Resolution No. 20-62 CITY OF TIGARD, OREGON
TIGARD CITY COUNCIL
RESOLUTION NO. 20- 6�
A RESOLUTION ADOPTING AND APPROVING THE TIGARD 2020 WATER SYSTEM MASTER
PLAN
WHEREAS, the City of Tigard owns and operates a public water system which supplies potable water to
city residents, businesses, and public institutions within the Tigard Water Service Area (TWSA). The TWSA
includes the Tigard Water District on Bull Mountain, the City of Durham, the City of King City, and a
majority portion of the City of Tigard. The area within the Tigard city boundary not included in the TWSA
is served by Tualatin Valley Water District (rVWD).
WHEREAS,City Council adopted the current Water System Master Plan for the TWSA in May 2010;and
WHEREAS,City Council adopted an addendum to the 2010 Water System Master Plan in June 2014;and
WHEREAS, on November 7, 2017,the City of Tigard contracted with Murray Smith&Associates engineering
to provide an updated Water System Master Plan. The project was completed on November 17,2020;and
WHEREAS,the Water Master Plan provides the City with information needed to develop long-term water
infrastructure decisions for the TWSA by:
• Documenting existing water system facilities and operational strategies,
• Estimating future water requirements including potential water system expansion areas consistent with
related City and regional planning efforts,
• Identifying deficiencies and recommending water facility improvements that correct deficiencies,
optim ze existing pressure zones,and provide for service area growth and expansion,
• Updating the City's water capital improvement program (CIP), and
• Complying with water system master planning requirements for Public Water Systems established under
Oregon Administrative Rules (OAR).
WHEREAS,the City Council received briefings on October 20,2020 and November 17, 2020 to provide
information on the project overview,and the findings and recommendations contained within the Water
System Master Plan;and
WHEREAS,the City's Water Advisory Board (WAB) received briefings on August 31, 2020 and October 14,
2020 that provided information on the project overview,findings,and recommendations described within the
Water System Master Plan;and
WHEREAS,the mayor and each city councilor received a copy of the 2020 Water System Master Plan on
October 20,2020 and an Executive Summary and the Water System Capital Improvement Project list was
provided to the public.
NOW,THEREFORE,BE IT RESOLVED by the Tigard City Council that:
SECTION 1: The 2020 Water System Master Plan is hereby adopted. The Executive Summary is attached
as Exhibit A.
RESOLUTION NO. 20-('a
it
Page 1
SECTION 2: This resolution is effective immediately upon passage.
PASSED: This day of.,/, 2020.
Mayor-City of Tigard
ATTEST:
6
City Recorder-City of Tigard
RESOLUTION NO. 20-
Page 2
EXHIBIT A
murraysmilh
Note: The entire report is not available
to the public for security reasons
CITY • - r
WATER SYSTEM MASTER PLAN
TIGARFinal r
November
0220
Water System Master Plan
City of Tigard
November 2020
FINAL DRAFT
Murraysmith
888 SW 5th Avenue
Suite 1170
Portland,OR 97204
Table of Contents
Executive Summary
Introduction .......................................................................................................................ES-1
Water System Overview.....................................................................................................ES-1
ServiceArea...............................................................................................................ES-1
Supply........................................................................................................................ES-1
DistributionSystem....................................................................................................ES-2
WaterDemand...................................................................................................................ES-2
AnalysisCriteria..................................................................................................................ES-2
WaterSupply.............................................................................................................ES-3
ServicePressure.........................................................................................................ES-3
StorageCapacity.......................................................................................................ES-3
PumpStations ...........................................................................................................ES-3
FireFlow....................................................................................................................ES-4
SupplyAnalysis...................................................................................................................ES-4
Supply Capacity.........................................................................................................ES-4
SupplyOptions ..........................................................................................................ES-4
Distribution System Analysis ..............................................................................................ES-4
Pressure Zone Optimization.......................................................................................ES-4
Pressures...................................................................................................................ES-5
StorageCapacity.......................................................................................................ES-5
PumpStations ...........................................................................................................ES-5
DistributionMains.....................................................................................................ES-6
Pipe Renewal and Replacement................................................................................ES-7
Seismic Resilience Evaluation.............................................................................................ES-7
SystemBackbone.......................................................................................................ES-7
Seismic Hazards Assessment.....................................................................................ES-7
Critical Facility Performance......................................................................................ES-7
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July 2020 City of Tigard
Seismic Resilience Conclusion....................................................................................ES-8
Recommended Capital Improvement Program (CIP).........................................................ES-8
CIPFunding ......................................................................................................................EW-9
1. Existing Water System
1.1 Introduction ............................................................................................................... 1-1
1.2 Service Area................................................................................................................ 1-2
1.3 Supply Sources ........................................................................................................... 1-2
1.3.1 Supply Overview............................................................................................. 1-2
1.3.2 Lake Oswego Tigard Partnership (LOT).......................................................... 1-3
1.3.3 Aquifer Storage and Recovery and Groundwater........................................... 1-3
1.3.4 Emergency lnterties........................................................................................ 1-5
1.3.5 Water Rights................................................................................................... 1-7
1.4 Current System Operation ......................................................................................... 1-7
1.4.1 Supply Operation............................................................................................ 1-7
1.4.2 Seasonal Changes........................................................................................... 1-7
1.4.3 Distribution Operation.................................................................................... 1-8
1.5 Distribution System .................................................................................................... 1-8
1.5.1 Pressure Zones................................................................................................ 1-8
1.5.2 Storage Reservoirs........................................................................................ 1-10
1.5.3 Pump Stations.............................................................................................. 1-11
1.5.4 Control Valves............................................................................................... 1-15
1.5.5 Distribution Pipes.......................................................................................... 1-15
2. Water Requirements
2.1 Water Service Area..................................................................................................... 2-1
2.1.1 Existing Service Area....................................................................................... 2-1
