The URL can be used to link to this page

Home My WebLink AboutGPA 15-02; OCEAN VIEW POINT; UPDATED GEOTECHNICAL INVESTIGATION REPORT; 2018-08-07w Cl IR.ISTIAN WI IEELER. [NC.IN[[~INC UPDATED GEOTECHNICAL INVESTIGATION REPORT CARLSBAD TRACT CT-15-07 TWAIN A VENUE CARLSBAD. CALIFORNIA SUBMITTED TO GAYLHYNEK PO BOX401 GILROY. CALIFORNIA 95021-0451 SUBMITTED BY CHRISTIAN WHEELER ENGINEERING 3980 HOME A VENUE SAN DIEGO, CALIFORNIA 92105 AUG 1 6 2018 CITY OF CARLSBAD PLANNING DIVl~!OM 3980 !!omc .\venue• ~an D,~go, C-\ ')2[05 • 619-350-1"'00 t f-i.-\X 619-.1.'i0-1 7 01 TABLE OF CONTENTS PAGE Introduction and Project Description ......... . ·•·•••••••••••••• .. •••••• ..................... 1 Project Scope ....... . •••••••••••••••••••••••••••••••••••••••••••••••••••••• .. 2 Findings ............... . . .................................................................... 2 Site Description .. ..2 General Geology and Subsurface Conditions ....................................... . . ..... 3 Geologic Setting and Soil Description ...... . Topsoil .... Subsoil Slopewash ..... . Old Paralic Deposits Santiago Formation. Goundwater .... Conclusions ........................................... . Recommendations .......................... . Grading and Earthwork General ........ . Pre-Grade Meeting ..................... . Observation of Grading ................ . Clearing and Grubbing ................. . Site Preparation Transition Building Pads .............. . Select Grading. Cut And Fill Slope Construction ..... Excavation Characteristics .......... . Processing of Fill Areas ................. . ..3 .3 .. 3 . ...... 3 .. 3 . .. .4 . ................ 4 . ............................................................................. 5 . ...... 6 •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• .. 6 . .............................................................. 6 . .... 6 . .... 6 . .... 6 ....... .7 . . .7 •••••••••••••••••••••••••••••••••••••• ................. 7 . .................. 7 . .. 8 Compaction and Method of Filling ........................................ . . .... 8 . ................ 8 Surface Drainage ..................... . Grading Plan Review ................................ . Slope Stability General .......................................... . Erosion Control ................... . Foundations General Footing Dimensions ......................... . Bearing Capacity Foundation Reinforcement .... . Post-Tensioned Foundations .. . Lateral Load Resistance ........ . Settlement Characteristics ...... . . ............ 8 . ...... 9 ........... 9 ··············· .................................................................. 9 . ................ 9 ................... 10 .................. 10 . ..... 10 ............ 10 . ................. 11 . .................... 11 . ........................... 11 . ......................... 12 Expansive Characteristics......................................... . ................. 12 Foundation Excavation Observation .......... 12 Foundation Plan Revtew .................................................................................................................................... 12 Soluble Sulfates ......... . ............................................................................................. 12 Seismic Design Factors .................................... . On-Grade Slab . General ............................... . Interior Floor Slab Under-Slab Vapor Retarders ............................... . Exterior Concrete Flatwork .. Swimming Pools ..... . ..................... 13 . .............. 13 ••••••••••••••••••••••••••••••••••• 13 .............. 13 ..14 . ... 14 , .... 15 CWE 2180124.02 Carlsbad Tract CT-15-07 Twain Avenue, Carlsbad, California Masonry Earth Retaining Walls Foundations ..................... 15 ........................................................... 15 Passive Pressure ................................................................................................................................................... 15 Active Pressures ................................................................................................................................................... 15 Waterproofing and Wall Drainage Systems........................... . ................. 16 Backfill.............. . ................................................................... 16 Limitations .......................................................................................... . ...................................................................... 16 Review, Observation and Testing .. . . .... 16 Uniformity of Conditions ................................ . . ....... 16 Change m Scope . Time Limitations Professional Standard Client's Responsibility FIGURES Figure 1 PLATES Plate 1 Plate 2 Plate 3 TABLES Table I Table II APPENDICES Appendix A Appendix B Appendix C ATTACHMENTS Site Vicinity Map Site Plan & Geotechnical Map Fill Over Natural Slope Detail Retaining Wall Subdrain Detail Post-Tensioned Foundations Seismic Design Factors . .... 17 .. 17 ••·••··············· 17 ••••••••••••••• 18 Data From CWE 201.116 Geotechnical Report References Recommended Grading Specifications -General Provisions CWE 2180124.02 Carlsbad Tract CT-15-07 Twain Avenue, Carlsbad, California w CHRISTIAN WHEELER [NGIN[[RING UPDATED GEOTECHNICAL INVESTIGATION REPORT CARLSBAD TRACT CT-15-07 TWAIN A VENUE CARLSBAD, CALIFORNIA INTRODUCTION AND PROJECT DESCRIPTION This report presents an updated geotechnical report for the subject residential subdivision and associated improvements to be developed at the southern end of Twain Avenue, in the city of Carlsbad, California. Figure Number 1, presented on the following page, provides a vicinity map showing the location of the project. It is our understanding that the subject project will consist of a 13-lot residential subdivision with associated improvements, including an access street. It is anticipated that the structures will be one and/or two stories high, and of wood-frame construction. Shallow foundations and conventional concrete slab-on-grade floor systems are anticipated. However, post-tensioned foundations may be utilized. Based on the available plans, grading will consist of cuts and fills of up to about 10 feet and 16 feet in depth, respectively. Proposed cut and fill slopes will be graded at a 2:1 (horizontal to vertical) or flatter inclination, and extend to a maximum height of about 10 feet and 31 feet, respectively. Bio-filtration basins are proposed for each lot. To aid in the preparation of this report, we were provided with a set of grading plans prepared by Landmark Consulting, plot date September 6, 2017. A copy of the grading plan has been used as the base for our Site Plan and Geotechnical Map, and 1s included herein as Plate No. 1. In addition, we have reviewed our "Updated Geotechnical Investigation Report, Kirgis Subdivision, Carlsbad Tract 02-06", dated October 10, 2013 (CWE 2110148.0lR). Appropriate data from this geotechnical report is presented in Appendix A. This data was used in the preparation of this updated report. 3980 !Tome .-\,·enue • ~an Diego, C.\ 92105 • 619-550-1700 • F.