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HomeMy WebLinkAboutPD 2021-0001; HAMDARD RESIDENCE; GEOTECHNICAL INVESTIGATON; 2020-12-18ALLIED EARTH TECHNOLOGY 7915 SILVERTON AVENUE, SUITE 317 SAN DIEGO, CALIFORNIA 92126 TEL : (858) 586-1665 (619) 447-4747 E-MAIL: ROBERTAET@ AOLCOM =======================~=====~====================================----------== GEOTECHNICAL INVESTIGATION PROPOSED RESIDENTIAL BUILDING SITE END OF LA CORUNA PLACE CARLSBAD, CALIFORNIA FOR MR. AMAN HAMDARD PROJECT NO. 20-1147Gl DECEMBER 18, 2020 ALLIED EARTH TECHNOLOGY 7915 SILVERTON AVENUE, SUITE 317 SAN DIEGO, CALIFORNIA 92126 TEL: (858) 586-1665 (619) 447-4747 E-MAIL: ROBERTAET@ AOL.COM ===--------====--=---------------------------=---=------===--------------~================ December 18, 2020 Mr. Aman Hamdard 2349 La Caringa Way, Suite 3 Carlsbad, Ca. 92009 Subject: Project No. 20-114701 Geotechnical Investigation Proposed Residential Building Site End of La Corona Place Carlsbad, California Dear Mr. Hamdard : In accordance with your request, we have completed the geotechnical investigation for the proposed residential building site on subject property, more specifically referred to as being Lot No. 181 of La Costa South, according to Map thereof No. 6117 (APN 216-160-23-00), in the City of Carlsbad, State of California. It is our understanding that a two-story single-family residence is proposed for the site. The proposed structure will be of wood-frame/stucco and slab-on-grade construction. We are pleased to submit the accompanying geotechnical investigation and geologic reconnaissance reports to present our findings, conclusions and recommendations relative to the proposed development of the site. The geotechnical investigation was conducted under the supervision of the undersigned. The scope of our work included field exploration, laboratory testing and soil engineering and geologic analysis. No major adverse geotechnical or geologic conditions were encountered which would prohibit the currently proposed development of the site. However, undocumented fill soils were encountered on the site. Recommendations to mitigate this adverse condition are presented herein. Project No. 20-l 147Gl La Coruna Place 12/18/20 Page 2 This opportunity to be of service is sincerely appreciated. Should you have any questions, please do not hesitate __ to -~Qnt~ur__ofi-t~ Respectfully submitt~cl,. ~ 1 .¾LIED EARTH ]TC~GY ,/ .. ---/,. ..,.,,- TABLE OF CONTENTS INTRODUCTION .............................................. . DESCRIPTION OF PROJECT ............................... . SCOPE OF WORK ............................................ . FIELD INVESTIGATION ................................... . LABORATORY TESTS ...................................... . SITE DESCRIPTION ......................................... . PROPOSED SITE DEVELOPMENT ...................... . GENERAL GEOLOGY AND SUB SURF ACE SOIL CONDITIONS Regional Geology ................................... . Site Geology and Subsurface Soil Conditions .. . Tectonic Setting ...................................... . GROUNDWATER .......................................... .. GEOLOGIC HAZARDS Ground Shaking ..................................... . Liquefaction Potential ............................. . Landslides .......................................... .. FINDINGS, CONCLUSIONS AND RECOMMENDATIONS General .............................................. . Expansion Index of On-Site Soils ............... . Sulfate Content of On-Site Soils ................. . Grading ............................................. . Page No. 1 1 2 3 3 4 4 4 5 5 6 6 6 6 7 7 7 TABLE OF CONTENTS (Cont'nd) Foundation and Slab Design ..................... . Under-Slab Vapor Retarders ..................... . Retaining Wall Design ........................... .. Seismic Earth Pressure ........................... . Lateral Loading .................................... . Slope Stability ...................................... . Seismic Coefficients .............................. . Surface Drainage and Maintenance .............. . Grading and Foundation Plans Review ........ . LIMITATION AND UNIFORMITY OF CONDITIONS Figure No. 1 -Site Location Map Figure No. 2 -Approximate Location of Exploratory Trenches Figure Nos. 3 to 6, inclusive -Boring Log Sheet Appendix I -General Grading and Earthwork Specifications Appendix II-Laboratory Test Results Appendix III -References Page No. 9 11 11 12 12 13 13 14 14 14 ALLIED EARTH TECHNOLOGY INTRODUCTION 7915 SILVERTON AVENUE, SUITE 317 SAN DIEGO, CALIFORNIA 92126 TEL: (858) 586-1665 (619) 447-4747 E-MAIL : ROBERTAET@ AOL.COM ---------------- December 18, 2020 GEOTECHNICAL INVESTIGATION This report presents the findings and conclusions of a geotechnical investigation conducted at the site of a proposed residence on subject property, located at the end of La Coruna Place, in the City of Carlsbad, State of California. Subject property is more specifically referred to as being Lot No. 181 of La Costa South, according to Map thereof No. 6117 (APN 216-160-23-00). The location of the property is shown on Figure No. 1, entitled, "Site Location Map". DESCRIPTION OF PROJECT It is our understanding that a single-family residence is proposed for the site. The proposed structure will be two stories in height; of wood-frame/stucco and slab-on-grade construction. SCOPE OF WORK The objectives of the investigation were to inspect and determine the subsurface geotechnical conditions and certain physical engineering properties of the soils beneath the site, and to evaluate any potential adverse geotechnical conditions that could affect the proposed project, in order that engineering recommendations could be presented relative to the safe and Project No. 20-114701 La Coruna Place 12/18/20 Page 2 economical development of the site; and checking and design of foundation for the proposed residence. In order to accomplish these objectives, a total of four exploratory trenches were excavated and inspected, and representative samples of the subsurface soils were collected for laboratory testing and analysis. The data derived from the field observations and laboratory test results were reviewed and analyzed, and a swnrnary of our preliminary findings, opinions and recommendations is presented in this report. FIELD INVESTIGATION The field exploratory phase of our investigation was performed on November 3, 2020. and involved a reconnaissance of the site, and the excavation of four exploratory trenches