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HomeMy WebLinkAbout6.7-366 Soils ReportSOILS ENGINEERING, INC. 4400 YEAGER WAY • BAKERSFIELD, CALIFORNIA 93313 • PHONE (661) 831-5100 • FAX: (661) 831-2111 GEOTECHNICAL INVESTIGATION FOR TRACTS 7141 MORNINGSTAR RANCH DEVELOPMENT MORNINGSTAR AVENUE BAKERSFIELD, KERN COUNTY, CA Prepared for: LGI Homes - California, LLC 495 E. Rincon Street, Suite 101 Corona, CA 92879 By: SOILS ENGINEERING, INC. SEI File 21-18239 February 10, 2022 ____________________________________ Tony M. Frangie P.E. Vice President ____________________________________ L. Thomas Bayne, G.E. President COPYRIGHT: All reports issued by the consultant are protected under copyright. Notwithstanding the fact that the Copyright in this document, and each portion contained herein, is the sole property of Soils Engineering, Inc., and without waiving or in any way transferring said Copyright, Soils Engineering, Inc. hereby grants LGI Homes - California, LLC the nonexclusive right to copy, reproduce, and distribute this report for his/her own non-commercial, in-house use. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 2 ©2022 SOILS ENGINEERING, INC. TABLE OF CONTENTS INTRODUCTION ...................................................................................................................................... 3 SITE INFORMATION A. SITE LOCATION AND CONDITIONS ......................................................................................... 4 B. GEOLOGIC SETTING ................................................................................................................ 4 C. SUBSURFACE CONDITIONS .................................................................................................... 4 D. GROUNDWATER ....................................................................................................................... 5 F. SEISMIC DESIGN VALUES ........................................................................................................ 5 EARTHWORK RECOMMENDATIONS A. COMPACTION AND OPTIMUM MOISTURE .............................................................................. 7 B. CLEARING AND GRUBBING ..................................................................................................... 7 C. GROUND SURFACE PREPARATION ........................................................................................ 8 D. ENGINEERED FILL ................................................................................................................... 10 E. IMPORTED FILL ....................................................................................................................... 10 F. DRAINAGE ................................................................................................................................ 10 G. SLOPES .................................................................................................................................... 11 FOUNDATION RECOMMENDATIONS ................................................................................................. 11 MODULUS OF SUBGRADE REACTION .............................................................................................. 12 LATERAL EARTH PRESSURES ........................................................................................................... 12 SLABS-ON-GROUND ............................................................................................................................ 13 SOIL CORROSIVITY .............................................................................................................................. 14 PAVEMENT FIELD INVESTIGATION & DESIGN DATA ...................................................................... 14 LIMITATIONS, OBSERVATIONS AND TESTING ................................................................................. 15 REVIEW OF EARTHWORK OPERATIONS .......................................................................................... 15 APPENDIX A, "GUIDE SPECIFICATIONS FOR EARTHWORK .......................................................... 17 APPENDIX B, "FIELD INVESTIGATION" ............................................................................................. 22 APPENDIX C, "SOILS TEST DATA" ..................................................................................................... 23 APPENDIX D, "SEISMIC DESIGN DATA" ............................................................................................ 24 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 3 ©2022 SOILS ENGINEERING, INC. GEOTECHNICAL INVESTIGATION FOR TRACTS 7141 MORNINGSTAR RANCH DEVELOPMENT MORNINGSTAR AVENUE BAKERSFIELD, KERN COUNTY, CA SOILS ENGINEERING, INC. File 21-18239 February 10, 2022 INTRODUCTION At your request, Soils Engineering, Inc. has prepared this Geotechnical Investigation for the subject site. This report includes recommendations for the site preparation and grading and for foundation design. Appendix A, "Guide Specifications for Earthwork,” is provide as supplement to Section I, “Earthwork,” in the recommendations of the report. Appendix B, “Field Investigation,” contains a boring location map, Figure 1, and Logs of Test Borings, Figures 2 through 7. Appendix C, “Soils Test Data,” contains tabulations of laboratory test data. Appendix D, “Seismic Investigation,” contains information provided by EQFAULT, and the USGS. We hope this provides the information you require. If you have any questions regarding the contents of our report, or if we can be of further assistance, please contact us. Respectfully submitted, SOILS ENGINEERING, INC. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 4 ©2022 SOILS ENGINEERING, INC. SITE INFORMATION A. SITE LOCATION AND CONDITIONS The proposed site consists of Phases 2 and 3 of Vesting Tentative Tract 7141. The project is bound on the north by Phase 1 of Vesting Tentative Tract 7141 and Morning Star Drive; on the west by Morning Drive; on the east by Tract 6383; and on the south by undeveloped, relatively flat, vacant land. Phase 2 and Phase 3 of Tract 7141 are located within APN: 531-011-30, which is also connected to Tract 6383. Currently, the project site is a flat, vacant lot covered with a sparse growth of low-lying annual weeds and grasses. Residential properties border the site to the north, residential properties and graded lots border the site to the east, and vacant lots form the southern and eastern border. The single-family dwellings are anticipated to be constructed of a combination of concrete, wood, masonry and/or metal framing and it assumed that the roads will be comprised of hot-mix asphalt over aggregate base. A more detailed description of the project is shown in Figure 1 in Appendix B, Boring Location Map. B. GEOLOGIC SETTING According to the 2010 Geologic Map of California the zone of influence for the proposed construction is located wholly within Pleistocene-Holocene marine and nonmarine (continental) sedimentary rock deposits (Q) within the southern San Joaquin Valley. Although the site is not located in an Alquist-Priolo (earthquake fault) Special Study Zone, there are various earthquake faults in the vicinity. Nearby faults, with distances from the site, are tabulated below. Kern Front .................................................... 7.6 miles/ 12.3 kilometers White Wolf .................................................... 16.1 miles/ 25.9 Kilometers Pleito Thrust ................................................. 28.2 miles/ 45.4 Kilometers Garlock (West) .............................................. 35.1 miles/ 56.5 Kilometers San Andreas – Whole M-1a, 1857 Rupture, Carrizo M-1c-2, Cho-Moj M-1b-1 39.8 miles/ 64.0 kilometers Big Pine ........................................................ 40.3 miles/ 64.9 Kilometers San Gabriel .................................................. 47.4 miles/ 76.3 Kilometers The largest estimated maximum site acceleration, based on deterministic methods, is 0.261g from a 7.3 magnitude earthquake on the White Wolf approximately 25.9 kilometers away. The information above is from the program EQFault (vers.3.0) and a complete listing of faults within 100-miles is presented in Appendix D. C. SUBSURFACE CONDITIONS Surface soils encountered in our field investigation consisted predominately of a light reddish brown, dry, to reddish-brown, Clay, Silty Clay, and Sandy Clay, with low to medium plasticity and containing traces of fine gravel, sand, and silt; These soils are classified as CL in the Unified Soil Classification System (USCS). Testing performed in our laboratory showed Expansion Indexes (EI) between 10 and 65, indicative of a low to medium potential for expansion. Expansive soils are defined in the 2019 California Building Code (CBC), Section 1803A.5.3. Soils are expansive when the EI result is greater than 20, per ASTM D4829, 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 5 ©2022 SOILS ENGINEERING, INC. Expansion Index of Soils. Design of foundations for structures shall be designed in accordance with the 2019 CBC, Sections 1808A.6.1, & 1808A.6.2. Most of the the near surface soils should provide adequate support for the proposed structures if soils having expansion indices exceeding 20 are removed and replaced with non-expansive soils; and loose, compressible materials are compacted as outlined in the earthwork recommendations of this report. Detailed descriptions of the various soils encountered during our field investigation are shown on Figures 2 to 7 in Appendix B, “Field Investigation.” A “Key to Symbols” legend describing the symbols in the boring logs is also attached. D. GROUNDWATER Groundwater was not encountered in any of the test borings of the field investigation. According to maps prepared by the State of California, SGMA Data Viewer indicates the depth to water of 174’ in the Spring of 2019 and 215’ in the Spring of 2021 near the site. Accordingly, groundwater should have no effect on site preparation, grading, or foundation design. E. SEISMIC DESIGN VALUES Per the 2019 California Building Code (CBC) and American Society of Civil Engineers (ASCE) 7-16 Section 20.3, and local knowledge the site is classified as Site Class D. Utilizing the USGS and ASCE 7-16 seismic design methodologies the following seismic design values were determined. SEISMIC DESIGN CRITERIA VALUE SOURCE Risk Category II 2019 CBC Table 1604.5 or 1604A.5 Site Class D 2019 CBC §1613.2.2 or 1613A.2.2; ASCE 7-16 Table. 