waste water modelling toc

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H A E S T A D M E T H O D S

F i r s t E d i t i o n


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OTHER BOOKS FROM HAESTAD PRESS

Advanced Water Distribution Modeling and Management, first edition

Haestad, Walski, Chase, Savic, Grayman, Beckwith, and Koelle

Computer Applications in Hydraulic Engineering , sixth edition

Haestad, Walski, Barnard, Durrans, and Meadows

Floodplain Modeling Using HEC-RAS , first edition

Haestad, Dyhouse, Hatchett, and Benn

Proceedings of the First Annual Water Security Summit , first edition

Haestad

Stormwater Conveyance Modeling and Design, first edition

Haestad and Durrans

Water Distribution Modeling , first edition

Haestad, Walski, Chase, and Savic

To order or to receive additional information on these or any other Haestad Press titles,

please call 800-727-6555 (US and Canada) or +1-203-755-1666 (worldwide) or visit

www.haestadpress.com.


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H A E S T A D M E T H O D S

F i r s t E d i t i o n

AuthorsHaestad Methods

Thomas M. WalskiThomas E. Barnard

Eric HaroldLaVere B. Merritt

Noah WalkerBrian E. Whitman

Managing EditorThomas E. Barnard

Project EditorsKristen Dietrich, Adam Strafaci, Colleen Totz

Contributing AuthorsChristine Hill, Gordon McKay, Stan Plante, Barbara A. Schmitz

Peer Review Board Jonathan Gray (Burns and McDonnell), Ken Kerri (Ret.),

Neil Moody (Moods Consulting Pty, Ltd.), Gary Moore (St. Louis Sewer District), John Reinhardt (Massachusetts Department of Environmental Protection),

Reggie Rowe (CH2M Hill), Burt Van Duin (Westhoff Engineering Resources)

HAESTAD PRESSWaterbury, CT USA


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Similar to Haestads earlier publications, Wastewater Collection System Modeling andDesign will become a classic over time. Well written, this book clearly links engineer-ing theory to practical modeling applications and offers many technical nuggets for

experienced professionals.-Bert van DuinWesthoff Engineering Resources, IncCanada

Traditional sewer design methodology suffers from old age. This book is a tremen-dous step forward in modernizing the sewer design process. Both novice and experi-enced designers should find this book an invaluable resource.

-LaVere B. Merritt, PhD, PE, DEEBrigham Young UniversityProvo, Utah

Wastewater Collection System Modeling and Design provides a unique blend of the prin-cipals and practices of engineering for academia and professional engineers. This textprovides its readers with modeling guidance that is both technically sound and rele-vant for improving the performance of existing systems.

-Gary Moore, PE Metropolitan St. Louis Sewer DistrictUSA

Wastewater Collection System Modeling and Design is a great addition to what has

become my Haestad Methods library. This book is a must for all practicing engineersthat work in sewer system design and is a great reference for use by college students.Finally, a single book that links fundamental sewer hydraulics to practical sewerdesign and modeling practiced by professional engineers.

-Brian E. Whitman, PhDWilkes UniversityUSA


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Wastewater Collection System Modeling and Design is the culmination of the efforts ofmany individuals, the most significant of which are the thousands of engineering pro-fessionals around the world who dedicate their careers to managing wastewater andproviding basic sanitation services to ensure the health of the public. Haestad Meth-

ods has been serving wastewater engineers around the world for over 20 years, andour discussions with the community have provided the inspiration to write this book.

Many authors contributed to the success of Wastewater Collection System Modeling andDesign. Primary credit goes to Tom Walski, Eric Harold, LaVere Merritt, Noah Walker,and Brian Whitman. Significant contributions were also made by Christine Hill, Gor-don McKay, Stan Plante, Barbara A. Schmitz, and the staff of Haestad Methods. Infor-mation on the individual authors and the chapters to which they contributed isprovided in the next section, Authors and Contributing Authors. It is the synthesisof everyone's ideas that really makes this book such a practical resource. Extra specialthanks to the project editors, Kristen Dietrich, Adam Strafaci, and Colleen Totz fortheir countless hours of hard work and dedication to weave the information frommany authors and reviewers into a cohesive and accessible textbook.

We greatly appreciate the efforts of our peer reviewers Jonathan Grey, Ken Kerri, NeilMoody, Gary Moore, John Reinhardt, Reggie Rowe, and Bert van Duin. They pro-vided exceptional insight and shared practical experiences that added enormously tothe utility of this book.

