EXHIBIT C - 2020 Phoenix Water System Seismic Resilience Plan.pdf

SEISMIC RESILIENCE PLAN

Prepared for City of Phoenix

May 2020

Project PHX 1019.054.02

Prepared by:

RH2 Engineering, Inc.

3553 Arrowhead Drive, Suite 200 Medford, OR 97504

1.800.720.8052 / rh2.com

City of Phoenix

Seismic Resilience Plan May 2020

Prepared by RH2 Engineering, Inc.

Prepared for City of Phoenix

Note: This Seismic Resilience Plan was completed under the direct supervision of the following Licensed Professional Engineers registered in the State of Oregon.

Sincerely, RH2 ENGINEERING, INC.

Signed: 05/15/2020

Signed: 05/15/2020

Table of Contents i 5/15/2020 9:38 AM J:\DATA\PHX\1019-054.02 SEISMIC\10 REPORTS\PHX WATER SYSTEM SEISMIC PLAN.DOCX

Executive Summary

Introduction

Background

Hazard Assessment

Data Review

Selected Earthquakes

Cascadia Subduction Zone Earthquake

Maximum Considered Earthquake

Hazard Level Assessment

Ground Motion Parameters

Liquefaction

Landslide

Backbone Infrastructure

Critical Customers

Critical Water Infrastructure

Performance Objectives

Seismic Performance Assessments

Pipe Assessment

Methodology

Results

Pump Station Assessment

Methodology

Results

Reservoir Assessment

Methodology

Results

Risk Assessment and Mitigation Plan

Risk Assessment ii

Overall City Risk Assessment

Mitigation Plan

Infrastructure Improvements

Administrative Improvements

Pipe Mitigation Plan

Seismic Capital Improvement Plan

Cost Estimates

Minor Pump Station Improvement Cost

Reservoir – Piping Seismic Retrofit Cost

Pipe Costs

Recommended Studies

ShakeAlert

Stockpile Materials

CIP Summary

Tables Table 1 – ASCE 41 Table 2-1 – Basic Performance Objective for Existing Buildings Table 2 – ALA Rate of Repair Equations Table 3 – ALA Fragility Curve Modification Factor K1 Table 4 – ALA Fragility Curve Modification Factor K2 Table 5 – Water System Seismic Risk – Summary of Consequences Table 6 – Estimate Pipe Time to Repair Assumptions Table 7 – Water System Seismic Risk Assessment Summary Table 8 – Recommended Seismic Design Standards Table 9 – Restrained Joint DIP Unit Costs Table 10 – ERDIP Unit Costs

Figures Figure 1 – Existing System Map Figure 2 – Hydraulic Profile Figure 3 – Oregon Seismic History Figure 4 – M9.0 CSZ Peak Ground Acceleration Figure 5 – M9.0 CSZ Peak Ground Velocity Figure 6 – M9.0 CSZ Liquefaction-Induced Permanent Ground Deformation iii

Figure 7 – M9.0 CSZ Landslide-Induced Permanent Ground Deformation Figure 8 – Critical Customers Figure 9 – M9.0 CSZ Liquefaction-Induced PGD Backbone Piping and Rates of Repair Figure 10 – Pipe Mitigation Decision Tree

Appendices Appendix A – Regional BPS Seismic Evaluation and Results Appendix B – Eastside Reservoir Seismic Evaluation and Results Appendix C – Pipe Mitigation Plan Appendix D – Seismic CIP

Executive Summary The City of Phoenix (City) is currently updating its Water Master Plan (WMP) for submittal to the State of Oregon Drinking Water Program for review. As of January 10, 2018, under Oregon Administrative Rules (OAR) 333-061-0060(5), the state requires completion of a Seismic Risk and Mitigation Plan (Seismic Plan) to be submitted with the WMP. This Seismic Plan includes all elements required by the state.

The Seismic Plan includes the following elements:

• Hazards – Identification of potential seismic geohazards.

• Backbone Infrastructure – Identification of the critical water supply locations and the encompassing infrastructure.

• Performance Objectives – Answers the question of how the City wants the water system to perform under varying earthquakes.

• Seismic Performance Assessments – Preliminary assessments of facility risk and pipeline fragility.

• Risk Assessment and Mitigation Plan – Categorization of apparent risks based on preliminary assessments and a plan to minimize the predicted risks.

• Seismic Capital Improvement Plan (CIP) – Schedule and estimated costs of recommended capital improvement projects to prepare the City for a seismic event.

This Seismic Plan is considered a planning-level document based on general statewide hazard mapping and high-level seismic performance analyses. The performance of facilities during an earthquake is estimated from published methodologies based on historical performance of other facilities and may not be accurate for the specific conditions of the City. The opinions presented herein are those of the engineer based on the available information. The system performance may vary from the performance estimated in this Seismic Plan.

Introduction

Background The City receives water from the Medford Water Commission (MWC) through a system known as the Talent-Ashland-Phoenix (TAP) Water System. The City also receives water from MWC through an older connection that includes the Experiment Road Booster Pump Station (BPS), the Shop Reservoirs, and the Shop BPS. The City’s recent WMP recommends abandoning these aging facilities (that are also below the pressure of City water customers); therefore, they are not included in this study. This Seismic Plan is focused specifically on the seismic risk of the TAP facilities, as well as infrastructure necessary to serve the end users identified as critical

Seismic Resilience Plan May 2020 customers. The critical facilities for the City evaluated specifically in this Seimic Plan include the TAP Regional BPS, the Eastside Reservoir, and the TAP supply transmission piping. The City’s water system plan and profile views are presented in Figure 1 and Figure 2.

