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HomeMy WebLinkAboutCT 81-10; Carlsbad Research Center Lot 29; Soils Report; 1991-07-25- - - - - - - - - - - - - - REPORT OF SOIL INVESTIGATION Proposed C 6 L International Building Lot 29 - Carlsbad Research Center Southeast Corner of Balfour Court and Rutherford Road Carlsbad, California Du%l3&!-51t F= 291.34 Job No. 91-6072 25 July 1991 Prepared for: Mr. Robert Plant Plant - Cook Architects - GEOTECHNICAL EXPLORATION, INC. SOIL & FOUNDATION ENGINEERING l GROUNDWATER HAZARDOUS MATERIALS MANAGEMENT . ENGINEERING GEOLOGY - 25 July 1991 - - - - - - - - - - - - - - Mr. Robert Plant PLANT - COOK ARCHITECTS 2385 Camino Vida Roble, Suite 107 Carlsbad, CA 92009 Job No. 916072 Subject: Report of Soil lnvertiqatlon Proposed C & L International Building Lot 29 - Carlsbad Research Center Southeast Corner of Balfour Court and Rutherford Road Carlsbad, California Dear Mr. Plant: In accordance with your request, Ceotechnlcal Exploratlon. Inc. has performed an investigation of the soil conditions at the subject lot. The field work was performed on July 10, 1991. it is our understanding that the previously graded lot is being developed to receive a 22,000 square foot commercial building and associated improvements. The structure is to be a maximum of one story in height and will be constructed of standard type building materials utilizing slab-on-grade construction. Our investigation revealed that the lot is underlain by dense formational materials and up to at least 18 feet of highly expansive, compacted fill soils that should provide adequate bearing strength for the proposed structure. In our opinion, if the conclusions and recommendations presented in this report are implemented during site preparation, the lot should be suited for the proposed development. The work performed and recommendations presented in this report are the result of an investigation and analysis which meets the contemporary standard of care in our profession within the San Diego County area. This opportunity to be of service is sincerely appreciated. Should you have any questions concerning the following report, please contact our office. Reference to our Job No. 916072 will help to expedite a response to your inquiry. Respectfully submitted, XPLORATION. INC. WRLllb 7420 TRADE STREET l SAN DIEGO, CALIFORNIA 92121 l (619) 549-7222 l FAX: (619) 549-1604 - - - - - .- .- - I. II. III. IV. V. VI. VII. VIII. IX. X. TABLE OF CONTENTS SCOPE OF WORK BACKGROUND INFORMATION SITE DESCRIPTION FIELD INVESTIGATION DESCRIPTION OF SOILS CROUNDWATER AND DRAINAGE CONDITIONS LABORATORY TESTS 8 SOIL INFORMATION CONCLUSIONS AND RECOMMENDATIONS GRADING NOTES LIMITATIONS FIGURES I. Plot Plan Ila-e. Trench Logs I Ila-e. Laboratory Test Results APPENDICES A. Unified Soil Classification Chart B. General Earthwork Specifications C. General Discussion of Expansive Soil Behavior - - - - - PAGE 1 2 2 3 3 4 5 6 18 16 - - - - - - - REPORT OF SOIL INVESTIGATION Proposed C E L International Building Lot 29 - Carlsbad Research Center Southeast Corner of Balfour Court and Rutherford Road Carlsbad, California Job No. 91-6072 The following report presents the findings and recommendations of Geotechnical Exploration, Inc. for the subject project. I. SCOPE OF WORK It is our understanding, based on communications with Ms. Robert Plant and review of site plans provided by Plant - Cook Architects, that the lot has been previously graded and is intended for the construction of a 22,000 square foot commercial building with associated improvements and parking areas. With the above in mind, the scope of work is briefly outlined as follows: 1. 2. 3. 4. 5. Identify and classify the surface and subsurface soils to depths, in conformance with the Unified Soil Classification System (refer to Appendix A). Recommend an allowable bearing pressure for the existing soils. Recommend site preparation procedures. Estimate the anticipated settlement of the natural-ground soils, as well as the compacted fill soils, under the anticipated structural loads. Provide preliminary foundation design informatlon and the active and passive earth pressures to be utilized in design of any retaining walls and foundation structures. - - - - - - - - - - - - - - - - - - Car lsbad Research Center Carlsbad, California II. BACKGROUND INFORMATION Job No. 91-6072 Page 2 During the course of our investigation, we discussed the project with Mr. Robert Plant and reviewed the following documents concerning the subject lots. 1. San Diego Ceotechnical Consultants, Inc., September 10, 1984, As-graded Ceotechnlcal Report, Rough Grading Completed -- Carlsbad Research Center, Phase II and I II, Carlsbad, California; Job No. SD1162-10. 2. San Diego Soils Engineering, Inc., July 26, 1982, Supplemental Preliminary Ceotechnical Investigation, Carlsbad Research Center, Phase II and Ill, Carlsbad, California; Job No. 1162-00. 3. Woodward-Clyde Consultants, April 27. 1981, Preliminary Soil and Geologic Investigation -- Carlsbad Research Center, Carlsbad, California. Ill. SITE DESCRIPTION The property is known as: Lot 29 of Carlsbad Research Center, Tract 81-10 in the City of Carlsbad, State of California. The previously graded lot consists of approximately 1.50 acres and is located at the southeast corner of Balfour Court and Rutherford Road in the City of Carlsbad. The property is bordered on the north by Rutherford Road, on the west by Balfour Court, and on the south and east by developed commercial and industrial properties. There were no structures on the lot at the time of our Investigation. However, a circular concrete storm drain inlet, roughly 5 feet In diameter, exists In the northwest corner of the lot. Vegetation on the - - - - - - - - - - - - - - - - - - Carlsbad Research Center Carlsbad, California Job No. 91-6072 Page 3 lot consists primarily of native weeds and grasses with ornamental landscaping and trees bordering the streets. It Is our understanding that a water main crosses the center of the lot, running from east to west. The property has been graded into a relatively level lot bounded on the east by the toe of a 6-foot-high fill slope, on the south by the toe of a 4-foot-high fill slope, and on the north and west by the toe of existing landscaped fill slopes. The lot slopes gently to the northwest with approximate elevations ranging from 280 feet MSL to 276 feet MSL. Survey information was obtained from a grading plan prepared by Rick Engineering Company, that was included in the As-built Ceotechnical Report, dated September 10, 1984. IV. FIELD INVESTIGATION Five test trenches were placed on the lot, specifically in areas where the structure and improvements are to be located and where representative soil conditions were expected. The trenches were located in the field by referring to a site plan, prepared by Plant-Cook Architects, dated March 29, 1991. The trenches were observed and logged by our field representative, and samples were taken of the predominant soils throughout the field operation. Trench logs have been prepared on the basis of our observations and the results have been summarised on Figure No. II. The predominant soils have been classified in conformance with the Unified Soil Classification System (refer to Appendix A). V. DESCRIPTION OF SOILS The lot, in general, Is overlain with a varying thickness of compacted fill soils reaching a maximum thickness of at least 18 feet in the northeast portion of the lot (T-3). The fills are medium dense and - - - - - - - - Carlsbad Research Center Carlsbad, California Job No. 91-6072 Page 4 consist of tan-gray and dark gray-brown, sandy silt with clay and dark gray-green and orange, clayey silt with rock fragments and siltstone chunks. These soils are considered to have a high expansion potential and low consolidation potential. On a portion of the lot, the fill soils are underlain by approximately 1 to 2 feet of natural topsoil consisting of dark gray, silty clay and sandy silt with clay and organics. The topsoil was only encountered in the southern portion of the site CT-2 and T-4). The deeper fill in the northern portion of the site (T-l and T-3) appears to be reworked slopewashlalluvium in what appears to be the bottom of a canyon fill (see Figure No. I and II). The entire site is underlain at depth by dense, silty and sandy, formational materials, which are considered to have a high expansion potential but have good bearing-strength characteristics. VI. GROUNDWATER AND DRAINAGE CONDITIONS Perched groundwater (seeps) were encountered at a depth of 10 feet in T-2 and T-4 during the course of our field investigation. At thls depth we do not expect the perched groundwater to cause significant problems, if the property is developed as presently designed and the building is well-drained and insulated. It should be kept in mind, however, that any required additlonal grading operations may 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 minor amounts of surface or near-surface water at locations where none existed previously. The damage from such water is expected to be minor