Water System Design Manual

[Pages:518]Water System Design Manual

DOH Pub 331-123 Revised June 2020

Acknowledgments This is the fourth edition of the Water System Design Manual. Many Department of Health (DOH) employees provided valuable insights and suggestions to this publication. In particular, we are proud to recognize the members of the group at the Office of Drinking Water who worked over many months to revise this edition of the design manual.

Andy Anderson Nancy Feagin Derek Pell Scott Torpie, Primary Author

Jeff Johnson Scott Mallery Sam Perry Linda Waring, Technical Editor

We are especially indebted to the drinking water professionals who contributed their time and expertise to reviewing drafts and providing helpful suggestions. We received extensive input from the following people, listed in alphabetical order.

Aziz Alfi (Seattle Public Utilities)

Frank Baird (DOH)

Stephen Baker (DOH)

William Bernier (DOH)

David Brown (WA State Parks)

Michele Campbell (RH2 Engineering)

Alex Chen (Seattle Public Utilities)

Steve Deem (DOH)

Terry Englehardt (Hach Company; retired)

Melinda Friedman (Confluence Engineering Group LLC)

Bill Heubach (Seattle Public Utilities)

Sheryl Howe (DOH)

Todd Krause (Northwest Water Systems)

Doug Lane (City of Bellevue)

Jolyn Leslie (DOH)

Melanie Mankamyer (Wilson Engineering)

Mathew Martinson (Indian Health Service; currently at USEPA Region 10)

Kevin O'Neil (Washington Water Service)

Doug Piehl (Northwest Water Systems)

Ryan Peterson (RH2 Engineering)

John Puccinelli (Washington Water Service) Barney Santiago (RH2 Engineering)

Brian Smith (Wilson Engineering)

Jeff Sutton (Erlandsen & Associates)

Ryan Withers (RH2 Engineering)

For more information Our publications are online at doh.drinkingwater.

Contact our nearest regional office from 8 AM to 5 PM, Monday through Friday. If you have an after-hours emergency, call 877-481-4901

Eastern Region, Spokane Valley 509-329-2100 Northwest Region, Kent 253-395-6750 Southwest Region, Tumwater 360-236-3030

Table of Contents

Chapter 1: Introduction................................................................................................. 1

1.0 Purpose and Scope...................................................................................................................................1 1.1 Safety, Risk, and Reliability....................................................................................................................1 1.2 Applying the Group A Rule...................................................................................................................2 1.3 "Must" versus "Should"...........................................................................................................................3 1.4 Engineering Requirements....................................................................................................................4 1.5 Minimum System Design Requirements........................................................................................4 1.6 Other Referenced Documents and Standards............................................................................4

Chapter 2: Project Reports and Construction Documents ................................... 6

2.0 General Engineering Project Submittal Requirements............................................................6 2.1 Project Reports, Construction Documents, and Planning Requirements......................6 2.2 Submitting Project Reports and Construction Documents..................................................7 2.3 Relationship between Project Approval and Operating Permit.........................................8 2.4 Project Reports............................................................................................................................................8

2.4.1 Project Description ................................................................................................................................... 9 2.4.2 Planning ...................................................................................................................................................... 9 2.4.3 Analysis of Alternatives .........................................................................................................................10 2.4.4 Water Quality ..........................................................................................................................................10 2.4.5 Engineer ing Calculations......................................................................................................................11 2.4.6 Design Criteria.........................................................................................................................................11 2.4.7 Water Rights and Other Legal Considerations ...............................................................................11 2.4.8 Operations and Maintenance Considerations ................................................................................13 2.4.9 State Environmental Policy Act Requir ements ...............................................................................13

2.5 Construction Documents.................................................................................................................... 13

2.5.1 Design Drawing Requir ements ...........................................................................................................14 2.5.2 Project Spec ifications .............................................................................................................................15 2.5.3 Design Changes after Project Approval ...........................................................................................15 2.5.4 Contrac tor-Supplied Design Components .......................................................................................16

2.6 Coordination with Local Approving Authorities...................................................................... 17 2.7 Design and Review Process............................................................................................................... 17 2.8 Submittal Exceptions for Miscellaneous Components and Distribution Mains ...... 17

