GEOTECHNICAL INVESTIGATION SAN TOMAS AQUINO CREEK LEVEES STATE ROUTE 237 TO SCOTT BOULEYA RD SANTA CLARA, CALIFORNIA TA 705.3 S368.G4 1999 IIJ Kl.E~ fEtDER kq KlEINFELDER I ~ GEOTECHNICAL INVESTIGATION SAN TOMAS AQUINO CREEK LEVEES STATE ROUTE 237 TO SCOTT BOULEYA RD SANTA CLARA, CALIFORNIA -~ ~~~N Prepared For: Santa Clara Valley Water District 5750 Almaden Expressway San Jose, California 95118 Attention: Mr. Mohammad Khan Copyright 1999 Kleinfelder, Inc. All Rights Reserved. This document was prepared for use only by Santa Clara Valley Water District only for the purposes stated and within a reasonable time from its issuance. Please read the "Limitations" section of this report. Unauthorized use or copying of this document is strictly prohibited. See "Application for Authorization to Use" located at the end of this document if use or copying is desired by anyone other than those indicated for the project identified above. January 20, 1999 12-3039-40( 1218R623)/sl k_ll{) KlEINFElDER IIJ KlE~NfEl.DER An crnployee owned compdny January 20, 1999 File: 12-3039-40 Santa Clara Valley Water District 5750 Almaden Expressway San Jose, California 95118 ATTENTION: Mr. Mohammed Khan SUBJECT: Geotechnical Investigation for the San Tomas Aquino Creek Levees, State Route 237 to Scott Boulevard, Santa Clara, California Gentlemen: We are pleased to submit our geotechnical investigation report for the subject project. The accompanying report provides the results of the field investigation, laboratory testing and engineering analyses. Conclusions and recommendations for the levees are also included. The primary consideration for levee stability is the moderate to high potential for liquefaction of sand strata located beneath the levees at approximately Stations 86+ 25 and 162+4 7. The results of liquefaction will likely be settlement and possibly lateral movement of the levees. These conditions are discussed in the report. If you have any questions regarding the information or recommendations presented in our report, please contact us at your convenience. Sincerely, KLEINFELDER, INC. Reviewed by Scott M. Leek, G.E. 2067 Chalerm "Beeson" Liang, G.E. 2031 Senior Geotechnical Engineer Geotechnical Department Manager cc: Addressee (6) 12-3039-40( 1218R623)/sl January 20, 1999 Copyright 1999Kieinfelder, Inc. I<LLINfTLDF:R 13(,2 Ridder I' ark Drive, San jose, CA 9513 ·1 (408) 436-1155 k_~ KLEINFElDER GEOTECHNICAL INVESTIGATION SAN TOMAS AQUINO CREEK LEVEES SCOTT BOULEVARD TO STATE ROUTE 237 SANTA CLARA, CALIFORNIA TABLE OF CONTENTS l. INTRODUCTION ................................................................................................................................................ ! 1.1 PROJECT DESCRIPTION ................................................................................................................................... 1 1.2 PURPOSE AND SCOPE OF SERVICES ................................................................................................................. 1 2.0 GEOLOGY ....................................................................................................................................................... 3 2.1 GEOLOGIC SETTING ........................................................................................................................................ 3 2.2 AREA AND SITE GEOLOGY .............................................................................................................................. 4 2.3 FAULTING AND SEISMICITY ............................................................................................................................ 4 3. SITE INVESTIGATION ..................................................................................................................................... S 3.1 SITE DESCRIPTION .......................................................................................................................................... 5 2.2 FIELD INVESTIGATION .................................................................................................................................... 6 2.3 SUBSURFACE CONDITIONS .............................................................................................................................. 7 2.4 LABORATORY TESTING .................................................................................................................................. 7 4. ENGINEERING ANALYSES ................................................................................................................................ 9 4.1 GENERAL ........................................................................................................................................................ 