Hazard Assessment The ground movement during a large earthquake poses a number of hazards to water infrastructure. The hazards of concern evaluated for this Seismic Plan include ground shaking, soil liquefaction, differential soil movement, and landslides. The severity of the hazards depends on the intensity and motion characteristics of the earthquake of concern and the local geological characteristics of the site. The following sections describe the selected earthquakes and resulting hazards assessed. It is important to note that this hazard assessment is based on statewide and local mapping data, and local geologic and geotechnical information included in soil boring logs; no site-specific geologic studies were performed.

Data Review The following data sources were used to assess the geologic hazards for the facilities evaluated in this Seismic Plan:

• Oregon Department of Geological and Mineral Industry (DOGAMI) Open File Reports

(DOGAMI O-13-06, 2013).

• DOGAMI GIS and HazVu Hazard Mapping.

• DOGAMI LIDAR Viewer.

• DOGAMI soil boring logs.

• National Earthquake Hazards Reduction Program (NEHRP) Soil and Geologic Maps (Soil Site Class).

• United States Geological Survey (USGS) Geologic Map of Oregon (for Mapped Geologic Unit).

• Natural Resources Conservation Service (NRCS) Web Soil Survey (Mapped Soil Type).

• American Society of Civil Engineers (ASCE) 7-10, Minimum Design Loads for Buildings and Other Structures.

Local geotechnical investigations were not available for the sites specific to this study and only a few soil boring logs were available for review. However, RH2 Engineering, Inc.’s (RH2) history of work in the region has informed the hazard assessment, as described further below.

Selected Earthquakes Figure 3 shows significant earthquakes in Oregon from 1840 through 1998. No recorded earthquakes larger than magnitude 6.0 have been recorded within 100 miles of the City since 1993. More recent earthquakes include August 29, 2019, and September 5, 2019, earthquakes approximately 180 miles from land off the southern Oregon Coast with Magnitude 6.3 and 5.9, respectively.

Figure 3 Oregon Seismic History (Graphic per ESRI 2007)

Based on construction dates, the facilities evaluated herein have not experienced local shaking or lateral loads larger than those experienced in the 1993 Magnitude 6.0 Klamath Falls earthquake, or the larger but much more remote Magnitude 6.3 earthquake off the coast in August 2019. Facility performance in a Magnitude 6.0 earthquake is not a relevant predictor of its expected performance in a Magnitude 9.0 earthquake. Magnitude is based on a logarithmic scale; each magnitude increase of 1 results in a 10-fold increase in ground motion and a roughly 32-fold increase in energy release. Therefore, a Magnitude 9.0 earthquake results in about 1,000 times (10 x 10 x 10) the ground displacement and about 30,000 times (32 x 32 x 32) the energy release of a Magnitude 6.0 earthquake.

Cascadia Subduction Zone Earthquake

The Oregon Health Authority (OHA) requires that water utility Seismic Risk and Mitigation Plans consider the impacts from a Magnitude 9.0 (M9.0) Cascadia Subduction Zone (CSZ) earthquake occurring anywhere along the length of the subduction zone. Oregon’s DOGAMI has prepared open-source, statewide hazard mapping estimating the severity of the hazards resulting from a M9.0 CSZ earthquake. These maps were used to evaluate site-specific hazard parameters. The M9.0 CSZ earthquake has an approximately 500-year return period, or an approximately 10 percent probability of occurring in any 50-year period (USGS Open File Report 2007-1437L).

Maximum Considered Earthquake

For design of new facilities, local and state building codes require designs to meet the maximum considered earthquake (MCE) lateral loads to provide adequate strength and flexibility for the worst anticipated scenario at each specific location. The MCE is defined by ASCE 7-10 Minimum Design Loads for Buildings and Other Structures (which is, in turn, adopted by the Oregon Structural Specialty Code). Site-specific lateral loads based on known fault locations and underlying geology are available through USGS and other online hazards tools, including the online Hazards by Location tool, as sponsored by the Applied Technology Council (ATC), and the online Seismic Design Maps tool, developed jointly by the Structural Engineers

Association of California (SEAOC) and California’s Office of Statewide Health Planning and Development (OSHPD). Local surface soil characteristics, when known, are used with these tools to identify site-specific lateral loads. The MCE is defined by code as the earthquake at a specific location which has a 2 percent chance of occurring in any 50 year interval.

Compared to the MCE that would be used for a new facility in the City, the M9.0 CSZ earthquake has a higher probability of occurrence, but a lower lateral load in the area surrounding the City. The M9.0 CSZ earthquake is anticipated to have a duration of up to 3 to 5 minutes. The MCE in the City has a lower probability of occurrence, but a greater lateral load, as the lower probability MCE earthquake magnitude would be greater than 9.0.

While the MCE and M9.0 CSZ lateral loads are unique to each site (based on soil and groundwater conditions at the time of the earthquake and the distance from the earthquake epicenter), the ratio between the two in a particular region is similar. As an example, the peak ground acceleration (expressed in acceleration due to Earths’ gravity, g) anticipated for the vicinity of the City’s pump station are as follows:

• 0.284 g for the MCE (before adjusting for soil class per NEHRP Hazards tool), and

• 0.168 g for the M9.0 CSZ.

