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Home My WebLink About6612; RANCHO CARILLO WATER SEEPAGE; GEOTECHNICAL EVALUATION; 2008-11-04nFrhnic,l And Fnvironmpntl Sciences Consultants -S GEOTECHNICAL EVALUATION SEEPAGE NEAR PEDESTRIAN BRIDGE CARRILLO RANCH CARLSBAD, CALIFORNIA PREPARED FOR City of Carlsbad Public Works and Engineering 1635 Faraday Avenue Carlsbad, California 92008 PREPARED BY Ninyo & Moore Geotechnical and Environmental Sciences Consultants 5710 Ruffin Road San Diego, California 92123 a-S November 4, 2008 Project No. 106431001 -a 5710 Ruffin Road • San Diego California 92123 • Phone (858) 576-1000 • Fax (858) 576-9600 ohm San Diego • Irvine • Ontario • Los Angeles Oakland • Las Vegas • Carson City • Phoenix • Centennial Geotechnical and Environmental Sciences Consultants November 4, 2008 Project No. 106431001 Mr. Jacob Moeder, P. E. City of Carlsbad Public Works and Engineering 1635 Faraday Avenue Carlsbad, California 92008 Subject: Geotechrtical Evaluation Seepage Near Pedestrian Bridge Carrillo Ranch Carlsbad, California Dear Mr. Moeder: In accordance with your authorization, we have performed geotechnical evaluation of seepage reported near the pedestrian bridge in the Carrillo Ranch area of Carlsbad, California. This report presents our geotechnical findings, conclusions, and recommendations for the site. We appreciate the opportunity to be of service on this project. Sincerely, NINYO & MOORE 1fL iS wo NO. 27 2 Emil Rudolph, P.E., G. Francis 0. Moreland, Senior Engineer Senior Geologist MAH/FOM/ERIgg No 2071 I,I CERTIFIED Distribution: (5) Addressee 't ENGINEERING \d GEOI.DGISI 5710 Ruffin Road • San Diego, California 92123 • Phone (858) 516-1000 • Fax (858) 576-9600 San Diego • Irvine • Ontario • Los Angeles . Oakland • Las Vegas • Carson City • Phoenix • Centennial Carrillo Ranch Seepage November 4, 2008 Carlsbad, California Project No. 106431001 TABLE OF CONTENTS Page INTRODUCTION....................................................................................................................1 SCOPE OF SERVICES ............................................................................................................ 1 SITE DESCRIPTION AND BACKGROUND ........................................................................1 SUBSURFACE EXPLORATION AND LABORATORY TESTING ....................................2 GEOLOGY AND SUBSURFACE CONDITIONS .................................................................2 5.1. Site Geology .................................................................................................................3 5.1.1. Fill.......................................................................................................................3 5.1.2. Santiago Peak Volcanics.....................................................................................3 5.2. Groundwater.................................................................................................................3 CONCLUSIONS AND RECOMMENDATIONS ...................................................................3 LIMITATIONS .......................................................................................................................... 4 REFERENCES.........................................................................................................................6 Figures Figure 1 - Site Location Map Figure 2— Boring Location Map Figure 3 - French Drain Detail Appendices Appendix A - Boring Logs Appendix B - Laboratory Testing IO643I00IRdoc fflgO8j1tIMW am a Carrillo Ranch Seepage November 4, 2008 Carlsbad, California Project No. 106431001 W. WM I. INTRODUCTION In accordance with your request and our proposal dated July 28, 2008, we have performed a geo- technical evaluation of seepage reported near the pedestrian bridge northwest of Via Conquistador, in the Carrillo Ranch area in Carlsbad, California (Figure 1). The purpose of our geotechnical services was to evaluate the source of the seepage and provide geotechnical recom- mendations for mitigating the observed seepage. 