January 2014 2013 SURVEILLANCE REPORT December 2012 through December 2013 LEROY ANDERSON DAM NO. 72-9 Santa Clara County San a Clara Valley 5750 Almaden Expressway, Son Jose, CA 951 l 8-361 J I ( 08) 265-2600 I www .volleywoter.or g Waler Dislric(J January 6, 2014 Mr. David A Gutierrez , Chief Division of Safety of Dams Department of Water Resources 1416 Ninth Street P.O. Box 942836 Sacramento, CA 94236-0001 Subject: Leroy Anderson Dam, No. 72-9, Santa Clara County December 2012 through December 2013 2013 Surveillance Report Dear Mr. Gutierrez: Please find enclosed two copies of our 2013 surveillance report for Leroy Anderson Dam covering the period from December 2012 to December 2013. Our review of the surveillance data and our periodic safety inspections indicate that Anderson Dam and appurtenant structures appear to show normal response to their environment , aging process, and external events. There were no major incidents or changes at the dam during 2013. All collected instrument data are well below established upper Action Levels. In addition , all collected instrument data are well above established lower Action Levels. Consequently , during the period of this report there were no surveillance instrumentation alarm conditions. The Santa Clara Valley Water District will continue with the current monitoring program and safety inspections and will keep DSOD informed of any significant changes pertaining to the surveillance or performance of Anderson Dam. During the current reporting period, there were no new activities at the site that would impact monitoring of this facility. Please contact me at (408) 630-2736, if you have any questions. Sincerely, Attachments cc/enc.: F . Maitski, T. Dougherty, H. Desai, M. Mooers, B. Baker, S. Wu, J. Nelson, library (4) cc: H. Desai, L. Lopez jn:mf 1231a-l.docx 2013 SURVEILLANCE REPORT December 2012 through December 2013 LEROY ANDERSON DAM NO. 72-9 Santa Clara County Date of photo 10/10/06 Photo shows temporary drill rig access roads and 2 drill rigs on dam crest for DIP Prepared for: State of California Department of Water Resources Division of Safety of Dams P.O. Box 942836 Sacramento, CA 95236 Prepared by: Santa Clara Valley Water District 5750 Almaden Expressway San Jose, CA 95118 January 2014 2013 SURVEILLANCE REPORT December 2012 through December 2013 LEROY ANDERSOJ'.'J DAM J'.'JO. 72-9 Santa Clara County The analysis and inferpretalion of the instrumentation and other relevant data presented in this report has involved the application of certain graphical and slatislical inlerpretive techniques common to the geosciences and earth dam engineering professions. The conclusions presented in this report were developed upon evaluating lhe performance of all instruments and other pertinent data during the specified period, and represent the professional judgment of its author. This report was published on December 31, 2013. Report prepared by: Ill 2013 Surveillance Report December 2012 - December 2013 Leroy Anderson Dam No 72-9 Quality Control/Quality Assurance This report has been reviewed and approved for publication by the undersigned professional engineers. l attest and confinn that the report was prepared by the individual who signed the report under my immediate direction and supervision and that the conclusions and recommendations presented herein are reasonable and supported by District management. Reviewed and approved by: mang Desai, P.. ngineering Uni Manager Dam Safety Program Unit iv 20 I 3 Survei ll a nce Re po rt Dece mber 2012 - December 20 l 3 Leroy Anderson Dam No 72-9 TABLE OF CONTENTS TEXT Section No. Title Page No. 1.0 INTRODUCTION ............................................................................................................................................................................ 1 1.1 Scope and Purpose ....................................................................................................................................................................... 1 1.2 DSOD’s Comments on Previous Report .................................................................................................................................... 1 1.3 Anderson Dam Seismic Retrofit Project (ADSRP) Design Consultant ................................................................................... 1 1.4 Changes to Surveillance Report .................................................................................................................................................. 1 1.4.1 General .................................................................................................................................................................................. 1 1.4.2 Proposed Implementation of “Reporting Requirement" Monitoring Program ............................................................. 2 1.4.3 Piezometer Monitoring Program ......................................................................................................................................... 2 1.4.4 Piezometer and Weir Cross Plots ........................................................................................................................................ 2 1.4.5 "Short Term" and "Long Term" Time Series Plots ............................................................................................................ 2 1.4.6 Action Levels ........................................................................................................................................................................ 2 1.4.7 Updated Action Levels ......................................................................................................................................................... 3 2.0 SEISMIC, SEEPAGE or OTHER SIGNIFICANT EVENTS, and OTHER CHANGES ...................................................... 3 2.1 Noteworthy Seismicity ................................................................................................................................................................ 