2.8.1 Categorically Exempt .............................................................................................................................17 2.8.2 Exempt Distr ibution Main Projects ....................................................................................................18

2.9 Submittal Exception: Distribution-Related Projects (not Distribution Mains).......... 18

2.9.1 Design and Constr uction Standards for Reservoirs and Booster Pump Stations ..................22 2.9.2 Rescinding Submittal Exc eption Authority ......................................................................................23

2.10 Resolving Disputed Department of Health Review Decisions ......................................... 23 2.11 Review Fees and Invoice...................................................................................................................... 24 2.12 Project Approval Letter and Construction Completion....................................................... 24 2.13 Construction Completion Report Forms..................................................................................... 24 2.14 Record Drawings..................................................................................................................................... 25 2.15 Safety............................................................................................................................................................ 25

Chapter 3: Estimating Water Demands................................................................... 27

3.0 Applicability............................................................................................................................................... 27 3.1 Demand versus Consumption.......................................................................................................... 27 3.2 Consumer Demand................................................................................................................................ 28

3.2.1 Evaluating Actual Water Demand .....................................................................................................29 3.2.2 Full-Time and Part-Time Single-Family Residential Users .........................................................30 3.2.3 Analogous Water Systems....................................................................................................................32 3.2.4 DOH Default Water Demand Design Criteria (Appendix D) ......................................................33

3.3 Water System Demand........................................................................................................................ 34 3.4 Estimating Water System Demands.............................................................................................. 35

3.4.1 Maximum Day Demand .......................................................................................................................35 3.4.2 Peak Hourly Demand (PHD) ...............................................................................................................36

3.5 Anticipating Changes in Demand: Systems with Mostly Residential Demand........ 38

3.5.1 Referenc ing Data from Prior Years ....................................................................................................38 3.5.2 Commercial, Industrial, and Public Facilities ..................................................................................39

3.6 Estimating Nonresidential Water System Demand ............................................................... 40

3.6.1 Procedures for Estimating Nonr esidential Demands ....................................................................41 3.6.2 Commercial, Industrial and Public Fac ility Demand ....................................................................43 3.6.3 Farming and Crop Irrigation Demand ..............................................................................................44 3.6.4 Recreational Development Demand .................................................................................................45 3.6.5 Anticipating Changes in Demand: Systems with Mostly Nonr esidential Demand ..............47

3.7 Establishing Needed Fire Flow......................................................................................................... 48 3.8 Factoring Distribution System Leakage (DSL) in Design..................................................... 48 3.9 Water Resource Issues ......................................................................................................................... 50 3.10 Source Adequacy and Reliability..................................................................................................... 50

3.10.1 Design and Operating Requirements ..........................................................................................50 3.10.2 Surface Water Source Reliability ...................................................................................................50 3.10.3 Groundwater Sourc e Reliability.....................................................................................................51 3.10.4 General Safety Factor and Contingency Planning ...................................................................52 3.10.5 Summary of Water Supply Reliability Recommendations .....................................................52

3.11 Factor of Safety........................................................................................................................................ 53 3.12 Example Exercises for Estimating Water System Demand................................................. 53

3.12.1 New Community Water System....................................................................................................53 3.12.2 Expanding (Existing) Community Water System ......................................................................54 3.12.3 New Mixed-Use Community Water System ..............................................................................56 3.12.4 Expanding Mixed-Use Community Water System ...................................................................57 3.12.5 Expanding Noncommunity Water System .................................................................................60 3.12.6 Assessing Full- and Part-Time Residential Use.........................................................................61

Chapter 4: Water System Capacity Analysis .......................................................... 66

4.0 Introduction............................................................................................................................................... 66 4.1 General Expectations............................................................................................................................. 67 4.2 ERUs, Connections, and Population.............................................................................................. 67

4.2.1 ERUs............................................................................................................................................................67 4.2.2 Connections Served ................................................................................................................................68 4.2.3 Population Served...................................................................................................................................69

4.3 Applying the Concept of Equivalent Residential Units in Design................................... 69 4.4 Determining Water System Capacity............................................................................................ 71

