Loading...
HomeMy WebLinkAboutTract Map 9833-3 Lot 9 Preliminary Geotechnical Investigation . 1. . RECEIVED FES 1 0 2003 CITY OF TEMECULA ENGINEERING. DEPARTMENT 0' W. C. HOBBS, CONSULTING ENGINEER 39697 CEDARWOOD DRNE MURRIETA, CALIFORNIA 92563 (909) 696-7059 Date: December 31, 2002 Project No: 02051-1 IMr. and Mrs. Boster :B:& E Properties 11342 Southhills:Drive :Chula Vista, California 91915 : Subject: Preliminary Geotechnical Evaluation, Proposed Development of Lot 9 otTract 9833-3, Calle De Velardo, City of Temecula, California : Dear Mr. Shirazi, : Pursuantto your authorization and a requirement by the City ofTemecula, a limited soil engineering ,evaluation was conducted on the subject lot to determine the distribution and engineering . characteristics of earth materials present. The results of field exploration, together with the results : of the laboratory tests, are summarized in the attached appendix. ,Additional information provided herein includes preliminary foundation design for proposed I residential construction. , Accompanying Maps and Appendices , Attached Appendix A, Summary of Laboratory and Field Test Results , Attached Appendix B, General Earthwork and Grading Specifications Scope of Work The scope of work performed for this study included the following: 1. Observation of a natural lot with a minor fill placed at the front resulting from street construction, 2. Evaluation of excavations, cut slopes on the subject site to observe the existing soil conditions and recover samples. 3. Laboratory testing, and; 4. Preparation of this report including conclusions and recommendations pertinent to the proposed construction. \ i. . Mr. & Mrs. Boster, Lot 9, Tract 9833-3, Calle De Velardo Project No: 02051-1 Page: 2 :Site Description IThe site is roughly rectangular in shape, fronting 483 feet along Calle De Velardo on the east and, :extending 375 i feet to the west. The site is currently not graded with the exception of a minor fill ,placed at the front to facilitate roadway construction. The site is undulating, with a ridge protruding .a northeasterly direction from the southem boundary of the site. Presently, the site is covered with :annual grasses and weeds that have not been recently cut. No visible signs of erosion were noted. : Field Work . Field work on the site consisted of observation of cut slopes on the site. Small excavations were . made on them for the purpose of recovering 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 pertinentto the site. : Observation of the cut slopes indicated that the existing materials were of a moderate to high density in place with no visible pores, and is dry at the surface, damp at 1 foot and moist below 3 feet. : Observation of the earth materials indicates a thin mantle of top soil with minor root materials, I transitioning quickly at a depth of 1 to 2 feet to native earth materials, (Pauba Formation). The I native earth materials are comprised of relatively clean silty sand. Grain sizes ranged from .01 mm I to 1 mm. The native earth materials were observed to be well bedded, with layers of different colors ; and grain sizes. The soils were observed to be damp and evenly moist below 4 feet or so. I Laboratory Testing The maximum dry density and optimum moisture content of the soil was determined in accordance , with ASTM test designation D 1557-82. The expansion index testing should be conducted on a representative sample at the completion of rough grading in order to determine the expansion potential of the near surface soils in the vicinity of proposed foundations. The expansion index test should be conducted in accordance with UBC 29-2. However, based on classification, the upper 4 . to 8 feet of soils .are expected to have an expansion potential of low to very low. w. C. HOBBS, CONSULTING ENGINEER <Z-- . . Mr. & Mrs. Boster, Lot 9, Tract 9833-3, Calle De Velardo Project No: 02051-1 Page: 3 CONCLUSIONS AND RECOMMENDATIONS :Conclusions The development of the 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. 11: The site is essentially untouched, graded only at the eastem edge for roadway construction. 2: The natural soil is observed to be loose in place in the upper 1 to 2 feet, then dense below that. : 3.0bservation, classification, indicate that the near surface soils have a very low expansion potential. I Recommendations The recommendations contained herein are contingent upon W. C. Hobbs, Consulting Engineer or , his assigns providing the services listed in the Construction section in order to confirm design : assumptions and review the field conditions of any excavations for possible anisotropic properties. Ilf 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 not be required. : Proposed grading consists of creating a driveway and pad and foundation areas and or the balance , placement of fills on the site for a pad area in the vicinity of the proposed structures and driveway. , All grading and retaining wall backfills should be placed in accordance with minimum standards presented a the