20.3-1; Site Specific Soils Report, and local knowledge. Mapped MCER Spectral Response Acceleration, short period SS 0.922g SEAOC-OSHPD software. 2019 CBC Figure 1613.2.1(1) Mapped MCER Spectral Response Acceleration, at 1-sec. Period S1 0.33g SEAOC-OSHPD software. 2019 CBC Figure 1613.2.1(2) Site Coefficient Fa 1.131 SEAOC- OSHPD software. 2019 CBC Table 1613.2.3(1) or 1613A.2.3(1) Site Coefficient Fv* 1.97* 2019 CBC Table 1613.2.3(2) or 1613A.2.3(2) Adjusted MCER Spectral Response Acceleration, short period, Fa * Ss SMS 1.043g SEAOC- OSHPD software. 2019 CBC §1613.2.3 or 1613A.2.3 Adjusted MCER Spectral Response Acceleration, 1-sec. period, Fv * S1 SM1* 0.650g* 2019 CBC §1613.2.3 or 1613A.2.3 Design Spectral Response Acceleration, short period, 2/3 * SMS SDS 0.695g SEAOC- OSHPD software. 2019 CBC §1613.2.4 or 1613A.2.4 Design Spectral Response Acceleration, 1-sec. period, 2/3 * SMI SD1* 0.433g* 2019 CBC §1613.2.4 or 1613A.2.4 Peak Ground Acceleration for Max. Considered Earthquake (MCEG)PGA 0.398g SEAOC- OSHPD software. ASCE 7-16 Fig 22-9 Site Coefficient, FPGA = 1.202 - 118.910109, FPGA* PGA PGAM 0.479g SEAOC- OSHPD software. ASCE 7-16 §11.8.3.2 Mapped Risk Coefficient at 0.2 second Spectral Response Period CRS 0.925 SEAOC- OSHPD software. ASCE 7-16 Figure 22-18A 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 6 ©2022 SOILS ENGINEERING, INC. SEISMIC DESIGN CRITERIA VALUE SOURCE Mapped Risk Coefficient at 1 second Spectral Response Period CR1 0.922 SEAOC- OSHPD software. ASCE 7-16 Figure 22-19A Seismic Design Category, short period D 2019 CBC §1613.2.5 Seismic Design Category, 1second period * D* 2019 CBC §1613.2.5 MCER = Maximum Considered Earthquake (risk targeted) MCEG = Maximum Considered Earthquake (geometric mean) * The project designer shall confirm that a ground motion hazard analysis is not required in accordance with ASCE 7-16 §11.4.8-Exception 2. The values tabulated above for SM1, SD1, and the Seismic Design Category/1-second period are based on the site coefficient, Fv, interpolated from 2019 CBC Table 1613.2.3(2) or 1613A.2.3(2). The use of that table is predicated on the above referenced Exception 2 being applicable for the site and the structure(s). Where the above referenced Exception 2 does not apply, the values for Fv, SM1, SD1, and for the Seismic Design Category/1-second period may not be applicable for the site and structure(s). EARTHWORK RECOMMENDATIONS A. COMPACTION AND OPTIMUM MOISTURE Unless otherwise specified herein, the terms "compaction" or "compacted", wherever used or implied in this report, should be interpreted as compaction to ninety percent (90%), or greater, of the laboratory maximum density (as determined in accordance with ASTM Test Method D1557). The term, “Optimum Moisture,” wherever use or implied within this report, should be interpreted as that obtained by the above- described test method. B. CLEARING AND GRUBBING Clearing and grubbing shall consist of removing all debris such as metal, broken concrete, trash, vegetation growth and other biodegradable substances, from all areas to be graded. Existing obstructions below shall be removed in accordance with the following procedures: Buried Utilities - such as sewer, water and gas lines or electrical conduits to remain in service shall be re-routed to pass no closer than four (4.0) feet to the outside edge of proposed exterior footings of structures. Lines to be abandoned shall be completely removed to a minimum depth of two (2.0) feet below finished building pad grade. Concrete lines deeper than two (2.0) feet below finished building pad grade and having diameters less than six (6.0) inches can be crushed in placed. Root Systems - shall be completely removed to a depth of four (4.0) feet below the existing grade, to a minimum depth of two (2.0) feet below the bottom of the lowest proposed structure footing, or to two (2.0) feet below finished subgrade, whichever depth is least. Root systems deeper than the elevation indicated above shall be excavated to allow no roots larger than two (2.0) inches in diameter. Cavities - resulting from clearing and grubbing or cavities existing on the site because of man-made or natural activity shall be backfilled with earth materials placed and compacted in accordance with Sections 5.3 and 5.4 of appendix A. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 7 ©2022 SOILS ENGINEERING, INC. Stripping - Prior to site grading, existing ground surfaces should be stripped of existing surface vegetation, and high-volume root masses. A stripping depth of one to three inches is generally adequate. Stripped organic material shall not be used as engineered fill or blended with or incorporated into any materials which will underlie any structures or other improvements on the project. Removal of trees or other large plants shall include all roots larger than ¾” diameter. If necessary, root remnants are to be removed by hand-picking. Remove existing structures and improvements, including within the limits of grading or as depicted in the project documents. C. GROUND SURFACE PREPARATION Prior to commencement of construction within this tract, surficial compaction of the previously completed earthwork should be tested at each lot and at various locations for the streets, sidewalks, and utilities. The compaction tests shall be done at 0' to 1’ and 1’ to 2’ from finished grade at each lot. Upon completion of the compaction testing program, further surface preparation recommendations may be issued if needed. If additional compaction is needed, the soils shall be moisture conditioned and compacted to a minimum of 90% and a maximum of 93% of the laboratory maximum density as determined in accordance with ASTM D1557. At the time of soil compaction, the soil moisture shall be not less than 2% over the optimum moisture, as determined in accordance with ASTM D1557. The elevated soil moisture should be maintained until placement of slabs/site concrete. Proposed Structure Areas: Existing soils encountered during our investigation are considered expansive in accordance with the 2016 CBC §1803.5.3. The expansive soils may be replaced by non-expansive soils, or the foundation/slab systems may be designed to accommodate the expected differential soil movement. If the expansive soils are to be removed and replaced, the depth of soil replacement will be dependent on the expansion potential and the depth of the existing expansive soils at each lot. Replacement soils should conform to recommendations elsewhere in this report and should have low permeability when compacted. Replacement soils should be moisture conditioned, placed, spread, and compacted as recommended in Appendix "A" of this report. Fill placement in excavations shall not proceed until the geotechnical engineer or his representative on the site has reviewed, tested as described above and accepted materials exposed at the bottom of the excavation. After the excavation has been reviewed and it has been determined that no additional excavation is required, place and compact the excavated soils, or approved import material, in thin lifts. Adjust the moisture content of the material to be compacted as needed prior to compaction. Apply compaction effort in conformance with the recommendations of this report, using means, methods, and equipment suitable for the type of material being compacted. Refer to paragraph “A” above and the attached Appendix A for compaction requirements. Foundation/slab systems designed to accommodate the anticipated movement of the expansive soils should be designed in accordance with the WRI/CRSI Design of Slab-on-Ground Foundations, or the PTI DC 10.5, or other acceptable method, in accordance with the 2019 CBC, §1808.6.1 and §1808.6.2. