CHRISTIAN WHEELER E N G I N E E R I N G

Transcription

1 CHRISTIAN WHEELER E N G I N E E R I N G REPORT OF GEOTECHNICAL INVESTIGATION PROPOSED FOUNDATION UNDERPINNING SMOKETREE CONDOMINIUMS, BUILDINGS 8 AND HENDERSON DRIVE LA MESA, CALIFORNIA SUBMITTED TO: SMOKETREE HENDERSON DRIVE OWNERS ASSOCIATION, INC. C/O HOA SOLUTIONS, INC LAKE MURRAY BOULEVARD LA MESA, CALIFORNIA PREPARED BY CHRISTIAN WHEELER ENGINEERING 3980 HOME AVENUE SAN DIEGO, CALIFORNIA H o m e A v e n u e San Diego, CA FAX

2 CHRISTIAN WHEELER E N G I N E E R I N G December 21, 2016 Smoketree Henderson Drive Owners Association, Inc. CWE c/o HOA Business Solutions, Inc Lake Murray Boulevard La Mesa, California Subject: Report of Geotechnical Investigation Proposed Foundation Underpinning, Buildings 8 and 9 Smoketree Condominiums, 6050 Henderson Drive, La Mesa, California Ladies and Gentlemen: In accordance with your request, we have prepared a geotechnical investigation of the distress at the subject buildings. We are presenting herein our findings and recommendations. In general, we found that the two subject buildings are underlain by a wedge of man-placed fill materials with fill depth differentials of up to about 9 feet and 5 feet across the footprints of Buildings 8 and 9, respectively. It is our opinion that the existing building distress is most likely the result of differential movement (settlement/expansion) of the supporting fill soils and underlying residual soils combined with slight softening of the adjacent fill slope. Specific design criteria are provided in the attached report to underpin the foundations of the subject buildings in order to minimize the potential for future settlement and distress of the structures. If you have any questions after reviewing this report, please do not hesitate to contact our office. This opportunity to be of professional service is sincerely appreciated. Respectfully submitted, CHRISTIAN WHEELER ENGINEERING Shawn Caya, R.G.E. #2748 David R. Russell, C.E.G. #2215 ec: steve@hoabusinesssolutions.com H o m e A v e n u e San Diego, CA FAX

3 TABLE OF CONTENTS PAGE Introduction and Project Description... 1 Project Scope... 2 Findings... 3 Site Description... 3 Existing Footings... 4 General Geology and Subsurface Conditions... 4 Geologic Setting and Soil Description... 4 Artificial Fill... 4 Residual Soil... 4 Mission Valley Formation... 5 Groundwater... 5 Tectonic Setting... 5 Geotechnical Analysis... 6 Conclusions... 6 Recommendations... 7 Micropiles... 7 General... 7 Minimum Micropile Dimensions... 7 Micropile Reinforcing... 7 Allowable Bond Strength... 7 Drag Load... 7 Lateral Pier Capacity... 8 Settlement Characteristics... 8 Cleaning Of Excavations... 8 Grouting... 8 Testing... 8 Plan Review... 8 Temporary Cut Slopes... 9 Compaction and Method of Filling... 9 Limitations Review, Observation and Testing Uniformity of Conditions Change in Scope Time Limitations Professional Standard Client s Responsibility Field Explorations Laboratory Testing CWE Smoketree Condominiums 6050 Henderson Drive, La Mesa, California

4 TABLE OF CONTENTS (Continued) FIGURES Figure 1 Site Vicinity Map, Follows Page 1 PLATES Plate 1 Site Plan and Geotechnical Map APPENDICES Appendix A Test Pit Logs Appendix B Laboratory Test Results Appendix C References CWE Smoketree Condominiums 6050 Henderson Drive, La Mesa, California

