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HomeMy WebLinkAboutSDP 15-14; REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION; 2015-09-08REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION Proposed L.W. Office Building 2055 Corte Del Nogal Carlsbad, California Job No. 15-10840 08 September 2015 Prepared for: Lloyd Wells Gift Trust RECE1VEID DEC 052017 LAND DEVELOPMENT ENGINEERING 64pill Geotechnical Exploration, Inc. sw SOIL AND FOUNDATION ENGINEERING.. GROUNDWATER* ENGINEERING GEOLOGY 08 September 2015 Lloyd Wells Gift Trust 17083 Old Coach Road Poway, CA 92064 Attn: Mr. Ed Fudurich Job No. 15-10840 Subject: ReDort of Preliminary Geotechnical Investigation Proposed L.W. Office Building 2055 Corte Del Nogal Carlsbad, California Dear Mr. Fuderich: In accordance with your request, and our proposal of July 27, 2015, Geotechnical Exploration, Inc. has performed a preliminary geotechnical investigation for the subject property. The fieldwork was performed on August 11, 2015. If the conclusions and recommendations presented in this report are incorporated into the design and construction of the proposed residence, it is our opinion that the site is suitable for the project. This opportunity to be of service is sincerely appreciated. Should you have any questions concerning the following report, please do not hesitate to contact us. Reference to our Job No. 15-10840 will expedite a response to your inquiries. Respectfully submitted, GEOTCHNICAL EXPLORATION, INC. Jfme A. Cerros, P.E. R.C.E. 34422/G.E. 200 Senior Geotechnical Engineer 7420 TRADE STREET• SAN DIEGO, CA. 921210 (858) 549-7222w FAX: (858) 549-1604• EMAIL: geotechgeI-sd.com TABLE OF CONTENTS A. PROJECT SUMMARY AND SCOPE OF SERVICES SITE DESCRIPTION [II. FIELD INVESTIGATION IV. SOIL DESCRIPTION V GROUNDWATER SEISMIC CONSIDERATIONS LABORATORY TESTS AND SOIL INFORMATION CONCLUSION AND RECOMMENDATIONS GRADING NOTES LIMITATIONS PAGE 1 1 2 4 4 5 6 7 21 21 FIGURES Vicinity Map Site Plan lila-c. Exploratory Boring Logs IVa-b. Laboratory Data APPENDICES A. Unified Soil Classification System REPORT OF PRELIMINARY GEOTECHNICAL INVESTIGATION Proposed L.W. Office Building 2055 Corte Del Nogal Carlsbad, California Job No. 15-10840 The following report presents the findings and recommendations of Geotechnical Exploration, Inc. for the subject proposed commercial office building. I. PROJECT SUMMARY AND SCOPE OF SERVICES It is our understanding that the existing commercial lot will receive a new two-story office building and associated improvements in the northeast corner of the parking lot. Foundation loads are expected to be typical for this type of relatively light construction. The scope of work performed for this investigation included a site reconnaissance and subsurface exploration program, laboratory testing, geotechnical engineering analysis of the field and laboratory data, and the preparation of this report. The data obtained and the analyses performed were for the purpose of providing design and construction criteria for the project earthwork, building foundations, slab-on- grade floors, and concrete driveways. II. SITE DESCRIPTION The subject site is known as Assessor's Parcel No. 213-061-08-00, a portion of Lot 8, per Recorded Map 10062, in the County of San Diego, State of California. For the location of the site, refer to the Vicinity Map, Figure No. I. Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 2 The approximately 3-acre property is bordered on the northeast and southeast by existing commercial properties, on the northwest by Corte Del Nogal and the southwest by Corte Del Abeto. Refer to the Plot Plan, Figure No. IL Vegetation consists primarily of grass, shrubbery and mature trees. The lot has been previously graded and consists of a commercial building in the southwest corner with a paved parking lot and associated improvements. Elevations across the property range from approximately 265 feet above Mean Sea Level (AMSL) at the northeast corner, to 231 feet AMSL at the southwest corner. Information concerning approximate elevations across the site was obtained from a topographic site plan prepared by Architect Bruce W. Steingraber, dated May 5, 2015. IlL FIELD INVESTIGATION The field investigation consisted of a surface reconnaissance and a subsurface exploration program using a truck-mounted flight auger drill to investigate and sample the subsurface soils. Three exploratory borings were drilled in the area of the proposed new commercial building on August 11, 2015, to a maximum depth of 10.5 feet. The soils encountered in the borings were continuously logged in the field by our geologist and described in accordance with the Unified Soil Classification System (refer to Appendix A). The approximate locations of the borings are shown on the Site Plan, Figure No. II. Representative samples were obtained from the exploratory borings at selected depths appropriate to the investigation. All samples were returned to our laboratory for evaluation and testing. Standard penetration resistance blow counts Mai Proposed L.W. Office Building 30b No. 15-10840 Carlsbad, California Page 3 were obtained by driving a 2-inch O.D. split spoon sampler with a 140-pound hammer dropping through a 30-inch free fall. The sampler was driven a maximum of 18 inches and the number of blows for each 6-inch interval was recorded. The blows per foot indicated on the boring logs represent the accumulated number of blows that were required to drive the last 12 inches or portion thereof. Samples contained in liners were recovered by driving a 3.0-inch O.D. California sampler 18 inches into the soil using a 140-pound hammer. Boring logs have been prepared on