\X 619-SS0-1701 CWE 2180124.02 August 7, 2018 Page No. 2 This report has been prepared for the exclusive use of Gay! Hynek and their design consultants for specific application to the project described herein. Should the project be changed in any way, the modified plans should be submitted to Christian Wheeler Engineering for review to determine their conformance with our recommendations and to determine whether any additional subsurface investigation, laboratory testing and/ or recommendations are necessary. Our professional services have been performed, our findings obtained and our recommendations prepared in accordance with generally accepted engineering principles and practices. This warranty is in lieu of all other warranties, express or implied. PROJECT SCOPE The scope of our services included a site reconnaissance, a review of our previous geotechnical reports, and a limited review of the current project plans. The update report includes providing any additional geotechnical recommendations that, in our opinion, are necessary, including updated seismic design parameters for the proposed project in accordance with the 2016 edition of the California Building Code (CBC). FINDINGS SITE DESCRIPTION The subject site is a nearly rectangular-shaped parcel of land approximately 21.9 acres in area, located at the southern end of Twain Avenue, in the City of Carlsbad, California. The site is further identified as Assessor's Parcel Number 212-010-03. Undeveloped canyon lands bound the site to the west, south, and east, while a residemiaJ subdivision bounds the site to the north. In general, a gently sloping mesa top that generally descends to the south characterizes the uppermost, northern portion of the site. Moderately steep canyon lands descend to south, east, and west from the uppermost, mesa top area of the site. The existing on-site elevations within those portions of the site to receive improvements range from about 330 feet in the northern portion of the site to about 270 feet in the southwestern portion of the site. The site appears to remain essentially unchanged from the time that we performed our previous observations. CWE 2180124.02 August 7, 2018 Page No. 3 GENERAL GEOLOGY AND SUBSURFACE CONDITIONS GEOLOGIC SETTING AND SOIL DESCRIPTION: The subject site is located in the Coastal Plains Physiographic Province of San Diego County and is underlain by a relatively minor amount of native residuum, Quaternary-age old paralic deposits, and Cretaceous-age deposits of the Santiago Formation. The following provides a discussion, based on our subsurface explorations and our past experience with nearby projects, of the soil types expeL"ted to be encountered beneath the property. TOPSOIL: A topsoil layer was encountered at the surface in most of our exploratory test trenches. The topsoil layer has an approximate thickness of 1 foot. The topsoil material generally consists of dark brown, moist, loose, silty sand (SM). It should be noted that topsoil was not encountered in our test trench T-9, excavated in the northwest portion of the site. These deposits were judged to have a low potential for expansion (EI between 21 and 50). SUBSOIL: A subsoil layer was encountered within our exploratory test trenches excavated in the northern, eastern, and southeastern portions of the proposed improvement area. The subsoil was generally noted below the topsoil layer, but was also noted at the surface within the northeast portion of the site. The thickness of the subsoil layer ranged from approximately 1 foot to 1 ½ feet. The subsoil was noted to primarily consist of brown, moist, loose to medium dense, clayey sand (SC). These deposits were judged to have a moderate potential for expansion (EI between 51 and 90). SLOPEWASH (Qsw): A layer of slopewash material was noted below the topsoil layer within our exploratory test trenches excavated in the southwest portion of the proposed improvement area. The layer had an approximate thickness ranging from 1 ½ to 2 feet. The materials within the slopewash layer generally consisted of dark brown, wet, soft, sandy clay with a slight amount of gravel and cobble (CL). These deposits were judged to have a moderate potential for expansion (EI between 51and 90). OLD PARALIC DEPOSITS (Qop): Underlying the topsoil and subsoil layers, a layer of old paralic deposits mantles the northern, eastern, and southeastern portions of the proposed improvement area. These deposits were identified in the referenced geotechnical report as • CWE 2180124.02 August 7, 2018 Page No. 4 terrace deposits. The approximate location of the contact between the old paralic deposits and underlying Santiago Formation is shown on Plate No. 1. This contact typically occurs at an elevation of 310 feet. Generally, the old paralic deposits are thickest within the upper areas in the eastern portion of the improvement area, and thin towards the lower portions. The old paralic deposits generally consisted of orangish-brown, moist, dense to very dense, clayey sand with some gravel and cobble (SC). The old paralic deposits were found to possess a very low expansion potential (EI=6). SANTIAGO FORMATION (Tsa): The site is ultimately underlain by Tertiary-age deposits of the Santiago Formation. The formational materials were noted below the terrace deposits in the northern, eastern, and southeastern portions of the proposed improvement area and below the topsoil, subsoil, and slopewash layers in the south-southwestern portions. The materials of the Santiago Formation mainly consisted of light brown to light orangish-brown, moist, dense to very dense, clayey sand (SC) and light brown to white, silty sand (SM). The formational materials also consisted of lesser amounts of light olive brown, moist, very stiff to hard, sandy day (CL). The sandy portions of the Santiago Formation were judged to have a low expansion potential (EI between 21 and 50). The clayey portions of the Santiago Formation, which appear to comprise a relatively small amount of the formational material, were found to possess a medium expansion potential (El=85). GROUNDWATER: No groundwater or seepage was encountered in any of the areas of the site investigated. However, it should be recognized that minor groundwater 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 result of an alteration in drainage patterns and/ or an increase in irrigation water. Based on the permeability characteristics of the soil and the anticipated usage and 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 occur CWE 2180124.02 August 7, 2018 Page No. 5 CONCLUSIONS In general, our findings indicate that the subject property is suitable for the construction of the proposed subdivision and associated improvements, provided the recommendations provided herein are followed. The main geotechnical conditions encountered that affect the proposed development are potentially compressible surficial soils, expansive soils, and cut/fill transitions. These conditions are discussed hereinafter. It should be recognized that some of the recommendations provided hereinafter to mitigate a certain potentially adverse condition may also be applicable to another condition. • A relatively thin mantle of potentially compressible topsoil, subsoil, and slopewash ranging between about 2 to 3 feet in combined thickness caps the site. Deeper compressible soils may exist in areas of the site not investigated. These materials are considered unsuitable, in their present condition, for the support of settlement sensitive improvements, and should be removed and replaced as compacted fill. • A relatively small percentage of the Santiago formation deposits encountered in our trenches was found to be moderately expansive (EI=85). It is recommended that select grading be performed to mitigate this condition. le should be realized that Santiago Formation deposits are inherently highly heterogeneous, and the relative amounts of different soils exposed in our trenches may not be representative of areas of the site not investigated. If select grading cannot be performed due to the lack of sufficient low expansive soils, the foundation recommendations contained in this report may have to be changed. • Proposed grading and site preparation will result in a cut/fill transition for some of the lots. Structures and improvements spanning cut/fill transitions may experience detrimental differential settlements due to the different compression characteristics of native and fill soils. In order to mitigate this condition, it is recommended that the cut portion of the lot be undercut as described hereinafter. Undercutting the cut portions of the lots will also facilitate future drainage, trenching and landscaping. The general geology and geologic hazards as described in the original report remains unchanged. The site is located in an area that is relatively free of geologic hazards that will have a significant effect on • CWE 2180124.02 August 7, 2018 Page No. 6 the proposed construction. The most likely geologic hazard that could affect the site is ground shaking due to seismic activity along one of the regional active faults. However, construction in accordance with the requirements of the 2016 edition of the California Building Code and the local governmental