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HomeMy WebLinkAbout106434001; Camino Hills Drive; Camino Hills Drive Slope Failure; 2008-11-06Geotechnical and Environmental Sciences Consultants PRELIMINARY GEOTECHNICAL EVALUATION CAMINO HILLS DRIVE SLOPE FAILURE CARLSBAD, CALIFORNIA PREPARED FOR City of Carlsbad 1635 Faraday Avenue Carlsbad, California 92008 PREPARED BY Ninyo & Moore Geotechnical and Environmental Sciences Consultants 5710RuffinRoad San Diego, California 92123 November 6, 2008 Project No. 106434001 5710 Ruffin Road • San Diego, California 92 123 • Phone (858) 576-1000 • Fax (858) 576-9600 San Diego • Irvine • Rancho Cucamonga • Los Angeles • Oakland • Las Vegas • Phoenix • Denver • El Paso • Tucson M ' f^. oore Geotechnical and Environmental Sciences Consultants November 6, 2008 Project No. 106434001 urn Mr. Jacob Moeder, P. E. Associate Engineer City of Carlsbad 163 5 Faraday Avenue Carlsbad, California 92008 Subject: Preliminary Geotechnical Evaluation Camino Hills Drive Slope Failure Carlsbad, California Dear Mr. Moeder: In accordance with your authorization, we have performed a preliminary geotechnical evaluation of the slope failure on the south side of Camino Hills Drive at Jackspar Drive in Carlsbad, Cali- fornia. This report presents our preliminary geotechnical findings, conclusions, and recommendations regarding the slope failure. We appreciate the opportunity to be of service on this project. Sincerely, NINYO & MOORE Emil Rudolph, P.E., G.E. Senior Engineer ER/FOM/RI/ek Distribution: (5) Addressee Francis O. Moreland, C. Senior Geologist 5710 Ruffin Road • San Diego, California 921 23 • Phone (858) 576-1 000 • Fax (858) 576-9600 San Diego • Irvine • Rancho Cucamonga • Los Angeles • Oakland • Las Vegas • Phoenix • Denver • El Paso • Tucson Camino Hills Drive Slope Failure November 6, 2008 Carlsbad, California Project No. 106434001 1 ? 3 4 5 6 7 8. TABLE OF CONTENTS INTRODUCTION SCOPE OF SERVICES SITE DESCRIPTION SUBSURFACE EXPLORATION AND LABORATORY TESTING GEOLOGY AND SUBSURFACE CONDITIONS 5.1. Site Geology 5.1.1. Fill 5.1.2. Landslide Deposits 5.1.3. Santiago Formation 5.2. Groundwater CONCLUSIONS AND RECOMMENDATIONS LIMITATIONS REFERENCES Page 1 1 2 2 2 3 3 3 3 3 4 4 7 ^ Figures Figure 1 - Site Location Map ** Figure 2 - Geotechnical Map w Figure 3 - Geologic Cross Section A - A' *** Appendices „», Appendix A - Test Pit Logs Appendix B - Laboratory Testing 10M34001 Rdoc Camino Hills Drive Slope Failure November 6, 2008 Carlsbad, California Project No. 106434001 1. INTRODUCTION In accordance with your request and our proposal dated August 1, 2008, we have performed a preliminary geotechnical evaluation of the slope failure located on Camino Hills Drive at Jackspar Drive in Carlsbad, California (Figure 1). This report presents our preliminary conclu- sions regarding the geotechnical conditions at the subject site and our recommendations for additional subsurface evaluation at the site. 2. SCOPE OF SERVICES Ninyo & Moore's scope of services for this project included review of pertinent background data, previous geotechnical reports, performance of a subsurface evaluation, and engineering analysis with regard to the subject slope. Specifically, we performed the following tasks: • Reviewing readily available published geotechnical literature, including geologic maps, geo- technical reports, engineering plans, and aerial photographs. • Performing a field reconnaissance to observe site conditions and to mark the locations of our subsurface explorations. • Contacting Underground Service Alert to clear the proposed subsurface exploration location for conflicts