the basis of our observations and laboratory test results. Logs of the borings are attached as Figure Nos. lila-c. The following chart provides an in-house correlation between the number of blows and the relative density of the soil for the Standard Penetration Test and the 3-inch sampler. SOIL DENSITY DESIGNATION 2-INCH O.D. SAMPLER BLOWS/FOOT 3-INCH O.D. SAMPLER BLOWS/FOOT Sand and Very loose 0-4 0-7 Nonplastic Silt Loose 5-10 8-20 Medium 11-30 21-53 Dense 31-50 54-98 Very Dense Over 50 Over 98 Clay and Very soft 0-2 0-2 Plastic Silt Soft 3-4 3-4 Firm 5-8 5-9 Stiff 9-15 10-18 Very stiff 16-30 19-45 Hard 31-60 46-90 Very Hard Over 60 Over 90 --- Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 4 IV. SOIL DESCRIPTION Existing fill soils, consisting of medium dense silty sands and clayey sands and very stiff sandy clay, were encountered in all the borings to depths of 2 to 6 feet. The materials encountered beneath the fill soils consisted of very dense clayey sands (formational sandstone). Based on our laboratory test results, the fill soils encountered are in a moderately compacted/medium dense condition. In our opinion, the sandy clay fill soils possess a medium to high potential for expansion. The exploratory boring logs and related information depict subsurface conditions only at the specific locations shown on the site plan and on the particular date designated on the logs. Subsurface conditions at other locations may differ from conditions occurring at these boring locations. Also, the passage of time may result in changes in the subsurface conditions due to environmental changes. V. GROUNDWATER Free groundwater was not encountered in the exploratory borings at the time of drilling. It must be noted, however, that fluctuations in the level of groundwater may occur due to variations in ground surface topography, subsurface stratification, rainfall, and other possible factors that may not have been evident at the time of our field investigation.. It should be kept in mind that grading operations can change surface drainage patterns and/or reduce permeabilities due to the densification of compacted soils. Such changes of surface and subsurface hydrologic conditions, plus irrigation of landscaping or significant increases in rainfall, may result in the appearance of surface or near-surface water at locations where none existed previously. The Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 5 appearance of such water is expected to be localized and cosmetic in nature, if good positive drainage is implemented, as recommended in this report, during and at the completion of construction. It must be understood that unless discovered during initial site exploration or encountered during site grading operations, it is extremely difficult to predict if or where perched or true groundwater conditions may appear in the future. When site fill or formational soils are fine-grained and of low permeability, water problems may not become apparent for extended periods of time. Water conditions, where suspected or encountered during construction, should be evaluated and remedied by the project civil and geotechnical consultants. The project developer and property owner, however, must realize that post-construction appearances of groundwater may have to be dealt with on a site-specific basis. VI. SEISMIC CONSIDERATIONS The San Diego area, as most of California, is located in a seismically active region. The San Diego area has been referred to as the eastern edge of the Southern California Continental Borderland, an extension of the Peninsular Ranges Geomorphic Province. The borderland is part of a broad tectonic boundary between the North American and Pacific Plates. The plate boundary is dominated by a complex system of active major strike-slip (right lateral), northwest trending faults extending from the San Andreas fault, about 70 miles east, to the San Clemente fault, about 50 miles west of the San Diego metropolitan area. Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 6 Based on our review of some available published information including the Geologic Map of the Oceanside 30'x60' Quadrangle, 2007 (Kennedy and Tan) there are no faults known to pass through the site. The prominent fault zones generally considered having the most potential for earthquake damage in the vicinity of the site are the active Rose Canyon and Coronado Bank fault zones mapped approximately 6 and 21 miles west of the site, respectively, and the active Elsinore and San Jacinto fault zones mapped approximately 30 and 52 miles northeast of the site, respectively. Although research on earthquake prediction has greatly increased in recent years, geologists and seismologists have not yet reached the point where they can predict when and where an earthquake will occur. Nevertheless, on the basis of current technology, it is reasonable to assume that the proposed residence may be subject to the effects of at least one moderate to major earthquake during its design life. During such an earthquake, the danger from fault offset through the site is remote, but relatively strong ground shaking is likely to occur. VII. LABORATORY TESTS AND SOIL INFORMATION Laboratory tests were performed on relatively undisturbed and bulk samples of the soils encountered in order to evaluate their index, strength, expansion, and compressibility properties. The following tests were conducted on the sampled soils: 1. Laboratory Compaction Characteristics (ASTM D1557-12) Determination of Percentage of Particles Smaller than No. 200 Sieve (ASTM 01140-14) Expansion Index (ASTM D4829-11) Ring-lined Barrel Density Test (ASTM D3550-07) Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 