and cosmetic in nature, if good positive drainage Is implemented at the completion of construction. Corrective action should be taken on a site-specific basis if, and when, it becomes necessary. -. Car lsbad Research Center Carlsbad, California Job No. 91-6072 Page 5 - - - - - - - - - - - - - - - - VII. LABORATORY TESTS AND SOIL INFORMATION Laboratory tests were performed on the disturbed and relatively undisturbed soil samples in order to evaluate their physical and mechanical properties and their ability to support the proposed structure. The following tests were conducted on the sampled soils: 1. Moisture/Density Relations (ASTM D1557-78, Method A) 2. Moisture Content (ASTM D2216-80) 3. Field Density Tests (ASTM D1188-83, D1556-82 and 02937-83) 4. Mechanical Analysis (ASTM D422-721 5. Atterberg Limits (ASTM D4318-841 6. Expansion Tests (UBC Method 29-2) 7. Consolidation Tests (ASTM D2435-80) The relationship between the moisture and density of undisturbed soil samples gives qualitative information regarding sol I strength characteristics and soil conditions to be anticipated during any future grading operation. The Mechanical Analysis and Atterberg Limit tests were used to aid in the classification of the soils according to the Unified Soil Classification System. The expansion potential of clayey soils was determined utilizlng the Uniform Building Code Test Method for Expansive Soils (UBC Standard No. 29-2). In accordance with the UBC (Table 29-C). expansive soils are classified as follows: Expansion Index 0 to 20 21 io 50 51 to 90 91 to 130 Above 130 Potential Expansion Very Low Low Medium High Very High - - - - - - -- Carlsbad Research Center Carlsbad, California Job No. 91-6072 Page 6 According to the UBC Test Method for Expansive Soils, the clayey soils tested have a high expansion potential, with an expansion index of 130. However, an additional test was run at approximately 5 percent above optimum moisture and 90 percent relative compaction, which yielded an equivalent expansion index of 50. Consolidation tests were performed on relatively undisturbed samples of compacted fill soils. The soils were contained In l-inch-high brass rings and loaded into a consolidometer. The specimens were subjected to increased loads and the resulting consolidations noted. The consolidation test aids in determining anticipated settlements of the fill soils under the proposed buildings loads and the weight of any overburden fill soils. - - - - - Based upon the above laboratory test data, observations of the primary soil types on the project, and our previous experience with laboratory testing of similar solls, our Geotechnical Engineer has assigned conservative values for friction angle cohesion to those soils which will have significant lateral support or bearing functions on the project. These values are presented in Figure No. Ill and have been utilised In recommending the allowable bearing value as well as the active and passive earth pressures for wall and footing designs. VIII. CONCLUSIONS AND RECOMMENDATIONS The following conclusions and recommendations are based upon the practical field investigation conducted by our firm, and resulting laboratory tests, in conjunction with our knowledge and experience with the soils in this area of the City of Carlsbad. GotechnIcal Exploration, Inc. revlewed the “As-graded Geotechnical Report -- Carlsbad Research Center -- Phase II and III,” dated September 10, 1984, prepared by San Diego Geotechnical Consultants, - - -. - - - .- - - - - - - Carlsbad Research Center Carlsbad, California Job No. 91-6072 Page 7 Inc. Based on our findings and review, it appears that site preparation and fill compaction was performed in accordance with the local industry standards. Our investigation revealed the lot is underlain by dense formational materials and up to at least 18 feet of compacted fill soils. The fill depth is greater toward the northeast, ranging from approximately 6 feet in the southwest corner of the lot (T-2) to at least 18 feet in the northeast corner [T-3). The fill soils were found to be generally well compacted and at or above optimum moisture. The upper 2 feet of fill soils, however, have become dried and cracked or soft since its placement (due to exposure to the elements) and should be reworked prior to site development. Although a few of the in-place density tests taken on samples of the encountered fill material yielded results of less than 90 percent of Maximum Dry Density in accordance with ASTM 1557-78 (90 percent represents the minimum industry standard for compaction of artificial fill soils), our qualitative assessment of the fill is that it was generally well compacted. For details and laboratory test results, refer to Figure Nos. II and Ill. The prevailing soils encountered on the subject site are highly expansive, apparently well-compacted fill soils. It Is our opinion that these soils should provide adequate bearing strength for the proposed structure, provided that the 2 feet of loose surface soils are removed and recompacted as part of the site preparation and that foundations are sufficiently reinforced for the expansion forces of the bearing soils. Drainage should be well controlled at all times to limit the effects of water on the expansive soil (refer to Appendix C of this report for a more in depth discussion of expansive soils). - .- - - - - - - -- - - - - - - Carlsbad Research Center Carlsbad, California Job No. 91-6072 Page 8 We have recommended pre-moisturlzing the existing surface soils and designing the foundation and slab for the anticipated expansion forces of the bearing soils. An alternative would be treating the soil with hydrated lime to decrease the expansion potential. On this site, it may be economically feasible to perform the lime treatment during the proposed grading, thus eliminating the need for extensive reinforcement of the foundation and slab. A. Preparation of Soils for Site Development 1. Any existing debris and vegetation observed on the lot must be removed prior to the preparation of the building pad and/or areas to receive structural improvements and be properly disposed of. 2. Due to the extensive deslccatlon cracks that exist on the surface of the lot, and to provide a uniform soil base for the proposed structure, improvements and pavement, the existing loose and desiccated surface soils shall be excavated to a depth of at least 2 feet, or as per the direction of our field technician. The excavated soils shall be cleaned of any debris and deleterious materials and watered to approximately 5 percent above optimum moisture content, but not less than 3 percent above the optimum. The bottom of the excavation shall be scarified moisture conditioned similarly and compacted to at least 90 percent of maximum dry density. The properly prepared fill soils should be placed in layers not exceeding 8 inches in thickness, and be compacted to at least 90 percent of Maximum Dry Density (ASTM D1557-78). Soils shall not be compacted over 93 percent, since the higher the density the higher the expansion potential. Carlsbad Research Center Carlsbad, California Job No. 91-6072 Page 9 - - - - - - -_ .- - - - - - - - - -~ 3. 4. 5. B. 6. If the lime treatment alternative is chosen, we recommend treatment to a depth of at least 1 foot below the bottom of the foundation (at least 3 feet). Highly expansive soils typically require between 3 and 8 percent lime to effectively decrease the expansion potential. If this alternative is chosen, our firm should perform additional testing to determine the actual amount of lime to be added to the soil. This option can be beneficial if the footings and slabs cannot be poured shortly after gradfng completion. No uncontrolled fill soils shall remain on the lot after completion of any future site work. In the event that temporary ramps or pads are constructed of uncontrolled fill soils during the grading operation, the loose fill soils shall be removed and/or recompacted prior to completion of the grading operation. Any buried objects which might be discovered on the lot shall be removed and the resulting excavation be properly backfilled with approved on-site or imported fill soils, and shall then be compacted to at least 90 percent of Maximum Dry Density. Any backfill soils placed in utility trenches or behind retaining walls which support structures and other improvements (such as patios, sidewalks, driveways, pavements, etc.) shall be compacted to at least 90 percent of Maximum Dry Density. Design Parameters for Foundations and Retaininq Walls The recommended allowable bearing value for design of founda- tions for the proposed structure is 3,000 pounds per square foot. This load-bearing value may be utillzed in the design of continuous foundations and spread footings when founded a - - - - - - - - - - - - - - - - - - Carlsbad Research Center Carlsbad, California Job No. 91-6072 Page 10 minimum of 24 inches into the firm natural ground or compacted fill, measured from the lowest adjacent grade at the time of foundation construction. This load-bearing value may be increased one-third for design loads that include wind or seismic analysis. If imported soils are required to bring the site to grade, the imported soils should be obtained from an approved off-site borrow area. We have recommended 24-Inch-deep footings to provide an added moisture barrier around the perimeter of the structure and also to help accommodate any minor deflections due to possible differential settlement caused by the variable thickness of fill under the structure and the typical soil heave experienced when constructing on highly expansive soil. Based on our laboratory test results, and our experience with the soil types on the subject site, the soils should experience differential settlement in the magnitude of less than 1 inch in 25 feet for any two adjacent columns under a structural load of 3.000 pounds per square foot. 7. Due to the highly expansive nature of the on-site soils, we recommend that all conventional footings and slabs contain at least a nominal amount of reinforcing steel to reduce the separation of cracks, should they occur. 