back of this report, Appendix B, Standard Specifications for Earthwork Construction. Grading should consist of the removal of the upper 2 feet of topsoil in the building area and approximately 5 feet beyond the perimeter and where ever fill is to be placed. Final determination for the depth of excavation shall be made in the field during grading operations. It is possible that additional excavations may result in more or less excavation due to the density of topsoil and any existing fill that may be present in the building area. Fills placed on the fill constructed by roadway construction need only to process the upper 12 inches of grade prior to the placement of fills, however, deep excavation to the basal surface of the fill should be conducted in the vicinity of the residence. w. C. HOBBS, CONSULTING ENGINEER :3 . . Mr. & Mrs. Boster, Lot 9, Tract 9833-3, Calle De Velardo Project No: 02051-1 Page: 4 Recommendations, continued iBearing Value and Footing Geometry :A safe allowable bearing value forfoundations embedded into native bedrock materials or properly :compacted fill is 2000 psf. This value may be increased at the rate of 100 psf per foot of depth and 1100 psf per foot of width over the minimums, but should not exceed 2500 psf. Continuous footings 'should have a minimum width of 12 inches and depth of 12 inches and conform to the minimum ,criteria of the UBC for single and or multistory construction for very low expansive soils. The use of lisolated column footings is not discouraged, however, where utilized, should have a minimum 'embedment of 12 inches below lowest soil grade. The minimum distance of the bottom of footings on the outside edge and the native slope face is 10 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 I pouring during hot or windy weather 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. Sands encountered on the site may qualify as slab underlayment. I Reinforcement I Continuous footings should be reinforced with a minimum of one number 4 steel bar placed at the I top and one at the bottom. Slabs should be reinforced with a minimum of number 3 steel bars I placed at the center of thickness at 18-inch centers both ways or welded wire fabric equivalent to 1 Ox1 0 10/10 may be used. It is understood that the sectional values for the two schedules are I different, and is of no design concem. The steel bars have been proven to have a better I performance history and selection is up to the builder. Additional requirements may be imposed by , the structural engineering design. W. C. HOBBS, CONSULTING ENGINEER ~ . . Mr. & Mrs. Boster, Lot 9, Tract 9833-3, Calle De Velardo Project No: 02051c1 Page: 5 Recommendations, continued Retaining Walls 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 of the wall. The active pressures indicated in the table are equivalent fluid densities. Walls that are not free to rotate or that are braced at the top should use active pressures ithat are 50% greater than those indicated in the table. RETAINING WALL DESIGN PRESSURES Slooe of adiacent around Active Pressure Passive Pressure 2:1 30 pcf 40 pcf 300 pcf 200 pcf LEVEL 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 : 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 : 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 sides of concrete ! footings or by friction along the bottom of concrete footings. The value of the passive resistance for i level ground may be computed using an equivalent fluid density of 300 pcffor level ground. The total I force should not- exceed 3000 psf. A coefficient of friction of .40 may be used for the horizontal ~ soiVconcrete 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 . . Mr. & Mrs. Boster, Lot 9, Tract 9833-3, Calle De Velardo Project No: 02051-1 Page: 6 , Recommendations, continued I F1ine Grading i Fine grading of areas outside of the residence should be accomplished such that positive drainage ! exists away from all footings. Run-off should be conducted off the property in a non erosive manner ! 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 to have the foundation excavations observed by a soil engineer prior the placement of construction . materials in them as consequential changes and differences may exist throughout the earth , materials on the site. It may be possible that certain excavations may have to be deepened slightly , if earth materials are found to be loose or weak. W. C. HOBBS, CONSULTING ENGINEER ~ . . , Mr. & Mrs. Boster, Lot 9, Tract 9833-3, Calle De Velardo . Project No: 02051-1 Page: 7 CLOSURE This evaluation was performed in accordance with generally accepted engineering practices. The I conclusions 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 I 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 Curve Letter Soil Descriotion Maximum Optimum Density oct Moisture % A SAND, sl. Silty, fine to med.. Tan to Brown (SM) 127.9 11.3 Maximum density and optimum moisture determined in accordance with test method ASTM D 1557-78. SUMMARY OF EXPANSION INDEX TEST Test Location Expansion Index Expansion Classification pad -1' 27 LOW Expansion index test conducted in accordance with UBC 29-2. w. C. HOBBS, CONSULTING ENGINEER '\ . . APPENDIX B GENERAL EARTHWORK AND GRADING SPECIFICATIONS W. C. HOBBS, CONSULTING ENGINEER \0 '. . GENERAL EARTHWORK AND GRADING SPECIFICATIONS 1.0 :GENERAL INTENT These specifications present general procedures and requirements for grading and earthwork as shown on the approved grading plans, including preparation of areas to be filled, placement offill, 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 perfonned by the consultant during the course of grading may resuttin new recommendations of the geotechnical report. 