7 Laboratory compaction tests establish the laboratory maximum dry density and optimum moisture content of the tested soils and are also used to aid in evaluating the strength characteristics of the soils. The test results are presented on the boring Logs at the appropriate sample depths. The particle size smaller than a No. 200 sieve analysis aids in classifying the tested soils in accordance with the Unified Soil Classification System and provides qualitative information related to engineering characteristics such as expansion potential, permeability, and shear strength. The test results are presented on the boring logs at the appropriate sample depths. Based on our visual classification and our past experience with similar soils, it is our opinion that the existing fill and formational sandstone materials encountered possess a medium to high potential for expansion. Laboratory dry density tests were performed on selected relatively undisturbed samples of the existing fill materials encountered to aid in evaluating their degree of compaction. The test results are presented on the boring logs at the appropriate sample depths. VIII. CONCLUSIONS AND RECOMMENDATIONS The following conclusions and recommendations are based on the field investigation conducted by our firm, our laboratory test results, and our experience with similar soils and formational materials. The opinions, conclusions, and recommendations presented in this report are contingent upon Geotechnical Exploration, Inc. being retained to review the final plans and specifications as they are developed and to observe the site earthwork and installation of foundations. Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 8 If the geotechnical consultant of record is changed for the project, work shall be stopped until the replacement has agreed in writing to accept the responsibility within their area of technical competence for approval upon completion of the work. It shall be the responsibility of the permittee to notify the governing agency in writing of such change prior to the commencement or recommencement of grading and/or foundation installation work. The primary features of concern are the presence of potentially compressible existing fill soils and or expansion of fill soils within the up 3 feet, which are unsuitable in their present condition for the support of building improvements. In order to minimize the potential for excessive differential settlements due to compression of the existing fill soils they should be removed and recompacted to a minimum degree of compaction of 90 percent and 3 to 5 percent over optimum moisture content in all areas to receive new improvements. Depths of removal are anticipated to be approximately 3 feet. A. Prenaration of Soils for Site DeveloDment 1. Clearing and Stripping: The areas of new construction should be cleared of the existing structures to be abandoned and miscellaneous debris that may be present at the time of construction. After clearing, the ground surface should be stripped of surface vegetation as well as associated root systems. Holes resulting from the removal of buried obstructions that extend below the proposed finished site grades should be cleared and backfilled with suitable material compacted to the requirements provided under Recommendation Nos. 4, 5, and 6 below. Prior to any filling operations, the cleared and stripped vegetation and debris should be disposed of off-site. Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 9 Removal and Recompaction of Existing Fill Soils: In order to provide suitable support for the proposed new commercial building and associated improvements such as sidewalks and driveways, we recommend that all existing fill soils be removed and replaced as structural fill compacted to a minimum degree of compaction of 90 percent and 3 to 5 percent over optimum moisture content. The limits of recompaction should extend at least 5 feet beyond the perimeter limits of all new improvements. The recompaction work should consist of: (a) removing all existing fill soils down to a depth of 3 feet or down to the undisturbed formational materials where the formation is shallow; (b) scarifying, moisture conditioning, and compacting the exposed natural subgrade or firm compacted fill soils; and (c) replacing the materials as compacted structural fill. The areal extent of and depths required to remove the existing fills should be determined by our recresentative during the excavation work based on his examination of the soils being exposed. In addition, we recommend that any existing low expansion soil from the required removals be selectively stockpiled for use as capping material and wall backfills as recommended below in Recommendation Nos. 4 and 8. Subgrade Preparation: After the site has been cleared, stripped, and the required excavations made, the exposed subgrade soils should be scarified to a depth of 8 inches, moisture conditioned to at least 2 percent above the laboratory optimum, and compacted to the requirements for structural fill.. Material for Fill: All on-site soils with an organic content of less than 3 percent by volume are in general suitable for reuse as fill. Any required imported fill material should be a low-expansive granular soil. In addition, all Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 10 fill material should not contain rocks or lumps over 6 inches in greatest dimension and not more than 15 percent larger than 2/2 inches. No more than 25 percent of the fill should be larger than ¼-inch. All materials for use as fill should be approved by our representative prior to filling. Fill Compaction: All structural fill should