7.1 A minimum of steel for continuous footings should include at least four No. 5 steel bars continuous, with two bars near the bottom of the footing and two bars near the top. 7.2 Isolated square footings should contain, as a minimum, a grid of No. 5 steel bars on 12-inch centers, in both directions, with no less than two bars each way. - - - - - - - - - - - - - Carlsbad Research Center Carlsbad, California Job No. 91-6072 Page 11 7.3 Floor slabs should be a minimum of 5 inches actual thickness and be reinforced with at least No. 3 steel bars on 15-inch centers, in both directions, placed at midheight in the slab. Slabs should be underlain by a 3-inch-thicic layer of clean sand (S-E. = 30 or greater) overlying a 6-mii visqueen membrane. It is particularly important to “pre- expand” expansive soils beneath the proposed concrete floor slab and foundation. Slab subgrade soil shall be thoroughly moistened prior to placement of the vapor barrier and pouring of concrete. We highly recommend that slab and foundation construction be performed immediately following the grading operation. This will help reduce problems that may occur from settlement due to soil shrinkage and dessication or soil expansion. In any case, it is recommended that moisture content of subgrade soil for slabs and footings be checked within 48 hours prior to concrete placement to verify that it is at least 5 percent above optimum and has penetrated at least 1 foot below subgrade and foundation bottom level. Water penetration in clayey soils is slow, and the fastest way to accomplish it is during grading. We recommend the project Civil/Structural Engineer incor- porate 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. In any case, spacing of control joints shall not exceed 25 feet between centers. 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 still be expected. - - - _- - - - - - - - - - - - - - - - Carisbad Research Center Carlsbad, California Job No. 91-6072 Page 12 NOTE: The project Structural Engineer shall review ail reinforcing schedules. The reinforcing minimums racom- mended herein are not to be construed as structural designs, but merely as minimum safeguards to reduce possible crack separations. The actual reinforcing schedule shall be as per the direction of the Structural Engineer based upon an anticipated differential settlement of less than 1 inch in 25 feet horizontally. It is important that the foundation and slab are designed for the actual anticipated loads and intended use. Though not required. we recommend that the Structural Engineer consider use of a post-tensioned slab foundatim due to the highly expansive soil. Such a foundation has typically performed well in similar site conditions. if a post-tensioned slab foundation is used, we recommend that a perimeter footing extending to at least 24 inches in depth is used. a. As a minimum for protection of on-site improvements, it is recommended that all nonstructural concrete slabs (such as patios, walkways, etc.) be underlain by at least 3 inches of clean sand, include 6 x 6-lO/lO welded wire mesh at the center of the slab, and contain adequate isolation joints spaced no farther than 15 feet apart or the width of the slab, whichever is less. It should be noted that standard concrete improvements may not perform well, due to the expansive soil conditions. As such, each improvement should be designed to tolerate the on-site conditions. The performance of on-site improvements can also be greatly affected by soil base preparation and the quality of construction, and Is therefore the responsibility of the designer and the contractor installing the improvements. Moisture content - - - - - - - - - - - - - - - - - Carlsbad Research Center Carlsbad, California Job No. 91-6072 Page 13 and compaction of subgrade soils verification for outside improve- ments is also recommended. A representative of our firm shall check that within 48 hours prior to concrete pouring. If moisture and/or compaction are inadequate, soil rework, reconditioning and recompaction will be recommended. C. Retaining Walls It is our understanding that a 4-foot-high retaining wall is proposed along the eastern property boundary adjacent to the proposed asphalt parking lot. The wall should be designed by the project structural/ civil engineer utilizing the following design criteria. 9. The active earth pressure (to be utilized in the design of canti- lever, walls) shall be based on an Equivalent Fluid Weight of 80 pounds per cubic foot (for level backfill only). Any surcharge load effect shall be added to the soil pressure and included in the retaining wall design if the load is within a horizontal distance equal to the height of the wall. In the event that a retaining wall is surcharged by sloping backfill, the design active earth pressure shall be based upon laboratory tests of the specific soils at the site of the proposed retaining wall. The design pressures presented above are based on utilisation of an uncontrolled mixture of soils native to the site in backfill operations. In the event that imported, clean granular fill soils or approved on-site clean sands are utilired as backfill material, this firm should be contacted for possible reduction of design pressures for level backfill, sloping backfill or restrained wall conditions. - - - - - - - - - - - - Carlsbad Research Center Job No. 91-6072 Carlsbad, California Page 14 10. 11. D. 12. in the event that a retaining wall is to be designed for a restrained condition, a uniform pressure equal to 15xH (fifteen times the total height of retained wall, considered in pounds per square foot) shall be considered as acting everywhere on the back of the wail in addition to the design Equivalent Fluid Weight, when utilising an uncontrolled mixture of existing soils as backfill. The passive earth pressure of the encountered natural-ground soils and compacted fill soils (to be used for deslgn of shallow foundations and footings to resist the lateral forces) shall be based on an Equivalent Fluid Weight of 275 pounds per cubic foot. This passive earth pressure shall only be considered valid for design if the ground adjacent to the foundation structure is essentially level for a distance of at least three times the total depth of the foundation and is properly compacted or dense natural soil. A Coefficient of Friction of 0.35 times the dead load may be used between the bearing soils and concrete foundations, walls, or floor slabs. Site Drainage Considerations Adequate measures shall be taken to properly finish-grade the site after the structures and other improvements are in place. Drainage waters from this site and adjacent properties are to be directed away from foundations, floor slabs, footings, and slopes, onto the natural drainage direction for this area or into properly designed and approved drainage facilities. Roof gutters and downspouts should be installed on ail structures, with runoff directed away from the foundations via closed drainage lines. - _- - - - - - - - - - - - - - - - - - Carisbad Research Center Carlsbad, California Job No. 91-6072 Page 15 Proper subsurface and surface drainage will help minimise the potential for waters to seek the level of the bearing soils under the foundations, footings, and floor slabs. Failure to observe this recommendation could result in uplift or undermining and differential settlement of the structure of other improvements on the site. We recommend placing a continuous concrete “apron” around the perimeter of all structures and that planter areas and planter boxes be kept outside the perimeter apron. In addition, appropriate erosion-control measures shall be taken at all time during construction to prevent surface runoff waters from entering footing excavations and ponding on finished building pads or pavement areas. Proper backdrains and subdrains shall be installed behind all retaining wails on the subject project. C&technical Exploration, Inc. will assume no liability for damage to structures which is attributable to poor drainage. 