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 8 ©2022 SOILS ENGINEERING, INC. Construction with post-tensioned or other specially reinforced foundation/slab systems on expansive soils does not eliminate differential soil and structure movement. It should be the intent of the design of the foundation/slab systems to provide sufficient rigidity such that damage to, and/or undue distortion of, structural elements and architectural finishes and elements is prevented. It is our opinion that pre- construction moistening of the upper three to four feet of soils and incorporating a perimeter moisture barrier a minimum of two and half feet below the adjacent subgrade, should reduce post-construction soil volume changes due to moisture fluctuations beneath the slab. It is recommended that sampling and testing, to confirm the moisture penetration, be performed. Soil volume changes can also be expected to cause differential movement of other site improvements such as sidewalks, patios, and driveways. Test borings, soil sampling, and expansion index (EI) tests indicate that wide variations in soil expansion potential from and EI=10 to EI=65 can occur in relatively small distances. Samples taken on a lot-by-lot basis were used to recommend foundation design and / or subsoil mitigation measures. Owing to variations which may occur as described above, we strongly recommend that foundation excavations, trenching, and slab-grading be reviewed on lot-by-lot basis during construction at which time changes in foundation recommendations or subsoil mitigation measures may be required. These recommendations may be modified in response to field observations by the GEOR and/or because of the additional testing described previously. Pavement: Ground surfaces to receive concrete driveways or bituminous pavements should be scarified and compacted to a minimum depth of 12 inches below the grading plane in cut areas or to 12 inches in areas to receive fill. Engineered fill placed in proposed pavement areas should conform to the requirements of Section 5.4, "Placing, Spreading and Compacting Fill Materials," of Appendix A. Compaction in proposed pavement areas should be a minimum of 90 percent of the maximum density as obtained by ASTM Test Method D1557 and should extend to a minimum of two feet beyond the outside edges of pavements. The top eight (8) inches of subgrade below the grading plane shall be compacted to a minimum of 95%. Utility Lines: Backfill for utility lines traversing areas proposed for facilities, pavements, concrete slabs-on-grade, or areas to receive engineered fill for future construction should be compacted in accordance with the same requirements for adjacent and/or overlying fill materials. Where utility trenches extend under, adjacent to, or near the structure, including patio(s), porch(es), garage, etc., the soil in the entire depth of the trench, shall be compacted. Compaction shall extend at least five feet beyond the outside the edge of the structure. Low-permeability, non-expansive, soils shall be used for backfill. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 9 ©2022 SOILS ENGINEERING, INC. Compaction should include haunch area, spring line and from top of pipe to finished subgrade. The haunch area up to one foot above the top of the pipe should be backfilled with "cohesionless" material. Cohesionless native materials may be used for trench and pipe, or conduit backfill. The term "cohesionless," as used herein, is defined as material which when dry, will flow readily in the haunch areas of the pipe trench. Pipe backfill materials should not contain rocks larger than two inches in maximum dimension. Where adjacent native materials exposed on the trench bottoms contain protruding rock fragments larger than two inches in maximum dimension, conduits and pipelines should be laid on a bedding consisting of clean, cohesionless sand (SP), in the Unified Soils Classification System. Compaction Requirements - where not otherwise specified in the project documents, or in the manufacturer's specifications, or in these recommendations, the following compaction requirements are applicable to all electrical, gas or water conduits: TABLE A Compaction Depth Area Haunch to 1 ft. Above Top of Pipe 1 ft. Above Top of Pipe To 2’6” Below Finish Grade 2’6” Below Finished Grade to Finished Subgrade Structural 90% 90%90% Pavements 90% 90%90% Non-Structural 90% 90%90% D. ENGINEERED FILL Earth materials obtained on site are acceptable for use as engineered fill if vegetation and other deleterious debris are removed by proper stripping and separation. Engineered fill material which has been moisture-conditioned to near the optimum moisture content, or to a moisture content commensurate with effective compaction and soil stability, should be placed in thin uniform layers (less than ten inches uncompacted thickness) and compacted to a minimum of ninety percent (90%) of the laboratory maximum density determined in accordance with ASTM Test Method D1557. Refer to “Placing, Spreading and Compacting Fill Materials,” in Appendix A. E. IMPORTED FILL The table shown below provides general guidelines for acceptance of import engineered fill. Materials of equal or better quality than on-site material could be reviewed by the Geotechnical Engineer of Record (GEOR) on a case-by-case basis. No soil materials shall be imported onto the project site without prior approval by the GEOR. Any deviation from the specifications given below shall be approved by the GEOR prior to import operations. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 10 ©2022 SOILS ENGINEERING, INC. Maximum Percent Passing #200 Sieve .............................................................. 40 Maximum Percent Retained 3" Sieve .................................................................... 0 Maximum Percent Retained 1½" Sieve for Building Footing Zones .................... 15 Maximum Percent Retained ¾" Sieve for Landscape Areas ................................ 5 Maximum Percent Retained ½" Sieve for Play Fields ........................................... 0 Maximum Liquid Limit ......................................................................................... 40 Maximum Plasticity Index .................................................................................... 14 Minimum R-Value for Pavement Areas ............................................................... 50 Maximum Expansion Index (per 2019 CBC) ....................................................... 20 Furthermore, the soils proposed for import shall be generally homogenous and shall not contain cemented or clayey and/or silty lumps larger than one inch. When such lumps are present, they shall not represent more than ten percent (10%) of the material by dry weight. Where a proposed import source contains obviously variable soils, such as clay and/or silt layers, the soils which do not meet the above requirements shall be segregated and not used for this project or the various layers shall be thoroughly mixed prior to acceptance testing by the Geotechnical Engineer. The contractor shall provide sufficient advance notice, prior to import operations, to allow testing and evaluation of the proposed import materials. Because of the time needed to perform the above tests, the contractor shall provide a means by which the Geotechnical Engineer or others can verify that the soil(s) which was sampled and tested is the same soil(s) which is being imported to the project. F. DRAINAGE Finish grading and construction of all improvements should be completed in such a manner that there will be no opportunity for water to collect on and/or percolate into the soils adjacent to or near the house and/or appurtenant structures or improvements (including patios, porches, garages, driveways, and sidewalks). Finish ground surfaces adjacent to the proposed structures should be graded to provide positive, free, and unobstructed drainage away from the foundations for at least three feet (3.0'). The recommended drainage should be established prior to enclosing the structure. Drainage should continue by way of drain inlets and pipes or by surface grading to the street. No construction or finish grading should be established or maintained that would allow surface water, from on-site or off-site sources to pond or accumulate near foundations or slabs or behind curbs. In areas where such adverse drainage conditions may exist or be created, area drains and/or catch basins with subsurface piping should be installed to collect and convey water to the adjacent street gutter. Landscape irrigation should be stringently controlled. Do not apply irrigation water more than that needed by the landscape plantings. No water shall be applied to the ground adjacent to or near the structure or appurtenant structures or improvements (including patio(s), porch(es), garage, driveways, sidewalks, etc.). Where ground surfaces adjacent to subsurface walls are to be landscaped, walls should be waterproofed. Installation of gravel-filled drains to route subsurface drainage away from walls is recommended. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 11 ©2022 SOILS ENGINEERING, INC. G. SLOPES Both fill and cut slopes should be constructed at 2:1 (horizontal to vertical) in accordance with the 2019 California Building Code. Finished slopes nearer than five feet from building foundations should be graded no steeper than five horizontal to one vertical (5:1). A slope ratio of two horizontal to one vertical (2:1) should provide adequate stability for slopes farther than five feet from footing lines. The fill slopes shall be compacted to a minimum of 90% of ASTM D- 1557 and in accordance with the Guide specifications for Earthwork, Appendix A. This may be achieved by overfilling the constructed slope and trimming to a compacted finished surface, rolling the slope face with a sheepsfoot as the level of the fill is raised, or any method that achieves the desired product. The cut portion of the slope should be constructed first. Prior to construction of the fill slope, incompetent surface soils should be removed from the top of the cut. Areas to receive fill or to support structures, slabs or pavements should be removed of all vegetation, debris, and disturbed soils. All existing uncertified fill soils should be excavated to expose competent native soils. Existing underground pipelines, private sewage disposal systems and any water or oil wells, if encountered during grading, should be removed, or capped in accordance with procedures considered acceptable by the appropriate governing agency. Tree roots to 2 inches in diameter should be removed. Both fill and cut slopes will be subject to erosion immediately after grading and should be designed to reduce surficial sloughing by implementing a permanent slope maintenance program as soon as practical after completion of slope construction. Slope maintenance should include proper care of erosion and drainage control devices, rodent control, and immediate planting with deep-rooting, lightweight, drought-resistant vegetation. An erosion control geotextile may also be used in combination with vegetation to control erosion. Experience has shown that slope performance is largely dependent upon proper slope maintenance (i.e., planting, proper watering, clearing of drainage devices, etc.). Slopes properly placed and conscientiously maintained are not expected to display excessive raveling or sloughing. FOUNDATION RECOMMENDATIONS The proposed structures can be adequately supported on either continuous or isolated reinforced concrete spread footings designed in accordance with the criteria given below in Table B. TABLE B FOUNDATION DESIGN CRITERIA Footing Type Minimum Width (ft.) Minimum Depth Below Lowest Adjacent Subgrade (ft.) Maximum Allowable Soil Bearing Pressure (lbs. / sq. ft.) Continuous 1 1 2500 Isolated 1 1 2500 Bearing pressures given above are applicable to foundations having the minimum widths and depths and the maximum allowable bearing pressures shown above for dead and sustained-live-loads; they may be increase by one-third for wind and/or seismic loading conditions. The proposed foundations shall be reinforced in accordance with the structural engineer’s recommendations. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 12 ©2022 SOILS ENGINEERING, INC. Settlement: Provided maximum allowable soil bearing pressures given above are not exceeded, total settlement should not exceed one inch. A major portion, two-thirds to one-half, of total settlement should occur before the end of construction. Differential settlements should occur before the end of construction. Differential settlements should, accordingly, be less than one-half of an inch. MODULUS OF SUBGRADE REACTION Modulus of subgrade reaction for use in design of foundations is based on ranges of values for soil types provided by Foundation Analysis and Design by Joseph E Bowles.1 Equation 1 should be used for footings on sandy soils. Foundations on clay soils should employ Equation 2. Equation 3 is for rectangular footings having dimensions w= b (width) and l = mb (length) the variable “m” being the ratio of the length to the width of the foundation. Ks1 is the modulus of subgrade reaction from the source referenced above based on a 1-foot x 1-foot square plate. For general guidance Ks1 of 150 kcf may be used for the subsurface sandy soils. Equation (1) ௦௙ ൌ ௦ଵ ൈ ቀ஻ାଵ ଶ஻ ቁଶ Equation (2) ௦௙ ൌ ௦ଵ ൈ Equation (3) ௦௙ ൌ ௦ଵ ൈ ௠ା.ହ ଵ.ହൈ௠ Values given above should be used for guidance. Local values may be higher or lower and should be based on results of in-situ plate bearing tests performed in accordance with ASTM Test Method D1194. LATERAL EARTH PRESSURES Lateral earth pressures and friction coefficients for determining the passive lateral resistance of foundations against lateral movement and the active lateral forces against retaining walls and subsurface walls, expressed as equivalent fluid pressures, are given below in Table C. Lateral earth pressures were computed assuming that backfill materials are essentially free draining and level; and that no surcharge loads, or sloping backfills are present within a distance from the wall equal to or less than the height (H)* of the wall. (H)* = the height of backfill above the lowest adjacent ground surface. TABLE C LATERAL EARTH PRESSURE Case Lateral Earth Pressures Active 35 P.C.F Passive 400 P.C.F. At-Rest 55 P.C.F. 1 Bowles, Joseph E; FOUNDATION ANALYSIS AND  DESIGN; McGraw‐Hill Book Company (1977); Table 9‐1 pg. 269 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 13 ©2022 SOILS ENGINEERING, INC. Active Case: Active lateral earth pressures should be used when computing forces against free standing retaining walls, unrestrained at the tops. Active pressures should not be used where tilting outward of the walls is greater than .002H would not be desirable. Passive Case: Passive lateral earth pressures should be used when computing the lateral resistance provided by undisturbed or compacted native soils against the movement of footing. When computing passive resistance, the upper one foot of embedment depth should be discounted. At-Rest Case: At-rest pressures should be used for subsurface walls restrained at their tops by floor diaphragms or tie-backs and for retaining walls where tilting outward greater than .002 H would not be desirable. Frictional Resistance: A friction coefficient of 0.45 may be used when computing the frictional resistance to sliding of footings, grade beams, and slabs-on-grade. Frictional resistance and passive lateral soil resistance may be combined without reduction. SLABS-ON-GROUND Slabs-on-ground may be supported on earth materials prepared in accordance with the recommendations of the Geotechnical Investigation. We recommend that moisture protection be provided for interior concrete slabs-on-ground that will receive moisture-sensitive floor coverings, or where moisture-sensitive equipment, products, or environments may be present. For exceptions to slab moisture protection, refer to the 2019 California Building Code, Section 1907.1. The project designer should provide specific details regarding construction of the concrete slab-on- ground, including a moisture barrier or vapor retarder/barrier, capillary break (if included), and blotter material (if included). The American Concrete Institute recommends a minimum moisture vapor retarder of 10 mil thick polyethylene. The vapor retarder should be protected from damage. Punctures and tears should be repaired prior to concrete placement. It has been common local practice to use a sandy material as a blotter layer between the moisture barrier and the concrete to absorb some of the bleed water and to potentially reduce slab curling. The blotter layer may act as a moisture reservoir and all apparent advantages of its use negated. Therefore, it should not be incorporated into the section design for moisture-sensitive slabs if it cannot be kept dry prior to concrete placement or if water may migrate into the layer after slab construction (ex. wet curing, rainfall). If the slab-on-ground section is to include a blotter layer between the moisture barrier and the concrete, it is our recommendation that the blotter material consist of crusher fines (rock dust) or sand with angular, interlocking grains. The material should be easily compacted and should be screened so that 100% of the material is finer than ¼". Do not use blotter material which may be potentially reactive with the alkalis in the concrete, or which has high sulfate content. At the time of concrete placement, the blotter material should be dry to damp, compact, and smooth. For slabs which are to be water-cured, a blotter layer should not be used. For further consideration, refer to the American Concrete Institute Manual of Concrete Practice 302.1R and 360. Slab thicknesses, reinforcing, and the concrete characteristics should be in accordance with the project designer's recommendations. The 2019 California Building Code, Section 1907.1 requires that the slab thickness be not less than 3½". Pressurized water lines should not be installed beneath slabs-on-ground. Where pressurized water lines must be routed beneath the slab, they should be routed entirely inside continuous sleeves with both ends open to the atmosphere above the slab surface. Gravity flow sewer lines may 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 14 ©2022 SOILS ENGINEERING, INC. underlie slabs-on-ground, but they should be routed to the point of connection by the shortest feasible path. SOIL CORROSIVITY Soluble Sulfates (SO4) The highest Sulfate (SO4) concentration measured was 1100 ppm. Based on Table 19.3.1.1 “Exposure categories and classes” of ACI 318-14 “Building Code Requirements for Structural Concrete” the soil exposure is classified as S0. Per Table 19.3.2.1 “Requirement for Concrete by Exposure Class” of the same reference, no restriction applies to the cement type or mix design. Chlorides (Cl) The highest Chloride (Cl) concentration measured was 120 ppm. Generally, chloride concentrations greater than 500 ppm are corrosive to foundation elements. (Ref: Caltrans Corrosion Guidelines / Version 1.0) pH The soil pH result was measured between 7.83 and 8.53. Generally, a pH level less than 5.5 are corrosive to foundation elements. (Ref: Caltrans Corrosion Guidelines / Version 1.0) Although preliminary test results indicate that soil corrosivity at the locations and depths tested is low to negligible, if the site grading operations will result in a blend of native and/or imported materials at finished subgrade elevations, additional tests should be performed after rough grading has been completed and prior to concrete and/or mechanical design. PAVEMENT FIELD INVESTIGATION & DESIGN DATA Three (3) borings were drilled in the proposed pavement area. Bore locations are shown on the attached Boring Location Map, Figure 1. Hot Mix Asphalt (HMA) pavement shall be designed based on the Resistant (R) Value test results. The results ranged from 13 to 15 according to our testing program. The laboratory test reports are provided as Figures D-1 through D-3. HMA design should meet the requirements of the 2010 or newer, State of California, Standard Specifications Manual (SSM), Section 39. Aggregate Base should also meet the Class 2 requirements of the SSM, Section 26. PCC design should meet the requirements of the American Concrete Institute (ACI) 330R, Guide for the Design and Construction of Concrete. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 15 ©2022 SOILS ENGINEERING, INC. Ground surfaces to receive HMA or Portland Cement Concrete (PCC) pavements should be scarified and compacted to a minimum depth of 12 inches below the grading plane in cut areas or to 12 inches in areas to receive fill. Engineered fill placed in proposed pavement areas should conform to the requirements of section 5.4, “Placing, Spreading and Compacting Fill Materials,” of Appendix A. Compaction in proposed pavement areas should be a minimum of 90 percent of the maximum density as obtained to ASTM Test Method D1557 and should extend to a minimum of two feet beyond the outside edges of pavements. These recommendations are valid only if the pavement is properly drained and shoulder areas are graded to prevent water ponding at pavement edges. All construction should be subject to adequate tests and observations to verify conformance with these recommendations. LIMITATIONS, OBSERVATION, AND TESTING Conclusions and recommendations in this report are given for the proposed Tracts 7141 Morningstar Ranch Development located within Morningstar Avenue, Bakersfield, Kern County, California and are based on the following: a. The information retrieved from six (6) exploratory borings drilled at the subject site to a maximum depth of 21.5 feet below the existing ground surface; b. Our laboratory testing program results; c. Our engineering analysis based on the information defined in this report; d. Our experience in the Kern County area. Variations in soil type, strength and consistency may exist between specific boring locations. These variations may not become evident until after the start of construction. If such variations appear, a re- evaluation of the soils test data and recommendations may be necessary. Unless a Geotechnical Engineer of this firm is afforded the opportunity to review plans and specifications, we accept no responsibility for compliance with design concepts or interpretations made by others about foundation support, fill selection, fill placement or other recommendations presented in this report. Changes in conditions of the subject property can occur with time because of natural processes or the works of man on the subject site or on adjacent properties. Changes in applicable engineering and construction standards can also occur as the result of legislation or from the broadening of knowledge. Accordingly, the finding of this report may be invalidated, wholly or in part, by changes beyond our control. Therefore, this report is subject to review and should not be relied upon without review after a period of two years or after any modifications to the site. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 16 ©2022 SOILS ENGINEERING, INC. REVIEW OF EARTHWORK OPERATIONS Review of earthwork operations relating to site clearing, ground stabilization, placement, and compaction of fill materials, and finished grading is critical to the structural integrity of building foundation and floor systems. While the preliminary Geotechnical investigation and report provide guidelines, which are used by the design team, i.e., architects, grading engineers, structural engineers, landscape engineers, etc., in completing their respective tasks, review of plans and site review and testing during earthwork operations are vital adjuncts to the completion of the Geotechnical engineer's tasks. The most prevalent cause of failure of a structure foundation system is lack of adequate review and testing during the earthwork phase of the project. Projects rarely reach completion without some alteration being required such as may result from a change in subsurface conditions, an amendment in the size and scope of the project, a revision of the grading plans or a variation in structural details. Occasionally, even minor changes can significantly affect the performance of foundations. The most prevalent secondary cause for foundation failure is inadequate implementation of Geotechnical recommendations during the formulation of foundation designs and grading plans. The error in a foundation design or an omission of a key element from a grading plan occurs most often because of inadequate communication between the various project consultants and -- when a change in consultants occurs -- improper transfer of authority and responsibility. It is imperative, therefore, that any revisions to the project scope, any change in structural detail, or change in consultant, be brought to the attention of Soils Engineering, Inc. to allow for timely review and revision of recommendations and for an orderly transfer of responsibility and approval. It is the responsibility of the owner or his or her representative to ensure that a representative of our firm is always present during earthwork operations relating to site preparation and grading, so that relative compaction tests can be performed, earthwork operations can be observed and compliance with the recommendations provided herein can be established. This engineering report has been prepared within the limits prescribed to us by the client or his or her representative, in accordance with the generally accepted principles and practices of Geotechnical engineering. No other warranty, expressed or implied, is included or intended in this report. Respectfully submitted, SOILS ENGINEERING, INC. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 17 ©2022 SOILS ENGINEERING, INC. APPENDIX A GENERAL GUIDE SPECIFICATIONS FOR EARTHWORK 1. GENERAL 1.1 Scope These specifications and plans include all earthwork pertaining to site rough grading including, but not limited to, furnishing all labor and equipment necessary for clearing and grubbing; stripping; preparation of ground surfaces to receive fill; excavation; placement and compaction of structural and non-structural fill; disposal of excess materials and products of clearing, grubbing, and stripping; and any other work necessary to bring ground elevations to the lines and grades shown on the project plans. Wherever discrepancies between these guide-specifications and the earthwork recommendations in Section I of the above geotechnical report, the most stringent recommendations shall supersede. 1.2 Performance: It shall be the responsibility of the contractor to complete all earthwork in accordance with project plans and specifications. No variance from plans and specifications shall be permitted without written approval of the Engineer-of-Record, hereinafter referred to as the “Engineer” or his or her designated representative, hereinafter referred to as the “Soils Engineer.” Earthwork shall not be considered complete until the “engineer” has issued a written statement confirming substantial compliance of earthwork operations to these specifications and to the project plans. The contractor shall assume sole responsibility for job site conditions during earthwork operations on the project, including safety of all persons and preservation of all property. This requirement shall apply continuously and not be limited to normal working hours. The contractor shall defend, indemnify, and hold harmless the owners, engineer, and soils engineer from all liability and claims, real or alleged, arising out of performance of earthwork on this project, except from liability incurred through sole negligence of the owner, engineers, or soils engineers. 2. DEFINITIONS 2.1 Excavations: Excavation shall be defined within the content of these specifications as earth material excavated for constructing fill embankment; grading the site to elevations shown on project plans; or placing underground pipelines, conduits, or other subsurface utilities or minor structures. Excavations shall be made true to the lines shown on project plans and to within plus or minus one-tenth (0.1) of a foot, of grades shown on the accepted site grading plans. 2.2 Engineered Fill: Engineered fill shall be construed within the body of these specifications as earth materials conforming to specifications provided in the soils or geotechnical report placed to raise the grade of the site, to backfill excavations, or to construct asphaltic concrete or Portland cement concrete pavement; and upon which the soils engineer has performed sufficient tests and has made sufficient observation during placement and compaction to enable him to issue a written statement confirming substantial conformance of the work to project earthwork specifications. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 18 ©2022 SOILS ENGINEERING, INC. 2.3 On-Site Material: On-site material is earth material obtained in excavation made on the project site. 2.4 Imported Material: Imported materials are earth materials obtained off the site, hauled in, and placed as fill. 2.5 “Compaction” or “Compacted:” Wherever expressed or implied within the context of these specifications shall be interpreted as compaction to ninety (90) percent of the maximum density obtainable by ASTM Test Method D1557. 