in general be compacted to a minimum degree of compaction of 90 percent at a moisture content at least 3 to 5 percent above the optimum based upon ASTM D1557-12. Fill material should be spread and compacted in uniform horizontal lifts not exceeding 8 inches In uncompacted thickness. Before compaction begins, the fill should be brought to the recommended water by either: (1) aerating and drying the fill if it is too wet, or (2) moistening the fill with water if it is too dry. Each lift should be thoroughly mixed before compaction to ensure a uniform distribution of moisture. Permanent "lo We recommend that any required permanent cut and fill slopes be constructed to an inclination no steeper than 2.0:1.0 (horizontal to vertical). The project plans and specifications should contain all necessary design features and construction requirements to prevent erosion of the on- site soils both during and after construction. Slopes and other exposed ground surfaces should be appropriately planted with a protective groundcover. Fill slopes should be constructed to assure that the recommended minimum degree of compaction is attained out to the finished slope face. This may be accomplished by "backrolling" with a sheepsfoot roller or other suitable equipment as the fill is raised. Placement of fill near the tops of slopes should be carried out in such a manner as to assure that loose, uncompacted Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 11 soils are not sloughed over the tops and allowed to accumulate on the slope face. Trench and Retaining/Basement Wall Backfill: All backfill soils placed in utility trenches or behind retaining/basement walls should be compacted to a minimum degree of compaction of 90 percent. Backfill material should be placed in lift thicknesses appropriate to the type of compaction equipment utilized and compacted to a minimum degree of 90 percent by mechanical means. In pavement areas, that portion of the trench backfill within the pavement section should conform to the material and compaction requirements of the adjacent pavement section. In addition, the low- expansion potential fill layer should be maintained in utility trench backfill within the building, adjoining exterior slab and pool decking areas. Trench backfill beneath the level of the low-expansion fill layer should consist of on- site soils in order to minimize the potential for migration of water below the perimeter footings at the trench locations. Our experience has shown that even shallow, narrow trenches, such as for irrigation and electrical lines, that are not properly compacted can result in problems, particularly with respect to shallow ground water accumulation and migration. Surface Drainage: Positive surface gradients should be provided adjacent to the proposed new building and roof gutters and downspouts should be installed on the structure so as to direct water away from foundations and slabs toward suitable discharge facilities. Ponding of surface water should not be allowed anywhere on the site. Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 12 B Foundation Recommendations Footings: We recommend that the proposed new building be supported on conventional, individual-spread and/or continuous footing foundations bearing on recompacted fill soils prepared as recommended above in Recommendation No. 2. All footings should be founded at least 24 inches below the lowest adjacent finished grade. At the recommended depths, footings may be designed for allowable bearing pressures of 2,500 pounds per square foot (psf) for combined dead and live loads and 3,300 psf for all loads, including wind or seismic. The footings should, however, have a minimum width of 12 inches. General Criteria For All Footings: Footings located adjacent to the tops of slopes should be extended sufficiently deep so as to provide at least 8 feet of horizontal cover between the slope face and outside edge of the footing at the footing bearing level. Footings located adjacent to utility trenches should have their bearing surfaces situated below an imaginary 1.0 to 1.0 plane projected upward from the bottom edge of the adjacent utility trench. All continuous footings should contain top and bottom reinforcement to provide structural continuity and to permit spanning of local irregularities. We recommend that a minimum of two No. 5 top and two No. 5 bottom reinforcing bars be provided in the footings. A minimum clearance of 3 inches should be maintained between steel reinforcement and the bottom or sides of the footing. In order for us to offer an opinion as to whether the footings are founded on soils of sufficient load bearing capacity, it is essential Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 13 that our representative inspect the footing excavations prior to the placement of reinforcing steel or concrete. NOTE: The project Civil/Structural Engineer should review all reinforcing schedules. The reinforcing minimums recommended herein are not to be construed as structural designs, but merely as minimum reinforcement to reduce the potential for cracking and separations. Seismic Design Criteria: Site-specific seismic design criteria for the proposed garage are presented in the following table in accordance with Section 1613 of the 2013 CBC, which incorporates by reference ASCE 7-10 for seismic design. We have determined the mapped spectral acceleration values for the site, based on a latitude of 32.1208 degrees and longitude of 117.2768 degrees, utilizing a tool provided by the USGS, which provides a solution for ASCE 7-10 (Section 1613 of the 2013 CBC) utilizing digitized files for the Spectral Acceleration maps. Based on our past