4.4.1 Step 1: Water Demands ........................................................................................................................71 4.4.2 Step 2: Source Capac ity.........................................................................................................................71 4.4.2.1 Water Rights .......................................................................................................................................72 4.4.2.2 Pumping Tests and Groundwater Reliability .............................................................................73 4.4.2.3 Surface Water (Watershed) Reliability ........................................................................................73 4.4.2.4 Installed Pump Capacity .................................................................................................................74 4.4.2.5 Interties.................................................................................................................................................74 4.4.2.6 Treatment Capac ity ..........................................................................................................................74 4.4.2.7 Determining ERUs based on Source Capacity...........................................................................75 4.4.3 Step 3: Capac ity Based on Storage ....................................................................................................77 4.4.3.1 ERUs Based on Equalizing Storage...............................................................................................78 4.4.3.2 ERUs Based on Standby Storage ...................................................................................................80 4.4.4 Step 4: Capac ity Based on Distr ibution Facilities ..........................................................................81 4.4.4.1 ERUs Based on Maintaining Adequate Residual Pressure under PHD Conditions .........82 4.4.4.2 Fire Flow Effects on Capacity .........................................................................................................82 4.4.5 Step 5: Factoring DSL into Capacity Analysis .................................................................................83 4.4.6 Step 6: Determine Limiting Cr iter ia and Water System Service Capacity in ERUs ..............83

4.5 Methodology to Determine Water System Capacity............................................................ 84

4.5.1 Step 1: Water Demands ........................................................................................................................84 4.5.2 Step 2: Source Capac ity.........................................................................................................................84 4.5.2.1 Water Rights .......................................................................................................................................85 4.5.2.2 Pumping Tests and Groundwater Reliability .............................................................................86 4.5.2.3 Surface Water (Watershed) Reliability ........................................................................................86 4.5.2.4 Installed Pump Capacity .................................................................................................................87 4.5.2.5 Interties.................................................................................................................................................87 4.5.2.6 Treatment Capac ity ..........................................................................................................................87 4.5.2.7 Determining Capacity based on Source of Supply ...................................................................88 4.5.3 Step 3: Capac ity Based on Storage ....................................................................................................89 4.5.3.1 Equalizing Storage ............................................................................................................................90 4.5.3.2 Standby Storage.................................................................................................................................90 4.5.4 Step 4: Capac ity Based on Distr ibution Facilities ..........................................................................90 4.5.4.1 PHD Conditions .................................................................................................................................91 4.5.4.2 Fire Flow Conditions .........................................................................................................................91 4.5.5 Step 5: Factoring DSL into Capacity Analysis .................................................................................92

4.6 Documenting Nonresidential Water System Capacity......................................................... 92 4.7 Examples of Nonresidential Water System Capacity Analysis ......................................... 92

Chapter 5: Source of Supply ....................................................................................106

5.0 Introduction.............................................................................................................................................106 5.1 Drinking Water Contaminants........................................................................................................106

5.1.1 Initial Sampling Requirements for New Sources .........................................................................107 5.1.2 Detecting Pr imary Drinking Water Contaminants .....................................................................109 5.1.3 Exceeding the Primary Dr inking Water MCL ................................................................................109 5.1.4 Secondary Contaminants ...................................................................................................................110 5.1.5 Groundwater Sourc e Construction-Related Contaminants ......................................................111

5.1.6 Source Sample Taps .............................................................................................................................112

5.2 Source Protection.................................................................................................................................112 5.3 Distribution Water Quality Effects from New or Modified Sources ............................113 5.4 Source Water Quantity and Reliability.......................................................................................115 5.5 Wells............................................................................................................................................................115

5.5.1 Steps to Take Before Drilling a Well................................................................................................116 5.5.2 Documenting Wellhead Protection .................................................................................................117 5.5.3 Groundwater Pumping Tests .............................................................................................................118 5.5.4 Seawater Intrusion................................................................................................................................119

5.6 Spring Sources .......................................................................................................................................119

5.6.1 Spring Source Safe Yield .....................................................................................................................120 5.6.2 Spring Source Water Quality.............................................................................................................120

5.7 Groundwater under the Direct Influence of Surface Water.............................................121 5.8 New Surface Water Supplies...........................................................................................................122

