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HomeMy WebLinkAboutCT 06-15; TABATA RANCH; GEOTECHNICAL; 2006-08-02RECEIVED AUG 0 7 ?n07 CITY OF CARLSBAD PLANNING DEPT Geotechnical Update Report and Grading Plan Review Proposed Tabata Ranch Subdivision Lemon Leaf Drive, Carlsbad, California August 2, 2006 Prepared For: MR. GREG HARRINGTON P.O. Box 679 Carlsbad, California 92018 Prepared By: VINJE & MIDDLETON ENGINEERING, INC. 2450 Vineyard Avenue, Suite 102 Escondido, California 92029 Job #01-364-P ViNTE & MIDDLETON ENGINEERING, INC. Job #01-364-P 2450 Vineyard Avenue Escondido, California 92029-1229 Phone (760)743-1214 Fax (760) 739-0343 August 2, 2006 Mr. Greg Harrington P.O. Box 679 Carlsbad, California 92018 GEOTECHNICAL UPDATE REPORT AND GRADING PLAN REVIEW, PROPOSED TABATA RANCH SUBDIVISION, LEMON LEAF DRIVE, CARLSBAD, CALIFORNIA Pursuant to your request, Vinje and Middleton Engineering, Inc., has completed the enclosed Geotechnical Update Report and Grading Plan Review for the above-referenced project site. The following report summarizes the results of our research and review of previous pertinent geotechnical reports and maps, current field inspections, additional laboratory testing and engineering analyses and provides update conclusions and recommendations for the proposed development as understood. From a geotechnical engineering standpoint, it is our opinion that the site is suitable for the planned residential subdivision provided the recommendations presented in this report are incorporated into the design and construction of the project. The conclusions and recommendations provided in this study are consistent with the indicated site geotechnical conditions and are intended to aid in preparation of final development plans and allow more accurate estimates of development costs. If you have any questions or need clarification, please do not hesitate to contact this office. Reference to our Job #01-364-P will help to expedite our response to your inquiries. We appreciate this opportunity to be of service to you. VINJE & MIDDLETON ENGINEERING, INC. Dennis Middleton CEG #980 DM/jt TABLE OF CONTENTS PAGE NO. I. INTRODUCTION 1 II. SITE DESCRIPTION / PROPOSED DEVELOPMENT 1 III. GEOTECHNICAL CONDITIONS 2 A. Earth Materials 2 B. Slope Stability 3 C. Seismicity 3 D. Added Laboratory Tests 3 IV. SITE CORROSION ASSESSMENT 4 V. CONCLUSIONS AND RECOMMENDATIONS 5 VI. LIMITATIONS 9 REFERENCES TABLE NO. Site Specific Seismic Parameters 1 pH and Resistivity Test 2 Sulfate Test 3 Chloride Test 4 Years to Perforation of Steel Culverts 5 PLATE NO. Grading Plan 1 Geologic Cross-Sections 2-3 Key and Benching Details 4-5 APPENDIX A Preliminary Geotechnical Investigation Dated October 24, 2001 GEOTECHNICAL UPDATE REPORT AND GRADING PLAN REVIEW PROPOSED TABATA RANCH SUBDIVISION LEMON LEAF DRIVE, CARLSBAD, CALIFORNIA I. INTRODUCTION Precise Grading Plans for the planned residential subdivision at the above-referenced property have recently been completed by Pasco Engineering. A copy of the plan is enclosed with this report as Plate 1. A previous study of the property by this office resulted in the following report of site geotechnical conditions: "Preliminary Geotechnical Investigation, Proposed 4-Lot Subdivision Tabata Ranch off Camino De Las Ondas And Lonicera Street, Carlsbad," Job #01-364-P, dated October 24, 2001 A copy ofthe above-referenced report is included with this report as Appendix A. The purpose of this work was to update the enclosed report to current codes and standards and to provide additional recommendations that are compatible to the enclosed plan. Our efforts also included a recent site inspection, and additional surface soil sampling and laboratory testing as required by the current building industry standards. II. SITE DESCRIPTION / PROPOSED DEVELOPMENT The scope of the planned new development is delineated on the enclosed Plate 1. The lower west portion ofthe property has been partially graded in connection with the recent development of the adjacent property to the west. The graded areas include much of an entrance roadway that will provide access to three of the proposed lots from Lonicera Street. The following technical reports relate to the west perimeter grading and improvements completed at the project site: 1. "Final Report of Testing and Observation Services During Site Grading, Tabata Property Driveway on Lot 35, City of Carlsbad Tract No. 98-14, Carlsbad, California", report prepared by GeoCon, dated February 8, 2006. "Final Report of Testing and Observation Services During Site Grading, Thompson / Tabata Property, Phase 2, Lot No's 16 through 54, and 177 through 197, City of Carlsbad Tract No. 98-14, Carlsbad, California", report prepared by GeoCon, dated September 30, 2004. ViNJH & MrODLETON ENCINFJ-IKING, INC. • 2450 Vineyard Avenue • Escondido, Califomia 92029-1229 • Phone (760) 743-1214 GEOTECHNICAL UPDATE REPORT AND GRADING PLAN REVIEW PAGE 2 LEMON LEAF DRIVE, CARLSBAD, CALIFORNIA AUGUST 2, 2006 The above-referenced reports were reviewed in connection with this effort and copies are available at this office. Resulting elevations in the graded areas of the property are as shown on the enclosed Plate 1 and geotechnical Cross-Sections enclosed herein as Plates 2 and 3. Other areas of the property remain the same as reported in the referenced Preliminary Geotechnical Investigation report, dated October 24, 2001. These include upper, nearly level terrain much of which presently supports a dwelling and associated structures planned for demolition. The Grading Plan (Plate 1) depicts the creation of 5 residential lots by minor to modest cut- fill grading. Slopes are programmed at 2:1 gradients and reach a maximum height of 16 feet. Access to the elevated Lots 1 and 2 will be provided from the Lemon Leaf Drive. The entrance cul-de-sac roadway will provide access to the proposed lots 3, 4 and 5 from Lonicera Street. A temporary slope is proposed at the end ofthe driveway on Lot 3 which will be redesigned /removed based on site adaptive architecture (see Plate 1). Building and foundation plans are not available. However, the use of conventional wood- frame with exterior stucco buildings supported on shallow foundations with stem walls and slab-on-grade floors or slab-on-ground with turned-down footings are assumed for the purpose of this update study. III. GEOTECHNICAL CONDITIONS Detailed site and geotechnical conditions at the project site were outlined in the referenced Preliminary Geotechnical Investigation Report. Except for the recently graded entrance roadway, surface and geotechnical conditions at the site remain the same as previously reported. A. Earth Materials The project site is underlain by Eocene age sedimentary bedrock units consisting of massive sandstone in a cemented condition. Surface terrain is mantied by a modest cover of topsoil / colluvium and old fill soils cover much of the south portion as shown on Plate 1. Much of the site surface soils will be removed by cut grading and exported from the property. Remaining surface soils will also be removed to underlying bedrock units prior to placing new fill as recommended in the referenced report. Details of site earth materials are given on the exploratory Test Trench Logs included in Appendix A (Plates 3-5). Trench locations are shown on the enclosed Plate 1. VlNJt; & MiDOLHTON ENCHNF.F.KINci, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 * Phone (760) 743-1214 GEOTECHNICAL UPDATE REPORT AND GRADING PLAN REVIEW PAGE 3 LEMON LEAF DRIVE, CARLSBAD, CALIFORNIA AUGUST 2, 2006 B. Slope Stability Slope instability is not indicated in site exposures. A large graded cut slope below the south margin of the property (above nearby Poinsettia Lane) has performed well since its creation. Site bedrock units are massive sandstone deposits that characteristically perform well in graded slope conditions and provide a good support for planned new fills, structures and improvements. Existing graded slopes below the west margin of the property have recently been constructed (see Plates 1 and 2) and were inspected by others . Details of exposed conditions are outlined in the referenced reports, prepared by GeoCon, Inc. C. Seismicity The seismic environment at the project site is outlined in the referenced Preliminary Report enclosed with this report as Appendix A. The following supplemental evaluations were also performed based on the indicated project seismic environment, and our experience with similar earth deposits in the vicinity of the project site, and will supersede those previously provided where appropriate and applicable: TABLE 1 Site Soil Profile Type Seismic Zone Seismic Zone Factor Seismic Source Type Seismic Response Coefficients Site Soil Profile Type Seismic Zone Seismic Zone Factor Seismic Source Type Na Nv Ca Cv T? To SD 4 0.4 B 1.0 1.1 0.44 0.70 0.635 0.127 According to Chapter 16, Divisions IV & V of the 2001 California Building Code. A site specific probabilistic estimation of peak ground acceleration was performed using the FRISKSP (T. Blake, 2000) computer program. Based upon Boore et al (1997) attenuation relationship, a 10 percent probability of exceedance in 50 years was estimated to produce a site specific peak ground acceleration of 0.30g (Design-Basis Earthquake, DBE). The results were obtained from the corresponding probability of exceedance versus acceleration curve. D. Added Laboratory Tests Added laboratory tests were conducted on representative site soil samples recently collected at the site. The following tests were completed: VlNJH & MiDDLKTON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, Califomia 92029-1229 • Phone (760) 743-1214 GEOTECHNICAL UPDATE REPORT AND GRADING PLAN REVIEW PAGE 4 LEMON LEAF DRIVE, CARLSBAD, CALIFORNIA AUGUST 2, 2006 1. pH and Resistivity Test: pH and resistivity of a representative sample of surface soils was determined using "Method for Estimating the Service Life of Steel Culverts," in accordance with the California Test Method (CTM) 643. The test result is presented in Table 2. TABLE 2 Soli Type IVIinimum Resistivity (OHM-CM) pH Surface Soils 594 6.46 2. Sulfate Test: A sulfate test was performed on a representative sample of surface soils in accordance with the California Test Method (CTM) 417. The test result is presented in Table 3. TABLE 3 Son Type Amount of Watat Soluble Sulfate (S04) In Soil (% by Weight) Surface Soils 0.015 Chloride Test: A chloride test was performed on a representative sample of surface soils in accordance with the California Test Method (CTM) 422. The test result is presented in Table 4. TABLE 4 Soil Type Amount of Wafer Soluble SulMe (cl) In Soil (% by Weight) Surface Soils 0.069 IV. SITE CORROSION ASSESSMENT A site is considered to be corrosive to foundation elements, walls and drainage structures if one or more of the following conditions exist: * Sulfate concentration is greater than or equal to 2000 ppm (0.2% by weight). * Chloride concentration is greater than or equal to 500 ppm (0.05 % by weight). * pH is less than 5.5. ViNjK & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, Califomia 92029-1229 • Phone (760) 743-1214 GEOTECHNICAL UPDATE REPORT AND GRADING PLAN REVIEW PAGE 5 LEMON LEAF DRIVE, CARLSBAD, CALIFORNIA AUGUST 2, 2006 For structural elements, the minimum resistivity of soil (or water) indicate the relative quantity of soluble salts present in the soil (or water). In general, a minimum resistivity value for soil (or water) less than 1000 ohm-cm indicates the presence of high quantities of soluble salts and a higher propensity for corrosion. Appropriate corrosion mitigation measures for corrosive conditions should be selected depending on the service environment, amount of aggressive ion salts (chloride or sulfate), pH levels and the desired service life of the structure. Limited laboratory testing performed on selected representative site samples indicated that the minimum resistivity is less than 1000 ohm-cm