4 2.2 Noteworthy Seepage .................................................................................................................................................................... 4 2.3 Other Events................................................................................................................................................................................. 4 2.4 Other Changes.............................................................................................................................................................................. 4 2.4.1 Tailwater and Headwater Alarms ........................................................................................................................................ 4 2.4.2 Tabulated Action Level Values ........................................................................................................................................... 5 2.4.3 Implemented Earthquake Assessment Software ShakeCast .............................................................................................. 5 3.0 RESERVOIR OPERATION ........................................................................................................................................................... 5 3.1 Reservior Restriction ................................................................................................................................................................... 5 3.2 Annual Reservoir Level .............................................................................................................................................................. 5 4.0 MONITORING DATA and ANALYSIS ....................................................................................................................................... 6 4.1 General ......................................................................................................................................................................................... 6 4.2 Presentation of Data..................................................................................................................................................................... 7 4.3 Treatment of Outlier Data ........................................................................................................................................................... 7 4.5 Piezometer Data ........................................................................................................................................................................... 8 4.5.1 General .................................................................................................................................................................................. 8 4.5.2 Original Pneumatic and Open Well Piezometers .............................................................................................................. 9 4.5.3 Pneumatic and Open Well Piezometer Data ..................................................................................................................... 10 4.5.4 Vibrating Wire Piezometers .............................................................................................................................................. 11 4.5.5 Vibrating Wire Piezometer (VWP) Data........................................................................................................................... 12 4.5.6 Outlier Piezometric Data .................................................................................................................................................... 14 4.6 Spillway Underdrain System .................................................................................................................................................... 14 4.6.1 General ................................................................................................................................................................................ 14 4.6.2 Spillway Underdrain Flow Data ........................................................................................................................................ 15 4.6.3 Outlier Underdrain Data ..................................................................................................................................................... 16 4.7 Survey Monuments .................................................................................................................................................................... 16 4.7.1 General ................................................................................................................................................................................ 16 4.7.2 Crest Monument Survey Data............................................................................................................................................ 17 4.7.3 Outlier Crest Monument Survey Data ............................................................................................................................... 18 4.7.4 Spillway Training Wall Monuments ................................................................................................................................. 18 4.7.5 Survey Data – Training Wall ............................................................................................................................................. 18 4.7.6 Outlier Training Wall Monument Survey Data ................................................................................................................ 19 4.8 In-Place Inclinometer Sensors (IPIs) ........................................................................................................................................ 19 4.8.1 In-Place Inclinometer Sensor (IPIs) Data ......................................................................................................................... 