EPA DOCUMENT AC-06
                                       RETURN TO MARTHA SEGALL
                                       ROOM 206, BLDG. A
0050
                           LITERATURE SUMMARIES
                               PREPARED FOR A
                          CSO GUIDANCE DOCUMENT

                  U.S. ENVIRONMENTAL PROTECTION AGENCY
                              WASHINGTON, D.C.

                              September 28,1989
      1.  An Analysis of the United States Environmental Protection Agency's Needs
         Survey (American Public Works Association), 1975.

      2.  Analyzing the Existing Collection System (Pisano), 1978-1981.

      3.  Assessment of Benefits Resulting from Control of Combined Sewer Overflows
         (Driscoll and Mancini), 1978.

      4.  Benefit Analysis for Combined Sewer Overflow Control (USEPA - Environmental
         Research Information Center), 1979.

      5.  Combined Sewer Overflow Abatement  Alternatives  - Washington, D.C.
         (Weston), 1970.

      6.  Combined Sewer Overflow Abatement  Program, Rochester, New York
         (Drehwig, Murray, Carleo, Jordan), 1981.

      7.  Combined Sewer Regulator  Overflow Facilities  (American  Public Works
         Association), 1970.

      8.  Control of Combined Sewer Overflows in Minneapolis-St.Pau! (Tucker), 1971.

      9.  Countermeasures for Pollution from Overflows: The State-of-the-Art (Field,
         Lager), 1974.

     10.  Dry-Weather Deposition and Flushing  for Combined Sewer Overflow Pollution
         Control (Pisano), 1979.

     11.  Methodology  of Analysis for a Combined Sewer Overflow Abatement Program
         (Murphy), 1978.
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  12.   Prevention and Correction of Excessive Infiltration and Inflow into Sewer
       Systems (American Public Works Association), 1971.

  13.   Relationship  Between Diameter and Height for the Design of  a Swirl
       Concentrator as a Combined Sewer Overflow Regulator (Sullivan, Conn, lire,
       Parkinson, Galiama), 1974.

  14.   Remote Control of Combined Sewer Overflows (Anderson, Gallery), 1974.

  15.   Retention Basin Control of Combined Sewer  Overflows (Springfield Sanitary
       District), 1970.

  16.   Sewer Flow Measurement:  A State-of-the-Art Assessment (EG & G Washington
       Analytical Services Center, Inc.), 1975.

  17.   Storage  and Treatment of Combined Sewer Overflow  (Liebenow, Beiging),
       1972.

  18.   A Strategy for Integrating  Storage Treatment Options with Management
       Practices (Heany, Nix), 1978.

  19.   Stream Pollution and Abatement From Combined Sewer Overflows (Burgess,
       Niple), 1969.

  20.   Surface and Sub-Surface Detention in Developed Urban Areas:  A Case Study
       (Walesh, Schoeffmann), 1984.

  21.   The Swirl Concentrator as a Combined Sewer Overflow Regulator Facility
       (Field), 1972.

  22.   Swirl and Helical Bend Pollution  Control Devices (Sullivan, lire, Parkinson,
       Zielinski), 1982.

  23.   Urban Runoff Pollution Control Technology Overview (Brunner, Field, Masters,
       Tafuri),1977.

  24.   Use of Street Cleaning Operations in Reducing Urban Runoff Pollution (Pitt),
       1978.

  25.   Useful Technologies Information on Sewer Flushing (Pisano), 1978.

  26.   Water Quality Characteristics of Storm and Combined Sewer Overflow (Ministry
       of Construction - Japanese Government), 1977.
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                    AN ANALYSIS OF THE UNITED STATES
                  ENVIRONMENTAL PROTECTION AGENCY'S
                              NEEDS SURVEY

                  AMERICAN PUBLIC WORKS ASSOCIATION

                                August 1975
Public Law 93-243 directed the U.S. Environmental Protection Agency to conduct a
survey in 1974 to determine the cost of wastewater facilities eligible for funding under
PL 92-500.  The National Commission  on Water Quality retained the APWA Research
Foundation to make an independent  study of the procedures used by states and
selected metropolitan communities to assess and report the cost estimates and to
assemble data concerning industrial use of municipal treatment facilities,  sludge
disposal, and proposed financing of the construction program.  The APWA study was
not intended either to duplicate or to validate the results of the USEPA survey.  Rather,
the study was designed to add interpretation to the 1974 Needs Survey.  This report
presents the findings of the APWA study.

The APWA study reviewed state policies and  procedures on non-federal financing of
local sewer systems and treatment facilities, industry-municipal inter-relations on
wastewater handling, private industry waste handling and disposal, non-utility private
wastewater treatment needs, cost factors not included in the 1974 needs estimates but
requiring consideration up to and after 1983, and opinions of state officials on the ability
of public agencies to complete needed sewer system and treatment facilities by the
deadlines established by PL 92-500. The APWA study also  explored potential impacts
of the major water quality controls stipulated by the Act on the state's surface water,
groundwater, air, and land resources. In addition, the reported needs of representative
metropolitan governmental units and their financing of required construction work were
examined.  The study identified areas where the 1974 Needs Survey reflects realistic
Construction costs for projects required by  PL 92-500 and ascertained how the states
determined their needs.  The study also evaluated the reasons for changes between the
1974 Survey and a previous survey conducted in 1973.

The study conducted by APWA included in-person interviews with  18 states and three
(3) metropolitan areas.  In addition, mail surveys  were conducted  in the remaining 32
states, the District of Columbia,  Puerto  Rico, the Virgin Islands, American Samoa, and
the trust territory of the Pacific Islands.
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The same needs categories which were used in the USEPA National Needs Survey for
1974 were used for this study.  They include the following:

       Category I - Secondary Treatment  and Best Practicable Waste Treatment
       Technology
       Category II - More Stringent Degrees of Treatment
       Category IIIA - Infiltration/Inflow Correction
       Category IIIB - Major Sewer System Rehabilitation
       Category IVA - New Collector Sewers and Appurtenances
       Category IVB - New Interceptor Sewers and Appurtenances
       Category V - Correction of Combined Sewer Overflows
       Category VI - Treatment and/or Control of Stormwater Discharges

The APWA study interviews and surveys covered the following information:

       Estimate of methods used by local authorities to develop cost estimates for the
       1974 Needs Survey: for facilities with no needs, facilities for which 1973 cost
       estimates were reported, and facilities with updated or newly estimated needs
       for all categories.

       Reasons for new or updated costs in  1974 survey not included in the 1973
       survey, increased facility capacities required,  new facility processes required,
       other reasons for new or updated 1974 costs for all categories.

       Methods used by states for cost estimates and evaluation procedures:  USEPA
       guidelines, state modifications of USEPA guidelines, state-developed guidelines
       for all categories.

       Basis for state variances from USEPA Guidelines for each category I - VI.

       Basis for state variances from engineering report estimates of local  authorities
       for each category.

       Basis for 1974  Needs estimates:  cost-effective analyses, engineering  studies,
       USEPA guidelines, rough local estimates-for all categories.

       Anticipated needs not included in the  1974 Needs Survey but required to meet
       1983 criteria, based on 1990 population estimates:  upgrading of water quality
       standards, land needs for treatment facilities and disposal areas for effluent and
       sludge  application,  system rehabilitation needs  (including treatment facilities),
       needs for privately owned (non-industrial) treatment system facilities, and
       facilities with undetermined needs--for  ail categories.
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      State policies on disposal and treatment of industrial wastes: encouragement
      by states of joint municipal-industrial treatment facilities, requiring cost recovery
      systems for industrial waste handling to qualify municipal facilities for state aid,
      invoking USEPA guidelines on industrial wastes cost-recovery arrangements,
      status of cost-recovery arrangements in the states.

      Wastewater character and volumes  produced by the ten major industries in
      each state:  listing of major industries in order of importance, MGD flow, BOD
      and Suspended Solids loadings.

      Estimated trends in industrial wastes production - 1974/1977/1983: volumes of
      wastewaters produced, volumes anticipated to be handled by municipal
      facilities - for each of the ten major industries of each authority.

      Estimated construction cost of probable industrial wastewater treatment facilities
      - 1974  to 1983:  for publicly owned plants  handling industrial wastes, for
      industry-owned facilities, dependent upon whether cost of municipal systems
      handling industrial wastes was included in  1974 needs and percentage of
      Category I needs included in the 1974 survey.

      Basis for population estimates for 1990 by local authorities:  USEPA regional
      estimates (Series E, Department  of Commerce); state own  population
      estimates, local or regional planning agency population studies and projections,
      or any combination of methods for estimating population trends.

      State estimates on progress in meeting goals of PL 92-500 for Categories I and
      II:  numbers and capacities of facilities  already completed,  numbers and
      capacities of facilities to be completed by 1977,  numbers  and capacities of
      facilities to be under construction in 1977,  numbers and capacities of facilities
      not yet begun in 1977, estimated cost of facilities to  be completed between 1974
      and 1977, and estimated  cost of facilities to be under construction or not yet
      begun in 1977.

      State authorization of local financing requirements for Category I and Category
      II facilities:  state aid arrangements, funds allocated for local water  pollution
      control  needs, types of taxes and/or other local funding methods for sewer
      systems and treatment works.
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       Detailed information on state and local infiltration/inflow control  actions
       (Category I1IA): allowable infiltration rates set by states for sewer  design,
       estimates of actual infiltration rates experienced  in sewer systems, amounts of
       infiltration that can cause sewer system and treatment plant problems, state
       regulations prohibiting inflow into sanitary sewers, status of local studies of
       infiltration/inflow problems, types of  local  corrective actions taken  or
       contemplated to correct infiltration/inflow  conditions - including sewer system
       rehabilitation, excess treatment facilities, percent of systems studied  to
       determine cost of correction actions, and percent of total sewer systems
       requiring infiltration corrective actions.

       Miles of sewers  in state requiring major rehabilitation {Category IIIB), due to:
       age of sewer system, defective  workmanship or  materials,  chemical
       deterioration,  establishment of  state  guidelines  or criteria  for major
       rehabilitation, and other causes.

       State policies and experiences on combined sewer overflows and  corrective
       actions (Category V):  state criteria on quality of combined sewer overflows,
       provisions to prevent or minimize overflows, state policies on elimination of
       combined sewer overflows, number of enforcement actions taken, methods and
       costs planned by the state for correction of overflow - sewer separation,
       treatment  equivalent to primary plus disinfection, treatment equivalent to
       secondary, storage off- system or in-system, flow routing and other means,
       state policies permitting new or extensions of combined sewers,  and amounts
       built from 1970 to 1974.

       State policies and procedures on  storm water discharge elimination  (Category
       VI):  states' estimates for 1974 needs in terms of quality of storm water runoff,
       rainfall events  covered by storm  sewer design, establishment of state
       stormwater control criteria to guide local  governments,  state requirements for
       stormwater discharge control or treatment - including storage and controlled
       release, storage in-system with release to treatment equivalent  to secondary
       treatment or other means.

       States' evaluation of the potential  environmental impact of compliance  with the
       goals of PL 92-500:  as envisioned by the 1974 needs estimates on surface
       water, groundwater, air and land resources.
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The findings of the APWA study by needs category are as follows:

Category I-	Secondary Treatment and Best Practicable Wastewater Treatment
                 Technology

       Population estimates seem high
       The extent of municipal facility use by industry is uncertain
       The cost of adequate sludge handling and disposal facilities has not been
       included in all cost estimates.
       High I/I flows may be included as the basis of facility design
       Costs for the facilities appear to be based generally upon engineering studies
       with well defined treatment requirements

Category II - More Stringent Treatment Required by Water Quality

       Population estimates seem high
       Assumptions concerning the level of treatment required are preliminary
       The extent of use of facilities of industry is uncertain
       High I/I flows may be included as the basis of facility design
       The cost of adequate sludge handling and disposal facilities has not been
       included in all cost estimates
       Uncertainty as to which facilities will  be required to meet water quality
       requirements suggests that reported costs are questionable; costs  may be high,
       low  or accurate

Category IMA - Correction of Infiltration/Inflow

       Few local authorities have conducted I/I studies
       Correctional cost versus cost of excess treatment capacity has  not been
       determined for most systems.
       Where relatively high I/I rates are allowed, the cost of Category  I and  II facilities
       will be higher than where more strict standards are in effect.
       Total costs for Category IIIA appear to be  low due to number of authorities not
       reporting costs for 1974

Category IIIB - Major Sewer  Rehabilitation

       Total costs will not be known until I/I studies have been conducted
       Since many local authorities did not report costs  in 1974, they  are probably
       understated
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Category IVA - New Collector Sewers

Methods used  to obtain cost estimates appear reliable;  however, some sewers
reported in the  Needs Survey may not be eligible for inclusion and high population
estimates could have produced overstated costs.

Category IVB - New Interceptor Sewers

Methods used to obtain cost estimates appear reliable; however, the size and cost of
systems is dependent upon the  accuracy of population and industrial flow estimates for
Category I and II facilities.

Category V - Correction of Combined Sewer Overflows

       Cost estimates may be high where they are based on sewer separation
       Many small local authorities apparently did not report their needs
       Sludge handling requirements were not always considered
       Control or treatment objectives are needed
       The net effect of the above factors could not be estimated

Category VI - Treatment and/or Control of Stormwater

       Estimates were missing from three states
       Control or treatment objectives are needed
       A significant portion of the costs reported were for storm sewers
       Costs are to be considered  speculative and a first estimate

The analysis for state-reported data concerning the  status  of plans for construction of
Category i and II treatment facilities indicated that 66 percent of the facilities would not
be completed by 1977, but 24 percent of them would be under construction.  In terms
of capacity, 43 percent could  be completed by 1977, 30 percent would be under
construction, and 27 percent would not be started.

Adequate methods were not available to evaluate the potential environmental impacts
of the pollution control program. However, the opinion of the key officials participating
in the survey was that receiving surface waters would be generally improved and that
groundwater and air resources would not be degraded by the construction of new
facilities.
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              ANALYZING THE EXISTING COLLECTION SYSTEM

                                   by

                          DR. WILLIAM C. PISANO
                   ENVIRONMENTAL DESIGN AND PLANNING, INC.

                               presented at

                EPA TECHNOLOGY TRANSFER SEMINARS ON
                      COMBINED SEWER OVERFLOW
                ASSESSMENT AND CONTROL PROCEDURES

                                1978-1981
The objective of this combined sewer management study was to study in fine detail the
impact of potential structural and non-structural control options for an old combined
sewer collection system and then to select the least cost program for that system. The
same problem was analyzed from three alternative points of view: a) remedial system
fixes; b) the vogue and prevailing 208  orientation  of street sweeping/sewer
flushing/roof top inflow control; and c) end-of-line detention storage.  Beforehand It
was believed that significant control of combined sewer overflows can in fact  be
accomplished through  a purposeful effort in restoring the condition of the existing
system and jointly maximizing any system control.

The principal motivation and emphasis of the study method was to demonstrate the
feasibility and practicality of developing low-cost, non-structural solutions for mitigating
the number and magnitude of combined sewer overflows from the prototype study
area.

This  study was extremely well-received by USEPA  as  a hallmark problem-solving
investigation which demonstrated  the clear and unmistakable need  to thoroughly
understand the piping system, optimize its performance and then consider additive
control measures. The study was presented at several Combined Sewer Overflow
Technology Transfers EPA sponsored between 1978-1981.

