&EFK
             United States
             Environmental Protection
             A}ency
             Great Lakes National
             Program Office
             536 South Clark Street
             Chicago, Illinois 60605
EPA-905/2-85-001 -B
In-System Storage
Controls For Reduction
Of Combined Sewer
Overflow - Saginaw, Michigan

Technical Report
                   Do not WEED. This document
                   should be retained in the EPA
                   Region 5 Library Collection.

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                                                               EPA-905/2-85-001 B
               IN-SYSTEM STORAGE CONTROLS  FOR  REDUCTION OF
                COMBINED SEWER OVERFLOW-SAGINAW, MICHIGAN

                             TECHNICAL  REPORT
                         WILLIAM C. Pisano, P.E.
                            Daniel J. Connick
                            Gerald L. Aronson

                  ENVIRONMENTAL DESIGN & PLANNING,  INC.
                            369 Winter Street
                       Hanover, Massachusetts 02339
                            Grant No. S005359
                                   for
                      DEPARTMENT OF PUBLIC UTILITIES
                             CITY OF SAGINAW
                            SAGINAW, MICHIGAN
Ralph G. Christensen                                Richard  Traver
Project Officer                    o,*»«MtnnAfltftCtf  Technical Assistance
                   U.S« tfiVilviillw"***
                   Region 5, Ubraiy(fU2J>
                   77 West Jackson Boulevard,
                   Chicago, It 6060V3590
                   GREAT LAKES NATIONAL PROGRAM OFFICE
                   U.S. Environmental Protection Agency
                          536 South Clark Street
                         Chicago, Illinois 60605

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                           DISCLAIMER


          This  report  has  been  reviewed by  the  Great  Lakes
National Program Office and the Municipal Environmental  Research
Laboratory,  U.  S. Environmental Protection Agency, and approved
for  publication.   Approval  does not signify that the  contents
necessarily  reflect  the  views  and  policies  of  the  U.   S.
Environmental Protection Agency,  nor does mention of trade names
or  commercial products constitute endorsement or  recommendation
for use.

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                            FOREWORD

         The  Environmental Protection Agency was created because
of increasing public and government concerns about the dangers of
pollution  to  the  health and welfare of  the  American  people.
Noxious air, foul water, and spoiled land are tragic testimony to
the  deterioration of our natural environment.  The complexity of
that environment and the interplay between its components require
a concentrated and integrated attack on the problem.

         Research  and demonstration is that necessary first step
in  problem  solving  and  it  involves  defining  the   problem,
measuring  its  impact,   and  searching  for  solutions.    This
publication is one of the products of that research, a most vital
communications   link   between  the  researcher  and  the   user
community.

         In  the implementation o'f PL92-500 Congress established,
through Section 108, demonstration funds for developing realistic
and  innovative management approaches to solve combined and storm
sewer  discharges impacting the Great Lakes.    This project  has
been  supported  by  Section 108 funds through  the  Great  Lakes
National Programs Office, Region V.

         The  deleterious effects of storm sewer  discharges  and
combined  sewer overflows upon the nation 's waterways have become
of increasing concern in recent times.  Efforts to alleviate  the
problem  depend  in part upon the utilization of  improved  urban
runoff control strategies.

         This   report  presents  the  results  of  a   five-year
implementation  program  effort for management of combined  sewer
overflows  from the City of Saginaw impacting the Saginaw  River.
A  CSO  Facility  Plan was  prepared  entailing  advanced  system
management  concepts for creating in-system transient storage for
later bleedback to a well-operated advanced wastewater  treatment
plant  coupled  with state-of-the-art swirl  solids  concentrator
complexes  for  handling residual overflows.   A portion  of  the
system  storage  management plan was implemented in 1984 and  was
field  evaluated.   Roughly  ten  percent of  total  wet  weather
related phosphorous loadings to the Saginaw River was reduced  by
this program.   In addition,  total wet weather related suspended
solids  and biochemical oxygen demand discharging to the  Saginaw
River  were  reduced  by  sixteen  percent  and  twenty  percent,
respectively, as a direct consequence of this implementation.

                      Peter Wise, Director
                  Great Lakes National Program
                             Office
                        Chicago, Illinois
                                111

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                            ABSTRACT
          This report details the results of a recently completed
five-year  combined  sewer  overflow  (CSC)  control  program  in
Saginaw,  Michigan (10,000 acres, pop. 85,000) funded through the
U.S.  EPA  108 Great Lakes Demonstration Program and conducted by
the  engineering contractor,  Environmental Design and  Planning,
Inc.  (EDP),  Hanover,  Mass.   The  implemented control  program
entailed  modification of 12 combined sewer  regulation  chambers
together  with construction of one new in-line control chamber to
maximize  transient  system  storage  of  wet  weather   combined
sewerage  for later bleedback to a well-operatea AWT/WWTP  having
phosphorous   removal  and  ample  treatment   capacity.    These
improvements,   "the  partial  BMP  plan",  represent  a  partial
completion  of the first of two phases of the City's CSO Facility
Plan.   The objective of Phase 1 was to maximize WWTP  processing
of  wet  weather  combined  sewage  generated  using  inexpensive
transient  system storage (less than $l/cu.ft.) so as to minimize
the extent,  scale and cost of satellite CSO treatment facilities
(Phase II).  The swirl concentratcr technology was recommended to
treat  residual overflows remaining after Phase  I  improvements.
Six  major Facilities were recommended and adopted as part of the
CSO Facility Plan.

          EDP  determined that city-wide availability of  in-line
storage  without threatening basement flooding was  extensive,  a
total  of 3.9 million cu.ft.   Regulation chamber internal  weirs
were  modified  in  one portion of the City  to  enhance  in-line
storage  and the first of fourteen new in-line storage  chambers,
(upstream  of regulators) was also constructed.   New  innovative
vortex  valve  flow  throttling  devices  were  used  to  replace
existing malfunctioning mechanical float-operated control  valves
at  regulation chambers and another installed at the new  in-line
control structure.   These devices actualized the notion of using
a  battery  of  system-wide flow controllers  within  the  hostle
environment of a sewer system to reliably and accurately throttle
flows,  pass  debris,  create storage and allow self-scouring  on
draindown  without  mechanical  or  electric  controls  or  human
interface.

          The  total  cost of the implemented  program  including
engineering and construction was approximately $516,000.   A post
construction   evaluation   measurement/modeling   program    was
conducted  by EDP in the Fall,  1984 to verify preproject  design
conditions.   Implementation of the reduced BMP plan is estimated
to have increased the percentage of total annual wet weather flow
directed  to the WWTP by 14.6% (from a previous "as is" level  of
37.7%) and is estimated to have incrementally reduced (beyond "as
is"  levels)  suspended solids loadings to the Saginaw  River  by
                                IV

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16%,  BOD  by  20%  and  total  phosphorous  by  8.5%  (secondary
treatment).   During  periods  of AWT treatment (pickling  liquor
addition) at the WWTP,  total phosphorous removals are  estimated
to   increase   to   12.6%   above   pre-implementation   levels.
Implementation of the remaining elements of the complete BMP plan
will  produce an overall incremental wet weather flow increase of
30% (increasing the total wet weather flow treated at the WWTP to
67.7%).

          In  sum,  expenditures of approximately $516,000  under
the  reduced BMP plan for low level sewerage system modifications
(entailing  a significant portion of proposed controls  for  one-
half  of  the City) resulted in decreasing the system-wide  total
phosphorous wet weather loadings to the river by about  10%.   No
adverse  conditions  resulted  from the  plan.   The  concept  of
inexpensive system controls to maximize transient in-line storage
of  combined  sewage  with bleedback to a high  performance  WWTP
worked well and is recommended as a management practice.

          This  project  was  funded by  U.S.  EPA  in  part,  to
demonstrate  new innovative full scale approaches for  mitigating
CSO  impacts on the Great Lakes.   The primary project justifica-
tion was to develop and document an innovative,  inexpensive  and
cost-effective  management approach  for mitigating  wet  weather
phosphorous loadings to Saginaw Bay (Lake Huron). The results are
currently  being used as part of U.S.  EPA's joint  efforts  with
Canada  to develop phosphorous limitation management  strategies.
In  addition, the  results of  this  demonstration  project  will
provide  valuable  insights  for  a number  of  projects  in  the
formative   preliminary  phase  investigating  in-system  storage
management to "clip" or eliminate CSO from small intensity,  high
frequency  events  as a first "stopgap" and  inexpensive  control
measure.

           This  report  was submitted in partial fulfillment  of
Grant  No.  S005359  by Environmental  Design  &  Planning,  Inc.
sponsored  by  a Section 108 grant from the Great Lakes  National
Program Office,  Region V, U.S. EPA with funds also from the City
of Saginaw.   This report covers a period of September,  1979  to
December, 1984 and work was completed as of April, 1985.

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                        TABLE OF CONTENTS

 Foreword  	  iii
 Abstract	   iv
 List   of  Figures   	   ix
 List  of Tables  	  xii
 Abbreviations and  Symbols  	 xiii
 Acknowledgments	  xiv

 Chapter 1   Project Description

      1.1    Background  	  1.1
      1.2    Chronological Overview of Project 	  1.1
      1.3    Details of  the  Phase 1 Evaluation 	  1.10
      1.4    Details of  the  Phase 2 Evaluation 	  1.16
      1.5    Details of  the  Phase 3 Evaluation	  1.17
      1.6    Reader's Guide  to Report 	  1.20

 Chapter 2   Conclusions

 Chapter 3   Recommendations

 Chapter 4   Description of City of Saginaw
            Sewerage System

      4.1    Descriptive Background Material 	  4.1
      4.2    Sewerage System Overview 	  4.2
      4.3    WWTP Details 	  4.6
      4.4    Regulator Chambers 	  4.8
      4.5    Hancock Street Storage/Treatment Facility 	  4.8
      4.6    Dry Weather Flow Characteristics 	  4.9
      4.7    Wet Weather Flow Considerations 	  4.13

Chapter 5   Screening of Combined Sewer Controls

      5.1    Foreword  	  5.1
      5.2    Modifications to Existing System 	  5.1
      5.3    Sources Control Practices 	  5.19
      5.4    Storage and Treatment 	  5.20
      5.5    Selection of Alternative Controls 	  5.29

Chapter 6   Combined Sewer Modeling

     6.1    Foreword  	  6.1
     6.2   Runoff Prediction 	  6.2
     6.3   Regulator Operation 	  6.4
     6.4    In-Line Storage 	  6.9
     6.5    Interceptor Model 	  6.13
     6.6   West Side Interceptor River
             Crossing Considerations 	  6.20
     6.7   Runoff Water Quality 	  6.28
     6.8   WWTP Simulation 	  6.32
     6.9   Model Calibration/Verification Efforts 	  6.33
     6.10   Phosphorous Modeling Data 	  6.45

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Chapter 7  Design of Reduced BMP  Plan Modifications
     7 .1   foreword	   7
     7.2   Regulator  Chamber Details  and Modifications  ....   7
     7.2   Proposed Weir Alterations  	   7
     7.4   Special Modification of  the Adams
             Street Type "E" Regulator 	   7
     7.5   Special Modification of  the
             Weiss Street Regulator Chamber  	   7
     7.C.   Weiss Street Fump Station  Wet
             Well Modification  	   7
     7.7   New Upstream Regulator Chsnber  	   7
Chapter 8  Reduced EM? Flan Implementation
                                                              8
                                                              8
                                                              8
                                                              8
                                                           1
                                                           1
                                                           8

                                                           11

                                                           14

                                                           16
                                                           18
8.1   Foreword
8.2   Special Construction Requirements 	
8.3   Installation 	
8.4   Chair.ber Modifications 	
8.5   Construction ard Installation of
        Flow Regulators 	  8.7
6.6   Weiss Street Fun ping Station Wet
        Well Modification 	  8.19
Chapter 9
     9
     9
     9
     9
     9.5
     c
     9,
     9,
     9,
  7
  8
  9
  10
      Field Monitoring Prograir, - Post BMP
       Implementation Data and Analysis
Foreword  	
Post Implementation Field Prcgrsm 	
System Eackwatering       	
Evaluation of Effectiveness of New
  In-line Storage Chamber Constructed
  at Salt and Vermont Streets 	
Monitcring and Evaluation at the
  Adams Street Regulator 	
Monitoring of the Weiss Street
  Fump St ation 	
Monitoring of the Wastewater Treatment Plant.
Field Verification of Flow Regulating Devices
Evaluation of the Cronk Ave     Regulator ...
Post Construction Chamber Inspection
  and Evaluation. „	,
                                                        9.1
                                                        9.1
                                                        9 .2
9.7

9.14

9.18
9.23
9.23
9.32

9.34
Chapter 10 Assessment cf Pre BMP Conditions and
             Evaluation of Proposed Prcgrams
    10 .1
    10.2
    10
    10
    10,
    10,
    10.7
      Foreword  	
      Overview of Analysis Criteria and
        Results Pr e sent at ion	,
      Pre BMP CSO Emission Estimates...
      Analysis of Weiss  Weir Alteration,
      Complete BMP Frcgrati Simulation..,
      Reduced BMP Program	,
      Phosphorous Analysis 	,
                                                 10.1

                                                 10.1
                                                 10.2
                                                 10.9
                                                 10.1C
                                                 10.14
                                                 10.17
                               VII

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Chapter 11 Application of Inlet Control Technology
             to the City of Saginaw Combined
                      Sewerage System

    11.1   Foreword  ,	   11.1
    11.2   Inlet Control Philosophy	   11.1
    11.3   Overview of Hydrologic Methodology	   11.9
    11.4   Saginaw Sewerage System	   11.13
    11.5   Analysis of the Congress Covrt Area	   11.15
    11.6   City-Wide Implementation of Inlet
             Control Technology	   11.23

Ref ei er.ces	 R.I
                               Vlll

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                         LIST OF FIGURES

Figure Number                                         Page

1.1  Location of Saginaw, Michigan	  1.2
1.2  Proposed Storage Basin and Regulator Modifications	  1.3
1. 3  Proposed EDP CSO Plan	  1.5
1.4  Layout of Weiss Street Combined Sewer
       Overflow Treatment Complex	  1.6
1.5  Webber Street Swirl Facility	  1.9
1.6  Typical In-Line Storage Device  (Regulator)	  1.14
1.7  Typical Float Actuated Type Flow Regulator	  1.15
1.8  Details of the Reduced BMP Plan	  1.18

2.1  Wet Weather Total Phosphorous Loading to
       Saginaw River	  2.8

4.1  Saginaw Combined Sewer Service Area	  4.3
4.2  Saginaw Regulator Chamber Catchment Area	  4.4
4.3  General Plan of Interceptor Sewer System	  4.5
4.4  Comparison of Storm Events -
       Saginaw vs Vassar (1975-1978)	  4.16
4.5  Annual Rainfall (accumulated) Cumulative
       Frequency Plot	  4.19

5.1  Schematic of Typical Dynamic  (Semi-Automatic)
       Combined Sewer Mechanical Float Operated
       Flow Controller	  5.3
5.2  Simple Model of Vortex Valve Representation	  5.8
5.3  Johannessen Type Conical Vortex Valve
       Flow Controller	  5.11
5.4  Brombach Type Conical Vortex Valve Flow Controller	  5.13
5.5  Flow Coefficient and Discharge Variations for
       Brombach Type Conical Vortex Valve	  5.15
5.6  Typical Vortex Valve Stage/Discharge Curve	  5.17
5.7  Saginaw Study Typical Storage Facility
       Process Schematic	  5.22
5.8  Saginaw Study Typical CSO Primary Treatment
       Process Scheme	  5.24
5.9  Helical Bend and Swirl  Concentrator	  5.28

6.1  Catchment Area  Modeling	 6.3
6.2  Discharge/Water Depth Curves
       Hancock Area Regulators	 6.6
6.3  Schematic of Regulator  Operation	 6.7
6.4  Interceptor Model  Overview	 6.17
6.5  Interceptor Model  Computation	 6.18
6.6  West Side River Crossing Model Area	 6.19
6.7  Details of River Crossing,  Saginaw Area	 6.21
6.8  Analysis of Saginaw River Crossing
       Discharge Levels	 6.23
6.9  Verification of Weiss Street Pump Station Weir
       Modification Effects  on Crossover Rates	 6.26
6.10 Saginaw Suspended  Solids Generating Equation
       Compared to Other Municipalities	 6.31
                               IX

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6.11 Single Event Comparison of Modeled
       and Recorded Events	 6.34
6.12 Single Event Time Sequencing	 6.36
6.13 Overflow into Weiss Street Pumping	 6.37
6.14 Overflow into Hancock Street Pumping Station	 6.38

7.1  Type "B" Regulator Chamber Schematics	 7.2
7.2  Type "A" Regulator Chamber	 7.3
7.3  Type "B" Regulator Chamber Flow Patterns	 7.5
7.4  Adarrs Street Regulator Chamber Modifications.....	 7.13
7.5  Weiss Street Regulator Chamber - Plan View	 7.15
7.6  Weiss Street Regulator Chamber Modification
       Section View	 7.17
7.7  Weiss Street Pump Station Wet Well
       Modification - Plan View	 7.19
7.8  Weiss Street Pump Station Wet Well
       Modification - Section View	 7.20
7.9  New Regulator Chamber at Salt/Vermont
       Street - Location and Profile	 7.22
7.10 Salt and Vermont Streets Chamber - Plan View	 7.23
7.11 Salt and Vermont Streets Chamber - Section View	 7.24

8.1  Typical Type "A" Regulator Chamber	 8.5
8.2  Typical Type "B" Regulator Chamber	 8.6
8.3  Partial Components of Brown and Brown
       Regulator Removed from Chamber	 8.8
8.4  Typical Type "B" Chamber Influent Area	;.. 8.9
8.5  Type "B" Chamber - Flapgate to River Area	 8.10
8.6  Type "B" Chamber - New Cross Weir	 8.11
8.7  Chamber Access Manholes and Gate Covers	 8.12
8.8  Segmented Vortex Valve Regulator -
       Disassembled and Partically Assembled	 8.13
8.9  Segmented Vortex Valve Regulator -
       Fully Assembled	 8.14
8.10 Salt/Vermont Street Charr.ber Vortex Valve	 8.15
8.11 Installed Vertex Valve Regulator at the
       New Salt/Vermont Streets Storage Chamber	 8.16
8.12 Adams Street Chamber Vortex Valve Regulator	 8.17
8.13 Installed Adams Street Chamber Vortex
       Valve Regulator	 8.18
8.14 Typical Installed Conical Type Vortex
       Valve Regulator	 8.20
8.15 Installed Conical Type Vortex Valve
       Regulator with Modified Inlet Sleeve	 8.21
8.16 Horizontal Type Vortex Valve Regulator	 8.22
8.17 Weiss Street Pump Station - New Weir
      and Splash Wall	 8.23

9.1  Hancock Street Area Cup Gage Location.	 9.4
9.2  Salt/Vermont Streets Area Cup Gage Locations	 9.5
9.3  Rain Accumulation vs Time	 9.8
9.4  Sewer Flow Depth vs Time 10/18/84 Event	 9.8
9.5  Volume  of Stored Combined Sewage vs Time
       10/18/84 Event 	 9.10

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9.6  Combined Sewage Inflow Rate vs Time
       10/18/84 Event	 9.11
9.7  Vortex Valve Discharge Rate vs Time
       10/18/84 Event	 9.13
9.8  Overflow into Weiss Street Pump Station	 9.20

9.9  Weiss Street Pump Station Suspended
       Solids Data	 9.22
9.10 WWTP Wet Weather Flow vs Rain Accumulation	 9.24
9.11 WWTP Mass Loadings Wet Weather Water Quality	 9.25
9.12 Hayes Street Vortex Valve Characteristics	 9.27
9.13 Adams Street Vortex Valve Characteristics	 9.28
9.14 Court Street Vortex Valve Characteristics	 9.29
9.15 Throop Street Vortex Valve Characteristics	 9.30
9.16 Ames Street Vortex Valve Characteristics	 9.31

11.1 Components of the Inlet Control System	11.3
11.2 Asphalt Contoured Speed Hump	11.5
11.3 Surface/Subsurface Storage Components of
       Inlet Control for Congested Areas	11.6
11.4 City of Saginaw Areas of Reported Basement
       Flooding	11.14
11.5 City of Saginaw Inlet Control Study Area -
       Congress Courts	.....11.16
11.6 Typical Congress Court Topography	11.17
11.7 Relationship of Storage Volume to CSO Total
       Phosphorous Reduction	11. 25
                               XI

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                         LIST OF TABLES
TITLE                                                          Page
"O    Pollution Abatement Effectiveness of
       Best Management Practives Program	  2.7
4.1    WWTP Flows 1978-1979	  4.11
4.2    System Distribution of Dry Weather  Flows	  4.12
4.3    Simulation Model Dry  Weather  Flows	  4.14
4.4    Comparison of Annual  Rainfall Totals	  4.17
4.5    Catchment Area  Runoff Coefficients	4.20

5.1    Conditions and  Demand for an  Ideal  Collecting
         System Flow Controller	  5.6
5.2    Lancaster, PA 1980-1981 Summary of  Swirl
         Regulator/Concentrator Performance	  5.26
5.3    Overview of Desirable CSO Controls  for  Saginaw	5.30

6.1    Typical In-Line Storage Volume Comparative  Analysis....  6.12
6.2    In-Line Storage Potential	  6.14
6.3    Comparison of Collection System Daily
         Deposition Loadings	  6.30
6.4    Predicted Versus Recorded Values  at WWTP  (1978)	  6.39
6.5    Model Calibration Results - Storm Event 7/8/80	  6.41
6.6    Pre Reduced BMP Construction  Storm  Data	  6.44
6.7    Post Reduced BMP Construction Storm Data	  6.46
6.8    Waste Water Treatment Plant Total
         Phosphorous Summary	  6.48
6.9    WWTP Phosphorous Removal Results  (1984)	  6.52

7.1    BMP Program Regulator Chamber Weiss
         Modifications	  7.6
7.2    Reduced BMP Program Regulator Chamber
         and Flow Regulation Data	  7.7
7.3    Vortex Valve Stage/Discharge  Characteristics	  7.9

8 .1    Flow Regulator  Details	  8.4

9.1    Cup Gage Monitoring of Peak Water Elevations	  9.3
9.2    Adams Street Chamber  Storm Samples	  9.16

10.1A  Pre BMP Conditions Simulation	  10.3
10.IB  Pre BMP Conditions Simulation	  10.4
10.2   Flow Summary Data	  10.6
10.3   TSS Summary Data	  10.7
10.4   BOD Summary Data	  10.8
10.5A  Complete BMP Plan Simulation	  10.12
10.5B  Complete BMP Plan Simulation	  10.13
10.6A  Reduced BMP Plan Simulation	  10.15
10.6B  Reduced BMP Plan Simulation	10.16
10.7   Total Phosphorous Summary Data	  10.18

11.1   Typical Inlet Control Worksheet	  11.19
11.2   City of Saginaw Congress Courts Sewer  System
         Hydraulic Evaluation	  11.20
11.3   City of Saginaw Congress Courts Rainfall/Storage
         Requirement Summary	  11.21
                               XII

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                    ABBREVIATIONS AND SYMBOLS
ac   acre
cos  cos 1 ne
cf   cubic feet
cfs  cubic feet per second
cm   centlmenter
dwf  dry weather flow
fpm  feet per minute
fps  feet per second
ft   feet
ft^  square feet
g    gram
gal  ga I I on
gpm  gallon per minute
h.   hour
Imp. Imperv I ous
In.  I nch
kg   k 1 1 ogram
L    liter
I b   pound
m    meter
mg/lmllllgram per  liter
ml   ml I I I I Iter
MG   ml I I I on gal I ons
sq   square
SWMM Storm Water Management Model (U.S. EPA)
A    Angle of lateral entry at junction
BOD  Biochemical Oxygen Demand (5 days)
CBOD Carbonacous Biochemical Oxygen Demand
CSO  Combined Sewer Overflow
DO   Dissolved Oxygen
Dp   Ratio of pipe diameters at junction
h    Depth of flow above regulator orifice
g    Acceleration of gravity
H    Head loss due to junction
I     Percent Imperv I ousness
K    Energy  loss coefficient
NBOD Nitrogenous Biochemical Oxygen Demand
PR   Ratio of flows at junction
TSS  Total Suspended Solids
WWTP Waste Water Treatment Plant
Z    Runoff coefficient
%    Percent

                               xiii

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                                ACKNOWLEDGEMENTS


     The authors would like to commend the EDP staff who worked so hard  to make
this program a success.  Through the diligent  efforts of many,  a study has been
prepared assessing the viability of a relatively new technology for solving a
complex combined sewer management problem in the City of Saginaw.

     We would like to thank the City of Saginaw Public Utilities Department for
their extreme cooperation and good will, including Robert Dust, Executive  Direc-
tor of Public Utilities, Mr. Jim Anderson, Superintendent and Fred Schulz,
Assistant Superintendent, Wastewater Treatment Division.

     We would like to also thank Mr. Ralph G.  Christensen, U.S. EPA Region V,
Great Lakes National  Program Office, for his support and assistance. The  Great
Lakes Program provided funds for this project.  In addition, Mr. Richard P.
Traver, U.S. EPA, Edison, New Jersey was extremely helpful in coordinating the
early phases of the project along with Mr. Doug Ammon and Mr. John English U.S.
EPA, Cincinnati, Ohio.

     Finally, we would like to express our sincerest appreciation  to Ms. Eunice
Harris for her patience in  typing this report.

     Environmental Design and Planning, Inc. was the engineering contractor for
his project.  Dr. William C. Pisano, P.E., President, EDP, was  the principal
investigator.  Mr. Daniel J. Connick, Sr. Design Engineer, was  the project
manager.  Mr. Gerald L. Aronson, Executive Vice President, EDP, supervised
field monitoring and evaluation efforts.
                                 xiv

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                            CHAPTER 1

                       PROJECT DESCRIPTION
1 . 1 Background

       In  1979  the  City of Saginaw  in  cooperation  with  the
108 Great Lakes National Program, Region V, U.S. EPA  embarked en
a  program  to implement and evaluate on a full-scale  basis  new
innovative  low-cost  technologies for mitigating combined  sewer
overflows  (CSO)  discharging from the City of  Saginaw  sewerage
system into the Saginaw River.  The Sagiraw Fiver discharges into
Saginaw Bay and ultimately into Lake Huron.  See Figure 1.1.  The
108  Program and subsequent funding was established  when  Public
Law  92-500 came into existence for the purpose of  demonstrating
on  full  scale bssis promising technologies for abating CSO  and
stormwater  pollution impacting the Great  Lakes.   Approximately
$1.1 million was allocated to the project. Environmental Design &
Planning,  Inc.  (EDP)  was chosen by U.S.  EPA and the  City  to
perform this work.

       The project progressed from 1979 until  1984,  culminating
with   implementation  and  evaluation  of  a  number  of  system
improvements.      The  overall  work effort  consisted  of  three
separate  phases.   Within Phase 1 EDP submitted a report to  the
City  of  Saginaw  which presented the results of  a  feasibility
study  in which the most cost effective means of treating CSO  in
the  City of Saginaw were established.   During this phase a  CSO
Facility   Plan   was   developed  and   adopted   as   well   as
recommendations  for implementating a demonstration project.   In
1983  (Phase  2) a  further investigation was prepared  due  to  a
lack of funds  to implement the Phase 1 recommended  demonstration
program.   Phase  2 efforts were directed at optimizing a reduced
scope  of  work plan for implementation  using  available  funds.
Following implementation cf the Phase 2 proposed improvements,  a
Phase 3 evaluation  was performed in 1984.  This effort  generated
a  greater   data  base for system  hydraulic  model  calibration
allowing  for  improved estimates of the effects of  plan elements
completed  to   date and the effects of  additional  plan  element
implementation .

1 . 2
          In  the early 70 's the City had adopted a  CSO  control
program  entailing  the  use  of  seven  sedimentation/detent icn/
chlorination  facilities.    In the mid 70 's one such facility was
constructed at the Hancock Street Pumping Station and  regulators
in  the  area  were modified to enhance flow  to  this  treatment
facility.   See  Figure  1.2  for the general  location  of  this


                               1.1

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HILIAUKEE
   CM ICACO
  ILLINOIS
Figure ] -1 Location of Saginaw, Michigan.

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                                                                                       LEOCNO:
                                                                                             EXISTING PUMPING STATION

                                                                                             EXISTING REGULATION
                                                                                             CHAMBER


                                                                                             EXISTING INTERCEPTOR
                                                                                       _.— CITY LIMITS
                                                                                             LIMITS OF SERVICE AREA
                                                                                             OUTSIDE CITY LIMITS
                                                                                                 , PROPOSED
                                                                                             STORAGE BASINS
                                                                                             Elements  completed
                                                                                               fin  1977
                          EXISTING COMBINED SEWER
                          AND OVERFLOW(TYPICAL)
     . HANCOCK ST.
STORAGE BASIN
                                             HANCOCK ST. PUMPING
                                                  STATION
               WEST 5OE
               INTERCEPTOR
              WEBBER ST. PUMPING
                   STATION
                 WEISS ST. PUMPING
                     STATION
                                 EMERSON ST. PUMPING
                                      STATION
                                               EAST SIDE
                                             INTERCEPTOR
                                                        EXISTING
                                                       WASTE WATER
                                                        TREATMENT
                                                          PLANT
                                                                FOURTEENTH ST.
                                                               PUMPING STATION
Figure  182    Location  of  Proposed Storage  Basins  and Regulator Modifications

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 facility,   other  proposed   detention   facilities   and   the   five
 modified regulators.

           The  objectives  of  the  Phase 1  (1979-1981)  EDP  study
 were twofold:  a)  preparation  of an alternative overall  framework
 plan  for   the  management   of CSO  from  the  City  of  Saginaw
 considering,  but not  limited to, the existing concepts of storage/
 treatment/ chlorination  facilities;   and  b) preparation  of  a
 detailed  preliminary plan for a portion of the envisioned  city-
 wide plan,  entailing  implementation of  a full-scale demonstration
 treatment   facility   devised in such a  way that it would  form  a
 logical  element of the overall CSO Facility Plan.

         During the  course   of the  Phase  1  planning  efforts
 (1,2,3)    by  EDP,  the most cost-effective City-wide programs  of
 CSO  abatement alternatives,  were  developed for varying levels of
 system  costs.   Runoff simulation  studies indicated that the  two
 most  singularly  effective measures for handling CSO in  Saginaw
 were  increased wet  weather loadings to  the  City's  wastewater
 treatment   plant  (WWTP) and inclusion of actions  termed,  "Best
 Management  Practices"  (BMP).   The  BMP  program  consists   of
 extensive   in-line storage and system modifications to  increase
 hydraulic   capacity so that the WWTP can handle more wet  weather
 combined  sewage.  Roughly  2 million cubic feet of  new  in-line
 system  storage would  be generated as a result  of  this  plan.
 Estimated cost  of  BMP plan equalled $2.6 million (1984 ENR=4300).

    ^  After  implementation of the complete BMP  plan,  residual
 CSO  would  still  remain at six   locations:   Weiss  Street  Pump
 Station,  Weiss  Street gravity line, Emerson Street Pump Station,
 Fourteenth  Street  Pump Station, Webber Street Pumping Station and
 the  Fraser  Street  Regulator.   See Figure 1.3  for locations of the
 elements of this plan.  The Phase 1 investigation recommended the
 use  of swirl solids concentrating facilities at these  locations
 as the most cost-effective technology for abating these  residual
 overflows.   Suspended  solids  removal optimization analysis  of
 various swirl configurations/sizes at the various overflow points
 (after  implementing the BMP program )  resulted  in  pin-pointing
 the  Weiss  Street  area as the most significant location  for  a
major  swirl concentrator facility.   See Figure  1.4.

       Although  the proposed BMP program elements  were the  most
 cost-effective  means  for abating CSO  in  Saginaw,  U.   S.   EPA
desired  at that time to implement and  evaluate the effectiveness
of  the swirl concentrator technology for reducing  CSO  pollutant
 loadings.   The 24-foot diameter swirl   concentrator (design  flow
- 40  cfs) in Lancaster,  Pennsylvania  showed significant promise
as  a new inexpensive technology in comparison to  sedimentation/
detention  for  reducing CSO  settleable  solids  and  floatables.
Although  the  suspended  solids  removal  results,   particularly
 * For moderate to heavy intensity  storms*
 ** Pump station and gravity discharge considered  as  composite  CSO.


                             1.4

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                                                                               EXISTING INTERCEPTOR
                                                                               LIMITS or SERVICE AREA
                                                                               OUTSIDE CITY LIMITS
                       ^/-Existing Hancock St.
                      < /  Storage/Treatment Facility
                     /{        ,'

                  ~**-       ^      '
                                                                                                   PROPOSED REGULATOR
                                                                                                   MODIFICATIONS •
                                                                                               •  TYPE A

                                                                                               A  TYPE B
                                                                               PROPOSED INUNE FLOW
                                                                               CONTROL/STORAGE DEVlCEl
                                                                        	TYPICAL EXISTING
                                                                                SEWER LINE
Proposed
Webber St.
Swirl Facility    N.
                                                           Proposed
                                                           Emerson swirl
.14—Weiss St. pumping station
 •—i  weir increase
                                                                  Proposed Weiss
                                                                  swirl facility (swirl degritter)
                                                                                       EXISTING
                                                                                      WASTE  WATCH
                                                                                       TREATMENT
                                                                                         PLANT
                                                        Proposed Fourteenth St.-*
                                                        swirl facility
Figure  1.3      Proposed EDP CSO plan.

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                                           PROPERTY  LINE
             iversion
             Cbambe
                                                  INTERCEPTOR^ ^
                                                  r-f *"7 ^" - -*---*"

                                                  RIVER  CROSSING
                               (PROPOSED)
                              -I-  DISIN----
                 Degntters
                 Proposed
                 Future
                      EXISTING
                     WAREHOUSE
                              -• CONTACT--
                              --CHAMBERS w
                              -.( FUTURE )•:-:-
 LEGEND
     SWIRL  PUMPED
 ^E:   INFLUENT
 --- SWIRL  FOUL SEWER
 	SWIRL  DEGRITTER
 _._. SUPERNATANT
r-—SWIRL  CLEAR WATER
PRIVATE
PROPERTY
                        Disinfection chemical
                                                                       SCALE:  1"
                                                              mca i
                                              storaqe building

Fiyure  1.4    Layout of Weiss Street combined sewer overflow treatment complex.
                                                             40'

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during "first flush" conditions,  were extremely favorable at the
swirl concentrator facility in Lancaster,  the evaluation program
was   plagued  with  numerous  flow  measurement  instrumentation
problems.   Since  a  number of swirl  concentrators  were  being
incorporated into designs throughout the U. S. at that time, U.S.
EPA  believed  that  the proposed evaluation program  at  Saginaw
would   answer  any  unresolved  questions  remaining  from   the
Lancaster  experience.   Moreover,  the Canadian Ministry of  the
Environment at the time was seriously considering this technology
for  widespread utilization in the Quebec Province (one facility
was constructed in Quebec City in 1984 and more facilities (1985)
are  in design).  A comprehensive and complete portrayal of swirl
performance  was  desired for technology transfer.  It  was  also
desired  by  U.S.  EFA at that time to construct and  evaluate  a
swirl concentrator of larger physical dimensions than the  device
at  Lancaster   to  expand  the evaluation  experience  for  this
emerging technology.

          The  Phase  1  study     also  recommended  within  the
budgetary  limitations  (of  the  demonstration  funding)   three
alternative  swirl concentrator demonstration facilities  located
at  the Weiss Street gravity overflow,  at  the Weiss Street Pump
Station  discharge  and at the gravity  discharge  at  Fourteenth
Street.  Estimated Construction costs (1984) including electrical
service  contingency and excluding disinfection chemicals for the
three facilities equalled $3.1 ,$2.6, and $2.38 million (ENR=4500) ,
respectively.  No  land costs were included.  The facility at the
Weiss Street gravity overflow was preferred.

       Because  of the significant cost savings for City-wide CSO
control  program  reported  from  the  Phase 1  study  and  as  a
mechanism  to facilitate Section 201 Construction Grants  funding
to  partially  support the costs of  the  proposed  demonstration
project  at  Weiss  Street,  EDP was instructed by  the  City  of
Saginaw and U.S. EPA in mid 1980 to expand the Phase 1 study into
a  proposed  CSO Facility Plan for the City  of  Saginaw '2' .  In
January,  1981 the proposed EDP CSO Facility Plan was adopted  by
the City of Saginaw.

       Although  the  magnitude of the overflow at  Weiss  Street
greatly exceeded those at other locations,  City-owned land space
to construct the proposed facility was extremely limited.  Design
of  the proposed swirl concentrator facility at Weiss Street  was
curtailed  due  to  the  envisioned long  and  protracted  period
required to acquire the necessary land.

      In mid 1981 ECP was instructed by the City and U.S.  EPA to
re-direct   efforts   for  plecetuent  of   the   proposed   swirl
concentrator facility at an alternative location within the City.
The  alternative  facility  was nevertheless to be  designed  and


                               1.7

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constructed  in  such a manner as to be a logical  and  congruent
element  of  the overall  adopted CSO Facility Plan.   The  Webber
Street  Pumping Station area  was chosen as the new  location  tc
place  the proposed demonstration facility.  An analysis of  this
catchment  was conducted supported by detailed field   measurement
programs (3). In 1981-1982 EDP prepared construction  plans,  spe-
cifications and bid documents for a new treatment complex consis-
ting  of an in-line diversion structure controlled by vortex flow
regulation devices to direct flow to the existing pump station,  a
new  80-cfs  low lift pumping plant,  a 38  foot  diameter  swirl
concentrator  with stainless steel inner assemblies and ancillary
piping and connections.  See Figure 1.5. The cost of  the facility
was estimated to be approximately $2.0  million (ENR=4500 , 1985 )

          Approximately  $.75 million was remaining from the  108
grant  and  additional  funding  was  requested  from  the    201
Construction Grants  Program. Eligibility status for  the proposed
project  was poor and it was forcasted that the low status  would
remain  for  the next several years.   It was finally decided  by
U.S.  EPA  that  the proposed  demonstration  swirl  concentrator
project be indefinitely postponed.

          In  early 1983,  U.S.  EPA and the International  Joint
Commission   (IJC)  (U.S.   and  Canada)  became  interested   in
developing  phosphorous limitations for the Great Lakes revolving
around   a   number  of  promising  BMP   practices   controlling
agricultural  and urban runoff  phosphorous  loadings.   Sewerage
system  management  employing  system controls  to  inexpensively
maximize transient in-line storage with bleedback to WWTP 's  with
high performance treatment was identified and viewed by U.S.  EPA
as  a promising management prospect in view of the continuing low
federal  funding  profile for the next several  years.   Since  a
number  of the major sewerage systems impacting the  Great  Lakes
are  combined,  relatively flat and discharge to high performance
WWTPs,  the  notion of evaluating inexpensive system storage  and
hydraulic  optimization in Saginaw was attractive,  feasible  and
logically  extendable  to  other areas  within  the  Great  Lakes
region, if proven to work.

          On  instruction  from U.S.  EPA and the City in  April,
1983, EDP embarked on Phase 2 of the overall program and prepared
a  preliminary  concept plan to best spend  the  remaining  grant
monies to implement and evaluate a significant portion of  the BMP
plan.  The  aim  was  to  accomplish as  much  as  possible  with
remaining  monies.  Runoff  simulation studies were performed  to
evaluate  numerous schemes varying the proposed modified   control
points.   Optimization  analysis  identified  a  plan  for   final
selection  which included sewerage system modifications  on  only
one side of the Saginaw River  (4).  In May, 1983 EDP met with the
City  and  U.S.  EPA to discuss the envisioned plan  which  would


                               1.8

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Figure 1.5   Webber  Street  Swirl  Facility

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realize  about half of the pollution control effectiveness of the
total  BMP plan.  As a result EDP was instructed by the City  and
U.S.  EPA  to  proceed  with an implementation  program  for  the
"reduced BMP" Plan.

          EDP prepared construction plans and specifications.  In
March  1984,   the  construction contract was awarded to Gary  D.
Steadman Inc.  of Bay City,  Michigan.  The construction began in
April, 1984 and was completed in September of 1984.

          During Phase 3 EDP directed a detailed pre-construction
and  a  post-construction field evaluation program  performed  by
City  of  Saginaw  personnel.    Rain  event  statistics,   river
elevations,  sewer depths, regulator chamber hydraulics and water
quality parameters were recorded at numerous locations throughout
the  City.   Pre- construction  data  was used to  calibrate  the
simulation model for discrete events.  The model was then run for
a  full  year  simulation   to  estimate  base   pre-construction
sewerage   system  overflows  during  storm  conditions.    Post-
construction  data  was  evaluated  and  compared  to   predicted
overflow  quantity and quality values based on the modified model
reflecting the pre-construction measurements.   Model  simulation
data  and  field  data were comparable such  that  further  model
calibration  was not required.   Full year model simulations were
then  performed to indicate the effectiveness of the  implemented
reduced   BMP  plan  followed  by  simulations   predicting   the
effectiveness  of completing  the entire BMP plan.

          This  report  documents  the  scope  of  work  and  the
simulation results for the five year, three Phase project.


1 . 3
         The  purpose of the Phase 1 evaluation was to develop  a
cost  effective  plan of action that mitigates impacts  on  water
quality  caused by CSO.   The Facility Planning Area  encompasses
the  City  of  Saginaw land mass including  pertinent  contingent
township  areas tributary to the Saginaw WWTP.  The scope of  the
plan was  limited to overflows within the facility planning area,
as  well  as  to  the water quality  parameters  defined  by  the
objectives and issues.

       The  CSO Facility Plan was developed using the  parameters
of  dissolved  oxygen and oxygen  demanding  materials,  coliform
bacteria,   and   suspended  solids  and  settleable  solids   as
indicators  of  CSO  impacts and target levels  to  be  attained.
Although  CSO  has  many other associated  pollutant  parameters,
such  as heavy metals, chlorinated organics, pesticides and other
toxics, this study did not qualitatively address them.


                               lolO

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       The  scope  of  the  Phase  1 report  was  limited  to  an
assessment and evaluation of water quality impacts resulting from
CSO and then the development of a plan to mitigate those  impacts
caused by CSO.   It was recognized that water quality is impacted
by  upstream  conditions  from areas outside the  combined  sewer
study area,  point source emissions and direct stormwater runoff.
The  study  made an assessment of the relative impact from  these
areas relative to CSO but did not pursue them in the  development
of the Recommended Plan.


1.3.1  Project Approach

       Phase  1  of  the project was developed in  the  following
manner:

       1.  Evaluation of existing conditions

       2.  Simulation   modeling  of  CSO  and   water   quality
           impacts

       3.  Evaluation/optimization of abatement alternatives

       4.  Development of the recommended plan

       Existing facilities were evaluated to generate an accurate
description   of  the  sewerage  system  including  physical  and
operating  characteristics  of the WWTPf  the Hancock Street  CSO
storage/treatment facility,  all pump stations and all  regulator
chambers.

       Formulation  of  the  basis of design  for  CSO   overflow
control  facilities  required input of data,  with regard to  the
quality and quantity of dry weather flows, so that network models
could be calibrated.   Efforts were made to determine the quality
of  dry  weather flows at various points in the City  of  Saginaw
system and to isolate catchment areas including the Saginaw WWTP.
A field measurement program was performed to enable estimates  of
dry weather flows per catchment area.

       Analyses  were  performed  to  assemble  the  wet  weather
predictive  design features including rainfall  characterization,
determination of runoff  parameters for the catchment areas,  and
evaluation of regulator chambers and pumping stations.

       A  comprehensive mathematical computer simulation  program
was developed to help determine overflow discharges and pollutant
concentrations as a result of hypothetical occurrence of  various
size design storms. The model provided an accurate representation
of the physical sewerage system, but also provided an opportunity


                              1.11

-------
to   determine  the  benefit  of  proposed  pollution   abatement
alternatives.  The  value  of  modeling lies in  the  ability  to
predict  the  outcome  of  dependent variables  as  a  result  of
hypothetical  modification  of  the  system.   These  projections
allowed  for more efficient evaluation of abatement  alternatives
formulated  to  meet established goals,  concepts  and  criteria.
Through  this  process the best alternatives  were  isolated  for
further cost-benefit analysis.

       The Saginaw Stormwater Management Model, developed by EDP,
provided   an  inexpensive  and  flexible  tool  for  preliminary
planning and sizing of Stormwater facilities.  The model provided
a  means  by which the Stormwater problem could be  analyzed  and
introduced  time and probability to the quantity,  frequency  and
duration  of  overflow  events  by  using  actual  rainfall  data
collected  over  a long period of time.  It was  used  to  screen
alternatives based on varying storm conditions.

       Feasible  abatement  programs  for CSO  pollution  control
required   evaluation   to   select   the   most   cost-effective
configuration  and  scale to achieve water  quality  goals.  This
study   examined   the  effectiveness  and  costs   of   selected
alternatives, and combined the estimates to develop a recommended
facility CSO pollutional abatement program.

       The  major  components of the Phase  1   recommended   CSO
abatement program are as follows:


       •    BMP program implementation
       •    Swirl Concentrator Facilities at:
               Weiss  Street Pump Station           300 cfs
               Weiss Street Gravity Line            100 cfs
               Emerson Street Pump Station          300 cfs
               Fourteenth Street Pump Station *       50 cfs
               Webber Street Pump Station            50 cfs
               Fraser Street                         50 cfs

               * Pump Discharge and Gravity Line
                 CSO handled by single facility.
1.3.2  Description of Complete BMP Program

          The  BMP program as proposed by EDP and adopted as part
of   the  Facility  Plan,   incorporates   low-level   structural
improvements  and management practices that can be implemented at
relatively  low cost.  The concept of the program is to  maximize
the use of existing WWTP facilities before further CSO  treatment


                               1.12

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facilities are implemented. The program maximizes in-line storage
already  available  in  the  system conduits  and  maximizes  the
conveyance  of storm flows to the WWTP.  To actualize this  plan,
the  existing regulators were to be modified,  new  flow  control
devices  were to be installed to increase in-line  storage,  weir
modifications  were  to be accomplished at the Weiss Street  Pump
Station  to  increase flow across the river,  and  the  operating
procedure of utilizing the extra aeration basins at the WWTP  for
off-line  storage  implemented.   (The  City was  utilizing  this
option at the time it was identified by EDP.)

          It  was envisioned to alter 24 regulators  (See  Figure
1.3)  to  yield  a  constant  discharge  during  initial  storage
filling,  with  excess flows beyond available storage diverted to
the  interceptor rather than the river.  In  addition,  the  five
modified Hancock area regulators (modified as part of the Hancock
Street  Detention  Facility  Implementation in 1977) were  to  be
replaced with constant underflow discharge devices (vortex  valve
flow  regulators) to increase the "first flush" diversion to  the
interceptor  and  maximize the use of the interceptor  throughout
the  storm event.  Furthermore,  six other regulators of  smaller
size  were  to be altered with weirs to divert most £Lowz to the
interceptor.  Fourteen upstream structures with vortex valve flow
regulators  were  to be constructed to yield  additional  in-line
flew control for storage upstream of the regulator chambers.  The
resulting  changes to the regulator operations would achieve  the
maximum useable  in-line storage potential of the system.

          Except  in extreme flow conditions,  the only  possible
points of overflow as a result of these potential actions are  at
Fraser,  Hancock,  Weiss (pump and gravity),  Webber, Emerson and
Fourteenth  Streets.  Weir  elevations at Webber  and  Fourteenth
Street  overflow points were to be raised slightly to insure that
the   high  post-rain discharges from  upstream  in-line  storage
devices  are totally diverted to the interceptor.  The  regulator
chamber   at  Fraser  Street  will  be  unaltered  although   the
regulating  device was to be  replaced and a flow control chamber
constructed  only a short distance upstream.  Figure 1.6 and  1.7
detail typical regulator modifications and the original underflow
control device to be removed.

          An  increased  weir elevation of five feet  was  to  be
imposed  at  the  Weiss Street Pumping Station to  reduce  pumped
overflows  at that point and increase the flow across  the  river
crossing and into the East Side Interceptor.  The aeration basins
at  the  WWTF were to continue to be utilized as additional  off-
line  storage devices.  The lift pumps at the WWTP were  to  pump
from  the interceptor up to maximum hydraulic capacity until  the
aeration  basins  are  filled.  The aeration  tank  contents  are
returned  to the primary treatment tanks at the end of the event.

* Using vortex flow control devices.
**For small to moderate storm events.

                                1.13

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Figure 1.6


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cal in-line storage device (regulator).
1.14

-------
                                                             Flap Gate
                                                             to River
Figure 1.7   Typical  Float Actuated Type Flow Regulator

-------
1.3.3  Swirl Concentrator/Swirl Degritter/Disinfection
         Facilities

          Swirl  concentrator facilities  were  proposed  at  each
of  the  six major overflow points.   The facilities were  to  be
tailored to the particular needs of each site.

          Pumping  stations  to drive the swirls  were  considered
necesssary  at each site.   New lift stations were to be  included
for  the Weiss Street gravity overflow and for the Fraser  Street
overflow.   A  battery  of  various size fixed  speed  pumps  were
considered for these stations.   The existing 100-cfs fixed speed
pumps  were  to  be used (after revamping/turning) for  all  other
stations as required.   New low capacity  (25-40 cfs) fixed  speed
pumps were   to  be included in all revamped stations  to  provide
variable  pumping  range using the revamped fixed  speed  100-cfs
pumps.

          A  swirl  degritter at the Weiss Street complex may  be
necessary if the proposed City-wide system of swirl concentrators
were  implemented  and  pending a careful  review  of  WWTP  grit
removal   capacity   under  sustained  wet  weather   high   flow
conditions.   This  degritter contingency was proposed to  ensure
that the WWTP's solids handling capacity would not be overtaxed.

          In  addition  to disinfection treatment at the  Hancock
Street Facility,  overflow disinfection was also considered at  the
six aforementioned overflow points. Disinfection process  is to be
sequential  - staged  chlorine/chlorine  dioxide  application   (8
ppm/2  ppm) with total of 2 minute detention.   Baffled  chambers
are to provide necessary detention.


1,4  Details oj£ the Phase 2 Evaluation

          The purpose of the Phase 2 evaluation was to  determine
the  optimum implementation plan for the reduction of CSO impacts
to the Saginaw River based on available money and the elements of
the  overall  CSO  Facility  Plan.   Optimization  included  cost
estimation  of  each plan element followed by a series  of  model
simulations  using  various combinations of elements  within   the
total allotted project budget.

          As a first step,   additicnal field evaluations of flow
patterns  at various regulator chamlers were  performed  allowing
further  calibration  of the simulation model.  A  limited  field
investigation  was performed including continuous water elevation
recording  at  several  regulators en each side  of  the  Saginaw
River.    This  data  was  combined  with  information  routinely


                              Iol6

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collected  by  City  personnel at the Weiss  Street  and  Hancock
Street  Fump  Stations  and at the WWTP  to  estimate  area  wide
hydraulic  conditions.  Simulations  then indicated  the  optimum
configuration  for a reduced BMP implementation plan.   This plan
consisted of modifications to the Saginaw sewerage system only on
the West Side of the Saginaw River.  See Figure 1.8 for locations
controlled as part of the reduced BMP plan.

          Since  the entire BMP plan was not to be implemented at
this time,  it was important that all elements of the reduced BMP
plan  be designed and implemented such that no modifications will
be required in the future.  Furthermore, the concept of the total
BMP  plan was to control the system such that  overflows  (except
for  extreme  events) would occur only at major pumped  discharge
points.  Since it was not envisioned to  modify      the  Emerson
Street  Pumping  Station at this time (for automatic  "turn-on"),
the reduced BMP plan was designed such that no additional capital
expenditure for pumpage and/or  operational problems vrould occur
as a result of the implementation.  In short, all elements of the
reduced  BMP  plan  were  to  be permanent  and  not  subject  to
modifications.   The entire BMP plan may  be accomplished in  the
future  and  all elements of the reduced BMP  project were to  be
designed  so that the conveyance/pumpage  characteristics  remain
unchanged.

          As part of the reduced BMP plan,  12 of 35, of the City
of   Saginaw's  combined  sewer  regulators  were   modified   in
accordance  with  the CSO Facility Plan Concept.  One of  the  14
upstream  in-system type structures was  also  constructed.   The
Weiss Street Pumping Station weir/wet well operation was modified
to  increase  river crossing discharge so that more of  the  West
Side "first flush" is transmitted to the WWTP.


1.5 Details of the Phase 3 Eva^luatjLon

          The  Phase  1 EDP sewerage system simulation model  was
used  to estimate City-wide emissions pre/post reduced  BMP  plan
implementation. Flow measurements using automatic  equipment were
made  at  a  number of representative regulators as part  of  the
Phase 2 measurements.

          After  the  reduced BMP plan project  was  implemented,
Phase  3  flow  measurements  were   conducted  to  document  the
effectiveness  of  the implemented controls on  a  representative
basis.  Automatic  continuous  level  sensors were  installed  in
representative   regulator   chambers   to   indicate   hydraulic
conditions  during  dry weather and wet  weather  conditions.   A
limited  post-implementation water quality sampling  program  _was
conducted using automatic sampler techniques to obtain composited


                               1.17

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00
                                                                                                                 LEGEND

                                                                                                                       EXISTING INTERCEPTOR


                                                                                                                 — •— CITY LIMITS

                                                                                                                 __ LIMITS or SEHVICC *"»E*
                                                                                                                       OUTSIDE CITY LIMITS

                                                                                                                       PROPOSED REGULATOR
                                                                                                                       MOOFICATIONS

                                                                                                                       TYPE A

                                                                                                                    • TYPES

                                                                                                                    •  MODIFIED  TYPE B

                                                                                                           f J     <£ PROPOSED INLINE FLOW
                                                                                                           I        ^ CONTROL/STORAGE DEVICE

                                                                                                                	TYPICAL EXISTING
                                                                                                                       SEWER LINE



                                                                                                                   O   ELEMENTS COMPLETED
                                                                                                                         IN 1984
                                       
-------
samples  from  one  major overflow point  (Weiss  Street  Pumping
Station),  at  one  regulator  (Adams Street) and  at  the  WWTP.
Samples  were analyzed for TSS,  BOD and total/soluble phosphorus
by the City of Saginaw.

          These documentary measurements were used to adjust  the
simulation model as necessary to note the technical effectiveness
of  the  flow controllers/in-line storage.  The simulation  model
was  then  re-applied to the entire system to  estimate  residual
emissions  as  a  result  of  the  plan.   Thus,  Phase  2   pre-
implementation   flow  measurements  were  used  to  sharpen  the
planning/design   phase   and   to   provide   a    "pre-project"
documentation.  Phase  3  post-implementation  measurements  were
again  used for documentation purposes as well as to  "fine-tune"
the  simulation model to incorporate the actual effectiveness  of
the plan elements. The resulting simulation model  thus estimates
residual  CSO  emissions incorporating to  a  reasonable  extent,
actual configuration  effectiveness.

          Detailed  observations  were  also  noted  by  City  of
Saginaw   maintenance   personnel  during  routine   post   storm
inspection   of   regulator   chambers  to   determine   physical
conditions.   One  aspect  of  the BMP plan was  to  include  low
maintenance flow regulating devices to replace the existing float
operated   type.    These  existing  devices   require   frequent
maintenance and are subject to failure. The new vortex valve flow
regulating  devices  performed  satisfactorily and  have  reduced
maintenance problems.

          Structural changes to regulator chambers were  intended
to  improve system storage capacities and flow hydraulics without
causing excessive surcharge or in-system  sedimentation.   Degree
of  backwatering was noted at numerous locations upstream in  the
sewerage system.  Debris accumulations in all regulator areas and
sedimentation  in  dry  weather flow channels  were  particularly
noted.   These  observations served to document the reduction  in
maintenance labor provided by reduced BMP plan implementation.

          The  post implementation documentary  effectiveness  of
the  reduced  BMP  plan improvements in terms  of  increased  wet
weather   pollutant  loadings  to  the  WWTP  was  close  to  pre
implementation predictions.   In sum,  expenditures of less  than
$516,000 under the reduced BMP plan for low level sewerage system
modifications   (entailing  a  significant  portion  of  proposed
controls  for  one-half of the City) resulted in  decreasing  the
system-wide  total phosphorous wet weather loadings to the  river
by about 10%.  No adverse conditions resulted from the plan.  The
concept of inexpensive system controls to maximize transient  in-
line  storage  of  combined  sewage  with  bleedback  to  a  high
                               1.19

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performance  WWTP worked well and is recommended as a  management
practice.


