EDISON WATER QUALITY RESEARCH DIVISION
NATIONAL ENVIRONMENTAL RESEARCH CENTER
Management and Control
of
Combined Sewer Overflows
PROGRAM OVERVIEW
ENVIRONMENTAL PROTECTION AGENCY
RESEARCH & MONITORING
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MANAGEMENT AND CONTROL OF COMBINED SEWER OVERFLOWS
Program Overview
by
Richard Field, P.E., Chief
Storm and Combined Sewage Pollution Control Branch
Edison Water Quality Research Division
National Environmental Research Center
Office of Research and Monitoring
U. S. Environmental Protection Agency
Edison, New Jersey 08817
Presented at
44th Annual Meeting of the New York Water
Pollution Control Association
New York Hilton
New York, New York
January 26-28, 1972
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MANAGEMENT AND CONTROL OF COMBINED SEWER OVERFLOWS
I. PREFACE
This paper will serve as a basic overview of the U.S. Government's
involvements toward developing countermeasures for combined sewer overflow
pollution.
The "Storm and Combined Sewer Pollution Control Research, Development
and Demonstration Program" was initiated not too long ago, under the auspices
of the U.S. Public Health Service, Department of Health, Education and Wel-
fare (PHS). In their (PHS) report (1) published in 1964, the nationwide
significance of pollution caused by storm generated discharges was first
identified. After going through several Federal Agency and name changes,
the Program is now part of the Office of Research and Monitoring, U.S.
Environmental Protection Agency (USEPA). Up to the present time over 100
grants and contracts totalling approximately $80,000,000, have been
awarded. USEPA's share being in the neighborhood of $40,000,000.
II. INTRODUCTION
The earliest sewers were built for the collection and disposal of storm
waters, and for convenience emptied into the nearest watercourse. In later
years, house sewage was discharged into these large storm drains, automat-
ically coverting them into "combined" sewers. Subsequently, combined sewers
came into widespread use in communities because they represented a lower
investment than the construction of separate storm and sanitary sewers.
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When the problems of sanitary sewage became recognized, the engineer
was confronted with how best to separate wet from the dry-weather flows to
enable proper treatment of the sanitary sewage portion. This was overcome
by designing overflow structures at selected points in the sewerage system.
New sewers were installed for intercepting and conveying the dry-weather
flows to the local sewage treatment works, whereas, combined sewage flows
greater than a predetermined multiple of mean dry-weather flow were dis-
charged directly into the receiving stream.
Overflow or relief points are also integral to separate sanitary sys-
tems. Nominal allowances are made for infiltration which increases with
pipe age. This problem is compounded by unauthorized connections, and re-
liefs in the "so-called" separate sanitary system are used as an immediate
and low cost solution. Studies conducted for the USEPA in Roanoke, Vir-
ginia(2); Oakland and Berkely, California(3); and by others(4) found that
separate systems, with excessive infiltration and other inflows, act essen-
tially as combined sewer systems.
The basic difficulty with combined and "nominal" sanitary sewers involves
their "built-in" inefficiencies, which are their overflow points. This will
be further explained in the following section.
III. COMBINED SEWER OVERFLOW PROBLEMS
Untreated overflows from combined sewers, particularly during wet-
weather, has proved to be a substantial pollution source(5,6,7,8,9,10,11,12)
in terms of impact upon receiving stream water quality (9,10,13,14)—even
though the percentage of sanitary sewage lost from the system by overflow is
small, that is, in the order of 3 to 5 percent(15,16,17,18,19).
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Pollution problems stemming from combined sewer overflows are widely dis-
tributed throughout the United States; the Northeast, Midwest, and Far-West
being the principal areas of concentration. All told nationwide, there are
estimated(20) to be over 3,000,000 acres of combined sewer drainage area
contained in more than 1,300 municipalities with a population of 54 million
served by some 55,000 miles of combined sewers.
The magnitude of the overflow problem was exemplified by a 2-year
study(21) conducted on a 229 acre combined sewer watershed in Northampton,
England. This study showed that the cumulative yearly biochemical oxygen
demand (BOD) load in the combined sewer overflows nearly equaled the BOD
load contained in the effluent of the local secondary treatment plant. Sus-
pended solids within the overflows^-were three times the load contributed
by the treatment works effluent.
The relatively poor flow characteristics of combined sewers during dry-
weather when sanitary wastes alone are carried, encourages settling and build-
up of solids in the lines until a surge of flow caused by a rainstorm purges
the system. Studies(18,22,23) in Buffalo, New York have shown that 20 to 30
percent of the annual collection of domestic sewage solids are settled and
evenutally discharged during storms. As a result, a large residual sanitary
pollution load, over and above that normally carried is discharged over a
relatively short interval of time, oftentimes resulting in what is known as
a "first flush" phenomenon.
Aside from the raw domestic (and industrial) sewage carried in the over-
flow, non-sanitary urban runoff in itself is a significant contributor to the
overflow pollution load(7,10,12,24,25,26,27). As the storm runoff drains
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from urban land areas, it picks up accumulated debris; animal droppings;
eroded soil(28,29,30); tire and vehicular exhaust residue; air pollution
fallout; deicing compounds(31,32), pesticides(33,34,35), fertilizers and
other chemical additives; decayed vegetation; together with many other
known and unknown pollutants(34,35,36,37). A study(34,35) on a 1,067 acre
drainage basin in Durham, North Carolina has shown that the annual BOD con-
tribution attributable to surface wash from storms is approximately equal to
that contribution of the secondary treated sanitary effluent, and the total
organic matter (chemical oxygen demand[COD]) was estimated to exceed the
amount in the raw sanitary sewage from a residential area of the same size.
It is important to note that there is no apt description of "typical"
combined sewage or stormwater runoff characteristics due to the variable
nature of the rainfall-runoff patterns. Tables I and II serve to illustrate
the general concentration ranges of the wastewater constituents listed for
combined sewer overflow and urban stormwater runoff, respectively.
III. SEWER SEPARATION
When considering combined sewer overflow problems, first attention is
generally given to the construction of separate sanitary and storm sewer sys-
tems. In constrast, the 1964 PHS study(1) stipulated that alternative solu-
tions be investigated to determine if means other than sewer separation
could be found at lower cost.
An American Public Works Association (APWA) study of combined sewer prob-
lems indicated that if all communities with combined sewers in this country
were to effect sewer separation, they would face an expenditure of approxi-
mately 70 billion dollars at today's cost(38). It was further estimated
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TABLE I
CHARACTERISTICS OF COMBINED SEWER OVERFU3WS
(SELECTED DATA)
5 30 TO 600 MG/L
TSS - 20 TO 1700 MG/L
TOT, SOL, - 150 TO 2,300 MG/L
VOL, TOT, SOL, - 15 TO 820 MG/L
pH - 4,9 TO 8,7
SETTL, SOL, - 2 TO 1,550 ML/L
ORG, N - 1,5 TO 33,1 MG/L
NHjN - 0,1 TO 12,5 MG/L
SOL, PO/j - 0,1 TO 6,2 MG/L
TOT, COLI, - 20,000 TO 9Qxl06/100 ML
FEC.COLI, - 20,000 TO 17xl06/100ML
FEC, STREP, - 20,000 TO MO^lOO ML
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TABLE II
CHARACTERISTICS OF URBAN STOWWTER
(SELECTED DATA)
1 TO >700 MG/L
COD 5 TO 3,100 MG/L
TSS 2 TO 11,300 MG/L
TOT, SOL, - 450 TO 14,600 MG/L
VOL, TOT, SOL, - 12 TO 1,600 MG/L
SETTL, SOL, - 0,5 TO 5,400 ML/L
ORG, N - 0,1 TO 16 MG/L
- 0,1 TO 2,5 MG/L
SOL, PO/j - 0,1 TO 10 MG/L
TOT, PO/j - 0,1 TO 125 MG/L
CHLORIDES 2 TO 25,000 MG/L*
OILS 0 TO 110 MG/L
PHENOLS - 0 TO 0,2 MG/L
LEAD - 0 TO 1,9 MG/L
TOT, COLI , - 200 TO 146xl#/100 ML
FEC, COLI, - 55 TO !J2xl06/100 ML
FEC, STREP, - 200 TO I,2xl06/100 ML
*Wrm HIGWAY DEICING
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that the use of alternate measures could reduce this cost to about 25 billion
dollars.
It is again emphasized that urban stormwater runoff itself can be a
significant source of stream pollution. Sewer separation would not cope
with this pollutional load. An EPA study(27) conducted in Bucyrus, Ohio,
revealed that if separation were used, the reduction in wet-weather pollu-
tion would be only 50 percent. The other 50 percent would remain in the un-
treated urban storm runoff.
IV. LEGISLATION
The Federal Water Pollution Control Act(39) recognizes the problem
of combined sewer overflows and accordingly authorizes funds for the develop-
ment of new and improved methods for controlling this source of pollution.
Demonstration grants can be made to any State, municipal, intermunicipal, or
interstate agency in amounts of up to 75 percent of the estimated project
cost. Contracts are also available to research and development oriented
firms for the implementation of worth-while projects.
V. CORRECTIVE METHODS
Our Program (16,40) has now funded over 100 research, development and'
demonstration projects which have provided significant results, and have
illustrated that alternatives to sewer separation in most cases are the
logical course of action. The Storm and Combined Sewer Pollution Control
R&D Program has categorized three basic approaches other than sewer separa-
tion. These are: control, treatment, and combinations of the two, which
are discussed in this section as follows:
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A. Control
Control of combined sewer overflows can be obtained by reduction
or equalization of peak stormwater flows, improved sewerage system
usage, and minimizing infiltration.
1. Existing System Control
Let us start by indicating what the "operator" can do to get
the most out of what he has to work with.
a. Maximize Sewage Treatment at Sanitary Plant During Wet-
Weather
First of all, he should try to contain as much flow or
treat as much sewage as possible during a storm flow occurrence.