agencies should provide a level of life-safety suitable for the type of development proposed. RECOMMENDATIONS GRADING AND EARTHWORK GENERAL: All grading should conform to the guidelines presented in Appendix J of the California Building Code, the minimum requirements of the City of Carlsbad, and the Recommended Grading Specifications and Special Provisions attached hereto, except where specifically superseded in the text of this report. PRE-GRADE MEEl'ING: It is recommended that a pre-grade meeting, including the owner's representative, grading contractor and a representative from Christian Wheeler Engineering, take place to discuss the recommendations of this report and address any issues that may affect grading and construction operations. OBSERVATION OF GRADING: Observation by the Geotechnical Consultant is essential during the mass grading operation to confirm conditions anticipated by our investigation, to allow adjustments in design criteria to reflect actual field conditions exposed, and to determine that the grading proceeds in general accordance with the recommendations contained herein. Continuous or periodic observation should be provided at the discretion of the Geotechnical Consultant. CLEARING AND GRUBBING: Site preparation should begin with the removal of all existing improvements and trash, as well as any existing vegetation from the areas of the site to be graded. The debris resulting from this operation should be disposed of off-site. This should include all root balls from trees, all natural brush and all significant root material. CWE 2180124.02 August 7, 2018 Page No. 7 SITE PREPARATION: It is recommended that existing topsoil, subsoil, and slopewash underlying proposed settlement-sensitive improvements, including all proposed fills, should be removed in their entirety. Based on the geotechnical information available, the anticipated removal depths range from about 2 feet to 3 feet. However, deeper removals may be needed in areas not investigated or due to unforeseen conditions. Actual removal depths will be determined by our representative. All excavated areas should be approved by the geotechnical engineer or his representative prior to replacing any of the excavated soils. Where necessary to achieve planned site grades, the removed materials may be replaced as compacted fill provided they are thoroughly mixed as described hereinafter, and moisture conditioned prior to placement. TRANSITION BUILDING PADS: It is recommended that old paralic deposits and formational soils underlying the cut portion of the proposed transition lots be undercut to a minimum depth of 4 feet below finish pad grade, or 2 feet below the bottom of footings {1 foot below retaining wall footing keys) whichever is deepest. The undercuts should be performed in such a way that low areas with impaired drainage are not created. Undercut areas should be backfilled with properly compacted, low expansive fill (EI between 21 and 50}. SELECT GRADING: Portions of the Santiago Formation were determined to possess a medium expansive potential {El=85). Expansive soils should not be placed within 5 feet from finish pad grade, and 20 feet from the face of fill slopes. In addition, expansive soils within 5 feet from finish pad grade in proposed cut areas should be removed and replaced with low expansive fill {EI between 21 and 50} compacted to at least 90 percent. CUT AND FILL SLOPE CONSTRUCTION: Cut and fill slopes may be constructed at an inclination of 2: 1 or flatter (horizontal to vertical}. Compaction of fill slopes should be performed by back-rolling with a sheepsfoot compactor at vertical intervals of 4 feet or less as the fill is being placed, and track-walking the face of the slope when the slope is completed. As an alternative, the fill slopes may be overfilled by at least 3 feet and then cut back to the compacted core at the design line and grade. Keys should be made at the toe of fill slopes in accordance with the recommendations presented under "Compaction and Method of Filling." A subdrain is recommended for transition fill over cut slopes. A subdrain detail is provided in the attached Plate No. 2. • CWE 2180124.02 August 7, 2018 Page No. 8 EXCAVATION CHARACTERISTICS: It is anticipated that the cuts proposed in the aforementioned grading plans may be achieved with conventional, large heavy-duty grading equipment in good working order. However, concretions requiring special grading and handling consideration may be encountered within the Santiago Formation. In addition, zones of very dense deposits that are difficult to excavate with light trenching equipment may be encountered within the Santiago Formation. PROCESSING FILL AREAS: Prior to placing any new fill soils or constructing any new improvements in areas that have been cleaned out to receive fill, the exposed soils should be scarified to a depth of about 12 inches, moisture-conditioned, and compacted to at least 90 percent relative compaction. In areas to support fill slopes, keys should be cut into the competent supporting materials. The keys should be at least ten feet wide, and be sloped back into the hillside at least two percent. The keys should extend at least one foot into the competent supporting materials. A subdrain is recommended at the heel of the keyway. Where the existing ground has a slope of 5:1 (horizontal to vertical) or steeper, it should be benched into as the fill extends upward from the keyway. COMPACTION AND MElHOD OF FILLING: All fill and backfill placed at the site should be compacted to a relative compaction of at least 90 percent of its maximum dry density as determined by ASTM Laboratory Test D1557. Fills should be placed at or slightly above optimum moisture content, in lifts six to eight inches thick, with each lift compacted by mechanical means. Fills should consist of approved earth material, free of trash or debris, roots, vegetation, or other materials determined to be unsuitable by the Geotechnical Consultant. Fill material should be free of rocks or lumps of soil in excess of twelve inches in maximum dimension, and free of rocks over six inches in diameter within the upper three feet of pad grade. Utility trench backfill within five feet of the proposed structures and beneath driveways, concrete flat work, and pavements should be compacted to a minimum of 90 percent of its maximum dry density. SURFACE DRAINAGE: The drainage around the proposed improvements should be designed to collect and direct surface water away from proposed improvements and the top of slopes CWE 2180124.02 August 7, 2018 Page No. 9 toward appropriate drainage facilities. Rain gutters with downspouts that discharge runoff away from the structure and the top of slopes into controlled drainage devices are recommended. The ground around the proposed improvements should be graded so that surface water flows rapidly away from the improvements without ponding. In general, we recommend that the ground adjacent to structure slope away at a gradient of at least 5 percent for a minimum distance of 10 feet. If the minimum distance of 10 feet cannot be achieved, an alternative method of drainage runoff away from the building at the tennination of the 5 percent slope will need to be used. Swales and impervious surfaces that are located within 10 feet of the building should have a minimum slope of 2 percent. Drainage patterns provided at the time of construction should be maintained throughout the life of the proposed improvements. Site irrigation should be limited to the minimum necessary to sustain landscape growth. Over watering should be avoided. Should excessive irrigation, impaired drainage, or unusually high rainfall occur, zones of wet or saturated soil may develop. GRADING PLAN REVIEW: The final grading plans should be submitted to this office for review in order to ascertain that the recommendations of this report have been implemented, and that no additional recommendations are needed due to changes in the anticipated development plans. SLOPE STABILITY GENERAL: All slopes at the subject development should be constructed at a slope ratio of 2: 1 (horizontal to vertical) or flatter. Maximum anticipated cut and fill slope heights will be less than about 