1.6  Readerxs Guide to Report

          Report conclusions and recommendations are presented in
Chapters  2 and 3,  respectively.   A general description of  the
Saginaw  sewerage system is presented in Chapter 4.   A review of
the  combined sewer overflow control technologies  considered  as
part  of the Facility Planning effort is presented in Chapter  5.
Details  of the modeling approach used throughout the project are
presented in Chapter 6.   Design and implementation  construction
details  for the reduced BMP plan are presented in Chapters 7 and
8,  respectively.   Details of the post construction  measurement
evaluation program are presented in Chapter 9.   WWTP phosphorous
removal  performance determinations conducted during this  period
are  reported in Chapter 8.   Final modeling results  documenting
overall  pollutant removal efficiency for the implementated  plan
are  given  in  Chapter 10.   Details  of  stormwater  management
investigations  intended to alleviate basement flooding  problems
due to surcharging sewers in upstream areas which also effect the
magnitude of downstream CSO levels are reported in Chapter 11.
                               1020

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                            CHAPTER 2

                           CONCLUSIONS

          EDP  has  completed a five year 3 Phased study of   CSO
pollution from the City of Saginaw,  Michigan and concludes  that
CSO  pollution in Saginaw is controllable at reasonable costs and
that  water quality improvements in the Saginaw River and  public
health  gains will be significant.  The conclusions are based  on
the  analyses  performed over the past five  years,  actual  data
collected concerning CSO and river quality,  previous analyses of
the  water  quality of the region and partial impletrentation  and
evaluation of proposed system modifications.   It should be noted
that  the conclusions stated below include those developed during
earlier  EDP  investigations  leading  to  the  development   and
adoption  of  a  CSO Facility Plan for  Saginaw.   These  earlier
conclusions  are presented to depict a perspective framework  for
the  more relevent and important conclusions resulting  from  the
implementation/evaluation  of the reduced BMP program which is an
integral element of the overall CSO Facility Plan.

          Conclusions are detailed in the  following order:

                        PLANNING & DESIGN

          A.  Combined Sewer System Data Reduction Analysis
          B.  CSO Management Model

                   IMPLEMENTATION & EVALUATION

          C.  Implementation of Reduced BMP Flan
          D.  Evaluation of Implemented BMP Plan

                        FUTURE
          E.  Optimization and the Recommended  Facility Plan
          F.  Cost Analysis of Completed and Proposed Future Work
          G.  Effects of Facility Plan Implementation on River
              Quality

A. Combined Sewer System Data Reduction Ana_ly_s_i.s

(1)    Extensive  data  concerning the  Saginaw   combined  sewer
system,  intercepting sewer systems, and storm and sanitary waste
water treatment facilities were  collected, reduced and analyzed.
Available data were supplemented by several  EDP measurement  and
inspection programs.
                                2.1

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                   Wastewater Treatment  Plant
(2)     The  secondary WWTP had the capacity   to  handle   combined
sewage  volumes greater than generally  flowing to the  plant.   An
analysis of  operating records  indicated  that both  hydraulic  and
treatment capacity for additional  loadings were available without
impairment of  overall WWTF treatment efficiency.   Increasing  the
flow  of  combined sewage to the WWTP was  a  primary  goal  of  this
study.   Pollutant  loads  to  the  river  are  expected   to   be
significantly reduced by increasing flow  to the WWTP  and storing
excesses  within  the system  until throughput  capacity   becomes
available.

(3)      Review of daily operating  records  (long term )   indicated
that  the BOD removal for the WWTP averages  approximately 89%  for
both  wet  days and dry days.   It was   concluded that  the  WWTP
could  handle higher wet weather flows  without  compromising  the
plant's pollutant removal capabilities.

(4)     Review of WWTP data indicate wet weather total  phosphorous
removal  of 50% without AWT .   Non- soluble phosphorous  removals
are 95% but no soluble phosphorous removal is achieved.    The  non
soluble fraction averages 54% of the total phosphorous.

(5)      Advanced Wastewater Treatment  (AWT)   (pickling liquor   or
FeS04 addition) is used, as required at the  WWTP to meet  effluent
standards.   Phosphorous  removals average 75% with AWT  and  the
entire  additional level removed beyond secondary treatment  rates
is attributable to a 50% reduction of soluble phosphorous.

(6)      A  decrease  in non-soluble  phosphorous  removal  occurs
during AWT   and is apparently due to incomplete settling of  the
floculant  material generated by the chemical reaction.    Soluble
phosphorous tied up in the unsettled floe appears as  non-soluble
phosphorous  in  the laboratory analysis.    Part of  the  soluble
phosphorous   removal  rate  reported  is  attributable  to  this
apparent  increase in the non-soluble fraction.

(7)     The  1984 field investigation   indicated  influent  WWTP
total   phosphorous   concentrations  for  all  flow   conditions
monitored to be 1.55 mg/1.   Wet weather samples at the WWTP grit
chamber indicated a weighted average of 1.3  mg/1 although  "first
flush"  values  were  as  high as  6  mg/1.    Wet  weather  total
phosphorous concentrations noted at the Weiss Street Pump Station
averaged  1.74 mg/1.
                               2.2

-------
                        Interceptor Sewer pata

(8)     The junction of the West Side Interceptor  river  crossing
and  the  East  Side Interceptor  was identified as  a  hydraulic
bottleneck.   The   Weiss   Street   Pumping   Station   relieves
backwater/surcharge  at the crossing and together with the  Weiss
Street  gravity overflow constitute the dominant  combined  sewer
overflow in the system.

(9)     The intercepting system's major  hydraulic  bottleneck  is
the  river  crossing.   Application  of additional  head  to  the
crossing  by  raising the weir level at the  Weiss  Street   Pump
station  would   increase flows across the  river.  A  five  foot
weir  height  increase  was  estimated  to  be  optimum.  Further
increases   provide  diminishing  marginal  gains  as  flows  are
increasingly diverted from Weiss Street to other overflow  points
rather than to  the  WWTP.


                         Regulator fiata

(10)   Regulators   (earlier modifed as part of the Hancock Street
Detention Facility  improvements (mid 1970's)) had been altered to
cause the underflow orifices to close rapidly,  limiting flows to
the  interceptor and thus committing the  "first flush" of a  rain
event  to in-line storage created at the  chamber.  EDP considered
it more advisable to maintain higher underflow discharges to  the
interceptor,  limited  only to what the interceptor can maximally
handle. Operation in this manner will commit the "first flush" of
a  rain event,  generally carrying the highest  concentration  of
pollutants, to the  interceptor, and eventually to the WWTP.

(11)    It  appeared during the EDP inspection program  that  the
mechanical  float-operated  mechanisms used to regulate  flow  at
the  regulation chambers were slow in responding to rising  water
levels,  and  it  was   speculated  that  a number  of  the  float
activated underflow orifices do not appreciably close during high
water  conditions.   The City reported that the devices  required
constant surveillance to maintain operation.

(12)      New  vortex flow throttling  devices  having  no-moving
parts,  large  aperture  openings  (in comparison to  conventional
orifices)  constructed of durable material (stainless steel)  and
reported  to be nearly clog-free were envisioned to  replace  the
existing  mechanical float operated mechanisms in the regulators.
These  new  vortex  flow throttling devices  combine  conventional
orifice  flow (high discharge with low head) with vortex  braking
operation   (low discharge with high head),  thus replicating  and
enhancing  the  flow  characteristic produced  by  the  variable-
orifice opening mechanical float-operated mechanisms.
                                203

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                               ®5!  Storage Data

 (13)     Potential  in-line  storage capacity  in the  Saginaw  sewer
 network  is   extensive.  A total  storage volume of  3.93  million
 cubic   feet   (29.4   million   gallons)  has  been   estimated  as
 available witho.ut  threatening   basement   flooding.   Regulator
 modifications and  in-line  storage devices  recommended to achieve
 this  in-line  storage potential are inexpensive,  and will be less
 costly to maintain than  present float-type  regulating devices.

 (14)     Regulators  on the West Side are typified  by  conditions
 where  the  influent trunk sewers are on a  steep incline  to  the
 regulation  chambers which then level- off not far upstream.  Far
 greater storage volumes  could  be  generated for these trunk sewers
 if  additional flow control structures were located upstream where
 the invert slopes  are less steeply inclined.


 B.    CSO Management Model

 (15)    The Saginaw CSO Management Model,  developed by EDP, is an
 inexpensive and flexible tool  for preliminary planning and sizing
 of  CSO facilities.   The model provided a means by which the  CSO
 problem  could be  analyzed and introduced time and probability to
 the quantity,  frequency and duration of overflow, events by using
 actual  rainfall data  collected over a long period of time.

 (16)     Modification  of   the original model  developed  in  1980
 (Phase  1) using extensive  field data collected in 1983 (Phase  2)
 and  1984   (Phase 3) has  resulted in a fine-tuned edition  which
 produces  flow  and   water quality data  closely  matching  field
 observations.

 (17)     During Phase  1 it was estimated that 25.6 percent of  all
 wet  weather  flow would arrive at the WWTP and implementation  of
 the  partial  and  complete  BMP  programs  would  increase  this
 percentage by factors of 1.31 and 1.93, respectively.

 (18)     Using   the  model  as  calibrated   (based   on   field
 investigation  performed in 1984)  it is currently estimated  that
 37.7%  of  wet  weather flow would arrive at the  WWTP  and  will
 increase by factors of 1.35 and 1.91 for the reduced and complete
 BMP plans, respectively.


C.  Implementation of Reduced BMP Plan

 (19)     Partial implementation of the reduced BMP plan including
modifications to 12 of 35 combined sewer regulators,  construction
of  one  upstream in-system storage structure  and increasing  the


                               2.4

-------
effective  head at the Weiss Street crossover was
the construction price of $315,000.
                                                   completed  for
(20)      Modification  of  regulator chambers  was  accomplished
under  ccr-trolled conditions such that no dry weather  sewage  or
wet   weather   combined   sewage  impacted  the   river   during
construction.

(21)     Conditions within regulators were controlled such   that
r.c debris generated as part of the modification progrBir  impacted
the river or interceptor sewer lines.

(22)      Existing chambers were modified using concrete fill  to
eliminate areas of debris accumulation and resulting odcrs.

(22)     Vertex  valve  flow  regulators  were  constructed   and
installed  in  variable  arrangements  to  confcrm  to   existing
conditions  vvithir.  the  regulator  chambers.  The  devices  were
segmented  for  ease  of installation particularly  where  access
space is limited.

(24)       Modification   of  regulator   chambers   was   easily
accomplished  using standard construction practices  particularly
saw- cutting of concrete,  core drilling and concrete forming and
pouring.
D.  Evaluaticn of_ Irp£l§roent_ed BMP Plan
          With the exception of limited pollutant removal at  the
         Street  Facility,  all  reduction of CSO impact  tc  the
                                                        transient
                                                        materials
                                                       that on
                                                        would
(25)
Hancock
Saginaw  River is attributable to increased  in-system
storage  coupled with increased flow and "first flush"
tc the WWTP.   Prior to this program,  it is estimated
annual  basis, 37.7%  of  all wet weather related  flew
an
be
handled by the  WWTP<
(26)     Implementation of the reduced BMP plan is  estimated  to
have  increased  the percentage of total annual wet weather  flow
directed  to the WWTP by 14.6% (from a previous "as is" level  of
37.7%).     Implementation  of  the  remaining  elements  of  the
complete  BMP plan could produce an overall incremental  increase
of 30% (increasing the total wet weather flov treated at the WWTP
to 67.7%).  For "Low Rainfall" events (less than 0.5 inches rain),
the  percentages cf increase flow to the WWTP due tc  iirplementa-
                               2.5

-------
tion of the reduced BMP plan and tre complete BMP plan are  esti-
mated as 19% and 34.6%, respectively.  For "High Rainfall" events
(greater  than 0.5 rainfall), the respective percentage  increases
are  10.5%  and  21.8%.   Table 2.1  presents  estimated  related
increase  of  total systemwide wet weather discharge to the  WWTP
for different rainfall conditions as a result of the reduced  and
complete BMP plans.

(27)      Implementation of the reduced BMP plan is estimated  to
have  incrementally   reduced (beyond "as is"  levels)  suspended
solids loadings tc the Saginaw River by 16%,  BOD by 20% and total
phosphorous  by 8.5%.   During periods of AWT   (pickling  liquor
addition)  at the WWTP,  total phosphorous removals will increase
12.6%     above    pre-implementation    levels.      The    rain
intensity/percentage increase relationship noted for flow to  the
WWTP  is  consistent for suspended solids,  BOD  and  phosphorous
reductions  for  the  Saginaw River.   The greatest  increase  in
reductions  occurs  during low intensity events  with  relatively
lesser  reductions udner high intensity  conditions.   Table  2.1
indicates  the  annual percentage reduction of  total  systemwide
suspended solids and BOD leadings to the Saginaw River.

(28)     Or. a weight basis,  the reduced BMP plan  implementation
is   estimated  to  have  reduced  wet  weather  suspended  solid
pollutant  loads to the river by 1.4 million pounds per year  and
BOD by 0.47 million pounds per year and total phosphorous by 3000
pounds per year.   Wet weather related total  phosphorous loadings
are  estimated  to  be reduced by 3000  to  4000  Ibs.  per  year
depending on application cf AWT .

(29)      Incremental  TSS and BOD removals of total wet  weather
loadings to river attributable to implementation cf the  complete
BMP program (when completed) are estimated to equal about 29% and
30%,  respectively.   Total  phosphorous reduction with secondary
treatment  is estimated to equal 16.7% and with AWT  would  equal
25% above pre BMP conditions. Mass removals due to implementation
of  the complete BMP plan (when completed) are estimated  as  2.5
million  pcunds  of SS,  0.68 million pounds  of BOD and  70CO  tc
10,000  pounds  of  total phosphorous (latter estimate  when  AWT
used).  Consistent  with  the  data  for the  reduced  EMP  plan,
increased  reductions  cf  loadings to  the  Saginaw  River  were
greater under low intensity rain conditions.

(30)       WWTP 1SS and BOD removal levels noted during the  post
construction  evaluation period (late 1984) have not  diminished,
confirming early Phase 1 and Phase 2 projections.

(31)      Figure 2.1 Graphically illustrates  the relative  annual
wet  weather  phosphorous loadings to the Saginaw River based  on
various treatment scenarios.  Two sets of bar craphs were used to
                                2.6

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                                         TABLE 2.1
                             Pollution Abatement Effectiveness
                           of Best MAnageirent Practices Program
                            Suspended Solids and BOD Emissions
                                     Saginaw, Michigan
A.  Annual Percentage
    of Total Systemwide
    Wet  Weather Sewage
    Discharge to WWTP

B.  Annual Percentage
    of Suspended Solids
    Loadings to WWTP

C.  Annual Percent
    Reduction of
    Total Systemwide
    Wet Weather
    Suspended Solids
    Loadings to
    Saginaw River

D.  Annual Percent
    Reduction of
    Total Systemwide
    Wet Weather
    Sewage BOD Loadings
    to Saginaw River

E.  Estimated Capital
    Cost (millions)
                            Pre
                            Project
                            Condition

                              L     H     T
53.0  28.5  37.7
50.0  26.0  35.6
46.5  24.2  33.1
53.4  27.6  36.6
                     Results
                     of Reduced
                     BMP Program
                     Implementation

                       L     H     T
72.0  39.0  52.3
72.0  38.0  52.3
67.0  35.3  48.7
67.6  41.8  57.0
                         Projected
                         Complete
                         BMP Program

                       L     H     T
87.6  50.3  67.7
91.0  48.0  66.0
84.6  44.6  61.4
77.4  50.0  66.7
    L = Low Accumulation   H = High Accumulation  T = All Events (1978 Rainfall )
         Rain Event
       (0.5" or less)
     Rain Event
 (greater than 0.5")
                                          2.7

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Key:   Total Phosphorous
                                     Soluble
                                     Phosphorous
  40 -i
o
S 30
o
   20  -
 o>
 10
 o
 a.
   10 .
            Total Vtet
         Weather Load
                        Pre BMP
                         Load
 Reduced
BMP Load
Complete
BMP Load
                        Secondary Treatment at WWTP
   40 -,
                                                             U  75

                                                                  % of
                                                               Total Load
                                                              -  50
                                                              -  25
                                                                 100
                                                                  75

                                                                  % of
                                                                Total Load

                                                                  50
                                                                •  25
  Figure
           ^tal W-t     Pre BMP     Reduced     Complete
          Weather Load     Load      BMP Load     BMP Load
                    AWT Tertiary Treatment at WWTP

         2.1  Wet Weather Total Phosphorous  Loading  to  Saginaw
                                      2.8

-------
indicate  estimated  removals with the WWTF  providing  secondary
(top of figure) and AWT  (bottom of figure).    In  additior,   the
soluble fraction of the tctal phosphorous is  illustrated.   Figure
2.1   clearly   illustrates  substantial  reductions   in    total
phosphorous  loadings  to the river due to treatment at the  WWTP
and  that  implementation of BMP measures greatly  enhance  total
removals.   Soluble phosphorous removal is non-existent with  the
WWTP providing only secondary treatment. Based on an annual total
wet weather load of 41,000 Ibs.,  the total estimated phosphorous
loadings  to the river would be 31,000 Ibs.  for the reduced  BMP
plan  and  27,600 Ibs.  for the complete BMP  plan with  secondary
(50%)  treatment  at  the WWTP.  The entire decrease  is  due  to
reduction  of  the non-soluble phosphorous  fraction.   With  AWT
(75%)  treatment,  residual  loads of total  phosphorous  to  the
Saginaw  River  would  be 26,000 Ibs.  and 21,000  Ibs.  for  the
reduced and complete BMP plans, respectively.

(32)    Under  optimum conditions of interceptor  flow  (lew  wet
well,  no  upstream  East Side flow) the maxinum river  crossover
rates  would increase from 53 to 73 cfs due to the  Weiss   Street
Pump  Station  weir modification.   Under the condition of   high
WWTP  wet  well  and  no upstream East  Side   flow,  the  maximum
crossover  rates would increase from 25 to 47 cfs due to  program
modifications.  Upstream  East Side Interceptor flow will   always
exist and this flow will induce greater heed  loss and surcharging
of the interceptor further reducing the potential crossover flow.
It is estimated that the modification of the  Weiss Street  Station
spillover weir level has increased the crossover rate by about 20
cfs under all conditions and that operation of the WWTP wet  well
within  the  alarm range can  handle this  range.


(33)     The  WWTP currently operates in a  near  optimum   manner
during  wet weather conditions.  Future modification of the  WWTP
hydraulic  conveyance  system between  major   treatment  elements
could increase peak pumpage rates and reduce  bypass.

(34)    Roughly   500,000 cubic feet of off-line storage is  used
at  the WWTP.    Two aeration basins  are used to store  combined
sewage  delivered  to  the plant at rates  limited  by  the  WWTP
conveyance  capacity  at  the grit chamber where  bypass  occurs.
Future modifications to increase hydraulic capacity may enable  a
greater  portion  of "first flush" materials  to be stored  in  the
aeration basins prior to bypass at the grit chamber.

(35)     WWTF  influent  is pumped from a wet well  tc  the  grit
chamber  using   6 lift pumps.   Pump combinations in use  at  any
time   are  manually  selected  to  maintain   proper   wet   well
elevations.   Wet  well alarms exist for high and low  conditions
but  operation  outside the alarm range  is  possible.   Original
                               2.9

-------
design drawings indicate a design wet well level 5 feet below the
present  low alarm level.  Although pump operation at the  design
wet  well level will increase wet weather river crossover  rates,
it  tray cause pump cavitaticn fcr certain pump combinations.

(36)     With the exception of a few minor reported incidences of
large  stick  debris  cloggage,  the  flow  and  solids  handling
performance  of  the  new vortex valve  flow  throttling  devices
replacing  the  mechanical float-operated controllers within  the
regulation chambers was satisfactory.   No adverse flow backup or
sedimentation problems were reported.   On several occasions  the
devices  were visually observed to pass "first flush" and scoured
solids  on  draindown.   Limited  flow  calibration  measurements
indicated   that   the   devices  generally   operated   as   per
manufacturer's specifications.

(37)      The performance of the new in-line control  chamber  at
Salt  &  Vermont Streets which generated at  maxirruir  capacity  a
transient  storage volume cf 175,000 cubic feet was satisfactory.
The  new vortex valve flow throttling device which controlled the
wet  weather discharge from this facility as well  as  permitting
passage  of normal dry weather sewage worked extremely well.   No
blockages,  sediment  buildup nor adverse backups were  reported.
Minor  odor problems with organic sediment buildup  within  "dead
corners"  of  the  in-line  control chamber were  noted  and  are
attributable to inccrrectly sloped concrete fillets placed during
construction.  This minor problem has since been corrected.


E. Optimization and the Recommended FacdJ-ijty FjLan (Future Actions)

(38)     Runoff simulation studies indicate that the  most singu-
larly effective measure for handling CSO in Saginaw is the inclu-
sion  of   Best   Management Practices  (BMP).  The  BMP  program
consists of extensive in-line storage and system modifications to
increase transient in-line storage and system hydraulic  capacity
so that the WWTP can handle more1 wet weather combined sewage.

(39)      After implementation  of the complete BMP  plan,  resi-
dual overflows will remain at six locations:  Weiss Pump Station,
Weiss  Street  gravity line,  Emerson  Pump  Station,  Fourteenth
Street  Pump  Station,  Webber  Street Pump Station  and   Fraser
Street (at the Queen Street/Fraser Street regulator).  CSO treat-
ment  is needed to treat these overflows remaining after the  BMP
plan  implementation.   The  most cost-effective program  cf  CSO
abatement  was developed using the swirl concentrator  technology
at  these  locations.  A non-linear optimization model  based  on
swirl concentrator suspended solids removal was used as an aid to
identifying optimal abatement configurations.
                               2.10

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(40)    Disinfection using sequential  chlorine/chlorine  dioxide
dosage  rates of 8 ppm/2 ppm for a total contact of 2 minutes  is
recommended,  as  required to maintain bacteria pollution in  the
Saginaw River at acceptable levels and would tend to minimize the
production of carcinogenic materials associated with conventional
chlorine application.

(41)    The  design maximum solids loading capacity at  the  WWTP
plant  is  estimated  tc  be exceeded  during  high  rain  events
(greater  than  0.5  inch rain) if the  entire  systemwide  swirl
concentrator  program  is implemented.   A swirl degritter  would
then  be   recommended at the Weiss Street treatment  complex  tc
handle solids generated from the swirl treatment units pending  a
more detailed hydraulic investigation of the crossover as well as
the grit removal capacity during high  flows at the WWTF. Removal
of  solids at Weiss Street using the swirl degritter (followed by
landfill  disposal) will maintain acceptable solids  loadings  at
the  WWTP  and  will eliminate any potential problem  of   solids
deposition at the river crossing.


F.  Cost of the Recommended Facility Plan (Future Actions)

(42)   Cost  estimates  are based on 1985. dollars (ENR  =  4500).
Capital  costs  for  the  recommended CSO  Facility  program  are
estimated  to  be  23.7  million  dollars.  The  recommended  CSO
Facility  plan  would  use  swirl  concentrator/swirl   degritter
technology,  and  the BMP in-line storage and system modification
plan.  The  costs do not include the presently operating  Hancock
Street  CSO facility (capital cost of $10.4 million, ENR=450Q),  nor
the cost of land acquisition for the new swirl facilities.


G.   Effects of Facility Plan Implementation On River Quality
            (Exerpted from EDP Facility Plan Report (2))

(43)    Available   storm-related water quality  of  the  Saginaw
River includes limited past storm-related data, an extensive one-
dimensior.al h^drologic and ecological model of the river and bay,
and   recent  data  collected tc   characterize  the  runoff  and
impact.  These  date sources and  previous analyses were reviewed
and analyzed.

(44)    CSO  has been identified as a major contributor  of   the
dissolved  oxygen deficits in the Saginaw River following   storm
events.  Dissolved oxygen was reduced frcm above 6 mg/1 to as low
as  4 mg/1 as a result of CSO from a storm event with  0.83  inch
total accumulation with typical river flow conditions. Lnder more
critical  conditions,  the  dissolved oxygen  deficits  will   be
greater.


                               2.11

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(45)  Sediirent pollution has been  identified as a major  problem
in the Sacinaw River. CSC is a contributor to sediment pollution.

(46)   Suspended  materials have been identified as  contributors
to  dissolved oxygen deficits by reducing light  penetration  and
algal  productivity. Suspended solids also  contribute to aesthe-
tically objectionable turbidity. Suspended solids may be carriers
of other pollutants such as toxic materials and algal nutrients.

(47)   CSO   has  been  identified  as  a  source  of   aesthetic
pollutants  including  floatable pollutants and suspended  solids
that increase turbidity.

(48)   A dissolved oxygen model based or. the classical  Streeter-
Phelps  equation was determined sufficient to model CSO   dissol-
ved oxygen impacts  on  the Saginaw River.  DO levels as low as 4
mg/1 have been predicted to be coir mo n as a result of CSO loadings.

(49)   Simulation  models  have been successfully  developed  and
calibrated  fcr predicting the operation of the Saginaw  combined
sewer  system  and  the Saginaw  River  water  quality  response.
Overflew  volumes  and quality in terms of suspended  solids  and
five  day  BOD  can be predicted on an  hourly  basis.  Dissolved
oxygen  in the Saginaw River can be predicted in response to  CSO
pollutant  loadings.  The  capability of  testing  CSO  abatement
alternatives has been incorporated in the  models.

(50)   Nonpoint  source  loadings resulting from  combined  sewer
overflows in the City of Saginaw are significant contributions to
pollutant  loadings  to the Saginaw  River.   CSO  loadings  were
estimated  using  a long terrr simulation model to  be   8,600,000
pounds  TSS  and 2,300,000  pounds BOD for the calendar  year  of
1977 consisting of  78 storns creating overflows.

(51)    Implementation  of the recommended CSO Facility   program
would raise the dissolved oxygen level from 3.2 mg/1 to 4.4  mg/1
for  a 1.9 inch storm  impacting July 8,  1980 river  conditions.
Dissolved  oxygen gains for less intense events would be smaller.
Significant  protection from excessive dissolved oxygen  deficits
would  occur  primarily for severe rain events at  or  above-.  0.8
inches  of  total accumulation with significant  rain  intensity.

(52)  The recommended control plan would substantially  eliminate
the  sediment  pollution  component caused  by   CSO.  Settleable
solids wou]d be over 80% reduced.

(53)    Over  half  the  wet  weather  related  suspended  solids
emmisions  would be eliminated.  The  suspended solids  reduction
will aid  dissolved oxygen levels by increasing light penetration
and  subsequently  alc,al  productivity,  and  by  lowering  algal
                               2.12

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nutrients  associated  with suspended solids.  Lowered  turbidity
levels  will  also  increase the aesthetic appeal  of  the  river
water.

(54)   Pollutants that can be associated with the removed  solids
in  CSO  will alsc be; removed.  These  pollutants  include  toxic
pollutants such as heavy metals and algal nutrients.

(55)   Aesthetic:  qualities of the river  will  be  significantly
improved  increasing the enjoyment of the river for  recreational
purposes. Floatables  and  suspended materials will be reduced.
                               2.13

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                            CHAPTER 3

                         RECOMMENDATIONS
          The  conclusions  stated  in Chapter 2 of  this  report
clearly indicate the effective use of elements of the BMP plan in
reducing CSO to the Saginaw River.   To date,  the entire BMP plan
has  not  been scheduled for completion as the  the  funding  for
implementation   of  complete  facility  plan   elements  is   not
available.   In  addition,  the 1984 investigation of the  system
hydraulics  during  the construction and post   evaluation  phases
indicated  areas of system operation where additional review  and
"fine-tuning"  may  be necessary in the future due  to  hydraulic
changes  induced  by implemented elements cf the  BMP  plan.  The
following recommendations of this study for the City of Sagiraw's
sewerage system are presented in order cf importance:

1)         The reduced BMP plan included modification of only 12
of 35 regulator chambers.    All other regulation chambers should
be  updated  to  include new vortex flow regulating  devices  and
appurtenances designed to maximize storage and minimize bypass to
the river.

2)         One of 14 proposed upstream in-line  storage  chambers
was completed.   Facilities for the remaining  locations should be
designed and constructed.   The recommended order of priority for
implementation of these locations is as follows:

                   In-line Storage Priority List

                   1.   River & Cambrey Streets
                   2.   Birch & Harris Streets
                   3.   Gratiot & Michigan Avenue
                   4.   Cass & Woodbridge Streets
                   5.   Hamilton & Williams Streets
                   6.   Union Avenue  & Delaware Street
                   7.   Jackson & Mason Streets
                   8.   MacKinaw Street & Michigan Avenue
                   9.   Troy & Boxwood Streets
                  10.   17th & Perkins Streets
                  11.   14th & Norir.an Streets
                  12.   Hayes Street  & Michigan Avenue
                  13.   Weiss & Delaware Streets

          The  in-line  storage  facility at  Weiss  Street   and
Delaware  Street should be completed as part of the CSO treatment
facility implementation at the Weiss Street Pump Station.
                                301

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 3)         Existing gate opening and pump "turn-on" sequencing at
 the  Hancock Street Pump Station should be reviewed to  ascertain
 whether  the  operation  is  optimal.   The  existing  monitoring
 equipment   at  the  Hancock  Street  Pump  Station   should   be
 upgraded,  if  necessary,  for the purpose of monitoring  station
 operation in compliance with optimization recommendations.

 4)         The pump initialization equipment at  the Weiss   Street
 Pump  Station  should  be reviewed to  optimize   turn-on/shut-off
 elevations  and   to  ascertain  whether  supplemental   operating
 controls are necessary due to the weir modification performed   as
 part of reduced BMP plan.

 5)         The operations of the Hancock Street  Facility and  the
 Weiss  Street Pump Station should be reviewed to ensure  that  the
 Hancock Street Station operates prior to the Weiss  Street Station
 during  a  storm event.    Detention   storage/treatment   currently
 available  at  Hancock  Street will  thus  be  utilized   prior   to
 untreated bypass at Weiss Street (for areawide storm events).

 6)         The  CSO  control facility for  the Weiss   Street  area
 should be implemented as overflows at this  location  are  still  the
 dominant  source  of wet weather pollutant  load   to   the  Saginaw
 River.

 7)        Under  extremely high rate  conditions,   wet  weather flow
 pumped to the WWTP grit  chamber is split with partial overflow  to
 the    WWTP bypass.   Overflow commences at  a  total rate less  than
 the  existing  WWPT flow-through capacity.  Possible replacement  of
 the   WWTP  overflow  bypass   weirs with  sluice  gates  may   allow
 initial  storm flow containing "first  flush" materials to pass   to
 the   aeration basins  for storage.    Later cleaner flows would   be
 bypassed,   if  necessary  due  to full  basin conditions,  by opening
 of the  sluice gates.

 8)       Currently   potential  pump cavitation  conditions  prevent
 maintaining WWTP wet well  levels at  the  initial design elevation.
 Although  the  City WWTP personnel maintain maximum  wet  weather
 throughput    whenever  possible  to   the  WWTP,   the  elevations
 currently  maintained,   reduce   the   hydraulic  capacity  of  the
 interceptor   system  during  major  events  causing  overflow  at
 upstream pump stations.   Hydraulic conditions of influent  pump
 intakes  at the WWTP wet  well should be investigated to  determine
 if baffles,   spoilers or  intake vanes could reduce cavitation and
allow  lower  operating   levels,  and result in  lesser  upstream
overflow magnitudes.

9)         Evaluation of  the WWTP layout for potential  hydrualic
bottlenecks  at maximum capacity should be  performed.   In   some
areas,  piping  systems are believed to be the limiting factor  in


                               3.2

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plant  operations  as opposed to the  performance  capability  of
treatment processes.  This investigation should ascertain whether
any  changes to increase flow rate would improve overall  WWTP wet
weather  capacity/reduce  bypass  and whether the  water   quality
benefits that may result would be cost effective.
                              3.3

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                            CHAPTER 4

         DESCRIPTION OF CITY OP SAGINAW SEWERAGE SYSTEM


4.1 Descriptive Background Material

          Saginaw  is  located  in the eastern  part  of  central
Michigan north of Detroit,  as shown in Figure 1.1.  The  Saginaw
River  is  a  short section of a major drainage area  leading  to
Saginaw Bay,  Lake Huron.  Saginaw is located at the start  of  the
river  and  on both banks for about a  five  mile  stretch.    The
Tittabawassee,  Shiawassee  and Cass Rivers are tributary to   the
Saginaw  River just upstream of the City.  The topography of   the
area  is flat,  and the elevation is approximately 600  ft.    The
Saginaw River divides the 10,437 acre area of the City of Saginaw
into  an East Side section having an area of 5,634 acres,   and a
West  Side  section of 4,803 acres.   The Saginaw River  drainage
basin above the City has an area of 6,200 sq.  mi.   The  average
daily  stream flow is estimated at 10,000 cfs with miniurnurn daily
flow of 500 cfs.  Flood flows of 62,000 cfs have been observed.

          The   entire   river   is  only about   22  miles   in
length   and  has  a  gradient  of about one inch   per mile   or
less  along  its entire  length.  The  river  is used extensively
as    a commercial waterway,   and it is  regularly dredged   by
the Corps  of Engineers to maintain  the  shipping  channel.   The
depth   of  this channel ranges  from 16.5  feet  at Green  Point
to 27   feet  at  river mouth.  There  are  five dredged  turning
basins  along  the  length of  the  river.  The   width  of   the
Saginaw  River  ranges   from 365  feet   at   Green   Point   to
1,700  feet  near    the Middle   Grounds.  Winds   significantly
affect  the  water  level in   Saginaw  Bay  and   in  turn this
water  level   strongly  affects the direction of   flow  in   the
Saginaw River.  Sustained southwesterly   winds lower  the  level
of    the  bay   and temporarily  increase the  river's  velocity
discharge.  Sustained  northeasterly winds,  on the  other  hand,
raise the  water level  in the bay and  decrease stream   veloci-
ty and discharge,  often  reversing   the  flow   of the  river.

          The area which is surrounded by the Great Lakes,  has a
quasi-marine environment.   Temperatures stay warmer later  in  the
year and cooler during the spring because of the influence  of  the
large  water  masses.   Saginaw1s normal annual precipitation  is
about  28.55  in.,  over  50% of which falls  during  the   summer
between March and September.   Summer storms occur as showers  and
thunderstorms.   Most  of the winter precipitation is snow  which
accumulates until the spring thaw.   Beginning in March or  April,
melting  snow  combined with rainfall can produce  high  overflow
volumes  and  increased discharge of pollutant  loadings  to   the


                                4.1

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river.   Most  of  the  storms  that occur  are  of  low  average
intensity.   Over  90%  of  the time,  the average  intensity  of
rainfall which produces runoff is less that 0.10 in./h.

          The  City  of  Saginaw is serviced by a combined  sewer
system.  Combined  sewer  overflows  during rain  events  are   a
significant  contributor  of pollutants  to  the  Saginaw  River.
Overflows  may  occur at 35 regulator chambers  during  increased
flow  events.  Overflows may also occur at the five pump stations
designed  to  relieve  the  system  during  flooding  conditions.
Overflows  occur when the flow in the combined collection  system
is  greater  than three to six times the dry  weather  flow  rate
depending upon the regulator location.  It is estimated that over
60 overflows occur per year.

          Impacts on the Saginaw River from CSO include dissolved
oxygen  depletion  in  the downstream segments of the  river  and
increased bacteria levels.  Public health impacts can be of equal
importance  to the organic loading to the river,  because of  the
high  level  of micro-organisms associated  with  combined  sewer
overflows.   Suspended  solids and floatable material also create
visual  problems  and  further aggrevate the  continual  need  to
dredge the channel for maintaining ccmmercial navigation patterns.


4 .2 Sewerage Sy_sitem Overview

          Saginaw   is  serviced by  a combined sewerage  system.
The  overall service area is  depicted in Figure  4.1.  Catchment
area boundaries of individual subsystems considered in this study
along  with proximate location of regulators are shown  in Figure
4.2.
          An  intercepting  sewer shown in Figure 4.3 runs  along
both banks of the Saginaw River,  eventually joining on the  East
Side  and  running to an advanced secondary WWTP.  The West  Side
interceptor  crosses the river at Weiss Street to join  the  East
Side  Interceptor,  which continues to the WWTP at the  northeast
limits of the City. A portion of the Saginaw township outside the
city  limits  is also serviced by the combined sewer system  with
dry  weather flow joining the Saginaw intercepting  sewer  system
and  eventually treated at the  WWTF.  There are also a number of
areas  within Saginaw whose stormwater runoff is not diverted  to
the  Saginaw  combined  sewer system.  State  Highway  1-75  with
downtown  connectors covers an area of about 100 acres and has its
own drainage system.  A large newly developed residential area in
the  southeast  section  of  the  City  has  a  separated   storm
sewer/sanitary   sewer  system.   A  number  of  industrial   and
commercial  areas near the river are drained to the river and are
independent of the combined sewer system.
                               4.2

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                                                                                             EXISTING PUMPING STATION


A                                                                                             EXISTING,
                                                                                             CHAMBER


                                                                                             EXISTING  INTERCEPTOR
                   EXISTING  COMBINED  SEWER
                    AND OVERFLOW(TYPICAL)
                                                                                      	CITY LIMITS
                                                                                             LIMITS OF SE^V'CE AREA
                                                                                             OUTSIDE CITY LIMITS
                                       HANCOCK ST PUMPING
                                             STATION
      WEBBER ST PUMPING
           STATION
WEISS ST PUMPING
                          EMERSON 51 PUMPING
                                STATION
                                                                                                    EXISTING
                                                                                                   WASTE
                                                            FOURTEENTH 5T
                                                           PUMPING STATION
Figure   4. i  Soginow combined sewer service area.

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*>.
                                                                                  LEGEND:
A                                                                                       EXISTING REGULATION
                                                                                       CHAMBER
                                                                                       EXISTING INTERCEPTOR
                                                                                  --- CITY LIMITS
                                                                                       LIMITS OF SERVICE AREA
                                                                                       OUTSIDE CITY LIMITS

                                                                                       DRAINAGE AREA
                                                                                       BOUNDARY
                                                  Y/v   i.
           Figure  4 -2    Saginaw regulator catchment areas.

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                                                                    SCALE (theuiondi of r«tt)


                                                                 O   I   2   3
Sewoge pumping station
and treatment plant
                              Weiss St.
                              pumping station
EAST SIDE INTERCEPTOR
WEST SIDE INTERCEPTOR
                                                                                                          Webhe,
                                                                                                          pumping
                                                                                                          station
                                                                    Emerson St.
                                                                    pumping station
• Hancock St.
 pumping station
    Figure  4.3General plan of interceptor sewer system.

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         Because  many of the sewers are below flood river stage,
the  problem  of collecting sewage  involves  stormwater  pumping
during periods of high river level.   Typically, flood stages can
exist  for  periods up to two weeks,  during which time  rainfall
producing runoff can  occur.   Flood stages of the Saginaw  River
have  all  occurred during the months of March,  April  and  May.
During  flood river levels,  storm flows will discharge over  the
regulator chamber weirs into the intercepting system.   Backwater
gates  will  prevent  discharge  of flood river  water  into  the
sewerage system.

         Flood pumping stations located at Webber,  Emerson,  and
Fourteenth  Streets  on  the East Side,  and  Hancock  and  Weiss
Streets on the West Side, pump either from the interceptor system
or  from tributary lines directly before the interceptor  system.
Stormwater  and  flood pumping stations are of  circular  caisson
type  construction.   The  station at Hancock  Street  has  eight
electric-driven  pumps,  and  the one at Weiss Street  has  three
electric-driven  pumps.   On the East Side the station at  Webber
Street  has  three  electric-driven  pumps;  the  Emerson  Street
Station has six gasoline engine-driven pumps;  and the Fourteenth
Street  Station has three electric-driven pumps.   All pumps  are
similar, each having a fixed capacity of 100 cfs, those at Webber
Street  and  Fourteenth  Street operate at 15-ft  head,  and  the
remainder at 28-ft head.

         The  interceptor system operates at hydraulic  gradients
independent  of  the  invert grade and has  sufficient  slope  to
convey  the stormwater laterally to the  pumping  stations.   The
intercepting  sewers  thus serve the dual purpose  of  collecting
sewage  and carrying storm flows during flood river levels.   The
interceptor  system consists of tunnel sewers ranging from 42  to
78   inches in diameter.   The tunnels are approximately 40  feet
below ground level.


4.3 WWTP Details

          The City of Saginaw operates a 32.7 mgd secondary  WWTP
located on the east bank of the Saginaw  River near the  Saginaw-
Buena Vista line. The plant receives wastewatwer from the City of
Saginaw,   portions   of  Saginaw,    Spaulding  and   Bridgeport
Townships,  and from a portion of  Buena Vista Township including
the  Saginaw Steering Gear complex.  The City of Saginaw1s  sewer
system  conveys stormwater as  well as municipal and   industrial
wastewater.  In the early 1970's, secondary  treatment facilities
were added to the  existing primary plant. By 1975 the  secondary
facilities  were operational and in 1976 phosphorous  removal  was
also provided.
                                 406

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          Wastewater  enters the plant in a  72-inch  interceptor
sewer.  After  screening  and  grit removal,  the  wastewater  is
settled  in four primary sedimentation  tanks.  Primary  effluent
passes  into  the  conventional  activated  sludge  system  where
ferrous   sulfate  or  waste  pickle  liquor  can  be  added  for
phosphorus  removal  as  necessary  to  meet  effluent  discharge
standards.  Final effluent is chlorinated before discharge to the
Saginaw River.

          The  current NPDES permit for the  plant requires  that
monthly  average  BOD  and suspended  solids  concentrations  not
exceed 25 and  30 mg/Lf  respectively. Effluent total phosphorous
concentrations must be less than 1 mg/L. In addition,  the permit
calls  for  fecal coliform concentrations  less than 200 per  100
ml, and  an effluent pH between 6.5 and 9.0.

          A review of plant operating records indicates that  the
monthly  average  BOD  and  suspended solids  concentrations  are
consistently  below  10-15 mg/L and thus in compliance  with  the
NPDES   permit.

          Prior  to  1968  sewage discharging from  the  City  of
Saginaw was given primary treatment with  chlorination.   Average
annual  design rate was 32 cfs with a peak hourly capacity of  80
cfs.  Wet well pumping capacity at the headworks totaled J.82 cfs.
Overflow  weir settings at the regulators in the system were  set
to  dischage  untreated  sewage mixed with  stormwater  at  rates
exceeding five times the dry weather flow.  Regulator weir levels
have  been adjusted several times over the years in an effort  to
minimize the amount of untreated sewage.

          The  primary  plant  was  then  upgraded  to  secondary
treatment including biological activated sludge with  phosphorous
removal.   Although  the modified plant is designed for a nominal
flow  of  50 cfs and an estimated maximum flow of  128  cfs,  the
secondary  treatment unit operations are sized for about 160  cfs
discharge.   All  storm flows entering the WWTP in excess of  108
cfs  are  split at the grit chamber with  bypass  receiving  only
chlorination.  Currently,   bypass  beyond  108 cfs occurs  at   a
spillover  weir such that increasing influent flow rates  results
in  simultaneous  increased flow through the plant and  increased
bypass. The average dry weather flow is  about 32 cfs.

          All  flow  beyond  the grit  chambers  receive  primary
treatment.  There are four secondary aeration tanks following the
primary  clarifiers.   Normally two aeration basins are used  for
dry  weather flow and wet weather discharges up to about 84  cfs.
The two other aeration basins are used as storage for wet weather
discharges  above  84  cfs.   If these basins  are  filled,  flow
through conditions result.   The storage contents after an  event
                                4.7

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 (or  when   influent  rate  significantly decreases)  of  these  two
 tanks  containing  primary treated wastes  (plus  some  additional
 detention)  then receive full primary/secondary treatment as these
 volumes  are pumped  back  to the headworks.   Any flows beyond  84
 cfs  and  in excess  of the two aeration tank storage volume  will
 receive  primary  treatment,  limited aeration  with  phosphorous
 removal  treatment (if necessary),  secondary  clarification  and
 disinfection.
4.4  Regulator Chambers

         The  regulator  chambers of interest  are  those  points
controlling  discharge to the interceptor or to the  river,  from
each  of  the  tributary catchment areas.  The  simulation  model
described  in  Chapter  6  incorporates the  operation  of   each
regulator  in  the  system.   Physical  operational  details  and
dimensions  were  required  such as orifice  underflow  openings,
weir  heights  and float operations.  Chamber  measurements  were
compared  with  details given in the system  plans,  and  missing
values filled-in from the plans.  If discrepencies occurred,  the
EDP  field measured values were used in the analysis of regulator
operation.   Regulator  details  and  modification  details   are
presented in Chapter 7.


4.5 Hancock Street Storage/Treatment Facility

          In  1977  the Hancock Street Flood Pumping Station  was
modified  to  include a 3.6 MG  storage/treatment  facility.  The
existing pumping station was upgraded to include  electric-driven
pumps.  A  multi-purpose underground storage/treatment   facility
with  above  ground municipal parking was  constructed.   In-line
storage  potential of the combined sewers in the  Hancock  Street
area was increased by modifying the existing static regulators in
the  system.   Modifications to the regulators included replacing
the tide gates at the outfall with motor-operated sluice gates to
increase  the  maximum storage capacity of  the  system.   Before
modification,  only dry-weather flows and some wet-weather  flows
were diverted to the interceptor during normal river stages; now,
significant flows are detained and diverted to the interceptor.

          Over   the   last  several  years  severe   operational
difficulties  during  intense rainstorms have arisen due  to  the
motor-operated sluice gates in the Hancock Street catchment area.
The  sluice gates  open or close in a finite period of  time.   If
the gates do not open to permit rapidly developing peak flows   to
overflow, then severe surcharge problems will result.  Replacement
of these gates with fixed-opening weir structures was  included in
                               4.8

-------
the  construction  project completed as part of the  partial  BMP
plan.

          During the storm events, combined flows diverted to the
interceptor by the regulators activate the Hancock Street pumping
station  as the interceptor flow level increases.   Sluice  gates
between  the  interceptor and the pumping station wet  well  open
automatically  and pumping is sequentially controlled by  sensing
the   wet   well   water   elevations.     All   flows   to   the
storage/treatment  basins  are  pumped.    During  extreme  river
flooding,  the  system  will revert back to operation as a  flood
control pumping station,  with flows to the basin being  diverted
to the river once the system has been filled to capacity.

          Combined  flows  pumped to the Hancock Street  storage/
treatment facilities sequentially fill a series of paired basins.
The facilities operate under two types of storm flow conditions:

          1. For certain flow volume storm events, the flow
             will be  captured  and  totally  stored,  with
             subsequent   release  to  the  interceptor  as
             capacity becomes available.

          2. For  storm  events producing flow that  exceeds
             the  basin  storage capacity,  the system  will
             store   and   treat   the  combined   flow   by
             sedimentation.  The  facility  is  designed  to
             disinfect  the overflow before discharge to the
             river.
4.6  Dry Weather Flow Characteristics

          Formulation  of  the basis of design  for  CSO   control
facilities required input of data, with regard to the quality and
quantity  of  dry  weather flows,  so that  network  models   (See
Chapter  6) could be calibrated.  This section summarizes  efforts
to determine the quantity of dry weather flows at various  points
in the City of Saginaw   system.  Dry weather  flow characteristics
at the Saginaw WWTP are  reviewed in section 4.6.1. Results of EDP
measurement program are  given in section 4.6.2.  Estimates of dry
weather flows per catchment area are given in section 4.6.3.


4.6.1 WWTP Dry Weather Flows

         Dry  weather  flows were investigated at  the  treatment
plant  and  throughout   the  system  to  establish   a   basis  for
simulating  catchment  area  dry weather  flows.  The   simulation
program described in Chapter 6 required estimates of dry   weather



                                4.9

-------
sewage  contributions per catchment area for spring  infiltration
(non-rainfall) conditions as well as for non-spring, non-rainfall
periods.  These two estimates were necessary since the simulation
model was geared to investigate rainfall/runoff conditions over a
calendar  year.   The  WWTP flow analysis was conducted  for  the
period  of 1978-1979.  Flows at the plant were separated  between
dry days and wet days,  and averaged (Table 4-1).  The period was
further  divided  between spring (April-June) and the other  nine
months  to account for high groundwater infiltration  conditions.
The average dry day,  non-spring flow was taken as the  long-term
dry  weather  flow  average  for the  year  including  industrial
contributions.  The  difference  between the dry  day  non-spring
average and the dry day spring average, 5.4 cfs,  was considered a
rough estimate of spring infiltration.


4.6.2 EDP Field Discharge Measurements

         During   October  of  1979,   EDP  conducted   a   field
investigation,  including sewer system flow measurements.   Flows
were  measured  both for rain conditions caused by a small  storm
that occurred during the investigation period and for dry weather
conditions throughout the system. Dry weather flows were measured
at  a number of the more important points throughout the  system,
with many of the measurements repeated at different times of  the
day for verification.   The measured values were used to estimate
flows  at  points where measurements were lacking   to develop  a
complete distribution of dry weather flows throughout the system.
Yield factors for known areas were calculated using the  measured
flow  values and the corresponding catchment areas.  For  unknown
neighboring  areas  similar land use yield factors were  used  to
generate  dry weather flow predictions based on catchment  areas.
All  measured  dry  weather flows were checked  using  this  same
procedure  of  comparing  similar  or  neighboring  areas'  yield
factors.

         Accumulations  of both measured and predicted values  in
the   interceptor  were  compared  to  measured  values  in   the
interceptor  to  check  for closure of the various  flow  values.
These  results  are  presented  in  Table  4.2.  From  the  field
inspection  program two areas of possible significant  industrial
contribution  were identified,  the foundry in the Fraser  Street
area  on the west Side,  and the lower industrialized  area  just
south  of  the WWTP on the East  Side.  The  differences  between
downstream  flow  measurements and upstream flow predictions  and
measurements  were used to estimate the industrial  contributions
at   these  two  points.   A  large  industrial  contribution  of
approximately 8.2 cfs   was noted for the West Side Fraser area .
A  smaller  contribution of 4.3 cfs was calculated for  the  East
Side   industrial  area.     Using  the  above  industrial   flow


                               4010

-------
                           TABLE  4.1
                   WWTP FLOWS, 1978-1979
Seasonal  Periods
                Flow
         Daily Average (cfs)
All Events     Uet Days	Dry Days
Spring
(April-June)
   46.9
   85.6*
65.5
83.8*
42.8
86.2*
Non-Spring
(Jan-March
  & July-Dec)
   40.4
   86.8*
56.0
86.5*
37.4
88.3*
All  Seasons
   42.2
   86.4*
59.8
85.5*
39.4
87.8*
*   BOD Removals
                            4.11

-------
TABLE 4.2 SYSTEM DISTRIBUTION OF  DRY  WEATHER FLOW  (cfs)
Meas. Pre- Accum-
Flow dieted ulative
Weber (
Birch (
Holland (
Atwater I
McCoskry (
Hoi den (
Emerson (
Hoyt (
Thompson (
Millard (
Janes (
Federal (
Genesee (
Johnson <
Fitzhugh (
Carlisle <
) 1.72
) 1.93
) 0.80
| 3.50 3.65
) 1.01
) 0.28
) 0.46
) 0.06
> 1.33
> 0.12
) 0.38
) 0.44
) 0.58
) 0.08
) 0.31
) 0.72
Washingtonli 9.40 9.56
First <

C) 0.37
Meas. Pre- Accum-
cfs dieted ulative
0.91 <
8.30 t
9.20 9.20 <
0.24 <
C
(
1.41 (
(
12.60 11.4 |j
.05 (
.31 <
.24 (
C
.24 (
.45 C
) Fraser
j Industrial
) Dearborn
llee
) Mackinaw
) Van Buren
)Cass
) Adams
> Court
] Hancock
) Ames
) Hayes
)Throop
)Miller
) Remington
) Genesee
.14 Cronk
12.70 1
15.9CW
3.2
1 Carroll ton
Weiss
L Weiss
Fifth       25.50
16th Street  2.60
14th Street
Industrial
                  25.50
          0.41
          4.30
-e-
•e-
WWTP
32.5
Pump Stations
Points on Interceptor
Regulator Points
 Before Interceptor
Industrial
                                    4.12

-------
estimates,  a reasonable flow balance was achieved throughout the
system. Measured flow values at various points in the interceptor
and  at the WWTP closely matched the accumulated dry weather  and
industrial contributions developed through the analysis of  field
inspection data.


4.6.3 Simulation Model Dry Weather Flows

         As  the  field inspection program occurred  in  October,
1979  the  dry  weather  flow analysis  presented  in  Table  4.2
represents  lower  than  average flow conditions typical  of  the
fall. These results   (excluding the industrial contribution) were
scaled upwards to match the long-term average dry weather flow as
calculated at the WWTP  (See Table 4.1).  The ratio of WWTP  long-
term  average  flow   (non-spring)  to  the  October,  1979  field
program   results  (See Table 4.1) were used to scale all the  dry
weather   flow  values throughout the system.  The same ratio  was
used  with the spring WWTP flow average  to complete the  spring-
time distribution.  The results are summarized in Table 4.3.  The
non-spring and spring dry weather sewage estimates per  catchment
area were then used as inputs in the simulation model.


4.7      Wet Weather Flow Considerations

          Wet  weather  flows in combined sewers consist  of  dry
weather   (sanitary) flow, infiltration, and storm-induced runoff.
The   storm-induced   runoff   includes   flows   from   building
connections,  such as roof leaders;  cellar,  yard and foundation
drains;   catch basins;  storm sewers;  and surface runoff through
manholes.  This  runoff  is collected and  transported  to  trunk
sewers  that  convey  flow  to  various  diversion  points.   The
diversion  points  regulate flow entering  interceptor  conduits,
which  carry  the flow to treatment facilities.  During  a  storm
event,    that   portion  of  the  flow  which  cannot  enter  the
interceptor,  overflows  at  the  regulator  connections  to  the
Saginaw River.

          Various  data sources and analyses used to assemble the
wet  weather  predictive  features of the  simulation  model  are
described in this section.  A discussion of rainfall analysis  is
presented  in  Section 4.7.1.  Details of the 31 catchment  areas
used  in  the modeling analysis are presented in  Section   4.7.2.
Runoff  parameters  for  the  catchment areas  are  presented  in
Section   4.7.3.  Details of the stormwater pumping  stations  are
discussed in Section 4.7.4.
                                4013

-------
 TABLE 4.3  SIMULATION MODEL DRY WEATHER FLOWS (cfs)
Oct.
Field
Analy.
Weber (
Birch (
Holland (
McCoskry <
Hoi den (
Emerson (
Emerson 0
Hoyt (
Thompson (
Mi Hard (
Janes <
Federal (
Genesee (
Johnson <
Fitzhugh (
Carlisle (
First (
) 1.72
) 1.93
) 0.08
) 1.01
) 0.28
) 0.46
]
) 0.06
) 1.33
) 0.12
) 0.38
) 0.44
) 0.58
) 0.08
) 0.31
) 0.72
) 0.37
Model
Non- 	
Spring Spring
2.12
2.37
0.10
1.24
0.34
0.57.

0.07
1.64
(X.15-
0.47-
0.54
0,7-1,
O.-IO*
0.38
0.86
0.46
2.59
2.91
0.12
1.53
0.42
0.69

0.09
2.01
0.18
0.57
0.66
0.86
0.12
0.47
1.05
0.56
Oct.
Field
Analy.
0.91
8.20
0
0.24
0
0
1.41
0.03

0.05
0.27
0.21
0.03
0.21
0.39
0.12
3.20
Non-
Spring
1.12
8.20
0
0.29
0
0
1.73
0.04

0.06
0.33
0.26
0.03
0.26
0.48
0.15
3.94
Model
Spring
1.20 <
8.20 (
0 (
0.36 (
0 (
0 (
2.13 (
0.05 (
(i
0.07 (
0.41 (
0.32 (
0.04 (
0.32 (
0.59 (
0.18 <
r
I
4.83 (

) Fraser
) Industrial
) Dearborn
) Mackinaw
) Van Buren
) Cass
) Adams
) Court
] Hancock
) Ames
) Hayes
) Throop
) Miller
) Remington
) Genesee
) Cronk
] Weiss
) Weiss
16th Street  2.60
14th Street  0.41
Industrial   4.30
WWTP        32.5


WWTP
(•)  Pump Stations
O  Regulators
                                      4.14

-------
4.7.1  Rainfall Analysis

         Rainfall  records  were required as data input  for  the
computer  simulation  work.   A  ten year period  (1969-1978)  of
hourly  recorded  rainfall  records at a number  of  stations  in
proximity  to  Saginaw were acquired from  the  National  Weather
Service.  Daily rainfall records recorded at the Saginaw WWTP and
the  Tri-City  airport   (near Saginaw)  were  also  acquired  and
examined  in  conjunction  with  the  hourly  analysis.    Hourly
rainfall information are collected in Saginaw.

