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HomeMy WebLinkAboutCDP 01-08; McGrady Residence; Soils Investigation; 2000-11-03SGC Southland Geotechnical Consultants SOILS INVESTIGATION PROPOSED SINGLE-FAMILY RESIDENCE 4100SUNNYHILLDRIVE CARLSBAD, CALIFORNIA Project No. 106H61 November 3, 2000 Prepared for: LARSON DESIGN AND CONSULTING 24362 Del Prado Avenue Dana Point, California 92629 7235 GREENFIELD DRIVE, SUITE A EL CAJON, CALIFORNIA 92021 • (619)442-8022 • FAX (619)442-7859 ^.- -^? SGC Southland Geotechnical Consultants • November 3, 2000 Project No. 106H61 • To: Larson Design and Consulting 24362 Del Prado Avenue I Dana Point, California 92629 Attention: Mr. Pete Larson Subject: Soils Investigation, Proposed Single-Family Residence, 4100 Sunnyhill I Drive, Carlsbad, California I Introduction Southland Geotechnical Consultants has performed a soils investigation for the I proposed single-family residence to be constructed at 4100 Sunnyhill Drive in Carlsbad. This report presents the results of our soils investigation and provides our conclusions and recommendations, from a geotechnical standpoint, relative to the I proposed development. I Purpose and Scope (The purpose of our soils investigation was to evaluate the soil conditions at the site and provide recommendations, from a geotechnical standpoint, relative to the proposed construction. The scope of our investigation included the following: I - Review of geologic maps and literature pertaining to the site and vicinity. A list of the documents reviewed is provided in Appendix A. • - Review of preliminary project plans indicating site improvements. I - Field reconnaissance to observe the existing surficial soil conditions at the * subject property and nearby vicinity. I - Investigation of the subsurface soil conditions by excavating, logging and sampling six exploratory trenches (with a Bobcat backhoe) at the site. | - Laboratory expansion index and sulfate content testing of a representative sample of the onsite soils. I I • 7235 GREENFIELD DRIVE, SUITE A EL CAJON, CALIFORNIA 92021 • (619)442-8022 • FAX (619)442-7859 Project No. 106H61 Geotechnical analysis of the data obtained. Preparation of this report summarizing the results of our soils investigation and presenting recommendations, from a geotechnical standpoint, for the proposed development. Site Description The subject property is located on the southeast corner of Sunnyhill Drive and Tamarack Avenue in Carlsbad (see Figure 1). Residential developments exist on the properties to the east and north of the site. A single-family residence and associated improvements exist on the western approximately one-half of the subject property. The eastern approximately one-half of the site (where the new residence is proposed) is vacant and generally consists of two relatively level graded pads. Overall, the subject property slopes to the west. Project Description We understand that site development will generally consist of a new single-family residence on the eastern portion of the subject property. The residence will consist of a one- or two-story, wood-framed structure with slab-on-grade and/or raised wood floors. A garage, retaining walls and other associated improvements are also proposed. We understand that some site grading will be performed to prepare the building area and attain design finished grades for the proposed development. Subsurface Investigation On October 26, 2000, six exploratory trenches were excavated at the site. The trenches were excavated with a Bobcat backhoe to a maximum depth of approximately 25 inches below existing ground surface. The exploratory trenches were logged by a geologist from our firm and representative samples of the subsurface soils encountered were obtained for visual soils classification and laboratory testing. Subsequent to logging and sampling, the exploratory trenches were backfilled. The approximate locations of the trenches are shown on Figure 2. The logs of the exploratory trenches are included in Appendix B. SGC Project No. 106H61 Soil/Geologic Units As encountered in our soils investigation, the subject property appears to be underlain by surficial soils consisting of fill soils and topsoil, and the geologic unit known as the Lindavista Formation. Following are brief descriptions of each unit: Fill soils - Fill soils were encountered in Trenches 3 and 4 during our investigation and consisted of brown silty fine sand and orange-brown and brown, silty fine to coarse sand with gravel/cobble. The fill soils were encountered to a maximum depth of 12 inches below the existing ground surface. Localized deeper accumulations of these soils may exist at the site. The fill soils are considered potentially compressible in their present state and should not be relied upon for support