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B-2019-0242 Soils ReportCAPER ENGINEERING INC. P.O. BOX 14198, FREMONT, CA 94539 Tel: (408) 609-1115 E-mail: capexinc888@gmail.com GEOTECHNICAL INVESTIGATION REPORT PROPOSED TWO-STORY NEW RESIDENCE AT 21164 LAURETTA DR. CUPERTINO, CA CAPEX ENGINEERING INC. Project No. 11241 December 22, 2018 [dl]:2=l:i9lki[6] Building Department REVIEWED FOR CODE COMPLIANCE Reviewed By: Phuong Devries Date: 04/01/19 CAPER ENGINEERING INC. P.O.BOX 14198, FREMONT, CA 94539 Tel :(408) 609-1 115 E-mail: capexinc888@gmail.com Eric Yeh/Luz Serrano 21164 Lauretta Dr. Cupertino, CA Project No. 11241 December 22, 2018 Subject: Proposed Two-story New Residence at 21164 Lauretta Dr. Cupertino, CA GEOTECHNICAL INVESTIGATION AND FOUNDATION RECOMMENDATION REPORT Dear Eric Yeh/Luz Serrano: In accordance with your authorization, CAPER ENGINEERING INC. has completed a geotechnical investigation at the subject site. Recommendations are based on our site investigation, laboratory test result analysis and proposed site plan. The accompanying report presents the results of our geotechnical investigation. Our findings indicate that the site is suitable, from a geotechnical standpoint, for the proposed two-story new residence provided the recommendations of this report are carefully followed and are incorporated into the project plans and specifications. We appreciate the opportunity to be of service to you. Should you have any questions relating to the contents of this report or should you require additional information, please do not hesitate to contact our office at your convenience. Very truly yours, CAPEX ENGINEERING INC. �a y A,—E---- - Principal U QRpFESSlczi Q��q it N o . CZ yo 4L Exp. P OF CAt P CAPER ENGINEERING INC. 2 TABLE OF CONTENTS Pam LETTER OF TRANSMITAL 2 1.0 Introduction 4 2.0 Site location & Description 4 3.0 Field Investigation 4 4.0 Soil Conditions 4 5.0 Laboratory Testing 5 6.0 C.B.0 Earthquake Design Criteria 5 7.0 Liquefaction Potential and liquefaction -induced lateral spreading Evaluation 5 8.0 Discussion, Conclusions & Recommendations 6 8.1 General 6 8.2 Grading & Compaction 6 8.3 Foundations 7 8.4 Concrete Slab on Grade 7 8.5 General Construction Requirement 8 9.0 Construction Observation 9 10.0 Limitations and Uniformity of Conditions 9 Figures: 1. Site Location Map 11 2. Site Plan 12 3. Log of Test Boring 13 CAPEX ENGINEERING INC. 3 1.0 INTRODUCTION The purpose of the geotechnical investigation for the proposed two-story new residence, development located at 21164 Lauretta Dr., Cupertino, California was to determine the surface and subsurface soil conditions at the subject site. Based on the data and information obtained, we have provided recommendations for foundation design and grading criteria for the site. The scope of our work included the following: 1. Site reconnaissance by Project Engineer. 2. Subsurface exploration consisted of boring exploration at 15 feet 3. Performed laboratory tests to provide engineering criteria. 4. The preparation and writing of this report which presents our findings, conclusions and recommendations. Our findings indicate that the proposed development is feasible from a geotechnical standpoint provided the recommendations in this report are included into the project plans and specifications and adhered to during and after construction. 2.0 SITE LOCATIONS AND DESCRIPTION The site is located on 21164 Lauretta Dr., Cupertino, CA. The proposed project is understood to consist of construction one-story new residence. The site is flat and the surrounding lots of the site are developed with residence. The above description is based on site reconnaissance by the project engineer and a site plan. 3.0 FIELD INVESTIGATION The field investigation was performed on December 12, 2018 and included a site reconnaissance by the project engineer and an excavation of one 15 feet deep boring at the proposed project area. 4.0 SOIL CONDITIONS The soil conditions were derived from our site reconnaissance and the information and samples obtained from our exploratory boring. Detailed descriptions of the materials encountered in the laboratory borings and the results of the laboratory tests are presented on "Log of Test Boring" (Figure 3). The subsurface soils condition was found to consist of brown silty clay to the maximum depth excavation of 15 feet. No rock strata encountered with depth of exploration at least 10 feet. CAPEX ENGINEERING INC. 4 No ground water was encountered during boring excavation operations. However, fluctuations in the groundwater table are anticipated with seasonal rainfall variations. The boring was backfilled on the date of excavation. 