13. Planter areas and planter boxes shall be sloped to drain away from the foundations, footings and floor slabs at a slope of at least 5 percent within 10 feet of structures. Planter boxes shall be constructed with a closed bottom and a subsurface drain, installed in gravel, with the direction of subsurface and surface flow away from the foundations, footings, and floor slabs, to an adequate drainage facility. We strongly suggest that landscaping consist of drought resistant vegetation. Minimal irrigation water and proper drainage of seasonal rainfall waters will minimise volume changes of the near- surface soils. - - - - - -- - - - - - - Carlsbad Research Center Carlsbad, California E. General Recommendations Job No. 91-6072 Page 16 14. Following placement of any concrete floor slabs, sufficient drylng time should be allowed prior to placement of floor coverings. Premature placement of floor coverings could result in degradation of adhesive materials and loosening of the finish-floor materials. 15. Consideration should be given to placement of a PCC slab beneath and in front of any proposed trash enclosures. It has been our experience that most concentrated point loads often occur surrounding the trash enclosures from both the trash vehicles and the wheel loads of the trash container, resulting in damage to the asphaltic pavement. 16. In order to minimize any work delays at the subject site during site development, this firm should be contacted 24 hours prior to any need for inspection 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 inspection of the excavations; in the event that our inspection reveals the need for deepening or redesigning foundation structures at any locations, any formwork or steel reinforcement 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.). F. Pavement Design Criterla 17. Contemporary pavement section design methods require compaction of the upper 12 inches of subgrade soils (natural ground or compacted fill) to 90 percent of Maximum Dry Density, and ail base materials to at least 95 percent of Maximum Dry Density. We - - - - - - - _- - .- - - - - - - - - - Carlsbad Research Center Carisbad, California Job No. 91-6072 Page 17 therefore recommend that the upper 12 inches of subgrade soils and all base material beneath the proposed driveway and parking area pavements be compacted to these standards. This recommen- dation also applies to the upper soils in backfilled trenches or behind retaining wails which will support pavement sections. As per your request, we have tested the surface soil at the subject site and determined a suitable preliminary structural section for the parking and driveway areas. A representative sample of the surface clayey soil was obtained, and an “R”-[resistance) Value Test was performed in accordance with California Test Method #301, in order to evaluate the pavement subgrade quality of this material. The result of this preliminary test indicates a design “R”-value of 18 due to the clay content in the soil. Based on a traffic index of 4.5 for parking areas, 6.0 for driveways and 8.0 for heavy truck traffic areas, we have developed the recommended pavement section alternatives in accordance with the “Structural Section Design Guide for California Cities and Counties” procedures. Additional R-Value tests can be conducted at the completion of the grading operation and the preliminary structural section may be re- evaluated. Asphalt Location Parking Areas Driveways Heavy Truck Traffic Concrete 3 inches 3 inches 4 inches Processed Misc. Base (Class II Aqqreqate Base) 7 inches 11 inches 16 inches - .- - - - - -. - - - - - Carlsbad Research Center Carlsbad, California IX. GRADING NOTES Job No. 91-6072 Page 18 Any required grading operations shall be performed in accordance with the General Earthwork Specifications (Appendix B) and the require- ments of the City of Carlsbad Grading Ordinance. 18. Ceotechnical Exploration, Inc. recommends that we be asked to verify the actual soil conditions revealed during site grading work and footing excavations to be as anticipated in this “Report of Soil Investigation.” In addition, the compaction of any fill soils placed during site grading work must be 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. 19. It is the responsibility of the owner and/or developer to ensure that the recommendations summarised in the report are carried out in the field operations and that our recommendations for design of the project are incorporated in the building and grading plans. 20. 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 reasonability of the contractor. The contractor should notify the owner if he considers any of the recommended actions presented herein to be unsafe. X. LIMITATIONS Our conclusions and recommendations have been based on all available data obtained from our field investigation and laboratory analysis, as well as our experience with the soils and formation materials located in - .- - - - - - -_ - -.. - - Carisbad Research Center Carlsbad, California Job No. 91-6072 Page 19 this area of the City of Carlsbad. Of necessity, we must assume a certain degree of continuity between exploratory excavations and/or natural exposures. 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. The work performed and recommendations presented herein are the result of an investigation and analysis which meet the contemporary standard of care in our profession within the San Dlego County area. No warranty is provided. This report should be considered valid for a period of three (3) years, and is subject to review by our firm following that time. If significant modifications are made to the building and/or grading 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. The firm of Ceotechnical 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. Once again, should any questions arise concerning this report, please feel free to contact the project coordinator. Reference to our Job No. 916072 will help to expedite a reply to your inquiries. Respectfully submitted, CEOTECHNICAL EXPLORATION. INC. JKHlJACllb - - .- - - - - - - - - - - - - -~ .- EQUIPMENT DIMENSION F. TYPE OF EXCAVATION DATE LOGGED CASE BACKHOE 2' x 15' x 16' TRENCH 7-10-91 SURFACE ELEVATION GROUNDWATER DEPTH LOGGED BY -+277’ NSL NOT ENCOUNTERED JKH FIELD DESCRIPTION AliD CLASSIFICATION DESCRIPTION AND REMARKS (Grain size, Density, Moisture, Color) FINE SANDY SILT with abundant rock frag- ments and chunks of siltstone. Loose to medium dense. Dry to damp. Tan-gray. ---------_______________________________-- CLAYEY SILT with abundant chunks of silt- stone. Medium dense. Moist. Dark gray- green and orange. --some asphalt and glass debris FILL SANDY SILT with some clay and organics. Medium dense. Very moist. Dark gray- brown. ,------------------______________________-. SANDY SILT with clay and some pebbles, rock fragments and minor caliche. Medium dense. Very moist. Dark gray-green and purple-brown (very mottled). --asphalt debris FILL ._ IL : ? - < z ? i 3 * : ‘I / I - 2: :i :: L’ .: - 5. 1. 90.1 93.6 - ; Y 5z EL f$ - 0. - 105 at se 39 - PROPOSED C 6 L INTERNATIONAL BUILDING n 'ITE L°CATroN LOT 29 CARLSBAD RESEARCH CENTER [XI iIl DRIVE SAMPLE SAND CONE/F.D.T - - - - - - - - - - - - - - - - - - EQUIPMENT DIMENSION & TYPE OF EXCAVATION DATE LOGGED CASE BACKHOE SURFACE ELEVATION *277’ MSL , ..-. -..-” -...-..-_ I FIELD DESCRIPTION AND ;; c i-t CLASSIFICATION :: - CT 2;; 2:: 7 d t: ..ez l” - w m, d I c-d g y DESCRIPTION AND REMARKS z'= 5% + ‘k, F g g (Grain size, Density, Moisture, Co10r) ‘J? :iz 2';; "4-2 ,r ELYI $E -= .i zs c, cfi % ic 5 2 5.p EE Lig 9 E go 22 rsza. kg" z s zg 3, FILL 24.C 98.6 (17.2 110 go 'OB NAME PROPOSED C & L INTERNATIONAL BUILDING 2! WATER TABLE SITE LOCATION LOT 29 CARLSBAD RESEARCH CENTER q LOOSE BAG SAMPLE CARLSBAD, CALIFQRNIA El JOB NUMBER REVIEWED BY LOG No. IN-PLACE SAMPLE 91-6072 DRIVE SAMPLE SAND CDNE/F.D.T. FIGURE NUMBER IIb EQUIPMENT DIMENSION 6 TYPE OF EXCAVATION DATE LOGGED \ CASE BACKHOE 2' x 10' x 11’ TRENCH 7-10-91 SURFACE ELEVATION 1 GROUNDWATER DEPTH LOGGED BY --I i280’ MSL SEEP ~10' JKH I - FIELD DESCRIPTION AND c z :: CI CLASSIFICATION k3> + - : DESCRIPTION AND REMARKS 7 2: ;, IGrain size. Density, Moisture, Color) c 1 ‘f IL 5: z ‘Z ii zi - FINE SANDY SILT with some clay, rock 94 fragments and chunks of siltstone. Loos! IL to medium dense. Dry to damp. Tan-gray ! * ! i ! 2 t , * / - ; 2: 2: :z ..1 - 2. 3.l ).( - ; Y 5: Et f; - 0. FILL J - CLAYEY SILT with abundant chunks of silt. HI L stone. Medium dense. Damp. Dark gray- green and orange. 2’ .------_________________________________-. __ 98.9 105 )4 .-. SANDY CLAY/CLAYEY SAND with some cobbles X, I and rock debris (reworked Qls debris). :L Medium dense. Moist. Purple-brown and green with pink and orange. FILL - SILTY CLAY with some pebbles and organics Cl . 2f 95.8 I1 Soft to firm. Moist. Dark gray-brown. ,_. TOPSOIL L-----------____________________________-~ CLAYEY SILT with fractured siltstone Ml chunks. Medium dense. Moist. Tan-brown and orange. 