9 4.2 EMBANKMENT PROTECTION ........................................................................................................................... 9 4.3 EMBANKMENT FILL COMPACTION ................................................................................................................ 10 4.4 EMBANKMENT AND FOUNDATION STABILITY ............................................................................................... 10 4.5 LIQUEFACTION ANALYSIS ............................................................................................................................ 13 4.6 SEEPAGE ANALYSIS ...................................................................................................................................... 14 4.7 SETTLEMENT ANALYSIS ............................................................................................................................... 15 5. CONCLUSIONS AND RECOMMENDATIONS ........................................................................................... 16 5.1 GENERAL ...................................................................................................................................................... 16 5.2 EMBANKMENT PROTECTION ......................................................................................................................... 16 5.3 EMBANKMENT FILL COMPACTION ................................................................................................................ 16 5.4 EMBANKMENT AND FOUNDATION STABILITY ................................................................................................ 17 5.5 LIQUEFACTION ............................................................................................................................................. 17 5.6 SEEPAGE ....................................................................................................................................................... 17 5.7 SETTLEMENT ................................................................................................................................................ 18 6. LIMITATIONS .................................................................................................................................................. 19 12-3039-40( 1218R623)/sl Page i of ii January 20, 1999 Copyright 1999 Kleinfelder, Inc. ...~. KLEINFELDER GEOTECHNICAL INVESTIGATION SAN TOMAS AQUINO CREEK LEVEES SCOTT BOULEY ARD TO STATE ROUTE 237 SANTA CLARA, CALIFORNIA TABLE OF CONTENTS, (continued) PLATES Plate 1 Site Vicinity Map Plates 2 and 3 Site Plan APPENDIX A Plates A-1 Boring Log Legend Plates A-2 through A-14 Boring Logs (B-1 through B-13) APPENDIXB Plates B-1 through B-3 Plasticity Chart Plates B-4 through B-14 Grain Size Analysis Plates B-15 through B-19 Triaxial Compression Test Results Plates B-20 through B-23 Consolidation Test Results Plate B-24 Permeability Test Results Plate B-25 Strength Test Results Plate B-26 Laboratory Compaction Tests APPENDIXC Logs of Previously Drilled Borings APPENDIXD Application for Authorization to Use 12-3039-40(1218R623)/sl Page ii of ii January 20, 1999 Copyright 1999 Kleinfelder, Inc. kq KlEINFELDER GEOTECHNICAL INVESTIGATION SAN TOMAS AQUINO CREEK LEVEES STATE ROUTE 237 TO SCOTT BOULEVARD SANTA CLARA, CALIFORNIA 1. INTRODUCTION This report presents the results of our geotechnical investigation for the San Tomas Aquino Creek levees between State Route 237 and Scott Boulevard in Santa Clara, California. The approximate location of the project site is shown on the Site Vicinity Map, Plate 1. This investigation has been performed for the Santa Clara Valley Water District (District) in general accordance with the Scope of Services presented in our proposal dated August 12, 1997 and the agreement between the District and Kleinfelder dated January 5, 1998. This report includes our conclusions and recommendations related to the geotechnical aspects of the levee stability. Conclusions and recommendations presented in this report are based on the subsurface conditions encountered at the locations of our exploration and the provisions and requirements outlined in the Limitations section of this report. Recommendations presented herein should not be extrapolated to other areas or used for other projects without our prior review. 1.1 PROJECT DESCRIPTION The project consists of a geotechnical evaluation of the existing levees on both sides of San Tomas Aquino Creek in Santa Clara, California. The project alignment stretches between approximately Station 25+00 at State Route 237 on the north and Station 175+00 near Scott Boulevard on the south. The levee alignments are shown on Plates 2 and 3. 