-
culties in modeling the river systems were the variable influence of Lake
Michigan in the lower reaches. The relatively clean, high DO and lower
temperature lake inflows could not be easily quanitified because of the
dependence of the inflows on wind speed, direction, lake level and other
variable factors. Final model calibration using a linearly decreasing flux
was found to match the continuous DO data generated during two years of
record.
The Milwaukee river exhibits tremendous DO sags in the lower reaches of
the river following runoff events. The modeling tasks of the CSO project
could not duplicate these sags using the instream concentrations found in
the monitoring program. Extensive field monitoring was then conducted to
quantify the source and mechanism of these sags. After numerous invest-
igations, the bottom sediments in the lower reaches were found to be the
source of the rapid DO declines. The mechanism was related to the scouring
action of submerged combined sewer outfalls.
In order to model the response of the river to discharge events, the
receiving water model was modified to include an expression which would pre-
dict the extent and duration of the scour action from the submerged outfalls.
Long term simulations of DO and other parameters were calibrated and verified
using the response of the river to a multitude of rainfall events.
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The use of this model network in the evaluation of alternatives for
abating combined sewer overflows produced magnitudes of DO and fecal coliform
impacts for each alternative using 20 years of rainfall record.
The results for the following alternatives are presented.
* existing conditions
* partial separation
* complete separation
* out-of-basin (storage-conveyance-treatment)
* end-of-pipe (EOF)
* 100% CSO removal
Discussions of how these results were quantified including the model
development will be discussed. The cost-benefits analyses that were used
to satisfy the EPA PG-61 requirements will also be detailed to provide the
reader with a methodology that has been successfully applied and approved
in the Milwaukee area.
URBAN STORMWATER IMPACTS ON RECEIVING
STREAMS IN NORTH CAROLINA
by
E. Ryland Brown and Ross S. Green
Technical Services Branch
Division of Environmental Management
North Carolina Department of Natural Resources
and Community Development
Raleigh, NC 27611
ABSTRACT
Studies were conducted in North Carolina by the Division of Environmen-
tal Management as part of the statewide 208 program to determine the extent
of water quality degradation in streams receiving urban stormwater runoff.
Selected streams were monitored in three of the larger urban areas within
the state; A^hgville, Raleigh, and Winston-Salem. The monitoring program
involved physical/chemical ~sam^Ting"Tmd^r"both" high (storm) and low stream-
flow conditions. Parameters sampled include pH, temperature D.O.jBODr COD,
fecal coliforms, ammonia-nitrogen, total Kjeldahl nitrogen, nitrite plus
nitrate nitrogen, total phosphorus, iron, mercury, lead, zinc, copper,
chromium, manganese, cadmium, nickel and suspended solids. Biological
sampling of _aq_uatic benthic macroinvertebrates was ^^ondu^te^^concurrently^^^
~To~~Tuft:h"er document water quality' conditions.
In Asheville, a stream draining a mixed land use urban area was studied.
In the Raleigh area, three streams were monitored, including one that drains
a highly impervious watershed comprised primarily of a shopping center.
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The most intensive sampling was conducted in thfe Winston-Salem area. In
this locality, streams draining both residential and Central Business
District watersheds were monitored to investigate water quality characteris-
tics associated with these different land use types. For comparison purposes,
control stations upstream of urban inputs were also monitored.
_All_of the_urban_s_treams were found to exhibit extensive water quality
_pjrob_lems_!- Physical/chemical sampling consistently revealed high pollutant
concentrations for several parameters under high flow conditions. Notable
problematic parameters included suspended solidsJ_J^e^_^_^nd__^ojBe^-nu.tr.ignts.
^S£ateral p^xamaJLexs-_w^rjLJ:Qimd--to_;f-raq-uen-feLy—be .-present in .high—co-neentrationi
_under lcwjjlowj_c^diti:pns also. Variations in pollutant concentrations from
the different land use types~~wefe" also observed.
The Division of Environmental Management's biological monitoring group
has developed an index of the macroinvertebrate organisms found in North
Carolina streams. As part of this index, each taxa is rated according to its
ability to withstand pollutional stressed conditions. —ALl_of_the urban
streams monitored were found to be_j|x£ensjuxfil^.biplogjLcally degraded.
Populations oj_IXipterar"anH'"OTigochaeta, pollution-tolerant organisms,
averaged ove^r 90/Qof the existing fauna. In contrast,_c_gn.tr-oJ station
population percentages of these organisms we r eamaxiiaum of_15% of the
._£_auna in the mountain stream, and 35% in Piedmont streams. Many""intolerant
groups wer-e~noli~j"usT~r"educed in number's""iti" the'urban" streams, they were
usually completely absent.
