Water_System_Pipe_Replacement_Report_-_2015.pdf

City of Palo Alto Water System

Pipe Replacement

Prepared for:

City of Palo Alto

Prepared by:

G&E Engineering Systems Inc.

6315 Swainland Rd Oakland, CA 94611

(510) 595-9453 eidinger@geEngineeringSystems.com

Principal Investigators:

John Eidinger, P.E., S.E., Darlene Holston P.E.

G&E Report 119.01.02, Revision 0 July 21, 2015

Palo Alto Pipe Replacement R119.01.02 Rev. 0. July 21, 2015

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TABLE OF CONTENTS

EXECUTIVE SUMMARY

1.0 INTRODUCTION

1.1 KEY FINDINGS

1.2 ACKNOWLEDGEMENTS

1.3 ABBREVIATIONS

2.0 SYSTEM DESCRIPTION

2.1 SFPUC SYSTEM SERVING PALO ALTO

2.2 PALO ALTO WATER SYSTEM

2.2.1 Overall Description, Water Demand

2.2.2 Historical Development of the Palo Alto Water System, 1894 to 1957

2.2.3 Water Demands Under Earthquake Emergency Conditions

2.2.4 Water Facilities – Modern System (2015)

2.2.5 Water Distribution System Pipelines

2.2.6 Service Laterals, Hydrants and Meters

2.2.7 Water Facilities in the Foothill Pressure Zones

2.3 FOOTHILLS TRANSMISSION CCP PIPELINE

2.3.1 Phase 1. Quarry to Boronda Reservoir Section

2.3.2 Phase 2. Boronda Reservoir to Monte Bello Reservoir Section

2.3.3 Pipe Relocation

2.4 SOIL RESISTIVITY

2.5 ABANDONED PIPES

2.6 PALO ALTO INCOME

3.0 SEISMIC HAZARDS

3.1 SEISMOLOGY AND SCENARIO EARTHQUAKES

3.2 STREAMS

3.3 GEOTECHNICAL HAZARDS

3.4 GROUND SHAKING HAZARD

3.5 LIQUEFACTION HAZARD

3.6 LANDSLIDE HAZARD

3.7 FAULT OFFSET HAZARDS

3.8 PAST EARTHQUAKES

3.8.1 Great San Francisco Earthquake of April 1906

3.8.2 Loma Prieta Earthquake of 1989

3.8.3 Palo Alto Park Mutual Water Company

3.9 BORING DATABASE

4.0 SEISMIC ASSESSMENT OF ALL PIPELINES

4.1 SERA ANALYSIS OF SITES

4.2 SERA ANALYSIS OF PIPES

4.3 SERA ANALYSIS OF PIPES – LOMA PRIETA EARTHQUAKE

4.4 SERA RESULTS FOR 24 SCENARIO EARTHQUAKE

4.5 SERA RESULTS FOR THE SAN ANDREAS M 8.0 EARTHQUAKE

4.6 SERA RESULTS FOR THE MONTA VISTA M 6.8 EARTHQUAKE

5.0 SEISMIC ASSESSMENT OF FOOTHILLS PIPELINE

5.1 FIELD RECONNAISSANCE – LANDSLIDE AND LIQUEFACTION

5.1.1 Monte Bello Reservoir

5.1.2 Alignment Between Monte Bello Reservoir and Dahl Reservoir

5.1.3 Dahl Reservoir and Booster Pump Station Site

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5.1.4 Alignment Along Arastradero Creek, Near Corte Madera Booster Station

5.1.4 Alignment at Corte Madera Booster Station

5.1.5 Alignment at Corte Madera Booster Station

5.1.6 Alignment along Old Page Mill Road

5.1.7 Quarry Booster Pump Station

5.1.8 Approaches to Refined the CCP Hazard Assessment

5.2 FOOTHILLS WATER SYSTEM PERFORMANCE AFTER SAN ANDREAS M 8

5.2.1 San Andreas M 8 – Pipeline Performance in Foothills (Zones 5, 6, 7, 8, 9)

5.2.2 San Andreas M 8 – Reservoir Drawdown and Fire Following Earthquake

5.3 PIPE REPAIR STRATEGIES

5.4 PIPE MITIGATION STRATEGIES

5.5 RECOMMENDATION FOR FOOTHILLS PIPELINES (SEISMIC)

6.0 PIPE AGING, REPAIR ANALYSIS AND PIPE REPLACEMENT

6.1 HISTORICAL PIPE REPAIRS

6.2 PIPE REPAIR RATE AS A FUNCTION OF MATERIAL AND DIAMETER

6.3 PIPE REPAIR RATE AS A FUNCTION OF AGE

6.3.1 Pipe Repair Rate as a Function of Age – AC Pipe

6.3.2 Pipe Repair Rate as a Function of Age – CI and PVC Pipe

6.4 PIPE REPAIR RATE AS A FUNCTION OF MONTH, YEAR

6.5 PIPE REPAIR RATE AS A FUNCTION OF SOIL CORROSIVITY

7.0 PIPE REPLACEMENT STRATEGIES

7.1 WATER MAIN REPLACEMENT PROGRAM

7.2 BENEFIT COST RATIO MODEL

7.3 PIPE REPLACEMENT FOR AGING ISSUES

7.3.1 Benefit Cost Analysis

7.3.2 Refined Pipe Replacement Strategy for Aging

7.3.3 Maps Showing Pipe Replacement due to Aging Issues

7.4 PIPE REPLACEMENT FOR SEISMIC ISSUES

7.4.1 Benefit Cost Model - Seismic

7.4.2 Seismic SIP-1, SIP-2, SIP-3, SIP-4

7.4.3 Seismic Projects

7.4.4 Water Main Risk Framework

8.0 FUNDING

9.0 REFERENCES

9.1 TECHNICAL

9.2 ELECTRONIC

9.3 DRAWINGS

APPENDIX A. SOIL RESISTIVITY TESTS

A.1 OVERVIEW

A.2 TEST RESULTS

A.3 REFERENCE

APPENDIX B. SEISMIC PERFORMANCE OF WATER PIPELINES IN THE 2014 NAPA

EARTHQUAKE

APPENDIX C. ASBESTOS CEMENT CORROSION

C.1 PALO ALTO USAGE OF AC PIPE

C.2 HOW DOES AC PIPE FAIL?