20 feet and 27 feet, respectively. Based on the strength parameters of the on-site soils in their natural and mechanically compacted states, it is our opinion that the proposed slopes will be stable in regards to deep-seated slope failure and surficial slope failure. All fill slopes should be constructed in accordance with the grading recommendations presented above. EROSION CONTROL: The placement of cohesionless soils at the face of slopes should be avoided. Slopes should be planted as soon as feasible after grading. Sloughing, deep rilling and slumping of surficial soils may be anticipated if slopes are left unplanted for a long period of time, • CWE 2180124.02 August 7, 2018 Page No. 10 especially during the rainy season. Care should be taken to ensure the proper drainage of all surface runoff away from the slope face. Saturation of the slope caused by excessive or improperly channeled runoff could detrimentally affect the surficial stability of the slope. Irrigation on and adjacent to slopes should be carefully monitored to insure that only the minimum amount necessary to sustain plant life is used. Over-irrigating could not only be erosive but may significantly increase the chance for slope surficial stability problems and should be avoided. FOUNDATIONS GENERAL: Based on our findings and engineering judgment, the proposed structures may be supported by conventional continuous and isolated spread footings, provided the site is prepared as recommended in this report. As an alternative post-tensioned foundations may be utilized. The following recommendations are considered the minimum based on soil conditions and are not intended to be lieu of structural considerations. All foundations should be designed by a qualified structural engineer. FOOTING DIMENSIONS: Spread footings supporting proposed single-and two-story structures should have a minimum embedment depth of 12 inches and 18 inches below lowest finish pad grade, respectively. Continuous footings for single-and two-story structures should have a minimum width of 12 inches and 15 inches, respectively. Isolated footings should have a minimum width of 24 inches. Minimum dimensions for footings supporting light exterior improvements should be 12 inches in depth and width. Minimum dimensions for footings supporting exterior retaining walls should be 18 inches in depth and 24 inches in width. Footings located adjacent to slopes should be extended to a depth such that a minimum horizontal distance of 10 feet exists between the bottom of the footing and the face of the slope. The footing setback distance from the top of slopes may be modified by using deepened footings. Plans for any footings that will not comply with the specified setbacks should be submitted to the Geotechnical Engineer for specific review and approval prior to construction. BEARING CAPACITY: Conventional continuous spread footings with a minimum embedment of 12 inches and width of 12 inches may be designed for an allowable soil bearing pressure of 2,500 pounds per square foot. This value may be increased by 700 pounds per square foot for each CWE 2180124.02 August 7, 2018 Page No. 11 additional foot of embedment and 400 pounds per square foot for each additional foot of width up to a maximum of 4,000 pounds per square foot. The bearing value may also be increased by one-third for combinations of temporary loads such as those due to wind or seismic loads. FOUNDATION RflNFORCEMENT: The project structural engineer should provide foundation reinforcement recommendations. However, based on the anticipated soil conditions, we recommend that the minimum reinforcing for continuous footings should consist of at least 2 No. 5 bars positioned near the bottom of the footing and 2 No. 5 bars positioned near the top of the footing. POST-TENSIONED FOUNDATIONS: Post-Tensioned foundations may be utilized for the support of the subject structures. We are providing in tabular form below the post tension related design parameters from the Post Tensioning Institute, 3'd edition. TABLE I, POST-TENSIONED FOUNDATIONS Post-Tensioning Institute (PTI)-3rd Edition Edve Moisture Variation, em Center Lift 1ft) 9.0 Edve Lift fh! 5.4 Differential Soil Movement, -um Center Lift fin) .19 Ed,ze Lift (in! .41 A minimum depth of 12 inches below adjacent finished grade is recommended for perimeter beams. Soil bearing values provided in the bearing capacity paragraph are also applicable for post tensioned foundations. Footings located adjacent to slopes should be extended to a depth such that a minimum horiwntal distance of 8 feet exists between the bottom of the footing and the face of the slope. LA 'fERAL LOAD RESISTANCE: Lateral loads against foundations may be resisted by friction between the bottom of the footing and the supporting soil, and by the passive pressure against the footing. The coefficient of friction between concrete and soil may be considered to be 0.35. The passive resistance may be considered to be equal to an equivalent fluid weight of 350 pounds per cubic foot. This assumes the footings are poured tight against undisturbed soil. If a combination of the passive pressure and friction is used, the friction value should be reduced by one-third. The upper CWE 2180124.02 August 7, 2018 Page No. 12 12 inches of footing embedment should not be considered when calculating passive pressures, unless the footing abuts a concrete slab-on-grade or a paved surface. SETTLEMENT CHARACTERISTICS: The anticipated total and differential settlement is expected to be less than about 1 inch and 1 inch over 40 feet, respectively, provided the recommendations presented in this report are followed. It should be recognized that minor cracks normally occur in concrete slabs and foundations due to concrete shrinkage during curing or redistribution of stresses, therefore some cracks should be anticipated. Such cracks are not necessarily an indication of excessive vertical movements .. EXP ANS IVE CHARACTERISTICS: Provided the site preparation recommendations described in this report are implemented, the prevailing foundation soils are assumed to have a low expansive potential (EI between 21 and 50). The recommendations within this report reflect these conditions. FOUNDATION EXCAVATION OBSERVATION: All foundation excavations should be observed by a representative of this office prior to the placement of forms or reinforcement in order to verify that the footings have the proper dimensions and that the soil conditions are as anticipated. FOUNDATION PLAN REVIEW: The final foundation plan and accompanying details and notes should be submitted to this office for review. The intent of our review will be to verify that the plans used for construction reflect the minimum dimensioning and reinforcing criteria presented in this section and that no additional criteria are required due to changes in the foundation type or layout. It is not our intent to review structural plans, notes, details, or calculations to verify that the design engineer has correctly applied the geotechnical design values. It is the responsibility of the design engineer to properly design/ specify the foundations and other structural elements based on the requirements of the structure and considering the information presented in this report. SOLUBLE SULFA TES: The water soluble sulfate content of foundation soils should be determined after grading in accordance with California Test Method 417. Nevenheless, Type II modified Portland cement is recommended for concrete in contact with soil. CWE 2180124.02 August 7, 2018 Page No. 13 SEISMIC DESIGN FACTORS The seismic design factors applicable to the subject site are provided below. The seismic design factors were determined in accordance with the 2016 California Building Code. The site coefficients and adjusted maximum considered earthquake spectral response acceleration parameters are presented in the following Table II. TABLE II: SEISMIC DESIGN FACTORS Site Coordinates: Latitude 33.138° LonP-itude -117.299° Site Class D Site Coefficient Fa 1.065 Site Coefficient Fv 1.582 Soectral Resoonse Acceleration at Short Periods S, 1.087 e Soectral Response Acceleration at 1 Second Period S1 0.418 • SMs-F,S, 1.158 • s~n -FvS1 