2. SCOPE OF SERVICES Ninyo & Moore's scope of services for this study included review of pertinent background data, performance of a subsurface evaluation, and engineering analysis with regard to the seepage. Specifically, we performed the following tasks: Reviewing available published geotechnical literature, including geologic maps, engineering plans, and aerial photographs. Performing a field reconnaissance to observe site conditions and to mark the locations of our ftw subsurface exploration. Contacting Underground Service Alert to clear the subsurface exploration locations for con- flicts with buried utilities. Performing subsurface exploration consisting of the excavating, logging and sampling of two exploratory soil borings. Bulk and in-place soil samples were obtained at selected inter- vals from the borings for laboratory testing. Performing geotechnical laboratory testing on selected samples. a Compiling and analyzing the data obtained from our background review, subsurface explora- tion, and laboratory testing. a Preparing this report presenting our geotechnical findings, conclusions, and recommenda- tions regarding the reported seepage and mitigation measures. aw 3. SITE DESCRIPTION AND BACKGROUND The subject site is located northwest of Via Conquistador near the southern abutment of the pe- destrian bridge in the Carrillo Ranch area of Carlsbad. Specifically, the site includes the relatively : R.doc . j/I1ffO&/ftlMwe Carrillo Ranch Seepage November 4, 2008 Carlsbad, California Project No. 106431001 flat area along the toe of the existing fill slope above the southern end of the pedestrian bridge. The slope rises toward Via Conquistador (Figure 2). The site elevation ranges from approxi- mately 210 to 220 feet above mean sea level (MSL). Vegetation at the site consists of a moderate aw growth of weeds, brush and trees on the slope above the site. am - It is our understanding that within the last several months, groundwater has been seeping into a - sewer manhole south of the southern abutment for the pedestrian bridge. During our field recon- naissance we observed active seepage at several locations along the toe of the slope south of the manhole and adjacent to the bridge abutment. A concrete swale is located at the base of this slope. Algae/moss is present where water is constantly flowing within the swale. The City of Carlsbad is concerned that the seepage could potentially damage the sewer and bridge abutment. fto GO- SUBSURFACE EXPLORATION AND LABORATORY TESTING Our subsurface exploration was conducted on October 6, 2008. The subsurface evaluation consisted of the drilling, logging, and sampling of two 8-inch diameter, hollow-stem exploratory borings (B-I and B-2). The exploratory borings were advanced to depths of up to 11 feet below existing grade. The borings were terminated at the depth where auger refusal on formational material was encoun- tered. Bulk and in-place soil samples were obtained at selected intervals from the borings. The samples were then transported to our in-house geotechnical laboratory for testing. The approximate — locations of the borings are shown on Figure 2. The boring logs are presented in Appendix A. Laboratory testing of representative soil samples included an analysis of grain size distribution and in-situ moisture content tests. The results of the in-situ moisture content tests are presented on the boring logs in Appendix A. The results of the other laboratory tests performed are pre- sented in Appendix B. GEOLOGY AND SUBSURFACE CONDITIONS Our findings regarding site geology and groundwater conditions are provided in the following sections. 106431001 Itdoc 2 411n1/o&/.jtoore No Carrillo Ranch Seepage November 4, 2008 Carlsbad, California Project No. 106431001 5.1. Site Geology The geologic units encountered during our subsurface evaluation included fill and materials of the Santiago Peak Volcanics. Generalized descriptions of the units encountered are provided in the subsequent sections. Detailed descriptions are also provided on the boring logs in Appendix A. 5.1.1. Fill The fill materials encountered within our exploratory borings, B-i and B-2, extended from the ground surface to depths of approximately 4.5 and 3 feet, respectively. The fill generally consisted of two types of materials. The fill encountered in boring B-i was generally a light brown, moist, stiff, silty clay. The fill encountered in boring B-2 was generally a brown, moist, moderately dense to dense, clayey medium sand with some gravel. 