These studies have shown that, under present conditions, almost all
urban streams,...will_be _unable to meet the 1983 water quality goals. The
Division of Environmental Management is currently finalizing guidelines for
a study to be centered in the Winston-Salem area to evaluate management
techniques aimed at reducing these documented water quality problems. This
three year project is in conjunction with the Environmental Protection
Agency ' s National Urban Runoff Program.
10
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DISSOLVED OXYGEN IMPACT FROM URBAN STORM RUNOFF
by
Thomas N. Keefer, Robert K. Simons, and Raul S. McQuivey
The Sutron Corporation
Arlington, VA 22209
ABSTRACT
One hundred and four water quality monitoring sites in and downstream
of urban areas throughout the country were considered for inclusion in this
study. These were screened from over 1000 monitors maintained by federal
and state agencies such as the U.S. Geological Survey, Environmental
Protection Agency (EPA) , Ohio River Valley Sanitation Commission and
Wisconsin Department of Natural Resources. Daily data were obtained and
processed for 83 of the 104 candidate sites. Of the 83 monitors considered,
42 percent or roughly one monitor in three of the 104 candidates demon-
strated a 60 percent or greater probability of a higher than average DO
deficit occurring at times of higher-than-average streamflow or on days with
rainfall. This result was obtained by considering daily da '-a for entire
water years. Not all years at any given station exhibited a 60 percent pro-
bability. One to three years out of five is typical. DO levels fell to less
than 75 percent saturation at most of the sites where 60 percent or greater
probability existed. Levels of 5 mg/1 or less were not uncommon.
Detailed hourly data analysis was made at_2^.of the sites with high
correlation between flow and DO deficit. Typically, at times of steady low
flow the DO fluctuates widely on a daily cycle. These cyclic changes range
from 1 to 7 mg/1. When a storm event occurs and the flow increases, the
diurnal cycle disappears. The minimum DO drops from 1 to 1.5 mg/1 below
the minimum values observed during steady flows and remains constant there
for periods ranging from one to five days. As the flow event subsides, the
DO level resumes its cyclic behavior. Of the 22 monitors examined on an
hourly basis, 11 would not meet a 5 .0-mg/lDOstandard . jSix_qf the 11_
mee £~the~ EPA- suggel2^J^mjj/I^^ Streeter-
__
Phelps analysis'~ilicfTcatedL_that two additional monitor sites at which hourly
data wer£._examined would not have met the EPA~'¥t"aTiira"f^~TTaT"Oiey^b^
•,,--3— --~ ~~ '' ' — •-- -. ,,,^, .. „-,,.--->- -, -' ••"•• „-.-*-.- ,•--'•- ' •• ' " -•--•.,- ___ ^ _. . — ... . ~f.,#«*fa* .*.-~. *•--•>••• '••- i -•»-=•— 't--j.~--=j — •• — - «/-*•--
located. ,An additionaL two sites at which hourly data could no t_ be
tiined would also not have met the EPA standard,.
11
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THE IMPACT OF COMBINED SEWER OVERFLOWS ON THE
DISSOLVED OXYGEN CONCENTRATION OF A SMALL STREAM
by
Thorkild Hvitved-Jacobsen
Institute of Civil Engineering
Aalborg, Denmark
ABSTRACT
The paper discusses the impact of combined sewer overflows on the dis-
solved oxygen concentration of a small stream. The different oxygen con-
sumption processes in the receiving stream have been studied at 4 con-
secutive stations during and after the passage of the discharged volume of
stormwater and untreated sewage. Two different effects on the DO-concen-
tration were observed in the stream:
I,1' An immediate effect caused by degradation of the soluble BOD-fraction
- in the polluted watervolume.
2. A delayed effect caused by degradation of the adsorbed colloidal and
outsetting particulate matter. ^ I ^^ tJ^\J -,
.fj <^^> ''1 s *"'•'
ad 1. This effect is caused by the degr^adation^ in_the water -body and by
, direct absorpjtio^_bv__£_ne animals (invertebrates) in tbTeTbqttom. The
deoxygenation constant K/[~~in thV~water volume ~ is about 0.15 days ,
but the total deoxygenation constant Kr for the whole stream is
about 0.55 days "-*-, which indicates the importance of the degradation
in the bottom .
Qd 2. After passage of the discharged polluted volume there is an effect on
the DO-concentration in the stream, which is attributable to jid^
_ sorption_of_co_lloi.dal organic matter _at. .thg.Jiattojn. The delayed de-
gradation may increase the fe"spiration of the bottom in certain
stations by 100%. This delayed effect may last 12-24 hours after
the stormwater passage.
The investigation shows that due to the delayed effect, the oxygen
consumption is spread over a long period compared to the passage time of the
polluted volume. The importance of this depends among other things on the
reaeration of the stream.