C.3 EBMUD EXPERIENCE

C.4 EXTERNAL CORROSION

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C.5 HARDNESS

C.6 ADDITIONAL EBMUD TESTS

APPENDIX D. PALO ALTO STANDARD PIPE INSTALLATION

D.1 EXAMPLE PALO ALTO AC PIPELINE INSTALLATION

D.2 AC PIPE SPECIFICATIONS – PALO ALTO

D.3 AC PIPE SPECIFICATIONS - CAPCO

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Executive Summary Beginning in the 1990s, the City of Palo Alto water department began a long term effort to replace water pipes, called the Water Main Replacement Program (WMRP). The work was originally planned out in 34 phases, with each phase generally being accomplished in about 1 year. Phases 1 through 24 are now essentially complete. Phases 25 through 34 have yet to be implemented, which would include about 145,000 feet (27.5) miles of pipe over the next decade. Phases 25 and 26 are currently (mid-2015) in various stages of design, but construction has not yet started.

This report presents a series of analyses that suggest that, going into the future, a different pipe replacement strategy might be adopted. Considering the pipes already replaced since the 1990s, it is evident that by implementing Phases 1 through 24, the City has already replaced many of the most leak-prone and deteriorated pipes; while most of the remaining pipes planned to be replaced in future Phases 25 through 34 are currently functioning as expected and have never leaked in the past two decades.

Given these findings, this report outlines a new pipe replacement program that can be implemented over the next decade. This new pipe replacement program includes about

13.5 of pipe, of which 2 miles are in deteriorated condition, 10 miles of pipe are seismically weak, and about 1.5 miles of pipe will deteriorate over the next decade to the point where they warrant replacement. The estimated cost for this pipe replacement program is $2.921 million (aging) plus $19.01 million (seismic) plus $2.3 million (future deteriorated pipe) or about $24.23 millionin total.

In the longer term, once the next ten years of pipe replacement is completed, there will continue to be a need to replace pipe, both for aging / deterioration purposes as well as lower priority pipes for seismic purposes. The benefit cost ratios computed for each pipe in the water system can be used to rank which pipes should be replaced. Assuming the rate of deterioration stays much the same as it is today, a long term pipe replacement rate of about 1 mile per year appears to be a cost effective strategy.

The recommended pipe replacement program (13.5 miles) is about half the currently planned effort (27.5 miles) over the next deacde. This recommended pipe replacement program would significantly reduce the capital requirements for pipeline replacement over the next decade, while still cost effectively addressing ongoing aging of pipes and seismic risks in Palo Alto.

1 All costs presented in this report are in constant $2015, and exclude the effects of inflation. The costs of inflation and financing should be factored into actual capital budgets.

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This new pipe replacement program is based on the following principles:

• All of Palo Alto's existing water pipes are aging. Many of these pipes continue to perform their function with little to no maintenance, and have adequate seismic capability if they are located in soils that are not prone to significant seismically-induced ground deformations.

• Most water pipes should not be replaced until such time that they sustain sufficient deterioration as to make them unreliable. Other pipes, located in soils prone to liquefaction, landslide or surface faulting, could be cost-effectively replaced with suitably seismic-designed pipes, if the existing pipe's failure in earthquakes will result in high adverse economic impacts to Palo Alto's customers.

• The expenditure of current capital dollars for pipe replacement should be balanced against the benefit of fewer day-to-day leaks as well as fewer damaged pipelines in future earthquakes.

• It is current US national policy that the cost to repair damage caused by future major earthquakes to Palo Alto's water system will be reimbursed at about a 75% rate by FEMA. To the extent that the current cost for Palo Alto to mitigate seismic impacts exceeds the future benefits, this report suggests that it is more cost effective for Palo Alto to accept the impacts of some level of seismic damage, and make repairs after the earthquake, the cost of which will be substantially reimbursed by FEMA.

• This report provides quantified valuation of the cost effectiveness for replacement for each pipe. This is done by computing a benefit cost ratio (BCR) for each pipe, for pipe replacement due to aging issues, for pipe replacement for seismic issues, and for both issues combined. This report uses the combined BCR of 1 to set the dividing line as to which pipes should be currently replaced (1 or higher) or left in service (under 1). Should Palo Alto wish to be more risk adverse, then more length of pipe can be replaced, by selected a lower BCR dividing line value. The databases provide the numeric BCR ranking for every pipe.

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1.0 Introduction

This report describes the seismic and aging performance and mitigation strategies for the City of Palo Alto water system.

The report is in several sections:

• Section 2. Describes the inventory of pipes and other facilities in the Palo Alto water system.

• Section 3. Describes the earthquake hazards in Palo Alto.

• Section 4 describes the system-wide performance of pipelines throughout Palo Alto in earthquakes

• Section 5 describes the seismic performance of the Concrete Cylinder Pipes in the Foothills.

• Section 6 describes leak analysis and pipe replacement strategies to address aging pipes.

• Section 7 provides a pipeline replacement program. This includes a pipe replacement program that addresses aging pipes (called the Aging Improvement Plan, AIP), and a combination of emergency response and pipe replacement strategy that addresses earthquakes (called the Seismic Improvement Plan, SIP).

An electronic database is provided that lists the replacement priority for each pipe.

• Section 8. Funding.

• Section 9. References.

• Appendix A. Results for Soil Resistivity Tests.

• Appendix B. Calibration of earthquake pipeline fragility models, considering the recent Napa 2014 earthquake.

• Appendix C. Asbestos Cement pipe corrosion.

• Appendix D. Palo Alto Standard AC Pipe Installation.

1.1 Key Findings

The City of Palo Alto water system includes about 2362 miles of transmission and distribution mains. Over the past two decades, the City has been selectively replacing older pipes.