suggesting presence of high quantities of soluble salts. Test results further indicated pH is greater than 5.5 and sulfate concentration is less than 2000 ppm. However, chloride concentration was found to be greater than 500 ppm. Based on the available limited corrosion analyses performed on selected samples, the project site is considered corrosive. Corrosion mitigation should be implemented and incorporated into the design of new structures and associated improvements. A corrosion engineer should be consulted in this regard and additional corrosion conformation testing may be considered at the completion of remedial grading and earthwork operations. The project site is not located within 1000 feet of sea or brackish water. The amount of water soluble sulfate (804) was found to be 0.015 percent by weight which is considered negligible according to the California Building Code Table No. 19-A-4. Portland cement Type II may be considered. However, due to the site corrosiveness, Portland cement Type V (minimum f c = 4500 psi, maximum water cement ratio = 0.45) and steel reinforcement covering greater than 3 inches or as determined appropriate by the project corrosion / structural engineer should be considered. Table 5 is appropriate based on the pH-Resistivity test results: TABLE 5 Design Soil Type Gage 18 16 14 12 10 8 Surface Soils Years to Perforation of Steel Culverts 8 10 12 17 22 27 V. CONCLUSIONS AND RECOMMENDATIONS Site geotechnical conditions remain the same as reported in the referenced Preliminary Geotechnical Report (Appendix A). The Project Grading Plan (Figure 1) also represents a feasible design from a geotechnical engineering viewpoint. All conclusions and recommendations provided in the referenced report remain valid and should be considered in final designs and implemented during the construction phase except where specifically superseded below: VINJF; & MIDDLETON ENGINEERING, INC. • 2450 Vincy.ard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 GEOTECHNICAL UPDATE REPORT AND GRADING PLAN REVIEW PAGE 6 LEMON LEAF DRIVE, CARLSBAD, CALIFORNIA AUGUST 2, 2006 1. Existing graded slopes to the western portions of project property are engineered embankments constructed under engineering observations of testing provided by others. The existing cut slopes below the project south margin are also underlain by competent sandstone units with no evidence of geologic instability. New graded slopes are also programmed for 2:1 gradients and will be constructed as recommended as specified. Slope stability is not considered a major geotechnical concern at the project site. Other adverse geologic conditions including faults or significant shear zone which could preclude site development were also not indicated at the property. 2. New graded slopes to be constructed as specified in the referenced report and as directed in the field in general accordance with the enclosed Typical Key Benching Details, Plates 4 and 5. All graded slopes greater than 30 feet in maximum vertical height should be provided with adequate drainage terraces per applicable codes and standards, unless othen/vise approved or specified. 3. Excavations, trenching and temporary backcut slopes adjacent to the existing structures/foundations and improvements shall be performed under inspections of the project geotechnical engineer. Undermining existing structures/improvements and underground utilities to remain shall not be allowed by the project earthwork operations and constructions. Top of temporary construction slopes and site excavations should maintain adequate set-backs (1-foot minimum) from the existing structures and improvements as directed in the field. Project temporary construction slopes and trench excavations less than 3 feet high may constructed at near vertical gradients. Construction slopes greater than 3 feet and less than 10 feet maximum exposing dense sandstone units may be constructed at near vertical gradient within the lower 3 feet and laid back at >^:1 gradients maximum within the upper portions. The backfill soils should then be properly benched and tightly keyed into the temporary side slopes as the backfilling progresses, and as directed in the field by the project geotechnical consultant. The construction slope should be protected from rain and irrigation water. Stockpiling the removed soils atop the construction slope should also not be allowed. Periodic inspections of the temporary slopes, trench excavations and backcut embankments shall be required and should be performed by the project geotechnical consultant. The need for flatter slope gradients or shoring shall be determined at that time based on actual field exposures and should anticipated. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 GEOTECHNICAL UPDATE REPORT AND GRADING PLAN REVIEW PAGE 7 LEMON LEAF DRIVE, CARLSBAD, CALIFORNIA AUGUST 2, 2006 The project contractor shall also obtain appropriate permits, as necessary, and conform to Cal-OSHA and local governing agencies for a safe construction site and protection of the workmen. Permits to perform off-site grading and earthworks, if applicable, should be obtained as appropriate and necessary. 4. Site remedial grading and proposed reconstructions is not expected to impact the adjacent properties provided our recommendations are incorporated into the field procedures and implemented during the construction phase. Added field recommendations, however, may also be necessary and should be given by the project geotechnical consultant for the protection of adjacent properties and should be anticipated. 5. Remedial grading and bearing/subgrade soils preparations will be required in all areas ofthe property to receive new fills, structures and improvements plus 10 feet outside the perimeter as specified in the referenced report. Approximate removal depths are also provided in the referenced report. However, specific removal depths should be given by the project geotechnical consultant in the field at the time of grading operations based on actual exposures. Locally deeper removals may be necessary and should be anticipated. Bottom of all removals should be additionally prepared and recompacted to a minimum depth of 6 inches as directed in the field. All grounds steeper than 5:1 receiving fills/backfills should be properly benched and keyed prior to fill/backfill placement. 6. Compaction procedures and fill materials specification remain the same as specified. A minimum 90% compaction levels will be required for all fills, and wall and trench backfills unless othenwise specified. Subgrade soils beneath the asphalt paving surfaces should be compacted to a minimum 95% ofthe corresponding maximum dry density within the upper 12 inches. 7. Expansive soils are not expected to be a factor in the site development. Project earth materials at final pad grades are anticipated to predominantly consist of silty sandy (SM) deposits with very low expansion potential (expansion index less than 21) according to the California Building Code classification (Table 18A-I-B). 8. Soil design parameters and foundation/slab recommendations will remain the same as specified. ViNiF & MIDDLETON ENGINBERINC;, INC. • 2450 Vincy.ird Avenue • Escondido, Califomia 92029-1229 • Phone (760) 743-1214 GEOTECHNICAL UPDATE REPORT AND GRADING PLAN REVIEW PAGE 8 LEMON LEAF DRIVE, CARLSBAD, CALIFORNIA AUGUST 2, 2006 Open or backfilled trenches parallel with a footing shall not be below a projected plane having a downward slope of 1-unit vertical to 2 units horizontal (50%) from a line 9 inches above the bottom edge ofthe footing, and not closer than 18 inches form the face of such footing. Where pipes cross under-footings, the footings shall be specially designed. Pipe sleeves shall be provided where pipes cross through footings or footing walls, and sleeve clearances shall provide for possible footing settlement, but not less than 1-inch all around the pipe. Foundations for all buildings, walls and structures, where the surface of the ground slopes more than 1-unit vertical in 10 units horizontal (10% slope) shall be level or shall be stepped so that both top and bottom of such foundation are level. Individual steps in confinuous footings shall not exceed 18 inches in height and the slope of a series of such steps shall not exceed 1-unit vertical to 2 units horizontal (50%) unless othenwise specified. The steps shall be detailed on the structural drawings. The local effects due to the discontinuity of the steps shall also be considered in the design of foundations as appropriate and applicable. Minimum pavement structural secfion design as specified in the referenced report or the minimum structural section required by the City of Carlsbad, whichever is more, may be considered for initial planning phase cost estimating purposes only for the on-site asphalt paving surfaces outside the public and private right-of-way. New pavement sections and street improvements within the public right-of-way shall conform to the minimum requirements established by the City of Carlsbaci standards and improvement plans. Actual design will also depend on the design traffic index (Tl) and approval of the City of Carlsbad. Revised structural sections may be necessary and should be anticipated. In the areas where the longitudinal grades exceed 10%, Va-inch asphalt should be added to the design asphalt thickness for each 2% increase in grade or portions thereof PCC paving surfaces are recommended for longitudinal grades over 15%. In the areas where PCC paving longitudinal grades exceed 20%, provide minimum 8 inches wide by 12 inches deep pavement shear anchors dug perpendicular to the driveway longitudinal profile into the approved subgrade at each 25 feet intervals maximum. The pavement shear anchors should be poured monolithically with the concrete paving surfaces. VINIE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 GEOTECHNICAL UPDATE REPORT AND GRADING PLAN REVIEW PAGE 9 LEMON LEAF DRIVE, CARLSBAD, CALIFORNIA AUGUST 2, 2006 VI. LIMITATIONS The conclusions and recommendations provided herein have been based on all available data obtained from the review of pertinent geotechnical documents, current site observations, soil sampling, laboratory testing, as well as our experience with the soils and formational materials located in the general area. The materials encountered on the project site and utilized in laboratory testing are believed representative of the total area; however, earth materials may vary in characteristics between exposures. Of necessity we must assume a certain degree of continuity between exploratory excavations and/or natural exposures. It is necessary, therefore, that all observations, conclusions, and recommendations be verified during the grading operation. In the event discrepancies are noted, we should be contacted immediately so that an inspection can be made and additional recommendations issued if required. The recommendations made in this report are applicable to the site at the time this report was prepared. It is the responsibility of the owner/developer to ensure that these recommendations are carried out in the field. It is almost impossible to predict with certainty the future performance of a property. The future behavior of the site is also dependent on numerous unpredictable variables, such as earthquakes, rainfall, and on-site drainage patterns. The firm of VINJE & MIDDLETON ENGINEERING, INC., shall not be held responsible for changes to the physical conditions of the property such as addition of fill soils, added cut slopes, or changing drainage patterns which occur without our inspection or control. The property owner(s) should be aware that the development of cracks in all concrete surfaces such as floor slabs and exterior stucco are associated with normal concrete shrinkage during the curing process. These features depend chiefly upon the condition of concrete and weather conditions at the time of construction and do not reflect detrimental ground movement. Hairline stucco cracks will often develop at window/door corners, and floor surface cracks up to Vs-inch wide in 20 feet may develop as a result of normal concrete shrinkage (according to the American Concrete Institute). This report should be considered valid for a period of one year and is subject to review by our firm following that time. If significant modifications are made to your tentative development plan, especially with respect to the height and location of cut and fill slopes, this report must be presented to us for review and possible revision. This report is issued with the understanding that the owner or his representative is responsible to ensure that the information and recommendations are provided to the project architect/structural engineer so that they can be incorporated into the plans. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Viney.ird Avenue • Escondiedo, California 92029-1229 • Phone (760) 743-1214 GEOTECHNICAL UPDATE REPORT AND GRADING PLAN REVIEW PAGE 10 LEMON LEAF DRIVE, CARLSBAD, CALIFORNIA AUGUST 2, 2006 Necessary steps shall be taken to ensure that the project general contractor and subcontractors carry out such recommendations during construction. The project soils engineer should be provided the opportunity for a general review of the project final design plans and specifications in order to ensure that the recommendations provided in this report are properly interpreted and implemented. The project soils engineer should also be provided the opportunity to field verify the foundations prior the placing concrete. If the project soils engineer is not provided the opportunity of making these reviews, he can assume no responsibility for misinterpretation of his recommendations. Vinje & Middleton Engineering, Inc., warrants that this report has been prepared within the limits prescribed by our client with the usual thoroughness and competence of the engineering profession. No other warranty or representation, either expressed or implied, is included or intended. Once again, should any questions arise concerning this report, please do not hesitate to contact this office. Reference to our Job #01-364-P will help to expedite our response to your inquiries. We appreciate this opportunity to be of service to you. VINJE & MIDDLETON ENGINEERING, INC. Dennis Middleton CEG #980 hdi S. Shi 46174 Steven J. Melzer CEG #2362 DM/SMSS/SJM/jt Enclosures Distribution: Addressee (1) Pasco Engineering; Attn: Mr. Jim Boeker (5) c:/jt/myfiles/06-updates/01 -364-P VINIE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, Califomia 92029-1229 • Phone (760) 743-1214 REFERENCES Annual Book of ASTM Standards, Section 4 - Construction, Volume 04.08: Soil And Rock (I); D 420-D 5611, 2005. Annual Book of ASTM Standards, Section 4 - Construction, Volume 04.09: Soil And Rock (II); D 5714 - Latest, 2005. Highway Design Manual, Caltrans. Fifth Edition. Corrosion Guidelines, Caltrans, Version 1.0, September 2003. California Building Code, Volumes 1 & 2, International Conference of Building Officials, 2001. "Green Book" Standard Specifications For Public Works Construction, Public Works Standards, Inc., BNi Building News, 2003 Edition. California Department of Conservation, Division of Mines and Geology (California Geological Survey), 1997, Guidelines for Evaluating and Mitigating Seismic Hazards in California, DMG Special Publication 117, 71p. California Department of Consen/ation, Division of Mines and Geology (California Geological Survey), 1986 (revised), Guidelines for Preparing Engineering Geology Reports: DMG Note 44. California Department of Consen/ation, Division of Mines and Geology (California Geological Survey), 1986 (revised). Guidelines to Geologic and Seismic Reports: DMG Note 42. EQFAULT, Ver. 3.00, 1997, Deterministic Estimation of Peak Acceleration from Digitized Faults, Computer Program, T. Blake Computer Services And Software. EQSEARCH, Ver 3.00, 1997, Estimation of Peak Acceleration from California Earthquake Catalogs, Computer Program, T. Blake Computer Services And Software. Tan S.S. and Kennedy, M.P., 1996, Geologic Maps ofthe Northwestern Part of San Diego County, Califomia, Plate(s) 1 and 2, Open File-Report 96-02, California Division of Mines and Geology, 1:24,000. UBCSEIS, Ver. 1.03, 1997, Computation of 1997 Uniform Building Code Seismic Design Parameters, Computer Program, T. Blake Computer Services And Software. "Proceeding of The NCEER Workshop on Evaluation of Liquefaction Resistance Soils," Edited by T. Leslie Youd And Izzat M. Idriss, Technical Report NCEER-97-0022, Dated December 31, 1997. "Recommended Procedures For Implementation of DMG Special Publication 117 Guidelines For Analyzing And Mitigation Liquefaction In California," Southern California Earthquake center; USC, March 1999. "Soil Mechanics," Naval Facilities Engineering Command, DM 7.01. "Foundations & Earth Structures," Naval Facilities Engineering Command, DM 7.02. "Introduction to Geotechnical Engineering, Robert D. Holtz, William D. Kovacs. "Introductory Soil Mechanics And Foundations: Geotechnical Engineering," George F. Sowers, Fourth Edition. "Foundation Analysis And Design," Joseph E. Bowels. Caterpillar Performance Handbook, Edition 29, 1998. Jennings, C.W., 1994, Fault Activity Map of California and Adjacent Areas, California Division of Mines and Geology, Geologic Data Map Series, No. 6. Kennedy, M.P., 1977, Recency and Character of Faulting Along the Elsinore Fault Zone in Southern Riverside County, Califomia, Special Report 131, California Division of Mines and Geology, Plate 1 (East/West), 12p. Kennedy, M.P. and Peterson, G.L., 1975, Geology of the San Diego Metropolitan Area, California: California Division of Mines and Geology Bulletin 200, 56p. Kennedy, M.P. and Tan, S.S., 1977, Geology of National City, Imperial Beach and Otay Mesa Quadrangles, Southern San Diego Metropolitan Area, California, Map Sheet 24, California Division of Mines and Geology, 1:24,000. Kennedy, M.P., Tan, S.S., Chapman, R.H., and Chase, G.W., 1975, Character and Recency of Faulting, San Diego Metropolitan Areas, Califomia: Special Report 123, 33p. Caterpillar Performance Handbook, Edition 29, 1998. Jennings, C.W., 1994, Fault Activity Map of California and Adjacent Areas, California Division of Mines and Geology, Geologic Data Map Series, No. 6. Kennedy, M.P., 1977, Recency and Character of Faulting Along the Elsinore Fault Zone in Southern Riverside County, California, Special Report 131, California Division of Mines and Geology, Plate 1 (East/West), 12p. Kennedy, M.P. and Peterson, G.L., 1975, Geology of the San Diego Metropolitan Area, Califomia: California Division of Mines and Geology Bulletin 200, 56p. Kennedy, M.P. and Tan, S.S., 1977, Geology of National City, Imperial Beach and Otay Mesa Quadrangles, Southern San Diego Metropolitan Area, California, Map Sheet 24, California Division of Mines and Geology, 1:24,000. Kennedy, M.P., Tan, S.S., Chapman, R.H., and Chase, G.W., 1975, Character and Recency of Faulting, San Diego Metropolitan Areas, California: Special Report 123, 33p. "An Engineering Manual For Slope Stability Studies," J.M. Duncan, A.L. Buchignani And Marius De Wet, Virginia Polytechnic Institute And State University, March 1987. "Procedure To Evaluate Earthquake-Induced Settlements In Dry Sandy Soils," Daniel Pradel, ASCE Journal Of Geotechnical & Geoenvironmental Engineering, Volume 124, #4, 1998. -exBTSehsmir omm Pipe \ a 8- a»BB mm- JE - SAi.ie WOP JS'flOPiiwE-Lf iMM: MUN- iflrt i // \ 25/01 SF I PLATE 1 ^ ^ TENTAWEivlAF TABATA RANCH CT/ CDP/HDP/Za GPA/LCPA Scale: 1"=40' 20 40 60 te ma atatmsm mp aauom un LJm Bim. aamata LOT MSt (BROn C •ED PREP, cannun Btm. axe v mieewr CEWBUNF MWSED smm IMUN wopom pemma mu. Biarme swm au» FROMOD TYW I"" etroi d*sm Pfema mv s-i on nter MOMS) SMR MUM PRomD wm wn L0r4 luooar yiv yp. /f» TEST THENCH (FROM 10-17-2001) GEOLOGIC CROSS-SECTION .20 00' ggj IS \ V>— ,®":~ 0 , m. sas77 , VEXP. 03/31/07 1 SHEET -300 Rough grading completed (TESTED AND INSPECTED BY OTHERS) FL 250 250 - 250 250 Proposed grade (WORK TO BE DONE) Rough grading completed (TESTED AND INSPECTED BY O THERS) ZL Rough grading completed (TESTED AND INSPECTED BY O THERS) •300 -250 - 300 250--250 D)0 Rough grading completed (TESTED.AND INSPECTED BY OTHERS) Proposed gradeb 300 - 250 Proposed grade (WORK TO BE DONE) 250 9 300 250 PLATE 2 Scale: 1"=40' PLATE 3 300- 250- Proposed grade (WORK TO BE DONE) ^—:7 -77^ - 300 - 250 Scale: 1"=40' KEY AND BENCHING DETAILS (Typical - no scale) existing ground, surface project 1:1 line from top of slope to outside edge of key finish cut pad pad overexcavation and recompaction per project geotechnical engineer / t bedrock or firip/ competent native ground per project geotechnical engineer Side Hin Stability Fill Slope finish slope finish pad existing ground surface Sffi remove unsuitable materials 15 • mm. 2' min. key width key depth competent bedrock or firm native ground per project geotechnical engineer Fill Slope Note: Key and benching details shown herein are subject to revisions by the project geotechnical engineer based upon actual site conditions. Back drains may also be necessary as determined by the project geotechnical consultant. PLATE 4 I I KEY AND BENCHING DETAILS (Typical - No Scale) finish slope finish pad. existing ground surface cut slope (to be excavated prior to fill placement) bench competent bedrock or firm native ground per- project geotechnical consultant Fill-Over-Cut Slope finish pad existing ground surface remove unsuitable materials project 1:1 line from toe of slope to competent materials cut slope (to be excavated prior to fill placement) bench per project geotechnical engineer in the field - also, see geotechnical report competent bedrock or firm native ground per project geotechnical consultant 2' min. key depth 15' min. key width Cut-Over-Fill Slope Note: Key and benching details shown herein are subject to revision by the project geotechnical engineer based upon actual site conditions. Back drains may also be necessary as determined by the project geotechnical consultant. PLATE 5 APPENDIX A Preliminary Geotechnical Investigation Proposed 4-Lot Subdivision, Tabata Ranch off Camino De Las Ondas and Lonicera Street Carlsbad, California (Parcel Map #2147054 and 72) October 24, 2001 Prepared For: MR. GREG HARRINGTON P.O. Box 679 Carlsbad, California 92018 Prepared By: VINJE & MIDDLETON ENGINEERING, INC. 2450 Vineyard Avenue, Suite 102 Escondido, California 92029 Job #01-364-P ViNTE & MIDDLETON ENGINEERING^ INC. Job #01-364-P October 24, 2001 2450 Vineyard Avenue Escondido, California 92029-1229 Phone (760) 743-1214 Fax (760) 739-0343 Mr. Greg Harrington P.O. Box 679 Carlsbad, California 92018 PRELIMINARY GEOTECHNICAL INVESTIGATION, PROPOSED 4-LOT SUBDIVISION, TABATA RANCH, OFF CAMINO DE LAS ONDAS AND LONICERA STREET, CARLSBAD, CALIFORNIA (PARCEL MAP #2147054 AND 72) Pursuant to your request, Vinje and Middleton Engineering, Inc., has completed the attached Preliminary Geotechnical Investigation Report forthe above-referenced project site. The following report summarizes the results of our research and review of pertinent geotechnical maps and reports, subsurface field investigation and soil sampling, laboratory testing, engineering analyses and provides conclusions and construction recommendations for the proposed development as understood. From a geotechnical engineering standpoint, it is our opinion that the site is suitable for the proposed 4-lot residential subdivision and the associated improvements, provided the recommendations presented in this report are incorporated into the design and reconstruction of the project. The conclusions and recommendations provided in this study are consistent with the site geotechnical conditions and are intended to aid in preparation of final development plans and allow more accurate estimates of the construction costs. If you have any questions or need clarification, please