with buried utilities. • Obtaining City of Carlsbad Right-of-Way permits. • Performing subsurface exploration consisting of the digging, logging and sampling of two exploratory test pits. Bulk soil samples were obtained at selected intervals from the test pit. • Performing geotechnical laboratory testing on selected samples. • Compiling and analyzing the data obtained. • Preparing this report presenting our preliminary geotechnical findings, conclusions, and rec- ommendations regarding the subject slope failure. Evaluating the global stability of the overall slope was beyond the scope of this report. tyinyo Camino Hills Drive Slope Failure November 6, 2008 Carlsbad, California Project No. 106434001 3. SITE DESCRIPTION As noted, the project involves the evaluation of a slope failure, which occurred on the south side of Camino Hills Drive, just west of Jackspar Drive, in Carlsbad, California. The failed area is located at the base of a 25 foot high, 2:1 (horizontal:vertical), northwest-facing slope which par- allels Camino Hills Drive. The slope failure is approximately 85 feet wide at the toe of the slope and extends approximately 8 feet laterally into Camino Hills Drive. The southward (upslope) ex- tent of the failure is not known. Observed distress features included an approximately 3-inch bulge in the street pavement and sidewalk, and approximately 3 inches of movement of the side- walk and curb to the northwest. The elevation of the project site varies from approximately 140 feet above mean sea level (MSL) at the toe of the failure to approximately 170 feet above MSL at the top of the slope. The slope is heavily vegetated with a moderate to dense growth of ground cover shrubs and moderately sized trees. Our evaluation of the subject slope failure was restricted to the Camino Hills Drive right-of-way. 4. SUBSURFACE EXPLORATION AND LABORATORY TESTING Our subsurface exploration was conducted on September 17, 2008 and consisted of excavating two exploratory test pits using a John Deere 410 backhoe to a depth of approximately 8 feet. Bulk soil samples were obtained at selected intervals from the test pits. The approximate loca- tions of the test pits are shown on Figure 2. The test pit logs are presented in Appendix A. Laboratory testing of representative soil samples included moisture content, Atterberg limits, maximum dry density and optimum moisture content, and corrosivity. The results of the labora- tory tests performed are presented in Appendix B. 5. GEOLOGY AND SUBSURFACE CONDITIONS Our findings regarding site geology and groundwater conditions are provided in the following sections. 106434001R doc -, A///IM//J& Camino Hills Drive Slope Failure November 6, 2008 Carlsbad, California Project No. 106434001 5.1. Site Geology The geologic units observed during our reconnaissance or encountered during our subsurface evaluation included fill and landslide deposits (Figure 2). Materials of the Santiago Formation un- derlie the site at depth (Figure 3). Generalized descriptions of the units encountered are provided in the subsequent sections. Detailed descriptions are also provided on the test pit logs in Appendix A. 5.1.1. Fill Fill is mapped overlying the landslide deposits at the site. The fill is derived from the under- lying Santiago Formation and landslide deposits. As observed and reported in the as-graded report for the adjacent property (Southern California Soil and Testing, Inc. [SCST], 1985), the fill generally consisted of light brown to light gray, clayey sandy silt and clayey sand. 5.1.2. Landslide Deposits Landslide deposits were encountered in our test pits from the