Many engineers at Haestad Methods contributed to editing, reviewing, content devel-opment, exercise review, and fact checking for this book, making its final delivery acompany-wide effort. Their input played an enormous role in shaping the text into itsfinal form. Special thanks to Brian Bauer, Jack Cook, Ryan Cournoyer, Norelis Floren-tino, Michael Glazner, Sharavan Govindan, Andres Gutierrez, Juan Carlos Gutierrez, Jennifer Hatchett, Gregg Herrin, Keith Hodsden, Ming Jin, Tasneem Khomusi, Eliza- beth Lipovsky, Douglas Maitland, Christopher Moks, Guillaume Pelud, RichardSappe, Mal Sharkey, Angela Suarez, Karthik Sundaresan, and Somchit Thor. Brian

Whitman and Tom Walski contributed to the discussion topics and exercises at theend of each chapter.

The illustrations and graphs throughout the book were created and assembled underthe direction of Mike Campbell with the assistance of Caleb Brownell. We also wish tothank the following individuals and organizations for providing us with additionalillustrations and photographs: Tom Walski, Getty Images, Cole Publishing, Universityof Iowa, Maria do Céu Almeida, John Barton, Daniel Sztruhar, Duncan Mara, PeerlessPump Company, Aquacraft, LNEC, MGD Technologies, Thel-Mar Company, Camp- bell Scientific, Marsh-McBirney, Unidata, Renaissance Instruments, Water Environ-


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ment Research Foundation, Pearson Education, R.D. Zande & Associates, ITT FlygtCorporation, and Environment One Corporation. Special thanks to Meredith Miller atcartoonbank.com for the New Yorker cartoons throughout the book.

Others involved in the production process for the book include Lissa Jennings (pub-lishing logistics), Rick Brainard and Jim O'Brien (cover design), Matt Cole (web pagedesign), Jeanne and David Moody (indexing and proofreading), David Klotz (format-ting and page layout), and Ann Drinan (indexing).

Finally, special thanks to Haestad Methods executive vice president, Niclas Ingemars-son, who provided the human resources and management guidance to get the jobdone, and to the company president, John Haestad, who provided the vision andmotivation to make this collection of ideas a reality.

Tom Barnard Author and Managing Editor

Haestad Methods, Inc.


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Wastewater Collection System Modeling and Design represents a collaborative effort thatcombines the experiences of over fifteen contributors and peer reviewers and theengineers and software developers at Haestad Methods. The authors and contributingauthors and the chapters they developed are:

Thomas M. Walski

Haestad Methods, Inc. (Chapters 1, 3, 12, 13)

Thomas E. Barnard

Haestad Methods, Inc. (Chapter 15)

Eric Harold

Buchanan Street Consulting (Chapters 7, 11)

LaVere B. Merritt

Brigham Young University (Chapters 2, 4, 6, 10)Noah Walker

Dudek and Associates (Chapters 8, 9)

Brian E. Whitman

Wilkes University (Chapter 5)

Christine Hill

XCG Consultants, Ltd. (Chapter 15)

Gordon McKay

Hong Kong University of Science and Technology (Chapter 15)

Stan Plante

CDM (Chapter 14)

Barbara A. Schmitz

CH2M Hill (Chapter 14)


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The Haestad Methods Engineering Staff is an extremely diverse group of profession-als from six continents with experience ranging from software development and engi-neering consulting, to public works and academia. This broad cross section ofexpertise contributes to the development of the most comprehensive software andeducational materials in the civil engineering industry. In addition to the specific

authors credited in this section, many at Haestad Methods contributed to the successof this book.

Thomas M. Walski, PhD, PE, Vice President of Engineering for Haestad Methods, has been named a Diplomat by the American Academy of Environmental Engineers. Overthe past three decades, Dr. Walski has served as an expert witness; Research CivilEngineer for the U.S. Army Corps of Engineers; Engineer and Manager of Distribu-tion Operation for the City of Austin, Texas; Executive Director of the Wyoming Val-ley Sanitary Authority; Associate Professor of Environmental Engineering at WilkesUniversity; and Engineering Manager for the Pennsylvania American Water Com-pany. Over the past decade, he has also taught more than 2,000 professionals in Haes-tad Methods' IACET-accredited hydraulic modeling courses. His experience inwastewater collection systems ranges from operating a large regional system made upof a mixture of sanitary and combined collection systems to evaluating small pressuresewer systems.

A widely published expert on hydraulic modeling, Dr. Walski has written several books, including Analysis of Water Distribution Systems , Water Distribution Simulationand Sizing (with Johannes Gessler and John Sjostrom), and Water Distribution Systems A Troubleshooting Manual (with Jim Male).