do not hesitate to contact this office. Reference to our Job #01-364-P will help to expedite our response to your inquiries. We appreciate this opportunity to be of service to you. VINJE & MIDDLETON ENGINEERING, INC. Dennis Middleton CEG #980 DM/jt TABLE OF CONTENTS PAGE NO. I. INTRODUCTION 1 II. SITE DESCRIPTION 1 III. PROPOSED DEVELOPMENT 1 IV. SITE INVESTIGATION 2 V. GEOTECHNICAL CONDITIONS 2 A. Earth Materials 2 B. Groundwater 3 C. Slope Stability 3 D. Faults / Seismicity 3 E. Geologic Hazards 6 F. Laboratory Testing / Results 6 VI. CONCLUSIONS 8 VII. RECOMMENDATIONS 9 A. Grading and Earthworks 9 B. Foundations and Interior Floor Slabs 14 C. Exterior Concrete Slabs / Flatworks 16 D. Soil Design Parameters 16 E. Asphalt and PCC Pavement Design 17 F. General Recommendations 19 VIII. LIMITATIONS 21 TABLE NO. Fault Zone 1 Site Specific Parameters 2 Soil Type 3 Maximum Dry Density and Optimum Moisture Content 4 In-Place Dry Density and Moisture Content 5 Expansion Index Test 6 Direct Shear Test 7 Removals and Ground Treatment 8 PLATE NO. Regional Index Map 1 Site Plan 2 Test Trench Logs (with key) 3-5 Fault - Epicenter Map 6 Isolation Joints and Re-Entrant Corner Reinforcement 7 Retaining Wall Drain Detail 8 PRELIMINARY GEOTECHNICAL INVESTIGATION PROPOSED 4-LOT SUBDIVISION, TABATA RANCH OFF CAMINO DE LAS ONDAS AND LONICERA STREET CARLSBAD, CALIFORNIA I. INTRODUCTION The property investigated in this work includes a 2y2-acre hillside parcel located between Camino De Las Ondas and Poinsettia Lane, in the La Costa area of the City of Cartsbad. The site locafion is shown on a Regional Index Map attached to this report as Plate 1. We understand that the property is planned for a subdivision into 4 individual lots upon which single-family dwellings will be supported. Consequently, the purpose of this study was to determine geologic and soil conditions beneath the property and their influence upon the planned construction. Test hole digging, soil sampling, and laboratory testing were among the activities conducted in connecfion with this study which has resulted in construction and development recommendations provided herein. II. SITE DESCRIPTinM The subject property is a rectangular shaped parcel with the longer axis running north- south. Site access is via a driveway located on the south side of Camino De Las Ondas across from Lonicera Street. The northern half of the site presently supports a single- family dwelling on a level graded cut pad with a fenced yard. Two trailer type storage facilities occupy the southeast portion of the site. The southem half of the site presently IS used for agncultural purposes and has recently been plowed over. Below the upper cut pad, site topography consists of gentiy sloping southwesterty draining terrain with grades approaching 6 (horizontal) to 1 (vertical). The southeast comer of the property is marked by a large 2 (horizontal) to 1 (vertical) cut slope which descends onto Poinsettia Lane below. Details of site topography are shown on a Site Plan attached to this report as Plate III- PROPOSED DEVELQPMFMT The planned site development is depicted on the attached Plate 2. As shown, 4 residential lots created by cut-fill grading will occupy the slope areas of the property An entrance roadway and cul-de-sac will provide access along the upper portion. Lower graded slopes will reach a maximum height of 25 feet at gradients of 2:1. Building plans are not available at this time. However, the use of a conventional wood- trame buildings with exterior stucco supported on shallow still concrete continuous strip and spread pad footings with slab-on-grade floor foundation is assumed for the purpose of this study. \'INIE & MIDDLETON ENGINEERINC, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 PREUMINARY GEOTECHNICAL INVESTIGATION PAGE 2 4-LOT SUBDIVISION, TABATA RANCH. CARLSBAD OCTOBER 24, 2001 IV. SITE INVESTIGATION Site geotechnical conditions were determined from geologic mapping of existing exposures and the excavation of 6 test trenches dug with a tractor-mounted backhoe. All excavations were logged by our project geologist. Representative soil/bedrock samples were retained from trench excavations at selected depths and intervals for subsequent laboratory testing. Exploratory trench locations are shown on Plate 2. Logs of the excavations are included with this report as Plates 3 through 5. Laboratory test results are summarized in a following section: V. GEOTECHNICAL CONDITIONS The project site is a natural hillside parcel underiain by sedimentary formational rocks mantled by a thin soil cover and artificial fill. No evidence of instability is apparent at the property. A. Earth Materials The following earth materials are recognized at the project location: Bedrock - Site terrain is underlain by sedimentary bedrock units of Eocene Age. The exposed rocks typically consist of fine to medium grained massive off-white to yellowish sandstone found in a friable and cemented condition. Site sandstone are stable units which should perform well in graded slopes and will generate good quality fill soils. Topsoil/Colluvium - Topsoil/colluvium overiie bedrock units throughout the site and represent a thin weathered reflection of the underiying sandstone. The soils consist chiefly of silty to clayey sands in a loose condition and range in thickness from r/a to 372 feet. Fill - In the southern portion ofthe site artificial fills mantle site topsoil. Some site fill soil was likely generated during the original grading of the existing cut pad. Additional site fill was imported from grading operations from the residential neighborhood directly north ofthe subject site. Site fill soil is typically light colored silty sands found in an overall loose condition. A small amount of trash and debris was encountered in fill soil exposed in test trench 3. Other local trashy deposits may also exist in site fill soils. As shown in our test trenches, site fill soil ranges from 5/4 feet in thickness. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 3 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD OCTOBER 24, 2001 Details of project earth materials are given on the attached Test Trench Logs, Plates 3 through 5. B. Groundwater Groundwater conditions were not encountered in our test excavations to the depths explored and are not expected to impact the planned development. However, like all hillside properties, the proper control of surface drainage is a critical factor in the continued stability of the graded lots. C. Slope Stability Landslides or other forms of geologic slope instability are not in evidence at the project site. Local bedrock units are characteristically stable materials which are expected to perform well in natural and graded slopes. The nearby areas, large-scale landslides are known within Eocene aged sediments with bedding structure inclined in an unsupported manner. Project sediments are for the most part massive units, or characterized by pooriy developed bedding structure which is flat-lying. Under these conditions, translational failures are not anticipated, and graded cut slopes are expected to be stable. Geologic inspections of cut embankments at the site should be inspected and approved by the project engineering geologist. D. Faults / Seismicity Faults or signiflcant shear zones are not indicated on or near proximity to the project site. As with most areas of California, the San Diego region lies within a seismically active zone; however, coastal areas of the county are characterized by low levels of seismic activity relative to inland areas to the east. During a 40-year period (1934-1974), 37 earthquakes were recorded in San Diego coastal areas by the California Institute of Technology. None of the recorded events exceeded a Richter magnitude of 3.7, nor did any of the earthquakes generate more than modest ground shaking or significant damages. Most of the recorded events occurred along various offshore faults which characteristically generate modest earthquakes. VINIE & MIDDLETON ENCHNEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD PAGE 4 OCTOBER 24, 2001 Historically, the most significant earthquake events which affect local areas originate along well known, distant fault zones to the east and the Coronado Bank Fault to the west. Based upon available seismic data, compiled from California Earthquake Catalogs, the most significant historical event in the area of the study site occurred in 1800 at an estimated distance of 7 miles from the project area. This event, which is thought to have occurred along an off-shore fault, reached an estimated magnitude of 6.5 with estimated bedrock acceleration values of 0.342g at the project site. The following list represents the most significant faults which commonly impact the region. Estimated ground acceleration data compiled from Digitized California Faults (Computer Program EQ Fault Ver. 2:01) typically associated with the fault is also tabulated. TABLE 1 Fault Zone Distance from Site Maximum Probable Acceleration <R.H.) Elsinore fault 25 miles 0.111g San Jacinto fault 48 miles 0.057g Coronado Bank fault 21 miles 0.154g Newport-lnglewood fault 10 miles 0.138g The location of significant faults and earthquake events relative to the study site are depicted on a Fault - Epicenter Map attached to this report as Plate 6. More recentiy, the number of seismic events which affect the region appears to have heightened somewhat. Nearly 40 earthquakes of magnitude 3.5 or higher have been recorded in coastal regions between January, 1984 and August, 1986. Most ofthe earthquakes are thought to have been generated along offshore faults. For the most part, the recorded events remain moderate shocks which typically resulted in low levels of ground shaking to local areas. A notable exception to this pattern was recorded on July 13, 1986. An earthquake of magnitude 5.3 shook County coastal areas with moderate to locally heavy ground shaking resulting in $700,000 in damages, one death, and injuries to 30 people. The quake occurred along an offshore fault located neariy 30 miles southwest of Oceanside. A series of notable events shook County areas with a (maximum) magnitude 7.4 shock in the early morning of June 28, 1992. These quakes originated along VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vmeyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD PAGE 5 OCTOBER 24, 2001 related segments of the San Andreas Fault approximately 90 miles to the north. Locally high levels of ground shaking over an extended period of time resulted; however, significant damages to local structures were not reported. The increase in earthquake frequency in the region remains a subject of speculation among geologists; however, based upon empirical information and the recorded seismic history of County areas, the 1986 and 1992 events are thought to represent the highest levels of ground shaking which can be expected at the study site as a result of seismic activity. In recent years, the Rose Canyon Fault has received added attention from geologists. The fault is a significant structural feature in metropolitan San Diego which includes a series of parallel breaks trending southward from La Jolla Cove through San Diego Bay toward the Mexican border. Recent trenching along the fault in Rose Canyon indicated that at that location the fault was last active 6,000 to 9,000 years ago. Thus, the fault is classified as "active" by the State of California which defines faults that evidence displacement in the previous 11,000 years as active. More active faults (listed on the preceding page) are considered most likely to impact the region during the lifetime of the project. The faults are periodically active and capable of generating moderate to locally high levels of ground shaking at the site. Ground separation as a result of seismic activity is not expected at the property. For design purposes, site specific seismic parameters were determined as part of this investigation in accordance with the Uniform Building Code. The following parameters are consistent with the indicated project seismic environment and may be utilized for project design work: TABLE 2 Site Soil Profile Type Seismic Zone Seismic Zone Factor Seismic Source Type Seismic Response Coefficients Site Soil Profile Type Seismic Zone Seismic Zone Factor Seismic Source Type Na Nv Ca Cv Ts To Sc 4 0.4 B 1.0 1.1 0.40 0.62 0.616 0.123 According to Chapter 16, Division IV ofthe 1997 Uniform Building Code. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD PAGE 6 OCTOBER 24, 2001 E. Geologic Hazards Geologic hazards are not presently indicated at the project site. Project slope terrain are stable, and proposed cut embankments are expected to expose stable units. The most significant geologic hazards at the property will be those associated with ground shaking in the event of a major seismic event. Liquefaction or related ground rupture failures are not anticipated. F. Laboratory Testing / Results Earth deposits encountered in our exploratory test excavations were closely examined and sampled for laboratory testing. Based upon our test trench data and field exposures, site soils have been grouped into the following soil types: TABLE 3 Soil Type Description 1 tan to red brown silty to clayey sand (fill-topsoil/colluvium) 2 off white to yellow/rust color fine to medium sand (sandstone) The following tests were conducted in support of this investigation: 1. Maximum Dry Density and Optimum Moisture Content: The maximum dry density and optimum moisture content of Soil Types 1 and 2 were determined in accordance with the ASTM D-1557. The test results are presented in Table 4. TABLE 4 Soil Maximum Dry Optimum Moisture Location Type Density (Ym-pcf) Content ((i)opt-%) T-2 @ 2' 1 125.9 11.7 T-2 @ 4' 2 117.9 14.7 In-Place Dry Density and Moisture Content: In-place dry density and moisture contents of representative soil deposits beneath the site were determined from relatively undisturbed chunk samples using the water displacement test method. The test results are presented in Table 5 and tabulated on the attached Test Trench Logs. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD PAGE 7 OCTOBER 24, 2001 TABLE 5 Sample Location Soil Type Fieid Moisture Content (0)-%) Field Dry Density (Yd-pcf) Max. Dry Density (Ym-pcf) Ratio Of in-Piace Dry Density To Max. Dry Density* (Yd/Ym X 100) T-2 @ 2' 1 18.5 102.1 125.9 81.1 T-2 @ 4' 2 12.2 112.2 117.9 95.2 T-3 @ 4' 1 12.8 104.9 125.9 83.3 T-3 @ 6' 1 5.7 111.2 125.9 88.3 T-3 @ 8' 2 9.0 114.5 117.9 97.1 T-4@2' 1 2.5 111.0 125.9 88.1 T-5 @ 2' 1 2.5 109.7 125.9 87.1 T-5 @ 4' 2 1.3 -125.9 sample disturbed * Designated as relative compaction for structural fills. Required relative compaction for structural fill is 90% or greater. 3. Expansion Index Test: Two expansion index tests were performed on representative samples of Soil Types 1 and 2 in accordance with the Uniform Building Code Standard 18-2. The test results are presented in Table 6. TABLE 6 Sample Location Soil Type Remolded U)(%) Saturation (%) Saturated UJ (%) Expansion Index (El) Expansion Potential T-2 @ 2' 1 10.6 49.4 20.0 14 very low T-2 @ 4' 2 11.9 51.0 16.6 0 very low (0)) = moisture content in percent. Direct Shear Test: Two direct shear tests were performed on representative samples of Soil Types 1 and 2. The prepared specimens were soaked overnight, loaded with normal loads of 1, 2, and 4 kips per square foot respectively, and sheared to failure in an undrained condition. The test results are presented in Table 7. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, Cahfomia 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD PAGE 8 OCTOBER 24, 2001 TABLE 7 Wet AhgEf of Apparent Sample Soil Sample Density int. Fric. Cohesion Location Type Condition (Yw-pcf) (O-Deg.) (c-psf) T-2 @ 2' 1 90% remolded 125.6 28 230 T-2 @ 4' 2 90% remolded 121.5 30 150 VI. CONCLUSIONS Based upon the foregoing investigation, development ofthe project site substantially as proposed, is feasible from a geotechnical viewpoint. The following conditions are unique to the project site and will influence grading procedures and development costs from a geotechnical viewpoint: * The project site is mantled by a cover of natural topsoil/colluvium, as well as old fill soil which occur in a loose condition. Below, sandstone bedrock units are stable, competent deposits which will adequately support planned improvements and graded fills. * Cut-flll grading is proposed at the site for the creation of project building pads. However, uniform soil conditions are recommended beneath finish grade pads and can best be accomplished by added removals of the cut portion of each pad. * Excavation difficulties or unusual grading problems are not expected at the project site. * Site soils are granular, non-expansive to very low expansive sandy deposits which work well in compacted fills. Based upon the anticipated grading scheme, flnish grade soils are expected to consist of silty sand deposits (SM) with very low expansion potential (El less than 21). Actual classification and expansion characteristic of finished grade soil mix can only be provided in the final as-graded compaction report based on appropriate testing. * On-site natural terrain and bedrock units are expected to be geologically stable. * The overall stability of graded building surfaces developed over sloping terrain is most dependent upon adequate keying and benching of fill into the undisturbed bedrock during the grading operations. At the project site, added care should be given to proper construcfion of keyways and benching during regrading. \'iN|E & MIDDLETON ENGINF.ERING, INC. • 2450 Vineyard Avenue • Escondido, Cahfornia 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 9 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD OCTOBER 24, 2001 * Natural groundwater is not expected to impact the project development or the long term stability of the developed site. * Adequate site surface drainage control is a critical factor in the future stability of the developed property. * Liquefaction and seismically induced settlements will not be factors in the development of the proposed structures and improvements, provided our soil treatment recommendations are implemented during the grading operations. * Post construction total and differential settlements after building construction are not expected to be factors in the development of the project site, provided our site improvement and foundation recommendations are implemented during the construction phase of the project. * Soil collapse will not be a factor in development of the study site, provided our recommendations for site development are followed. VII. RECOMMENDATIONS The following recommendations are consistent with the indicated geotechnical conditions at the project site and should be reflected in the final plans and implemented during the construction phase. Added or modified recommendations may be appropriate and can be provided at the plan review phase when final grading and building plans are available and actual building locations are established: A. Grading and Earthworks The planned construction areas are directly underiain by loose fills and topsoil/colluvium. Treatment of these deposits will be required as specified below. All grading and earthworks should be completed in accordance with the Appendix Chapter 33 ofthe Uniform Building Code, City of Carlsbad Grading Ordinances, the Standard Specifications for Public Works Construction, and the requirements ofthe following sections: 1. Clearing and Grubbing: Existing vegetation, deleterious materials and debris should be removed from areas to receive fills, structures, and improvements plus 10 feet. All trash and construction debris generated from the demolitions ofthe existing structures/improvements should be properly disposed of from the site. Removals should be inspected and approved by the project geotechnical engineer or his designated field representative prior to grading. VINJE 8d MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD PAGE 10 OCTOBER 24, 2001 All existing underground facilities and utility improvements should be potholed, identified and marked prior to the initiation of the actual grading works. In the event there is a conflict between depths/locations of existing underground improvements/utilities and the recommended depths of over- excavations, this office should be notified to provide further recommendations. Removals and Ground Treatment: The most effective soil improvement method to mitigate loose and compressible upper fills and topsoil/colluvial deposits, will utilize removal and recompaction grading techniques. Site existing loose soils should be removed to the specified depths as recommended herein and placed back as properly compacted fill. Removals should extend a minimum of 10 feet beyond the building perimeter, while extending the removals at a minimum of 3 feet from outside perimeter of the planned improvements, may be adequate unless othenwise specified in the field. Typical removal depths in the vicinity of individual exploratory test sites are shown in Table 8. The tabulated values are subject to changes by the project geotechnical consultant in the field, also depending on the location of the planned buildings and improvements. Locally deeper removals may be necessary based on the actual field exposures and should be anticipated. TABLE 8 Location Total Depth m Estimated Depth to Ground- water (ft) Estimated Removal Depths (ft) Comments T-1 T n/e 372' fill slope, keyway/benching depth may govern T-2 472' n/e 272' fill slope, keyway/benching depth may govern T-3 872 n/e 7' pad areas, existing fill contains trash T-4 5' n/e ZVz pad areas T-5 472 n/e 372' fill slope, keyway/benching depth may govern T-6 472 n/e 3' pad/slope areas, benching depth may govern VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 11 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD OCTOBER 24. 2001 Notes: 1. All depths are measured from the existing ground levels. 2 Actual depths may vary at the fime of construcfion based on seasonal condifions and actual subsurface exposures. 3. Bottom of all removals should be prepared and recompacted as directed in the field. 4. In the parking, roadway and drive lane areas removals will consist of depths to firm native ground or 1-foot below the deepest utility or 3 feet but not less one foot minimum as directed in the field. 5 .Exploratory trenches excavated in connection with our study at the indicated locations were backfilled with loose and uncompacted deposits. The loose/uncompacted backfill soils within these trenches shall also be re-excavated and placed back as properly compacted fills as a part of the project grading operafions. 6 n/e = not encountered. 3. Cut-fill Transition: Ground transition from excavated cut to placed fill should not be permitted underneath the proposed structures and improvements. Transition areas will require special treatment. The cut portion of the cut-fill pads plus 10 feet should be undercut to a sufficient depth to provide for a minimum of 3 feet of compacted fill mat below rough finish grades, or at least 12 inches of compacted fill beneath the deepest footing whichever is more. In the roadways, driveway, parking and on-grade slabs/improvement transition areas, there should be a minimum of 1 foot of compacted soil below rough finish subgrades. 4. Temporary Construction Slopes: Construction slopes required during removal operations should not exceed %:1 gradients maximum. Minor sloughing and caving of the temporary slopes may occur and can be anticipated which will not impact the overall gross stability of the temporary cut banks. Temporary slopes created by the removal operations should not impact the adjacent structures/improvements and existing underground utilities. All underground utilities should be marked and identified prior to grading. Temporary support and shoring may be required for the protection of nearby underground utilities and structures/improvements, and should be anticipated. Appropriate recommendations should be given by the project geotechnical engineer during the grading operations. Safety requirements enforced by the governing agencies for open excavations apply. 