of fill and/or structural loads. Topsoil - Topsoil was found to mantle the Lindavista Formation in Trenches 1, 2, 5 and 6. As encountered, these soils generally consisted of brown, silty, fine sand with occasional gravel. The topsoil was encountered to a maximum depth of 3 inches below the existing ground surface and appeared to be disturbed. Localized deeper accumulations of these soils may exist at the site. The topsoil is considered potentially compressible and, in its present state, should not be relied upon for the support of fill and/or structural loads. Lindavista Formation - Based on our observations of the soil conditions exposed in the exploratory trenches, the subject property appears to be underlain by the Pleistocene-aged Lindavista Formation. The Lindavista Formation appears to underlie the entire site and, as encountered, generally consisted of brown and orange-brown, well-cemented fine to coarse sandstone with some rounded gravel. This unit generally exhibits favorable bearing characteristics. A sample of the Lindavista Formation (Trench 3, Sample 1) was tested in general accordance with DEC test standard 18-2 and found to have a very low expansion potential (expansion index = 0). Groundwater and Surface Water Indications of a static, near-surface groundwater table were not observed or encountered during our investigation. Groundwater is not anticipated to be a constraint to the proposed development. However, our experience indicates that near- surface groundwater conditions can develop in areas where no such groundwater SGC I Project No. 106H61 I conditions previously existed, especially in areas where a substantial increase in (surface water infiltration results from landscape irrigation or unusually heavy precipitation. It is anticipated that site development will include appropriate drainage provisions for control and discharge of surface runoff. I I I I Earthwork I Some site grading is anticipated to construct relatively level building pads for construction of the proposed structures. Site grading should be performed in I accordance with the following recommendations and the Recommended Earthwork Conclusions and Recommendations Based on the results of our soils investigation, it is our opinion that development of the site for construction of the proposed structure is feasible from a geotechnical standpoint. The following sections provide recommendations, from a geotechnical standpoint, which should be considered for design and construction of the proposed project. Specifications provided in Appendix C. Site Preparation - Prior to grading and construction activities, the site should be cleared of vegetation, debris and loose soils. Vegetation and loose debris should be properly disposed of off site. Holes resulting from removal of buried obstructions which extend below finished site grades should be filled with properly compacted soils. I - Removal/Recompaction of Compressible Soils - The existing fill soils and topsoil are considered compressible and unsuitable for the support of fill and structural I loads in their present condition. We recommend that these soils be removed in areas planned for structures, surface improvements or fill placement. As encountered in our exploratory trenches, these soils apparently underlie the I majority of the site and were encountered to a maximum depth of approximately 12 inches below the existing ground surface. The thickness and extent of these soils may vary and should be evaluated by the geotechnical consultant during I removal of these unsuitable soils. These soils are considered suitable for re-use " as compacted, structural fill provided they are free of organic material, deleterious debris and oversized materials (rocks with a maximum dimension of I greater than 6 inches). SGC I • . § Project No. 106H61 I Excavations - It is anticipated that excavation of the onsite soils can be (accomplished by conventional grading equipment in good operating condition. However, the onsite Lindavista Formation is a well-cemented sandstone and may locally require extra effort for excavation. * - Structural Fill Placement - Areas to receive fill and/or surface improvements should be scarified to a minimum depth of 6 inches, brought to near-optimum I moisture conditions, and compacted to at least 90 percent relative compaction, based on laboratory standard ASTM D1557. Fill soils should be brought to near-optimum moisture conditions and compacted in uniform lifts to at least 90 I percent relative compaction (ASTM D1557). The optimum lift thickness to produce a uniformly compacted fill will depend on the size and type of I construction equipment used. In general, fill should be placed in uniform lifts not exceeding 8 inches in loose thickness. Placement and compaction of fill should be observed