ground surface to the depths explored of up to approximately 8.5 feet. The landslide deposits are derived from the un- derlying Santiago Formation. As encountered, the landslide deposits generally consisted of light gray and light brown, soft to stiff, silty to sandy clay and clayey silt. Based on but- tress depths reported in the as-graded report for the adjacent property (SCST, 1985), we anticipate that the landslide deposits extend to a depth on the order of 20 feet. 5.1.3. Santiago Formation Although not observed, materials of the Santiago Formation are mapped as underlying the landslide debris in the site area. Based on our experience in the site area, the materials of the Santiago Formation generally consist of a light brown to light grayish brown, moderately indu- rated claystone and siltstone, and weakly cemented, clayey fine- to medium-grained sandstone. 5.2. Groundwater Groundwater was not encountered in our test pits. Fluctuations in groundwater level may occur due to seasonal variations, irrigation, groundwater withdrawal or injection, and other factors. 106434001 R doc Camino Hills Drive Slope Failure November 6, 2008 Carlsbad, California Project No. 106434001 6. CONCLUSIONS AND RECOMMENDATIONS Based on our review of the referenced background data, geologic field reconnaissance, subsur- face evaluation and laboratory testing, it is our opinion that the features observed at the subject site are the result of a landslide developing within the adjacent slope. During grading for the ad- jacent mobile home park in the mid-1980's, landslide deposits underlying the subject slope were left in place and a buttress constructed beneath Camino Hills Drive (Figure 2). Additional fill was placed over the landslide deposits to create the graded pads above the slope. Based on a review of the observation and testing report for the mobile home project (SCST, 1985), the buttress beneath Camino Hills Drive extends to a depth of more than 23 feet. Although the geotechnical report for the project is not available, the buttress depth would indicate a slide plane depth on the order of 18 to 20 feet. Based on the location where the current slide is toeing out (approximately 8 feet from the curb), it is our opinion that the current slide is a new, shallower landslide which has de- veloped within the older slide mass and fill buttress (Figure 3). Due to site constraints and equipment limitations, insufficient data was acquired to define the geometry of the subject landslide. We therefore recommend that additional subsurface evaluation be performed to further define the subsurface conditions and geometry. We anticipate that the ad- ditional subsurface evaluation would include the installation of two slope inclinometers within the slide and inside the City of Carlsbad right-of-way. The slope inclinometers would provide information on the rate of slide movement and the depth to the current slide plane. The incli- nometers would be measured on a monthly basis, or when City survey indicates movement of the landslide, until the depth of the slide plane can be defined. Once the depth and extent of the land- slide is defined, repair recommendations would be prepared. A proposal for our additional subsurface evaluation can be provided upon request. 