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SESSION FIVE
Tuesday, November 27, 1979
8:30 - 10:00
IMPACTS OF INTERMITTENT URBAN DISCHARGES ON RECEIVING WATERS
by
John L. Mancini
Manhattan College
Bronx, NY 10471
ABSTRACT
The paper will present an illustration of the impacts of CSO discharges
on bathing beach areas of New York City. The illustration will also define
the treatment required and the costs for controlling water quality. A
unique statistical analysis used in the project will be discussed.
The proposed paper will be divided into two segments.
Segment #1 - will discuss an analysis of coliform distribution in New
York Harbor. The paper will present calculated and observed time variable
coliform distributions over several storm events for the major water bodies
that make up New York Harbor. Data and calculations will be presented for
different size rainfalls and for different Hudson River flows. This seg-
ment of the paper will conclude with economic data on the cost of controlling
coliform levels at selected beach locations in New York Harbor. Therefore,
loads, fate and effects of storm water associated coliform distributions
will be discussed.
Segment #2 - will address the fate and effect of intermittent discharges
of toxics. In particular, information from data in the Trinity River, will
be employed to calculate partition coefficients and equivalent removal rates
for Cd, Cu, and other metals. Comparable calculations for the equivalent
removal of Lindane, DDE, DDT and several other organic toxics will also be
provided. This will be a discussion of fate of toxics.
The effects part of this segment will employ dose response data for Cd
to illustrate calculations of mortality of an organism due to a storm load.
The effect part of the paper will present a procedure for calculations. In
situ data are not available to test the calculation procedure. The issues of
concern in rational evaluation of effects will be identified in a quantitative
manner.
13
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THE RESPONSE OF GREAT LAKE ESTUARIES TO STORMWATER RUNOFF
by
John R. Adams and Stephen M. Yaksich
U.S. Army Corps of Engineers
Buffalo, NY
ABSTRACT
Glacial rebound of the northern shore of Lake Erie has resulted in
drowned rivermouths of southern shore tributaries. Transport of material
through these estuaries depends not only on river stage but also lake stage.
This paper describes studies carried out in two Lake Erie tributaries during
high and low flow conditions. It also examines the effect of localized urban
runoff on one of the estuaries.
Three separate studies of water chemistry in the lower Maumee River, an
estuarine river section, were conducted by the Toledo Metropolitan Council
of Governments, the Buffalo District Corps of Engineers, and others, during
1974 and 1975. Base flow river conditions and the resultant estuary
chemical variations were measured during the summer of 1974. Winter storm
runoff effects were measured during January and February, 1975. Additional
sampling and analysis was conducted during the summer of 1975, giving a
fairly complete record of water chemistry variability.
Winter storm runoff was also measured in the estuary of the Cuyahoga
River, with simultaneous river and estuary sampling over the hydrograph
for selected pollutants.
This paper outlines the problems and complexities of chemical measure-
ments of water quality in estuarine systems of the Great Lakes during
varying hydrologic conditions. The studies in the Maumee River point out
the importance of sampling program design, and the difficulty in evaluating
the transport of pollutants through such estuarine systems. The summer
studies were conducted by TMACOG as part of an evaluation of in situ
water quality, as effected by a number of waste discharges from the Toledo
area. The winter storm runoff measurements, made simultaneously at both an
upstream riverine station and a downstream estuary station were designed to
evaluate whether the mass transport being carried out into the basin was
passing through the estuary and out into the lake. The question of an in-
crease or decrease in mass transport was also considered, to evaluate
scouring and depositional mechanisms in the estuary.
The results of the Maumee estuary measurements were compared with the
Cuyahoga estuary in Cleveland, where similar sampling of river and estuary
transport was carried out for the same storm periods.
14
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WATER QUALITY AND URBAN RUNOFF IN SELECTED CANAL COMMUNITIES
ALONG THE TEXAS COAST
by
Allen Messenger* and Tom D. Reynolds**
*Environmental Science and Engineering, Inc.
Austin, Texas
**Professor of Civil Engineering
Texas A & M University
College Station, Texas
ABSTRACT
Water and runoff samples from seven waterfront communities in the
Galveston Bay area were collected and analyzed in order to evaluate causes
of canal water quality problems. Until present, community design has been
based on optimum utilization of land area with little or no regard toward
the effect of development on water quality. The primary cause of water
quality problems in these communities appears to be urban runoff.
Samples of canal waters were collected over a five-month period and
analyzed for nutrients, oxygen demand, pesticides, and hydrological vari-
ables, including Rhodamine dye concentrations. In general, canal waters
exerted BOD values of 2-10 mg/1 with no problems associated with toxic
substances. Evaluation of domestic wastewater data from centralized treat-
ment facilities indicates that these wastewater streams are not major sources
of pollution loading.