2 About 232.3 miles of pipes as of 2010.

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Pipe Aging

The report examines the historic leak and repair rates for Palo Alto's water mains. This report provides tables that show the rate of repair by pipe diameter, by pipe material, by pipe age, and by soil resistivity. Using these historic repair rates, the report describes a Benefit Cost Ratio (BCR) model that is used to rank the cost effectiveness of a pipe replacement program that addresses aging issues only. Pipes with a BCR greater than 1 are cost effective for replacement for aging issues alone. The analysis shows that there are currently about 0.7 miles of pipe that have historically had such a high repair rate that current pipe replacement is cost effective. Considering that it often practical to replace segments of pipe from valve to valve, or street intersection to street intersection, and in consideration of street moratoria and other practicalities, there are 1.95 miles of pipes recommended to be replaced due to aging issues, costing about $2.92 million. The specific pipes recommended for replacement are listed in Tables 7-5 and 7-6.

Earthquakes

The report examines the performance of the Palo Alto water system for 24 different scenario earthquakes. By "scenario earthquake", it is meant that a particular earthquake is assumed to occur on a specific fault, with a specific epicenter and specific magnitude.

The 24 scenario earthquakes include a complete range of possible earthquakes on the nearby San Andreas fault, from Magnitude 6.0 up to 8.0, as well as large earthquakes on other nearby active faults including the Hayward, Calaveras, San Gregorio, Greenville, Mount Diablo Thrust, and Rodgers Creek faults. Two scenario earthquakes were run that represent repeats of the historic 1989 Loma Prieta and 2014 West Napa earthquakes.

Additional scenarios were run on less active nearby faults, for the Monte Vista - Shannon and Zayante – Vergeles fault zones.

Depending on the earthquake, pipe damage in the Palo Alto water system can range from none or a few pipe repairs (for smaller or more distant earthquakes), up to 200 to 300 pipe repairs for a large earthquake on the nearby San Andreas fault. The bulk of the repairs will occur to older "non-seismic-designed" pipes located in areas prone to liquefaction. By "non-seismic-designed" pipes, it is meant older cast iron and asbestos cement pipes, as well as newer ductile iron and PVC pipes with push-on-type joints. Of these, cast iron and asbestos cement pipes are the worst performers when located in soils that suffer permanent ground deformations due to liquefaction or similar phenomena.

Given the pipe damage, and assuming that other facilities are suitably seismically sound (water tanks, booster pump stations, wells, service connections to the SFPUC), water outages were estimated due to the pipe repairs. System hydraulics for damaged pipeline systems, were considered as well as the time needed to repair the broken pipes. The system hydraulics depends primarily on the amount of pipe damage, while the repair times depend mostly on the number of pipe repair crews available. The gross regional product of Palo Alto was established, and the impact on the economy should there be a loss of water supply was estimated.

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For the existing water system, it was assumed that the pipeline network reflects how it is currently configured, plus using only Palo Alto's in-house pipe repair capability (2 crews). In this case, the economic impact of a San Andreas M 8.0 earthquake is substantial: about $477 million in direct economic impacts attributable to damage to the pipeline network. This includes loss of economic activity due to loss of water (about 75 to 85% of the total); the amount of damage in Palo Alto due to fires that burned structures (about 15 to 20% of the total), aggravated by the lack of water in many places, and the cost to make the actual pipe repairs (about 1% of the total).

Four possible strategies were considered to reduce the economic impacts due to pipe damage in earthquakes. These are called Seismic Improvement Plans SIP-1, SIP-2, SIP-3 and SIP-4. SIP-1 is meant to be the lowest cost with the highest benefit; SIP-2 includes SIP-1, and adds in upgrade of the most critical water pipes; SIP-3 includes SIP-2, and adds in upgrade of additional pipes; SIP-4 includes SIP-3 and adds in replacement of additional pipes. Table 1-1 lists the costs.

Item SIP-1 SIP-2 SIP-3 SIP-4 Emergency Response $1,000,000 $1,000,000 $1,000,000 $1,000,000 Foothills Pipeline $738,000 $738,000 $738,000 Seismic Projects

1. 17,932 ft, Zone 3 $6,049,820 $6,049,820 $6,049,820

2. 127 ft, El Camino R $35,560 $35,560 $35,560

3. 746 feet, Wilkie $156,660 $156,660 $156,660

4. 332 ft, Laguna $123,400 $123,400 $123,400

5. 576 ft, El Camino R $165,720 $165,720 $165,720

6. 2,857 ft. Los Robles $943,720 $943,720 $943,720

7. 1,203 ft. Matadero $278,350 $278,350 $278,350

8. 8,735 ft. Embarcadero $3,399,710 $3,399,710 $3,399,710

9. 911 ft. Middlefield $298,400 $298,400 $298,400

10. 1,103 ft. Park $364,360 $364,360 $364,360

11. 18,546 ft. Zone 1 $5,452,090 $5,452,090

12. 66,380 feet, Zone 1 $16,616,160

12. 24,645 feet, Zone 1 Ext $6,370,060

13. 3,576 feet, Zone 1 Other $2,627,560 Total $1,000,000 $13,553,700 $19,005,790 $44,619,570 Recommended Very High High Over 10 Years Marginal

Table 1-1. Seismic Upgrades – Pipes – Priority SIP-1, SIP-2, SIP-3 and SIP-4.

Tables 7-13 through 7-33 list the specific pipes included in Table 1-1. Total pipe length recommended for replacement for seismic reasons is 53,068 feet (10.05 miles), with an estimated cost of $19,005,790.

The attached databases gives the benefit cost ratios for every pipe in the water system, both for aging and seismic reasons.

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Overall.

Beginning in about 1990, the Palo Alto water department began a long term effort to replace water pipes, called the Water Main Replacement Program (WMRP). The work was originally planned out in 34 phases, with each phase generally being accomplished in about 1 year. Phases 1 through 24 are now essentially complete. Phases 25 through 34 have yet to be implemented, which would include about 145,000 feet (27.5) miles of pipe over the next decade or so.