Therefore, for the City’s facilities, the M9.0 CSZ loads are about 60 percent (0.168/0.284) of the MCE loads.

Hazard Level Assessment The following sections discuss the anticipated hazards of concern resulting from the M9.0 CSZ and MCE for the area surrounding the City. Site-specific ground motion parameters and hazards are summarized in the performance assessments for each facility, included in the appendices.

Figure 4 through Figure 7 present the hazard characteristics in the vicinity of the City.

Ground Motion Parameters

To evaluate performance of a facility in a specific earthquake, a design engineer relies on several ground motion parameters. The ground motion parameters considered for this study include:

• Spectral Acceleration (SA): Approximate acceleration that would be experienced by a building, as modeled by a particle on a massless vertical rod having the same natural period of vibration as the building;

• Peak Ground Acceleration (PGA): Approximate maximum acceleration that would be experienced by a particle on the ground;

• Peak Ground Velocity (PGV): The greatest speed of shaking recorded at particular point during an earthquake; and,

• Permanent Ground Deformation (PGD): Large scale ground displacement, a measure of distance related to soil shear strength.

DOGAMI predicted PGA and PGV values for a M9.0 CSZ earthquake are presented in Figure 4 and Figure 5, respectively. PGD may be caused by either liquefaction or landslide, which are discussed as follows.

Liquefaction

DOGAMI Open-File Report O-13-06 mapping identifies the estimated liquefaction and PGD caused by liquefaction based on soil type in the area. Figure 6 presents the liquefaction-induced PGD for the M9.0 CSZ earthquake. Similar values of PGD and liquefaction risk may be presumed for the MCE scenario.

As seen in Figure 6, DOGAMI predicts very low liquefaction potential in the vicinity of the City, with exceptions along Bear Creek. The mapping indicates no PGD in most areas; however, in riparian areas, the mapping indicates PGD in the range of 5 to 10 inches.

Landslide

The DOGAMI Open-File Report O-13-06 mapping also identifies the estimated landslide-induced PGD, largely based on ground slope. Figure 7 presents the landslide-induced PGD for the M9.0 CSZ earthquake. Under the M9.0 CSZ, DOGAMI mapping indicates no landslide-induced PGD in the vicinity of the City.

Backbone Infrastructure Backbone infrastructure consists of the key assets in a water system that will need to be operational as soon as possible after a seismic event to provide water service to critical customers.

Critical Customers Critical water customers were identified and confirmed with the City. The critical customers are the end users that will need immediate access to water in an emergency. The fire department, police department, and emergency community meeting centers (such as schools) were identified as critical customers. No hospitals or urgent care facilities are located within the City, otherwise they would also be considered critical customers. A map of the City’s critical customers is presented in Figure 8.

Critical Water Infrastructure Critical water infrastructure consists of the facilities that will need to be functional to provide water to critical customers. Together, the critical water infrastructure is considered the “backbone” of the water system. The entire TAP System is considered the backbone water infrastructure for the City.

In the City, the TAP Regional BPS and Eastside Reservoir are considered the critical pumping and storage facilities. Additional backbone pipes within the City were selected for supplying critical customers from the TAP supply system, as shown in Figure 8.

Performance Objectives The Oregon Resilience Plan (Oregon Seismic Safety Policy Advisory Committee, 2013) provides post-earthquake performance guidelines for water systems under the CSZ earthquake. For cities in the “valley” region of Oregon, these include having the water system backbone operational within 24 hours following an earthquake. Because the selected backbone facilities are needed for firefighting and other critical functions, all backbone facilities are considered Risk Category IV (essential) facilities per ASCE 7. Risk Category IV facilities have an “Immediate Occupancy” (IO) objective for structural performance and a “Position Retention” objective for nonstructural performance. Per ASCE 41, Table 2-1 (Table 1), “Immediate Occupancy” is defined as a building that “remains safe to occupy and essentially retains its pre-earthquake strength and stiffness.” “Position Retention” of nonstructural elements within those structures can be expected to remain in place during the seismic event without posing physical danger to the structure or people within the structure.

Table 1 ASCE 41 Table 2-1 – Basic Performance Objective for Existing Buildings

To meet the ORP guidelines, which specify that critical backbone facilities are operational after the M9.0 CSZ event, the performance objective for pumps and equipment is “Operational.”

Operational status of pumps, valves, and other supporting equipment is defined as “able to provide the functions they provided…before the earthquake.” It should be noted that significant damage may still occur, even for IO and Operational facilities and components.

Seismic Performance Assessments The City’s backbone facilities were evaluated for their performance during the selected earthquakes following industry standards and methodologies for high-level planning studies.

The methodologies and results are presented in the following sections. Appendix A and Appendix B include detailed technical memoranda for the TAP Regional BPS and Eastside Reservoir, respectively.

Pipe Assessment

Methodology

American Lifelines Alliance (ALA) guidelines were used to assess the City’s pipes. ALA has developed mathematical relationships between pipe materials, earthquake hazards, and anticipated damage to pipes based on historical performance of pipes in different earthquakes around the world. The equations, called “fragility curves,” estimate the repair rate (RR), expressed as number of repairs per 1,000 feet of pipe, given the PGV and PGD from a selected earthquake. These equations are presented in Table 2.