2.6 Grading Plane: The grading Plane is the surface of the basement material upon which the lowest layer of subbase, base, asphaltic or Portland cement concrete, surfacing, or another specified layer is placed. 3. SITE CONDITIONS The contractor shall visit the site, prior to bid submittal, to explore existing subsurface conditions; to survey site topographic, and to define the nature of materials that may be encountered while performing its work under this contract. Moreover, the contractor shall make his or her own interpretation of the contents of the Geotechnical Report, as they pertain to said conditions. The contractor shall assume all liability under the contract for any loss sustained because of variations which may exist between specific soil boring locations or changed conditions resulting from natural or man-made circumstances occurring after the date of the Preliminary Field Investigations. 4. CLEARING AND GRUBBING 4.1 Clearing and Grubbing Clearing and grubbing shall consist of removing all debris such as metal, broken concrete, trash, vegetation growth and other biodegradable substances, from all areas to be graded. Existing obstructions below shall be removed in accordance with the following procedures: 4.1.1 Slabs and Pavements - Shall be completely removed. Asphaltic or Portland Cement, concrete fragments may be used in engineered fills provided they are broken down to a maximum dimension of six (6.0) inches and thoroughly dispersed within a friable soil matrix. Engineered fill containing said fragments should not be placed above the elevation of the bottom of the lowest structure footing. 4.1.2 Foundations - Existing at the time of grading shall be removed to a depth not less than two (2.0) feet below the bottom of the lowest structure footing. 4.1.3 Basements, Septic Tanks – Buried concrete containers of similar construction located within areas destined to receive pavements, structures, or engineered fills should be completely removed and disposed of off the site. Basements, septic tanks, etc., 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 19 ©2022 SOILS ENGINEERING, INC. situated outside structures, or structural fill areas shall be disposed of by breaking an opening in bottoms to permit drainage, and by breaking walls down to not less than two (2.0) feet below finished subgrade. 4.1.4 Buried Utilities – Such as sewer, water and gas lines or electrical conduits to remain in service shall be re-routed to pass no closer than four (4.0) feet to the outside edge of proposed exterior footings of structures. Lines to be abandoned shall be completely removed to a minimum depth of two (2.0) feet below finished building pad grade. Concrete lines deeper than two (2.0) feet below finished building pad grade and having diameters less than six (6.0) inches can be crushed in place. 4.1.5 Root Systems – Shall be completely removed to a minimum depth of two (2.0) feet below the bottom of the lowest proposed structure footing or to two (2.0) feet below finished subgrade, whichever depth is lower. Root systems deeper than the elevation indicated above shall be excavated to allow no roots larger than two (2.0) inches in diameter. 4.1.6 Cavities – Resulting from clearing and grubbing or cavities existing on the site because of man-made or natural activity shall be backfilled with earth materials placed and compacted in accordance with Sections 5.3 and 5.4 of these specifications. 4.1.7 Preservation or Monuments, Construction Stakes, Property Corner Stakes, or other temporary or permanent horizontal or vertical control reference points shall be the responsibility of the contractor. Where these markers are disturbed, they shall be replaced at the contractor’s expense. 5. SITE GRADING Site grading shall consist of excavation and placement of fills to lines and grades shown on the project plans and in accordance with project specifications and recommendations of the Preliminary Soils Report, whichever is more stringent. The following are recommendations issued in this report: 5.1 Areas to Receive Fill: 5.1.1 Surfaces to receive fill shall be scarified to a depth of at least six (6.0) inches, or as recommended in this report, whichever is greater, until the surface is free from ruts, hummocks or other uneven features which would tend to prevent uniform compaction by the equipment to be used. 5.1.2 After the area to receive fill has been cleared and scarified, it shall be moistened and compacted to a depth of at least six (6.0) inches in accordance with specifications for compacting fill material in paragraph 5.4, below. 5.2 Excavation: 5.2.1 Excavations shall be cut to elevations plus or minus 0.1 foot of the grades shown on the accepted plans. 5.2.2 When excavated materials are to be used in engineered fill, the excavation shall be made in a manner to produce as much mixing of the excavated materials as practicable. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 20 ©2022 SOILS ENGINEERING, INC. 5.2.3 When excavations are to be backfilled, and where surfaces exposed by excavation are to support structures or concrete floor slabs, the exposed surfaces shall be scarified, moistened, and compacted, as stated above, for areas to receive fill. Over excavation below specified depths will not eliminate the requirement for exposed surface compaction. 5.3 Fill Materials: 5.3.1 Materials obtained from on-site excavations will be considered satisfactory for construction of on-site engineered fills, unless otherwise stated in the Soils Report or Foundation Investigation. If unexpected pockets of poor or weak materials are encountered in excavations, and they cannot be upgraded by mixing with other materials or by other means, they may be rejected by the soils engineer for use in engineered fill. Rocks larger than 12 inches in size in any dimension shall not be allowed in the proposed building area. If many rocks greater than 12 inches in size in any dimension is encountered, a rock disposal area shall be located on the grading plan. Rocks shall be mixed with well-graded soils to assure that the voids in these areas will fill properly. 5.3.2 When imported fill materials are necessary to bring the site up to planned grades, no material shall be imported prior to its approval and acceptance by the soils engineer. 5.3.3 The soils engineer shall be given notice of the proposed source of imported materials with adequate time allowance for his or her testing of the proposed materials. The time required for testing will vary with different types of materials, job conditions, and ultimate function of filled areas. Under best conditions the time requirement will not be less than 48 hours. 5.4 Placing, Spreading, and Compacting Fill Material: 5.4.1 The fill materials shall be placed in layers which, when compacted, shall not exceed six (6.0) inches in thickness. Each layer shall be spread evenly and shall be thoroughly mixed during the spreading to insure uniformity of material in each layer. Increased thickness of layers may be approved by the soils engineer when conditions warrant. 5.4.2 All fills shall be placed in level layers; layers shall be continuous over the area of any structural unit, and all portions of the fill shall be brought up simultaneously within the area of any structural unit. When imported material is used, it must be placed so that its thickness is as uniform as possible within the area of any structural unit. 5.4.3 When materials are to be excavated and replaced in a compacted condition, segmented, or leap-frogging of cut-fill operations within the area of any structural unit will not be permitted unless the method is specifically described by the soils engineer. 5.4.4 When the moisture content of fill material is below the lower limit specified by the Soils Engineer, water shall be added until the moisture content is as specified; and when it is above the upper limit specified, the material shall be aerated by blading or other satisfactory methods until the moisture content is as specified. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 21 ©2022 SOILS ENGINEERING, INC. 5.4.5 After each layer has been placed, mixed, and spread evenly, it shall be thoroughly compacted to not less than ninety (90) percent of maximum density in accordance with ASTM Density Test Method D1557. Compaction shall be by equipment of such design that it will be able to compact the fill to specified density. When the soils engineer specifies a specific type of compaction equipment to be used, such equipment shall be used as specified. 5.4.6 Compaction of each layer shall be continuous over its entire area and the equipment shall make sufficient trips to ensure that the desired density has been obtained. 5.4.7 Field density tests shall be made by the soils engineer. The compaction of each layer of fill shall be subject to testing. Where sheepsfoot rollers are used, the soil may be disturbed to a depth of several inches. Density tests shall be taken in the compacted material below the disturbed surface. When tests indicate the density of any layer of fill or portion thereof is below the required ninety (90) percent density, the layer or portion shall be re-worked until the required density has been obtained. 