5 CHRISTIAN WHEELER E N G I N E E R I N G REPORT OF GEOTECHNICAL INVESTIGATION PROPOSED FOUNDATION UNDERPINNING SMOKETREE CONDOMINIUMS, BUILDINGS 8 AND HENDERSON DRIVE LA MESA, CALIFORNIA INTRODUCTION AND PROJECT DESCRIPTION This report presents the results of a geotechnical investigation related to the distress within Buildings 8 and 9 at the existing Smoketree condominium complex located at 6050 Henderson Drive, in the city of La Mesa, California. Figure Number 1, presented on the following page, provides a vicinity map showing the location of the property. As part of this investigation, we have reviewed miscellaneous building and grading plans associated with the original construction of the subject development. We have also been provided with and have reviewed the reports listed below. Caitlin Engineering, Inc., 1986, Preliminary Limited Site and Structural Investigation, Smoke Tree Condominiums, 6050 Henderson Drive, La Mesa, California, dated October 1. SD Engineering, 1998, Limited Inspection of Structural Soundness, 6050 Henderson Drive #35, La Mesa California, dated October 26. SD Engineering, 2016, Limited Evaluation of Foundation Soundness, 6050 Henderson Drive #34, #35, and #36, La Mesa, California, dated March 31. We understand that the existing buildings have experienced on-going distress that appears to be the result of differential soil displacement. Per the recommendations of the SD Engineering (2016) report, underpinning of the foundation system of the Building 8 was previously proposed but not performed. Currently, the Home Owners Association would like to evaluate the geotechnical conditions for both Building 8 and Building 9, in order to design underpinning systems for these structures. It is our H o m e A v e n u e San Diego, CA FAX

6 SITE VICINITY OpenStreetMap contributors PROJECT SITE DATE: DECEMBER 2016 BY: SRD SMOKETREE CONDOMIUMS 6050 HENDERSON DRIVE LA MESA, CALIFORNIA JOB NO.: FIGURE NO.: 1 CHRISTIAN WHEELER E N G I N E E R I N G

7 CWE December 21, 2016 Page 2 understanding that the information developed in our investigation will possibly be used to design and make repairs to the distressed units within Building 8 and Building 9. We understand that a structural engineer or other design professional will prepare any plans, calculations and other documents needed to complete the recommended repairs. This report has been prepared for the exclusive use of Smoketree Henderson Drive Owners Association, Inc., and its design consultants, for specific application to the project described herein. Should the project be changed in any way, the modified plans should be submitted to Christian Wheeler Engineering for review to determine their conformance with our recommendations and to determine if any additional subsurface investigation, laboratory testing and/or recommendations are necessary. Our professional services have been performed, our findings obtained and our recommendations prepared in accordance with generally accepted engineering principles and practices. This warranty is in lieu of all other warranties, express or implied. PROJECT SCOPE Our geotechnical investigation consisted of surface reconnaissance, subsurface exploration, obtaining representative soil samples, laboratory testing, analysis of the field and laboratory data, and review of relevant readily available geologic literature. In consideration of the conditions at the site and site access constraints, we the following services were provided as part of our investigation. Excavate eight hand-dug test pits to explore the subsurface conditions and to obtain soil samples for laboratory testing. Expose and measured the depth and width of the existing footings in at least 2 locations at each building. Evaluate, by laboratory tests and our past experience with similar soil types, the engineering properties of the various strata that may influence the existing structure, including bearing capacities, expansive characteristics and settlement potential. Describe the general geology at the site, including possible geologic hazards that could have an effect on the existing or future construction, and provide the seismic design parameters as required by the 2016 edition of the California Building Code.