and tested by the geotechnical consultant. In general, (placement and compaction of fill should be performed in accordance with local grading ordinances, sound construction practices, and the Recommended Earthwork Specifications presented in Appendix C. • - Transition (Cut/Fill) Condition - The potential for a transition (cut-fill) condition underlying the area of the proposed structure should be checked when project I plans are finalized and in the field during grading so that appropriate recommendations can be provided to reduce the potential for damage due to differential settlement of the structure across the transition. A typical I recommendation might include overexcavation or removal of the cut or natural portion underlying the building and replacement with moisture-conditioned fill soils compacted to at least 90 percent relative compaction (ASTM D1557). The recommended depth of overexcavation can vary depending on the actual conditions encountered during grading. A typical recommended depth of overexcavation is approximately three feet below finished pad grade extending for a distance of at least 5 feet beyond the perimeter of a proposed building. Trench Backfill - The onsite soils are generally suitable as trench backfill provided they are screened of organic matter and clasts over 6 inches in diameter. Trench backfill should be compacted by mechanical means to at least 90 percent relative compaction (ASTM D1557). SGC Project No. 106H61 Top-of-Slope Structural Setback A minimum horizontal setback distance from the faces of slopes is recommended for all structural footings and settlement-sensitive structures located near the tops of slopes. The recommended minimum setback is 7 feet for slopes less than 15 feet in height and 10 feet for slopes higher than 15 feet. This distance is measured from the outside edge of the footing, horizontally to the slope face (or to the face of a retaining wall). For footings founded in dense formational materials, the recommended minimum setback may be reduced to 5 feet. Soils within the setback zone possess poor lateral stability, and improvements (such as sidewalks, fences, etc) constructed within this area may be subject to damage due to lateral movement and/or differential settlement. Foundations We understand that the proposed single-family residence will be supported on continuous and/or spread footings with slab-on-grade floors and/or raised wood floors. Foundations and slabs should be designed in accordance with structural considerations and the following recommendations. These recommendations assume that the near- surface soils will have a low expansion potential. The proposed structure may be supported by continuous footings bearing entirely in firm natural soils or entirely in properly compacted fill soils at a minimum depth of 12 inches beneath the lowest adjacent grade for one-story structures (18 inches for two-story). Continuous footings should have a minimum width of 12 inches (1 5 inches for two-story) and be reinforced, at a minimum, with two No. 4 rebars (one near the top and one near the bottom). Spread footings should be designed in accordance with structural considerations and have a minimum width of 24 inches. For footings designed in accordance with the above recommendations, an allowable soil-bearing capacity of 2,000 pounds per square foot may be assumed. This value may be increased by one-third for loads of short duration such as wind and seismic loads. SGC Project No. 106H61 Slabs Concrete slab-on-grade floors and driveways should be designed in accordance with structural considerations and the following recommendations. Concrete slabs underlain by firm natural soils or properly compacted fill soils with a low expansion potential should have a minimum thickness of 4 inches and be reinforced at midheight with No. 3 rebars at 18 inches on center each way (or No. 4 rebars at 24 inches on center each way). Care should be taken by the contractor to insure that the reinforcement is placed at slab midheight. Slabs should be designed with crack control joints at appropriate spacings for the anticipated loading. Slabs should be underlain by a 2-inch layer of clean sand (sand equivalent greater than 30) which is underlain by a 10-mil moisture barrier which is underlain by a 2-inch layer of clean sand. The potential for slab cracking may be lessened by careful control of water/cement ratios. The use of low slump concrete is recommended. Appropriate curing precautions should be taken during placement of concrete during hot weather. We recommend that the upper approximately one foot of soil beneath concrete slabs-on-grade be moistened prior to placing concrete. We recommend that a slipsheet or equivalent be used if crack-sensitive flooring is planned directly on concrete slabs. Please