The current analysis suggests that there are currently about (3,442 feet plus 6,874 feet, total 1.95 miles of pipe that should be replaced based on aging issues (total of Tables 7-5 and 7-6). This will cost about $2.92 million. This is a lot less than the 27.5 miles planned in the current WMRP. Over time, as more pipes begin to regularly leak, it will be cost effective to replace more than this initial 1.95 mile estimate, and the BCR model described in this report can be updated as new pipe repair data becomes available. Even so, the clear observation is that replacement of pipes for aging issues along can be reduced, while still being cost effective.

The current analysis also shows that a pipe replacement program to address seismic issues is warranted. The current WMRP is not geared to lower materially improve the water system for earthquakes, for two reasons: first, most of the pipes selected for replacement in the current WMRP are already located in geologically stable soils, and thus do not present very large seismic risks; second, the replacement pipes being adopted, being PVC-C900, are not seismically sufficient to be reliable in liquefaction zones. We recommend that new pipes installed in zones prone to liquefaction be seismically-sound, and these might include: HDPE (fusion welded); PVCO (a new PVC product that is reported to be able to sustain over 1% ground strain); ductile iron seismic-chained pipe from Kubota; similar ductile iron pipe from US Pipe (or others) with chained joints;

heavy wall steel pipe. All metal pipes need suitable corrosion protection systems if placed in soils with low resistivity (Rho much under 3,000 ohm-cm, which is most of the flat-land areas of Palo Alto). In areas with Rho much under 1,500 ohm-cm, an initial preference for use of plastic pipes might be suitable.

Given these findings, we suggest that Palo Alto updated its WMRP, and develop a new ten-year program to upgrade about 12 miles of pipe. These pipes should be selected from Tables 7-5, 7-6 (Aging pipes) and Table 7-34 (SIP-2 and SIP-3 pipes).

Pipes will continue to deteriorate over time in Palo Alto. As described in this report, this deterioration will manifest itself within increasing rates of pipe leaks on select pipes.

There is no simple formula that will predict when each individual pipe will reach its cost effective replacement age; but monitoring ongoing leak rates is a very sound indicator.

Based on the current trends, it appears that about 1,000 to 2,000 feet of pipe will be annually become so deteriorated as to warrant replacement. The BCR model for pipe aging could be updated with additional leak data once a year, and this model will identify those pipes that are good candidates for near-term replacement. The cost effective

G&E Engineering Systems Inc. Page 7 replacement rate for pipes that are not yet leaking, and which are not identified as candidates for seismic pipe replacement, will likely be about 0.2 to 0.4 miles per year over the next decade.

The total recommended pipeline replacement program for the next decade is thus composed of three elements: replacement of pipe that are currently deteriorated (

1.2 Acknowledgements

This report was prepared by John Eidinger and Darlene Holston of G&E Engineering Systems Inc. Dr. Donald Duggan assisted with soil resistivity testing. Dr. Stephen Dickenson developed information about the Foothills pipelines. Mr. Bruce Maison (retired, EBMUD) and Prof. Mike O'Rourke (Rennselaer Polytechnic Institute) provided review of pipeline seismic and aging models. Ms. Jennifer Cioffi and Mr. Romel Antonio of the Palo Alto Utilities Department directed the work.

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1.3 Abbreviations

ACP Asbestos Cement Pipe BDPL Bay Division Pipeline CCP Concrete Cylinder Pipe CGS California Geological Survey CIP Cast Iron Pipe cm Centimeter DIP Ductile Iron Pipe FEMA Federal Emergency Management Agency Fy Yield stress for steel g acceleration of gravity (=32.2 feet / second / second) G&E G&E Engineering Systems Inc.

GIS Geographic Information System km kilometer ksi kips per square inch (1 kip = 1,000 pounds) M Magnitude (Moment) MG Million Gallon NEHRP National Earthquake Hazards Reduction Program soil classifications A, B, C, D, E, F NS North South PCCP Prestressed Concrete Cylinder Pipe PE Polyethylene Pipe PGA Peak Ground Acceleration (measured in g) PGD Permanent Ground Deformation (measured in inches, cm) PGV Peak Ground Velocity (measured in inches/sec, cm/sec) psf pounds per square foot psi pounds per square inch PVC Polyvinyl Chloride Pipe SFPUC San Francisco Public Utilities Commission ULDH Ultra Large Diameter Hose VCP Vitrified Clay Pipe Vs30 Average shear wave speed over top 30 meters of soil, meters / second WMRP Water Main Replacement Program

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2.0 System Description

2.1 SFPUC System Serving Palo Alto

The City of Palo Alto Utilities Department owns and operates the potable water distribution system for the City of Palo Alto.

Figure 2-1 shows an overall view of the Palo Alto water system. This map shows the SFPUC pipelines that deliver potable water to Palo Alto, the major pipes within the Palo Alto water system itself, and the major facilities (booster pump stations, tanks and reservoirs, and wells) in the City water system.

There are five turnouts which connect the SFPUC system with the Palo Alto system, two of which are on the Palo Alto pipeline, and 2 of which are on BDPL 3 and 4 pipelines:

• Near the intersection of El Camino and Lytton is turnout #75 from the 36-inch SFPUC Palo Alto Pipeline to the City of Palo Alto distribution system. Near the intersection of El Camino and California Ave is turnout #77 from the 36-inch SFPUC Palo Alto Pipeline to the City of Palo Alto distribution system. A third turnout is located near Sand Hill Road, from the Palo Alto pipeline to the Palo Alto distribution system.

• Near Arastradero is turnout #54 from the 72-inch and 90-inch SFPUC BDPL 3 and 4 pipelines to the City of Palo Alto distribution system. Near the intersection of Page Mill Road and Junipero Serra Blvd is turnout #57 from the 72-inch and 90-inch SFPUC BDPL 3 and 4 Pipelines to the City of Palo Alto distribution system.

The water in the SFPUC system is normally potable. Under normal conditions, this water comes from the Hetch Hetchy reservoir in Yosemite National Park, and / or from Calaveras reservoir via the Sunol Water Treatment Plant.

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2.2 Palo Alto Water System

2.2.1 Overall Description, Water Demand

The Palo Alto water system serves the City of Palo Alto and a small portion of nearby unincorporated areas. The Palo Alto water system does not serve Stanford University.