5.1.2. Santiago Peak Volcanics Materials of the Santiago Peak Volcanics were encountered beneath the fill materials to the depths explored. As observed, the materials generally consisted of a grayish brown, weathered metavolcanic rock. that was excavated as a clayey gravel with sand to a silty sand and gravel. 5.2. Groundwater A perched groundwater condition was noted within boring B-I. Additionally, various zones of seepage were observed along the toe of the adjacent fill slope (underlying Via Conquistador). Based on the observed seepage and the algae and efflorescence on the existing swale, we antici- pate that the groundwater is perched at, or close to the elevation at which the less permeable low Santiago Peak Volcanics was encountered. Fluctuations in groundwater level may occur due to seasonal variations, irrigation, groundwater withdrawal or injection, and other factors. S dw 6. CONCLUSIONS AND RECOMMENDATIONS The purpose of our geotechnical services was to evaluate the source of the seepage and provide - geotechnical recommendations for mitigating the observed seepage. Based on our review of the referenced background data, geologic field reconnaissance, subsurface evaluation and laboratory — 106431001 R.doc 3 f.jlnj/o&/.ftutwe Carrillo Ranch Seepage November 4, 2008 Carlsbad, California Project No. 106431001 testing, it is our opinion that mitigation of the subject seepage is feasible from a geotechnical standpoint. Geotechnical considerations include the following: The source of the observed seepage is potentially irrigation water from the residential devel- opment above the subject site. The water percolates through the fill material to the underlying less permeable Santiago Peak Volcanics and travels along the contact downward to the subject site where the contact daylights. To mitigate the effects of seepage, we recommend that a French drain be constructed at the toe of the fill slope south of the abutment to the approximate extent shown in Figure 2. The French drain should be constructed in general accordance with Figure 3 and should extend to a depth of approximately 5 feet below the existing grade. The actual depth should be evalu- ated in the field by Ninyo & Moore during excavation. The drain should be tight lined to a free outlet. - • The on-site fill and materials of the Santiago Peak Volcanics are generally excavatable with conventional heavy-duty earth moving equipment. However, less weathered zones may be encountered within the Santiago Peak Volcanics, which would entail heavy ripping or the use of rock breakers. A perched groundwater table and seepage were noted during our evaluation. The contractor should anticipate these conditions during construction and the potential for caving of the un- supported trench walls. 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, 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. — 0643100I Rdoc 4 I0ji11//0&?ft130' fto 106431001 Rdoc 5 aw vim Carrillo Ranch Seepage November 4, 2008 Carlsbad, California Project No. 106431001 aw 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. am 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. 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. Carrillo Ranch Seepage November 4, 2008 Carlsbad, California Project No. 106431001 a — 8. REFERENCES California Building Standards Commission , 2007, CBC, Title 24, Part 2, Volumes I and 2. City of Carlsbad, 2008, Engineering Standards, Volume 1, General Design Standards, 2004 Edi- tion: revised June 30. County of San Diego, 1963, Topographic Survey, Sheet 346-1695, Scale I" = 200'. County of San Diego, 1975, Topographic Survey (Orthotopographic), Sheet 346-1695, Scale 1" = 200'. International Code Council, Inc., 2006, International Building Code. Geocon Incorporated, 1993, Preliminary Geotechnical Investigation for Rancho Carrillo, Villages N, 0, Q, R, T, and U, Carlsbad, California: dated February 16, 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. Ninyo & Moore, 2008, Proposal for Geotechnical Services, Seepage Evaluation, Carrillo Ranch, Carlsbad, California: dated July 28. Norris, R. M. and Webb, R. W., 1990, Geology of California, Second Edition: John Wiley & Sons, Inc. Pib1ic Works Standards, Inc., 2006, "Greenbook," Standard Specifications for Public Works Construction. United States Department of the Interior, Bureau of Reclamation, 1998, Engineering Geology Field Manual. United States Geological Survey, 1968 (photo-revised 