8 CWE December 21, 2016 Page 3 Address potential construction difficulties that may be encountered due to soil conditions, groundwater or geologic hazards, and provide geotechnical recommendations to deal with these difficulties. Provide geotechnical design parameters for the type of repair and underpinning anticipated. Prepare this written report discussing our findings and geotechnical recommendations for the proposed repairs. FINDINGS SITE DESCRIPTION The subject units are within two adjacent townhome structures located in the southeast portion of the Smoketree Henderson Drive development at 6050 Henderson Drive in La Mesa, California. The subject structures, which were originally constructed around 1975/76, are one- to two-stories high with attached garages along the front (northern) portions of each unit. The structures are anticipated to be supported by conventional shallow foundations with concrete floor slabs. The structures are constructed on relatively level building pads with engineered slopes of up to about 12 feet in height to the south of the buildings. An engineered slope of up to about 5 feet in height exists between the two structures. An approximately 4-foot-high masonry retaining wall exists along the toe of the slope along the south side of the subject structures. Outdoor patio slabs are present at the rear (southern) sides of the subject units. We understand that the distress features in Building 8 (Units 33-36) and Building 9 (Units 29-32) include cracks in walls, ceilings and the concrete floor slabs. We have been informed that periodic cosmetic repairs to wall and ceiling cracks have been previously performed. In addition, some of the exterior patio slabs behind the two structures may be rotated downward to the south. A floor level survey was done in Unit 35 in 1998 by SD Engineering. Level surveys were again done by SD Engineering in 2016 in Units 34, 35, and 36. In both Units 34 and 35, the largest difference in relative elevation of the floor slabs was approximately 1½ inches. There was virtually no difference in the level survey results in Unit 35 between 1998 and In Unit 36, the largest difference in relative floor slab elevation was between the central portion of the home and the southeast corner, with an approximate difference of 2½ inches.

9 CWE December 21, 2016 Page 4 EXISTING FOOTINGS The subject buildings are supported by convention shallow foundations with on-grade concrete floor slabs. The existing perimeter foundations were exposed at three different locations for each building (see Appendix A). In general, the existing perimeter foundations were observed to extend approximately 16 to 20 inches below the adjacent grade and were 10 to 12 inches wide. One exception was within test pit P-5, where the footing was measured to be approximately 21 inches wide. In each case the exposed footing was supported by artificial fill soil. GENERAL GEOLOGY AND SUBSURFACE CONDITIONS GEOLOGIC SETTING AND SOIL DESCRIPTION: The subject site is located in Coastal Plains Physiographic Province of San Diego County. Based on the results of our subsurface explorations and our review of the referenced reports as well as pertinent, readily available geologic literature, we have determined that the site is underlain by artificial fill and natural residual soil that is in turn underlain by Tertiary-age sedimentary deposits locally referred to as the Mission Valley Formation. The encountered geologic units are described below in order of increasing age. ARTIFICIAL FILL (Qaf): We understand that the site was graded to its current configuration sometime around Based on the Site Development Plan prepared by Arevalo & Safino (1974), the project grading for Buildings 8 and 9 consisted of placing up to about 10 feet of fill along the southern (rear) sides of the pads. Within our test pits, the existing fill was found to be approximately 10 to 11 feet thick at the rear of Building 8 and 6 to 7 feet thick at the rear of Building 9. At the front of each building, the fill was approximately 2 feet thick at the northeast corner and 5 to 6 feet thick at the northwest corner. In general, the fill materials consisted of light to medium brown and grayish-brown, moist to very moist, medium dense, clayey sand (SC). This material was found to have a low to medium Expansion Index. RESIDUAL SOIL: A layer of natural residuum was encountered below the fill layer within each of our exploratory test pits except P-1. The residual soil typically consisted of a 1-foot to 2-feet-thick layer of topsoil over a similarly thick layer of subsoil. In general, the topsoil materials consisted of medium brown, damp to moist, very loose, silty sand (SM) while the