This project was described in the 1978 report to Congress on Control of Combined
Sewer Overflow in the  United States. It best signifies Environmental Design and
Planning's cost-effective philosophical approach to combined sewer management
planning. The following is excerpted from the report to Congress:
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"The major objective of collection system management is to implement a continual
remedial repair and maintenance program to provide maximum transmission of flows
for treatment and disposal while minimizing overflow, bypass, and local flooding. It
requires an understanding of how the collection system works  and patience to locate
unknown malfunctions of all types, poorly  optimized regulators,  unused in-line storage,
and pipes clogged with sediments in old combined sewer systems.

The first phase of analysis in a sewer system study is an extensive inventory of data and
mapping of flowline profiles. This information is then used to conduct a detailed
physical survey of regulator and storm drain  performance.  In  this detailed  study,
Pisano found that minor repairs of four overflow  structures and several small alterations
of storm sewer piping obtained a 43.9 percent reduction of the  present BOD load due
to combined sewer overflow at a cost of $26,000.  An additional 23 percent BOD
reduction was obtained at a cost of $4,678,000  using sewer flushing, street sweeping,
inflow correction  and storage. This type of sewer system inventory and study should
be the first objective of any combined sewer overflow pollution abatement project."
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               ASSESSMENT OF BENEFITS RESULTING FROM
               CONTROL OF COMBINED SEWER OVERFLOWS
                                    by
                EUGENE D. DRISCOLL AND JOHN L MANCINI
                           HYDROSCIENCE, INC.

                               presented at

                EPA TECHNOLOGY TRANSFER SEMINARS ON
                      COMBINED SEWER OVERFLOW
                ASSESSMENT AND CONTROL PROCEDURES

                                   1978
The nature of surface water quality problems present around metropolitan areas is quite
varied. Local factors have a predominant influence on the class of problem, its severity,
and the specific source or sources which are contributing to the problem. The local
factors which affect water quality include climate, geography, population, population
concentration, the nature and degree of industrialization in an area, the receiving water
system, its nature, size and hydrology; and the nature of the surrounding area - both
upstream and downstream of the urban area itself.

The objective of water quality management, particularly facilities planning activities, is
improvement in water use. The definitions of water quality problems used in 201
studies should be related to water uses.  This type of water quality problem definition
will provide a sound basis for focusing pollution control activities, facility  evaluations
and efforts to benefit estimates.

Facility plans must provide answers to three implicit questions which are raised by
public administrators and citizens. These are:

            Why commit any resources at all to these water quality management
            activities?

            Why commit these resources now?

            Why commit these resources in the way recommended?
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Estimates of water quality and water use benefits provides part of the information
needed to answer these questions. The reason a community, a state or EPA would
want to commit resources to water quality management activities, regardless of time
frame, would be that the perceived benefits are larger than the anticipated costs.

A common element of all levels of benefit estimates is the ability to quantitatively project
water quality impacts  of pollution  control activities.  There are several methods of
estimating the benefits of water quality management.

The first is Application of Available Technology.  The essence of this approach is a
fundamental assumption that the benefits to be derived from the proposed activities are
so large that they will automatically justify the allocation of the required  resources. The
controlling factor is assumed to be the availability of technology for obtaining the water
quality benefits.

A second measure which can be  considered in benefit estimates concerns
achievement of "water quality standards."  The basic assumption is that standards are
somehow tied to protection of certain water uses.  A major requirement of this type of
an evaluation is the ability to directly relate  proposed pollution  control activities to
improvements in receiving water quality.

An additional level of resolution may be obtained through translating improvements in
water quality into "Estimates of Increased  Water Use Potential." Physical scales such
as useable beach length and water surface area can be related to the number of
individuals that could utilize those  resources.  Once the level of water quality
improvement has been defined as suggested above, these factors may be used to
estimate  the  potential  increased  water  resource utilization  that could be
accommodated.

The final level of benefit analysis is the classical cost benefit analysis  in which each
anticipated water usage is assigned a dollar value as a measure of unit worth or
willingness to pay.  The actual projected usage in each water use category is multiplied
by the unit value and the sum represents an estimate of the value of the total benefits.
The benefit total value is compared to total costs.

The analysis of receiving water impacts is a common element to  each of the benefit
estimating techniques previously discussed.

Streams and rivers can often  be characterized as one-dimensional flowing systems
where dispersion of mass can be neglected.  For a complete specification of stream
responses to pollutant  loads under these  assumptions, the initial pollutant
concentration,  the reaction  rate, and the river flow and cross-sectional areas must be
defined.  Concentrations are assumed to be constant throughout the depth and across
the width of the  receiving water. The receiving  water geometry is, therefore,
approximated by a series of constant geometry and constant flow segments.  For a first
assessment, a single  segment model should be used with a spatially aggregated
average stormwater load.
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One or two spatial dimensions may be of importance  in estuaries, although initial
assessments may simplify the problem to a one-dimensional analysts.  The primary
difference  between estuaries and the one-dimensional river flow situation is the
dispersive  mass transport due to tidal mixing. This forms an important transport
phenomena in combination with to the net freshwater flow through the estuary and, as
such, must be included specifically in the analysis.

Lakes and reservoirs can  involve either two  or three spatial dimensions. Initial
assessments of long-term stormwater impacts  in lakes and reservoirs may be made
with a few simplifying assumptions.  To determine the average concentration of slowly
reactive constituents (i.e., dissolved solids,  persistent organics, etc.), the water body
may be assumed to be completely mixed.

The objective of a 201 Facilities Plan for CSOs should include the following elements.
First, the need for controlling waste  loads from each source should be assessed.  The
need should be defined in terms  of sufficient impacts on receiving water quality which
violate water quality standards and as a consequence impair or deny desired beneficial
uses of the receiving water body. Secondly, where a need for CSO control  has been
established, the 201 planning effort should identify a control strategy for which cost-
effectiveness is justified in terms of the receiving water benefits expected to accrue.

In order to  determine receiving water impacts, it is necessary to identify the magnitude
of the waste loads which enter the receiving water.  The determination of point source
continuous loads is straightforward, being defined by the volume and quality of the
discharge.  However, intermittent waste loads, which result from the rainfall process,
are more difficult to characterize. The intermittent nature of rainfall, the number and
wide spatial distribution of overflow points, and the variability in both size of storm event
and pollutant concentrations found  in runoff, make a definitive determination of such
loads impractical, if not virtually impossible.

Once the magnitude of stormwater impacts on  receiving water quality are  estimated,
control strategies for the reduction of these impacts may be analyzed. A variety of
stormwater control alternatives are available.  These are generally grouped into two
types of approaches:

       1.     Structural, end-of-pipe treatment devices
       2.     Management practices
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Structural, end-of-pipe alternatives include devices which capture and store runoff, such
as interceptors and retention basins, and devices which reduce  the  pollutant
concentration of runoff or overflows, such as screens, filters, concentrators, and
disinfection systems. Management practices include source controls, such as street
sweeping and erosion control; and collection system management techniques, such as
sewer flushing and  polymer injection to increase the flow capacity of  the sewerage
system. The projected  improvement in receiving water quality due to the modification
of stormwater loads represents the benefit of potential stormwater control  actions.
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      BENEFIT ANALYSIS FOR COMBINED SEWER OVERFLOW CONTROL

              TECHNOLOGY TRANSFER SEMINAR PUBLICATION
            ENVIRONMENTAL RESEARCH INFORMATION CENTER
                          CINCINNATI, OHIO  45268

                             EPA-625/4-79-013

                                 April 1979
Approximately 40 million people (one-fifth of the nation's population) are served by
combined sewers.  There are between 1,100 and 1,300 combined sewer systems,
covering an area of more than 2 and one-half million acres. Seventy-seven major cities,
including 10 of the country's 14 largest have combined sewer overflow control needs of
$50 million or more.  They account for 96 percent of urbanized area combined sewer
overflow control needs and 64 percent of national needs.

Some of the options for controlling  combined  sewer overflows, especially those
involving the division  of the combined sewers into separate storm and sanitary
systems, necessitate monumental expenditures that severely strain local budgets and
state construction grant allocations.

As a tool to relate proposed expenditure to anticipated benefit, a properly executed
benefit analysis helps a municipality, and thus the U.S. government, avoid unnecessary
costs. A benefit analysis provides justification for funding requested from the state and
EPA, and it demonstrates to the taxpayers that  their tax dollars are  being used to
achieve desirable objectives.

To succeed in obtaining approval and funding assistance for a combined sewer
overflow (CSO) project, it is necessary  to know the regulations and policies that have
an impact on ultimate grant application approvals. A clear understanding should be
developed at the beginning of the process, because the plans must provide  special
outputs  and must meet a number of  criteria peculiar to combined sewer overflow
control planning.

In any well executed planning process in the public realm, there are two general
principles regarding the preparation of objectives. First, the effort to define them should
begin early in the project.  Second, though decisions on objectives can be facilitated by
the technicians and consultants who can suggest alternatives and indicate  the range of
choices, the actual choices must be made by elected officials.  A third principle has
applicability to many types of projects but is of critical importance to planning for
control of pollution from combined sewer overflows.  The tasks of developing a
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combined sewer overflow control program that will qualify for EPA approval and funding
and then  obtaining the funding as well as local support for the proposal will be
immensely easier if the combined sewer overflow control objectives are related to
benefits and expressed in such a way that measurement of benefit is made  possible. It
is the benefits that are the results of pollution abatement - the improvements expected
in receiving water uses - that must be demonstrated.  Because this is the case, it makes
sense to select as pollution control objectives the maintenance of or improvement in
specific beneficial uses.

The determination of both required and desired uses of local receiving water is only the
beginning of the analysis  necessary to plan for combined sewer overflow control
projects that are to be funded by the federal government. One criterion for federal
approval  of combined sewer overflow projects  is that the analysis  must have
"...demonstrated that the level of pollution control provided will be  necessary to protect
a beneficial use of the  receiving water even after technology-based standards...are
achieved by industrial point sources and at least  secondary treatment is achieved for
dry weather municipal flows in the area." Combined sewer overflow control must also
be shown to be more  cost  effective than "the  addition of treatment higher than
secondary treatment for dry  weather municipal flows in the area."  Taken together,
these criteria mean among other things, that in order for a CSO project to qualify for
federal  funding, the pollutants  to be controlled must  be identified with a specific
beneficial use and that a primary contributor of that pollutant must be demonstrated to
be combined sewer overflows.

Selecting from among the alternatives available for controlling combined sewer
overflows  does not enter the planning process until many decisions about desired
benefits have been  made and data gathering is quite far advanced. The water quality
parameters associated with the desired beneficial uses provide the link between
objectives and control alternatives. The objectives must first be translated into the
water quality criteria necessary to protect the uses.  Then the reductions in specific
pollutant inputs required to meet the criteria can be calculated.   With this work
completed, two tasks remain:  the development of a control strategy and the selection
of control alternatives.

Technologies to control pollution from combined sewer overflow, many of which are
also applicable to urban stormwater runoff, can be grouped in  three  main  categories:
source  controls to reduce the amounts of  pollutants  entering the sewer system,
collection system control to improve the system's effectiveness in storing and handling
the flows, and off-line storage and treatment to remove pollutants from combined sewer
flows. The control alternative selected for any given situation may include  techniques
from one or more of these groups.
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Most source controls are non-structural in nature. The principle common to all of them
is reduction of pollutant accumulation on impervious surfaces in the drainage basin or
in portions of the collection system itself, so that pollutant loadings in combined sewer
flows during storm events are lowered.  Included under the category of source controls
are: street cleaning, combined sewer flushing, and catch basin cleaning.

Techniques of collection system controls are intended to ensure that the sewer  system
operates as efficiently as possible and that maximum advantage is taken of any
opportunities it offers for combined sewer overflow pollution reduction. All of these
measures require detailed knowledge of the sewer system. Some are structural and
some are  nonstructural.  Included under collection system controls are the  following:
existing system management, flow reduction techniques, sewer separation and in-line
storage.

When the  list of control alternatives has been narrowed down to those that look most
promising, each should  be tested again for effectiveness in providing the desired
benefit-that is, in meeting the criteria to protect that benefit.

The analysts and planning for combined  sewer overflow correction has rested  solidly on
a determination of desired or required beneficial uses of a receiving water body and the
most cost effective controls that will result in these beneficial uses.  The culmination of
this process in a decision to proceed depends on the presentation of the answers to
three basic questions:

           What are the benefits?
           How costly is the project?
           Do the  benefits expected justify the commitment of public funds  and other
           resources?
The key to a successful outcome of this stage is that the questions be answered in a
clear, logical, and realistic manner. The dollar amounts involved in combined sewer
overflow control projects are invariably large enough to attract more than casual
interest.  If it is not possible to demonstrate to the taxpayers a favorable relationship of
benefits to costs, it is not likely that they will lend their support to the undertaking.
896CMS4.WS5

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         COMBINED SEWER OVERFLOW ABATEMENT ALTERNATIVES
                            WASHINGTON, D.C.

                                    by

                           ROY F. WESTON, INC.
               ENVIRONMENTAL SCIENTISTS AND ENGINEERS
                      WEST CHESTER, PENNSYLVANIA

                                    for

                       THE WATER QUALITY OFFICE
                  ENVIRONMENTAL PROTECTION AGENCY

                                August 1970


Most United States cities today  are served both by combined sewers and by separate
sanitary and storm sewer systems.  As determined  from a 1967 survey sponsored by
the Water Quality Office of the Environmental Protection Agency, approximately 29
percent of the total sewered  population  of the United States is served by combined
sewer systems. Approximately three percent of the total annual flow of sewage and as
much as 95 percent of the sewage produced during periods of rainfall is carried with
combined sewer overflows to the surface waters.

The District of Columbia follows this pattern, with an area of approximately 20 square
miles (one-third of the total area of the District) being served by combined sewers. The
hydraulic capacity of the system is often exceeded during periods of precipitation, and
raw sewage mixed with surface runoff is discharged to the watercourses of the District.

The Potomac Estuary is polluted and continues to experience problems with low
dissolved oxygen, excessive algae growths, sediments, high concentrations of fecal
bacteria and repulsive floating matter. All of these problems, except sediments, are
complicated by combined sewers.  Although combined sewer overflow adds to the
sediment load, the primary source of sediment is the heavy silt load included  in the
runoff from areas with significant agricultural and construction activity. In addition to
the effects of combined overflow on the Potomac River, overflows into Rock Creek
detract from the natural and recreational features of this small, scenic  stream flowing
through the District.

After review and interpretation of pertinent information, four methods of abating
pollution from combined sewer overflows appeared  to offer sufficient promise to  justify
consideration as alternative approaches for the District:

       1-     Sewer Separation
            This alternative would completely separate storm and sanitary sewers.
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      2.     Storage Reservoirs
             Sufficient underground storage volume would be provided to hold the
             combined sewer overflows caused by each storm  until the storm
             subsides and stored wastewater would then be pumped the back  into
             the sewerage system for conveyance to a centralized treatment plant.

      3.     Treatment at Overflow Points
             A treatment facility would be located at each existing overflow point,
             except where  conditions either prevent this or  dictate that certain
             overflow points be combined.

      4.     Tunnels and Mined Storage
             Combined sewer overflow would drop through a vertical shaft down to
             an underground system of tunnels and mined storage.  The tunnels
             would convey the overflow at high velocity to mined storage.  After the
             storm subsides, the retained overflow would be pumped back into the
             regular sewers.

Cost is an essential factor in selecting the appropriate alternative for abating combined
sewer overflows. In summary, the costs for each alternative were as follows:
       1. Storage Reservoirs
       2. Treatment at Overflow Points
       3. Conveyance Tunnels and Mined Storage
       4. Sewer Separation
$5,560,000
$6,820,000
$3,500,000
Considerably greater than
the above 3
To determine which of the feasible alternative approaches would offer the best
opportunity for abatement of the combined sewer overflow problem requires careful
consideration of many factors.  Cost comparison obviously is essential, but there are
other factors which also have a significant bearing on the selection of the most
favorable plan. The most important of these other factors are reliability, flexibility, land
requirements, public convenience, implementation, and solids disposal and gas
production.

