Report of Findings on the Overtopping and Embankment Breach of the Upper Dam - Taum Sauk Pumped Storage Project, FERC No. 2277 FERC Taum Sauk Investigation Team April 28 2006 - 2 - Table of Contents Preface i Executive Summary Section 1 Project Description........................................................................................- 9 - 1.1 General..........................................................................................................- 9 - 1.2 Dams .............................................................................................................- 9 - 1.2.1 Upper Dam....................................................................................................- 9 - 1.2.2 Lower Dam .................................................................................................- 10 - 1.3 Gravel Trap Dam ........................................................................................- 11 - 1.4 Spillways.....................................................................................................- 12 - 1.4.1 Upper Dam Spillway...................................................................................- 12 - 1.4.2 Lower Dam Spillway ..................................................................................- 12 - 1.5 Powerhouse.................................................................................................- 12 - 1.6 Intake and Outlet Works .............................................................................- 12 - 1.6.1 Upper Dam Outlet Works ...........................................................................- 12 - 1.6.2 Lower Dam Outlet Works...........................................................................- 13 - 1.7 Standard Operating Procedures...................................................................- 13 - Section 2 Project History ............................................................................................- 16 - 2.1 History of Construction of the Upper Reservoir Dam................................- 16 - 2.2 Geology.......................................................................................................- 16 - 2.2.1 Geology of Southeast Missiouri..................................................................- 16 - 2.2.2 Upper Reservoir Geology ...........................................................................- 19 - 2.2.3 Breach Foundation Geology .......................................................................- 21 - 2.2.4 Geology of Johnson’s Shut-Ins State Park..................................................- 27 - 2.3 Design and Stability....................................................................................- 28 - 2.3.1 Embankment Design and Stability Analysis...............................................- 28 - 2.3.2 Parapet Wall Design and Stability ..............................................................- 28 - 2.4 Geomembrane Design.................................................................................- 33 - Section 3 Historical Performance of Upper Reservoir ...............................................- 34 - 3.1 Settlement ...................................................................................................- 34 - 3.2 Crest Elongation..........................................................................................- 37 - 3.3 Vertical Deflections of Parapet Wall ..........................................................- 38 - 3.4 Parapet Wall Horizontal Panel Misalignment at Joints ..............................- 38 - 3.5 Parapet Wall Cracking ................................................................................- 39 - 3.6 Leakage.......................................................................................................- 40 - Section 4 Post Breach Survey and Estimates of Overtopping ....................................- 43 - 4.1 Post Breach Survey and Estimate of Overtopping......................................- 43 - 4.1.1 Estimate of Peak Pool Elevation from Parapet Wall Elevations ................- 43 - 4.1.2 Estimate of Volume Overpumped on December 14, 2005.........................- 45 - 4.2 Damage on Downstream Slope...................................................................- 46 - - 3 - Section 5 Instrumentation and Controls......................................................................- 54 - 5.1 General........................................................................................................- 54 - 5.2 Instrumentation History ..............................................................................- 54 - 5.3 Description of Instrument Structural Support System................................- 55 - 5.4 Upper Reservoir Overpumping Emergency Control ..................................- 56 - 5.5 Pre-Breach Events – Indication of Problems with Reservoir Monitoring System.........................................................................................................- 58 - 5.5.1 September 2005 - Wave Overtopping.........................................................- 58 - 5.5.2 October 2005 – Deterioration of Instrument Structural Support System ...- 59 - 5.6 Programming Logic Controls for the Upper Reservoir Controls and Emergency Controls....................................................................................- 60 - 5.7 Post Breach Inspection of Instrumentation and Analysis of Operations Data.... .....................................................................................................................- 65 - 5.7.1 Bowing in HDPE Tubes..............................................................................- 65 - 5.7.2 High Water Marks on the HDPE Pipes.......................................................- 66 - 5.7.3 Comparison of Penstock Transducer and Druck Pressure Transducer.......- 68 - 5.7.4 Assessment of the Reservoir Level Indicator Readings versus the Pump Back Times on December 13th and 14th, 2005 of Taum Sauk .............................- 72 - 5.7.5 Druck Pressure Transducers - Signal Variability........................................- 75 - 5.7.6 Evaluation of Extended Seepage Pond Pump Back Times for September – December 2005 ...........................................................................................- 79 - 5.7.7 Seepage Collection - Pump Back Operation December 7 and 8, 2005. .....- 80 - Section 6 Taum Sauk Upper Reservoir Breach Time Line.........................................- 83 - Section 7 Meteorology..............................................................................................- 101 - 7.1 General......................................................................................................- 101 - 7.2 September 25, 2005 ..................................................................................- 101 - 7.3 September 27, 2005 ..................................................................................- 103 - 7.4 December 14, 2005 ...................................................................................- 104 - Section 8 Hydrology and Hydraulics........................................................................- 105 - 8.1 Upper Dam................................................................................................- 105 - 8.1.1 Drainage Area/Surface Area/Storage........................................................- 105 - 8.1.2 Flood of Record ........................................................................................- 105 - 8.1.3 Inflow Design Flood .................................................................................- 105 - 8.1.4 EAP Dam Break Analysis.........................................................................- 105 - 8.1.5 Actual Dam Breach Parameters................................................................- 107 - 8.1.6 Outflow hydrograph generation................................................................- 108 - 8.1.7 Wave Height Estimates.............................................................................- 111 - 8.1.8 Velocity of Flows over Parapet Walls ......................................................- 114 - 8.1.9 Estimated Outflow for Loss of One Section of Parapet Wall...................- 114 - 8.2 Lower Dam ...............................................................................................- 115 - 8.2.1 Drainage Area/Surface Area/Storage........................................................- 115 - 8.2.2 Spillway Curve..........................................................................................- 115 - 8.2.3 Flood of Record ........................................................................................- 116 - 8.2.4 Inflow Design Flood .................................................................................- 116 - 8.2.5 Freeboard Adequacy .................................................................................- 117 - 8.2.6 EAP Dam Break Analysis.........................................................................- 117 - - 4 - 8.2.7 Maximum Lower Reservoir Level Following Upper Reservoir Breach ..- 118 - Section 9 Stability Analysis......................................................................................- 120 - 9.1 Utexas4 Embankment Stability Analysis..................................................- 120 - 9.1.1 Reconstruction of the Embankment Section.............................................- 120 - 9.1.2 Original downstream slope angle..............................................................-