         Pour  stations  recording hourly  rainfall  values  were
considered including Vassar - 20 miles east of Saginaw; Sebewaing
and   Beaverton   - over  30  miles  northwest   and   northeast,
respectively;  and  Stanton - 50 miles west of Saginaw.  Rainfall
data  collected at Vassar was selected for use in this study  due
to  its proximity to Saginaw,  and due to the lack of  any  major
geographical  features   that  may render  Saginaw  rain  patterns
substantially  dissimilar from Vassar rain  patterns.   Sebewaing
was  not  selected  due  to its location on Saginaw  Bay  and  the
likelihood  of local weather anomalies  (discussed further below).
Stanton  and Beaverton were not considered since their  distances
from Saginaw are greater than Vassar.

           Standard  procedures were followed to analyze the  ten
year  period  storm intensities and frequencies,  and  for  total
annual  rainfall.   A  scatter diagram was developed  to  compare
Saginaw  rainfall  as recorded daily at the WWTP  to  the  Vassar
rainfall records (See Figure 4.4). Distinct events were discerned
from the Saginaw records using a decision rule of at least twenty
four  hours  of low or no precipitation between major rain  days.
Rainfall  was totalled for the resulting periods and compared  to
the  totals for the corresponding periods in the Vassar  records.
All  individual  events  for a period between 1975 and  1978  were
plotted. Points lying further from the 45 degree equivalence line
were noted to be primarily spring events when local variations in
precipitation  are  more likely.  The scatter  diagram  shown  in
Figure  4.4 suggests a reasonably good comparison between the two
rain gages.  Similarity  in annual rainfall totals given in  Table
4.4  for  Vassar,  Sebewaing and the Tri-City Airport in  Saginaw
further support this conclusion from the scatter diagram.

         Since the prior CSO management study  (1) in the  Saginaw
area  had  used  rainfall  records at Sebewaing as the  basis  for
modeling  Saginaw rainfall,  Sebewaing  rainfall  characteristics
were    compared   to  Vassar  and   Tri-City   Airport   rainfall
characteristics.  The  cumulative rainfall of the one-year design
storm used to size the seven detention basins in the prior  study
equalled 1.9 inches of rainfall.
                                4.15

-------
                                  T
                                  1.6
    I     1    I
)         1.2

Vassar (rainfall in inches)
T
2.0
Figure  4-4  Comparison of storm events-
             Saginaw vs. Vassar -1975 to 1978.
T
Z4
                       4.16

-------
                                TABLE 4.4

                   COMPARISON OF ANNUAL RAINFALL TOTALS

YEAR*
1956 - 1965
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
ANNUAL
Vassar
N.A.
22.12
34.41
22.09*
34.44
28.58
28.00
36.00
35.50
33.00
21.00 +
RAINFALL (INCHES)
Sebewaing
25.35**
23.09
26.61
17.54***
24.06
25.11
25.90
25.92
22.18
26.20
16.28 +

Tri-City Airport
N.A.
20.14
N.A.
N.A.
N.A.
N.A.
N.A
N.A.
30.05
29.33
20.97 +
*   Calendar year
**  Computed , average per year
*** Missing November
+   Missing December

    N.A. - not available
                                4.17

-------
         Annual rainfall totals given in Table 4.4  suggest  that
Sebewaing  (for  a different ten year period) had  received  less
total rainfall than Saginaw and Vassar during the ten year period
analyzed  in this report.   A frequency plot comparison shown  in
Figure  4.5 of Vassar rainfall (1969-1978) to the plots  prepared
for  Sebewaing  (1956-1965)  in the previous study  (1)  and  for
Sebewaing  (1969 - 1977) in this study verify the differences  in
rainfall exhibited by the annual results given in Table 4.4.

          It  is  interesting to note that  the  one-year  design
storm  of  1.9  inches used in the design of the  Hancock  Street
facility derived from an analysis of Sebewaing data  (1956-1965).
The  one-year  design  storm  for the next  ten  year  period  at
Sebewaing equals 1.45 inches.  The  rainfall plot at Vassar indi-
cated that the storm with a recurrence interval of one year has  a
cumulative  volume of approximately two inches.    Using a strict
definition of 6 dry hours between events, an average of 67 events
per- year was calculated for the Vassar Station,  with an  average
of  0  .3  inches per event.  The average antecedent  dry  period
between rain events at Vassar was estimated to be four days.

          A full year rainfall period was used in the  simulation
modeling efforts.  A full year of overflow events would provide  a
better  assessment  of overall CSO control efficiencies  since   a
variety  of different storm intensities including  low  intensity
but high frequency events would be included.  The year of 1977 at
Vassar  was  selected for the model simulation runs.  The  annual
total rainfall was slightly above average.  It had numerous small
events,  yet  also contained several events in excess of the  one
year storm volume of 1.9 inches used in the prior study,  and the
one-year recurrence storm for the Vassar  Station.   The frequency
plot for 1977 is also shown in Figure 4.5.


4.7.2  Catchment Areas

         Catchment  areas were outlined for each of 31 regulators
but  one   minor area was eliminated and  was added  to  a  larger
tributary  area   (there are a total of 34 regulators)  while  two
other  areas have alternative overflow points depending on  river
conditions  and potential combined sewer  overflow points.   These
locations  and  associated  catchment  areas  are  summarized   in
schematic form in Table 4.5.  The areas were outlined on the City
sewer  map.  Divisions  between catchment areas  were  determined
primarily by review of  the sewer system  plans.   EDP  inspected  a
number  of points along catchment boundaries for further clarity.
These catchment areas are  roughly depicted on Figure  4.2.

         It was noted in delineating the  catchment areas that the
older  sewerage  system  had been upgraded by a number of   relief


                                4.18

-------
      12  -
      10  -
       8  -
I
       6  -
       4  -
       2  -
                       VOSMT Station
                       1969-1978
                       1969-1977
                                                   Sebewaing Station
                                             1956-1965
                                             Vossor Station 1977
           0.0
I
J.O
 I
2.0
 1
3.0
                                           Accumulated Rainfall per event (inches)

        Figure 4.5  Annual rainfall (accumulated)  cumulative frequency plot.

-------
TABLE  4.5
CATCHMENT AREA /RUNOFF COEFFICIENTS
Catchment    %
 Area (ac)   Imp.
                                     Catchment
                                     Area (ac)
                             Imp.
Webber (
Webber G
Birch (
Holland (
McCoskry (
Hoi den (
Emerson (
Emerson (j
Hoyt (
Thompson (
Mi Hard (
Janes (
Federal (
Genesee (
Johnson (
Fitzhugh (
Carlisle (

First (
)
] 1020
>
) 150
) 550
) 70
) 30
J
) 43
) 290
) 30
) 90
) 80
) 36
) 60
) 130
) 90

) 190

25

10
40
70
85

80
35
90
40
50
90
80
25
30

15

0.34

0.23
0.45
0.68
0.79

0.75
0.41
0.83
0.45
0.53
0.83
0.75
0.34
0.38

0.26
440
10
470
45
1030

45

160
240
20
170
470
380



2100
35
6C
60
95
40

95

50
90
90
70
30
30



20
0.41 (
0.60 (
0.60 <
0.86<
((
0.45 (
(
0.86 0
(
0.53 (
0.83(
0.83 (
0.68 (
0.38 <
0.38<


r
) Fraser
) Dearborn
) Mackinaw
) Van Buren
) Cass
) Adams
) Court
] Hancock
) Ames
) Hayes
) Throop
) Miller
) Remington
) Genesee
) Cronk


Weiss
ki r\
TSu w
0.30 Weiss
14th Street

16th Street
Z = Runoff coefficient
                                ® Pump Stations

                                O Regulators
                                   4.20

-------
systems  on both sides of the river meant to  provide  additional
capacity during storm events. The result was a complex network of
pipes and overlapping stormwater catchment areas.

         A  number of bifurcation points where new relief  sewers
connect into older systems caused uncertainty in how flow divides
at  these  points.  An  EDP field inspection  program  noted  dry
weather  flow  directions and also checked  diversion  weirs  not
noted  on the sewer plans.  A hydraulic analysis was performed to
estimate  the relative flows in different directions at  division
points  during  high flow events.  Dynamics  were  considered  if
obvious, otherwise flow was apportioned to the relevant catchment
areas using a Manning's equation formulation.  Fixed flow factors
were  computed assuming half-full flow conditions in the upstream
pipe  and  the  plan and profile slopes  of  the  two  downstream
receiving  conduits.   This approach was deemed suitable for  the
purposes  of dividing average hourly discharge in the  simulation
model.

          Bifurcation  estimates were prepared for the West  Side
intersection points at Brockway and Thurman,  Adams and Congress,
Houghton and Clinton,  State and Carolina,  Union and Woodbridge,
State  and Woodbridge/  Superior and Vermont,  W.  Remington  and
Harrison, State and McEwen; and on the East Side at Remington and
Alger,  Holland and Good, Hoyt and Sheridan, Weadock and Johnson,
and  Seventh  and Johnson.  The results were used to  divide  the
shared drainage areas between the competing regulators.

         There were also a few separated sewer areas not included
in the network,  particularly the area south of Webber Street and
the drainage system for the interstate highway.  Dry weather flow
from  all separated areas were included in the modeling  efforts.
Runoff  from  all separated areas draining directly to the  river
was not included in the modeling effort.


4.7.3  Runoff Coefficients

         Estimates   of  imperviousness  and  calculated   runoff
coefficients  for each of the catchment areas are  summarized  in
Table 4.5.  Estimates of imperviousness were prepared from aerial
photographs  of Saginaw.  Representative sections in a few of the
major  drainage  areas  were  analyzed  by  comparing  the  areas
occupied  by  housing and streets to open spaces,  to  arrive  at
estimates  for  percent  imperviousness.   These  estimates  were
compared to standard percent imperviousness factors for different
types of land use to check for reasonableness.  The 31  different
drainage  areas  were  heuristically scaled to  the  major  areas
analyzed in detail, yielding percent imperviousness estimates for
                               4.21

-------
each  catchment area in the system.  The total system average was
34% impervlousness.

         Actual  runoff coefficients were then calculated on  the
basis  of  the  percent  imperviousness  calculations.   Standard
procedures  presented  in simplified SWMM(2) were computed  using
equation 1:

                        Z = 0.15 + 0.75 x I                  (1)

where  Z  is the runoff coefficient representing the fraction  of
rain that appears as runoff,  and I is the percent imperviousness
of the catchment area  (in fractionalized form).


4.7.4  Stormwater Pumping Stations

         Of  particular  interest to the storm overflow  analysis
are the five major pumping stations designed to pump flood waters
and/or combined sewer  overflows to the river.  The Hancock Street
Station  on  the West  Side is presently connected to  a  3.6   MG
storage  basin,  with  eight - 100 cfs pumps  available.  Further
downstream of Hancock  Street Station is the Weiss Street  Station
with  three - 100 cfs  pumps.  On the East Side the Emerson Street
Station  has eight - 100 cfs pumps.  The Emerson  Street  Station
along  with Hancock and Weiss are the only  stations that can pump
water  directly from the interceptor with flows depending on  the
heights of weirs separating the interceptor from the pump station
wet  wells.  The two other pump stations,  Webber and  Fourteenth
Streets both have gravity outlets to the river,  and only operate
when  river elevations are high enough to prevent  the  backwater
gates  at the gravity  outlets from discharging the high  runoffs.
Both  Webber and Fourteenth Street Stations have three - 100  cfs
pumps each.

         The amount of time each pump in the system operated  was
periodically  recorded,  and this  information was used to analyze
the operation of the five pumping  stations. It was noted that the
Weiss  and  Hancock  Street Stations are frequently  used    with
Webber  and  Fourteenth  Street  Stations   operating  much   less
frequently,   and   Emerson   Street  Station   (manual   start-up
operation)  only   rarely   .  This  comparison  is  not  surprising
considering  the  hydraulic  bottleneck at  the  West  Side  river
crossing,   (see Chapter 6) the  relatively high weir height at the
Emerson  Street Station above the  East Side interceptor  and  the
potential  at  the  Webber  and Fourteenth  Street  Stations  for
gravity discharges short-circuiting these pump stations.

         Curves  were  developed by EDP for the Weiss Street  and
Hancock  Street  Stations  relating total volume  pumped  to  the


                                4.22

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amount  of  rainfall  per  event.    Distinct  rain  events  were
associated with the amount pumped at these two overflow points by
comparing  pump usage records to rains recorded at the  WWTP.  It
was noted, as expected, that both volume pumped and the number of
pumps  used  increased with increasing amounts  of  rain.  Spring
events resulted in higher volumes pumped due to infiltration  and
spring melts.  In addition to being a useful indication of system
stress points,  the pumping station analyses were used as a rough
check  of  the simulaton model.  Data plots of Weiss and  Hancock
Street  Stations'  pumping  operations,  as  functions  of  total
rainfall  per event,  are presented with the  simulation  model's
predicted values in Chapter 6.
                                4.23

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                          CHAPTER 5

             SCREENING OF COMBINED SEWER CONTROLS
5.1 Foreword
          The  development  of realistic CSO  abatement  concepts
for  Saginaw  included determination of the degree  of  abatement
required, assessment of available technologies and identification
of  realistic  options based on that technology  assessment.   In
this  chapter available CSO alternatives ranging from inexpensive
system  modification to total capture and treatment of  overflows
are reviewed.  The roost promising and feasible abatement  options
are  selected  in  this  Chapter  and are  further  described  in
Chapter 6.

          The  three  general  approaches  listed  below  briefly
describe the state of the art of CSO abatement:

          (1)  sewage system structural modifications to  improve
system  operations  and to enhance hydraulic conveyance  capacity
together   with  improved  sewer  system  flow   controllers   at
regulation  points to enhance operational ease in flow  splitting
and/or  to  create  maintenace free in-line  transient  detentive
storage;    (2)  pollutant source control and upstream   stormwater
management  practices,  and;   (3) combinations of major  off-line
storage and treatment facilities.

          Existing  system modifications are reviewed in  section
5.2.  Source  control  practices  are reviewed   in  section  5.3.
Storage  and  treatment  options are discussed   in  section  5.4.
Selection  of feasible practical and realistic   alternatives   for
further evaluation is discussed in section 5.5.


5.2 Modifications to Existing System

          Reduction  of overflow discharges can  be achieved by  a
wide  range of modifications from low   cost,  minimal   structural
procedures   involving  maintenance  improvements  to   structural
intensive   sewer   separation.   The   following  methods   were
investigated:

          Regulator  Improvements  - Utilization of  new   vortex
valve technology to enhance  the capability of existing  regulators
to efficiently  pass   "first  flush" to  WWTP   in  a   relatively
maintenance-free fashion  and to effectively  control underflows to
the interceptor  systems at maximum  storm   conditions.   Transient
in-line   system  storage  configurations  can be   developed  where

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applicable,   at  the  regulating  chambers  by  modification  of
chamber's  internal  weirs and inclusion  of  positive  discharge
control  devices.   A discussion of vortex valve flow  throttling
equipment is presented in section 5.2.1.
          Sewer §ep_arati.on ~ Tne separation of storm and sanitary
sewers  significantly reduces combined sewer overflows.  Sanitary
flows are treated prior to discharge to receiving  waters.  Storm
runoff  pollutants discharge directly to receiving waters  unless
additional  treatment is provided.  To achieve total  separation,
the  difficult  task of disconnecting roof leaders is  necessary.
The principal disadvantage of sewer separation is its  tremendous
cost  and  time requirement.
                       jLzjatj.on  °J[ Existing  E££l!lti§s  - Unused
and/or  increased capacity for conveyance/storage within existing
sewerage system can often be realized at little cost.  Increasing
and/or  improving hydraulic capacity at critical control  points,
i.e.,   pumping  stations,  constrictions,  etc.,  are  classical
examples .
          I^zl-iH6. Storage - System control using in-line  storage
represent  promising  alternatives  in areas where  conduits  are
large,  deep,  and  flat  (i.e.,  backwater  impoundments  become
feasible)  and interceptor capacity is high.  Costs  for  storage
capacity gained in this manner range from 10 to 50 percent of the
cost  of   off-line  facilities.   Because  system  controls  are
directed toward maximum utilization of existing facilities,  they
rank among the first of alternatives to be considered.
5.2.1  Vortex Va _lve Throttling P.!:Zi£e_s-
         In  general ,   the  purpose of  flow  regulating  devices
is   to   control  discharge  from  a  combined  sewer  into   an
intercepting  pipe  leading to the  WWTP.    In  practice,  three
classes of devices are used:   static,  dynamic (semi-automatic),
and dymanic ( fully-automatic) ( 1 ).

         The  schematic of a dynamic (semi-automatic) device used
in  regulator  chambers  in Saginaw is depicted  in  Figure  5.1.
During  normal dry weather flow conditions,  the float is in  the
down position permitting maximal aperature opening on the orifice
discharge  leading  to the interceptor.   During  a  wet  weather
event,  the  flow level within the combined sewer rises and  flow
enters  through the telltail opening into the float chamber.   As
                               5.2

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                                        DIVERSION
                                            wcm
Figure 5.1  Schematic of Typical  Dynamic(Semi-Automatic)
           Combined Sewer Mechanical  Float-operated
           Flow Controller
                  5.3

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the level of water in the chamber increases, the float rises, and
through mechanical connections, the moveable shutter lowers, thus
continually  decreasing  the orifice aperature.  As  the  orifice
aperature  decreases with increasing head during a  storm  event,
the  resulting flow to the interceptor will be throttled to  pre-
determined limits. Mechanical float-operated systems of this type
were  state-of-the-art  technology  in  the  40"s  and  50's  and
thousands were installed throughout the U.S. and Canada.

          Regulation is controlled by movements of the float.  In
the  larger sizes,  the float diameter may be as much as 5  feet.
This  requires  a large size floatwell which may trap  grit  that
creates a maintenance problem.  Accumulation of floating material
on  the float may cause malfunctioning of the system.   Since the
entire  system is in fine balance,  proper operation requires  at
least biweekly maintenance  (1).    Without proper maintenance the
shutter  can  "stick"  and "freeze-up" resulting  in  an  unknown
aperature  opening and hence,  unknown discharge.  Frequently the
shutter head "sticks" in a down position after a storm event  due
to  its inertial and must be released by physically "kicking"  or
jarrying  the  head.    An  additional problem  arises  when  the
devices must operate on high head differentials.   As the shutter
opening decreases,  the risk of cloggage increases.   Operational
problems with this type of device needs no documentation.


             Justification ^ Vortex Valve Technology

         Over  the last several decades significant  improvements
in sewerage system control have occurred in the USA,  Germany and
Scandinavia.   It  has been recognized that a further improvement
of  the efficiency of WWTP will,  when viewed in  overall  terms,
have  relatively  little effect as long as a large proportion  of
the pollutants fails to reach the WWTP during wet weather.   This
applies  particularly to combined sewerage schemes with  numerous
storm overflows.

         An  improvement  of  the efficiency  of  the  collecting
system  is  possible,  by installing additional  reservoirs  with
heavily   throttled  outflows  in  the  the  form  of  stormwater
detention  reservoirs,  storm water overflow  detention/retention
tanks   or  through  the  use  of  in-system  transient   storage
configurations.    This type of control strategy,  however, makes
discharge   control   from   such   collecting   system   storage
configuration, a new and central problem.

         Modern  CSO   control philosophies focus on the  "first-
flush"  to  separate the dirtier water from  the  less  polluted.
This  can  be done easily and  reliably the  shorter  the  combined
passages of foul water and storm water outflows are.   This means
                                 504

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that  collection  system storage configurations will have  to  be
present  in  greater  numbers and will  have  to  be  decentrally
situated.   It  follows then that these units may be infrequently
serviced, but nevertheless, they must operate reliably.

         The  sophisticated methods of urban hydrology  employing
mathematical  models  to  accurately  estimate  required  storage
volumes lose this effectiveness if the flow control element fails
to  maintain the desired flow.   The accuracy and reliability  of
conventional  type throttles as described above are not  reliable
nor  are they accurate  (2).   Table 5.1 summarizes in  a  general
sense  characteristics  encountered and design parameters for  an
ideal  remote type sewerage system flow controller.   The  vortex
valve technology satisfies these requirements.


         Historical Background of Vortex Valve Technology

         The  roots  of  vortex valve technology date  back  many
years.   Around  1930  a  non-return valve or  vortex  diode  was
invented in Germany in order to reduce the danger of uncontrolled
blow-off  of  hot  steam in the case  of  pipe  fractures.   This
invention  was left without any practical application  until  the
sixties.  It was then re-discovered and was modified and used for
control functions in which maximum reliability was required, such
as  the  control of rocket motors and emergency cooling  circuits
for  nuclear power stations.   In Germany so-called  low-pressure
vortex  amplifiers  have  been developed  since  about  1970  for
purposes  of  hydraulic  engineering  (3).   The  first  practical
applications began in 1976  (4).   In Germany there are about 1000
vortex  devices  of different types and  size  in  operation.   A
patent was applied for by H. Brombach in USA and was received.

         At the same time,  independent experiments were conducted
in  Scandinavia  with vertically arranged "Hydro-Brakes."   These
were  tested as inlet throttles in catch basins.   Later  conical
in-line types were developed.   Hydro-Brakes have their origin in
this  branch  of development.   There are several  thousand  such
devices  in  operation  in North America,  mostly  the  catchbasin
throttle  type.   A  patent  was  applied for in  USA  by  J.  M.
Johannessen and was received.


       Simplified Justification fif Vortex Flow Controllers

         Vortex  devices  work  exclusively  with  flow  effects.
There are no moving parts and there is no external energy supply.
The  flow  effects are  three-dimensional and determined by  fluid
friction.    To  date,  there  is  no  satisfactory  quantitative
                                505

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                     TABLE 5.1

        Conditions and Demands for an Ideal
       Collecting System Flow Controller (2)
Conditions:
Requirements
decentral and multiple
installation
simple and easy to under-
stand function
rare supervision/ installed
in wet and dark
simple maintanencer no
special tools or meters
required
reliability
no moving parts, no
external energy supply,
self-cleaning
small flows
large cross sectional
openings, no backwater
in dry weather
long-term operation
durability, corrosion
protection
refined hydrology
accuracy, stable
characteristics
changes in catchment
adjustable flow rates
                           5.6

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description  of the flow processes   by means of  a  mathematical
model.

          The  operating  principles of this  technology  can  be
demonstrated  considering  the simplified model shown  in  Figure
5.2.   An  infinitely large container is connected via a  channel
(C)  to  a  cylindrical  vessel  (V) .    The  vessel  (V)  has  a
centralized  hole at the bottom of diameter (Do) or of area  (Ao).
If the pipe (C) is routed so that the water enters the vessel  (V)
perfectly  radially,  e.g.  via  a ring pipe  with  small  radial
nozzles,  (see  Figure  5.2A),  the result is a sink flow in  the
direction of the outlet orifice.   The outflow jet is constricted
so that the flow rate becomes


                   Qr = S0 mr V2gh

If the outlet is of sharp-edged design (orifice plate),  the loss
coefficient is approximatelymr = .6.

          Figure 5.2B shows the same setup, but the inlet nozzles
are arranged tangentially.  The difference is striking.  There is
a  free vortex generated under these conditions.   The  nearer  a
water  particle  comes to the center line of the  vessel (V), the
greater  its peripheral velocity becomes.   The centrifugal  force
becomes so great that a vortex core is formed through the  outlet
hole  and  allows the water to flow out in the form of  a  hollow
jet.  This effect can be observed in a bath tub vortex.  The flow
obeys the same function


                    Qt = AQ mt

but the flow coefficient drops to approximately,mt =0.15.

         A particularly remarkable feature of this vortex flow is
that each disturbance of the flow,  e.g.  due to entrained solids
or air pockets, leads to a weakening of the centrifugal force and
thus  to  an  increase  of  the  flow.   This  unusual  hydrualic
behavior,  also  known as the self-cleaning effect,  has  obvious
advantages  in  flow  control of waste streams  with  solids  and
debris.

         Although  the two experiments in Figure 5.2 differ  only
slightly  in the arrangement of the inlet nozzles,  the  flow  is
very different, namely



                    VQr =
                               5.7

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PHYSICAL JUSTIFICATION
FOR VORTEX  VALVES	
             A.
,1
                         -.I- Do
                             Qr
B.
                  Do

                  Qt
           A,
                  O
     o
                   B,
          A, RADIAL SINK FLOW
     B, FREE VORTEX FLOW
          Figure 502 Simple Model  of Vortex Valve Representation

-------
The  flow  rate  is  reduced to about 1/4  as  a  result  of  the
tangential  supply  of  water.    Expressed  differently,   it  is
possible  under vortex flow conditions to obtain the same flow as
a simple orifice,  but the area  (Ao) of the outlet nozzle will be
4  times the size of the comparable simple orifice.  If  it  were
possible to switch automatically between the two flow states, the
result  would be flow valves whose flow rate is adjustable  in the
ratio of 1:4.

          Vortex  flow  controllers can be designed  to  uniquely
combine  both types of orifice and vortex flow principles into   a
single stage/discharge characteristic.  Operation descriptions of
how  this  combination of flow effects occurs are provided   below
for  vortex valve equipment of Scandinavian origin and   then for
vortex  valve  equipment developed in Germany which are  relevent
for combined sewer regulator applications.


        Conical Type Vortex Valves - Scandinavian Origin

          In 1980 J.M. Johannssen of Denmark tested and  developed
an  in-line vortex control device for in-line applications  (inlet
and  outlet invert elevations are the same).  The conical   device
shown in Figure 5.3A can be described as follows.   It includes  a
truncated  cone section,  a circular plate  at the  inlet end,   a
cylindrical  inlet,  an  oval  plate  at the  outlet  end   and   a
cylindrical outlet.

          The  cylindrical  inlet   section  consists of   a   formed
circular section which lies in a level horizontal position   along
its  longitudinal axis and is diagonally cut such that the   inlet
intersects the cone body at a 45 degree angle.   The inlet   plate
is  circular  and  is  solidly welded to the  large  end of the
truncated cone and includes an oval orifice located at the  bottom
of  the  plate.   The orifice exactly matches the diagonally cut
surface  of  the inlet segment.   The inlet  segment  is solidly
welded  to  the  inlet plate at  the  inlet  plate  orifice.   The
truncated  cone  section acts as the main body of the device and
provides  structural  rigidity.   An  oval-shaped  end   plate   is
solidly  welded to the small end of the truncated  cone   segment.
Integral  to  the end plate is a circular orifice at the base   of
the  oval  end plate sized to exactly match the  truncated  cone
small  end.   In  the  installed position the oval end   plate   is
parallel  to  the  circular end  plate  on   the   inlet  end.   The
cylindrical  outlet  is a roll formed pipe  solidly welded to the
oval  end plate,  and is diagonally cut at  the  same angle as the
truncated cone such that the  outlet .tube exactly matches the oval
end plate.   The oval end plate  and cylindrical  outlet are   sized
as necessary to match field conditions.
                              5,9

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          Cylindrical outlet segments normally incorporate rubber
 "0"  ring stops for standard push-fit installation.   Slip flange
 ends,  victaulic coupling ends,  clamps or other specialized  end
 connections are constructed as required for special connections.

          J.  M.  Johannessen  had  earlier developed in  1977  a
 proto-type  conical  device  with  an inlet slot  cut  along  the
 longnitudal  axis  of a truncated cone with an  internal  orifice
 located at the outlet back plate.  Incoming flow would impact the
 back plate and then enter the device through the inlet  slot.   A
 family  of  stage discharge curves is generated by  altering  the
 internal orifice dimension.   The large end of the truncated cone
 is  a  fixed  multiple  of the  internal  orifice.   He  was  not
 satisfied  with  the performance of this prototype unit  for  the
 following   reasons:   a)   the  flow-through  pattern  was   not
 satisfactory;  b) the vortex braking effect was not satisfactory;
 c)  the  rated  flow capacity of the unit was  dependent  on  the
 mounting position of the inlet slot (any deviation from  absolute
 vertical alignment would alter the flow characteristic;  and,  d)
 the  structural  rigidity of the cone was greatly reduced due  to
 the  inlet slot along the cone length (typical hydraulic  surges,
 i.e.,  vibrations may cause large units to collapse)  (5).  It was
 for these reasons that he developed the conical type  shown  above
 in Figure 5.3.A.

          A   typical  stage/discharge  characteristic  for   the
 conical  device developed by J.M.  Jchannessen is shown in Figure
 5.3.B  and is described as follows:   As the unit begins to  fill
 under increasing head, it will discharge similar to a sharp-edged
 orifice (see segment 0-1,  Figure 5.3.B)  With greater  head, air
 will  become  trapped in the upper portion of the chamber  and  a
 special  characteristic will be formed as the discharge increases
 along  segments 1-2-3.   Finally,  when the head level  increases
 above the chamber,  full braking effect is achieved along segment
 3-4, (Figure 5.3.B).   As the need for braking decreases (falling
 head),   discharge  follows sements 4-3-5,   (Figure 5.3.B and then
 drains   as  a  sharp-edged  orifice.    This  sudden  increase  in
 discharge provides a desireable flushing effect on the unit as to
maintain self-cleaning conditions.

          Families  of  stage/discharge curves for  this  conical
 configuration  can  be generated by simultaneously  altering  the
dimensions  of  the  truncated cone large end  and  the  internal
 orifice  located  at the truncated cone small end.  For  example,
 increasing  the dimensions of the truncated cone large end  while
 keeping  the internal orifice fixed increases the vortex  braking
 effect.  Thus,  Johannessen greatly increased design   flexibility
with  the  improved  conical version.   The opening of  the  inlet
 section is either equal to or greater  than the internal  orifice.
The  outlet discharge pipe is always  equal to or larger than  the
                               5olO

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A.
AFI  MC Series
Inlet and outlet at same
elevation
     Figure
                  discharge
     Figure  5.3  Johannessen Type  Conical  Vortex Valve  Flow
                 Control 1er
                           50ll

-------
internal orifice.   The commercial technology discharge range for
the Johnannessen conical vortex valve is 0.3 cfs to about 20 cfs.
          The coefficient of discharge in the vortex braking
for  Johannessen 's device ranges from 0.18 up to 0.37,  depending
upon the particular geometry configuration.   These  coefficients
can  be  favorably  compared  to  the  mechanical  float-operated
regulator shown in Figure 5.1, which vary from 0.95 (100% shutter
opening)  down to 0.725 (5% shutter opening) (6).   It is for this
reason that vortex valves can throttle discharge with much larger
aperature  openings  in comparison to  a  standard  orifice.  The
vortex valves can pass more efficiently debris and solids through
the  chamber  due  to the spiraling flow action  created  by  the
vortex action.   Furthermore,  the vortex valve can operate as an
orifice  under low head conditions (and pass large flows) and the
switch  to the vortex mode with increasing head.   Vortex  valves
can automatically switch to an fro, from a orifice characteristic
to a vortex mode.   The notion of the name "vertex valve" derives
from  the device's ability to vary flew resistence as a  function
of inlet pressure.

                             Valves   German Oriin
          In  the  late  70 's  Dr.   H.  Brombach,  West  Germany
developed the conical vortex valve,  shown in Figure  5. 4. A.   It
consisted  of an inclined housing.   The lower generating line of
the  conical  part of the housing is  horizontal .    A  tangential
inlet pipe joins into the housing.   The size of the central exit
port is variable by means of exchangeable orifices.   The housing
has  a  hinged cover as well as vents  (an  important stabilizing
improvement ) .

          The  switching to and fro between radial sink flow  and
free  vortex flow occurs as follows (2):   If the  pressure at the
tangential inlet to the vortex chamber is low,  then the  housing
is filled with water only in the lower part.   Due  to the included
position  of  the housing the body cf water is  not  rotaticnally
symmetrical.  Despite the tangential inlet it is not possible for
any vortex flow to develop, but instead there is more of a nozzle
flow of low flow resistance,   see Figure 5.4.B.     The higher the
pressure in the inlet,  the more completely the  vortex chamber is
filled  with water and the excess air escapes.  The body of water
loses  its  non-rotational  symmetry more  and  more.   When  the
chamber is fill to the peak,   Figure 5.4.C, the  inclined position
of the chamber no longer has any effect since water is weightless
in  water.   The vortex now operates unhindered  by asymmetry  and
greatly  throttles the flow.    The central air opening draws  air
into  the vortex core.   The vent at the top   of the  chamber  is
subjected  to  over  pressure and must,  therefore   be  extended
beyond the highest water level.


                               5.12

-------
        (y slorm water tank
        (?) control shaft
        © vortex flow controller
        © vent
splash protection
slide valves
bypass
pipe to sewage treatment plant
Typical installation of
a conical single inlet
vortex va1ve
Automatic Vortex Row Controller
          A.
                                    tow resistance
                                        B.
      Figure 5.4  Brombach  Type  Conical
               Vortex  Valve  Flow  Controller
                                         5013
                               high resistance
                             Row pattern in the valve housing
                             a valve housing
                             bcpne
                             c hinged cover
                             d exit port
                             e dischauge ba
                              baffle
                             f vent.
                                                                                             C.

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          Figure 5.5.A shows the hydraulic behavior of a model of
valve  used in numerous applications in Germany.   The  left-hand
part  of the figure shows the water levels in the vortex  chamber
at various inlet pressures and flow rates.  If the rate  and flow
coefficient  based  on  a  pressure of  15  inlet  diameters  are
plotted, graphs shown in Figures 5.5.B and 5.5.C result (2).  The
exit orifice has the same cross sectional area as the  tangential
inlet.

          It  can be seen by inspection of Figure 5.5 that  there
are  four different flow characteristic regions.   The lower-most
section,  partial filling,  is the region in which the water runs
through  the device with a free level.   The  rapidly  increasing
flow   coefficient   (see  Figure  5.5.B)  is  determined  by  the
hydrualic  behaviour  of the tangential  inlet.   In  the   second
section,  the  characteristic of the flow coefficient swings into
the vertical and remains at a value of about 3.25.   The  maximum
theoretical  possible value of 4 is not quite reached.   This  is
due  to  the fact that the incident flow on the exit  orifice  in
this  state  is not entirely free of circulation.   The  complete
filling  of  the housing is reached at a pressure head  of  about
four inlet diameters.   The flow coefficient drops  sharply.   In
the  third section,  the transition zone,  the device reacts very
sensitively to fluctuations in pressure.  This makes it difficult
to obtain precise measurements of the flow coefficient.  For this
reason, this region is shown by a broken line.  In the upper most
zone  of the characteristic,  there is stable vortex  flow.   The
water  leaves the vortex chamber at high speed in the form  of  a
swirling hollow jet.   The flow coefficient drops slightly  as the
pressure  rises.   This  is because the air-filled  vortex  core,
which  tends to rise upwards due to its buoyancy in the  inclined
chamber, is progressively driven towards the axis as the pressure
rises  and  so is progressively less able to disturb  the   vortex
action.

          Figure 5.5.C shows the discharge-stage  relation.   The
flow  rate rises continuously to a peak flow and then drops back.
This  results in a saw-tooth-shaped flow curve.   By  comparison,
the flow curve of a simple orifice is shown.   This achieves  the
same desired flow at the end of the curve.

          The  characteristic  of  the German  vortex  valves  is
basically   the   product  of  the  following  four   geometrical
parameters:  a)  inlet diameter, b)  outlet diameter, c)  housing
diameter,  and, d) angle of inclination; and the pressure on  the
inlet side.   If the valve does not freely discharge, but aqainst
a back-pressure, there is a further parameter.

          Systematic  variation  of  the  geometrical  parameters
results  in  an  entire family of vortex  valves.   Although  the


                               5.14

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              HYDROVEX
            VORTEX VALVE
               MODEL K15/30/45
                              hstot
                                    /ON
   "stot
/ON
         Planview
      vent
                                                            15-
                                                            10
                                                          o
                                                          o
                                      -Ullllllllimiiii,,
(A)
                                     1
Water levels at various ( B ) Characteristics of flow coefficient
    inlet heads
                                                           for com-
                                                           parison
                                                           ideal
                                                           orifice
                                                                             vortex flow
                                                                             transition
                                                                   Illlllllllllllllllll
                                                                           -O-
                           iQmax
                                                                                  Q/Q.
(C)  Characteristics of volume flow
                        Figure  5.5 Flow Coefficent  and  Discharge Variations
                                    For  Brombach Type Conical  Vortex  Valve
                                                 5.15

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hydraulic properties cannot be adjusted at will,  there ia a wide
degree of flexibility.   Thus, for example, there are valves with
a highly pronounced saw-tooth,  and others where the change  from
nozzle  flow to vortex flow is such that the flow curve is almost
vertical .

          The  hydraulic  dimensioning of the  W.  German  vortex
valves   is   based  on  extensive    full   scale    calibration
measurements.   In  practical applications of the vortex  valves,
slide  valves and connecting pipes are often positioned  upstream
of the valve itself.   Correct dimensioning must, therefore, take
account   of   the  influence  of  these   additional   hydraulic
resistances.   Only  in  this way is it possible to guarantee  an
accuracy of +/-5% of the desired flow (7).

          The  discharge  loss  coefficients for  the  W.  German
vortex valves are below 0.15 and range up to 0.3.  The commercial
technology  discharge range is 0.1 cfs up to about 100 cfs for  a
single device with no upper head limitation.   In Europe there is
an  installation throttling about 1 cfs of stormwater  containing
sand  and gravel under a head drop of 1600 feet.   All of the  W.
German  type vortex valves useful for combined  sewer  regulation
are constructed with hinged hatches allowing for easy maintenance
access  and  permitting rapid replacement of  adjustable  plastic
and/or  steel orifice inserts to alter the units  stage/discharge
characteristic.    A  wide range of different flow characteristic
curves  can  be  accomplished  through  replacement  of   inserts
allowing for capacity expansion/reduction and seasonal effects.

          In  sum,  the W.  German devices developed  by  Dr.  H.
Brombach   provide  more  degrees  of  design  freedom  than  the
Scandinavian  devices  and are based upon  extensive  full  scale
hydraulic  testing.   The  W.  Germany  devices  include  venting
systems  which stablize flow characteristics during switching and
minimize any hysterisis effects guaranteeing that  rising/falling
stage curves are nearly identical .
          Figure    5.6     shows   a   typical   vortex    valve
stage/discharge   characteristic.    As  it  can  be  seen   from
inspection,  the  lower  portion of the curve  increases  (rising
head)  to  a defined peak (orifice  characteristic),  "kick-back"
occurs in the transition zone (energy re-arrangement from orifice
to  vortex made),  and then rises when in the  vortex  mode.    On
falling head, the characteristic curve is essentially the same.
                               5.16

-------
n
          Typical
          orifice plate
    Storm regime
   Transition
   regime
                                   Fiut*
Dry weather regime
  Figure 506 Typical  Vortex Valve Stage/Discharge   Curve
                   5.17

-------
          This   characteristic   provides   for  a   number   of
interesting  design  possibilities.    First,  the  "first-flush"
passage can be designed about the initial peak.  Second, overflow
spill weirs can be accurately established when the vortex mode is
first established.   Third,  the upper most portion of the vortex
curve  can  be  used to establish controlled flow  rates  at  the
maximum  design storm condition i.e.,  25 year design storm  such
that  discharge  at maximum head could be the same or  even  less
than   the  peak  "first-flush"  flow  occurring  at   low   head
conditions.   The  WWTP  would therefore receive at most no  more
than either of these two hydraulic limits.  Fourth, a system-wide
utilization  of  these  positive  acting  controllers  could   be
employed  to apportion interceptor capacity to carry only "first-
flush" to the WWTP from each of the contributing sewer sheds  and
allowing only the clearer flows during increased storm conditions
to overflow.   Lastly,  the orifice flow characteristic on drain-
down   (falling  curve)  can be explicitely used to  ensure  self-
scouring  when  considering in-line and/or  off-line  storage  of
wastes heavily laden with settleable solids.  It was  exactly for
this   last  design  consideration  that  motivated  Brombach  to
explicitly research, hydraulically test and develop vortex valves
having  well  defined switching (orifice  to  vortex,  vortex  to
orifice) characteristics.

          The  typical  characteristic curve shown in Figure  5.6
can  be  altered by changes in the geometric design  of  a  given
vortex    valve   to   increase/decrease   peak   initial   flow;
increase/decrease  height at which the initial peak flow  occurs;
increase/decrease the degree of "kick-back";  and flatten/steepen
the slope of the vortex mode portion of the curve.


            Commercial Availability Q£ Vortex Valves

          Advanced Fluidics,  Inc.   (AFI) located in Hanover,  MA
acquired exclusive U.S.A.  and Canadian licensing rights from  J.
M.  Johannessen to market and sell his technology in 1982.  These
devices  were sold under the trade  name,  Hydro-Brake.   Conical
type vortex valves were designed,  fabricated and supplied to the
City   of Saginaw by AFI in mid 1984 and were installed as part of
the reduced BMP implementation program.

          John Meunier,  Inc.   (JMI) located in Montreal,  Canada
acquired North American licensing  rights in-mid 1984 from Dr.  H.
Brombach  to  market  and sell the patented  line of  West  German
vortex valves.

          Recently, JMI and AFI have mutually agreed to merge the
two  vortex valve product lines and to combine  licensing  rights
for marketing a a single product line called the "HYDROVEX" .


                                5.18

-------
5.3 Source Control Practiceg

          Management   Practices   include  source  control   and
collection  system  management.  Whereas  storage  and  treatment
technologies are generally more costly  alternatives,  management
practices  concentrate  on   the  source  of  pollutants   (source
control) and means of conveyance at a minimum cost.

        A.  Source  Control  technologies  which   were  reviewed
during screening are listed below:

          Street Cleaning - Urban runoff pollution is reduced and
aesthetics are improved by regular street cleaning.  Fine  solids
fraction  of  street surface dirt is removed by broom brushes  or
the more efficient vacuum-type cleaners. The efficiency of street
cleaning  in large metropolitan areas is reduced due to  problems
with heavy street traffic and  parked vehicles.

          Solid  Waste  Management - Urban  runoff  pollution  is
mitigated by improving trash collection and reducing litter.  The
greatest  benefit  is aesthetic improvement rather  than   overall
solids reduction.

          Erosion ControJ. - Improved construction practices, such
as   proper   landscaping,   protection  of  drainage   channels,
protection  of  stockpiles,  and  the  installation  of  sediment
retention   basins/dams  provide  for  a  reduced   fine   solids
contribution to existing sewer facilites.

          Catch   Basin  Cleaning  - There  are  several   methods
available for catch basin cleaning which will  reduce clogging  of
storm  and  combined  sewers.  Removing a large fraction   of  the
collected  solids  can reduce  the solids  pollution  and   prevent
shock loadings of grit and silt materials.

          Roof  Storage - Additional storage of urban runoff  for
flow  attenuation is available in an urban area of high  building
density  provided  that  the   roof structure   is  constructed  to
accomodate  rainfall  storage.  A large amount of  roof  area  is
required to make this option attractive.

          Parking  kot  JS tor age  - Similar to  roof  top   garage,
temporary   storage  may  be   available  at  parking   lots   and
playgrounds.  Outlet controls  are necessary for this method to be
effective. A regular maintenance  program for  debris  removal of
deposited material is necessary.

          Natural Flow Attenuation Techniques  - Natural  drainage
impoundment  can  be  used  for runoff  attenuation  by  creating
temporary detention.  Specific examples are lagoons, debris dams,


                               5.19

-------
and recharge berms.  These applications are not feasible for  CSO
problems in major urban areas.

          Porous  Pavements - The use of special pervious subbase
and base course material for streets, sidewalks/ and parking lots
allow  rainfall to permeate through the pavement for  groundwater
recharge. This technique is generally limited to new construction
in  mild  climate.
        B.  Collection System ffajiagement Teghflio^es - which  were
screened are listed below:

          Polymer  injection  - The  use of  polymer  can  reduce
hydraulic   friction  and  thereby  increase  system   conveyance
capacity,   but  reasonable  results  can  only  be  attained  in
hydraulic  systems with limited capacity.  Polymer injection is a
temporary  means of overflow control and is relatively  expensive
due to high chemical cost.

          Sewer   Flushing  - High  flows  push  settled   solids
downstream  in  sewer  reaches which are too  flat  to  be  self-
cleansing.  Sewer flushing is usually limited to relatively small
diameter sewers.

          Sewer  Cleaning  - Periodic cleaning can restore  sewer
pipes to full hydraulic capacity using rodding  machines,  bucket
machines  and  drag  lines.  These  methods  have  proved  to  be
relatively costly and time consuming.


5.4 Storage and Treatment

          The  use of storage and treatment technologies to abate
CSO  pollution  encompasses  a broad  spectrum  of  possibilities
ranging  from structurally intensive,  high cost alternatives  to
minimal   structurally   intensive,    low   cost   alternatives.
Structurally  intensive  projects are outlined in  the  following
manner: System conveyance, storage and treatment.

          System  Conveyance  - The collection  and  transfer  of
combined  sewer overflow to treatment and storage facilities  may
be  accomplished either by gravity or by pumping,  depending upon
the  hydraulic  conditions  in the  system.  If  storage   is  not
available or is impractical,  conduits and pumps must be sized to
handle  peak  flows  resulting from  design  storm  runoff.  With
storage capabilities, conduits and pumps can be sized such that a
combination  of storage,  conveyance,  and treatment will  process
peak  runoff at minimum cost.  The CSO conveyance system   may  be
continuous,  collecting all overflows or selective,  intercepting
                                5.20

-------
and  combining only particular overflows.  Hydraulic  conditions,
design storm, solids composition, and  service area determine the
size and shape of the conveyance facilities.

          Storage  - Off-line storage is used to attenuate  storm
flow peaks,  reduce storm overflows, and capture the first flush,
or  provide  treatment in the form of sedimentation when  storage
capacity is exceeded.  Off-line storage facilities may be located
at overflow points or near WWTP facilities, depending on the type
and function of the storage facility to be used. Off-line storage
may also be used for on-site storage of runoff.  Disadvantages of
storage  facilities  include their large  size,  high  cost,  and
dependency  on  other  treatment facilities  for  processing  the
retained  water  and  settled solids.  CSO generally  results  in
solids  handling  problems  so consideration  must  be  given  to
conveyance  system  slopes and flows and  also to the  number  of
storage  vessels  which  can be feasibly  maintained.  A  typical
process diagram is shown in Figure 5.7.

          Treatment  - Treatment  facilities may be localized  or
centralized.  The  number  and location of  treatment  facilities
depends upon system hydraulics, characteristics of the pollutants
and  feasibility of operation.  If hydraulic conditions are  such
that  expensive pumping facilities are required for  transporting
relatively  small amounts of overflow,  then localized  treatment
may  be  more  cost-effective.   If  hydraulic  conditions  allow
consolidation of overflows, larger more centralized CSO treatment
facilities become more feasible. The nature of pollutant loadings
also determines the type and location of facilities. For example,
if  a relatively small area contributes a very high grit  loading
which  would aggravate the conveyance system hydraulics,  then it
would  be  advantageous  to locally  remove  the  grit.  Treatment
technologies available for intercepted wet weather flows  include
physical   alternatives which remove  settleable,  suspended  solids
and floatable materials from combined sewer overflow.
5.4.1 Physical Treatment  Processes

           Physical     treatment     systems    have     demonstrated
capabilities  to  handle high  and  variable  influent   concentrations
and  flow   rates and  operate  independently   of  other   treatment
processes   except   for the disposal of  residual  solids.   Primary
level   treatment can   be achieved by  any   of  several   methods
available   for   high  rate  application,    including   gravity
sedimentation,    swirl   regulator/concentrators,     screening,
dissolved  air flotation,  high rate filtration and high  gradient
magnetic   separation.   Descriptions of  each  of these  methods   are
presented  below.
                               5021

-------
NJ
NJ
    Inf.
                   Screenings
                      to
                   Disposal
                     J
  COARSE

SCREENING
                   Clarified
                   Effluent
                                             DISINFECTION
                                 -*~TO  SAGINAW RIVER
STORAGE

 TANKS
                                                        SETTLED
                                                        SOLIDS
•*-    TO INTERCEPTOR
               Figure 5.7  Soginow study typical storage facility process schematic.

-------
        Gravity Sedimentation - Gravity sedimentation of CSO  has
been  evaluated  in facilities utilizing surface  overflow  rates
higher  than  conventional primary rates of 800-1,200  gpd/sq.ft.
Early  experiments  with  primary  treatment  facilities  in  Los
Angeles  demonstrated that suspended solids  removal  efficiences
did  not decrease markedly when overflow rate was increased  over.
2,000 gpd/sq.ft. Studies conducted on primary facilities treating
combined sewage in Toronto,  Canada; Rochester, New York; and New
York   City  also  show  reasonable  performance  with  increased
overflow rates.  Studies also show considerable  cost/performance
improvements  with  chemical addition such as polymer  and  alum.
Despite the apparent improvements, gravity sedimentation requires
tanks,  thus introducing significant land requirements and solids
handling   problems  similar  to  that  of  conventional  storage
facilities.

          Swirl   Regulator/Concentrators   - Swirl    regulator/
concentrators  achieve  both quantity and quality control of  CSO
laden with suspended material. A typical process diagram is shown
in  Figure 5.8.   The swirl functions  on the basis of  having  a
tangentially  induced  waste stream which is directed  around  the
circular  unit  to  form  a spiral-type  flowpath.  Solids/liquid
separation is achieved by two means:  centrifugal forces separate
and  concentrate solids due to inertial differences;  and  solids
fall out of the  wastestream and are concentrated in the floor of
the  swirl  due to gravitational effects  derived  from  lowering
particle  velocities  and   elongating the   particles  flowpath.
Floatables are effectively trapped and stored during storm  event
and  later discharged to receiving sewer.

          Extensive mathematical and hydraulic modeling has  been
performed  with materials simulating particle size  distributions
and  specific  gravities encountered in  combined  sewage.  These
models  were extended to prototype scale using Froude Law scaling
of   particle   settling  velocities  and  design   flow   rates.
Verification  of  model  projections  has  been  demonstrated  in
facilities at Lancaster,  PA;  and at Rochester and Syracuse, New
York.

          A  12-foot diameter swirl  concentrator  in   Syracuse,
New   York  with  a  design flow   of  6.8 mgd  exhibited   total
mass   loading  removals   for  suspended solids   ranging   from
44%    to  65% with   concentration    reductions   ranging  from
18%   to   55%.  The foul sewer   discharge  was    approximately
10%.  The   higher  mass loading reduction  through  the    swirl
concentrator    is   due    to   both   flow  and    concentration
reduction.   Data performance   from the  Syracuse prototype unit
indicate    good  removals  at  the beginning  of   storms   (when
influent concentrations  were  high) and  at the  end of  the storm
(when flow rates were  low)  such that a high  percentage  of   the


                                5023

-------
                                                                                             Grit
                                                                                              To
                                                                                           Disposal
                        Screenings
                            To
                         Disposal
U1
                             Concentrated
                                Swirl
                               Underflow
                         Coarse
                        Screening
Pumping
  Primary
  Treatment
  By Swirl
Concentration
                                                     Grit
                                                    Removal
                                                                                        To Interceptor
                                                                                             System
                                                                        Clarified
                                                                          Swirl
                                                                        Effluent
                                                                                       Disinfection
                                                                                       To Receiving
                                                                                          Water
             Figure 5.8 Soginaw study typical CSO primary treatment process scheme.

-------
flow discharged  to  the foul sewers. The data based on 11  storm
events  showed average storm hydraulic  loading  rates  as   high
as  6600 gpd/ft. (8).

          The  24-ft  diameter dual-functioning swirl  regulator/
concentrator  constructed in  Lancaster,  Pennsylvania,  under  a
demonstration  grant from the U.S.  EPA treats CSO at one of  the
City^s  overflow  points to the Conestoga River.   Data from  the
evaluation period (1980-1981) conducted by EDP indicated that the
swirl  is  an  efficient treatment device to  remove  heavier  or
"first-flush"-related    suspended   solids     (9).     Treatment
efficiencies exceeded 60% for flows exceeding 20 cfs.

         A  special  cross-sectional sampler  capable  of  taking
complete  vertical  "slices" of flow over  an entire  pipe  cross
section in an automatic discrete mode was developed and installed
by EDP Technologies,  Inc.,  Hanover,  MA.  in the 36-in influent
conduit  to the swirl to obtain representative  suspended  solids
samples.   The  new  cross-sectional sampler and a Manning  model
6000 sequential sampler were used during four storm  events.   An
anlysis  of  the data indicated that suspended solids of  samples
collected by the new sampler were 6 to 7 times more  concentrated
than  samples  collected  (at the same instant)  by  the  Manning
sampler  during  the first 10 minutes of the storm's peak  "first
flush".   Concentration  factors  reduced to 2 to 4  for  samples
collected mid-event and then down to 0.5 to 2.0 for  end-of-event
samples.

          A  summary of the  swirl suspended solids  removals  for
five  events  monitored with the cross-sectional samplers  is  as
shown  in  Table  5.2.   The removal and  efficiency  percentages
associated with the indicated estimated flows are also presented.
Removal  is  defined  as  the percentage  of  the  influent  mass
contained in the foul underflow line.   Efficiency is defined  as
the  removal minus the percentage of inflow contained in the foul
underflow  line.    These  results  were  derived  primarily   by
inspection  of  raw  data.   Overall  flow-weighted  removal  and
efficiency  calculations are not given because of the approximate
nature   of   flow  measurements.    Flow   meters   continuously
malfunctioned during the course of the project.

          It   appears  that  the  swirl  provided  significant
suspended  solids   removal   near  design  flow  conditions.    As
expected,  efficiency deteriorated at lower flow rates because of
the  flow  splitting phenonomenon.   In  most   cases,  efficiency
exceeded  60%  for  flows  of  about  20  cfs   or  greater.    As
anticipated,   most  of  the  suspended  solids  were  settleable
inorganic  grit.   The  swirl  appears to provide the  degree  of
treatment that it was orignally designed for,   i.e.,  90% removal
of  settleable  material   (defined as grit  having  an  effective


                               5c25

-------
                     TABLE 5.2
            Lancaster, Pa.  1980 - 1981
Summary of jSsuLtJ. Regul at or /Concentrator  Performance
Dgte of Event

9/10/80


10/2/80



5/10/81



7/2/81


7/20/81 pm
Estimated
Plow rate
  CfiisJ
Removal
   $
    18
     7

    50
     7
     2

    20
     8
     6

    55
    20

     5
    46
  70
  50

  52
  46
  80

  12
  23
  35

  76
  86

  41
  83
                                             Efficiency
                                                62
                                                39

                                                47
                                                24
                                                 5

                                                 5
                                                 5
                                                10

                                                73
                                                78

                                                11
                                                80
                       5.26

-------
diameter  of  0.35 mm and a specific gravity of 2.61)  at  design
flow of 40 cfs.

         Similar  in  function to the  swirl,  the  helical  bend
concentrator/regulator  appears more practical as in-line devices
rather than satellite or off-line devices.   Details of the swirl
and  helical  bend regulator/solids concentrators  are  shown  in
Figure 5.9.

         Screening  - Screens  have been used to  attain  various
levels   of  suspended  solids  and  floatable  solids   removal.
Screening methods can be separated into two groups:

         1.  Course screening used to remove the coarse floatable
materials  and larger suspended solids.   In  many cases,  coarse
screening is used as a pretreatment prior to further treatment to
enhance  the control process or to protect downstream  equipment.
Suspended solids removals of 5-10% can be expected.