2.0 :EARTHWORK 0BSERVATION AND TESTING Prior to Ithe commencement of grading, a qualified geotechnical consultant (soils engineer and engineering geologisL and their representatives) shall be employed for the purpose of observing earthwork and testing the fills for confonnance 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 detennine 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 <jgency 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 detennine the degree of compaction will be perfonned in accordance with the American Society ofT esting and Materials tests method ASTM D 1557-78. 3.0 :PREPARATlON OF AREAS TO BE FILLED 3.1 Clearing and Grubbing: All brush, vegetation and debris shall be removed or piled and otherwise disposed of. 32 Processing: The existing ground which is detennined to be satisfactory for support offill shall be scarified to a minimum depth of 6 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 clay lumps or clods and until the working surface is reasonably unifonn and free of uneven features which would inhibit unifonn compaction. 3.3 Ove~excavation: Soft, dry, spongy, highly fractured or otherwise unsuitable ground, extending to such a depth that the surface processing cannot adequately improve the condition, shall be over excavated down to finn 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 unifonn moisture content near optimum. 3.5 Recompaction: Over excavated and processed soils which have been property 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 finn material, and shall be approved by the consultant Other benches shall be excavated in finn material for a minimum width of 4 feet Ground sloping flatter than 5 : 1 shall be benched or otherwise 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 '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 consultant. Soils of poor gradation, expansion, or strength characteristics shall be placed in areas designated by consultant or shall be mixed with other soils to serve as satisfactory fill material. 4.2 Oversize: Oversize material defined as rock, or other irreducible material with a maximum dimension greater than 12 inches, shall not beburied 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 or densified fill. Oversize material shall not be placed within 10 feet vertically of finish grade orwithin the range of future 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 IFILL PLACEMENT AND COMPACTION 5.1 Fill Lifts: Approved fill material shail be placed in areas prepared to receive fill in near-horizonlallayers 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 aerated by scarification or shall be blended with drier material. Moisture-oonditioning 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, it shall be uniformly compacted to not less than gO percent of maximum dry density. Compaction equipment shall be adequately sized and shall be either specifically designed for soil compaction or of proven reliability, to efficientiy 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 atfrequent increments of2to 3 feetin fill elevation gain, orbyothermethods producing satisfactory results. Atthe completion of grading, the relative compaction of the slope out to the slope face shall be at least gO 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 interval not exceeding 2 feet in vertical rise and/or 1,000 cubic yards of embankment. 6.0 : SUBDRAIN 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 surveyed for line and grade after installation, and sufficient time shall be allowed for the surveys, prior to commencement of filling over the subdrains. W. C. HOBBS, CONSULTING ENGINEER \1.- < . . 7.0 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 performed, and/or remedial grading of cut slopes shall be performed. 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 granular soil to a depth of at least one foot over the top of the pipe. The sand backfill shall be uniformly jetted into place before the controlled backfill is placed over the sand. 8.3 Fill Placement: 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 CO'11paction: The controlled backfill shall be compacted to at least 90 percent of the maximum laboratory density as determined 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 uniform 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 \!:>