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HomeMy WebLinkAboutTract Map 9833-1 Lot 26 Preliminary Soil Engineering Evaluation -7. . . \'(2. 'i'~~-I \...0'\ z:~ W. C. HOBBS, CONSUL liNG ENGINEER 30833 LILAC CIRCLE MURRIETA, CALIFORNIA 92563 (909) 696-7059 Date: January 17, 2006 Project No: 06001-2 I Mr. and Mrs. Householder ; 33269 Elizabeth Road T emecula, California 92592-4388 : Subject: Preliminary Soil Engineering Evaulation, Proposed Residence, Lot 26 of Tract 9338.1, 31685 Pio Pico Road, City of Temecula Riverside County, Calif"APN 959.{)20.{)26 I Dear Mr. and Mrs. Householder, I Pursuant to your authorization, a limited soil engineering evaluation was conducted on the subject. I lotto determine the distribution and engineering characteristics of earth materials present in the area I of proposed grading and the proposed residence. The results offield exploration, together with the I results of the laboratory tests, are summarized in the attached appendix. Additional information provided herein indudes preliminary foundation design for proposed residential construction. , Accompanying Maps and Appendices . Attached Appendix A, Summary of Laboratory and Field Test Results , Attached Appendix S, General Earthwork and Grading Specifications . Scope of Work The scope of work performed for this study induded the following: 1. Observation of a lot with undocumented fill upon it, 2. Laboratory testing, and; 3. Preparation of this report induding conclusions and recommendations pertinent to the proposed construction. \ . . I Mr. and Mrs. Householder, Preliminary Soils ,Project No: 06001-2 Page: 2 : Site Description 'The site is a generally rectangular shaped lot, roughly 2.34 acres in size with flat to gentle : topographic relief. The lot drains to the southeast. In the vicinity of the proposed residence and : grading the lot slopes an average of 1-2 percent to the northwest. In the area of the proposed . residence, which is near Pio Pico Road. minor cuts and fills will be required to achieve final grades : and appropriate drainage. I Fiield Work I Field work on the site consisted of observation a small excavation for the purpose of recovering I samples of representative earth materials for laboratory testing. The results of these tests are : contained in the attached Appendix A. Additionally, a reconnaissance of the nearby area was : conducted in order to obtain information pertinent to the site. Supplemental to sample recovery, a : backhoe was obtained to dig a trench in the central portion of the lot. i Oservation of the excavation indicated that the existing materials were of moderate density in place , with no visible pores, and is damp at the surface. Observation of the earth materials indicates I natural lot consisting of a thick mantle of colluvial and alluvial soils in vicinity of the proposed I residence. The earth materials consist of slightly silty sands. I Laboratory Testing , The maximum dry density and optimum moisture content of the soil was determined in a=rdance 'with ASTM test designation D 1557-82. The expansion index testing should be conducted on a I representative sample at the completion of rough grading in order to determine the expansion I potential of the near surface soils in the vicinity of proposed foundations. The expansion index test : should be conducted in a=rdance with use 29-2. W. C. HOBBS, CONSULTING ENGINEER 2- . . I Mr, and Mrs. Householder, Preliminary Soils ! Project No: 06001-2 Page: 3 CONCLUSIONS AND RECOMMENDATIONS I Conclusions , The development ofthe site for single or multi-story residential construction is both feasible and safe ! from a geotechnical standpoint provided that the recommendations contained herein are implemented during design and construction. , 1: The site is in a natural configuration. ; 2: There is a nominal cut at the in the front of the lot, for previous roadway construction. : 3. Observation, dassification, indicate that the near surface soils have a low expansion potential. I Recommendations The recommendations contained herein are contingent upon providing the services listed in the I Construction section in order to confirm design assumptions and review the field conditions of any : excavations for possible anisotropic properties. If observation indicates that the conditions are . different than those indicated in this report, additional, or modifications to the, recommendations may 'become necessary. ! Site Grading In order to provide proper support for building foundations, remedial grading will be required due to ,the 'loose nature of the near surface colluvial soils in the vicinity of the proposed residence. : Proposed grading should consist of the removal and replacement of all loose soils. Additionally, , when removed, the earth materials that support fill for residential construction should be evaluated 'at the time of construction. It may be necessary to over excavated some colluvial and or alluvial . materials to provide adequate support for fills and structural foundations. The depth of removal for : colluvial soils should be estimated to be 5 feet below existing grade and or 3 feet below the bottoms : of proposed foundations, whichever is the greater. All grading and retaining wall backfills should be . placed in a=rdance with minimum standards presented a the back of this report, Appendix S, : Standard Specifications for Earthwork eonstruction. W. C. HOBBS, CONSULTING ENGINEER .?