         2.   Pine screening used as a primary treatment process.
Fine  screens  include static,  drum or rotary screens  and  also
micro-screens.   Microstrainers or microscreens have been applied
to  polishing  of secondary effluents at  conventional  rates  of
around  110  gpd/sq ft.  for 30 micron mesh.  Tests of  CSO  have
indicated  suspended solids removals of 17-40 percent when  using
420  micron screens,  26.6 percent when using 105 micron screens,
10-43 percent when using 70 micron screens and 20-93 percent when
using   23   micron   screens.   Microstrainers   are   available
commercially  in  a number  of  configurations.   Fine  screening
devices  tend  to  perform best with low  to  moderate  hydraulic
loading  rates.   Fine  screening  devices are  characterized  by
relatively high operation and maintenance requirements needed  to
maintain   adequate  removal  efficiencies  and  to  dispose   of
collected solids.
         Dissolved  Ail Floatation - Pilot results from treatment
of  CSO  by dissolved air floatation are being used to  design  a
full scale plant in San Francisco.   These data inciate suspended
solids  removal rates of 51 percent at an overflow rate of  4,320
gpd/sq. ft.

         High-Rate  Filtration - High-rate,  multi-media  filters
have   been  studied  extensively  for  polishing  of   secondary
effluents.   CSO  have  been  applied  to  high-rate  filters  at
Washington D.  C. ;  Cleveland,  Ohio:   Syracuse,  Rocheste, r New
York,  and  New York City.   Filter media included  fiber  flass,
anthracite and garnet in Washington D.  C. studies and anthracite
and  sand in the Cleveland and Rochester studies.   The  Syracuse
studies also evaluated use of plastic pellets in conjunction with
sand and anthracite.   The Washington D. C. studies employed flux
                               5o27

-------
                                                             INLETV
           CHANNEL  FOR
           OVERFLOW
Ul
•


00
    OUTLET  TO
    STREAM
                                                   TRANSITION
                                                   SECTION
                                     STRAIGHT
                                  \  SECTION
                            HELICAL
                            BEND  60
                           OUTLET TO
                           SEWER
                ISOMETRIC  VIEW  OF
                HELICAL  BEND  REGULATOR
                                                                   SCUM  BAFFLE
                                                                                   FENCE
                    EMERGENCY
                         WEIR
                    CONCENTRATE
                    RETURN TO
                    SEWER
                      EFFLUENT
                      TO STREAM
     SECTION

XCONCENTRATE
  RETURN TO
  SEWER
    EMERGENCY
    WEIR
:   EFFLUENT  TO STREAM OR
   ADDITIONAL  TREATMENT
                                                    PLAN
                                                      SWIRL CONCENTRATOR
            Figure 5.9 Helical bend and smnrl concentrator.

-------
rates  of  5-15 gpm/sq/ft while the Cleveland and Rochester  work
evaluated loadings as high as 25-40 gptn/sq/ft.   Suspended solids
removal   rates  ranaged  from  30-70  percent  without  chemical
treatment and 85-98 percent with polyelectrolyte treatment.
                             mBtlc.  SeEarjatjj.cn  - High   gradient
magnetic  separation  (HGMS)  is  applicable  for  CSO  treatment
technology.  HGMS provides extremely high pollutant removal rates
(in  excess  of  90%)  and permits flux rates in  excess  of  150
gpm/sq.  ft.   The disadvantages of this technology are the  high
capital and operational costs.


5 . 5  Selection of Alternative Controls

         An  assessment  of alternative CSO  control  options  is
presented  in Table 5.3.   System modifications,  source controls
and collection system management options are broadly  encompassed
as  preventive  BMP controls in Table 5.3.   Structural  controls
have been assessed as treatment controls.

         The overview management concept for CSO emission control
in  Saginaw  is to provide a fairly moderate to  high  degree  of
physical  treatment at low overall capital and operational costs.
Floatables  and settleable solids removal are important from  the
standpoint  of  boating  and  general  aesthetics.    Settleables
removal will control to a degree,  CSO heavy metals emission  and
dissolved  oxygen  sediment demand.   Control of  fine  suspended
solids  is  more  difficult and more expensive but will  tend  to
reduce  oxygen  demanding substances  and  turbidity.   Turbidity
reductions  in turn provide fcr better light  penetration,  algal
productivity  (to  a  limit) and  eventually  enhanced  dissolved
oxygen levels.

         Acceptable  CSO control technologies in Saginaw must  be
cost effective from both first cost (capital) and operations cost
standpoints.   The City of Saginaw invests heavily in its various
public  works departments.   The street and sewerage systems  are
both  well  maintained  and  operated.   In  addition,  the  City
efficiently  operates  the WWTP providing  nearly  constant  high
quality  treatment levels and maintains and operates the  Hancock
Street  CSO  storage/treatment  facility.   Any  alternative  CSO
treatment  technology must have comparable treatment  performance
characteristics,  but  be less expensive to both build,  maintain
and operate.

         The   following   CSO   control  options   satisfy   the
aforementioned  considerations and are further  investigated  and
detailed throughout the remainder of this report.
                               5029

-------
PREVENTATIVE CONTROLS TREATMENT CONTROLS
CONTROL TYPE
SYSTEM MODIFICATIONS
Regulator Improvements
Sewer Separation
Improved Utilization
of existing facilities
In-line Storage
Increase WWTP Utilization
OURCE CONTROL
Street Cleaning
Solid Waste Management
Erosion Control
Catchbasin Cleaning
Roof Storage
Parking Lot Storage
Natural Flow Attenuation
Porous Pavement
OLLECTION SYSTEM MANAGEMENT
Polymer Injection
Sewer Flushing
Sewer Cleaning
TRUCTURAL CONTROLS
Storage/treatment facilities
Swirl Regulator/Concentrators
Screening (Coarse)
Screening (Fine)
Dissolved Air Floatation
High-rate Filtration
High gradient Magnetic
Separation
1

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         A.  System Mod if ica_tj._p|i

             . regulator improvements
             . enhanced hydraulic conveyance
             . increased in-system storage

         B.  Structural Controls

             . storage/treatment facilities
             . swirl regulators/concentrators

         Fine  screening  (rotary/micro screens),  dissolved  air
floatation,  high-rate  filtration  and  high  gradient  magnetic
separation  are  technologies that meet  CSO  emission  reduction
expectations and would attain perceived water quality goals,  but
they  would not satisfy Saginaw's need for cost-effective capital
and more importantly,  operationally inexpensive solutions.

          The  combination  of "system modification"  options  is
hereinafter referred to as the BMP plan.
                               5.31

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                              CHAPTER 6
                     COMBINED SEWER MODELING
6.1 Foreword


          The Saginaw CSO Management Model,  developed by EDP, is
an  inexpensive  and flexible tool for preliminary  planning  and
sizing of CSO facilities. The model provided a means by which the
CSO problem could be analyzed and introduced time and probability
to  the  quantity,  frequency and duration of overflow events  by
using actual rainfall data collected over a long period of  time.
It  was  used  to  screen alternatives  based  on  varying  storm
conditions.

          The  purpose of this chapter is to outline the modeling
tools,  and  their utilization in the development of the  various
proposed  and implemented control programs for treating  combined
sewer overflows. A comprehensive mathematical computer simulation
program  was developed to help determine overflow discharges  and
pollutant  concentrations as a result of hypothetical  occurrence
of various size design storms.  Such a model not only provided an
accurate representation of the physical sewerage system, but also
provided  an  opportunity  to determine the benefit  of  proposed
pollution abatement alternatives.

          The  value of modeling lies in the ability  to  quickly
predict  the  outcome  of  dependent variables  as  a  result  of
hypothetical modification of the system.  These quick projections
have  allowed  for  more time-efficient evaluation  of  abatement
alternatives formulated to meet established goals,  concepts, and
criteria.   Through  this  process  the  best  alternatives  were
isolated for further cost-benefit analysis.

          Model  development and calibration was  performed  over
three time periods.   Initially,  during 1979-1980, EDP developed
the  basic model which was used to prepare the CSO Facility Plan,
(Phase 1 of the project).  During 1983 (Phase 2) further modeling
was performed to detail the Reduced BMP program. During that time
minor model modifications were performed to optimize  calibration
based  on  available  data.   Phase 3 of the  modeling  work  was
performed  during  1984  before and after implementation  of  the
Reduced BMP plan.   An extensive (Fall, 1984) field investigation
provided  the necessary data base to further calibrate the  model
using  improved  knowledge  of  rainfall/runoff  characteristics,
regulator performance and pump station operations.

          The  culmination  of the preceding efforts  provides  a
documented    assessment  of   appropriate    technologies    for
                               6.1

-------
abating combined sewer overflows.  This is a recommended plan  of
action  resulting  from a complex analysis of a  complex  problem
with a wide range of variables and associated costs and benefits.

          Runoff volume and quality are predicted on the basis of
hourly  rainfall,  dry weather sewerage flow (and  infiltration) ,
street  washoff.  dry weather sewerage and deposits.    Regulator
operations  are  simulated  for  each  of   31  catchment   areas
previously  defined.    Resulting  overflows  to  the  river  are
retained  for  statistical analysis and flows to the  interceptor
passed  into  the  interceptor  model.   The  interceptor   model
simulates  the  operation  of the intercepting  system  including
overflow  and quality into the pump stations on the  interceptor,
the  river  crossing flows,  and flows and quality to  the  waste
water treatment plant.  Treatment operation (s)  are simulated both
at  the  existing WWTP and at any overflow  point  upstream.  The
costs  and  effectiveness  of the various  options  available  to
Saginaw  for stormwater management are calculated and  summarized
for  any  given combination of  alternatives.  The  entire  model
operates on an hourly time increment.

          Details of the runoff prediction computations are given
in  Section  6.2.  Regulator and in-line storage  operations  are
discussed  in  Section 6-3 and  6.4,  respectively.   Interceptor
model  details are given in Section 6.5.  West  Side  Interceptor
river  crossing details are given in Section 6.6.   Water quality
modeling details of the sewerage system are discussed in  Section
6.7.  WWTP simulation details are given in Section 6.8. Discharge
calibration  details  are  given  in  Section  6.9.   Phosphorous
modeling details are presented in Section 6.10.


6.2  Runoff
          An  overview of the simulation model runoff volume  and
water  quality estimation procedure for each of the 31  catchment
areas  is shown in Figure 6.1.   Runoff volume for each catchment
area  is  calculated  for  each hour of  rain  using  the  runoff
coefficients,  the  catchment  area and average  hourly  rainfall
intensity.

          For  most  catchment  areas the  runoff  is  considered
delivered  to  the  regulator chamber during  the  same  hour  of
recorded  rain  occurance.  For the Weiss and  Fourteenth  Street
catchment areas, a one hour time delay is used for the section of
the  catchment area estimated to be over an hour away during full
pipe  flow  conditions.  Hourly  dry weather  sewerage  flow  per
catchment area is added to the runoff flow. For the spring months
of April - June-  infiltration estimates per catchment area   are

-------
ey>
co
        r
                                                 Hourly Rain
             Storm Runoff Loadings
             = f(Rain Per Event)
           Deposition
           =  f(Days  Since Last.Rain)
Sewage Loadings Long
Term Average
Runoff
= f(Rain, Catchment Area, K)

Water Quality

= f(Sewage Loadings,
    Deposition, Storm
    Runoff)
                                                 TO REGULATORS
                                                                K,  Runoff Coefficient
                                                                = f(% Imperviousness)
                                                                 Dry Weather  Flow
                                                                              Spring Infiltration
                                                                                                    J
              Figure e. i Catchment area modeling.

-------
also  added to the runoff.  Diurnal dry weather   variations  are
not considered.

          During  Phase  3  of the  modeling  effort,  EDP  field
investigations  and continued model calibration efforts  resulted
in increased times of concentration for several catchment  areas.
Regulator  operation simulations were modified to more   suitably
match the expanded data base developed.  All other aspects of the
Phase  1 evaluation were unchanged.  Regulator operations pre and
post  the Reduced BMP Program are discussed in Section  6.3.


6.3   Regulator Operation!

                 1979-1981 Considerations ^ Phase 1

          Three  general types of regulators were encountered  in
Saginaw.   Type "B" regulators have variable  underflow  openings
altered  by  a float operation (Brown &  Brown  mechanical  float
operated  systems).  As  water levels  rise,  underflow  orifices
close.   Type  "A"  regulators  have  fixed  underflow  orifices,
generally about 1/2 foot by 1/2 foot. The third type of regulator
encountered  are the five modified Type "B" regulators located in
the  Hancock Street area.  These regulators were modified  during
the  implementation  of  the  Hancock  Street   storage/treatment
facility to increase the closure rate of the underflow orifices.

          At  two  of  the five locations  backwater  gates  were
replaced  with  automatic sluice gates set to open  at  regulator
storage  depths  above  the  level  of  the  spill  weir  to  the
interceptor. At the other three locations sluice gates were added
downstream of the backwater gates. Increased closure of underflow
orifices will decrease flow to the interceptor.  The sluice gates
captured  and stored combined sewerage that otherwise would  have
passed  through  the  backwater  gates to the  river  (except  in
extreme   flooding  conditions).   The  intent  of  these   prior
modifications was to increase in-line storage, and to divert flow
in  excess  of  the  in-line  storage  to  the  interceptor  (and
eventually the Hancock facility).

          In  the unmodified Type "B" regulators high  flows  not
handled  by the underflows would be discharged through  backwater
gates  to  the river.  The operation of the backwater  gates  was
dependent  on their seat elevations and relative river elevation,
and could be prevented or hindered from opening in some cases for
high  river  conditions.  Most backwater gates were in  the  same
chamber  as  the  regulator.    At  Cronk  and   Genesee  Streets
backwater  gates were separated from the regulation  chamber  and
were proximate to the river.
                               6.4

-------
         Regulator  performance data was limited to the operation
of the modified Type "B" regulator chambers in the Hancock Street
area on the West Side.  Strip charts recording stage of backed-up
combined  sewage  as a function of time during storm events  were
available  for five regulators located at  Mackinaw  Ave.f  Adams
Street,  Throop Street,  Hayes Street and Remington  Street.  The
recording devices at the Mackinaw regulator was defective and was
eliminated  from  the  analysis.  These  data  were  analyzed  to
determine dynamic operation of the regulator float devices during
rain  events.  Zero  reference  points on the strip  charts  were
impossible  to  determine and the rate of  water  level  increase
during  rising portion of the hydrographs were not considered  to
be   reliable  since  discharge  over  the  weir  levels  to  the
interceptor may have occurred which would not have been noted  on
the  strip charts.   The fall of water level over time during the
recession  of  the storm event  (drainage/  in-line  storage)  was
considered  accurately  recorded.   Underflow  discharges,  as  a
function  of  time were estimated using the strip charts rate  of
depth change and estimated storage volume changes associated with
the depth change.  Underflow rates as a function of stage for the
four regulators are summarized in Figure 6.2.

         System  operation data were not available for the  other
Type  "B" regulators.   Underflow dynamics were estimated on  the
basis  of  dimension measurements and visual inspections  by  EDP
field engineers during storm events.   It appeared during the EDP
inspection  program  that  the  float  mechanisms  were  slow  in
responding  to rising water levels,  and it was  speculated  that
many  underflow  orifices did not appreciably close  during  high
water   conditions.   Underflow   drain  pipes  leading  to   the
interceptor were determined to be large enough to handle  maximum
underflow discharge.

          The  dynamics  of  existing  regulator  operation  were
modeled as depicted in Figure 6.3 for the hourly averaged  runoff
flows. All underflows were calculated as a function of depth. The
available  data  for  the Hancock area regulators  were  used  to
generate  functions  for simulation .  Underflow in  these  cases
decreased as depth of flow increased.  Other regulator underflows
in  the  system were calculated on the basis of a constant   area
orifice  discharge to free space given by equation:

             underflow = area x square root (2gh)


where  h  is  the  depth of  flow  above  the  orifice.   It  was
determined  that  connecting lines to the interceptor were  large
enough to handle high flows,  so the limiting aspect of flows  to
the interceptor was the operation of the orifice openings.
                                6,5

-------
                2.0-
Ol
              o
              cT
              £  i.
-------
CT>
                                       Catchment Area Runoff Estimates
             Hancock Area Discharge
             To  Interceptor

             = Runoff-Storage
             Overflow = 0
Other Regulators Dis-
charge to Interceptor

= Underflow

Overflow = Runoff
         - Under Flow
         - Storage
                 EDP Regulator
                 Modifications
                                               r	1
Regulator Discharge to
    Interceptor

= f(Runoff, Underflow,
    Regulator Operation;

Regulator Overflow to
       River

= f(Runoff, Discharge to
    Interceptor, Backwater
    Gate Operations)
                                                                Backwater  Gate Operations
                                                                = f(River  Elevation)
                                                                                Underflow

                                                                                =  f(Depth of Flow)
                                                                                s  f(Volume)
                                                                               Storage

                                                                               =  f(Depth of Flow)
                                                                               =  f(Volume,  Available
                                                                                   Volume)
                                                                          	4
                                                                             	I
                              OVERFLOW

                            WATER QUALITY
                  OVERFLOWS

                  FLOWS TO
                  INTERCEPTOR
EDP In-line Storage
Modifications
                Figure 6.3  Schematic of regulator operation.

-------
          As a result of later simulation model calibations,  the
assumption  of  free-fall  discharge conditions  through  maximum
regulator orifice openings was used for modeling those regulators
where data was lacking.   Type "A" regulator discharges were also
estimated in this manner.

          For the five Hancock area regulators,  flows in  excess
of  the  underflow and available storage volume were diverted  to
the interceptor.  During the Phase 1 and 2 evaluations  discharge
to  the  river  was considered eliminated in  these  five  cases.
During  the  Phase  3 investigation it  was  necessary  to  allow
extreme  flows to outflow to the river to accurately match  field
and modeled data.

          For  the other regulators in the system the dynamics of
the  backwater gates were incorporated.  The depth of  flow  that
would  cause the gates to open was calculated on the basis of the
gate  seat elevation,  or the river elevation depending on  which
was higher-  Backwater gates are typical flap-type swinging gates
(with  the  exception  of the five modified  Type  "B"  regulator
chambers).  In  most  cases only a minimal amount of  storm  flow
increase  is needed to raise water depth enough to open the  flap
gates  and  cause a discharge to the river.  The gates  are  also
sensitive to river elevations as most gate seats are located near
average river elevation.

          The  Weiss Street gravity line is about five feet below
average river elevations. High river flows can restrict this gate
operation and subsequently require higher depths of flow to cause
discharges to the river.  Varying river stage can have a somewhat
random  effect  in increasing the amount of  in-line  storage  of
storm flow and decreasing overflows.  An additional one-half foot
elevation  was  added  to account for the dynamics  of  the  gate
movement  itself,  and  to  insure that the  simulated  regulator
operation  would  at  least divert all dry weather  flow  to  the
interceptor.  Any flows in excess of the underflows and available
storage volumes were then diverted to the river.

         The  modified  Type "A" regulator chambers  had  a  weir
placed  between the backwater gate and the flow  channel,  and  a
lower   weir  between  the  flow  channel  and  the   interceptor
connection.   Flows  in excess of what is discharged through  the
underflow  orifices or stored in the system behind the weir  will
first overflow the lower weir and be directed to the interceptor.
Only extremely high flows will  overflow the weir separating  the
backwater  gate  portion  of the chamber and be directed  to  the
river. This weir arrangement was considered by EDP to be both the
least  expensive and most available method of limiting  overflows
at any of the unmodified regulator chambers in the system.
                               6.8

-------
       Regulator Operation; 1984 Considerations - Phase 3.

          Under  the complete BMP Plan it is envisioned that  all
regulator chambers be converted to act in a similar storage  mode
as  the Hancock area modified Type "B" regulators,  but with  the
addition  of constant underflow discharge devices.  As stated the
Type  "B"  regulators   earlier modifed as part  of  the  Hancock
Street  detention  improvements  had been altered  to  cause  the
underflow  orifices  to  close rapidly,  limiting  flows  to  the
interceptor  and thus committing the first flush of a rain  event
to in-line storage created at the chamber. EDP considered it more
advisable   to  maintain  higher  underflow  discharges  to   the
interceptor,  limited  only to what the interceptor can maximally
handle. Operation in this manner will commit the first flush of a
rain  event,  generally  carrying the  highest  concentration  of
pollutants,  to the interceptor, and eventually to the WWTP. This
mode  of operation is preferable to capturing the first flush  in
system  storage which may become overflow at a later time if  the
rain continues.  Furthermore,  this mode can be accomplished with
constant  discharge devices that are more reliable and easier  to
maintain than the present float mechanisms. These devices will be
discussed further in  Chapter 7.

     For the five Hancock  area regulators,  CSO in excess of the
underflow  and  available  storage volume were  diverted  to  the
interceptor-  River discharge was considered eliminated in  these
five  cases except during extreme events.    Underflows were  set
equal  to approximately six times dry weather flow unless  higher
underflows  were needed to handle the dry hour discharges of  in-
line storage pools created further upstream.  Weirs were adjusted
to   create  in-line  storage  at  the  regulator   chamber,   as
appropriate. With the exception of Fraser, Webber, Fourteenth and
Weiss  Street  regulators,  all  but extreme  excess  flows  were
diverted to the interceptor. Fraser, Webber, Fourteenth and Weiss
Street regulators were allowed to overflow when runoff flows were
in excess of underflows and available in-line storage volumes.

          Under  the  Reduced BMP plan all West  Side  regulators
were modified to act in the preferred mode and modeled as such in
the Reduced BMP plan simulations.

6.4  In-line Storage

         One  concept  of this study is  to maximize the  use  of
existing facilities such as in-line storage already available  in
the  system  conduits.  The   in-line  storage  concept  for  the
complete    BMP    plan   consisted   of   alteration    of    31
regulator/backwater  chambers  for in-line storage  purposes  and
construction   of   14  flow  control  points  upstream  of   the
appropriate regulator chambers.
                               6.9

-------
          The purpose of the upstream control points was,  in some
cases, to avoid the steeply sloping inverts on the West Side near
the river and,  in other cases,   to simply add a second level  of
flow control in addition to control at the regulator.  Regulators
on  the  West Side are typified  by conditions where the  influent
trunk  sewers are on a steep incline to the  regulator   chambers
which  then  level-cff  not far   upstream.  Far  greater  storage
volumes  could  be generated for these trunk sewers if  the  flow
control structures were located  upstream where the invert  slopes
are  less steeply inclined.  Control structures in the Fourteenth
and  Webber areas were moved upstream to avoid possible  flooding
due to low ground surfaces. The  structure for the Fraser area was
moved  upstream  to  avoid  possible  negative  interaction  with
privately owned sewers in that area.

          During the Phase 1  modeling, in-line storage potential
was  assessed.   Pertinent  details  of  the  sewer  system  were
transferred  from the sewer plans to a city-wide base  map.   All
pipes  equal to and greater than 36 inches were outlined  on  the
base map.  Pipe sizes, invert elevations and manholes were noted.
Contours of ground surface elevation (2-foot interval) were added
as an overlay to the resulting base map.

         An  interactive  computer program was  developed  during
Phase  1  to calculate in-line storage that would result by  flow
restrictions  at  any  point in  the system.  Area of  flow  as  a
function  of  depth was calculated for all  typical  pipe  cross-
sections in the Saginaw system,   including:   circular, oval, egg
and horseshoe-shaped sections.   The in-line storage program used
these  area   functions  to calculate volumes stored  behind  any
given  weir  height  associated   with the level  pool  in  static
conditions.  The  resulting storage volumes were conservative  in
that  the  dynamics of flow had  been ignored in  the  level  pool
approximation.   Invert   slopes   were  also  included  in   the
calculations   allowing  volumes  over  changing  slopes  to   be
accurately calculated.

         One  new aspect of the  Phase 2 modeling was  a  detailed
review  of  in-line  storage potential of all piping  within  the
system.  Where  potential  backup  could occur  it  was  included
regardless of pipe size.   A more accurate estimate of the actual
potential storage volume resulted by inclusion of pipes under the
previous  36 inch limitation.   Storage volume increases  due  to
this  procedure  varied throughout the city.   In some areas  the
trunk  lines  are shallow and most lateral lines are  subject  to
backwatering,  whereas  in others,  lateral lines feed deep trunk
lines at drop manholes and backwatering would be nonexistent.

          Flow   dynamics'  implications  to  storage  were  also
considered  in  lieu  of the previous static  pool  level  volume
                               6.10

-------
estimation.   Rainfall/runoff  data  generated  in  the  Phase  1
evaluation were utilized in Phase 2 to predict nominal flow rates
within the piping system.   Flow was determined as a function  of
overall area drainage and the fractional portion of area upstream
of  each pipe segment.   Friction-induced head loss  calculations
were   performed  and  accumulated  with  distance  upstream   to
formulate  a hydraulic profile within the system.   Use of  these
flow  dynamics  also resulted in a more accurate estimate of  the
actual  potential  storage  as the volume  of  storage  increases
beyond the static, level pool model.

        Hydraulic  profiles and resultant storage volumes at  any
time were shown to be a function of flow rate  (a direct result of
rainfall intensity).   A nominal intensity of 0.1 inches per hour
was  selected  for final analysis.   Estimates of storage  volume
also varied throughout the city dependent upon the relative  pipe
sizes  to  areas  served.  Large areas  generate  greater  runoff
volumes  than  small  areas  such that for any  given  pipe  size
frictional head loss and resultant hydraulic profile levels  were
greater  implying  fuller  pipe conditions  and  greater  storage
potential.

          Table  6.1  shows the relative increases  in  estimated
storage  volume due to the various aforementioned  considerations
for  the  Throop  Street catchment area.   A  substantial  volume
increase of 14.8% is attained by considering all pipe sizes, with
an additional 21.7% volume increase based on manhole volumes  and
flow  dynamics  as  compared with  earlier  calculations.   These
values  are based on a backwatering weir levels at the pipe  crown
elevations.  Actual  volume increase percentages will  vary  with
weir  height  at this location and will vary widely at all  other
locations.

          Although  the  revised method  of  storage  calculation
tends   to  increase  the  predictable  storage  volume  at  each
location,  the   final storage volume may not increase above  the
1981 predicted amount.  Exact design hydraulic evaluation of each
chamber reduced the final weir elevations in several chambers for
the partial BMP plan implementation thereby reducing  anticipated
storage volumes.  Similar reductions will probably occur at other
regulators  during final complete BMP implementation of East Side
regulators  such  that overall storage volumes  provided  may  be
similar to those estimated during 1981.

         The  potential for in-line storage was  estimated  using
the   in-line   storage  computer  program  for  selected   sites
(regulators  and  further  upstream  control  points).   In   the
selection  of  upstream sites no point was considered  for  which
ground elevation was less than ten feet above the resulting water
elevations  after considering weir heights and flow hydraulics at


                                6.11

-------
                                 TABLE  6.1
             TYPICAL IN-LINE STORAGE VOLUME COMPARATIVE  ANALYSIS

             LOCATION:  THROOP STREET  -  WEIR 5-5   FEET ABOVE INVERT
TOTAL STORAGE PIPES 36" AND ABOVE
              NO FLOW DYNAMICS
              NO MANHOLE VOLUME

TOTAL STORAGE ALL PIPING
              NO FLOW DYNAMICS
              NO MANHOLE VOLUME

TOTAL STORAGE ALL PIPING
              WITH FLOW DYNAMICS
              NO MANHOLE VOLUME

TOTAL STORAGE ALL PIPING
              NO FLOW DYNAMICS
              WITH MANHOLE VOLUME

TOTAL STORAGE ALL PIPING
              WITH FLOW DYNAMICS
              WITH MANHOLE VOLUME
                       18000
                       20662  FT3
                       24531  FT3
                       21233  FT3
                       25155  FT3
  ANALYSIS MODE

ALL PIPING"

FLOW DYNAMICS""

MANHOLE VOLUME*"

FLOW DYNAMICS PLUS
MANHOLE VOLUME
SUMMARY

VOLUME INCREASE

   5662

   3919

   571

   4493
PER-CENT INCREASE

  14.8

  19.0

   2.7

  21.7
*  COMPARISON OF ALL SYSTEM PIPING TO PIPES OVER 36 INCHES

** BASED ON ALL SYSTEM PIPING
                                     6012

-------
peak  rates to insure later plan implementation would  not  flood
basements.  Also, no point was considered that would cause backup
beyond a point where trunk sewer lines intersected. The intention
of  this  limitation  was  to avoid  altering  the  flood  relief
patterns for which the relief system had been originally designed
and  built/  and to avoid diverting flows to different regulators
through the bifurcation points.

          Empirical  functions were developed at  each  candidate
in-line  storage  control  point relating stage (of  back-up)  to
storage  volume.   These  functions were prepared  by  using  the
interactive   computer  program  to  determine  in-line   storage
estimates for several plausible elevations and then curve fitting
the results.  These empirical functions were then utilized in the
simulation model.

          Pre  BMP in-line storage conditions were analyzed based
on  average  river conditions with  the  gate-river  interactions
determining the extent of storage in many cases.   The total  pre
BMP  storage volume was calculated to be 327,000 cubic feet.  The
total  potential  capacity for system storage including  the  two
aeration tanks at the WWTP is estimated to be 3.93  million cubic
feet,  or  the  equivalent of approximately seven of the  Hancock
Street  sized  storage  basins.   In-line  sewer  system  storage
including  the interceptors account for 58 percent of the  total.
Storage estimates for individual catchment areas are presented in
Table   6.2    Storage  estimates  are  provided  for  pre    BMP
conditions and for the final BMP plan as determined by EDP.

          Exact  storage  volumes for locations  to  be  modified
under  the  complete  BMP program will be  dependent  upon  final
selection  of weir elevations.   This selection will be based  on
detailed  hydraulic evaluation similar to those performed for the
regulators  modifed  under the reduced BMP plan and  detailed  in
Chapter 7.


6.5  Interceptor Mfidj£l

          The  interceptor model is summarized  schematically  in
Figures 6.4 and 6.5. Figure 6-4 is an overview of the model while
Figure 6.5 illustrates the computational procedure.

          The  interceptor  model divides the interceptor  system
into  four  sections.   Each  section  is  treated  as  a   quasi
independent  "tub."   A mass balance is performed to account  for
influents,  effluents  and pump station overflows.  Dynamics  are
incorporated  to  model  the  river  crossing  and  to  calculate
discharge from one section to the next.
                               6.13

-------
         TABLE 6.2




IN-LINE STORAGE POTENTIAL
Location
of
Flow Control
Device
1 . Downstream
East Side
14th
First
Carlisle
Fitzhugh
Johnson
E.Genesee
Federal
Janes
Millard
Thompson
Hoyt
Emerson
Holden
McCoskry
Holland
Webber
Estimated
"Pre BMP" Storage
(Low River)
(1000 Cubic Feet)


25
2.4
5
36
1.3
0.7
4.5
4.5
1.2
35.2
1.4
2.4
1.4
66
2.7
38
ESTIMATED "BMP"
Storage
Capacity
(1000 Cubic Feet)


25*
4.7
15
70
27
6.9
25
125
6.7
63
5.3
5.8
14
110
22
38
          6.14

-------
TABLE 6.2  INLINE STORAGE POTENTIAL  (CONTINUED)
Location
of
Flow Control
Device
West Side
Weiss
(ave. river)
Cronk
W. Genesee
Remington
Throop
Hayes
Adams
Mackinaw
Fraser
2 . Upstream
14th area:
at 17th & Perkins
at 14th & Normal
Webber area:
at River St. & Cam
at Birch & Harris
at Troy & Boxwood
Fraser area:
at Vermont & Salt
Estimated
"Pre BMP" Storage
(Low River)
(1000 Cubic Feet)

23

36
1.0
3.8
3.8
3.3
51
1.9
24


-
-

brey
-
-

-
ESTIMATED "BMP"
Storage
Capacity
(1000 Cubic Feet)

66

54
19.0
2.5
4.1
2.6
21
1.6
24


253
106

191
153
42

191**
                               6.15

-------
TABLE 6.2  IN-LINE STORAGE POTENTIAL
        Location
           of
       Flow Control
          Device

        Mackinaw area:
   Estimated
"Pre BMP"  Storage
   (Low River)
 (1000 Cubic Feet)
    at Hamilton &  Williams


    at Gratoit & Michigan

    at Mackinaw &  Michigan

      Adams area:

    at Jackson & Mason

    at Cass &  Woodbridge

      Hayes area:

    at Hayes & Michigan

      Cronk area:

    at Union & Delaware


      Totals

      Interceptor
       Storage

      WWTP

      Total Storage***
       327


       770

       500

      1597
  ESTIMATED "BMP"
    Storage
    Capacity
(1000  Cubic Feet)
                                92


                               125

                                54



                                60

                                67
       133


      2655


       770

       500

      3925
      *   Storage control was not located at regulator chamber
         plan  in lieu of upstream control

     **   Included as part of reduced BMP Plan underflow
         control modification
    * **
        Does not  include Hancock street storage basin
                              6.16

-------
Douglas (OWF only))
Webber >-
Birch J

Holland
McCoskry
Emerson
Hnut .,. 	 .,
Thompson
Ml Hard
Janes
Federal
Genesee
Johnson
Fltzhugh
Carlisle
First
1^ tn e* c». ..«
14th St. (4 Lines)



WEB
•k. ARE




Emerso
BER FW
A AF
fc FMrP^ON PUMP STATION
i i
on 3
n Area






i
Sectl
	 * Fourtee
Are
HANCOCK
STORAGE BASIN
t

Sectl
Hancoc
ISER < (Fraser
IEA ^ ( Dearborn

Mackinaw
van Buren/cass
Adams
k Area Hayes
Thrnoo





i i
on 4
nth St.
a

RIVER
CROSSING
Sect
Weiss
Miller
Remington




i W. Genesee
Ion 2 « 	 \ Cronk
Area ( Weiss Street
1 1
WWTP WEISS PUMP STATION
1 ._ 	 » ArRATTflN RACTNC AT UUTP
Figure e.,4 Interceptor model overview.

-------
Prediction of Flow
to Interceptor and
Water Quality



Lj
r"
L_.
i —
L_
SECTION 1
Ml
Vol - Flow In
+ Previous Volume
- Flow Out
| ITERATION
Flow Out - f (Head)
'

i *
Pump
Overflow » Vol
- Maximum Vol
1 '
1 •
SECTION 2
1 •
Vol.
,, ITERATION '
Flowout
I
Pump Overflow
SECTION 3









•WM i


j
1
1
1
1

... . ,._ 	 	
_» Head Down Stream) 1
1
Max Vol. - f (Weir at !
Pump Station) j
Max Head - f (Max. Vol.) |
i
1
1
1
__ i
Head 1

' i
_. .»~.v,.
Max. Head |
1
1
1
Figure 6.5 Interceptor model computations.
                           6.18

-------
Head,  West Side
                           Effective  Head
                           =  f(Applied Head
                              -  Head Loss)
                          Velocity
                          = f(Effective  Head)
                        Head Loss
                        = f(Velocity, Physical
                            Restrictions)
                                  1
                           FLOW ACROSS RIVER
     Figure  6-6West Side river crossing model.
Head, East Side
   ITERATION
                                  6.19

-------
          The calculation procedure is to proceed from section  1
to  section  4.  Volume  is calculated from the  time  stream  of
regulator  flows to the interceptor added to the existing  volume
in  the  interceptor,  minus  the  flow into  the  next  section.
Overflow  is any volume in excess of the available  volume  after
the  volume calculations are completed.  Flow between sections is
calculated  on the basis of head differentials between  sections.
An  iteration  scheme is used to balance  the  volume,  head  and
discharge   calculations   for  each  section.   The  West   Side
Interceptor  river crossing simulation model depicted  in  Figure
6.6  operates  on basically the same principle of  head/discharge
balance through an iteration procedure.

          Options  for altering the operation of the  interceptor
were included in the model.  Pump station weirs could be  altered
to increase available interceptor storage volume if possible, and
to  increase the head differential between sections.  This option
was used at the Weiss Street Station to increase the flow  across
the river.   Alterations at the WWTP as described below were also
built  to  interact  with the interceptor model by  altering  the
allowable  discharge  to the plant from  interceptor  section  4.


6.6  West Side Interceptor £iy_ej: Crossing Consider^tj.pi\s

          The   junction  of  the  West  Side  Interceptor  river
crossing and the East Side Interceptor  has been identified as  a
hydraulic  bottleneck.  The Weiss Street Pumping Station relieves
backwater/surcharge at the crossing and is a major combined sewer
overflow.  It is clear from an analysis of the frequency of  pump
operation  and pumping plant discharge rates at the Weiss  Street
Station  during rain events,  that flow across the river into the
East  Side  Interceptor  is  severely  limited.    Coupling  this
understanding  with the   objective of handling more wet  weather
flow  through the use of aeration tank  storage and/or  increased
WWTP  flow-through  rates  suggested consideration  be  given  to
increasing flow across the river. An iterative procedure was used
during modeling to simulate the river crossing as illustrated  in
Figure 6.6.

Phase I ModeJ.j.jig Considerations (1979-1981)

          Details of the West Side Interceptor river crossing are
shown in Figure 6-7.    The crossing is accomplished through a 42
in.  pipe under the river,  and 48 in. pipes near the end on each
side  of  the  river.   Maximum head differential  at  the  river
crossing  is  based  on the spillover weir height  at  the  Weiss
Street  Station from the West Side interceptor.   This head range
can  vary  between negative values  and 8 feet depending  on  the
flow conditions in the East Side Interceptor at the junction.
                              6C20

-------
                       66'
                        from east side
                                                                   from west side and river crossing
72"
to WWTP
r>o
                                                        PLAN VIEW
                       66'
                                                        PROFILE  VIEW
                Figure  6.7 Details of river crossing, Saginaw.

-------
          Examination   of  the  river  crossing   suggests   two
important  physical restrictions to flow.   One.  the small  pipe
sizes  used  to carry the flow across the river will  limit  flow
depending  on  the energy applied to the flow.  The other is  the
near  right-angled  junction of East and West  Side  Interceptors
which  may  result in a large energy loss due  to  the  turbulent
mixing of the two flows.  The actual head applied to the crossing
was  expected  to be the primary parameter for  determining  flow
across the river during storm events.

          The  relative  importance  of East/West  Side  junction
energy  losses  in Saginaw to the flow across  the  river  during
storm events is summarized in Figure 6.8.  Here, the maximum flow
across  the river is plotted as a function of flow depths in  the
East  Side  Interceptor.   Calculations were made  using  Darcy's
equation  and  average friction factors for  concrete  pipes.   A
computer  program was developed to handle the changing pipe sizes
in the section crossing the river.   Head values on the West Side
were based on the weir evaluations at Weiss Street Station, above
which  flow is diverted from the West Side Interceptor  to  Weiss
Street  Station.   Therefore,  the curves presented represent the
maximum  flow across the river just as overflow occurs  at  Weiss
Street Station.

          The  lower  set of curves in Figure 6.8  represent  the
pre  BMP   conditions.   The upper set represents flows under  an
additional  head  of  five  feet  at  the  Weiss  Street  Station
(presumed  relative  easy  to  accomplish  by  raising  the  weir
elevation).In each set of curves, the lower line included K = 1.8
junction  energy  loss  factor,  while the  upper  curve  ignores
junction  energy loss.   Therefore,  the two lines in each set of
curves  form the upper and lower bounds of what the true flow  is
expected  to be.   Estimates of the ratio Q   are also shown  for
different levels of stage in the East Side Interceptor.

          The  most likely range of operation is when high  flows
in  the  West Side Interceptor are matched by high flows  in  the
East Side Interceptor,  probably around full pipe conditions.  As
Figure 6.8 demonstrates,  flow from the West Side Interceptor  is
severely   reduced  as  water  level  rises  in  the  East   Side
Interceptor,  and  can be entirely shut down if two and  one-half
feet of surcharging occurs in the East Side Interceptor.  At full


pipe East Side Interceptor conditions,  flow across the river has
been reduced from a maximum of around 60 cfs  (no flow in the East
Side Interceptor) to less than 36 cfs.

          Adding an additional five feet of head on the spillover
weir  at the  Weiss Street Station,  such as by  raising the weir


                                6022

-------
                    100 -
cr>
ro
CO
                                                                                    Row from West

                                                                                    Flow in East
                                                                                                        5 foot head addition
                                                                                                        at Weiss
                                                                  5678

                                                              Depth of flow, East Interceptor (feet)
10
                    Figure  6.8      Analysis  of Saginaw  River crossing discharge levels.

-------
elevation  into  the station's wet well,   does a  great  deal  to
increase flow across the river.  This is  particularly true in the
operating  ranges  of high East Side Interceptor flow.    At  full
East Side pipe flow,  flow across the river can be increased from
below  36 cfs to above 60 cfs,  and the gain is even greater  for
surcharged conditions in the East Interceptor.  However,  even for
the more unlikely  events of high West Side Interceptor flow  and
low  East Side Interceptor flow,  the gain by increasing the head
differential is still substantial.

          Figure 6.8 also demonstrates the relatively unimportant
role played by energy loss at the junction itself.  Gains made by
improving  head loss conditions at this junction could  be no more
than  a  few  cfs,  with  these gains  decreasing  as  East  Side
Interceptor  flow  rises  and becoming very small  in   the  most
likely range of operation ( QR = 3).  This result suggests  that
the  junction  itself  may not be the best candidate  for  future
improvements .

          The  additional  five feet of head at the Weiss  Street
Pump Station will not significantly impact the pumping  pool level
at  the  Hancock  Street  Pump  Station  considering  level  pool
conditions but due to the increased water elevation (and the  net
head  reduction  between Weiss and Hancock) will serve  to  reduce
flow rates between Hancock and Weiss. This result will  reduce the
pump  chattering noticed from the Hancock records.  It   would  be
advantageous  to  further investigate and optimize  the  relative
turn-on elevations of the pumps at Weiss  Street and Hancock Street
facilities   to   ensure  initial  operation  at  Hancock   where
storage/treatment  is  currently  available  as  opposed  to  the
untreated pumpage at Weiss Street.

          In summary,  theoretical analysis of the river crossing
strongly  indicates that flow is being severely restricted during
storm events.   This is due to the small  pipe sizes used to  make
the crossing, and the lack of necessary high energy differentials
to overcome friction in the small pipes,   particularly  when flows
are  also high in the East Side Interceptor.   Based on empirical
and theoretical work on energy loss at pipe junctions,  the nature
of  the  East/West Interceptor appears to be a  relatively  trinor
cause of river crossing flow restrictions.


                   3 Model in  Conisiderat ions   934
          The  above  analysis  was  based  on  system  hydraulic
conditions  as established during Phase 1.   During the  Phase  3
analysis  it  was  determined  that the influent  pump  wet  well
includes  high  and low levels alarms set at 551  and  556  feet,
respectively.   Original   design  and  construction    hydraulic
                               6.24

-------
profiles had indicated an operating wet well elevation of 547 ft.
Actual   operation  at  this  elevation  can  cause  severe  pump
cavitation.

          The relative elevations of the WWTP influent pumps  wet
well  and  the 6 foot East Side Interceptor are such that  normal
plant   operation  between  these  alarm  points  backwaters  the
interceptor to varying degrees.   Operation of the WWTP  influent
pumps  is performed manually and higher or lower wet well  levels
are  possible.  Level pool backwatering at the  alarm  elevations
translate  to  depths of 1.5 ft and 6.5 ft in the 6  ft  diameter
East  Side  Interceptor at the junction of the 48 inch West  Side
Crossover.   Given  that the 48 inch crossover line invert is 0.5
ft.  above the 6 ft interceptor invert, backwater  effects  range
from  1 ft depth to 6 ft depth (2 ft surcharge) in the  crossover
line.

          The  crossover analysis prepared in 1979-1981 (Phase 1)
presented  in  Figure  6.8 was modified in  Phase  3  considering
interceptor wet well alarm levels and the results are depicted in
Figure 6.9.

          Low  alarm  (551 ft) and high alarm  (556 ft)  WWTP  wet
well  induced backwater levels are indicated on Figure 6.9 at the
interceptor  depths of 1.5 and 6.5 ft respectively.  In addition,
a line indicating the hydraulic capacity of the interceptor  with
varying  depth is shown.   The significance of this line is  that
any  wet well level and total interceptor flow condition  falling
to  the left of the line will induce an interceptor liquid  level
governed  by the interceptor flow rate and will be unaffected  by
backwatering.   The actual interceptor depth will be as indicated
by the intereceptor flow rate at the capacity line.

          Wet well levels and interceptor flow rates to the right
of  the capacity line indicate  backwater-controlled  conditions.
Flow  in  the East Side Interceptor and the West  Side  Crossover
will  be  a function of the degree of surcharging in  each  line.
Surcharging  of the West Side Interceptor crossover is limited by
spillover into the Weiss Street Station wet well.

         Under   conditions   existing   prior   to   the    weir
modifications implemented under the reduced  BMP  plan, crossover
flow  was  limited to the rates indicated by the lower "pre  BMP"
line  shown in Figure 6.9.   Assuming a low alarm WWTP  wet  well
level,  the  maximum  crossover  flow was about  53  cfs.   Under
potential  high wet well conditions,  (even during dry  weather),
crossover  flow was limited to 30 cfs prior to spillover  at  the
Weiss   Street   Station   (assuming  level   pool   conditions).
Considering  head losses between the junction and the  WWTP,  the
maximum crossover rate would be 25 cfs.   As indicated on  Figure
                                6.25

-------
                    WO -
INJ
X
H-
n
n
o
»
n

5
A
                 O
                 Ml
                 a
                                  ,East Side Interceptor
                                   Maximum Capacity at Depth
                                 WWTP Low Met
                                 Well Alarm
                                 Level
                                  WWTP High Wet
                                  Well Alarm
                                  Level
                                                                                 in Crossover
                                                                                Reduced BMP Levels
                                                                           East Side Interceptor Surcharged
                                                                              Pre BMP Levels
                                                             Pre BMP Flap
                                                             Gate Seat Elev.
                       .3   I
                                                                                                Post BMP Weiss
                                                                                                Weir Elev. (562.25')
                             4      9      6      7      8     9     10     1 I

                                 Depth of Flow, East Side  Interceptor  (Feet)
                               Figure 6.9   Verification  of Weiss Street Pump Station Weir Modification
                                           Effects  on Crossover Rates

-------
6.9 the spillover elevation into the Weiss Street Station is 8 ft
above the East Side Interceptor invert and only 1.75 ft above the
WWTP  wet  well high alarm water level.   Head losses within  the
East  Side  Interceptor and the crossover and occurences  of  wet
well  levels above normal may  contribute to spillover into Weiss
at minimal crossover rates.  Modification of the Weiss Street wet
well  inlet  by  increasing  the  spillover  elevation  by  5  ft
eliminated early spillover and maximized crossover flow.

          Estimated potential crossover rates after reduced  BMP
modification are indicated by the upper line of Figure 6.9.   The
maximum  crossover  rate under optimum conditions (low alarm  wet
well level,  no East Side Flow) is 73 cfs.  The maximum crossover
rate  under high alarm wet well level conditions is estimated  to
be 50 cfs.   Adjusting this value for surcharge due to head  loss
in  the interceptor between the WWTP and the junction indicates a
maximum crossover of 47 cfs.

          In  sum,  under optimum conditions (low  wet  well,  no
upstream  East  Side  flow)  the maximum  crossover  rates  would
increase from 53 to 73 cfs due to the weir modifications.   Under
the condition of high wet well and no upstream East Side flow the
maximum  crossover rates would increase from 25 to 47 cfs due  to
program modifications.  Upstream East Side flow will always exist
and  this flow will induce greater head loss and  surcharging  of
the  interceptor  further reducing the potential crossover  flow.
The  conclusions  of this analysis are that modification  of  the
Weiss  Street  Station  spillover weir level  will  increase  the
crossover  rate  by about 20 cfs under all  conditions  and  that
operation  of  the WWTP wet well within the alarm range can  vary
the crossover flow rate  by 25 cfs.
                                  Cros_s_:Lng HY-ElH^Jii0-0.
          One  aspect  of  the  post  evaluation  (1984)  was  to
document the improved river crossing flow regime by evaluation of
the WWTP wet weather flow records.   It was expected that greater
volumes  of flow would reach the plant during storm events  after
Weiss Street Pumping Station weir modifications were performed.

          Following the Nov.  1,  1984 event high WWTP flow rates
were  observed for several days.   Total flows were greatly above
additional   volumes   expected   due  to   Weiss   Street   weir
modifications.   Field  investigations discovered a  log  jarring
open  a  backwater gate allowing river water into the  West  Side
Interceptor.    Although  this  situation  rendered  invalid  any
attempt  to document relative storm related flow volume  increase
at  the plant,  the several days of additional inflow provided  a
near  perfect  situation  for  evaluating  river  crossover  flow
conditions.   During  the period of river inflow,  WWTP  influent
                              6.27

-------
rates  remained near 71 cfs for several days,  and the West  Side
Interceptor  level  was reported to be just at the  Weiss  Street
weir  level.   Based on the early  morning WWTF flow rates  prior
to,  during  and after this event it was estimated that 37 cfs of
river  water  entered  the  interceptor.   Remaining  flows  were
estimated as:  other West Side - 16.6 cfs,  upstream East Side
9.8  cfs  and additional downstream - 8 cfs based on  the  system
distribution detailed in Chapter 5.

     Figure  6.9  was  utilized  to demonstrate  that  this  data
verifies  the  predicted potential  crossover  rates.   The  only
unknown factor was the WWTP wet well elevation.   Estimating head
loss in the interceptor between the junction and the WWTP for the
71  cfs  flow rate as 4.2 ft and assuming the low alarm wet  well
condition,   results  in  a  depth  of  flow  in  the  East  Side
Interceptor  of 5.7 ft.   Point "A" on Figure 6.9 indicates  that
for the estimated crossover rate of 53.6 cfs this data set  falls
to  the  left of the predicted line.   Increasing the  wet  well
liquid  elevation above the low alarm level would shift the  data
point to the right closer to the prediction line.  Alternatively,
using  the  West Side Interceptor level and estimating  the  head
loss of 53 cfs through the crossover at 5 ft placed the East Side
Interceptor data point , Point "B",  just on the prediction line.
This  would  indicate  a WWTP wet well level of 2.3 ft above  the
low end of the 5 ft alarm range, a quite probable condition.

          Based on this analysis and the uncertainty of the exact
wet well condition it appears that the prediction line accurately
portrays  maximum river crossing flow rates prior to spillover to
the modified Weiss Street Station wet well.

6 . 7 Runof_f_ Wja ter Qua 1 j.ty_

          Runcff    water   quality  is  calculated  from   three
components:  dry weather sewerage, cumulated dry weather sewerage
deposition and street washoff.

          The  dry  weather BOD and suspended solids  (TSS)  mass
loadings  at the WWTP were used as data inputs in  the simulation
model.    Total  dry  weather  mass  loading  at  the  WWTP   was
apportioned  to  the different catchment areas in the  simulation
model   on  the  basis  of  relative  contributory  dry   weather
discharges.  This  procedure  implies uniform  dry  weather  flow
concentrations throughout the system.

          Since most  of Saginaw is flat and dry weather sewerage
deposition are expected to be considerable,  pollutant deposition
loadings  during dry intervals between storm events were included
in the simulation model. Deposition rates were based on the above
calculated  long  term  dry  weather  flow  averages.   Empirical


                               6.28

-------
equations  developed  by EDP  (1) were used to  approximate  daily
deposition  rates for the more important  drainage  areas.  These
equations  require  as input  the following quantities:  a)  total
collection system pipe length;  b) average collection system pipe
slope; and c) the average per capita waste rates.  For simulation
work  a constant daily deposition rate equalling 15% of  the  dry
weather  pollutant  loading   for each  catchment  area  was  used
throughout  the system.  Comparison between the empirical results
derived for  four catchment areas and an arbitrary assumption  of
15%  of  the  total dry weather load is shown in  Table  6.3  and
suggest  that the 15% simplification is  reasonable.  Resuspended
deposited   loadings   are  assumed  to  be  distributed   evenly
throughout  any  rain  events.  It is further  assumed  that  all
deposited loadings would be scoured and completely flushed in  an
given  event,  that is,  there would be no carryover of  residual
loadings  to  the next event.   This assumption may  distort  the
"first  flush" estimates for  both high and slight runoff  events,
but would yield on the average, satisfactory estimates.

          Street   runoff  water  quality  was  estimated   using
empirical  equations based on rainfall and percent imperviousness
of each catchment area (2).  The empirical equations given  below
for  street  runoff  were adjusted to better match  the  expected
values in Saginaw.  The equations used as a starting point in the
calibration analysis are as follows:
                                                    1.05
        TSS (Ib/acre) = I/(0.136 + 0.00384 (I)(rain)    )

        BOD (Ib/acre) = (614/1)(rain)0.82             (2)

        where  I is percent imperviousness and rain is the  total
for the event in inches.

          Because  street  washoff  water  quality  is  the  most
difficult  component of the analysis to predict without  adequate
local  data,  manipulation  of the empirical curves developed  in
other  communities  was considered necessary.  Dry  weather  flow
loadings  and  deposition  rates  were  left  unaltered.  Initial
simulation runs showed both excessively high TSS and BOD loadings
and runoff concentrations.  Street washoff pollutant formulations
were altered (reduced) to better match Saginaw conditions.

          Several  of  these  curves  for a  number  of  different
municipalities  are  shown in Figure 6.10.  Imperviousness is  an
implicit  parameter  in  developing  these  curves.  Saginaw  was
considered  to be cleaner than the municipalities used to  derive
the  equations (streets are well swept,  for example) and it  was
expected that Saginaw washoff solids loadings to be on the  lower
end of the group.  Saginaw loadings fell to the higher end of the
group  of curves shown in Figure 6.10 using a 34% overall average


                              6.29

-------
                                       TABLE 6.3

              COMPARISON OF COLLECTION SYSTEM DAILY DEPOSITION LOADINGS
Collection
System
                      Method A
                  TSS*
                BOD*
                                       Method B
                   TSS*
                 BOD*
ADAMS
WEISS
WEBBER
McCOSKRY
 530
1100
 520
 280
300
600
300
160
 540
1700
 960
 440
240
720
420
200
Method A:  Dally Dry Weather Collection System Deposition Loadings Equal to
           15% of Total Daily Load.

Method B:  Prepared using empirical equations  (1)

*  - pounds solids deposition per day
                                   6.30

-------

-------
imperviousness.   The solids washoff formulation was reduced by a
factor  of four (See Figure 6.10)  to lower the solids  curve  for
Saginaw in comparison to other municpalities,  and to better match
the available Saginaw suspended solids data.

         The  street  washoff  BOD loading formulation  given  by
equation  was also adjusted.   For example, the computed ratio of
TSS to BOD loadings using the equation (2) is  6:1 for a 0.1  inch
storm. More common ratios are 20:1, 24:1 and  7:1 for residential,
industrial,   and  commercial  areas,   respectively  (3).    This
comparison  suggested  the  BOD  predicting  equations  used  for
simulation  were also high.  EDP used data from previous work (4)
to  adjust the BOD predicting equations.   Literature surveys  of
BCD street accumulation rates had  found these rates to be   equal
to 0.15,  0.21,  0.64,  0.53 and 0.11 pounds  per acre per day for
single family, multiple family, commercial, industrial, open land
uses,  respectively.   An  average of 0.3 pounds per acre per day
was estimated for Saginaw land use mix.  Using an average of four
days between rain events and a nominal washoff factor,  0.1  inch
rain will produce approximately 0.3 pounds per acre cf BOD.  This
value  is one sixth the value from the simulation equations.  The
equations were therefore lowered by a factor  of six.


6.8  WWTP Simulation

          The   TSS  and  BOD  efficiencies  at  the  WWTP    were
established at 93% and 89% using long-term average data. Maximal
plant  throughput  flow of 128 cfs was allowed.  Additional  flow
above  108 cfs was assumed to be split at the  grit  chamber  with
half bypassing the main plant facility. Excess flow above 128 cfs
was  allowed to backup resulting in overflow  at the Weiss  Street
Pump Station.

          Phase  1 modeling investigations (1979 -1981) indicated
a  potential  for increased utilization of the  WWTP  during  wet
weather. It was envisioned that increased utilization of the WWTP
capacity  during wet weather would be an extremely cost-effective
option in the overall combined sewer control  management  approach
for Saginaw.

         During  the  Phase  1 modeling,  it  was  believed  that
additional  wet  weather flow could be  handled.   A  rudimentary
analysis   was   conducted  to  assess  the   pollutant   removal
effectiveness at the WWTP during wet weather flow conditions. BOD
removal  efficiencies  were investigated during  high  flows  and
compared  to  low flow conditions to ascertain the feasibility  of
this approach.   A year and a half period of WWTP daily operating
records for  1978-1979 was examined.  The BCD removal for the WWTP
averaged approximately 89%  for both wet days and dry days.   It was
                               6.32

-------
tentatively  concluded  that  the WWTP could  handle  higher  wet
weather  flows without compromising the plant's pollutant removal
capabilities.