7. LIMITATIONS The field evaluation, laboratory testing, and geotechnical analyses presented in this geotechnical report have been conducted in general accordance with current practice and the standard of care exercised by geotechnical consultants performing similar tasks in the project area. No warranty, 106434001 Rdoc Camino Hills Drive Slope Failure November 6, 2008 Carlsbad, California Project No. 106434001 expressed or implied, is made regarding the conclusions, recommendations, and opinions pre- sented in this report. There is no evaluation detailed enough to reveal every subsurface condition. Variations may exist and conditions not observed or described in this report may be encountered during construction. Uncertainties relative to subsurface conditions can be reduced through addi- tional subsurface exploration. Additional subsurface evaluation will be performed upon request. Please also note that our evaluation was limited to assessment of the geotechnical aspects of the project, and did not include evaluation of structural issues, environmental concerns, or the pres- ence of hazardous materials. This document is intended to be used only in its entirety. No portion of the document, by itself, is designed to completely represent any aspect of the project described herein. Ninyo & Moore should be contacted if the reader requires additional information or has questions regarding the content, interpretations presented, or completeness of this document. This report is intended for design purposes only. It does not provide sufficient data to prepare an accurate bid by contractors. It is suggested that the bidders and their geotechnical consultant per- form an independent evaluation of the subsurface conditions in the project areas. The independent evaluations may include, but not be limited to, review of other geotechnical reports prepared for the adjacent areas, site reconnaissance, and additional exploration and laboratory testing. Our conclusions, recommendations, and opinions are based on an analysis of the observed site con- ditions. If geotechnical conditions different from those described in this report are encountered, our office should be notified, and additional recommendations, if warranted, will be provided upon re- quest. It should be understood that the conditions of a site could change with time as a result of natural processes or the activities of man at the subject site or nearby sites. In addition, changes to the applicable laws, regulations, codes, and standards of practice may occur due to government ac- tion or the broadening of knowledge. The findings of this report may, therefore, be invalidated over time, in part or in whole, by changes over which Ninyo & Moore has no control. 106434001 Rdoc tyinyo Camino Hills Drive Slope Failure November 6, 2008 Carlsbad, California Project No. 106434001 This report is intended exclusively for use by the client. Any use or reuse of the findings, conclu- sions, and/or recommendations of this report by parties other than the client is undertaken at said parties' sole risk. 106434001 R doc tew Camino Hills Drive Slope Failure November 6, 2008 Carlsbad, California Project No. 106434001 8. REFERENCES California Building Standards Commission (CBSC), 2007, California Building Code (CBC), Ti- tle 24, Part 2, Volumes 1 and 2. County of San Diego, 1975, Topographic Survey (Orthotopographic), Sheet 354-1677, Scale 1" = 200'. Kennedy, Michael P. and Tan, Siang S., 2005, Geologic Map of the Oceanside 30' X 60' Quad- rangle, California: Regional Geologic Map Series, Map No. 2. Southern California Soil and Testing, Inc., 1985, Report of Field Observation and Relative Com- paction Tests and As-Graded Geologic Report, Proposed Camino Hills Mobilehome Subdivision, El Camino Real and Camino Hills Drive, Carlsbad: dated June 3. United States Geological Survey, 1968 (photo-revised 1975), San Luis Rey Quadrangle, Califor- nia, San Diego County, 7.5-Minute Series (Topographic): Scale 1:24,000. Source USDA Date 4-11-53 AERIAL PHOTOGRAPHS Flight Numbers | AXN-8M 68 and 69 Scale 1:20,000 10643400] Rdoc Afinyo ra»*| „ *$rjB"f*4' mR $£ ** /C''"/>v^-Ii '^ ••" *A /T* »• -'•!;« °-i .