note that the recommendations provided for slabs are minimums. They do not represent an adequate lesser substitute for those that may be recommended by the structural consultant. In addition, our recommendations are not intended to eliminate the possibility of cracks due to concrete shrinkage. Shrinkage cracks develop in nearly all slabs which are not specifically designed to prevent them. We recommend that a structural consultant or qualified concrete contractor be consulted to provide appropriate design and workmanship requirements for mitigation of shrinkage cracks. Lateral Resistance and Retaining Wall Design Parameters Footings and slabs founded in firm, natural soils or properly compacted fill soils may be designed for a passive lateral bearing pressure of 350 pounds per square foot per foot of depth. A coefficient of friction against sliding between concrete and soil of 0.4 may be assumed. These values may be increased by one-third when considering loads of short duration, such as wind or seismic forces. SGC I I I I I I I I I I I I I Project No. 106H61 Cantilever (yielding) retaining walls may be designed for an "active" equivalent fluid pressure of 35 pounds per cubic foot. Retaining walls which are rigid or restrained at their upper ends (non-yielding) may be designed for an "at-rest" equivalent fluid pressure of 50 pounds per cubic foot. Walls subject to surcharge loading of traffic from passenger vehicles located within a distance behind the wall equal to the wall height should be designed for an additional uniform pressure of 75 psf. If walls are surcharged by trucks or adjacent structures, the wall design should take into account the surcharge load. These values assume horizontal, nonexpansive granular backfill and free-draining conditions. Retaining wall footings should be designed in accordance with the previous foundation recommendations. We recommend that retaining walls be provided with appropriate drainage provisions. Appendix C contains a typical detail for drainage of retaining walls. The walls should also be appropriately waterproofed. Waterproofing treatments and alternative, suitable wall drainage products are available commercially. Design of waterproofing and its protection during construction should be provided by the project architect. Wall backfill should be compacted by mechanical means to at least 90 percent relative compaction (ASTM D1557). Care should be taken when using compaction equipment in close proximity to retaining walls so that the walls are not damaged by excessive loading. Seismic Considerations The principal seismic considerations for most structures in southern California are damage caused by surface rupturing of fault traces, ground shaking, seismically-induced ground settlement or liquefaction. The seismic hazard most likely to impact the site is ground shaking resulting from an earthquake on one of the major active regional faults. The possibility of damage due to ground rupture is considered minimal since no active faults are known to cross the site. The potential for liquefaction or seismically-induced ground settlement due to an earthquake is considered very low because of the dense nature of the underlying Lindavista Formation and anticipated absence of a static, near-surface groundwater table at the site. The effects of seismic shaking can be reduced by adhering to the most recent edition of the Uniform Building Code and current design parameters of the Structural Engineers Association of California. Based on our understanding of the onsite geotechnical I 8 I SGC Project No. 106H61 conditions, the seismic design parameters from the 1 997 Uniform Building Code, Section 1636, Tables 16-J, 16-S, 1 6-T and 16-U are provided below. UBC Table 16-J - Based on our understanding of the onsite geotechnical conditions and our review of UBC Table 1 6-J, the soil profile type for the subject property is SD ("Stiff Soil Profile"). UBC Table 16-U - Based on our review of the Active Fault Near-Source Zones map (0-36) prepared by the California Division of Mines and Geology, the nearest known active fault is the Rose Canyon fault zone located approximately 7 kilometers to the west of the site. The fault is considered a seismic source type B based on UBC Table 16-U. UBC Table 16-S - Based on our understanding of the onsite geotechnical conditions and minimum distance to the nearest known active fault (Rose Canyon fault zone), the Near-Source Factor (Na) is 1.0. UBC Table 16-T - Based on our understanding of the onsite geotechnical conditions and minimum distance to the nearest known active fault (Rose Canyon fault zone), the Near-Source Factor (Nv) is 1.1. Surface Drainage Drainage at the site should be directed away from foundations and collected and tightened to an appropriate discharge