2.1.2 Future Service Area......................................................................................... 2-1
2.2 Planning Period .......................................................................................................... 2-1
2.3 Water Demand Description........................................................................................ 2-2
2.4 Historical Water Demand........................................................................................... 2-2
2.4.1 Peaking Factors.............................................................................................. 2-3
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July 2020 City of Tigard
2.4.2 Demands by Pressure Zone............................................................................. 2-3
2.4.3 Water Demand by Customer Type.................................................................. 2-4
2.S Future Water Demand Forecast................................................................................. 2-7
2.5.1 Projected Residential Water Demand............................................................. 2-7
2.5.2 Projected Commercial Water Demand........................................................... 2-9
2.5.3 Projected Industrial Water Demand............................................................... 2-9
2.5.4 Projected Irrigation Water Demand............................................................... 2-9
2.5.5 Projected Hydrant Use.................................................................................... 2-9
2.5.6 Non-Revenue Water....................................................................................... 2-9
2.5.7 Summary of Projected Demand.................................................................... 2-10
2.6 Projected Water Demand by Pressure Zone............................................................ 2-11
3. Planning and Analysis Criteria
3.1 Introduction ............................................................................................................... 3-1
3.2 Performance Criteria.................................................................................................. 3-1
3.2.1 Water Supply.................................................................................................. 3-1
3.2.2 Service Pressure.............................................................................................. 3-2
3.2.3 Storage Capacity............................................................................................ 3-4
3.2.4 Pump Stations ................................................................................................ 3-5
3.2.5 Required Fire Flow.......................................................................................... 3-6
3.2.6 Seismic Resilience........................................................................................... 3-7
4. Water Supply Analysis
4.1 Introduction ...............................................................................................................4-1
4.2 Supply Sources ...........................................................................................................4-1
4.2.1 LOT................................................................................................................. 4-2
4.2.2 ASR................................................................................................................. 4-3
4.2.3 Groundwater.................................................................................................. 4-5
4.2.4 Emergency Interties........................................................................................ 4-5
4.3 Water Rights...............................................................................................................4-7
4.3.1 Groundwater Rights....................................................................................... 4-7
4.3.2 Surface Water Rights...................................................................................... 4-8
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July 2020 City of Tigard
I
4.3.3 Instantaneous Water Rights.........................................................................4-13
4.3.4 Annual Water Rights ....................................................................................4-13
4.4 Water Supply Analysis..............................................................................................4-13
4.4.1 Supply vs. Demand....................................................................................... 4-13
4.4.2 Supply5trotegy.............................................................................................4-16
4.5 Water Quality...........................................................................................................4-17
4.5.1 Status of Drinking Water Regulations.......................................................... 4-17
4.5.2 Chemical Contaminant Rules........................................................................ 4-18
4.5.3 Lead and Copper Rule...................................................................................4-19
4.5.4 Radionuclides Rule........................................................................................ 4-20
4.5.5 Disinfectants/Disinfection By-Products Rule................................................. 4-20
4.5.6 Ground Water Rule....................................................................................... 4-21
4.5.7 Revised Total Coliform Rule..........................................................................4-22
4.5.8 Surface Water Treatment Rules................................................................... 4-23
4.5.9 Right to Know............................................................................................... 4-25
4.5.10 National Secondary Drinking Water Regulations .........................................4-25
4.5.11 Unregulated Contaminants..........................................................................4-26
4.6 Water Supply Summary............................................................................................4-27
S. Distribution System Analysis
5.1 Introduction ............................................................................................................... 5-1
5.2 Hydraulic Network Modeling ..................................................................................... 5-1
5.3 Pressure Zones........................................................................................................... 5-1
5.3.1 Pressure Zone Descriptions............................................................................. 5-2
5.3.2 Pressure Zone Analysis................................................................................... 5-3
5.4 Storage ....................................................................................................................... 5-7
5.4.1 Existing Storage Capacity............................................................................... 5-7
5.4.2 Future Storage Capacity................................................................................ 5-10
5.5 Pump Stations .......................................................................................................... 5-14
5.5.1 Pump Station 1............................................................................................. 5-14
5.5.2 Pump Station 2............................................................................................. 5-14
5.5.3 Pump Station 5............................................................................................. 5-14
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July 2020 City of Tigard
5.5.4 Pump Station 8............................................................................................. 5-15
5.5.5 Pump Station 11........................................................................................... 5-15
5.5.6 Pump Station 13........................................................................................... 5-15
5.5.7 Pump Station 17........................................................................................... 5-15
5.6 Control Valves .......................................................................................................... 5-21
5.7 Emergency Power .................................................................................................... 5-23
5.8 Hydraulic Performance Analysis............................................................................... 5-23
5.8.1 Fire Flow Availability..................................................................................... 5-23
5.8.2 High Pressures.............................................................................................. 5-24
5.8.3 Low Pressures............................................................................................... 5-25
5.8.4 Pipe Head Losses.......................................................................................... 5-25
5.9 Water Quality........................................................................................................... 5-25