This would serve to reduce wet-weather bypassing which at the
beginning of storm flow can have a high pollutant concentration,
as previously described. It is recognized this extra plant
burden may decrease treatment efficiencies somewhat, and create
added sludge or solids handling problems. However, these prac-
tices for only short periods during storm flows, are well worth
the effort. If the operator determines the hydraulic loading
will cause a serious upset of a unit process(es), then primary
treatment plus disinfection, should be considered as a minimum
measure.
In Detroit(41), where the prevailing direction of storms
is known, the operator receives advanced information on storms
from a remotely stationed rain gage. The treatment plant pump-
ing is increased, thus lowering the interceptor gradient and
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allowing for greater interceptor storage capacity and convey-
ance. This practice has enabled the city to entirely contain
and treat many intense spot storms, plus many scattered city-
wide rains.
b. Improve Regulator Maintenance
The operator should concern himself with improved regulator
inspection and maintenance and preventive schedule so as to
minimize the occurrence of overflows(38,41,42,43). Overflows
during dry as well as wet-weather due to malfunctioning devices,
can thus be alleviated. Tide gate conditions allowing backwater
intrusion can be corrected, and diversion structure settings
can be raised to obtain more interceptor carrying capacity. The
USEPA has long realized the need for better operation of over-
flow regulators and accordingly, the APWA has recently completed
a study resulting in two publications(42,43); 1) a state-of-the-
art assessment on, "Combined Sewer Regulator Overflow Facilities",
and 2) "Combined Sewer Regulation and Management, A Manual of
Practice".
Next, how may municipalities control combined sewer overflows with-
out large and costly modifications? Here we are concerned with: 1)
infiltration and extraneous inflow control; 2) "housekeeping", such as
cleaning of street surfaces, catch basins, and sewer lines to reduce
solids, etc.; 3) the possible use of friction reducing polymers to in-
crease flow carrying capacity; and 4) the implementation of certain
land use regulations, zoning requirements and construction site (and
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other) erosion control practices, all of which would be helpful in
reducing runoff contamination by solids and other substances.
c. Infiltration and Extraneous Inflow Control
Most consulting engineers and municipal people will agree
that excess flow due to infiltration is a major thief of ca-
pacity which should otherwise be available to transport sewage,
and can thereby affect proper operation of sewerage systems,
and consequently, the quality of our streams. Other adverse
impacts due to infiltration include(38,44,45,46): 1) surcharging
and backflooding into streets and private areas, and need for
relief sewers ahead of schedule; 2) surcharging of treatment
plants and pumping stations, causing flow bypassing, decrease
in treatment efficiency, and higher treatment costs; and 3)
greater incidence and duration of overflows, and diversion of
raw sewage. The APWA has reported that infiltration was a pro-
nounced problem during dry-weather in 14 percent of communities
surveyed(38), and 53 percent of the communities during wet-
weather. The APWA also indicates(44,45) that other sources
of extraneous inflow compounding the problem include: roof
leaders; depressed manhole covers; cellar, foundation and
yard drains; air conditioning and industrial cooling waters;
and other connections(46).
Control of infiltration should first take place during
sewer pipe installation. Better construction materials are
necessary together with proper installation techniques(44,45,46).
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Preliminary laboratory testing(47) has indicated that conven-
tional sewer pipe can be coupled with durable, watertight
joints using heat shrinkable plastic tubing made of polyolefin-
polymeric base hot melt adhesive, a material shown to be supe-
rior and economically comparable to existing jointing mechanisms,
The new methods of sewer sealing should be fully evaluated
before major rehabilitation or replacement is undertaken.
Shrinkage upon drying, and structural weakness previously as-
sociated with the conventional sealants, may possibly be min-
imized using modified polymeric and other new materials(48).
Limited tests(49) have shown that significant corrosion resist-
ance may possibly be achieved through the employment of such
surface coatings as: vinyl-vinylidene chloride, vinyl acetate-
acrylic, nitrile rubber latex, nitrile-phenolic rubber, an
emulsified reclaimed rubber, and a rubber base adhesive,at one-
tenth the cost of epoxy and plastic liners. Improvements in
corrosion resistance, impermeability, and strength of concrete
pipe can also be achieved by impregnation with such materials
as hydrofluoric acid and sulfur(49).
Infiltration surveys should be undertaken when extraneous
inflows are suspected. Such surveys may use T.V. and other
visual pipeline inspection, smoke tests, air and water pressure
tests, and various flow techniques. Figure 1 illustrates the
result of an infiltration smoke test. The APWA under USEPA
sponsorship has developed a manual of practice(45) on infiltra-
tion control containing guidelines on allowable inflow, con-
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struction methods and materials, and types and application of
sewer sealants for reducing infiltration.
Building connections to street sewers are a major source
of infiltration(44,50). As much as 70 to 80 percent of the
infiltration load can occur in these lines. Accordingly, the
aforementioned infiltration control practices should be strictly
followed here.
The City of Springfield, Illinois Sanitary District has
recently engaged in a concerted program to remove improper
connections and extraneous inflows to their sewerage system(50).
Over a two-year period utilizing a public relations campaign,
various questionnaires, building inspections, and good follow-
up effort, the District was able to substantially reduce down-
spout connections to its sewers. Besides improving the use of
the sewerage system, the profound significance was in the elim-
ination of numerous public complaints regarding basement flood-
ing. From a cost standpoint, the District has estimated that
the cost of removing the roof leaders will be fully returned
within 16 months by virtue of reduced operation and maintenance
costs for the sewerage system.
However, before a municipality considers removing extraneous
inflows, the following basic factors should be considered:
1) Determination of what a "clean" or unpolluted inflow
really is. For instance, subsurface drainage may be
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contaminated leachate or contain toxic material washed
from basement floors.
2) Sewer septicity and odor conditions which may arise
because of lowered flow from the elimination of long-
standing inflow sources.
3) Effect on the public of any sudden decision to eliminate
inflow sources and the associated problems of enforcement.
4) The strong possibility that communities will be forced
to treat separate urban runoff sometime in the future,
indicates that the re-connection of certain so called
"clean" waters from sanitary to storm drains may be a
practice done in vain.
d. Surface "Housekeeping"
Studies(37,51) have indicated that it may be cheaper to
remove solids from the street surfaces by sweeping, etc. than
by eliminating them via the sewerage system. One set of figures
received(Sl) showed street sweeping to cost 25 to 30 dollars per
ton of solids removed as compared to 60 to 70 dollars per ton of
solids removed by way of the sewerage system. What may even be
more important is that the wet-weather overflow polluting poten-
tial of ihese solids are eliminated by the urban surface removal
practice. Certain land use, zoning(25,41), and construction site
erosion control practices(25,28,29,30) are other ways of alleviat-
ing the solids burden to the receiving streams or treatment plants
by surface source prevention.
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e. Polymers to Increase Flow Capacity
If there is insufficient carrying capacity in the system,
polymer addition may serve to measurably reduce fluid friction.
Recent research(52,53,54) for the USEPA has shown that polymeric
injection can increase flow capacity as much as 2.4 times at a
constant head. This method can be used as a short or long-term
measure to correct troublesome pollution-causing conditions
such as localized flooding and excessive overflows. A prelim-
inary cost comparison(53) for a 15-inch sewer in Garland, Texas,
indicated that polymer use for overflow control would cost one-
fourth as much as relief sewer construction. However, additional
cost verification is necessary for other locations.
2. Advanced Control Systems
In this segment of the paper, some of the newer and more advanced
technology being developed by our Program will be described.
a. Flow Regulation
Several methods have been used to reduce operation problems
associated with the conventional regulator devices. Cincinnati,
Ohio(55) utilizes telemetered monitoring to detect unusual or
improper dry-weather overflows. More sophisticated approaches
are being applied by the Minneapolis-St. Paul Sanitary District
and the Cities of Detroit, and Seattle. Funded by Federal grants,
all three jurisdictions are making use of unused storage capacity
within the existing sewerage system for the purpose of reducing
the frequency and volumes of overflows(41,42,43,56,57). The gen-
eral approach comprises remote monitoring of rainfall, flow levels,
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and sometimes quality, at selected locations in the network,
together with a centrally computerized control console for posi-
tive regulation of the overflow structures. In developing abate-
ment programs for the combined sewer communities, this type of
system should be considered as a major first step to minimize
overflow occurrences. Figure 2 depicts the computer console
and strategy room in Seattle, Washington and is a preview of what
the operator in 1980 may be contending with.
New types of regulators are showing considerable prom-
ise(41,42,43). Positive control gates and inflated rubberized-
fabric dams have been used by Minneapolis to regulate flows as
part of their demonstration(42,43,56) project. A USEPA project
in Philadelphia, Pennsylvania(42,43,58,59) has resulted in the
development of a unique overflow device now being designed for
full-scale demonstration, utilizing fluidic technology. This
device requires no moving parts or external power since operation
is entirely dependent upon motion of the wastewater. Improved
regulator capability, as well as reduced operation and mainte-
nance costs, are anticipated. Additional improvement in regula-
tors is now in progress.
b. Storage
Storage offers direct control by containing the wastewaters
produced during wet-weather periods. In-system storage by tak-
ing advantage of excess capacity in the trunk or interceptor
sewer has been previously cited. The use of storage facilities
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Figure 1. Using the smoke test to detect an infil-
tration problem, Montgomery Co., Ohio.
Figure 2. Computer console for augmented flow
control system, Seattle, Washington.
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for controlling combined sewer overflows has been convincingly
demonstrated. The general procedure involves the return of
retained overflows to the conventional treatment works for sub-
sequent treatment during low flow, dry-weather periods.