point. Consideration may be given to collecting roof drainage by eave gutters and directing it away from foundations via non-erosive devices. Water, either natural or from irrigation, should not be permitted to pond, saturate the surface soils or flow over the tops of slopes. Landscaping requiring a heavy irrigation schedule should not be planted adjacent to foundations or paved areas. Sulfate Content Test Results A sample (Trench 3, sample 1) of the onsite soils at the subject property was tested to assist in an evaluation of the degree of sulfate attack on ordinary (Type II) concrete. The test was performed in general accordance with California Test Method No. 417 and yielded a soluble sulfate content of 81 ppm. The test result indicates a SGC Project No. 106H61 "negligible" degree of sulfate attack based on UBC Table 19-A-3 criteria. The type of concrete specified and used should be determined by the project structural engineer. Plan Review/Construction Observation and Testing The recommendations provided in this report are based on our understanding of the project and interpolated subsurface conditions based on widely-spaced exploratory trenches. Final project drawings should be reviewed by Southland Geotechnical Consultants prior to construction to check that the geotechnically-related aspects of the project design are in accordance, with the recommendations of this report. Subsurface conditions should be checked in the field during construction. Geotechnical observation during site grading (removal/recompaction) and field density testing of compacted fill (including backfill of retaining walls) should be performed by Southland Geotechnical Consultants. Geotechnical observation of footing excavations should also be performed by the geotechnical consultant to check that construction is in accordance with the recommendations of this report. 10 SGC Project No. 106H61 If you have any questions regarding our report, please call. We appreciate the opportunity to be of service. Sincerely, SOUTHLAND GEOTECHNICAL CONSULTANTS Susan E. Tanges, CEG 1386 Managing Principal/Engineer! Attachments:Figure 1 - Site Location Map Figure 2 - Exploratory Trench Location Map Appendix A - References Appendix B - Logs of Exploratory Trenches Appendix C - Recommended Earthwork Specifications Distribution:(3) Addressee SGC \ N SITE LOCATION MAP Project No. 106H61 2733 Sunnyhill Drive, Carlsbad, California Scale (approximate): 1 inch = 2,000 feet Base Map: Recent slope failures, ancient landslides, and related geology of the north-central coastal area, San Diego County, California by F.H. Weber, 1982 FIGURE 1 SGC \ N EXPLORATORY TRENCH LOCATION MAP Project No. 106H61 4100 Sunnyhill Drive, Carlsbad, California Scale: Not to Scale LEGEND B Approximate location of T-6 exploratory trench Base map based on Site Plan provided by Larson Design and Consulting FIGURE 2 SGC APPENDIX A Project No. 106H61 APPENDIX A REFERENCES 1. California Division of Mines and Geology, 1994, Fault activity map of California and adjacent areas: CDMG Geologic Data Map No. 6. 2. Hart, E.W., 1997, Fault-rupture hazard zones in California: California Division of Mines and Geology, Special Publication 42, revised. 3. Tan, S.S., and Giffen, D.G., 1995, Landslide hazards in the northern part of the San Diego metropolitan area, San Diego County, California: California Division of Mines and Geology, Open-file Report 95-04. 4. Weber, F. H., Jr., 1982, Recent slope failures, ancient landslides, and related geology of the north-central coastal area, San Diego County, California: California Division of Mines and Geology, Open-file Report 82-12LA. SGC Project No. 106H61 APPENDIX B LOGS OF EXPLORATORY TRENCHES TRENCH NO. Trench 1 DEPTH DESCRIPTION 0-3" Topsoil (disturbed) - Brown, dry to slightly damp, medium dense, silty fine sand (SM); porous, fine roots, occasional gravel, gradational to: 3"-16" Lindavista Formation - Orange-brown, dry to slightly damp, very dense, slightly clayey fine to coarse sand (SC); with some rounded gravel, carbonate flecks Total depth = 16 inches (difficult excavation) No groundwater encountered Excavated and backfilled 10-26-00 Bag sample at 12" to 16" Trench 2 0-2" 2 "-8" Topsoil (disturbed) - Brown, dry, loose, silty fine sand (SM); porous, roots Lindavista Formation - Mottled gray and orange-brown, very dense, silty fine to coarse sandstone (SM); with occasional rounded gravel Total depth = 8 inches (difficult excavation) No groundwater encountered Excavated and backfilled 10-26-00 Bag sample at 2" to 8" Trench 3 0-12" Fill - Brown and orange-brown, dry, loose, silty fine to coarse sand (SM); with gravel/cobble, porous, roots 12"-25" Lindavista Formation - Brown grading with depth to orange- brown, dry, silty fine to medium sandstone (SM); some roots and pores in upper