5.9.1 Water Age.................................................................................................... 5-26
5.9.2 Water Quality Complaints............................................................................ 5-26
5.10 Pipeline Renewal and Replacement Program .......................................................... 5-27
5.10.1 Inventory...................................................................................................... 5-27
5.10.2 Risk Analysis Strategy................................................................................... 5-28
5.10.3 Likelihood of Failure Parameters.................................................................. 5-28
5.10.4 Consequence of Failure Parameters.................. .......................................... 5-31
5.10.5 Results Matrix...............................................................................................5-32
5-11 Summary of Recommended Projects....................................................................... 5-35
6. Seismic Resilience Evaluation
6.1 Introduction ............................................................................................................... 6-1
6.2 Oregon Resilience Plan............................................................................................... 6-1
6.3 Water System Backbone ............................................................................................ 6-4
6.4 Seismic Hazards Evaluation ........................................................................................ 6-5
6.4.1 Seismic Setting................................................................................................ 6-5
6.4.2 Hazard Assessment........................................................................................ 5-5
6.4.3 Geotechnical Seismic Hazards........................................................................ 6-6
6.5 Critical Facility Performance....................................................................................... 6-8
6.5.1 ASR Wells........................................................................................................ 6-8
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July 2020 City of Tigard
6.5.2 Reservoirs....................................................................................................... 6-8
6.5.3 Pump Stations .............................................................................................. 6-10
6.6 Pipe Fragility Analysis ............................................................................................... 6-10
6.6.1 Analysis Method........................................................................................... 6-10
6.6.2 Pipe Installation and Materials (K Value Selection)...................................... 6-11
6.6.3 Pipe Fragility Seismic hazard values............................................................. 6-12
6.6.4 Pipe Fragility Findings................................................................................... 6-12
6.7 Design Standards for Seismic Resilience .................................................................. 6-13
6.7.1 Pipelines ....................................................................................................... 6-13
6.7.2 Reservoirs..................................................................................................... 6-14
6.7.3 Pump Stations .............................................................................................. 6-15
6.7.4 ASR Wells...................................................................................................... 6-15
6.8 Next Step..................................................................................................................6-15
7. Distribution System Operations and Maintenance
7.1 Introduction ............................................................................................................... 7-1
7.2 0&M Regulations and Guidelines .............................................................................. 7-1
7.3 Existing Operations Structure..................................................................................... 7-1
7.4 Current 0&M Practices and Procedures .................................................................... 7-3
7.4.1 System Operation........................................................................................... 7-3
7.4.2 System Preventative Maintenance................................................................. 7-4
7.4.3 Asset Management........................................................................................ 7-4
7.4.4 Customer Complaints..................................................................................... 7-5
7.5 Conclusions and Recommendations .......................................................................... 7-5
8. Capital Improvement Program (CIP)
8.1 Project Cost Estimates................................................................................................ 8-1
8.2 Timeframes ................................................................................................................ 8-1
8.3 Supply......................................................................................................................... 8-2
8.3.1 Aquifer Storage and Recovery Wells............................................................... 8-2
8.3.2 Supply Expansion............................................................................................ 8-2
8.4 Storage Reservoirs......................................................................................................8-3
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July 2020 City of Tigard
8.4.1 Reservoir 18.................................................................................................... 8-3
8.4.2 Reservoir 19.................................................................................................... 8-3
8.5 Pump Stations ............................................................................................................8-3
8.5.1 Pump Station 8............................................................................................... 8-3
8.5.2 Pump station 13............................................................................................. 8-4
8-6 Distribution Mains...................................................................................................... 8-4
8.6.1 Hydraulic Performance................................................................................... 8-4
8.6.2 560 Pressure Zone Consolidation.................................................................... 8-5
8.6.3 Pipeline Replacement and Renewal Program.................................................8-6
8.7 Abandonments........................................................................................................... 8-6
8.8 Planning Studies ......................................................................................................... 8-7
8.8.1 Seismic CIP...................................................................................................... 8-7
8.8.2 ASR Feasibility Study....................................................................................... 8-7
8.8.3 System-wide Planning .................................................................................... 8-7
8.8.4 Water Management and Conservation Plan.................................................. 8-7
8.9 CIP Funding................................................................................................................. 8-7
Figures
1-1 Water Service Area Map ...............................,.......................................................... 1-16
1-2 Water System Schematic.......................................................................................... 1-17
1-3 Pressure Zones......................................................................................................... 1-18
2-1 2019 Average Water Consumption by Customer Type.............................................. 2-5
2-2 Projected ADD by Customer Type............................................................................ 2-10
2-3 Projected ADD, MDD, and PHD................................................................................ 2-11
4-1 Water Production by Source 2012 to 2019................................................................4-2
4-2 Supply vs. Maximum Day Demand with New Supply Sources..................................4-15
5-1 Zone Consolidation 560A-560D................................................ ............................... 5-37
5-2 Zone Consolidation 560D-560F, 640........................................................................ 5-38
5-3 Zone Consolidation 560F-560A, 530........................................................................5-39
5-4 Fire Flow Deficit........................................................................................................5-40
5-5 Water Age 2020 ....................................................................................................... 5-41