Concrete (and steel) holding tanks are the most commonly used
type of storage facility(15,16,60,61,62,63,64,65,66,67,68). The
storm stand-by tanks at Columbus, Ohio constructed as early as
1932, were recently modernized(62,65) through USEPA grant assist-
ance, by installation of sludge collection and automatic flow
control equipment. Figure 3 shows the Columbus tanks. The City
of Boston has commenced operation of an overflow holding
tank(61,67) designed to provide 10-minute settling plus chlorina-
tion for treating excess overflows of 233 million gallons per
day (MGD). New York City(68) and Milwaukee have similar facili-
ties under construction. Chippewa Falls, Wisconsin has con-
structed an asphalt-lined basin providing storage for up to 3.5
million gallons of overflow(53). These last four projects have
also been supported by the USEPA R&D Program. Figure 4 shows
the Chippewa Falls installation. A concept worthy of notation
here, which was successfully demonstrated in London, England, is
the conversion of existing or abandoned sanitary treatment units,
in this case sedimentation tanks, to storm holding facilities
as part of a plant expansion(69). Also, Orchard Park, Erie
County, New York has proposed plans to utilize an abandoned trick-
ling filter as a storage tank for stormwater infiltration(70).
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Figure 3. Storm Stand-by tank with upper portion
of sludge collection mechanism visible, Columbus
Ohio.
Figure 4. Asphalt-lined basin providing storage
for up to 3.5 M3, Chippewa Falls, Wisconsin.
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Two basic problems encountered by conventionally-designed
storage facilities in urban areas are land cost and availa-
bility, and adverse aesthetic impacts. In this regard, the
USEPA is seeking new concepts. A major demonstration in
Chicago(41,71,72,73) involves the new concept of "deep tun-
nels"(22,53). Chicago is constructing a 12-foot and 17-foot
diameter deep tunnel, which is over 4 miles in length. The
cost of a Metropolitan Chicago tunnel storage system is esti-
mated at one billion dollars as contrasted to four billion
for sewer separation. Another subsurface storage idea that
is to be demonstrated by our Program is the underground "silo".
The use of a 50-foot diameter, 100-foot deep silo could afford
over 1 million gallons of storage.
Other designs with little or no urban land requirements
include off-shore storage and the use of natural underground
formations. Two USEPA demonstration projects(74,75) have
evaluated the use of flexible neoprene-coated nylon fabric
material as underwater containers, for the temporary storage
of combined sewer overflows in the Washington, B.C. area.
Figure 5 illustrates a conceptual drawing for off-shore storage
in Cleveland, Ohio(76,77).
Design criteria should be based upon the pollution abate-
ment results expected. For example, Milwaukee utilizes a mathe-
matical model to determine size and projected efficiency of their
holding tanks(78). The engineer and operator will be inter-
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ested in the sludge-handling aspects of temporary storage. Two
possibilities are: The re-suspension of solids by agitators or
other means; and settling prior to pump-back (or bleed-off). Re-
suspension can provide easier draw-off and is being evaluated by the
Program. However, if sludge is settled, on-site sludge disposal in
lieu of solids pumped back in stored flow, should be considered.
c. Porous Pavement
Another method to attenuate flows, having exhibited laboratory
and pilot-scale feasibility(79), is by the installation of porous
pavement. This pavement is made of asphalt-cement, and has been
developed for structural soundness and an ability to allow 60
inches per hour of rainfall to permeate through its depth while
retaining water at 15 percent of its bulk volume. If this mate-
rial were to be used for major highway, street, parking lot, etc.
paving projects, it would have the potential for reducing capacity
and associated costs for both sewer and wet-weather flow treatment
systems, a feature attributable to the porous pavement's ability to
equalize flows entering or divert flows away from the sewerage
system. This type of pavement installation can also offer a sub-
stantial benefit by recharging water supplies. However, when
porous pavement is considered, we must realize that such features
as geographical area temperature, sub-surface soil condition, and
the possibility of groundwater contamination may play an important
part in design and site .selection.
d. New Sewer Systems
New types of sewer systems based on vacuum and pressure
operation are being demonstrated. By using a pressure or
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vacuum system for the collection and conveyance of sanitary
sewage, we can reduce the waste volume generated, reduce conduit
sizes, eliminate infiltration, minimize associated installation
and treatment costs, and also alleviate overflows. The American
Society of Civil Engineers(80) has completed a feasibility study
on installation of pressure sewers within existing combined
sewers as an alternate means of sewer separation. It was found
that the vast majority of lines in urban systems are too small
in diameter for this type of installation.
A pressure system in the Albany, New York area(81), being
demonstrated successfully, employs previously developed(80)
grinder-pump units placed in twelve homes for macerating and
transferring sewage through 1-1/4" diameter plastic (polyethylene)
pipe into a 3" plastic pressure header pipe in the street. It is
hoped the pressure sewer system will serve as an adjunct to con-
ventional gravity sewers and offer the designer a new degree of
freedom in providing sewer service. In the meantime, this ap-
proach is available to solve current, non-system oriented problems
as connecting low-lying units such as lake-front cottages and low-
lying basements to the existing sewerage system.
B. Treatment
Other than waste storage, it may be considered necessary that com-
bined sewer overflows be treated, either at the individual outfall
locations, or at a centralized facility. It is noted that centraliza-
tion, although offering benefits in reduced plant costs, invariably
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requires high expenditures for the installation of large, combined
sewer transport conduits or interceptors.
Conventional treatment processes apply basically to the nearly
steady-state conditions of sanitary sewage, whereas, combined sewer
overflows occur on an intermittent and random basis. Following rain-
fall, these flows exhibit highly-varying patterns in both quality and
quantity over short periods of time(10,15,16,20,56,82). No data on
quality of either combined sewage or urban stormwater can be considered
"typical". Unlike municipal sewage, we cannot typify BOD and suspended
solids concentration for design or operation of abatement facilities.
Consequently, it has been diffiuclt to directly adapt existing treat-
ment methods to storm generated overflows, especially the microorganism
dependent biological processes. Adverse flow conditions and unpredic-
able shock loadings make it advisable to consider the newer chemical
and/or physical treatment techniques, and the incorporation of auto-
mated control into the intended storm treatment facility to achieve
optimum efficiency.
Rather than independent units, biological treatment systems are
applied by our Program as auxiliary facilities at the conventional sew-
age plant for treating excess flows. Two such biological treatment pro-
cesses are on-going USEPA projects. One uses activated sludge to treat
overflows at Kenosha, Wisconsin. The other at New Providence, New
Jersey utilizes plastic media, and compares this with standard rock media,
in high-rate trickling filters for treating sanitary sewage with a
high degree of infiltration.
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Treatment methods currently under investigation by the Storm and
Combined Sewer Pollution Control Program include the following(16,40,
41,53):
1. Fine-mesh screening and microscreening
2. Dissolved-air flotation
3. Rotating biological contactors
4. High-rate plastic media trickling filters
5. High-rate, single and multi-media filtration
6. Vortex and helical separators
7. Advanced disinfection methods, e.g., high-rate application,
on-site generation, automated operation, ozonation, and use
of combined halogens (chlorine and iodine) and chlorine dioxide
8. Tube settlers
9. Powdered and granular activated carbon adsorption
10. Polymer and other chemical additives for improved settling(83),
microscreening, filtration, and flotation
11. Chemical oxidation
12. In-line or in-sewer treatment
13. Sludge handling and treatment
14. Regeneration of carbon and coagulants, and
15. Reclamation and reuse
Time does not allow a detailed discussion of each of these methods.
However, mention of some of our more promising combined sewer overflow
treatment projects is worth-while.
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Since high throughput rates are necessary for combined sewer over-
flows, the conventional treatment processes are being studied for pos-
sible modifications. For example, the microstrainer is conventionally
designed for polishing secondary sewage plant effluent at an optimum
2
rate of around 10 gallons per minute per square foot (gpm/ft ) (84).
Tests on a pilot microscreening unit in Philadelphia(85,86) supported by
USEPA funds, are showing that(87) at high.flux rates of 35 to 45 gpm/
2
ft , suspended solids removals in combined overflows exceeding 99 per-
cent can be achieved. Since overflows are not continuous as sanitary
flows are, occurring about three percent of the total time, a sacri-
fice of screen life for increased hydraulic treatment rate is worth-
while. (A similar philosophy applied to grit removal for the purpose
of extending the useful life of piping, pumps and appurtenance, indicates
the requirement for degritting needs re-evaluation for combined sewer
overflow treatment, and possibly elimination in many design considera-
tions. )
At this point it is appropriate to bring out an important fact of
which future designers of storm overflow treatment facilities must be
cognizant—process efficiency should not be considered in the usual
terms of percent removal used in municipal treatment. It was found dur-
ing the microstrainer operation, that due to extreme variation of the
influent suspended solids concentration, removal efficiency would also
vary, while the more desirable, effluent concentration remained rela-
tively constant at approximately 10 mg/1 and less. For example, a
typical effluent concentration of 10 mg/1 suspended solids would yield
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a reduction of 99.0 percent for an influent concentration of 1,000 mg/1,
whereas the suspended solids reduction would be only 50 percent if the
influent concnetration were 20 mg/1. This phenomenon is apt to reoccur
in other physical-chemical stormwater treatment operations.
Increased flow rates greatly reduce capital costs and space require-
ments. Increased throughputs have also been obtained with other fine-
mesh screening processes(41,88,89), fiberglas filtration(90,91,92), and,
with dissolved-air flotation(41,93,94,95).
A USEPA study that was conducted in Cleveland, Ohio(96,97) showed
high potential for treating combined sewer overflows via ultra high-rate
filters using anthrafilt and sand within a 7 to 8 foot deep bed.
Figure 6 depicts the three-six inch diameter filter column arrangement,
a major portion of the pilot plant at the Cleveland site. With the
2
high loadings of 16 to 32 gpm/ft surface area, removal of solids is
effectively accomplished throughout the entire depth of filter column.
This compares to conventional filters operating in the range of 0.5
2
to 5 gpm/ft where solids are essentially only eliminated in the first
few inches of filter media. A rough pre-treatment provided by a 40
mesh rotating drum screen was required to allow longer filter runs.