          The  WWTP  portion  of the simulation  model  used  for
assessment   of  the  reduced  BMP  and  complete   BMP   program
effectiveness  is described as follows.   Interceptor  discharges
beyond  a pre-set maximum of 128 cfs was assumed to backwater and
overflow  upstream.   All flows less than 108 cfs  received  full
treatment.  Discharges beyond 108 cfs but limited to 128 cfs were
flow-split  at  the grit chamber with half the excess  continuing
through  the plant and the residual by passed (and  disinfected) .
All flows continuing past the grit chamber receive full treatment
(BOD efficiency = 89% and suspended solids removal = 93%) .

          These assumptions approximate current plant operations.
For small to moderate intensity storms the model assumptions very
closely replicate practice.  For major storms of short intensityr
the assumed procedure is adequate provided the storage volume   of
the two aeration basins used for detention are not exceeded.  The
model  slightly  overestimates  treatment  efficiency  for  storm
events  in which the aeration tank volume is exceeded and through
flow conditions result for the aeration tanks.
6.9  Model Cal ibr a tj op/Ver j. jLJcafrJ-jMl fiffpjts

            Phase 1 JHojfleJL Calibration r. 1979 Fj.ow Data

          The  Saginaw  CSO  simulation  model  was  designed  to
provide  a rough approximation of the degree and distribution  of
overflow problems.  As such, and recognizing the severe limits of
the  available recorded calibration data,  it was not appropriate
to fine-tune the model to the degree model calibration may  imply.
Rather,  available  data  were  used primarily  as  a  check  for
reasonableness, and actual calibration was kept to a minimum.

          The  hydraulic simulation as developed on the basis  of
the   systems  physical  characteristics  was  not  substantially
altered after initial comparison to recorded values during  Phase
1.  The major point of concern was the operation of the regulator
chambers   as  operation  data  were  available  only  for   four
regulators  in  the  Hancock  Street  area.  Different  regulator
operational  schemes  were tested in the simulations analysis  in
selecting the scheme that yielded the most reasonable  comparison
of the predicted interceptor to measured flow data.

          A number of single rain events were simulated to  check
the  adequacy of the model.  The reasonableness of the simulation
model  is  demonstrated  in Figure 6.11  showing  the  comparison
                                6033

-------
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     volume of flow


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              6034

-------
between  a  0.3  inch modeled event occurring  over  a  two  hour
period,  and  a  0.33 inch actual rain event occurring  over  two
hours on November 1,  1979.   Flow at the WWTP compared favorably
with  predicted flows peaking slightly less than recorded values.
Flows  at Lee Street on the West Side also  compared  well.  Spot
measurments  (not shown) made on the East Side also compared well
to  predicted values.   As shown in the table in Figure 6.11  the
predicted  pumped  volumes  from the  Hancock  and  Weiss  Street
Stations   closely  approximate  volumes  computed  from  pumping
records.   For  the  same rainfall event the  predicted  temporal
sequencing of flows at the Hancock Station, the Weiss Station and
at  the  WWTP are shown in Figure 6.12 and  agree  with  observed
operation of the system.

          Predicted  overflows  at the pumping stations  compared
well  with  recorded  values.  Figures 6.13  and  6.14  show  the
comparison  of predicted and recorded stormwater pumped per  rain
event for the Weiss and Hancock Street Stations respectively. The
circled  data points represent  recorded values developed in  the
pumping  station  analysis  and the square data points  represent
predicted  values  for  different  rainfall  events.   The  model
somewhat  underestimates spring conditions of high  snowmelt  and
concurrent  rainfall.   Simulated overflows at the Emerson Street
Pump Station occurred only for extreme rain events in  accordance
with the observed operation of the Emerson Street Station.

          The  results  of a full year of simulations  (1978)  are
compared  in Table 6.4 with WWTP records that were available  for
the same period.  The simulation model summarizes flow and  water
quality  as  rain  contributions  above  a  nominal  dry  weather
loading.  This  calculation was performed so events of  different
durations could be compared with their total loadings. An attempt
was  made  to discern the same statistic from the  recorded  WWTP
records.  Plant  flow records were analyzed to eliminate a period
around  a  rain occurrence.  The estimation of wet  weather  flow
contribution  changes  substantially depending on the  length  of
period selected around a rain event.  Table 6.4 demonstrates  the
range  using  two to four days as the period eliminated  after  a
rain  event  to average the dry weather loadings.  The  simulated
rain  contribution fell within the range for excess flow  at  the
WWTP.

              Phase 1 - Calibration 19JJH Hatej: Quality

          A storm generating combined sewer overflows was sampled
on  July 8,  1980.  The sampled storm was 0.83 inches of rainfall
occuring  over  a little less than two hours as recorded  at  the
Saginaw  WWTP.  For  comparison  EDP simulated a 0.8  inch  storm
occuring over two hours.
                               6.35

-------
CT>
CO

CT>
                  400-
            ft
                  300-
                   200-
                    100-
                                                                          modeled event •  0.3" over 2 hours,  beginning hour 1
                                                                mwmimi   predicted flow Into Weiss pump  station
                                                                itmiiiiiiiiii   predicted flow Into Hancock pump station
                                                                mrnrr^   predicted at  WWTP
MB^MWV.^
i
|
H
5
} \
1 I
1 I
1 I

IMM
1

78     9     10     II

 Hours into event
                                                                                       12     13    14
                              Figure 6-12  Single event time sequencing.

-------
CTl
CO
                  6 -
                  5 -
          O
          
-------
CTi
•


00
                    3-
            O
            er
                    2-
            li
            n A
                    I -
                                        O (heavy flows due to spring thow)
                                                      °0
                                                      O
                                    8
                                      0°
                                I
                               .2
 I
.4
 I
.6
 I
.8
I
1.0
I
1.2
                                             LEGEND

                                             O Recorded Values
                                             D Predicted Values
                                                       Rain inches per event

                   Figure  6-14 Overflow into Hancock Street  pumping station I978-I9T9.

-------
                             TABLE   6.4




           PREDICTED  VERSUS RECORDED VALUES AT WWTP (1978)*.
Predicted Recorded
Total Volume
of Flow
x 106 ft3
Volume of
Rain Contribution
x 106 ft3
TSS
x 106 Ibs.
TSS
Rain Contribution
x 106 Ibs.
BOD
x 106 Ibs.
BOD
Rain Contribution
x 106 Ibs.
1071 1130
57-140
89 (estimated)
11.7 10.3
1.9 0.8-1.2
(estimated)
6.2 5.7
0.7 0.1-0.3
(estimated)
* - (1978:  304 day period, January - October.)
                              6.39

-------
          The   EDP  simulated  storm  generated  slightly   more
overflow  volumes and slightly lower flows at the WWTP.  Not  all
overflow  points  were  measured by  the  sampling  program.  The
primary  overflow  point  at the Weiss Street  Pump  Station  was
measured  and compared well with the simulated value.  Table  6.5
summarizes the hydraulic comparisons.

          Measured  water  quality  data was converted  to  total
pollutant  loadings  in pounds for comparison  to  EDP  simulated
values  (Table  6.5)  Concentrations of pollutants were  sampled,
however,  flows at the time of sampling were not available. Since
the Weiss Street Pump Station uses constant capacity  pumps,  and
for a storm of .8 inch only one 100 cfs pump would be expected on
at  any  given  time,   an  identical flow for  each  sample  was
assumed.  Total pollutant loads were calculated using the numeric
average  of  the water quality samples and the  times  the  total
volume  pumped.  The resulting total loads compare well with  EDP
simulated loads.

                  Phase 2. — Model Calibration

       EDP  directed  detailed wet weather  field  investigations
peformed  by  City  of Saginaw personnel  at  several  regulators
during the summer of 1983 and an intense program between July and
November,  1984.   Completion  of  the reduced  BMP  construction
program occurred at the end of September 1984 so that some  events
represent   pre  BMP  and  others  represent  post  reduced   BMP
conditions.

          As  a  check to the accuracy of the model developed  in
Phase  1,  the  hourly rain data for each storm  event  occurring
during  the  1984  pre  reduced BMP period was used  as  a  model
simulation input.   Modeled results included WWTP flow volumes at
40 to 65 per cent of measured volumes, Weiss Pump Station volumes
at 40 to 125 percent of measured volumes and Hancock Pump Station
volumes at 160 to 280 percent of measured volumes.   Based  on the
consistently low values at the WWTP and consistently high   values
at  the  Hancock Street Pump Station the model was  reviewed  and
modified   in  an  attempt  to  improve  field  and  model   data
correlation.

          It  should be noted that several changes to the Saginaw
sewerage  system  had occurred since the original Phase  1  model
calibration,  the most significant of which was the alteration of
relative initiation points at the Weiss Street and Hancock  Street
Pump  Stations.   This  alteration was performed by the  City  to
better  utilize  the  storage  capacity  at  the  Hancock   Street
detention  facility  prior to pumped overflow discharge at  Weiss
Street and constituted a major change in system operation.
                               6.40

-------
                            TABLE  6.5
         MODEL CALIBRATION RESULTS - STORM EVENT,  7/8/80
                       FLOW/VOLUME RESULTS

     A.      Sampled Storm: 0.83 Inches July 8,  1980
                   Simulated Storm: 0.8 Inches

                Overf 1 ow jfpl umes LLO.fi. cub Ic -feet)
                   Measured            Mode Ied

Weiss Pump        2.2                      2.4
 Station
Hancock Basin     0.3                      0.6
Fourteenth         *                       0.9
 Street

* pump station was  sampled gravity overflow  was not so total
overflow volume is not known.

                        WWTP Flows (mgd)

               July 8,  I960            Simulated

                    45                       37
B. Weiss Pump

Time
(am)
1:25
1:45
2:05
2.25
2.45
numerical
average
total vol ume
Station Overflow W
of July 8, 1980
Measurements
BODs
mg/l
102
84
158
102
74
104
overf 1 ow = 16 mill
Total Pollutant Loadings at We
ater Quality Calibration

TSS
mg/l
188
192
1032
656
46
423
Ion gal 1 ons
Iss(pounds)
           Measurement               Simulated  by  Mode
TSS          56,500                      59,300

BOD5         13,900                      15,300

                              6.41

-------
         The model was re-calibrated based on improved  knowledge
of  actual regulator operation,  rainfall/runoff  characteristics
and intuitive estimation of system hydraulics.   For this purpose
the storm event occurring on July 10-11,  1984 was selected as it
included  a  high  rain accumulation (1.14 inches)  and  occurred
prior to implementation of any elements  of the reduced BMP Plan.
Model  modification  in  general  included,   varying   regulator
underflow/backwater  gate  characteristics,   refining  estimated
times   of  concentration  in  several  drainage   subareas   and
alteration of interceptor stage/discharge dynamics.

          The  effects of these  modifications,  particularly  of
increased  time  of concentration,  were such that  event  runoff
durations  increased  and  peak  flow   rates  decreased  reducing
modeled pumpage volumes at the Hancock  Pump Station and providing
additional  flow  to the WWTP.   For the 7/10-11/84  event  final
ratios of field data volumes to modeled data volumes were 1.15 at
the  WWTP,  1.05  at  Weiss Street Pump Station and 0.90  at  the
Hancock  Street Pump Station.   It should be noted that for  each
event,  rain  data  was  recorded hourly at  the  Emerson  Street
Station  and  daily  by NOAA at the City  Water  Works  Building.
Variances in rain data values  at the two nearby locations,  which
represent  variable  rain  conditions   within  the   City,   were
typically  much  greater than  the differences in field and  model
data  recorded for the 7/10-11/84 and most other events.

          Considering  the  close correlation of  the  7/10-11/84
field   and  model  data,   the  model  was  considered  suitably
calibrated  for  prediction  of  pre-BMP  condition  system  flow
volumes.  Each of the 1984 monitored storm events occurring prior
to  completion  of  the reduced BMP plan construction  was  rerun
using  the upgraded simulation model.   Results   including  field
measured   data  to  modeled   data,   volumes  ratios  and   rain
characteristics data are included in Table 6.6.

         Model   results   are  closely   correlated   to   field
measurements  at the WWTP for  the first 5  events.  For the  final
event  the field to model ratio of 1.52 is high based on  Emerson
Street  Station rain data,  however rain data also indicates   the
NOAA  Station recorded 1.95 times the Emerson  Street Station  rain
accumulation.   In this case the average  rain at  both  stations is
1.47  times  the Emerson Street value and  would probably  produce
model data closer to the field value.

          Weiss   Street  Pump Station  data   tends   to   differ
substantially from  field data  after the first event. Later events
with  high field to model volume  ratios are probably due  to   the
occurrence   of these events during the  construction   period.    A
number  of   the   original   regulating devices   at the   regulator
chambers  were  removed and a  number of weeks passed   before   new
                                6.42

-------
regulating  devices were installed.   This would produce  greater
flows  to the West  Side Interceptor which in turn would  require
greater pumpage at the Weiss Street Station (prior to the station
weir modification). High values for the last event correlate with
the previous WWTP flow discussion.

          As  depicted  in Table 6.6,  the  Hancock  Street  Pump
Station  data  indicate reasonable  correlation.   Typically, the
model  predicts  higher  values  than the  field  data  which  is
probably  due  to  the  model assumption of  a  300  cfs  station
capacity  when  potentially only 1 or 2 pumps  actually  operated
simultaneously.   Exact  "turn on" water elevations for the three
pumps are unknown and future study is required to optimize  these
locations.   Data  presented is overflow to the river at  Hancock
and  does  not include wet weather flows pumped to the  detention
basin and bled  back to the interceptor.  For this reason events
indicating  non-zero model data flow and zero from the field may
be  misleading  since the event may have actually  activated  the
Hancock  Station  but produced no flow to  the  river.   In  sum,
variances  between  Hancock Station field and model data for  the
three locations  are minor on an actual volume basis.
         Phase i - Ppst Construction Model Verification

          Monitored Storm events occuring in October and November
of  1984  provided field data representative of field  conditions
existing  after complete implementation of the reduced BMP  Plan.
All  West  Side  regulating  devices were  replaced  with  vortex
valve  control  regulators,  one  upstream  storage  chamber  was
completed  and  the Weiss Street Pump Station weir was  modified.
Unfortunately,  few major events occurred during this period  and
for  several  of  these  events,  field  data  validity  required
intuitive interpretation.  Results are included in Table 6.7.

          An  event  on 10/18/84 indicated  reasonable  agreement
between  field  and modeled data at the WWTP.   The Weiss  Street
data indicated a low model value which proved to be a  consistent
trend  for  all  events as discussed below.   No field  data  was
recorded  at the Hancock Street Facility and the model  data  was
combined with the 10/21/84 value for evaluation.

          During  the  10/21/84  event,  one  regulator  flapgate
became   lodged-open  allowing  river  water  to  flow  into  the
interceptor until manually corrected.  Data at the WWTP indicates
good  correlation between model data and first day WWTP  recorded
flow.   Thereafter,  plant flows continue to remain above normal,
presumably   due to the open gate since similar  rain  conditions
during other events produced only single day effects at the WWTP.
Weiss Street model data was again typcially low.   Model data for
                               6043

-------
                        TABLE 6.6

              PRE REDUCED BMP CONSTRUCTION
                 TOTAL FLOW - 1000 CU FT
        TREATMENT   PLANT
WEISS PUMP STATION
DATE
7/10-11
8/5
8/8
8/18
8/27-30
9/7-11
FIELD
5300
2620
3120
2500
7715
5591
MODEL
4594
2432
2995
2233
6900
3671
R
1.15
1.08
1.04
1.12
1.18
1.52
UJELfi
3360
613
3032
1950
3233
2452
HQfiJSL
3212
791
1837
1160
4320
1533
R
1.05
0.77
1.65
1.68
0.75
1.60
FIELD
1207
0
220
0
-
0
HANCOCK PUMP STATION
         E2EEL    £

         1339  0.90

          518     0

          309  0.71

          112     0

         2626

           0      1
Ratio of Field/Model
                           6.44

-------
the  10/21/84  event at the Hancock Street Station when  combined
with the 10/18/84 event model data, agreed well with the recorded
value  representing both events.  Correlation between  field  and
model data for this event is considered good.

          Following a minor rain on 10/25/84,  WWTP flow remained
high  for  several days producing flow equal to the  model  value
after  2  days and 35 percent greater after the third  day.   The
NOAA  Station  recorded twice the rain recorded  at  the  Emerson
Street Station (used in the model) for the three day period which
again  indicates  the significance of storm  intensity  variation
throughout  the drainage area.   The other significant aspect  of
the event is that minimal flows were modeled and also recorded at
Weiss Street and Hancock Street facilities somewhat verifying the
"low-end" calibration of the model.

          Both events occurring during November in Table 6.7 were
subject  to adverse conditions.   On November 1 the  large  Weiss
Street  flapgate  lodged open,  allowing large amounts  of  river
water  to  enter the system.   On November  8-11 a four  day  wet
period   was  mostly  snow,   making  accumulations  and   runoff
predictions  difficult.   In  general  WWTP  and  Hancock  Street
Station  flows  modeled  were in the range of recorded  flow  and
Weiss  Street  Station flow volumes predicted  in  comparison  to
measured values were low.

          Low  predicted  flow values at the  Weiss  Street  Pump
Station  are  probably  attributable to reduced  river  crossover
flows,  a direct result of the wet well levels at the WWTP  being
manually controlled.

          As   part  of  this  study's  recommendations   it   is
envisioned  that the pump control  systems at Hancock  Street,  at
Weiss  Street and the WWTP be evaluated and optimized for maximum
pollution  reduction  using  existing  facilities.   The  general
conclusion resulting from the foregoing discussion is that  based
on  currently  available field data,  the model,  as modified  to
match pre-construction data,  reasonably predicts the effects  of
the reduced BMP implementation as  recorded at the WWTP and at the
Hancok Street Pump Station.


6.10  Phosphorous Modeling Details

          Phase 1 .& Phase 2. Considerations  (1979-1983)

          In  addition to the TSS  and BOD  parameters  previously
detailed,  an  analysis  of potential total phosphorous  removals
were  performed for each simulation.  Evaluation  of  phosphorous
loads in wet weather and dry weather flows and potential removals
                               6.45

-------
                                              TABLE  6.7
                              POST REDUCED BMP CONSTRUCTION STORM DATA
                                       TOTAL  FLOW  -  1000  CU  FT
DATE
10/18
10/21
Day 2
10/25
Day 2
Day 3
11/1
Day 2
11/9
Day 2
Day 3
Day 4
TREATMENT PLANT
FIELD MODEL £
3475
4679
68182
935
2139
2807
2807
60162
3060
6444
10900
11400
2889
4862
2121
3379
3333
4367
7700
1.2
0.98
1.4
0.44
1.0
1.32
0.83
1.78
1.48
WEISS PUMP STATION
FIELD MODEL £
1768
**
4000
108
2562
2454
849 2.1
1439 2.8
0
839 3.0
605
387
992 2.47
HANCOCK
FIELD
1136*

0
774
540
                                                      HANCOCK PUMP STATION   Rain Accumulation
  * - Combined Data 10/18 & 10/21
 ** - Backwater Gate Reported Stuck  Open
*** - Rain/Snow Mixture
.g Emerson
0.96 0.75
0.79
1 0.17
2.0 0.61
0.73
NOAA
0.67
1.0
0.35
0.80
***
0.65
£
1.18
1.27
2.06
1.31


-------
at  the  WWTP,  began  with  a  review  of  existing  phosphorous
concentration records at various locations in the system.

          A  pilot study performed between October  and  December
1969   for  assessing  various  methods  of  phosphorous  removal
reported WWTP,  raw sewerage total phosphorous concentrations  to
range  from 3 to 10 mg/1 and averaged 6.4 mg/1   (5).   Review  of
report  data  indicated wet weather flow concentrations to  range
from 3 to 5.3 mg/1.  During the July 8,  1980 storm event samples
were  collected at selected overflow points.   Total  phosphorous
concentrations  ranged from 0.2 to 7.5 mg/1 at the  Weiss  Street
overflow  and  from  0.15 to 1.3 mg/1 at  the  Fourteenth  Street
overflow.  Flow rates were not recorded and flow-weighted average
concentrations   could  not  be  computed.    Total   phosphorous
concentrations  of  several  influent  samples   at  the  Hancock
Storage/Treatment Facility were averaged to yield a concentration
of 2.8 mg/1.

          Table 6.8 presents summary results of  total phosphorous
loadings  to  the   WWTP for the period  from  October,  1978  to
September 1979, as determined from treatment plant records. Total
phosphorous   concentrations  were  highest  during  fall  months
presumably  due to the effects of decayed foliage.  Average  WWTP
influent  phosphorous concentrations for all  weather  conditions
are  somewhat less than reported for the 1969 October to December
pilot  study.   Wet  weather concentrations  during  October  and
November,  2.5 and 3.46 mg/1, respectively, are  comparable to the
1969  results.   It is assumed that the dry weather concentration
reduction  was  due to a change in consumer use  of  phosphorous-
based  products during the time between the two  data periods  and
that   the  more  recent  data  accurately   represent   existing
conditions.

          Average monthly WWTP total phosphorous removals for the
1978-79  period  varied  from 63.5% to 82.2 % and  averaged  75%.
Average  monthly  wet weather concentrations  indicate  a  yearly
average  concentration  of  2 mg/1.   Further  analysis  of  WWTP
removal efficiencies during wet weather conditions indicated that
the   WWTP     could  adequately  pass  increased  flow   without
efficiency  reduction.   For the simulation  model  calculations,
total  phosphorous entering the WWTP during wet  weather flow  was
set  at a nominal concentration of 2 mg/1 and a WWTP removal  was
set at 75 percent during Phase 1 and Phase 2 evaluations.   Based
on  the  range  of total phosphorous concentrations  observed  at
Weiss Street,  Fourteenth Street,  and at the Hancock Facility, a
total   phosphorous  concentration  of  2.8  mg/1  was   set   as
representative  of  all overflows.     Considering the  floatable
nature  of materials within CSO and the post storm  draindown  of
late  event  cleaner stormwater to the WWTP it would be  expected
that  overflow  concentrations  at regulator  chambers  would  be


                               6.47

-------
         TABLE  6.8




WASTE WATER TREATMENT  PLANT



 TOTAL PHOSPHOROUS SUMMARY
Month
7/79
8/79
9/79
6/79
5/79
4/79
3/79
2/79
1/79
12/78
11/78
10/78
Average
Influent
Concentration
MG/L
2.3
2.5
3.0
2.86
2.6
2.2
2.2
3.9
3.5
3.5
3.3
3.4
Average
EFFLUENT
Concentration
MG/L
.99
.89
.94
.85
.89
.76
.59
.67
.86
.85
.88
1.06
Average
Removals
a
A*
63.8
63.5
68.9
68.6
65.8
66.2
72.8
82.2
75.4
75.2
71.2
76.3
Wet Weather
Average Influent
Concentration
MG/L
1.74
1.98
-
2.45
2.08
2.1
1.52
-
-
-
2.5
3.46
                                    75.
2.00
            6.48

-------
greater than WWTP concentrations. These concepts are reflected in
the above values.


            Phase 3_ Additional Considerations (1384^

     The  above phosphorous analysis was based on data  collected
during  the  late  1970's  when standard  practice  at  the  WWTP
included  the use of waste pickling liquor or ferrous sulfate for
phosphorous removal.   In the last several years,  lower influent
phosphorous  concentrations have enabled the City of  Saginaw  to
meet  effluent  standards  without  the continuous  use  of  this
specialized phosphorous treatment.   The effects of  discontinued
pickling  liquor  treatment on overall phosphorous removal  rates
were investigated in Phase 3 of this study.

          During this period of the study, U.S. EPA requested EDP
to   investigate  the soluble fraction of the  total  phosphorous
load  as  it  is  the soluble  fraction  which  is  most  readily
available to aquatic growth in Saginaw Bay.

          Up until this time,  the standard procedure at the WWTP
included  evaluation of total phosphorous  concentrations.  Plant
records  for summer/fall periods in the years 1978 and 1979,  the
base  data years of the original study,  were available and  were
used  in  conjunction  with current plant data  for  analysis  of
phosphorous  removal efficiencies.   Historical data  review  was
limited  to  total phosphorous removal efficiency  determination.
Soluble   phosphorous data was attained as a special task  during
this period.

     The Phase 3  (1984) field investigation indicated lower  WWTP
influent  total  phosphorous concentrations than reported  during
earlier periods.   Average WWTP concentrations for  all flows  for
the  5 month June to October period were 1.55 mg/1.   Wet weather
samples at the WWTP grit chamber indicated a weighted average  of
1.3  mg/1,  although "first flush" values were as high as 6 mg/1.
Wet  weather  concentration  in the  Weiss  Street  Pump  Station
averaged 1.74 mg/1.

         All loading calculations performed in the  evaluations of
Chapter  10 of this report were made using values of 1.3 mg/1 for
wet weather flows to the WWTP and 1.74 mg/1 for  system overflows.
Previous  model  analyses were based on WWTP influent  phosphorous
concentrations   of 2.0 mg/1 and overflow values  of  2.8 mg/1 based
on data generated in the late 1970s.

          WWTP   data  for  the  summer/fall  periods,   July  to
September,  1978 and July to October,  1979 were separated accor-
ding  to  dry  and wet weather conditions and  with  and  without
                               6.49

-------
tertiary treatment (pickling liquor or FeS04 addition) and  total
phosphorous  removal efficiencies were computed.  Results were as
follows:

                 %Removal   of  Total   Phosphorous

                           Secondary Treatment  Tertiary Treatment


     Dry Weather                   60                69
     (No. days)                    (21)             (151)

     Wet Weather                   56                69
     (No. days)                    ( 9)              (34)

     Average                       59                69

          The  above  results  indicate a    9%  to  13%  removal
increase  using  tertiary treatment.   Although a 4% decrease  in
total phosphorous removal  occurred during wet weather  secondary
treatment,  no  change was noted from dry to wet conditions  with
tertiary treatment.

          A  review  of WWTP data  obtained  for  the  summer/fall
period  June  to  September,  1984  indicates  an  average  total
phosphorous   removal  efficiency  of 54%  (120 days) for  combined
dry  and  wet  weather conditions  without  secondary  treatment.
Beginning  on September 17, 1984 both total and soluble  forms of
phosphorous were investigated.   In addition,  on October 7, 1984
teritary  treatment  (pickling liquor addition)  was  re-instated
allowing  for  analysis of the removal efficiency for both  total
and soluble phosphorous while under optimum treatment conditions.
Resulting  data  shown  in  Table  6.9    indicate  a  50%   total
phosphorous  removal efficiency with secondary treatment which is
9%  below 78/79 data and 4% below  June to September 1984  average
data.   No  removal of soluble phosphorous was noted.  After  the
renewal  of tertiary treatment,  a 70.4%  removal  efficiency  was
attained.

          Inspection of the results in Table  6.9  indicates that
total phosphorous removal with secondary  treatment is limited  to
the  removal  of the non-soluble phosphorous  fraction.   On  the
average  95.5% of the non-soluble  fraction was removed.   Soluble
concentrations actually increased  an average of  4%.  Considering
this  removal efficiency and that  the influent phosphorous  is 54%
nonsoluble  on average,  the 50% total phosphorous removal  value
reported above is normally attained.  Inspection of the  results in
Table 6.11B indicates that tertiary treatment provides  removal of
both the soluble and non-soluble fractions.   Non-soluble removal
was  88%,  and the soluble removal increased to  47.4%.  Influent


                               6.50

-------
phosphorous concentrations were 45% soluble  (similar to the 45.9%
reported above - see Table 6.11A) such that  the total  efficiency
of 70.4% was attained.

          In conclusion, tertiary treatment  increases the soluble
fraction  removal by 47%,  and reduces the non-soluble removal by
7.5%,  resulting in a total phosphorous removal of 70.4% or 20.6%
above  that attained without special treatment.  The decrease  in
non-soluble  phosphorous removal  (95.5% as compared to 88%)    is
apparently  due to incomplete secondary clarifier settling of the
floculant material generated by the chemical  reaction.   Soluble
phosphorous  tied  up in the unsettled floe  would appear as  non-
soluble  phosphorous  in the laboratory analysis.   Part  of  the
soluble phosphorous removal rate  reported is attributable to this
apparent  increase  in  the non-soluble fraction and  on  a  total
phosphorous basis the effects tend to cancel each other out.

          Results   of  these  analyses  were  used  to  evaluate
potential  WWTP  efficiencies  and  therefore  the  net  possible
reductions in  river loadings under the various treatment schemes.
Values  of 50% and 75%  removal were selected to represent  annual
averages of total phosphorous removal efficiencies for conditions
with  secondary and tertiary treatment, respectively.
                               6051

-------
                              TABLE 6.9
               WWTP Phosphorous Removal  Results (1984)
    Effects of  Treatment With/Without Pickling Liquor (FeS04)

             A.   Treatment Without FeS04 (17  Days)
Influent

  Total P
  Soluble P
  Non Soluble P
   Avg.  cone,  mg/1

       2.70
       0.95
       1.12
% of Total

   100.0
    45.9
    54.1
Effluent

  Total P
  Soluble P
  Non Soluble P
       1.04
       0.99
       0.05
   100.0
    95.2
     4.8
              B.
Influent
  Total P
  Soluble P
  Non Soluble P
             % Removal

       Total P          49.8

       Soluble P        -4.0

       Non Soluble P    95.5

Treatment HUtti ££SJ24 (8 Days)
       1.69
       0.76
       0.83
   100.0
    45.0
    55.0
Effluent

  Total P
  Soluble P
  Non Soluble P
       0.50
       0.40
       0.10
   100.0
    80.0
    20.0
                              % Removal

                         Total P        70.4

                         Soluble P      47.4

                         Non Soluble P  88.0
                           6.52

-------
                           CHAPTER 7

             DESIGN OF REDUCED BMP PLAN MODIFICATIONS
7.1  Foreword
         Throughout  the  preliminary  Phase 1  modeling  efforts
(1979-1981),   simulations   were  run  varying  the    hydraulic
operations  of  regulator  chambers  based  on  general  physical
modification  concepts.   Design  of the exact  physical  changes
required  within each chamber was completed  during the design of
the reduced BMP Plan implementation  (Phase 2).

        Physical  details  of  regulator  chambers  and   typical
modifications   are   presented   in   Section   7.2.     Special
modifications  required at the Adams Street Regulator and at  the
Weiss  Street  Regulator  are presented in Sections 7.3  and  7.4
respectively.  Section 7.5 details the work performed to increase
the  effective head at the Weiss Street Pump  Station.    Section
7.6  details  the  single new  upstream  in-line  storage/control
chamber  constructed under the reduced BMP Plan  at  Salt/Vermont
Streets.


7.2  Regulator Chamber Details and Modifications

         Three  general types of regulators were  encountered  in
Saginaw  and  have  been classified  as Type   "A",  Type  "B"  and
modified  Type  "B".  All  regulators  are  underground  concrete
structures  consisting mainly of the four concrete  walls,  floor
and ceiling,  a central open top conduit,  concrete side weirs,  a
flap gate to the river,  a wall cavity with manual sluice gate in
one  side weir and a conduit leading to a drop manhole above  the
main intercepting sewer.


       Type   "A"   regulators  have  fixed  underflow    orifices,
generally   about 1/2 foot by 1/2 foot.  Type  "B"  regulators  are
typically much larger than Type "A"  regulators and also  contain  a
Brown  & Brown flow regulator consisting of a  wall thimble,  swing
gate,  a  float  and transmission apparatus.   The  regulator  is
located  on the downstream side of  the side  weir containing  the
manual sluice gate.   A separate adjacent chamber was constructed
to  contain the float device and the transmission  apparatus  was
located overhead connecting the float to the  gate.

         Figure  7.1 illustrates the layout of a typical Type "B"
chamber.  Type  "A" chambers are similar without the float chamber
and Brown and Brown regulator as depicted in  Figure 7.2.    Figure


                                7.1

-------
   »   To River
          Manual Sluice Gate
                Brown & Brown
                Flow
To
River
       .
Automatic
Sluice Gate

Flap Gate
                  Connector
                  to Interceptor
                         Plan View
                                              Float
                                              Chamber
                                          Transmission Device
                                                        Valve
                                             Float

                                     Brown &Brown Regulator
                      Section View A-A
         Figure 7.1   Type "B" Regulator Chamber Schematics
                            7.2

-------
                               To Interceptor
              Plan View
                           Access Manhole
                                    To Chamber
        Chamber
        Underflow
              Section A-A
Figure 7.2   Type  "A" Regulator Chamber
                 7.3

-------
7.3 is a plan view of a Type "B" chamber depicting flow patterns.
Type  "B"  regulators have variable underflow rates altered by  a
float gate operation.   As water levels rise,  underflow orifices
close.  Table 7.1 includes pertinent regulator chamber dimensions
used  in  the  hydraulic  calculations  and  Table  7.2  includes
pertinent original and modified weir data.

         In  the  unmodified  Type "B"  and  Type  "A"  regulator
chambers  high  flows  not  handled by the  underflows  would  be
discharged through backwater gates to the river.   The  operation
of the backwater gates was dependent on their seat elevations and
relative river elevation, and could be prevented or hindered from
opening in some cases for high river conditions.   Most backwater
gates were in the same chamber as the regulator.  A few backwater
gates  were  separated  and  situated closer to  the  river  (for
example at the Cronk and Genesee Street Regulators).

         Backwater gates are typical flap-type swing gates  (with
the  exception of the five modified Type "B" regulator chambers).
In  most  cases only a minimal amount of storm flow  increase  is
needed  to  raise water depth enough to open the flap  gates  and
cause a discharge to the river.   The gates are also sensitive to
river  elevations  as most gate seats are  located  near  average
river elevations. The Weiss Street gravity line is notably  about
five  feet below average river elevations.   High river flows can
restrict  the  gate  operation and  subsequently  require  higher
depths of flow to cause river discharges.    Varying river  stage
can  have   a somewhat random effect in increasing the amount  of
in-line storage of storm flow and decreasing overflows.

         The  third group of regulators encountered are the  five
Type  "B" regulators located in the Hancock Street area  modified
during  construction of the Hancock Street Detention Facility  in
1977.  The  intent of the modifications was to  increase  in-line
storage,  and  to divert flow in excess of the in-line storage to
the interceptor (and eventually to the Hancock Street Facility).

         The  regulators had been altered to cause the  underflow
orifices to clcse rapidly,  limiting flows to the interceptor and
thus  committing the first flush of a rain event to in-line  sto-
rage created at the chamber.  EDP considered it more advisable to
maintain  high underflow discharges to the  interceptor,  limited
only to what the interceptor can maximally handle.   Operation in
this manner will commit the first flush of a rain event, general-
ly  carrying  the  highest concentration of  pollutants,  to  the
inteceptor,  and eventually to the WWTP.   This mode of operation
is preferable to capturing the "first flush" in storage which may
become overflow at a later time if the rain continues and can  be
accomplished  with  constant  discharge devices that  are    more
reliable and easier to maintain than the present float mechanisms.
                               7.4

-------
Ul
                     CS to
                     Float
                     Chamber"
                       DWF to
                       Chamber
'."<
                                                           DWF to
                                                           Interceptor
f
                                              |   CS to
                                              1 Interceptor
                                                    »

                                                           f
                                                          •"
                                                       SO
                                             CSO to River
                      Figure 7.3    Type  "B" Regulator Chamber Flow Patterns

-------
                      TABLE  7.1
           BMP  Program Regulator Chamber Weir Alterations
LOCATION
ELEMENT
OF REDUCED
PROGRAM
EXISTING WEIR
LEVEL ABOVE
INVERT  FT.
BMP WEIR   EXISTING   NEW OVERFLOW
LEVEL      OVERFLOW   WEIR FT.
  FT.      WEIR FT.
REMINGTON Y
THROOP Y
FITZHUGH
JOHNSON
FEDERAL
W. GENESEE Y
MACKINAW Y
HAYES Y
CARLISLE
E. GENESEE
MILLARD
HOYT
HOLDEN
HOLLAND
EMERSON
WEBBER
McCOSKRY
ADAMS Y
JANES
THOMPSON
CRONK Y
FRASER Y
WEISS Y
FOURTEENTH
FIRST
MILLER
AMES Y
COURT Y
CASS
VANBUREN
DEARBORN Y
5.0
4.4
6.9
3.96
4.36
5.78
3.*
2.94
3.84
3.76
2.58
3.15
3.67
4.35
3-9
0
8.2
5.67
5.2
7.*
6.65
9.0
0
0
3.42
2
1.25
1.1
1.3
.9
.9
2.16
3.17
5.17
.96
1.2
.18
.9*
.14
.37
.5
1.09
1.3
0
1.09
1.34
8
4.16
2.94
.5
6.5
3.28
9-0
10.0
4.8
.5
2
1.25
1.1
1.3
.9
.9
—
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
2
1.25
2.8
2.0
1.9
1.9
6.0
5.4
6.42
2.7
2.9
1.6
4.4
1.2
1.4
1.5
2.65
2.95
1.0
2.7
3-4
3-25
6.5
5.28
2.0
8.5
4.95
5-67
9-0
2.8
2-5
3-6
3-75
2.8
2.0
1.9
1-9
                                7.6

-------
         TABLE 7.2




REDUCED BMP  PROGRAM REGULATOR CHAMBER
AND FLOW REGULATION DATA
Name/Location Type
Remington B*
Throop
W Genesee
Mackinaw
Hayes
Adams
Cronk
Fraser
Weiss
Ames
Court
Dearborn
B*
B
B*
B*
B
B
B
B
A
A
A
Salt/Vermont Upstream
* Modified
** Length of
** Length af
Hancock Area
Chamber
Dimensions
Length**Widtn Between
Side Weirs***
Ft.
12'6"
12'6"
18'6"
12'6"
9 '6"
30 '9"
12'6"
-
5'6"
4'
41
4'
Chamber
Ft.
6'0"
6'0"
4'0"
5 '3"
4'0"
7.4..
6'0"
-
2 '2"
3'6"
2 '9"
,,,

Flow Regulator
Design Criteria
Discharge
CFS
1.56
1.56
2.9
1.74
2.0
10.38
8.8
24.0
22.2
.37
.3
.3














Regulator
existing weirs to be altered (see
new weirs to be constructed (see
Table 7.1)
Table 7-1)

               7.7

-------
         Selection   of  appropriate  vortex  valves   for   each
regulator chamber location modified under the reduced BMP program
was  based  on  apportioned  flow rates (six  times  average  dry
weather  flow - Table 7.2) considering WWTP capacity and  modifed
chamber  configurations.   Vortex  valve  head-discharge   curves
characteristically include low level orifice peak, switchback and
near  constant (low rate of flow increase) vortex flow condition.
Vortex valve selection was accomplished by comparing a particular
chamber's   design  flow/perceived  operating  head  range   with
manufacturer's rating stage/discharge data.   The mcst desireable
selection results when the chamber 's operating head range extends
from  at  least  low  head orifice peak  for  the  device  up  to
conditions  where full vortex braking occurs.   A less desireable
but  still  acceptable  choice  (if  minor  flucuations  can   be
tolerated)  occurs when the upper end of the configuration's head
range  does  not  fall  within  the  devices  establihsed  vortex
operating   range  but  in  the  switchback  zone.   The   design
stage/discharge  characteristics for each of the vertex valves is
listed in Table 7.3.

         The  regulators were modified in the reduced BMP program
to  ensure  that flows in excess of what is  discharged   through
the  underflow regulating devices or stored in the system  behind
the  weir,  will first overflow the side weir and be directed  to
the  interceptor.   Only extremely high flows will  overflow  the
new  cross  weir separating the backwater gate  portion  of   the
chamber and be directed to the river.   This weir arrangement was
considered  by  EDF  tc  be both the  least  expensive  and  most
available  method  of limiting oveflows at any cf  the  regulator
chambers in the system.


 7 . 3 Proposed We_ir Alterations

         The  reduced BMP program included the alteration of   12
existing regulator chambers.  Each of these regulator chambers is
located on the West Side of the Saginaw River.   Table 7.1  lists
all  the  existing  regulator  chambers  and  the  proposed  weir
alterations  under the complete BMP program.  Regulator  chambers
altered under the reduced BMP plan are noted.  Typical details of
regulator  chamber  alterations were shown in Chapter  1,  Figure
1.6.

         Regulator   modifications  included  construction  of  a
concrete cross weir wall between the backwater gate and the  flow
channel   sluiceway  of  sufficient  elevation  to  insure   that
stormwater volume in excess of available in-line storage capacity
flows  to the interceptor with only extreme flows discharging  to
the river.   The new cross weir is located just downstream cf the


                               7.8

-------
                            TABLE 7.3
          Vortex Valve Stage/Discharge Characteristics*
                         Discharge (1/s)
Head  (ft)
B
H
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
7.
8.0
9.0
10
11
12


470
530
570
600
620
600
570
550
600
658
710
760
804
850
891

240
265
285
300
285
260
255
270
285
300
325






190
230
250
230
190
180
175
180
195
200
220
240
260



68
77
82
72
79
87
95
102
108
113
119






50
57
51
44
46
48
51
54
58
62
64






38
44
39
31
29
31
33
35
36
38
40
43



(1

40
48
42
33
34
35
37
40
44
47
50
55



cfs = 28

10
7
8
9
10
11
12
12+
13
13+
14
15



.3 1/s)

4+
5
5+
6+
7
7+
8+
8+
9+
9+
10+






A - Weiss
B - Adams
C - Salt/Vermont
D - W. Genesee
E - Hayes
              F - MacKinaw
              G - Remington/Throop/Cronk
              H - Ames
              I - Court
 *  As per data  provided  by  Advanced  Fluidics,  Inc.
                               709

-------
dry  weather sluiceway and extends across the chamber between the
existing  side  weirs.  Lengths  of  the  new  cross  weirs   are
indicated in Table 7.2.  Existing side weirs creating the in-line
storage were modified to ensure that the water surface  elevation
due  to  backwatering and flow dynamics satisfied  the  arbitrary
criteria  of a 10 foot buffer zone to the ground elevation in the
area.  The  side  weirs  generally extend  the  length  of  the
regulator  chamber and are modified the  entire  distance.   Side
weir lengths are included in Table 7.2.  Extreme stormwater flows
in   excess  of  the  interceptor  capacity  will  backwater  the
regulator chamber and spill over the side weirs downstream of the
new cross weir and discharge tc the river.

         An  inter-active  computer  program  was  developed   to
determine optimum crest elevations of the modified side weirs and
new cross weir.  Typical storm flows (2 and 5 year design storm),
extreme flows (50 year storm),  weir lengths,  and chamber outlet
capacity  and  other physical dimensions were considered  in  the
program.   Conceptually  it  was  intended to select  a  modified
configuration wherein maximum storage would be provided prior  to
side weir spillover to the interceptor. In addition, maximum flow
to the interceptor would occur prior to bypass to the river.  The
cross  weir elevation was selected such that flew would top  this
weir  at  the  same  time bypass to the  river  occurred  due  to
interceptor  capacity limitations.  The need to ensure sufficient
unrestricted  passage  for extreme storm flows was  the  limiting
factor  in maximizing storage potential.   Due to  the  uncertain
nature  of  the actual flow hydraulics under  probable  turbulent
conditions within the chamber,  conservative weir elevations were
selected.

         Four  locations  were designated to  include  adjustable
side  weirs  and cress weirs accomplished by  attaching  moveable
stainless steel plates to the concrete weirs.  Based on operating
data within the chamber and stcrmwater backup conditions upstream
of the chamber,  these plates can be adjusted to increase storage
if excess surcharge does not appear probable.

         Curing the 1977  Hancock Street Facility  Implementation
the  flap  gates  were removed at the West Remington  Street  and
at the Throop Street Type "B"  regulators, and were replaced with
automatic sluice gates.  These flap gates were re-installed under
the reduced BMP plan.  Both flap gates and automatic sluice gates
exist at Adams Street,  Mackinaw Street and Eayes Street.   Under
the  "reduced BMP" plan implementation, all automatic sluice gates
were  raised  and  left  in  the  full  cpen  position  at  these
locations.

         In  general   the scope of work at Type  "A"  chambers  at
Ames Street and Court  Street included:   a)  removal of   existing
                               7.10

-------
regulator slide gate,  gate stem, supports, brackets anchor bolts
and  appurtenances;  and,   b)  installation of new vortex  valve
regulating device and accessories.

         Modifications  to  the Type "A"  Regulator  at  Dearborn
Street  included:   a)  adjusting the existing slide gate to a  6
inch  vertical  opening,  b)  cutting down walls and  resurfacing
crest on existing side weirs; and c) constructing new cross weir.

         The general scope of work at type "B" chambers included:
a)   removing  existing  float  operated  mechanical   regulators
including float,  gate,  operating mechanism,  cables,  supports,
anchor bolts and appurtenances;  b)   removing existing stainless
steel weir plate and supports,   c)   installing new vortex valve
flow regulating device and accessories, d) cutting down walls and
resurface  crest  of existing side weirs,  e)   constructing  new
cross weir,  f)   installing adjustable stainless steel weirs  on
the  two modified side weirs and on the new cross weir;  and   g)
recontouring  fleer  sections  with concrete fillets  to  prevent
debris buildup and direct flow.

          In  addition to the above items at Type  "B"  regulator
chambers  at  West Remington Street and at Throop  Street,  ether
modifications   included:  removing and salvaging  the   existing
automatic sluice gates and installing new tide gates.


 7.4  Sp_ec.ia_l Modification o f_ the Adams_ Street Type "E"
        Regulator

        The  placement of the new flow regulating devices  within
most  Type "E" chambers was behind the side weir wall next to the
interceptor outlet (See Chapter 8 for additional  details).   The
installation  of  the new flow regulator could not  be  similarly
accomplished  at  the Adams Street Regulator due to the  relative
flow regulator size and the chamber size.   Considering the  very
large  drainage area serviced by the Adams Street Chamber the new
flow  regulator  was  roughly twice the size of  other  "B"  type
chamber devices.

         The chamber area downstream cf the side wall  containing
the  original Brown and Brown regulator is 4 ft.  wide and due to
this  limited  space,  it was necessary to locate  the  new  flow
regulator  directly in the sluice area of the chamber.   As  with
all other chambers,  the design of the final configuration was to
include  the  following functions:  a) allow dry weather flow  to
pass  through the flow regulator to the  interceptor;  b)   store
initial wet weather flow; c)  pass additional wet weather flow to
the interceptor;  and, d) to limit river bypasses to extreme flow
conditions.
                                7.11

-------
         Only  one  of the typical two side weirs existed at  the
Adams Street Chamber which limited the weir length available  for
stormwater  overflow to the interceptor prior to overflow to  the
river.  The need for additional side weir length coupled with the
difficulty  in  placing  the new flow regulator and a  desire  to
minimize  debris  accumulation in remote chamber areas led  to  a
complete modification of the chamber interior.

         Figure 7.4 illustrates the final configuration selected.
Two  new  cross  weirs were  constructed  in  the  chamber.   The
upstream  cross weir was placed at an angle to the side walls for
the dual purpose of maximizing the available overflow length  and
to  direct  flow to the regulator device inlet.   This  weir  was
constructed  at  the same elevation as the modified,  (cut  down)
side weir such that storm flow in excess of storage capacity will
top these weirs simultaneously and pass to the interceptor.

         Concrete fillets were used upstream of the cross wall to
assist   directing   flow  to  the  inlet  and   prevent   debris
accumulation.   Downstream  of the cross wall,  the sluiceway was
concrete filled and the existing regulator device and the  manual
side wall sluice gate were removed.   No overflow weir existed at
this  side  wall  and to allow passage of  new  regulator  device
outflow and cross wall overflow,  a section of the side wall  was
removed.   A  wall cut of 5 ft by 7 ft was selected based on both
flow  volume  criteria and to accommodate workman passage  between
chamber sections.

         Concrete  filling  of the original sluiceway flush  with
the  chamber  inlet floor provided the large area  necessary  for
installation  of the new flow regulator.   A  cast-in-place  wall
thimble was designed for inclusion in the upstream cross weir for
mechanical  attachment of the flow regulator.   In addition,  the
device  was  secured to a cast-in-place  floor  bracket.   Again,
concrete  fillets  were designated to minimize  areas  of  debris
deposition and direct flow to the outlet.

         Control  of  flow  to the river is accomplished  by  the
downstream  cross  weir  and  the  original  side  weir   section
downstream of this cross weir.  The intent is that all flow up to
the  interceptor capacity be stored or pass either through the  5
ft  by  7  ft opening or over the side weir to  the  interceptor.
Storm flows greater than the interceptor capacity would top  both
the  downstream cross weir and the downstream section of the side
weir,  pass  through the backwater flap gates and to  the  river.
Modification of the downstream side weir section and construction
of the downstream cross weir were designed at the same elevations
as the upstream cross weir and modified upstream side weir.  This
                               7.12

-------
u>
                                   New Downstream
                                   Cross Weir
                                                                              New Upstream
                                                                              Cross Weir
   Hollow Underflow
   Area (Beneath Slab)\
^ ••: fry •.*'.-'. -"• i/•Jsgrr-77
•   i;          -I'f^-jTT    i:
                                                                                  /Side Weir
                                                           New Vortex Valve
                                                           Flov; Regulator
                 n • L_IJ	EF-Eyd
                   r."v.v v-: •.::-..-
                                                            Concrete Fill

                                                          ^Concrete Filled
                                                            Sluice
                                                            To Interceptor
                      Figure 7.4   Mams Street Regulator Chamber Modification

-------
elevation, 2.4 feet below the original side weir elevation, and 1
foot above the backwater gate seat elevation was calculated to be
optimum  to maximize storage and provide sufficient clear passage
to the river under extreme flow condiitions.


7.5  Special Modification Q£ the Weiss Street Regulator Chamber

         Flow  originating upstream of the Weiss Street  area  is
regulated  within a small structure located between the 120  inch
gravity  line serving the area and the Weiss Street Pump Station.
Unlike most other "B" type regulators,  this location contains no
side  spillover  weirs (See Figure 7.5).   Flow rates  above  the
regulated allowance will backwater the chamber,  the inlet to the
chamber  pipe  and  the 120 inch gravity  line.  Flap  gates  are
located  at the end of the 120 inch line with seat elevations 3.6
feet above the invert.   Stormwater storage above this level  can
pass to the river depending on the river elevation.   The average
river  elevation   is 2.09 feet above the gate seat such  that  a
normal  storage depth of about six feet within the 120 inch  line
is attained prior to bypass to the river.

         Downstream of the regulator chamber a 36 inch pipe leads
to  the  diversion  chamber  section of  the  Weiss  Street  Pump
Station.   Details of that location are included within the Weiss
Street Pump Station modifications discussed in the next section.

         Modifications to the Weiss Street Regulator were limited
to removal of the existing float/gate type regulating device, and
replacement with a vortex type unit and minor structural changes.
These   modifications  hydraulically  altered  the  flow  through
pattern  from  one  of decreasing flow to  the  interceptor  with
increased  depth  of  backwatering to a  situation  wherein  flow
increased  with  backwatering  to a rate of  six  times  the  dry
weather rate.  This maximum rate is based on the WWTP capacity to
normal flow ratio and was used at all modified regulators.

         As  with the Adams Street Regulator the area  served  by
the  Weiss  Street Regulator is quite large and the size  of  the
regulating  device  is  about twice the size of  those  at  other
locations.  Both  the 120 inch gravity line and the pump  station
diversion chamber were deemed unsuitable for flow regulation such
that installation options included modification of the regulating
chamber  interior  and exterior walls or placing the unit in  the
existing space.

         Although   the  space  within  the  existing  regulation
chamber  was  extremely limited and required placing  the  outlet
orifice  section in the outlet pipe and removal of  one  interior
wall section, this option was considered the most cost effective.
                               7014

-------
                                           SPECIALIZED
                                           INLET TRANSITION
         C.I.WALL CASTING
           SLIDE GATE    x
                                                                        NEW FLOW REGULATOR
                                                                        MC TYPE (SEGMENTED)
-o
•
en
FROM 120"
SEWER
                                                               6" WIDE WALL CUT
               Figure 7.5  Weiss Street Regulator Chamber - Plan View

-------
A  specialized  adapter  was required for  the  dual  purpose  of
transforming  the  flow  pattern from  the  existing  rectangular
regulator wall thimble to the required round inlet  configuration
and to offset the unit for proper alignment of the outlet orifice
with  the  chamber outlet pipe.   Unit performance would  not  be
adversely affected by this mode of installation.

         An  emergency  spillway was provided in the  chamber  by
cutting  a 3-1/2  ft.  by 5 ft hole in the chamber interior  wall
above  the  wall thimble at a base elevation equal to  the  crown
elevation of the 120 inch pipe (See Figure 7.6).  If extreme high
river  elevation conditions surcharged the 120 inch pipe during a
storm  event,  spillover  at the regulator wall  would  commence,
bypassing the regulating device.   Excess flow would then pass to
the  Weiss  Street Pump Station wet well and  be  pumped  to  the
river.

         Storage  volume  at  this location  remained  unchanged.
Alteration  of the existing river outlet flap gate  assembly  was
not  a practical method of increasing in-line storage considering
the relative normal river elevation to the 120 inch pipe location
and  the  need to ensure that extreme storm flow passage  to  the
river.  Benefits  of  the  BMP  program  implementation  at  this
location  included:  a)  replacing the float/gate type  regulator
with  a  near  maintenance free vortex  type  regulator,  and  b)
altering the storm period hydraulic configuration from one  which
limits the passage of "first flush" flows to the WWTP to a system
which passes "first flush" flow and maintains a rate as allocated
by the WWTP total capacity.


7.6 Weiss Street Pump Station Wet Well Modification

         Simulations  of  flow  conditions  in  the   interceptor
system demonstrated the value of altering conditions at the Weiss
Street Pump Station wet well to produce greater cross river  flow
rates  and  reduce Weiss Street Station  pumpage.    Optimization
analysis   of increasing the water surface elevation required  to
spill into the wet well dictated that a 5 foot  increase would  be
the most effective.

         The  existing structure at the Weiss Street Pump Station
included a circular cassion wet well diversion  chamber.   Most of
the  cassion was utilized as the wet well serving   three  100-cfs
pumps.   One  section,  separated  from  the wet well acted   as   a
diversion chamber.   All West  Side Interceptor  flow and regulated
Weiss Street 120 inch gravity  line flow  enters  this chamber.  Dry
weather flow exits the chamber through a 36 inch  sluice gate to  a
48  inch conduit leading to a  42  inch conduit beneath the Saginaw
River  connecting  to  the East  Side  Interceptor.   A  12  inch


                                7,16

-------
         SAW CUT 3'6* BY
         -) HIGH NALL HOLE
         IN EXISTING MALL
     S.S. BACK PLATE

     EXISTING SLIDE GATE AND
     MALL CASTING .
        EXISTING J5
        SEWER "IPE

        FROM
        120" SEWER
                                                                   S.S. PROTECTIVE DEFLECTOR PLATE
                                                                   !/<," S.S. FRONT PLATE
NEW FLOW REGULATOR
HC TYPE
                                                                         I/
          EXISTING 3t" PIPE
          TO INTERCEPTOR
           TO  PUMP STATION
           DIVERSION  CHAMBER
                                                            CAST ANCHOR ASSEMBLY IN NEM  BASE SLAB
                                                            AND SECURE NEM FLON REGULATOR
Figure 7.6   Weiss  Street  Regulator  Chamber Modifications-Section View

-------
concrete  wall separates the diversion chamber and wet well areas
and contains two 4-foot by 5-foot flap gates with seat elevations
2.75 feet above the diversion chamber floor (See Figures 7.7  and
7.8).

         Several  possibilities  were considered to increase  the
depth of flow in the diversion chamber prior to spillover to  the
wet well.  These options included, in general terms,  construction
of a wall or baffle system in the diversion chamber,   removal and
relocation  of  the  two  flap gates to  a  higher  elevation  or
construction of a wall within the wet well. Although space within
the  wet well was limited due to the location of bar screens  the
last  option  was  considered to be the most  feasible  and  cost
effective.

         Criteria  used in the wall design and location were  the
following:  a)  increase the diversion chamber depth five feet at
spillover;  b) induce free discharge over the new weir wall; and,
c)   maintain  water surface levels below the station  mid  floor
level  during  maximum  pump  rates.  The  selected  wall  design
maintained  an  elevation 4.75 feet above the existing flap  gate
seat  elevation and provided sufficient length such that  at  the
300  cfs pump capacity flow rate  (all pumps on) the water surface
behind  the weir wall would be one-half foot below the  station's
mid-level floor elevation.  Further protection was to be provided
for the station 's mid-level floor by the construction of a 3-foot
splash wall around the open wet well area,  with splash plates at
an existing stairway.

