CEMEX Eliot Quarry Geotechnical Characterization Report Alameda County, California May 7, 2015 CEMEX Eliot Quarry Geotechnical Characterization Report Alameda County, California May 7, 2015 Project No. GT13-16 Prepared for: CEMEX 5180 Golden Foothills, Parkway El Dorado Hills, California 95762 7400 Shoreline Drive, Ste. 6 Stockton, California 95219 Tel: 209-472-1822 Fax: 209-472-0802 www.kanegeotech.com THIS PAGE INTENTIONALLY LEFT BLANK KANE GeoTech, Inc. -ii- EXECUTIVE SUMMARY CEMEX Eliot Quarry Geotechnical Characterization Report Alameda County, California In response to Alameda County reclamation requirements for Eliot Quarry, CEMEX, Inc. was asked to assess the stability of pit slopes in the areas of Lakes A , B, and J. KANE GeoTech, Inc. was retained to perform the pit stability study under reclaimed conditions as presented in the CEMEX reclamation plan amendment. The study included drilling and logging 22 boreholes, performing in-situ and laboratory testing for geomaterial strength parameters, and analyzing slope stability using current standard of practice methods for static and seismic conditions following the guidelines set forth in the California Geological Survey’s 2008 Special Publication 117A. The Safety Factor is the ratio of the resistance that can be mobilized to the driving forces that would cause a failure. Geomaterials have an inherent strength called shear strength to resist failure. Characteristics in slopes that govern the driving forces are the weight of the geomaterials, slope and strata angles, the presence of water, and accelerations due to a seismic event. For slope stability in general, a Safety Factor of 1.5 for static and 1.0 for seismic conditions are accepted as standard-of-practice minimum values. A safety factor higher than the minimum is not a guarantee that slope failure is impossible. However, it does indicate that the possibility has been found from experience to be negligible. For seismic conditions, a pseudo-static approach is used in which the weight of the material is increased by a seismic coefficient to simulate the effects of additional ground acceleration. The Standard of Practice is described in “2008 Guidelines for Evaluating and Mitigating Seismic Hazards in California” Special Publication 117A, California Department of Conservation. A seismic coefficient of 0.21 was prescribed for Lake A and 0.16 for Lake B. Because of Lake J’s close proximity to Stanley Boulevard, the conservative 0.21 seismic coefficient was utilized for the analyses. The required factors of safety under static and seismic conditions are achieved when slopes are at a 2H:1V with the exception of slopes in Lake J which would need to transition to a 3H:1V gradient at 150-ft MSL for the final 20-ft of mining to 130-ft MSL. Current plans do not call for Lake A to be mined. There are five documents contained in this project submittal. They are: 1. Geotechnical Characterization Report. This document which describes all the geotechnical background information used in preparation of the analyses. 2. Geotechnical Characterization Appendices. The Appendices document contains all available laboratory information for the geotechnical investigations in the Chain of Lakes. It also contains copies of all reports, technical memos, and maps related to the lakes. 3. Lake A Focus Report. This report contains the results of the analyses for Lake A. 4. Lake B Focus Report. This report contains the results of the analyses for Lake B. 5. Lake J Focus Report. This report contains the results of the analyses for Lake J. KANE GeoTech, Inc. THIS PAGE INTENTIONALLY LEFT BLANK KANE GeoTech, Inc. -iv- TABLE OF CONTENTS EXECUTIVE SUMMARY. -iii- TABLE OF CONTENTS. -v- 1. INTRODUCTION.. 1 1.1 Purpose. 2 1.2 Scope of Work. 2 2. SITE DESCRIPTION.. 3 2.1 General.. 3 2.2 Site Geology. 3 2.2.1 Site Lithology. 3 2.2.2 Site Hydrogeology. 4 3. BACKGROUND.. 12 4. GEOTECHNICAL INVESTIGATION. 19 4.1 Field Study. 19 4.2 Laboratory Study. 23 4.3 Slope Stability Analyses. 23 4.4 Review of Slope Stability Methods Used in Analyses.. 25 4.4.1 Simplified Bishop Method. 25 4.4.2 Sarma Method.. 25 4.5 Seismic Analysis.. 26 4.5.1 Special Publication 117A (SP117A) Criteria. 26 4.5.2 Seismic Analysis Method. 27 5. RESULTS. 33 6. SUMMARY OF WORK PERFORMED BY KANE GEOTECH.. 33 7. CONCLUSIONS AND RECOMMENDATIONS. 34 8. REFERENCES & BIBLIOGRAPHY.. 34 9. LIMITATIONS. 