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HomeMy WebLinkAboutTract Map 3883 Lot 81 Supplemental Soils , . . . ~.~ I...c:>\ 81 W. C. HOBBS, CONSULTING ENGINEER 31526 RAILROAD CANYON ROAD, SUITE 1 . CANYON lAKE, CAUFORNIA 92587 (909) 244-5177 . Mr. Scott Teulscher , 42200 Moraga, Aparbnent 41 F Temecula, Carlfomia 92591 Date: May 18, 1995 Project No: 95038-1 , Subject Supplemental So~ Engineering Design Criteria Lot 81, Tract 3883, 40685 Cannefrta Cin::Ie City of Temecula, California . Reference: Compaction Test Report, For the Proposed Residential Development Lot 81, Tract 3883, A.P.N. 919-071-003, Located at 40685 Cannelita Cin::Ie Temecula, California, prepared by Datum Geotechnica~ dated May 1, 1995 Project No: 2208-C1-95. . Dear Mr. Teulscher, Pursuant to your authorization, a supplemental soil engineering evaluation was conducted on the subject lot to determine the distribution and engineering characteristics of earth materials present at the site. The results of field exploration, together with the results of the laboratory tests, are summarized in the report and attached appendix. The approximate location of the subsurface exploration is plotted on a portion of the original Grading Plan (Plate 1) obtained from the ACC office of the CLPOA. Additional information provided herein in dudes preliminary foundation design for proposed iresidential construction. 'Accompanying Maps and Appendices .'. ~ , ./ Site Vidnity Map, Page 2 Summary of Laboratory Test Results, Attached Appendix A ~ , "'---- \ \ \ \ " . . Mr. Scott Teutscher, 40685 Cannelita Circle, Temecula Project No: 95038-1 Page: 2 Scope of Wor1< The scope ofwor1< performed for this study induded the following: 1. Review of Compaction Test Report; 2. Sample Recovery for Expansion Index Testing of Near Surface Soils; 2, Laboratory testing, and; 3, Preparation of this report induding condusions and recommendations pertinent to the proposed construction, .... "C:~~ELfV~ ~ S'7C~y/. . C/? . 'P.\...I:>~f1 ~ )11 A NolZ:-if; SITE VICINITY MAP ~ Not to Scale i~ W, C. HOBBS. CONSULTING ENGINEER z... . ' . . . Mr. Scot! Teutscher, 40685 Cannelita Circle, Temecula Projectl\'J: 95038-1 Page:3 'Site Description 'The site's approximately rectangular, measuring 120 feet across the front and 160 feet across the rear and having a depth of 190 feet. The site was recently graded as a matter of compacting fills in the building area and not to substantially alter the original topography of the site. It is boundec on the north and south sides by existing residences, to the west by the vacant land and east by t'le street. Presently, the site has been recently stripped of annual grasses and weeds, Review wi the referenced report indicates the presence of a fill cap across the lot approximately :4 to 7 feet in thickness Field WOl'k Field wo~~ on the site consisted of the observation of the existing geometry and sample recovery of near ~rface soil testing, .Laboratoly Testing Expansion index testing was conducted on a representative sample in order to determine the 'expansion potential of the near surface soils, The expansion index test was conducted in accordance with UBC 29-2, W, C, HOBBS, CONSULTING ENGINEER ..3 . . , Mr. Scott Teutscher, 40685 Cannelita Circle, Temecula : Project No: 95038-1 Page: 4 CONCLUSIONS AND RECOMMENDATIONS . Conclusions . The development of the site for single or 2 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 substantially in it's original graded configuration, 2, The site is underlain by approximately 4 to 7 feet of fill. . 3, Observation, dassification, and laboratory test results indicate that the near surface soils have 'a low expansion potential. RECOMMENDATIONS The recommendations contained herein are contingent upon W: C. Hobbs being retained to provide the following services listed in the construction section in order to confirm design assumptions and review the field conditions of any excavations for possible anisotropic properties, Site Grading In order to provide proper support for building foundations and any fill placed on the lot, remedial grading will not be required, Areas where fill is to be placed, and this indudes retaining wall back fill, should have the top 1 foot of soil processed and compacted in place prior to the placement of any earth materials. Any additional proposed or future earthwor1< should be conducted in accordance with Appendix 8, Standard Spedfications for Earthwor1< Construction. W, C, HOBBS, CONSULTING ENGINEER .q . . Mr. Scott Teutscher, 40685 Carmelita Circle, Temecula