         Construction  of  the  overflow  weir  wall  created   a
separate  chamber  within  the  wet  well.    End-of-storm  evert
drainage  of  this chamber required placing a valve in  the  wall
base.   A   manually  operated valve was deemed the simplest  and
preferable  to  an automatic valve or a  constant-open  low  rate
orifice.

         The   final  design  allowed  construction  work  to  be
accomplished during dry weather conditions with no need to divert
dry  weather  flow or protect the interceptor from  loose  debris
washout.
7 . 7  New Up_stre^m Regulator Chamber

         As part of the demonstration aspect of this project, one
of  the fourteen in-line storage control structures  upstream  of
the  regulators  under the complete BMP program was selected  for
completion under the reduced BMP plan.

         An existing junction chamber is located upstream of  the


                               7.18

-------
36" Pipe
From
Regulator
Chamber
                                        Existing Sluice
                                        Gate
     West Side
     Interceptor
     Figure 7.7  Weiss Street Pump Station Wet Well
                 Modification - Plan View
                              7019

-------
   Pump
 Discharg
 Bar Screen
Pump Intake I
                                                   New 3'
                                                   Splash  Wall
                                                  New Weir  Wall
                                                  Existing Flap
                                                  Gates

                                                  Sluice  Gate
                                                  to  River
                                                  Crossover
   Figure 7.8  Weiss Street Pump Station Wet  Well Modification
               Section View
                                7020

-------
regulator  at Fraser Street on the West Side at the  intersection
of  Salt Street and Vermont Street was initially  selected.   The
chamber  consists of a 90 inch reinforced concrete pipe from Salt
Street  joining a 72 inch reinforced concrete pipe  from  Vermont
Street to form a 108 inch pipe.  All pipes are circular  with the
90  inch  and  72 inch pipe inverts elevated above the  108  inch
discharge pipe invert.  Concrete fillets within the chamber serve
to  provide smooth transitions between pipes.   Upon  inspection,
the chamber interior was deemed unsuitable for implementation  of
the intended stormwater storage and control devices envisioned.

          A   new regulator chamber was designed just  downstream
of this junction chamber which allows for control of wet weather
flow.  Locational plan and profile views are shown in Figure 7.9.
Concrete  weirs  were  constructed  within  the  new  chamber  to
backwater stormwater.   A new flow regulating device controls the
outlet  rate  to 6 times the dry  weather  flow  rate.   Combined
sewage  flow  in excess of the storage capacity  overflows    the
weir  and  continues to the Fraser Street Regulator.   A  special
large  diameter vent attached to the center line of the  device's
back  plate  (as can be seen in Figure 7.10) is provided for  this
configuration  which extends up to the crest of the  three-walled
internal weir.   When backed up sewage reaches this level  within
the  chamber,  this vent will flood causing the vortex action  to
cease,  thereby  increasing  rate  of flow discharging  from  the
device.   As  the water level recedes below the weir  crest,  air
will  again enter the device through the vent and vortex  braking
will  again  commence.   Thus  this vent  acts  to  increase  the
discharge  from the device whenever extreme high water levels are
reached.

         Figures 7.10 and 7.11  illustrates the conceptual layout
of the new regulator.  The chamber is approximately 20 feet wide,
17  feet  long  and 14 feet floor to ceiling with  a  three  wall
internal  weir providing 23 linear feet of  overflow  length.   A
new vortex valve flow control device is located within the bottom
of  the  weir wall.   This device arrangement allows dry  weather
flow to pass through the structure without undue depositon and up
to  six  times  dry weather flow to pass  to  the  Fraser  Street
Regulator while backwatering most of the flow for in-line storage
(175,000  cubic  feet).   Wet  weather flow  beyond  the  storage
capacity  will  overtop the weir.   It is estimated that the  one
year  storm flow would crest 1.4 feet above the weir top and  the
25 year storm flow would crest 2.9 feet above the weir top.   The
weir top is set at the crown elevation of the 108 inch pipe.

         Concrete  fillets were designated upstream of  the  weir
wall  to  limit debris depositon and to direct flow to  the  flow
regulator  inlet.   Downstream,  beyond and beside the weir wall,
concrete  fillets  were again designated to direct  flow  to  the
                              7021

-------
                            Existing Chamber
                                Existing
                                Chamber
               New Chamber
                                                    RIPE SEWER
                                                      N
                                                72" PIPE SEWER
                        Location
Figure 7.9  New Regulator  Chamber at Salt/Vermont Streets
             Location and  Profile
                          7022

-------
~j
*
NJ
           CONCRETE FI
           CONFORM TO
           FOR 1/4 PIPE DIAMETER
           THEN SLOPE I
New Vortex Valve  Flow
Regulator with Vent
                                                                                   CAST-IN-PLACE ANCHOR ASSEMBLY
                                                                              SECURE FLOW REGULATOR TO SLAB

                                                                             CONCRETE FILLETS CONFORM TO 103" PIPE
                   :>
                                                                                      «o' iewe*.
                                                                                            \
                     Figure 7.10   Salt and Vermont  Streets Chamber - Plan View

-------
               New Chamber
  9' Weir Wall
        v-EXISTING JUNCTION CHAflKR
HP	V
I * *   «   •  o   « ' '  ».   «
                                                                   X
                                                       Flow
                                                      <	
                                       New Vortex  Valve Flow fRegulator
Figure  7.11  Salt and Vermont  Streets Chamber  -  Section View

-------
outlet  pipe and limit deposition  The ground elevation is nearly
25  feet above the level of the chamber floor.   The  minimum  10
foot  buffer  between maximum water elevation and ground  surface
requirement was easily attained.
                               7.25

-------
                            CHAPTER 8

                  REDUCED BMP PLAN IMPLEMENTATION
8.1   Foreword

          During the period of late 1983 plans and specifications
were  prepared  for the implementation of the reduced  BMP  plan.
The contract was awarded in March, 1984 to Gary D. Steadman Inc.,
Bay  City Michigan .   A startup meeting held on April  30,  1984
marked   the  beginning  of  the  construction  phase  which  was
completed in September of 1984.


8 .2   Special Construction Requirements

         One  aspect  of the construction project was  to  modify
existing sanitary/stormwater regulating chambers and to construct
one  new  in-line control chamber on an existing  combined  sewer
line.  Each  of  these locations continually passes  dry  weather
sewage  flows  and  is subject to extreme flow rates  during  wet
weather conditions.

         The Contractor performed all work without bypass of  any
dry  weather flow to the river.    Only stormwater flow conditions
which  previously created discharge to the river were allowed  to
discharge to the river during the contract work.   The Contractor
was required to provide all necessary means of work protection by
backwatering,  pumping,  and  bypassing  arcund the work  to  the
interceptor all dry weather flow and to protect all work from the
effects of wet weather flow and correct any damage caused  during
increased flow conditions was required to prevent any material or
debris  required  for construction or created  during  demolition
from entering the sewage flow.

         The  Contractor was made aware that most regulators  are
below  potential river levels and that he was to prevent the flow
of river water into the regulator chambers,  particularly  during
sluice  gate removal and tide gate installations at Throop Street
and  Remington  Street.   Compliance with these requirements  was
ensured by inspection during the work.

         The existing flow regulators were to be removed prior to
installation of the new regulators.   The Contractor removed  the
float-operated  regulator  at nine "B" type regulators  including
the  gate,  float,  operator,  cables, suports and appurtenances.
The upstream slide gate,  seat,   stem, supports and appurtenances
were to remain.   The existing cast iron wall casting was left in
place to simplify demolition and new regulator installation.   At
                               8.1

-------
two "A" type chambers existing slide gates, seats, stems supports
and appurtenances were removed and replaced with new  regulators.
At  one  "A"  type  regulator,   Dearborn  Street,  the  existing
regulator  was adjusted but not removed.   One new flow regulator
was  installed  in the new control chamber at  Salt  and  Vermont
Streets.  A total of 12 new flow regulators were installed.


8.3  Installation

         The  new  flow regulating devices and  accessories  were
designed  to simplify installation procedures.   In general  each
unit was supplied  with accessory plates designed to be  attached
to  the  existing  chamber weir wall using through  bolts  and/or
anchor bolts.   Studs or threaded holes on the back plate allowed
for mechanical attachment of the flow regulator.  Integral anchor
pads  on  each regulator allowed for securing the device  to  the
chamber base slab with anchor bolts set into existing concrete or
onto  cast-in-place  anchor  assemblies where  new  concrete  was
designated.  At Adams Street the flow regulator was attached to a
new wall using a cast-in-place wall anchor.   At the new  chamber
constructed at Salt/Vermont Streets,  the flow regulator included
an  integral  wall mounting plate conforming to the 42 inch  wall
thimble cast by the Contractor.

         Flow  regulators for which the overall size exceeded the
dimensions of available accessways or manholes,  were supplied as
segmented units capable of passing through the existing openings.
These devices consisted of two to three segments assembled  using
bolted  connections.   Devices  were supplied assembled with  the
intent  that  the Contractor disassemble the  units,  place  each
segment into the chamber,  and reassemble the unit.  Intact units
were then properly positioned within the chamber and mechanically
secured to the wall plate assembly and the floor slab.

         The  flow regulator at the new regulator chamber at Salt
and Vermont Streets is equipped with a 6 inch vent pipe. The vent
pipe  is removable from the flow regulator and segmented to allow
placement in the chamber.  Vent pipes are supported by attachment
to the chamber wall using anchor bolts and an adjustable  bracket
assembly.

         Three types of flow regulators were suppled including 10
conical "MC"type,  one horizontal "MH" type and one orifice plate
regulator.  The "MC" types were used to replace existing existing
float-operated  regulators at all the "B" type chambers and  the
manual  gate  at the "A" type chamber  at  Court  Street.   These
devices are general conical in shape with flow entering through a
circular end plate.   One new "MH" type flow regulator, installed
at  the type "A" regulator at Ames Street,  consists of two  flat


                               8.2

-------
plates  connected  by a band around the outer  edge.   The  final
device  was  a simple orifice plate consisting of a square  plate
with a circular hole which was installed within the Fraser Street
chamber.  Pertinent details of flow regulator characteristics are
presented in Table 8.1 (which was included in the bid document to
provide  the Contractor with a means of estimating the   handling
involved in the installation of the devices.


8.4  Chamber Modifications

         Photographs  were  taken to  document  the  modification
process.  The photograph in Figure 8.1 displays the interior of a
typical  "A" type regulator chamber as previously modified  under
the  Hancock  Street Detention Facility construction  program  in
1977.   Sewage  enters  the chamber via the pipe on the left  and
drops  into a small sluice.   During dry weather conditions  flow
then drops through a 6 inch x 6 inch opening in the side wall  at
the  end  of the sluice to a chamber section leading to  the  DWF
outlet  pipe.   This pipe,  located in the upper left part of the
picture,  leads  to the interceptor drop manhole.   Moderate  wet
weather  flow,  which will not pass through the 6 inch x  6  inch
opening,  is backed up in the chamber by the sluice end-walls and
the cross wall seen to the right of the sluice.   This cross wall
was constructed during the previous modification program.   Prior
to  its construction,  wet weather flow would continue flowing to
the right and pass through flap gates to the river.

         Wet   weather  flow  volume  greater  than  the  storage
capacity of the system will pass over the sluice end walls and to
the  intercepter.   Extreme wet weather flow rates  sufficient  to
backwater  the interceptor will cause flow in  the  chamber to  be
routed around the cross wall,  back over the side wall beyond the
cross wall, and through the flap gates to the river.

         Although  not shown in the photograph,  a  small  manual
gate  was  located  on  the  back side  of  the  sluice  end-wall
regulating  flow through the 6 inch x 6 inch  opening.   As  part
"reduced  BMP"  project the sluice gate was removed and  replaced
with vortex flow regulating devices at two locations as  detailed
later.

         Typical "B" type regulators are much larger than the  "A"
type.  Figure  8.2   depicts the modified weir area and new  flow
regulators  within a typical "B" type regulator.    Basically  the
chambers are enlarged versions of the "A" Type with the  addition
of  a  float  chamber  next to the  chamber  outlet  pipe.   Flow
regulation  was  controlled  automatically  by  a   float-operated
regulator  located between the sluiceway and the  chamber  outlet
pipe.  During  the  current  program this assembly  was  entirely
                                803

-------
               Table 8.1  Flow Regulator Details
00
Regulator
1A Weiss
2 Cronk
5 W.Genesee
6 Remington
8 Throop
9 Hayes
12 Court
11 Ames
13 Adams
16 Mackinaw
1? Dearborn
17A Fraser
Ib Salt/
Vermont
» *
Type
MC
MC
MC
MC
MC
MC
MC
MH
MC
MC
N
0
MC
OVE
Length
(in.)
74
37
38
38
38
38
25
22
60
38
—
18
79
RALL
rtfidth
(in.)
63
28
30
30
30
30
15
22
52
30
...
18
56

Height
(in.)
53
24
25
25
25
25
13
4
44
25
...
0.5
49
•*
Approx.
Wt. (Ib)
700
130
130
130
130
130
40
30
400
130
...
40
500
***
Segmented
Cone No. segments)
—
2
2
2
2
2
—
—
3
?
—
—
...
Diameter
Intake (in)
25
8
12
8
8
10
4"
4"
19
10
—
—
?3
                                                                                               Vented
                  -  Key:   Ml - conicjl  tym- vortex valve
                          MH - horuontdl ly|>f  vorte* valve
                           0 - or it ue  pldtr
                           M • no devtcr
* excludes  wt. fittings
***  see 6D-3

-------
Figure 8.1  Typical Type "A"  Regulator Chamber
                     8,5

-------
Figure 8.2   Modified  Area  of Typical  Type  "B"  Chamber
                       8.6

-------
removed  and replaced with vortex flow regulating  devices.   The
photograph in Figure 8.3 shows parts of a removed  float-operated
flow regulator.

          The "B" type chambers also included manual gates on the
upstream side of the side wall.   Photograph A,  Figure 8.4 is  a
view  looking  upstream of the sewer pipe entering  the  chamber,
spill  to the sluice and the manual gate in the sluice side-wall.
Photograph B, Figure 8.4 also includes the sluice and the gate as
viewed  from above.   Similar to the "A" type chambers  most  wet
weather  flows were originally allowed to pass through  backwater
gates  to the river.   The photograph in Figure 8.5 illustrates a
typical backwater gate.

         Modifications  to  the  type  "B"  regulators  generally
included  removal  of  the  existing  float-operated   regulator,
installation of a vortex flow regulating device,  cutting down of
the  side  overflow-walls  and the construction  of  the  central
cross-wall.   The photograph in Figure 8.6 displays the new cross
weir  and the cut-down weir on each side.   Adjustable weirs were
installed  at  four regulator locations and can be seen  in  this
photograph.


8.5  Construction and Installation of Flow Regulators

         Flow  regulating  devices used in this project  were  of
variable  types and dimensions as required by the degree of  flow
regulation and the conditions of the installation.  Access to the
existing  regulator  chambers  was  typically  via  manholes   or
backwater gate access holes as shown in the photograph in 8.7. In
a number of  instances,  the sizes of the new flow regulators were
much larger  than the available openings such that segmentation of
the device were required.   Photographs A and B in Figure 8.8 and
8.9  illustrate a device disassembled,  partially assembled  and
completely assembled respectively.   This device was installed in
the  Weiss   Street  Regulator and included  a  specialized  inlet
transition   section.   Photographs  A  and  B  in  Figure  8.10,
illustrate   the  device  for the  Salt/Vermont  Street  regulator
chamber which  incorporated an integral wall mounting flange and  a
removable high level stack vent.   The photograph in Figure  8.11
shows the unit installed in the new chamber weir wall.

          As  detailed  Chapter  7,  the Adams  Street  regulator
chamber  vortex flow regulating device installation  utilized  an
upstream cross wall and wall thimble.   The device and detachable
cast-in place  wall thimbles are shown  in the Photograph in Figure
8.12.   The  installed device and upstream cross wall, designed to
direct flow  to the inlet,  are  shown in Photograph A, Figure 8.13.
                                807

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00
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                  Figure 8.3  Partial Components of Brown and Brown Regulator
                              Removed From Chamber

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Figure 8.5  Type "B" Chamber - Flapgate to River Area
                           8.10

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Figure 8.6  Type "B"  Chamber - New Cross  Weir
                      8.11

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Figure 8.7  Chamber Access Manholdes and Gate Covers
                       8.12

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                       (A)
                       (B)
Figure 8.8  Segmented Vortex Valve Regulator -
            Disassembled and Partially Assembled
                      8013

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Figure 8.9  Segmented Vortex Valve Regulator -
            Fully Assembled
            (Unit Installed at Weiss Street Chamber)
                        8.14

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                           (A)
                           (B)
Figure 8.10  Salt/Vermont Street Chamber Vortex Valve
                           8.15

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Figure 8.11 Installed Vortex Valve Regulator at the
            New Salt/Vermont Streets Storage Chamber
                              8016

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Figure 8.12 Adams Street Chamber Vortex Valve Regulator
                           8017

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Figure 8.13  Installed Adams Street Chamber Vortex
             Valve Regulator              	
                        8.18

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         Most  of the vortex flow regulators used in this project
were the conical type as shown in the Photograph in Figure  8.14.
Each  unit  was provided with a mounting plate,  designed  to  be
permanently   mounted  to  the  wall,   incorporating  studs  for
attachment  and removal of the device.   For most  installations,
the  unit's  inlet  sleeve was perpendicular  to  the  wall.   In
several  instances,  the  existing wall casting and  the  chamber
outlet  were  positioned such that modifications were  necessary.
The  photograph in Figure 8.15 illustrates a unit with the  inlet
sleeve modified by changing the sleeve angle in the wall modified
to  orient  the device outlet to properly direct  flow  into  the
chamber outlet pipe.

         A  horizontal  type  vortex flow regulating  device  was
deemed  most  suitable  for the Ames Street  location  since  the
chamber  outlet  was  located in a side wall as  opposed  to  the
standard opposite wall, limiting available space for installation
and orientation.  Photograph A, Figure 8.16 illustrates a typical
horizontal  type unit which has a side inlet and  bottom  outlet.
On  this unit the outlet is located directly below the inspection
port  (the cover of which is seen on the top plate).   This  unit
was  mounted  flush to the wall with the plate shown and  a  wall
bracket.   Photograph B,   Figure 8.16 illustrates the  installed
unit  with the inspection port cover plate removed.   The chamber
outlet  is located at the bottom of the wall to the left  of  the
unit.


8.6  Weiss Street Pumping Station Wet Well Modification

         The  last program element of the reduced BMP program was
the  Weiss  Street  Pump Station wet  well.  The  intent  was  to
increase   the  depth  of  water  five  feet  in  the  West  Side
Interceptor  to  maximize  flow  crossover  the  the  East   Side
Interceptor  prior  to spillover into the pump station wet  well.
This was accomplished by construction of a spill over wall  inside
the  wet well between the flap gates and the  bar  screens.   The
wall  is  shown  in Photograph A,  Figure 8.17 and  has  a  crest
elevation  4.75 ft.  above the flap gate seat elevation.    At the
base  of the cross wall a manual gate valve is located  to  allow
drainage  of water trapped between the walls.   A three foot high
wall  was also constructed at the mid floor level all  round  the
open chamber area as seen in Photograph B, Figure 8.17 to contain
extreme flow levels and minimum excess splashing conditions.
                                8.19

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Figure 8.14  Typical  installed Conical Type
             Vortex Valve Regulator
                       8020

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                        (A)
                       (B)
Figure 8.16  Horizontal Type Vortex Valve Regulator
                       8.22

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                                                                      B
                     Figure  8.17  Weiss  Street Pump Station ->New Weir
                                  and Splash Wall

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                            CHAPTER 9

                  FIELD AND MONITORING PROGRAM
                     POST BMP IMPLEMENTATION
                        DATA AND ANALYSIS


9.1 Foreword

          Numerous locations were selected throughout the Saginaw
drainage  area  during  all three phases of this  study  for  the
collection of data pertinent to the generation,  calibration  and
operation of the system simulation model and later for monitoring
of the reduced BMP system modifications.

          Field  monitoring programs conducted for the purpose of
Phase  1 and Phase 2 simulation model generation and  calibration
are  presented in Chapter 6.   Chapter 9 presents the results  of
the Phase 3 field monitoring program conducted after the  reduced
BMP  program was implemented.   Section 9.2 briefly describes the
components  of  the field program.   Section 9.3  summarizes  the
results  of a program documenting backwatering effects  resulting
from  partial  BMP  plan modifications.   Sections  9.4  and  9.5
present  data collected at the Salt/Vermont Streets chamber   (new
in-line  storage  facility) and at the  Adams  Street  regulation
chamber, respectively.   Evaluation program data collected at the
Weiss  Street  Pump  Station  and at the WWTP  are  presented  in
Sections 9.6 and 9.7,  respectively. Field discharge measurements
for  several  of the new vortex valves are presented  in  Section
9.8.  Cronk Street regulator chamber data is evaluated in Section
9.9.   Field observations of the modified regulators are detailed
in Section 9.10.
9.2  Post Implementation Field Program

         Elements  of the post reduced BMP  implementation  field
program   were   designed  to  facilitate  a  final  review   and
calibration  of  the  simulation  model  and  to  determine   the
practicality   and   effectiveness  of  the   regulator   chamber
modifications  in  terms of in-system storage generation and  the
suitability of the new flow regulating devices.

         Similar to earlier phases of the evaluation program, CSO
rates  and water quality data were recorded.   In  addition,  the
post  implementation  field  program   included  river  elevation
determinations,  in-line storage evaluation, discharge monitoring
of new vortex valve flow regulating devices and documentation  of
maintenance requirements for the new regulating devices.
                               9.1

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         Water  quality  analysis  included  evaluating  combined
sewage  passing to the West Side Interceptor at Adams Street  and
CSO to the river at this location.  Water quality sampling at the
Weiss  Street  Pump  Station wet well and the WWTP  grit  chamber
which  were  performed  during  earlier  phases  was  also  again
conducted during this period.

         Water surface elevations were continuously monitored  at
the  new  Salt/Vermont  regulator chamber,  at the  Cronk  Street
backwater gate chamber,  at two locations within the Adams Street
regulator  chamber  and upstream of the Throop  Street  regulator
chamber.    Peak  water  surface  elevations  were  monitored  at
manholes  at five locations in the in-line storage area  upstream
of  the new Salt/Vermont regulator chamber,  at single  locations
upstream  of two other regulator chambers  (Adams Street and  West
Remington  Street)  and within three regulator  chambers   (Throop
Street, Hayes Street and West Remington Street).

         The original intent was to monitor all post construction
rain  events  within  a  six week  period  and  select  the  most
pertinent  events for complete review.   Storm event  measurments
occurring during this period were less than ideal due to   adverse
conditions  such  as  faulty backwater gate operation  and  mixed
rain/snow precipitation, however, sufficient data was attained to
reasonably  assess  the  overall  impact   of  the  implementation
program.


9.3  System Backwatering

         Monitoring  of the post  reduced BMP plan  implementation
conditions  included recording peak water  elevations at  selected
regulator   chambers  and  at  locations   upstream  of   modified
regulator chambers and at  the new in-line  storage chamber  at Salt
and Vermont Streets.  Peak water  surface elevation determinations
for  wet  weather  periods were  accomplished  using  cup gages
constructed   of  1-1/2  inch PVC pipe end caps with aluminum plate
splash  covers attached at  equal  incremental spacings to  sections
of electrical tubing. Gages were  designed  and  installed by EDP to
be  easily  removed after  each event for  inspection  by  City  of
Saginaw maintenance crews. Most  gages were installed  in manholes
upstream  of  regulator  chambers and allowed  for   removal  from
street  level.    Remaining gages  were   installed   in  regulator
chambers and  accessed from within the regulator chambers.

         Table   9.1 includes  pertinent data for the  10  cup gage
locations and the  downstream  regulator chambers.   Total  rainfall
accumulations  for five  storm events monitored are also given   in
Table   9.1.   Locations  of these  measurement  points  are shown   in
Figures 9.1 and  9.2.   The  intent  of  this  program  was to determine
                                9.2

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                                                          TABLE 9.1

                                        CUP GAGES MONITORING OF PEAK WATER ELEVATIONS
co
LOCATION DOWNSTREAM
NO. fi£ MANHOLE REGULATOR
1
2
3
4
5
6
7

8
9
10
GROUT fc STANLEY
SALT t HOLMES
SYLVAN fc HAMILTON
STEWART t SALT
FRASER 6 BRALEY
ADAMS t HARRISON
HARRISON W.
LOCATION AT REGULATOR
HAYES
THROOP
REMINGTON
STORM EVENT PEAK ELEVATION


FRASER
FRASER
FRASER
FRASER
FRASER
ADAMS
REMINGTON




RECORDED

MANHOLE
INVERT
ELEVATION
582
579
582
577
582
580
584

583
579
582
.72
.64
.74
.21
.30
.22
.42

.30
.69
.95
AT REGULATOR


REGULATOR
WEIR
ELEVATION
584.42
584.42
584.42
584.42
584.42
581.50
585.45

584.97
582.60
585.45
FRASER:
ADAMS:
RAIN ACCUMULATION (INCHES)
1984 STORM DATES/PEAK ELEVATIONS
Ifi/JLfi lfl/21 10/26 11/1
584
583
*
584
584
>587
587

585
583
586
584
582
0
.30
.64

.88
.63
.39
.50

.13
.52
.28
.40
.30
.75
<584.30
584.64
>589.00
584.88
584.63
>587.39
587.00

585.63
583.02
585.28
584.65
582.44
0.79
<584.30
583.64
584.00
585.88
584.63
581.89
586.00

<584.13
<580.52
586.28
577.18
581.34
0.17
<584.30
584.64
585.00
584.88
588.63
>587.39
587.50

585.13
583.52
586.28
584.90
582.85
0.61
11/1
584.30
585.64
>589.00
582.88
*
>587.39
587.50

585.63
583.52
585.28
584.40
582.85
0.73
        *  ALL CUPS PARTIALLY FULL - INDICATES POSSIBLE SPLASHING EFFECT
           FROM CATCHBASIN LEADER PIPE DISCHARGE

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                                   JLJLJ1
LEGEND:
Modified Chamber
Cup Gage Location
                   Figure 9.1  Hancock Street Area Cup Gage Locations

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ID
•
Ul
                                                Cupgage Location
                   Figure  9.2  Salt/Vermont Streets Area Cup Gage  Location

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if   any   adverse  conditions  developed  due   to   implemented
modifications.  Undesireable levels of stormwater backup would be
recorded  as  peak upstream water elevations  sufficiently  above
levels  in  the regulator chamber to  indicate  backwater-induced
surcharge conations.

         The  first five cup gage locations are upstream  of  the
new Salt/Vermont Street in-line storage chamber (Table 9.1).   At
four  of  these locations peak water elevations indicate that  no
surcharge  occurred  in that portion of the sewer  system  during
storm  conditions.   Data  at  the  Sylvan  and  Hamilton  Street
location  indicated surcharge conditions for two events.   It  is
possible that cup gage readings at this location were  influenced
by  splashing effects from a catchbasin leader pipe entering high
in  the manhole,  since for one additional event most  cups  were
noted  to be only partially full.  No basement floodings had ever
been   noted  in  this  drainage  area  prior  to   the   chamber
construction  nor  were  any noted during the  post  construction
monitoring.   If surcharging had occurred, depths were limited to
less  than  problem levels which is quite possible since  the  54
inch pipe serving the area is 20 ft. below ground level.

          No  indication of surcharge conditions was evidenced at
the  Harrison   Street  location upstream of  the  West  Remington
Street regulator chamber.

           Although  four  of five events  indicated  high  water
conditions  at  the  Adams  Street and  Harrison  Street  manhole
upstream of the Adams Street regulator,  available data indicates
that the new weir with a crest elevation of 3.3 ft. above the 7.5
ft.   pipe  invert  does  not  induce  backwatering.    Based  on
calculation  of the pipe capacity at the upstream manhole as  253
cfs,  and  the  estimated hydraulic profile and net flow  capacity
over the regulator chamber spillover weir at the recorded  depth,
no  restriction  was evidenced.

          Hydraulic  limitations of the connector pipe  from  the
Adams  regulator chamber to the West Side Interceptor sewer  have
been  calculated to cause flow bypass to the  river at storm flows
less than the inlet  sewer capacity.   Overflow to the river would
result and was  evidenced during several of the monitored  events.
Backwatering  due  to the connector pipe  hydrualic restriction at
the Adams Street  regulator is sufficient to  cause   spillover  to
the river  but not to  surcharge the inlet   sewer.   Flap  gates
allowing flow  to the river provide near free-flow  conditions  and
no   excessive depths were noted with  the continuous  level  sensors
within the chamber.   High water depths within the sewer  line  at
the cup gage monitoring station appear  to be due  to the   limited
hydrualic  capacity  of  the  sewer  in  relation  to  peak  flow  condi-
tions.   No   basement flooding has been  reported in  the  drainage
                                9.6

-------
area  either before or after the modification work.   As with the
Fraser Street regulator tributary drainage area,  the sewer trunk
lines are more than 20 ft. deep and surcharging of the line would
not necessarily create basement flooding conditions.

          At  the  final three locations  (Hayes  Street,  Throop
Street and Remington Avenue regulators) cup gage data from within
the  three  regulator chambers did not indicate  excessive  water
levels.   Depths were generally less than one foot over the cham-
ber weirs such that no sewer surcharge or spillover to the  river
occurred.   Under  the orignal design it was intended that excess
flows  above the allotted rate through the new regulating  device
spill  to the interceptor.  Under extreme conditions,  where  the
interceptor  capacity was exceeded flow would pass both over  the
new cross weir and back over the side weirs to the river.   Moni-
tored  events  indicated that no flows have yet passed  over  the
cross  weir which was as expected considering the mild  intensity
of  the  events  which occurred.   Field data collected  to  date
indicate  that  the  cross weir elevations  selected  during  the
design phase have been adequate to prevent premature flow to  the
river.

         In sum,  no adverse hydraulic profiles were noted at any
of  the  locations  during the post  reduced  BMP  implementation
evaluation program.
9.4 EvMjflajtijpn M Effectiveness Q£ Hew. In-line Storage
     Chamber Constructed at Sal t and Vermont Streets

          Prior  to  the reduced  BMP  plan  implementation,  the
Fraser Street regulator chamber controlled  flows from a 441 acre
area  in  the  southwest part of the city.   Location  of  a  new
upstream  storage/regulator  chamber was selected to be  450  ft.
upstream   of   the  existing  Fraser  Street  chamber   at   the
intersection  of  Salt  and Vermont Streets  (Figure  9.2).   See
Chapters 7 and 8 for design and implementation details.

          Monitoring  of  wet weather flow depths at  the  Fraser
Street   regulator  was  performed  during  the  Phase  2   field
evaluation period of 1983.   Data accummulated are representative
of  conditions existing prior to implementation of the  BMP  Plan
modifications in this area.   After Phase 3 construction in 1984,
monitoring of stormwater depths was performed at the new chamber.
The  difference  in  sewer  invert  elevations  between  the  two
chambers  is  negligible  for comparative hydraulic  analysis  of
pre/post conditions.

          Figure  9.3 illustrates the rain accumulation data  for
storms occuring on 8/1/83 and 10/18/84.  The 8/1/84 and  10/18/84
                                 907

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                                    8'6
 DEPTH OF FLOW

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                                           RAIN ACCUMULATION

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events were selected for detailed hydraulic evaluation since they
are  representative of the hydraulic conditions typical of  their
respective  pre/post reduced BMP plan implementation  period  and
are  generally similar in terms of rain intensity,  duration  and
total accumulation.

         Sewer  flow depths shown in Figure 9.4 roughly  indicate
the  rainfall  to runoff time relationships.   The shape  of  the
8/1/83  event  combined sewage depth of flow curve is typical  of
all  pre-BMP Plan events observed.   The rate of depth  increases
varied  among events dependent upon the rain condition,  but  all
events  displayed the rapid rate of depth decrease at storm  end.
Initiallyf   the  backwater  gates  allowed  rapid  discharge  of
combined  sewage to the river down to a sewer depth of just  over
half the 9 ft.  pipe diameter.   Thereafter,  the existing float-
operated regulator controlled the outflow rate.

          The  shape  of the 10/18/84 sewer flow depth  curve  is
typical  of all post-BMP plan implementation events.   Depths  of
flow  during  the initial storage volume fill  period  varied  as
before (correlating with storm intensities),  but always resulted
in long-term drain down periods.

          Since only rainfall and water depths within the chamber
were monitored,  calculations were performed using available data
and  the  manufacturer's  rating for the flow control  device  to
determine  the degree of  inflow/outflow/storage  balance.   This
procedure is described below:

         Figure  9.5,  which  indicates the volume of  stormwater
storage  throughout the 10/18/84 event,  was prepared  using  the
depths  recorded  in  the field  (Figure 9.4)  and  the  depth  to
storage  volume relationship developed during Phase 1 and Phase 2
studies.   Using the storage volume curve of Figure 9.5, the rate
of change in storage volume was estimated   throughout the  event
since  it  is a direct function of the inflow rate,  the  outflow
rate through the regulating device and spillover,  if  any.   For
this  event  total rain accumulation was recorded at the  Emerson
Street  Station and at the City Water Works Building as 0.57  and
0.67 inches respectively,  averaging 0.62 inch.   Considering the
land  use  (and appropriate runoff factor),  a  total  stormwater
volume of 397,000 cu.ft would be expected.   Dry weather flow for
the  total  rain  and system draindown period  of  18  hours  was
estimated  to  equal 72,600  cu.ft.  using dwf rates  established
during Phase 1 and 2 measurement programs.

        The   rate  of  inflow   (Figure  9.6)  at  any  time  was
calculated as the rate of volume change plus the rate of outflow.
For  periods  of  no spillover,  outflow  was  limited  to  rates
controlled by the new vortex valve regulatpr.  Using the device's
                                9.9

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                        FIGURE 9.5 VOLUME OF STORED COMBINED SEWAGE VS TIME

                                   10/18/84 EVENT POST BMP PLAN IMPLEMENTATION
10
o
M
O
200

160

120 -

 80 _

 40 -

  0
              0
                        I
                        4
8
10
 i
12
14
16
18
                                              TIME  - HOURS

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                              FIGURE 9. 6  COMBINED SEWAGE INFLOW RATE VS TIME

                                         10/18/84 EVENT POST BMP PLAN IMPLEMENTATION
160 _
120  ^
 80  .
40   _
 0
     0
I
4
i
8
10
12       14
16
 i
18
                                  TIME - HOURS

-------
stage/discharge  characteristic  data (See Chapters 5  &  7)  and
sewer  flow  depth  indicated in Figure 9.4,  the  outflow  rates
depicted in Figure 9.7  were calculated.   The curve  illustrates
the  unique  ability  of the vortex valve  throttling  device  to
maintain  a near constant outflow rate with change in  depth  and
the characteristic final high flow through rate which is intended
to  promote scouring.  In addition  to the curve values shown  in
Figure  9.7,   inflow would also include the volume of spillover,
if  any.   Figure  9.4  indicates that the  chamber  water  depth
remained   at  the weir level for a very short period of time  at
the 2 hour duration point of the event implying that little or no
overflow would have occurred.

         Integration of the vortex valve regulator device outflow
rate  curve   (Figure 9.7) over the event duration  results  in  a
total estimated outflow of 454,000 cu.  ft.  This value is 15,000
cu.  ft.  less  than  the estimated combined dry and wet  weather
flows noted above and represents either the overflow volume,  the
error in values estimated or both.  This difference represents 3%
of the total  storm flow and since minimal spillover occurred,  it
is concluded  that the flow analysis is reasonably accurate.  This
implies that  the vortex valve throttling device operates properly
according  to the manufacturer's design  curve,  the   depth  to
storage  volume  relationship  developed for the pipe   system  is
reasonable    and  the  runoff  coefficient  and  land   size   are
accurately estimated.

         A  similar  evaluation  of   the  pre- BMP  conditions  is
difficult  due to the unknown and variable  flow rates through the
existing float-operated  regulator and the backwater flap gate  to
the  river.    For   comparative  purposes   of  pre  and  post BMP
conditions, rough estimates of hydraulic conditions were made for
the 8/1/83 event as  follows.

          Total  rain accumulation for  this event was recorded at
the  Emerson  Street  Station and at the  City Water Works  Building
as  0.43  and 0.49 inches,  respectively,  yielding  an  estimated
runoff volume of 292,000 cu. ft.  Dry weather flow for  the  4 hour
event  totalled 16,000 cu.  ft.  Considering the unknown  outflow
rates, storage volume fill  rates were not used to estimate  inflow
rates.   Combined sewage depths in the  chamber above 5  ft.   cause
overflow to the river.   Depths above  this level occurred for over
2  hours of  the 4 hour event. The in-system  storage volume of   the
87,000 cu.  ft. is available and the average outflow  rate from  the
regulator for the 1  hour drain-down period  recorded was estimated
as  24  cfs.   Since this outflow  rate  is much greater  than  the
allowable   rate  from this  drainage area based on  WWTP capacity
constraints,  it is assumed  that a  large portion of the  flow would
either  overflow  directly  at  this location or be pumped  to  the
river  from either the Hancock Street facility or from  the   Weiss


                                9.12

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                         ere
        Discharge  - cfs

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-------
Street Pumping Station.  Using the two extremes of:  1)  only flow
through the backwater gates spills to the river or;   2) all flow
above the allotted volumes based on WWTP capacity either flows or
is  pumped to the river,   CSO discharges are estimated to  range
from 124,000 cu. ft. up to 178,000 cu.ft.  For the 8/1/83 pre-BMP
event, 40% to 58% of the combined sewage inflow is thus estimated
to discharge to the river.

          Comparison  of the two pre/post-BMP storm events  shows
the  effectiveness of the in-line storage concept.   As stated, a
typical  post  implementation  event  (10/18/84)  with  40%  more
rainfall  than  the  pre  implementation  event,  resulted  in  a
discharge  of  at  most 3% of the  incoming  combined   sewage  in
comparison  to an estimated overflow of 40-58% under  pre-project
conditions.

          In   conclusion,   implementation   of  the   BMP   plan
recommended  upstream   storage  facility  at  this  location  has
substantially   reduced  pollutant  loading  to  the    river   by
dissipating  peak flow  conditions in the system and allowing  for
long draindown periods  to the WWTP.


9.5  Monitoring and Evaluation at the Adams Street Regulator

           Intensive  monitoring  efforts were performed  at  the
Adams  Street  regulator  chamber as part of  the  overall  field
evaluation.   During  the  pre BMP  period  a  level  sensor  was
installed to monitor water elevations within the dry/wet  weather
flow  channel  of   the  regulator chamber upstream  of  the   float-
operated   regulating device.   No flow monitoring was  performed
during the reduced  BMP  construction phase in the chamber.   After
modifications  were completed,  sensors were placed  to  monitor
water levels both in the dry/wet weather flow channel upstream of
the new vortex valve flow  regulator and at the downstream end  of
the   side weir to monitor  spillover of  extreme event flow to   the
river.  In addition, automatic sampling devices were installed at
each  location,  activated  by flow elevation,  and  intended  to
produce    representative   samples  of   total   flow through   the
regulator  and of spill  to  the  river.

           The   control  concepts   used  during   the design  phase
included   assuming   "first  flush" effects  within the  combined
sewage.    This   effect  is the  result  of   initial flow  volumes
during  storm events incorporating high concentrations  of   street
washoff   materials   and  scouring  sediment  in   the sewer   lines.
Scouring   should occur  early  in  the  event  followed by   relatively
cleaner   flow representing sewage  diluted  with  clear   stormwater.
At this  stage two  scenarios may  occur.   Under  low rate  stormwater
flow  conditions,   velocities  within  the sewer  may be  conducive to


                                9014

-------
settling  of  solids  materials.   High flow  rates  may  produce
velocities negating any deposition effects.   After the end of  a
storm  event  and  near the end of the  storage  pool  drain-down
period,  an  increase  in  flow rate,  designed as  part  of  the
operating  characteristic of the vortex valve regulating  device,
should  occur.   It  is  expected  that  if  settling  of  solids
materials occurred  in the backwatered stormwater, then the final
flow  increase would create a second scouring phase and increased
pollutant concentrations.

          Samples  were  collected from within the  Adams  Street
dry/wet  weather flow channel on four occasions and at  the  weir
spilling over to the river on one occasion.  Samples collected at
half  hour  intervals  were composited to  represent  the  "first
flush",  "mid-event"  and  "drain-down" (post storm) periods  and
analyzed for SS, BOD and total/soluble phosphorous.  In addition,
discrete sample analysis was performed on occasion,  to determine
time-variant solids concentrations.

          Table  9.2  summarizes the data  generated.   For  each
event,  concentrations  of  the  four  pollutant  parameters  are
indicated based on the three storm periods.  Discrete samples (if
any)  are  then  listed giving solids concentration and  time  of
collection.  As a rough comparison of peak storm flows, depths in
inches  over  the side weir to the regulator and over  the  cross
weir to the river, are included in Table 9.2.  It should be noted
that  the  highest  peak  flow over  the  upstream  weir  is  not
necessarily the most likely event to cause overflow to the river.
It  is mainly the interceptor capacity that governs if  surcharge
and  overflow to the river will occur.   Rain data for each event
including  total accumulation and peak hourly intensity are  also
recorded in Table 9.2.

          Monthly   average  influent  WWTP   concentrations   of
suspended  solids and BOD were 71 mg/1 solids and 55 mg/1 BOD  in
October  and  72 mg/1 solids and 51 mg/1 BOD in  November,  1984.
Data  for the first three events clearly includes  initial  storm
samples  of  flow passing to the interceptor with  concentrations
much  higher  than  WWTP averages confirming  the  "first  flush"
effects.      "Mid-storm"    sample    concentrations    decrease
substantially  but  are still in the range of  dry  weather  flow
values.  Dilution of dry weather flow alone with clean stormwater
would  produce  lower  concentrations such that the  "mid  storm"
values recorded indicate continued effects of scouring and street
washoff.   Considering  that  the  pipe volume  upstream  of  the
regulator  is  backwatered,  it could be expected  that  not  all
scoured   material  would  immediately  flow  to  the  regulator.
"Post  storm"  samples are consistently  less  concentrated  than
"mid-storm"   samples  and  monthly  average  dry  weather   flow
indicating  a  condition of sewage diluted with relatively  clean
                                9ol5

-------
                                                       TABLE  9.2
CTl
                                       ADAMS ST. REGULATOR  CHAMBER  STORM  SAMPLES
                                                  Concentrations  mg/1

                                                       PEAK FLOW  DEPTH  (INCHES)
                                                                      R
                                                                      :IVER
                                                                      SIDE


DATE PARAMETER
START
STORH
MID
STORM
POST
STORM
REG RIVER)
10/21



11/1



DISCRETE
1
2
3
4
5
6
11/9



DISCRETE
1
2
SS
TP
SP
BOD
SS
TP
SF
BOD

SS
SS
SS
SS
SS
SS
SS
TP
SP
BOD

SS
SS
105
1.59
.85
67
424
3.88
.77
258

60
7
40
60
34
30
428
3.81
1.33
138

38
81
73
.83 (.
(.
27
54
.54
.28
51

Midstorm:
Poststorm:
After post
• •
• •
• M
77
1.04
.59
68

Midstorm:
Midstorm:
30
25) .89
21) .73
25
10
.55
.52
21

at max rate of
at predicted
storm: 28 hrs
29 "
30 "
31 "
21
.46
.35
19

OVER WEIR
REGULATOR RV
SIDE S
12.



17.




depth decrease
flush depth
after 12
• •
• •
• •
18.




Just after peak conditions
During end of
stored
                                                                            RAIN  DATA
                                                                          ACCUMULATION
                                                                             INCHES


                                                                              0.79
                                                                                      0.61
                                                       PEAK INTENSITY
                                                           IN/HR.

                                                            0.20
                                                                                               0.32
                                                                                      0.33
                                                                                               0.09
                   SS
                   176  Midstorm:
 stormwater drain down
Second  flow  peak  level
 condition
        11/11      SS               21

                      Suspended Solids
                      Total Phosphorous
                      Soluble Phosphorous
                      Biochemical Oxygen Demand
Code:  SS  -
       TP  -
       SP  -
       BOD -
                                         48
                                          0.38
0.09

-------
stormwater  possibly  in  combination  with  materials   settling
effects.  The  significance from a pollution reduction standpoint
is  that the initial highly concentrated flow would pass  to  the
interceptor  and  later  overflow,  if any,  would  be  far  less
concentrated.

          Visual  observations  of final drain-down periods  were
recorded  by  EDP  personnel  during  flow  calibration   of  the
installed  vortex  valve regulating devices.   A short period  of
noticably  concentrated material was visually noted   ("black"  in
color)  discharging  from the device during the draindown  period
following a rainstorm occurring in early October.  Unfortunately,
the  flow  calibration crew was not setup for  sampling  at  that
instant.   The  field sampling program thereafter was tailored to
analytically verify "post storm" scouring.

          Discrete stormwater samples were visually inspected  to
determine   if   any  highly  concentrated  conditions  occurred.
Samples  with  a darker appearance were tested  individually  for
solids  concentration.  If  no increase  was  visually  apparent,
samples  for  discrete analysis were selected based on  depth  of
flow   data  to  determine  predicted  peak  flow  and  therefore
potential scouring conditions.

          For the 11/1/84 event the first discrete sample   (Table
9.2)  represented  "mid  storm" conditions during the  period  of
maximum depth decrease rate.   The resulting solids concentration
value  of 60 mg/1 was close to the average storm period value  of
54  mg/1 indicating no particular flushing effect at  that  time.
The  second  discrete sample was  selected  from the  "post   storm"
period  and  also indicated no flushing effect.   The final  four
samples were taken over 28 hours  after the flow rate  stablized at
just above DWF levels.   Solids concentrations are high but  data
is inconclusive as to whether this is a flushing effect or  normal
DWF concentrations.

          The  11/9/84  event consisted of two  intense  rainfall
periods  and two distinct water storage periods.   Three discrete
sample  periods  were selected  for  solids  analysis.   Discrete
samples   from   the   first   two   periods   indicated    solids
concentrations  similar  to  "mid  storm"  composite  conditions.
Analysis  of the last discrete sample,  collected at  peak  storage
conditions during the second storage period  indicated a  definite
increase  in  the  solids concentrations potentially  due   to  the
combined  effects  of additional  street washoff and   scouring  of
materials  settled  during the initial  drain  down   period.   No
samples  collected  during  the second  drain  down   period  were
noticeably  polluted  and  no analyses were  run  to  investigate
flushing effects.
                               9.17

-------
          In sum, "first flush" effects were clearly indicated by
the   field  data  for  three  complete  storm  events  monitored
justifying  the improvement plan concept of  modifying  regulator
operation  to maximize initial flow rates to the interceptor  and
maintain  underflow during the event.   Final flush effects  were
visually  noted on one occasion but not analytically  documented.
"First  flush" conditions included rapid depth increase and  high
flow   rates   which  would  scour  most  pipe  segments   nearly
simultaneously.   Conditions under which final flush might  occur
are  limited  to  less pronounced depth changes and  flow  rates.
Scouring may occur at various times along the sewer making a peak
concentration undeterminable.

          BOD  and  phosphorous data collected at  the  regulator
appear   to  follow  similar  trends  as  the  suspended   solids
results.   The  correlation coefficient for for paired solids and
BOD  data is 0.91.   The correlation coefficient for  solids  and
total phosphorous data is 0.99.  It can be concluded that most of
the BOD and phosphorous is tied up in the solids matter.  Soluble
phosphorous  fractions of total phosphorous loads ranged  between
20  and  93  per  cent  resulting in  a  poor  total  to  soluble
phosphorous  correlation coeficient of 0.75.   A trend was  noted
toward  higher fractions of soluble portions of total phosphorous
increasing  from an average of 36% for "start storm"  samples  to
59%  for  "mid storm" samples and to 84% for post storm  samples.
This  trend inversely follows the declining solids  concentration
values  and indicates that soluble phosphorous is not related  to
solids concentrations.

          For  the single storm event where overflow to the river
occurred,  the  period of overflow was brief such that  only  one
sample was obtained and only phosphorous data could be generated.
Total   phosphorous  concentration  for  the  single  "mid-storm"
overflow  sample was 30% of the composited "mid storm"  underflow
sample phosphorous concentration.  Overflow to the river (surface
water  of  the backwatered flow) was thus much less  contaminated
than  water  sampled  at the mid depth  sampler  intake  for  the
dry /wet  weather flow channel.   These percentages  reaffirm  the
phenomenon of solids settling in the backwatered flow and passing
to the interceptor and confirm the design concept.
9 . 6  Mor^itorvinj; °f ill6, Wei s_s_ Street Pump S ta_t ion

          Modifications  to  the Weiss Street Pump  Station  were
limited  to the construction of a weir wall within the  pump  wet
well  area  designed to eliminate or delay pump "turn on"  during
storm  events.   The delay was caused by preventing the West Side
Interceptor  flow from spilling (at about springline depth)  into
the pump station wet well.   Backwatering would result as greater
head  would  be  needed to push flow  thorugh  the  hydraulically
                              9.18

-------
constrained  river crossing.   Spillover would finally occur  but
only  after  a  higher  depth of  flow  had  been  reached.   The
advantage of this delay is that at both the beginning and the end
of storm periods,  greater flows rates will exist in the West  to
East  Crossover  Interceptor  due to increased  West  Side  water
elevation.    In   concept,   the  crossover  modification  would
considerably   modify  and  lessen  overflows  for  the   smaller
intensity  storms  and have appreciably lesser impact  for  large
major  storms.   Thus  an increase in the crossover  rate  should
reduce  the  overall  pumped overflow at the  Weiss  Street  Pump
Station.

           Post-BMP plan system hydraulics are complicated by the
regulator modifications which were intended to increase flows  to
the  West  Side  Interceptor  leading to the  Weiss  Street  Pump
Station.   Net results of the opposing effects of increased  flow
to  the  Weiss Street Pump Station and increased  crossover  flow
rates  could,  depending on event intensity,  either increase  or
decrease  actual  pumpage  volumes at the  Weiss  Street  Station
compared to pre-BMP conditions.  The reasons for this flow regime
are as follows.   The CSO Facility Plan concept was to reduce the
number  and  magnitude  of  individual regulator  overflows to  a
minimum   (by  either  maximizing  in-system  storage  and/or   by
modifying  overflow  sidewalls within the regulators  to  enhance
interceptor  flows) and allowing any excessive interceptor  flows
during   major   storm  events  to  be  handled  by  CSO   control
configurations located at the major pump overflow stations.  Such
a wet weather overflow treatment facility was programmed for  the
Weiss  Street area.   Overall,  it was envisioned that as part of
the  BMP  design,  pumped overflows volumes at the  Weiss  Street
Station   requiring  treatment would be smaller  for  minor  storm
events  and be greater for major events as compared with  pre-BMP
conditions.

          Data   collected during the post  implementation  period
included  total  operating times of the pumps using the  permanent
time clocks and  stormwater quality based on samples collected via
a  temporary  sampler  installed  by  EDP.    Total  pumpage  was
calculated,   neglecting  minor  pump  capacity   changes   due  to
variable  sump levels, using a value of 100 cfs per pump.   Samples
were  composited and tested for suspended solids, BOD and  total/
soluble phosphorous.

          Figure 9.8  illustrates pumped discharge volumes of CSO
to   the Saginaw  River at  the Weiss Street Station.   This  figure
was  earlier used in Chapter 6 to indicate the  rainfall  to  pumpage
relationship  and  has  been  updated to include  1984  data  for
periods   representing  pre  and  post-BMP  modifications   at  the
upstream   regulators and  at the Weiss Street Pump Station.   All
1984 data falls  within the  range of previous data.  On  this basis
                                9019

-------
                                                     (/>
                                                     M
                                                     i
                                                    00
      Overflow volume
Cubic feet x  10* per event
            9020

-------
it  would  appear  that  the effects of  increased  flow  to  the
interceptor  at  the regulator chambers  has  been  substantially
offset by the increased East/West crossover flow.  There appears,
however,  some tendency for post BMP pumped flows to be less than
pre  BMP  conditions  for small storms and  higher  for  rainfall
events exceeding 0.7 inches.

          As  stated,  the  present data is limited and  as  such
exact trends cannot be defined.   In general, it can be concluded
that  for  light to moderate intensity events  Weiss  Street  CSO
pumpage  has  not increased above pre  modification  rates.   The
important  point  is,  that due to implementation of the  partial
BMP plan,  overflows at numerous untreated locations were reduced
or eliminated.   Stormwater flow is thus directed at an increased
rate  to  the  WWTP  where treatment  is  available  with  excess
overflow concentrated at the Weiss Street Pump Station.   The CSO
Facility   Plan  concept  requires  that  overflow  treatment  be
provided in the future.

          Water  quality  data at the Weiss Street  Pump  Station
consisted of BOD,  SS and total and soluble phosphorous analysis.
Evaluation of phosphorous data was included in Chapter  6,  where
the  primary purpose was to determine WWTP phosphorous levels and
WWTP  removal efficiencies.   BOD and solids data were both field
collected and predicted for each storm event using the simulation
modeling program.

         Figure 9.9  includes suspended solids concentration data
for each event during the 1984 portion of the  pre-implementation
evaluation program.   Data  is seperated by period within an event
including  the "pre-peak" condition,  during which time the  flow
rate in the system is increasing from base dry weather conditions
to the  peak flow rate, followed by the "mid-storm" condition when
flow  rates   remain  at elevated levels,  and  the   "post"  storm
conditions    (flow   rates   dropped  to  "pre-storm"  conditions).
Figure  9.9   clearly   illustrates the  effects  of  "first   flush"
conditions at the Weiss Street Station particularly  for the first
several events.  High  "pre-peak" solids concentrations are  due  to
the  combined  effects of street washoff  and scouring  of   system
sediments.    Lesser   "mid  storm"  concentrations   are  due    to
dilutional  effects  of  increased flow and a reduction  in   solids
materials.   "Post storm" levels are indicative of diluted   sewage
and minor  amounts of remaining washoff materials.

           The   simulation  model was  used to estimate  SS and  BOD
loadings   at  the Weiss Street  Station  for these  monitored  events.
Average modeled BOD  and SS  overflow loadings equalled  86 and  75%
of average measured  loadings  indicating reasonable closure.
                                9021

-------
1200,
1000-
 800-
  o
  c
  o
  u
 600-
 CO
 400-
 200-
                           Legend


                         • Pre  Peak


                         A Mid  Storm


                         D Post Storm
A-"     \
       8/4         8/8        8/18       8/28       3/30       9/2

                                 Date


    Figure 9.9  Weiss Street Pump Station Suspended Solids Data
                               9.22

-------
9.7   Monitoring a_t the Waste Water Treatment Plant

         Data  collection  at  the WWTP consisted  of  continuous
influent  rate  monitoring  and total bypass  flow  during  storm
events  and  stormwater  quality  monitoring   based  on  samples
collected  via a temporary sampler installation at  the  influent
grit/overflow chamber.  Samples were composited on a flow-weighed
basis during the storm period.

          The  intent  of  much of the reduced BMP  plan  was  to
increase  overall  wet weather flows to the  WWTP.   Figure  9.10
illustrates  cummulative  WWTP  wet weather  flow  volumes  above
normal dry weather flow for the day of an event, second and third
calender  days   (cumulated)   if flow rates had  not  returned  to
average   dwf  values.    Discrete  pre  construction  and   post
construction  data points for the 1984 evaluation are  separately
depicted.    Figure 9.10 indicates that most of both the pre  and
post  construction  data are  similar although there  are  several
events   during   the  post   construction  period  indicating   a
substantially increased flow  at the WWTP.  On this evidence it is
difficult  to  definitely verify the effects of the  BMP  program
elements  implementation  to  date.  It appears that  there  is  a
tendency for increased  flows at the WWTP.

        As  with the Weiss Street data,  the approach used was to
ensure  a  reasonable correlation between the field  results  and
predicted model data.   With  the model suitably  calibrated,  the
effectiveness  of  the program implementation could  be  reviewed
based   on  long  term  data  simulations.    Results  of   these
simulations is presented in Chapter 10.