25 89.5 5 TRANSITION/FORNATION --seep (west wall) SILTSTONE, moderately fractured. Dense. ii Moist. Dark gray-green and orange FORMATION - BOTTOM OF HOLE AT 11’ - - JOB NAME PROPOSED C 6 L INTERNATIONAL BUILDING n WATER TABLE SITE LOCATION LOT 29 CARLSBAD RESEARCH CENTER lx CARLSBAD, CALIFORNIA LOOSE BAG SAMPLE q JOB NUMBER REVIEWED BY LOG No. IN-PLACE SAMPLE 91-6072 n DRIVE SAMPLE FIGURE NUMBER T-2 El IIC SAND CONE/F.D.T. - - - - - - - - - - - - - - - - - - - .- EQUIPMENT DIMENSION B TYPE OF EXCAVATION DATE LOGGED CASE BACKHOE 2' x 15' x 18' TRENCH 7-10-91 __- SURFACE ELEVATION GROUNDWATER DEPTH LOGGED BY +27B' MSL NOT ENCOUNTERED JKH FIELD DESCRIPTION E CLAiSi%!ATlON z c g E’ c 2;; :: CI .d . i2: u- cl- d I l--d z d y DESCRIPTION AND REMARKS " zz zr rE + F % t?z E!Tl $E F" .; ‘k, CL : z s (Grain size, Density, Moisture, Color) L: 4:: 2 ZP !zg zg Sk 55: xc2 '!2 9: %?5 W" mu ‘n1 2;s 2s: ,: FINE SANDY SILT with abundant rock frag- SW _,.. '. . .'., ments and chunks of siltstone. Loose to ML 1 ;.... :.. D medium dense. Dry to damp. Tan-gray. Medium dense. green to orange. SANDY SILT with clay, organics and sow Medium dense. Hoist. Dark rock fragments and asphalt debris. Medium dense. Moist. Dark gray-brown and purple-green (very mottled). n WATER TABLE !a LOOSE BAG SAMPLE El IN-PLACE SAMPLE n DRIVE SAMPLE El SAND CONE/F.D.T. JoB NAME PROPOSED C 6 L INTERNATIONAL BUILDING 'ITE LDCAT1oN LOT 29 CARLSBAD RESEARCH CENTER CARLSBAD, CALIFJRNIA JOB NUMBER REVIEWED BY LOG No. 91-6072 FIGURE NUMBER T13 IId - EQUIPMENT DIMENSION 6 TYPE OF EXCAVATION DATE LOGGED CASE BACKHOE 2' x 15' x 18' TRENCH 7-10-91 I SURFACE ELEVATION GROUNDWATER DEPTH *278' MSL - 1 NOT ENCOUNTERED JKH - - - - - - - - - - - - FIELD DESCRIPTION AND CLASSIFICATION DESCRIPTION AND REMARKS Grain size, Density, Moisture, Color) SANDY SILT with clay, siltstone chunks, rock fragments, concrete and wire debris. Medium dense. Very moist. Tan-brown and gray-green. ---------------_________________________-, SANDY SILT/SILTY SAND with clay and silt- stone chunks. Loose to medium dense. Very moist. Dark gray-brown and black. FILL BOTTOM OF HOLE AT 18' 7 c v E MI _. 4, 0. 4. 96.1 - # :I :I ;i - 7. - - : : 3. - 95 37 - : : - i ; Gi ;I :: - - JoB NAME PROPOSED C 6 L INTERNATIONAL BUILDING a WATER TABLE SITE LOCATION LOT 29 CARLSBAD RESEARCH CENTER IXI CARLSBAD. CALIFORNIA LOOSE BAG SAMPLE q IN-PLACE SAMPLE JOB NUMBER REVIEWED BY LOG No. 91-6072 DRIVE SAMPLE FIGURE NUMBER T-3 SAND CONE/F.D.T. II.3 c - EQUIPMENT DIHENSION E TYPE OF EXCAVATION DATE LOGGED - CASE BACKHOE 2' x 10' x 11’ TRENCH 7-10-91 SURFACE ELEVATION GROUNDWATER DEPTH LOGGED BY ---I I *281' NSL 1 SFFPS k) 4' AN" I,,’ I .IY” - I _ _ _. _ _ .- - - I “..,. - - - - - - - - - - - - - - - - 1 1 L I ments and siltstone chunks. CLAYEY SILT with abundant chunks of silt- stone and some glass debris. Medium dense. Moist. Dark gray-brown and --layer of dark brown clay BOTTOM OF HOLE AT 11’ JoB NAME PROPOSED C & L INTERNATIONAL BUILDING v WATER TABLE SITE LOCATION LOT 29 C+RLSBAD RESEARCH CENTER El LOOSE BAG SAMPLE CARLSBAO. CALIF_ORNIA ITI JOB NUMBER REVIEWED BY LOG No. IN-PLACE SAMPLE 914072 DRIVE SAMPLE FIGURE NUMBER T-4 SAND CONE/F.D.T. IIf - - - - ,- - - - - - - - - - EQUIPMENT DIMENSION .% TYPE OF EXCAVATION DATE LOGGED CASE BACKHO 2' x 5' x 5' TRENCH 7-10-91 _.._ SURFACE ELEVATION GROUNDWATER DEPTH LOGGED BY k279' MSL NOT ENCOUNTERED JKH FIELD DESCRIPTION AND iT c z c 25 :: - &u t CLASSIFICATION .d 2 y DESCRIPTION AND REMARKS .“,z - “,> rs 02 d I . + E Ox z 2 $E z:' .A -.oIL % z $ (Grain size, Density, Moisture, Color) VI =jz c1 42 25 z; kg Lig ;;s zg s :: z8z a.‘ r Y! z eP 2: ZE YU mum. si8 22:: SANDY SILT with abundant siltstone chunks ML Loose. Dry. Tan-gray. 1 2 CLAYEY SILT with abundant siltstone Medium dense. Moist. Gray- 3 brown and orange. 4 BOTTOM OF HOLE AT 5' JoB NAME PROPOSED C 6 L INTERNATIONAL BUILDING I v WATER TABLE SITE LOCATION LOT 29 CARLSBAO RESEARCH CENTER I lil LOOSE BAG SAMPLE ITI IN-PLACE SAMPLE DRIVE SAMPLE SAND CONE/F.D.T. CARLSBAD. CALIFSRNIA JOB NUMBER REVIEWED BY LOG No. 91-6072 FIGURE NUMBER T-5 119 LABORATORY SOIL DATA SUMMARY Fines 0 10 20 30 40 . SPEC IFIC CRAVI iTY ZERO AIR VOIDS i CUR’ VES LABORATORY COMPACTION TEST SOIL TlPE SOIL CLASSIFICATION BORING TRENCH No. No. MPTH 1 CLAYEY SILT. Dark gray-green and orange. T-l 2’ 2 SANDY SILT with clay. Dark gray-brown. T-3 12' 3 SWELL TEST DATA INITIAL DR1 DENSITY (pcf) INITIAL U4TER COWTENT (I) LoAD (PSf) UBC EXPANSION INDEX la lb 2 92.0 35.2 - 15.3 25.5 - 144 144 - 130 50 - FIGURE NUMBER I I la JOB NUMBER 91-6072 ATTERBERG LIMIT BETERMiNATIONS - - - - - - - - - - - - - (ASTM D423 AND D424) PLASTlClTV INDEX: PI = LL- PL 50 40 30 20 10 7 4 0 10 20 30 40 50 60 70 80 90 100 LIQUID LIMIT. 11 FIQURE WUY6LR I I I b JOB WUYBER 91-6072 CONSOLIDATION - PRESSURE CURVE I NO-L PRESSURE - LBS./SQ.PT. 1 10 1 1 4 ! E 5 2 3 2 6 3 7 Trench Number 1, Depth: 8 Feet RUN DIM3ER 2.5 IlKlIES FIWPXllllMR IlfC Carved from Undisturbed Sample JOB lM9ER gl-6u:z I I I I I I I I I I I / I I I I I / I CONSOLIDATION - PRESSURE CURVE NORMAL PRESSURE - LBS./SQ.FT. 100 lwo 1o.ooo 1 2 c a 2 3 2 I 4 5 2 5 2 f 6 7 Trench Number 3, Depth: 16 Feet 111116 DIAllirrR 2.5 1lmEs FIWRElllHlER llld Carved from Undisturbed Sample JO0 -ER 91-6372 I I I I 1 I 1 1 I 1 I I I I 1 i I I CONSOLIDATION - PRESSURE CURVE NORMAL PRESSURE - LBS./SQ.PT. I I IIIII I I I IIIIII t I I I1111 I I I IIII!I t I’~[- i I I _I I I ! I I I I I I 0 m1ciiw IN~ISTU~E 0 SRNWTED - COlWJLIMT1(yI --._ REBOUlO Trench Number 4, Depth: 8 Feet Carved from Undisturbed Sample RI16 01NETEu 2.5 IRCIFS FIGURE-R Ilie ~00 N-R 91-6072 - - .- - - -~ - - - - - - - - - - - - - APPENDIX A UNIFIED SOIL CLASSIFICATION CHART SOIL DESCRIPTION COARSE-GRAINED More than half 01 mrbrbl Is brger than a No. 200 aleve GRAVELS, CLEAN GRAVELS More than half of coarse fraction is larger than GW Well-graded gravels, gravel and sand mix- No. 4 sieve size. but smaller than 3” tures, little or no fines. GP Poorly graded gravels, gravel and sand mix- tures, little or no fines. GRAVELS WITH FINES (appreciable amount) GM Silty gravels, poorly graded gravel-sand-silt mixtures. GC Clay gravels, poorly graded gravel-sand-silt mixtures. SANDS, CLEAN SANDS SW Well-graded sand, gravelly sands, little or no More than half of coarse fraction is smaller than a no fines. No. 4 sieve. SP Poorly graded sands, gravelly sands. little or no fines. SANDS WITH FINES (appreciable amount) SM Silty sands, poorly graded sand and silty mixtures. SC Clayey sands, poorly graded sand and clay mixtures. FINE-GRAINED Mom than halt ot materbl Is smalbr than a No. 200 l bve SILTS AND CLAYS ML Liquid Limit Less Than 50 CL Liquid Limit Greater Than 50 HIGHLY ORGANIC SOILS OL Ml-l CH OH PT Inorganic silts and very fine sands, rock flour. sandy silt and clayey-silt sand mixtures with a slight plasticity. Inorganic clays of low to medium plasticity. gravelly clays, sandy clays, silty clays. clean clays. Organic silts and organic silty clays of low plasticity. Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic sills. Inorganic clays of high plasticity. fat clays. Organic clays of medium to high plasticity. Peat and other highly organic soils - - - - - - - - - - - APPENDIX B GENERAL EARTHWORK SPECIFICATIONS General The objective of these specifications is to properly establish procedures for the clearing and preparation of the existing natural ground or properly compacted fill to receive new fill; for the selection of the fill material; and for the fill compaction and testing methods to be used. Scope of Work --, - The earthwork includes all the activities and resources provided by the contractor to construct in a good workmanlike manner all the grades of the filled areas shown in the plans. The major items of work covered in this section include all clearing and grubbing, removing and disposing of materials, preparing areas to be filled, compacting of fill, compacting of backfills, subdrain installations, and all other work necessary to complete the grading of the filled areas. Site Visit and Site Investigation 1. The contractor shall visit the site and carefully study it, and make all inspections necessary in order to determine the full extent of the work required to complete all grading in conformance with the drawings and specifications. The contractor shall satisfy himself as to the nature, location, and extent of the work conditions, the conformation and condition of the existing ground surface; and the type of equipment, labor, and facilities needall prior to and during prosecution of the work. The contractor shall satisfy himself as to the character, quality, and quantity of surface and subsurface materials or obstacles to be encountered. Any inaccuracies or discrepancies between the actual field conditions and the drawings, or between the drawings and specifications, must be brought to the engineer’s attention in order to clarify the exact nature of the work to be performed. 