5.8.1 Surface Water Safe Yield ....................................................................................................................124

5.9 Purchased Water and Emergency Interties..............................................................................124

5.9.1 Reliability of Purchased Water (Nonemergency Interties) ........................................................125 5.9.2 Emergency Interties..............................................................................................................................127

5.10 Unconventional Sources....................................................................................................................128

5.10.1 Rainwater Collection ......................................................................................................................128 5.10.2 Trucked and Hauled Water ..........................................................................................................129 5.10.3 Desalination......................................................................................................................................129 5.10.4 Aquifer Storage and Recover y .....................................................................................................129

5.11 General Source Design Considerations.....................................................................................130

5.11.1 Power Supply Reliability ................................................................................................................130 5.11.2 Criteria for Multiple Sources or Multiple Pumps per Source ...............................................131

5.12 Water Resource Analysis and Water Rights ............................................................................132

5.12.1 Temporary Water Rights ...............................................................................................................132 5.12.2 Interruptible Water Rights ............................................................................................................132 5.12.3 Leased Water Rights .......................................................................................................................133

5.13 Placing a New or Modified Source into Service....................................................................134

Chapter 6: Transmission and Distribution Main Design ...................................140

6.0 Introduction.............................................................................................................................................140 6.1 Hydraulic Analysis.................................................................................................................................141

6.1.1 Data Collection......................................................................................................................................142 6.1.2 Hydraulic Model Development .........................................................................................................143 6.1.3 Hydraulic Model Calibration .............................................................................................................143 6.1.4 Hydraulic Model Analysis ...................................................................................................................146 6.1.5 Extended Period Simulation...............................................................................................................148 6.1.6 Hydraulic Transients (Water Hammer) ..........................................................................................148

6.2 Sizing Pipelines......................................................................................................................................149

6.2.1 Sizing Procedur es..................................................................................................................................149 6.2.2 Minimum Size ........................................................................................................................................149 6.2.3 Peak Hourly Demand ..........................................................................................................................150 6.2.4 Fire "Suppr ession" Flow.......................................................................................................................150 6.2.5 Minimum Distribution System Pressure .........................................................................................151

6.2.6 Maximum Velocity................................................................................................................................151 6.2.7 Excess Pressure ......................................................................................................................................152 6.2.8 Surge and Transient Control .............................................................................................................152 6.2.9 Assessing Water Quality Effects on the Existing Distribution System....................................153

6.3 General Design Considerations for Mains................................................................................153

6.3.1 Installation ..............................................................................................................................................154 6.3.2 Depth of Pipe Burial.............................................................................................................................154 6.3.3 Spec ial Design Considerations ..........................................................................................................155 6.3.4 Separation from Nonpotable Conveyance Systems....................................................................155 6.3.5 Separation from Other Potential Sources of Contamination ...................................................156 6.3.6 Pipe Mater ials ........................................................................................................................................157 6.3.7 External Corrosion Control.................................................................................................................157 6.3.8 Location of Pipes in Geologically Vulnerable Areas ...................................................................158 6.3.9 Layout of Mains.....................................................................................................................................159 6.3.10 Protection Against Cross-Connection ............................................................................................160

6.4 Appurtenant Design Considerations...........................................................................................161

6.4.1 Valves .......................................................................................................................................................161 6.4.2 Vacuum Relief and Air Release Valves ...........................................................................................161 6.4.3 Flushing Valves, Blow-offs and Hydrants ......................................................................................163 6.4.4 Fire Hydrants..........................................................................................................................................163 6.4.5 Sampling Stations.................................................................................................................................163 6.4.6 Yard Hydrants ........................................................................................................................................164 6.4.7 Angle, Curb or Meter Stops ................................................................................................................164 6.4.8 Individual Pressur e-Reducing Valves ..............................................................................................164 6.4.9 Automatic Control Valves ..................................................................................................................165

6.5 Construction Documents for Pipelines......................................................................................165

6.5.1 Construction Specif ications for Pipelines .......................................................................................166

6.6 Placing a Water Main into Service ...............................................................................................166

Chapter 7: Reservoir Design and Storage Volume .............................................171