experience with similar conditions, we have assigned a Site Soil Classification of D. TABLE I MaDned Spectral Acceleration Values and Design Parameters [ S S1 I F8 I FI, Sms Smi SdS Sd1 I 1.071 0.414 1 1.072 1 1.586 1.148 0.656 0.765 0.437 Lateral Loads: Lateral load resistance for the structures supported on footing foundations may be developed in friction between the foundation bottoms and the supporting subgrade. An allowable friction coefficient of 0.35 is considered applicable. An additional allowable passive resistance equal to an equivalent fluid weight of 275 pcf acting against the foundations may be used in design provided the footings are poured neat against the adjacent properly Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 14 compacted fill materials. These lateral resistance values assume a level surface in front of the footing for a minimum distance of three times the embedment depth of the footing and any shear keys. Settlement: Settlements under building loads are expected to be within tolerable limits for the proposed structure. For footings designed in accordance with the recommendations presented in the preceding paragraphs, we anticipate that total settlements should not exceed 1 inch and that post-construction differential settlements should be less than 1/240. Retaining/Basement Walls: Based on the plans provided, there is no indication retaining walls will be utilized on the project. However, if small retaining walls will be used (i.e., elevator pit) we suggest the following recommendations. Retaining walls must be designed to resist lateral earth pressures and any additional lateral pressures caused by surcharge loads on the adjoining retained surface. We recommend that unrestrained (cantilever) walls with level backfill be designed for an equivalent fluid pressure of 38 pcf. We recommend that restrained walls (i.e., basement walls or any walls with angle points that restrain them from rotation) with level backfill be designed for an equivalent fluid pressure of 56 pcf. Wherever walls will be subjected to surcharge loads, they should also be designed for an additional uniform lateral pressure equal to one-third the anticipated surcharge pressure in the case of unrestrained walls and an additional one-half the anticipated surcharge pressure in the case of restrained walls. Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 15 For seismic design of unrestrained walls, we recommend that the seismic pressure increment be taken as a fluid pressure distribution utilizing an equivalent fluid weight of 14 pcf. For restrained walls, we recommend the seismic pressure increment be waived. The preceding design pressures assume that the walls are backfilled with low expansion potential materials (Expansion Index less than 50) and that there is sufficient drainage behind the walls to prevent the build-up of hydrostatic pressures from surface water infiltration. We recommend that back drainage be provided by a composite drainage material such as Miradrain 6000/6200 or equivalent. The back drain material should terminate 12 inches below the finish surface where the surface is covered by slabs or 18 inches below the finish surface in landscape areas. A subdrain (such as Total Drain or perforated pipe in an envelope of crushed rock gravel a maximum of 1 inch in diameter and wrapped with geofabric such as Mirafi 140N), should be placed at the bottom of retaining walls. Backfill placed behind the walls should be compacted to a minimum degree of compaction of 90 percent using light compaction equipment. If heavy equipment is used, the walls should be appropriately temporarily braced. C Concrete Slab-on-grade Criteria 15. Minimum Floor Slab Reinforcement: Based on our experience, we have found that, for various reasons, floor slabs occasionally crack, causing brittle surfaces such as ceramic tiles to become damaged. Therefore, we recommend that all slabs-on-grade contain at least a minimum amount of reinforcing steel to reduce the separation of cracks, should they occur, -s Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 16 1.5.1 Interior floor slabs should be a minimum of 5 inches actual thickness and be reinforced with No. 4 bars on 18-inch centers, both ways, placed at midheight in the slab. Slab subgrade soil should be verified by a Geotechnical Exploration, Inc. representative to have the proper moisture content within 48 hours prior to placement of the vapor barrier and pouring of concrete. 15.2 Following placement of any concrete floor slabs, sufficient drying time must be allowed prior to placement of floor coverings. Premature placement of floor coverings may result in degradation of adhesive materials and loosening of the finish floor materials. Concrete Isolation Joints: We recommend the project Civil/Structural Engineer incorporate isolation joints and sawcuts to at least one-fourth the thickness of the slab in any floor designs. The joints and cuts, if properly placed, should reduce the potential for and help control floor slab cracking. We recommend that concrete shrinkage joints be spaced no farther than approximately 20 feet apart, and also at re-entrant corners. However, due to a number of reasons (such as base preparation, construction techniques, curing procedures, and normal shrinkage of concrete), some cracking of slabs can be expected. Slab Moisture Protection and Vapor Barrier Membrane: Although it is not the responsibility of geotechriical engineering firms to provide moisture protection recommendations, as a service to our clients we provide the following discussion and suggested minimum protection criteria. Actual recommendations should be provided by the architect and waterproofing consultants. Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 17 Soil moisture vapor can result in damage to moisture-sensitive floors, some floor sealers, or sensitive equipment in direct contact with the floor, in addition to mold and staining on slabs, walls and carpets. The common practice in Southern California is to place vapor retarders made of PVC, or of polyethylene. PVC retarders are made in thickness ranging from 10- to 60- mu. Polyethylene retarders, called visqueen, range from 5- to 10-mil in thickness. These products are no longer considered adequate for moisture protection and can actually deteriorate over time. Specialty vapor retarding products possess higher tensile strength and are more specifically designed for and intended to retard moisture transmission into and through concrete slabs. The use of such products is highly recommended for reduction of floor slab moisture emission. The following American Society for Testing and Materials (ASTM) and American Concrete Institute (ACI) sections address the issue of moisture transmission into and through concrete slabs: ASTM E1745-97 (2009) Standard Specification for Plastic Water Vapor Retarders Used in Contact Concrete Slabs; ASTM E154-88 (2005) Standard Test Methods for Water Vapor Retarders Used in Contact with Earth; ASTM E96-95 Standard Test Methods for Water Vapor Transmission of Materials; ASTM E1643-98 (2009) Standard Practice for Installation of Water Vapor Retarders Used in Contact Under Concrete Slabs; and ACI 302.2R-06 Guide for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials. 17.1 Based on the above, we recommend that the vapor barrier consist of a minimum 15-mil extruded polyolefin plastic (no recycled content or woven materials permitted). Permeance as tested before and after Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 18 mandatory conditioning (ASTM E1745 Section 7.1 and sub-paragraphs 7.1.1-7.1.5) should be less than 0.01 perms (grains/square foot/hour in Hg) and comply with the ASTM E1745 Class A requirements. Installation of vapor barriers should be in accordance with ASTM E1643. The basis of design is Stego wrap vapor barrier 15-mu. We recommend that the recommended vapor barrier be placed directly on properly prepared subgrade soils and the floor slabs be poured directly on the vapor barrier 17.2 Common to all acceptable products, vapor retarder/barrier joints must be lapped and sealed with mastic or the manufacturer's recommended tape or sealing products. In actual practice, stakes are often driven through the retarder material, equipment is dragged or rolled across the retarder, overlapping or jointing is not properly implemented, etc. All these construction deficiencies reduce the retarder's effectiveness. In no case should retarder/barrier products be punctured or gaps be allowed to form prior to or during concrete placement. 17.3 Vapor retarders/barriers do not provide full waterproofing for structures constructed below free water surfaces. They are intended to help reduce or prevent vapor transmission and/or capillary migration through the soil and through the concrete slabs. Water- proofing systems must be designed and properly constructed if full waterproofing is desired. The owner and project designers should be consulted to determine the specific level of protection required. Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 19 17.4 Following placement of concrete floor slabs, sufficient drying time must be allowed prior to placement of any floor coverings. Premature placement of floor coverings may result in degradation of adhesive materials and loosening of the finish floor materials. Exterior Slab Reinforcement: As a minimum for protection of on-site 4 improvements, we recommend that all exterior pedestrian concrete slabs be founded on properly compacted and tested fill, with No. 3 bars at 18-inch centers, both ways, at the center of the slab, and contain adequate isolation and control joints. The performance of on-site improvements can be greatly affected by soil base preparation and the quality of construction. It is therefore important that all improvements are properly designed and constructed for the existing soil conditions. The improvements should not be built on loose soils or fills placed without our observation and testing. The exterior slabs should be provided with a thickened edge penetrating at least 8 inches into the on-site expansive soils and should include at least two No. 4 bars. For exterior slabs with the minimum shrinkage reinforcement, control joints should be placed at spaces no farther than 15 feet apart or the width of the slab, whichever is less, and also at re-entrant corners. Control joints in exterior slabs should be sealed with elastomeric joint sealant. The sealant should be inspected every 6 months and be properly maintained. D. Pavements Concrete Pavement: We recommend that concrete driveway pavements, including the garage slab, subject only to automobile and light truck traffic be Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 20 5 inches thick and be supported directly on properly prepared/compacted on- site subgrade soils. The concrete for areas subject to occasional heavy truck traffic (such as fire access) should have a minimum thickness of 6 inches. The upper 8 inches of the subgrade below the slab should be compacted to a minimum degree of compaction of 90 percent just prior to paving. The concrete should conform to Section 201 of The Standard Specifications for Public Works Construction, 2006 Edition, for Class 560-C-3250. In order to control shrinkage cracking, we recommend that saw-cut, weakened-plane joints be provided at