ENGINEERING GEOLOGY AND GEOTECHNICAL ENGINEERING REPORT FOR REPLACMENT WATER TANKS AT WELL SITE 31C/31D, AND WELL SITE 32, TAPO CANYON AREA, VENTURA COUNTY, CALIFORNIA PROJECT NO.: 303079-001 MAY 16, 2019 (REVISED SEPTEMBER 18, 2019) PREPARED FOR CANNON ASSOCIATES BY EARTH SYSTEMS PACIFIC 1731-A WALTER STREET VENTURA, CALIFORNIA Earth Systems 0 1731 Walter Street, Suite A I Ventura, CA 93003 I Ph : 805.642 .6727 I www.earthsystems. com May 16, 2019 Project No.: 303079-001 (Revised September 18, 2019) Report No.: 19-5-45 Attention: Eric Porkert Cannon Associates 11900 West Olympic Boulevard, Suite 530 Los Angeles, CA 90064 Project: Replacement Water Tanks Well Site 31C/31D and Well Site 32 Tapo Canyon Area Ventura County, California As authorized, we have performed a geotechnical study for proposed water tanks that would replace aging existing tanks servicing Well Site 31C/31D and Well Site 32 in the Tapo Canyon area of Ventura County, California. The accompanying Engineering Geology and Geotechnical Engineering Report presents the results of our subsurface exploration and laboratory testing programs, as well as our conclusions and recommendations pertaining to geotechnical aspects of project design. This report completes the scope of services described within our Proposal No. VEN -19-02-008 dated February 15, 2019, and authorized by Cannon Standard Task Orders dated May 13, 2019. We have appreciated the opportunity to be of service to you on this project. Please call if you have any questions, or if we can be of further service. Respectfully submitted, EARTH SYSTEMS PACIFIC Engineering Geologist Geotechnical Engineer Copies: 4 - Eric Porkert (3 via US mail, 1 via email) 1 - Project File TABLE OF CONTENTS INTRODUCTION ............................................................................................................................... 1 PURPOSE AND SCOPE OF WORK .................................................................................................... 1 GEOLOGY ................. ........................................................................................................................ 2 GEOLOGIC HAZARDS ............................ ......................................................... ... .... ........................... J SEISMIC SHAKING ................................................................................................................ 3 FAULT RUPTURE ................ ................................................................................................... 6 LANDSLIDING AND ROCK FALL ............................................................................................. 7 LIQUEFACTION ..................................................................................................................... 7 SEISMIC-INDUCED SETTLEMENT OF DRY SANDS ................................................................. 7 FLOODING ............................................................................................................................ 8 SOIL CONDITIONS AT WELL SITE 31C/31D .................................................... ................................. 9 SOIL CONDITIONS AT WELL SITE 32 ................................................. ........... .... ................................ 9 GEOTECHNICAL CONCLUSIONS AND RECOMMENDATIONS ............................ ........................... 10 GRADING ............................................................................................................................ 12 Pre-Grading Considerations ................................................................................... 12 Rough Grading Recommendations ........................................................................ 12 Excavations ............................................................................................................ 13 Utility Trenches .............................................................................. ........................ 14 STRUCTURAL DESIGN ......................................................................................................... 15 Ring Foundations ................................................................................................... 15 Mat Foundations ..................................................................................................... 15 Frictional and Lateral Coefficients ......................................................................... 17 Settlement Considerations .................................................................................... 17 ADDITIONAL SERVICES .................................................................................................................. 