Dingee Reservoir Final Seismic Report - East Bay Municipal Utility ...

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The Dam has a crest level at approximately Elevation 773.5 feet above Mean Sea Level (MSL) (National Geodetic Vertical Datum, 1929) with a crest width of 15 feet, a maximum height of about 18 feet, and a storage capacity of approximately 4.2 million gallons at the overflow elevation of 772 feet. The dam fill materials consist of excavated material from Franciscan Sandstone and Shale. The upstream slope of the dam embankment has a slope of about 2 Horizontal to 1 Vertical. The maximum downstream slope of the dam embankment has a slope of about 1.3 Horizontal to 1 Vertical. The reservoir basin floor is at Elevation 755.9 feet. The maximum depth of the reservoir is approximately 16 feet. 2.3 Reservoir Outlet and Drainage Since 1999, the reservoir has been operated with the water surface typically ranging from Elevation 764 feet to 768 feet. In 2007, an additional drain valve was installed on Estates Drive to allow periodic drain valve exercises. Reference drawing 6318-G in Appendix C shows the overflow and drain system improvements. 2.3.1 Emergency Spillway Structure The spillway structure is located near the southwest corner of the reservoir close to the left abutment of the dam. The spillway consists of a 1-foot by 2-foot drop-inlet-box. This structure is designed to discharge water in emergencies into a 10-inch wrought iron pipe, which leads to the old 10-inch outlet pipe. Spillway flow is transferred through a 12-inch cast iron pipe to a catch basin, and eventually drains into the storm drain. The 1939 construction improvements included a new location for the overflow, and the old 10-inch outlet line was converted for use as a drain-overflow pipe. The time required to drain the reservoir is approximately 13 hours. 2.3.2 Reservoir Lining In 1931, a new lining was placed over the old lining. The 1931 lining consisted of a 3-inch gunite lining reinforced with 4-inch x 4-inch #10 mesh overlying approximately 2 feet of pneumatically tamped fill, which separates the old and new linings. 2.3.3 Surface Drainage Facilities The surface drainage facilities, which primarily collect rainfall runoff from the reservoir roof, consist of V-Ditches with drop inlets and storm drain pipes around the reservoir perimeter. Rainfall on the roof runs off either east or west to the paved perimeter access road. The runoff flows across the access road to the V-Ditches and enters the drop inlets and the storm drain pipes which are connected to the City of Oakland storm drain system. Reference drawing 5553-G in Appendix C shows the drainage improvements, which included installation of perimeter V- Ditches and drop inlets that were made to the site in 1969. Seismic Stability Evaluation Report Dingee Reservoir Dam 4 August 2008
3.0 Geotechnical Exploration and Laboratory Testing The geotechnical exploration program consisted of exploratory borings for subsurface investigation and installation of a new inclinometer. The laboratory testing program consisted of index and strength tests on the subsurface materials. 3.1 Review of Existing Information To develop the field exploration program, we reviewed available geotechnical data from the following reports and documents: U.S. Geological Survey Geologic Map published in 1969. U.S. Geological Survey Landslide Map published in 1975. Alquist-Priolo Special Studies Zones Map published in 1982. 1971 District piezometer boring logs and laboratory testing. 3.2 Field Exploration Program 3.2.1 Previous Investigations In 1971, the District drilled several geotechnical borings in and around the dam. Open standpipe piezometers were constructed at boring locations XV-1, 2, 3, and 8 upon completion of the borings. Plate 5808-G-2 in Appendix C, shows the locations of the previous borings/piezometers installed by District staff. Plate 5808-G-3 shows the stick logs of the borings. Analysis performed by the District in 1971 concluded that the reservoir is stable under long-term (static) and short term (earthquake and rapid drawdown) loading conditions. In 1991, Alan Kropp & Associates performed an investigation at 6045 Estates Drive, west of the dam fill. Laboratory index test results preformed for the previous investigations included: in-situ moisture contents and dry unit weights of the dam fill and of the foundation materials. The test results from these investigations are summarized on Table B-1 in Appendix B. Shear strength tests, including Unconfined Compression (UC) and Consolidated Undrained Triaxial Compression (TXCU) tests, were also performed for the previous investigations. The results of the previous shear strength tests are summarized on Plates B-3 and B-4 in Appendix B. Seismic Stability Evaluation Report Dingee Reservoir Dam 5 August 2008
Page 1 and 2: Seismic Stability Evaluation Report
Page 7 and 8: 1.0 Introduction 1.1 Background Thi
Page 9: 2.0 Project Description 2.1 Site Se
Page 13 and 14: advanced using a hollow stem auger.
Page 15 and 16: 3.3 Laboratory Testing Soil and roc
Page 17 and 18: 5.0 Subsurface Conditions Based on
Page 19 and 20: Native Material The in-situ moistur
Page 21 and 22: For slope stability analyses, both
Page 23 and 24: We have tabulated the results for b
Page 25 and 26: Table 8 Seismic Slope Stability Ana
Page 27 and 28: 8.0 Conclusions and Summary of Dam
Page 29 and 30: Mitigating Liquefaction Hazards in
Page 31 and 32: Reservoir Roof B A A’ XV-11 (Sta.
Page 33 and 34: DINGEE RESERVOIR DAM SEISMIC STABIL
Page 35 and 36: Elevation (Feet) 780 770 760 750 Re
Page 37 and 38: U-Line: PI =0.9*(LL-8) 60 50 40 30
Page 39 and 40: Total Density (PCF) 775.0 770.0 765
Page 41 and 42: 0.200 0.300 0.400 0.500 0.600 0.700
Page 43 and 44: 5000.0 4500.0 4000.0 3500.0 3000.0
Page 45 and 46: 5000.0 4500.0 4000.0 3500.0 3000.0
Page 47 and 48: 5000.0 4500.0 4000.0 3500.0 3000.0
Page 49 and 50: Material m (pcf) Dam Fill 126.8 Na
Page 51 and 52: Material m (pcf) sat (pcf) c (psf
Page 53 and 54: Material m (pcf) sat (pcf) C T (p
Page 55 and 56: 1.5 Displacement (ft) 1.0 0.5 Kobe
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Appendix B Laboratory Test Results
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2 62 63 64 65 66 67 68 69 70 71 72
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TABLE B-1 SUMMARY OF LABORATORY TES
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TABLE B-3 SUMMARY OF CONSOLIDATED U
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TABLE B-4 UNCONFINED COMRESSION TES
Page 109:
Appendix C Reference Drawings: LIST
Page 125 and 126:
Appendix E Ground Motion Studies Pa
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The next Generation Attenuation rel
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Table 1 Target Response Spectrum: A
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Figure 1. Median plus 1-sigma respo
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Figure Set 2 (cont.) PACIFIC ENGINE
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