The water system is divided into nine main and three smaller pressure zones. Figure 2-2 shows a hydraulic profile of the modern (2015) water system. Figure 2-3 shows the geographic areas of each main zone.

The lower zones (zones 1, 2, 3) are gravity zones, normally served by pressure in the SFPUC's BDPL 1, 2, 3, 4, 5 and Palo Alto pipelines. About 90% of all customers are in the gravity zones. The Quarry Zone (zone 4) gets water from a pressure regulator from Zone 5, or by opening the valves between Zones 2 and 4. The Lytton pump station can boost pressure and flows into Zone 3.

There are five pumped zones (zones 5, 6, 7, 8, 9), extending almost to the highest elevation of the Peninsula mountains, with the highest served area at about elevation 2,400 feet. The function of the upper-most zones (Monte Bello, Dahl, Park) is mostly to provide water for fire fighting purposes in the upper elevations; there are a few customers in these areas. About 10% of all customers are in the pumped zones.

There are several wells in the system. Zones 1 and 2 are situated over a ground water basin. Prior to the construction of the SFPUC system (pre-1935 or so), all of the water in Palo Alto was taken via wells from the ground water basin, with 10 wells in service in the 1950s. By 1999, there were five wells remaining, of which Hale, Rinconada and Peer Park were then in then in-service with Fernando and Matadero then out-of-service. Since 2000, three additional wells have been constructed.

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Figure 2-2. Schematic Profile

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Figure 2-3. Pressure Zones

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Based on a planning report from 1999 (Carollo, 1999), average day water demand (ADD) in the Palo Alto system was then about 13.8 MGD (FY 1999-2000). Annual Maximum Day water demand varied from 15 MGD to about 32 MGD during the time period from 1982 to 1998, and is expected to be about 32 MGD at build-out of the city.

By 1999, Palo Alto regularly used only one normal source of water, being the SFPUC system at turnouts 54, 57, 75, 77. As of 2015, Palo Alto continues to use nearly all of its normal water supply form the SFPUC, with local wells providing backup / emergency supply.

In the year 2000, there were five wells in Palo Alto (see Figure 2-1). These wells were taken out of normal use in 1962, when the City of Palo Alto switched over to the SFPUC system for 100% of its normal water supply. This switchover to the SFPUC system was in part a response to regional subsidence and water quality concerns. Today (2015), there are 7 wells in the Palo Alto water system, with two new wells being added over the past decade. The wells are not now (as of 2015) in normal use. The nominal combined capacity of the older five wells is 4,300 gpm, of which 3,575 gpm is currently deemed operational at three of the five wells (6.2 MGD total / 5.1 MGD operational). Under an emergency such as a large earthquake, it is reasonable to use the wells to supply water to Palo Alto, recognizing that normal water quality will be compromised.

2.2.2 Historical Development of the Palo Alto Water System, 1894 to 1957 To appreciate the configuration of the water system as of 2015, a review of the historical development of the water system is in order.

The earliest recorded history of Palo Alto dates from 1769. It is assumed that the water supply of the small community of the time was taken via surface water from the various creeks that traverse Palo Alto.

By 1855, the township of Mayfield was formed. By 1906, the northern part of Palo Alto was developed. Figure 2-4 shows a historical map of the San Francisco Peninsula and the major Spring Valley Water Company (SVWC) water works at the time of the 1906 earthquake. Figure 2-5 (modified from USGS Topographic Map of Palo Alto, California, 1/62,500, 1899) indicates that two areas of Palo Alto were then developed:

• Between Alma and Middlefield, Embarcadero and San Francisquito Creek (northwest part of modern Zone 1).

• Near the modern location of Mayfield Reservoir (modern Zone 2).

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Figure 2-4. Water Works, circa 1906

Figure 2-5. Topographic Map, Palo Alto Area, 1899

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1896. The City of Palo Alto was incorporated in 1894. Prior to 1894, the small population centers (highlighted in Figure 2-5) were served by a number of small, privately-owned water companies, each of which operated one or more relatively shallow wells. In 1896, two years after incorporation, the City of Palo Alto Utilities (CPAU) began, with a bond issue for purchase by the city of the companies then serving the majority of the population. Since that time, the system was expanded both by construction of new facilities and by additional purchases of private companies. The Barron Park Water Company was purchased in 1953, having about 400 water services. The Spinks Water Company was purchased in January 1951.

1923. BDPL 1 is constructed. This is the first pipeline bringing Hetch Hetchy water to the San Francisco Bay area, terminating at Pulgas Tunnel and then emptying into Crystal Springs reservoir. For much of its length, it is a 60-inch riveted steel pipeline. BDPL 1 remains in use in 2015 (the Bay Crossing reach is expected to be abandoned in the next few years).

1932. BDPL 2 is constructed. This is the second pipeline bringing Hetch Hetchy water to communities around the San Francisco Bay, terminating at Pulgas Tunnel and then emptying into Crystal Springs reservoir. For much of its length, it is a 66-inch welded steel pipeline. It remains in use in 2015 (the Bay Crossing reach is expected to be abandoned in the next few years).

1938. The Palo Alto Pipeline (PAPL) is a 36-inch pipeline, and is a part of the SFPUC water transmission system. This pipeline is connected to BDPL 1 and 2 in Redwood City, and then continues southeastward to Palo Alto where it terminates. Water supply from the SFPUC Palo Alto 36-inch pipeline is believed to have started in 1938.

There are two turnouts from the PAPL to Palo Alto. Using the SFPUC's numbering system (see Figure 2-2), turnout 75 is a 12-inch diameter turnout, located at El Camino and Lytton Avenue; turnout 77 is a 12-inch diameter turnout, located at El Camino and California Street. Both connections are equipped with meters and pressure reducing valves. The maximum grade line in the PAPL at times of low flow in the SFPUC system might be on the order of 320 feet, with minimum about 280 feet or so, which would imply a upper pressure at sea level in Zone 1 of about 139 psi or so; at this pressure, water would overflow in the Mayfield reservoir (overflow 179.5 feet); therefore, the turnouts have pressure reducing valves.