portion Total depth = 25 inches No groundwater encountered Excavated and backfilled 10-26-00 Bag sample at 12" to 25" SGC Project No. 106H61 LOGS OF EXPLORATORY TRENCHES (continued) TRENCH NO. Trench 4 DEPTH DESCRIPTION 0-3" Fill - Brown dry, loose, silty fine sand (SM) 3"-16" Lindavista Formation - Brown and orange-brown, dry, very dense, silty fine to medium sandstone (SM); occasional rounded gravel Total depth = 16 inches (difficult excavation) No groundwater encountered Excavated and backfilled 10-26-00 Trench 5 0-5" Topsoil - Brown, dry to slightly damp, medium dense, silty fine sand (SM); porous, fine roots, occasional gravel, gradational to: 5"-18" Lindavista Formation - Orange-brown, dry to slightly damp, very dense, slightly clayey fine to coarse sand (SC); with some rounded gravel, carbonate flecks Total depth =18 inches (difficult excavation) No groundwater encountered Excavated and backfilled 10-26-00 Bag sample at 5" to 18" Trench 6 0-2' 2"-8' Topsoil (disturbed) - Brown, dry, loose, silty fine sand (SM); porous, roots Lindavista Formation - Mottled gray and orange-brown, dry, very dense, silty fine to coarse sandstone (SM); with occasional rounded gravel Total depth = 8 inches (difficult excavation) No groundwater encountered Excavated and backfilled 10-26-00 SGC APPENDIX C RECOMMENDED EARTHWORK SPECIFICATIONS 1.0 General Intent These specifications are presented as general procedures and recommendations for grading and earthwork to be used in conjunction with the approved grading plans. These general earthwork specifications are considered a part of the recommendations contained in the geotechnical report and are superseded by recommendations in the geotechnical report in the case of conflict. Evaluations performed by the consultant during the course of grading may result in new recommendations which could supersede these specifications or the recommendations of the geotechnical report. It shall be the responsibility of the contractor to read and understand these specifications, as well as the geotechnical report and approved grading plans. 2.0 Earthwork Observation and Testing Prior to grading, a qualified geotechnical consultant should be employed for the purpose of observing earthwork procedures and testing fill placement for conformance with the recommendations of the geotechnical report and these specifications. It shall be the responsibility of the contractor to keep the geotechnical consultant apprised of work schedules and changes, at least 24 hours in advance, so that he may schedule his personnel accordingly. No grading operations shall be performed without the knowledge of the geotechnical consultant. The contractor shall not assume that the geotechnical consultant is aware of all site grading operations. It shall be the sole responsibility of the contractor to provide adequate equipment and methods to accomplish the work in accordance with applicable grading codes and agency ordinances, recommendations of the geotechnical report, and the approved grading plans. If, in the opinion of the geotechnical consultant, unsatisfactory conditions, such as unsuitable soil, poor moisture condition, inadequate compaction, adverse weather, etc., are resulting in a quality of work less than recommended in the geotechnical report and the specifications, the consultant will be empowered to reject the work and recommend that construction be stopped until the conditions are rectified. 3.0 Preparation of Areas to be Filled 3.1 Clearing and Grubbing: Sufficient brush, vegetation, roots, and all other deleterious material should be removed or properly disposed of in a method acceptable to the owner, design engineer, governing agencies and the geotechnical consultant. SGC The geotechnical consultant should evaluate the extent of these removals depending on specific site conditions. In general, no more than one percent (by volume) of the fill material should consist of these materials. In addition, nesting of these materials should not be allowed. 3.2 Processing: The existing ground which has been evaluated by the geotechnical consultant to be satisfactory for support of fill, should be scarified to a minimum depth of 6 inches. Existing ground which is not satisfactory should be overexcavated as specified in the following section. Scarification should continue until the soils are broken down and free of large clay lumps or clods and until the working surface is reasonably uniform, flat, and free of features which would inhibit uniform compaction. 