Each strategy offers a different level of costs, pollutant loadings, and benefits. While
the selection of the appropriate strategy rested partially on factors beyond the scope of
this study, the information presented within this article indicated that the appropriate
District-wide  solution would utilize mined storage and conveyance tunnels.  The total
project costs of the recommended alternative  was estimated to be $318,000,000 in
1970.
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  COMBINED SEWER OVERFLOW ABATEMENT PROGRAM, ROCHESTER, N.Y.

                    VOLUME I: ABATEMENT ANALYSIS

                                   by

                            FRANK J.DREHWIG
                        CORNELIUS B. MURRAY, JR.
                            DAVID J. CARLEO
                           THOMAS A. JORDAN

                     O'BRIEN & GERE ENGINEERS, INC.
                          SYRACUSE, NEW YORK

                                July 1981

                           EPA NO. 600/2-81-113
Pollution abatement analyses, conducted in conjunction with system network modeling
studies and supported by combined sewer overflow (CSO) monitoring and sampling,
were initiated with the ultimate goal of formulating a cohesive and workable Master Plan
for CSO  reduction and control in  Rochester, New York.  The  Master Plan was
developed in light of fiscal constraints, sewer system complexities, necessity for
optimized benefits from minimal capital and operating expenditures, and best use
policies for the affected receiving waters. The present methodology is considered
applicable to other urban areas.

Overflow monitoring and sampling data from thirteen CSO locations within the
Rochester, New York Pure Waters District collected during the period January through
December, 1985 served as the basis for network modeling studies. Within each of
these overflow discharge conduits, an electronic flow measuring system was installed
to determine the hydrograph and thus the quantity of combined sewer overflow
discharged from the tributary drainage area.

To collect  the  samples, samplers were installed at  each  of  the overflow
locations. Samples were collected at approximately 15-minute intervals unless the
pumping  distance dictated suction and purge times greater than 15 minutes. At the
completion of an overflow event, the samples were collected and transported to the
laboratory for analyses.
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A system of 12 rain gauges was installed within the Rochester Pure Waters District. The
location of each gauge was selected by dividing the District into 12 units of equal area.
Within each of the units, a building of significant height {school, firehouse, pump
station) with no observable influences from adjacent buildings or trees was selected for
installation. The total system of gauges allowed an evaluation  of differences of rainfall
patterns and their possible effect on the intercepting sewer system.

The flow, analytical, and rainfall data that were monitored and recorded served two
main purposes.  First, the data was used directly in the calibration and verification
process associated with the application of the SWMM.  Secondly, much of the data was
used for developing valuable relationships between rainfall and overflow quantity and
quality through the use of statistical procedures.

In the  overall effort to develop an abatement and  management program for the
combined sewer overflows, the physical characteristics of the entire study area were
defined. A brief description of the scope of work outlined for the drainage areas
surveys follows:

       1}     Each of the 13 CSO locations were divided into  a  maximum  of sixty
             subcatchments ranging in size from ten to fifty acres.  Division was made
             on the basis of land slope and zoning classifications such as residential,
             commercial, industrial, or open.

       2)     Each drainage area subcatchment was characterized  by determining the
             average ground slope,  percent of the  area that is pervious and
             impervious,  total area, average drainage width, total length of gutters,
             total number of  catch basins and stored volume of each, the BOD5
             contained in the volume of stored water in  those catch basins, and any
             available surface storage capacities.

       3)     The estimation of dry-weather flow for each subcatchment was made by
             collecting statistics as to the number of dwelling units, average  number
             of people per unit, market value of average  units, average family income,
             percent of units with garbage grinders, and information as to industrial
             process flows.

       4)     Other information required to complete  the characterization of the
             drainage basin included total population, street  cleaning frequency,
             average number of sweeper passes, and location of inlet manholes.

       5)     Information was  obtained to characterize the sewer network including
             length of sewer conduits, conduit slope, type, size and roughness, and
             manhole invert and ground elevations.
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The two models selected for demonstration and use in the evaluation of various
combined sewer overflow abatement alternatives proposed under this program were
the SWMM (II) and the Simplified Storm Model (7). The Simplified Stormwater Model
was developed by Metcalf & Eddy, Inc.  Each model was selected for a specific
purpose.  Preliminary screening of various abatement alternatives was accomplished
with the use of the Simplified Stormwater Model, whereas, the SWMM  was used to
evaluate specific alternatives under the application of varying design storms.

There are three general approaches available for the control of Stormwater and CSO
discharges. A combination of storage and treatment can be applied through the use of
structurally intensive measures to attain defined water quality standards.  Secondly, the
sources of the pollutants discharged into the sewer system can be addressed through
the application  of the Best Management Practices (BMP)  concept.  Thirdly,  a
combination of the two can be applied.  In general, the most cost-effective abatement
alternative will be the application of structural and nonstructural (BMP) measures.

For this article, the alternatives that were evaluated can be classified as nonstructural,
minimal structural, and structurally intensive. The first two classes of abatement
alternatives are those generally considered in developing a BMP program.

Nonstructural Alternatives

       1) -     Land Use Policies
              -  Land use policies and sewer system maintenance procedures can
                significantly affect both the quantity and quality of combined sewer
                overflows.
       2) -    Street Cleaning Practices
       3) -     Increased Sewer Maintenance
              -  Sewer maintenance  has potential for not only reducing  system
                flooding but also minimizing first flush effects.
       4) -     Land Use Planning
             -  Increased imperviousness adversely affects the quantity and quality of
                Stormwater and combined sewer overflow.
       5) -    Surface Storage

Minimal Structural Alternatives

       1)     Abandoned Treatment Facilities
       2)      Multi-Purpose Upstream Impoundment for Overflow Control
       3)      Use of In-System Regulators and Control Structures for Increased In-
             System Storage
       4)      Upgrading the Existing St. Paul Interceptor
       5)     Selective Blockage of High Impacting Combined Sewer Overflows
       6)     Selective Overflow Weir Evaluation
       7)      Regulator Capacity Evaluation
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Structural intensive Alternatives

Alternative 1:  This alternative considered capturing the first-flush from all the river
overflow sites and treating all post first-flush flows with primary swirl devices. The
temporarily stored first-flush volume would be released back into the interceptor system
on termination of system overflows.

Alternative 2: This alternative involved evaluating various storage and treatment
options for capturing the total overflow to the Genesee River.

Alternative 3: The only difference between Alternatives 2 and 3 was the location of the
treatment facility.

Alternative 4:  This alternative is similar to Alternate 1 with the exception that the post
first-flush would not be treated, but directly discharged to the river.

Alternative 5:  Primary swirl concentrators would be located on each of the river
overflow locations for treatment of the entire overflow volume.

Alternative 6:  This  alternative involved construction of an interceptor to convey
overflows from the western portion of the collection system to  the Cross-lrondequoit
Tunnel.  The latter facility served the eastern portion of the city and  had in-system
storage available.

Cost benefit analyses of all structurally  intensive alternatives were conducted using
optimum treatment process train configurations developed from pilot plant evaluations,
as reported in Volume II of the project's report.

Based on the results of this investigation, the following conclusions were made.

General

       1.     A rigorous definition of the existing  system of  CSO and stormwater
             facilities is fundamental to the development of an abatement program.
             This definition includes the identification of major drainage basins, major
             trunk and intercepting sewers, and CSO and stormwater relief points.

       2.     The installation and proper maintenance of  overflow monitoring
             instrumentation is essential for both receiving water problem definition
             and any subsequent sewer network and water quality  model calibration
             and verification.
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      3.     Accurate rainfall data collection and subsequent statistical analyses,
             including design storm definition and  formulation, is essential in
             evaluating  the response of the existing system as well as  the
             effectiveness of various abatement alternatives.

      4.     Development of a methodology of approach and definition of applicable
             abatement alternatives early in the program ensures that the purpose of
             the study is not lost, and all data collection activities are conducted
             according to the required analyses.

      5.     SSM is capable of providing a preliminary screening of  potential
             abatement alternatives involving a balance between storage and
             treatment.

      6.     SWMM (USEPA Stormwater Management Model-Version II) can project
             the urban storm runoff and quantities within acceptable confidence limits
             but is presently limited in its ability to simulate overflow quality.

      7.     Overflow quality can be better simulated through the application of
             statistical techniques using actual monitoring overflow data.

      8.     The ability to abate CSO pollution resulting from an infrequent design
             storm event will require 1he  implementation of structurally  intensive
             facilities, minimal structural improvements to the  existing sewer system,
             or the implementation of nonstructural abatement alternatives, known as
             BMPs.
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                       COMBINED SEWER REGULATOR
                           OVERFLOW FACILITIES

                  AMERICAN PUBLIC WORKS ASSOCIATION
                       DEPARTMENT OF THE INTERIOR

                                  July 1970

                         PROGRAM NO. 11022 DMU
An in-depth investigation of combined sewer regulator practices was carried out by the
American Public Works Association. The focus of this investigation was on design
application, performance, operation and maintenance practices, and equipment.  The
study provided information upon which to base recommendations on the more effective
use and management of existing regulator facilities and on maximizing the quality of
wastes discharged to receiving waters. This report was dedicated entirely to regulator
facilities and was not concerned with other aspects of combined sewer systems.

The findings and major recommendations of this study included the following:

             It is economically infeasible to  apply  expensive and sophisticated
             regulator devices in small regulator structures which handle flows of 2 cfs
             or less. Consolidation of small regulator-overflow locations would make
             it feasible to provide more effective control facilities.

             Regulators should be designed to control both quantity and quality of
             overflows.  Too often,  design is concerned only with the quantity of the
             overflow.

             Management of control for an entire sewer system could result in less
             overflows than would be seen in a system which has all independently
             controlled devices.

             Control systems should have the ability to direct excess flow in one part
             of a system to another part of the system which may have available
             capacity to handle the excess flow.

             Dynamic-type regulators, while more costly for initial installation, are
             better able to reduce overflows than static devices.  This is a result of the
             dynamic regulators' ability to react to sewer system hydraulic conditions.
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             Many existing dynamic-type regulators have been removed or disabled
             because of maintenance and repair costs. Each type of regulator should
             be given the attention required to achieve maximum performance
             (instead of being neglected).

             Regulator  facilities should be designed such that they are easily
             accessible for routine maintenance purposes.  Inaccessible regulator
             stations tend  to discourage the frequency  and effectiveness of
             inspections and maintenance.

             Training is extremely important for the proper operation of an overflow
             control device. Maintenance crews should be adequately staffed and
             provided with the necessary equipment and tools to service  the
             equipment.

             Corrosion and wear can shorten the life of overflow control equipment.
             Adequate specifications  must be prepared to address existing
             environmentai conditions.

             Tide gates are often poorly  located for maintenance purposes.  Design
             should provide sufficient access.

             State water pollution control  agencies have not exerted enough regulator
             control over sewer overflows.

             Manufacturers, officials, and designers should communicate more often
             on overflow matters.  This would produce a better knowledge base for
             reducing overflows.

             A Manual of Practice has been developed on the design, operation, and
             maintenance of combined sewer overflow regulators and tide gates, as
             part of this study.

             Clogging  is  the most frequent cause of regulator malfunction.
             Maintenance should be designed to reduce these effects.

             Local jurisdictions should gather information on the frequency and extent
             of overflow events.

             European practices have been effective and should be studied for use in
             the United States and Canada.
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                CONTROL OF COMBINED SEWER OVERFLOWS
                        IN MINNEAPOLIS-SAINT PAUL

                             SCOTT L TUCKER
                      DEPARTMENT OF THE INTERIOR

                                October 1971

                              NTISPB-212903
This report represented one phase of a larger scale study which was designed to
develop criteria and a rationale for the establishment of centralized metropolitan water
intelligence systems in urbanized and urbanizing areas.  This particular phase of the
overall project (Phase I) was focused on real-time automation and control facilities for
combined sewers. Basic objectives of Phase I were to:

             Investigate and describe modern automation and control systems for
             combined sewer systems,

             Develop criteria for managers, planners, and designers for the operation
             of combined sewer systems, and

             Study the feasibility of automation and control systems for combined
             sewer systems.

This report was prepared in connection with one task of Phase L which examined
existing planned automation and control systems.  The planning, design, operation,
and  maintenance of  computer controlled systems was studied.   Regulators were
redesigned and rebuilt; rainfall, water level, and water quality data were monitored and
transmitted to computer based data logging and processing centers; and regulators,
gates, and pumps were remotely controlled.  These controls were not designed as
integral parts of complete metropolitan systems, but were implemented to demonstrate
concepts and hardware.

Existing overflow regulators were replaced with power operated gates at 16 key
diversion locations. The new regulators will control flows and levels in the sewers  by
adjusting gate position (tied to a telemetering system). River water quality was also
monitored at five (5) locations. The CSO control system had basically five (5) functions:

             Scan and print readings of river quality, regulator activities, interceptor
             conditions, and rainfall;
896RHG6.WS5

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             Control regulator gate positions;

             Perform analyses of data;

             Provide an operational model  that could aid the operator during
             rainstorm events; and

             Perform any other functions for management that would not affect
             performance during rainstorm events.

Data acquisition for the system program emphasized providing immediate information
on river quality, including dissolved oxygen, chloride, ORP, pH, and temperature.
Additionally, depth of flow in the trunk sewers, depth of flow in the overflow pipe,
position of the regulator, and rainfall data were immediately available. Control functions
included operating gates to predetermined set points based on system conditions. The
main concerns of the operator were  to prevent:

             surcharging of the trunk sewers
             excessive pressure buildup on the inflatable dams and gates.

Operation of the system, as of 1971, consisted only of deflating system dams (allowing
an overflow) if system pressures  became too high.  No attempts were made to utilize
the control system as a storage area for excessive combined sewer flows.

The demonstration project discussed in this article was a definite success insofaras
demonstrated the feasibility of controlling of combined sewer overflows.  Overflow
regulators could be remotely controlled based on parameters monitored throughout
the interceptor system.  The conclusions stated, however, that the demonstration
project was not being used up  to its potential.  No attempts were being made to
optimize storage of combined sewage overflows in the interceptor system and  the
prediction model developed to assist an operator was not being used.
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         COUNTERMEASURES FOR POLLUTION FROM OVERFLOWS

                         THE STATE OF THE ART

                                  by

                            RICHARD FIELD
      STORM AND COMBINED SEWER SECTION (EDISON, JEW JERSEY)
         ADVANCED WASTE TREATMENT RESEARCH LABORATORY
             NATIONAL ENVIRONMENTAL RESEARCH CENTER
                        CINCINNATI, OHIO 45268

                                  and

                            JOHN A. LAGER
                         METCALF & EDDY, INC.
                     PALO ALTO, CALIFORNIA 94303

                             December") 974
Control and/or treatment of stormwater discharges and combined sewer overflows
from urban areas are problems of importance in the field of water quality management.
Over the previous decade, much research effort was expended and a large amount of
data was  generated, primarily  through  the actions and support of the U.S.
Environmental Protection Agency's Storm and Combined Sewer Research and
Development Program.

Combined  sewer overflows are major sources of water pollution, but even discharges
of stormwater  alone can seriously affect water quality. Current approaches involve
control of overflows, treatment and combinations of the two. Control may involve
maximizing treatment with existing facilities, control of infiltration and extraneous
inflows, surface sanitation and management, as well as flow regulation and storage.

