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HomeMy WebLinkAboutTract Map 9833-3 Lot 15 Prelim Geotechnical *, -., I' 1 ~ LDb!/~/~ -rKrf~3v3a{/~ W. C. HOBBS, CONSUL liNG ENGINEER 39281 VIA PAMPLONA MURRIETA, CALIFORNIA 92563 (909) 696-7059 \,\.IY\"'~ 0 U-l\ I Mr. CyPtIs Pourshirazi 143360 Corte Rialto 'Temecula, California 92592 Date: August 27, 2001 Project No: 01055-1 I Subject: Preliminary Geotechnical Evaluation, Proposed Development of Lot 15 of Tract 9833-3, Calle De Velardo, City ofTemecula, California I Dear Mr. Shirazi, i Pursuant to yourauthorization and a requirement by the City ofT emecula, a limited soil engineering ,evaluation was conducted on the subject lot to determine the distribution and engineering : characteristics of earth materials present. The results offield exploration, together with the results of I the laboratory tests, are summarized in the attached appendix. I Additional information provided herein includes preliminary foundation design for proposed I residential construction. I Accompanying Maps and Appendices I Attached Appendix A, Summary of Laboratory and Field Test Results I Attached Appendix 8, General Earthwork and Grading Specifications I Plate 1, Portion of Grading Plan : 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 I 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. \ , ; 'Mr. Shirazi, Lot 15, Tract 9833-3, Calle De Velardo 'Project No: 01055-1 Page: 2 ! Site Description The site is roughly rectangular in shape, fronting 236 feet along Calle De Velardo on the east and, ! extending 545 .:t 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 protrudingin !a southwesterly direction from the northeast comer 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. :See Plate 1 for Details of existing topography and Grading Proposed on the Site. IField Work : Field work on the site consisted of observation of cut slopes on the site. Small excavations were . made on them forthe 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 orderto obtain information pertinentto the site. : Observation of the cut slopes indicated that the existing materials were of a moderate to high density lin 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, Itransitioning quickly at a depth of 1 foot to native earth materials, (Pauba Formation). The native !earth materials are comprised of relatively clean silty sand. Grain sizes ranged from .01 mm to 1 mm. IThe native earth materials were observed to be well bedded, with layers of different colors and grain isizes. The soils were observed to be damp and evenly moist below 4 feet or so. :Observation of a Backhoe trench excavated in the front of the lot indicates that the fill was placed on !competent ground and no visible signs of roots or organic materials were noted. .Laboratory Testing IThe maximum dry density and optimum moisture content of the soil was determined in acoordance '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 acoordance 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 1..- . ,. I Mr. Shirazi, Lot 15, Tract 9833-3, Calle De Velardo I Project No: 01055-1 Page: 3 CONCLUSIONS AND RECOMMENDATIONS I Conclusions . The development of the site for single or multi-story residential construction is both feasible and safe I from a geotechnical standpoint provided that the recommendations contained herein are implemented during design and construction. , 1: 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. 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 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. IAlI grading and retaining wall backfills should be placed in acoordance 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. 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. w. C. HOBBS, CONSULTING ENGINEER :7 'Mr. Shirazi, Lot 15, Tract 9833-3, Calle De Velardo :Project No: 01055-1 Page: 4 I Recommendations, continued I Bearing Value and Footing Geometry I A safe allowable bearing value for foundations embedded into native bedrock materials or properly : compacted fill is 2000 pst. This value may be increased at the rate of 100 pst per foot of depth and , 100 psf per foot of width over the minimums, but should not exceed 2500 psf. Continuous footings I 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 ,isolated column ifootings 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, I should be underlain by 6 mil visqueen properly protected from puncture with an additional 1 inch of I 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 orwindyweatherconditions, 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 thiclkness 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 I the structural engineering design. W. C. HOBBS, CONSULTING ENGINEER A.. I Mr. Shirazi, Lot 15, Tract 9833-3, Calle De Velardo I Project No: 01055-1 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 atthe back of the wall. The active pressures indicated in the table are equivalentfluid I densities. Walls that are not free to rotate or that are braced atthe top should use active pressures I that are 50% greater than those indicated in the table. RETAINING WALL DESIGN PRESSURES Slooe of adiacent qround Active Pressure Passive Pressure 2:1 30 pet 40 pet 300 pet 200 pet 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 I pressures beyond the design values. It is imperative that all retaining wall backfills be compacted to i 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. . 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 : level ground maybe computed using an equivalent fluid densityof300 petforlevel ground. Thetotal , force should not exceed 3000 psf. 