10 CWE December 21, 2016 Page 5 subsoil consisted of grayish-brown, moist, medium stiff to stiff, sandy clay (CL). The topsoil was judged to have a low Expansion Index while the subsoil was judged to have a medium to high Expansion Index. MISSION VALLEY FORMATION (Tmv): Tertiary-age sedimentary deposits of the Mission Valley Formation were encountered below the fill and/or residual soil in our exploratory test pits. These formational materials were observed at depths ranging from 2 to 14 feet below the existing site grades. The Mission Valley Formation generally consisted of yellowish-brown, damp to moist, dense to very dense, silty sand (SM). This material was judged to have a very low Expansion Index. GROUNDWATER: Groundwater was not encountered in our test pits; however, it can be anticipated that localized seepage may be encountered at the contact between the fill and underlying formational soil. TECTONIC SETTING: No faults are known to traverse the subject site. However, it should be noted that much of Southern California, including the San Diego County area, is characterized by a series of Quaternary-age fault zones that consist of several individual, en echelon faults that generally strike in a northerly to northwesterly direction. Some of these fault zones (and the individual faults within the zone) are classified as active according to the criteria of the California Division of Mines and Geology. Active fault zones are those that have shown conclusive evidence of faulting during the Holocene Epoch (the most recent 11,000 years). The Division of Mines and Geology used the term potentially active on Earthquake Fault Zone maps until 1988 to refer to all Quaternary-age (last 1.6 million years) faults for the purpose of evaluation for possible zonation in accordance with the Alquist-Priolo Earthquake Fault Zoning Act and identified all Quaternary-age faults as potentially active except for certain faults that were presumed to be inactive based on direct geologic evidence of inactivity during all of Holocene time or longer. Some faults considered to be potentially active would be considered to be active but lack specific criteria used by the State Geologist, such as sufficiently active and well-defined. Faults older than Quaternary-age are not specifically defined in Special Publication 42, Fault Rupture Hazard Zones in California, published by the California Division of Mines and Geology. However, it is generally accepted that faults showing no movement during the Quaternary period may be considered to be inactive.

11 CWE December 21, 2016 Page 6 A review of available geologic maps indicates that the active Rose Canyon Fault Zone is located approximately 12 miles west of the subject site. Other active fault zones in the region that could possibly affect the site include the Newport-Inglewood and Palos Verdes Fault Zones to the northwest, the Coronado Bank Fault Zone to the southwest, the Elsinore and Earthquake Valley Fault Zones to the northeast and east, respectively. GEOTECHNICAL ANALYSIS Eight relatively undisturbed chunk samples of the existing fill soil were subjected to single point oedometer tests in which the specimen was loaded to the approximate in-situ stress and inundated with water to measure the response in terms of the change in thickness. The results, which are summarized in Appendix B (Figure B-3), showed that the six of the samples expanded upon wetting while the remaining two consolidated. The displacement for each test was less than two percent. CONCLUSIONS The existing buildings are supported by artificial fill materials that generally increase in thickness from northeast to south-southwest. The total thickness is expected to range from a minimum of about 2 feet in the northeast corner of each building to a maximum of 11 feet along the southern side of Building 8 and 7 feet along the southern side of Building 9. The fill consists predominantly of clayey sand soils that are potentially compressible under normal conditions but may become moderately to highly expansive with increases in moisture content. This soil is also susceptible to softening when used to construct slopes such as those along the southern side of the buildings. Based on these conditions, it is our opinion that the existing building distress is most likely the result of differential movement (settlement/expansion) of the supporting fill soils and underlying residual soils combined with slight softening of the adjacent fill slope. We understand that the distress to the existing buildings has re-occurred several times since their construction and appears to be on-going. If it is desired to mitigate the potential for additional building distress, the existing perimeter foundations can be stabilized by underpinning with deep foundations that extend through the fill/residual soil and are embedded in the underlying formational soils. Additional mitigation would include underpinning the interior foundations as well. Though different underpinning types are available, specific design recommendations for underpinning via micropiles are presented in the