Examples of source controls include flow attenuation, erosion control, restrictions on
chemical use {deicing compounds, pesticides), and improved neighborhood sanitation
practices.  The theory behind source controls is to limit the supply of contaminants.
The benefits are not only reduced water pollution but also cleaner and healthier
environments.
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Examples of collection system controls include flushing, polymer feed, inflow/infiltration
control, improved regulator devices, sewer separation, and remote monitoring/control
systems.  The emphasis, with the exception of sewer separation, is upon optimal
utilization of the existing facilities.

Storage facilities possess characteristics which are also beneficial in stormwater
treatment: 1) they are capable of providing flow equalization or attenuation and, in the
case of tunnels, flow transmission; 2) they are simple to design and operate; 3) they
respond without difficulty to intermittent and random storm behavior; 4) they are
relatively unaffected by flow and quality changes; and 5) frequently they can  be
operated  in concert with  regional dry weather flow treatment plants for benefits during
both dry and  wet-weather conditions.  Disadvantages of storage facilities include their
large size, high cost, and dependency on other treatment facilities for dewatering and
solids disposal.

Physical treatment processes in many ways are well suited to stormwater applications,
particularly with respect to solids removal.  These processes include sedimentation,
dissolved air flotation, screening, filtration, and flow regulation.  Handicaps appear to
be sensitivities to flows and loadings, high maintenance requirements, and the absence
of effective utilization between storms.

Biological treatment of storm wastewaters must overcome some serious drawbacks: 1)
the biomass used to assimilate the waste constituents must either  be kept alive during
times of  dry  weather or allowed to develop for each storm event; and 2) once
developed, the biomass is highly susceptible to washout by hydraulic surges or
overload.

Physical/chemical processes are of particular importance to stormwater treatment
because  of their adaptability to automated operation, rapid startup  and shutdown
characteristics, and very  good resistance to shock-loads.   Drawbacks  to
physical/chemical treatment include high initial costs, high chemical requirements, and
increased sludge (by dry weight) to be disposed of.

By far the most promising approaches to urban stormwater management involve the
integrated use of control and treatment with an areawide, multidiscipltnary perspective.
Integrated approaches are notably demonstrated in programs underway in Chicago,
San Francisco, Seattle, Washington, D.C., and Rochester, New York.
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Two directions for further study were suggested:  1) Characterization and Evaluation:
Simulation  Models,  Nationwide Assessment of Urban  Runoff Impacts, Combined
Sewage Sludge, Uniform Procedures for Analysis and Evaluation of Storm Flow
Characteristics and Treatability, Flow Measurement, Consideration of Trace Pollutants,
and Pathogen Detection, and 2) Control Methodology:  New Sewer Design, Upstream
Impoundment, Catch Basins, Runoff Attenuation by Porous Pavement, Dual Use
Facilities, Swirl and Helical Separators, Comparisons of Screening Devices,
Hydrologic-Hydraulic Design  Rationale, and Beneficial Use of Stormwater.

A nationwide characterization and evaluation of the impact of new methods for the
determination of pathogenic pollution would be required in addition to a reevaluation of
disinfection requirements.   Methods of controlling and treating heavy metals and
organics found in runoff should be developed.   Detention, both in-line and upstream,
needs further development  to optimize its effectiveness as a pollution abatement
procedure.

Multi-billion dollar treatment plant upgrading and expansion programs now in progress
throughout the country will do much to alleviate water pollution.  However, means of
mitigating the effects of urban runoff must also be found if we hope to abate the
pollution in an optimal manner.
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                 DRY WEATHER DEPOSITION AND FLUSHING
          FOR COMBINED SEWER OVERFLOW POLLUTION CONTROL

                                    by

                       DR. WILLIAM C. PISANO, et. al.
                    NORTHEASTERN UNIVERSITY AND
               ENVIRONMENTAL DESIGN AND PLANNING, INC.

                                August 1979

                           EPA NO. 600/2-79-133
This report summarizes the results of a two-year study aimed at addressing the
feasibility, cost-effectiveness and ease of application of upstream solids control as an
integral part of overall combined sewer management.  The project was functionally
divided into four major phases. The first three phases were intensive field engineering
investigations, while the fourth phase was relegated to data reduction and desk-top
analytical efforts.

In the first phase of field work, four test segments on different streets in the Boston
sewerage system were field flushed over an extended period using different flushing
methods.  External sources of fresh water, as well as treated sewage, were used.  The
experiments were aimed at quantifying the  effectiveness  of flushing deposition
accumulations from a single pipe segment on a routine basis, as well as roughly
estimating deposition characteristics within collection system laterals.  Removals of 75
to 90 percent for grit, organic and nutrient contaminants can be expected for single
manhole to  manhole small  diameter combined and separated sewer laterals.  All
flushing methods yielded comparable flushing pollutant removals. The most effective
flushing method was an application of about 50  cubic feet (1.42 cubic meters) of water,
injected at discharge rates exceeding 0.5 cfs (14.4 liters per second).

The second phase of field work was concerned with the problem of flushing a long flat
stretch of combined sewer laterals.  Flushes were injected into the uppermost manhole
and pollutant levels in the flush wave passing three downstream manholes were
monitored. Work was divided into two subphases.  Initially, pollutant removals over the
three segments were determined for different flushing conditions established in the first
manhole, providing insights into flushing effectiveness over three segments of pipe.
The results of these experiments indicated that a single flushing at the upper end of the
street was reasonably effective in removing most of the deposited load along the 675-
foot (206 m.) stretch of 12-inch (30.5 cm.) combined sewer lateral. Next, settleability
tests were performed for the purpose of crudely extrapolating  how far beyond the
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flushing monitoring manholes the materials would be carried. The experiments showed
that heavier grit fractions would quickly resettle, leaving the lighter solid fractions in
suspension. Roughly 20 to 30 percent of suspended solids and about half of the BOD
and nutrient loads would remain in suspension after 30 minutes of settling time.
Analysis of the heavy metals results from the settleability experiments indicated that
about 20 to 40 percent of the heavy metals would not settle within two hours of settling.

In the final phase of field operation, an automatic sewer flushing module was designed,
fabricated, installed, and operated on a single segment for an extended period.
Flushed  pollutant loads  were determined for seven flushing events, and were
comparable to removals noted in the first phase of work, where  flushing was
accomplished by manual means using a flush truck. The purpose of this work was to
begin to develop operational experience using automated flushing equipment. The
state-of-the-art with respect to operational automated flushing methods, equipment,
and sensing interfaces has not been fully demonstrated at this point in time. The effort
in this study is viewed as a pilot prototype investigation.

In the fourth phase, various predictive deposition loading and flushing criteria were
generated from the large data base developed during the field programs.  These
formalisms  allow for scanning of large-scale sewer systems to identify problem pipes
with respect to deposition.  The refined tools will allow for comparative analysis of
upstream solids control vs. selected structural options to compare program
efficiencies.
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                 THE METHODOLOGY OF ANALYSIS FOR A
           COMBINED SEWER OVERFLOW ABATEMENT PROGRAM

                       CORNELIUS B. MURPHY, JR.

               U.S. ENVIRONMENTAL PROTECTION AGENCY
                   TECHNOLOGY TRANSFER PROGRAM

                           CHICAGO, ILLINOIS

                             July 25-26,1978
The Fifth Annual International Joint Commission (UC) Report on Great Lakes Water
Quality acknowledged the impact of urban runoff in the Great Lakes Basin:

      "The Commission  believes that combined  sewer overflows  and
      stormwater flows from urban areas are reaching serious proportions and
      contribute significant amounts of a wide range of harmful substances in
      the Great Lakes."

Urban runoff is composed of two major components, stormwater and combined sewer
overflow. Stormwater discharges consist of runoff from various impervious areas which
have been contaminated by pollutants accumulated on the various surfaces due to
chemical spillage, air pollution, atmospheric washout, the application of highway
deicing agents, fecal matter of animal origin, and the accumulation of surface debris
and litter. The combined sewer overflows contain stormwater and sanitary sewerage.

The problem of combined sewer overflows is extensive insofaras one-fifth of the
nation's population is served by combined sewer systems. Furthermore, ten (10) of the
nation's fourteen (14) largest cities are served by a combined system  in whole or in
part.

The objective of facilities planning is the development of cost effective, environmentally
sound and implementable conveyance and treatment  systems which will meet
applicable requirements of Sections 201 (g), 301, and 302 of PL 92-500.
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Consistent with 40 CFR Part 35, Subpart E (Grants for Construction of Treatment Works
- Federal Water Pollution Control Act Amendments of 1972) a facilities plan is to
include:

             A description of the treatment works for which construction drawings and
             specifications are to be prepared,

             A description of the selected wastewater treatment system covering all
             elements of the system,

             Infiltration/inflow documentation,

             A cost-effectiveness analysis of the alternatives,

             Identification of effluent limitations (permit),

             Required comments or approvals of relevant state, interstate, regional
             and local agencies,

             Brief summary of pertinent public hearings or meetings, and

             Brief statement demonstrating the implementability of the project.

The facilities planning  activities are essentially the  same for conventional treatment
facilities as for combined sewer overflow facilities.   However, there were  some
difficulties in the planning process.  As a result,  EPA established certain specific
policies (PRM 75-34 and PRM 77-4) which described how these issues were to  be
addressed in the facility planning for combined sewer overflow abatement facilities.

PRM 77-4 outlined  a cost allocation procedure for multiple purpose projects, allowing
EPA and the applicant to select the abatement alternative which offers the highest cost-
effectiveness relative to pollution control.  PRM 75-34 outlines the procedure to  select
the alternative and the sizing necessary to optimize the marginal cost/marginal benefit
ratio of the abatement options.

In the process of conducting the Rochester, New York CSO study, a methodology  for
the analysis of CSO abatement  alternatives was developed. The abatement alternative
analysis involved the logical development of a data base which analyzed activities in
fifteen major categories.
896CMS6.WS5

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A number of points were stressed in the development of the methodology sequence.
The first of these points was the need to define the applicable abatement alternatives
very early in the program.  This process ensure that the purpose of the study is not lost
and all data gathering activities be conducted according to the required analyses.

Another important step was the calibration and verification of all models that were used
for CSO analysis in the study area. The models selected for application were based on
the urban area and collection system requirements as well as the objectives defined in
the initial phase of the program. The Simplified Stormwater Model was used in the
Initial screening of alternatives. The final analysis was conducted on a selected number
of abatement alternatives with the use of SWMM Version II.  In conducting the network
model activity, it became apparent that one should not use models which are more
complex than the analysis requires.  One should be certain to utilize the simplest model
which will attain  the defined objectives.  It is for this reason  that the Simplified
Stormwater  Model or an equivalent planning tool was recommended in the initial
screening of alternatives, while the use of SWMM Version II was recommended in the
final analysis of a select number of abatement alternatives.

The following major tasks are considered to be most important in the methodology
necessary to develop a combined sewer overflow master plan: definition of program
objectives, definition of existing conveyance  and treatment systems, definition  of
drainage areas and their characteristics, review of the meteorological data base,
selection of detailed network model to be utilized in the hydraulic analysis of the
existing system  and the proposed alternatives, initiation of the overflow and
meteorological monitoring  program necessary to  augment the  existing data base,
establishing  relevant abatement  alternatives,  use of a simplified Stormwater model  to
evaluate the  existing  system  -  long-term simulation,  initial  evaluation   of
storage/treatment - capital intensive alternatives using the simplified Stormwater model,
calibration and verification of the detailed network model, application of the detailed
network model to the preliminary evaluation of non-structural alternatives, selection and
verification of wet weather quality predictive models, evaluations of applicable treatment
processes, detailed analysis of the prime  alternatives, development of the  CSO
abatement Master Plan.

In light  of the very significant capital and operating costs associated with the
implementation of capital intensive storage/treatment  alternatives, a more exacting
system  analysis is necessary to evaluate the  application of less capital intensive
measures which may be particularly effective  in optimizing the  performance of the
existing  system.  The methodology and tools of analysis are presently available which
allow the development of a comprehensive and cost-effective combined sewer overflow
abatement program.
896CMS6.WS5

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        PREVENTION AND CORRECTION OF EXCESSIVE INFILTRATION
                     AND INFLOW INTO SEWER SYSTEMS

                           MANUAL OF PRACTICE

                                   by the

                  AMERICAN PUBLIC WORKS ASSOCIATION

                                January 1971
As a result of a national study of the sources and prevention of infiltration and inflow, a
Manual of Practice was proposed. The Manual is intended to serve as a guide to local
officials in evaluating their construction practices, conducting surveys to determine the
extent and location of infiltration and inflow, the making of economic analyses of the
cost of excessive infiltration/inflow waters, and instituting corrective action.

"Infiltration" covers the volume of groundwater entering sewers and building sewer
connection from the soil, through defective joints, broken or cracked pipe, improper
connections, manhole wails, etc.

"Inflow" covers the volume of any kinds of water discharged into sewer tines from such
sources as roof leaders; cellar and yard area drains; foundation drains; commercial and
industrial  so-called "clean water"  discharges;  drains from springs and swampy areas;
etc. It does not include, and is distinguished from, "infiltration".

"Infiltration/Inflow" is the volume of both infiltration water and inflow water found  in
existing sewer systems, where the indistinguishability of the two components  of
extraneous waters makes it possible to ascertain the amounts of both or either.

Infiltration and inflow conditions have two characteristics in common, in that each
problem  is  divided into two parts:  prevention of excessive extraneous flows, and
correction of conditions already imposed on existing sewer systems.

In the case of infiltration, prevention of excessive entries into new sewer systems
depends on effective design; choice of effective materials of sewer construction;
imposition  of rigid  specifications  limiting  infiltration allowances; and alert  and
unremitting inspection and testing of construction projects to assure tightness  of
sewers and minimization of infiltration waters.
896CMS2.WS5

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Correction of infiltration conditions in existing sewer systems involves evaluation and
interpretation of sewage flow conditions to determine the presence and extent of
excessive extraneous water flows from sewer system sources, the location and gauging
of such infiltration flows, and the elimination of these flows by various corrective, repair
and replacement methods.

Prevention of excessive inflow volumes is a matter of regulating sewer uses and
enforcement of such precepts  and codes by means of vigilant surveys and surveillance
methods. Correction of  existing inflow conditions involves location of points of inflow
connections;  determination  of their legitimacy or illicit nature; evaluation of the
responsibility for correction of  such conditions; establishment of inflow control policies
where none have been in effect; institution of corrective policies and measures, backed
up by investigative and enforcement procedures to make such policies potent.

The initial area of concern in reducing or eliminating infiltration involves the production
of a pipe system and appurtenances which are water-tight and do not permit ground-
water leakage. The realization of this objective begins during design. A number of
preliminary activities are  necessary to provide vital background information before any
design decisions are made. Soil and  groundwater conditions must  be considered if the
design for a proposed sewer system is to avoid  infiltration. The four methods of
obtaining the necessry design information include: reconnaissance (the gathering of
available information on  soils  and groundwater conditions), subsurface investigations,
lab testing, and in-situ testing.

Also, the above concern is important to improvements in pipe material which ensure
that the designer can provide proper materials to meet rigid infiltration allowances.

The most critical factor relative to  the prevention of infiltration in new sewers is
construction.  All of the currently manufactured pipes and joints are capable of being
assembled into sewer systems with minimal infiltration. This capability must be
coupled with good workmanship and adequate inspection.