about 15-foot centers both ways. The pavement slabs should be saw-cut as soon as practical but no more than 24 hours after the placement of the concrete. The depth of the joint should be one-quarter of the slab thickness and its width should not exceed 0.02-feet. Reinforcing steel is not necessary unless it is desired to increase the joint spacing. recommended above. Asphalt concrete pavement, if used, should consist of similar pavement section to the existing adjacent areas. E. General Recommendations 21. Project Start Up Notification: In order to minimize any work delays during site development, this firm should be contacted 24 hours prior to any need for observation of footing excavations or field density testing of compacted fill soils. If possible, placement of formwork and steel reinforcement in footing excavations should not occur prior to observing the excavations; in the event that our observations reveal the need for deepening or redesigning foundation structures at any locations, any formwork or steel reinforcement Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 21 in the affected footing excavation areas would have to be removed prior to correction of the observed problem (i.e., deepening the footing excavation, recompacting soil in the bottom of the excavation, etc.). IX. GRADING NOTES Geotechnical Exploration, Inc recommends that we be retained to verify the actual soil conditions revealed during site grading work and footing excavation to be as anticipated in this "Report of Preliminary Geotechnical Investigation" for the project. In addition, the compaction of any fill soils placed during site grading work must be observed and tested by the soil engineer. It is the responsibility of the grading contractor to comply with the requirements on the grading plans and the local grading ordinance. All retaining wall and trench backfill should be properly compacted. Geotechnical Exploration, Inc. will assume no liability for damage occurring due to improperly or uncompacted backfill placed without our observations and testing. X. LIMITATIONS Our conclusions and recommendations have been based on available data obtained from our document review, field investigation and laboratory analysis, as well as our experience with similar soils and formational materials located in this area of San Diego. Of necessity, we must assume a certain degree of continuity between exploratory excavations. It is, therefore, necessary that all observations, conclusions, and recommendations be verified at the time grading operations begin or when footing excavations are placed. In the event discrepancies are noted, additional recommendations may be issued, if required. ZAM Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 22 The work performed and recommendations presented herein are the result of an investigation and analysis that meet the contemporary standard of care in our profession within the County of San Diego. No warranty is provided. This report should be considered valid for a period of two (2) years, and is subject to review by our firm following that time. If significant modifications are made to the building plans, especially with respect to the height and location of any proposed structures, this report must be presented to us for immediate review and possible revision. It is the responsibility of the owner and/or developer to ensure that the recommendations summarized in this report are carried out in the field operations and that our recommendations for design of this project are incorporated in the structural plans. We should be retained to review the project plans once they are available, to see that our recommendations are adequately incorporated in the plans. This firm does not practice or consult in the field of safety engineering. We do not direct the contractor's operations, and we cannot be responsible for the safety of personnel other than our own on the site; the safety of others is the responsibility of the contractor. The contractor should notify the owner if any of the recommended actions presented herein are considered to be unsafe. The firm of Geotechnical Exploration, Inc. shall not be held responsible for changes to the physical condition of the property, such as addition of fill soils or changing drainage patterns, which occur subsequent to issuance of this report and the changes are made without our observations, testing, and approval. Proposed L.W. Office Building Job No. 15-10840 Carlsbad, California Page 23 Once again, should any questions arise concerning this report, please feel free to contact the undersigned. Reference to our Job No. 15-10840 will expedite a reply to your inquiries. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. <a—e— ~' - 1iThACerros, P.fi R.C.E. 34422/G.E. 2007 Senior Geotechnical Engineer Ja . elser Senior Project Geologist CESSI No.002007 W- EXP9/3Q", VICINITY MAP Thomas Bros Guide San Diego Counti pg 1127-D3 LW Office Building 2055 Corte Del Nogal Carlsbad, CA. Figure No. I Job No. 15-10840 W OFFJUILD?NG ii =9 :--- -- /-•--/ -- -- /1- -- -T" ------1 C RTE DEL N O - - I - - - - A - I 2 B-I _ B- I - SCALE: 1 =80 i \ - ' \I I - - - 7 - / LEGEND - ApproxImate Location F. 115 B-3 of Exploratory Boning / - DEL \. - -.- // PLOT PLAN / - LWOffllce Building / --- - - 2086 Cofle Del NogaI Carlsbad, CA REFERENCE: This Plot plan was prepared from SITE PLAN Figure No.!! an ejloflng SIW PLAN byArohftect-Bsuce W Job No. 15-10840 SI&ngreberdalsd 5-5-16 .smi from on-Me field reconnaissance pet'tormed by GE1 IWTWM Exptlon, Inc. August 2016 15-10810.p.d EQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED Truck-mounted Hollow Stem Drill Rig 84nch diameter Boring 8-11-15 SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH LOGGED BY ± 260' Mean Sea Level Not Encountered JAB FIELD DESCRIPTION - AND CLASSIFICATION 0 l DESCRIPTION AND REMARKS (Gain size, Density, Moisture, Color) N Mel - GRASS AND LANDSCAPE TOPSOIL - - - - - - SILTY SAND, fine-grained, with roots and SM - rootlets. Medium dense. Dry. Yellow-brown. 