with a tractor-mounted backhoe equipped with a 24-inch bucket. The exploratory trenches were excavated at various locations on the site accessible to excavating equipment where the most useful information relative to subsurface soil conditions may be obtained. The exploratory trenches were excavated to depths varying from 6 to 7 feet below existing ground surface. The location of the exploratory trenches was recorded at the time of excavation, and is shown on Figure Nos. 3 to 6, inclusive, each entitled, 'Trench Log Sheet". The soils were visually and texturally classified by the field identification procedures set forth on the Unified Soil Classification Chart. Representative samples and in-situ density tests were obtained at various depths in the exploratory trenches. Project No.20~114701 La Coruna Place 12/18/20 Page 3 LABORATORY TESTS The samples collected during our field investigation were subjected to various tests in the laboratory to evaluate their engineering characteristics. The tests were performed in accordance with current A.S. T.M. testing standards or other regulatory agency testing procedures. A summary of the tests that were performed and the final test results are presented in Appendix II hereto. The tests that were performed included determinations of the maximum dry densities and optimum moisture contents; shear strength; sulfate contents and Expansion Indices of the soils encountered. SITE DESCRIPTION Subject property is a pentagonal-shaped property of 0.44 acres, situated on the north side. at the west end of La Coruna Place. The original terrain on the site may be described as sloping down in a westerly direction at gradients on the order of 10 to 12 percent. Currently a relatively level pad occupies the upper, south end of the site. The pad had been previously graded by excavating soils along the west side, and placing it along the east side, with maximum depth of fill soils placed on the order of 5 feet. A long length of retaining wall, with maximum height on the order of 5 feet, was observed along the west property line. The property is located in a developed area of the City of Carlsbad. The site is currently vacant, and bounded on the east and west sides by existing residences; on the north by La Costa A venue; and on the south by La Coruna Place. Project No. 20-114701 La Corona Place 12/18/20 Page4 PROPOSED SITE DEVELOPMENT It is our understanding that the property is to be developed into a site for a single-family residence, with attached garage. The proposed structure will be two-stories in height; of wood- frame/stucco and slab-on-grade construction. Behind the proposed residence, three terraced level areas will be created. At the north end of the property, adjacent to La Costa A venue, a landscaped/ future sports area will be created. Estimated earthwork will be 1,266 cubic yards of fill; 753 cubic yards of excavation; with 463 cubic yards to be imported. GENERAL GEOLOGY AND SUBSURFACE SOIL CONDITIONS Regional Geology The subject property is located within the southern coastal strip region of the Peninsular Range Geomorphic Province of California. This geomorphic province is characterized by mountainous terrain to the east composed mostly of Mesozoic igneous and metamorphic rocks and relatively low-lying coastal terraces to the west underlain by late Cretaceous, Tertiary and Quaternary sedimentary rocks. The westerly portion of the City of Carlsbad, including the site, occurs within the westerly region and is underlain by sedimentary rocks. Site Geology and Subsurface Soil Conditions A review of geologic map of the Encinitas quadrangle as well as observations made during our subsurface exploration indicated that the general area is underlain by Tertiary Santiago Formation. On subject property, the Santiago Formation was encountered in the form of dense to very dense, olive green silty sands. In Trench Nos. 2 and 3, undocumented fill soils, consisting of brown clay on the order of 3 to 5 feet in thickness were encountered. Project No. 20-114701 La Coruna Place 12/18/20 Page 5 Tectonic Setting No evidence of faulting was noted during our surface reconnaissance or in our exploratory Trenches. A review of available geologic literature did not reveal any major faulting in the area. It should be noted that much of southern California, including the City of Carlsbad, is characterized by a series of Quaternary-age fault zones which typically strike in a northerly to northwesterly direction. Some of these fault zones (and the individual faults within the zone) are classified as active while others are classified as only potentially active according to the criteria of the California Division of Mines and Geology. A review of available geologic maps indicate that the subject property is approximately 9.54 km (5.96 miles) from the Rose Canyon Fault zone and 17.7km(11.1 miles) the Newport- Inglewood Fault zone. GROUNDWATER No groundwater was encountered in the exploratory trenches to the maximum depth of exploration at 7 feet. No major groundwater related problems, either during or after construction, are anticipated. However, it should be recognized that minor seepage problems may occur after development of a site even where none were present before development. These are usually minor phenomena and are often the results of an alteration of the permeability characteristics of the soils; alteration in drainage patterns due to grading; and an increase in the use of irrigation water. Based on the permeability characteristics of the soils and anticipated usage of the development, it is our opinion that any seepage problems which may occur will be minor in extent. It is further our opinion that these problems can be most effectively corrected on an individual basis if and when they develop. Project No. 20-1147G1 La Coruna Place 12/18/20 Page 6 GEOLOGIC HAZARDS Ground shaking -The most likely geologic hazard to affect the site is ground shaking as a result of movement along one of the active fault zones mentioned above. For seismic design purposes, soil parameters in accordance with the 2019 edition of the California Building Code were determined, and presented hereinafter. Liquefaction Potential -In consideration of the competent formational soils underlying the site, and the lack of a permanent water table near the ground surface, it is our opinion that soil liquefaction does not present a significant geotechnical haz.ard to the proposed site development. Landslides -A review of available geologic maps did not reveal the presence of any ancient landslides on subject or adjacent properties. The potential for landslides on subject and adjacent properties is considered minimal. FINDINGS, CONCLUSIONS AND RECOMMENDATIONS General 1. Based on the results of the investigation, it is our opinion that the currently proposed site development is feasible from a geotechnical engineering standpoint, provided that the recommendations presented in this report are incorporated into the design plan(s) and are properly implemented during the construction phase. 