The correction of infiltration involves a lengthy, systematic approach. The first step is to
identify the system by obtaining  maps of the sewer system. The maps should be
analyzed to develop a series of small drainage areas.  Next, identify the scope of
infiltration by obtaining actual  dry-weather and wet-weather flow measurements at key
manholes.  If the infiltration/inflow problem has been  identified as  rain-connected and
the system is supposedly separate, a rainfall simulation in the storm sewers can help
pinpoint the source. It is  also very important that a physical survey of the sewer system
be taken to check  for the effects of poor soil conditions and groundwater conditions.
Next, a planned sewer cleaning program should  be established.  Clean sewers are  a
necessary prerequisite for any  television inspection program and also for any correction
sealing procedures.  As a result of the findings  of the previous stages, the best
utilization of television or photographic inspection can now be determined. Based on
the results and recommendations of the inspection report, sound budgeting and
planning for the restoration of the system can now be achieved.
896CMS2.WS5

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Control of inflow, like control of infiltration, resolves itself into two practices:  prevention
of new inflows, and correction  of existing inflows.  Prevention involves exclusion of
inflow connections by edict, and the rejection of any such flows when new structures
are built, or when existing building operations are modified.  Correction involves the
location of existing sources and their elimination by physical separation of any such
connections in accordance with set policies of the jurisdictions.

Guidelines have been given for the control of infiltration and inflow conditions.  Each
jurisdiction must determine its own policies and practices, using these indicators as to
what can be accomplished by new criteria and actions.
896CMS2.WS5

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            RELATIONSHIP BETWEEN DIAMETER AND HEIGHT
              FOR THE DESIGN OF A SWIRL CONCENTRATOR
              AS A COMBINED SEWER OVERFLOW REGULATOR

                  RICHARD H. SULLIVAN, MORRIS M. COHN
                    JAMES E. URE, FRED E. PARKINSON
                            GEORGE GALIAMA

                 AMERICAN PUBLIC WORKS ASSOCIATION

                               July 1974

                           EPA 670/2-74-039
This report is a supplement to the report entitled "The Swirl Concentrator as a
Combined Sewer Overflow Regulator Facility" which was published in September of
1972. The 1972 studies demonstrated that the swirl device was capable of removing
floatable and suspended solids from  sanitary  sewage and stormwater.   They
established a suitable relationship between chamber depth and diameter and their
effect on solids removal efficiencies. The purpose of this supplemental report was to
investigate the depth to width ratio established by the 1972 report and to define  the
dimensions which would provide optimum construction economy and operating
efficiency in terms of solids.

The studies for this report were conducted on a hydraulic model of the swirl
concentrator at the LaSaile Hydraulics Laboratory in  Montreal.  The concentrator
configuration was similar to that which was used in the 1972 study.  The model
diameter remained constant  at 36 inches  with a 20-inch diameter clear liquid overflow
weir and a 24-inch diameter scum ring.

The variable factors chosen to provide the chamber depth-to-width relationships were
weir height and the inlet pipe diameter.  The study covered five rates of discharge,
including the probable ranges that would be imposed on a full-scale unit. These
fiowrates on a 1:12 scale of laboratory model to prototype, were: 50; 100; 150; 200; and
300 cfs. Four inlet pipe diameters were studied:  3; 4; 5;  and 6 foot. The inlet
wastewater line was set at a slope of 1:1,000 to provide tangential flow of incoming
liquid in the swirl concentrator chamber.

At least three weir heights, or chamber depths, were tested for each inlet pipe diameter.
The range selected for the hydraulic study was: 6; 7; 9;, 11; and 13 feet.
896RBS3.WS5

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The incoming wastewater was composed of water supplied from a constant level tank
in the laboratory, and synthetic solids of proper composition injected into the inflow
stream by a vibrating feed unit.

The clear water outlet from the swirl concentrator was through a 6-inch diameter pipe
which was installed upward through the bottom of the model centerline. The height
could be varied at will by adding or removing segments to or from the top of the pipe.
The foul outlet consisted of a 2-inch diameter flexible tube, leading to a solids settling
tower fitted with an adjustable level outlet pipe which could  be raised or lowered to
regulate the rate of discharge of the solids flow.

The grit increment of the synthetic solids injected into the stream flow to the swirl was
assumed to have a specific gravity of 2.65 and a straight line grain size distribution was
selected as a representative average of samples taken from existing combined sewer
systems - from No. 70 to No. 10 sieve sizes. The concentration range was 20 to 360
mg/l.

The organic material contained in the flow to the swirl concentrator, was defined as
having a specific gravity of 1.2 and a grain size distribution from less than 0.1 to 5 mm.

The floatable increment injected in the flow had  a specific gravity of 0.9 to 0.998 and a
size range from 5 to 25 mm.  The concentration range was 10 to 80 mg/l.

The hydraulic model could not duplicate the variations in inflow rates and in combined
wastewater solids concentration, which normally occurs in sewer system operations.

The pilot study which evaluated solids recovery  for four sizes of inlet pipes and various
weir heights produced the following conclusions:

          Design parameters can be definitively established, covering swirl
          concentrator  chamber  diameter,  inlet pipe  dimensions, and internal
          chamber  facilities, to provide  specific solids removal efficiencies for
          prototype combined sewer overflow systems.

          For chambers having a ratio of chamber diameter to chamber depth of 4 : 1
          it was found that the depth had little effect on recovery rate.  The same
          condition was found when the ratio of chamber diameter to inlet dimension
          was in the range of 6 : 1 or 7.2 :  1.  When the ratio of chamber diameter to
          inlet dimension was increased to 9 :  1 or 12 : 1, the depth or weir height had
          more influence on recovery rates.
896RBS3.WS5

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           For any given discharge the use of a smaller ratio of chamber diameter to
           inlet dimension  results in lower inlet velocity and lower chamber area and
           volume. Hence for economy reasons, the designer should attempt to
           reduce this ratio as close to six as is possible with the use of the design
           curves given in this report.

           Where circumstances are not favorable for the standard design with a ratio
           of chamber diameter to depth of 4 : 1,  it is possible to decrease the
           chamber depth to a value equal to the inlet dimension.  This also results in
           an  increase in the chamber diameter and chamber area.  The chamber
           volume may also be somewhat affected either up or down by this change.

 The report recommended  that the swirl concentrator  principle be utilized  more
 extensively for the removal of solids pollutants of both inorganic and organic nature
 which are contained in combined sewer overflow wastes.
896RBS3.WS5

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           REMOTE CONTROL OF COMBINED SEWER OVERFLOWS

               JAMES J. ANDERSON AND ROBERT L GALLERY

        JOURNAL OF THE WATER POLLUTION CONTROL FEDERATION

                              November 1974

                         Vol 46, No. 11 pp. 2555-2564
The Minneapolis - St. Paul combined sewer system was modified with the installation of
a computer-assisted, real-time monitoring and remote control to reduce number and
volume of combined sewer overflows.  The combined sewers service area, some of
which has been partially separated, is approximately 30 sq. miles (77.7 sq. km.). Initial
sewer gauging had indicated that the 30 mile interceptor system conveyance capacity
was  not fully utilized during wet weather events. This was because of inflexible
regulator devices, and non-uniform distribution of rainfall over the service area.

The control system was designed to provide variable flow control to the interceptor
system, based on current conditions in the sewer system.  Rain gauges, level sensors,
and gate and dam sensing devices transmit information to a central control system
over leased telephone wires.  The amount of flow diverted to the interceptor is
controlled by inflatable fabric dams and hydraulicaily operated gates.

Gates and dams may be controlled remotely by an internal program, or manually by an
operator at a console.  The position or pressure of each dam and gate is addressed,
and brought back to the proper value if the position or pressure has changed.  This
control system has a mathematical model to assist the operator in anticipating sewer
flow  conditions, based on rainfall location and intensity,  and to test a change in
operation before initiating it. The control system cannot operate independently,
because it does not have a feedback routine in the model. The operational strategy is
to maximize downstream interceptor capacity, while preventing surcharging of trunk
sewers. Costs for the system in 1969 included $500,000 for regulator modifications;
$185,000 for the underground control vaults, polemount cabinets, telephone and the
level gauging system; and $370,000 for the central computer, level transducers,
telemetry, and supervisory contact equipments.

During 1969 and 1970, overflow events were reduced by 58 and 52 percent
respectively.  Duration was reduced by 88 and 84 percent. Snowmelt overflow events
were virtually eliminated.
896BJK5.WS5

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       RETENTION BASIN CONTROL OF COMBINED SEWER OVERFLOWS

                                     by

                      SPRINGFIELD SANITARY DISTRICT
                           SPRINGFIELD, ILLINOIS

                                   for the

                   ENVIRONMENTAL PROTECTION AGENCY
                          WATER QUALITY OFFICE

                                 August 1970
Storm overflow from combined sewers discharged through the Cook Street Pumping
Station of the Springfield Sanitary District into Sugar Creek has resulted in repeated fish
kills during previous years. A study was undertaken to evaluate the ability of a retention
basin to prevent such deterioration of water quality.  Anticipated possible effects of the
basin include attenuation of peak flows, sedimentation, and biological degradation. An
anticipated adverse effect of the retention basin was the discharge of algae synthesized
in the basin.  Performance of the lagoon during the 20-month period of observation
indicated that it was successful in  preventing severe  deterioration of downstream water
quality due to combined sewer overflows.

Performance of the lagoon was monitored by daily collection of composite samples
from the  lagoon influent and effluent and by grab sampling of stations in Sugar Creek
above and below the point of lagoon discharge. Interpretation of the capabilities and
limitations of the facility was limited by the lack of capability for measuring influent flow
rate and  the lack of influent and effluent samples collected at various periods during
storms.  Hence, it was not possible to conduct mass balance computations on the
basin to determine its overall effectiveness. Best evidence of the efficiency of the facility
was afforded by observation of the fact that incidence of  fish kills was limited following
installation of the retention basin.

While the movement of individual storm flows through the  lagoon could not be traced, it
was observed that the average annual reduction of BOD was 27  percent and total
coliform reduction averaged 72 percent. However, during the period from June through
October 1969, production of algae in the basin caused  the effluent BOD to consistently
exceed that of the influent.  This observation was  substantiated by the  increase in
suspended solids in the effluent during these periods, increased effluent pH and
supersaturation of dissolved oxygen during periods of high radiant energy.  It would
appear that the suitability of retention basins of the type used  at Springfield should be
considered on an individual basis because of the possibility of adverse water quality
conditions being created as a result of the release of high concentrations of algae
during parts of the year.
896CMS1.WS5

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Considerable reductions in the concentration of indicator organisms occurred in the
retention basin, averaging 72 percent. However, influent total coliform density was high
(averaging  1,250,000/100 ml) and thus the effluent coliform density was significant
(353,000/100 mi).

While the analysis of the performance of the basin is limited on a quantitative basis, it
was shown to be an adequate solution  for the existing problem at Springfield, Illinois.
Only one fish kill occurred during the  period of study, and it happened during  a period
when the basin was drained for repair.

It was not  possible to quantitatively  determine the relative effect of the various
mechanisms which could account for the basin's performance.  Sedimentation can
reasonably be  accredited with some water quality  improvement since sludge
accumulated in the basin.  However, the contribution of bacteria and algae synthesized
in the  basin to this sediment is not known. Similarly, the amount of biological
degradation of soluble and colloidal  organic material has not been established. It is
postulated that an appreciable amount of the observed improvement could  be
attributed to retention  of storm flow with slow  release at diminished rates to the
receiving stream.

The analysis of basin performance could not provide a rational basis for determining
the desirable size of storm water retention facilities at other installations. This is
because the available instrumentation did not afford a measure of influent flow  rate and
because a portion of high storm water overflows were bypassed and did not enter the
retention facility. On the basis of an  increase in biochemical oxygen demand during
summer months,  it was anticipated  that difficulty might be experienced at certain
installations because of deterioration of downstream  water quality or because of
aesthetic objection to the high algae  densities. Sizing retention facilities clearly
depends upon the water quality objective involved.  For example, where appreciable
reductions in the density of indicator  organisms  is  necessary, retention  times
approximating those  provided at Springfield would  not be sufficient.  An additional
consideration in determining basin volume is the requirement for storage of solids
retained in the basin.
896CMS1 .WS5
896CMS1.WS5

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                       SEWER FLOW MEASUREMENT
                    A STATE-OF-THE-ART ASSESSMENT

                                    by

                            PHILIP E. SHELLEY
                         GEORGE A. KIRKPATRICK

         EG & G WASHINGTON ANALYTICAL SERVICES CENTER, INC.
                       ROCKVILLE, MARYLAND 20850

                              November*! 975
In order to characterize stormwater and combined sewer overflows and to facilitate the
development, demonstration, and evaluation of treatment and control systems for
combating the problem, it is necessary to have accurate and reliable determinations of
the quantity and quality of the flows. Both the quantity and quality of urban stormwater
runoff are highly variable and transient in nature, because of meteorological and
climatological  factors, topography, hydraulic characteristics of the  surface and
subsurface conduits, and  land use activities.  Conventional flow measurement devices
and techniques have been developed mainly for the relatively steady-state flows as
found in irrigation canals, sanitary sewers, and large streams  rather than the highly
varying surges encountered in storm and combined sewers.

Measurements of quantity of flow, usually in conjunction with sampling for flow quality,
are essential to nearly all aspects of water pollution control.  Research, planning,
design, operation and maintenance, and enforcement of pertinent laws are activities
which rely on flow measurement to be effective. For some activities, very precise, time
synchronized, continuous flow records are needed.  With others, occasional, fairly
rough estimates of flow may suffice.

The various flow measuring devices and techniques are summarized in Table 1. These
evaluations were made with a storm or combined sewer application in mind and will not
necessarily be applicable for other types of flows.

A second table offers a comparison of some of the primary devices or techniques that
are  used to measure  storm  and combined sewer discharges.  Each method is
numerically evaluated in terms of its percent of achievement of several desirable
characteristics.  Dilution techniques as a class promise accuracy in  a number of
applications. They are probably most  useful as a tool for in-place calibration of other
primary devices.  They have also been extremely useful for general survey purposes
and have found some application when added to other primary devices during periods
of extreme flow such as pressurized flow in a conduit that is normally open channel.
896CMS10.WS5

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Acoustic open channel devices are dependent on the velocity profile a resultant
requirement for several sets of transducers. They are presently justifiable for very large
flows because of the expense involved.

The Parshall flume is a commonly used flow measurement device. The requirement for
a drop in the flow is a disadvantage, and submerged operation may present problems
at some sites.  Known uncertainties in the head-discharge relations (possibly up to 5
percent), together  with possible geometric deviations, make calibration in place a
requirement for high accuracy.  Palmer-Bowlus type flumes are very popular overall.
They can be used as portable as well as fixed devices in many instances, are relatively
inexpensive, and can handle solids in the flow without great difficulty.

All point velocity measuring devices were included in the current meter category. In the
hands of an experienced operator, good results can be obtained.  They are often used
to calibrate primary devices in place or for general survey work. They are generally not
suited for unattended operation in storm and combined sewer flows, however.

Electromagnetic  flowmeters  show considerable promise where pressurized flow is
assured as do closed pipe acoustic devices. Neither can be considered portable if one
requires that the acoustic sensors be wetted, a recommended  practice for most
wastewater applications.

Open flow nozzles  and sharp-crested weirs are often used where  the required head
drop is available. Weirs will require frequent cleaning and are best used as temporary
installations for calibration purposes.  Flow tubes  and venturies are only suitable  for
pressurized flow sites such as might be encountered, for example, at the entrance to a
treatment plant.