12 CWE December 21, 2016 Page 7 following section as these are typically the most cost effective based on materials and ease of construction. Alternative types of underpinning can be evaluated upon request. RECOMMENDATIONS MICROPILES GENERAL: A micropile is a small-diameter, drilled and grouted pile that is typically reinforced using a single steel bar. The vertical loads applied to the micropile are transferred to the surrounding soil through bond friction at the interface between the grout and soil. We recommend that micropiles used to underpin the existing foundations extend through the existing fill layer and be embedded in the underlying formational soils. Only the bond strength developed between the grout and formational should be considered in the capacity evaluation. Based on the relatively small diameter of the micropiles, end bearing is considered to be negligible. The project structural engineer should design all pile locations, dimensions, and reinforcing using the recommendations and design parameters presented below. MINIMUM MICROPILE DIMENSIONS: We recommend that micropiles be embedded at least 10 feet into competent formational soils with a minimum total depth of 15 below the existing grade. Approximate depths to the formational contact can be estimated once the initial pile layout is determined. Micropiles should have a minimum diameter of 4 inches. MICROPILE REINFORCING: Micropile reinforcing should be specified by the project structural engineer. ALLOWABLE BOND STRENGTH: For design purposes, we recommend that the allowable bond strength between the grout and formational soil be taken as 1,500 pounds per square foot per foot of embedment into the formational soils. The bond strength between the grout and existing fill should be neglected. The design bearing value may be increased by one-third when considering wind and/or seismic loads. DRAG LOAD: In addition to the building dead load, the required structural capacity of the micropile should consider the potential drag load from continued settlement of the fill layer after installation. The

13 CWE December 21, 2016 Page 8 drag load, in kips, can be taken as 1.75(D)(L) where D is the micropile diameter in feet and L is the depth in feet to the formational soils. LATERAL PIER CAPACITY: The allowable lateral bearing resistance to lateral loads may be assumed to be 250 pounds per square foot per foot of depth up to a maximum of 3,500 psf. This value may be assumed to act on an area equal to twice the pier diameter. If necessary, our firm can provide more detailed analyses of the induced deflections, shears and moments in the pier foundations once the initial pile geometries and loads are determined. SETTLEMENT CHARACTERISTICS: The anticipated total and/or differential foundation settlements are expected to be less than about one-half inch, provided the recommendations presented in this report are followed. CLEANING OF EXCAVATIONS: When open-hole drilling methods are being used, the Contractor should have hole cleaning tools on-site suitable for cleaning drilled holes along their full length just prior to bar insertion and grouting. GROUTING: The length of drilled hole should be verified and recorded by the Geotechnical Consultant before grouting. Grout should be injected at the low end of the drilled hole and should fill the drilled hole with a dense grout free of voids or inclusion of foreign material. Cold joints should not be used in grout placement. Micropiles should be grouted full length. After placing the grout, the micropiles should remain undisturbed for the appropriate cure time. TESTING: We recommend that at least one test pile be installed with monitoring by the Geotechnical Consultant to evaluate the contractor's installation procedures and equipment as well as our design assumptions. We recommend the maximum test load be two times the design load. Based on the subsurface conditions encountered, we recommend using the Quick Load Test Method referenced in ASTM D1143. We recommend the 100 percent load application be held and monitored for a period of four hours. PLAN REVIEW: The final foundation plan and accompanying details and notes should be submitted to this office for review. The intent of our review will be to verify that the plans used for construction