Project No: 95038-1 Page: 5 Recommendations, continued , Bearing Value and Footing Geomeby A safe allowable bearing value for foundations embedded into competent fill materials is 1500 psf, This value may be increased at the rate of 100 psf per foot of depth and 100 psf per foot of width over the minimums, but should not exceed 1800 psf. Continuous footings should have a minimum width and depth of 12 inches and a minimum of 5 feet of cover to any slope face, The . use of isolated column footings on slopes is discouraged, however, where utilized, should have . a minimum embedment of 18 inches below lowest soil grade or 5 feet of horizontal cover to any . slope face, Interior column footings need not be tied to perimeter footings, but should meet the minimum embedment criteria of 18". Exterior column footings should be tied to the building perimeter by grade beams if located out on descending slopes. . Settlement The bearing value recommended above refiects a total settlement of 0.5" and a differential . settlement of 0,25", This settlement is expected to occur during construction and as the loads are being applied, Concrete Slabs All concrete slabs on grade should be 4 inches thick. They should be underlain by 3 inches of sand or gravel. In this case, onsite soils may be suitable if prior approval by the soil engineer is obtained. 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, 3 inches of sand and subgrade soil. Contractors should be advise that when pouring during hot or windy weather conditions, they should provide .large slabs with suffidently deep weakened plane joints to inhibit the development of irregular or lunsightly cracks, :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, 6/6 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 perfonTIance history and selection is up to the builder. Additional requirements may be imposed by the structural engineering design, W, C, HOBBS, CONSULTING ENGINEER 5' , . . . . Mr. Scott Teutscher, 40685 Cannelita Circle, Temecula , Project No: 95038-1 Page:6 : Recommendations, continued : 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 may be computed using an equivalent fluid density of 250 pd, The total force should not exceed 2000 psf, A coefficient of friction of ,35 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. : Rebining 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 that are 50% Qreater than those indicated in the table. RETAINING WAll. DESIGN PRESSURES Slope of adiacent qround Active Pressure Passive Pressure LEVEL 33 pd 450 pd 250 pd 2:1 48 pd 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 drainage and 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, W. C. HOBBS, CONSULTING ENGINEER (, , ' . . Mr, Scott Teutscher, 40685 Carmelila Circle, Temecula Project No: 95038-1 Page: 7 Recommendations, continued i Fine Grading , 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, , Construction A soil engineer should be present during the excavation of the foundations, as well as earthwor1< 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 is of particular importance that any excavations into the fill areas of the lot are observed by the soil engineer to verify the competence of the foundation materials. It may be possible that certain excavations may have to be deepened slightly if fill materials are found to be loose or weak, CLOSURE This evaluation was performed in accordance with generally accepted engineering practices, The condusions and recommendations contained in this report were based on the data available and the interpretation of such data as dictated by our experience and background, Hence, our condusions and recommendations are professional opinions; therefore, no other warranty is offered or implied. Respectfully Submitted, W. C. HOBBS, CONSULTING ENGINEER Bill Hobbs, RCE 42265 Civil Engineer Distribution: ( Addr see (4) Attachments: '----- mmary of Laboratory and Field Test Results, Earthwor1< Spedficaitons W, C, HOBBS, CONSULTING ENGINEER 1 . APPENDIX A SUMMARY OF TEST RESULTS . W. C, HOBBS, CONSULTING ENGINEER 8 . APPENDIX A . SUMMARY OF EXPANSION INDEX TEST Test Location Expansion Index building area 44 Expansion index test .conducted in accordance with UBC 29-2, Expansion Classification LOW W, C, HOBBS, CONSULTING ENGINEER q . . APPENDIX 8 SUMMARY OF TEST RESULTS . W. C, HOBBS, CONSULTING ENGINEER ~o . . 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 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 consu~ant during the course of grading may resu~ in new recommendations of the geotechnical report. 