5-6 Water Age 2040 ....................................................................................................... 5-42
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July 2020 City of Tigard
5-7 Water Quality Complaints........................................................................................5-43
5-8 Risk Score Analysis.............................................._.,................................................... 5-44
6-1 Oregon Resilience Plan Target States of Recovery for Willamette Valley Water
Utilities ....................................................................................................................... 6-2
6-2 Water System Backbone .......................................................................................... 6-16
6-3 Liquefaction Settlement........................................................................................... 6-17
6-4 Lateral Spreading...................................................................................................... 6-18
6-5 Landslide Displacement............................................................................................ 6-19
6-6 Ground Shaking........................................................................................................ 6-20
7-1 Water Utility Organization Chart................................................................................ 7-2
Tables
ES-1 Projected Water Demand..........................................................................................ES-2
ES-2 Capital Improvement Program............................................................................... ES-10
1-1 Well Summary............................................................................................................ 1-4
1-2 Reservoir Summary.................................................................................................. 1-10
1-3 Pump Station Summary............................................................................................ 1-11
1-4 Distribution System Pipe Summary.......................................................................... 1-14
1-5 Pressure Zone Summary........................................................................................... 1-15
2-1 Historical System-wide Water Demand Summary ..................................................... 2-3
2-2 2019 Demand by Pressure Zone ................................................................................ 2-4
2-3 Residential Households.............................................................................................. 2-6
2-4 Historical Residential Demand per Capita.................................................................. 2-6
2-5 Historical Non-Residential Water Demand................................................................. 2-7
2-6 Projected Residential Demand................................................................................... 2-8
2-7 Projected ADD by Customer Type............................................................................ 2-10
2-8 Projected ADD, MDD, and PHD................................................................................ 2-11
2-9 Water Demand by Pressure Zone ............................................................................ 2-12
3-1 Performance Criteria Summary.................................................................................. 3-8
4-1 Groundwater Rights ...................................................................................................4-8
4-2 WRWC Water Rights Allocation Summary ...............................................................4-10
4-3 WIF Capacity Summary ............................................................................................4-10
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July 2020 City of Tigard
4-4 Surface Water Rights................................................................................................4-12
4-5 Timing of New Supply Sources (in mgd)...................................................................4-14
4-6 Summary of Contaminants.......................................................................................4-18
4-7 2019 Quarterly DBP Sample Results.........................................................................4-21
4-8 LOT Treatment Goals................................................................................................4-25
4-9 Secondary Drinking Water Standards.......................................................................4-26
5-1 Pressure Zone Summary............................................................................................. 5-2
5-2 560 Pressure Zone Consolidation Summary............................................................... 5-6
5-3 Reservoir Inventory.................................................................................................... 5-8
5-4 Storage Analysis— Existing ......................................................................................... 5-9
5-5a Storage Analysis-2025............................................................................................ 5-11
5-5b Storage Analysis-2030............................................................................................ 5-12
5-5c Storage Analysis-2040............................................................................................ 5-13
5-6 Pump Station Inventory............................................................................................5-16
5-7 Pump Station Analysis—Existing.............................................................................. 5-17
5-8a Pump Station Analysis—2025 ..................................................................................5-18
5-8b Pump Station Analysis-2030.................................................................................. 5-19
5-8c Pump Station Analysis-2040........................_......_.................................................. 5-20
5-9 Control Valve Inventory............................................................................................5-22
5-10 Generator Inventory.................................................................................................5-23
5-11 Pipe Length by Material and Installation Decade..................................................... 5-27
5-12 Pipe Length by Diameter.......................................................................................... 5-28
5-13 LOF Parameter Weights ........................................................................................... 5-30
5-14 COF Parameter Weights........................................................................................... 5-32
5-15 LOF/COF Priority Levels............................................................................................ 5-33
5-16 Priority Matrix ..........................................................................................................5-33
5-17 Miles of Pipe by Risk Level........................................................................................ 5-34
5-18 Distribution System Recommendations................................................................... 5-36
6-1 Critical Facilities Performance Summary.................................................................... 6-9
6-2 Pipe Fragility K Values............................................................................................... 6-12
6-3 Pipe Fragility Seismic Hazard Values ........................................................................ 6-12
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July 2020 City of Tigard
6-4 Estimated Pipe Repairs by Pressure Zone ................................................................ 6-13
7-1 Operator Certification Status ..................................................................................... 7-3
8-1 Capital Improvement Plan.......................................................................................... 8-9
Appendix
A Water System Map
B Intergovernmental Agreements
C Pipeline Renewal and Replacement Maps
D Tigard Seismic Hazards Evaluation Technical Memorandum
E Cost Estimates
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July 2020 City of Tigard
Acronyms & Abbreviations
A
AACE Association for the Adcancement of Cost Engineering International
ADD average day demand
ALA American Lifelines Alliance
AMR Automatic Meter Reading
ASR aquifer storage and recovery
AWWA American Water Works Association
C
CCI Constfuction Cost Index
CCL Contaminant Candidate List
CCR Consumer Confidence report
cfs cubic feet per second
CGWA Critical Ground Water Area
Cl cast iron (pipe)
CIP capital improvement program
City City of Tigard
COF Consequence of Failure
CSZ Cascadia Subduction Zone
D
D/DBP Disinfectants/Disinfection By-Products
DBP disinfection byproduct
DI ductile iron (pipe)
DOGAMI Oregon Department of Geology and Mineral Industries
DRC direct responsible charge
DWP Drinking Water Program
E
ENR Engineering News-Record
EPA Environmental Protection Agency
EPS extended period simulation
F
FEMA Federal Emergency Management Agency
fps feet per second
G
GIS Geographic Information Systems
gpm gallons per minute
GSI Groundwater Solutions, Inc.