20 4.8.2 Outlier In-Place Inclinometer Data ................................................................................................................................... 21 4.9 U.S.G.S. and District Strong Motion Accelerometers ............................................................................................................ 21 4.9.1 U. S. Geological Survey Accelerometers .......................................................................................................................... 21 4.9.2 District Accelerometer ....................................................................................................................................................... 21 5.0 VISUAL INSPECTIONS .............................................................................................................................................................. 22 5.1 DSOD Inspection ....................................................................................................................................................................... 22 5.2 Other District Inspections ......................................................................................................................................................... 22 6.0 CONCLUSIONS and RECOMMENDATIONS.......................................................................................................................... 22 6.1 Conclusions ................................................................................................................................................................................ 22 6.2 Recommendations for Next Surveillance Period ..................................................................................................................... 23 7.0 MONITORING REFERENCES ................................................................................................................................................... 23 v 2013 Surveillance Report December 2012 – December 2013 Leroy Anderson Dam No. 72-9 TABLE OF CONTENTS (cont.) TABLES Table No. Title In Body of Text 1 – Locations of Vibrating Wire Piezometers, Pneumatic and Open Well Piezometers page 9 2 – Recent Piezometer Data – Non ADAS Read Piezos page 11 3 – Recent Piezometer Data –Vibrating Wire Piezometers pages 12 & 13 4 – Recent Weir Discharge Data – Spillway Underdrains page 15 5 – Vertical and Local Transverse Data – Crest and Abutment Monuments page 17 6 – Vertical Displacement Data, Spillway Training Wall Monuments page 19 7 – Locations of In-place Inclinometer Sensors (IPIs) page 20 FIGURES Figure No. Title Following Body of Report 1. Topographic Map, Surveillance Instrumentation Leroy Anderson Dam 2. Cross Section A-A’ 3. Cross Section B-B’ 4. Longitudinal Cross Section C-C’ 5. Daily Reservoir Elevation and Rainfall 2006-2013 6. Long and Short Term Piezometric Data – Pneumatic and Open Wells – Embankment & Downstream Foundation 7. Long and Short Term VW Piezometer Data Section A-A’ – Embankment 8. Long and Short Term VW Piezometer Data Section B-B’ – Embankment 9. Long and Short Term VW Piezometer Data Section C-C’ – Embankment 10. Long and Short Term VW Piezometric Data – Foundation 11. Long and Short Term VW Piezometric Data – Transition Zones 12. Long and Short Term Weir Discharge Data – Spillway Underdrains 13. Long and Short Term Local Vertical Displacement –Downstream and Upstream Crest Monuments 14. Long and Short Term Local Transverse Displacement – Downstream and Upstream Crest Monuments 15. Long and Short Vertical Displacements – Spillway Training Walls 16. Recent In-Place Crest Inclinometer Sensor Data 17. Regional Fault Map, Showing Noteworthy Earthquakes vi 2013 Surveillance Report December 2012 – December 2013 Leroy Anderson Dam No. 72-9 1.0 INTRODUCTION 1.1 Scope and Purpose The focus of this report is to provide a summary of our review of the annual monitoring data collected by the surveillance instrumentation at Leroy Anderson Dam, No. 72-9, from December 2012 through December 2013, and to make assessments of general data trends. If any significant geotechnical or operational events have occurred (i.e., earthquakes, sustained elevated reservoir levels, significant operational or maintenance changes, or dam instrumentation/monitoring changes), these are addressed as soon as possible after detection and summarized in this report. This report provides historic long-term data plots (since the installation date of sensor) and short- term plots (~ 5 years) of instrument readings. The reader is referred to previous reports for earlier data plots and observations. 1.2 DSOD’s Comments on Previous Report Our annual surveillance reports address comments by DSOD on surveillance reporting from the last DSOD field inspection report, or other dam related issues. During the current reporting period DSOD performed an annual inspection of Anderson Dam on April 22, 2013. According to their latest inspection report dated May 8, 2013, DSOD (2013) stated that “The available instrumentation data indicates the dam is performing satisfactorily. No additional instrumentation is deemed necessary at this time.” 1.3 Anderson Dam Seismic Retrofit Project (ADSRP) Design Consultant The Anderson Dam Seismic Retrofit Project (ADSRP) is currently in the design phase. URS is the District’s design consultant. Completion of design is expected by 2015 and construction is expected to be completed by 2018. 1.4 Changes to Surveillance Report 1.4.1 General Based on input from DSOD we have made several changes to this report involving data presentation and analysis. Specific details of changes made to this report are summarized in this section. We intend to make appropriate additional changes in future reports to further optimize data review. Despite the changes to the reporting format, the District will continue to internally review and evaluate all active instrumentation and data under all conditions on a monthly basis. The District will also continue our periodic inspections, and will keep DSOD informed of any significant changes pertaining to surveillance or performance of the dam. The following sections present our modified approach. 