2. It is noted that some of the recommendations may have to be modified and supplemental recommendations may have to be presented, depending on the actual subsurface conditions encountered during construction. Project No. 20-114701 La Coruna Place 12/18/20 Page 7 3. The existing undocumented fill soils similar to those encountered in Trench Nos. 2 and 3 on the site are loose and compressible in their current state of compaction, and are not considered to be capable of providing safe and reliable support to the proposed residential structure or improvements. 4. Site grading and earthwork constructions will not impact the adjacent properties provided our recommendations are incorporated into the final designs and implemented during the construction phase. Additional field recommendations, however, may also be necessary properties and should be anticipated. 5. Prior to commencement of construction, a preconstruction conference should be held at the site with the owner, grading contractor, civil engineer and geotechnical engineer in attendance. Special soil handling and/or grading/improvement plans requirements can be discussed at that time. Expansion Index of On-Site Soils 6. The clayey soils encountered on the site possess high expansion potential (Expansion Index= 92). Recommendations presented hereinafter reflects this on-site soil condition Sulfate Content of On-Site Soils 7. The soils encountered on the site are subject to negligible sulfate exposure (sulfate content of 95 ppm). Grading 8. It is recommended that all earthwork be accomplished in accordance with the Project No. 20-114701 La Coruna Place 12/18/20 Page 8 Grading Ordinance of the City of Carlsbad, cmTent edition of the California Building Code, Appendix I attached hereto, entitled, "'General Grading and Earthwork Specifications", and recommendations as presented in this Section. 9. Where the recommendations of this Section of the report conflict with those of Appendix I, this Section of the report takes precedence. 10. Grading operations should begin with the clearing and grubbing of the site, and hauling away of the debris to an approved dump site. 11. The existing uncompacted fill soils encountered in Trench Nos. 2 and 3 along the northerly end of the building pad should be removed and temporarily stock-piled on site. Any trash or unsuitable material encountered in the fill soils should be segregated and removed from the site. 12. A keyway should be excavated along the toe of the proposed fill slope of the building pad, extending through the upper soils at least 12 inches into the underlying fonnational soils. The stock-piled fill soils should then be properly moistened, placed and uniformly compacted in lifts on the order of 6 to 8 inches. 13. In order to provide uniform settlement characteristics to the proposed structure, it is recommended that that the natural soils on the building pad to a depth of at least 3 feet, or 12 inches below the bottom of the deepest footing, be removed. The area of Project No. 20-114 7G 1 La Corona Place 12/18/20 Page 9 removal should extend at least 5 feet outside the foundation line of the proposed structure. The bottom of the excavation should be inspected and approved by our firm, and the removed soils should be properly moistened, replaced and uniformly compacted in lifts on the order of 6 to 8 inches until finished grade is achieved. 13. The terraced pad areas and the landscaped/future sports area along the northerly, lower portion of the property should be properly cleared and grubbed, with all vegetation removed. Any loose residual/topsoils remaining below finished grade should be removed and properly compacted, prior to the placement of additional fill soils. 13. Additional imported fill soils will be required to achieve finished grade. It is recommended that these soils consist of non-expansive soils (SW, SP, SM; Expansion Index< 50); and be approved at the borrow site prior to importation. 14. All fill soils should be compacted to at least 90 percent of maximum dry density at approximately 120 percent of optimum moisture content, in accordance with A.S.T.M. D1557. Foundation and Slab Design 15. It is recommended that a safe allowable soil bearing value of2,000 pounds per square foot be used for the design and checking of continuous footings that are 12 inches in minimum horizontal dimension, and isolated pier footings that are 15 inches in minimum horizontal dimension. As a result of the presence of highly expansive soils on the site, these footings should be embedded at least 24 inches below the lowest adjacent ground Project No. 20-114701 La Coruna Place 12/18/20 Page 10 surface. 16. The above safe allowable soil bearing value may be increased by one-third when considering wind and/or seismic forces. I 7. The settlement of foundation, when designed and loaded as outlined above, are expected to be less than ¾ inch total and ½ inch differential over a span of 40 feet. 18. It is recommended that all continuous footings be reinforced with a minimwn of 4 #5 re bars; two rebars located near the top, and the other two rebars near the bottom of the footings. All isolated pier footings should be reinforced with a minimum of 2 #5 rebars in both directions, placed near the bottom of the footings. 19. The concrete slab-on-grade should be 4 ½ inches in thickness, and be reinforced with #3 rebars @ 18 inches on center in both directions, placed at mid-height of concrete slab. The concrete slab should be underlain by 4 inches of clean sand. The above foundation and slab reinforcement requirements are based on soil characteristics, and should be superseded by the requirements of the project architect. 20. It is recommended that all footings placed on the proposed fill slope be setback such that the bottom of the footing at the outer edge is at least 7 feet back from the face of slope at that level. 