14 CWE December 21, 2016 Page 9 reflect the minimum dimensioning criteria presented in this section and that no additional criteria are required due to changes in the foundation type or layout. It is not our intent to review structural plans, notes, details, or calculations to verify that the design engineer has correctly applied the geotechnical design values. It is the responsibility of the design engineer to properly design/specify the foundations and other structural elements based on the requirements of the structure and considering the information presented in this report. TEMPORARY CUT SLOPES We anticipate that temporary excavations will typically be less than about 5 feet in depth. Temporary cut slopes can be excavated vertically up to 5 feet in height and at an inclination of 1.0 to 1.0 (horizontal to vertical) or flatter for heights greater than 5 feet (not exceeding 20 feet). Our firm should be contacted to observe all temporary cut slopes during grading to ascertain that no unforeseen adverse conditions exist. No surcharge loads such as foundation loads, or soil or equipment stockpiles, vehicles, etc. should be allowed within a distance from the top of temporary slopes equal to half the slope height. Where there is not enough room to construct temporary slopes in accordance with the above recommendations, temporary shoring of the excavation sides will be necessary. The contractor is solely responsible for designing and constructing stable, temporary excavations and will need to shore, slope, or bench the sides of trench excavations as required to maintain the stability of the excavation sides. The contractor s competent person, as defined in the OSHA Construction Standards for Excavations, 29 CFR, Part 1926, should evaluate the soil exposed in the excavations as part of the contractor s safety process. Temporary cut slopes should be constructed in accordance with the recommendations presented in this section. In no other case should slope height, slope inclination, or excavation depth, including utility trench excavation depth, exceed those specified in local, state, and federal safety regulations. COMPACTION AND METHOD OF FILLING All structural fill and backfill material placed at the site should be compacted to a relative compaction of at least 90 percent of maximum dry density as determined by ASTM Laboratory Test D1557. Fills should be placed at or slightly above optimum moisture content, in lifts six to eight inches thick, with each lift

15 CWE December 21, 2016 Page 10 compacted by mechanical means. Fills should consist of approved earth material, free of trash or debris, roots, vegetation, or other materials determined to be unsuitable by our soil technicians or project geologist. Fill material should be free of rocks or lumps of soil in excess of six inches in maximum dimension. LIMITATIONS REVIEW, OBSERVATION AND TESTING The recommendations presented in this report are contingent upon our review of final plans and specifications. Such plans and specifications should be made available to the Geotechnical Engineer and Engineering Geologist so that they may review and verify their compliance with this report and with the Uniform Building Code. It is recommended that Christian Wheeler Engineering be retained to provide continuous soil engineering services during the earthwork operations. This is to verify compliance with the design concepts, specifications or recommendations and to allow design changes in the event that subsurface conditions differ from those anticipated prior to start of construction. UNIFORMITY OF CONDITIONS The recommendations and opinions expressed in this report reflect our best estimate of the project requirements based on an evaluation of the subsurface soil conditions encountered at the subsurface exploration locations and on the assumption that the soil conditions do not deviate appreciably from those encountered. It should be recognized that the performance of the foundations and/or cut and fill slopes may be influenced by undisclosed or unforeseen variations in the soil conditions that may occur in the intermediate and unexplored areas. Any unusual conditions not covered in this report that may be encountered during site development should be brought to the attention of the Geotechnical Engineer so that he may make modifications if necessary.

16 CWE December 21, 2016 Page 11 CHANGE IN SCOPE This office should be advised of any changes in the project scope or proposed site grading so that we may determine if the recommendations contained herein are appropriate. It should be verified in writing if the recommendations are found to be appropriate for the proposed changes or our recommendations should be modified by a written addendum. TIME LIMITATIONS The findings of this report are valid as of this date. Changes in the condition of a property can, however, occur with the passage of time, whether they are due to natural processes or the work of man on this or adjacent properties. In addition, changes in the Standards-of-Practice and/or Government Codes may occur. Due to such changes, the findings of this report may be invalidated wholly or in part by changes beyond our control. Therefore, this report should not be relied upon after a period of two years without a review by us verifying the suitability of the conclusions and recommendations. PROFESSIONAL STANDARD In the performance of our professional services, we comply with that level of care and skill ordinarily exercised by members of our profession currently practicing under similar conditions and in the same locality. The client recognizes that subsurface conditions may vary from those encountered at the locations where our borings, surveys, and explorations are made, and that our data, interpretations, and recommendations are based solely on the information obtained by us. We will be responsible for those data, interpretations, and recommendations, but shall not be responsible for the interpretations by others of the information developed. Our services consist of professional consultation and observation only, and no warranty of any kind whatsoever, express or implied, is made or intended in connection with the work performed or to be performed by us, or by our proposal for consulting or other services, or by our furnishing of oral or written reports or findings.