5.0 LABORATORY TESTINGS 5.1 All samples were visually classified in the laboratory in accordance with the Unified Soil Classification System per ASTM D-2487 and/or D-2488 in order to verify the field classification. 5.2 The natural moisture contents and dry unit weights were determined for all undisturbed samples per ASTM D-2216. 5.3 Gradation tests were performed on selective samples per ASTM D-442 in order to provide engineering characteristics of the material and for liquefaction potential evaluation. 5.4 Atterberg Limits were performed per ASTM D-D427 for swell/shrink potential evaluation The results of Atterberg Limits test indicate that the near surface soils exhibit a medium percentage of fines and are subject to a medium swell/shrink potential with variation in moisture content. (P.I = 14.5) 6.0 C.B.0 (2016 EDITION) EARTHQUAKE DESIGN CRITERIA The seismic design parameters for the site per Chapter 16 of the California Building Code (2016 Edition) are follows: Latitude: 37.327201 (degree); Longitude:-122.044571 (degree) Site Class = D Short Term Spectral Response Parameter Ss=1.89 g Design Short Term Spectral Response Parameter SDs=1.26 g 1 Second Spectral Response Parameter S 1=0.716 g 1 Second Design Spectral Response Parameter SDi=0.716 g 7.0 LIQUEFACTION POTENTIAL AND LIQUEFACTION -INDUCED LATERAL SPREADING EVALUATION Liquefaction occurs primarily in relatively loose, saturated, cohesionless soils which can be subjected to a temporary loss of strength due to the buildup pore pressures, especially as a result of cyclic loading such as induced by earthquakes. Evaluation of liquefaction potential on this site was based on the soil type, density of the site soils, and the presence of groundwater. Based on the data obtained during our field and laboratory investigations, it is our opinion that the liquefaction potential at this site is nil. CAPEX ENGINEERING INC. 8.0 DISCUSSION, CONCLUSIONS AND RECOMMENDATIONS 8.1 General From a geotechnical standpoint, for the proposed addition development is feasible for construction on the subject site provided the recommendations presented in this report are carefully followed and are incorporated into the project plans and specifications. 8.2 Grading & Compaction 8.2.1 Prior to any grading, demolition of the site should be completed. This should include the removal of the existing residential structure and any concrete foundations, underground utilities or any other surface or sub -surface structure which may be encountered. Any tree root system, debris or trashes that are encountered should also be removed. It is vital that CAPEX ENGINEERING INC. observe the demolition operation and be notified in ample time to ensure that no sub -surface structures are covered and that any tree root system completely removed. 8.2.1 All on -site material having an organic content of less than 1% by volume and free from other deleterious materials are suitable for use as fill on site. All fill material should have a maximum particle size of 6 inches with no more than 15% larger than 2.5 inches. 8.2.2 Any import fills which is predominately granular in nature and with plasticity index of 12 or less can be used. The soil engineer should give final approval of any import fill material prior to placement. The contractor shall notify the soil engineer 5 working days in advance of his intention to import soil from any other source outside the site area and shall permit the engineer to sample as necessary for the purpose of performing tests to establish the qualities of the material. 8.2.3 After preparation of the native ground soils, the site may be brought to the desired finish grade by placing on -site native material or import material in lifts not to exceed 8 inches in uncompacted thickness. Compacted to a minimum of 90% as determined by ASTM D-1557-91 laboratory testing procedure. 