21 It is recommended that our firm inspect the foundation trench excavations for the proposed residential structure to ensure proper embedment into competent natural Project No. 20-114701 La Coruna Place 12/18/20 Page 11 or compacted fill soils. Under-Slab Vapor Retarders 22. The concrete slab should be underlain by a 10-mil plastic membrane vapor retarder over 3 inches of clean sand. The seams of the plastic membrane should be sealed and should extend at least 12 inches down the sides of the interior and perimeter footings. The membrane should be placed in accordance with the recommendation and consideration of ACI 302, "Guide for Concrete Floor and Slab Construction" and ASTM 1643, "Standard Practice for Installation of Water Vapor Retarder Used in Contact with Earth or Granular Fill Under Concrete Slabs". The above foundation and slab reinforcement requirements are based on soil characteristics, and should be superseded by the requirements of the project architect. Retaining Wall Design 23. It is recommended that retaining walls be designed to withstand the pressure exerted by equivalent fluid weights given below : Back.fill Surface (horizontal : vertical) Level 2: 1 1 ½: 1 Equivalent Fluid Pressure (pcf) 35 50 58 The above values assume that the retaining walls are unrestrained from movement, and have a granular backfill. For retaining walls restrained from movement at the top, such as basement retaining walls, an uniform horizontal pressure of 7H (where H is the height of Project No. 20-114 7G 1 La Coruna Place 12/18/20 Page 12 the retaining wall in feet) should be applied in addition to the active pressures recommended above. 24. All retaining walls should be supplied with a backfill drainage system adequate to prevent the buildup of hydrostatic pressure. The subdrain should consist of one- inch gravel and a perforated pipe near the bottom of the retaining wall. The width of this subdrain should be at least 12 inches, and extend at least 2/3 height of the retaining wall. The subdrain should be enclosed in a geotextile fabric such as Mirafi 140N or equal. Seismic Earth Pressure 25. Seismic earth pressures can be taken as an inverted triangular distribution with a maximum pressure at the top equal to 12H pound per square foot (with H being the height of retained earth in feet). This pressure is in addition to the static design wall load. The allowable passive pressure and bearing capacity can be increased by 1/3 in determining the stability of the wall. A factor-of-safety of 1.2 can be used in determining the stability of the retaining wall under seismic conditions. Lateral Loading 26. To resist lateral loads, it is recommended that the pressure exerted by an equivalent fluid weight of 300 psfbe used for footings or shear keys poured neat against competent natural or compacted fill soils. The upper 12 inches of material in areas not protected by floor slabs or pavements should not be included in the design for passive resistance. This value assumes that the horizontal distance of the soil mass extends at least 10 feet or three Project No. 20-114 7G l La Coruna Place 12/18/20 Page 13 times the height of the surface generating the passive pressure, whichever is greater. 28. A coefficient of sliding friction of 0.32 may be used for cast-in-place concrete on competent natural or compacted fill soils. Footings can be designed to resist lateral loads by using a combination of sliding friction and passive resistance. The coefficient of friction should be applied to dead load forces only. 29. All backfill soils behind the retaining wall should consist of soils having low expansion potential (Expansion Index< 50), and be compacted at least 90 percent of maximum dry density. Slope Stability 30. Minor fill sloped W1der IO feet are proposed for the development of the site. It is our conclusion that these slopes, with a slope ratio of 2 : 1 (horizontal : vertical), or flatter, will have a factor of safety against massive slope failure exceeding 1.5. 31. The above conclusions assume that surface water is not permitted to flow over the top of slopes, and that all slopes are properly planted and irrigated in accordance with the requirements of the City of Carlsbad. Seismic Coefficients 32. The seismic design factors were determined in accordance with the 2019 California Building Code, and presented on the following page: Project No. 20-114701 La Coruna Place 12/18/20 Page 14 Site Coordinates : Latitude = 33.0875 Longitude = -117.2564 Site Class: = C Spectral Response Acceleration At Short Periods Ss = 0.991 g Spectral Response Acceleration At I-second Period SI = 0.36 g Sms = FaSs = 1.19 g Sml = FvSl = 0.54 g Sds = 2/3*Sms = 0.793 g Sdl = 2/3*Sml = 0.36 g Seismic Design Category = D Fa = 1.2 Fv = 1.5 Surface Drainage and Maintenance 33. Adequate drainage control and proper maintenance of all drainage facilities are imperative to minimize infiltration of surface water into the underlying soil mass in order to reduce settlement potential and to minimize erosion. The building pad should have drainage swales which direct storm and excess irrigation water away from the structures and into the street gutters or other drainage facilities. No surface runoff should be allowed to pond adjacent to the fowidation of structures. Grading and Foundation Plans Review 34. It is recommended that our firm review the final grading and foundation plans for the proposed site development to verify their compliance with our recommendations. LIMITATION AND UNIFOR\'.IITY OF CONDITIONS 1. The preliminary findings and recommendations contained in this report pertain Project No. 20-114701 La Coruna Place 12/18/20 Page 15 only to the site investigated and are based on the assumption that the geotechnical conditions beneath the entire site do not deviate substantially from those disclosed in the exploratory trenches. If any variations or undesirable conditions are encountered during grading, or if the scope of the project differs from that planned at the present time, our firm should be notified in order that supplemental recommendations can be presented, if necessary. 2. This report is issued with the understanding that it is the responsibility of the Owner, or his representative, to ensure that the information and recommendations presented herein are brought to the attention of the Project Architect and Engineer and are incorporated into the plans and specifications for the project. Furthermore, the Owner, or his representative, will also be responsible for taking the necessary measures to ensure that the Contractor and subcontractors properly carry out the recommendations in the field. 