Trajectory coordinate techniques, such as the California pipe or Purdue methods,
require a pipe  discharging freely into the atmosphere with sufficient drop to allow a
reasonably accurate vertical measurement to be made, a situation not often
encountered in storm or combined sewers. Slope area methods, as explained earlier,
must generally be considered as producing estimates only and, consequently, should
be considered as the choice of last resort.
896CMS10.WS5

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        STORAGE AND TREATMENT OF COMBINED SEWER OVERFLOW

                 WILBUR R. LEIBENOW, BEIGING, JAMES, K.,

                  ENVIRONMENTAL PROTECTION AGENCY
                  OFFICE OF RESEARCH AND MONTIRONIG

                               October 1972
                                122 pages.

                              EPA-R2-72-070
The objective of this  study was to demonstrate the feasibility and economic
effectiveness of a combined wastewater overflow detention basin.  Wastewater in
excess of existing transportation/treatment system capacities overflows to a detention
basin during wet weather, and is later treated during periods of low flow.

A paved asphalt detention basin with a storage volume of 8.66 acre feet was
constructed at Chippewa Falls, Wisconsin to receive overflow from a 90 acre combined
sewer area including all of the central business district. The system was designed so
that the stored combined sewage could be pumped to the wastewater treatment plant
when precipitation subsided.

Project construction began in October of 1967 and was completed in March of 1969.
Total capital cost for the demonstration project was approximately $610,000.  This cost
can be subdivided into the following components:
      Detention Pond Construction
      Pumping Station, Pond Structures, Piping
      Combined Relief Sewer and Separate Sewer
      Electrical Work
      Treatment Plant Revisions
      Land
$  60,000
 158,000
 223,000
   21,000
 117,000
    2,000
                                             Total
$610,000
896RHG3.WS5

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This study was conducted over the two-year time frame of 1969 and 1970.  Results
indicated several positive effects from installation of this basin. During 1969, due to dry
weather, the pond received flow during only 16 events, but completely filled twice and
overflow to the river occurred.  During 1970, there were 46 discharges to the pond with
only one overflow to the river. Over the study period, 37.75 million gallons of combined
sewage (93.7 percent of the total discharge  volume) were withheld from the river for
subsequent treatment.  This included 49,520 pounds of BOD5 and 90,390 pounds of
suspended solids which were withheld  from  the river and  were subsequently treated.
These loads represented 98.2 percent of the total BOD5 and 95.8 percent of the total
suspended solids which  were contained in the overflows  from the existing
transport/treatment system.

There were no observed detrimental effects  on treatment plant operation due to the
increased intermittent flows from the detention pond. Although the basin is  located in
close proximity to the business district, no complaints were received regarding any
phase of the pond operation. The overflow basin stored combined sewage for periods
up to 14 hours without odors developing.  Substantial relief from basement flooding in
the downtown area was also observed as a result of the basin.

The estimated average operating and maintenance cost attributed to the storage basin
system was $7,300 per year over the two year period.  The largest portion of this annual
cost (75 percent) was attributed to additional treatment plant operations while pumping
and pond cleaning accounted for the remaining portions (7.5 percent and 17.5 percent
respectively).
896RHG3.WS5

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      A STRATEGY FOR INTEGRATING STORAGE TREATMENT OPTIONS
                      WITH MANAGEMENT PRACTICES

                     JAMES P. HEANY, STEPHEN J. NIX

               USEPA - TECHNOLOGY TRANSFER SEMINAR ON
  COMBINED SEWER OVERFLOW ASSESSMENT AND CONTROL PROCEDURES
                     WINDSOR LOCKS, CONNECTICUT

                       May 18 and 19,1978
A methodology was presented to provide planners with a tool to develop preliminary
cost estimates and strategies for wet-weather poflution control facilities.  The primary
emphasis was placed on procedures to integrate storage/treatment options with other
management practices.

Previous assessments published by the authors indicated that nationwide capital costs
for wet-weather pollution control ranged from $2.5 billion at 25 percent BOD control to
$41.9 billion at 85 percent BOD control. The plotted curve of function of percent BOD
removal is an exponential type curve.  Graphical solutions were used by the authors to
evaluate a wide range of wet-weather control options.

Wet-weather pollution control costs were estimated based on production theory and
marginal  cost analysis from economics.  A seven-step graphical procedure was
developed to produce this estimate.  Production functions were established for street
sweeping, combined sewer flushing, and storage treatment.  A unit cost  of $7.00 per
curb mile was  established for street sweeping and $11.78 per foot of sewer was
established as a unit cost for sewer flushing.  Unit costs for storage treatment were
taken from existing EPA publications.

The methodology was applied to a hypothetical city  of 1,000,000 people. Pollutant
loads were  estimated, and a control  network consisting of  street sweeping, sewer
flushing and storage/treatment was analyzed.  The results demonstrated that other
management practices used in conjunction with storage/treatment can  give a savings
of 5 to 45  percent over storage/treatment alone.

The results of the paper represent simplified estimates  of system savings and  pollution
control, however they do suggest that management practices should be considered as
part of a stormwater pollution control package.  The  methodology was stated to be
capable of estimating the costs  and cost savings of pollution control management
practices.
896RHG4.WS5

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                   STREAM POLLUTION AND ABATEMENT
                   FROM COMBINED SEWER OVERFLOWS

                              BUCYRUS, OHIO

                FEDERAL WATER QUALITY ADMINISTRATION
                      DEPARTMENT OF THE INTERIOR

                                    by

                       BURGESS AND NIPLE, LIMITED

                              November 1969
This report presents the findings of a study conducted to evaluate the pollutional effects
from combined sewer overflows on the Sandusky River at Bucyrus, Ohio.  It also
presents the benefits, economics,  and feasibility of abating pollution from combined
sewer overflows. The study compares physical sewer separation to alternate methods
of reducing or eliminating the pollution resulting from combined sewer overflows. This
study focuses on determining if there are methods of abating pollution from combined
sewer overflows which would accomplish the task better than physical separation and
at a lesser cost.

One of the primary objectives of the study was to determine the relationship  of rainfall
events to overflow events and the volume of flow in the Sandusky River.  Historical
records of rainfall and flow in the Sandusky River were evaluated along with data
collected during the  one-year study period.  Weirs for measuring overflow volumes
were installed at three locations.  Samples were also collected at these locations to
determine overflow characteristics and effects on the stream. From this information a
two-year, one-hour design storm was selected for use in sizing intercepting devices and
treatment facilities.

The city of Bucyrus is located near the upper end of the Sandusky River Basin which is
tributary to Lake Erie.  Bucyrus has an incorporated area of about 2,340 acres, a
population of 13,000, and a combined sewer system  with an average dry weather
wastewater flow of 2.2 million gallons per day.
896RBS6.WS5

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The results of the study show that any 20 minute rainfall greater than 0.05 inches will
produce an overflow. The combined sewers will overflow about 73 times each year
discharging an estimated annual volume of 350 million gallons containing 350,000
pounds of BOD and 1,400,000 pounds of suspended solids.  The combined sewer
overflows had an average BOD of 120 mg/l,  suspended solids of 470 mg/l, total
conforms of 11,000,000 per 100 ml and fecal conforms of 1,600,000 per 100 ml. The
BOD concentration of the Sandusky River, immediately downstream from Bucyrus,
varied from an average 6 mg/l during dry weather to a high of 51 mg/l during overflow
discharges. The total conforms varied from an  average of 400,000 per 100 ml during
dry weather to a high of 8,800,000 per 100 ml during overflow discharges.

Six methods of controlling the pollution from combined sewer  overflows were evaluated
for degree of protection, advantages, disadvantages and estimated costs. The
methods evaluated are presented below with their associated costs.

       Complete Separation of Sanitary Wastewater and Stormwater
       - New Sanitary Sewer System                               $9,300,000
       - New Storm Sewer System                                 $8,800,000

       Interceptor Sewer and Lagoon System
       - Interceptor, Pump Station and Aerated Lagoon               $5,220,000
       - Holding Tanks, Interceptor, Pump Station                    $5,860,000
        and Aerated Lagoon

       Stream Flow Augmentation                                  $5,000,000

       Primary Treatment of Overflows                              $8,810,000

       Chlorination of Overflows                                    $3,000,000

       Off-Stream Treatment                                       $1,700,000

Sewer separation was the most costly alternative to controlling combined sewer
overflows and would only reduce the pollutants discharged to the river by 50 percent.
In this report  it was shown that the stormwater runoff from urban areas contains a
significant amount of contaminants  harmful to stream water quality. The degree of
pollution from stormwater varies from that of very dilute sewage to strong sewage.

Construction and operation of the Interceptor and Lagoon System or Off-Stream
Treatment would be the most economicaf method of reduction or controlling pollution
from overflows.
896RBS6.WS5

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The interceptor and lagoon system would be designed to protect the stream from all
overflows from storms less than the two-year, one-hour storm. The lagoon could also
provide tertiary treatment for effluent from the existing wastewater treatment plant. The
Off-Stream Treatment Alternative involves construction of a pump station to divert the
flow in the Sandusky River to lagoons for treatment during combined sewer overflows.
This alternative would only provide downstream water quality protection and would not
change the water quality in the river reach within the city.

Stream flow augmentation is a method of controlling pollution from overflows by
providing sufficient dilution water from storage impoundments to maintain a desired
concentration of dissolved oxygen downstream during overflows.  This is not feasible at
Bucyrus due to the lack of suitable reservoir sites.

Primary treatment of overflows is very costly and it would only reduce the waste loads
discharged to the river by 50 to 70 percent.

Chlorination of overflows would reduce the bacteria count discharged to the river but
would not significantly reduce the concentration of any of the other pollutants present in
the combined sewer flows.

The study recommended two phases of construction.  The first phase would involve
construction of Off-Stream Treatment to include construction of a pump station, a low
head dam, and  a lagoon system.  When it has been adequately demonstrated that the
lagoon treatment is capable of  providing the water quality protection required, the
second phase would be constructed. The second phase would involve construction of
the interceptor. The first phase would provide downstream water quality protection.
The second phase would provide water quality protection for entire stream reach within
Bucyrus and downstream.

This alternative is less costly than complete  sewer separation and it provides treatment
for storm runoff as well as sanitary flow.  Sewer Separation would result in all urban
storm runoff being directly discharged to the river.
896RBS6.WS5

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                SURFACE AND SUB-SURFACE DETENTION IN
                        DEVELOPED URBAN AREAS:
                              A CASE STUDY

                                    by

                         STUART G. WALESH, P.E.
                                   and
                       MARK L. SCHOEFFMANN, P.E.

                PRESENTED AT THE AMERICAN SOCIETY OF
                      CIVIL ENGINEERS CONFERENCE
                           "URBAN WATER-84"

                          BALTIMORE, MARYLAND

                              May 28-31,1984
Stormwater detention facilities are technically sound, economically attractive, and
environmentally acceptable elements in urban stormwater control systems serving
newly developing areas.  A potential, fundamentally different approach is retrofitting
detention into an existing stormwater system.  A carefully engineered runoff control
system (RCS)  including on-street storage and subsurface tank storage may be
implemented to control the stormwater flow into a combined sewer  system to mitigate
basement flooding and control stormwater runoff to mitigate surface flooding.

Presented in this article is the process leading to and the status of an ongoing project
incorporating surface and subsurface detention to prevent sewer surcharging and
basement flooding in a completely urbanized 1,200-acre combined sewer service area
in Skokie, Illinois. The Village of Skokie, Illinois, a northern suburb of Chicago, is within
the service area of the Metropolitan Sanitary District of Greater Chicago (MSDGC). The
1200-acre Howard Street Sewer District (HSSD) is on the south side of the Village.

The fully developed  district contains approximately 80 percent residential land use, 15
percent industrial and 5  percent commercial.  The gross population density is
approximately 15 people per acre. Average annual precipitation is about 34 inches and
all seasons are  marked by occasional intense storms.  Runoff from these storms,
particularly in the spring and summer, cause severe surcharging and basement
flooding.  For 1 hour, 1-, 10-, and 100-year recurrence interval rainfall events, rainfall
amounts are 1.19, 1.94, and 2.80 inches respectively. For a 24-hour period, the 1-, 10,
and 100-year amounts are 2.21, 3.86, and 6.70 inches respectively.
896CMS11.WS5

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The HSSD slopes generally eastward along Howard Street, the main east-west artery,
towards the North Shore Channel. Slopes vary from 0.1 to 1 percent and the overall
slope of the district is 0.2 percent.

Surface drainage moves from front lawns,  driveways, and  alleys to the streets.
Stormwater moves in gutters along the curb lines to the nearest inlets which are located
at mid-block points and immediately outside of intersections.

Stormwater and sewage from the HSSD are conveyed to an interceptor owned and
maintained by the MSDGC. Interception takes place at the east end of the HSSD near
the North Shore Channel.  The MSDGC has completed Phase I  of the Tunnel and
Reservoir Plan (TARP) which was scheduled to go  into operation in early 1985.  TARP
was to increase the interceptor capacity and reduce  overflows into the North Shore
Channel. Although TARP will improve the outlet conditions for runoff events from the
HSSD, it will not change flow capacities or conditions in most of the HSSD.

The MSDGC obtained funding for TARP form the USEPA and it appeared Skokie may
be eligible for similar funding to be used for a conveyance system within the Village.
The estimated cost for the conveyance system was $78,000,000 for the entire Village.

By 1981, it was  evident that EPA funds for this plan would not be available. Another
study was undertaken and it concluded with the idea of a system which  would
incorporate runoff control with surface and subsurface storage within the developed
area.

The following design criteria were established at the beginning of the engineering
process or evolved during the course of the process.

       Use the 10-year recurrence interval storm.

       Make maximum utilization  of existing sewer system but reduce  sewer
       surcharging to prevent  sewage backup caused by overloading of the sewer
       system.

       Make maximum utilization of available street storage capacity without causing
       flood damage to adjacent property.

       Minimize flooding on state and county highways.

       Assume TARP is completed and the HSSD discharges into it.

       Utilize a gravity-operated system, in preference to a pumped system, and make
       minimal use of electrical  and mechanical controls and equipment.
896CMS11.WS5

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Watershed  modeling and analysis was used to  diagnose the hydrologic-hydraulic
behavior of  the HSSD. A three-phased approach was used in the watershed modeling
and analysis.

Phase I  was a static condition analysis which determined if flood levels on the North
Shore Channel would cause basement flooding solely as a result of backwater. The
analysis was conducted to determine if there were  portions of the HSSD in which flood
control could not be achieved by in-HSSD runoff control. The analysis concluded that
there were  no significant areas in which basement flooding would result solely from
backwater of the North Shore Channel.

The intent of Phase II. Sewer Capacity Analysis, was to determine the maximum rate in
which stormwater runoff could be released into the combined sewer system without
exceeding the established surcharge level  The sewer capacity analysis  was carried
out using the computer program System Analysis  Model (SAM), which permitted
simulation of the entire HSSD and provided the computational means of accounting for
system surcharges and hydraulic grade lines for each trunk and branch sewer.

Street Ponding Analysis, Phase III, determined the street ponding which  would occur as
a result of regulating the rate at which stormwater runoff could enter the combined
sewer system.  Overall, the street ponding analysis indicated that keeping  water out of
basements  via surface and subsurface  ponding was feasible but the number of streets
subject to ponding would increase.

The recommended Runoff Control System consists  of:

      425 flow regulators functioning in conjunction with 215 berms.

      12 subsurface storage facilities.

      9,500 feet of 30-inch to 72-inch separate relief sewer for the commercial,
      downstream end of the HSSD.

The system would perform such that the average maximum depth of street ponding is
approximately 0.7 feet measured from the gutter at  the lowest point in the block and the
average ponding duration is 5 hours under the  design 10-year storm condition. The
estimated late 1983 cost for the recommended runoff control system was  $8.1 million
or about 20  percent of the cost of a conventional runoff control system.