2 FILL (Qaf) CLAYEY SAND, fine-grained, low SC 50/ plasticity. Very dense. Moist. Light gray. 5.5" - SANTIAGO FORMATION (Tsa) 83 2" - Bulk sample from 2'- 41. - 40% passing #200 sieve. 10.5 122.5 36 6 - - abundant iron oxide staining from 6'- 7'. - 50/ 31 5.5" 8- 67 2" 10- Bottom @9' Y PERCHED WATER TABLE I JOSNAME L.W. Office Building BULK BAG SAMPLE SITE LOCATION J IN-PLACE SAMPLE 2055 Corte del Nogal, Carlsbad, CA MODIFIED CALIFORNIA SAMPLE JOB NUMBER REVIEWED BY LDRIJAC I LOG No. 15-10840 we B=1[] NUCLEAR FIELD DENSITY TEST STANDARD PENETRATION TEST1 lila 'QUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED Truck-mounted Hollow Stem Drill Rig 8-inch diameter Boring 8-11-15 SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH LOGGED BY 1261' Mean Sea Level Not Encountered JAB DESCRIPTION loll CLASSIFICATION DESCRIPTION AND REMARKS _ AND ___ FIELD ______ NOMMIMrn!URJEU SANDY CLAY, with minor angular gravel ;*!V*'N*1 to 1/2" in diameter. Very stiff. Moist. Dark gray iI'(i wt. some !ran o)dde staining; low plasticity; organics. . I.. • flit trace of 1 Bulk sample from X- 6'. 61% passing #200 sieve. CLAYEY SAND, fine-grained. Very • dense Dark gray-brown with SANTIAGO FORMATION (Tsa) ØyUBulk Isample fromw#.-rsJ.1. Ii I PERCHED WATER TABLE BULK BAG SAMPLE IN-PLACE SAMPLE MODIFIED CALIFORNIA SAMPLE [] NUCLEAR FIELD DENSITY TEST STANDARD PENETRATION TEST JOB NAME L.W. Office Building SITE LOCATION 2055 Corte del Nagai, Carlsbad, CA JOB NUMBER REVIEWED BY LDR!JAC LOG No. B-2 15-10840 FIGURE NUMBER IlIb EQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED Truck-mounted Hollow Stem Drill Rig 8-inch diameter Boring 8-11.15 SURFACE ELEVATION GROUNDWATER/ SEEPAGE DEPTH LOGGED BY 1260' Mean Sea Level Not Encountered JAB FIELD DESCRIPTION AND CLASSIFICATION la 11 it 0 DESCRIPTION AND REMARKS (Grain size, Density, MosIure, Color) ill g .6 J ft DEAD GRASS AND LANDSCAPE TOPSOIL - - - - - - CLAYEY SAND, fine-grained, with minor rootlets SC - and organics; low plasticity. Medium dense. Dry to slightly moist. Dark gray-brown. FILL (Qaf) 2- 701 311 • _____________________________________ 9.8 106.1 11.5' CLAYEY SAND, tine-grained. Very dense. SC - Moist Light gray with some iron oxide and yellow staining. SANTIAGO FORMATION (Tsa) 81 2' 4- Bulk sample from 3'- 7'. 6- - - heavy iron oxide staining; trace manganese . staining, becomes red-brown. 8 84 2' Bottom @ 8.5' 10- 1 PERCHED WATER TABLE BULK BAG SAMPLE J IN-PLACE SAMPLE MODIFIED CALIFORNIA SAMPLE [] NUCLEAR FIELD DENSITY TEST STANDARD PENETRATION TEST JOB NAME L.W. Office Building SITE LOCATION 2055 Corte del Nogal, Carlsbad, CA JOB NUMBER REVIEWED BY LDR/JACI LOG No. 15.10840 _________ Gio(aduikall FIGURE NUMBER siploneon. tnc. B=3 IlIc ••UUU••UikI uiuui•u•u& U•U•••UILVL IU••U••UUiI1 EMEMEMENEEMBEL MOOMMEMEREaskal MOMMEMEMEMOMM EMERIMMEMENOWKS UUUUUIU•IRULUL U1IJtILJ Immommommisrunkil I.-l i e U: ...U•Wi•U&I?LII ••uui•••ii...ni. ' I ••u••uur1••u•uuI•i MEMAIMMOMMOMMEMEMON EMEMEMMUMMEMEMOMMI .....R..........' MEMOMMEMEMEEMEMEMOR .••••U•U•U••UU•Uh ••uuuuu•u•u•.ui••••i ••U••i••UiiU•IlIUI•ih uu•u•i• •••U••S•I•lh - u••u•i•uu•u•u•••uu••iisi .......u....I.............. 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MMMMMMMMMMMwMm MMEMEMERIMEME u••ua•••••iuiii - - fu I- I MMAIMEMEMIMMEWMENU ••UU••ULJ••••iIik ••u•••wuuuiu•i MMMMMMMvMMMMMmMm MEMNON i& Uiil•i••i••••I•IiL MMMMMMMMMMMMMMMMMM MMMMMMMMMMMMAIMMIMMMMXM Wall UUUU•U••UUU•RUI1IL i•Ui••••UUUi••L uu••••••••••u•u•iii II u A 'I -I •••••U•UUUUUUUUR••Ik ....................'. ••iuu•iuuaa•uau•i&e •••uuuiu••u••u•uu•im•tu ••u•u•iu•uu•uu•uuuuu•i u••••umuiu••u•••••i•iu•. ••U•••••U••••U•••••••U•••IIk 'WI, ••a•uuu••u•••uium•uu•uuu•u•i ••uuuuuu•••u••iuuuu•uuuuuuuuu uu•uu••••u•••••••u•••R••a••uuuiui uu•uuu•iuu•uuu•uuuuuuu•u••u•uuuuu•rni uu..uuu•u••••u•••i••uuuuuuuu•••u••uauumt ••••a•••••.••••••.R•••••••••••u•••••••••••• APPENDIX A UNIFIED SOIL CLASSIFICATION CHART SOIL DESCRIPTION Coarse-grained (More than half of material is larger than a No. 200 sieve) GRAVELS, CLEAN GRAVELS GW Well-graded gravels, gravel and sand mixtures, little (More than half of coarse fraction or no fines. is larger than No. 4 sieve size, but smaller than 3") OP Poorly graded gravels, gravel and sand mixtures, little or no fines. GRAVELS WITH FINES (Appreciable amount) SANDS, CLEAN SANDS (More than half of coarse fraction is smaller than a No. 4 sieve) SANDS WITH FINES (Appreciable amount) GC Clay gravels, poorly graded gravel-sand-silt mixtures SW Well-graded sand, gravelly sands, little or no fines SP Poorly graded sands, gravelly sands, little or no fines. SM Silty sands, poorly graded sand and silty mixtures. SC Clayey sands, poorly graded sand and clay mixtures. Fine-grained (More than half of material is smaller than a No. 200 sieve) SILTS AND CLAYS Liquid Limit Less than 50 ML Inorganic silts and very fine sands, rock flour, sandy silt and clayey-silt sand mixtures with a slight plasticity CL Inorganic clays of low to medium plasticity, gravelly clays, silty clays, clean clays. OL Organic silts and organic silty clays of low plasticity. Liquid Limit Greater than 50 MH Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts. CH Inorganic clays of high plasticity, fat clays. OH Organic clays of medium to high plasticity. HIGHLY ORGANIC SOILS PT Peat and other highly organic soils (rev. 6105) 4