3. Professional opinions and recommendations presented in this report are based partly on our evaluation and analysis of the technical information gather during the study, partly on the currently available information regarding the proposed project, and partly on our previous experience with similar soil conditions and projects of similar scope. Our study has been performed in accordance with the minimum standards of car exercised by other professional geotechnical consultants currently practicing in the same locality. We do not, however, guarantee the performance of the proposed project in any respect, and no warranties of any kind, expressed or implied, are made or intended in connection with the study performed by our firm. Project No. 20-l 147Gl La Coruna Place 12/18/20 Page 16 4. The findings and recommendations contained in this report are valid as of the present date. However, changes in the conditions of the property could occur with the passage of time, whether they be due to natural processes or due to man- made actions on the subject and/or adjacent properties. In addition, changes in applicable or appropriate standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated, wholly or partially, by changes outside of our control. Therefore, this report is subject to review by our firm and should not be relied upon after a period of two years. Figure Nos. 1 to 6, inclusive, and Appendices I, II and III are parts of this report. • La Coruna Pl NOTTO SCALE PROJECT NO. 20-1147 G1 FIGURE N0.1 "'5 APPROX/MA EXPLORATO:i T~OCATION OF ,~ENCHES PROJECT NO · 17-1267 J7 LEGEND ~ Approximate Loe . Exp/oratory 1i atron of u rench ndocumented F.'II Tsa Sa t.r 1 n ,ago Formation FIGURE N0.2 ~ NOT;~t .,, .. '" I J ,, ' \. ' ' < ' ., I I 1. '-1' i ' , I I l J I I ' . l ·j FT. 0 1 2 3 4 5 6 TRENCH LOG SHEET TRENCHNO.1 Elev. 150' msl DESCRIPTION Olive green, dry, medium dense (Santiago Formation) (D Moist, dense @ Very dense Bottom of Trench (No Refusal) LEGEND -N--Indicates representative sample O -Indicates in-situ density test Project No. 20-114701 SOIL TYPE SIL TY SANDS (SM) 10.5* 111.9*91.7%* Figure No. 3 FT. I \ I 0 1 \ ~ 2 3 1/ 4 5 ,; ·. 6 ' 7 I TRENCH LOG SHEET TRENCHN0.2 Elev. 145' msl DESCRIPTION Olive green, dry loose (undocumented fill) I Brown, moist, soft ' I (undocumented fill) t© Olive green, moist, medium dense I (Santiago Formation) I SOIL TYPE SIL TY SANDS (SM) 7.5*106.8*87.5%* CLAY (CH) SIL TY FINE SANDS (SM) Bottom of Trench (No Refusal) Project No. 20-114 7G 1 Figure No. 4 I FT. ;, 0 1 I 2 r ., . 3 4 I 5 I 6 7 J TRENCH LOG SHEET TRENCHN0.3 Elev. 145' msl DESCRIPTION Brown/olive green, damp, loose (Undocumented fill soils) (D Olive green, moist, medium dense (Santiago Formation) SOIL TYPE SIL TY FINE SANDS/CLAY (SM)/(CH) SIL TY FINE SANDS (SM) Bottom of Trench (No Refusal) Project No. 20-114701 Figure No.5 I I . ., I ·i . -, . -. I ., ; FT. 0 1 2 3 4 5 6 TRENCH LOG SHEET TRENCH NO. 4 Elev. 133' msl DESCRIPTION Olive green, damp, loose (Topsoils) Olive green, moist, medium dense (Santiago Fonnation) <D SOIL TYPE SIL TY FINE SANDS (SM) SIL TY FINE SANDS (SM) Bottom of Trench (No Refusal) Project No. 20-114 7G 1 Figure No. 6 1.0 APPENDIX I GENER-U GRADING A~D EARTHWORK SPECIFICATIONS General 1.1 All earthwork shall be accomplished in accordance with the Grading Ordinance of the Agency having jurisdiction; Chapter 18 and l 8A, and Appendix J of the 2016 edition of the California Building Code; Appendix I hereinafter, and recommendations as presented in the Geotechnical Report. 1.2 These recommended grading and earthwork specifications are intended to be a part of and to supplement the Geotechnical Report(s). In the event of a conflict, the recommendations of the Geotechnical Report(s) will supersede these specifications. Observations during the course of earthwork operations may result in additional, new or revised recommendations that could supersede these specifications and/or the recommendations in the Geotechnical Report(s). 1.3 The Owner or his authorized representative shall procure the services of a qualified Geotechnical Consulting Finn, hereinafter to be referred to as the "GeotechnicaJ Consultant" (often the same entity that produced the Geotecbnical Report(s). 1.4 The Geotechnical Consultant shall be given a schedule of work by the Earthwork contractor for the subject project, so as to be able to perform required observations; testing and mapping of work in progress in a timely manner. 1.5 The work herein includes all activities from clearing and grubbing through fine grading. Included are trenching, excavating, backfill compaction and grading. All work shall be as shown on the approved project drawings. 1.6 The Geotechnical Consultant or a qualified representative shall be present on the site as required, to observe, map and document the subsurface exposures so as to verify the geotechnical design suppositions. In the event that observed conditions are found to be significantly different from the interpreted conditions during the design phase, the Geotechnical Consultant shall notify the Owner, recommended appropriate changes in the design to suit the observed conditions and notify the agenc(ies) having jurisdiction, where required. Subsurface areas to be geotechnically observed, mapped, record elevations or tested included cleared natural ground for receiving fill or structures, "remedial removal" areas, key bottoms and benches. APPENDIX I Page 2 1. 7 The guidelines contained herein and any standard details attached herewith represent this firm's recommendations for the grading and all associated operations on the subject project. These guidelines shall be considered to be a part of these Specifications. 1.8 If interpretation of these guidelines or standard details result in a dispute(s), the Geotechnical Consultant shall conclude the appropriate interpretation. 1.9 The Geotechnical Consultant shall observe the processing of subgrade and fill materials and perfonn the necessary compaction testing. The test results shall be provided to the Ov,,ner and the Contractor and if so required, to the agenc(ies) having jurisdiction. 1.1 O The Geotechnical Consultant shall not provide "supervision" or any "direction" of work in progress to the Earthwork Contractor, or to any of the Contractor's employees or to any of the Contractor's agent. 