1983), Rancho Santa Fe Quadrangle, Cali- fornia, San Diego County, 7.5-Minute Series (Topographic): Scale 1:24,000. AERIAL PHOTOGRAPHS Source Date Flight Numbers Scale USDA I 4-11-53 AXN-8M I 20 and 21 1:20,000 — 106431001 Rdoc 6 /II15O&FftflWc PA 7> 4STA -J 13 A 3 4" L I "'q, MCCLELUM 4 j ILI A~MRT 7- PA Xj — I CT ! So C 1SB DRr , I :+ " 24 >1 23 71 I LA Z 71 71 Ict REFERENCE: 2005 THOMAS GUIDE FOR SAt. DIEGO COUNTY, STREET GUIDE AND DIRECTORY, C 2400 4800 APPROXIMATE SCALE IN FT OTI.: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE. 1ap . Rand "aftR.LO7.S.I29 IVA War *earn SITE LOCATION MAP FIGURE CARRILLO RANCH SEEPAGE CARLSBAD, CALIFRNIA DROJECT NO. DATE 1Q6431001 11108 Ii I I I I I I I 1 I I I I I IT Li FE I Li —m mom m m men — — — — — — — :"l4w 1.r elf PROPOSED FRENCH DRAIN rl Yr ZZ04 _ Z1 EGENO APPROXIMATE LOCATION OF EXPLORATORY 13ORING TD=TOTAL DEPTH IN FEET NOTE ALL DIMIMSIONS, DIRECTiONS AND LOCATIONS ARE APPROXIMATE. R9ERENCE MICROSOFT LIVE SEARCH MAPS. 2008. 1no&A/loure BORING LOCATION MAP FIGURE I APPROXIMATE SCALE PROJECT NO. I DATE CARRILLO RANCH SEEPAGE 2 0 60 120 FEET 106431001 11/08 CARLSBAD, CALIFORNIA NOT TO SCALE tfin ,ffo&ffiuurp. PROJECT NO. DATE 106431001 11108 FRENCH DRAIN DETAIL CARRILLO RANCH SEEPAGE CARLSBAD, CALIFORNIA FIGURE 3 PIPE WITH A 1% GRADIENT TO A SUITABLE OUTLET (PERFORATIONS DOWN) APPENDIX 0 Carrillo Ranch Seepage November 4, 2008 Carlsbad, California Project No. 106431001 APPENDIX A BORING 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 soil bor- ings. The samples were bagged and transported to the laboratory for testing. Field Procedure for the Collection of Relatively Undisturbed Samples Relatively undisturbed soil samples were obtained in the field using the following method. The Modified Split-Barrel Drive Sampler The sampler, with an external diameter of 3.0 inches, was lined with 1-inch long, thin brass rings with inside diameters of approximately 2.4 inches. The sample barrel was driven into the ground with the weight of a hammer. The samples were removed from the sample barrel in the brass rings, sealed, and transported to the laboratory for testing. 106431001 Rdoc U) - - ° CD C) P :. -J Z BORING LOG EXPLANATION SHEET Bu1ksaniple. IModified split-barrel drive sampler. No recovery with modified split-barrel drive sampler. I Sample retained by others. P Standard Penetration Test (SPT). 5- - No recovery with a SPT. xxixx Shelby tube sample. Distance pushed in inches/length of sample recovered in inches. H No recovery with Shelby tube sampler. Continuous Push Sample. 9 Seepage. to- -. Groundwater encountered during drilling. - - Groundwater measured after drilling. SM ALLUVIUM: Solid line denotes unit change. - - --- cFargJ Attitudes: Strike/Dip b: Bedding - C: Contact Is- j: Joint - f: Fracture F: Fault cs: Clay Seam - Sr Shear bss: Basal Slide Surface - sf: Shear Fracture - sz: Shear Zone - - sbs: Sheared Bedding Surface - The total depth line is a solid line that is drawn at the bottom of the boring. BORING LOG EXPLANATION OF BORING LOG SYMBOLS PROJECT NO. ::=Re1/03 FIGURE U.S.C.S. METHOD OF SOIL CLASSIFICATION MAJOR DIVISIONS SYMBOL TYPICAL NAMES GW Well graded gravels or gravel-sand mixtures, little or no fines GRAVELS GP Poorly graded gravels or gravel-sand Cn • (More than 1/2 of coarse •: mixtures, little or no fines O fraction HJ Cl) N Mfl GM Silty gravels, gravel-sand-silt mixtures > No. 4 sieve size) SANDS o (More than 1/2 of coarse 0 fraction <No. 4 sieve size) Cl) - = SILTS & CLAYS Liquid Limit <50 4>1 • 0 N SILTS & CLAYS Liquid Limit >50 HIGHLY ORGANIC SOILS GC Clayey gravels, gravel-sand-clay mixtures SW Well graded sands or gravelly sands, little or no fines SP Poorly graded sands or gravelly sands, little or no fines SM Silty sands, sand-silt mixtures SC Clayey sands, sand-clay mixtures ML Inorganic silts and very fine sands, rock flour, silty or clayey fine sands or clayey silts with - CL Inorganic clays of low to medium plasticity, - gravelly clays, sandy clays, silty clays, lean OL Organic silts and organic silty clays of low - plasticity MH Inorganic silts, micaceous or diatomaceous - fine sandy or silty soils, elastic silts CH Inorganic clays of high plasticity, fat clays OH Organic clays of medium to high plasticity, - organic silty clays, organic silts - Pt Peat and other highly organic soils GRAIN SIZE CHART