FAULT CROSSING DESIGN OF 66 INCH PIPELINE SAN FRANCISCO HETCH HETCHY WATER SYSTEM. Arne Nervik, P.E. (California) Black & Veatch Corporation

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1 FAULT CROSSING DESIGN OF 66 INCH PIPELINE SAN FRANCISCO HETCH HETCHY WATER SYSTEM Arne Nervik, P.E. (California) Black & Veatch Corporation

2 AGENDA SFPUC Water System Seismic Hazards Pipeline Response to Faulting Analysis Methodology Design Long Term Monitoring

3 ABOUT SFPUC Department of the City and County of San Francisco Water Retail water services to San Francisco Wholesale water to four Bay Area counties Serving 2.6 million customers Wastewater services to San Francisco Hydroelectric and solar power to San Francisco's municipal departments

4 SFPUC WATER SYSTEM

5 SEISMIC HAZARD High probability of a major earthquake in the San Francisco Bay Area

6 SEISMIC HAZARD Alameda Siphon No. 4

7 WATER SYSTEM IMPROVEMENT PROGRAM (WSIP) Program Overview $4.6 billion infrastructure improvement program Started 2005 Forecast Complete 2016 LOS AS4 Goals Minimum 120 mgd required within 24 hours of a major earthquake Minimum 160 mgd required within 30 days of a major earthquake AS4 Project Goals Reliable water transmission across Sunol Valley

8 CALAVERAS FAULT CROSSING N Overflow Pipe 66-inch, WSP Calaveras Fault Zone Mixing Chamber X15 X35 X25 Alameda West Portal X25/ X35 X15/ X55 Flow Meters #1 & #3 Flow Meters #2 & #4 Siphon 2 Siphon 3 96-inch PCCP (1966) 90-inch WSP (1952) Siphon 4 66-inch, WSP X14 Siphon 1 69-inch RCCP (1933) Chemical Injection X10 X2 0 X30 X50 Alameda East Portal

9 PROJECT DETAILS Project Components AS4 pipeline AEP connection/upgrade Other Constraints Connection to 1930s Infrastructure Proximity of Calaveras Road Uncertainty in fault location Project Cost Approved Total Budget $65m Status Const. completion: Mar, 2013 Pipeline Monitoring Survey

10 DESIGN CONSIDERATIONS

11 PIPELINE DAMAGE IN PAST EARTHQUAKES Rupture in 120-inch Soledad Siphon (1994 Northridge Earthquake)

12 FAULT RUPTURE

13 PIPELINE RESPONSE TO FAULTING Segmented Pipeline Ref: O Rourke and Liu

14 PIPELINE RESPONSE TO FAULTING Caving Active Wedge A Fault Crossing Angle Central Wedge B Heaving Passive Wedge Initial Configuration C A B Displaced Configuration C Continuous Pipeline Logarithmic Spiral Failure Surface

15 PIPELINE RESPONSE TO FAULTING Pipeline Pipeline in tension and bending Pipeline Pipeline in compression in bending and bending Pipeline Strike-Slip Fault Strike-Slip Fault Strike-Slip Fault Pipeline Angle 90 Degree of Crossing Angle of < > Crossing 90 Degrees

16 SPECIAL DESIGN REQUIREMENTS Acceptance Criteria Average Tensile Strain Limit = 4% Compressive Strain Limit = 3.7% (D/t ratio) Controlled Plasticity Material Properties Yield Strength Yield to Ultimate Strength Ratio

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18 PIPE OVALIZATION STUDY ¾ inch pipe thickness (Grade 36 steel) Max Displacement = 5 ft 1 inch pipe thickness (Grade 36 steel) Max Displacement = 6 ft

19 Final Design 71-4 to to to 9.2 COR 48 to 60 1 Overflow pipe AS

20 RELATIVE SLIP AT SOIL/PIPE INTERFACE

21 PowerPoint Sample 6 June 2011 CONSIDERATIONS AWWA silent regarding fault crossings and strain based design AWWA C200 is the readily available pipe Bulk of project will be standard water pipe Owner is a water utility and familiar with AWWA Contractor will have water pipeline experience 21

22 ADDITIONAL REQUIREMENTS Maximum yield strength (42 ksi) for pipe in certain areas. Butt Welds Shop welding as much as possible Material traceability Limited heats in certain areas Limitations on pass holes and nozzles in certain areas. Limitations on where closure pieces can be used. 100% NDE in certain areas

23 PowerPoint Sample 6 June 2011 PIPE SCHEDULE 23

24 PowerPoint Sample 6 June 2011 MATERIAL PROPERTIES OF STEEL PLATE Stress (PSI/100) % 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Percentage of Samples Yield Tensile 24

25 PowerPoint Sample 6 June 2011 ASTM A 36 STRESS/STRAIN % 1.00% 2.00% 3.00% 4.00% 5.00% 6.00% 7.00% 25

26 PowerPoint Sample 26 December 2012 CONCLUSIONS Fault displacement design requires strain based design, AWWA M11 is not sufficient. ALA and PRCI provide guidelines for strain based design of pipelines. AWWA C200 pipe can work for these applications. Need to control parameters Material properties Coating Trench Other More rigorous quality control (ASME BPV) Address variability and specify limits. (minimum and maximum rather than just minimum) 26

27 LONG TERM MONITORING

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30 FAULT MONITORING PIPE POSITION

31 FAULT MONITORING PIPE STRAIN Monitoring Riser Fiber Optic Strain Gauge

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