1.11 The Earthwork Contractor : The Earthwork Contractor ( contractor) shall be qualified, experienced and knowledgeable in earthwork logistics; preparation and processing of ground to receive fill, moisture condition and processing of fill and compacting fill. The Contractor shall review and accept the plans, geotechnical report(s), and these Specifications prior to commencement of grading. The Contractor shall be solely responsible for performing the grading in accordance with the plans and specifications. The Contractor shall prepare and submit to the Owner and the Geotechnical Consultant a work plan that indicates the sequence of earthwork grading, the number of "'spreads" of work and the estimated quantities of daily earthwork contemplated for the site prior to commencement of grading. The Contractor shall inform the Ov.-ner and the Geotechnical Consultant of change in work schedules and updates to the work plan at least 24 hours in advance of such changes so that appropriate observations and tests can be planned and accomplished. The Contractor shall not assume that the Geotechnical Consultant is aware of all grading operations. The Contractor shall have the sole responsibility to provide adequate equipment and methods to accomplish the earthwork in accordance with the applicable grading Codes and agency ordinances, these Specifications and the recommendations in the approved geotechnical report(s) and grading plan(s). If, in the opinion of the Geotechnical Consultant, unsatisfactory conditions, such as unsuitable soils, APPENDIX I Page 3 improper moisture conditions, inadequate compactions, insufficient buttress key size, adverse weather, etc. are resulting in a quality of work less than required in these specifications, the Geotechnical Consultant shall reject the work and may recommend to the 0½ner that construction be stopped until the conditions are rectified. 2.0 Preparation of Areas to be Filled 2.1 Clearing and grubbing : vegetation, such as brush, grass, roots, and other deleterious materials shall be sufficiently removed and properly disposed of in a method acceptable to the Owner, governing agencies, and the Geotechnical Consultant. The Geotechnical Consultant shall evaluate the extent of these removals depending on specific site conditions. Earth fill material shall not contain more than l percent of organic materials (by volume). No fill lifts shall contain more than 5 percent of organic matter. Nesting of the organic materials shall not be allowed. If potentially hazardous materials are encountered. the Contractor shall stop work in the affected areas. and a hazardous material specialist shall be infonned immediately for proper evaluation and handling of these materials prior to continuing to work in that area. As presently defined by the State of California, most refined petroleum products (gasoline, diesel fuel. motor oil, grease. coolant, etc.) have chemical constituents that are considered to be hazardous waste. As such, the indiscriminate dumping or spillage of these fluids onto the ground may constitute a misdemeanor, punishable by fine and/or imprisonment and shall not be allowed. Materials used for fill, either imported or on-site, shall not contain hazardous materials as defined by the California Code of Regulations. Title 22, Division 4, Chapter 30, Article 9 and 1 O; 40 CRF; and any other applicable local, state or federal laws. The Consultant shall not be responsible for the identification or analysis of the potential presence of hazardous materials. However, if observations, odors or soil discoloration cause Consultant to suspect the presence of haz.ardous materials, the Consultant may request from the Owner the termination of grading operations within the affected area. Prior to resuming grading operations, the Owner shall provide a written report to the Consultant indicating that the suspected materials are not hazardous as defined by applicable laws and regulations. -------------------------------·-·---------- APPENDIX I Page 4 2.2 Any asphaltic pavement material removed during clearing operations should be properly disposed of at an approved off-site facility. Concrete fragments which are free of reinforcing steel may be placed in fills, provided that they are placed in accordance with Section 3 .1 of this document. 2.3 During grading, soil or groundwater conditions other than those identified in the Geotechnical Report may be encountered by the Contractor. The Consuitant shall be notified immediately to evaluate the significance of the unanticipated conditions. 2.4 Processing : Existing ground that has been declared satisfactory for support of fill by the Geotechnical Consultant shall be scarified to a minimum depth of 6 inches. Existing ground that is not satisfactory shall be over-excavated as specified in the following section. Scarification shall continue until soils are broken down and free of large clay clumps or clods and the working surface is reasonable unifonn, flat, and free of uneven features that would inhibit uniform compaction. 2.5 Over-excavation: In addition to removals and over-excavations recommended in the approved geotechnical report(s) and the grading plan, soft, loose, dry, saturated, spongy, organic-rich highly fractured or otherwise unsuitable ground shall be over- excavated to competent ground as evaluated by the Geotechnical Consultant during grading. 2.6 Benching : Where fills are to be placed on ground with slopes steeper than 5 : 1 (horizontal : vertical), the ground shall be stepped or benched. Please see the Standard Details for a graphic illustration. The lowest bench or key shall be a minimum of 15 feet wide and at least 2 feet deep into competent material as evaluated by the Geotechnical Consultant. Other benches shall be excavated a minimum height of 4 feet into competent material or as otherwise recommended by the Geotechnical Consultant. Fill placed on ground sloping flatter than 5 : 1 (horizontal : vertical) shall also be benched or otherwise over-excavated to provide a flat subgrade for the fill. 2.7 Evaluation/Acceptance of Fill Areas : All areas to receive fill, including removal and processed areas, key bottoms, and benches, shall be observed, mapped, elevations recorded and/or tested prior to being accepted by the Geotechnical Consultant as suitable to receive fill. The Contractor shall obtain a written acceptance from the Geotechnical Consultant prior to fill placement. A licensed surveyor shall provide the survey control for determining elevation of processed areas, keys and benches. APPENDIX I Page 5 3.0 Fill Material 3.1 General : Materials to be used as fill shall be essentially free of organic matter and other deleterious substances evaluated and accepted by the Geotechnical Consultant prior to placement. Soils of poor quality. such as those with unacceptable gradation, high expansion potential or low strength shall be placed in areas acceptable to the Geotechnical Consultant or mixed with other soils to achieve satisfactory fill materials. 