AAPPPPEENNDDIIXX CC GGEEOOTTEECCHHNNIICCAALL EEXXPPLLOORRAATTIIOONN GEOTECHNICAL EXPLORATION 24765 HESPERIAN BOULEVARD HAYWARD, CALIFORNIA Submitted to: Mr. John Treble Three Cedars, LLC 1201 Howard Avenue, Suite 206 Burlingame, California 94010 Prepared by: ENGEO Incorporated January 11, 2016 Project No: 12684.000.0000 Copyright © 2016 by ENGEO Incorporated. This document may not be reproduced in whole or in part by any means whatsoever, nor may it be quoted or excerpted without the express written consent of ENGEO Incorporated. GEOTECHNICAL ENVIRONMENTAL WATER RESOURCES CONSTRUCTION SERVICES Project No. 12684.000.000 January 11, 2016 Mr. John Treble Three Cedars, LLC 1201 Howard Avenue, Suite 206 Burlingame, CA 94010 Subject: 24765 Hesperian Boulevard Hayward, California GEOTECHNICAL EXPLORATION Dear Mr. Treble: ENGEO prepared this geotechnical report for 24765 Hesperian Boulevard in Hayward, California. We characterized the subsurface conditions at the site to provide the enclosed geotechnical recommendations for design. Our experience and that of our profession clearly indicate that the risk of costly design, construction, and maintenance problems can be significantly lowered by retaining the design geotechnical engineering firm to review the project plans and specifications and provide geotechnical observation and testing services during construction. Please let us know when working drawings are nearing completion, and we will be glad to discuss these additional services with you. If you have any questions or comments regarding this report, please call and we will be glad to discuss them with you. Sincerely, ENGEO Incorporated Seema Barua, EIT Robert H. Boeche, CEG sb/rhb/bvv 6399 San Igancio Avenue, Suite 150 San Jose, CA 95119 (408) 574-4900 Fax (888) 279-2698 www.engeo.com Three Cedars, LLC 12684.000.000 24765 Hesperian Boulevard January 11, 2016 TABLE OF CONTENTS Letter of Transmittal 1.0 INTRODUCTION ......................................................................................... 1 1.1 PURPOSE AND SCOPE .......................................................................................1 1.2 SITE LOCATION AND DESCRIPTION ...........................................................1 1.3 PROPOSED DEVELOPMENT ...........................................................................1 1.4 HISTORICAL AERIAL PHOTOGRAPH AND HISTORICAL TOPOGRAPHIC MAP REVIEW ........................................................................2 2.0 GEOLOGIC CONDITIONS ........................................................................ 2 2.1 REGIONAL AND LOCAL GEOLOGY .............................................................2 2.2 REGIONAL FAULTING AND SEISMICITY ...................................................2 3.0 FIELD EXPLORATION ............................................................................... 3 3.1 FIELD LOGGING .................................................................................................3 3.1.1 Cone Penetration Tests ................................................................................3 3.2 SURFACE CONDITIONS ....................................................................................3 3.3 SUBSURFACE CONDITIONS ............................................................................3 3.4 GROUNDWATER CONDITIONS ......................................................................4 3.5 LABORATORY TESTING ..................................................................................4 4.0 GEOLOGIC AND GEOTECHNICAL HAZARDS ................................... 4 4.1 SEISMIC HAZARDS ............................................................................................4 4.1.1 Ground Rupture ...........................................................................................5 4.1.2 Ground Shaking ...........................................................................................5 4.1.3 Ground Lurching ..........................................................................................5 4.1.4 Soil Liquefaction ..........................................................................................5 4.1.5 Seismic-Induced Settlement Analyses .........................................................6 4.1.5.1 Liquefaction Settlement ................................................................6 4.1.5.2 Dynamic Densification Settlement ...............................................6 4.1.6 Liquefaction-Induced Surface Rupture ........................................................7 4.1.7 Lateral Spreading .........................................................................................7 4.2 EXISTING FILL ....................................................................................................7 4.3 EXPANSIVE SOIL ................................................................................................8 4.4 FLOODING ............................................................................................................8 4.5 2013 CBC SEISMIC DESIGN PARAMETERS .................................................8 4.6 SULFATE CONTENT AND CORROSIVITY ...................................................9 5.0 CONCLUSIONS .......................................................................................... 11 6.0 RECOMMENDATIONS ............................................................................. 11 6.1 GRADING ............................................................................................................11 6.1.1 Demolition and Stripping ...........................................................................11 Three Cedars, LLC 12684.000.000 24765 Hesperian Boulevard, Hayward January 11, 2016 TABLE OF CONTENTS (Continued) 6.1.2 Selection of Materials ................................................................................12 6.2 EXISTING FILL ..................................................................................................12 6.3 DIFFERENTIAL FILL THICKNESS ...............................................................12 6.4 OVER-OPTIMUM SOIL MOISTURE CONDITIONS ..................................13 6.5 SURFICIAL PAD TREATMENT......................................................................13 6.6 FILL PLACEMENT ............................................................................................13 6.7 GRADED SLOPES ..............................................................................................14 6.8 MONITORING AND TESTING........................................................................14 6.9 FOUNDATION DESIGN ....................................................................................14 6.9.1 Seismic Foundation Design Consideration ................................................15 6.9.2 Post-Tensioned Mat Foundation Design ....................................................15 6.9.3 Subgrade Treatment for Mat Foundations .................................................15 6.9.4 Moisture Vapor Reduction .........................................................................16 6.10 UTILITIES ...........................................................................................................16 6.11 SECONDARY SLAB-ON-GRADE CONSTRUCTION ..................................17 6.12 RETAINING WALLS .........................................................................................17 6.13 TEMPORARY EXCAVATIONS .......................................................................18 6.14 PAVEMENT DESIGN ........................................................................................19 6.14.1 Flexible Pavements ....................................................................................19 6.14.2 Rigid Pavements ........................................................................................19 6.14.3 Pavement Subgrade Preparation ................................................................20 6.15 DRAINAGE ..........................................................................................................20 6.16 STORMWATER INFILTRATION AND BIORETENTION AREAS ..........21 6.17 REQUIREMENTS FOR LANDSCAPING IRRIGATION .............................22 7.0 LIMITATIONS AND UNIFORMITY OF CONDITIONS ...................... 22 FIGURES APPENDIX A – Cone Penetration Tests (CPTs) APPENDIX B – Laboratory Test Data APPENDIX C – Liquefaction Analysis APPENDIX D – Supplemental Recommendations Three Cedars, LLC 12684.000.000 24765 Hesperian Boulevard January 11, 2016 1.0 INTRODUCTION 1.1 PURPOSE AND SCOPE The purpose of this geotechnical report, as described in our proposal dated November 24, 2015, is to provide design-level geotechnical recommendations associated with the proposed residential development of the site. We performed the following services: Review of available literature and geologic maps for the study area. Subsurface exploration consisting of three cone penetration test (CPT) soundings. Near-surface sampling and testing. Geotechnical data analyses. Report preparation summarizing our conclusions and recommendations for the proposed development. For our use, we received a preliminary site plan prepared by KTGY Group, Inc., April 28, 2014. We prepared this report exclusively for Three Cedars, LLC and their design team consultants. ENGEO should review any changes made in the character, design or layout of the development to modify the conclusions and recommendations contained in this report, as necessary. This document may not be reproduced in whole or in part by any means whatsoever,