In 1948, a consulting firm, Forbes and Jenks, examined the problem of turbidity and taste and odor in the Palo Alto water system. They recommended that a water treatment plant be constructed in Palo Alto. This was not built. It was then suggested that purchased water from the PAPL (from SFPUC) was resulting in general tuberculation, presumed for the unlined cast iron pipes, then in common use. It was thought that SFPUC water was under saturated in dissolved salts, principally calcium carbonate.

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In 1950, a consulting firm, Burns and McDonnell, examined the problem of "red water"" in the Palo Alto water system. They attributed the red water condition to the presence of iron bacteria, with the SFPUC upstream aqueduct tunnels as the most likely source of the infestation. They also suggested construction of a water treatment plant in Palo Alto to treat both SFPUC water as well as local well water.

In 1952, Burns and McDonnell indicated the possibility of softening only the local well water, and then mixing it with untreated SFPUC water. They also envisioned future water sources for Palo Alto from the impoundment of San Francisquito Creek (never happened) or from the Feather River (ultimately called the State Water Project, with water now being delivered to Santa Clara County for SCVWD's transmission system).

While Palo Alto is in Santa Clara County, and is eligible to receive surface water from the SCVWD, there has never been a SCVWD pipeline extended to Palo Alto to make such surface water deliveries; and this report will not make any such recommendation for purposes of seismic reliability.

In 1948, the SFPUC completed construction of BDPL 3, along an alignment to the south of the PAPL. Water supply via BDPL 3 is from the same SFPUC source as PAPL. The maximum grade line in BDPL 3 at times of low flow in the SFPUC system, pressure within BDPL 3 might be as high as 320 feet or as low as 280 feet or so, which would imply an upper pressure at sea level in Zone 1 of about 139 psi or so. In 2015, water from BDPL 3 (and BDPL 4) is delivered into Zone 2 via pressure reducing valves; from Zone 2, water flows by gravity into Zone 1 (via pressure reducing valve) or into / from Zone 4 (similar elevation as Zone 2. As Zone 4 is slightly higher in elevation that Zone 2, normal flow into Zone 4 is via the Quarry booster pump station and Zone 5 via a pressure reducing valve. Should the Quarry pump station not be available, a gate valve can be opened between Zones 2 and 4.

In 1954, Brown and Caldwell reported that the SFPUC began, as of January 1951, treatment of SFPUC aqueduct water with lime, in order to maintain a condition which would inhibit corrosive action in metallic distribution pipe. It was recommended that dosing of water at each source with a polyphosphate, such as sodium heaxa-metaphosphate; this type of treatment would inhibit corrosion and minimize the precipitation of calcium, magnesium, manganese and iron. Following that recommendation, chemical feeders were installed and polyphosphate treatment was started at all stations. Results thus obtained were reported to be generally excellent.

Figure 2-6 shows the water supply for Palo Alto, as of c. 1956. In 1956, there were 11 stations with 15 wells. The well capacity, as of 1956, assuming peak capacity of each well, was about 11 MGD. It was believed that the ground water basin in northern Santa Clara Valley, was being over drafted, and the potential of drilling new wells and increasing water supply was thought limited. Older wells were showing signs of deterioration, and were expected to decline both in yield and quality. If pumping was kept high, the yield was expected to drop to perhaps 8 MGD. However, if the wells were kept as emergency supply, and the ground water basin allowed to recover, then possibly yield on an emergency basis would increase.

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Figure 2-6. Palo Alto Water Supply, Circa 1956

In 1957, the cost of well water was about $15 per acre-foot, and the cost of SFPUC water was about $60 per acre-foot (in 1957 dollars). There was a desire to keep overall cost of water as low as practically consistent with the other needs of the water system, so

G&E Engineering Systems Inc. Page 19 therefore, the concept was to ensure that the maximum reliable supply from wells could be used consistently throughout the year, supplementing local well water with SFPUC water during peak demand months.

The lengths and sizes of water pipes (6-inches and larger) in the distribution system in 1956 was 118.2 miles, with a breakdown in Table 2-1.

Diameter (inches)

Cast Iron (feet)

Asbestos Cement (feet)

Other (feet)

Total (feet)

6 161,200 240,600 3,100 404,900 8 45,400 100,600 200 146,200

10 18,000 5,900 100 24,000 12 7,400 32,600 900 40,900 14 600 6,000 16 5,800 5,800 18 1,500 1,500

Total (feet) 239,900 379,700 4,300 623,900 Total (miles) 45.4 71.9 0.8 118.2

Table 2-1. Length of Pipes, as of July 1 1956

In addition, as of July 1 1956, there were 339,100 feet (64.2 miles) of service lines, either ¾-inches (common), 1-inch (most common) or greater than 1 inch (limited).

The Cast Iron pipe are believed to be unlined bell and spigot pipe. The AC pipe are believed to have begun being installed around 1940, using rubber ring compression joints.

Brown and Caldwell (1957) report that older sections of the system had various combination of one, two three and four valves at main intersections. In some cases, the one and two valves intersections result in runs as long as 1,600 feet without a shut-off.

Post 1960, it can be assumed that new four-way intersections all have three valves.

In 1957, Brown and Caldwell developed a planning document as to how to improve the Palo Alto water system. The following outlines their findings.

By 1957, water supplies were adequate, with "practically unlimited quantities" available by purchase from the SFPUC. Because, however, due to the high cost of SFPUC water, most water use in Palo Alto was from Palo Alto's own wells. The goals of the design of the water system post-1957 included:

• Ensure full use of the local ground water consistent with the safety of the ground water basin.

• Anticipate short term outages of the SFPUC water system.

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• Prior to 1957, there were deficiencies in the water system, including complaints of low pressure (in some areas as low as 10 psi); taste and odor and turbidity complaints; control and instrumentation systems that were outdated.

The plan outlined in 1957 was geared to resolve these issues. Much of the infrastructure now in place (2015) reflects the improvements contemplated in 1957.