0.662 • 5Ds=2/3*5Ms 0.772 • $01 =2/3*$Mt 0.491 • Probable ground shaking levels at the site could range from slight to moderate, depending on such factors as the magnitude of the seismic event and the distance to the epicenter. It is likely that the site will experience the effects of at least one moderate to large earthquake during the life of the proposed improvements. ON-GRADE SLABS GENERAL: It is our understanding that if conventional foundations are utilized for the support of the proposed structures, the floor system for the proposed structures will consist of an on-grade concrete slab. The following recommendations are considered the minimum slab requirements based on the anticipated soil conditions, are not intended in lieu of structural considerations. INTERIOR FLOOR SLABS: The minimum floor slab thickness should be 4 inches (actual), and the floor slab should be reinforced with at least No. 3 reinforcing bars placed at 18 inches on center each way. Slab reinforcement should be supported on chairs such that the reinforcing bars are CWE 2180124.02 August 7, 2018 Page No. 14 positioned at mid-height in the floor slab. The slab reinforcement should extend into the perimeter foundations at least 6 inches. UNDER-SLAB VAPOR RETARDERS: The following recommendations apply to conventional slabs-on-grade. Steps should be taken to minimize the transmission of moisture vapor from the subsoil through the interior slabs where it can potentially damage the interior floor coverings. Local industry standards typically include the placement of a vapor retarder, such as plastic, in a layer of coarse sand placed directly beneath the concrete slab. Two inches of sand are typically used above the plastic. In this case it is further recommended that the plastic be underlain by a 6- inch-thick gravel layer placed over filter fabric such as Mirafi 140N or equivalent. The vapor retarder should be at least 15-mil Stegowrap® or similar material with sealed seams and should extend at least 12 inches down the sides of the interior and perimeter footings. The sand should have a sand equivalent of at least 30, and contain less than 10% passing the Number 100 sieve and less than 5% passing the Number 200 sieve. The membrane should be placed in accordance with the recommendation and consideration of ACI 302, "Guide for Concrete Floor and Slab Construction" and ASThl E1643, "Standards Practice for Installation of Water Vapor Retarder Used in Contact with Earth or Granular Fill Under Concrete Slabs." It is the flooring contractor's responsibility to place floor coverings in accordance with the flooring manufacturer specifications. EXTERIOR CONCRETE FLA TWORK: Exterior concrete slabs on grade should have a minimum thickness of 4 inches and be reinforced with at least No. 3 bars placed at 18 inches on center each way (ocew). Driveway slabs should have a minimum thickness of 5 inches and be reinforced with at least No. 4 bars placed at 12 inches ocew. Driveway slabs should be provided with a thickened edge a least 12 inches deep and 6 mches wide. All slabs should be provided with weakened plane joints in accordance with the American Concrete Institute (ACD guidelines. Special attention should be paid to the method of concrete curing to reduce the potential for excessive shrinkage cracking. It should be recognized that minor cracks occur normally in concrete slabs due to shrinkage. Some shrinkage cracks should be expected and are not necessarily an indication of excessive movement or structural distress. CWE 2180124.02 August 7, 2018 Page No. 15 SWIMMING POOLS Swimming pools may be constructed as part of the proposed development or by future individual homeowners. If the proposed pool is a settlement sensitive vanishing edge pool or a zero edge pool, it is recommended that it be founded in the formational soils underlying the compacted fill. Depending on the pool location, this recommendation may necessitate a foundation system consisting of concrete cast-in-place piers. Appropriate foundation recommendations will be provided by this office after the proposed swimming pool layout is available. EAR1HRETAINING WALLS FOUNDATIONS: Foundations for proposed retaining walls should be constructed in accordance with the recommendations for shallow foundations presented previously in this report. PASSIVE PRESSURE: The passive pressure forthe anticipated foundation soils may be considered to be 300 pounds per square foot per foot of depth. The upper foot of embedment should be neglected when calculating passive pressures, unless the foundation abuts a hard surface such as a concrete slab. The passive pressure may be increased by one-third for seismic loading. The coefficient of friction for concrete to soil may be assumed to be 0.30 for the resistance to lateral movement. When combining frictional and passive resistance, the friction should be reduced by one-third. ACTIVE PRESSURE: The lateral soil pressure for the design of unrestrained earth retaining structures with level backfill may be assumed to be equivalent to the pressure of a fluid weighing 35 pounds per cubic foot (pd). An additional 13 pcf should be added to the above value for a 2:1 {horizontal to vertical) sloping backfill condition. These pressures do not consider any other surcharge. If any are anticipated, this office should be contacted for the necessary increase in soil pressure. These values are based on a drained backfill condition. Seismic lateral earth pressures may be assumed to equal an inverted triangle starting at the bottom of the wall with the maximum pressure equal to 8.SH pounds per square foot (where H = wall height in feet) occurring at the top of the wall. • CWE 2180124.02 August 7, 2018 Page No. 16 WATERPROOFING AND WALL DRAINAGE SYSTEMS: The need for waterproofing should be evaluated by others. If required, the project architect should provide (or coordinate) waterproofing details for the retaining walls. The design values presented above are based on a drained backfill condition and do not consider hydrostatic pressures. Unless hydrostatic pressures are incorporated into the design, the retaining wall designer should provide a detail for a wall drainage system. Typical retaining wall drain system details are presented as Plate No. 3 of this report for informational purposes. Additionally, outlets points for the retaining wall drain system should be coordinated with the project civil engineer. BACKFILL: All backfill soils should be compacted to at least 90 percent relative compaction. Expansive or clayey soils should not be used for backfill material. The wall should not be backfilled until the masonry has reached an adequate strength. LIMITATIONS REVIEW, OBSERVATION AND TESTING The recommendations presented in this report are contingent upon our review of final plans and specifications. Such plans and specifications should be made available to the Geotechnical Engineer and Engineering Geologist so that they may review and verify their compliance with this report and with the 2007 edition of the California Building Code. It is recommended that Christian Wheeler Engineering be retained to provide continuous soil engineering services during the earthwork operations. This is to verify compliance with the design concepts, specifications or recommendations and to allow design changes in the event that subsurface conditions differ from those anticipated prior to start of construction. UNIFORMITY OF CONDITIONS The recommendations and opinions expressed in this report reflect our best estimate of the project requirements based on an evaluation of the subsurface soil conditions encountered at the subsurface exploration locations and on the assumption that the soil conditions do not deviate appreciably from CWE 2180124.02 August 7, 2018 Page No. 17 those encountered. It should be recognized that the performance of the foundations and/ or cut and fill slopes may be influenced by undisclosed or unforeseen variations in the soil conditions that may occur in the intermediate and unexplored areas. Any unusual conditions not covered in this report that may be encountered during site development should be brought to the attention of the Geotechnical Engineer so that he may make