Runoff samples were collected from three rainfall-runoff events and
were found to contain signficant amounts of carbonaceous material. Also,
the possibility of canal sediment resuspension by point discharge of runoff
was investigated using a canal model. The two-year frequency rainfall event
for the Galveston area was found to produce significant resuspension of
high BOD,- benthic sediments. These data were applied using the modified
Streeter-Phelps equations for estuarine dissolved oxygen analysis and were
found to fit actual conditions with reasonable accuracy.
15
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SESSION SIX
Tuesday, November 27, 1979
10:30 - 12 noon
THE RESPONSE OF INFAUNAL COMMUNITIES TO SEASONAL
VARIATIONS IN WASTE WATER DISCHARGE
by
Ronald M. Thorn
College of Fisheries
University of Washington
Seattle, Washington
ABSTRACT
Certain aspects of the structure of macroinfaunal communities in the
subtidal sediments adjacent to an intertidal combined sewage overflow were
studied. The impact of this ephemeral source of raw waste water and street
runoff on the communities was evaluated using samples taken after periods of
high (April) and low (August) frequency of discharge. In April, the
community nearest the overflow was characterized by a high number of
individuals, low number of taxa, a lo^ species diversity, a high abundance
of the polychaeta Capitella capitata , and a high relative number of poly-
chaetes. Subsurface deposit feeding species dominated the community.
Infaunal abundance was markedly low in the region immediately beyond the
area of acute impact. Diversity and number of taxa were highest at the sites
furthest (i.e. > 1000m) from the overflow. Bivalve molluscs were in re-
latively high abundance, and carnivores, surface deposit feeding and sub-
surface deposit feeding species were approximately equally abundant at
these sites.
The samples in August showed similar trends relative to the overflow in
number of individuals, number of taxa, species diversity and community
composition by phyla and feeding type. However, differences among all sites
in these parameters were less pronounced during this period. Capitella
capitata was not in low abundance, and the loptostracan Crustacea
Nebalia pugettensis was in highest abundance at the site nearest the overflow.
A cluster analysis of the communities indicated that the communities
closest to shore and northward from the overflow were most altered. The
communities at the sites nearest the overflow appear to be primarily
affected by intense scouring and deposition, whereas those communities
further away appear to respond largely to input of organic debris. The
decreased frequency of overflows in August may be responsible for the
relative decrease in differences among the communities at all distances
from the overflow.
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PRODUCTIVITY RESPONSES OF LAKE EOLA
WATER TO URBAN RUNOFF
by
Harvey H. Harper, Yousef A. Yousef, and Martin P. Wanielista
Department of Civil Engineering and Environmental Sciences
University of Central Florida
Orlando, Florida
ABSTRACT
Lake Eola is a land-locked lake located in downtown Orlando, Florida. Its
surface area is approximately 27.0 acres (11.0 Ha) and water depth is
2 to 3 feet (0.6 to 0.9 meters) near the shore area and 22 feet (6.7 meters)
toward the center. The lake directly drains 85 acres (34.4 Ha) of im-
pervious land and 56 acres (22.7 Ha) of pervious land from commercial and
residential areas. Currently there are coarse screening devices (1^ inch
opening) on inlet storm drains which are called grass catchers.
Lake Eola is a focal point for the City of Orlando and is visited by
many tourists for its aesthetic appeal. No swimming, motor boating, or
fishing is allowed. The lake was drained down exposing 40% of the bottom
and approximately 4 feet of mud was removed in 1972-1973. However, input
nutrients, organics and other compounds from street stormwater runoff have
not been effectively managed. Five years later, excess fish and algae have
to be removed periodically and the water quality of Lake Eola is again
questioned.
A research project sponsored by the U.S. Environmental Protection Agency,
the Florida State Department of Environmental Regulation and the City of
Orlando is currently underway to determine the lake impacts of pollutants
in stormwater runoff and to develop a methodology for determining optimal
combinations of stormwater management methods.
Periodical water samples are being collected from the lake for various
stormwater events. Changes in water quality parameters with time through
each storm event are documented. Parameters analyzed include alkalinity,
hardness, solids, BOD-, TOC, Nitrogen, Phosphorus, and heavy metals for
particulate and dissolved fractions. Analytical methods followed Standard
Methods for the examination of water and wastewater and EPA's Methods for
Chemical Analysis of Water and Wastewater. Heavy metals including, Zn, Cd,
As, Ni, Cu, Fe, Pb, and Cr are being analyzed using a plasma spectrometer,
SMI Spectrospanlll. Loading rates from nutrients and heavy metals released
to Lake Eola due to stormwater runoff are analyzed, and lake impacts are
evaluated.