«.'ffik/4; ^*IC.^1««HB^--* ?il^w REFERENCE: 2005 THOMAS GUIDE FOR SAN DIEGO COUNTY, STREET GUIDE AND DIRECTORY, APPROXIMATE SCALE IN FEET NOTE: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE Map © Rand McNally, R.L07-S-129 SITE LOCATION MAP CAMINO HILLS DRIVE SLOPE FAILURE CARLSBAD, CALIFORNIA o ot| u- IO o O co -^CO Ofi^ 00o o^x < Q.XDQ-UJ3_j<uji-<oa «/) UJ O O I O UJ oLJJ O UJ ujz Q-goo -JU-COIJ UJ < Q< -^ <OO o UJ OLCL (1SV\I '133d) NOI1VA313 UJIT =3 COo ' o HoLJJ CO CO CO Ooioo oo_ioLU O a: UJ Za. £o o_J LL CO o o <o HI (1SIAI '133d) NOI1VA313 £ Q CO t0 | Q. euj £a \L <OuJ "J r^^ 8 « I 00% 1 <_J CO Ll_Ozg oUJcc DICATESOVEMENn**Z (A CO 00^? APPENDIX A Camino Hills Drive Slope Failure November 6, 2008 Carlsbad, California Project No. 106434001 APPENDIX A TEST PIT LOGS Field Procedure for the Collection of Disturbed Samples Disturbed soil samples were obtained in the field using the following method. Bulk Samples Bulk samples of representative earth materials were obtained from the exploratory test pit. The samples were bagged and transported to the laboratory for testing. 106434001 Rdoc FIGURE U.S.C.S. METHOD OF SOIL CLASSIFICATION MAJOR DIVISIONS V)COARSE-GRAINED SO(More than 1/2 of soil>No. 200 sieve size)</)_J TZ ^ Q U(N > Z ' '~ o ^ ' O ° E GRAVELS (More than 1/2 of coarse fraction > No. 4 sieve size) SANDS (More than 1/2 of coarse fraction <No. 4 sieve size) SILTS & CLAYS Liquid Limit <50 SILTS & CLAYS Liquid Limit >50 ; SYMBOL TYPICAL NAMES HISH • t %P i. *". • • • i "i < Wg 1» xxx (// 4= IH ^!W - : HIGHLY ORGANIC SOILS GW GP GM GC SW SP SM SC ML CL OL MH CH OH Pt Well graded gravels or gravel-sand mixtures, little or no fines Poorly graded gravels or gravel-sand mixtures, little or no fines Silty gravels, gravel-sand-silt mixtures Clayey gravels, gravel-sand-clay mixtures Well graded sands or gravelly sands, little or no fines Poorly graded sands or gravelly sands, little or no fines Silty sands, sand-silt mixtures Clayey sands, sand-clay mixtures Inorganic silts and very fine sands, rock flour, silty or clayey fine sands or clayey silts with Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean Organic silts and organic silty clays of low plasticity Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts Inorganic clays of high plasticity, fat clays Organic clays of medium to high plasticity, organic silty clays, organic silts Peat and other highly organic soils GRAIN SIZE CHART CLASSIFICATION BOULDERS COBBLES GRAVEL Coarse Fine SAND Coarse Medium Fine SILT & CLAY RANGE OF GRAIN SIZE U.S. Standard Sieve Size Above 12" 12" to 3" 3" to No. 4 3" to 3/4" 3/4" to No. 4 No. 4 to No. 200 No. 4 to No. 10 No. 10 to No. 40 No. 40 to No. 200 Below No. 200 Grain Size in Millimeters Above 305 305 to 76.2 76.2 to 4.76 76.2to 19.1 19.1 to 4.76 4.76 to 0.075 4. 76 to 2. 00 2.00 to 0.420 0.420 to 0.075 Below 0.075 PLASTICITY CHART §40 B § n s s/ / CL- H / L f / CL / f ML / / 10L / / / CH / / MHi X OH / Q X) 20 30 40 5O 60 70 80 90 100 LIQUID LIMTT(LL), % U.S.C.S. METHOD OF SOIL CLASSIFICATION USCS Soil Classification Updated Nov 2004 r I r-^Wf r o Q. W UJ I- D111 o X LU 111 CD Q LU O O O LU_l LU Q Occ o oXLU LLo Qo X LU oo g Q. a:o (T> LLJ D —o~ rt TD _s •a o JE o ft <J <-> ft Ml o " ft s «~ II• •> S— (L>)-) J= =; P£ c5 C ot-< CQ a>C ID O 'o . 3 •*-* OO o ^1<o ^> oo ~ON O 3 O OO fc C8H O PQ 'S'O'S'n NOI1VOUISSV10 (JOd) A1ISN3Q AJdQ r L CD O D_ \- (f) LJJ 3 P-. 