5. Fill Materials and Compaction: Soils generated from on-site removals are sandy materials suitable for reuse as new compacted site fills. Trash and construction debris shall not be allowed in compacted fills. Trash contaminated soils may be exported from the site. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 12 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD OCTOBER 24, 2001 Unifomi bearing soil conditions should be constructed at the site by the grading operations. Site soils should be adequately processed, thoroughly mixed, moisture conditioned to near optimum moisture levels, placed in thin uniform horizontal lifts and mechanically compacted to a minimum of 90% of the corresponding laboratory maximum dry density, per the ASTM D-1557, unless OthenA/ise specified. 6. Soil Shrinkage-Bulking and Import Soils: Based upon our analyses, on-site existing fills and topsoil/colluvium may be expected to shrink approximately 5% to 10%, and the soils generated from the excavations ofthe on-site bedrock may be anticipated to bulk nearly the same amount on a volume basis when compacted to at least 90% of the corresponding maximum density. Import soils, if required to complete grading/backfilling, should be non- expansive sandy granular deposits (expansion index less than 21 unless otherwise specified), tested and approved by the project geotechnical engineer prior to delivery to the site. 7. Permanent Graded Slopes: Graded cut-fill slopes should be programmed for 2:1 gradients maximum. Graded slopes constructed as recommended herein, will be grossly stable with respect to deep seated and surficial failures for the anticipated design maximum vertical heights. All fill slopes shall be provided with a lower keyway. The keyway should maintain a minimum depth of 2 feet into the competent bedrock with a minimum width of 12 feet as approved by the project geotechnical engineer or his designated representative. The keyway should expose competent bedrock or firm ground throughout with the bottom heeled back a minimum of 2% into the natural hillside. Additional level benches should be constructed into the natural hillside as the fill slope construction progresses. Fill slopes should also be compacted to 90% (minimum) of the laboratory standard out to the slope face. Over-building and cutting back to the compacted core, or backrolling at a minimum of 3-foot vertical increments and "track-walking" at the completion of grading, is recommended for site fill slope construction. Geotechnical engineering inspections and testing will be necessary to confirm adequate compaction levels within the fill slope face. Cut slopes should be inspected and approved by the project geotechnical consultant during the grading to confirm stability. Additional recommendations will be provided at that time based upon the actual field exposures if necessary. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 13 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD OCTOBER 24, 2001 8. Drainage and Erosion Control: A critical element to the continued stability of the building pads and slopes is an adequate surface drainage system and protection of the slope face. This can most effectively be achieved by appropriate vegetation cover and the installation of the following systems: * Drainage swales should be provided at the top and toe of the graded slopes per the project civil engineer design. * Building pad surface run-off should be collected and directed away from the planned buildings and improvements to a selected location in a controlled manner. Area drains should be installed. * The finished slope should be planted soon after completion of grading. Unprotected slope faces will be subject to severe erosion and should not be allowed. Over-watering ofthe slope faces should also not be allowed. Only the amount of water to sustain vegetation should be provided. 9. Engineering Inspections: All grading operations including removals, suitability of earth deposits used as compacted fill, and compaction procedures should be continuously inspected and tested by the project geotechnical consultant and presented in the final as-graded compaction report. The nature of finished subgrade soils should also be conflrmed in the final compaction report at the completion of grading. Geotechnical engineering inspections shall include, but not limited to the following: * Initial Inspection - After the grading/brushing limits have been staked, but before grading/brushing starts. * Keyway/bottom of over-excavation inspection - After the natural ground or bedrock is exposed and prepared to receive fill, but before fill is placed. * Cut slope/excavation inspection - After the excavation is started, but before the vertical depth of excavation is more than 5 feet. Local and CAL-OSHA safety requirements for open excavations apply. * Fill/wall backfill inspection - After the fill/wall backfill placement is started, but before the vertical height of fill/backfill exceeds 2 feet. A minimum of one test shall be required for each 100 lineal feet maximum, with the exception VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 14 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD OCTOBER 24, 2001 of wall backfills where a minimum of one test shall be required for each 25 lineal feet maximum. Finished rough and final pad grade tests shall be required regardless of fill thickness. * Foundation trench inspection - After the foundation trench excavations, but before steel placement. * Foundation bearing/slab subgrade soils inspection - Within 72 hours prior to the placement of concrete for proper moisture and specified compaction levels. * Geotechnical foundation/slab steel inspection - After the steel placement is completed, but 24 hours before the scheduled concrete pour. * Subdrain/wall back drain inspection - After the trench excavations, but during the actual placement. All material shall conform to the project material specifications and approved by the project geotechnical engineer. * Underground/utility trench inspection - After the trench excavations, but before installation ofthe underground facilities. Local and CAL-OSHA safety requirements for open excavations apply. Inspection of the pipe bedding may also be required by the project geotechnical engineer. * Underground/ufility trench backfill inspection - After the backfill placement is started above the pipe zone, but before the vertical height of backfill exceeds 2 feet. Testing of the backfill within the pipe zone may also be required by the governing agencies. Pipe bedding and backfill materials shall conform to the governing agencies' requirements and project soils report if applicable. All trench backfills shall be compacted to a minimum 90% compaction levels unless othenwise specified. * Pavement/improvements subgrade and basegrade inspections - Within 72 hours prior to the placement of concrete or asphalt for proper moisture and specified compaction levels. B. Foundations and Interior Floor Slabs The following preliminary recommendations are consistent with very low expansive (El less than 21) silty sand (SM) foundation bearing soil. Final foundation and slab ciesign will depend on expansion characteristics of finish grade soils and the actual \'INJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, Cahfornia 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 15 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD OCTOBER 24, 2001 fill differential thickness underneath the proposed buildings. All recommendations should be confirmed and/or revised as necessary in the rough grading compacfion report based on-site as-graded geotechnical conditions and actual testing ofthe foundation bearing earth materials. Individual building sites may require specific foundation/slab design and may be anticipated. Additional specific recommendations may also be necessary and should be given at the time of the plan review phase when detailed grading and structural/architectural drawings are available. 1. Continuous wood stud bearing wall foundations should be sized 15 inches wide and 18 inches deep for single and two-story structures. Isolated pad footings should be at least 24 inches square and 12 inches deep. Footing depths are measured from the lowest adjacent ground surface, not including the sand/gravel beneath floor slabs. Exterior continuous footings should enclose the entire building perimeter. 2. Continuous interior and exterior foundations should be reinforced by at least 4- #4 reinforcing bars. Place a minimum of 2-#4 bars 3 inches above the bottom of the footing, and a minimum of 2-#4 bars 3 inches below the top of the footing. Reinforcement details for spread pad footings should be provided by the project architect/structural engineer. 3. All interior slabs should be a minimum of 4 inches in thickness, reinforced with #3 reinforcing bars spaced 16 inches on center each way, placed mid-height in the slab. Slabs should be underiain by 4 inches of clean sand (SE 30 or greater) which is provided with a 6-mil plastic moisture barrier placed mid-height in the sand. In the case of good quality sandy subgrade soils, as approved by the project geotechnical engineer, the 6-mil plastic moisture barrier may be laid directly over the slab subgrade and covered with a minimum of 2 inches of clean sand (SE 30 or greater). 4. Provide "soft-cut" contraction/control joints consisting of sawcuts spaced 10 feet on center maximum each way for all interior slabs. Cut as soon as the slab will support the weight of the saw and operate without disturbing the final flnish which is normally within 2 hours after final finish at each control joint location or 150 psi to 800 psi. The sawcuts should be a minimum of 1-inch in depth but notto exceed 1%-inches. Anti-ravel skid plates should be used and replaced with each blade to avoid spalling and raveling. Avoid wheeled equipments across cuts for at least 24 hours. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, Cahfornia 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 16 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD OCTOBER 24, 2001 5. Provide re-entrant corner reinforcement for all interior slabs. Re-entrant corners will depend on slab geometry and/or interior column locations. The attached Plate 7 may be used as a general guideline. 6. Foundation trenches and slab subgrade soils should be inspected and tested for proper moisture and specified compaction levels, and approved by the project geotechnical consultant within 72 hours prior to the placement of concrete. C. Exterior Concrete Slabs / Flatworks 1. All exterior slabs (walkways, and pafios) should be a minimum of 4 inches in thickness, reinforced with 6x6/10x10 welded wire mesh carefully placed mid- height in the slab. 2. Provide "soft-cut" contraction/control joints consisting of sawcuts spaced 10 feet on center (not to exceed 12 feet maximum) each way for all exterior slabs. Cut as soon as the slab will support the weight of the saw and operate without disturbing the final finish which is normally within 2 hours after final finish at each control joint location or 150 psi to 800 psi. The sawcuts should be a minimum of 1-inch in depth but not to exceed 1%-inches. Anti-ravel skid plates should be used and replaced with each blade to avoid spalling and raveling. Avoid wheeled equipments across cuts for at least 24 hours. 3. All exterior slab designs should be confirmed in the final as-graded compaction report. 