Algal bioassay studies are performed to investigate stormwater impacts
on Algal productivity. Periodical water samples are being collected from
various locations in the lake, mixed and filtered for limiting nutrient
studies using various concentrations of N, P, and Fe.
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Unialgal species of Selenastrum, Cholorella and indigenous species are
used and changes in chlorophyll "a" and biomass are measured. Initial
results indicate that phosphorus or nitrogen can be limiting at some-
times of the year. However, the ratio of P:N can be more important than
actual concentration of phosphorus and nitrogen separately. Maximum
standing crop seem to occur at N:P ration of 15-20:1.
Also, similar bioassays are performed on a mixture of stormwater,
coagulated stormwater and lake water at different ratios. Higher con-
centrations of stormwater would inhibit algal productivity and smaller ratios
would significantly increase productivity. Additionally, no increase in
productivity is observed when coagulated runoff water is used. These
experiments can be used as useful tools to facilitate stormwater management
decisions.
WATER QUALITY AND BIOLOGICAL EFFECTS
OF URBAN RUNOFF ON COYOTE CREEK
by
Robert Pitt and Martin Bozeman
Woodward Clyde Consultants
San Francisco, CA
ABSTRACT
This preliminary report presents the initial results and conclusions
from the EPA-sponsored demonstration study of the water quality and bio-
logical effects of urban runoff on Coyote Creek, near San Jose, California.
This first phase included investigating various field procedures that would
be most sensitive in evaluating water, sediment and biological changes in
the creek as it passed through the urban area. The procedures identified
as most promising are currently being used in additional Coyote Creek studies.
The report describes the characteristics of urban runoff affecting the
creek, sources of urban runoff pollutants, effects of urban runoff and
potential controls for urban runoff. Local urban runoff characterization
information is summarized, based on a previous EPA sponsored demonstration
project in the area (Demonstration of Non-Point Pollution Abatement
Through Improved Street Cleaning Practices-EPA grant No. S-804432, Pitt
1979) and from the local "208" study (Metcalf and Eddy 1978) . Sources of
urban runoff pollutants in the study area are being investigated as an
important part of the field activities of the project and include sampling
runoff from many source areas (such as street surfaces, parking lots,
landscaped areas, rooftops and rain).
Various short- and long-term biological sampling techniques were used
to evaluate the fish, benthic macroinvertebrate and attached algae condi-
tions at many stations in the creek, above and within the urban area.
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Creekwater and sediment samples were also obtained and analyzed for a
broad list of parameters. In most cases, very pronounced gradients of these
creek quality indicators were observed, with the urbanized portion of the
creek being significantly degraded. Current additional monitoring is
being conducted to identify the urban runoff control goals necessary to
improve creek quality to adequate levels.
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SESSION SEVEN
Tuesday, November 27, 1979
1:20 - 3:00
NATIONWIDE ASSESSMENT OF URBAN STORMWATER
IMPACTS ON RECEIVING WATER BODIES
by
James P. Heaney, Wayne C. Huber and Melvin E. Lehman
University of Florida
Gainesville, Florida
ABSTRACT
Urban stormwater runoff has been recognized in recent years as a po-
tential major contributor of pollution to receiving water bodies. Assess-
ment of urban stormwater runoff pollutant quantities and characteristics
have been made for several areas throughout the United States, the most
ambitious being the Environmental Protection Agency's 208 Areawide Waste-
water Management Planning Program. Price tags for abating urban stormwater
pollution (though elimination or reduction of discharges) range in the
billions of dollars. Projections of high costs have forced a look beyond
abatement of discharges to the receiving water bodies for insight as to what
are the impacts, where are they, and are they significant?
First-year results of a nationwide search for documented case studies of
impacts of urban runoff receiving waters indicate that well-documented cases
are scarce. Impacts previously attributed to urban stormwater runoff may
be point source impacts in disguise, or they may be masked by greater con-
tributions from other sources. In some cases they are offset by hydro-
logical, biological, or geological attributes of the receiving water body.
The lack of documentation and clear definition of urban stormwater impacts
makes the task of assessing importance of this pollution source even more
difficult. Efforts to address this aspect include relating sources of
pollutants and pollutant types to receiving water characteristics and effects
on desired water uses. Characteristics such a& stream or lake bed hy-
draulics, present and potential water uses, established stream standards,
ecological data and water quality information are being summarized for the
documented cases to determine how the urban runoff pollutants might behave
or react in the receiving water and what potential use they might affect most
adversely. Results of these analyses are to be used as a basis for de-
vising simple criteria for analyzing an urban area to determine whether
a potential impact does or would occur.