8.2.4 The moisture content of the fill material should be 0 to 3% above optimum and sufficient to obtain the required density. Water should be added or other satisfactory method shall aerate the fill material in order to have acceptable range for moisture. CAPEX ENGINEERING INC. 6 8.3 Foundations 8.3.1 The proposed structure can be satisfactory supported on spread and continuous (grade beams) footings foundation system provided the site is prepared as previously recommended. 8.3.2 The following soil design parameters apply: a. Allowable soil bearing pressure (DL + LL )------1,500 psf b. Allowable soil bearing pressure (All Loads) ------ 2,000 psf C. Lateral passive pressure ------------------------------- 150 pcf d. Coefficient of sliding ----------------------------------- 0.25 8.3.3 Extend all footings at least 24 inches below the undisturbed ground surface. Foundation widths should conform to CBC minimum standards provided the soil bearing stress recommendations of this report are not exceeded. Footings should be reinforced using a minimum of one # 4 bar at the top and the bottom. The footings should be reinforced as determined by the Structural Engineer based upon the building loads. 8.3.4 Total settlement of the subsoil beneath foundation depth at normal loading is expected to be on the order of 1.0 inch and differential settlement of 0.5 inch. 8.4 CONCRETE SLAB ON GRADE 8.4.1 Concrete slab should be structurally reinforced using at least No. 4 bars, within the middle of slab, at 18 inches on centers both ways. The structural engineer may determine that additional reinforcement is required based on the intended use and loading of the slab. 8.4.2 Slab on grade should be underlain by a minimum of 6 inches of granular material conforming to Caltrains Specifications for Class II permeable material in order to provide a capillary moisture break. An impervious membrane of 10 mils minimum thickness should be placed over the granular material in order to provide vapor barrier. 8.4.3 All flatwork slabs should be poured structurally independent of the foundations. A 30-pound felt strip, expansive joint material, or other positive separator should be provided around the edge of all floating slabs to prevent bond to the structure foundation. CAPEX ENGINEERING INC. 7 8.5 GENERAL CONSTRUCTION REQUIREMENTS Surface Drainage and Irrigation: 8.5.1 All finish grades should provide a positive gradient to an adequate discharge point in order to provide rapid removal of surface water runoff away from all foundations. No stilling water should be allowed on the pad or adjacent to the foundations. These lot slopes should be provided to aid in the removal of water from the pads and to reduce the amount of water to seep beneath the buildings. Surface drainage should be provided as designed by the project engineer and maintained by the property owner at all times afterwards. 8.5.2 All finish grade drainage swales must be cut into compacted finish grade. Construction of the drainage swales using uncompacted loose surface fill does not meet the recommended grading requirement. 8.5.3 Continuous roof gutters are recommended. Water from the gutter/downspout shall be discharged away from the foundation, thus reduce the possibility of soil saturation adjacent to the foundations and engineered fill. 8.5.4 Planters should be avoided adjacent to the foundation. Should planters be constructed, foliage requiring little irrigation should be considered to further reduce the amount of water that could affect the foundation. Alternatively, a watertight planter box with controlled discharge should be provided. Utility Trenches: 8.5.5 Any utility trenches extending under the building areas should be backfilled with native on -site soils or approved import materials. Backfill should be properly compacted to prevent water migration through the utility trenches extending underneath the structure. 8.5.6 Utility trenches extending underneath all traffic areas must be backfilled with native or approved import material and compacted to a relative compaction of 90% to within 12 inches of the subgrade. The upper 12 inches should be compacted to 95% relative compaction. Backfilling and compaction of these trenches must meet the requirement set forth by the City of Cupertino, Department of Public Works. 