17 CWE December 21, 2016 Page 12 CLIENT S RESPONSIBILITY It is the client s responsibility, or their representatives, to ensure that the information and recommendations contained herein are brought to the attention of the structural engineer and architect for the project and incorporated into the project's plans and specifications. It is further their responsibility to take the necessary measures to insure that the contractor and his subcontractors carry out such recommendations during construction. FIELD EXPLORATIONS Eight subsurface explorations were made November 16, 2016 at the locations indicated on the attached Plate Number 1. These explorations consisted of a hand-dug test pits. The fieldwork was conducted by an engineering geologist. Bulk samples and relatively undisturbed chunk samples of the encountered earth materials and transported to our laboratory for testing. The explorations were carefully logged when made. The boring logs are presented Appendix A. The soils are described in accordance with the Unified Soils Classification System. In addition, a verbal textural description, the wet color, the apparent moisture and the density or consistency are provided. The density of granular soils is given as very loose, loose, medium dense, dense or very dense. The consistency of silts or clays is given as either very soft, soft, medium stiff, stiff, very stiff, or hard. LABORATORY TESTING Laboratory tests were performed in accordance with the generally accepted American Society for Testing and Materials (ASTM) test methods or suggested procedures. A brief description of the tests performed and the subsequent results are presented in Appendix B.

18 P-8 P-7 P-5 P-4 P-6 P-3 Qaf Tmv P-1 P-2 CWE LEGEND 0 40' 80' P-8 Qaf Tmv APPROXIMATE TEST PIT LOCATION ARTIFICIAL FILL OVER MISSION VALLEY FORMATION SCALE: 1" = 40' SITE PLAN AND GEOTECHNICAL MAP DATE: DECEMBER 2016 BY: SD SMOKETREE CONDOMINIUMS 6050 HENDERSON DRIVE LA MESA, CALIFORNIA JOB NO.: PLATE NO.: 1 CHRISTIAN WHEELER E N G I N E E R I N G

19 Appendix A Boring Logs (CWE 2006, 2007, 2008)

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28 Appendix B Laboratory Test Results

29 Laboratory tests were performed in accordance with the generally accepted American Society for Testing and Materials (ASTM) test methods or suggested procedures. Brief descriptions of the tests performed are presented below: a) CLASSIFICATION: Field classifications were verified in the laboratory by visual examination. The final soil classifications are in accordance with the Unified Soil Classification System and are presented on the exploration logs in Appendix A. b) MOISTURE-DENSITY: In-place moisture contents and dry densities were determined for representative soil samples. This information was an aid to classification and permitted recognition of variations in material consistency with depth. The dry unit weight is determined in pounds per cubic foot, and the in-place moisture content is determined as a percentage of the soil's dry weight. The results of these tests are summarized in the exploration logs presented in Appendix A. c) GRAIN SIZE DISTRIBUTION: The grain size distributions of selected samples were determined in accordance with ASTM C136 and/or ASTM D422. d) COLLAPSE POTENTIAL: Collapse potential tests were performed on a selected undisturbed soil samples. The tests were generally performed in accordance with ASTM D e) SOLUBLE SULFATES: The soluble sulfate content was determined for samples of soil likely to be present at the foundation level. The soluble sulfate content was determined in accordance with California Test Method 417. f) MAXIMUM DENSITY & OPTIMUM MOISTURE CONTENT: The maximum dry density and optimum moisture content of typical soils were determined in the laboratory in accordance with ASTM Standard Test D-1557, Method A. g) EXPANSION INDEX TEST: The expansion index of selected soils were determined in accordance with ASTM D4829. A 1-inch-thick by 4-inch-diameter specimen was prepared by compacting the soil with a specified energy at approximately 50 percent saturation. The specimen was placed in a consolidometer with porous stones at the top and bottom and a total normal pressure of psf was applied. The specimen was allowed to consolidate for a period of 10 minutes and then saturated. The change in vertical movement was recorded until the rate of expansion became nominal. CHRISTIAN WHEELER E n g i n e e r i n g SMOKETREE CONDOMINIUMS 6050 HENDERSON DRIVE LAN MESA, CALIFORNIA LAB SUMMARY BY: SCC DATE: DEC 2016 REPORT NO.: FIGURE NO.: B-1