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STATISTICS OF ADVECTIVE DISPERSIVE SYSTEM
RESPONSE TO RUNOFF
by
Dominic M. Di Toro
Environmental Engineering and Science Program
Manhattan College, Bronx, NY
ABSTRACT
An analysis is presented for the mean and variance of a one dimensional
advective dispersive system that is subjected to random inputs of runoff.
Analytical solutions are available for which the mass input is represented as
a Poisson process of delta functions. The effects of event to event
variability of runoff mass discharges are included in the formulation as
are the random times between overflows. The method of solution evaluates
the overlapping effects in the receiving water due to the persistence of
discharged mass. Both conservative, first order reactants, and sequentially
reacting substances are considered.
The solutions have certain unexpected properties. In particular, the
normalized variance of BOD and DO are symmetric about the discharge point,
whereas the means of the concentration are not. This is explained in terms
of the effects of advection and dispersion of flucuations. The analytical
solutions are compared to simulated results using an observed hourly rain-
fall sequence. The results indicate that the within event variability is not
significant, if the receiving water dispersion is large enough. It is also
pointed out that treatment devices such as retention basins which remove a
certain average fraction of the overflowing mass are less effective in re-
moving variance in the receiving water. This phenomena is of importance
in the evaluation of the probable benefit of runoff treatment.
CONTINUOUS RECEIVING WATER QUALITY MODELING FOR
URBAN STORMWATER MANAGEMENT
by
Miguel A. Medina, Jr
Duke University
Durham, NC
ABSTRACT
A simplified continous receiving water quality model has been developed
to permit preliminary planning and screening of areawide urban wastewater
treatment alternatives, in terms of frequency of water quality violations
and more traditional approaches such as dissolved oxygen profiles. The
model name is Level Ill-Receiving.
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It simulates the hypothetical reponse of the stream or tidal river system
to the separate and combined effects of waste inputs from: 1) upstream
sources, 2) dry weather urban sources, and 3) wet weather urban sources.
The total hours of runoff-producing rainfall throughout a year are separated
into storm events by defining a minimum interevent time. For a given storm
event, the runoff and pollutant loads are summed and critical dissolved
oxygen concentrations are estimated as a function of several hydrodynamic
and biochemical parameters. Alternative control strategies are evaluated
in terms of relative impacts by determining the probability of occurrence 0%
water quality violations. Model output includes the downstream dissolved
oxygen sag curves computed per each event, and the dissolved oxygen profile.
computed at a user-specified location downstream for all simulated events.
An application to the Des Moines River at Des Moines, Iowa, has been made.
POTENTIAL OF STORMWATER IMPACTS BASED ON CAMPARATIVE ANALYSIS
OF WET AND DRY WEATHER POLLUTANT LOADING
by
Douglas C. Ammon and fUch&fd field
sU.S. Environmental Protection Agency
V~ . ,' — "-— -~r~~—-~- __fc _ _ _~— —. r~--,—_,^.—,_ _ - —*~-j **<^ , , . . __^
"Edison, New Jersey
ABSTRACT
Recent work indicates that urban runoff and combined sewer overflows
can be significant contributors to the trace contaminant input to urban
receiving waters. For example, a 1975 National Academy of Science Study
estimates that on a global basis, 2 to 8 percent of the petroleum hydro-
carbons entering the ocean Is from urban runoff. This paper summarizes
much of the stormwater characterization data for trace contaminants and
several conventional parameters, such as BODr and COD. Comparisons are
made among loadings and concentrations from urban runoff, combined sewer
overflows and secondary treatment plant effluents. Finally, the signi-
ficance of each contaminant is Identified based on loading potentials or,
whenever possible, based on toxicity to aquatic organisms.
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SESSION EIGHT
Tuesday, November 27, 1979
3:30 - 5:00
THE USE OF RECEIVING WATER QUALITY MODELS IN URBAN
RUNOFF POLLUTION ABATEMENT:
APPLICATION TO MARGINAL BENEFIT - MARGINAL COST ANALYSIS
by
Cornelius B. Murphy, Jr.*
Dwight A. MacArthur* and Raymond P Canale**
*0'Brien & Gere Engineers, Inc.
Syracuse, New York
**University of Michigan
Ann Arbor, Michigan
ABSTRACT
Urban storm runoff has been determined by a number of investigations to
be a significant portion of the water pollution problem and abatement of this
source has been recognized as a necessary consideration in achieving the
national water quality goals of PL 92-500. However, due to the highly ir-
regular nature of the runoff phenomenon, abatement measures that address this
problem tend to be very expensive. Thus, in the EPA construction grants
program great importance has been placed on careful planning demonstrating the
cost-effectiveness of proposed projects (Program Guidance Memorandum 61).