> ~ . . I Mr. and Mrs, Householder, Preliminary Soils 'Project No: 06001-2 Page: 4 I Recommendations, continued I Bearing Value and Footing Geometry , A safe allowable'bearing value for foundations embedded into properly compacted fill is 1,500 pst. , eontinuous footings should have a minimum width of 12 inches and depth of 18 inches and conform i to the minimum criteria of the use for single and or multistory construction for low expansive soils. 'The use of isolated column footings is not discouraged, however, where utilized, should have a , minimum embedment of 18 inches below lowest soil grade. The minimum distance of the bottom : of footings on the outside edge and the native slope face on the south is 8 feet. : Settlement The bearing value recommended above reflects a total settlement of 0.5" and a differential , settlement of 0.5". Most of this settlement is expected to occur during construction and as the loads , are being applied. I Concrete Slabs , All concrete slabs on grade should be 4 inches thick. They should be underlain by 2 inches of sand 'or gravel. Areas that are to be carpeted or tiled, or where the intrusion of moisture is objectionable, , should be underlain by 6 mil visqueen properly protected from puncture with an additional 1 inch of 'sand over it. This arrangement of materials would result in a profile downward of concrete, 1 inch : of sand, 6 mil visqueen, 2 inches of sand and subgrade soil. Contractors should be advise that when : pouring during hot orwindyweather conditions, they should provide large slabs with sufficiently deep ,weakened plane joints to inhibit the development of irregular or unsightly cracks. Also, 4 inch thick ,slabs should be jointed in panels not exceeding 12 feet in both directions to augment proper crack ,direction and development. i Reinforcement : Continuous footings should be reinforced with a minimum of one number 4 steel bar placed at the :top and one at the bottom. Slabs should be reinforced with a minimum of number 3 steel bars , placed at the center of thickness at 18-inch centers both ways or welded wire fabric equivalent to '10x10 10/10 may be used. It is understood that the sectional values for the two schedules are : different, and is of no design concem. The steel bars have been proven to have a better ,performance history and selection is up to the builder. Additional requirements may be imposed by ;the structural engineering design. W. C. HOBBS, CONSULTING ENGINEER ~ . . . I Mr, and Mrs. Householder, Preliminary Soils I Project No: 06001-2 Page: 5 I Recommendations, continued I Retaining Walls I Retaining walls should be designed to resist the active pressures summarized in the following table. , The active pressure is normally calculated from the lowermost portion of the footing to the highest ; ground surface at the back ofthe wall. The active pressures indicated in the table are equivalentfluid ; densities. Walls that are not free to rotate or that are braced at the top should use active pressures : that are 50% greater than those indicated in the table. RETAINING WALL DESIGN PRESSURES Slooeof adiacent around Active Pressure Passive Pressure LEVEL 2:1 30 pet 42 pet 300 pet 200 pet , These pressures are for retaining walls backfilled with noncohesive, granular materials and provided ,with drainage devices such as weep holes or subdrains to prevent the build-up of hydrostatic i pressures beyond the design values. It is imperative that all retaining wall backfills be compacted to 'a minimum of 90 percent relative compaction in order to achieve their design strength. Failure to i provide proper drainage and minimum compaction may result in pressures against the wall that will , exceed the design values indicated above. Surface waters should be directed away from retaining , wall backfill areas so as not to intrude into the backfill materials. I Lateral Loads The bearing value of the soil may be increased by one third for short duration loading (wind, : seismic). Lateral loads may be resisted by passive forces developed along the sidllS of concrete I footings or by friction along the bottom of concrete footings. The value of the passive resistance for level ground may be computed using an equivalent fluid density of300 petfor level ground. The total ! force should not exceed 3,000 pst. A coefficient of friction of .40 may be used for the horizontal ,soil/concrete interface for resistance of lateral forces. If friction and passive forces are combined, I then the passive values should be reduced by one third. W. C. HOBBS, CONSULTING ENGINEER 5' . . I Mr. and Mrs. Householder, Preliminary Soils i Project No: 06001-2 Page: 6 I Recommendations, continued I Fiine Grading I Fine grading of areas outside of the residence should be a=mplished such that positive drainage I exists away from all footings. Run-off should be conducted off the property in a non erosive manner I toward approved drainage devices at the street or the rear of the property per approved plans. I Construction , A soil engineer should be present during the excavation of the foundations, as well as earthwork : construction, to test and or confirm the conditions encountered during this study. It is recommended I to have the foundation excavations observed by a soil engineer prior the placement of construction I materials in them as consequential changes and differences may exist throughout the earth I materials on the site. It may be possible that certain excavations may have to be deepened slightly i ifearth materials are found to be loose or weak. : Seismic Considerations . This