The recommended runoff control system was tailored to the unique combination of
topographic, land use, hydrologic and hydraulic  characteristics of the combined sewer
service area in Skokie.  However, the analytic  techniques used, particularly the
hydrologic-hydraulic computer  models,  and the surface and subsurface facilities and
hardware employed are likely to be applicable  to other fully developed urban areas
experiencing sewer surcharging and other flooding  problems.
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                       THE SWIRL CONCENTRATOR AS
                      A COMBINED SEWER OVERFLOW
                           REGULATOR FACILITY

                               RICHARD FIELD

                               September 1972

                               EPA-R2-72-008
In 1969-70 The American Public Works Association  (APWA) Research Foundation
carried out a national investigation of the means by which municipal jurisdictions in the
U.S. and Canada regulate and control overflows from combined sewer systems, and of
methods by which the pollutional effects of these discharges into receiving waters can
be minimized.

The major finding of the study was that in American practice, little or no effort was made
to improve the quality of the overflow liquids and, thereby, to reduce the pollutional
impact on receiving waters.  Regulators were only capable of controlling the quantity of
overflows; and even  this function had been carried out with only limited success.  The
investigation also disclosed  that European practices emphasized  improvement of the
quality of  storm overflows from  combined sewers by various mechanical-hydraulic
means. One of the methods of quality control  being used in Bristol, England, was the
so-called "vortex" device. The APWA study recommended that  further research be
conducted on new devices which could induce separation of solids from the liquid.

This led to the study  of the swirl concentrator which is a modified version of the "vortex"
device. This study found that a vortex flow pattern should be avoided when working
with larger flows in minimum-sized chambers.  However, it showed  that inducing a swirl
action in the wastewater was  very effective in causing a liquid-solids  separation.

The American Public Works Association, under contract with the City of Lancaster, PA,
completed this study with the intent that Lancaster would construct a demonstration or
prototype swirl concentrator.  The study included hydraulic modeling studies
conducted at the  LaSalle Hydraulic Laboratory in Canada; and mathematical modeling
to determine design relationships and the degree  of efficiency which  might be
associated with construction of such facilities. The objectives of the study were to
determine swirl concentration configurations, flow patterns, and settleable solids
removal efficiency.
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The device, as developed by the study, consists of a circular channel in which rotary
motion of the sewage is induced by the kinetic energy of the sewage entering the
chamber. Settleable solids underflow discharges through an orifice called the foul
sewer outlet, located at the bottom and near the center of the chamber.  Clarified liquid
discharges over a circular weir around the center of the tank and is conveyed to storage
treatment devices as required or to receiving waters. The concept is that the rotary
motion causes the sewage to follow a long spiral path through the circular-chamber. A
free surface vortex was eliminated by using a flow deflector, preventing flow completing
its first revolution in the chamber from merging with inlet flow.  Some rotational
movement remains, but in the form of a gentle swirl, so that water entering the chamber
from the inlet pipe is slowed down and diffused with very little turbulence. The particles
entering the  basin spread over the full cross section of the channel  and settle rapidly.
Solids are entrained along the bottom, around the chamber, and are concentrated at
the foul sewer outlet.

The following conclusions were drawn from the hydraulic and mathematical modeling:

          The swirl concentrator is a practical, simple facility which offers a high
          degree of performance in reducing the amount of settleable solids
          contained in combined sewer overflows.

          The swirl concentrator is very efficient in separating both  grit and settleable
          solids in their middle (>0.2 mm) and  larger grain size ranges.  By weight,
          these fractions represent about two-thirds  of the respective materials in the
          defined combined sewer.  Separation of the small grain sizes was less
          efficient, although still appreciable.

          The floatables trap and storage  arrangements should capture most of the
          lighter than  water pollutants and convey them to the foul  sewer.  Its
          dimensions are such that oversize floating objects would not be captured,
          and would tend to go over the effluent weir rather than stay in the chamber
          to clog the foul outlet.

          Both the floatables trap and foul outlet are easy to inspect and  clean out if
          necessary, during dry weather flows.

          There must be sufficient hydraulic head  available to allow flows to pass
          through the swirl concentrator facility  without  causing backups or flooding
          upstream in the system. Sufficient head should be available to  operate the
          foul  sewer discharge by gravity.   If sufficient head is not available, the foul
          sewer discharge may require continuous pumping.
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                        SWIRL AND HELICAL BEND
                     POLLUTION CONTROL DEVICES

                   RICHARD H. SULLIVAN, JAMES E. URE,
                  FRED PARKINSON, AND PAUL ZIELINSKI

                 AMERICAN PUBLIC WORKS ASSOCIATION
                            CHICAGO, ILLINOIS

                               prepared for

               MUNICIPAL ENVIRONMENTAL RESEARCH LAB
                            CINCINNATI, OHIO

                                July 1982

                           EPA NO. 600/8-82-013
In 1970, an EPA state-of-the-art report on regulators indicated that two British devices
showed possibilities for application as combined sewer overflow regulators in the
United States.  These were the  vortex-flow regulator, later called the swirl
regulator/separator, and the helical bend regulator/separator. Both have been
modified for adaptation to North American treatment practice.

The design criteria used for the  English regulators differ  from those used in North
American practice, primarily in the ratio of wet-weather flow to dry-weather flow allowed
to enter the interceptor for treatment.  Thus, it was necessary to conduct hydraulic
model studies to develop units for United States practice.

The swirl combined sewer overflow regulator/separator is of simple annular-shaped
construction and requires no moving parts to achieve a relatively high degree of
separation of settleable and floatable solids from a waste stream. While accomplishing
the separation  of solids, it also regulates the flow to the interceptor sewer system.
Wastes are concentrated into what should  be a more economical  method to treat the
waste stream.   Treatment of the concentrate could be with either conventional
wastewater treatment facilities or special combined sewer overflow treatment units.
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The device consists of a circular channel in which rotary motion of the sewage is
induced by the kinetic energy of the incoming sewage.  Flow to the treatment plant is
deflected and discharged through an orifice called the foul sewer outlet, located at the
bottom and near the center of the chamber.  Excess flow in storm periods discharges
over a circular weir around the center of the tank and is conveyed  to storage treatment
devices as required or to receiving waters.  The concept is that the rotary motion
causes the sewage to follow a long spiral path through the circular chamber.  A flow
deflector prevents flow completing its first revolution in the chamber from merging with
inlet flow. Some rotational movement remains, but in the form of a gentle swirl, so that
water entering the chamber from the inlet pipe is slowed down and diffused with very
little turbulence.  The particles entering the basin spread over the full cross section of
the channel and settle rapidly.  Solids are entrained along the  bottom, around the
chamber, and are concentrated  at the foul sewer outlet.  Flow through the foul sewer
outlet is limited to the hydraulic capacity of downstream facilities.

The device is essentially without moving parts and performs well under a variety of flow
conditions. The primary features of the unit include: Inlet Ramp, Row Deflector, Scum
Ring, Overflow Weir and Weir Plate, Gutters, Downshaft and Secondary Overflow Weir.

Three flow quantities must be considered in the design:   1) the peak dry-weather flow;
2) the design flow, i.e., the flow for which  the optimum treatment is desired; and 3) the
maximum flow likely to occur through the chamber.

The following procedure should be used when designing a swirl regulator/separator.

       1.     Select design discharge
      2.     Select the recovery efficiency desired:
             -  One of four performance efficiencies can be chosen -
               either 100,90,80 or 70 percent recovery of settleable solids
      3.     Find the inlet dimension--D1, and chamber diameter--D2
      4.     Check discharge range covered
      5.     Recovery rates
      6.     Foul discharge
      7.     Find dimensions for the whole structure
      8.     Geometry modifications
      9.     Foul discharge modifications

The location of the swirl regulator/separator  is dependent upon the elevation of the
combined sewer and the location of the interceptor sewer.  In some instances, it may
be feasible to construct the facility underground in the public right-of-way.  The site
should minimize construction of transition sewers from the collector and the clear
overflow discharge to receiving waters.
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The operation and maintenance requirements for swirl regulators/separators has been
assumed to be constant for all sizes of units. Cleaning of the unit may be done with
automatic washdown facilities. With these washdown facilities, only one or two special
site visits to remove large objects can be anticipated.

Results from three demonstration units are available which have tended to validate the
laboratory testing. The units which have been constructed include those by Onondaqa
County (Syracuse), New York; Lancaster, Pennsylvania; and Boston, Massachusetts.

The experience of all three agencies with  the operation of the swirl unit has been very
good. Generally, operational problems which have become apparent have been due to
design deficiencies.

Monitoring for treatment evaluation has been performed at the Syracuse facility.
Efficiency has been calculated on the values based upon the laboratory work.

Relatively good SS  removal efficiencies were determined over the entire storm flow
range at the Syracuse prototype.  Total mass  loading and concentration removal
efficiencies ranged  from 33 to 82 percent and 18 to 55 percent, respectively, with
flowrates from 0.54 cu m/min (0.2 mgd) to 20.5 cu m/min (7.6 mgd).  Suspended
solids influent concentrations greater than 250 mg/l generally resulted in removals of
better than 50 percent of the total mass loading to the swirl.

Care must be taken in evaluating swirl solids treatability since under dry-weather flow
conditions,  all regulators are designed to deliver the entire flow volume and associated
solids to the intercepting sewer until a predetermined overflow rate is reached.

If the swirl  regulator was replaced by a conventional flow regulator, the net mass
loading  reductions  (attributable to the SS conventionally going to the  intercepted
underflow) would have ranged from 17 to 64 percent as compared to a more effective
range of 33 to 82 percent for the swirl.

Prototype analyses indicated BOD5 removals of 50 to 82 percent for mass loading, and
29 to 79 percent in terms of concentration.

The helical bend combined sewer overflow regulator/separator consists of an enlarged
section of the sewer which acts as a solids and floatables trap prior to diversion of the
overflow to  additional treatment or receiving waters.  The device requires considerable
space to construct. Operation and maintenance are minimized  as there are no
mechanical or moving parts within the device.  The channel is curved to develop helical
secondary motions  within the flow.  The  helical motion effectively captures particles
which have a greater settling velocity than the upward velocity of the helical motion.
Relatively high velocities are achieved as the chamber empties to treatment at the end
of the storm event which will remove deposited solids. Thus, the helical bend separator
is unique in that most of the removed solids are released at the end of the storm event.
896CMS8.WS5

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The helical bend combined sewer overflow separator was developed in Great Britain.
The design developed for USEPA was based upon English experience as well as
hydraulic and mathematical model studies. A demonstration unit has been installed
(September 1979) in  Boston, Massachusetts, where it was to be tested on both
combined sewage and separate stormwater flows.

Available data indicates that the helical bend separator can be as efficient as the swirl
separator/regulator.   The helical bend separator compared to the swirl  separator
should have less head loss, may require less acquisition of additional right-of-way, and
allows the short period of time at the end of the  storm event.  However,  the cost of the
device may be up to 50 percent more than an equivalent swirl separator/regulator and
almost 3 times more than a swirl unit designed to remove 80 to 90 percent of the solids.

The location and depth of the combined sewer  will determine the area  required for its
installation.  The depth of the sewer may suggest that an underground chamber is
appropriate. If this is the case or if adjacent land is expensive, it may be desirable to
construct a chamber for the separator along the existing right-of-way of the sewer.

The available head at a specific site may be a critical factor in the  choice of the specific
type of combined sewer regulator to be used.  The head loss must be  considered for
two conditions: 1) for periods of dry-weather flow, and 2) for periods of wet-weather
flow.  The available head during dry-weather flow will  depend on the difference  in
elevation between the combined sewer and the  interceptor that will convey the flow to
the wastewater treatment plant. The  available head during wet-weather flow will
depend on the difference in  elevation  between the combined sewer  and the water
surface of the receiving stream.

The helical bend separator was tested extensively in Nantwich, England.  The first full
size unit has been built in Boston,  Massachusetts. A purpose of the  demonstration
project was  to compare the  efficiency of the unit as  compared to a  swirl
separator/regulator.  The unit was to be tested  on combined sewer  overflows and
stormwater discharges. Test results were not available at the time of preparation of the
article. Construction costs were very low due to the fact that the unit was prefabricated
from wood and is not intended for permanent use.

It appears that the principal advantages  of the helical bend separator are the low head
requirements and the discharge to treatment of the captured solids at the end of the
storm event. The swirl regulator/separator in turn requires less space  and  should be
less expensive to construct.  Use of the swirl regulator/separator where insufficient
hydraulic head is available for its normal mode of operation may require dry weather
bypassing the device.  As both units have been designed  to minimize the cost of
operation and maintenance problems, they are considered comparable.
896CMS8.WS5

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      URBAN RUNOFF POLLUTION CONTROL TECHNOLOGY OVERVIEW
                        C.B. BRUNNER, R.I. FIELD
                        H.E. MASTERS, A.N. TAFUR1

           MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
                OFFICE OF RESEARCH AND DEVELOPMENT
               U.S. ENVIRONMENTAL PROTECTION AGENCY
                           CINCINNATI, OHIO

                             PROCEEDINGS

               5TH UNITED STATES/JAPAN CONFERENCE ON
                   SEWAGE TREATMENT TECHNOLOGY

                             TOKYO, JAPAN

                             December 1977

                           USEPA 600/9-77-027
Control and treatment of stormwater discharges and combined sewage overflows from
urban areas  are problems of increasing  importance in the field of water quality
management. Over the past decade much research effort has been expended and a
large amount of data has been generated, primarily through the actions and support of
the U.S. Environmental Protection Agency's Storm and Combined Sewer Research and
Development Program.

The program starts with "Problem Definition" broken into "Characterization" and
"Solution Methodology".

The average BOD concentration in combined sewer overflow is approximately one-half
the raw sanitary sewage BOD.  However, storm discharges must be considered in
terms of their shockloading effect due to their great magnitude. A not uncommon
rainfall intensity of 1 inch/hour will produce urban flowrates 50 to 100 times greater than
the dry-weather flow from the same area.

Approximately one-half of the stream miles in this country are water quality limited and
30 percent of these stream lengths are polluted to a certain degree with urban runoff.
Therefore, secondary treatment of dry-weather flow is not sufficient to produce required
receiving water quality; and control of runoff pollution becomes an alternate for
maintaining stream standards.  Accordingly, both water  quality planning and water
pollution abatement programs need to be based on  an  analysis of the total urban
pollution loads.
896CMS12.WS5

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Until the urban stormwater situation is analyzed and efficient corrective measures
taken, there may be no point to seeking higher levels of treatment efficiency in existing
plants.

The second area under Problem Definition, "Solution Methodology" naturally followed
initial "Characterization" for providing a uniform and necessary background for the user
community.

The first and most fundamental approach should be a more accurate assessment of
the problem.  Ideally, this should involve acquiring data on a city-wide basis for both
dry-weather flow and wet-weather flow.

Integrated with a more accurate assessment is the  consideration of cost-effective
approaches to wet-weather flow pollution control.

User Assistance Tools are divided into "Instrumentation" and "Simulation Models".

The qualitative and quantitative measurement of  storm overflows is essential for
planning, process design, control, evaluation, and enforcement. "Urban intelligence
systems" require real-time data from rapid remote sensors in order to achieve remote
control of a sewerage network.  Sampling devices do not provide representative
aliquots, and in-line  measurement of suspended solids and organics is  needed.
Conventional rate-of-flow meters have been developed mainly for relatively steady-state
irrigational streams and sanitary flows and  not for the highly varying surges
encountered in storm and combined sewers.