38 -v- KANE GeoTech, Inc. THIS PAGE INTENTIONALLY LEFT BLANK KANE GeoTech, Inc. -vi- 7400 Shoreline Drive, 1441 Kapiolani Boulevard, Suite 6 Suite 1115 Stockton, California 95219 Honolulu, Hawaii 96814 209-472-1822 Phone 209-472-0802 Fax 808-356-2668 Phone [email protected] www.kanegeotech.com CEMEX Eliot Quarry Geotechnical Characterization Report Alameda County, California Project No. GT13-16 1. INTRODUCTION KANE GeoTech, Inc. (KANE GeoTech) was retained by CEMEX, Inc. (CEMEX) to investigate Eliot Quarry, Livermore, California. This report was prepared by KANE GeoTech for its client, CEMEX of El Dorado Hills, California, to provide information on the assessment of the stability of the slopes of the quarry. CEMEX is proposing a reclamation plan amendment which will take place in Lakes A, B, and J, Figure 1. It is noted that Lakes A and B will be the a part of the Chain of Lakes system controlled by the Alameda County Flood Control and Water Conservation District, Zone 7. Lake J is included in the reclamation plan, but will not be a part of the Chain of Lakes. Figure 1. Air photo of the Chain of Lakes complex in Livermore, California. CEMEX Eliot Quarry Geotechnical Characterization Report Alameda County, California Page 2 The quarry is located between Stanley Boulevard and the Arroyo Del Valle. Lakes A and B are transected by Isabel Avenue. Access to the quarry is located on Stanley Boulevard which is adjacent to Lake J and parallels Arroyo Del Valle. Figures 1 and 2 show the location of the CEMEX Eliot Quarry. This Report reflects the reviews and comments by the County of Alameda’s geotechnical reviewer, ENGEO, Inc. (ENGEO) of San Ramon, California. Figure 2. Project location near San Francisco, California. 1.1 Purpose The purpose of this report is to provide the background information and results of all of the prior studies, field testing, and lab analyses that are used in the Lake Evaluation Reports at Eliot Quarry (KANE GeoTech, 2015a, 2015b, 2015c). The Lake Evaluation Reports are where the results of the slope stability analyses are presented for each lake. 1.2 Scope of Work The scope of services provided by KANE GeoTech included the following: 1. Literature Review. KANE GeoTech reviewed existing literature and other archived materials such as geotechnical investigations, maps, and aerial images. CEMEX made available previous reports and exploration drill logs for the site. A stratigraphic history of the area was constructed and used to interpret the depositional environment of the Livermore Formation. 2. Geotechnical Investigation. CEMEX retained a drilling contractor to drill and sample the site. KANE GeoTech performed pocket penetrometer strength testing and collected grab samples for further analyses. Split spoon tests were obtained by the driller at locations and depths determined by KANE GeoTech in the field depending on the strata encountered. 3. Materials Testing. Laboratory testing was performed on samples to evaluate moisture content and density, Atterberg limits, grain size, USCS identification, and shear strength. KANE GeoTech, Inc. CEMEX Eliot Quarry Geotechnical Characterization Report Alameda County, California Page 3 4. Engineering Analyses. Final slope configurations were analyzed for stability using standard of practice analyses tools including slope stability analysis software. 5. Report of Findings. KANE GeoTech provides this Report of Findings stamped by a licensed California civil engineer experienced in slope stability. This Geotechnical Characterization Report contains background information and results of all of the prior studies, field testing, lab analyses used in the Lake Evaluation Reports, and an explanation of the data for each lake to conduct the slope stability analyses consistent with standards of practice (2015a, 2015b, 2015c). An Appendix is included as a separate document with all supporting documentation. The three Lake Evaluation Reports contains a summary of each investigation, analyses results, calculated safety factors for the slopes, and conclusions. 2. SITE DESCRIPTION 2.1 General Eliot Quarry is located at latitude 37E39'19" N, longitude 121E48' 20" W, Alameda County, California, in the Altamont 7½’ Geologic Quadrangle. Surface elevations along Lakes A, B, and J vary between 380-ft and 450-ft MSL. The nearest fault is the Las Positas fault located about two miles to the southeast. The nearest major fault is the Greenville Fault (about 11.5-mi to the southwest. The pit slopes are generally bare and covered with light vegetation in places. Eucalyptus trees are adjacent to the slopes at some locations. 2.2 Site Geology 2.2.1 Site Lithology The original surficial soil mapping was completed by the Soil Conservation Service (SCS, 1957) as mostly Holocene with some Pleistocene and Pliocene Alluvium. The Holocene and Pleistocene epochs are the most recent geologic time periods. Alluvium is a geologic term for material that has been deposited by flowing water, usually caused by large storm events, and often contains clay, silt, sand, and gravel. Flowing water transports the sediment from high to low topographic areas, where the stream energy is dissipated, depositing the sediment. Geologic deposits are described by their relative age to surrounding earth materials. A detailed investigation of ground water in the Livermore and Sunol Valleys was performed by Department of Water Resources (DWR) (1966). The investigation was conducted by the DWR and gave a detailed description of the Livermore Valley’s lithology. The report further explained the characteristics of the Upper and Lower Livermore gravels, as well as the overlying Quaternary Alluvium.