Table 2 ALA Rate of Repair Equations

Rates of repair for pipes are further refined using fragility curve modification factors, K1 and K2, which are based on the pipe material, joint type, soil type, and diameter (Table 3 and Table 4).

Therefore, the final equations become:

• RR = K1(0.00187)PGV (for wave propagation)

• RR = K2(1.06)PGD0.319 (for permanent ground deformation)

RR = Rate of repair (per 1,000 feet of pipe).

For this analysis, DOGAMI hazard mapping data for M9.0 CSZ was downloaded to GIS and overlapped with the City’s pipe data to estimate the repair rate for water mains in the City and the TAP pipelines.

Table 3 ALA Fragility Curve Modification Factor K1

Table 4 ALA Fragility Curve Modification Factor K2

Results

Overall, the City is underlain by soil with moderate to high soil strength as seen in the DOGAMI mapping in Figure 4 through Figure 7. PGV in the project area resulted in repair rates of approximately zero per 1,000 feet of pipe; therefore, it is not mapped or discussed further in this Seismic Plan. PGD due to liquefaction and landslide were also assessed. Landslide-induced PGD is zero in the entire project area. Liquefaction-induced PGD is the most critical M9.0 CSZ scenario for the City’s pipes, resulting in repair rates of close to 2 per 1,000 feet of pipe in some areas. Figure 9 shows the M9.0 CSZ liquefaction-induced PGD overlaid with the City’s backbone piping and calculated rates of repair.

The majority of the City’s water distribution system is outside of the PGD hazard area that is generally near Bear Creek. Earthquake-induced breaks are predicted along the Bear Creek Greenway, as seen with the red and orange pipe color coding in Figure 9. RH2’s experience with construction projects in the Bear Creek riparian area indicate hard bedrock is present, underlying shallow sand and silt soil. DOGAMI soil boring logs confirm that the area consists of sand, silt, and gravel with a depth to groundwater of approximately 6 to 12 feet. Given this data, it is assumed that the DOGAMI statewide predicted hazard mapping is appropriate for this area, and it is likely the bedrock is located below the loose soils near Bear Creek. Additionally, the TAP pipeline that appears in a seismic hazard area is located in fill material that was used to build the northbound lane of Highway 99. Therefore, it is assumed that the mapped liquefaction risk are correct for this pipeline.

The ALA fragility curves predict a range of repair rates from 0 to 1.51 repairs per 1,000 feet, and a total of 3.7 breaks in the City’s pipelines and TAP pipelines combined. The performance of the City’s pipes during the MCE earthquake is not evaluated herein; system-wide hazard mapping is not available as it is for the CSZ M9.0 earthquake. It is assumed that design engineers will consider the MCE when designing any pipe improvements identified for the City.

Pump Station Assessment

Methodology

The following methods were used to assess the performance of the Regional BPS:

• Review available as-constructed record drawings for the facility;

• Perform a site visit to assess material condition and general quality of construction;

• Evaluate the BPS building, including both nonstructural (architectural, mechanical, and electrical systems) and structural elements, using ASCE 41-13, Seismic Evaluation and Retrofit of Existing Buildings, Tier 1 Screening Checklists (2014);

• Evaluate the pumps based on ASCE Technical Council on Lifeline Earthquake Engineering (TCLEE) Monograph 22, Seismic Screening Checklists for Water and Wastewater Facilities (2003).

Results

TAP BPS Results

The full seismic evaluation and results of the Regional BPS are provided in Appendix A. The Regional BPS is a critical facility for the City’s seismic resilience. Most of the City’s water is pumped to the City by the Regional BPS. In addition, the Regional BPS provides all supply to the

City of Talent and emergency supply to the City of Ashland. On July 30, 2019, RH2 performed a site visit and visual observation of the Regional BPS, completing those parts of the ASCE 41 and TCLEE Monograph 22 performance screening checklists that can be completed by visual observation. Following observation, the calculations associated with ASCE 41, within the limits of available data, were completed.

Because it is needed for firefighting and critical supply to numerous cities, the Regional BPS is considered a Risk Category IV (essential) facility per ASCE 7. Its performance objective is Immediate Occupancy (IO) for structural performance and Position Retention for nonstructural performance. The seismic evaluation identified adequate and inadequate elements as follows.

Adequate elements of the pump station include the following:

• Structural elements:

o Structural building elements included on the as-constructed records, including connections between primary structural elements (it is assumed that they were constructed in accordance with the design plans).

• Nonstructural elements:

o Lighting and heating, ventilation, and air conditioning (HVAC) elements.

o Backup power.

Inadequate or unknown elements of the pump station include the following:

• Structural elements:

o No structurally inadequate elements noted.

• Nonstructural elements:

o Anchorage of the pumps (no anchors exist between steel base plate and concrete foundation below).

o Anchorage of electrical/controls cabinets (anchors were inaccessible during site visit; anchorage of cabinets to walls should be confirmed and/or added.)

The Regional BPS building is expected to achieve immediate occupancy and position retention nonstructural performance following a CSZ M9.0 seismic event and an MCE event. The pumps will have met the TCLEE 22 seismic screening criteria if they are anchored to their pump pads.

The control panels were locked during RH2’s site visit, therefore, cabinet anchorage to the walls and/or floor could not be observed. RH2 recommends that cabinet anchorage be verified or added if it does not yet exist.