          Comparison  of WWTP field data to model  data  included
the  flow  analysis discussed in Chapter 6,   which  resulted  in
minor  modifications  to  the  model and a  good  correlation  of
measured to modeled data.   On a water quality basis the relative
measured  to model data are presented in Figure  9.11.   Discrete
data  for  pre  construction  and post  construction  periods  are
included.   For  both the suspended solids and BOD water  quality
parameters,   the   model  reasonably  predicted  both   pre/post
implementation conditions.

9.8  Field Verification p.f FJ.OW Regulating Device Calibration

          Simulation  of CSO  backup and drain-down was  performed
at several of the modified chambers by EDP personnel to allow on-
isite  calibration  of  the new vortex  flow  regulating  devices.
Physical    chamber   conditions   precluded   direct   discharge
measurements  at  most of the regulation  chambers.   Backup  was
produced either by closing the manual sluice gate or by placing a
flat plate in front of the weir wall thimble.  Depth measurements


                               9023

-------
  100-1
M
C
o
rH
rH
flj
C
O
•H
•H
s
O
-P


O

     0
              .4
                   .8      1.2      1.6

                   Rain Accumulation
Figure 9.10 WWTP Wet Weather Flow
               2.0

              Inches
2.4
2.8
                                9o24

-------
         40 n
          30
FIELD
DATA
BOC
MASS      20
1000 LBS
          10  •
                                          - Equivalence Line
                                          -t
                    10      20       30      40

            Model Data  BOD Mass  - 1000  Ibs.
                                               Legend

                                               pre BMP
                                               post BMP
FIELD
DATA
TSS
MASS
1000 LBS
          2001
          150
          100
           50-
                                         - Equivalence Line
                          —i—
                           100
                                          t
                  50     100     150    200

            Model Data TSS Mass - 1000 Ibs.

Figure 9.11  WWTP Wet Weather Water Quality Mass Data

-------
were  recorded at frequent intervals with  simultaneous  velocity
measurements  made  with a Marsh-McBirney velocity probe  at  the
flow  regulator inlet pipe.   Conversion of velocity data to flow
rates  was based on known inlet cross sectional  areas.   Results
for   each   location   were  plotted   on   the   manufacturer's
head/discharge curve for each device.  In general, the field data
verified manufacturer's specifications.

         Figures 9.12 through 9.16 illustrate the head  discharge
characteristics  for the five flow regulator devices measured  in
the  field.   Each figure depicts both design characteristics and
field data.  In some cases field data is limited to a narrow head
range due to the limited volume of dwf available for backwatering
and  in  all  cases  by  the  range  of  operation  during  storm
conditions  based  on  side  weir  elevations.    Each  regulator
chamber,  except  the modified Adams Street chamber,  contains  a
sluiceway with a top elevation at the influent sewer invert and a
depth of up to 30 inches.   At Hayes Street and Throop Street the
volume within this sluice was insufficient to allow low head flow
regulator calibration considering the high rates of discharge and
rapidly falling head conditions.

         Figure  9.12  details  the  data  for  the  Hayes  Street
installation.   Data  is   limited to a minimum head of  two  feet
which  corresponds  to  the top of the sluiceway  and  the  sewer
invert.    Field  data  is  somewhat  scattered  but  all  within
reasonable  limits of the  design curve.   For this  location  the
water  level  at  the  point  of side weir  spillover  is  at  an
equivalent head value of 3.5  ft.  Thus,  the range of field values
shown  in Figure 9.12 covers  the entire  range of  unit  operation
during storm events and indicates good control of outflow  rates.

         Figure  9.13  details  the  data for  the  Adams  Street
installation.   The range  of  field data  shown include  head values
between the regulating device inlet  crown and 9  inches below  the
spillover  weir crest.   Field data  indicates that the   observed
flow pattern follows the characteristic  curve.   In  sum,  flow  rate
control  at  this location is well within  reasonable   limits  for
proper operation  of this portion of  the  BMP plan.

         The  vortex valve discharge rates field-measured at  the
Cronk  Street  regulator  ,   Figure 9.14,   and at the  Throop  Street
regulator   device.   Figure  9.15,   also  demonstrate   reasonable
agreement   with  the   design curves.     Data   scatter   may    be
attributable   to  actual  unit  accuracy  limitations and/or  to  field
measurement   techniques.    Each  of  these locations  was  monitored
twice   in   the  field and  two  data  sets are  shown on  each  curve.
Data  repeatability,   though  not perfect,   is  quite   reasonable.
Field  notes   indicated that  at  each location  the second run  was
less  prone  to debris  fouling the  measuring  equipment   since   the


                               9026

-------
 10
Figure 9.12  Hayes Street Vortex Valve Characteristics
                          9027

-------
00
        CO
St
o
            200
            100
                                         Head - Feet
            Figure  9.13   Adams Street Vortex Valve Characteristics

-------
 CO
 8
                        Head - Feet
Figure 9.14   Court Street Vortex Valve Characteristics
                          9029

-------
vo
oo
o

Figure 9.15
                                                  34

                                               Head  -  Feet
                                Throop  Street Vortex Valve Characteristics

-------
    10
     9
     8
     7
     6
     5
                 0.5
1.5
Figure 9.16  Ames Street Vortex Valve Characteristics
                        9C31

-------
first  run  promoted scouring of the sewer line and  allowed  for
relatively clean water flow during the second run.

         The  four  flow regulator units investigated above  were
the conical configuration type devices.   The device installed at
Ames  Street  is  of  a  different  design  commonly  termed  the
"horizontal"  type as the vortex flow pattern is developed  in  a
horizontal plane.   Field data shown in Figure 9.15 fall slightly
above the vortex flow regulator design head/discharge curve.  The
significant  aspect  of  the  field data is  that  it  reasonably
matches design data shown and demonstrates a narrow range of flow
rate for the head conditions encountered in this application.

          Field  calibration  at  other  regulator  chambers  was
impractical  due  to  field conditions.   Based  on  those  units
actually investigated, it is concluded that the vortex valve flow
regulators adequately control outflow rates to ranges within  the
design conditions necessary for proper operation of the BMP plan.


9.9  Evaluation of the Cronk Avenue Regulator

         Two  original regulator chambers on the West Side of the
Saginaw  River  were   unlike all other regulators  in  that  the
backwater  gates  which allow for excess stormwater overflow   to
the  river  were not located in the  regulator  chamber,  but  in
separate remote chambers nearer the river.   Each location, Cronk
Avenue and West Genessee Avenue, operated such that flow from two
directions   entered   the  regulator   chamber.    Under   storm
conditions,  flow  would  backwater and reverse direction in  one
feed  line.     A chamber with an overflow gate to the river  was
constructed at a remote location.

          During the design phase of the reduced BMP program,  it
was determined that modifications to the backwater gate  chambers
would  be  costly considering the minimal increase in  stormwater
storage  attainable,  and  that all flow not allowed  to  gravity
spill  to  the   river might be pumped as overflow  at  the  Weiss
Street Pump Station at additional cost.  These modifications were
not  deemed  desireable until satellite wet weather treatment  is
provided at the Weiss Street Pump Station.  Modification at these
chambers  was  limited  to  replacement  of  the   existing  float-
operated  regulating  devices with  new  vortex  valve  throttling
devices.

          Post   reduced   BMP  plan   implementation   evaluation
included  monitoring  of the depth  of  flow at  the  Cronk   Avenue
backwater  gate  chamber and the peak depth at  a location upstream
in  the Cronk Avenue  drainage area.    Six events   were  monitored
during  the period  each demonstrating  similar  characteristics  of
                                9.32

-------
stormwater  draindown  rates.    Draindown  periods  consistently
lasted  several  days  such that in some cases drainage  was  not
complete at the start of a subsequent event.   Flow to the  river
appears  to  have occurred for all events which ranged  in  total
accumulation  from  0.17  to 0.77 inches and in duration  from  2
hours to 12 hours.   The limited storage available is   indicated
by the apparent spillover to the river after 4 hours for an event
with 0.17 inches accumulated over 5 hours.

          The  draindown periods were assumed attributable to the
upstream hydraulic/hydrologic conditions.  Based on the estimated
storage volume of 49,000 cu.ft.,  the estimated dry weather  flow
rate  and  the vortex valve design discharge  rate,  a  draindown
period of 12 hours is predicted.  The 65 to 75 hour periods field
recorded   appear   to  be  attributable  to   either   continued
inflow/infiltration  to this part of the Saginaw sewerage system,
a higher than estimated dry weather flow base rate or both.

          Two  upstream  off-line storage  chambers  are  located
within  the drainage area.   The Congress Avenue chamber consists
of approximately 1300 ft.  of 77 in. by 121 in. pipe and provides
about 86,000 cu.  ft. of storage.  The second chamber is actually
located  in the Township area (above the City of Saginaw  limits)
and consists of an underground concrete structure of  rectangular
shape providing about 100,000 cu. ft. of storage.  During extreme
events creating surcharge conditions,  combined sewage  overflows
side  weirs  of  the main 60 inch trunk line  into  the  Congress
Avenue  chamber.   City personnel release the stored water  after
events  by  manually  opening a butterfly  valve.   City  records
indicate  that for the period of October and  November,  1984  no
overflow to the chamber occurred.   At the Jameson Street chamber
pumping of stored water is required.   Although pump records were
available  it  was calculated that the volume of storage  in  the
Jameson  Street  chamber or even the combined storage volumes  of
both chambers were insufficient to account for the volume of flow
noted after each event at the Cronk regulator.

          Based  on a detailed evaluation of available  data,  it
appears  the  long  draindown periods are due to  a  current  dry
weather  flow   rate  including infiltration,  much  greater  than
previously  estimated  during  Phase 1 and  Phase  2.   The  only
adverse  effects  of  the existing conditions  are  the  lack  of
storage volume  available for  secondary storm events.   No adverse
problems  have  been reported in terms of excessive surcharge  or
basement flooding under modified conditions.   In addition,  it is
intended  that  both the Cronk Avenue and  West  Genessee  Avenue
chambers  be  modified  concurrently with the  implementation  of
treatment at the Weiss Street Station.
                               9.33

-------
9.10  Post     truct ,ion Chamber
          Evaluation  of new flow regulating devices and  chamber
modifications  was performed during the post construction period.
Post  storm  observations  were by City  of  Saginaw  maintenance
personnel .

         Observations  were recorded at each  modified  regulator
chamber  after each storm event.   Records indicate the  relative
intensity  of  the storm event,  flow conditions in  the  chamber
upstream   and  downstream  of  the  new  regulating  device  and
conditions at the device.   Observations were made of the  sewage
flow  to  determine  if  free  flow  conditions  existed  without
blockage.   All  chamber areas and related piping were  inspected
for debris accumulation in areas subject to storm conditions  and
for debris sedimentation in areas of dry weather flow.

          Operating  conditions at most chambers were reported as
good with little or no debris accumulation or sedimentation.  One
general  exception is the occurrence of debris remaining  on  the
top surface of concrete weir walls.  During the design phase this
possibility  was  noted,  however as these surfaces also  act  as
walkways  within  the chamber it was deemed preferable  to  allow
small  amounts  of  debris accumulation than  to  produce  unsafe
footing  by sloping or crowning weir tops.   Debris accumulations
were  predicted and have been found to be insufficient  to  cause
odor problems.

          Locations  with adverse conditions reported on  one  or
more  occasions included the Ames Street regulator  chamber,  the
Court  Street regulator chamber and the Salt/Vermont Streets  in-
line  regulator  chamber.   At the Ames Street regulator  chamber
near  complete blockage of the wall orifice leading to  the  flow
regulator was reported on one occasion and blockage of the device
on  two  other occasions.  Apparently large deposits of scale  or
grease  were present and the City personnel cleaned the area  and
the  device.   It  is believed these conditions resulted  from  a
combination of factors,  including large amounts of grease within
a relatively small discharge waste stream.   The particular  flow
through pattern of the horizontal type vortex valve may have  had
an  additional  negative impact since no cloggage  problems  have
been  reported  for the conical type device at the  Court  Street
chamber  which  passes similar low flow rates  (0.33 cfs) but  not
large quantities of grease noted at Ames Street.   Although it is
difficult to conclude from these observations that the horizontal
type  device should not be used in the future for very  low  flow
rates having high grease content,   care and discretion should be
used  when this type of device is used to regulate small sewerage
flows .
                               9034

-------
          Construction  of  the new chamber at  the  Salt/Vermont
Street  location  included the use of concrete fill  material  to
contour  all  chamber  areas in an effort to prevent  debris  and
sediment  accumulation.   After construction several  areas  were
noted  to  be  improperly  sloped  and  debris  accumulation  has
resulted in the production of  odors in the chamber.   Corrective
action requires only additional concrete material to match design
conditions  and  should eliminate problem  areas.  Otherwise  the
entire  chamber  and new regulator have been reported to  operate
quite satisfactorily.   No upstream deposition problems have been
noted  as  a  result of the in-line  storage  generated  at  this
location.

          The  Cronk  Street regulator chamber is  one   location
where  persistent problems related to the new  regulating  device
have been reported.     On several occasions the chamber has been
backwatered due to flow blockage resulting from sticks,  rags and
other  materials lodged within the flow regulating device and  at
the  sluice  gate.   The problem is compounded by  the  difficult
access  at this location.   Weir walls extent to within 17 inches
of  the chamber ceiling making human    access  difficult  and  no
access  manhole originally existed for the area between the  weir
walls.   The City has since provided a new access manhole  to the
chamber  above the sluiceway simplifying the unclogging  process,
when necessary.

         Blockages at the Cronk Street regulator appear to be due
to  an  unusual  amount  of large  floating  materials  from  the
upstream  drainage area.  The high weir walls within the  chamber
prevent any overflow to the interceptor.   Accumulations of large
floatable  material may ensue and during final draindown  combine
to clog the regulating device.

          During   the  design  phase  of  the  project  it   was
determined  that  altering the remote backwatering gate  and  the
chamber  side weirs at the Cronk Street Chamber would not be cost
effective  at  this  location  considering  the  limited  storage
available  and the need to pump excess flow at the  Weiss  Street
Station.   The  intent  was  to make  these  modifications  after
treatment  was  provided at Weiss Street.  The problem  of  large
floatable  accumulations due to the lack of an overflow area  was
not  anticipated.   It  is  recommended  that  the  situation  be
observed  further and resolved,  if found necessary,  either   by
lowering  the  weir walls to allow overflow  of  large  floatable
debris or by installing an upstream stick-trapping device.

          In   general,   the   new   regulating   devices   have
demonstrated  the  ability at most of the installations  to  pass
typical sewage and CSO materials.  Any items physically too large
to pass through the device may become trapped.


                               9.35

-------
                           CHAPTER 10

              ASSESSMENT OF PRE BMP CONDITIONS AND
                 EVALUATION OF PROPOSED PROGRAMS


10.1 Foreword

          The  present water quality of the Saginaw River and Bay
is determined by a wide variety of events both induced by man and
of  natural  origin.  CSO  are  only one aspect  of  the  general
problem.  However, CSO have been shown to be significant in their
deleterious  impacts yet controllable.    Although  the  proposed
activities  will  improve river  water quality and the degree  of
improvement  can  be assessed for  selected  parameters,  general
water quality improvements will  be of a wider nature than can be
presently quantified.


10.2   Overview of Analysis Criteria and Results Presentation

          Assessment  of  "pre BMP"  conditions  makes   use   of
EDP's  stormwater runoff simulation model to estimate   pollutant
emission to Saginaw  River.    The simulation  runs present annual
summaries   of  combined  sewer  overflows and  loadings  at  each
overflow  point,  and for the  system in  general.  Overflows  and
loadings  are  considered to be those  resulting from wet  weather
rainfall  events.   Snowmelt and infiltration during  non-rainfall
periods  are implicitly  included  in  the dry weather flow and  are
not  tallied in the wet weather loadings.

          Dry  weather   loadings   at  the   WWTP   are   considered
adequately  handled  by the plant and  not part of the CSO problem.
Total wet weather rainfall  impacted  loadings to the river  include
both loadings caused by overflows in  the  system  upstream  of  the
WWTP,   as   well   as  the WWTP loadings  during   rainfall   events
 (excluding  normal  dry weather effluent contributions).  The 1978
WWTP removal  efficiencies   for   TSS  and  BOD   of  93%   and  89%,
respectively,  were  considered maintainable during storm   events
and  were used to  calculate  the residual stormwater loadings from
the   WWTP. Review of  wet  weather data  for   the September   to
November, 1984 post  construction  period indicated TSS  removals  to
average 93.3%   and BOD to  average  86.1%.   TSS  removals were
therefore   consistent with  earlier 1978 data.   Lower  BOD   values
during  wet  weather  were  apparently consistent  with slightly lower
overall efficiencies.    The three month period averaged 87.4%  BOD
removal efficiency.    On this basis  it was assumed that no change
 in  removal  efficiency  for TSS  or BOD resulted from  the  reduced
plan implementation and  the original yearly average  removal rates
were  attainable  and  as such,  used for   model  simulations.   As
                                 10.1

-------
previously discussed, phosphorous loadings to the WWTP were based
on a nominal influent concentration of 1.3 mg/1 and  WWTP removal
efficiencies of 50 and 75 percent for treatment without and  with
pickling  liquor  treatment.  Phosphorous  loadings  at  overflow
points were based on a 1.74 mg/1 concentration.

         Table  10.1 presents the "pre BMP" model run and  offers
an example of a typical simulation run summary.   Part "A" of the
summary   table  will  typically  present  overflow  and  related
discharge  information  while  part  "B"  will  present  overflow
pollutant (TSS and BOD) loadings to the Saginaw  River.   Results
are  always presented for the entire period simulation (for 1977,
there are 78 rainfall events),  for "low" rainfall events defined
as less than 0.5 inches of accumulated rainfall (for 1977,  there
are  60 such events),  and for "high" rainfall events defined  as
greater than 0.5 inches of accumulated rainfall (for 1977,  there
are 18 such events).

         For each of the three periods overflow and water quality
loadings are presented for seven major overflow points,  for  the
rest  of the overflow points on the East and West Sides,  and for
flows  and  loadings influent to the WWTP.   Gravity  and  pumped
discharges   are  lumped  together  for  the  Fourteenth   Street
overflow.   The  Weiss  Street  gravity  overflow  discharge   is
separately  reported  from pumped overflows at the  Weiss  Street
Pumping Station.  All quantities reported from overflow locations
are effluent discharges to the Saginaw River after treatment,  if
applicable.   For  example,  overflow and pollutant loadings from
the Hancock Street Station reflect excess overflow discharge from
the  sedimentation  units not bledback to the  WWTP.   Peak  WWTP
flows reported such as in Table 10.1 represent the highest hourly
average  flow rate into the WWTP.    Reported  mean and  standard
deviations  are computed on the basis of non-zero  events.  Event
durations  ranged  between  one hour and three days  for  the  78
storms in 1977.   Yearly discharge volumes and pollutant loadings
are also reported.   Total hours reported in the tables represent
the total number of hours that some overflow occurred (gravity or
pumped).   All  flow volumes are in thousands of cubic feet.  All
pollutant  loadings are in thousands of  pounds.   Average  river
elevations  were used for all runs unless otherwise noted (580.15
feet - USGS datum).
10.3   Pre BMP  CSO  nviion Est ima t e s
          Simulation analysis results for "pre BMP"   conditions,
that  is,  the original system configuration with Hancock  Street
Facility  are  given  in  Table  10.1.  Although  the  "pre  BMP"
simulation was also run during Phase 1 and Phase 2 of the overall
project  (1978-1983),  results presented are those based  on  the
                               10«-2

-------
                          TABLE lOolA

                PRE BMP CONDITIONS SIMULATION
                         PLOWS - OVERFLOWS

PERIOD :  1 / 6  TO  12 / 26     78  EVENTS   33  INCHES TOTAL RAIN
WWTP
PEAK FLOW
VOLUME *
MEAN **
STND DEV
NO. EVENTS
FULL PERIOD
128
158968
2038
1707
78
LOW RAIN ***
128
84398
1407
741
60
HIGH RAIN •**
128
74570
4143
2254
18
OVERFLOW POINTS
                 FULL PERIOD        LOW RAIN ***        HIGH RAIN ***
                        VOLUME*             VOLUME*           VOLUME*
FRASER     76 EVENTS 405 MRS  58 EVENTS 230 MRS   18 EVENTS 175 HRS
 YEAR TOT                11199                2507                8692
 MEAN **                   147                  43                 483
 STND DEV                  391                  58                 698

HANOOCK    16 EVENTS 50 HRS   5 EVENTS 9 HRS      11 EVENTS 41 HRS
 YEAR TOT                15131                1930               13200
 MEAN **                   946                 386                1200
 STND DLV                 1390                 204                1607

WEISS      76 EVENTS 405 HRS  58 EVENTS 230 HRS   18 EVENTS 175 HRS
 YEAR TOT                64306               23010               41296
 MEAN **                   846                 397                2294
 STND DEV                 1525                 269                2616

WEISS PUMP 63 EVENTS 358 HRS  45 EVENTS 161 HRS   18 EVENTS 197 HRS
 YEAR TOT                59013              19375               39368

 MEAN **                   937                 431                2202
 STND DEV                 1126                 394                1344

WEBBER     20 EVENTS 49 HRS   5 EVENTS 7 HRS      IS EVENTS 42 HRS
 YEAR TOT                 5110                 317                4793
 MEAN **                   255                  63                 320
 STND DEV                  557                  43                 630

EMERSON    0 EVENTS 0 HRS     0 EVENTS 0 HRS      0 EVENTS 0 HRS
 YEAR TOT                    000
 MEAN **                     000
 STND DEV                    0                   0                   0

FOURTEENTH 77 EVENTS 504 HRS  59 EVENTS 280 HRS   18 EVENTS 224 HRS
 YEAR TOT                10129                2507                7622
 MEAN **                   132                  42                 423
 STND DEV                  306                  41                 532

WEST RESID 76 EVENTS 354 HRS  58 EVENTS 198 HRS   18 EVENTS 156 HRS
 YEAR TOT                41249                8319               32930
 MEAN **                   543                 143                1829
 STND DEV                 2031                  94                3901

EAST RESID 76 EVENTS 405 HRS58 EVENTS 230 HRS18 EVENTS 175 HRS
 YEAR TOT                55659               16684               38974
 MEAN **                   732                 288                2165
 STND DEV                 1685                 225                 3023
  *  -  1000 CUBIC FEET - ABOVE DRY WEATHER FLOW  **  -  PER NON-ZERO EVENT
  ***  - LOW RAIN 0.5 INCHES OR LESS - HIGH RAIN GREATER THAN 0.5 INCHES


                                 10.3

-------
                         TABLE 10.IB
                PRE  BMP CONDITIONS SIMULATION
WATER QUALITY
PERIOD : 1 /
WWTP

TOT LOAD
MEAN *•
STND DEV
6 TO
FULL
TSS *
3075
39.4
31.7
12 / 26
PERIOD
BOD *
939
12.0
7.3
78 EVENTS
LOW RAIN
TSS *
1673
27.9
15.2
33 INCHES TOTAL RAIN

BOO *
605
10.1
5.0
HIGH
TSS *
1402
77.9
40.8
RAIN *•*
BOD *
334
18.5
9.4
OVERFLOW POINTS


FRASER
TOT LOAD
MEAN **
STND DEV
HANOCCK
TOT LOAD
MEAN **
STO) DEV
WEISS
TOT LOAD
MEAN **
STM) DEV
WEISS PIMP
TOT LOAD
FULL
TSS *

254
3.3
8.8
305
19.1
30.8

1590
20.9
34.2

1001
MEAN *MEAN ** 15.9
STND DEV
WEBBER
TOT LOAD
MEAN **
STND DEV
EMERSON
TOT LOAD
MEAN **
STM) DEV
FOURTEENTH
TOT LOAD
MEAN **
STM) DEV
WEST RESIDUAL
TOT LOAD
MEAN **
STND DEV
EAST RESIDUAL
TOT LOAD
MEAN **
STND DEV
20.4
116
5.8
12.8

0
0.0
0.0

221
2.9
6.7

891
11.7
43.1

1178
15.5
35.6
PERIOD
BOD *

35
0.5
0.8
36
2.2
3.0

496
6.5
6.7

317
5.0
5.0
17
0.9
1.6

0
0.0
0.0

63
0.8
1.3

137
1.8
4.1

245
3.2
4.4
LOW RAIN
TSS *

60
1.0
1.3
31
6.2
5.1

646
11.1
6.5

308
6.8
7.1
7
1.4
0.9

0
0.0
0.0

57
1.0
0.9

198
3.4
1.9

375
6.5
4.5
***
BOD *

13
0.2
0.2
6
1.1
0.7

258
4.5
2.3

126
2.8
2.4
2
0.3
0.2

0
o.b
0.0

22
0.4
0.3

56
1.0
0.4

115
2.0
1.0
HIGH
TSS *

194
10.8
15.8
274
24.9
35.5

944
52.4
59.3

693
38.5
24.8
109
7.2
14.5

0
0.0
0.0

163
9.1
11.8

692
38.5
83.1

803
44.6
64.6
RAIN ***
BOD *

22
1.2
1.3
30
2.8
3.5

238
13.2
10.7

191
10.6
5.4
16
1.0
1.8

0
0.0
0.0

41
2.3
2.2

81
4.5
7.8

130
7.2
7.5
 * - 1000 POUNDS      •• - PER NON-ZERO EVENT
*** - LOW RAIN 0.5 INCHES OR LESS - HIGH RAIN GREATER THAN 0.5 INCHES
                                     10.4

-------
final model editions as calibrated in Phase 3 (1984).  Regulators
were set to operate as they originally existed.   In-line storage
was  composed  of  the  storage generated by  the  five  modified
regulators in the Hancock Street area,  and the available storage
(up  to  the  point backwater gates would  open)  for  all  other
regulators.   The   interceptor  system  operated  as  originally
perceived  with  the  Weiss Street Station wet  well  weir  level
unadjusted.  The   WWTP flow rate was throttled to allow  only  a
throughput  maximum  flow of 128 cfs,  the maximum rate  observed
during the 1984 field investigation.

         The total annual wet weather rainfall impacted  combined
sewage  discharge  for 1977 delivered to the WWTP and to all  the
overflow/pumping  station  locations equals 420.8  million  cubic
feet.   Approximately 37.7% of this total or 159.0 million  cubic
feet  is delivered to the WWTP with an untreated balance of 261.8
million  cubic  feet.    The  fraction  of  the  combined  sewage
discharge  at the WWTP during 60 low rainfall events is 53.0%  of
the overall low rainfall total (140.1 million cubic feet) and  is
2.8.5%  for the 18 high rainfall events.   The high  rainfall event
subtotal   equals  62.1.%  of the  annual  overall  combined  sewer
overflows.

           The  "pre BMP" overflow summary results in  Table  10.2
indicate   that  the Weiss Street area  (Weiss Street Pump  Station
and  the Weiss Street gravity overflow from the Township) is  the
primary overflow  in the system representing 47.1%  of the  annual
system CSO (excluding discharge to the WWTP).  The  Hancock Street
overflow is second,  representing 5.8% of the total untreated CSO
suggesting that  the  bottleneck  at  the river  crossing  has   a
substantial   impact at both the Hancock and Weiss Street  Station
discharge  points.   Overflows at Webber Street, Fourteenth Street
and Fraser Street represent 2.0%, 3.9% and 4.3%, respectively, of
the  annual CSO discharge.   The Emerson Street Station  was  not
used  during  any  events.  The  remainder of   the   system's  CSO
discharge  points  from both the East  and  West  Side   regulators
accounted  for 37.1% of the  total, 21.3% and  15.8%  respectively.

           The  "pre BMP" total annual  (1977) wet weather TSS  and
BOD  pollutant loadings generated in  the system and delivered  to
the  WWTP  and all overflow/pumping station locations  equal  8.63
and  2.29 million pounds, respectively  (See Tables 10.3  and 10.4).
TSS  and   BOD loadings to the WWTP represent 35.6%  and  41.1%   of
the  overall  wet weather load.   (Tables 10.3 &  10.4)  After  WWTP
treatment, however,   the   residual  wet weather WWTP  TSS and  BOD
loadings   represent   less   than  10%  of  the   total  wet  weather
loadings   to  the  river.    Pollutant emissions from  Hancock   and
Weiss   Street locations  are   the   dominant  source  of   organic
loadings  to the  river  from  the major overflow  points.    Pollutant
emissions  from  the  60  low  rainfall  events  represent  roughly   54%
                                 1005

-------
                              TABLE 10.2

                          FLOW SUMMARY DATA
                    PRE BMP
                  TOTAL FLOW
   BMP
TOTAL FLOW
REDUCED BMP
 TOTAL FLOW

WEISS
HANCOCK
FRASER
14TH
WEBBER
EMERSON
EAST
WEST
SUBTOTAL
WWTP
TOTAL

WWTP % OF
WEISS % OF
1000 FT3
123,319
15,131
11,199
10,129
5,110
0
55,659
41,249
261,796
158,968
420,764

TOTAL FLOW
TOTAL FLOW
*%
47.1
5.8
4.3
3.9
2.0
0
21.3
15.8
100


SUMMARY
37.7
29.3
1000 FT3 %
95,861 66.0
27,228 18.7
5,558 3.8
12,855 8.9
3,752 2.6
0 0
0 0
0 0
145,254 100
303,823
449,077
STATISTICS
67.7
21.3
1000 FT3
81,404
30,017
5,376
13,296
4,144
0
55,709
29,036
218,982
240,508
459,490



%
37.1
13.7
2.4
6.1
1.9
0
25.4
13.4
100



52.3
17.7
* % OF SUBTOTAL FLOW - EXCLUDING WWTP
                                   10.6

-------
                           TABLE 10.3

                        TSS SUMMARY DATA
LOCATION



WWTP LOAD

WWTP REMOVAL

WWTP NET TO RIVER

WEISS TO RIVER

ALL OTHER TO RIVER

TOTAL WET WEATHER LOAD

TOTAL LOAD TO RIVER
  PRE BMP
TOTAL LOAD
     BMP
TOTAL LOAD
 REDUCED BMP
TOTAL LOAD
WWTP  %  OF  TOTAL  WET
    WEATHER LOAD

WWTP  %  REMOVAL OF
    WWTP LOAD

WWTP  %  REMOVAL OF
    TOTAL LOAD

WWTP  RESIDUAL %  OF
    RIVER LOAD

 CONTROL PROGRAM NET
    %  REMOVAL
1000 LBS
3,075
2,860
215
2,591
2,965
.D 8,631
5,771
SUMMARY
35.6
93
33.1
3.7
0
1000 LBS
6,068
5,643
325
2,053
1,031
9,152
3,509
STATISTICS
66.3
93
61.7
9.3
28.6
1000 LBS
5,140
4,780
360
1,778
2,892
9,810
5,030

52.4
93
48.7
7.2
15.6
                                    10.7

-------
                           TABLE  10.4

                        BOD SUMMARY DATA
LOCATION
 PRE BMP
TOTAL LOAD
   BMP
TOTAL LOAD
REDUCED BMI
TOTAL LOAD

WWTP LOAD
WWTP REMOVAL
WWTP NET TO RIVER
WEISS TO RIVER
ALL OTHER TO RIVER
TOTAL WET WEATHER LOAD
TOTAL LOAD TO RIVER
WWTP % OF TOTAL WET
WEATHER LOAD
WWTP % REMOVAL OF
WWTP LOAD
WWTP % REMOVAL OF
TOTAL LOAD
WWTP RESIDUAL % OF
RIVER LOAD
CONTROL PROGRAM NET
% REMOVAL
1000 LBS
939
836
103
813
533
2,285
1,449
SUMMARY
41.1
89
36.6
7.1
0
1000 LBS
1,944
1,730
214
492
163
2,599
869
STATISTICS
74.8
89
66.6
24.6
30.0
1000 LBJ
1,802
1,604
198
466
547
2,815
1,211
64.0
89
57.0
16.4
20.4
                                10.8

-------
of  the  total implying that considerable pollutant removal  gain
can  be achieved by control of overflow during low level  storms.
The annual "pre BMP" wet weather related TSS and BOD loadings  to
the  Saginaw  River (for the simulation year of 1977) equal  5.77
and 1.45 million pounds, respectively. See Tables 10.3 and 10.4.


10.4   Analysis of Weiss Weir Alteration

         "Pre  BMP"  conditions  were  also run  during  Phase   2
simulations  (1983) with the Weiss Street regulator weir raised   5
feet  to assess its impact on the system.  Summary results of the
earlier   simulations   are  reported  here   to   indicate   the
significance of the weir modification.

         Model operation simulating the Weiss Street Pump Station
weir  alteration  as  the  only  change  to  the  Saginaw  system
indicated  that volumes of overflow  at specific locations  would
change,  particularly  at  the WWTP  where total  flow  increased
20.2%.  The  flow   increase to the WWTP  is mainly offset by  the
substantial  change  in  pumpage requirements  at  Weiss  Street.
Increasing   the Weiss Street Station weir elevation  also acts   to
pond more water in  the West Side Interceptor system  as  evidenced
by  a  minor increase in overflow at the Hancock Street  Station.
The  flow  increase at Hancock Street  exactly balanced  the  WWTP
increase  and  the  Weiss  Street  decrease.   No    changes  were
recorded  in  the  simulation  results for any of the   other   large
overflow  points  or for totals of the  smaller regulator  chambers
on either river side.

          Considering   the effectiveness of the WWTP  in handling
wet weather  flow,  and using the  Phase  3  "pre BMP"  model volumes,
overall   reductions  in wet weather loadings  potentially  gained
from   the single  act  of raising  the Weiss Street weir  height  are
0.58 and  0.17  million pounds  for TSS and BOD, which  are 10.0%  and
9.2% of the  present total  loadings.

          The results  support  the hypothesis that  the  interceptor
river  crossing is a major  bottleneck  to flow.   Restricted  pumpage
rates   at the WWTP  wet  well  quickly back   up   the  East   Side
Interceptor   which,   in turn  throttles flow across  the river  and
backs   up the West  Side  Interceptor.   An   important   step  to
relieve the  system is to  reduce  overflow at  the Weiss Street Pump
Station  by   increasing the weir height into  the   wet  well,  and
thereby  increase  the  flow  across  the river  and   to  the  WWTP.
Excess  system  capacity  appears available  in  the   Emerson  area,
suggesting diversion  of all  the  smaller East  Side  overflow points
to   the  East  Side interceptor with  pumping  relief   and   overflow
treatment provided at  the Emerson  Street Pumping   Station.   This
action should also increase  the  flow  to the WWTP.
                                10.9

-------
10.5     Complete BMP Program Simulation

          The complete BMP program incorporates all the low level
structural  improvements  and management practices that could  be
implemented at relatively low cost.   The concept of the  program
is  to maximize the use of existing facilities before further CSO
treatment facilities  are implemented.  The program maximizes in-
line  storage  already  available  in  the  system  conduits  and
maximizes  the  conveyance  of  storm  flows  to  the  WWTP.   To
effectuate this plan, the 33 existing regulators are modified, 14
new  flow  control  devices  are   installed  within  new  control
chambers to increase in-line storage,  and weir modifications are
accomplished  at the Weiss Street  Pump Station to  increase  flow
across the river.

          Complete  BMP implementation includes  modification  of
the  Type  "B"  regulators to yield a constant  discharge  during
initial  storage  filling,  with excess  flows  beyond  available
storage  diverted  to  the  interceptor rather  than  the  river.
Modifying  the  Type  "B" regulator chambers  includes  adding   a
cross  weir between the backwater  gate and the flow channel,  and
altering the existing side weirs between the flow channel and the
drain system leading to the interceptor.  In this manner flows in
excess  of what is discharged through the new vortex  valve  flow
regulating  device or stored in the system behind the weir,  will
first   overflow   the  lower  weir  and  be  directed   to   the
interceptor.  Only  extremely high flows will  overflow the cross
weir separating the backwater gate portion of the chamber, and be
directed  to the river.  This weir arrangement was considered  by
EDP  to be both the least expensive and most available method  of
limiting  overflows  at  all of the  regulator  chambers  in  the
system.  The   modified Hancock area regulators are also to  have
the  automatic  sluice gates leading to the  river  replaced  with
flap gates.  Six additional regulators of smaller size  (Type  "A")
are  to  be  altered  with  weirs  to  divert  all  flows  to  the
interceptor.  Alterations  to produce this effect  were  proposed
under  the previous Hancock area modification plan in 1977 and it
is the intent of the BMP program to complete these modifications.

        The  regulator chamber at Fraser Street is to be unaltered
except   for   removal   of  the   float   operated   swing    gate
regulator. An increased  weir   elevation of  five  feet   is  to  be
imposed  at  the  Weiss Street  Pumping Station to  reduce  pumped
overflows  at that point and increase the flow across the   river.
Fourteen  upstream   structures  are to be constructed  and  vortex
valve  regulating devices are to be installed to yield   additional
in-line  flow  control  for  storage  upstream  of  the    existing
regulator  chambers.    The   resulting changes  to  the   regulator
operations   achieve  the maximum in-line  storage  potential  of   the
system without causing  system  flooding.
                                 10.10

-------
          The  only  points  of  overflow as a  result  of  these
actions are at Eraser, Hancock, Weiss (pump and gravity), Webber,
Emerson  and  Fourteenth  Streets  except  in  extreme   flooding
conditions.   Weir  elevations  at Webber and  Fourteenth  Street
overflow  points  would  be raised slightly to  insure  that  the
fairly  high  post rain discharges from upstream in-line  storage
devices are totally diverted to the interceptor.     An  upstream
flow control device is intended only a short distance upstream.

         The total annual wet weather rainfall impacted  combined
sewage  discharge  for 1977 delivered to the WWTP and to all  the
overflow/pumping  station  locations equals 449.0  million  cubic
feet  as  simulated by the Phase 3 (1984) model for the  complete
BMP program  (see Table 10.5).   Approximately 67.7% of this total
or  303.8  million cubic feet is delivered to the WWTP   with  an
untreated balance of 145.2 million cubic feet.   The fraction  of
the  combined sewage discharge to the WWTP during 60 low rainfall
events  is 87.5% of the overall low rainfall total and  is  50.3%
for  the  18  high  rainfall events.   The  high  rainfall  event
subtotal  equals  53%  of  the  annual  overall  combined   sewer
overflows.

          The complete BMP plan overflow summary results in Table
10.2   indicate that the Weiss Street area  represents 66% of the
annual system CSO  (excluding discharge to the WWTP).  The Hancock
Street  overflow represents 18.7% of the  total.    Overflows  at
Webber  Street,  Fourteenth  Street and Fraser  Street  represent
2.6%,  8.9%  and 3.8%,  respectively, of the annual CSO discharge.
The  complete BMP plan would eliminate discharge of CSO from  all
other points on both the East and West Sides.

          The  complete BMP plan total annual  (1977) wet  weather
TSS  and  BOD  pollutant loadings generated  in  the  system  and
delivered  to the WWTP and all overflow/pumping station locations
equal 9.15 and 2.6 million pounds,  respectively. See Tables 10.3
and 10.4.    TSS and BOD loadings at the WWTP represent 66.3%  and
74.8%  of the overall wet weather total before treatment.   After
WWTP  treatment,  the  residual  wet weather  WWTP  TSS  and  BOD
loadings  represent only 9.3% and 24.6% of the total wet  weather
loadings to  the river.  Overall, the WWTP reduces the TSS and BOD
loadings  by  61.7  and 66-6%,  respectively,  resulting  in  wet
weather related discharges of 3.5 and 0.87 million pounds of  TSS
and BOD,  respectively, to the Saginaw River.  Pollutant emissions
from  Hancock  and  Weiss  Street  locations   are  the  remaining
dominant  source of organic loadings to the river from  the  major
overflow points.

          Comparing the above flow and pollutant summary data  to
that  developed  earlier for the "pre BMP"  simulation  indicates
substantial  reductions  in  overall CSO loadings  to   the  river


                                10.11

-------
                           TABLE  10.5A

                  COMPLETE BMP  PLAN  SIMULATION
                          FLOWS - OVERFLOWS

PERIOD :  I / 6  TO  12 / 26    78  EVENTS   33  INCHES TOTAL RAIN
WWTP
PEAK FLOW
VDUME *
MEAN **
STND DEV
NO. EVENTS
FULL PERIOD
128
303823
3895
2633
78
LOW RAIN ***
128
183031
3051
1782
60
HIGH RAIN ***
128
120792
6711
3020
18
OVERFLOW POINTS
                 FULL PERIOD        LOW RAIN ***        HIGH RAIN ***
                        VOLUME*             VOLUME*           VOLUME*
FRASER     18 EVENTS 73 HRS   4 EVENTS 7 HRS      14 EVENTS 66 MRS
 YEAR TOT                 5558                203                5355
 MEAN **                   309                 51                 383
 STND DEV                  650                 39                 719

HANCOCK9 EVENTS 37 HRS0 EVENTS 0 HRS9 EVENTS 37 HRS
 YEAR TOT                27228                  0               27228
 MEAN **                  3025                  0                3025
 STND DEV                 5207                  0                5207

WEISS46 EVENTS 237 HRS28 EVENTS 94 HRS18 EVENTS 143 HRS
 YEAR TOT                40646               8929               31718
 MEAN **                   884                319                1762
 STND DEV                 1686                210                2435

WEISS PUMP 63 EVENTS 362 HRS45 EVENTS 1 63 EVENTS 362 HRS
                              45 EVENTS 168 HRS   18 EVENTS 194 HRS
 YEAR TOT                55215              12719               42496
 MEAN **                   876                283                2361
 STND DEV                 1529                355                2186

WEBBER11 EVENTS 39 HRS1 EVENTS 1 HRS10 EVENTS 38 HRS
 YEAR TOT                 3752                 34                3718
 MEAN **                   341                 34                 372
 STND DEV                  661                  0                 686

EMERSON0 EVENTS 0 HRS0 EVENTS 0 HRS0 EVENTS 0 HRS
 YEAR TOT                    0                  0                  0
 MEAN **                     000
 STND DEV                    000

FOURTEENTH 76 EVENTS 837 HRS  58 EVENTS 492 HRS   18 EVENTS 345 HRS
 YEAR TOT                12855               4073                8782
 MEAN **                   169                 70                 488
 STND DEV                  349                 56                 609
WEST RESID 0 EVENTS 0 HRS
YEAR TOT
MEAN **
STND DEV
0 EVENTS 0 HRS
0
0
0
0 EVENTS 0 HRS
0
0
0

0
0
0
EAST RESID 34 EVENTS 127 HRS   16 EVENTS 36 HRS    18 EVENTS 91 HRS
 YEAR TOT                   0                   0                  0
         000
 MEAN **                    000
 STND DEV                   000

 * - 1000 CUBIC FEET - ABOVE DRY WEATHER FLOW  ** - PER NON-ZERO EVENT
 *** - LOW RAIN 0.5  INCHES OR LESS - HIGH RAIN GREATER THAN 0.5 INCHES
                                       10.12

-------
                         TABLE 10.5B

                  COMPLETE BMP PLAN SIMULATION
MATER QUALITY
PERIOD : 1 /
WWTP

TOT LOAD
MEAN **
STND DEV
6 TO
FULL
TSS *
6068
77.8
47.2
OVERFLOW POINTS
FULL

FRASER
TOT LOAD
MEAN **
STND DEV
HANCOCK
TOT LOAD
MEAN **
STND DEV
WEISS
TOT LOAD
MfcAN **
STND DEV
WEISS PUMP
TOT LOAD
MEAN **
STND DEV
WEBBER
TOT LOAD
MEAN **
STND DEV
EMERSON
TOT LOAD
MEAN **
STND DEV
FOURTEENTH
TOT LOAD
MEAN **
STND DEV
WEST RESIDUAL
TOT LOAD
MEAN **
STND DEV
EAST RESIDUAL
TOT LOAD
MEAN **
STND DEV
TSS *

125
6.9
14.8
559
62.1
108.9
944
20.5
38.1
1109
17.6
31.5
85
7.7
15.2
0
0.0
0.0
268
3.5
7.3
0
0.0
0.0
0
0.0
0.0
12 / 26
PERIOD
BOD *
1944
24.9
13.5
PERIOD
BOD *

12
0.7
1.2
53
5.9
10.3
254
5.5
7.2
238
3.8
4.7
12
1.1
1.9
0
0.0
0.0
86
1.1
1.6
0
0.0
0.0
0
0.0
0.0
78 EVENTS
LOW RAIN
TSS *
3728
62.1
31.0
LOW RAIN
TSS *

4
1.1
0.8
0
0.0
0.0
225
8.0
4.7
252
5.6
7.2
1
0.7
0.0
0
0.0
0.0
91
1.6
1.2
0
0.0
0.0
0
0.0
0.0
33 INCHES TOTAL RAIN
***
BOD *
1364
22.7
12.0
***
BOD *

1
0.2
0.1
0
0.0
0.0
81
2.9
1.5
77
1.7
2.0
0
0.1
0.0
0
0.0
0.0
37
0.6
0.4
0
0.0
0.0
0
0.0
0.0
HIGH
TSS *
2340
130.0
54.0
HIGH
TSS *

120
8.6
16.4
559
62.1
108.9
719
39.9
55.4
857
47.6
45.7
84
8.4
15.8
0
0.0
0.0
177
9.8
12.9
0
0.0
0.0
0
0.0
0.0
RAIN ***
BOO *
580
32.2
15.7
RAIN ***
BOD *

12
0.8
1.3
53
5.9
10.3
173
9.6
10.1
161
8.9
5.4
12
1.2
2.0
0
0.0
0.0
49
2.7
2.6
0
0.0
0.0
0
O.C
0.0
   - 1000 FOUNDS      "" - PER NON-ZERO EVENT
*** - LOW RAIN 0.5 INCHES OR LESS - HIGH RAIN GREATER THAN 0.5 INCHES
                                      10.13

-------
(Tables  10.3,  10.4).   Simulations  of  the 1977  storm  events
indicate that implementing the total EMF would reduce the  annual
"Pre BMP" wet weather induced TSS loading to the Saginaw River by
28.6%,  the  BOD by 30%.  As detailed below,  implementation of a
reduced BMP plan results in slightly lower overall reductions due
tc increased overflows at the smaller regulators.


10.6         Reduced BMP Program

          The   reduced BMP program incorporated mcst cf the  low
level structural improvements of the complete BMP program for the
West  Side.   No alterations are recommended on the East Side  as
the    numerous   simulations   performed    demonstrated    that
implementation of East Side improvements in full or in part, will
result in excess flow tc the Emerson Street facility.  Under "pre
BMP"  flow conditions, use of this manually operated facility was
virtually  unnecessary  and  one preference of  the  reduced  BMP
program was to avoid increased manpower requirements.   West Side
regulators  were  modified  as discussed under the  complete  BMP
program  with weirs set to elevations as detailed in  Chapter  7.
The  five  foot  weir  elevation increase  at  the  Weiss  Street
Pump Station was completed.

          One  of the original fourteen upstream in-line  storage
locations   was  selected  as  a  demonstration  site   fcr   the
construction of a new flow regulation/backwater/storage facility.
This location is upstream of the existing Eraser Street regulator
and provides an estimated 175,000 cubic feet of storage,  a major
reason for selection of this site.

         Utilizing  the reduced BMP program including  the  Weiss
Street Pump Station weir adjustment, the total annual wet weather
rainfall impacted combined sewage discharge for 1977 delivered to
the WWTP and to all the overflow/pumping station locations equals
459.5   million   cubic  feet  (see  Tables  10.6   and    10.2).
Approximately 52.3% of this total or 240.5 million cubic feet  is
delivered  to the WWTP  with an untreated balance of 219  million
cubic feet.  The fraction of the combined sewage discharge to the
WWTP  during  60 low rainfall events is 72.1% of the overall  low
rainfall total and is 39% for the 18 high rainfall  events.   The
high  rainfall event subtotal equals 59.1% of the annual  overall
combined sewer overflows.

          The  flow summary results in Table 10.4  indicate  that
the Weiss Street area  described earlier as  the primary overflow
in  the  system   represents  37.1%  of  the  annual  system  CSC
(excluding discharge tc the WWTP).   The Hancock Street  overflow
represents  13.7%  of the total.     Overflows at  Webber  Street,
Fourteenth  Street  and  Fraser Street represent 1.9%,   6.4%  and


                              L0014

-------
                         "TABLE I0.6A

                    REDUCED BMP PLAN SIMULATION
                          _________________


PERIOD I   1 / 6  TO  12 / 26     78  EVENTS   33  INCHES TOTAL RAIN

WWTPRJLL~PERl65          LOW~hAlN~»»»        HISH~RAIN~««
 PEAK FLOW                 128                 128                  128
 VOLUME »               24O508              135226               1O52B2
 MEAN »*                  3083                2254                 S849
 STND DEV                 2336                1387                 2690
 NO.EVENTS        78                  60                  18

6viRFLQW~p6lNTS
                 FULL PERIOD         LOW RAIN ***        HIGH RAIN ***
                        VOLUME*             VOLUME*           VOLUME*
FRASER     18 EVENTS 71 HRS    4 tVENTS 6 HRS      14 EVENTS 65 HRS
 YEAR TOT                 5376                 16O                 5216
 MEAN **                   299                  4O                  373
 SfND DEV                  652                  39                  722

HANCOCK14~EVENTS~56~HRS3~EVENTS~9~HRS11~EVENTS~4/~HRS
 YEAR TOT                3OO17                1186                28831
 MEAN »*                  2144                 395                 2621
 STND DEV                 4351                 107                 4799

WElii76~EVENTS~&87~HRS5i~IvENTS~34B~HRSIi~EVENTS~239~HRS
 YEAR TOT                43037               1OS33                325O4
 MEAN »»                   566                 182                 18O6
 STND DEV                 1402                 23O                 2473

WElsS~PUMP~48~iviNTS~257~HRS3O~£VENTS~9S~HRiIi~EV£NTS~l62~HRS
 YEAR TOT                38367               10238                28129
 MEAN **                   799                 341                 1563
 STND DEV                  866                 306                  955

WEBBER13~EVENTi~49~HRS2~EVENTS~3~HRSll~IvENTS~46~HRi
 YEAR TOT                 4144                  99                 4O45
 MEAN **                   519                  50                  368
 STND DEV                  630                  11                  673

EMERSON0~EVENTi~0~HRSO~IvENTS~O~HRSO~EVENTS~O~HRi
 YEAR TOT                    0                   O                    O
 MEAN *»                     0                   O                    O
 STND DEV                    O                   O                    O

FOUR?lENTH~76~EVEN7s~79r~HRS58~EVENTS~4i6~HRSlB~EVEN?i~365~HRS
 YEAR TOT                13296                41O9                 9187
 MEAN **                   175                  71                  510
 STND DEV                  359                  61                  621

WEST~RESID~76~EVENTi~692~HRi5i~EVENri~4li~HRiTi~EVENTi~274~HRi
 YEAR TOT                29036                9265                19771
 MEAN *»                   382                 16O                 1O98
 STND DEV                  762                 125                 1316

EASr~RESTD~76~iviNTS~4i5~HRb5i~IvENTS~279~HRSI8~£VENTS~204~HRS
 YEAR TOT                55709               16759                38951
 MEAN **                   733                 289                 2164
 STND DEV                 1688                 234                 3O29

~»™~IoOO~Cu6lC~FEiT~-~AiovI~5RY~WEATHER~FL5w*»~-~PER~N5N-zlRO~IvENT
 *** - LOW RAIN O.5 INCHES OR LESS - HIGH RAIN GREATER THAN 0.5 INCHES
                               10.15

-------
                            TABLE  10.6B

                      REDUCED BMP  PLAN SIMULATION
WATER QUALITY
PERIOD t 1/6
WWTP

TOT LOAD
MEAN *«
STND DEV
OVERFLOW POINTS


FRASER
TOT LOAD
MEAN **
STND DEV
HANCOCK
TO! LOAD
MEAN »»
STND DEV
WEISS
TOT LOAD
MEAN »«
STND DEV
WEISS PUMP
TOT LOAD
MEAN **
STND DEV
WEBBER
TOT LOAD
MEAN «*
STND DEV
EMERSON
TOT LOAD
MEAN **
STND DEV
FOURTEENTH
TOT LOAD
MEAN »»
STND DEV
WEST RESIDUAL
TOT LOAD
MEAN »•
STND DEV
EAST RESIDUAL
TOT LOAD
MEAN »»
STND DEV
TO
FULL
TSS *
S14O
65. 9
44.1

FULL
TSS »

121
6.7
14.8

612
43.7
92.0

1OO8
13.3
31. B

770
16. 1
17.4

94
7.2
14.5

O
o.o
o.o

291
3.8
7.9

613
8.1
16.0

1161
IS. 3
35. b
12 / 26
PERIOD
BOD *
1802
23.1
12.7

PERIOD
BOD *

12
0.7
1.2

61
4.4
8.7

277
3.6
6.3

189
3.9
3.2

13
1.0
1.8

O
O.O
0.0

87
1. 1
1.6

133
1.7
1.9

241
3.2
4.4
76 EVENTS
LOW RAIN
TSS «
3041
SO. 7
27.2

LUW RAIN
TSS »

3
0.9
O.8

17
3.7
2.7

271
4.7
5.4

212
7.1
6.3

2
1. 1
O.2

O
0.0
0.0

94
1.6
1.3

206
3.5
2.5

367
6.3
4.6
33 INCHES TOTAL RAIN
«**
BOD *
1233
20.6
10.9

«««
BOD *

O
O.I
0.1

2
O.8
O.3

10O
1.7
1.8

66
2.2
1.9

O
0.2
O.O

O
O.O
O.O

37
O.6
0.4

65
1.1
0.6

112
1.9
l.O
HIGH
TSS *
210O
116.7
51.2

HIGH
TSS •

117
8.4
16.4

595
54.1
101.4

737
41. 0
56.2

558
31. 0
19.5

92
8.3
15.5

0
O.O
0.0

197
10.9
13.8

407
22.6
27.9

795
44.1
64.4
RAIN »»»
BOD «
568
31.6
14.4

RAIN ***
BOD «

11
0.8
1.3

59
5.3
9.6

177
9.9
10.2

123
6.8
2.8

13
1.2
2.O

0
0.0
0.0

SO
2.8
2.5

68
3.8
2.9

129
7.2
7.5
 * - 1000  POUNDS       »« - PER NON-ZERO EVENT
**» - LOW  RAIN 0.5 INCHES OR LESS -  HIGH RAIN GREATER THAN O.5  INCHES
                                 10.16

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2.4%,   respectively,   of the annual CSO discharge.    The  Emerson
Street  Station was not used during any events.   The remainder of
the system's CSO discharge points on the East Side  accounted  for
25.4%  of the total.  CSO discharged from the West Side regulators
accounted  for  13.4%.   These CSO are due to limited  structural
changes  at the Crcnk Street and  W.  Genessee Avenue regulators.
Presently,  available  storage at these locations is limited  and
excess flow if not allowed to pass by gravity to the river  would
require pumping at the Weiss Station.  Until the control facility
is implemented at Weiss Street to handle pumped  overflows, it was
not deemed appropriate to alter the present overflow patterns.

          The  reduced BMP program annual (1977) wet weather  TSS
and BOD pollutant loadings generated in the system  and  delivered
to the WWTP and all overflow/pumping station locations equal 9.81
and  2.82  million  pounds,  respectively (see  Tables  10.3  and
10.4  ).   TSS  and BCD loadings at the WWTP represent 52.4%  and
64.0%  of the overall wet weather total before WWTP.   After  WWTP
treatment,  the  residual  wet weather WWTP TSS  and BOD  loadings
represent  only 7.2% and 16.4% of the total wet  weather  loadings
to the river.   Overall, the WWTP  reduces the loading of TSS and
BOD  by  48.7  and 57%,  respectively resulting  in  wet  weather
related  discharges of  5.03 and 1.21 million pounds of  TSS  and
BOD,  respectively,  to  the Saginaw River.   Pollutant emissions
from  Hancock  and  Weiss  Street  locations  are  the  remaining
dominant  source of organic loadings to the river from the  major
overflow points.