Encouraging results(96) indicated removals of 35 and 68 percent for
BOD and suspended solids, respectively, at the high hydraulic loading
2
of 24 gpm/ft . Supplemental test work further showed process effi-
ciency in regard to suspended solids removal can be achieved up to
and exceeding 90 percent, and BOD removals can be upgraded to fall
between the range of 57 to 80 percent, through the addition of poly-
25
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Figure 5. Conceptual design of combined sewage
retention-stabilization basin, Cleveland, Ohio.
Figure 6, View of deep bed, dual
media, high rate filter arrange-
ment, Cleveland, Ohio.
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electrolytes and sometimes alum. Substantial reductions, in the
order of 30 to 80 percent of phosphates can also be obtained in this
deep-bed, high-rate filtration system via addition of appropriate chem-
icals.
When dealing with combined sewer overflows, we are much more
concerned with treating high flow rates and optimizing absolute waste
loads removed. With ultra high-rate filtration we are willing to sac-
rifice some loss in percent waste reduction for short peak periods if
in turn we can handle loads some 6 to 25 times greater than that
accepted across a conventional filter. With this in mind, it is brought
to your attention that the filter pilot plant efficiencies were deter-
mined under constant hydraulic loads, whereas in reality a plant will
reach or exceed overflow design capacity only a small fraction of total
operating time. Therefore, average overall removals will be higher in
a real situation.
Results from a 5.0 MGD screening and dissolved-air flotation demon-
stration grant pilot plant in Milwaukee, indicate that greater than 70
percent removals of BOD and suspended solids are possible(41,93).
This facility is considered a pilot plant only because of the very
large magnitude of storm flow generally dealt with. For many sanitary
sewage treatment plants today, it could be considered a full-scale oper-
ation. Findings reveal 95 to 97 percent reduction in suspended solids
during first flushes and 85 percent reduction during extended overflows,
and also better than 90 percent reduction in phosphate can be achieved
as an additional benefit, by employing chemical coagulants. At the
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present time, the Program is also sponsoring two air flotation treatment
facilities at Racine, Wisconsin, having capacities of 20 and 40 MGD,
respectively. Another dissolved air flotation plant is being evaluated
in the San Francisco area(94) under the auspices of our Program, which
has a storm runoff treatment capacity of 24 MGD.
A unique variation of the usual coagulation - adsorption, physical-
chemical treatment process(98,99,100) is now being demonstrated for
USEPA in Albany, New York. This system is comprised of a 0.01 MGD
trailer mounted pilot plant where both powdered carbon and coagulants
are added in a static mixing-reaction pipeline, and the resultant
coagulated matter is flocculated downstream, separated by tube-settlers
and polished by multi-media filtration. The project is also demonstrating
regeneration of alum and activated carbon by fluidized-bed incineration.
Another demonstration project in Milwaukee has studied a new bio-
logical process(101,102), described as the rotating biological contactor
consisting of a series of shaft-mounted rotating disks. Similar in prin-
ciple to trickling filtration, a biological growth attaches onto the
disks. Under steady loading rates, efficiencies exceeding those of the
trickling filter have been attained, but a surge tank appears essential.
Figure 7 illustrates the rotating biological contactor in operation, and
Figure 8 gives a close-up of the rotating disks.
Another approach in overcoming the extreme variation in overflow
rates is to provide surge facilities prior to the storm treatment plant
or the municipal plant. The surge basin(s) (or existing combined
sewers) could furthermore serve a dual function in equalizing not only
28
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Figure 7. Overall view of rotating
biological disks, Milwaukee, Wisconsin.
Figure 8. Close-up of rotating biological disk,
Milwaukee, Wisconsin.
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wet-weather flows but dry-weather flows as well. In this way, a single
future treatment system can readily be designed for storm and sanitary
flow conditions. This could also assist presently overloaded sanitary
plants in obtaining more uniform operation. Short-term storage incor-
porated into the treatment plant would even out the daily cycle of
dry-weather flows allowing for more efficient use of the treatment
process over the entire 24 hours. Equalization would permit reduced
treatment process design capacity. Further analysis is necessary to
determine the most economical break-even point between the amount of
storage versus the treatment capacity.
The Sewerage and Water Board of New Orleans is carrying forth a
demonstration project on the use of sodium hypochlorite for disinfec-
tion of storm flows as high as 11,000 cubic feet per second (cfs), to
both reclaim and protect public bathing beaches(14,15,53). In order to
economically provide the large quantities of disinfectant required, an
on-site hypochlorite batching plant was constructed. Figure 9 shows
the batching plant, and Figure 10 gives a view of the massive-size
chlorine contact basin under construction. The basin has since been
completed as illustrated in Figure 11. The basin is a forebay to the
major drainage pumping station. Another method of on-site generation
of hypochlorite in this case by electrolysis, is being conducted for
the USEPA in the Boston area.
The disinfection of combined sewage entails certain differences,
which make the design and operation of facilities difficult when
compared to sanitary sewage. The highly varying qualitative and
30
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Figure 9. Stormwater disinfection project - hypo-
chlorite batching plant, New Orleans, Louisiana.
Figure 10. Stormwater disinfection project-chlorine
contact basin under construction, New Orleans,
Louisiana.
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quantitative character of the storm generated inflows require disin-
fectant dosages to be based on a predicted rather than an established
technique. Bernarde, et al.(103), have shown the importance of the
temperature variable in their highly controlled disinfection studies.
Specifically, with the following held constant: pH, initial bacteria
count, and chlorine dioxide dosage, it required five times as much
contact time to obtain a 99 percent kill at 5°C (40°F) as it did to
obtain the same kill at 30°C (80°F). This points to the importance
of temperature in addition to the usual (time and dosage) disinfection
control parameters, as temperature is apt to have a much wider range
during the year for runoff waters than it does for domestic sewage flows.
It may very well be, that the yearly temperature fluctuation in combined
sewage in many urban areas would be similar to the range (40°F to 80°F)
tested for by Benarde, et al., and as a result, require disinfectant
dosage to vary seasonally or as effected by ambient temperature.
We are also searching for high-rate disinfection systems, to save on
large tankage requirements for the high storm flow rates encountered,
with the help of more rapid oxidants (such as chlorine dioxide(104)), and
by imparting greater turbulence to the flow. Successful attempts toward
high-rate disinfection are being noticed at our Philadelphia Pennsyl-
vania (87) and Onondaga County, New York(104) demonstration sites. The
Philadelphia project(85) is also making an evaluation of ozone, gener-
ated on-site for disinfection pruposes. Another study(92) proposes the
use of combined halogens (chlorine and iodine) to provide more effective
disinfection of viruses as well as bacteria in a swimming lake. This
32
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study(92) also supports dechlorination by activated carbon or use of
ozone, with a relatively short half life, in lieu of chlorine to
alleviate residual toxicity problems to fish life.
C. Combinations
When a single method is not likely to produce the best possible
answers to a given pollution situation, various treatment and control
measures—as previously described—may be combined for maximum flex-
ibility and efficiency. One such combination might be: in-sewer or
off-system storage for subsequent overflow treatment in specifically
designed facilities, followed by groundwater recharge or recovery for
water sports and aesthetic purposes. Another combination might be flow
retention with pump or gravity feed-back to the sanitary sewerage sys-
tem.
The temporary storage concept, previously discussed as a control
process, also provides for a certain degree of treatment by settling,
for excessive overflows greater than the design storage capacity dis-
charging directly to the receiving stream. Likewise, this settling
potential for flows less than design capacity together with on-site
solids disposal usually overlooked, should be definitely considered.
The proposed prototype demonstration for Lancaster, Pennsylvania, pre-
viously cited, plans to microstrain and disinfect discharges greater
than the storage capacity of the "silo" structure. Bio-oxidation of
stored flows may also be taking place. For example, open retention
ponds or lagoons can be designed to provide both equalization and stab-
ilization. A prototype lagoon installed in Springfield, Illinois(105)
33
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has given good information on how to proceed with future design.
Results indicated a moderate degree of treatment, however, undesirable
levels of algae were present in the lagoon effluent. Future stabili-
zation basins should consider periodic solids removal, and multi-cell
installations. Shelbyville, Illinois is now involved in a multi-
celled treatment lagoon project. Another lagoon approximately 40
feet deep, employing both aerobic and anaerobic decomposition, is
presently being evaluated in East Chicago, Indiana.
Mt. Clemens, Michigan is proceeding with a project involving
discharge of combined sewage overflows into a series of three "lake-
lets", each equipped with surface aerators. Effluents will pass from
one pond to the next through microstrainers, and the final effluent
wili"be chlorinated. This control and treatment scheme is designed
to have no adverse aesthetic impacts, and the possibility of reusing
these waters for recreational purposes will be explored.
A conceptual engineering study for the Washington, B.C. area(92)
has shown that it would be feasible to construct a control-treatment
facility to handle combined sewer overflows up to 3,000 cfs. A 175
million gallon storage facility is tentatively planned with an over-
head parking garage, coupled with a 50 MGD high rate filtration-
adsorption-disinfection plant. This treatment complex is intended to
produce reclaimed waters suitable for swimming, boating, and fishing.
Our Program has refined and is demonstrating the vortex flow reg-
ulator/solids-liquid separator(41,42,43,60,106,107,108) which has had
a successful history in England. The device is of simple annular-
34
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shaped construction requiring no moving parts. It provides a dual
function, regulating flow by a central circular spillway, while
simultaneously treating combined sewage by vortex action which imparts
liquid-solids separation. The low-flow concentrate is diverted to
the sanitary sewerage system, and the relatively-clear liquid over-
flows the spillway and receives further treatment or is discharged
to the stream. Figure 12 shows an overall view of the vortex unit
with the influent, low-flow concentrate, and overflow effluent lines
visible. Figure 13 contains a plan view of the device with the fluid
action and clean overflow visible. Figure 14 shows the empty vortex
with a view of the bottom dry-weather effluent channel. This device
is capable of functioning efficiently over a wide range of combined
sewer overflow rates having the ability to effectively separate
settleable and light weight organic suspended matter at a small
fraction of the 'detention time required for conventional sedimentation.