232 <u o *; CSJ < FIGURE A-1 i i E H o LU QLUi<o XLU LU 2 CO Q LU OOo O g LU_l LU Q Z =3Otro o oXLU LL O D OII- LU Oo Q. or O (f)LJJ Q OO oo u P 1a o ffi _>, "u a,o. 00 'H.g.-3 00 •3•a<um .g '? h-1U a CX3 O >O 1 <D O 00 •a CJ S OJo ooS -o<o oc o t ^H O pq NOI1VOIJISSV10 (dOd) A1ISN3Q FIGURE A-2 APPENDIX B Camino Hills Drive Slope Failure November 6, 2008 Carlsbad, California Project No. 106434001 APPENDIX B LABORATORY TESTING Classification Soils were visually and texturally classified in accordance with the Unified Soil Classification System (USCS) in general accordance with ASTM D 2488. Soil classifications are indicated on the log of the exploratory test pit in Appendix A. Moisture Content The moisture content of samples obtained from the exploratory excavations was evaluated in ac- cordance with ASTM D2216. The test results are presented on the logs of the exploratory excavations in Appendix A. Atterberg Limits Tests were performed on selected representative fine-grained soil samples to evaluate the liquid limit, plastic limit, and plasticity index in general accordance with ASTM D 4318. These test re- sults were utilized to evaluate the soil classification in accordance with the Unified Soil Classification System. The test results and classification are shown on Figure B-l. Proctor Density Test The maximum dry density and optimum moisture content of a selected representative soil sample was evaluated using the Modified Proctor method in general accordance with ASTM D 1557. The results of the test are summarized on Figure B-2. Soil Corrosivity Tests Soil pH, and resistivity tests were performed on representative samples in general accordance with California Test (CT) 643. The soluble sulfate and chloride content of selected samples were evaluated in general accordance with CT 417 and CT 422, respectively. The test results are pre- sented on Figure B-3. 106434001 Rdoc SYMBOL • LOCATION TP-1 TP-2 DEPTH (FT) 5.0-6.0 2.0-4.0 LIQUID LIMIT, LL 30 46 PLASTIC LIMIT, PL 8 32 PLASTICITY INDEX, PI 22 14 uses CLASSIFICATION (Fraction Finer Than No. 40 Sieve) CL ML uses (Entire Sample) CL ML NP - INDICATES NON-PLASTIC Q. XLU Q O 60 50 40 30 20 10 s_:L-ML CL or OL ML or OL CHorOH -MHorOH- 0 10 20 30 40 50 60 70 80 90 100 LIQUID LIMIT, LL PERFORMED IN GENERAL ACCORDANCE WITH ASTM D 4318-05 PROJECT NO. 106434001 DATE 11/08 ATTERBERG LIMITS TEST RESULTS CAMINO HILLS DRIVE SLOPE FAILURE CARLSBAD, CALIFORNIA FIGURE B-1 106434001 ATTERBERG PAGE l.xls 140.0 130.0 120.0 u_oa. LU Q CC Q 110 100.0 90.0 80.0 Zero Air Void Line (Specific Gravity = 2.70) Zero Air Void Line (Specific Gravity = 2.60) Zero Air Void Line (Specific Gravity = 2.50) 10 15 20 25 MOISTURE CONTENT (%) 30 35 40 Sample Location TP-1 Depth (ft) 5.0-6.0 Soil Description Silty CLAY (CL) Dry Density and Moisture Content Values Corrected for Oversize (ASTM D 4718-87) Maximum Dry Density (pcf) 110.0 Optimum Moisture Content (%) 18.5 PERFORMED IN GENERAL ACCORDANCE WITH 0 ASTM D 1557-02 D ASTM D 698-OOa METHOD0A PROJECT NO. 106434001 DATE 11/08 PROCTOR DENSITY TEST RESULTS CAMINO HILLS DRIVE SLOPE FAILURE CARLSBAD, CALIFORNIA FIGURE B-2 106434001 PROCTOR TP-1 @ 5.0-6.0.xls SAMPLE LOCATION TP-1 SAMPLE DEPTH (FT) 1.0-2.0 pH1 5.2 RESISTIVITY 1 (Ohm-cm) 520 SULFATE CONTENT 2 (ppm) 50 (%) 0.005 CHLORIDE CONTENT 3 (ppm) 110 1 PERFORMED IN GENERAL ACCORDANCE WITH CALIFORNIA TEST METHOD 643 2 PERFORMED IN GENERAL ACCORDANCE WITH CALIFORNIA TEST METHOD 417 3 PERFORMED IN GENERAL ACCORDANCE WITH CALIFORNIA TEST METHOD 422 ^fc^0&yyv*u>re PROJECT NO. 106434001 DATE 11/08 CORROSIVITY TEST RESULTS CAMINO HILLS DRIVE SLOPE FAILURE CARLSBAD, CALIFORNIA FIGURE B-3 106434001 CORROSIVITY PAGE 1 xls