30 GRAIN SIZE DISTRIBUTION (ASTM D422) Cobble Gravel Sand Coarse Fine Coarse Medium Fine U.S. Standard Sieves Silt and Clay 6" 3" 2"1½" 1"¾" ½" #4 #8 #16 #30 #50 #100 # Percent Passing Grain Size (mm) Symbol Sample No. 0-5' Liquid Plastic Plasticity Limit Limit Index D 10 D 30 D 60 C u C c USCS SC B-2

31 COLLAPSE POTENTIAL (ASTM D5333) Sample No. Consolidation Initial Initial Final Axial Before After Collapse Moisture Dry Density Moisture Stress Inundation Inundation Potential (%) (pcf) (%) (ksf) (%) (%) (%) 5' ' ' ' ½' ½' ' ' B-3

32 CORROSIVITY TESTS Sample No. CALTEST 417 CALTEST 643 CALTEST 422 Sulfate Content ph Resistivity Chloride Content (% SO 4 ) (ohm-cm) (ppm) 4½'-10' B-4

33 MAXIMUM DENSITY AND OPTIMUM MOISTURE CONTENT (ASTM D1557) Dry Density (pcf) Moisture Content (%) Sample No Sample Description Method Maximum Dry Density (pcf) Optimum Moisture Content (%) 0-5' Light brown, clayey sand (SC) A B-5

34 EXPANSION INDEX (ASTM D2849) Sample No. Initial Initial Final Expansion Expansion Moisture Dry Density Moisture Index Potential (%) (pcf) (%) 0-5' Medium 0-5' Low CLASSIFICATION OF EXPANSION POTENTIAL Expansion Index Expansion Potential 1-20 Very Low Low Medium High > 130 Very High B-6

35 Appendix C References

36 CWE December 21, 2016 Appendix C, Page C-1 REFERENCES Arevalo & Safino, Inc., 1974, Grading Plan for Greenleaf Terrace, La Mesa Tract No. 74-7, Sheets 1-5. Arevalo & Safino, Inc., 1974, Smoke Tree Condominium Plan, Sheets 1-11, Project SD California Division of Mines and Geology, 1998, Maps of Known Active Fault Near-Source Zones in California and Adjacent Portions of Nevada. Catlin Engineering, 1986, Preliminary Limited Site and Structural Investigation, Smoke Tree Condominiums, 6050 Henderson Drive, La Mesa, California, Project No. 55F5L, dated October 1, Jennings, C.W., 1975, Fault Map of California, California Division of Mines and Geology, Map No. 1, Scale 1:750,000. SD Engineering, 1998, Professional Service, File #981016ASG, Limited Inspection of Structural Soundness, 6050 Henderson Drive, La Mesa, California, dated October 16, SD Engineering, 2016, Professional Service, File #160331ASG, Limited Evaluation of Foundation Soundness, 6050 Henderson Drive #34, #35, & #6, La Mesa, California, dated March 31, Wesnousky, S.G., 1986, "Earthquakes, Quaternary Faults, and Seismic Hazards in California, in Journal of Geophysical Research, Volume 91, No. B12, pp 12,587 to 12,631, November 1986.