2. A soils investigation report has been prepared for this project by CEI. It is available for review and should be used as a reference to the surface and subsurface soil and bedrock conditions on this project. Any recommendations made in the report of the soil investigation or subsequent reports shall become an addendum to these specifications. - - - - 82 The soils engineer -shall have, in conjunction with the engineering geologist, the authority to approve the preparation of natural ground and toe-of-fill benches to receive fill material. The engineering - geologist shall have the authority to evaluate the stability of the existing or proposed slopes, and to evaluate the necessity of remedial measures. If any unstable condition is being created by cutting or filling, the engineering geologist and/or soils engineer shall advise the contractor and owner immediately, and prohibit grading in the affected area until such time as corrective measures are taken. - - -- - - - The owner shall decide all questions regarding: ( 1 j the interpretation of the drawings and specifications, (2) the acceptable fulfillment of the contract on the part of the contractor, and (3) the matter of compensation. Clearinq and Grubbing 1. 2. 3. Clearing and grubbing shall consist of the removal from all areas to be graded of all surface trash, abandoned improvements, paving, culverts, pipe. and vegetation (including -- but not limited to -- heavy weed growth, trees, stumps, logs and roots larger than l-inch in diameter). Authority of the Soils Engineer and Enqineering Ceoloqist - ,- The soils engineer shall be the owner’s representative to observe and test the construction of fills. Excavation and the placing of fill shall be under the observation of the soils engineer and his/her representative, and he/she shall give a wrltten opinion regarding conformance with the specifications upon completion of grading. The soils engineer shall have the authority to cause the removal and replacement of porous topsoils, uncompacted or improperly compacted fills, disturbed bedrock materials, and soft alluvium, and shall have the authority to approve or reject materials proposed for use in the compacted fill areas. - - - - - - All organic and inorganic materials resulting from the clearing and grubbing operations shall be collected, piled, and disposed of by the contractor to give the cleared areas a neat and finished appearance. Burning of combustible materials on-site shall not !>e permitted unless allowed by local regulations, and at such times and in such a manner to prevent the fire from spreading to areas adjoining the property or cleared area. It is understood that minor amounts of organic materials may remain In the fill soils due to the near impossibility of complete removal. The amount remaining, however, must be considered negligible, and in no case can be allowed to occur in concentrations or total quantities sufficient to contribute to settlement upon decomposition. - - - 83 Preparation of.-Areas to be Filled - - -. - - 1. 2. 3. 4. After clearing and grubbing, all uncompacted or improperly compacted fills, soft or loose soils, or unsuitable materials, shall be removed to expose competent natural ground, undisturbed bedrock, or properly compacted fill as indicated in the soils investigation report or by our field representative. Where the unsuitable materials are exposed in final graded areas, they shall be removed and replaced as compacted fill. The ground surface exposed after removal of unsuitable soils shall be scarified to a depth of at least 6 inches, brought to the’ specified moisture content, and then the scarified ground compacted to at least the specified density. Where undisturbed bedrock is exposed at the surface, scarification and recompaction shall not be required. All areas to receive compacted fill. including all removal areas and toe-of-fill benches, shall be observed and approved by the soils engineer and/or engineering geologist prior to placing compacted fill. Where fills are made on hillsides or exposed slope areas with gradients greater than 20 percent, horizontal benches shall be cut into firm, undisturbed, natural ground in order to provide both lateral and vertical stability. This is to provide a horizontal base so that each layer is placed and compacted on a horizontal plane. The initial bench at the toa of the fill shall be at least 10 feet in width on firm, undisturbed, natural ground at the elevation of the toa stake placed at the bottom of t!ie design slope. The engineer shall determine the width and frequency of all succeeding benches, which will vary with the soil conditions and the steepness of the slope. Ground slopes flatter than 20 percent (5.O:l.O) shall be benched when considered necessary by the soils engineer. - - .- - - Fill and Backfill Material Unless otherwise specified, the on-site material obtained from the project excavations may he used as fill or backfill, provided that all organic material, rubbish, debris, and other objectionable material contained therein is first removed. In the event that expansive materials are encountered during foundation excavations within 3 feet of finished grade and they have not been properly processed, they shall be entirely removed or thoroughly mixed with good, granular material before incorporating them in fills. No footing shall be allowed to bear on soils which. in the opinion of the soils engineer, are detrimentally expansive -- unless designed for this clayey condition.- - - - 84 - - - - - - - - - - - - - - However, rocks, boulders, broken Portland cement concrete, and bituminous-type pavement obtained from the project excavations may he permitted in the backfill or fill with the following limitations: 1. 2 3. 4. 5. 6. 7. 8. 9. The maximum dimension of any piece used In the top 10 feet shall be no larger than 6 inches. Clods or hard lumps of earth of 6 inches in greatest dimension shall be broken up before compacting the material In fill. If the fill material originating from the project excavation contains large rocks, boulders, or hard lumps that cannot Se broken readily, pieces ranging from 6 inches in diameter to 2 feet in maximum dimension may be used in fills below final subgrade if all pieces are placed in such a manner (such as windrows) as to eliminate nesting or voids between them. No rocks over 4 feet will be allowed in the fill. Pieces larger than 6 Inches shall not be placed within 12 inches of any structure. Pieces larger than 3 inches shall not be placed within 12 inches of the subgrade for paving. Rockfills containing less than 40 percent of soil passing 3/4-inch sieve may be permitted in designated areas. Specific reco:nmendations shall be made by the soils engineer and be subject to approval by the city engineer. Continuous cbservation by the soils engineer is required during rock placement . Special and/or additional recommendations may be provided in writing by the soils engineer to modify, clarify, or amplify these specifications. During grading operations, soil types other than those anaiyzed in the soil investigation report may be encountered by the contractor. The soils engineer shall be consulted to evaluates the suitability of these soils as fill materials. Placing and Compactinq Fill Material -- _ . . -- -~-. --- 1. After preparing the areas to be filled, the approved fill material shell he placed in approximately horizontal layers, with lift thickness compatible to the material being placed and the type of equipment being used. Unless otherwise approved by the soils engineer, each layer spread for compaction shall not exceed 8 inches of loose thickness. Adequate drainage of the fill shall he provided at all times during the construction period. - - - 35 - - - - - .- - - .- - - 2. When the moisture content of the fill material is below that specified by the engineer, water shall be added to it until the moisture content is as specified. 3. When the moisture content of the fill material is above that specified by the engineer, resulting in inadequate compaction or unstable fill, the fill material shall be aerated by blading and scarifying or other satisfactory methods until the moisture content is as specified. 4. After each layer has been placed, mixed, and spread evenly, it shall be thoroughly compacted to not less than the density set forth In the specifications. Compaction shall be accomplished with sheepsfoot rollers, multiple-wheel pneumatic-tired rollers, or other approved types of acceptable compaction equipment. Equipment shall he of such design that it will be able to compact the fill to the specified relative compaction. Compaction shall cover the entire fill area, and the equipment shall make sufficient trips to ensure that the desired density has been obtained throughout the entire fill. At locations where it would be impractical due to inaccessibility of rolling compacting equipment, fill layers shall be compacted to the specified requirements by hand-directed compaction equipment. 5. When soil types or combination of soil types are encountered which tend to develop densely packed surfaces as a result of spreading or compacting operations, the surface of Mach layer of fill shall be sufficiently roughened after compaction to ensure bond to the succeeding layer. 