GWR Ground Water Rule
18-2163 Page 1 Water System Master Plan
November 2020 Acronyms &Abbreviations City of Tigard
H
HAA5s Haloacetic Acids
HDPE high density polyethylene
HGL hydraulic grade line
hp horsepower
I
IGA intergovernmental agreement
IOcs Inorganic Contaminants
J
JWC Joint Water Commission
K
kW kilowatt
L
LCR Lead and Copper Rule
LF linearfeet
LOF Likelihood of Failure
LOT Lake Oswego Tigard Partnership
LT1 SWTR Long Term 1 Enhanced Surface Water Treatment Rule
LT2 SWTR Long Term 2 Enhanced Surface Water Treatment Rule
M
M9 magnitude 9.0
MCLS maximum contaminant levels
MDD maximum day demand
MG million gallons
mg/L Miligrams per liter
mgd million gallons per day
N
NCV normally closed valve
NRCS National REsoierce Conservation Service
O
O&M Operations and Maintenance
OAR Oregon Administrative Rules
ODOT Oregon Department of Transportation
OFC Oregon Fire Code
OHA Oregon Health Authority
OPSD off-peak season demand
ORP Oregon Resilience PLan
ORS Oregon Revised Statutes
OWRD Oregon Water Resources Department
P
PGD permanent ground deformation
PGV peak ground velocity
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November 2020 Acronyms&Abbreviations City of Tigard
PHD peak hour demand
PN Public Notification
PRC Population Research Center
PRV pressure reducing valve
PS pump station
psi pounds per square inch
PW Public Works
PWB Portland Water Bureau
PZ pressure zone
R
RIPS River Intake Pump Station
ROV remotely operated vehicle
RR rates of repair
RTCR Revised Total Coliform Rule
S
SCADA Supervisory Control and Data Acquisition
SDCs system development charges
SDWA Safe Drinking Water Act
SMCLs secondary maximum contaminant levels
SOCS Synthetic Organic Contaminants
T
TC total coliform
TCR Total Coliform Rule
TTHMs Total Trihalomethanes
TVFR Tualatin Valley Fire and Rescue
TVWD Tualatin Valley Water District
TWSA Tigard Water Service Area
U
UCMR 4 fourth Unregulated Contaminant Monitoring Rule
URA Urban Reserve Area
V
VFD variable frequency drive
VOCs Volatile Organic Contaminants
W
WIF Willamette Intake Facility
WIF Commission Willamette Intake Facility Commission
WMCP Water Management and Conservation Plan
WRWC Wilammette River Water Commission
WRWTP Willamette River Water Treatment Plant
WSM P Water System Master Plan
WTP water treatment plant
WWSP Willamette Water Supply Project
WWSS Willamette Water Supply System
18-2163 Page 3 Water System Master Plan
November 2020 Acronyms&Abbreviations City of Tigard
murraysmilh
Executive Summary
Executive Summary
Introduction
The purpose of this Water System Master Plan (WSMP) is to provide the City of Tigard (City) with
the information needed to inform long-term water infrastructure decisions. The objectives of the
WSMP include:
• Document existing water system facilities and operational strategies
• Estimate future water requirements including potential water system expansion areas
consistent with related City and regional planning efforts
■ Identify deficiencies and recommend water facility improvements that correct
deficiencies, optimize existing pressure zones, build a more resilient water system, and
provide for service area growth and expansion
■ Update the City's water capital improvement program (CIP)
■ Comply with water system master planning requirements for Public Water Systems
established under Oregon Administrative Rules (OAR)
Water System Overview
Service Area
The City of Tigard owns and operates a public water system which supplies potable water to a
majority of existing city residents, businesses, and public institutions. The Tigard Water Service
Area (TWSA) includes the Tigard Water District on Bull Mountain, the City of Durham, and the City
of King City. The area within the Tigard city boundary not included in the TWSA is served by
Tualatin Valley Water District (TVWD).
Supply
The City currently receives all water supply needed to meet existing demands from the Lake
Oswego Tigard Partnership (LOT) water treatment plant (WTP). During peak summer demand, the
City's aquifer storage and recovery(ASR)wells and groundwater Well 2 can be used to supplement
available supply, if needed. In an emergency, the City's distribution system can also be supplied
through interties with the Portland Water Bureau (PWB), the City of Beaverton, and the City of
Lake Grove.
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November 2020 Executive Summary City of Tigard
Distribution System
The City's existing water distribution system includes six main pressure zones and eight subzones
served by 14 active storage reservoirs, six pump stations, and multiple flow and pressure control
valves.The City's distribution piping includes approximately 260 miles of primarily ductile iron and
cast iron piping in sizes up to 36 inches in diameter.