3.3 Overexcavation: Soft, dry, organic-rich, spongy, highly fractured, or otherwise unsuitable ground, extending to such a depth that surface processing cannot adequately improve the condition, should be overexcavated down to competent ground, as evaluated by the geotechnical consultant. For purposes of determining pay quantities of materials overexcavated, the services of a licensed land surveyor or civil engineer should be used. 3.4 Moisture Conditioning: Overexcavated and processed soils should be watered, dried, or blended as necessary to attain a uniform near- optimum moisture content as determined by test method ASTM D1557. 3.5 Recompaction: Overexcavated and processed soils which have been properly mixed, screened of deleterious material, and moisture- conditioned should be recompacted to a minimum relative compaction of 90 percent as determined by test method ASTM D1557. 3.6 Benching: Where fills are placed on ground sloping steeper than 5:1 (horizontal to vertical), the ground should be stepped or benched. The lowest bench should be a minimum of 15 feet wide, excavated at least 2 feet into competent material as evaluated by the geotechnical consultant. Ground sloping flatter than 5:1 should be benched or otherwise overexcavated when recommended by the geotechnical consultant. 3.7 Evaluation of Fill Areas: All areas to receive fill, including processed areas, areas of removal, and fill benches should be evaluated by the geotechnical consultant prior to fill placement. SGC 4.0 Fill Material 4.1 General: Material to be placed as fill should be sufficiently free of organic matter and other deleterious substances, and should be evaluated by the geotechnical consultant prior to placement. Soils of poor gradation, expansion, or strength characteristics should be placed as recommended by the geotechnical consultant. 4.2 Oversize Material: Oversize fill material, defined as material with a maximum dimension greater than 6 inches should not be buried or placed in fills unless the location, materials, and methods are specifically recommended by the geotechnical consultant. 4.3 Import: If grading operations include importing of fill material, the import material should meet the requirements of Section 4.1. Sufficient time should be given to allow the geotechnical consultant to test and evaluate proposed import as necessary, prior to importing to the site. 5.0 Fill Placement and Compaction 5.1 Fill Lifts: Fill material should be placed in areas properly prepared and evaluated as acceptable to receive fill. Fill should be placed in near- horizontal layers approximately 6 inches in compacted thickness. Each layer should be spread evenly and thoroughly mixed to attain uniformity of material and moisture content throughout. 5.2 Moisture Conditioning: Fill soils should be watered, dried or blended as necessary to attain a uniform near-optimum moisture content as determined by test method ASTM D1557. 5.3 Compaction of Fill: After each layer has been evenly spread, moisture conditioned, and mixed, it should be uniformly compacted to not less than 90 percent of maximum dry density as determined by test method ASTM D1557. Compaction equipment should be adequately sized and be either specifically designed for soil compaction or of proven reliability to efficiently achieve the specified degree and uniformity of compaction. 5.4 Fill Slopes: Compaction of slopes should be accomplished, in addition to normal compaction procedures, by backrolling slopes with sheepsfoot rollers at increments of 3 to 4 feet in fill elevation gain, or by other methods producing satisfactory results. At the completion of grading, the relative compaction of the fill, including the embankment face should be at least 90 percent as determined by test method ASTM D1557. SGC 5.5 Compaction Testing: Field tests of the moisture content and degree of compaction of the fill soils should be performed by the geotechnical consultant. The location and frequency of tests should be at the consultant's discretion based on observations of the field conditions. In general, the tests should be taken at approximate intervals of 2 feet in elevation gain and/or each 1,000 cubic yards of fill placed. In addition, on slope faces, as a guideline, one test should be taken for each 5,000 square feet of slope face and/or each 10-foot interval of vertical slope height. 6.0 Subdrain Construction Subdrain systems, if recommended, should be constructed in areas evaluated for suitability by the geotechnical consultant. The subdrain system should be constructed to the approximate alignment in accordance with the details shown on the approved plans or provided herein. The subdrain location or materials should not be modified unless recommended by the geotechnical consultant. The consultant may recommend modifications to the subdrain system depending on conditions encountered. Completed subdrains should be surveyed for line and grade by a licensed land surveyor or civil engineer. 