Reservoir Assessment

Methodology

The following methods were used to assess the performance of the Eastside Reservoir:

• Review available as-constructed record drawings for the facility.

• Perform a site visit to assess material condition and general quality of construction.

• Evaluate the reservoir per the ASCE TCLEE Monograph 22, Seismic Screening Checklists for Water and Wastewater Facilities (2003).

• Evaluate the reservoir structural capacity.

Results

Eastside Reservoir Results

The full seismic evaluation and results of the Eastside Reservoir are provided in Appendix B.

Because it is needed for firefighting and other critical functions, the Eastside Reservoir is considered a Risk Category IV (essential) facility per ASCE 7. While ASCE 41 does not specifically address non-building structures, RH2 has evaluated it in a similar manner, with an IO objective for structural performance and a Position Retention objective for nonstructural performance.

On July 30, 2019, RH2 performed a site visit and visual observation of the Eastside Reservoir, completing those parts of the TCLEE Monograph 22 performance screening checklists that can be completed by visual observation. Following observation, an approximation of calculations associated with ASCE 41 were completed to check expected structural performance. The seismic evaluation identified adequate and inadequate elements as follows.

Adequate elements of the reservoir include the following:

• Foundation.

• Adequate roof anchorage to withstand sloshing wave loads.

Inadequate or unknown elements of the reservoir include the following:

• Flexibility has not been provided in the inlet, outlet, or drain piping to allow for differential movement between the tank and surrounding utilities in a seismic event.

• Piping corrosion was observed.

• Areas of rebar corrosion and concrete spalling were observed on the reservoir walls.

With the completion of some routine maintenance and the addition of flexible inlet, outlet, and drain piping to allow tank movement in a seismic event, the Eastside Reservoir can be made to meet TCLEE 22 checklist requirements and be expected to achieve position retention/ operability following a M9.0 CSZ seismic event. Maintenance elements include some recoating of corroding piping and a check for and repair of spalling concrete at areas of corroding rebar on the tank walls.

Flexible Piping and Possible Seismic Valve

Differential movement between the tank and supporting soils is not uncommon in a design-level earthquake. At the Eastside Reservoir, the most likely mechanism of differential movement is the tank sliding or rotating on its gravel sub-base, particularly if that sub-base should become saturated. If that should occur, the piping could become separated or damaged and the tank contents lost. Damage or separation may be prevented by including a segment of flexible piping near the edge of the tank. A valve on the tank side of the flexible piping is usually added to allow tank isolation. If a seismic valve is added at this location, the valve may be automatically closed in the event of significant ground shaking in combination with rapid flow of contents from the tank.

Risk Assessment and Mitigation Plan

Risk Assessment Risk can be defined as the probability of occurrence combined with the consequences of an event occurring. If an event has a low likelihood of occurring but high consequences, its risk might be categorized as medium compared to an event with a high likelihood and high consequences. Many tools are available for assessing risk; due to the nature of this high-level seismic assessment for the entire water system, the risk assessment uses qualifiable terms such as low, medium, and high, rather than attempting to quantify actual losses. The following sections define the probability of occurrence and consequences used for this Seismic Plan and assesses the overall risk for the City.

Probability of Occurrence

In this Seismic Plan, the probability of occurrence is defined as the probability of a specified type of damage occurring as a result of the design-level earthquake. This is a high level evaluation based on engineering judgement, and the overall likelihood is characterized as low, medium, or high for this Seismic Plan.

Consequences

The consequences of an earthquake are categorized under loss of service, economic losses, or emergency response impact. Loss of service includes the loss of pressure, loss of stored water, and/or the inability to restore pressure and storage volume until repairs are made. The immediate consequence is loss of potable water supply at adequate pressure to City customers.

The duration of the loss of service is impacted by several factors: availability of crews, materials, and equipment to make repairs, and interdependencies on other critical infrastructure such as roads, bridges, communication systems, power, and fuel services. The duration of the loss of service impacts economic losses, in particular businesses that rely on water to function. While they seem aggressive, the ORP guidelines for a quick recovery following the M9.0 CSZ earthquake aim to meet the water supply needs to mitigate potential economic collapse in local communities. Businesses will likely fail if they are closed for several weeks and have no revenue from customers. The consequence of loss of service impacts emergency response efforts, including firefighting, emergency potable water supply to critical customers, and emergency response staff.

A summary of the consequences for each major facility, TAP pipelines, and City backbone pipelines are provided in Table 5. The table includes the following elements:

• Failure Mode: A summary of the anticipated failure given the results of performance assessments for that facility.

• Loss of Service:

o Impacts on the water system: The key impact on the water system from that failure mode.

o Loss of Water/Pressure: Ranked as low, medium, or high impacts on loss of water volume or pressure.

o Reliance on Grid Power: Is operation of the facility reliant on grid power to operate? If yes, repair times may be longer.

o Reliance on Telecommunications: Is operation of the facility reliant on telecommunications? If yes, repair times may be longer.

o Access Difficulty: Would access to the facility require crossings of major creeks, highways, railroad tracks, or irrigation canals?

o Estimated Time to Repair: Estimated labor hours using the assumptions provided in Table 6.

• Economic Losses: Assumed impacts to local businesses given the estimated time to repair. If the repair time is less than 2 weeks, the economic losses are assumed to be low. Economic losses do not include losses due to fire (fire is accounted for in Emergency Response Impact).