3.2 Oversized Material : Oversize material defined as rock, or other irreducible material with a maximum dimension greater than 8 inches shall not be buried or placed in fill unless location, materials and placement methods are specifically accepted by the Geotechnical Consultant. Placement operations shall be such that nesting of oversized material does not occur and such that oversize material is completely surrounded by compacted or densified fill. Oversize material shall not be placed within 10 vertical feet of finished grade or ·within 2 feet of future utilities or underground construction. 3.3 Import : If importing of fill materials is required for grading, proposed import material shall meet the requirements of Section 3.1 The potential import source shall be given to the Geotechnical Consultant at least 48 hours (2 working days) before importing begins so that its suitability can be detemtlned and appropriate tests performed. 4.0 Fill Placement and Comp:1ction 4.1 Fill Layer: Approved fill material shall be placed in areas prepared to receive fill (per Section 3 .0) in near vertical layers generally not exceeding 8 inches in thickness when compacted. The Geotechnical Consultant may accept thicker layers if testing indicates that the grading procedure can adequately compact the thicker layers. Each layer shall be spread evenly and mixed thoroughly to attain relative uniformity of material and moisture throughout. 4.2 Fill Moisture Conditioning: Fill soils shall be watered. dried back blended, and/or mixed as necessary to attain a relatively wuform moisture content at or slightly over optimum. Maximum density and optimum moisture content tests shall be perfonned in accordance with the American Society of Testing and Materials (ASTM Test Method D1557). APPENDIX I Page 6 4.3 Compaction of Fill : After each layer has been moisture-conditioned, mixed and evenly spread, it shall be uniformly compacted to not less than 90 percent of maximum dry density (AST\1 D 1557). Compaction equipment shall be adequately sized and be either specifically designed for soil compaction or of proven re iability to efficiently achieve the specified level of compaction v.ith uniformity. 4.4 Compaction of Fill Slopes : In addition to normal compaction procedures specified above, compaction of slopes shall be accomplished by backrolling of slopes with sheepsfoot rollers at increment of 3 to 4 feet in fill elevation, or by other methods producing satisfactory results acceptable to the Geotechnical Consultant. Upon completion of grading, relative compaction of the fill, out to the slope face, shall be at least 90 percent of maximum dry density per ASTM Test Method D1557. 4.5 Compaction Testing: Field tests for moisture content and relative compaction of the fill soils shall be performed by the Geotechnical Consultant. Location and frequency of tests shall be at the Consultant's discretion based on field conditions encoW1tered. Compaction test locations will not necessarily be selected on a random basis. Test locations shall be selected to verify adequacy of compaction levels in areas that are judged to be prone to inadequate compaction (such as close to slope faces and at the fill/bedrock benches). 4/6 Frequency of Compaction Testing: Tests shall be taken at intervals not exceeding 2 feet in vertical rise and/or 1,000 cubic yards of compacted fill soils embankment. In addition as a guideline, at least one test shall be taken on slope faces for each 5,000 square feet of slope face and/or each 10 feet of vertical height of slope. The Contractor shall assure that fill construction is such that the testing schedule can be accomplished by the Geotechnical Consultant. The Contractor shall stop or slow down the earthwork construction if these minimum standards are not met. 4.7 Compaction Test Locations : The Geotechnical Consultant shall document the approximate elevation and horizontal coordinates of each test location. The Contractor shall coordinate ·with the project surveyor to assure that sufficient grade stakes are established so that the Geotechnical Consultant cdan determine the test locations with sufficient accuracy. At a minimum, two grade stakes within a horizontal distance ofl 00 feet and vertically less than 5 feet apart from potential test locations shall be provided. APPENDIX I Page 7 5.0 Subdrain Installation Subdrain systems shall be installed in accordance with the approved geotechnical report(s), the grading plan, and the Standard Details. The Geotechnical Consultant may recommend additional subdrains and/or changes in subdrain extent, location, grade, or material depending on conditions encountered during grading. All subdrains shall be surveyed by a land surveyor/civil engineer for line and grade after installation and prior to burial. Sufficient time should be allowed by the Contractor for these surveys. 6.0 Excavation 7.0 Excavations, as well as over-excavation for remedial purpose, shall be evaluated by the Geotechnical Consultant during grading. Remedial removal depths shown on geotechnical plans are estimates only. The actual extent of removal shall be determined by the Geotechnical Consultant based on the field evaluation of exposed conditions during grading. Where fill-overcut slopes are to be graded, the cut portion of the slopes shall be made, evaluated, and accepted by the Geotechnical Consultant prior to placement of materials for construction of the fill portion of the slope. unless otherwise recommended by the Geotechnical Consultant. Trench Backfill 7. I The Contractor shall follow all OSHA and Cal/OSHA requirements for safety of trench excavations. 7.2 All bedding and backfill of utility trenches shall be done in accordance with the applicable provisions of Standard Specifications of Public Works Construction. Bedding material shall have a Sand Equivalent greater than 30 (SE> 30). The bedding shall be placed and compacted to at a minimum of90 percent of maximum dry density from 1 foot above the top of the conduit to the swface. 