For these reasons serious thought is now being given to the use of
vortex units in series and in parallel solely as wet-weather treatment
plant systems. Great Britain has also developed a helical or spiral
type regulator/separator based on similar principles as the vortex
device(41,42,43).
D. Flow Measurement
The quantitative and qualitative measurement of storm overflows is
essential for process design, control, and evaluation. The "urban
intelligence systems" previously mentioned (under Section V.2.a.)
require real-time data from rapid, remote sensors in order to remotely
35
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Figure 11. Stormwater disinfection project-chlorine
contact basin construction completed, New Orleans,
Louisiana.
Figure 12. Overall view of vortex
flow regulator/solid separator pilot
study for Lancaster, Pa. Grant No.
11023 GSC, La Salle, Quebec.
-------
Figure 13. Plan view of vortex device depicting
fluid action, LaSalle, Quebec.
Figure 14. Plan view of empty vortex device
with bottom dry-weather effluent channel
visible, LaSalle, Quebec.
-------
control a sewerage network. Conventional flow meters have been
developed mainly for relatively steady-state irrigational, stream
and sanitary flows, and not for the highly-varying surges encountered
in combined sewers. In a combined sewer, a measuring device may be
subjected to very low flow rates, submergence, reverse flow, and
surcharge, all during a single rainstorm. These severe flow conditions
rule out the reliable and accurate application of conventional devices,
such as, weirs and flumes at many locations. Consequently, the Storm
and Combined Sewer Pollution Control Program is deeply involved in the
development and demonstration of sophisticated and new flow measuring
equipment utilizing the various principles of: vibratory damping,
hot-film anemometers, electrical capacitance of induced foreign matter,
and ultrasound. A dual Venturi flume - Venturi meter and a magmeter
for both open channel and pressure flow conditions are also being
evaluated.
Our Program has contributed towards the development of a prototype
monitor capable of instantaneous, in-situ, rapid measurement of suspended
solids based on the optical principles of light depolarization(106,107).
At one demonstration site an in-situ suspended solids meter utilizing
photometries is also being evaluated. This instrument appears prom-
ising and may have the needed ability to overcome interferences from
color or dissolved matter.
E. USEPA Stortnwater Management Model (SWMM)
The capability to analyse various component flows and pollution
loads throughout a sewerage system is one of the keys to better design
38
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of control and treatment systems. Due'to complexities of the rainfall-
runoff-flow phenomena, past analyses have been less than adequate,
resulting in poor estimates of flow and predicted system responses to
a storm. By virtue of previous undertakings, our Program now has avail-
able an operational "descriptive" mathematical model(112,113,114,115,116,
117,118) which can overcome former analytical deficiencies. The model
has been demonstrated at five combined sewer sites throughout the
country, varying from 187 to 5,400 acres. During demonstration the SWMM
has been verified(113) to be capable of representing the gamut of urban
stormwater runoff phenomena for various catchment systems. This includes
both quantity and quality, from the onset of precipitation on the basin,
through collection, conveyance, storage, and treatment systems, to points
downstream from outfalls which are significantly affected by storm dis-
charges. The computer program(115) is intended for use by municipalities,
government agencies, and consultants as a tool for evaluating the pollu-
tion potential of existing systems, present and future, and for compar-
ing alternate courses of remedial action. Use of correctional devices
in the catchment and their cost/effectiveness evaluation has been dem-
onstrated also. It is still felt that simplification of the SWMM
\
program should be explored, as long as model output is not impaired.
Other models to assist in the complicated challenge against wet-weather
pollution have also been developed and utilized(9,11,78,119,120) .
We are now in the initial phase of demonstrating the application
of this method for "decision-making"(108,117), that is, its ability
39
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to analyse a major combined sewer system; to select and to design
control and treatment approaches based on cost/effectiveness; and
to design a computerized means of overall management of the system
during storm flows. It is the eventual goal to handle all (wet and
dry-weather) flows in this manner.
VI. PROGRAM PROJECT NEEDS
Looking ahead, the Storm and Combined Sewer Pollution Control Program
needs are vast and numerous. At present, we are considering the award of
demonstration grants to State and local governments for the evaluation of
the following full-scale prototype treatment processes:
A. Deep-bed, multimedia, ultra high-rate filtration,
B. Physical-chemical processes including the concepts of in-line or
in-pipe coagulant mixing and activated carbon adsorption with on-
site regeneration of coagulants and carbon,
C. Vortex treatment systems, and
D. Helical (or spiral) flow regulation/solids separation.
Special consideration should ~be given to adapting these processes for dual
treatment of dry and wet-weather flows, as well as for automated control.
Wet-weather treatment systems built in conjunction with existing sanitary
plants can demonstrate their synergistic benefit by polishing secondary dry-
weather effluents or increasing dry-weather treatment capacity during the
vast majority of the time, when it is not raining.
There are also certain major control methods requiring further develop-
ment. "Upstream" storage or other control processes to decrease the storm-
water runoff effect on lower portions of the system is one case in point.
40
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An example of this would be the temporary storage or attenuation of storm-
water at the building or immediate area through the use of holding tanks;
seepage pits, possibly for recharge(121); roof tops(121); parks and play
grounds(121); backyard detention facilities; porous pavement(70), previously
discussed or neighborhood, decentralized stormwater collection sumps
including storage facilities under streets(122). Upstream control systems
should automatically regulate discharge from storage to the groundwater, a
watercourse, or sewer system. Plans for reuse of stored water for irriga-
tion, street cleaning, sewer flushing, aesthetic and recreational ponds(92,
123), potable supply(124) and other purposes is also encouraged(121,125,126).
Another "so-called" control practice, requiring further study is the
conventional employment of catch basins. We are seeking answers to such
questions as:
1. What is their actual need as used today?
2. Can new types be developed or existing ones be improved?
And very importantly, with wet-weather control requirements evident(127
128.129,130,131,132,133), now is the time to encourage our colleges and
universities to cover the concepts of stormwater runoff and combined sewer
overflow pollution in their graduate school curriculum on water pollution
control. After all, the students of today will be the problem solvers of
tomorrow.
Many more ideas and concepts could be added—some may be more significant
than those discussed. Submission of ideas, project proposals or grant applica-
tions to the USEPA is strongly encouraged. Some of the criteria for evaluat-
ing such proposals includes:
41
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A. Overall budget appropriation for research, development and demon-
stration projects.
B. At least 20 percent of the total project cost should be allocated
for research, evaluation and study efforts.
C. Minimal duplication of past or on-going projects. However, some
duplication may be necessary in order to provide evaluation under
suitable variety of conditions, and
D. The proposed development or demonstration should have nationwide
importance and application a& opposed to having limited geographical
use.
VII. CONCLUSION
The Storm and Combined Sewer Pollution Control R&D Program has imple-
mented many projects directed to full-scale treatment and control. Most of
these projects are still under construction or evaluation, and we are pres-
ently awaiting operational results.
This paper has been limited to pollution abatement of combined sewer
overflows. However, it should be noted that similar technological applica-
tion can and should be employed for the treatment and control of separate
stormwater runoff.
Abatement or prevention of pollution from stormwater runoff and combined
sewer overflows is one of the most challenging areas in the sanitary engineer-
ing field. The facts of life - from an engineering standpoint - are difficult
to face in terms of .design and cost. Operational problems can be just as
foreboding.
42
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The full impacts of "marginal" pollution, particularly that caused by
uncontrolled overflows, must be recognized now, and planning initiated, to
improve sewerage system efficiencies and so bring all wastewater flows under
control. Municipal programs with this objective cannot begin too soon be-
cause corrective action is time-consuming. Efforts devoted to improving
sewerage systems will pay significant dividends in complete control of
metropolitan wastewater problems and pollution abatement. Research and
development being undertaken cooperatively by Federal, State and local enti-
ties, including industry and the academic world, are majing available important
answers on the most efficient and least costly methods needed to restore and
maintain our water resources for maximum usefulness to man.
It is clearly seen that abatement requirements for combined sewer over-
flow (and stormwater runoff(133)) pollution are forthcoming. Already, Federal,
State and local governments(127,128,129,130,131,132,133) have promulgated
wet-weather flow treatment and control standards and guidelines. The USEPA
Research and Devleopment Program will continue its intensive efforts as a
prime support for this real-world application.
VIII. ACKNOWLEDGEMENTS
Sincere thanks are given to Messrs. William A. Rosenkranz, Chief,
Municipal Technology Division, Darwin R. Wright, Chief, Treatment and Control
Optimization Section; and Francis J. Condon, Staff Engineer, Municipal Pol-
lution Control Section, all of the Office of Research'and Monitoring, USEPA,
Washington, D.C., whose past efforts in the Storm and Combined Sewer Pollu-
tion Control Program have contributed valuably to the technological advance-
ment and the contents of this paper.
43
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We also express our appreciation to Mr. Anthony N. Tafuri, Staff
Engineer, Storm and Combined Sewage Pollution Control Branch, Edison, New
Jersey for his unselfish cooperation and assistance in editing.
44
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IX. REFERENCES
1. "Pollution Effects of Stormwater and Overflows from Combined Sewer
Systems - A Preliminary Appraisal", U.S. Public Health Service,
November 1964.
2. "Engineering Investigation of Sewer Overflow Problems - Roanoke,
Virginia", 11024 DMS 05/70, Hayes, Seay, Mattern and Mattern,
Architects-Engineers, Report for the USEPA, May 1970.
3. "Storm Water Problems and Control in Sanitary Sewers - Oakland and
Berkeley, California", 11024 EQG 03/71, Metcalf and Eddy, Inc.,
Engineers, Report for the USEPA, March 1971.