7.0 Excavations Excavations and cut slopes should be evaluated by the geotechnical consultant during grading. If directed by the geotechnical consultant, further excavation, overexcavation, and/or remedial grading of cut slopes (i.e., stability fills or slope buttresses) may be recommended. 8.0 Quantity Determination The services of a licensed land surveyor or civil engineer should be retained to determine quantities of materials excavated during grading and/or the limits of overexcavation. SGC RETAKING WALL DRAINAGE SOIL BACKFILL. COMPACTED TO 9O PERCENT RELATIVE COMPACTION* FILTER FABRIC ENVELOPE (MIRAF1 140N OR APPROVED EQUIVALENT) ** "—S-SSCOMPACTED RETAINING WALL WALL WATERPROOFING PER ARCHITECT'S SPECIFICATIONS WALL FOOTING NOT TO SCALE SPECIFICATIONS FOR CALTRANS CLASS 2 PERMEABLE MATERIAL U.S. Standard Sieve Size 1" 3/4" 3/8" No. 4 No. 3 No. 30 No. 50 No. 200 % Passing 100 90-100 40-100 25-40 18-33 5-15 0-7 0-3 Sand Equivalent>75 3M'-1-1/2' CLEAN GRAVEL 4' (WIN.) DIAMETER PERFORATED PVC PIPE (SCHEDULE 4O OR EQUIVALENT) WITH PERFORATIONS ORIENTED DOWN AS DEPICTED MINIMUM 1 PERCENT GRADIENT TO SUITABLE OUTLET 3' MIN. COMPETENT BEDROCK OR MATERIAL AS EVALUATED BY THE GEOTECHNICAL CONSULTANT * BASED ON ASTM 01557 **IF CALTRANS CLASS 2 PERMEABLE MATERIAL (SEE GRADATION TO LEFT) IS USED IN PLACE OF 3/4'-1-1/2* GRAVEL, FILTER FABRIC MAY BE DELETED. CALTRANS CLASS 2 PERMEABLE MATERIAL SHOULD BE COMPACTED TO 90 PERCENT RELATIVE COMPACTION * NOTECOMPOSITE DRAINAGE PRODUCTS SUCH AS MIRADRAJN :OR J-DRAJN MAY BE USED AS AN ALTERNATIVE TO GRAVEL OR CLASS Z INSTALLATION SHOULD BE PERFCRKCD IN ACCORDANCE WITH MANUFACTURER'S SPECIFICATIONS. SGC TRANSITION LOT DETAILS CUT-FILL LOT EXISTING GROUND SURFACE 5' }v^j;£'3ir£ir£ii;: v\t^ lr_ri:tr^^"^"^^^"^'^-^"^^--r- 38" MIN. OVEREXCAVATE AND RECOMPACT COMPETENT BEDROCK OR MATERIAL EVALUATED BY THE GEOTECHN1CAL CONSULTANT CUT LOT EXISTING GROUND SURFACE -C- REMOVE ^--UNSUITABLE MATERIAL ^ AND RECOMPACT ^COMPETENT BEDROCK OR MATERIAL EVALUATED. BY THE GEOTECHNICAL CONSULTANT *NOTE: Deeper or laterally more extensive overexcavation and recompaction may be recommended by the geotechnical consultant based on actual field conditions encountered and locations of proposed improvements SGC KEY AND BENCHING DETAILS FILL SLOPE PROJECT 1 TO 1 UNE FROM TOE OF SLOPE TO COMPETENT MATERIAL EXISTING QHOUNO SURFACE- \ REMOVE UNSUITABLE MATERIAL BENCH rf^K£2* MIN.g^j ' MIN.—4 WEST I 2' KEY LOWES OEPTH BENCH (XEY3 FILL-OVER-CUT SLOPE EXISTING GROUND SURFACE I U—15* WIN.—j 2' ' LOWEST ' MiN. SEHCH REMOVE UNSUITABLE MATERIAL CUT SLOPE (TO SS EXCAVATED PRIOR TO FILL PLACEMENT} EXISTINGGROUND SURFACE- CUT-OVEH-FILL SLOPE CUT SLOPS (TO BE EXCAVATED PRIOR TO FILLPLACEMENT) PflCJECT t TO 1 UN6 FROM TOE OF 3LOPS TO COMPETENT MATERIAL REMOVE UNSUITABLE 'MATERIAL BENCH T f-^15* MIN.——I 2- MIN. I LOWS3T I KHY DEPTH ^^b« aJterad baaed on field conditions encountered. SGC ROCK DISPOSAL DETAIL • FINISH ORAOE 3LOPE FACE fcTiNl:iS5€g§5?H:- :5™as=5oir^A~cfID >iCC~^^p^^S^S^-"—^^Jg-r-E-iass-^ OVSHSIZE WINDROW QRANULAfl SOIL (3.£^ 3O) TO BE OEN3IF1EO IN PLACE BY FLOODING DETAIL TYPICAL PROFILE ALONG WINDROW 1) Rock with maximum dimensions greater than 6 inches should not be used within 10 feetvertically of finish grade (or 2 feet below depth of lowest utility whichever is greater), and t5 feet horizontally of slope faces. 2) Rocks with maximum dimensions greater than 4 feet should not be utilized in fills. 3) Rock placement, flooding of granular soil, and fill placement should be observed by the geotechnical consultant. 4) Maximum size and spacing of windrows should be in accordance with the above details Width of windrow should not exceed 4 feet. Windrows should be staggered vertically (as depicted). 5) Rock should be placed in excavated trenches. Granular soil (S.E. greater than or equalto 30) should be flooded in the windrow to completely fill voids around and beneath rocks. SGC FILL / BUTTRESS OUTLET PIPES 4' 0 NONPERFORATEO PIPE. 100' MAX. O.C. HORIZONTALLY, 30' MAX. O.C. VERTICALLY ^BACK CUT 1:1 OR FLATTER SEE SUBORAIN TRENCH DETAIL LOWEST SUBORAIN SHOULD BE SITUATED AS LOW AS POSSIBLE TO ALLOW SUITABLE OUTLET ^ 10' MIN. EACH SIDEPERFORATED NON-PERFORATED OUTLET PIPE - O-N NECTION DETAIL KEY DEPTH KEY WIDTH AS NOTED ON GRADING PLANS 15' MIN. 6* MIN. OVERLAP 3/4'-1-1/2' CLEAN GRAVEL (3ft?/ft. MIN.) 4' 9NON-PERFORATED FILTER FABRIC ENVELOPE (MIRAFI 140N OR APPROVED EQUIVALENT)* SEE T-CONNECTION DETAIL 6' MIN. COVER PERFORATED PIPE 4' MIN. BEDDING SUBDRAIN TRENCH DETAIL *IF CALTRANS CLASS 2 PERMEABLE MATERIAL IS USED IN PLACE OF 3/4'-1-1/2* GRAVEL, FILTER FABRIC MAY BE DELETED SPECIFICATIONS FOR CALTRANS CLASS 2 PERMEABLE MATERIAL U.S. Standard Sieve Size 1" 3/4" 3/8" No. 4 No. 8 ' No. 30 No. 50 No. 200 Passing 100 90-100 40-100 25-40 18-33 5-15 0-7 0-3 Sand Equt'valent>75 NOTES: ^ Class 200,SOR 21 should b« used for maximum (III depths of 10O fast. SGC