4. Subgrade soils should be tested for proper moisture and specified compaction levels, and approved by the project geotechnical consultant within 72 hours prior to the placement of concrete. D. Soil Design Parameters The following preliminary soil design parameters are based on the tested representative samples of on-site earth deposits. All parameters should be re- evaluated when the characteristics of the final as-graded soils have been specifically determined: * Design wet density of soil = 121.5 pcf. * Design angle of internal friction of soil = 30 degrees. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 17 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD OCTOBER 24, 2001 * Design active soil pressure for retaining structures = 40 pcf (EFP), level backfill, cantilever, unrestrained walls. * Design at-rest soil pressure for retaining structures = 60 pcf (EFP), non- yielding, restrained walls. * Design passive soil pressure for retaining structures = 365 pcf (EFP), level surface at the toe. * Design coefficient of friction for concrete on soils = 0.36. * Net allowable foundation pressure for on-site compacted tills (minimum 15 inches wide by 18 inches deep footings) = 1750 psf. * Allowable lateral bearing pressure (all structures except retaining walls) for on- site compacted fill = 150 psf/ft. Notes: * Use a minimum safety factor of 1.5 for wall overturning and sliding stability. However, because large movements must take place before maximum passive resistance can be developed, a safety factor of 2 may be considered for sliding stability where sensitive structures and improvements are planned near or on top of retaining walls. * When combining passive pressure and frictional resistance, the passive component should be reduced by one-third. * The net allowable foundation pressures provided herein were determined for footings having a minimum width of 15 inches, and a minimum depth of 18 inches. The indicated value may be increased by 20% for each additional foot of depth, and 20% for each additional foot of width to a maximum of 3500 psf if needed. The allowable foundation pressures provided herein also applies to dead plus live loads and may be increased by one-third for wind and seismic loading. * The allowable lateral bearing earth pressures may be increased by the amount ofthe designated value for each additional foot of depth to a maximum of 1500 pounds per square foot. E. Asphalt and PCC Pavement Design Specific pavement design can best be provided at the complefion of rough grading based upon R-value tests ofthe actual finish subgrade soils; however, the following structural sections may be considered for cost estimating purposes only (not for construction): VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vmeyard Avenue • Escondido, Cahfornia 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 18 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD OCTOBER 24, 2001 1. A minimum section of 3 inches asphalt on 6 inches Caltrans Class 2 aggregate base may be considered for on-site asphalt paving surfaces. Actual design will also depend on the design Tl and approval ofthe City of Carlsbad. Base materials should be compacted to a minimum of 95% of the corresponding maximum dry density (ASTM D-1557). Subgrade soils beneath the asphalt paving surfaces should also be compacted to a minimum of 95% ofthe corresponding maximum dry density within the upper 12 inches. 2. Residential PCC driveways and parking supported on non-expansive to very low expansive (El less than 21) granular subgrade soils should be a minimum of 5 inches in thickness, reinforced with #3 reinforcing bars at 18 inches on center each way, placed mid-height in the slab. Subgrade soils beneath the PCC driveways and parking should be compacted to a minimum of 90% of the corresponding maximum dry density. Provide "soft-cut" contraction/control joints consisting of sawcuts spaced 10 feet on center (not to exceed 15 feet maximum) each way. Cut as soon as the slab will support the weight ofthe saw, and operate without disturbing the final finish which is normally within 2 hours after flnal finish at each control joint location or 150 psi to 800 psi. The softcuts should be a minimum of 1-inch in depth but notto exceed 1%-inches. Anti-ravel skid plates should be used and replaced with each blade to avoid spalling and raveling. Avoid wheeled equipments across cuts for at least 24 hours. 3. Subgrade and basegrade soils should be tested for proper moisture and the specified compaction levels, and approved by the project geotechnical consultant within 72 hours prior to the placement of the base or asphalt/PCC finish surface. 4. Base section and subgrade preparations per structural section design, will be required for all surfaces subject to traffic including roadways, travelways, drive lanes, driveway approaches and ribbon (cross) gutters. Driveway approaches within the public right-of-way should have 12 inches subgrade compacted to a minimum 95% compaction levels and provided with a 95% compacted Class 2 base section per the structural section design. Base section may not be required under curb and gutters, and sidewalks in the case of non-expansive subgrade soils (expansion index less than 21). Appropriate recommendations should be given in the final as-graded compaction report. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, Cahfornia 92029-1229 • Phone (760) 743-1214 I PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 19 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD OCTOBER 24, 2001 F. General Recommendations 1. The minimum foundation designs and steel reinforcement provided herein are based on soil characteristics and are not intended to be in lieu of reinforcement necessary for structural considerations. All recommendations should be further evaluated in the site specific study for each individual lot and confirmed by the project architect/structural engineer. 2. Adequate staking and grading control is a critical factor in properly completing the recommended remedial and site grading operations. Grading control and staking should be provided by the project grading contractor or surveyor/civil engineer and is beyond the geotechnical engineering services. Inadequate staking and/or lack of grading control may result in unnecessary or additional grading which will increase construction costs. 3. Footings located on or adjacent to the top of slopes should be extended to a sufficient depth to provide a minimum horizontal distance of 7 feet or one-third of the slope height, whichever is greater (need not exceed 40 feet maximum) between the bottom edge of the footing and face of slope. This requirement applies to all improvements and structures including fences, posts, pools, spas, etc. Concrete and AC improvements should be provided with a thickened edge to satisfy this requirement. 4. Expansive clayey soils should not be used for backfilling of any retaining structure. All retaining walls should be provided with a 1:1 wedge of granular, compacted backfill measured from the base of the wall footing to the finished surface. Retaining walls should be provided with a back drainage in general accordance with the attached Plate 8. 5. All underground utility trenches should be compacted to a minimum of 90% of the maximum dry density ofthe soil unless othenwise specified. Care should be taken not to crush the utilities or pipes during the compaction of the soil. Non-expansive, granular backfill soils should be used. 6. Site drainage over the finished pad surfaces should flow away from structures onto the street in a positive manner. Care should be taken during the construction, improvements, and fine grading phases not to disrupt the designed drainage patterns. Roof lines ofthe buildings should be provided with roof gutters. Roof water should be collected and directed away from the buildings and structures to a suitable locafion. Considerafion should be given to adequately damp-proof/waterproof the basement walls/foundations and VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vmeyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 20 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD OCTOBER 24, 2001 provide the planter areas adjacent to the foundafions with an impermeable liner and a subdrainage system. 7. Final plans should reflect preliminary recommendations given in this report. Final foundations and grading plans may also be reviewed by the project geotechnical consultant for conformance with the requirements of the geotechnical investigation report outlined herein. More speclflc recommendations may be necessary and should be given when final grading and architectural/structural drawings are available. 8. All foundation trenches should be inspected to ensure adequate footing embedment and confirm competent bearing soils. Foundation and slab reinforcements should also be inspected and approved by the project geotechnical consultant. 9. The amount of shrinkage and related cracks that occur in the concrete slab-on- grades, flatworks and driveways depend on many factors, the most important of which is the amount of water in the concrete mix. The purpose of the slab reinforcement is to keep nomnal concrete shrinkage cracks closed tightly. The amount of concrete shrinkage can be minimized by reducing the amount of water in the mix. To keep shrinkage to a minimum, the following should be considered: * Use the stiffest mix that can be handled and consolidated satisfactorily. * Use the largest maximum size of aggregate that is practical. For example, concrete made with % inch maximum size aggregate usually requires about 40 lbs more (nearly 5 gal.) water per cubic yard than concrete with 1-inch aggregate. * Cure the concrete as long as practical. The amount of slab reinforcement provided for conventional slab-on-grade construction considers that good quality concrete materials, proportioning, craftsmanship, and control tests where appropriate and applicable are provided. 10. A preconstruction meeting between representatives of this office, the property owner or planner, the grading contractor/builder, and the city inspector is recommended in order to discuss grading/construction details associated with site development. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, Cahfornia 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION PAGE 21 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD OCTOBER 24, 2001 VIII. LIMITATIONS The conclusions and recommendations provided herein have been based on available data obtained from pertinent reports and plans, subsurface exploratory excavations as well as our experience with the soils and formational materials located in the general area. The materials encountered on the project site and utilized in our laboratory testing are believed representative of the total area; however, earth materials may vary in characteristics between excavations. Of necessity we must assume a certain degree of continuity between exploratory excavations and/or natural exposures. It is necessary, therefore, that all observations, conclusions, and recommendations be verified during the grading operation. In the event discrepancies are noted, we should be contacted immediately so that an inspection can be made and additional recommendations issued if required. The recommendations made in this report are applicable to the site at the time this report was prepared. It is the responsibility of the owner/developer to ensure that these recommendations are carried out in the field. It is almost impossible to predict with certainty the future performance of a property. The future behavior of the site is also dependent on numerous unpredictable variables, such as earthquakes, rainfall, and on-site drainage patterns. The firm of VINJE & MIDDLETON ENGINEERING, INC., shall not be held responsible for changes to the physical conditions of the property such as addition of fill soils, added cut slopes, or changing drainage patterns which occur without our inspection or control. The property owner(s) should be aware that the development of cracks in all concrete surfaces such as floor slabs and exterior stucco are associated with normal concrete shrinkage during the curing process. These features depend chiefly upon the condition of concrete and weather conditions at the time of construction and do not reflect detrimental ground movement. Hairiine stucco cracks will often develop at window/door corners, and floor surface cracks up to Vs-inch wide in 20 feet may develop as a result of normal concrete shrinkage (according to the American Concrete Institute). This report should be considered valid for a period of one year and is subject to review by our firm following that time. If significant modifications are made to your tentative development plan, especially with respect to the height and location of cut and fill slopes, this report must be presented to us for review and possible revision. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, Cahfomia 92029-1229 • Phone (760) 743-1214 PRELIMINARY GEOTECHNICAL INVESTIGATION 4-LOT SUBDIVISION, TABATA RANCH, CARLSBAD PAGE 22 OCTOBER 24, 2001 Vinje & Middleton Engineering, Inc., warrants that this report has been prepared within the limits prescribed by our client with the usual thoroughness and competence of the engineering profession. No other warranty or representation, either expressed or implied, is included or intended. Once again, should any questions arise concerning this report, please do not hesitate to contact this office. Reference to our Job #01-337-P will help to expedite our response to your inquiries. We appreciate this opportunity to be of service to you. VINJE & MIDDLETON ENGINEERING, INC. Steve Melzer RG #6953 DM/SMSS/SM/jt Distribution: Addressee (5) c:\jt\prelims.01\01-364-P VINIE & MIDDLETON ENGINEERING, INC. • 2450 Vineyard Avenue • Escondido, California 92029-1229 • Phone (760) 743-1214 117°19'00" W TOPOl map printed on 10/17/01 from "SanDiego.tpo" and "Untltled.tpg" IIT-IB'OO" W WGSa4 117''17'00" W o o. CD o o m wm^: -mm.. / VSjREGIONAL INDEX MAP fv;!-;-: : I, VME JOB mi-364-^(y v''\'' TN+/MK 117°19'00" W PlintadfioittTOPOI ©199P WMflowmrPiMiiictinis (www.lopOOTm) PLATE 2 SITE PLAN LEGEND APROXIMATE LOCATION OF TEST TRENCH APPROXIMATE LIMITS OF EXISTING FILL Showing existing site conditions and tentative improvements. NOTE: Site Plan copied from Tentative Parcel Map by Pasco Engineering and is for geotechnical purposes only. VME JOB #01-364-P PRIMARY DIVISIONS GROUP SYMBOL SECONDARY DIVISIONS CO _j O CO Q LU Z < OC o LU 05 < o o < oc LU ^ LU 2 N < CO cc < _l CO CO _J O CO Q Ol 2 < CC <D UJ LU cn bl m CO dm < > CO « CO o — o E O UJ z <i GRAVELS MORE THAN HALF OF COARSE FRACTION IS LARGER THAN NO. 4 SIEVE SANDS MORE THAN HALF OF COARSE FRACTION IS SMALLER THAN NO. 4 SIEVE CLEAN GRAVELS (LESS THAN 5% FINES) GW Well graded gravels, gravel-sand mixtures, little or no fines. GP Poorly graded gravels or gravel-sand mixtures, little or no fines. GRAVEL WITH FINES GM Silty gravels, gravel-sand-silt mixtures, non-plastic fines. GC Clayey gravels, gravel-sand-clay mixtures, plastic fines. CLEAN SANDS (LESS THAN 5% FINES) SW Weil graded sands, gravelly sands, little or no fines. SP Poorly graded sands or gravelly sands, little or no fines. SANDS WITH FINES SM Silty sands, sand-silt mixtures, non-plastic fines. SC Clayey sands, sand-clay mixtures, plastic fines. SILTS AND CLAYS LIQUID LIMIT IS LESS THAN 50% ML Inorganic silts and very fine sands, rock flour, silty or clayey fine sands or clayey silts with slight plasticity. CL Inorganic clays of low/ to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays. OL Organic silts and organic silty clays of low plasticity. SILTS AND CLAYS LIQUID LIMIT IS GREATER THAN 50% 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 silts. HIGHLY ORGANIC SOILS PT Peat and other highly organic soils. GRAIN'SIZES U.S. STANDARD SERIES SIEVE 200 40 10 CLEAR SQUARE SIEVE OPENINGS 3/4" 3" 12" SILTS AND CLAYS SAND FINE MEDIUM COARSE GRAVEL FINE COARSE COBBLES BOULDERS RELATIVE DENSITY CONSISTENCY SANDS, GRAVELS AND NON-PLASTIC SILTS BLOWS/FOOT VERY LOOSE 0 - 4 LOOSE 4-10 MEDIUM DENSE 10 - 30 DENSE 30 - 50 VERY DENSE OVER 50 CLAYS AND PLASTIC SILTS STRENGTH BLOWS/FOOT VERY SOFT 0 - VA 0 - 2 SOFT VA - 'A 2 - 4 FIRM V2 - 1 4 - 8 STIFF 1 - 2 8 - 16 VERY STIFF 2 - 4 16-32 HARD OVER 4 OVER 32 1. Blow count, 140 pound hammer falling 30 inches on 2 inch O.D. split spoon sampler (ASTM D-1586) 2. Unconfined compressive strength per SOILTEST pocket penetrometer CL-700 A = undisturbed chunk sample im = disturbed sample = sand cone test Standard Penetration Test (SPT) (ASTM D-1 586) with blow counts per 6 inches ^4g = California Sampler with blow counts per 6 inches VINJE & MPDLETON ENGINEERING, INC. 2450 Vineyard Ave., #102 Escondid6, CA 92029-1229 KEY TO EXPLORATORY BORING LOGS Unified Soil Classification System (ASTM D-2487) PROJECT NO. KEY I f i i i i i i I I I I i Date: 10-17-2001 Logged by: DM DEPTH (ft) SAMPLE T-1 uses SYMBOL MOISTURE (%) DRY DENSITY (pcf) RELATIVE COMPACTION (%) DEPTH (ft) SAMPLE DESCRIPTION uses SYMBOL MOISTURE (%) DRY DENSITY (pcf) RELATIVE COMPACTION (%) - 0 -FILL: Silty sand. Red brown. Loose. ST-1 SM -TOPSOIL: Silty to clayey sand. Brown. Moist. Stiff. ST-1 SM/SC - 5 -BEDROCK: Sandstone. Off-white color. Medium grained. Cemented friable. At 5' thin rust colored seam. Nearly horizontal. ST-2 SP -10- End Test Trench at 7'. No Caving. No Groundwater. Date: 10-17-2001 Logged by: SM DEPTH SAMPLE T-2 uses SYMBOL MOISTURE DRY DENSITY RELATIVE COMPACTION (ft) DESCRIPTION (%) (pcf) (%) - 0 -FILL: Siltv sand. Tan. Loose. ST-1 SM TOPSOIL: SM/SC 18.5 102.1 81.1 -Silty to clayey sand. Fine grained. Moist. Stiff. ST-1 - -BEDROCK: Sandstone. Medium grained. Off-white to yellowish color. Friable. Cemented. Rust colored stains. No apparent structure. ST-2 SP 12.2 112.2 95.2 - 5 -BEDROCK: Sandstone. Medium grained. Off-white to yellowish color. Friable. Cemented. Rust colored stains. No apparent structure. ST-2 ; -10- End Test Trench at 434'. No Caving. No Groundwater. I i i i I VINJE & MIDDLETON ENGINEERING, INC 2450 Vineyard Avenue, Suite 102 Escondido, California 92029-1229 Office 760-743-1214 Fax 760-739-0343 TESTTRENCH LOGS TABATA RANCH, CARLSBAD PROJECT NO. 01-364-P PLATE 3 • Sand Cone Test Bulk Sample • Chunk Sample Q Driven Rings I I i i i i i i i i Date: 10-17-2001 Logged by: SM DEPTH (ft) SAMPLE T-3 uses SYMBOL MOISTURE DRY DENSITY RELATIVE COMPACTION DEPTH (ft) DESCRIPTION (%) (pcf) {%) - 0 -FILL: Silty sand. Tan color. Dry. Loose. From IVz grades to brown color. Moist. Loose. At 5' mulch and pieces of plastic and metal rebar. ST-1 - 5 -• \0H-9 83.Z -• TOPSOIL: Siltv to clavev sand. Fine arained. Moist. Soft. ST-1 SM/SC 5.7 111.2 88.3 BEDROCK: SP 9.0 , 114 5 97 1 -10-Sandstone. Medium grained. Rust to yellowish color. Friable. Weaklv cemented. Moist. ST-2 - End Test Trench at 8V2'. No Caving. No Groundwater. Date: 10-17-2001 Logged by: SM DEPTH SAMPLE T-4 uses SYMBOL MOISTURE DRY DENSITY RELATIVE COMPACTION (ft) DESCRIPTION (%) (pcf) (%) - 0 - • COLLUVIUM: Silty sand. Light brown color. Dry. Blocky. Dense. Small rootlets throughout. ST-1 SM 111/5 88 \ - 5 — V BEDROCK: Sandstone. Fine to medium grained. Off-white color. Cemented. - No apparent structure. ST-2 SP N BEDROCK: Sandstone. Fine to medium grained. Off-white color. Cemented. - No apparent structure. ST-2 -10- End Test Trench at 5'. No Caving. No Groundwater. i i i I VINJE & MIDDLETON ENGINEERING, INC 2450 Vineyard Avenue, Suite 102 Escondido, California 92029-1229 Office 760-743-1214 Fax 760-739-0343 TEST TRENCH LOGS TABATA RANCH, CARLSBAD PROJECT NO. 01-364-P PLATE 4 T Sand Cone Test Bulk Sample • Chunk Sample O Driven Rings I ' Date: 10-17-2001 Logged by: SM 1 DEPTH 1 (ft) SAMPLE T-5 uses SYMBOL MOISTURE DRY DENSITY RELATIVE COMPACTION 1 DEPTH 1 (ft) DESCRIPTION (%) (pcf) (%) [- 0 - •• COLLUVIUM: Silty sand. Light tan to light brown color. Dry. Locally dense from 272' to 372. Very loose. ST-1 SM 2.5 109.7 87.1 1 -• BEDROCK: Sandstone. Fine to medium grained. Off-white color. Cemented. Locally friable. ST-2 SP 1.3 -- J- 5 -BEDROCK: Sandstone. Fine to medium grained. Off-white color. Cemented. Locally friable. ST-2 / 11-10- End Test Trench at AV^. No Caving. No Groundwater. Date: 10-17-2001 Logged by: SM Jl DEPTH SAMPLE T-6 uses SYMBOL MOISTURE DRY DENSITY RELATIVE COMPACTION (ft) DESCRIPTION (%) (pcf) (%) |- 0 -COLLUVIUM: Silty sand. Fine grained. Light tan color. Locally dense. ST-1 SM 1 " BEDROCK: Sandstone. Fine to medium grained. "Dirty" color with rust colored staining. Cemented. No apparent structure. ST-2 SP 1- 5 - BEDROCK: Sandstone. Fine to medium grained. "Dirty" color with rust colored staining. Cemented. No apparent structure. ST-2 1" End Test Trench at 414'. No Caving. No Groundwater. -10- VINJE & MIDDLETON ENGINEERING, INC 2450 Vineyard Avenue, Suite 102 Escondido, California 92029-1229 Office 760-743-1214 Fax 760-739-0343 TEST TRENCH LOGS TABATA RANCH, CARLSBAD PROJECT NO. 01-364-P PLATE 5 T Sand Cone Test Bulk Sample • Chunk Sample Q Driven Rings FAULT - EPICENTER MAP SAN DIEGO COUNTY REGION INDICATED EARTHQUAKE EVENTS THROUGH 75 YEAR PERIOD (1900-1974) Map data is compiled from various sources including California Division of Mines and Geology, California Institude of Technology and the National Oceanic and Atmospheric Administration. Map is reproduced from California Division of Mines and Geology, "Earthquake Epicenter Map of California; Map Sheet 39." Earthquake Magnitude . 4.0 TO 4.9 O 5.0 TO 5.9 (D 6.0 TO 6.9 • PROJECT: 01-364-P O 7.0 TO 7.9 TABATA RANCH, LA COSTA Fault, PLATE NO. __6 . ISOLATION JOINTS AND RE-ENTRANT CORNER REINFORCEMENT Typical - no scale RE-ENTRANT CORNER * REINFORCEMENT NO. 4 BARS PLACED I.5" BELOW TOP OF SLAB RE-ENTRANT CORNER CRACK NOTES: 1. Isolation joints around the columns should be either circular as shown in (a) or diamond shaped as shown in (b) If no isolation joints are used around columns, or if the comers of the isolation joints do not meet the contraction joints, radial cracking as shown in (c)may occur (reference ACI). 2. In order to control cracking at the re-entrant comers (±270° comers), provide reinforcement as shown in (c). 3. Re-entrant corner reinforcement shown herein is provided as a general guideline only and is subject to verification and changes by the project architect and/or structural engineer based upon slab geometry, location and other engineenng and construction factors. VINJE & MIDDLETON ENGINEERING, INC. PLATE 7 RETAINING WALL DRAIN DETAIL Typical - no scale drainage Granular, non-expansive backfill. Compacted.;' Waterproofing Perforated drain pipe Filter iVlaterial. Crushed rock (wrapped in filter fabric) or Class 2 Permeable Material (see specifications below) Competent, approved soils or bedrock SI»ECIF1CAT10NS rORCALTRAfiS t ?mmmM MATERIAL (68.1.025) U.S. STANDARD % PASSING 1" 10Q 3/4 90-100 3/8 *D-100 No. 4 25H40 No 8 18-33 No 30 5-15 No. 50 0-7 Mo. 200 0-3 Sand Equivalent > 75 CONSTRUCTION SPECIFICATIONS: 1. Provide granular, non-expansive backfill soil in 1:1 gradient wedge behind wall. Compact backfill to minimum 90% of laboratory standard. 2. Provide back drainage for wall to prevent build-up of hydrostatic pressures. Use drainage openings along base of wall or back drain system as outlined below. 3. Backdrain should consist of 4" diameter PVC pipe (Schedule 40 or equivalent) with perforations down. Drain to suitable outlet at minimum 1 %. Provide %" -1 Vi crushed gravel filter wrapped in filter fabric (Mirafi 140N or equivalent). Delete filter fabric wrap if Caltrans Class 2 permeable material is used. Compact Class 2 material to minimum 90% of laboratory standard. 4. Seal back of wall with waterproofing in accordance with architect's specifications. 5. Provide positive drainage to disallow ponding of water above wall. Lined drainage ditch to minimum 2% flow away from wall is recommended. * Use 1 % cubic foot per foot with granular backfill soil and 4 cubic foot per foot if expansive backfill soil is used. VINJE & MIDDLETON ENGINEERING, INC. PLATE 8