19 LIMITATIONS AND UNIFORMITY OF CONDITIONS ....................................................................... 20 AERIAL PHOTOGRAPHS INTERPRETED FOR THIS STUDY ............................................................. 21 BIBLIOGRAPHY .............................................................................................................................. 21 APPENDIX A Vicinity Map Regional Geologic Map Seismic Hazard Zones Map Historic HighGroundwater Map Field Study Geologic Maps Geologic Cross-Sections Logs of Exploratory Borings EARTH SYSTEMS TABLE OF CONTENTS {Continued) APPENDIX B Laboratory Testing Laboratory Test Results Table 1809.7 APPENDIX C 2016 CBC & ASCE 7-10 Seismic Parameters US Seismic Design Maps Fault Parameters APPENDIX D Analyses of Liquefaction and Seismic-Induced Settlement of Dry Sands EARTH SYSTEMS May 15, 2019 1 Project No.: 303079-001 (Revised September 18, 2019) Report No.: 19-5-45 INTRODUCTION This report presents results of an Engineering Geology and Geotechnical Engineering study performed for two proposed bolted steel water tanks in the Tapo Canyon area of Ventura County, California (see Vicinity Map in Appendix A). We understand that a 25,000-gallon, 15.5-foot diameter, 16-foot high tank would replace an existing tank near Simi Wells 31C and 31D, and replace an existing tank near Simi Well 32. The aging existing tanks will be demolished as part of the proposed project. Given the 16-foot height of both proposed tanks, and a relatively light roof load, total loads generated by the fully loaded tanks are expected to range up to about 1,200 psf. If actual loads vary significantly from these assumed loads, Earth Systems should be notified since reevaluation of the recommendations contained in this report may be required. The tanks will be situated on existing pads; thus, grading is expected to be limited to preparing near-surface soils to support the new loads generated by the tanks. The tanks are planned to be designed in accordance with current AWWA standards. PURPOSE AND SCOPE OF WORK The purpose of the geotechnical study that led to this report was to analyze the geology and soil conditions of the site with respect to the proposed improvements. These conditions include potential geohazards, surface and subsurface soil types, expansion potential, settlement potential, bearing capacity, and the presence or absence of subsurface water. The scope of work included: 1. Reconnaissance and geological mapping of the site. 2. Reviewing aerial photographs taken ofthe site and surrounding areas on October 26, 1945 by Fairchild Aerial Surveys, Inc. 3. Reviewing pertinent geologic literature. 4. Drilling, sampling, and logging two hollow-stem auger borings at each tank site to study geologic, soil, and groundwater conditions. 5. Laboratory testing of soil samples obtained from the subsurface exploration to determine their physical and engineering properties. 6. Consulting with owner representatives and design professionals. EARTH SYSTEMS May 15, 2019 2 Project No.: 303079-001 (Revised September 18, 2019} Report No.: 19-5-45 7. Analyzing the geotechnical data obtained. 8. Preparing this report. Contained in this report are: 1. Descriptions and results of field and laboratory tests that were performed. 2. Discussions pertaining to the local geologic, soil, and groundwater conditions. 3. Conclusions pertaining to geohazards that could affect the site. 4. Conclusions and recommendations pertaining to site grading and structural design. GEOLOGY The site lies within the Simi Hills, which in turn lie within the western Transverse Ranges. The Simi Hills and the Transverse Ranges are characterized by ongoing tectonic activity. In the vicinity of the subject sites, Tertiary and Quaternary sediments have been folded and faulted along predominant east-west structural trends. Although there are several faults located within the region, the nearest known fault of significant activity (i.e. the Santa Susana Fault} is located approximately 4,000 feet north of the subject sites. The project area is not located within any of the "Fault Rupture Hazard Zones" that have been specified by the State of California (C.D .M .G. 1972, Revised 1999). Near-surface soils underlying both sites are comprised of a combination of artificial fill materials over alluvial deposits. Fill soils consisting of gravelly sands were encountered in the upper 2 to 2.5 feet of the proposed tank area at Well Site 31C/31D, and to depths between 4 and 5 feet at Well Site 32. Alluvial deposits at both sites were found to be pale brown to grayish brown to dark brown sands with variable quantities of grave[. Bedrock underlying the alluvium is the Saugus Formation (QTs} of Plio-Pleistocene age. The Saugus Formation is comprised of units originating from a combination of shallow