Most existing City customer connections are within the 410 Pressure Zone (410 PZ) supplied by
Pump Station 5 (PS 5), which pressurizes water from the LOT supply. PS 5 also pumps to the
system's largest reservoir, Reservoir 10, which is pumped to the higher elevation pressure zones
and can back feed the 410 PZ through pressure and flow control valves.
Water Demand
Water demand refers to all water required by the system including residential, commercial,
industrial, and irrigation uses. Demands are described using water metrics including average day
demand (ADD) and maximum day demand (MDD). Current water demands by pressure zone are
estimated based on customer billing records and total water production from the LOT(through PS
5), ASR and groundwater wells, and distribution system storage. In 2019,the ADD was 5.77 million
gallons per day (mgd) and the MDD was 10.48 mgd.
Future expansion of the City's water service area will include continued development in the River
Terrace area as well as in the Urban Reserve Areas (URA) 6C and 6D (King City West). Population
growth within the water service area was projected based on population forecasts from the
Population Research Center (PRC, Portland State University, 2019). Historical demand data was
used to forecast water use per residential customer as well as water use for other customer
categories including commercial, industrial, and irrigation accounts. MDD was projected based on
the historic ratio of MDD to ADD, also called a peaking factor. Both ADD and MDD were forecasted
through 2050, shown for the planning years of 2025, 2030, 2040, and 2050 in Table ES-1.
Table ES-1
Projected Water Demand
Year DD DD
2025 8.06 16.12
2030 8.78 17.56
2040 10.16 20.33
2050 11.19 22.38
Analysis Criteria
Performance guidelines and system criteria are used with water demands presented in Table ES-
1 to assess the water distribution system's abilityto provide adequate water service under existing
conditions and to guide improvements needed to provide for future water needs. Criteria are
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November 2020 Executive Summary City of Tigard
established through a review of City design standards, state requirements, American Water Works
Association (AWWA) acceptable practice guidelines, Ten States Standards,the Washington Water
System Design Manual, and practices of other water providers in the region.
Water Supply
Supply capacity must be sufficient to provide MDD from all sources operating together, including
ASR wells, during the peak summer season. During the off-peak season, the supply system must
be capable of providing off-peak season demand plus water for ASR injection from the LOT.
Service Pressure
The acceptable service pressure range under ADD conditions is 40 to 80 pounds per square inch
(psi). Under MDD conditions, 30 psi is considered the minimum City standard. Per the Oregon
Plumbing Specialty Code, maximum service pressures must not exceed 80 psi. During a fire flow
event or emergency, the minimum service pressure is 20 psi as required by Oregon Health
Authority Drinking Water Services regulations.
Storage Capacity
Adequate storage capacity must be provided for each pressure zone. Recommended storage
volume is the sum of four components.
■ Operational Storage: the volume of water between operational setpoints of pumps filling
the reservoir
• Equalization Storage: the volume of water dedicated to supplying demand fluctuations
throughout the day, estimated as 25 percent of MDD
■ Fire Storage: the volume of water needed in each zone to meet the largest required fire
flow for the duration specified in the Oregon Fire Code
■ Emergency Storage: the volume of water needed to supply customers in each zone in the
event of an emergency that makes supply to the zone temporarily unavailable, estimated
as twice the ADD
Pump Stations
Pump stations should have adequate firm capacity to meet MDD in the pressure zones they serve.
Firm capacity is defined as the station's pumping capacity with the largest pump out of service. In
the case that a pump station serves a closed zone, or a zone with no storage or additional sources,
the pumps station must provide peak hour demand plus fire flow.
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Fire Flow
The distribution system should be capable of supplying recommended fire flows while supplying
MDD and maintaining minimum residual pressures of 20 psi everywhere in the system.
Supply Analysis
The City currently receives its supply from the LOT, where it is stored in the Waluga Reservoir and
pumped to the distribution system through PS 5. Two ASR wells are available to help meet peak
demands in the summer. Additionally, one groundwater well is available for emergencies only. A
third ASR well has been drilled, and the City plans to equip this well for an in-service date in 2022.
Supply Capacity
Existing supply from the LOT and ASR Wells 1 and 2 are adequate to meet existing demands. Once
ASR 3 is online, assuming the capacity of this well is similar to ASR Well 2,the total supply capacity
of the LOT and ASR Wells is projected to be adequate through 2030, at which time a new supply
source will be needed.
Supply Options
Currently, hydraulic restraints limit the City's LOT supply use to 14 mgd. The City is planning to
invest in the projects necessary to utilize their full LOT allotment of 18 mgd. This is included in the
CIP as project S-1 and described further in Section 4.2.1. Additionally, the City plans to continue
development of their ASR program to meet growing demands beyond what the LOT supply can
provide. ASR wells provide a dispersed and robust supply source, making them a valuable asset for
emergency supply after a natural disaster like the Cascadia Subduction Zone earthquake. It is
anticipated that two additional ASR wells may be needed to meet future water demands.
The City should also explore additional supply options to ensure supply security and resilience in
the future. There is the possibility that new ASR wells will not be a viable option or that water
drawn from the Clackamas River is restricted. In these scenarios, access to other water supplies,
such as the Willamette Water Supply Project (WWSP), may be a vital resource.