• Emergency Response Impact:

o Reduced firefighting ability due to lost pressure or stored water.

o Reduced water supply to critical customers for immediate use following the earthquake.

• Overall Consequences: Low, medium, or high given the loss of service, economic losses, and emergency response impacts.

Table 5 Water System Seismic Risk – Summary of Consequences

FA

C

IL

IT

Y

FA

IL

U R

E M

O D

E

LOSS OF SERVICE

EC

O

N O

M

IC

L O

SS

ES

EMERGENCY

RESPONSE IMPACT

O V

ER

A

LL

C

O N

SE

Q

U

EN

C

ES

Im p ac t o n

W at er

Sy st em

Lo ss o f

W at er /P re ss u re

R el ia n ce o n G ri d

P o w er el ia n ce n

Te le co m m u n ic at io n s

A cc es s

D if fi cu lt y

Es ti m at ed T im e to ep ai r

(H o u rs

Im p ac ts

S u p p ly t

C ri ti ca l C u st o m er s

Im p ac ts

F ir e F ig h ti n g

TAP

Transmission

Main

Leaks/breaks near Bear Creek

Supply disruption at main location to distribution system and other TAP users

Medium No No Low 173 Low High High High

City Backbone

Pipes

Leaks/breaks near Bear Creek

Decreased ability to draw/refill Eastside

Reservoir Medium No No Low 228 Low Medium High Medium

Regional BPS

Pump and possibly control equipment damage due to no anchoring

Supply disruption to entire TAP system

High

Depends on hours of generator operation

Yes Medium 24 Low High Medium High

Eastside Reservoir

Inlet/outlet pipe break

Draining main storage reservoir impacts short- / long-term storage

High

Secondary reliance on pump power to fill

Yes Medium 24 Low High High High

5/20/2020 4:06 PM J:\DATA\PHX\1019-054.02 SEISMIC\10 REPORTS\PHX WATER SYSTEM SEISMIC PLAN.DOCX

Table 6

Estimated Pipe Time to Repair Assumptions

Diameter (inches) Number of Staff Hours Per Staff Total Hours per

Repair

6 4 8 32

8 4 12 48

10 4 12 48

12 4 16 64

Table 7 presents the summary of the overall consequences from Table 5, combined with the probability of occurrence and the resulting overall relative risk for each of the major facilities in the City. Table 6 provides the probability of occurrence (low, medium, or high) based on the performance assessments and the relative risk, which combines the overall consequences and probability of occurrence expressed as low, medium, or high. The relative risk is essentially the priority for mitigation of the facilities and is considered in the mitigation plan recommended for the City.

Table 7 Water System Seismic Risk Assessment Summary

Facility Overall

Consequences Probability of

Occurrence Relative Risk/Priority for Mitigation

TAP Transmission Main High Medium High

City Backbone Pipes Medium Medium Medium

Regional BPS High Low Medium

Eastside Reservoir High Low Medium

Overall City Risk Assessment

With no improvements to the current infrastructure, the seismic performance assessments indicate that in the event of a M9.0 CSZ or MCE earthquake, the City will likely lose water from the Eastside Reservoir, lose water pressure in the TAP transmission main along Bear Creek, and possibly incur pump damage, requiring pump replacement, or repair at the Regional BPS.

Together, these vulnerabilities would result in water system pressure losses resulting in the inability to fight fires and provide domestic water supply. Fortunately, the hazard mapping indicates that the majority of the City’s water distribution system has very low risk of damage and no significant required repairs. Given the anticipated leaks and breaks in the piping that crosses Bear Creek, the east and west sides of the City’s distribution system could be isolated, with the exception of one pipe crossing Highway 99 in Rose Street. Damage to the east-west pipe crossing Bear Creek to connect to the Eastside Reservoir would disrupt the ability to draw from or fill the Eastside Reservoir; however, the City has redundant piping that could provide limited transmission between the reservoir and the distribution system.

The City’s secondary supply, including the Experiment Station Road BPS, transmission piping, Shop Reservoirs, and Shop BPS were not evaluated for their performance objectives as this system is recommended for eventual abandonment. While they are in place, it is not likely that the City could rely on this supply source in lieu of the TAP system, which was built much more recently and with better materials and construction methods. Further, this system is below the pressure of City water customers and relies on the Shop BPS to boost water to meet system pressures. Reliance on this supply source is discussed further in the Mitigation Plan section.

One of the biggest risks to the City’s water supply after an earthquake is the ability of MWC to continue to provide water through the TAP system after an earthquake. This risk is out of the City’s control; pursuing discussions with MWC on the resilience of its water system for providing service to the City is recommended.

It should also be noted that dependence on other non-water infrastructure, including roads and power, may affect the City’s ability to make necessary repairs. In addition, staff availability will be critical to implementing repairs. It is recommended that the City undertake further emergency planning tasks, outside of the scope of work of this study, to address the needs of employees and their families following an emergency, to aid in making employees available to assist with post-emergency repairs and other tasks.

Mitigation Plan The recommended improvements to mitigate the seismic risks identified for the City are a combination of infrastructure improvements and administrative efforts. The scope of this Seismic Plan does not include preparing an Emergency Response Plan that considers post-event protocols and detailed operation plans; however, a general mitigation plan is considered.

Infrastructure Improvements

The following infrastructure improvements are recommended for the City.