          Comparing  the above flow and pollutant summary data to
that  developed  earlier for the "pre BMP"  simulation  indicates
substantial  reductions  in overall CSO loadings  to  fthe  river.
Simulations  of the 1977 storm events indicate that  implementing
the  reduced  BMP plan lowered the annual "Pre BMP"  wet  weather
induced  TSS  loadings to the Saginaw River by 15.6% and the  BOD
loadings by 20.4%.  Comparison of these values to those  detailed
at  the  end  of Sections 10.4 and 10.5 indicate removals  to  be
greater than that attained by altering the Weiss Street regulator
chamber  weir  and less than that provided by  the  complete  BMP
program.
10.7    Phosphorous_ Ana l%s :L s_
         Assessment  of total phosphorous loadings and  potential
reductions  under  various  simulation schemes is  summarized  in
Table 10.7.  A nominal WWTP concentration of 1 . 3 mg/1 was set for
stormwater  flows  to  the WWTP  under  "pre  BMP  "  conditions.
Removal  efficiencies  recorded at the  WWTP  were typically  50%
for  secondary treatment  and 75% with AWT phosphorous treatment.
These rates were used in the computations.  The total phosphorous


                               10cl7

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                                TABLE 10.7
                      TOTAL PHOSPHOROUS SUMMARY DATA
LOCATION
WWTP LOAD*
WWTP AVG CONG MG/L
WWTP BYPASS (2%)
ADD FROM HANCOCK
WWTP REMOVAL 50%
            (75%)
WWTP NET TO RIVER 50%
                  (75%)
HANCOCK LOAD
HANCOCK REMOVAL  (13%)
HANCOCK NET TO RIVER
WEISS TO RIVER
ALL QTHER TO RIVER

TOTAL WET WEATHER LOAD

TOTAL LOAD TO RIVER
    50% WWTP REMOVAL
    (75% WWTP REMOVAL)
**
                           PRE
                           BMP
                           Ibs

                          12,900
                            1.3
                            258
                            213
                          6,248
                          (9,641
                          6,685
                          (3,472)
                          1,642
                            213
                          1,429
                          13,386
                          13,389

                          41,317
    34,889
   (31,676)
 REDUCED
   BMP
   Ibs

 21,351
   1.42
    427
    423
 10,674
(16,010)
 10,676
 (5,341)
  3,257
    423
  2,833
  8,836
 11,675

 45,119
                                            34,020
                                           (28,685)
COMPLETE
  BMP
  Ibs

  28,331
  1.44
    566
    384
 14,074
(21,112)
 14,650
 (7,603)
  2,955
    384
  2,571
 10,405
 2,406

 44,097
                   30,032
                  (22,985)
                              SUMMARY  STATISTICS
 WWTP  %  OF  TOTAL LOAD      31.2
 WWTP  %  REMOVAL  RATE       50/75
 WWTP  %  REMOVAL  OF
  TOTAL  LOAD  50% RATE     15.5
             (75% RATE)    (23.3)

 HANCOCK %  REMOVAL  OF
   TOTAL LOAD               0.5
                      47.3
                     50/75

                      23.6
                     (35.5)
                       0.9
                                                              61.8
                                                             50/75

                                                              31.8
                                                             (47.9)
                                                               0.9
NET % REMOVAL OF
  TOTAL LOAD 50% RATE     16.0
            (75% RATE)   (23.8)

CONTROL PROGRAM NET %
  REMOVAL  50% RATE        0
          (75% RATE)      (0)
                                             24.5
                                            (36.4)
                                              8.5
                                            (12.6)
                                        32.7
                                        (48.8)
                                        16.7
                                        (25.0)
  *  WWTP LOAD BASED ON 1.3 mg/1, ALL OTHER AT 1.74 mg/1
 **  TOTAL  LOAD  IS PRE BMP TOTAL LOAD FACTORED BY  MODEL  VOLUME
     RATIOS.  WWTP IS TOTAL LOAD MINUS OTHER LOADS AT 1.74 mg/1
                                10cl8

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concentration  at all untreated overflow points was set  at  1.73
mg/1.

          Phosphorous  loadings to the WWTP  for other than  "pre
BMP"  conditions  were determined as the "pre BMP"  total  system
load  less the estimated loading to the river from the  untreated
overflows.   Average   concentrations  at  the  WWTP   were  then
calculated  based  on  total WWTP   flow  and  total  phosphorous
loading. On this basis the total phosphorous concentration in the
WWTF   influent  was estimated as 1.44 mg/1 for the complete  BMP
and  1.42  mg/1 for the  reduced   BMP  programs,   respectively.
Table   10.7   presents  summary  results  of   estimated   total
phosphorous loadings and removals.

          Inspection of Table 10.7 indicates that  implementation
of the complete BMP program is estimated to increase the relative
wet  weather  phosphorous  loadings to the WWTP  by 30.6%  up  to
61.8% of the total area load.  At this rate,  32.7% removal would
be  expected,  16.7%  above  existing  conditions,  assuming  50%
removal at the WWTP.   Under conditions providing 75% phosphorous
removal   (teritary  treatment  - pickling  liquor),  the   total
phosphorous  removal  percentage attained would be 48.8%  or  25%
above existing conditions.

          Performing  the  construction and  alteration  measures
outlined  in  the  reduced BMP program will provide  50%  of  the
phosphorous  reduction gain estimated attainable by the  complete
BMP  program.  The  WWTP would receive 47.3% of the  wet  weather
system phosphorous load and remove 24.5% of the total load at the
50%  rate  and  36.4%  of  the  total  load  at  the  75%   rate.
Incremental  removal gains above pre BMP conditions would be 8.5%
and 12.6%, respectively.

          Based  on  an annual total wet weather load  of  41,000
Ibs.  the total estimated phosphorous loadings to the river would
be 34,000 Ibs.  for the reduced BMP plan and 30,000 Ibs.  for the
complete  BMP  plan with secondary (50%) treatment of  the  WWTP.
Using pickling liquor (or FeSO4) for AWT treatment, the residuals
would be about 29,000 Ibs.  and 23,000 Ibs.,  for the reduced BMP
and  complete BMP plans,  respectively.  Figure 10.1  graphically
illustrates  the relative annual wet weather phosphorous loadings
to  the Saginaw River based on various treatment  senarios.   Two
sets of bar graphs were used to indicate estimated removals  with
the  WWTF  providing secondary  (top of figure) and AWT  treatment
(bottom  of figure).    In addition,  the soluble fraction of  the
total phosphorous is illustrated.   The total wet weather load of
41,000 pounds per year  is shown as 100%.    River loadings for pre
BMP,  reduced BMP,  and proposed  complete  BMP conditions are then
shown  in  terms of pounds  and percentages  of soluble   and  total
phosphorous.   The upper  figure represents  removal  rates based on
                              10.19

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standard secondary treatment.   Phosphorous removal is due to the
non  soluble fraction tied in with solids materials.   The  lower
figure illustrates the effects of AWT treatment for  phosphorous.

       Soluble  fractions are reduced as shown but no  additional
non-soluble reduction occurs.   Although some phosphorous remvoal
is  provicded with solids settling at  Hancock Hancock,  most  of
the  reduction  occurs  at  the  WWTP.   Figure  2.1  graphically
illustrates  substantial reductions in total phosphorous loadings
to the river due to treatment at the WWTP and that implementation
of  BMP  measures  greatly  enhance  total   removals.    Soluble
phosphorous  removal is non-existent with the WWTP providing only
secondary treatment.

          AWT  treatment  at  the WWTP using pickling  liquor  is
shown  in  Figure  2.1 as it further  reduces  total  phosphorous
loadings to the river.   The entire decrease is due to  reduction
of the soluble phosphorous fraction.
                              10o20

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                           CHAPTER 11

                  APPLICATION OF INLET CONTROL
                        TECHNOLOGY TO THE
            CITY OF SAGINAW COMBINED SEWERAGE SYSTEM


11,1   Foreword

          Surcharging sewer/basement flooding problems, which can
occur  during  storm conditions within sewerage  systems  of  all
types  (seperated,  adjacent  and combined), have been identified
in  many parts of the country.  The extent of these problems  has
led to investigations in the area of inlet control or  stormwater
management  to  develop  inexpensive solutions in  comparison  to
traditional outlet sewer relief sewer programs.

          The  focus of the Saginaw sewerage system evaluation so
far has been on the incidence and reduction of CSO to the Saginaw
River.   For  this reason most of the control  technologies  have
been  focused  near  the  river with  only  partial  emphasis  on
upstream control.  Upstream control concepts have been limited to
recommendations  of in-line structures intended to create in-line
storage.

          Basement  flooding from surcharging collection  systems
has been reported from time to time in the City and this  chapter
represents   a  brief  review  of  this  problem  and   considers
potentially suitable inlet-control technologies and their effects
on mitigating basement flooding and reducing CSO.

          Section 11.2 describes the philosophy of inlet  control
technology.   Section  11.3  details  the  methods  used  in  the
evaluation   and   further  details  the  concepts   of   control
technologies.   Stormwater  induced problems reported  upstream  in
the City of Saginaw sewerage system are  reviewed in Section 11.4.
The   Congress Courts area was selected for detailed  analysis   as
described  in   Section 11.5.   City-wide implementation of   inlet
control technology is considered  in  Section 11.6.


11.2  Inlet Control Philosophy

           In the  simplest  of terms  "inlet control" starts at   the
very  top of a sewershed and controls/manages  sewage/stormwater  so
that   the  pipes   do not overload as  you  move  downstream.   All
possible   forms of above/underground  storage  are used  to hold  the
water  till  the   receiving  pipe can  handle   the   flow  without
surcharge.   If  sufficient  potential  cannot  be  feasibly  generated
then   additional  conveyance  capacity,   i.e.,   relief   sewers   are


                                11.1

-------
necessary.  The  analysis  begins  at the top of the  system  and
progressively moves downstream to the outlet. If the sewer outlet
is backwatered,  then the conveyance capacity has to be  adjusted
to properly reflect outlet deficiencies.

          The  aim of the stormwater runoff control program is to
develop  surface and subsurface controls such that  the  sewerage
system would discharge under full pipe conditions  (or acceptable
surcharge  levels) during any given design storm without  causing
any  adverse minor street surface ponding and/or adverse overland
flow across private property.  Basement flooding protection for a
given  design  storm  becomes eguatable with  ensuring  that  the
rehabilitated sewer system during a given design storm would flow
at acceptable levels with no adverse street ponding/overland flow.

          The  following set of control strategies are  typically
considered    in    stormwater   management     (inlet    control)
investigations:

          a)  Manhole rehabilitation,
          b)  Placement of overland flow training berms and
              depressed gutters,
          c)  Placement of surface storage berms to maximize
              surface storage potential,
          d)  Reconstruction of low curbs to maximize surface
              storage potential,
          e)  Placement of vortex valves into catchbasins to
              either maximize street surface storage or to create
              controlled overland flow that can be intercepted by
              downstream catchbasins and/or underground storage,
          f)  Construction of new catchbasins to intercept
              overland flow,
          g)  Construction of shallow drains to dewater low
              "trapped" street areas,
          h)  Construction of underground off-line storage tanks
              to detain excess surface runoff and/or  spilled
              overflow from sewerage system,
          i)  Disconnection of residential downspouts,
          j)  Placement of Eave-N-Flow eavestrough regulators to
              restrict downspout flows, and
          k)  Placement of orifice restricting  segments or weirs
              or  vortex valves into sewerage system as to create
              controlled surcharge conditions.

           Figure  11.1 pictorially shows some  of "inlet  control"
methods.  The  various  methods and/or the implements,  that  is,
devices  used in the implementation of "inlet control",   can  be
broadly  classified  as "small scale technology alternatives  for
flooding relief". For example, a widely employed method of "inlet
control"  is to reduce direct uncontrolled flow to the  sewer  by
                               1102

-------
             surface  storage
                )*jr*        underground
                flow controller |storage
   controller
supplementary
surface water
storage (potent lal source
for groundwater recharge)
                                                                   directly connected
                                                                   roof  and  yard water
                                                                   (re-route if feasible
                                                                   or control)
                                                    <***«
                                                         KEY
          main
          controlled to
          acceptable
          maximum flow    	                      Ml  Rainwater storage

                                                    MM  System storage

                                                    OHH)  Underground  storage

Figure 11.1   Components of  the Inlet  Control System

-------
rerouting  roof  downspouts to splash pads with drainage  to  dry
wells/created pervious areas/street catchbasins.  One device used
to  augment  this method is a "Eave-N-Flc"  eavetrough  regulator
placed in the downspout.  Soakways, dutch drains, porous pavement
are  other  examples of potential inlet control methods  used  to
increase perviousness/infiltration in urban areas.

          Temporary  street  ponding is still another  method  of
"inlet control". Flow controllers can be placed in catchbasins to
create  temporary  controlled street  ponding.  Pipes  connecting
catchbasins  to  the  sewer are typically over-sized  to  prevent
clogging  from debris washed into catchbasins.  Flow  controllers
either  regulate flow into a sewage collection system  or,  after
the  water  is  in  the system,  they  regulate  the  flow  to  a
predetermined  rate.  Controllers  placed  at  stormwater  inlets
control  the flow of water into the combined sewer system,   thus
causing the water to pond in the streets,  parking areas, etc. By
preventing or slowing the overload,  the sewage system is able to
cope  with  the water,  thus preventing  overflows  and  basement
backups.

          Flow  controllers can also be placed in catchbasins  to
strategically  induce overland flow into areas more suitable  for
surface/subsurface  storage.  Speed  humps (contoured  berms  not
speed  bumps)  can be placed either to direct overland flow  away
from sensitive areas and into more suitable storage capture areas
or   to  maximize  street  storage  potential.   Taken   together
catchbasin  flow  controllers  and a system of  speed  humps  can
generate at  low cost, controlled street storage.

          The distinction between speed "bumps" and speed "humps"
is  shown in Figure 11.2 Speed bumps are typically not envisioned
as these devices are a vehicular nuisance and interfere with snow
plowing operations.

          Placed  at  specific points within the  system  in-line
flow  controllers  can  also act as damming  devices  to  utilize
storage space that may be available in the existing sewers and/or
direct   flow   to   off-line   storage    facilities.    Shallow
underground/open  off-line  storage  tanks/basins  placed  behind
curbline/parkways/back  alleys or in open park areas  (see  Figure
11.3)  are  other methods of "inlet control" which are  meant  to
temporarily  store  excess stormwater beyond street  storage  for
later  controlled bleedback into sewer system.  Shallow new storm
drains  connected  into  existing  and/or  new  catchbasins   and
draining   to  storage  tanks  are  often  necessary  to  utilize
underground storage.

          The  ability  to accurately control the rates  of  flow
entering  the  piped drainage system enables the effects  of  the
                               11.4

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Ol
                                          Speed Bump/Speed Hump Comparison
                                                  FIGURE 11.2



                                             Asphalt - Contoured Speed Hunp

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                     directly connected (or modified)
                      roofs and yards
                               surface storage

                                     or induced overland  flow
                                                    supplementary
                                                      urface water
                                                        storage tank
                                                                curb
                                                                  intake
                                   system storage^
                                   mobilized by -^
underground
storage tank
which fills
when system
storage is full
                        main sewer
                        controlled to
                        acceptable
                        maximum  flow
system
control
           Figure n.3       Surface / Subsurface  Storage
         Components of Inlet Control for Congested Areas
                                11.6

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inevitable  major  storms  to be  designed  for,  and  consequent
downstream damage and pollution minimized.  When rates of  inflow
exceed  the  controlled system inputs any excess will  either  be
retained  adjacent  to  the intakes in  local  transient  storage
(street ponding and then in off-line storge),  or enter the major
overland drainage system to streams and rivers.  If all available
forms  of  storage  are fully utilized and overland  drainage  is
limited,  restricted  or  not possible,  then the  potential  for
excess  street flooding becomes a consideration  requiring  other
forms of control, i.e., positive relief conveyance.

          Street surface conditions and street surfacing programs
impact  effectiveness  of potential street ponding  since  ponded
waters  could  infiltrate  through cracked  pavement  potentially
causing  subsurface  soil  problems and  could  drain  back  into
infiltrating sewer lines.  House foundation drain-back cycling is
a  consideration  in  this regard.  Types  of  manhole  lids  are
important.  Replacement of perforated lids with solid covers is a
traditional  method  of cutting inflow and is a consideration  in
the  assessment  of street  ponding  viability.  Installation  of
vented  neoprene  inserts,  "safeguards",  below manhole lids  is
another method and has been successfully used in  other cities in
the USA to cut inflow.

          Street ponding as a form of transient storage is always
carefully engineered to meet specific local conditions. Draindown
times  are always a major concern as it impacts emergency vehicle
access and is a public nuisance. Time for draindown is a function
of  the  surface intake rates,  sewer  conveyance  capacity  (and
outlet conditions) and overland flow potential. The singular most
controlling  factor  is sewer system conveyance capacity and  its
outlet condition.

          All  of the above "inlet control" methods  assume  that
the sewerage system and its appurtenances can in fact receive and
convey  a controlled and predictable amount of  combined sewage to
an interceptor system.  Local systems are old and have many well-
known problems.  Part of  "inlet control" must ultimately   involve
study  of system soundness including,  condition of  catchbasins,
sewer  deposition  and  sediment  accumulations,   potential  for
siltation, and conveyance capacity limitations.  Consideration of
relief  sewer  segments in upstream areas to  mitigate  hydraulic
bottlenecks  is  not beyond the purview of   "inlet  control".  An
integral  part of the  "inlet control" engineering analysis  is  to
analyze  and portray the  physical and economic  trade-offs  between
creating  temporary  upstream   storage   (street ponding/off-line
facilities)   and  the  constructing  positive   relief    segments
 (systems) to accomplish the  same  effect.
                                11.7

-------
          Benefits  of using the "inlet control" method in  local
areas  with  combined sewers can generally be summarized  as:  A)
minimizes  the  need and degree for sewer  separation  and  local
relief  sewers;  B) provides immediate relief in areas with  most
severe basement flooding problems, leaving implementation in less
critical  areas when funds become available;  C) lessens combined
sewer overflows and pollution since retained transient stormwater
(and  combined  sewer stored in-line) drain back  to  sewers  for
treatment;  D)  lessens local sewer deposition/reduced conveyance
and decreases sewer cleaning frequency and costs;  E) provides an
extremely  adaptive management approach for overall control  that
can  be applied inexpensively and quickly in stages and  then  as
time  and  funds  permit,  be  integrated  with  positive  relief
measures to provide ultimate protection;  and F) greatly enhances
basement  flooding protection levels for areas that have  already
provided local positive relief.

          "Inlet Control" has a strong positive benefit for large
complicated tunnel/lift station/conveyance/treatment systems. The
net  effect of applying "inlet control" to a number of  catchment
areas  tied  into  a major system is to  "base-load"  the  system
output  implying  that  flow  peaks would  be  smaller  and  less
frequent  and  that a higher system-wide base flow would  result.
Operational  efficiency of any large hydraulic/electrical  system
always improves with "base-loading" system throughputs.

          The "inlet control" approach can be immediately applied
to  provide initial benefits with balance of  plan  incrementally
applied  as funds become available.  Community investment  levels
for  "inlet control" can be relatively continuous in contrast  to
other  approaches  that  are  more  "lumpy"  in  nature  and   in
realizeable  gains.  Communities  can expend and realize year  by
year  incremental  low  level  investments  and  their   additive
attendent  benefits  in contrast to a single "lumped"  investment
taking many years both to accomplish and to realize the benefit.

          "Inlet control" can be readily added to areas where new
local  positive  relief segments have been or are in  process  of
being installed.  The "inlet control" engineering analysis simply
assumes that the existing sewer system supplimented with the  new
relief  components/system  now represents the  target  conveyance
capacity  for  restricting  inflows.  Extremely  high  levels  of
basement   flooding   protection   can    be   easily   achieved.
Furthermore,  "inlet control" could be implemented along with the
positive  relief program and visibly add no greater inconvenience
to  local  residents  than  would  the  positive  relief   system
construction.  Depending  on  the  area  and  the  potential  for
generating  off-line  storage,  street  flooding  protection  may
slightly deteriorate. The exact trade-off has to be assessed on a
case-by-case basis.
                               11.8

-------
          Amount   of  stormwater  that  can  be  reasonably  and
feasibly  detained  by  "inlet  control" methods  is  in  part  a
function  of the sewer system's capacity to convey flow.  If  the
outlet  conditions are unfavorable,  i.e.,  backwater  conditions
prevail,  then the full conveyance capacity of trunks and  branch
lines   cannot  be  realized,   hence  shifting  the  stress  for
additional storage further upstream.  If the outlet control for .a
given  subsystem is adverse then the benefits of "inlet  control"
are obviously limited.  "Inlet control" has the intrinsic benefit
of  enabling  the  designer to  maximize  the  detentive  storage
potential  of  any  system  given its ability  to  convey  flows.
Rigorous  application of "inlet control" philosophy does in  fact
reveal  the true cost effectiveness of positive relief  measures.

          The  commercial availability of a  self-acting,  liquid
flow-limiting,  non-clogging  device has made possible  the  wide
spread   and  cost-effective  implementation  of  "inlet-control"
drainage  and pollution control  solutions.  Stated  simply,  the
maintenance-free  vortex valve technology detailed in  Chapter  5
permits  solutions  entailing  multitudes of "micro"  level  flow
controls in a given system.  Without this technology  controlling
hundreds  (or  perhaps thousands) of inlets in a  given  sewerage
system  would  be extremely difficult.   Prior to the  advent  of
vortex  valves "inlet control" philosophy for controlling adverse
flow situations was limited.
11.3   Overview of Hydrologic Methodology

          Hydrologic  analysis  within  a  given  study  area  is
accomplished  in the following stages of work.  The watershed  is
subdivided into  logical subcatchments.  Subareas are defined  on
the   basis  of  topographic  divides  and  on   sewer  subsystem
configuration.  Overall imperviousness per catchment is  computed
using  aerial maps.  Directly connnect areas such as  residential
and  commercial  roof  areas  are  estimated  and  tabulated  per
subcatchment.  The number of residential and commercial buildings
is tallied per subcatchment.

           Hydraulic analysis of the  drainage system within  the
study  area is performed to determine conveyance capacity  of each
manhole  to  manhole  segment  throughout  the  system  and   per
subcatchment  area.  Identification of key drainage pipe segments
and   their   respective  full-pipe  or   allowable    conveyance
capacities  per  catchment  forms  the  basis  to  compute total
required  storage  (system,  surface and underground) for a given
design storm per subcatchment.  Allowable capacity is defined  as
some  flow  rate   less than the segment  capacity.  The  additive
capacity of some lateral segments can exceed the capacity  of  the
main  trunk line.  Prevention of adverse surcharge of  the trunk
                               11.9

-------
line  sometimes  requires  that the lateral  line  capacities  be
artificially lowered to a selected allowable rate of flow.

          Design of rainfall storm intensities for the 5,  10, 15
and  25  year  events  is  extracted  from  established  rainfall
intensity/duration  curves.  A  computer  model  using  the  Unit
Hydrograph  approach is then used to analyze  all   subcatchments
for   each  design  storm  with  and  without  roof-top  directly
connected   areas.   Design  curves  are  established  for   each
subcatchment  per design storm relating total volume of  required
storage  to the rate of subcatchment outlet discharge  (full-pipe
or allowable pipe flow conditions). These curves are then used to
compute total required storage with/without downspout control per
subcatchment per design storm.

          Total  required storage per design storm for full  pipe
outlet  discharge  conditions (or allowable discharge)  are  then
compared  with available storage computed for each  subcatchment.
Available storage equals the sum of system storage (pipe  volumes
plus manholes/catchbasins) and allowable surface storage. Storage
deficits  (total  required  - available) are  treated  either  by
direct underground storage or by allowing overland flow. Controls
are  prepared  for  a given subcatchment and for a  given  design
storm.   If the sum of the uncontrolled peak roof discharge  plus
controlled street catchbasin discharge do not exceed full pipe or
allowable  subcatchment  outlet conditions,  then  no  additional
control  is  necessary.  If outlet flow or  allowable  conditions
cannot  be met,  then the downspouts in a given subcatchment  are
controlled  for  a  given design storm such that the sum  of  the
controlled roof peak plus controlled catchbasin flow plus release
rates from underground storage tanks, if necessary, approximately
equals  the  full  pipe  or  allowable  subcatchment   conveyance
capacity.

          Draindown  times from the new underground storage tanks
(a function of release discharge rates) is a critical concern  in
the  analysis. This problem is further compounded by the need to
control  household  roof downspouts to a reasonable and  feasible
extent.

          Control requirements within a subarea are a function of
the  hydrologic,  topographic and sewer system characteristics of
the  subarea  and  the effect of the  subarea  sewer  system  and
overland flows on downstream areas. As described above, allowable
flows are sometimes utilized rather than  capacities.   Allowable
flow  rates are adjusted where possible to ensure that the degree
of  control  required is reasonably  homogeneous  throughout  the
area.  Surface  storage  usage  is maximized in  all  cases  with
overland  flow  being  promoted  wherever  possible  in  lieu  of
underground storage to minimize the number of underground storage


                               11.10

-------
locations.   Underground  storage  tanks are utilized  to  detain
street runoff from catchbasins without flow controllers.
                  Sewer Hydraulic Analysis

          The conveyance capacity of the  sewer system within the
study  area  is  analyzed using a computerized network  model  of
each segment (manhole to manhole).    Pipe length,  diameter, and
pipe slope for each segment are tabulated and data-processed into
a network system to determine maximum full pipe flow. The purpose
of  this investigation is to compute the maximum stormwater  flow
allowable in each segment.

          Maximum  flow  capacities per segment are then used  in
two further investigations.  First, they  are compared segment to
segment  to ensure that each downstream segment is of  sufficient
capacity to handle upstream flow. Next, the segment downstream of
each pipe junction is reviewed to ensure it can pass the combined
capacity of upstream branches.

          Control  schemes  for  each subarea are then devised  to
ensure adequate protection in each area and adjusted as  possible
to utilize consistent control measures among sub areas.

          Subarea  control plans are formulated as follows.  Sub-
areas  are reviewed to indicate  the "allowable" flow,  the  degree
of  catchbasin  and downspout control  required  to  achieve that
flow,  required  storage at that flow,  available storage  (system
plus  surface) and the net storage deficit.  Storage deficit  can
then   be  met  using  underground  storage  or   overland    flow.
Minimizing  the  number of underground  storage  sites  is   always
considered  advantageous. Routing  of   overland   flow  to   common
collection  points  is  always   preferred.   One  limitation  to
overland  flow  routing   is the  street  gutter  capacity  to pass
accumulated flows without curb topping.


                      Downspout  Regulation

          Directly connected  roof  downspout  discharges  can exceed
full  pipe  conveyance  capacity.    In  some  cases,    no   amount   of
surface/subsurface   storage   will  eliminate  this  problem.   It   is
recognized  that control  of downspouts  is  considered  undesireable.
All  other  forms of control are maximized  to  the  extent  considered
feasible   and practical  before downspout  control   is  considered.
The   aim  of  this  strategy is  to  minimize  the extent  and  degree of
downspout  regulation.  Furthermore,  every  effort  is  typically made
in  the   analysis  to  develop  as  reasonably  uniform  policies   as
possible  per  area  per  design  storm.


                                 11.11

-------
        Two  different  approaches are  possible  for   roofwater
control analysis and include,

        a)       disconnect both front of the house downspouts
                with placement of splash pads,
        b)       disconnect both of front of house downspouts and
                place Eave-N-Flo regulators in rear of the house
                downspouts.

        Each  subcatchment  area  is analyzed to  ascertain  what
degree  of  roofwater  control is necessary to  ensure  that  the
resulting roofwater discharge together with catchbasin controlled
flow and allowance for underground storage tank discharges  would
not exceed sewerage system full pipe discharge.


Surface Storage Improvements

          The  concept of surface storage of stormwater  requires
that the natural overland routes for surface water be altered  to
create storage areas.  The degree to which these alternatives can
be  accomplished without excessive citizen inconvenience dictates
the overall effectiveness of this flood protection technique. Two
typical  criteria  established to maximize storage  and  minimize
inconveniences  are that storage berms  (speed-humps)  constructed
across roadways be spaced a minimum of 300 feet apart and surface
ponding not exceed in the curb height.

          Berms  are  constructed of asphalt  with  an  elevation
equal to the elevation of the curb.  The berm at the street edges
would  equal  the  curve  elevation.   As  the  street  elevation
increases toward the crown the effective berm height would lessen
(elevation  constant).  This  implies that storage  berm  heights
would  vary  across the street based on curb heights  and  street
contours.  Construction  of  storage berms would  recognize  this
effect by adjusting the length of the berm to minimize the "speed
bump"  effect.  Based  on  these criteria the  effective  storage
capacity of any street section is a function of the street slope,
street cross section and curb heights.

          Two  types of street storage are available.  The  first
utilizes  existing  low areas in the street  profile.  A  maximum
desirable depth of ponding is first determined based on available
curb  heights and acceptable center street depths at  the  lowest
point  in the center of street.  Street slopes in each  direction
are  then  used  to determine the distances to which  water  will
pond.  Ponded  water volume is calculated as a function  of  this
distance   and  the  average   cross- sectional   area.    Volume
calculations  for  ponding in low areas utilizes the  backwatered
distances  in each direction.  It is necessary  that  catchbasins


                               11.12

-------
exist  or  be  constructed in the low area to act  as  continuous
drains.

          The  second  type of street ponding utilizes  the  berm
construction  (speed-hump) technique to reduce surface runoff  on
mildly sloped  streets.   The effectiveness depends substantially
on the slope of the street.  Berm site location is typically just
downhill  of  existing   catchbasins  to  allow  final  drainage.
Storage  volume is calculated in a similar manner as above  using
curb height, street contour and slope data.

          Several  criteria  are used in the final  selection  of
proposed  storage sites.  First,  storage capacity of low  areas,
where the street slopes uphill in each direction,  is calculated
on  the basis of allowing the stored water to pond to a level  up
to the street side of the sidewalks. Storage capacity of slightly
sloped areas is calculated as surface waters being ponded to   the
curb   line.   Second,    it  is  typically  assumed  that   berm
construction  is cost effective only if the volume of storage  is
provided at a unit cost under $9/cu.ft.


11.4 Saqinaw Sewerage System

          Reported  occurrences of basement flooding in many areas
within  the  City of Saginaw have been recorded for  many  years.
The  City has somewhat reduced the problem by  simply  installing
orifice  plates  in numerous catchbasins in an effort  to  reduce
inflow.   This  effort  represents  a limited  program  of  inlet
control  planning  and implementation.   Figure 11.4  illustrates
areas  within  the  City where basement  flooding  problems  have
occurred  and  the catchbasin orifice-plate  solution  attempted.
Success of this approach  has been mixed in Saginaw somewhat   due
to  the  reported  practice  of residents  removing  the  orifice
plates.

          As  part  of  the sewerage system  evaluation  of  this
study, upstream areas of basement flooding were reviewed.  A City
supplied  base  map indicated the  historical  problematic  areas.
(Figure 11.4)  Twenty seven areas were identified within the City
to  have  reported one or more occurrences of basement  flooding.
Sizes  of areas ranged from individual households to several acres
with   a total problem area of roughly 455  acres.   Problem  areas
are  scattered throughout  the City.

          Each  area  was visually  inspected by EDP personnel   to
determine   land topography and usage and   other  characteristics.
In  general,  it was found that most areas  were  relatively  flat,
densely   populated   and  afforded  little  open   space.     The
significance  of  open  space   is   its  potential  usage   as    an


                              11.13

-------
Figure 11.4   City of Saginaw areas of Reported Basement Flooding

-------
underground  storage  location.   Although streets  and  sidewalk
areas are useable, construction costs in open areas are less.  In
general, areas of Saginaw where little or no open space exists do
include some sidewalk spaces without trees.   Underground storage
chamber  placement is preferred in sidewalk as opposed to  street
areas, but is sometimes not practical due to tree-lined streets.

          City    records   were  available  indicating   basement
flooding  complaints  by  households up until  the  late  1970's.
Since  that  time, complaints have lessened and  gone  unrecorded.
One problem area  was isolated for detailed review as reported  in
Section  11.5 to  illustrate typical evaluation techniques and  to
form the basis for system-wide extrapolation of results.


11.5  Analysis of the Congress Courts Area

          One  isolated area in the northwestern part of the City
has been the source of frequent basement flooding complaints   and
was  reviewed in  detail.   This area contains about 16 acres   and
includes  Congress  Avenue between Brenner Street and Bay  Street
and  the  four  Congress  Courts,    (A,B,C,and D).  (Figure 11.5)
Each  court is approximately 300 ft long extending from  Congress
Avenue  to a cul-de-sac.   The courts are  serviced by a  combined
sewer system with 12 inch pipes in each street.

          As  part  of  the detailed  analysis  each  street   was
completely  surveyed  and  a contour map of the   area  developed.
Figure  11.6 illustrates a portion of the  contour  map  including
one  court which  is typical of the surface topography in Congress
Courts A,  B and  C.   Each of  these  streets slopes downhill  from
Congress  Avenue  to  the  start  of  the  cul-de-sac  and   rises
thereafter.   Catchbasins are  located on each side of each street
in  the  lowest area at the cul-de sac and  at  Congress  Avenue.
Congress  Court   D  slopes downhill  from   the  cul-de-sac  toward
Congress  Avenue  the entire length of the  street.   Directions of
overland  flow are indicated on Figures 11.5 and  11.6.   For   the
purpose of computer-aided evaluation,  each court was  designated
as  a separate drainage area.   Hydrologic and hydraulic analyses
were  then  performed  according to  the  procedures  outlined   in
Section 11.3.  Standard evaluation procedures would have included
detailed  analysis  of surface storage potential  based  on  area
topography  and street curb elevations.    For the purpose of this
illustration  a   nominal  value  of  300   cubic   feet  per   acre
 (24.4m3/Ha)   (typical  of this type  topography) was  utilized   in
Table 11.1.

          Table   11.1  depicts a standard  work sheet utilized   by
EDP   for   subarea  evauations  and Table  11.2  includes    the
computerized hydraulic analysis of the area  sewer network.   Table


                               11015

-------
       cr
       UJ
       z
       z
       UJ
       tr
       CD
	/2W/690J
         Figure 11.5   City of Saginaw  Inlet Control Study Areas - Congress  Court

-------
                                       Contour Interval 0.2 Feet

                                       < - Existing Catchbasin

                                     RMMM-Proposed Berm

                                       «•*  Overland Flow
                                       Typical Contours
                                       Congress COurts A, B & C
                                       Court D Slopes Toward
                                        Congress Avenue
                                                  Congress Avenue
Figure 11.6   Typical Congress Court Topography
                               11.17

-------
11.2  was  developed  based on manhole to  manhole  pipe  segment
lengths  and  slopes  generated  from  Figure  11.5.   Individual
segment capacities,  cumulative flows rates and other  statistics
are then calculated within Table  11.2 as required for completion
of the worksheet in Table 11.1.   In addition,  a rainfall/runoff
and  storage requirement relationship is developed.   Table  11.3
illustrates   a   typical   computer  printout   indicating   the
relationship  of  allowable  subarea outflow  rates  to  required
volumes requirement of storage.  For the Congress Court subareas,
the  12 inch pipe capacity of 49 1/s (Table 11.2) necessitates  a
total storage volume of 86 cubic meters for the 10 year frequency
storm  event  as  found  by  interpolation  within  Table   11.3.
(Downstream  restrictions to Congress Courts A and B outflow  are
discussed later.)

          The  concept of the remaining calculations is to select
an appropriate combination of roof stormwater control, catchbasin
inlet  rates,  surface storage draindown rates,  and  underground
tank  draindown  rates,  which will minimize post  storm  surface
ponding,  minimize  underground  tank  storage  requirements  and
draindown  times  while  still maintaining  total  outflow  rates
within allowable levels.

          Table  11.1  indicates  that  available  storage  would
include  surface storage of 24.4 m3 and system storage of 7.9  m3
for  a total of 33 m3.   For the 2 year design storm,  a  storage
tank volume of 23.3 m3 (845 ft3) is required and would drain in 1
hour  which is generally acceptable.  No roof control is requird.
Two  of the four catchbasins (those located at  Congress  Avenue)
would  be  restricted with vortex valves at an outflow rate of  3
1/s.  The two catchbasins at the cul-de-sac would be uncontrolled
and directly connected to the storage tank.

          Designs  for the 5 and 10 year storms  included  similar
control except each design required that roof front downspouts be
disconnected  and larger storage tanks be provided.   Control  of
roof  discharges  allows for increased tank discharge  rates  and
results in draindown times less than that designed for the 2 year
event.   Design  for  the  25 year storm resulted  in  a  lengthy
storage tank draindown time of 130 minutes for the case of  front
roof control.   Additional control of rear downspouts would allow
greater   tank  discharge  rates  and  substantially  reduce  the
draindown time.   In general, the inlet control strategy is often
a  case  of such alternatives.   Here the choice is  between  the
extent of roof runoff control and tank draindown time.   It is at
this point where engineering judgement is required to select  the
best combination of options.

          Although straightforward, inlet control design is often
a complicated series of analyses.   For the Congress Courts  area


                               11.18

-------
                                TABLE 11.1
                   TYPICAL  INLET  CONTROL WORKSHEET
      Congress Courts  Saginaw, Michigan
!' !
Description of
i impervious}
Jubarea
Courts A

,B,C • 1.16
Ha 1
i
|
|
                          Roof Area:
                                               % Roof Area:  ?4 I
                           NO. of Commercial Buildings
                                  Ho. Inlets:
Time of-_ConcentrationXMitu_)	L.
Capacity	--
                                      49
                                               Half  Full Pipe I/S:
_ System Storage Eull-P-ipe-ml-
                                      7.9
„. _ Surf ace-Storage.	m3 : _ 24.4
                                                Design Storm
                                          .2  Year ...5. Year .10 Year 2
1 	 ~^i — '• — r 1 It
! Average RamtaliL.

Intensity

in /I
_mmZ
ir
ir

74

92

105

"124 "
i

                                                                        -1	'
r ° i »
! i i
; Total 	
lotal 	
Street


154 191
~117 	 145
218 , 258
166
196
Rl Ronf 37 46 52 62
1 Front n-isr.nnnectpd 'R2 Roof .18 23 26 31
..; Rear Restricted. . .]Ra_Ro.o.£
lp Surface Storage

as, .Gutt
i
erJToa,

. 	 ^ •-
^ Design Flow ' Roof '
Storm |

Control
' , 17s ! 1/S
! 2 i 4"9 JRl 37 !
; 5 49 R2 23 i
! ii 10 i 49
! 25 49 j
: 25 alt.
1 i; ; 	 ]
' i F
. H * Notet 2 of 4
1 "IT"
,

R2 26 !
R2 31
R3 13
CB Rat^


jp3


13 |



> * Storage
13 13


13

1



Surface
Req . ± Avail . L Need Storage

Us
2@3=6 '
6
6
6
o X)isch.
m^
m I nP 1/s
56 ! 1 23
75 j
86 !
106
6 T 106


(Total) (j

!B lead tc


i

> tank storage
i


; ii 1
'! 1

I





. — r, 	 ~l 	 " ""





11.19


i


42 !
53
73
73










r
-
-










Tank

!



'



Drain |
Storage* Time j
Disch.
1/s
6
20
17
12
!

66 min
36 min
53 min
103 min
30 41 min
J_ . 	 i






:

*— }




1
i
i i
1




-------
TABLE 11.2   City  of Saginaw Congress  Courts Sewer System Hydraulic Evaluation
     SEEM CRMN CPOA KR CENSES CDLFB
o
1
2
3
4
5
6
7
8
rccKncN
CUKE
CDLFm
:
1 01
I .01
1 .02
12.01
1 .03
1 .04
1 .05
DIA(M)
1.520
0.305
1.520
0.305
1.520
1.520
1.520
SKFE
0.14
0.29
0.12
0.29
0.12
0.12
0.11
IflGffl
76.20
99.10
77.70
99.10
73.20
79.20
88.40
F. FICW(L/S) F. tB/DffiEN VEL.(M/S) TRAVEL (MIN) PEE VCL.(OJ M) lEC KBS(M) TDIEL ICBS(M)
2694.65
54.30
2510.00
54.30
2531.18
2477.89
2467.09
0.00
54.30
2455.70
0.00
21.18
-2563.30
-10.80
1.49
0.75
1.39
0.75
1.40
1.37
1.36
0.9
2.2
0.9
2.2
0.9
1.0
1.1
138.27
7.24
140.99
7.24
132.83
143.72
160.41
0.10
0.29
0.09
0.29
0.09
0.09
0.10
0.10
0.39
0.48
0.29
0.57
0.66
0.76

-------
TABLE 11.3   City  of Saginaw Congress Courts Rainfall/Storage
              Requirement Summary

                       SUMMARY OF STORM HYDROGRAPH
                                 FOR
         DETERMINATION OF REQUIRED STORAGE AT DESIGN FLOW BASED ON
         SYSTEM CAPACITY AND THE STOPM/AREA CHARACTERISTICS
         JOB--SAGINAW  CONGRESS AVE AREA

         CASE—H   10 YEAR
         TIME OF CONCENTRATION (MINS)= 7.5
         TOTAL IMPERMEABLE AREA (HA) = .4640001
         MEAN RAINFALL INTENSITY (MM/HR)  = 105
         RAINFALL CLASS  (%) = 50

         MAX.  RATE OF STORM FLOW (L/S) = 218.4
         -•• ——•••.••.—•.•.-••.•••• .••••••••• ••»••. —•—•••••.••• •••
         VOLUMES OF STORM FLOW RELATED TO
         DIFFERENT OUTFLOW RATES

         RATE OF OUTFLOW     VOLUME OF STORMWATER
            (L/S)                  (CU.M.)

            0                     108
            21                    98
            87                     73
            109                    66
            131                    59
            152                    53
            174                    46
            196                    37
            218                    21
                            11.21

-------
the  inlet  control  plus storage option detailed above  must  be
compared  to  a  relief sewer system  on  feasibilityf  cost  and
consequence  basis.  The  relief sewer option is  dependant  upon
sufficient  capacity  at  some downstream location  to  pass  all
upstream flows.

          Figure  11.5  indicates  that a 60  inch  sewer  serves
Congress Avenue.  Field monitoring and/or upstream and downstream
evaluations can be performed to determine if sufficient  capacity
is  available  to  carry fully unrestricted  stormflow  from  the
Congress  Courts.   If  so,  cost  analysis should  be  performed
comparing  storage  tank construction to that of a  relief  sewer
system.  As an example, 200 ft. of 18 inch relief sewer at a cost
of $120/ft would require $24,000 to relieve one court area.  At a
cost  of  $9/ft3,  2670 ft3 (75m3) of surface  storage  could  be
constructed for the same sum.   On this basis,  and reviewing the
storage requirements of Table 11.1,  design for the 25 year event
should  consider a relief system as an alternative.   As detailed
in  Section  11.6,  inlet control plus storage will  afford  some
downstream  CSO reduction and this aspect must be  considered  as
part of the overall engineering evaluation.

          Hydraulic  analysis  of the  existing  Congress  Courts
sewer  system indicates additional complications within the area.
As  seen in Figure 11.5 sewer lines servicing Congress  Courts  C
and  D  discharge directly to the 60 inch Congress  Avenue  trunk
line  at drop manholes.   Unless extreme surcharge exists in  the
60 inch line, then free discharge from Congress Courts C and D is
expected.   Sewers  servicing  Congress  Courts A and  B  do  not
discharge  to  the  60 inch line but join at a 12 inch  sewer  in
Congress  Avenue leading to another 12 inch sewer in Bay  Street.
Table  11.2  indicates  that  this  junction  represents  a  flow
restriction based on accumulated flows.

          One   optional   solution  would   entail   designating
"allowable"  flow rates in each upstream sewer.  Considering  the
downstream capacity at the junction of 50 1/s each,  the upstream
sewer could be "allowed" a rate of 25 1/s.   Calculations similar
to  the  worksheet of Table 11.1 and data from Table 11.3 for  an
outflow  rate of 25 1/s indicate that even for the 2-year  event,
complete roof runoff control and storage of about 96 m3 would  be
required.  Clearly an alternative would be desireable.

          The   most   apparent  viable  alternative   would   be
connection  of  the sewer from Court B to the  60  inch  Congress
Avenue sewer.   This would allow the full capacity of the Court A
sewer  to  flow  to  the 12 inch  Congress  Avenue  sewer.   This
alternative is again dependent upon conditions within the 60 inch
sewer.   However,  considering  the  degree  of  restriction  and
storage required under the "allowable" 25 1/s flow rate it  would


                              11.22

-------
appear preferable to "create" capacity within the 60 inch line by
implementation  of inlet control in other upstream and downstream
areas as necessary.   This alternative would lead to the  storage
requirements detailed in Table 11.1.  As stated earlier. Congress
Court D slopes toward Congress Avenue the entire length.   If, the
60  inch  Congress Avenue sewer can handle the outflow from  this
areaf  then  only  suitable catchbasin and  connector  piping  is
required.   If  the  60 inch pipe capacity allowance is  limited,
then underground storage will be necessitated at this location.

          In  sum,  the  analysis of the  Congress  Courts  areas
demonstrates  the complexity of inlet control/storage  technology
planning.  The need to evaluate hydraulic conditions of receiving
sewers  dictates  that  even  analysis of a  small  subarea  will
require  some  degree of overall area review.   The key  to  cost
effective inlet control technology  is to not overly restrict  one
subarea in relation to another or to allow excessive outflow from
one  subarea  at the expense of the alllowable outflow rate  from
another  subarea.   Outflow rates should be selected both on  the
basis  of  existing  hydrualic  capacities  and  the  effects  of
increased/decreased rates on overall area hydraulics.


11.6  City Wide Implementation of Inlet Control Technology

          EDP's  city-wide  visual  review of the   storm  related
problem  areas  of Saginaw indicated that these areas  are  quite
similar to areas of other cities where similar problems  existed,
were  evaluated and solved using inlet control  technology.   The
detailed  review   of  the  Congress Courts  area   indicates  that
solutions  used  in  other cities   including  downspout  control,
catchbasin control,  storage, repiping and construction of  relief
sewers are applicable to Saginaw.

          Optimum  implementation   of  inlet  control  technology
requires  that the entire drainage  system be evaluated to   ensure
appropriate allotment of trunk line capacity to subareas.   Based
on previous inlet  control studies in areas similar to Saginaw,  it
is estimated  that  available  surface storage which  can be feasibly
generated, amounts to  300 ft3/acre.   Analysis of  the  Congress
Courts area indicated that mixed usage of underground storage  and
added  relief sewers or  short connections is   optimal.   Although
underground storage requirements are  related to  sewer   capacities
in addition to topographic conditions,   most  sewerage  systems,  on
the   average,    are   similarly  designed  and   provide    similar
capacities.    On   this  basis,   underground storage requirement of
1000  ft3/acre (typical of previous inlet control   study   results
for   5   year   to  10 year design  storm protection)   is   reasonably
applicable  and   agrees well with  the  10 year   storm  requirement
 (900  ft3/acre)  for Congress  Courts.
                               11.23

-------
          For  the 455 acre area of Saginaw reportedly subject to
basement  flooding  the potential available  surface  storage  is
estimated  as  136,500  ft3  while  a total  of  455,000  ft3  of
underground  storage  can be  feasibly  generated.   Creation  of
storage areas using the methods detailed in section 11.2 may be a
cost  effective  alternative in comparison to construction  of  a
relief sewer systems and has the added advantage of reducing peak
flow  conditions  in  downstream areas.   In  Saginaw  peak  flow
conditions  often  translate into CSO and related  Saginaw  River
pollution.

          Creation of upstream off-line storage under the program
of  inlet control affects downstream conditions  essentially  the
same way as implementation of upstream in-line storage.   Much of
the  BMP plan development of this study evaluated the effects  of
upstream in-line storage on downstream CSO conditions.  This data
can be used to predict the effects of inlet control strategies.

          Since EPA has placed much emphasis on the reduction  of
phosphorous in the evaluation of CSO impacts, reductions of total
phosphorous  loading to the Saginaw River were therefore used  to
evaluate the impact of potentially solving the purported basement
flooding in the 455 acres using stormwater management techniques.
Figure   11.7  illustrates  the  percentage  reduction  of  total
phosphorous loading to the Saginaw River as related to  in-system
storage volumes.  Zero reduction would imply complete overflow to
the  river  with  no  treatment  at  the  WWTP.   Storage  values
represented  volumes  generated  at  regulator  chambers  and  in
upstream  acres.   At  the present time the reduced BMP plan  has
been  completely implemented.   Storage volumes  estimated  under
inlet  control  strategies  were added to the  reduced  BMP  plan
storage  volumes to represent predicted conditions.   Two  curves
are  shown in  Figure 11.7.  The solid line  represents   percent
system  wide  wet  weather phosphorous reduction  versus  storage
volume   based  on  data for  pre  BMP  conditions,  reduced  BMP
conditions  and  complete BMP conditions simulations detailed  in
Chapter 10 and included in Table 10.7.

          On  the  basis  of  this  curve  (Figure  11.7)   total
phosphorous reduction would equal 29% after implementation of the
surface  storage  provisions  (300  ft3/acre)  of  inlet  control
technology  and   construction of underground storage  facilities
(1000  ft.3/acre).   This values is 4.5% above the  current  post
reduced BMP level of 24.5% (Table 10.7).

         A  substantial  portion of the CSO  pollution  reduction
attributable  to the reduced BMP plan was due to  increased  flow
rates at the Weiss Street crossover junction.  The dashed line in
Figure   11.7   represents  a  revised  relationship   of   total
phosphorous reduction to storage volume without including effects


                               11.24

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NJ
cn

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of  the  increased crossover flow.   The inlet control scheme  is
estimated  to reduce loadings to the Saginaw River by 4.0%  above
current post reduced BMP plan levels.

          In  sum,   inlet  control  technology  may  be  a  cost
effective alernative to relief sewer construction in the  Saginaw
area.   Inlet  control  combined  with  provisions  for  adequate
storage  will mitigate basement flooding problems while  reducing
CSO pollution to the Saginaw River.
                              11.26

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                            REFERENCES

                            CHAPTER  1

 1.    Pisano,  Rhodes and Aronson,  "Preliminary Engineering Study
      for the Control and Treatment of Combined Sewer Overflows to
      the Saginaw River", June, 1980, EDP.

 2.    Pisino,  Rhodes and Aronson,  "Facility Plan for the Control
      anu  Treatment  of Combined Sewer Overflows to  the  Saginaw
      River",  November, 1980,  EDP.

 3.    Environmental   Design  &   Planning,   Inc.,   Design   and
      Development  Document Webber Street Combined Sewer  Overflow
      Treatment Facilities, June,  1981.

 4.    Connick,  D. and Pisano,  W., "Design Development Document In
      System Storage Program, December,  1983, EDP.

 5.    Personnel Communication,  J.  M.  Johannessen,  1981.

 6.    Brown & Brown,  Inc.,  "Automatic  Sewage Regulators",  Bull.
      83A, 1960,  Lima, Ohio.

 7.    John Meunier, Inc., HYDROVEX Product Literature, 1984.

 8.    Drehwing,  F.  J.  et al,  "Disinfection/Treatment of Combined
      Sewer Overflows,  Syracuse,   New York",  August,  1979, EPA-
      600/2-79-134.

 9.    Pisano,  W., Connick, D.  and Aronson, G.,  "Swirl and Helical
      Bend  Regulator/Concentrator  for  Storm and   cosfcbined  Sewer
     Overflow Control," October 1984, EDP EPA-600/S2-84-151.
                            CHAPTER 4

1.   Metcalf & Eddy,   Inc.,   "Report to City of Saginaw,  Michigan
     on Preliminary Design of the Hancock Street Combined  Sewage
     Overflow Storage and Treatment Facility,"  March 16,  1973.

2.   Lager,   Didrikson and Otte,   "Development  and Application  of
     Simplified  Stormwater  Management Model,"   Aug.,   1976,   EPA
     600/2-76-218.
                            CHAPTER  5

1.   American  Public Works  Association,   "Manual   of   Regulation
     Practice," 1971.

2.   Brombach,   H.  and Meunier,  G.,  "Latest  Developments  in Sewer
     Flow  Control   Using the  Vortex Principle,"  57th   Conference
     WPCF,  New  Orleans,  1984


                               Rl

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3.   Brombach,  H.,   "Vortex Amplifiers for Low Control  Pressure
     Ratios."  Proc. of  the 7th Cranfield  Fluidics  Conference,
     BHRA, Cranfield, England, 1975.

4.   Quadt,  K.  S.  and Brombach, H.,  "Practical Experiences from
     Vortex  Throttles  Controlled  Storm Water  Overflow  Tanks"
     Korrespondenz Abwasser, volume 1,  1978,  p. 5-9, in German.


                            CHAPTER 6

1.   Pisano,  Aronson  and Queiroz,  "Dry-Weather Deposition  and
     Flushing  for  Combined Sewer Overflow  Pollution  Control,"
     August, 1979.,  EPA-60012-79-133.

2.   Diniz, E.V.,  "Water Quality Prediction for Urban Runoff - An
     Alternative   Approach,   "Proceedings  of  the   Stormwater
     Management  Model  (SWMM) Users Group  Meeting,  May  24-25,
     1979., EPA 600/9-79-026,  June, 1979.

3.   Lager,  Didrikson and Otte,  "Development and Application of
     Simplified Stormwater Management Model," August,  1976, EPA-
     600/2-76-218.

4.   Environmental Design and  Planning,   Inc., "Section 208 Area-
     Wide   Non-Point   Source   Emissions   Analysis,"   Central
     Massachusetts Regional Planning Commission,  1978..

5.   Metcalf & Eddy, Inc., "Sludge Management Facilities Plan for
     the Saginaw Metropolitan  Area," May,  1979.
                              R2

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                                   TECHNICAL REPORT DATA
                           (Please read Instructions on the reverse before completing)
              -001 B
                             2.
                                                           3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE    „...•,  .o
  In-System  storage Controls for
  Reduction  of Combined Sewer
  Overflow-Saginaw, Michigan
                                                           B. REPORT DATE
             6. PERFORMING ORGANIZATION CODE

               5GL
  AUJHOR(S)
  William  C.  Pisano, P.E.,
  Daniel J. Connick and Gerald L. Aronson
                                                           8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
  Department  of Public Utilities
  City  of  Saginaw
  Saginaw,  Michigan
                                                           10. PROGRAM ELEMENT NO.
             11. C6NTRACT/GRANT NO.
               R005359-01
12. SPONSORING AGENCY NAME AND ADDRESS
 U.S.  Environmental Protection  Agency
 Great  Lakes  National Program Office
 536 South  Clark Street, Room 958
 Chicago,  Illinois 60605
             13. TYPE OF REPORT AND PERIOD COVERED
               Technical  9/79 - 12/84
             14. SPONSORING AGENCY CODE
             Great  Lakes National Program
             Office-USEPA, Region V
15. SUPPLEMENTARY NOTES
 Ralph  G.  Christensen
 Project Officer
16 ABSTRACT
 This  report  details the results  of  a  recently completed five-year Combined Sewer
 Overflow (CSO)  control program in Saginaw, Michigan (10,000  acres, pop. 85,000)
 funded  through  the U.S. EPA  108  Great Lakes Demonstration  Program and conducted
 by the  engineering contractor, Environmental Design and Planning, Inc. (EDP),
 Hanover, Massachusetts.  The implemented control program entailed modification of
 12 combined  sewer regulation chambers together with construction  of one new in-
 line  control  chamber to maximize transient system storage  of wet  weather combined
 sewerage for later bleedback to  a wel1-operated AWT/WWTP having phosphorus removal
 and ample treatment capacity.  These  improvements, "the partial BMP plan",
 represent a  partial completion of the first of two phases  of the  City's CSO
 Facility Plan.   The objective of Phase I was to maximize WWTP processing of wet
 weather combined sewage generated using inexpensive transient system storage
 (less than $l/cu.ft.) so as to minimize the extent, scale  and cost of satellite
 CSO treatment facilities (Phase  II).   The swirl concentrator technology was
 recommended  to  treat residual overflows remaining after Phase I improvements.
 Six major Facilities were recommended and adopted as part  of the  CSO Facility Plan.
                                KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
                                              b.lDENTIFIERS/OPEN ENDED TERMS  C. COSATI Field/Group
 Storm  Sewer
 Combined  Sewer Overflows
 Swirl  Concentrator
 Suspended Solids
 Total  Phosphorus
13. DISTRIBUTION STATEMENT[)OCUment -j 5
 to the public through the National Techni-
 cal Information  Service,  Springfield, VA
19. SECURITY CLASS (This Report)
                                                                         21. NO. OF PAGES
                             220
20. SECURITY CLASS (This page)
                           22. PRICE
EPA Form 2220-1 (9-73)
                                                        * U.B. GOVERNMENT PRINTING OFFICE: 1986-841-492/648

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