He has served on numerous professional committees and chaired several, includingthe ASCE Water Resources Systems Committee, ASCE Environmental Engineering

Publications Committee, ASCE Environmental Engineering Awards Committee, andASCE Water Supply Rehabilitation Task Committee. He also served on the commit-tees that produced the Water Environment Federation's Pump Station Design (FD-4)and Energy Conservation (MFD-2) manuals.

Dr. Walski has written over 50 peer-reviewed papers and made roughly 100 confer-ence presentations. He is a three-time winner of the best paper award in Distributionand Plant Operation for the Journal of the American Water Works Association and is apast editor of the Journal of Environmental Engineering. He received his MS and PhD inEnvironmental and Water Resources Engineering from Vanderbilt University. He is aregistered Professional Engineer in two states and a certified water and wastewaterplant operator.

Thomas E. Barnard, PhD, PE, is a senior engineer with Haestad Methods. He hasmore than 20 years of experience in environmental engineering working as a consult-ant, researcher, educator, and author. He holds a BS in civil engineering from the Uni-versity of Vermont, an MS in environmental engineering from Utah State University,and a PhD in environmental engineering from Cornell University. His expertiseinclude water and wastewater treatment, hazardous waste management, surfacewater hydrology, and water quality monitoring systems. His major consulting


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projects include RCRA permitting for hazardous and radioactive wastes at the RockyFlats Plant in Colorado; water quality modeling of receiving wastes and analysis ofwastewater treatment/disposal alternatives in Alexandria, Egypt; and investigationsof regional water quality monitoring programs in the Chesapeake Bay watershed ofthe United States.

Dr. Barnard is a contributing author to Computer Applications in Hydraulic Engineering

and Stormwater Conveyance Modeling and Design. He has contributed chapters to Princi- ples of Environmental Chemistry and Chemometrics in Environmental Chemistry. He hasalso served as a book reviewer for Water Environment and Technology and as a peerreviewer for the Journal of the American Water Resources Association. He is a registeredprofessional engineer in Pennsylvania.

Eric M. Harold, PE, currently serves as Director of Buchanan Street Consulting. Mr.Harold is an environmental engineer with over 13 years experience in combinedsewer overflow (CSO) and sanitary sewer overflow (SSO) analysis, hydrologic andhydraulic modeling, sanitary sewer and stormwater flow monitoring, water quality

monitoring and modeling, and database management. He has made numerous pre-sentations in hydraulic and hydrologic modeling. Mr. Harold holds a BS degree inCivil and Environmental Engineering from the University of Cincinnati. He is a regis-tered professional engineer in Maryland, Virginia, and the District of Columbia.

Dr. Merritt, Professor of Civil and Environmental Engineering at Brigham Young Uni-versity, has broad research and design experience in sewer systems. Of particular noteis his experience in design optimization, cost sensitivity to design parameters, designflow rates, infiltration and inflow analysis, and tractive force approaches to self-cleansing. His publications include over 10 peer-reviewed technical papers and over50 research and consulting reports. He has made numerous technical presentations,mainly on water quality and computer-aided sanitary engineering design.

S. M. Noah Walker, P.E. is the Principal Utility Planner for Dudek and Associates, Inc.and Chief Technical Officer of 3-Waters Technical Services. Over the past 25 years, Mr.Walker has served as Process Engineer for Continental Grain Co.; Assistant Directorof Systems Planning and Systems Services (IT) for the Water and Wastewater Utility inAustin, Texas; Chief of Collection Systems, City of Las Vegas; and Regional Engineer-ing Manager and Product Line Manager for software at ADS Environmental Services.

Over the past decade, he has taught hundreds of engineering professionals to useleading collection system modeling software including through Haestad Methods'IACET-accredited sewer modeling course. His career focus has been on applying rap-idly changing hardware and software technologies to improve the management ofwater, wastewater, and storm water utilities.

During his career, Mr. Walker has been involved in the implementation of large scaledata networks and temporary and permanent wastewater flow measurement installa-tions. He has also developed graphical user interfaces for hydraulic models, devel-oped software for the analysis and integration of wet weather flows, and contributed


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significantly to most of the major collection system modeling software applications inuse today. Mr. Walker has been responsible for the preparation of over fifty utilitymaster plans and over one hundred inflow and infiltration analysis reports.

He has served on numerous professional committees, including the Standard Con-struction Specifications Committees for the City of Austin, Texas and Clark County,Nevada; the GIS Management Committee for Clark County, NV; and the Growth

Management Utility Committee for the City of Austin. He was also a contributor tothe Water Environment Federation Manual of Practice 7, Wastewater Collection Systems Management.