Distribution System Analysis
A hydraulic network computer model was used to analyze the distribution system, which was
evaluated based on the performance criteria described above and projected demands
summarized in Table ES-1. Recommended CIP projects and pressure zone configuration or
operational changes were developed based on the deficiencies identified through this analysis.
Pressure Zone Optimization
Under existing conditions, water is pumped from the 410 PZ to the 713 PZ and then dropped down
through pressure reducing valves (PRVs) to six hydraulically separated areas all with a hydraulic
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grade line (HGL) of 560 feet.These six areas, called the 560 subzones, forma ring around the base
of Bull Mountain.An additional 560 HGL area is served by Reservoir 16, which is filled by pumping
through PS 17 from Reservoir 10. Reservoir 16 has adequate capacityto serve a much larger area
were the 560 subzones to be connected to the reservoir service area. Combining all the areas at
the 560 HGL would provide a variety of benefits ranging from reduced pumping energy to
increased storage capacity in those areas. Zone consolidation would also include a portion of the
existing 640 PZ and some customers located in high pressure areas of the 713 PZ.
Additionally, it is recommended that the 530 PZ be consolidated with the new 560 PZ. With the
existing configuration,the 530 PZ is pressurized from the 410 PZ through PS 1 without the benefit
of gravity storage. PS 1 does not have adequate capacity to supply fire flow. Adding a connection
to the consolidated 560 PZ would add storage and improve fire flow in the 530 PZ.
Consolidation of the 560 subzones and the 530 and 640 PZs is described in more detail in Section
5.3.2. CIP projects identified to achieve consolidation are D-2 through D-8.
Pressures
An area of the 713 PZ near SW 150th Avenue and SW Burgundy Court experiences low pressures.
Adding a connection from the 830 PZ to this area would increase pressures. This is CIP project D-
1, described in more detail in Section 5.8.3.
Storage Capacity
The existing 713 PZ has a storage deficit and there is limited space available for additional storage
in this zone. With the consolidation of the 560 subzones, demand from the 713 PZ reservoirs
would be decreased, but new storage would be needed in the new 560 PZ. A new 3 million gallon
(MG) reservoir, Reservoir 18, is recommended to serve the consolidated 560 PZ. Section 5.4.2
contains more information on system storage needs. Construction of Reservoir 18 is identified as
CIP project R-1.
The 410 PZ currently has adequate storage capacity; however, many of the reservoirs in this zone
are at the end of their useful life and/or are not ideally located to serve customers based on how
the distribution system has changed and grown over the years. Ratherthan invest in rehabilitation
of these older reservoirs in challenging locations,facility abandonment is recommended. As water
demand grows on the west end of the system, a new reservoir, Reservoir 19, will be needed to
serve this growth. Addition of this reservoir is included in the CIP as project R-2 and further detail
can be found in Section 5.4.2.
Pump Stations
The existing PS 13 is a single-pump temporary pump station that is intended to be used as a backup
to PS 17. It is recommended PS 13 be updated to a permanent pump station and expanded to
include pumping from Reservoir 13 (410 PZ) to the proposed Reservoir 18 (560 PZ). This PS 13
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project should be completed concurrent with construction of the proposed Reservoir 18 as part
of CIP project R-1. More information on this project can be found in Section 5.4.2.
The existing PS 8 has five pumps that have reached the end of their useful life. Additionally, the
pump station is split between two locations, with two pumps located across the street from the
other three. It is recommended a new pump station be built to replace the existing facilities and
house five updated pumps. The proposed PS 8 replacement is recommended at a new location,
the existing Reservoir 8-3 site. Existing Reservoir 8-3 (713 PZ) is in poor condition and should be
abandoned as rehabilitation is not feasible given the site constraints. A pump station analysis is
contained in Section 5.5 and the construction of the new PS 8 is included as CIP project PS-1.
Distribution Mains
In general, the City's distribution system is well looped with adequately sized pipes. One exception
is the pipe that extends across Fanno Creek connecting PS 5 to the 410 PZ, a critical path for
bringing LOT water into the City's distribution system. This pipe is 12 inches in diameter and
restricts the flow available from PS 5. Constructing an additional 24-inch diameter crossing would
eliminate this flow restriction and add redundancy in case of failure of the existing creek crossing.
Addition of this pipe is also critical to increasing LOT supply delivery to 18 mgd, and therefore is
included as part of CIP project S-1. More information on this portion of the project can be found
in Section 5.8.4.
As water demands increase and supply from the LOT is increased to 18 mgd, flow restrictions will
occur in the pipeline between the Waluga Reservoir and PS 5. Additional large diameter pipe is
needed to prevent high pipe velocities and pressure losses. As described in Section 5.8.4 and
Section 6, this stretch of pipe is also identified as part of the seismic backbone, meaning that it
should be capable of delivering LOT supply to the system after a major earthquake. A new pipe
between the Waluga Reservoir and SW Bangy Road is recommended as part of CIP project S-1.