1 2013 Surveillance Report December 2012 – December 2013 Leroy Anderson Dam No. 72-9 1.4.2 Proposed Implementation of “Reporting Requirement Monitoring Program” (RRMP) During a teleconference on Thursday July 11, 2013, the District and DSOD discussed details of the Reporting Requirement Monitoring Program (RRMP) for District Dams that attempts to reduce the number of reported data and expedite review of relatively large amounts of surveillance data. The July 11 discussion focused primarily on monitoring at Stevens Creek Dam. Consequently, the District used the general discussion of requirements taken from Stevens Creek and applied them to all District Dams where applicable. In this section we provide details for establishing an RRMP for Anderson Dam sensors. At some dams there are more than enough sensors (i.e. piezometers, discharge weirs, survey monuments, in-place inclinometers) to adequately characterize site conditions and dam performance. With DSOD concurrence, the program will aid review of overall dam performance by eliminating redundant or less critical sensors reported in the annual surveillance reports, unless we detect some noteworthy trends that warrant notification of DSOD. The Reporting Requirement program does not affect the District's internal review process. The District will continue to plot and review all surveillance data. For Anderson Dam the only anticipated change is that plots of in-place inclinometers will not be provided in the annual surveillance reports and discussed in Section 6.2.1 No Longer Provide Plots of In-Place Inclinometer Data. 1.4.3 Piezometer Monitoring Program We will continue to monitor and report on all of the existing piezometers in the embankment and foundation in this and future annual surveillance reports. 1.4.4 Piezometer and Weir Cross Plots As discussed, to streamline the surveillance report review process, and as requested by DSOD, we will no longer include piezometer and weir cross plots in our surveillance reports. However, the District will continue to internally produce and review cross plots as part of our regular monthly review of surveillance data. 1.4.5 "Short Term" and "Long Term" Time Series Plots To comply with a DSOD request, the District will provide two types of time-series plots in annual surveillance reports. During a recent telecom on July 11, 2013, DSOD engineers Andy Mangney and Bill Vogler indicated DSOD prefers dual plots, which consist of a "short term" plot, that shows data trends over the last ~5-years, and a "long term" plot that shows historic data trends during the entire life of the sensor. 1.4.6 Action Levels The District previously developed and plotted Action Levels in the 2012 report (Nelson, 2012) based on historic data for each monitoring instrument. Based on input from DSOD, we have reviewed and revised the definition and determination of 2012 Action Levels. Revised Action Levels values will be provided in this report and will be updated in future reports as needed. 2 2013 Surveillance Report December 2012 – December 2013 Leroy Anderson Dam No. 72-9 1.4.7 Updated Action Levels Updated Piezometric Action Levels - Based on input from DSOD and to aid in evaluating the ongoing performance of Anderson Dam, we will now use an appropriate “design” maximum phreatic line(s) in the maximum section through the dam (Figure 3) to define Action Levels representative of the upper/maximum/design condition. The objective for ongoing dam safety surveillance reviews is to compare the maximum excursion of the phreatic surfaces during any given year from piezometer data, to the design phreatic line. For the first time in this report, we provide Action Level values for each sensor at the bottom (yellow shading) the respective table (Tables 2 through 7). The 1996 stability analysis of record for establishing the phreatic surface is herein considered to be the third Part 12D Safety Inspection and Report by R.L. Volpe & Associates (1997). The phreatic surface from sections developed in 1996 by R.L. Volpe & Associates (1997) for stability analysis is shown in Figures 2 and 3. The GEI evaluation of thresholds values and action levels (GEI, 2009) are based on the R.L. Volpe & Associates analysis. Also, for this report we added approximate equipotential lines developed by GEI (2009) to Figures 2 and 3. Action Levels of Piezometers – We have elected to use single value Action Levels for the piezometers as summarized on the bottom of Tables 2 and 3 in yellow highlight (pages 11, 12, and 13). These are based on an estimated projection of the historic maximum at the 2011 reservoir elevation restriction of ~602.3 feet. Updated Spillway Underdrain Weir Action Levels – We have elected to use a single value of ~172 gpm for the new Action Level for total underdrain discharge from weirs No. 1 and No. 2 at the left terminus of the spillway chute as summarized in Table 4 in yellow highlight (page 15). This is based on an estimated projection of the historic maximum at the reservoir elevation restriction ~602.3 feet. Updated Survey Action Levels – The District did not update the +0.05 feet Action Level values for the annual monitored survey monument movement data from Anderson Dam crests as shown on Table 5, page 17. This Action Level is the current value for all District Dams. Updated In-Place Inclinometer Action Levels – The District did not update the +0.05 feet Action Level values for the in-place inclinometer movement data from Anderson Dam as shown on Table 7, page 20. This Action Level is the current value for all District Dams. Remainder of Page Intentionally Left Blank 3 2013 Surveillance Report December 2012 – December 2013 Leroy Anderson Dam No. 72-9