Mr. Walker has written numerous professional articles and conducted presentationsincluding Data Infrastructure Planning for Large Water Utilities , Implementing HighlyIntegrated Capital Improvements Programs with GIS , Costs of SSO Management The Aus-tralian Experience , Inspection of Military Industrial Waste Systems , USEPA CMOM Com- pliance , and Hybrid Collection System Modeling. Additionally, he was the primaryauthor of training materials for Haestad Methods' SewerCAD program and has pre-pared training materials for other collection system models. He has served as a techni-cal reviewer for the ASCE Journal of Hydraulics.

Mr. Walker received his B.S. in Agricultural Engineering from Auburn University. Heis a registered professional engineer in Texas.

Brian Whitman, PhD, is an Associate Professor of Environmental Engineering atWilkes University in Wilkes-Barre, PA. He holds a MS in Civil Engineering and PhDin Environmental Engineering from Michigan Technological University. He has exten-sive experience teaching hydraulic modeling software for use in water distributionsystem design, wastewater collection system design, and water resources engineering.

Christine Hill is an Associate and Manager of the Municipal Infrastructure Group atXCG Consultants Ltd. Ms. Hill obtained a Masters of Engineering Degree from theUniversity of Toronto in 1994. She is an expert modeler with extensive experience inthe use of hydraulic models for the purposes of facility planning and evaluation andhas been involved in many combined sewer overflow, sanitary sewer overflow, andinfrastructure needs studies. Over the past 15 years, she has worked on many largemulti-disciplined projects in a number of jurisdictions in both Canada and the UnitedStates, including major projects in Toronto, Ottawa, Thunder Bay, Halton, Windsor,Welland and Hamilton, Ontario; Edmonton, Alberta; and Cincinnati and Cleveland,Ohio.

Professor Gordon McKay, currently with the Department of Chemical Engineering,Hong Kong University of Science and Technology, has over 30 years experience in aca-demia and industry.

He established his own company, Consultancy Process Engineering and ManagementSystems, in 1987, and from 1991 to 1995 he was a subcontractor for Project Manage-ment Ltd. Foster Wheeler Ireland. He was appointed as their Senior Process Special-


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ist to head up the Process Safety and Environmental Management teams and acted asProject Manager for certain key projects. His work in the safety area included per-forming Safety Audits and serving as Hazop Chairman and Process Safety TrainingManager. In the environmental area, his work included responsibility for environ-mental impact statements, environmental audits, acquisition audits, IPC license appli-cations, and implementation of environmental management systems.

Prior to establishing his own consultancy, Professor McKay was in the Chemical Engi-neering Department at Queens University, Belfast for 17 years. He has published over300 research papers and authored/contributed to five books in the fields of environ-mental management systems and the design of environmental treatment systems. Heis currently Chairman of the Chemical Discipline for the Hong Kong Institution ofEngineers.

Stan Plante, PE, is a principal engineer with CDM and directs various informationtechnology projects in Ohio and surrounding states. Throughout his career, Mr. Plantehas focused on development and application of hydraulic models to support waterdistribution and wastewater collection master plans. He has managed many waterand sewer master plan projects for both slow- and rapid-growth situations, and hasalso provided technical direction and troubleshooting on modeling efforts around theUnited States, particularly for water distribution projects. In the last few years, Mr.Plante has worked on GIS implementation projects for a variety of environments(large city, small city, airports, etc.), several of which have included modeling integra-tion components.

Barbara A. Schmitz is a senior GIS consultant and project manager with more than 18years of experience in developing and applying geospatial technologies. She is thefirm-wide technology leader at CH2M Hill for GIS applications related to water,wastewater, and water resources management projects. Ms. Schmitz has expertise inthe integration of GIS technologies with water and wastewater utility maintenancemanagement systems for facilitating utility system inventories and digital mapping,condition assessments, combined sewer overflow and sewer infiltration/inflow man-agement, and general utility maintenance and management planning. She integratesGIS databases with modeling applications, such as hydraulic models, to support sys-tem design, analysis, and optimization. Ms. Schmitz also provides training in GIS andrelated technologies for CH2M Hill clients and in-house staff.

Ms. Schmitz has authored several peer-reviewed papers and conference presentationson a variety of GIS topics. She has also contributed chapters on GIS applications toseveral books about sewer and water system modeling and to a manual of practice forimplementing geographic information systems in utilities.