modifications if necessary. CHANGE IN SCOPE This office should be advised of any changes in the project scope or proposed site grading so that we may determine if the recommendations contained herein are appropriate. It should be verified in writing if the recommendations are found to be appropriate for the proposed changes or our recommendations should be modified by a written addendum. TIME LIMITATIONS The findings of this report are valid as of this date. Changes in the condition of a property can, however, occur with the passage of time, whether they are due to natural processes or the work of man on this or adjacent properties. In addition, changes in the Standards-of-Practice and/ or Government Codes may occur. Due to such changes, the findings of this report may be invalidated wholly or in part by changes beyond our control. Therefore, this report should not be relied upon after a period of two years without a review by us verifying the suitability of the conclusions and recommendations. PROFESSIONAL STANDARD In the performance of our professional services, we comply with that level of care and skill ordinarily exercised by members of our profession currently practicing under similar conditions and in the same locality. The client recognizes that subsurface conditions may vary from those encountered at the locations where our borings, surveys, and explorations are made, and that our data, interpretations, and recommendations are based solely on the information obtained by us. We will be responsible for those data, interpretations, and recommendations, but shall not be responsible for the interpretations by others of the information developed. Our services consist of professional CWE 2180124.02 August 7, 2018 Page No. 18 consultation and observation only, and no warranty of any kind whatsoever, express or implied, is made or intended in connection with the work performed or to be performed by us, or by our proposal for consulting or other services, or by our furnishing of oral or written reports or findings. CLIENT'S RESPONSIBILITY It is the responsibility of the Client, or her representatives, to ensure that the information and recommendations contained herein are brought to the attention of the structural engineer and architect for the project and incorporated into the project's plans and specifications. It is further their responsibility to take the necessary measures to insure that the contractor and all subcontractors carry out such recommendations during construction, Appendix A Data from CWE 201.116 Geotechnical Report j ' LIGENQ -~~TFiiTPEM::tit..OC,.f,0,,, ~COHfACr --Qt w ::v~~'l~vrtn• Tsa r 1.nt~IIX:N1'-'L.MCl,A.1:1 .. r"""""'1< 1-O:,.t,11-Q.l ~~ '°'""' 1 •••• , LOG OF TEST TRENCH NUMBER T-1 Date Excavated: 2/15/01 Logged by: DRR Equipment: Backhoe Project Manager: CHC Existing Elevation: 313 feet Depth to Warer: l/A Proposed E levation: 328 feet Bucket Size: 24 inches (.J g ,.., ...., ,.... :r:: ~ E-< p. ii: ~ Cl 2 (.J .... I . . .. .... •·· ., . .. 2 .... -.. .. .... •· -.. .,. .. -3 ... ... .. ·• ... . .. , .. -4 . ,·· ... •··· ... .. •···,.•· -5 ... .. ... .. ..•· .•· -6 ... .. ... •···· .... •·· -7 ... __ ., .•· ... . .. .. .. 8 ... - -9 .,_ 10 SAMPIFS ..; :?: 'u' 'o' > c ~ ·c '-' -0 ~ ::::: .... ~ < 0 SUivfNURY OF SUBSURFACE CONDITIONS ~ ..... E: ~ ;::) .-l ;:) f--, p. co :I! ';;;-C/1 ~ z ~ c < ~ 0 ~ e ~ Topsoil: Dark brown, SIL TY S.-\ND (SJ\.1), moist, loose, fine-to medium- grained. Subsoil: Medium brown, CL'\ YEY SAND (SC), moist, loose to medium dense fine-to medium-Qrained . Terrace Deposits (Ot): Orangish-browo, CL:\ YEY SAND (SC), moist, dense, fine-to coarse-grained . CK 7-1 CK 6.4 Terminated at 8 feet. ·w PROPOSED 5-LOT RESIDENTIAL PROJECT West of Faraday Road, Carlsbad, California Q u ~ ~ t: z ;::) >-, p:,: Cl II I.I 115.5 ~ 0 (/) E-< r' ~ (/) 0~ co :5 S,\ m MD DS CHRISTIAN WHEELER BY: SCC DA IB: February 27, 2001 Engi ne e rin g OBNO.: 201.116 PU .TE NO.: 2 LOG OF TEST TRENCH NUMBER T-3 Dace Ei.cavared: 2/15/01 Logged by: DRR Equipment: Backhoe Project Manager: CHC Existing Elevation: 317 feet Depth to Water: /A Proposed Elevation: 314 feet Bucket Size: 24 inches SAMPLES c., 0 u ,...._ 0 P:.l z "" 'o' ...e, ~ $ .....l ~ > ~ g ·t:; ~ :r: ;d 'U gJ C II) ::.: ...... f--< ::i:: ~ 0 f--< t-< 0... SU~L\RY OF SUBSURFACE CONDITIONS >Il .....l ..::: ::i f--< ~ U) Ul 0... ,-l ::i ~ -0 ~ e: CQ ~ ....... $ 0 I=: (j ~ z 3 0 ilO ..:; ~ 0 >-< ~ :,_ e ~ ~ .....l 0 Topsoil: Dark brown, SIL1Y SAND (Si\1), moist, loose, fine-to medium- I !!rained. -.. .. ... Subsoil: Medium brown, CL-\ YEY SA D (SC), moist, loose to medium ... .... 2 .... •····· dense, fine-co medium-grained. . . ... •· -.. •· .. •· 3 ...... Terrace Deposits (Ot): Orangish-brown, CLAYEY SAND (SC), moist, -... .. •···· dense to very dense, fine-to coarse-grained with occasional 3 inch cobble. , . .. • .. CK -4 ~·· ... .. •,; ..... . . ..... •· -5 .. ...... .. •· -6 Santiago Formation (Tsa): Light brown to white, SIL 1Y SAND (S:VI), moist, dense to very dense, fine-to medium-grained. -7 CK 11.0 111.9 -8 .... 9 -10 Terminated at 10 feet. PROPOSED 5-LOT RESIDENTIAL PROJECT w West of Faraday Road, Carlsbad, California C HR ISTIAN WHEELER BY: sec D:\TE: February 27, 2001 E n ginee r ing JOBNO.: 201.116 PLATE NO.: 4 LOG OF TEST TRENCH NUMBER T-4 Date Excavated: 2/15/01 Logged by: DRR Equipment: Backhoe Project Manager: CHC Existing Elevation: 317 feet Depth to Water: N I A Proposed Elevation: 314 feet Bucket Size: 24 inches SAMPI.F.S l? c;:;--u g 0 !I.! z '<>' 'o' .E:, ~ +--< ~ > ~ ~ ·i: ....; ::c u .,, ~ ~ 0 {/) ~ ~ .... t""' 5:: C i--, r-' 11.. SU~Th1ARY OF SUBSURFACE CONDITIO s ~ ...:i ,i ;:) i--, ~ {/) w p., +--< :J SJ ti z 0~ 0 ~ ~ .a ....__ V, ~ z ~ 5 ::> QO l'.) Ji ~ ;e, ?-~ j 0 ~ Topsoil: Dark brown, SIL 'TY SAJ\.TD (SM), moist, loose, fine-ro medium- 1 grained. I-... .... • Subsoil: Medium brown, CL-\ YEY S,-\ND (SC), moist, loose to medium .. . . .. .. • dense, fine-to medium-grained . -2 .. • .. ... -... •· .. .. .. • Terrace Deposits (Ot): Orangish-brown, CLAYEY SAND/SIL 'TY SAND 3 .. • -..... ~···· (SC/S;\'I), moist, dense co very dense, occasional gravel and cobble . .... .. -4 .. •· ..... .... •· .... CK .. .. ,-5 .. .,.. ~ ... ~·' .. .. ... ,-6 ··••• 1111111 ... •······ .... 7 ... •······ -8 Terminated at 7 feet. -9 ._ 10 w PROPOSED 5-LOT RESIDENTIAL PROJECT West of Faraday Road, Carlsbad, California CHRISTIAN WHEELER BY: sec D:\TE: February 27, 20()1 En gineer i ng JOB NO.: 201.116 PL-\TE J\:O.: 5 LOG OF TEST TRENCH NUMBER T-5 (Continued) Date Excavated: 2/15/01 Logged by: ORR Equipment: Backhoe Project Manager: CHC Existing Elevation: 290 feet Depth to Water: N/A Proposed Elevation: 306 feet Bucket Size: 24 inches SAMPLES l'.) = g ,-_ tI.l z ~ ~ ~ >-..., > ....l t: 0 ·c e..., ~ p,: -u ::: -0 ~ 0 E 5: ~ ~ '; r<~ SUNIMARY OF SUBSURFACE CONDITIONS !Il ....l ~ :J t: ~ (/) tI.l Po. --l :J t.... t; 0~ a ~ Cl., i:Q ~ ....... z ~ z ~ c :J i:Q l'.) ~ :I: 0 ~ j './: Q.. e ::E 0 .. .. Santiago Formation (Tsa): Light brown to light orangish~brown, .~ .. ·•· .... CLAYEY SAND (SC), moist, very dense . .. ..... 11 . , .. ~···· ... ' .. ... -~ -12 ... .. ·•' .. .... r:.'' .. . . •· ... 13 .. •· ... .... • .. _ .. ,.• -14 .... •· .. .. .. •· .. ..... ~···· CK 15.5 113.2 .,__ 15 .,__ 16 Terminated at 15 feet . -17 -18 ,-19 .. 20 PROPOSED 5-LOT RESIDENTIAL PROJECT ·w West of Faraday Road, Carlsbad, California CHRISTIAN WHEELER BY: sec DATE: February 27, 2001 E n g i neer in g TOB NO.: 201.116 PL'\TENO.: 7 LOG OF TEST TRENCH NUMBER T-8 Date Excavated: 2/15/01 Logged by: DRR Equipment: Backhoe Project Manager: CHC Existing Elevation: 314 feet Depth to Water: N/A Proposed Elevation: 315 feet Bucket Size: 24 inches SA.~IPLES C) c:::-u g '"' w z <i' ,-... --9, >-....., .. ~ ...... ~ C :g ~ ~ i:.:: l: u ~ ~ 'o ~ e u: f--, :2 < ~~ ::i., SUM},L\RY OF SUBSURFACE CONDITIONS Jl.l ...... e: ,±: ~ t: w ~ i--l :::i /:l.. C!'.l : .... ...... z C E--Q ~ -"' C) ?-z 3 0 :::i ~ < i 0 >-j u:: e ?-i:.:: Q Topsoil: Dark brown, SIL TY S,u'\lD (Sl'vl), moist, loose, fine-to medium- I-1 l?