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, , then the passive values should be reduced by one third. W. C. HOBBS, CONSULTING ENGINEER ~ I Mr. Shirazi, Lot 15, Tract 9833-3, Calle De Velardo ; Project No: 01055-1 Page: 6 I Recommendations, continued I Fine Grading : Fine grading of areas outside of the residence should be acoompljshed such that positive drainage i exists away fromall 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 If> , I Mr. Shirazi, Lot 15, Tract 9833-3, Calle De Velardo 'Project No: 01055-1 Page: 7 CLOSURE . This evaluation was performed in acoordance with generally accepted engineering practices. The , 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 ; and recommendations are professional opinions; therefore, no other warranty is offered or implied. , The opportunity to be of service is appreciated. Should questions orcomments arise pertaining to this I 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 obbs, RCE42265 , CMI Engineer Distribution: , Attachments: Addressee (4) Appendix A - Summary of Laboratory and Field Test Results Appendix B - General Earthwork and Grading Specifications Plate 1, Portion of Grading Plan 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 DescriDtion Maximum Optimum Density oct Moisture % A SAND, sl. Silty, fine to med.. Tan to Brown (SM) 128.8 10.1 Maximum density and optimum moisture determined in acoordance with test method ASTM D 1557-78. SUMMARY OF EXPANSION INDEX TEST Test Location Expansion Index Expansion Classification Trench 1@1' 23 LOW Expansion index test conducted in acoordance 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 I GENERAL INTENT These specifications present general procedures and requirements for grading and earthwork as shown on the approved grading pians, 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 performed by the consultant during thecourseofgrading may result in new recommendations of the geotechnical report. 2.0 I EARTHWORK OBSERVATION AND TESTING Prior to: the commencement of grading, a qualified geotechnical consultant (soils engineer and engineering geologist, and their representatives) shall be employed for the purpose of obselVing 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 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 accordingiy. 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 drydensitytests used to detennine the degree of compaction will be perfonned in accordance with the American SocietyofT esting and Materialstests method ASTM 0 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 otherwise disposed of. 3.2 Processing: The existing ground which is detennined 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 clay lumps or clods and until the working surface is reasonably unifonn and free of uneven features which would inhibn unifonn compaction. 3.3 Overexcavation: Soft, dry, spongy, highlyfractured or otherwise unsuitable ground, extending tosuch a depth thatthe 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, andlormixed, as required to attain a unifonn 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 finn material, and shall be approved by the consultant. 0ther 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-<lf-fill benches shall be approved by the consuitant 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 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 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 cot11pacted or densified fill. Oversize material shall not be placed within 10 feet vertically of finish grade or within the range of future uWities 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 beplaced in areas prepared to receivefill 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 unifonnity 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-amditioning and mixing of fill layers shall continue until the fill material is at a unifonn,moisture content or "ear optimum. 5.3 CO'1"paction of Fill: After each layer has been evenly spread, moisture conditioned, and mixed, it shall be unifonnly compacted to not less than 90 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 efficiently achieve the specified degree of compaction. 5.4 Fill Slopes: Compaction of slopes shall be accomplished, in addition to nonnal compacting procedures, by backfilling of slopes with sheepsfoot rollers at frequent increments of2 to 3 feetin fill elevation gain, orbyothermethods producing satisfactory results. M.the completion of gradi~g, 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 perfonned by the consultant. The location and frequency of tests shall be at the consultant's 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 SUBDRAlN INSTALLATION Subdrain systems, if required, shall be installed in approved ground to confonn 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 \t-- . 7.0 I EXCAVATION Excavation and cut slopes willbe examined during grading. If direcled 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-Qver -QJt 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: Mer the utility pipe has been laid, the space under and around the pipe shall be backfilled with dean sand or approved granulansoil 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: Theons~e materials, orothersoils approved by the engineer, shall bewatered and mixed as necessarypriorto 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 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 ':b " --.- r~ r " fTl ~ en :=j Z o "lJ )> o ~ (J) o i+ i. i, ---- , " ~ ~~ e .0 ~ - ~O - ~~~~ s,-~~ ~~ - '~-... _",~'<~,,/ hi." 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