4. "The Quality of Storm Water Flow", Akerlindh, Nordisk Hygienisk
Tidsskrift, Vol. 31, No. 9, 1950.
5. "Chemical and Physical Comparison of Combined and Separate Sewer
Discharges", R.J. Burn, D.F. Krawczyk, and G.L. Harlow, Journal
Water Pollution Control Federation, Vol. 40, No. 1, January 1968.
6. "Bacteriological Comparisons Between Combined and Separate Sewer
Discharges in Southeastern Michigan", R.J. Burn, R.D. Vaughn, Journal
Water Pollution Control Federation, Vol. 38, No. 3, March 1966.
7. "Discharges from Separate Storm Sewers and Combined Sewers", W.J.
Benzie and R.J. Courchaine, Journal Water Pollution Control Federa-
tion, Vol. 38, No. 3, March 1966.
8. "The Pollutional Effects of Stormwater Overflows from Combined Sewers",
C.L. Palmer, Sewage and Industrial Wastes, Vol. 22, No. 2, February
1950.
9. "Spring Creek Auxiliary Water Pollution Control, Final Report - Year
1 - City of New York", 11023 FAO, H.F. Ludwig and Associates, Draft
Report for the USEtA, May 1970.
10. "Character of Separate Storm and Combined Sewer Flows", J.A. DeFilippi
and C.S. Shih, Journal Water Pollution Control Federation, Vol. 43,
No. 10, October 1971.
11. "Urban Runoff Characteristics", 11024 DQU 10/70, University of Cin-
cinnati, Phase I Interim Report for the USEPA, October 1970.
12. "Urban Storm Runoff and Combined Sewer Overflow Pollution - Sacramento,
California", 11024 FKM 12/71, Aerojet-General Corporation, Report for
the USEPA, December 1971.
13. "Onondaga Lake Study - Onondaga County, New York", 11060 FAE 04/71,
/ O'Brien and Gere, Inc., Report for the USEPA, November 1969.
45
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14. "Stonnwater Disinfection at New Orleans", E.H. Pavia and J.P. Crawford,
Journal Water Pollution Control Federation, Vol. 41, No. 4, April 1969.
15. "Storm and Combined Sewer Research and Development", A. Cywin and
W.A. Rosenkranz, Paper Presented at the American Society of Civil
Engineers, Annual and Environmental Meeting, Chicago, Illinois,
Meeting Preprint 1039, October 13-17, 1969.
16. "Storm and Combined Sewer Demonstration Projects - January 1970"
11000 01/70, (DAST-36), Storm and Combined Sewer Pollution
Control Branch, Office of Research and Development, USEPA, Jan-
uary 1970.
17. "Effect of Combined Sewage Overflows on Waters Around New York City",
H. Romer, G. Lacerre and T. Gallagher, Compilation of Papers Presented
at the Metropolitan Section, American Society of Civil Engineers,
Sanitary Engineering Division Symposium, Treatment of Storm Sewage
Overflows, New York University, Bronx, New York, April 17, 1962.
18. "Quantity and Composition of Storm Sewage Overflows", W.E. Dobbins,
Compilation of Papers Presented at the Metropolitan Section, American
Society of Civil Engineers, Sanitary Engineering Division Symposium,
Treatment of Storm Sewage Overflows, New York University, Bronx, New
York, April 17, 1962.
19. "Loss of Sanitary Sewage Through Storm Water Overflows", J.E.. McKee,
Journal Boston Society of Civil Engineers, Vol. 34, No. 2, April 1947.
20. "Problems of Combined Sewer Facilities and Overflows - 1967", 11020
12/67, (WP-20-11), American Public Works Association, Report for
the USEPA, December 1967.
21. "Storm Water Investigations at Northampton", A.L.H. Gameson and R.N.
Davidson, the Institute of Sewage Purification, Conference Paper No.
5, Annual Conference, Llandudno, England, June 19-22, 1962. /
22. "The Deep Tunnel Plan", D.R. Horsefield, Journal Boston Society of
Civil Engineers, October, 1968.
23. "Summary Report of Storm Flow Studies on Albany, Swan and Bird Avenue
Sewers - May to October, 1936", G.E. Symons, Buffalo Sewer Authority,
Bird Island Laboratory, December 22, 1936.
24. "Urban Land Runoff as a Factor in Stream Pollution", S.R. Weibel,
R.J. Anderson, and R.L. Woodward, Journal Water Pollution Control
Federation, Vol. 36, No. 7, July 1964.
25. "Storm Water Pollution from Urban Land Activity", 11034 FKL 07/70,
AVCO Economic Systems Corporation, Report for the USEPA, July 1970.
26. "Combined Sewer Overflow Abatement Alternatives", 11024 EXF 08^/70,
R.F. Weston Co., Report for the USEPA, August 1970.
46
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27. "Combined Sewer Overflows - Bucyrus, Ohio", 11024 FKN 11/69, Burgess
and Niple, Ltd., Consulting Engineers, Report for the USEPA, November
1969.
28. "Urban Soil Erosion and Sediment Control", 15030 DTL 05/70, National
Association of Counties Research Foundation, Report for the USEPA,
May 1970.
29. "Community Action Guidebook for Soil Erosion and Sediment Control",
M.D. Powell, W.C. Winter, and W.P. Bodwitch, National Association of
Counties Research Foundation, Under USEPA Grant No. 15030 DTL, March
1970.
30. "Sediment in Small Reserviors Due to Urbanization", H.P. Guy and
G.E. Ferguson, Journal Hydraulics Division, American Society of
Civ.il Engineers, March 1962.
31. '"Environmental Impact of Highway Deicing", 11040 QKK 06/71, Storm
and Combined Sewer Overflows Section, R&D Branch, Edison Water Quality
Laboratory, USEPA, June 1971.
32. "Proceedings Street Salting Urban Water Quality Workshop", Syracuse
University, August 1971.
33. "Pesticides and Other Contaminants in Rainfall and Runoff", S.R.
Weibel, R.B. Weidner, J.M. Cohen, and A.G. Christiansen, Journal
American Water Works Association, Vol. 58, No. 8, August 1966.
34. "Quality of Stormwater Drainage From Urban Land", E.H. Bryan, Work
Supported by the Office of Water Resources Research, Department of
the Interior, Draft Paper Presented at the Seventh American Water
Resources Conference, Washington, D.C., October 28, 1971.
35. "Quality of Stormwater Drainage from Urban Land Area in North Caro-
lina", E.H. Bryan, Department of Civil Engineering, Duke University,
Report No. 37, June 1970.
36. "Water Pollution Aspects of Urban Runoff" 11030 DNS 01/69, (WP-20-15),
American Public Works Association, Report for the USEPA, January 1969.
37. "Source Control of Urban Water Pollution", J.P. Heaney and R.H.
Sullivan, Journal Water Pollution Control Federation, Vol. 43, No. 4,
April 1971.
38. "Problems of Combined Sewer Facilities and Overflows - 1967", 11020
12/67, (WP-20-11), American Public Works Association, Report for
the USEPA, December 1967.
39. Federal Water Pollution Control Act, as amended by the Federal Water
Pollution Control Act Amendments of 1961 - (PL 87-88), the Water
Quality Act of 1965 - (PL 89-234), and the Clean Water Restoration
Act of 1966 - (PL 89-753).
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40. "Progress Report - Storm and Combined Sewer Pollution Control Pro-
gram - September 1970", Storm and Combined Sewer Overflows Section,
R&D Branch, Edison Water Quality Laboratory, USEPA, September 1970.
41. "Combined Sewer Overflow Abatement Technology - June 1970", 11024
06/70, Compilation of Papers Presented at the Federal Water Quality
Administration (USEPA) "Symposium on Storm and Combined Sewer Over-
flows", Chicago, Illinois, June 22-23, 1970.
/
42. "Combined Sewer Regulator Overflow Facilities", 11022 DMU 07/70,
American Public Works Association, Report for the USEPA, July 1970.
43. "Combined Sewer Regulation and Management - A Manual of Practice",
11022 DMU 08/70, American Public Works Association, Report for the
USEPA, July, 1970.
44. "Control of Infiltration and Inflow Into Sewer Systems", 11022 EFF
12/70, American Public Works Association, Report for the USEPA,
December 1970.
45. "Prevention and Correction of Excessive Infiltration and Inflow
Into Sewer Systems - A Manual of Practice", 11022 EFF 01/71, American
Public Works Association, Report for the USEPA, November 1970.
U
46. "Minimizing Sewer Infiltration", E.W. Spinzig, Jr. and A.T. Brokaw,
Paper Presented at the American Public Works Association Annual Con-
gress and Equipment Show, Philadelphia, Pennsylvania, September 15,
1971.
47. "Heat Shrinkable Tubing as Sewer Pipe Joints", 11024 FLY 06/71, the
Western Company, Report for the USEPA, June 1971.
48. "Improved Sealants for Infiltration Control", 11020 DIH 06/69, the
Western Company, Report for the USEPA, June 1969.
49. "Impregnation of Concrete Pipe", 11024 EQE 06/71, Southwest Research
Institute, Report for the USEPA, June 1971'.
50. "Reduction of Hydraulic Sewer Loadings by Downspout Removal", G.L.
Peters and O.P. Troemper, Paper Presented at the Annual Meeting of
the Central States Water Pollution Control Association, St. Paul,
Minnesota, June 12, 1968.
51. "Federal Water Quality Administration (USEPA) Symposium on Storm and
Combined Sewer Overflows", Verbal Discussion, Chicago, Illinois,
June 22-23, 1970.
52. "Polymers for Sewer Flow Control", 11020 DIG 08/69, (WP-20-22), the
Western Company, Report for the USEPA, August 1969.
48
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53. "Combined Sewer Overflow Seminar Papers - November 1969", 11020
03/70, (DAST-37), Compilation of Papers Presented at the Federal
Water Pollution Control (USEPA) Seminar, Edison Water Quality Labora-
tory, Edison, New Jersey, November 4-5, 1969.