The electromagnetic, ultra-sound, and passive sound flowmeters have been developed
to overcome these adverse storm flow conditions. Passive sound instruments offer the
additional benefit of extremely low power requirements rendering them amenable to
installation at remote overflow locations and integration into city-wide, in-sewer,
sensing, and control systems.

Math models are needed to predict complex dynamic responses to variable and
stochastic climatological phenomena.  Models have been subcategorized into three
groups:  1) simplified for preliminary planning, 2) detailed for planning and design, and
3) operational for supervisory control.

The Storm Water Management Model (SWMM) provides a detailed simulation of the
quantity and quality of stormwater during a specified precipitation event.  Its benefits for
detailed planning and design have been demonstrated and the model is widely used.
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Wet-weather flow control can be assumed to involve aspects as follows.  First, there is
the choice as to where to attach the problem:  at the source (e.g., the street, gutters,
and catchment areas) by land management, in the collection system,  or off-line by
storage.  Second, there is the choice of how much control or degree of treatment to
introduce. Third, there is the impact assessment, public exposure, and priority ranking
with other needs.

Land  Management includes all measures for  reducing urban and construction site
stormwater runoff and pollutants before they enter the downstream drainage system.
On-site measures include structural, semi-structural  and non-structural techniques that
affect both the quantity and quality of runoff.

Structural and semi-structural control measures require physical modifications in a
construction or urbanizing  area and includes  such techniques  as on-site storage,
porous pavement, overland flow modifications and solids separation.

Non-structural control measures involve surface sanitation, chemical use control, urban
development resource planning, use of  natural drainage, and  certain erosion/
sedimentation control practice.

The next  category, collection system control pertains to those management alternatives
concerned with wastewater interception and transport.  These alternatives include
sewer separation; improved maintenance and design of catch basins, sewers,
regulators, and tide gates; and remote flow monitoring and control. The emphasis, with
the inception of sewer separation, is on optimum utilization of existing facilities and fully
automated control.  Because added use of the existing system is employed, the
concepts generally involve cost-effective, low-structurally intensive control alternatives.

Storage  is  perhaps the most  cost-effective method available for reducing pollution
resulting from combined sewer overflows  and managing urban stormwater runoff.
Furthermore, it is the best documented abatement measure in present practice.

Storage facilities  possess many of the favorable attributes desired in combined sewer
overflow  control:  1) they are basically simple in  structural design and operation; 2) they
respond without difficulty to intermittent and random storm behavior; 3) they are
relatively unaffected by flow  and quality changes; and 4) they are capable of providing
flow equalization  and, in the case of sewers and tunnels, transmission.
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                THE USE OF STREET CLEANING OPERATIONS
                  IN REDUCING URBAN RUNOFF POLLUTION

                               ROBERT PITT
            EPA - TECHNOLOGY TRANSFER SEMINAR SERIES ON
              COMBINED SEWER OVERFLOW ASSESSMENT AND
                          CONTROL PROCEDURES

                                   1978
In many cases, street cleaning operations can be used to reduce the amount of
pollutants entering urban  runoff.  This paper described the  effectiveness and cost
characteristics of street cleaning operations.  Information was summarized from many
different studies conducted over the last 20 years, but was mostly based upon the
results of a study completed for the Storm and Combined Sewer Section of the USEPA
(Edison,  New Jersey) entitled, Demonstration of Non-Point Pollution Abatement
Through Improved Street Cleaning Practices.

This demonstration project included several hundred street cleaning tests  conducted
over a period of a year in San Jose, California.  More than 20,000 samples were
collected  and analyzed in describing street surface loading conditions during specially
scheduled street cleaning operations.  Five different study areas were examined
ranging from downtown commercial areas to suburban residential areas.  The study
areas ranged in size from 50 to 200 acres. This study was unique in that it measured
the effectiveness of street cleaning over large areas under the influence of  many real-
world conditions, such as different land uses, variable street dirt loadings, changing
weather characteristics, varying parked  car conditions and different street surface
pavement conditions.  Previous street cleaning effectiveness studies only examined
street cleaning equipment operating under very strictly controlled conditions in strip test
or very small scale (about 40 foot cleaning paths) actual  street and curb tests.
Therefore, these results typically show the effectiveness of street cleaning operations to
be somewhat less effective than under the earlier more  controlled tests.   However,
street cleaning practices can be used to significantly reduce the quantities of some
street surface contaminants in urban runoff, if the street cleaning program is adequately
designed.

The type  of street  contaminants present are generally a  function of local  geological
conditions,  motor  vehicle  emissions and wear, and inputs from surrounding areas.
Accumulation rates of street surface contaminants vary widely with geographical
location, season, land use, traffic, and other conditions.  Nationwide accumulation rates
vary from 3 to 2700 Ib/curb-mile/day with an average around 150 Ib/curb-mile/day.
896RHG5.WS5

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This study showed that higher concentrations of contaminants are seen with
decreasing particle size. Additionally, typical street sweeping activities are most
effective at removing larger size particles.  Street cleaning is still an important control
measure because the larger size particles are typically the most abundant and contain
significant quantities of contaminants. The largest particles (>6370>() had removal
rates as high as 55 percent during this study.

Another important aspect of an effective street sweeping operation is to implement
measures to eliminate parking interferences.  This study found that the percent of total
street solids loading removed by sweeping was negatively impacted by the percentage
of curb length occupied by parked cars. Under most conditions, removal of parked
cars during street sweeping operations can significantly improve the street cleaning
effectiveness.

The San Jose study found  the following removal rates and costs for several
contaminants during the street cleaning operations:
                                   Average Removal
                                   (!b/curb-mile)
               Average Unit Cost
                ($/lb removed)
      Total Solids
      TSS
      BOD5
      Lead
      Cadmium
200
100
 12
  0.80
  0.002
    0.08
    0.16
    1.34
   20
8000
As shown, removal rates and  costs vary widely for different types of surface
contaminants.

Information from this  study was presented in a generic manner that should be
applicable to most areas of the country.  Specific local monitoring activities are
necessary before final design of an adequate street cleaning  program  can be
completed.
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                USEFUL TECHNOLOGICAL INFORMATION ON
                            SEWER FLUSHING

                                   by

                          DR. WILLIAM C. PISANO
               ENVIRONMENTAL DESIGN AND PLANNING, INC.

                               Presented at

                EPA TECHNOLOGY TRANSFER SEMINARS ON
             COMBINED SEWER OVERFLOW ASSESSMENT AND
                         CONTROL PROCEDURES

                                  1978

Combined sewer systems are generally old, well  constructed, but often because of
neglect, function poorly, particularly during wet weather flow conditions,  in the past,
overflow regulation was often set to minimize retained wet weather flows for treatment
even though there was ample hydraulic conveyance capacity. Many repairs and
patchwork such as the connection of new separated areas into combined systems over
the years have greatly confounded piping complexity.  Understanding how the system
works is no simple task.  Sewer maps are generally old, piece meal, out-of-date, and
difficult to use.  Detailed operational information in  a simple concise form simply does
not exist.

Municipal maintenance funds are generally limited and are largely relegated to reaction
policies such as cleaning clogged sewers. Active maintenance programs aimed at
ensuring  proper collection  system  performance  during both dry and wet weather
conditions are almost non-existant for most communities.  The maintenance issue is
further compounded by the fact that in many cities there is a functional division of
responsibility and authority  between upstream collection system control  and
management, and downstream overflow collection, conveyance, and treatment.  The
downstream authority generally views its mission as abating combined sewer overflows
within the spatial limits of their jurisdiction.  Downstream control generally means
expensive structural programs.  Institutional  differences often preclude the downstream
authority from assuming the role for active management of the upstream areas.  The
net result in many cases, is that both known and unknown upstream system problems
having a high pollution control  cost-effectiveness, often go undetected  and
uncontrolled, and management is focused instead  on downstream solutions  resulting
in high program costs.
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Putting aside institutional and jurisdictional issues,  it is the author's belief that the
financial interests of the federal government would be best served if in fact, Step 1 201
Combined Sewer Facilities Planning both mandated and funded for each and every
facility study in reasonably sized communities, thorough and comprehensive sewer
mapping activities, intensive physical surveys and measurement programs during all
flow conditions for the entire sewerage system of concern. This assertior is based on
the belief that there are unknown malfunctions of all types, poorly optimized regulators,
unused  in-line storage and pipes clogged with  sediments in old combined sewer
systems. Furthermore, detection and correction of these maladies would in fact, result
in extremely cost-effective solutions for partial if  not significant control of combined
sewer overflow emissions. It is a further belief that  wet weather emissions/water quality
response measurement programs should then be instituted to ascertain whether further
planning and additional control is necessary.  In  some situations it will be clear that
additional control is necessary. In some situations it will be clear that additional
management and control will be immediately necessary.  For many small communities
already faced with  taxed  financial resources for dry  weather treatment, the
measurement and wait/see option will be meaningful.

In short, combined sewer management planning should be "front-end" loaded with
intensive mapping and field sleuthing and measurement activities. This proposition
represents a fairly radical departure from current planning methodologies where often
the orientation seems to be heading toward heavy  "back-end" loaded SWMM modeling
and "desk top" analysis efforts with inventory and survey efforts kept to a minimum.
The author believes that a change in the opposition direction would be in the long run,
be more cost-effective to the government, provided that the institutional and funding
mechanisms can  be resolved.

The findings of a recent section 208 combined sewer management study for portions of
the sewerage system in the City of Fitchburg, MA demonstrate this viewpoint.  The
results showed that sewerage system remedial repairs and slight piping modifications
were an order of magnitude  less expensive than the nominal BMP practices of sewer
flushing, street sweeping and catchbasin cleaning, and several orders of magnitude
less than alternative structural options.
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                  WATER QUALITY CHARACTERISTICS OF
                STORM AND COMBINED SEWER OVERFLOW

                            April 26-28,1977
                             TOKYO, JAPAN

                      MINISTRY OF CONSTRUCTION
                        JAPANESE GOVERNMENT

                             PROCEEDINGS

               5TH UNITED STATES/JAPAN CONFERENCE ON
                   SEWAGE TREATMENT TECHNOLOGY

                             TOKYO, JAPAN

                             December 1977

                           USEPA 600/9-77-027
In Japan as of 1975, 583 municipalities had sewage works. In 1976, 65 new
municipalities were expected to begin wastewater treatment.

In Japan, many cities have combined sewer systems. According to a 1972  survey
conducted by the Ministry of Construction, combined sewer systems acbounted for 73
percent of the total sewered area, covering 69 percent of the total sewered population.

Many municipalities which  have combined sewer systems have adopted separate
sewer systems in new sewered areas, so the proportion of combined sewer systems is
decreasing gradually. Nevertheless, the significance of the combined sewer overflow
on the contribution to pollution loads in waters has not yet been reduced significantly.
In large cities where steps toward improvement through secondary treatment have
been made, the contribution for water pollution by combined sewer overflow will be
increased more and more.

Large costs have stood in the way of changing combined systems to separate systems.
Narrow width of road in densely populated areas, and the fact that stormwater from
storm sewers itself is populated, have also limited separation. Converting 1o a separate
system is not always considered to be the best solution.               >
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Most of the measures taken or being planned to control the water pollution by
combined sewer overflow are either detention or sedimentation of wet-weather
overflow.

In Japan, there are three practical examples of measures to control water pollution due
to combined sewer overflow, two in Osaka and one in Yokohama.

In 1975, the Osaka Municipal Government constructed a stormwater sedimentation
tank consisting of two basins. The dimensions of each basin is 3.5m in width, 20.2m in
length  and 4.5m to  5.0m in depth.   Four  additional basins  were to have  been
constructed.  With all the basins complete,  the storage capacity was estimated at
2,000m3.  This facility is the only example in  Japan of measures against wet-weather
overflow. In Osaka, flooding frequently occurs in lowlands because of marginal use of
catch basins and settling due to excessive use of groundwater.  In order to solve this
problem, installation of a new interceptor was planned and has been underway since
1973.  This trunk sewer is planned to control water pollution  due to wet-weather
overflow without detriment to the original purpose of flood control.

The Yokohama Municipal Government was in the process of constructing a stormwater
sedimentation tank consisting of 18 6.0m wide by 35m long by 6.0m deep basins with a
total capacity of 22,680m3.  These tanks  are expected to reduce the pollution loads by
10 percent or more in SS and almost the same degree in BOD compared to sewer
separation.

For the purpose of collecting extensive data on the characteristics of wet-weather
combined sewage, 12 drainage areas different in drainage system and  land use were
selected as the study areas in 11 member municipalities.

Following is a list of survey areas and a brief explanation of each.

Combined Sewer Survey Areas:

  A.  Single-family residential area apart form the city's center
  B.  Populated urban area with a mixed variety of residential houses and stores
  C.  Area with small to medium factories, residential houses and stores
  D.  Area with residential zones and shopping quarters
  E.  Residential area on a terrace bordering on an urban area
  F.  Area  with low-story and  medium-story shopping  quarters and amusement
       quarters
  G.  Area with low-story shopping quarters, amusement  quarters, and medium-story
       business quarters.
  H.  Dense area packed with  low-story residential houses,  stores and factories
       mainly of textile and dyeing
  I.    Typical high-story civic and business center
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  J.  Area with residential quarters, commercial quarters, wholesale markets and
      small factories along a trunk road
  K.  Suburban residential area on a terrace with many company-owned residential
      houses.
  L.  Amusement quarters

Separate Sewer Survey Areas:

  M. Tier on the sea, with business quarters, commercial quarters, hotels, public
      facilities, government institutions, multi-family residential houses
  O. Newly developed residential area on a suburban terrace, with single-family
      houses

In each  survey area sewage flow was measured and once every 30 minutes sampling
was conducted for water quality analysis.

Following are the water quality characteristics of respective survey areas in dry-weather
and the factors which are considered attributable to them.

  C. Industrial quarters count for 75 percent of total area,  discharging high
      concentrations of heavy metals
  E. Residential, but high in BOD, COD and SS
  H. A good number of textile and dyeing factories in the area resulting in high BOD,
      COD and SS
  I.   Typical business quarters discharging weak effluents having a soluble-to-total
      BOD ratio of 14.4 percent
  K. Low BOD; quantities of  pipeline deposits are suspected
  L.  Densely built amusement quarters generating a large volume of sludge for the
      area; high BOD

While these areas have different characteristics, they also have something in common
with each other:

  a.  VSS/SS is in the range  of 0.63 to 0.88, except for one survey area.

  b.  Three survey areas (F,  G, and L) show flow rate 10 to 30 percent less in winter
      than in summer, and an increase in BOD of 30 to 40 percent on the average in
      winter over summer.

  c.  No definite differences by land use are noticed.

Wet-weather surveys were conducted two to four times in each survey area.
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The runoff coefficient is largely influenced by the impervious area ratio.  Some survey
areas had a large impervious area ratio of more than 90 percent. In these areas, the
runoff coefficient is high. Taken altogether, the runoff coefficient lies  in the range of 40
to 80 percent.

After a light rainfall, BOD, T-P and K-N become far larger in concentration than in dry
weather.  In the case of a large scale storm, the concentrations are reduced by dilution
effects and the loadings are held within several times those in dry weather. Regarding
SS, the reduction in concentration is far less than others even in the case of a large-
scale rainfall.  It remains almost the same as in dry weather.  This shows that the bulk of
SS was conveyed into the sewer from the ground surfaces.

The surveys on combined sewer overflow in the 12 representative cities in Japan have
disclosed the following:

   1.   In wet weather, BOD, T-P and T-K are diluted  significantly  while SS remains the
       same.

  2.   In wet weather, water quality in the combined sewers seriously decreases.

  3.   In wet weather the combined sewers experience an increase in inorganic SS
       and at the same time an increase in refractory organics.
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