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Libraries are wondrous institutions. Rows and rows of books create a feeling of aweas they rise high above the floors of the great libraries of the world, such as the Biblio-thèque Nationale in Paris, The John P. Robarts Research Library at the University ofToronto, and the Library of Congress in Washington, D.C. But, the true magnificence

of libraries lies in their ability to set in motion imagination and excitement in learning.The books and other materials they house provide the opportunity to understand and benefit from what others have experienced, and expand our ability to make informeddecisions. Indeed, the mission statement of the Library of Congress states theLibrarys aim to sustain and preserve a universal collection of knowledge and cre-ativity for future generations.

Study of the decisions, actions, and results of others past activities under conditionsanalogous to ones own situation helps in predicting the results of current decisions.Social science scholars study human behavior and develop hypotheses or explana-tions of what to expect from humans in certain group interactions. Military scientistsexplore the principles that control the conduct of war, and then apply those principlesto battle conditions. Scientists study the research and experiments of other scientists

to better understand the causes and effects of material, force, and environment varia-tion. Each of these examples represents the premise of simulation and model softwaredevelopment, which is that the past helps predict the future when combined with sci-entific or mathematical principles.

Like libraries, models can activate the imagination and generate excitement becausethey provide information and knowledge that, in turn, enables more informed deci-sions or solutions. Decision makers use modeling tools to simulate actual conditionsand generate performance and functional assessments significantly more quickly thanwith real-time observations. Generally, the only technical restriction on what can besimulated is the complexity and power of the model.

The value and benefit of using models is increasingly being recognized. In the waste-water industry, utilities use hydraulic models in all phases of the collection and treat-

ment systems life cycle: planning, design, construction, and operation. Hydraulicmodels allow costly and complicated collection systems to be comprehensively evalu-ated prior to expending a community's limited resources to solve service or regula-tory issues. Proposed infrastructure components can be assessed against the risk ofnot achieving a utilitys mission and goals, or of incurring harmful health and envi-ronment consequences due to poor or unexpected performance.

Once wastewater collection and treatment systems have been built and put into ser-vice, their performance can be measured. Utility decision makers can then use themeasurement information to gauge earlier decisions and expectations. Knowledge


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gained from past experience will aid the utility in achieving future goals, and canassist others in similar situations if documented and exchanged in technical publica-tions, manuals, or reference books.

This book has done an excellent job of capturing and communicating the knowledgeof several experienced hydraulic modelers. It presents a good, balanced perspective ofthe alternatives and informational needs of a modeler starting a modeling project,including how to build and assemble the hydraulic components and apply the soft-ware tool efficiently.

Undoubtedly, this book too will appear in libraries and be on the shelves of hydraulicmodelers who want to gain from the knowledge and experiences of their peers andpredecessors.

Reggie Rowe, PECH2M Hill


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Preface xi

Continuing Education Units xv

About the Software xvii

1.1 Wastewater Collection System Overview 1

Terminology...................... ................ .............. ................. .............. ........... 2Sources of Wastewater ............................................................................ 2Types of Conveyance................. ................ ................ ................ .............. 3

1.2 Modeling 5Applications of Collection System Models .......................................... 5Types of Collection System Modeling .................................................. 7

1.3 Historical Perspective on Collection System Analysis 7Collection Systems................................................................................... 7Hydraulics History................................................................................ 11Historical Summary .............................................................................. 16

1.4 The Modeling Process 16

2.1 Fluid Properties 24

Density and Specific Weight ................................................................ 24Viscosity .................................................................................................. 24

Fluid Compressibility............................................................................ 27Vapor Pressure ....................................................................................... 27

2.2 Fluid Statics and Dynamics 28Static Pressure ........................................................................................ 28Absolute Pressure and Gauge Pressure ............................................. 29Velocity and Flow .................................................................................. 30Reynolds Number.................................................................................. 31Velocity Profiles ..................................................................................... 31


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3.3 Hydrodynamic Equations 95Saint-Venant Equations.................... ................ ................ ................. .... 95Approximation to Hydrodynamic Equations ................................... 96

Diffusion Analogy ................................................................................. 97Kinematic Wave ..................................................................................... 97Muskingum Routing............................................................................. 98Muskingum-Cunge Routing ................................................................ 98Convex Routing ................................................................................... 100Weighted Translational Routing................. ................ ................ ....... 100Level Pool Routing .............................................................................. 100Summary of Methods.......... ................ ............... ............... ................. . 101

3.4 Complications to Routing Methods 101Manholes and Junction Tables........................................................... 103Surcharging .......................................................................................... 103Overflows and Diversions.................................................................. 104Parallel Pipes and Loops..................................................................... 105

Flow Reversal ....................................................................................... 106Dry Pipes............................................................................................... 107Drop Structures.................................................................................... 107