[ained. .. .. •· Subsoil: Medium brown, CLAYEY SAND (SC), moist, loose to medium ... .. -2 , ..... •·· dense, fine-to medium-grained. .. . •· .... .... • .. ...... Terrace Deposits (Ot): Orangish-brown, CLAYEY SAND (SC), moist, 3 ... .... . . .. .... ·• dense to very dense, fine-to coarse-grained, occasional 2½ inch gravel. CKlilllllll •' .. .. , 6.0 113.0 ..... 4 ... ..•· .. : .. ·• .. .. .. .. -5 .. ..... .. .. •· .. •· 111111111 .. 6 ... • -.... .. CK .... . . 7 ...... •~· - I-8 Terminated at 7 feet. -9 -10 PROPOSED 5-LOT RESIDENTIAL PROJECT w West of Faraday Road, Carlsbad, California CHRISTIAN WHEELER BY: sec DATE: February 27, 2001 Engineering TOB NO.: 201.116 PLATE NO.: 11 - ... ... - - t- ... .... - - - LOG OF TEST TRENCH NUMBER T-9 Date Excavaced: 2/15/01 Logged by: DRR Eguipment: Backhoe Project Manager: CI-IC Existing Elevation: 314 feet Depth co Water: N/,-\ Proposed Elevation: --Bucket Size: 24 inches g Cl 0 .....l ::r: ~ !--< P-, ::i:: ttl P-, Q ;:z (.'.) .. . •· .. ... .. •··· .. 1 .. .... •·· ... •· ... 2 .. •··· . . .. .. .... ·' .. 3 ~-···· , . .. .. •· .. ... 4 .... •· .. .. .. • ... ... ~·· 5 ... .... ,• ... ., . 6 .... •·· . .. •······ .. .. .. 7 .. •· ..•· .... ·•• 8 .... •···· ..... •··· .... ·•• 9 .. • ... .... •·· 10 ... •····· SAMPLES Cil z <I'" ;€' > ~ C :.g ~ ~ ._ ~ < C SUMMARY OF SUBSURFACE CONDITIONS Cil .....l ;:::: J:: ;:) ...., ;:) !;; ~ ;!:I ;., ----6 ; a < 0 3:: e ::2 (/J Subsoil: Medium brown, CL-\ YEY SA..i"JD (SC), moist, loose to medium dense, fine-to medium-grained . Terrace Deposits (Ot): Orangish-brown, CL-\. YEY SAND (SC), moist, very dense, fine-to coarse-grained, abundant gravel and cobble . CK 5.7 Santiago Fonnation (Tsa): Light olive brown, CL:\ YEY SAND (SC), • moist, dense to very dense, fine-to medium-grained . CK 15.8 11111111 CK CKIIIIIIIII Terminated at 10 feet. w PROPOSED 5-LOT RESIDENTIAL PROJECT West of Faraday Road, Carlsbad, California C u __e:, ~ t: z ::, >-~ Q 122.8 111.0 ~ ,..., V V) !--< !--< ~ (/J i:<l O!--< ;!l :s CHRISTIAN WHEELER BY: SCC DATE: February 27, 2001 En ginee ring OBNO.: 20l.116 PLATE NO.: 12 LABORATORY TEST RESULTS PROPOSED FIVE-I.OT RESIDENTIAJ, PROJECT \X'EST OF FAR.ADAY ROAD PO\'{' A Y CA.LIFOR:\lIA MAXIMUM DENSITY/ OPTIMUM MOISTURE CONTENT Sample :\lumber Description Maxunum Density Optimum Moisture Content DIRECT SHEAR TEST Sample Number Description Angle of Internal Faction Apparent Cohesion GRAIN SIZE DISTRIBUTION Sample Nwnber T-1@ 2'-8' Sieve Size Percent Passmg #4 100 #8 93 #15 78 #30 59 #50 37 #100 22 #200 19 0.05 mm 18 0.005 mm 11 0.001 mm 8 Classification SC EXPANSION INDEX TESTS Sample Number: Initial Moisture: Initial Dn· Density: Final :\fo1sture: Expansion Index: CW'E 201.116.1 Trench T-1 @ 2'-8' Orangish-bto\lm, clayey sand (SC) 127.1 pcf 8.5 percent Trench T-1@ 2'-8' Rcmolded To 90 Percent 33 degrees 100 psf T-2 @4'-6' Percent Passing T reneh T-8 @ 2' -8' 8.0 percrcnt 108.3 pcf 17.7 percent 6 (very low) l\farch 14, 2001 100 99 98 97 87 70 60 ,, _, 18 CL Trench T-6@ 3'-12' Brown, sandy clay (CL) 106.0 pcf 18.S pcf Trench T-6 @ 3'-12' Remolded to 90 Percent 21 degrees 300 psf T-6@ 3'-12' Percent Passing 100 699 98 96 84 69 55 21 ' ' CL Trench T-6@3'-12' 13.7 percent 101.4 pcf 29.5 percent 85 (medium) Plate No. 13 Appendix B References CWE 2180124.02 August 7, 2018 Appendix B•l REFERENCES Bryant, W. A. (compiler), 2005, Digital Database of Quaternary and Younger Faults from the Fault Activity Map of California, version 2.0: California Geological Survey Web Page, http://www.consrv.ca. gov/ CGS/information/ publications/ Quaternary Faults_ ver 2.htm Christian Wheeler Engineering, Updated Geotechnical Investigation Report, Kirgis Subdivision, Carlsbad Tract 02-06", dated October 10, 2013, Report CWE 2110148.0lR Historic Aerials, NETR Online, historicaerials.com Jennings, C.W. and Bryant, W. A., 2010, Fault Activity Map, California Geological Survey, Geologic Data Map No. 6, http:/ /www.quake.ca.gov/gmaps/F AM/faultactivitymap.html Kennedy, Michael P. and Tan, Siang S., 2007, Geologic Map of the Oceanside 30'x60' Quadrangle, California, California Geologic Survey, Map No. 2. Tan, S.S., 1995, Landslide Hazards in the Northern Part of the San Diego Metropolitan Area, San Diego County, California, California Division of Mines and Geology Open-File Report 95-04. U.S. Geological Survey, U.S. Seismic Design Maps Web Application, http://geohazards.usgs.gov/ designmaps/ us/ application. ph p U.S. Geological Survey, Quaternary Faults in Google Earth, http://earthquake.usgs.gov/hazards/ qfaults/ google.php • Appendix C Recommended Grading Specifications -General Provisions CWE 2180124.02 August 7, 2018 Appendix C, Page C-1 RECOMMENDED GRADING SPECIFICATIONS -GENERAL PROVISIONS GENERAL INTENT CARLSBAD TRACT CT-15-07 TWAIN A VENUE CARLSBAD, CALIFORNIA The intent of these specifications is to establish procedures for clearing, compacting natural ground, preparing areas to be filled, and placing and compacting fill soils to the lines and grades shown on the accepted plans. The recommendations contained in the preliminary geotechnical investigation report and/or the attached Special Provisions are a part of the Recommended Grading Specifications and shall supersede the provisions contained hereinafter in the case of conflict. These specifications shall only be used in conjunction with the geotechnical report for which they are a part. No deviation from these specifications will be allowed, except where specified in the geotechnical report or in other written communication signed by the Geotechnical Engineer. OBSERVATION AND TESTING Christian Wheeler Engineering shall be retained as the Geotechnical Engineer to observe and test the earthwork in accordance with these specifications. It will be necessary that the Geotechnical Engineer or his representative provide adequate observation so that he may provide his opinion as to whether or not the work was accomplished as specified. It shall be the responsibility of the contractor to assist the Geotechnical Engineer and to keep him appraised of work schedules, changes and new information and data so that he may provide these opinions. In the event that any unusual conditions not covered by the special provisions or preliminary geotechnical report are encountered during the grading operations, the Geotechnical Engineer shall be contacted for further recommendations. If, in the opinion of the Geotechnical Engineer, substandard conditions are encountered, such as questionable or unsuitable soil, unacceptable moisture content, inadequate compaction, adverse weather, etc., construction should be stopped until the conditions are remedied or corrected or he shall recommend rejection of this work. • • CWE 2180124.02 August 7, 2018 Appendix C, Page C-2 Tests used to determine the degree of compaction should be performed in accordance with the following American Society for Testing and Materials test methods: Maximum Density & Optimum Moisture Content -ASTM D1557 Density of Soil In-Place -ASTM D1556 or ASTM D6938 All densities shall be expressed in terms of Relative Compaction as determined by the foregoing ASTM testing procedures. PREPARATION OF AREAS TO RECEIVE FILL All vegetation, brush and debris derived from clearing operations shall be removed, and legally disposed of. All areas disturbed by site grading should be left in a neat and finished appearance, free from unsightly debris. After clearing or benching the natural ground, the areas to be filled shall be scarified to a depth of 6 inches, brought to the proper moisture content, compacted and tested for the specified minimum degree of compaction. All loose soils in excess of 6 inches thick should be removed to firm natural ground which is defined as natural soil which possesses an in-situ density of at least 90 percent of its maximum dry density. When the slope of the natural ground receiving fill exceeds 20 percent (5 horizontal units to 1 vertical unit), the original ground shall be stepped or benched. Benches shall be cut to a firm competent formational soil. The lower bench shall be at least 10 feet wide or 1-1/2 times the equipment width, whichever is greater, and shall be sloped back into the hillside at a gradient of not less than two (2) percent. All other benches should be at least 6 feet wide. The horizontal portion of each bench shall be compacted prior to receiving fill as specified herein