In 1962, the City of Palo Alto began purchasing nearly its entire water supply from SFPUC, largely discontinuing the use of wells. According to Palo Alto staff, this decision was based on input from the community, with the desire to have higher quality Hetch Hetchy water rather than the local ground water, even it that SFPUC water was more expensive.

In 1970, the SFPUC completed construction of BDPL 4, along an alignment parallel to

BDPL 3.

In 1989, the Loma Prieta earthquake occurred. In the 1989 Loma Prieta earthquake, there was surface evidence of liquefaction in very locations in Palo Alto, near the Bay shoreline. The level of ground shaking in Palo Alto in that earthquake was likely in the PGA = 0.10g to 0.15g range. The duration of strong ground shaking (PGA over 0.05g) was likely in the 6 to 8 second range. Within the Palo Alto water system service area, there were few liquefaction zones and few landslides in the hills. Section 3.8.2 describes the known damage to have occurred to Palo Alto's water tanks, pump stations, pipeline and wells in the Loma Prieta earthquake. A joint pulled apart (but did not leak) in BDPL 2 where it transitions from the Dumbarton Strait reach (soon to be taken out of service) to the on-land portion in East Palo Alto.

In 2015 (or soon thereafter), the SFPUC will complete BDPL 5, including a new Bay Tunnel, along an alignment parallel to BDPL 1 and 2. As of March, 2015, water is flowing in the new Bay Tunnel. Water from BDPL 1, 2, and 5 will be able to be delivered to Palo Alto via the 36-inch PAPL. Soon thereafter, the SFPUC currently intends to retire portions of BDPL 1 and 2 for their 5-mile reach across the Bay;

retirement of those two older pipelines that cross the Bay will reduce the reliability of water supply to Palo Alto, especially should the new Bay Tunnel be taken out of service (for maintenance) or due to unforeseen occurrence (damage for any reason); the cost savings to the SFPUC from avoiding future maintenance on BDPL 1 and 2 may be modest compared to the material impacts to SFPUC customers should the Bay Tunnel be damaged, especially with concurrent damage to BDPL 3 and 4. Although the risk of damage to all the BDPL pipelines at the same time, even in an earthquake, is thought to be small by design, the reduction in seismic reliability due to construction defects (such as those in BDPL 5 that were not mitigated) or unexpected seismic hazards cannot be entirely ruled out. Given these issues, keeping some or all of Palo Alto's wells in service would serve to provide a source of water after earthquakes, should the SFPUC transmission system be damaged.

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2.2.3 Water Demands Under Earthquake Emergency Conditions

Under earthquake emergency conditions, loss of water supply from SFPUC turnouts 54, 57, 75, and 77 would begin to impact customers when local Palo Alto water storage is emptied, assuming no re-supply from the Palo Alto wells, and assuming there was no damage to the Palo Alto distribution system.

For planning purposes, it is assumed that it is desirable to provide at least Average Day Demand (ADD) indefinitely after major earthquakes. If the earthquake were to take place during summer time conditions, immediate water rationing would be put in place, whereby outside irrigation would be curtailed until such time that the water system could reliably deliver full summer time flows.

It is recognized that within the first hours to days after a major earthquake, there may be variations in water demand due to the following issues:

• Damage to distribution system pipelines can cause severe leakage of water in the system, resulting in drop in pressure until such time that the leaking pipelines can be valved out, and then eventually repaired. Leaks can occur in Palo Alto-owned distribution pipe as well as customer owned service connections.

• Fires may ignite after a major earthquake. If these fires spread substantially, there may be a material increase in water demand in the system for purposes of fire fighting. In the Oakland Hills firestorm of 1991, peak water demands used for fire fighting reached about 30,000 gpm (43 MGD) for about 48 hours after the initial ignition.

• Concurrent earthquake damage to residential and commercial and industrial customers will alter normal water demands by those users. Ideally, it is desired to be able to restore at least ADD to all customers within 3 days after a major earthquake; in this way, the water system will not be the limiting factor in restoring the local economy to pre-earthquake levels.

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2.2.4 Water Facilities – Modern System (2015)

As of 2015, there are six primary water storage tanks in the Palo Alto system. These are listed in Table 2-2.

Reservoir Capacity (Million Gallons)

Overflow Elev, Feet

Bottom Elev, Feet

Diam, Feet

Height, Feet

Description

Mayfield 4.027 179.5 163.0 208 x

16.5 Rectangular, in-ground, concrete

lined. Lightweight roof, known to suffer from corrosion; recently the roof was replaced. Includes altitude valve. Built 1928.

Corte Madera

1.5 520 478 80 42 Steel tank at grade, built 1969.

Boronda 1.5 922 894 96 28 Prestressed concrete tank, built 1960. 4 feet below grade, 24 feet above grade. Walls are 8-inches thick, including 1" to 1.5" spray on gunite over prestressing wires.

Roof is 8.5" flat concrete slab.

Park 1.0 1430 1402 80 28 Steel tank at grade, built 1965.

Unanchored on ring beam. Flat steel roof. Scheduled to be seismically upgraded.

Dahl 1.0 1893 1871 90 22 Steel tank at grade, built 1965.

Unanchored on ring beam. Flat steel roof. Scheduled to be seismically upgraded.

Monte Bello

1.5 2432 2405 100 27 Steel tank at grade, built 1965.

Unanchored on ring beam. Flat steel roof. Scheduled to be seismically upgraded.

Total 10.5

Table 2-2. Water Storage Tanks

Note: we have not surveyed the elevations of the reservoirs. Older documents likely provide elevations in 1928 vertical datums (or other), while most modern elevations usually use the 1988 NAVD. For example, the Carollo (1999) report lists the overflow of Mayfield at 179.5 feet, while the 1957 Brown and Caldwell report reports it at 167.8 feet.

The overflow and bottom elevations listed in Table 2-2 are based on various source documents, some of which may use conflicting vertical datums; it is recommended that these be verified with modern survey before being used for design-related purposes.

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In 2010, V&A conducted field measurements of the water tanks. Pertinent information from that report is tabulated in Table 2-3. Steel plate thicknesses are based on ultrasonic testing.