• Regional BPS:

o Add pump anchors.

o Check anchorage of motor controls and electrical panels.

• Eastside Reservoir:

o Replace inlet/outlet piping with flexible couplings.

o Install an electrical actuator to control the reservoir from the City’s SCADA system.

o Install ShakeAlert to give the City time to close the valve ahead of shaking and isolate water in the tank. The City is a pilot partner with the USGS ShakeAlert Program, but will need automated controls installed. The ShakeAlert signal can also be used to close down pumps and close other valves as determined by City staff.

Seismic Resilience Plan February 2020 o Perform regular inspections and maintenance to address corrosion and concrete spalling.

• TAP Transmission Pipeline:

o Replace pipe with earthquake-resistant ductile iron pipe (ERDIP) as funding allows.

Allow the small risk of a break in this section of the TAP pipeline until funding is obtained for replacement of this section of pipe with ERDIP. Of the TAP Pipeline that is in the hazard area, only 580 feet have unrestrained joints. The City will plan to prioritize any repairs to this pipeline as the most critical repair in the City. The City should confirm this approach with other TAP Partner Cities.

• City Backbone Piping:

o For the City backbone piping that crosses under Bear Creek, eventually replace with ERDIP as funding allows. Until the pipe is replaced, the City will accept the risk of a break in this pipe. In the event of a break, the City shall isolate the pipe with valves on both sides of the creek crossing and rely on other pipes that cross Bear Creek in less-hazardous areas to connect the east and west sides of the distribution system.

o Other City backbone piping: replace as prioritized in Pipe Mitigation Plan.

• Other City Pipes:

o Replace as prioritized in Pipe Mitigation Plan.

o Adopt seismic design standards.

• Telecommunications:

o Possibly switch to cellular services.

o Anchor radio towers securely.

o Requires further study to confirm recommendations.

• Operation Centers:

o Perform ASCE 41 seismic evaluation for operation center.

Administrative Improvements

• Coordinate with MWC for supply system resilience.

• Stockpile repair materials.

• Develop retainer agreements with local contractors for staff and equipment for repair work.

• Develop an Emergency Response Plan to coordinate with other critical support systems like power, cellular providers, fire, police, and the County, considering all interdependencies.

Pipe Mitigation Plan

The recommended mitigation plan for the City’s transmission and distribution piping considers the risk of the pipes, the overall cost, and industry-accepted seismic improvements.

Table 8 presents the recommended pipe seismic design standards depending on the pipe criticality and hazard. As seen in the Table 8, pipes with high criticality and high hazards are recommended to be designed or replaced with ERDIP. DIP is recommended because the City uses DIP as their standard pipe material; however, HDPE and some PVC pipes have also proven resilient in earthquakes. Pipes with low criticality and low hazards are recommended to follow current City standards or considered to be restrained where needed as determined by a design engineer. For pipes with low hazard and high criticality, or low criticality and high hazard, restrained-joint DIP is recommended.

Table 8 Recommended Seismic Design Standards

Pipe Criticality Low Hazard High Hazard

Backbone Pipe Restrained-Joint DIP Earthquake Resistant DIP1

Non-backbone Pipe Current design standards

(DIP, restrained as determined by engineer)

Restrained-Joint DIP2

1 Pipes should include flexible joints, joint restraints, and capability to withstand one percent strain.

2 Confirm with design engineer on additional flexibility/compression as needed.

Earthquake Resistant Pipe

No official seismic design standards for pipes are currently available, although standards are in the process of being developed by ASCE. Additionally, the International Organization for Standardization (ISO) has developed pipe performance guidelines, including recommended maximum joint compression and expansion, joint deflection angle, and slip-out resistance to withstand earthquake forces. These guidelines are based on the historic performance of earthquake pipe in other countries, particularly ERDIP manufactured by Kubota Pipe in Japan. In the U.S., ERDIP is currently manufactured by two companies: American Pipe and U.S. Pipe.

Pipe Prioritization

Replacing all the City’s backbone piping or pipes located in hazardous areas would be too costly for the City to perform all at once. For this reason, the pipes were prioritized for replacement based on several factors: hazard, criticality, risk to the City, and pipe age.

A decision tree was developed for assigning a mitigation action as shown in Figure 10. The mitigation options are defined as follows:

1. Do nothing. In this case, either a pipe improvement is not warranted, or a pipe may leak or break and the City will plan to perform some pipe repairs after the earthquake.

2. Replace with Restrained-Joint DIP Low Priority. This mitigation is recommended for pipes with lower risk. Replacement with restrained-joint DIP is recommended when replacement is required for maintenance purposes.

3. Replace with Restrained-Joint DIP High Priority. This mitigation is recommended for critical pipes, or less critical pipes that are aging.

4. Replace with ERDIP Low Priority. This mitigation is recommended for high criticality pipes that may only have a few leaks or breaks that the City will prioritize for repair after an earthquake. Replacement with ERDIP is recommended when replacement is required for maintenance purposes.

5. Replace with ERDIP High Priority. This mitigation is recommended for high risk pipes for which the City is not willing to accept risk of failure following an earthquake.

Figure 10 Pipe Mitigation Decision Tree

A detailed list of the City pipes recommended for seismic mitigation is included in Appendix C.

Appendix C presents the location of each pipe, whether it is a backbone pipe or not, year installed, material, the estimated number of repairs or leaks, estimated hours for repairs, recommended mitigation action, and replacement cost estimates (as described in Cost Estimates).