4.1 Friction Losses 113

Darcy-Weisbach Equation .................................................................. 116Colebrook-White Equation and the Moody Diagram............. ....... 117Hazen-Williams Equation .................................................................. 118Swamee-Jain Equation ........................................................................ 120Manning Equation ............................................................................... 120

Pipe Roughness Changes ................................................................... 121Comparison of Friction Loss Methods ............................................. 121

4.2 Minor Losses 122Minor Loss Valve Coefficients ........................................................... 123

4.3 Energy Addition Pumps 125Pump Head-Discharge Relationship ................................................ 125System Head Curves ........................................................................... 126Other Pump Characteristic Curves ................................................... 128Fixed-Speed and Variable-Speed Pumps ......................................... 129Affinity Laws for Variable-Speed Pumps ........................................ 129Power and Efficiency..................... ................ .............. ................ ........ 130

5.1 Developing the Modeling Plan 137

5.2 The Modeling Process 138Purpose and Objectives of a Model............ ............... .................. ...... 138Develop Alternatives........................................................................... 141Scales of Models................................................................................... 141Software Selection and Training .............. .................. .............. .......... 143


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Define Data Requirements............ .............. ................ ................ ........ 143Identify Data Sources .......................................................................... 144Collect Data........... .............. .................. .............. ................. ................ . 146

Validate the Data................ ................. ................ ................ ................ . 147Build the Model.................... ................ .............. ................ ................ .. 148Identify Data Gaps............................................................................... 148Sensitivity Analysis .............................................................................148Calibrate the Model ............................................................................. 148Validate the Model................. .............. ................ ............... ................ . 148Run Simulations................................................................................... 149Develop Solutions................................................................................150Bookkeeping ......................................................................................... 151

5.3 Constructing the Sewer Model 152Level of Detail........ ............... ................ ................ ................ ............... . 153Subbasin Delineation................ ................ ................ ............... ............ 154Pipes....................................................................................................... 154

Manholes ............................................................................................... 160Pumps.................................................................................................... 164Wet Wells............. .............. ................ ................ ............... ............... ...... 168

6.1 Definition of Flow Rates 175

New Systems ........................................................................................175Existing Systems............ ................ ............... ................ ................ ........ 176

6.2 Unit Load Factors 176Residential............................................................................................. 176Commercial Sources ............................................................................ 177Industrial Wastewater Flows.................... .............. ................ ............ 179Fixture Unit Method............................................................................ 181Land-Use Methods .............................................................................. 183Measured-Flow Methods.................... .............. ................ ............... ... 185Assigning Loads to a Model.................... ................ ................ ........... 187

6.3 Peaking Factors 187Peaking Factor Charts and Equations................ .............. ................. 188Minimum Flows................................................................................... 190Selection of Flow Generation Rate and Peaking Factor ................. 191

6.4 Time-Varying Flows 193Diurnal Curves..................................................................................... 193

Developing Systemwide Diurnal Curves.................... ................ ..... 195Defining Usage Patterns Within a Model............... ................ .......... 196

7.1 Wet Weather Flow Definitions 204

What Is Wet Weather Flow? .............. ................ ................ .............. ... 204Components of Flow in Wastewater Collection Systems............... 204Modeling Wet Weather Flows............... ................. .............. .............. 206


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7.2 Wastewater Collection System Hydrology 208Combined Sewer System Hydrology ............................................... 208Modeling Combined Sewer Systems................................................ 210

Separate Sanitary Sewer System Hydrology................................... 212Modeling Separate Sanitary Sewer Systems............... ................ ..... 213Continuous versus Event Hydrology ............................................... 216

7.3 Rainfall 217Rainfall Data......................................................................................... 217Selecting Model Simulation Events................ ................ ................ ... 218Calibration Events ............................................................................... 219Design Storms ...................................................................................... 219Continuous Records............................................................................ 228

7.4 Modeling Runoff 229Rainfall Abstractions........................................................................... 230Horton Equation .................................................................................. 233

Green-Ampt Equation......................................................................... 233Rational Method .................................................................................. 234NRCS (SCS) Method............ ................ ................. .............. ................. 236

7.5 Determining Hydrographs from Runoff Volumes 239Determining Peak Flow and Time to Peak.............. .................. ....... 240Snider Triangular Hydrograph................ ................ ................ .......... 240Unit Hydrograph Approach .............................................................. 242NRCS (SCS) Dimensionless Unit Hydrograph ............................... 243Nonlinear Reservoir ............................................................................ 246