6. Unless otherwise specified, fill slopes shall not be steeper than 2.0 horizontal to 1 .O vertical. In general, fill slopes shall be finished in conformance with the lines and grades shown on the plans. The surfac:? of fill slopes shall be overfilled to a distance from finished slopes such that It will allow compaction equipment to operate freely within the zone of the finished slope, and then cut back to the finished grade to expose the compacted core. Alternate compaction procedures include the backrolling of slopes with sheepsfoot rollers in increments of 3 to 5 feet in elevation gain. Alternate methods may be used by the contractor, but they shall be evaluated for approval by the soils engineer. 7. Unless otherwise specified, all allowed expansive fill material shall be compacted to a moisture content of approximately 2 to 4 percent above the optimum Lnoistalrr. content. Nonexpansivl? fill shall he compacted at near-optlmum moisture content. All fill shall be compacted, unless otherwise specified, to a relative compaction not less than 95 percent for fill in the upper 12 inches - - - 86 - -. -- - - - - - - - - .- - a. of subgrades~ under areas to be paved with asphalt concrete or Portland concrete, and not less than 90 percent for other fill. The relative colnpaction is the ratio of the dry unit weight of the compacted fill to the laboratory maximum dry unit weight of a sample of the same soil, obtained in accordance with A.S.T.M. O- 1557 test method. The observation and periodic testing by the soils engineer are intended to provide the contractor with an ongoing measure of the quality of the fill compaction operation. It is the responsibility of the grading contractor to utilize this information to establish the degrees of compactive effort required on the project. More importantly, it is the responsjbility of the grading contractor to ensure that proper compactive effort is applied at all times during the grading operation, including during the absence of soils engineering representatives. Trench Backfill _ _- 1. Trench excavations which extend under graded lots, paved areas, areas under the influence of structural loading, in slopes or close to slope areas, shall be backfilled under the observations and testing of the soils engineer. All trenches not falling within the aforementioned locations shall be backfilled in accordance with the City or County regulating agency specifications. 2. IJoless otherwise specified, the minimum degree of compaction shall be 99 percent of the laboratory maximum dry density. 3. Any soft, spongy, unstable, or other similar material encountered in the trench excavation upon which the bedding material or pipe is to be placed, shall be removed to a depth recommended by the soils engineer and replaced with bedding materials suitably densified. Bedding material shall first be placed so that the pipe is supported for the full length of the barrel with full bearing on the bottom segment. After the needed testing of the pipe Is accomplished, the bedding shall be co~nplated to at least 1 foot on top of the pipe. The bedding shall be properly densified before backfill is placed. Bedding shall consist of granular material with a sand equivalent not less than 30, or other material approved by the engineer. 4. No rocks greater than 6 inches in diameter will be allowed in the backfill placed between 1 foot above the pipe and 1 foot below finished subgrade. Rocks greater than 2.5 inches in any dimension will not be allowed in the backfill placed within 1 foot of pavement subgrade. 87 - - .- - - - - - - 5. 6. 7. 8. Material for mechanically compacted backfill shall be placed In lifts of horizontal layers and properly moistened prior to compaction. In addition, the layers shall have a thickness compatible with the material being placed and the type of equlpment being used. Each layer shall be evenly spread, moistened or dried, and then tamped or rolled until the specified relative compaction has been attained. Backfill shall be mechanically compacted by means of tamping rollers, sheepsfoot rollers, pneumatic tire rollers, vibratory rollers, or other mechanical tampers. Impact-type pavement breakers (stompers) will not be permitted over clay, asbestos cement, plastic, cast iron, or nonreinforced concrete pipe. Permission to use specific compaction equipment shall not be construed as guaranteeing or implying that the use of such equipment will not result In damage to adjacent ground, existing improvements, or improvements Installed under the contract. The contractor shall make his/her own determination in this regard. Jetting shall not be permitted as a compaction method unless the soils engineer allows it in writing. Clean granular material shall not be used as backfill or bedding in trenches located in slope areas or within a distance of 10 feet of the top of slopes unless provisions are made for a drainage system to mitigate the potential buildup of seepage forces Into the slope mass. Observations and Testing 1. The soils engineers or their representatives shall sufficiently observe and test the grading operations so that they can state their opinion as to whether or not the fill was constructed in accordance with the specifications. 2. The soils engineers or their representatives shall take sufficient density tests during the placement of compacted fill. The contractor should assist the soils engineer and/or his/her representative by digging test pits for removal determinations and/or for testing compacted fill. In addition, the contractor should cooperate with the soils engineer by removing or shutting down equipment from the area being tested. 3. Fill shall be tested for compliance with the recommended relative compaction and molsture conditions. Field density testing should be performed by using approved methods by A.S.T.M., such as A.S.T.M. 01556, 02922, and/or D2937. Tests to evaluate density of compacted fill should be provided on the basis of not less than one test for each 2-foot vertical lift of the fill, but not less than one test for each 1,000 cubic yards of fill placed. Actual test 0a - - - - - - - - - - - - - intervals may vary as field conditions dictate. In fill slopes, approximately half of the tests shall be made .at the fill slope, except that not more than O:V? test needs to be made for each 59 horizontal feet of slope In each 2-foot vertical lift. Actual test intervals may vary as field conditions dictate. 4. Fill found not to be in conformance with the grading recommendations should be removed or otherwise handled as recommended by the soils engineer. Site Protection It shall be the grading contractor’s obligation to take all measures deemed necessary during grading to maintain adequate safety measures and working conditions, and to provide erosion-control devices for the protection of excavated areas, slope areas, finished work on the site and adjoining properties, from storm damage and flood hararcl originating on the project. It shall be the contractor’s responsibility to maintain slopes in their as-graded form until all slopes are in satisfactory compliance witn the jd> specifications, all berms and benches have been properly constructed, and all associated drainage devices have been installed and meet the requirements of the specifications. All observations, testing services, and approvals given by the soils engineer and/or geologist shall not relieve the contractor of his/her responsibilities of performing the work in accordance with these specifications. After grading is completed and the soils engineer has finished his/her observations and/or testing of the work, no further excavation or filling shall be done except under his/her observations. Adverse Weather Conditions 1. Precautions shall be taken by the contractor during the performance of site clearing, excavations, and grading to protect the worksite from flooding, ponding, or inundation by poor or improper surface drainage. Temporary provisions shall be made during the rainy season to adequately direct surface drainage away from and off the worksite. Where low areas cannot be avoided, pumps should be kept on hand to continually remove water during periods of rainfall. 2. During periods of rainfall, plastic sheeting shall be kept reasonably accessible to prevent unprotected slopes from beconirlg saturated. Where necessary during periods of rainfall, the contractor shall install checkdams, desilting basins, rip-rap, sandbags, or other devices or methods necessary to control erosion and provide safe conditions. B9 - - - - - .- -- - - -- - - - - - - 3. During periods of rainfall, the soils engineer should be kept informed by the contractor as to the nature of remedial or preventative work being performed (e.g. pumping, placement of sandbags or plastic sheeting, other labor, dozing, etc.). 4. Following periods of rainfall, the contractor shall contact the soils engineer and arrange a walk-over of the site In order to visually assess rain-related damage. The soils engineer :nay also recommend excavations and testing in order to aid in his/her assessments. At the request of the soils engineer, the contractor shall make excavations in order to evaluate the extent of rain- related damage. 