5.4.8 When the soils engineer specifies compaction to other standards or to percentages other than ninety (90) percent, such specification, with respect to the items, shall supersede these specifications. 5.4.9 The fill operation shall be continued in six (6) inch compacted layers, as specified above, until the fill has been brought to within 0.1 foot, plus or minus, of the finished slopes and grades, as shown on the accepted plans. The finished surface of fill areas shall be graded or bladed to a smooth and uniform surface and no loose material shall be left on the surface. 5.4.10 No fill materials shall be placed, spread, or compacted while it is frozen or thawing or during unfavorable weather conditions. When work is interrupted by weather conditions, fill operations shall not be resumed until the soils engineer indicates that moisture content and density of previously placed fill are satisfactory. 5.5 Observations and Testing: The soils engineer shall be provided with a 48-hour notice, in order that he may be present at the site during all earthwork activities related to excavation, tree root removal, stripping, backfill, and compaction and filling of the site and to perform periodic compaction tests so that substantial conformance to these recommendations can be established. 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 22 ©2022 SOILS ENGINEERING, INC. APPENDIX B FIELD INVESTIGATION Six (6) test borings were drilled at the subject site and terminated at a maximum depth of 21.5 feet below the existing ground surface. Borings were advanced using an eight (8.0) inch hollow-stem auger. Test data and descriptions from these holes form the basis of the conclusions and recommendations contained in this report. Undisturbed samples and disturbed bulk samples were obtained. Undisturbed samples were taken using either a 2-3/8” (inside diameter) split-barrel sampler or a 1-3/8” (inside diameter), 2” (outside diameter) Standard Penetration Sampler (SPT). Penetration resistance of undisturbed soils was obtained by driving the above-described sampler using a one-hundred-forty-pound hammer falling thirty inches (30"). Blow counts for each six inch (6") driven increment was recorded and are reported on the Test Borings Logs. In addition, bulk soil samples, selected as most representative of near surface soils encountered, were taken for laboratory testing. As drilling progressed, earth materials encountered were logged and classified in accordance with the Unified Soils Classification System and presented graphically on Logs of Test Borings, Figures 2 through 7, along with the Legend. Approximate locations of test borings are shown on the Boring Location Map, Figure 1. 23-40000013 07/12/23 %RULQJ/RFDWLRQ0DS5%%%5%%5%23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 23 ©2022 SOILS ENGINEERING, INC. APPENDIX C SOIL TEST DATA SIEVE ANALYSES (ASTM D422 and/or ASTM D1140) Grain size distributions for specimens retrieved from various subsurface elevations were tested to classify the materials. Test results are presented on Figures A-1 and A-2. IN-SITU DENSITY & MOISTURE RELATIONSHIPS (ASTM D2216 & D2937) Moisture & density data for undisturbed native soils was obtained by use of a 2-3/8-inch (inside diameter) split-barrel sampler. Test results are given on the Logs of Test Borings, Figures 2 through 7. CONSOLIDATION TESTS (ASTM D2435) Compressibility of soils was determined on saturated, undisturbed samples of native materials. Consolidation Test Diagrams, Figures B-1 through B-3, graphically express the relationship of vertical strain vs. applied vertical (normal) load for earth materials selected as most representative of the soil strata within the anticipated zone of influence of foundation loads. DIRECT SHEAR TESTS (ASTM D3080) Quick-consolidated direct shear test was performed on an undisturbed, saturated sample of native earth materials. This test provides information on soil shear strength vs. normal load and is used to determine the angle of internal friction and cohesion of earth materials under essentially drained conditions. Test results are presented on Figure C-1. EXPANSION INDEX (ASTM D4829) The Expansion Index test is designed to measure a basic index property of soil and in this respect is comparable to other index tests such as the Atterberg Limits. In formulating the test procedures, no attempt has been made to duplicate any moisture or loading conditions which may occur in the field. Rather, an attempt has been made to control all variables which influence the expansive characteristics of a particular soil and still retain a practical test for general engineering usage. Near surface soils were obtained and tested for expansiveness. Test results are presented on the Laboratory Testing Recap Table 1. R-VALUE TESTS (CTM-301) R-Value tests were performed to obtain flexible pavement design data. Test results are presented on Figures D-1 through D-3. SOIL CORROSIVITY (SO4 / pH / Chlorides) Tests for Soluble Sulfates (SO4), Soluble Chlorides (Cl), and pH values were performed on three (3) composite samples retrieved from the upper 0-5 feet to determine the corrosion potential of the soils. Corrosion prevention measures and the extent to which measures should be taken (if any) should be addressed with the corrosion engineer. Soluble Sulfates and Soluble Chlorides values were determined according to EPA 300.0M. The pH values were determined according to EPA Method 9045C. Results of all the constituents are discussed in the Soil Corrosivity section. 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 23-40000013 07/12/23 SOILS ENGINEERING, INC. Geotechnical Investigation Tracts 7141 Morningstar Ranch Development Morningstar Avenue, Bakersfield, Kern County, CA SEI File 21-18239 February 10, 2022 Page 24 ©2022 SOILS ENGINEERING, INC. APPENDIX D SEISMIC INVESTIGATION SEISMIC DESIGN INFORMATION USGS Design Map Summary and Detail Report EQFAULT Version 3.00 California Fault Map 23-40000013 07/12/23 1/5/22, 12:08 PM U.S. Seismic Design Maps https://seismicmaps.org 1/2 18239 Tract 7141 Morningstar Ranch Development Latitude, Longitude: 35.399743, -118.910109 Date 1/5/2022, 12:08:51 PM Design Code Reference Document ASCE7-16 Risk Category II Site Class D - Stiff Soil Type Value Description SS 0.922 MCE R ground motion. (for 0.2 second period) S1 0.33 MCE R ground motion. (for 1.0s period) SMS 1.043 Site-modified spectral acceleration value SM1 null -See Section 11.4.8 Site-modified spectral acceleration value SDS 0.695 Numeric seismic design value at 0.2 second SA SD1 null -See Section 11.4.8 Numeric seismic design value at 1.0 second SA Type Value Description SDC null -See Section 11.4.8 Seismic design category Fa 1.131 Site amplification factor at 0.2 second Fv null -See Section 11.4.8 Site amplification factor at 1.0 second PGA 0.398 MCE G peak ground acceleration FPGA 1.202 Site amplification factor at PGA PGAM 0.479 Site modified peak ground acceleration TL 12 Long-period transition period in seconds SsRT 0.922 Probabilistic risk-targeted ground motion. (0.2 second) SsUH 0.997 Factored uniform-hazard (2% probability of exceedance in 50 years) spectral acceleration SsD 1.5 Factored deterministic acceleration value. (0.2 second) S1RT 0.33 Probabilistic risk-targeted ground motion. (1.0 second) S1UH 0.358 Factored uniform-hazard (2% probability of exceedance in 50 years) spectral acceleration. S1D 0.6 Factored deterministic acceleration value. (1.0 second) PGAd 0.5 Factored deterministic acceleration value. (Peak Ground Acceleration) CRS 0.925 Mapped value of the risk coefficient at short periods CR1 0.922 Mapped value of the risk coefficient at a period of 1 s 23-40000013 07/12/23 1/5/22, 12:08 PM U.S. Seismic Design Maps https://seismicmaps.org 2/2 DISCLAIMER While the information presented on this website is believed to be correct, SEAOC /OSHPD and its sponsors and contributors assume no responsibility or liability for its accuracy. The material presented in this web application should not be used or relied upon for any specific application without competent examination and verification of its accuracy, suitability and applicability by engineers or other licensed professionals. SEAOC / OSHPD do not intend that the use of this information replace the sound judgment of such competent professionals, having experience and knowledge in the field of practice, nor to substitute for the standard of care required of such professionals in interpreting and applying the results of the seismic data provided by this website. Users of the information from this website assume all liability arising from such use. Use of the output of this website does not imply approval by the governing building code bodies responsible for building code approval and interpretation for the building site described by latitude/longitude location in the search results of this website. 23-40000013 07/12/23                                                          ***********************                                                          *                                         *                                                          *       E Q F A U L T       *                                                          *                                         *                                                          *       Version 3.00         *                                                          *                                         *                                                          ***********************                                                      DETERMINISTIC ESTIMATION OF                                          PEAK ACCELERATION FROM DIGITIZED FAULTS JOB NUMBER: 18239                                                                                                          DATE: 01‐06‐2022 JOB NAME: LGI Homes Tract 7141 CALCULATION NAME: Test Run Analysis FAULT‐DATA‐FILE NAME: CGSFLTE.DAT SITE COORDINATES:      SITE LATITUDE:  35.3997      SITE LONGITUDE:  118.9101 SEARCH RADIUS:     100  mi ATTENUATION RELATION:     3) Boore et al. (1997) Horiz.  ‐ NEHRP D (250)      UNCERTAINTY (M=Median, S=Sigma): M             Number of Sigmas:  0.0      DISTANCE MEASURE:  cd_2drp      SCOND:     0      Basement Depth:  5.00 km         Campbell SSR:               Campbell SHR:      COMPUTE PEAK HORIZONTAL ACCELERATION FAULT‐DATA FILE USED:  CGSFLTE.DAT MINIMUM DEPTH VALUE (km):  0.0 23-40000013 07/12/23                                                                   ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐                                                                  EQFAULT SUMMARY                                                                   ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐                                                     ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐                                                    DETERMINISTIC SITE PARAMETERS                                                     ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Page  1 ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐                                                                |                           |ESTIMATED MAX. EARTHQUAKE EVENT                                                                | APPROXIMATE  |‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐                    ABBREVIATED                     |     DISTANCE     | MAXIMUM  |     PEAK     |EST. SITE                    FAULT  NAME                     |     mi     (km)  |EARTHQUAKE|     SITE     |INTENSITY                                                                |                           | MAG.(Mw) | ACCEL. g |MOD.MERC. ================================|==============|==========|==========|========= Kern Front                                           |     7.6(  12.3)|     6.3       |     0.260  |     IX WHITE WOLF                                           |  16.1(  25.9)|     7.3       |     0.261  |     IX PLEITO THRUST                                     |  28.2(  45.4)|     7.0       |     0.146  |  VIII GARLOCK (West)                                   |  35.1(  56.5)|     7.3       |     0.119  |     VII SAN ANDREAS  ‐ Whole M‐1a               |  39.8(  64.0)|     8.0       |     0.156  |  VIII SAN ANDREAS  ‐ Carrizo M‐1c‐2       |  39.8(  64.0)|     7.4       |     0.114  |     VII SAN ANDREAS  ‐ 1857 Rupture M‐2a |  39.8(  64.0)|     7.8       |     0.140  |  VIII SAN ANDREAS  ‐ Cho‐Moj M‐1b‐1       |  39.8(  64.0)|     7.8       |     0.140  |  VIII BIG PINE                                               |  40.3(  64.9)|     6.9       |     0.086  |     VII SAN GABRIEL                                         |  47.4(  76.3)|     7.2       |     0.089  |     VII GARLOCK (East)                                   |  50.5(  81.3)|     7.5       |     0.099  |     VII So. SIERRA NEVADA                             |  52.9(  85.1)|     7.3       |     0.105  |     VII SAN ANDREAS  ‐ Mojave M‐1c‐3         |  53.4(  86.0)|     7.4       |     0.090  |     VII SAN ANDREAS  ‐ Cholame M‐1c‐1       |  54.2(  87.2)|     7.3       |     0.085  |     VII SANTA YNEZ (East)                             |  56.2(  90.4)|     7.1       |     0.074  |     VII SAN CAYETANO                                       |  60.7(  97.7)|     7.0       |     0.081  |     VII 23-40000013 07/12/23 SAN JUAN                                               |  61.7(  99.3)|     7.1       |     0.069  |     VI M.RIDGE‐ARROYO PARIDA‐SANTA ANA |  62.7( 100.9)|     7.2       |     0.087  |     VII LENWOOD‐LOCKHART‐OLD WOMAN SPRGS|  65.9( 106.0)|     7.5       |     0.081  |     VII SANTA SUSANA                                       |  66.9( 107.7)|     6.7       |     0.064  |     VI HOLSER                                                   |  67.0( 107.8)|     6.5       |     0.057  |     VI LITTLE LAKE                                         |  67.9( 109.2)|     6.9       |     0.058  |     VI OAK RIDGE (Onshore)                         |  69.4( 111.7)|     7.0       |     0.073  |     VII NORTHRIDGE (E. Oak Ridge)             |  69.7( 112.1)|     7.0       |     0.072  |     VII NORTH CHANNEL SLOPE                         |  69.8( 112.3)|     7.4       |     0.089  |     VII RED MOUNTAIN                                       |  70.6( 113.7)|     7.0       |     0.072  |     VI GREAT VALLEY 14                                 |  71.8( 115.5)|     6.4       |     0.052  |     VI SIMI‐SANTA ROSA                                 |  71.8( 115.6)|     7.0       |     0.071  |     VI SIERRA MADRE (San Fernando)         |  71.9( 115.7)|     6.7       |     0.060  |     VI VENTURA  ‐ PITAS POINT                     |  72.6( 116.9)|     6.9       |     0.067  |     VI SANTA YNEZ (West)                             |  73.1( 117.7)|     7.1       |     0.060  |     VI OWENS VALLEY                                       |  75.6( 121.6)|     7.6       |     0.077  |     VII OAK RIDGE MID‐CHANNEL STRUCTURE |  76.8( 123.6)|     6.6       |     0.054  |     VI SAN LUIS RANGE (S. Margin)           |  78.7( 126.7)|     7.2       |     0.073  |     VII VERDUGO                                                 |  79.0( 127.1)|     6.9       |     0.062  |     VI CHANNEL IS. THRUST (Eastern)       |  80.6( 129.7)|     7.5       |     0.084  |     VII SIERRA MADRE                                       |  81.6( 131.4)|     7.2       |     0.071  |     VI SAN ANDREAS  ‐ Parkfield                 |  82.0( 131.9)|     6.5       |     0.040  |       V GRAVEL HILLS  ‐ HARPER LAKE           |  82.6( 132.9)|     7.1       |     0.055  |     VI HELENDALE  ‐ S. LOCKHARDT               |  82.7( 133.1)|     7.3       |     0.061  |     VI                                                     ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐                                                    DETERMINISTIC SITE PARAMETERS                                                     ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Page  2 ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐                                                                |                           |ESTIMATED MAX. EARTHQUAKE EVENT                                                                | APPROXIMATE  |‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐                    ABBREVIATED                     |     DISTANCE     | MAXIMUM  |     PEAK     |EST. SITE                    FAULT  NAME                     |     mi     (km)  |EARTHQUAKE|     SITE     |INTENSITY                                                                |                           | MAG.(Mw) | ACCEL. g |MOD.MERC. ================================|==============|==========|==========|========= LOS ALAMOS‐W. BASELINE                   |  83.9( 135.1)|     6.9       |     0.059  |     VI BLACKWATER                                           |  84.4( 135.8)|     7.1       |     0.054  |     VI ANACAPA‐DUME                                       |  86.2( 138.8)|     7.5       |     0.080  |     VII GREAT VALLEY 13                                 |  86.6( 139.3)|     6.5       |     0.047  |     VI OAK RIDGE(Blind Thrust Offshore)|  87.0( 140.0)|     7.1       |     0.064  |     VI LIONS HEAD                                           |  87.9( 141.4)|     6.6       |     0.049  |     VI INDEPENDENCE                                       |  89.0( 143.2)|     7.1       |     0.063  |     VI LOS OSOS                                               |  89.2( 143.6)|     7.0       |     0.060  |     VI RINCONADA                                             |  90.3( 145.3)|     7.5       |     0.063  |     VI CLAMSHELL‐SAWPIT                               |  90.5( 145.7)|     6.5       |     0.045  |     VI MALIBU COAST                                       |  91.0( 146.5)|     6.7       |     0.050  |     VI 23-40000013 07/12/23 CASMALIA (Orcutt Frontal Fault) |  91.4( 147.1)|     6.5       |     0.045  |     VI TANK CANYON                                         |  91.7( 147.6)|     6.4       |     0.043  |     VI HOLLYWOOD                                             |  91.9( 147.9)|     6.4       |     0.043  |     VI UPPER ELYSIAN PARK BLIND THRUST |  93.1( 149.9)|     6.4       |     0.042  |     VI PUENTE HILLS BLIND THRUST             |  94.0( 151.3)|     7.1       |     0.061  |     VI RAYMOND                                                 |  94.4( 152.0)|     6.5       |     0.044  |     VI SANTA MONICA                                       |  94.4( 152.0)|     6.6       |     0.046  |     VI NEWPORT‐INGLEWOOD (L.A.Basin)     |  98.2( 158.0)|     7.1       |     0.048  |     VI ******************************************************************************* ‐END OF SEARCH‐     59 FAULTS FOUND WITHIN THE SPECIFIED SEARCH RADIUS. THE Kern Front                                             FAULT IS CLOSEST TO THE SITE. IT IS ABOUT 7.6 MILES (12.3 km) AWAY. LARGEST MAXIMUM‐EARTHQUAKE SITE ACCELERATION: 0.2610 g 23-40000013 07/12/23 23-40000013 07/12/23