54. "Increasing Sewage Flow Velocity by Using Chemical Additives", J.K.
Overfield, J.K. Baxter, H.R. Crawford, and I.W. Santry, Paper Pre-
sented at the WPCF Annual Conference, Chicago, Illinois, September
22-27, 1968.
55. "Monitoring Storm Water Overflows", A.C. Caster, Journal Water
Pollution Control Federation, Vol. 37, No. 9, September 1965.
56. "Dispatching System for Control of Combined Sewer Losses", 11020
FAQ 03/71, Metropolitan Sewer Board, St. Paul, Minnesota, Report for
the USEPA, March 1971.
57. "Real-Time Computer Control of Urban Runoff", J.J. Anderson, Journal
of the Hydraulics Division, Proceedings of the American Society of
Civil Engineers, Vol. 96, No. HY1, January 1970.
58. "Design of a Combined Sewer Fluidic Regulator", 11020 DGZ 10/69,
(DAST-13), Bowles Fluidic Corporation, Report for the USEPA, October
1969.
59. "Combined Sewer Regulation with Fluidic Regulators", P.A. Freeman,
Journal Water Pollution Control Federation, Vol. 43, No. 5, May 1971.
60. "Technical Committee on Storm Overflows and the Disposal of Storm
Sewage - Final Report", Ministry of Housing and Local Government,
Her Majesty's Stationery Office, London, England, 1970.
61. "Combined Sewer Overflow Detention and Chlorination Station", K.P.
Devenis, Paper Presented at the USEPA Technology Transfer Program
Design Seminar for Wastewater Treatment Facilities, Boston, Massa-
chusetts, May 26-27, 1971.
62. "Evaluation of Storm Standby Tanks, Columbus, Ohio", 11020 FAL 03/71,
Dodson, Kinney and Lindblom, Report for the USEPA, March 1971.
63. "Diversion and Treatment of Extraneous Flows in Sanitary Sewers",
L.W. Weller and M.K. Nelson, Journal Water Pollution Control Federa-
tion, Vol. 37, No. 3, March 1965.
64. "Storm Water Tanks in the Combined Sewerage System in Berlin", A.
Cohrs, Gus and Wasserfach, Vol. 103, No. 36, September 7, 1962.
65. "Intercepting Sewers and Storm Stand-By Tanks at Columbus, Ohio",
J.H. Gregory, R.H. Simpson, 0. Bonney, and R.A. Allton, American
Society of Civil Engineers Transactions, Paper No. 1887.
49
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66. "Effect of Storage and Skimming on Combined Sewage Overflows", G.E.
Hubbell, Paper Presented at the 39th Annual Conference of the Water
Pollution Control Federation, September 25-30, 1966.
67. "Boston University Bridge Store Water Detention and Chlorination
Station", K.P. Devenis, Paper Presented at the New England Water
Pollution Control Association Spring Meeting, June 11, 1968.
68. "Description of the Spring Creek Overflow Retention Basin Project
for the City of New York", R. Foerster, Paper Presented at the 44th
Annual Meeting of the New York Water Pollution Control Association,
New York, New York, January 25-28, 1972.
69. "The Greater London Council's Beckton and Crossness Wastewater Treat-
ment Plants", A. Bruce, Journal Water Pollution Control Federation,
Vol. 41. No. 4, April 1969.
70. "Written Correspondence" Department of Public Works, Erie County,
New York, 1970. X
71. "The Chicago Area Deep Tunnel Project - A Use of the Underground
Storage Resource", V.A. Koelzer, W.J. Bauer, and F.E. Dalton, Journal
Water Pollution Control Federation, Vol. 41, No. 4, April 1969.
72. "Tunnels Will Store Storm Runoff", Anon, Engineering News Recrod,
November 30, 1967.
73. "Underflow Sewers for Chicago", M. Pikarsky and C. Keifer, Civil
Engineering - American Society of Civil Engineers, May 1967.
74. "Combined Sewer Temporary Underwater Storage Facility", 11022 DPP
10/70, Melpar, An American-Standard Company, Report for the USEPA
October 1970.
75. "Control of Pollution by Underwater Storage", 11020 DWF 12/69,
(DAST-29), Underwater Storage, Inc. and Silver, Schwartz, Ltd.
Report for the USPEA, December 1969.
76. "Feasibility of a Stabilization-Retention Basin in Lake Erie at
Cleveland, Ohio", 11020 05/68, Havens and Emerson, Report for
the USEPA, May 1968.
77. "Treatment of Combined Sewer Overflows and Surface Waters At Cleve-
land, Ohio", G.D. Simpon, Paper Presented at the 41st Annual Con-
ference of the Water Pollution Control Federation, Chicago, Illinois,
September 23, 1968.
78. "Combined Sewers and Computers", J.L. Mancini, E.D. Driscoll and
J.P. Watkins, Paper Presented at the 43rd Annual Meeting of the New
York Water Pollution Control Association, New York, New York,
January 27, 1971.
50
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79. "Investigations of Porous Pavements", 11034 BUY, (14-12-924), the
Franklin Institute Research Laboratories, Draft Report for the USEPA,
October 1971.
80. "Combined Sewer Separation Using Pressure Sewers", 11020 EKO 10/69,
(ORD-4), American Society of Civil Engineers, Report for the USEPA,
October 1969.
81. "The Grinder Pump - A New Tool for the Sewer Designer", R.P. Farrel,
Jr. and I.G. Carcich, Presented at the 43rd Annual Meeting of the
New York Water Pollution Control Association, New York City, January
27-28, 1971.
82. "Characteristics of Combined Overflows", N. Nash, J. Degen and R.
Epstein, Paper Presented at the 43rd Annual Meeting of the New York
Water Pollution Control Association, New York, New York, January
27-28, 1971.
83. "Chemical Treatment of Combined Sewer Overflows", 11023 FDB 09/70,
Dow Chemical Co., Report for the USEPA, September 1970.
84. "Verbal Contact" W. Keilbaugh, Manager, R&D, Cochrane Division,
Crane Co., May 1971.
85. "Microstraining and Disinfection of Combined Sewer Overflows" 11023
EVO 06/70, Crane Company, Report for the USEPA, June 1970.
86. "Microstraining of Combined Sewer Overflows", E.W.J. Diaper and
G.E. Glover, Journal Water Pollution Control Federation, Vol. 43,
No. 10, October 1971.
87. "Combined Sewers—Microstraining Pilot Tests", USEPA Demonstration
Grant No. 1123 FWT, Monthly Progress Reports, July-November, 1971.
88. "Demonstration of Rotary Screening for Combined Sewer Overflows",
11023 FDD. 07/71, Department of Public Works, City of Portland, Oregon,
Report for the USEPA, July 1971.
89. "Rotary Vibratory Fine Screening of Combined Sewer Overflows", 11023
FDD 03/70, Cornell, Rowland, Hayes and Merryfield, Report for the
USEPA, March 1970.
90. "Ultra High Rate Filtration of Dilute Sewage Flows", J.A. Lee, C. Shun
Shik, and J.A. DeFilippi, Paper Presented at the 43rd Annual Meeting
of the New York Water Pollution Control Association, New York, New
York, January 27, 1971.
91. "Combined Sewer Overflow Abatement Alternatives, Washington, D.C.",
11024 EXF 08/70, Roy F. Weston, Inc., Report for the USEPA, August
1970.
51
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92. "Conceptual Engineering Report - Kingman Lake Project", 11023 FIX
08/70, Roy F. Weston, Inc., Report for the USEPA, August 1970.
93. "Treatment of Combined Sewer Overflows with Screening/Flotation",
11023 FDC, Rex Chainbelt, Inc., Draft Report for the USEPA, June 1970.
94. "Dissolved Air Flotation - City and County of San Francisco, Cali-
fornia", Engineering-Science, Inc., Report for San Francisco, Sup-
ported by USEPA Demonstration Grant No. 11023"DXC, July 1971.
95. "Dissolved-Air Flotation Treatment of Combined Sewer Overflows",
11020 FKL 01/70, Rhodes Corp., Report for the USEPA, January 1970.
96. "Study of High-Rate Filtration for Treating Combined Sewage Storm
Overflows", 11023 EYI, Hydrotechnic Corporation, Draft Report for
the USEPA, December 1971.
97. "Ultra High Rate Filtration System for Treating Overflows from
Combined Sewers", R. Nebolsine, P.J. Harvey, and C.Y. Fan, Paper
Presented at the 44th Annual Conference of the Water Pollution Con-
trol Federation, San Francisco, .California, October 3-8, 1971.
98. "Treatment of Raw and Combined Sewage", A.J. Shuckrow, et al., Water
and Sewage Works, April 1971.
99. "Pilot Plant Evaluation of a Physical/Chemical Process for Treatment
of Raw and Combined Sewage Using Powdered Activated Carbon", A.J.
Shuckrow, et al., Paper Presented at the 44th Annual Conference of
the Water Pollution Control Federation, San Francisco, California,
October 3-8, 1971.
100. "Physical-Chemical Treatment of Combined Sewer Overflows", A.J.
Shuckrow, Paper Presented at the 44th Annual Meeting of the New York
Water Pollution Control Association, New York, New York, January 26-
28, 1972.
101. "Municipal Sewage Treatment with a Rotating Biological Contactor",
Contract No. 14-12-24, Allis-Chalmers, Draft Report for the USEPA,
May 26, 1970.
102. "Rotating Discs Fulfill Dual Wastewater Role", R. Antonie and K.
Van Aacken, Water and Wastes Engineering, January 1971.
103. "Kinetics and Mechanism of Bacterial Disinfection by Chlorine Dioxide",
M.A. Benarde, W. B. Snow, V. P. Olivieri, and B. Davidson, Applied
Microbiology, Vol. 15, No. 2, March 1967.