site is located approximately 1 km from a type B fault. (Plate 0-34). The soil profile that is I recommended is SD' : Seismic Zone 4 : Soil Profile is SD : Seismic eoefficient ea is O.44Na : Seismic eoefficient ev is O.64Nv I Near-Source Factor Na is 1.3 I Near-Source Factor Nv is 1.6 W. C. HOBBS, CONSULTING ENGINEER fe . . I Mr. and Mrs. Householder, Preliminary Soils I Project No: 06001-2 Page:? CLOSURE , This evaluation was performed in a=rdance with generally accepted engineering practices. The : condusions and recommendations contained in this report were based on the data available and the I interpretation of such data as dictated by our experience and background. Hence, our conclusions i and recommendations are professional opinions; therefore, no other warranty is offered or implied. , The opportunity to be of service is appreciated. Should questions or comments arise pertaining to I this document, or if we may be of further service, please do not hesitate to call our office. I Respectfully Submitted, I W, C. HOBBS, CONSULTING ENGINEER ( Bill Hobbs, ReE 42265 . eivil Engineer Distribution: , Attachments: Addressee (4) Appendix A - Summary of Laboratory and Field Test Results Appendix B - General Earthwork and Grading Specifications W. C. HOBBS, CONSULTING ENGINEER 1 . APPENDIX A SUMMARY OF TEST RESULTS . W. C. HOBBS, CONSULTING ENGINEER ~ . . APPENDIX A SUMMARY OF MAXIMUM DENSITY TEST RESULTS eurve Letter Soil Descriotion Maximum Optimum Densitv ocf Moisture % A SAND, fine to med., sl. Silty Tan (SM) 128.6 10.1 Maximum density and optimum moisture determined in a=rdance with test method ASTM D 1557-78. W. C. HOBBS, CONSULTING ENGINEER 9. . APPENDIX B . GENERAL EARTHWORK AND GRADING SPECIFICATIONS W. C. HOBBS, CONSULTING ENGINEER \0 . . GENERAL EARTHWORK AND GRADING SPECIFICATIONS 1,0 I GENERAL INTENT These specifir.ations present general procedures and requirements for grading and earthworK as shown on the approved grading plans, including preparation of areas to be filled, placement of fill, installation of subdrains, and excavations. The recommendations contained in the geotechnical report are a part of the earthworK and grading specifications and shall supersede the provisions contained hereinafter in the case of conflict. Evaluations performed by the consultant during the course of grading may result in new recommendations of the geotechnical report. 2.0 I EARTHWORK OBSERVATION AND TESTING Prior tOI the commencement of grading, a qualified geotechnical consultant (soils engineer and engineering geologist, and their representatives) shall be employed for the purpose of observing earthworK and testing the fills for conformance with the recommendations of the geotechnical report and these specifications. It will be necessary that the consultant provide adequate testing and observation so that he may determine that the worK was accomplished as specified. It shall be the responsibility of the contractor to assist the consultant and keep him apprised of worK schedules and changes so that he may schedule his personnel accordingly. 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 or agency ordinances, these specifications and the approved grading plans. If in the opinion of the consultant, unsatisfactory conditions, such as questionable soil, poor moisture condition, inadequate compaction, adverse weather, etc., are resulting in a quality of worK less than required in these specifications, the consultant will be empowered to reject the worK and recommend that construction be topped until the conditions are rectified. Maximum dry density tests used to determine the degree of compaction will be performed in accordance with the American Society ofT esting and Materials tests method ASTM D 1557-78. 3.0 I PREPARATION OF AREAS TO BE FILLED 3.1 Clearing and Grubbing: All brush, vegetation and debris shall be removed or piled and othelWise disposed of. 3.2,Processing: The existing ground which is determined to be satisfactory for support offill shall be scarified to a minimum depth of6 inches. Existing ground which is not satisfactory shall be over excavated as specified in the following section. Scarification shall continue until the soils are broken down and free of large day lumps or dods and until the worKing surface is reasonably un~orm and free of uneven features which would inhibit un~orm compaction. 3.3,Overexcavation: Soft, dry, spongy, highly fractured orothelWise unsuitable ground, extending to such a depth that the surface processing cannot adequately improve the condition, shall be over excavated down to firm ground, approved by the consultant. 3.4,Moisture Conditioning: Over excavated and processed soils shall be watered, dried-back, blended, and/or mixed, as required to attain a un~orm moisture content near optimum. 3,5 Recompaction: Over excavated and processed soils which have been properly mixed and moisture- conditioned shall be recompacted to a minimum relative compaction of 90 percent. 3.6,Benching: Where fills are to be placed on ground with slopes steeper than 5: 1 (horizontal to vertical units), the ground shall be stepped or benched. The lowest bench shall be a minimum of 15 feet wide, shall be at least 2 feet deep. shall expose firm material, and shall be approved by the consultant. Other benches shall be excavated in firm material for a minimum width of 4 feet. Ground sloping flatter than 5 : 1 shall be benched or othelWise over excavated when considered necessary by the consultant. 