for compacted natural ground. Ground slopes flatter than 20 percent shall be benched when considered necessary by the Geotechnical Engineer. Any abandoned buried structures encountered during grading operations must be totally removed. All underground utilities to be abandoned beneath any proposed structure should be removed from within 10 feet of the structure and properly capped off. The resulting depressions from the above CWE 2180124.02 August 7, 2018 Appendix C, Page C-3 described procedure should be backfilled with acceptable soil that is compacted to the requirements of the Geotechnical Engineer. This includes, but is not limited to, septic tanks, fuel tanks, sewer lines or leach lines, storm drains and water lines. Any buried structures or utilities not to be abandoned should be brought to the attention of the Geotechnical Engineer so that he may determine if any special recommendation will be necessary. All water wells which will be abandoned should be backfilled and capped in accordance to the requirements set forth by the Geotechnical Engineer. The top of the cap should be at least 4 feet below finish grade or J feet below the bottom of footing whichever is greater. The type of cap will depend on the diameter of the well and should be determined by the Geotechnical Engineer and/ or a qualified Structural Engineer. FILL MATERIAL Materials to be placed in the fill shall be approved by the Geotechnical Engineer and shall be free of vegetable matter and other deleterious substances. Granular soil shall contain sufficient fine material to fill the voids. The definition and disposition of oversized rocks and expansive or detrimental soils are covered in the geotechnical report or Special Provisions. Expansive soils, soils of poor gradation, or soils with low strength characteristics may be thoroughly mixed with other soils to provide satisfactory fill material, but only with the explicit consent of the Geotechnical Engineer. Any import material shall be approved by the Geotechnical Engineer before being brought to the site. PLACING AND COMPACTION OF FILL Approved fill material shall be placed in areas prepared to receive fill in layers not to exceed 6 inches in compacted thickness. Each layer shall have a uniform moisture content in the range that will allow the compaction effort to be efficiently applied to achieve the specified degree of compaction. Each layer shall be uniformly compacted to the specified minimum degree of compaction with equipment of adequate size to economically compact the layer. Compaction equipment should either be specifically designed for soil compaction or of proven reliability. The minimum degree of compaction to be achieved is specified in either the Special Provisions or the recommendations contained in the preliminary geotechnical investigation report. • • CWE 2180124.02 August 7, 2018 Appendix C, Page C-4 When the structural fill material includes rocks, no rocks will be allowed to nest and all voids must be carefully filled with soil such that the minimum degree of compaction recommended in the Special Provisions is achieved. The maximum size and spacing of rock permitted in structural fills and in non- structural fills is discussed in the geotechnical report, when applicable. Field observation and compaction tests to estimate the degree of compaction of the fill will be taken by the Geotechnical Engineer or his representative. The location and frequency of the tests shall be at the Geotechnical Engineer's discretion. When the compaction test indicates that a particular layer is at less than the required degree of compaction, the layer shall be reworked to the satisfaction of the Geotechnical Engineer and until the desired relative compaction has been obtained. Fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment. Compaction by sheepsfoot roller shall be at vertical intervals of not greater than four feet. In addition, fill slopes at a ratio of two horizontal to one vertical or flatter, should be trackrolled. Steeper fill slopes shall be over-built and cut-back to finish contours after the slope has been constructed. Slope compaction operations shall result in all fill material six or more inches inward from the finished face of the slope having a relative compaction of at least 90 percent of maximum dry density or the degree of compaction specified in the Special Provisions section of this specification. The compaction operation on the slopes shall be continued until the Geotechnical Engineer is of the opinion that the slopes will be surficially stable. Density tests in the slopes will be made by the Geotechnical Engineer during construction of the slopes to determine if the required compaction is being achieved. Where failing tests occur or other field problems arise, the Contractor will be notified that day of such conditions by written communication from the Geotechnical Engineer or his representative in the form of a daily field report. If the method of achieving the required slope compaction selected by the Contractor fails to produce the necessary results, the Contractor shall rework or rebuild such slopes until the required degree of compaction is obtained, at no cost to the Owner or Geotechnical Engineer. CWE 2180124.02 August 7, 2018 Appendix C, Page C-5 CUT SLOPES The Engineering Geologist shall inspect cut slopes excavated in rock or lithified formational material during the grading operations at intervals determined at his discretion. If any conditions not anticipated in the preliminary report such as perched water, seepage, lenticular or confined strata of a potentially adverse nature, unfavorably inclined bedding, joints or fault planes are encountered during grading, these conditions shall be analyzed by the Engineering Geologist and Geotechnical Engineer to determine if mitigating measures are necessary. Unless otherwise specified in the geotechnical report, no cut slopes shall be excavated higher or steeper than that allowed by the ordinances of the controlling governmental agency. ENGINEERING OBSERVATION Field observation by the Geotechnical Engineer or his representative shall be made during the filling and compaction operations so that he can express his opinion regarding the conformance of the grading with acceptable standards of practice. Neither the presence of the Geotechnical Engineer or his representative or the observation and testing shall release the Grading Contractor from his duty to compact all fill material to the specified degree of compaction. SEASON LIMITS Fill shall not be placed during unfavorable weather conditions. When work is interrupted by heavy rain, filling operations shall not be resumed until the proper moisture content and density of the fill materials can be achieved. Damaged site conditions resulting from weather or acts of God shall be repaired before acceptance of work. RECOMMENDED GRADING SPECIFICATIONS -SPECIAL PROVISIONS RELATIVE COMPACTION: The minimum degree of compaction to be obtained in compacted natural ground, compacted fill, and compacted backfill shall be at least 90 percent. For street and • • • • CWE 2180124.02 August 7, 2018 Appendix C, Page C.6 parking lot subgrade, the upper six inches should be compacted to at least 95 percent relative compaction. EXPANSIVE SOILS: Detrimentally expansive soil is defined as clayey soil which has an expansion index of 50 or greater when tested in accordance with the Uniform Building Code Standard 29-2. OVERSIZED MATERIAL: Oversized fill material is generally defined herein as rocks or lumps of soil over 6 inches in diameter. Oversized materials should not be placed in fill unless recommendations of placement of such material are provided by the Geotechnical Engineer. At least 40 percent of the fill soils shall pass through a No. 4 U.S. Standard Sieve. TRANSITION LOTS: Where transitions between cut and fill occur within the proposed building pad, the cut portion should be undercut a minimum of one foot below the base of the proposed footings and recompacted as structural backfill. In certain cases that would be addressed in the geotechnical report, special footing reinforcement or a combination of special footing reinforcement and undercutting may be required.