1.2 PURPOSE AND SCOPE OF SERVICES The purpose of our geotechnical investigation was to explore and evaluate subsurface conditions along the levee alignment in order to evaluate the conditions and stability of the levees against major earthquake and the 10 0-year flood in accordance with Federal Emergency Management 12-3039-40( 1218R623)/sl Page I of 20 January 20, 1999 Copyright 1999 Kleinfelder, Inc. .~.~ ~ KlEINFELDEIR Agency (FEMA) guidelines set forth in Section 65.10(b) Parts (3), (4), and (5) of the National Flood Insurance Program (NFIP) The services performed for this investigation included a review of available geologic and geotechnical information in our office, site reconnaissance, directing the subsurface exploration program, reviewing laboratory testing performed by others, engineering analyses of field and laboratory data, and preparation of this report. The results of our engineering evaluation included the following items in the NFIP: • Embankment Protection: • Embankment and Foundation Stability; • Liquefaction; • Seepage; and • Settlement. Environmental services such as a chemical analysis of soil and groundwater were not included in our scope of services. 12-3039-40( 1218R623)/sl Page 2 of 20 January 20, 1999 Copyright 1999 Kleinfelder, Inc. kq KLEINFELDER 2.0 GEOLOGY 2.1 GEOLOGIC SETTING The San Francisco Bay Area lies within the Coast Range Geomorphic Province, a more or less discontinuous series of northwest trending mountain ranges, ridges, and intervening valleys characterized by complex folding and faulting. Geologic and geomorphic structure within the San Francisco Bay area is controlled by the San Andreas fault (SAF). This right-lateral strike-slip fault which extends from the Gulf of California, in Mexico, to Cape Mendocino, off the coast of Humboldt County in northern California, forms a portion of the boundary between two independent tectonic plates on the surface of the earth. To the west of the SAF is the Pacific plate, which moves north relative to the North American plate, located east of the fault. In the San Francisco Bay area, movement across this plate boundary is concentrated on the SAF; however, it is also distributed, to a lesser extent across a number of other faults which include the Hayward and Calaveras, among others. Together, these faults are referred to as the SAF system. The northwest trend of the faults within the system are responsible for the strong northwest structural orientation of geologic and geomorphic features in the San Francisco Bay area. Basement rock west of the SAF is generally granitic, while to the east it consists of a chaotic mixture of highly deformed marine sedimentary, submarine volcanic and metamorphic rocks of the Franciscan Complex. Overlying the basement rocks are marine and non-marine sedimentary rocks with some continental volcanic rock. These Tertiary rocks have typically been extensively folded and faulted largely as a result of movement along the SAF system which has been ongoing for about the last 25 million years. The inland valleys as well as San Francisco Bay are filled with unconsolidated to semi-consolidated deposits. Continental deposits (alluvium) consist of sand, silt, clay and gravel while the bay deposits typically consist of very soft organic rich mud (bay mud) or sand. 12-3039-40( 1218R623)/sl Page 3 of 20 January 20, 1999 Copyright 1999 Kleinfelder, Inc. k."ff KlEINFELDER 2.2 AREA AND SITE GEOLOGY The project site is located in the central portion of a broad alluvial basin known as the Santa Clara Valley. Materials underlying the site are mapped as medium grained alluvium and fine grained alluvium. These units are unconsolidated, moderately sorted, permeable fine sand, silt and clayey silt with a few lenses of coarse sand and unconsolidated, plastic, moderately to poorly sorted carbonaceous silt and clay. Our boring data indicates that the subsurface soils contain primarily silty clays with occasional lenses or channel deposits of fine to coarse grained sand most likely resulting from the wandering channel of San Tomas Aquino Creek. 2.3 FAULTING AND SEISMICITY The closest active or potentially active fault is the southeast extension of the Hayward fault, located about 10 km northeast of the site. Other nearby faults include: the Monte Vista-Shannon fault, located approximately 12 km southwest of the site; the Hayward fault, located about 12 km northeast of the site; the Calaveras fault, located about 15 km northeast of the site; and the San Andreas fault, located about 17 km southwest of the site. A major seismic event on these faults could cause significant ground shaking at the site. 12-3039-40(1218R623)/sl Page 4 of 20 January 20, 1999 Copyright 1999 Kleinfelder, Inc.