3.7 Approval: All areas to receive fill, including processed areas, removal areas and toe-of-fill benches shall be approved by the consultant prior to fill placement. W. C. HOBBS, CONSULTING ENGINEER \\ , . . . 4,0 I FILL MATERIAL 4.1 General: Material to be placed as fill shall be free of organic matter and other deleterious substances, and shall be approved by the consultanLSoils of poor gradation, expansion, or strength characteristics shall be placed in areas designated by consultant or shall be mixed with other soils to seNe as satisfactory fill material. 4.2 Oversize: Oversize material defined as rock, or other irredudble material with a maximum dimension greater than 12 inches. shall not be buried or placed in fills, unless the location, materials, and disposal methods are specifically approved by the consultant. Oversize disposal operations shall be such that nesting of oversize material does not occur, and such that the oversize material is completely surrounded by compacted ordensified fill. Oversize material shall not be placed within 10 feet vertically of finish grade or within the range of Mure utilities or underground construction, unless specifically approved by the consultant. 4.3 Import: If importing of fill material is required for grading, the import material shall meet the requirements of Section 4. 1. 5.0 I FILL PLACEMENT AND COMPACTION 5.1 Fill Lifts: Approved fill material shall be piaced in areas prepared to receive fill in near-horizontal layers not exceeding 6 inches in compacted thickness. The consultant may approve thicker lifts if testing indicates the grading procedures are such that adequate compaction is being achieved with lifts of greater thickness. Each layer shall be spread evenly and shall be thoroughly mixed during spreading to attain uniformity of material and moisture in each layer. 5.2 Fill Moisture: Fill layers at a moisture content less than optimum shall be watered and mixed, and wet fill layers shall be aeraled by scarification or shall be blended with drier material. Moisture-conditioning and mixing of fill layers shall continue until the fill material is at a uniform moisture content or near optimum. 5,3 Compaction of Fill: After each layer has been evenly spread, moisture conditioned, and mixed, ~ shall be uniformly compacted to not less than 90 percent of maximum d'Y density. Compaction equipment shall be adequately sized and shall be either specifically designed for soil compaction or of proven reliability, to effidentiy achieve the specified degree of compaction. 5.4 Fill Slopes: Compaction of slopes shall be accomplished, in addition to normal compacting procedures, by backfilling of slopes with sheepsfoot rollers atfrequentincrementsof2 to 3 feet in fill elevation gain, orbyothermethods producing satisfacto'Y results. Atthe completion of gradi99, the relative compaction of the slope out to the slope face shall be at least 90 percent. 5.5 Compaction Testing: Field tests to check the ill moisture and degree of compaction will be performed by the consultant. The location and frequency of tests shall be at the consultanfs discretion. In general, the tests will be taken at an inteNal not exceeding 2 feet in vertical rise and/or 1:,000 cubic yards of embankment. 6.0 ,SUBDRAlN INSTALLATION Subdrain systems, if required, shall be installed in approved ground to conform to the approximate alignment and details shown on the plans or herein. The subdrain location or materials shall not be changed or modified without the approval of the consultant. The consultant, however, may recommend and upon approval, direct changes in subdrain line, grade or material. All subdrains should be SUNeyed for line and grade after installation, and suffident time shall be allowed for the sUNeys, prior to commencement of filling over the subdrains. W. C. HOBBS, CONSULTING ENGINEER \2-- 4' .. . . 7.0 I EXCAVATION Excavation and cut slopes will be examined during grading. If directed by the consultant. further excavation or over excavation and refilling of cut areas shall be perfonned, and/or remedial grading of cut slopes shall be perfonned. Where fill-over-cut slopes are to be graded, unless otherwise approved, the cut portion of the slope shall made and approved by the consultant prior to placement of materials for construction of the fill, portion of the slope. 8.0 ' TRENCH BACKFILL 8.1. Supervision: Trench excavations for the utility pipes shall be backfilled under engineering supervision. 8.2 Pipe Zone: After the utility pipe has been laid, the space under and around the pipe shall be backfilled with clean sand or approved granula~ soil to a depth of at least one foot over the top of the pipe. The sand backfill shall be unifonnly jetted into place before the controlled backfill is placed over the sand. 8.3 Fill Rlacement: The onsite materials. or other soils approved by the engineer. shall be watered and mixed as necessary prior to placement in lifts over the sand backfill. 8.4 Compaction: The controlled backfill shall be compacted to at least 90 percent of the maximum laboratory density as detennined by the ASTM compaction method described above. 8,5 Observation and Testing: Field density tests and inspection of the backfill procedures shall be made by the soil engineer during backfilling too see that the proper moisture content and unifonn compaction is being maintained. The contractor shall provide test holes and exploratory pits as required by the soil engineer to enable sampling and testing. W. C. HOBBS, CONSULTING ENGINEER '8