7.0 Introduction.............................................................................................................................................171 7.1 Reservoir Sizing......................................................................................................................................172

7.1.1 Storage Components ...........................................................................................................................172 7.1.1.1 Operational Storage .......................................................................................................................172 7.1.1.2 Equalizing Storage ..........................................................................................................................176 7.1.1.3 Standby Storage...............................................................................................................................177 7.1.1.4 Fire Suppr ession Storage ...............................................................................................................179 7.1.1.5 Dead Storage ....................................................................................................................................180 7.1.2 Storage Used for Treatment Purposes ............................................................................................181 7.1.3 Source Definition Used in Sizing New Reservoirs ........................................................................181 7.1.4 Storage for Consecutive Water Systems.........................................................................................182 7.1.5 Storage for Noncommunity Water Systems ..................................................................................183

7.2 Geometry, Elevation, and Integration with Existing and Future Facilities................184

7.2.1 Establishing Overflow Elevations......................................................................................................184

7.3 Location and Site Considerations.................................................................................................185

7.3.1 Natural Hazard Considerations........................................................................................................186

7.4 Construction Materials and Design Elements ........................................................................187

7.4.1 Partially Buried and Underground Reservoirs ..............................................................................188 7.4.2 Piping and Appurtenances - General..............................................................................................189 7.4.3 Reservo ir Drains ....................................................................................................................................189 7.4.4 Reservoir Overflows..............................................................................................................................190 7.4.5 Reservoir Atmospheric Vents .............................................................................................................191 7.4.6 Access Hatches ......................................................................................................................................193 7.4.7 Roof Drainage........................................................................................................................................194 7.4.8 Reservoir Secur ity..................................................................................................................................194

7.5 Operational Constraints and Considerations..........................................................................194

7.5.1 Reservoir Valves ....................................................................................................................................195 7.5.2 Reservoir Level Control........................................................................................................................195 7.5.3 Backup Power Facilities.......................................................................................................................195

7.6 Reservoir Water Quality and Sampling Access......................................................................195

7.6.1 Water Circulation and Stagnation...................................................................................................196 7.6.2 Tank Materials in Contact with Potable Water ............................................................................197

7.7 Placing a Reservoir into Service.....................................................................................................198

Chapter 8: Booster Pump Station Design.............................................................202

8.0 Introduction.............................................................................................................................................202 8.1 Booster Pump Station Capacity.....................................................................................................202

8.1.1 Open System Booster Pump Station Sizing Guidelines ..............................................................203 8.1.2 Closed System Booster Pump Station Sizing Guidelines ...........................................................204 8.1.3 Fire Flow Requirements for Pump Stations in Coordination Act Ar eas .................................205 8.1.4 Flow Control for Booster Pump Stations ........................................................................................205

8.2 General Booster Pump Station Site Considerations............................................................206

8.2.1 Natural Hazard Considerations........................................................................................................207

8.3 Booster Pump Station Design Details ........................................................................................208 8.4 Individual Booster Pumps.................................................................................................................210

8.4.1 Cross-Connec tion Control for Individual Booster Pumps..........................................................211

8.5 Placing a Booster Pump Station into Service..........................................................................211

Chapter 9: Pressure Tanks ........................................................................................213

9.0 Introduction.............................................................................................................................................213 9.1 Pressure Tank Sizing............................................................................................................................213

9.1.1 Bladder Tank Sizing .............................................................................................................................214 9.1.2 Bladder Tank Design Proc edur es .....................................................................................................214 9.1.3 Hydropneumatic Tank Sizing Equations (bottom outlet) ..........................................................216 9.1.4 Hydropneumatic Tank Design Proc edures ....................................................................................217 9.1.5 Reduced Pressure Tank Sizing...........................................................................................................221

9.2 Labor and Industries Standards for Pressure Tanks............................................................222 9.3 Locating Pressure Tanks....................................................................................................................223 9.4 Piping..........................................................................................................................................................223 9.5 Hydropneumatic Pressure Tank Appurtenances...................................................................223 9.6 Pressure Tank Sizing - Examples...................................................................................................224

Chapter 10: General Water Treatment ..................................................................226

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