Reservoir Mayfield Repair cracks in sloped concrete liner. Replace corrugated metal roof sheets. Lead found in vault pipe coating. Concrete liner is 6 inches thick (bottom) or 4 inches thick (sloped sides). 1928-vintage roof is corrugated metal supported by timber beams and concrete columns.

Many cracks observed in 2010 in the sloped concrete liner, some previously repaired.

Corte Madera Lead found in exterior tank and vault pipe coating. Recommended recoat of interior and exterior surfaces of tank. Center column. Five courses (0.67, 0.551, 0.438, 0.290, 0.271 inches, bottom to top, 0.198 inches roof, 0.474 inches columns)

Boronda Repair roof cracks. Patch exterior crack exposing pre-stressing wire.

Lead found in vault pipe coating. Concrete roof supported by center column and 6 columns.

Park Lead found in exterior tank and vault pipe coating. Recommended recoat of interior and exterior surfaces of tank. Center column and 5 columns;

all columns are pipe-type. Bottom level mixing pipe. Four courses (0.454, 0.353, 0.282, 0.236 inches, bottom to top, 0.206 inches roof,

0.269 inches columns)

Dahl Lead found in exterior tank and vault pipe coating. Recommended recoat of interior and exterior surfaces of tank. 3 courses. Center column and 6 columns; all columns are pipe-type. Bottom level mixing pipe. Three courses (0.386, 0.265, 0.256 inches, bottom to top, 0.199 inches roof,

0.279 inches columns)

Monte Bello Lead found in exterior tank and vault pipe coating. Recommended recoat of interior and exterior surfaces of tank. Center column and 9 columns;

all columns are pipe-type. Bottom level mixing pipe. Four courses (0.505, 0.395, 0.265, 0.253 inches, bottom to top, 0.192 inches roof,

0.287 inches columns)

Table 2-3. Water Storage Tank Field Observations

Table 2-4 lists the capacities for the booster pump stations. The listed capacities assume all pumps in operation, and are the sum of individual pump capacity. Actual capacity if all pumps are in service will be somewhat smaller due to hydraulic head losses. Rated capacity should exclude the largest pump, assuming it is out of service for maintenance.

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Pump Station Capacity (gpm)

Number of pumps

Pump nameplate horsepower

Description

Mayfield 8,300 4 This pump station is used to increase flow into Zone 1 at times of maximum demand. Built 2012.

Lytton 4,650 3 Emergency lift, Zone 1 into Zone 3, if PAPL is out of service

Quarry 2,500 3 3 x 200 Corte Madera 1,360 3 3 x 200 Boronda 1,730 Park 1,230 Dahl 510 2 2 x 150 Check: 3 x 170?

Table 2-4. Water Pump Stations

Table 2-5 lists the well capacities. The capacities are based on 1974 pump tests, updated by 2010 Palo Alto report on then current capacities.

Well Station Nominal Capacity

(gpm)

Local Tank

(gallons)

Tank Type (as of 1957)

Tank Description

Hale 1,425 295,000 At grade concrete Tank exists but not in service in 2015

Rinconada 1,250 220,000 At grade concrete Tank no longer exists Peers Park 900 83,000 At grade concrete Tank no longer exists Matadero 800 63,000 At grade wood stave Out of service in 1999.

The tank no longer exists.

Fernando 800 none Out of service in 1999.

The tank no longer exits

Eleanor Pardee 1000 none Built post 2000. No tank.

Main Library 600 none Built post 2000. No tank.

Table 2-5. Wells

The City of Palo Alto also has pipeline interconnects with Mountain View, Stanford and East Palo Alto. The following describes the reliability of the interconnections under normal (planned outage) and post-earthquake (major event on the nearby San Andreas fault) conditions.

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• Stanford interconnection. Should normally be able deliver limited flow from Stanford's water system (higher pressure) to Palo Alto zone 3 (lower pressure).

Stanford interconnects can deliver limited water flows from Stanford (higher pressure) to Palo Alto zone 3 (lower pressure). May be able to provide supply from Stanford to Palo Alto's zone 3 after an earthquake.

• Mountain View. There is a 6-inch diameter pipe connection between the Mountain View and Palo Alto water systems on Silva Avenue, in Palo Alto's Zone 2, adjacent to Mountain View's Zone 2. Mountain View obtains its water supply either from the SFPUC, from the SCVWD or via local wells. Between Mountain View's Zone 2 and Palo Alto's Zone 2, the soils are generally stable, so an interconnection between Zone 2 could be somewhat reliable post-earthquake.

• In Mountain View's lowest elevation pressure Zone 1, that is southeast and adjacent to Palo Alto's Zone 1, the geologic conditions and pipelines are similar to those in Palo Alto: some moderate to very high liquefaction susceptibility, and a lot of asbestos cement pipe. There are several locations where the two systems could be temporarily interconnected between nearby fire hydrants. However, the poor soils and seismically-weak pipes means that should there be a large earthquake, Mountain View will be busy repairing pipe damage in their Zone 1, and the transfer of water between Palo Alto and Mountain View would not be reliable.

• East Palo Alto. East Palo Alto's water system does not have local storage tanks, drawing its water directly from SFPUC's BDPL 1, 2 and 5 pipelines. East Palo Alto's water system is located immediately north of Palo Alto's Zone 1, across San Francisquito Creek. From a post-earthquake point of view, it is more likely that East Palo Alto will have relatively more pipeline damage than Palo Alto, and possibly with a more limited capability to make pipe repairs. Laying hose across the creek would be a challenge. A connection located north of Highway 101 may exist, but in that area, liquefaction can be widespread, so the ability to transfer water between the systems after an earthquake, would not be immediately reliable.

• PHWD's top elevation is at the Page Mill Tank, elevation 1085 feet. It would take about a mile of flex hose (12-inch diameter) to temporarily connect this PHWD tank / pressure zone to Palo Alto's system along Page Mill Road, which would allow water from the Dahl reservoir (1,893 feet) to flow to PHWD. Due to the great change in pressure (350 psi difference) and long length of pipe required, it is doubtful that this is a practical interconnection point.