7.3 The jetting of the bedding arotmd the conduits shall be observed by the Geotecbnical Consultant. 7.4 The Geotechnical Consultant shall test the trench backfill for relative compaction. At least one test should be made for every 300 feet of trench and 2 feet of fill. APPENDIX I Page 8 7.5 Lift thickness of trench backfill shall not exceed those allowed in the Standard Specifications of Public Works Construction unless the Contractor can demonstrate to the Geotechnical Consultant that the fill lift can be compacted to the minimum relative compaction by his alternative equipment and method. ------------· ·-•-------·----·---------------- FILL SLOPE PROJECT PLAN 1 TO 1 Min. FROM TOE OF SLOPE TO APPROVED GROUND FILL OVER CUT SLOPE CUT FACE SHALL BE CONSTRUCTED PRIOR TO FILL PLACEMENT TO ASSURE ADEQUATE GEOLOGIC CONj).!)J9'<1 ---- CUT OVER FILL SLOPE PROJECT PLAN 1 TO 1 Min. FROM TOE OF SLOPE TO APPROVED GROUND KEYING AND BENCHING DESIGN DETAIL A NATURAL GROUN~__... ...... CUT FACE TO BE ,,,,"'"' ,,,,,,,, ....... CONSTRUCTED / /"' PRIOR TO FILL /,,,, PLACEMENT NATURAL -ROUND ALLIED EARTH TECHNOLOGY OVER SIZE WINDROW • OVER SIZE ROCK IS LARGER THAN INCHES IN LARGEST DIMENSION • EXCAVATE A TRENCH IN THE COMPACTED FILL DEEP ENOUGH TO BURY ALL THE ROCK JETTED OR FLOODED GRANULAR MATERIAL • BACKFILL WITH GRANULAR SOIL JffiED OR FLOODED IN PLACE TO FILL ALL THE ROCK VOIDS • DO NOT BURY ROCK WITHIN 10 FEET OF FINISH GRADED. • WINDROW OF BURIED ROCK SHALL BE PARALLEL TO THE FINISH SLOPE FILL. FINISH GRADE SECTION "AA' JETTED OR FLOODED GRANULAR MATERIAL PROFILE ALONG WINDROW OVER SIZE ROCK DISPOSAL DETAIL B ALLIED EARTH TECHNOLOGY DETAIL OF CANYON SUBDRAIN TERMINAL GRADE - I ··T;:-~ .::::: ;~~~~~~~~ -! -··-· --~ SUB9RAIITT"Rm - EXISTING GROUND SURFACE SEE DETAIL BELOW FILTER FABRIC MIRAFI CALTRAN CLASS II PERMEABLE 140 OR APPROVED OR # 2 ROCK ( 3 CU. FT /Fn NT!. WRAPPED IN FILTER FABRIC \ . ;_ 12" Min. OVERLAP FROM THE TOP _.:_ HOG RING TIED EVERY 6 FEET POSITIVE SEAL SHOULD BE PROVIDE AT THE JOINT OUTLET PIPE ( NON PERFORATED PIPE ) -,--~--==-::..:1 r=;;~_. T-CON EtilO COLLECTION PIPE TO OUTLET PIPE FILTER FABRIC --..n---MIRAFI 140 N OR APPROVED EQUIVALENT CANYON SUBDRAIN DETAILS ALLIED EARTH TECHNOLOGY DETAIL C 2• Min. .------- KEY DEPTH -r _j OUTLET PIPES, 4" NON PERFORATED, 100' Max. O.C. HORIZONTAL I -- 30' Mox. O.C. VERTICAL TS' Min. LOWEST BENCH ( KEY) 1 CALTRAN CLASS OR# 2 ROCK( WRAPPED IN Fl 12" Min. OVERLAP FROM TH HOG RING TIED EVERY 6 POSITIVE SEAL SHOULD BE PROVIDE AT THE JOINT 7 5.0%Min -· OUTLET PIPE ( NON __/ PERFORATED PIPE ) ---- ,.. 15' Min;/'.._______1 ~□ FILTER FABRIC MIRAFI 140 OR APPROVED EQUIVALENT L f . CONNECTION FOR COLLECTION PIPE TO OUTLET PIPE SUBORAIN INSTALLATION-SUBDRAJN COLLECTOR PIPE SHALL BE INSTALLED WITH PERFORATIONS DOWN OR UNLESS OTHERWISE DESIGNED BY THE GEOTECHNICAL CONSULTAN. OUTLET SHALL BE NON-PERFORATED PIPE. THE S UBDRAIN PIPE SHALL HAVE AJ LEAST 8 PERFORATIONS UNIFORMLY SPACED PER FOOT. PERFORATION SHALL BE 1/4" TO 1/2" IF DRILLED HOLES ARE USED. ALL SUBDRAIN PIPES SHALL HAVE A GRADIENT AT LEAST 2% TOWARD THE OUTLET. SUBORAIN PIPES-SUBDRAIN PIPE SHALL BE ASTMO 2751, SOR 23.5 OR ASTMD 1527, SCHEDULE 40, OR ASTMO 3034, SOR 23.5, SCHEDULE 40 POLYVINYL CHORIDE PLASTIC (PVC) PIPE. ALL OUTLET PIPE SHALL BE PLACED IN A TRENCH NO WIDER THAN TWICE THE SUBDRAIN PIPE, PIE SHALL BE IN SOIL OF SE>30 JETTED OR FLOODED IN PLACED EXCEPT FOR THE OUTSIDE 5 FEET WHICH BE NATIVE SOIL BACKFILL BUTTRESS OR REPLACEMENT SUBDRAIN DETAIL D ALLIED EARTH TECHNOLOGY PROJECT PLAN 1 TO 1 Min. FROM TOP OF SLOPE TO OUTSIDE EDGE OF KEY OVERBURDEN OR UNSUITABLE MATERIAL FINISH SLOPE SURFACE NOTE: SUBDRAIN DETAILS AND KEY WIDTH RECOMMENDATIONS TO BE PROVIDED BASED ON EXPOSED SURFACE CONDITIONS HILLSIDE STABILITY FILL DETAIL E ALLIED EARTH TECHNOLOGY Project No. 20-1I47G 1 La Coruna Place 12/18/20 APPENDIX II LABORATORY TEST RESULTS =====---==== 1. The maximum dry density and optimum moisture content of the fill soils encountered were determined in accordance with ASTM D1557, Method A. The results of the test are presented as follows : Trench# 1 Sample #1 Depth 2.0' Soil Description Olive green silty fine sand (SM) Maximum Dry Density (lbs/cu.ft.) 122.0 Optimum Moisture Content (% Dry Wt.) 11.5 2. The Expansion Index of the most clayey soils was determined in accordance \\-1th ASTM D4928-08. The results of the test are presented as follows: Trench #2 Sample #1 Depth4.0' Soil Description Brown clay (CH) Expansion Index 95* *Considered to possess HIGH expansion potential Project No.20-1147Gl La Coruna Place 12/18/20 APPENDIX II LABORATORY TEST RESULTS (CONT'ND) =====---==== 3. The sulfate content of the soils encountered were determined in accordance with California Test No. 317. The results are presented below : Trench #2 Sample #1 Depth 4.0' Soil Description Brown CLAY (CH) Sulfate Content (ppm) 95 Negligible Project No. 20-114701 La Coruna Place APPENDIX Ill REFERENCES California Building Code, 2019, Title 24, Part 2 Volume 1 & 2 12/18/20 -California Department of Conservation, Division of Mines and Geology (California Geological Survey), 1997. DRP Enterprises -Grading Plans for La Coruna, Carlsbad, CA. Guidelines for Evaluating and Mitigating Seismic Hazards in California, DMG Special Publications 17. 7 Ip. Foundation and Earth Structures, Naval Facilities Engineering Command, DM7 .02 "Green Book" Standard Specifications for Public Works Construction, Public Works Standards, 2018 edition. Joyner, W.B. and Boore, D.M. 1982, Prediction of Earthquake response spectra, U.S. Geological Survey Open File Report 82-922, l 6pp. Kennedy, M.P. and Tan S.S., 2005 Geologic Map of the San Diego 30' x 60' Quadrangle, California Geologic Survey and U.S. Geological Survey digital map series. Lindavall, S.C., Rockwell, T.K., and Lindvall, C.E., I 990, the seismic hazard of San Diego revised : New evidence of Magnitude 6+ Holocene earthquakes on the Rose Canyon Fault Zone, in Proceedings of U.S. National Conference on Earthquake Engineering, Palm Springs, California, vol 1 : Earthquake Engineering Research Inst., p. 679-688 Residential Design, Building Plan Hamdard Residence, La Corona Place, Carlsbad, CA. Tan, S.S., and Kennedy, M. P., 1996 Geologic Maps of the Northwestern Part of San Diego County, California, Plate I, Geologic Maps of the Oceanside, San Luis Rey, and San Marcos 7.5 Quadrangles., Div. Mines and Geology Open File Report 96-02.