Seismic Capital Improvement Plan A seismic capital improvement plan (Seismic CIP) was developed to provide an improvement schedule and budgetary costs for the City’s use in implementing the seismic mitigation plan.

The Seismic CIP costs are separated into short-, mid-, and long-term and are included in Appendix D. Short-term is within the next 10 years (2020 to 2030), mid-term is 10 to 30 years in the future (2031 to 2050), and long-term is 30 to 50 years in the future (2051 to 2070).

Backbone? High Hazard? City willing to accept risk of breaks/leaks?

Yes

No

High Hazard?

Yes

No

No

Yes Yes

No 5 2, Case by Case

Pipe Age: 20 years or older?

No

Yes

1. Do nothing

2. Replace with RJDIP (Low Priority)

3. Replace with RJDIP (High Priority)

4. Replace with ERDIP (Low Priority)

5. Replace with ERDIP (High Priority)

Cost Estimates Cost estimates were prepared for each scenario. The cost estimate is a planning-level American Association of Civil Engineers (AACE) Class 5. This assumes 0 to 2 percent of project definition.

Estimated costs are assumed to be within the range of plus 50 percent to minus 30 percent of the average of contractors’ bids. The costs are based on 2018 dollars; no allowance is made for inflation in future years. Costs assume Engineer News Record Construction Cost Index (ENR CCI) of 11,062 for 2018.

Construction costs are based on a compilation of previous RH2 projects. Contingency is assumed to be 30 percent of construction costs. Engineering, legal, and administration is assumed to be 30 percent of constructions costs.

Minor Pump Station Improvement Cost

Minor pump station improvements include anchoring pumps and checking anchorage of controls and electrical equipment. These improvements are recommended in the short term.

Reservoir – Piping Seismic Retrofit Cost

Construction costs are to include (or exclude) a seismic actuator on the Eastside Reservoir. This retrofit is recommended in the short term.

Pipe Costs

Pipe projects are categorized into short-, mid-, or long-term based on the prioritization identified in the Pipe Prioritization section. Unit costs for construction for restrained-joint DIP are estimated based on previous RH2 project experience and presented in Table 9.

Table 9 Restrained-Joint DIP Unit Costs

Diameter (inches) Unit Cost

(2018 $/LF)

6 $186

8 $232

10 $243

12 $248

16 $258

18 $268

20 $289

24 $310

ERDIP is assumed to cost 30 percent more than restrained-joint DIP for materials and installation. Again, this is based on RH2’s previous project experience. Unit costs for ERDIP are presented in Table 10.

Table 10 ERDIP Unit Costs

Diameter (inches) Unit Cost

(2018 $/LF)

6 $242

8 $302

10 $316

12 $323

16 $336

18 $349

20 $376

24 $403

Pipe seismic upgrade projects are separated into three categories in Appendix C: 1) TAP transmission; 2) City backbone; and 3) City non-backbone.

Recommended Studies

A seismic evaluation of the City’s operations center is recommended in the short term.

America’s Water Infrastructure Act (AWIA) requires the City to have an emergency response plan. Development of an emergency response plan is recommended in the short term.

ShakeAlert

ShakeAlert can give earthquake early warnings and signal to SCADA systems. ShakeAlert can be programmed with the City’s SCADA to perform automatic functions such as turning off a pump or closing a valve to prevent loss of contents in a reservoir.

Stockpile Materials

The City’s ability to repair or replace broken equipment and piping quickly is in part dependent on the materials available. It is recommended that the City budget for stockpiling of materials so that City staff can quickly make repairs.

CIP Summary As seen in Appendix D, the City’s total anticipated Seismic CIP is approximately $6.6 million. In the short term, the largest costs are improving the inlet/outlet piping of the Eastside Reservoir.

The mid-term projects include replacing backbone piping that is currently over forty years old and made of asbestos-cement pipe. Long term projects include all backbone pipes and other pipes at risk to eventually be replaced with improved pipe materials and joints as needed for maintenance or if/when funding is available.

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Vicinity MapFigure 1

City of PhoenixCity of Phoenix Existing System Map

Seismic Resilience PlanSeismic Resilience Plan 1 in ch = 800 feet

Esri, HERE, Garm in , (c) Open StreetMap con tributors, This m ap is a graphic represen tation derived from the City of Phoen ix Geographic In form ation System . It was design ed an d in ten ded for City of Phoen ix staff use on ly; it is not guaranteed to survey accuracy. This m ap is based on the best in form ation available on the date shown on this m ap.

An y reproduction or sale of this m ap, or portion s thereof, is prohibited without express written authorization by the City of Phoen ix.

This m aterial is own ed an d copyrighted by the City of Phoen ix.

Eastside Reservoir

Shop BPS

Skyline BPS

Shop Reservoirs

Date:

Filename:

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Phoenix 1681 Zone

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Talent BPS

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Figure 2 Hydraulic Profile City of Phoenix

Seismic Resilience Plan 12/23/2019

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Vicinity MapCity of Phoenix Seismic Resilience Plan

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Any rep roduc tion or sa le of this m a p , or p ortions thereof, is p rohib ited without exp ress written a uthoriza tion b y the City.

This m a teria l is owned a nd c op yrighted b y the City.

TAP Regional BPS

Eastside Reservoir

Talent BPS

Belmont 2 Reservoir

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