7.6 Empirical Methods for Generating Hydrographs 248Percentage of Rainfall Volume (R-Factor) ................ ............... ......... 249Unit Hydrographs from Flow Measurements........... ............... ....... 249

Simplifications to Unit Hydrograph................................................. 250Inflow Coefficient Method................................................................. 250Rainfall/Flow Regression.................................................................... 252RTK Hydrograph Method.................................................................. 254Unit Loads for Design Studies........................................................... 261

7.7 Snowmelt 262Runoff Potential ................................................................................... 262Snowmelt Models ................................................................................ 263

8.1 Flow Measurement Considerations 271

Components of Flow........................................................................... 272Review of Existing Information..................... ................ ................ .... 273Selection of Metering Locations............... ............... ................. .......... 273Safety Considerations ......................................................................... 274

8.2 Flow Measurement 275Hydraulic Control Sections in Open Channels ............................... 275In-Pipe Methods................................................................................... 280Manual Methods.................................................................................. 281


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8.3 Instrumentation 283Depth ..................................................................................................... 284Velocity Meters ................. ................ .............. .................. .............. ...... 287

8.4 Precipitation Measurement 292Precipitation Data Acquisition................ ................. ............... ........... 293Measurement of Rainfall..................... ................. .............. ................. 293Gauge Operation Considerations...................................................... 294Radar Imagery...................................................................................... 295

9.1 Basic Calibration Concepts 302

Overview of Calibration ..................................................................... 302Calibration Parameters................ ................ ................ ................. ....... 303Building-Block Approach ................................................................... 305

Steady-State and Extended-Period Simulations............... ............... 305

9.2 Dry Weather Flows 305

9.3 Wet Weather Flows 309Constant Unit Rate Method........... ............... ................ ................ ...... 310Percentage of Rainfall Volume (R-Value) ............. .............. .............. 312Percentage of Stream Flow ................................................................. 313RTK Hydrograph................................................................................. 315Predictive Equation Based on Rainfall-Flow Regression ............. .. 316

9.4 Special Considerations in Calibration 320Volume Differences................ .............. ................ ................ ............... . 321Shape Considerations.......................................................................... 322

Timing Shifts........... ............... ................ ................ .............. ................. 3239.5 Understanding Overflows 324

Estimating Combined Sewer Overflow............. ................. .............. 325Estimating SSOs ................................................................................... 326Detecting Overflows with Scattergraphs ......................................... 326

10.1 Materials 334

Pipes....................................................................................................... 334

Manholes ............................................................................................... 335Other Appurtenances.......................................................................... 336

10.2 Initial Planning 337Decision to Provide Sewer Service to an Area................. ............... . 337Types of Conveyance....................... ................ ............... ............... ...... 338Separate versus Combined Systems............ ................ ................ ...... 338

10.3 Preliminary Design Considerations 339Data Requirements .............................................................................. 340Alternatives.................... ................ ............... ................ .............. .......... 341


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10.4 Initial System Layout 341Gravity Sewer Layout ......................................................................... 342Manhole Location and Spacing ......................................................... 342

Location of Pumping Facilities .......................................................... 343Sewer Easements.................................................................................. 343Example of a Sewer Network Layout ............................................... 344

10.5 Flows in Sanitary Sewers 346Low Flows in Early Years ................................................................... 346Allowances for Infiltration and Inflow................. ................ ............ 346Phased/Staged Construction.............................................................. 348

10.6 Horizontal and Vertical Alignment 348Pipe Slopes............................................................................................ 348Curved Sewer Alignment................................................................... 349Minimum Depth of Cover.................................................................. 349Maximum Depth.................................................................................. 352

10.7 Hydraulic Design 352Pipe Sizing ............................................................................................ 354Manholes............................................................................................... 355Computer Modeling for System Design............. ................ .............. 356Steady Flow versus Extended-Period Simulation

(EPS) Analysis ................................................................................ 356Design Maximum Flow Rates with Pumping................................. 358

10.8 Special Installations 358Sewers in Steep Terrain............ ................ ............... ................ ............ 358Sewers Along Streams.......... ................ ................ ................ ............... 359Elevated Crossings .............................................................................. 359Inverted Siphons (Depressed Sewers) .............................................. 360

10.9 Wastewater Collection System Optimization 361

11.1 Planning for System Characterization 372

Performance Requirements................................................................ 373Current Performance........................................................................... 374Approach to System Characterization...................... ................ ........ 375

11.2 System Characterization 376Review Existing Records .................................................................... 376

Update System Inventory................................................................... 378Collection System Condition Investigation ..................................... 379Inspection of the Condition of Controls and