RANGE OF GRAIN SIZE CLASSIFICATION U.S. Standard Grain Size in Sieve Size Millimeters BOULDERS Above 12" Above 305 COBBLES 12' 1o3' 305 to 76.2 GRAVEL 3' to No. 4 76.2 to 4.76 Coarse 3' to 3/4" 76.2 to 19.1 Fine 3/4" to No.4 19.1 to 4.76 SAND No. 4 to No. 200 4.76 100.075 Coarse No. 4 to No. 10 4.76 to 2.00 Medium No. 10 to No. 40 2.00100.420 Fine No. 40 to No. 200 0.420 to 0.075 SILT & CLAY Below No. 200 Below 0.075 ,44f/fl44fJ &4flrQ U.S.C.S. METHOD OF SOIL CLASSIFICATION USCS Sod Clui0ottoo Updated Nov.2004 (I) Uj Q. _____ - !. U) 0 w 0 Z <U, _______ DATE DRILLED 10106/08 BORING NO. B-I GROUND ELEVATION 210' ±(MSL) SHEET I OF METHOD OF DRILLING 8" Diameter Hollow Stem Auger (Baja Excavation) DRIVE WEIGHT 140 lbs. (Auto-Trip Hammer) DROP 30" SAMPLED BY PN LOGGED BY PN REVIEWED BY RI DESCRIPTION/INTERPRETATION U -- 9 p _ 18.9 fiu CL _ FILL: Light brown (mottled), moist, stiff, silty CLAY; trace sand and gravel. Increase in moisture content. - 50/I" ______ ________ SANTIAGO PEAK VOLCANICS: Brown and gray, damp, weathered, METAVOLCANIC ROCK; excavated as clayey gravel with sand. Encountered perched water at soil/rock interface. - - - 10- 15- _6.Lj = - Total Depth = 6.1 feet. (Auger Refusal) Seepage encountered at approximately 4.5 feet during drilling. Backfilled shortly after drilling on 10/06/08. Groundwater may rise to a level higher than that measured in borehole due to seasonal variations in precipitation and several other factors as discussed in the report. - - - - - - - N1nuo&Muur 7 BORING BORING LOG CARRILLO RANCH SEEPAGE CALIFORNIA __ CARLSBAD, __________ PROJECT NO. 106431001 DATE 11/08 FIGURE A-I CL 0 U) LL 0 (I) - !. X D 0 . CO w 0 co > Z DATE DRILLED 10/06/08 BORING NO. n-2 GROUND ELEVATION 210't (MSL) SHEET I OF METHOD OF DRILLING 8' Diameter Hollow Stem Auger (Baja Excavation) DRIVE WEIGHT 140 lbs. (Auto-Trip Hammer) DROP 30" SAMPLED BY PN LOGGED BY PN REVIEWED BY RI 75 DESCRIPTIONIINTERPRETATION SC Ellk Brown (mottled), moist, medium dense to dense, clayey SAND; some gravel. SANTIAGO PEAK VOLVANICS: 85/1I" 7.7 Grayish brown, damp, weathered, METAVOLCANIC ROCK; excavated as silty sand and - gravel. 5- - P 50/3" 6.2 50'5" - ! 10- - - - - Total Depth 11 feet. (Auger Refusal) Groundwater not encountered during drilling. Backfihled shortly after drilling on 10/06/08. - - - Note: Groundwater, though not encountered at the time of drilling, may rise to a higher level due to seasonal variations in precipitation and several other factors as discussed in the report. 2 2 2 - - -- N1nuo&Mnwt I BORING LOG CARRftLORANCH SEEPAGE CARLSBAD, CALIFORNIA — - - PROJECT NO. DATE FIGURE L 106431001 11/08 A-2 APPENDIX Carrillo Ranch Seepage November 4, 2008 Carlsbad, California Project No. 106431001 APPENDIX B LABORATORY TESTING Classification Soils were visually and texturally classified in accordance with the Unified Soil Classifica- tion System (USCS) in general accordance with the American Society for Testing and Materials (ASTM) D 2488. Soil classifications are indicated on the log of the exploratory soil borings in Appendix A. Moisture Content The moisture content of samples obtained from the exploratory borings was evaluated in accor- dance with ASTM D 2216. The test results are presented on the logs of the exploratory soil borings in Appendix A. Gradation Analysis Gradation analysis tests were performed on selected representative soil samples in general accordance with ASTM D 422. The grain-size distribution curves are shown on Figure B-i. These test results were utilized in evaluating the soil classifications in accordance with the USCS. 106431001 R.doc U.S. STANDARD SIEVE NUMBERS HYDROMETER Z 1W I'W w 4 100.0 8 18 30 50 100 200 I11ffI 90.0 80.0 I -t -t -I-- I - - - - - - - - - - - - - - - 70.0 II I I if - 60.0 I I - ---- 500 - LL I I I iJT ui 40.0 It 30.0 -i- Lu -- - ---- -- -- 20.0 10.0 I__I_i III 0.0 100 10 1 0.1 0.01 0.001 0.0001 GRAIN SIZE IN MILLIMETERS PERFORMED IN GENERAL ACCORDANCE WITH ASTM 0 422-63(02) /I/fl//C&F/ftOXW GRADATION TEST RESULTS FIGURE PROJECT NO. DATE CARRILLO RANCH SEEPAGE B-I 106431001 11/08 CARLSBAD. CALIFORNIA 0-I J.U-0.U.Xfl GRAVEL SAND FINES Coarse Fine Coarse Medium j Fine SILT CLAY Symbol I Sample Depth I Liquid I Plastic I Plasticity D 10 D D00 I C C0 I Passing I Equivalent Location (ft) I Limit Limit Index No. 200 USCS • 5-2 30-6.0 -- - -- -- -- I 30 SM