5. Rain-related damage shall be considered to include, but may not be limited to, erosion, silting, saturation, swelling, structural distress, and other adverse conditions identified by the soils engineer. Soil adversely affected shall 1) e classified as Unsuitable Materials, and shall be subject to overexcavation and replacement with compacted fill or other remedial grading, as recommended by the soils engineer. 6. Relatively level areas, w!iere saturated soils and/or erosion gullies exist to depths of greater than 1.0 foot, shall be overexcavated to unaffected, competent material. ‘Where less than 1.0 foot in depth, unsuitable materials may be processed in place to achieve near-optimum moisture conditions, then thoroughly recompacted in accordance with the applicable specifications. If the desired results are not achieved, the affected materials shall be over- excavated, then replaced in accordance with the applicable specifications. 7. In slope areas, where saturated soils and/or erosion gullies exist to depths of greater than 1.0 foot, they shall be overexcavated and replaced as compacted fill in accordance with the applicable specifications. Where affected materials exist to depths of 1 .O foot or less below proposed finished grade, remedial grading by moisture-conditioning in place, followed by thorough recompaction in accordance with the applicable grading guidelines herein presented may he attempted. If materials shall be overexcavated and replaced as compacted fill, it shall be done in accordance with the slope-repair recommendations herein. As field conditions dictate, other slope-repair procedures may be recommended by the soils engineer. APPENDIX c - .- - .- - .- - - - GENERAL DISCUSSION OF EXPANSIVE-SOIL BEHAVIOR Expansive-Soil Uplift of Concrete Slabs and Flatwork In general, the measured “doming” -- relatively higher slab areas near the center of a floor slab over expansive soils -- is due to the inability of moisture accumulating In subslab soils to evaporate, or dry out, as do soils in planters or uncovered yard areas around the structure. The extent to which new floor slabs will t0dome88 depends on the swell potential of the soil, the initial moisture content of the soil when the slab is constructed, and the potential for additional wetting of the expansive soil due to surface or subsurface water infiltration. Nonuniform “doming, ” which generally results in more damage than a uniform rise and fall across a slab, is due to variable slab design and reinforcement, variable loads on the slab, nonuniform initial soll characteristics and conditions, and/or differential wetting of the soil by localized water sources (e.g., leaking utility line, ponding of water against a footing, overwatering of planters next to footing, etc.). The “Active@’ Soil Zone In general, the “wetting-drying” zone in Southern California ranges from 2 to 3 feet below a ground surface not covered by some form of moisture barrier (e.g., concrete slab, polyethylene sheeting). This “wettingdryingk zone is the depth to which seasonal rainfall will wet unprotected soil, and the depth to which appreciable drying of unprotected soil (due to evaporation) will occur during summer months. Even if no surface water is allowed to soak into clayey soil which is uncovered and subject to soil-moisture evaporation, the soil below a certain depth will remain at a relatively constant moisture level. This is due to two mechanisms; temperature decreases and humidity increases result in evaporation being less effective with depth, and soil moisture at depth is constantly drawn up into fine-grained clayey soils by capillary action. The bottom of the “wettingdrying” zone is the depth at which evaporative and capillary forces are In a state of equilibrium. The clayey soil at any given depth below this zone remains at a relatively constant moisture level, and therefore does not undergo volume changes. The soil above the equilibrium depth -- the “active” soil zone -- alternately expands and shrinks (withln certain vertical limits) as soil moisture increases and decreases, respectively. -- - -. - Design Criterla for Contemporary Slabs on Expansive Soil When a large, concrete slab Is constructed on expansive soil, the under- lying soil in both the “actives zone and the lower “equilibrium” zone is prevented from losing moisture due to evaporation. As a result, soll molstures In the former “equilibrium’@ zone will rise to a higher soil c-2 - - - .- - - - - -. - - - - moisture content and, the moisture content In the upper “active” zone will increase. In response to the long-term moisture increase, the lightly loaded soils beneath the interior slab areas expand and lift the slab. The perimeter footings and slab areas do not lift as high as interior slab areas because the heavily loaded footings better resist the soil expansion, and because unprotected ground areas adjacent to the slab perimeter allow soil moisture to evaporate from beneath footings and the outermost portions of the slabs. In gneral, contemporary site development and foundation plans for residential structures on expansive soil are not intended to eliminate long-term soil-moisture increases beneath a new slab; such a foundation system would not be economically feasible for a typical residential structure, and is not considered warranted for such a structure. Instead, current design features include: deepened perimeter footings to reduce infiltration of surface water beneath slabs; sloping of ground surfaces away from all footings, to prevent ponding of water next to footings; and placement of reinforcing steel bars or post-tensioned cables in the slabs, to reduce the potential for significant nonuniform slab ?!oming.n The reinforcing steel is also intended to limit vertical or horizontal separations across any cracks in the concrete slab; it is usually not intended to prevent such cracks from developing. New Concrete Slabs It is important for owners of new homes on expansive soil to realize that capillary rise of moisture beneath new concrete slabs will probably result in some minor slab movement and resultant minor cracking of wall, ceiling and floor coverings. Such minor cracking is .expected and should be regarded as normal for a residential structure on expansive soil. Maintaining good drainage away from a house perimeter will help to reduce the sire and extent of cracks due to soil movement, but minor cracking will still occur due to long-term moisture Increases beneath the newer concrete slabs. Older Concrete Slabs It has been our experience that expansive soils beneath concrete slabs that are more than 8 to 10 years old are typically very moist to wet. Soil-moistures beneath older slabs (due to capillary rise) have usually reached - or are approaching -- a new Wequllibrium” level; in other words, years of capillary rise have increased the moisture content to a level which probably will not change appreciably over time, so long as sigificant changes in the general g-ound water table at depth do not occur. Much of the observed Woml~@ of an older floor slab probably occurred over past years, while the soil moistures were still Increasing up to a hl#er “equilibrlum~ level. C-3 - - -. - - - - In general, significant movement of an older structure on expansive soil is due primarily to preventable sources of water entering the soil, due to inadequate yard drainage, overwatering of planters adjacent to footings, or leaks in utility lines. Since the soils beneath older concrete slabs are generally much wetter than the soils beneath new slabs, the potential for significant soil uplift due only to general capillary rise is low beneath older slabs. Therefore, good long-term performance of an older structure on expansive soil is dependent on lnstitutlon and maintenance of very positive site drainage by the homeowner. If positive drainage Is maintained on a lonpterm basis, then soil moisture levels beneath perimeter footings will stabilire over time. As the soil molsture becomes stabilized, the size and frequency of cracking should become less over time. If the homeowner desires to reduce future damage to a level below what is considered normal and acceptable for a residential structure, this can be accomplished by installing additional moisture-control and/or foundation structures. Such structures might include: 1. 2. 3. 4. 5. 6. 7. 8. locating and repairing any significant cracks in concrete floor slabs; placing a continuous concrete “apron” around the perimeter of a structure; placing a subsurface french drain or moisture cut-off wall around a structure; intrusion-grouting the soil beneath perimeter footings to reduce moisture infiltration; deepening the perlmeter footing; replaclng interlor floor slabs with a new, more heavily reinforced slab; replacing interior floor slabs with a very thick mat foundation reinforced with grids of conventional steel bars or post-tensioned cables; and/or placing the entire structure on a raised pier-and-grade-beam foundat ion. - - -~ - -