Ancillary Structures....................................................................... 382

11.3 Hydraulic Investigations 384Field Data Collection........................................................................... 385Data Analysis ....................................................................................... 386Application of Hydraulic Modeling ................................................. 390Assess Hydraulic Performance.......................................................... 394


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11.4 Evaluating Rehabilitation Strategies 395Preventive Maintenance Program ............. ................. ................ ....... 399Source Controls.................................................................................... 399

Sewer Separation....................... .............. .................. ............... ............ 400Pipe Rehabilitation/Replacement ...................................................... 401Inflow/Infiltration Control..................... ................ ................. ............ 402Interbasin Transfers ............................................................................. 405Real-Time Controls .............................................................................. 405Storage Facilities .................................................................................. 406Wet Weather Treatment Facilities .............. ................. ................ ....... 407

12.1 Need for Pump Stations 420

12.2 Pump Station Overview and Design Considerations 423

Components.......................................................................................... 423Design Decisions.................................................................................. 425Pump Capacity ..................................................................................... 425Pump Station Configuration .............................................................. 426Pump Types and Selection....................... ................. ............... ........... 427Wet Well Sizing .................................................................................... 432Net Positive Suction Head................ ................ .............. ................ .... 433Appurtenances ..................................................................................... 435

12.3 Force Main Sizing with a Single Pump Station 435Determining Pipe Sizes....................................................................... 436Developing System Head Curves........... ................ ................ ........... 437Selecting Economical Pipe Size............... ................ ................ ........... 438

12.4 Modeling Pumped Systems 441Modeling Pumps.................................................................................. 442Downstream Flow Attenuation ......................................................... 442Identifying Potential Problems .......................................................... 443Modeling a Pipeline with Multiple High Points ............................. 444

12.5 Efficiency Considerations 448Constant-Speed Pumping................... ................ ............... ................ . 448Variable-Speed Pumping ....................................................................451Automated Energy Calculations ....................................................... 455

12.6 Force Mains with Multiple Pump Stations 455

12.7 Hydraulic Transients 457

13.1 Description of Pressure Sewers 468

Storage Tanks.................... .............. .................. ............... ............... ...... 470Service Lines.........................................................................................470Pressure Mains ..................................................................................... 471Air-Release/Vacuum-Breaker Valves ............... ................ ................ . 471Discharge Points............... ................ ................ ................ ............... ..... 471


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13.2 Estimating Flows 472Empirical Approaches......................................................................... 473Poisson Distribution to Estimate Loads ........................................... 475

13.3 Pressure Sewer Design Considerations 47813.4 Modeling Pressure Sewers 479

Modeling to Size Pressure Mains...................................................... 480Representing All Service Connections as Nodes ............................ 481Detailed Models................................................................................... 482

14.1 GIS Fundamentals 490

Data Management ............................................................................... 491Geographic Data Representations..................................................... 494

14.2 Developing an Enterprise GIS 495Keys to Successful Implementation .................................................. 495Needs Assessment............................................................................... 496Design.................................................................................................... 497Pilot Study ............................................................................................ 504Production ............................................................................................ 504Rollout................................................................................................... 505

14.3 Model Construction 505Model Sustainability and Maintenance.................. ................ .......... 506Communication Between the GIS and Modeling Staff .................. 507Network Components......................................................................... 508Wastewater Loads.................. ............... ................ .............. ................ . 510

Building the Model.............................................................................. 515Pitfalls in Constructing Models from GIS........................................ 517Loading Model Results to GIS ........................................................... 520

14.4 GIS Analysis and Visualization 520Basic GIS Uses and Examples ............................................................ 520Advanced GIS Uses and Examples ................................................... 522

15.1 United States Laws and Regulations 529

Clean Water Act ................................................................................... 530U.S. Federal Regulations..................................................................... 531

Water Quality Standards and Total MaximumDaily Loads (TMDLs).................................................................... 537

Section 404 Dredge and Fill Permits ................................................. 538

15.2 Canadian Laws and Regulations 538Sanitary Sewer Systems ...................................................................... 539Combined Sewer Systems .................................................................. 539

15.3 European Union Laws and Regulations 546Urban Wastewater Treatment Directive (UWWTD) ...................... 546


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Water Policy Framework Directive (WPFD) ................... ................ 549Integrated Pollution Prevention Control Directive (IPPC) ............ 549Product Directives ............................................................................... 549

Control of CSOs in EU Member States ............................................. 549Design Criteria for CSOs............... ................ ................. ............... ...... 550

15.4 Use of Models for Regulatory Compliance 551

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