104. "Disinfection/Treatment of Combined Sewer Overflows-Syracuse, New
York", USEPA Demonstration Grant No. 11020 HFR, Monthly Progress
Reports, October and December 1971.
52
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105. "Evaluation of a Stabilization Pond for Treatment of Combined Sewer
Overflows", 11020 --- 08/71, Springfield Illinois Sanitary District,
Report for the USPEA, August 1971.
106. "Design, Construction and Performance of Vortex Overflows", B. Snfisson,
Symposium on Storm Sewage Overflows, Institute of Civil Engineers,
Chapter 8, William Clowes and Sons, Ltd., London and Beccles, England.
107. "The Vortex Drop", P. Ackers and E.S. Crump, Proceedings of the
Institute of Civil Engineers, England, Vol. 16, August 1966.
108. "Demonstration of an Underground Storage Silo-Vortex Regulator/Solids
Separator for the Control of Combined Sewer Overflows-Lancaster,
Pennsylvania", USEPA Demonstration Grant No. 11023 GSC , Monthly
Progress Reports, July-December 1971.
109. "Develop a Suspended Solids Monitor", American Standard, Inc., USEPA
Contract No. 11024 DZB, (14-12-494), Monthly Progress Reports, April
1969 through May 1970.
11C>; "Development of a Suspended Solids Monitor", 11024 DZB, American
Standard, Inc., Interim Report - Phase I - for the USEPA, September
30, 1969.
111. "Study of High Rate Filtration for Treating Combined Sewage Storm
Overflows", Hydrotechnic Corp., Consulting Engineers, Contract No.
11023 EYI, (14-12-858), Monthly Progress Reports, August-October
1971.
112. "Storm Water Management Model, Vol. I, Final Report", 11024 DOC
07/71, Metcalf and Eddy, Inc., University of Florida, and Water
Resources Engineers, Inc., Report for the USEPA, July 1971.
113. "Storm Water Management Model, Vol. II, Verification and Testing",
11024 DOC 08/71, MetcaM- and Eddy, Inc., University of Florida and
Water Resources Engineers, Inc., Report for the USEPA, August 1971.
114. "Storm Water Management Model, Vol. Ill, User's Manual", 11024 DOC
09/71, Metcalf and Eddy, Inc., University of Florida, and Water
Resources Engineers, Inc., Report for the USEPA, September 1971.
115. "Storm Water Management Model, Vol. IV, Program Listing", 11024 DOC
10/71, Metcalf and Eddy, Inc., University of Florida and Water
Resources Engineers, Inc., Report for the USEPA, October 1971.
116. "Development of a Simulation Model for Stormwater Management",
J.A. Layer, R.P. Shubinski, and L.W. Russell, Journal Water Pollu-
Control Federation, Vol. 43, No. 12, December 1971.
117. "USEPA Stormwater Management Model", W.C. Huber, Paper Presented at
the 44th Annual Meeting of the New York Water Pollution Control
Association, New York, New York, January 28, 1971.
53
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118. "Routing Model for Combined Sewage", W.C. Huber, L.W. Russell, E.E.
Pyatt, Paper Presented at the American Society of Civil Engineers,
National Water Resources Engineering Meeting, Memphis, Tennessee
Meeting Preprint 1108, January 26-30, 1970.
119. "Urban Runoff Characteristics-Interim Report", 11024 DQU, University
of Cincinnati, Phase II Draft Report for the USEPA, October 1971.
120. "Upgrading City Sewer Installations", F.G. Ritter and C. Warg,
Engineering Digest, April 1971.
121. "Storm Water for Fun and Profit", J.R. Sheaffer, Water Spectrum,
Army Corps of Engineers, Fall 1970.
122. "San Francisco Master Plan for Waste Water Management-Preliminary
Summary Report", City and County of San Francisco Department of
Public Works, September 15, 1971.
123. "Reusing Storm Runoff", Hittman Associates, Inc., Environmental
Science and Technology,^Vol. 2, No. 11, November 1968.
124. "Use of Storm Runoff for Artificial Recharge", J.E. Berend, M. Rebhun,
and Y. Kahana, Transactions of the American Society of Agricultural
Engineers, Vol. 10, No. 5, 1967.
125. "The Beneficial Use of Storm Water", 11030 DNK 08/68, Hittman Assoc.,
Inc., Report for the USEPA, August 1968.
126. "Reclaimed Water Will Help Fill Lakes", Anon., Public Works, March
1965.
127. "Federal Guidelines for Design, Operation and Maintenance of Waste-
water Treatment Facilities", USEPA, September 1971.
128. "The Great Lakes Enforcement Conference", Under the "Federal Water
Pollution Control Act"—Sets 1977 as Target for Combined Sewer Over-
flow Pollution Control.
129. "Resolution No. 70-93, Amending Resolution No. 67-64, Special Time
Schedule for the City and County of San Francisco Relative to
Regulation of Discharges from Combined Sewers", California Regional
Water Quality Control Board-San Francisco Bay Region, November 24,
1970.
130. "Regulation No. R70-3, Secondary Treatment Dates, Mississippi River",
Illinois Pollution Control Board, January 6, 1971.
131. "WPC Technical Policy 20-24, Design Criteria—Waste Treatment Plants
and Treatment of Sewer Overflows", State of Illinois Environmental
Protection Agency, Revised July 1971.
54
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132. "Proposed Final Draft Rules and Regulations Nos. R70-8, R71-4, and
R71-20; Effluent Criteria, Water Quality Standards Revisions and
Water Quality Standards Revisions for Interstate Waters (SWB-14),
Respectively", Illinois Pollution Control Board, November 11, 1971.
133. "Proposed Standard Criteria for Sub-Division Development, Section
9.6.4: Disposition of Storm Water Runoff", Orange County Planning
Department, Florida, October 1971.
55
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
NATIONAL ENVIRONMENTAL RESEARCH CENTER
Edison, New Jersey 08817
R RATA SH
TO: Recipients of Report, "Management and Control of Combined Sewer
Overflows - Program Overview"
It has been found necessary to make the following changes to the report:
1. Page 3, third paragraph: After the last sentence, add the following
new sentence, This can produce "shock loadings" detrimental to receiv-
ing water life.
2. Page 4, second line: Add number 41 to references.
3. Page 7, first sentence under V. CORRECTIVE METHODS: Change sentence
to read as follows, program (16, 40) research, development and demon-
stration projects have provided significant results, and have illustra-
ted that alternatives to sewer separation in most cases are the logical
course of action.
4. Page 14, first sentence: Replace the word system with pipelines.
5. Page 14, in section 2 a. Flow Regulation, after second sentence (line
20) add, The mechanism for this is a simple electric switch immersed
at a preset height in the outfall pipe which when submerged by the
flow closes the circuit creating an alarm at a central receiving sta-
tion. This provision can also serve as a warning system for unwanted
backwater intrusion.
6. Page 15, after line 8 add the following new paragraph: Before con-
cluding the subject of in-line storage, it is emphasized that prior
to new sewer construction an additional alternative of designing a
combined sewer system with oversized pipelines to not only convey wet-
weather flows but contain (store) them as well, be considered. This
system may be justified economically since the cost difference for
added pipe diameter could easily be less expensive than facilities for
off -system storage.
7. Page 19, first paragraph: After the fifth sentence (line 10) add,
Additional benefits of tunnel or in-sewer storage are attributed to
the installation's coverage of an expanded area or length. Because
of this, storage is more readily available to remote areas; hydro-
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graphs can possibly be smoothed or volumetrically reduced for treat-
ment facility design since many intense storms are over small areas;
and excessive overflows, greater than storage capacity, could be selec-
tively and automatically discharged to stream locations based on water
usage and assimilation capacity.
8. Page 20, under Porous Pavement, after the fifth sentence (line 20)
add, Even more important are the safety features which could be
realized, that is, an increased coefficient of friction which will
help prevent wet skidding or hydroplaning accidents, and enhanced
visability of pavement markings due to a more rapid removal of water
from the surface and because the marking material will penetrate the
pavement voids to present an oblique view.
9. Page 25, third line: Change concnetration to concentration.
10. Page 30, first paragraph: After the last sentence add, The designer,
in his evaluation of the optimum surge-treatment system, should recog-
nize the wet-weather treatment plant's capability to continuously
draft stored flow while it is raining.
11. Page 32, first paragraph: In the third complete sentence (line 11)
eliminate, during the year.
12. Page 32, first paragraph: Change the last sentence to read, It may
very well be, that the temperature fluctuation during the year in
combined sewage in many urban areas would be similar to the range
(40 F to 80 F) tested for by Benarde, et al., and as a result, re-
quire disinfectant dosage to vary seasonally or as affected by
ambient temperature.
13. Page 32, second paragraph: In the second sentence add a comma after
Philadelphia.
14. Page 32, third line from bottom: Change pruposes to purposes.
15. Page 34, third line from bottom: Change the word vortex to swirl.
16. Page 35, third line: Change the word vortex to swirl.
17. Page 35, first paragraph: In the last sentence, Change the word
vortex to swirl.
18. Figure 12: Change the words vortex and solid in the caption to
swirl and solids, respectively.
19. Figures 13 and 14: Change the word vortex to swirl.
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20. Page 38, second paragraph: In the first sentence eliminate the word
rapid and change references (106, 107) to (109, 110).
21. Page 38, second paragraph: Add at the end of the second sentence,
(111).
22. Page 40, second paragraph under VI. PROGRAM PROJECT NEEDS: Change
the word vortex contained in item C to swirl.
23. Page 42, second paragraph under VII. CONCLUSION: Add after the
last sentence, Many concepts are also adaptable for sanitary sewage.
24. Page 43, first paragraph under VIII. ACKNOWLEDGEMENTS: In the
first sentence (line 2) add a semicolon after Division.
25. Page 43, first paragraph: In the forth sentence (line 9) change
majing to making.
26. Page 53, Reference Number 117: Change 1971 to 1972.
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