The benefits of runoff pollution abatement measures must be evaluated in
terms of projected receiving water quality conditions relative to some defined
quality standards. There is considerable experience in the establishment of
water quality standards and resultant effluent limitations for non-transient
municipal and industrial discharges, generally through the use of mathematical
models. Generally, these models are applied against a "design" receiving
water hydrologic regime (for instance, 10-year, 7-day low flow) and effluent
limitations selected which will meet the desired water quality standards.
This steady-state analysis assumes a toleration of water quality contravention
from the discharge of a low frequency corresponding to the designated low flow.
This approach is not wholly adequate to analysis of the problem posed
by intermittent storm runoff discharges. These analyses require alternate
modeling approaches and a restatement of pertinent standards to reflect the
short-term high variability of the storm runoff event.
Using ongoing studies of combined sewer systems in Rochester, New York
and Washington, D.C., as case studies, a procedure is presented for the
application of receiving water analyses in urban runoff planning. The studies
in both areas have included the development of water quality models based on
familiar concepts of mass balance and calibrated against detailed field sur-
veys and laboratory experiments.
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In the Rochester study, steady state models of dissolved oxygen in the
Genesee and fecal coliform concentrations in the Rochester Embayment of Lake
Ontario are used to project receiving water conditions under dry-weather loads
and an envelope of expected impacts of the combined sewer overflows under
various system configurations. A time-variable model of Rock Creek and the
Potomac and Anacostia Rivers has been used to project transient fecal coliform
nutrient and dissolved oxygen concentrations resulting from overflows from
the District of Columbia sewer system.
In an analysis of marginal costs and marginal benefits associated with
various combined sewer overflow abatement alternatives, a series of model
runs are made to project the impact of various waste discharges from the
alternate system configurations on the receiving waters under several
hydrologic regimes and ambient temperatures. The conjoint probabilities of
the receiving water conditions and storm loads are determined on the basis
of historical records and used to project the expected water quality under
the alternative system configurations. These projections can be quantified
as water quality improvements in terms of expected degree of contravention
of stream standards with regards to frequency, duration, areal extent and
peak concentration. On the basis of this analysis of project cost estimates
drawn from generalized cost curves, marginal costs and benefits can be dis-
played graphically for each alternative.
The analysis of the Syracuse, New York, Rochester, New York and the
District of Columbia combined sewer facilities planning activities are dis-
cussed relative to this marginal cost-marginal benefit approach as case
studies.
COMBINED SEWER OVERFLOW IMPACTS ON URBAN LAKE
AND ASSOCIATED ABATEMENT METHODOLOGY
by
Peter E. Moffa, John C. Byron, Steven D. Freedom,
and John M. Karanik
Stearns & Wheler
Cazenovia, New York
ABSTRACT
A general methodology is presented for the evaluation of the impact and
abatement of combined sewer overflows on receiving waters. It was developed
from experience with Onondaga Lake, an urban lake in Central New York that
receives major combined sewer overflows from the City of Syracuse via two
tributary streams.
Field investigations of the combined sewer system and the receiving
water must first be undertaken.
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The field work includes flow measurement and water-quality sampling of the
sewer overflows and the receiving waters during several different storms.
Use of a computerized data bank has been found virtually essential for the
storage and manipulation of the large quantity of data resulting from the
sampling and analysis.
Mathematical modeling of the receiving water is undertaken to evaluate
water quality as a function of pollutant load; the storm sewer system is
modeled to determine the quantities of pollutants discharged during storms
of various recurrence intervals. Prior to the modeling effort, analysis of
local rainfall records is necessary to develop the classical intensity-
duration-frequency relationships. After assessing the water-quality impact
of dry-weather pollutants from wastewater treatment plants and other sources,
the results of the two models can be combined to express the reduction in
stormwater pollutants needed to achieve a particular water-quality objective
as a function of storm frequency or storm recurrence interval.
Abatement alternatives, and their respective costs, for the reduction of
pollutants from wet-weather sources, particularly combined sewer overflows,
are next investigated. Using engineering judgment of the most effective and
economic abatement measures, a relationship is then developed between abate-
ment cost and storm frequency for each of several water-quality criteria or
standards. From the cost-benefit relationships thus developed, a graphical
determination can be made of the "general optimum solution" (COS) for re-
duction or treatment of combined sewer overflows.
It is recognized that the quality of the receiving water resulting from
the COS may not be acceptable to the general public or regulatory agencies.
In that case, a decision to provide greater (or lesser) pollution abatement
will be based upon social or political considerations, but the governmental
body making the decision will be cognizant of its economic implications.