8.5.7 The soils generated from trenching may be used as backfill with the exception of cobbles greater than 6 inches in largest dimension. Compaction of the trench backfill should comply with the requirements set forth by the City of Cupertino, Department of Public Works. CAPEX ENGINEERING INC. 8 Trench Shoring and Temporary Slopes 8.5.8 Applicable safety standards require that trenches in excess of 5 feet must be properly shored or that the walls of the trench slope back to provide safety for installation of lines. If trench wall sloping is performed, the inclination should vary with the soil type. The underground contractor should request an opinion from the soil engineer as to the type of soil and the resulting inclination. Slope of 1:1 (horizontal to vertical) may be utilized for stable cohesive soils while 2:1 will be required for the more granular loose soil. 9.0 CONSTRUCTION OBSERVATION The recommendations of this report are based upon assumptions regarding design concepts, and construction materials and procedures. To validate these recommendations, Capex Engineering Inc. must be retained to: a. Review the drainage and foundation plans. b. Review the structural calculations related to the foundations. C. Observe the preparation of the site for slab -on grade construction. d. Observe the foundation excavations to determine if the exposed soil conditions are substantially the same as those encountered in this report; and, to make alternative recommendations based upon professional judgment. e. Observe the initial and final site grading and installation of surface and subsurface drainage. 10.0 LIMITATIONS AND UNIFORMITY OF CONDITIONS 10.1 The recommendations of this report are based on the assumption that the soil conditions do not deviate from those disclosed and from a reconnaissance of the site. Should any variations or undesirable conditions be encountered during the construction, Capex Engineering Inc. will provide supplemental recommendations as dictated by the field conditions. 10.2 This report is issued with the understanding that it is the responsibility for owner or his representative, to ensure that the information and recommendations contained herein are brought to the attention of the Architect, Engineer and Contractor for the project and incorporated into the plans and that the necessary steps are taken to see that the contractor and subcontractor carry out such recommendations in the field. CAPEX ENGINEERING INC. 9 10.3 This report specifically recommends that Capex Engineering Inc. be retained to review the project plans and to provide observations and/or testing services during construction. It is the responsibility of the client to retain Capex Engineering Inc. and to inform Capex Engineering Inc. of the need for such services. 10.4 The conclusions and recommendations contained in this report will not be considered valid after a period of two (2) years, unless the changes are reviewed and conclusions of this report modified or verified in writing. 10.5 Capex Engineering Inc. does not provide design services, nor does Capex Engineering Inc. act as a builder. Our professional findings and recommendations were prepared in accordance with generally accepted engineering principals and practices. NO other warranty, expressed or implied, is made. CAPEX ENGINEERING INC. 10 LOCATION MAP Hazelbrook Or Rum`oro Dr �21164 Lauretta Drive 10 min drive - home F arKWood Or Chr a Glen PI Cupertino R rCe eat y�I & Community Servil Go gle 4 ' Alvnc n. Figure 1 Project No. 11241 December 22, 2018 CAPER ENGINEERING INC. 21164 L.auretta Dr. Cupertino, CA SITE PLAN Approximate Location of Test Borings Project No. 11241 CAPEX ENGINEERING INC Figure 2 December 22, 2018 21164 Lauretta Dr. Cupertino, CA 21164 Lauretta Dr., Cupertino Project No. 11241 22 December 2018 LL O Z C •- O 0 :r � p J p N N Description u d EL Remarks s CLE S N _ 30 �Ci r- o m c m o�d`b'F N� U) 1 Light brown Silty Clay 2 3 Light Brown Silty Clay with gravel, moist , very stiff 1-1 CL 22 114.5 14-0 2.0 Unconfined Compressive 4 Uc =2,350 psf 5 Atterberg Limits Test PI=14.5 6 Same As Above 7 8 9 Light Brown Silty Clay with gravel, moist, stiff 1-2 CL 24 115.0 14.5 2.5 10 11 12 Same As Above 13 14 15 Light brown Silty Clay with gravel, moist, stiff 1-3 CL 65 115.5 15.0 2.5 Terminated of Boring at depth of 15 feet, 16 groundwater was not encountered during boring 17 18 19 20 21 22 23 24 25 BORING LOG NO. 1 Figure No. 3 CAPEX ENGINEERING INC. - - - --- -- - - Date Drilled. 12/17/2018 By: G.H Project No. 11241