Pipe Renewal and Replacement
The City does not currently have a robust pipeline replacement and renewal program. Failure to
proactively replace aging pipe can have catastrophic financial implications as pipes continue to
age. Rather than replace pipes solely based on age, a desktop risk assessment was completed for
all system pipes to determine each pipe's likelihood of failure and consequence of failure. The
results of the analysis provide the City with a road map for prioritizing pipeline replacement
projects.Section 5.10 provides a more detailed description of this analysis. It is recommended that
the City address all system pipes in a 100-year timeframe. The first year of this program should be
used as a planning and design phase, followed by two years of replacing one to two miles of pipe
per year. By 2024, it is anticipated that the City will have built up the resources and efficiencies
needed to replace three miles of pipe per year. This is included in the CIP as project D-9.
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Seismic Resilience Evaluation
System Backbone
Consistent with the Oregon Resilience Plan (ORP) guidelines, the City identified critical facilities
and customers that will need uninterrupted or quickly restored water service following the
anticipated magnitude 9.0 Cascadia Subduction Zone(CSZ) earthquake. Critical customer locations
along with critical water supply and distribution facility locations were used to develop a water
system "backbone' connecting key facilities and water mains. Elements of the backbone were
classified as Tier 1,Tier 2, or Tier 3, addressing supply sources and storage reservoirs first,followed
by critical pipelines.
Seismic Hazards Assessment
Seismic hazards all have the potential to damage buried water mains and other water facilities.
Within the Tigard water service area, these hazards were evaluated based on existing magnitude
9.0 CSZ earthquake hazard maps published for the Portland Metro region by the Oregon
Department of Geology and Mineral Industries (DOGAMI). These maps were refined using
geotechnical exploration data and subsurface boring logs from reservoirs, pump station sites, and
various projects constructed near critical water facilities in the City's water service area.
The likelihood and magnitude of four sources of seismic hazard were analyzed.
• liquefaction settlement — areas around Bull Mountain are at low risk due to shallower
bedrock than in low-lying areas,this risk increases at lower elevations around Fanno Creek
and the Tualatin River.
■ lateral spreading displacement—as with liquefaction, the risk in the TWSA is relatively low
and higher near Fanno Creek and the Tualatin River.
• landslides — flat areas are at low risk, steep areas along the sides of Bull Mountain are
susceptible to landslide.
■ strong ground shaking — estimated ground shaking intensity depends on the distance to
fault rupture and subsurface materials.
Critical Facility Performance
Distribution Pipelines
In general, most of the backbone system piping is in lower liquefaction risk areas with the
exception of SW Bonita Road and SW Hall Boulevard as well as pipes crossing Fanno Creek and
pipes that cross drainage area on the north side of Bull Mountain.Additionally, much ofthe system
pipe is cast iron, which does not perform well in a seismic event.
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ASR Wells
The City s existing ASR well system is anticipated to largely withstand the impacts of a CSZ
earthquake. Groundwater wells have historically performed better than surface water supply
systems during a seismic event as surface water treatment plants have the potential to suffer more
damage. Additionally, prior planning work indicates restoring power to the LOT water treatment
plant is anticipated to take up to three months.
Storage Reservoirs
Most of the City's water system reservoirs are located at high elevation areas on Bull Mountain.
In these areas, bedrock is shallow and unstable sediments are relatively thin making them low risk
for soil liquefaction.The highest risk for the Tigard reservoirs is the potential for landslide. Of the
identified backbone reservoirs, only Reservoir 13 is in a potential seismic landslide area. It is
recommended that a geotechnical investigation be conducted to determine the soil stability at the
Reservoir 13 site following a large earthquake.
Pump Stations
Of the City's critical pump stations, only PS 5 was identified as being at risk in a seismic event. It is
supported on a footing foundation, which is susceptible to differential settlement from soil
liquefaction and lateral spreading. While a seismic analysis was incorporated into the design of
this pump station, additional exploration is recommended to better understand soil characteristics
at the site.
Seismic Resilience Conclusion
This initial seismic evaluation demonstrates that there are significant risks to the City's water
system during a seismic event. It is recommended that the City:
■ continue coordination with emergency managers to refine understanding of post-disaster
water needs which will inform water facility performance goals and design choices, and
• pursue a more detailed analysis of vulnerable facilities to develop a 50-year seismic CIP
consistent with the ORP.
Recommended Capital Improvement Program (CIP)
A summary of all recommended improvement projects and estimated project costs is presented
in Table ES-2.This CIP table provides for project sequencing by showing prioritized projects for the
5-year, 5 to 10-year, and 10 to 20-year timeframes defined as follows.
■ 5-year timeframe - recommended completion through 2025
• 5 to 10-year timeframe - recommended completion between 2026 and 2030
■ 10 to 20-year timeframe - recommended completion between 2030 and 2040
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Estimated project costs presented in the OF are intended to provide guidance in system master
planning and long-range project scheduling and implementation. Final project costs will vary
depending on actual labor and material costs, market conditions for construction, regulatory
factors, final project scope, project schedule, and other factors. Cost estimate details and project
descriptions can also be found in Appendix E.
CIP Funding
The City may fund the water system CIP from a variety of sources including governmental grant
and loan programs, publicly issued debt, and cash resources and revenue such as water rates and
system development charges (SDCs). SDCs are intended to recover a fair share of the costs of
existing and planned facilities that provide capacity to serve new growth. Table 8-1 provides an
estimate of the costs to be allocated to growth. An evaluation of water rates and SDCs in support
of the water system CIP will be completed by the City as follow-on work to this WSMP.
I
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