In the study for Onondaga County, New York, from which the methodology
was developed, 35 overflows from the combined sewers of the City of Syracuse,
which serve an area of about eight square miles, were monitored for a period
of one year. Onondaga Lake, the principal receiving water, is approximately
four and one-half square miles in surface area; it was sampled at tne sur-
face locations, each at two distinct depths, for the period of influence of
each of six storms. The Storm Water Management Model (SWMM) was applied to
the City's sewer system. A 27-segment, three-dimensional, dynamic water-
quality model with capability of predicting enteric bacteria, dissolved
oxygen, nutrients, and toxic materials, was developed.
From the models, it was determined that the impact of CSO's on dissolved-
oxygen concentrations in Onondaga Lake will not be critical after tertiary
treatment facilities for dry-weather wastewaters are placed in operation; a
maximum DO deficit of 2.8 milligrams per liter was predicted for a 10-year,
two-hour storm. Combined sewer overflow contributions of phosphorus will be
negligible in comparison to those from other sources.
In an average rainfall year, 38 violations of the fecal coliform standard
will occur in the area of the lake intended for contact recreation.
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If abatement of CSO pollution were to follow the "optimum general solution"
of this methodology, there would still be 13 annual violations, ten of which
persists for about three days, more extensive CSO abatement will be required
if the projected recreational usage of Onondaga Lake is to be realized.
A WATER QUALITY PLANNING METHODOLOGY FOR URBAN AREAS
by
Franklin W. (Skip) Ellis* and Ron Wycoff**
*CH2M HILL, Reston, Virginia
**CH2M HILL, Gainesville, Florida
ABSTRACT
The Environmental Protection Agency's (EPA) 1978 Needs Survey reported
that an estimated $36 billion is required to construct necessary municipal
wastewater treatment facilities. Additionally- $26 billion is required to
control pollution from combined sewer overflow, and $46 billion is required
to control urban stormwater runoff. In light of the current trend toward
reduced taxes, local funds for water quality projects will become more limi-
ted. Moreover, the public should demand that such projects demonstrate per-
ceptible improvements in water quality and are required for the protection
of the intended beneficial use of the receiving water. Further, the most
cost-effective pollution control alternatives should be used. Without this
assurance, required pollution abatement projects may well go unfunded.
Based upon information gained in the performance of the EPA's 1978
Needs Survey, a two-phase approach to water quality planning is presented
that determines the most cost-effective mix of control alternatives and their
impacts on the receiving water. This approach is general in nature but is
oriented toward combined sewer overflow (CSO) areas and the requirements of
EPA's Program Requirements Memorandum, PRM No. 75-34.
Phase I is an initial assessment designed to answer the following
questions:
1, What is the intended beneficial use of the receiving water? foup^C/i
2.» What water quality goals or criteria are required to ensure this
use?
3, Based on the goals, is there a water quality problem?
4). Can CSO, urban runoff, or domestic wastewater abatement techniques
solve the problem, and what degree of controls is required?
5. If the problem can be solved, what controls, in general, are the
most cost effective, and what is the nature of the tradeoffs be-
tween cost, degree of control, and receiving water quality?
6, Considering these tradeoffs, are changes in the water quality
goals, or in the desired beneficial use for the receiving water
indicated?
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This two-phase approach is designed to achieve water quality goals
established to protect a given beneficial use of the receiving water.
Rather than a fixed limit, such as a minimum dissolved oxygen standard,
statistical water quality responses are used as the goals. Examples from
the EPA's 1978 Needs Survey illustrate this point.
Phase I involves the use of a simple, continuous receiving water
quality model and the Heaney-Nix economic optimization procedure. The model,
the Continuous Stormwater Pollution Simulation Sy stem__(CSPS^l , incorporates
f™an urban area~ancTTCs^receiving water. A very
brief description of CSPSS is given. The economic optimization is per-
formed using estimated areawide production functions for a first-cut analysis
of the costs required for various levels of pollution abatement. The water
quality model uses these relationships to produce cost-water quality relation-
ships that can be used to guide planners as to the desirability of various
pollution abatement projects. Studies from areas with CSO's are presented.
If the results of the Phase I analysis indicate that there are water
quality problems that can be corrected with affordable solutions , the de-
tailed analysis of Phase II is required. This phase considers, in much
greater detail, the area's hydrology, combined sewer system hydraulics,
nonpoint and point source pollutants, and the receiving water quality re-
sponse, thus requiring more sophisticated data and models.
The product of the Phase II analysis is a description of the optimal
mix of control alternatives, the total plan costs, and the receiving water
quality response due to the plan. The description of the alternatives in-
cludes the level of effort required, the area to which the alternative
applies, the expected pollutant reduction due to the alternative, and the
cost of the alternative.
In summary, this two-phase approach can result in substantial
monetary savings by obtaining economically optimal solutions. Use of this
methodology also explicitly evaluates the benefits or improvements in
water quality as a result of the project. These features satisfy EPA
planning requirements and should assure the public that their tax dollars
are wisely spent.
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