2.0 i EARTHWORK OBSERVATION AND TESTING Prior to the commencement of grading, a qualified geotechnical consu~ant (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 consu~ant 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 consu~ant and keep him apprised of work schedules and changes so that he may schedule his personnei 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 consu~ant, unsatisfactory conditions, such as questionable soil, poor moisture condition, inadequate compaction, adverse weather, etc" are resu~ing in a quaiity of work less than required in these specifications, the consu~ant 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 of Testing and Materials tests method ASTM D 1557-78, 3.0 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 determined to be satisfactory for support of fill shall be scarified to a minimum depth of 6 inches, Existing ground which is not satisfactory shall be overexcavated 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 uniform and free of uneven features which would inhibit uniform compaction. 3.3 Overexcavalion: 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 overexcavated down to firm ground, approved by the consu~ant. 3,4 Moisture Conditioning: Overexcavated and processed soiis shall be watered, dried-back, blended, and/or mixed, as required to altain a uniform moisture content near optimum. 3.5 Recompaction: Overexcavated and processed soils which have been properly mixed and moisture- conditioned shall be recompacted to a minimum relative compaction of 90 percent. W, C, HOBBS, CONSULTING ENGINEER \\ . . 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 th,e consu~ant. 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 otherwise overexcavated when considered necessary by the consu~ant. 3.7 Approval: All areas to receive ill, including processed areas, removal areas and toe-of-fill benches shall be approved by the consu~ant prior to fill placement. 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 consu~ant. Soils of poor gradation, expansion, or strength characteristics shall be placed in areas designated by consu~ant or shall.be mixed with other soils to selVe 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 consu~anl. 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 or within the range of future utilities or underground construction, ,unless specifically approved by the consu~ant. 4.31'11port If importing of fill material is required for grading, the import material shall meet the requirements of Section 4. 1, 5.0 FILL PLACEMENT AND COMPACTION 5.1 Fill Ufts: Approved fill material shall be placed in areas prepared to receive fill in near-horizontal layers not exceeding 6 inches in compacted thickness, The consu~ant 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-{;onditioning 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 un,iformly 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 normal compacting procedures, by backfilling of slopes withsheepsfoot rollers at frequent increments of2 to 3 feet in fill elevation gain,or by other methods producing satisfactory resu~s, At the, completion of grading ,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 consu~ant. The location and frequency of tests shall be at the consu~anl's discretion, In general, the tests will be taken at an intelVal 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 W, C, HOBBS, CONSULTING ENGINEER \2- . . 6;0 SUBDRAIN INSTALLATION Subdrain systems, if required, sh",1 De installed in approved ground to conform to the approximate alignment and details shown on the plans or herein. The subdrar location or materials shall not be changed or modified without the approval of the consu~anl. The :consu~ant, however, may re~:mmend and upon approval, direct changes in subdrain line, grade or material. All subdrains should be surveyed for line and gr~:" after installation, and sufficient time shall be allowed for the surveys, prior to commencement of filling over the subdrains. 7.0 EXCAVATION Excavation and cut slopes will be ~.: amined during grading, If directed by the consu~ant, further excavation or overexcavation and refilling of cut areas shall be perfo-,ed, and/or remedial grading of cut slopes shall be performed, Where fill-over-cut slopes are to be graded, <R>unless otherwise approved, 1"" cut portion of the slope shall made and approved by the consu~ant prior to placement of materials for construction of the fil Jortion of the slope, 8.0 TRENCH BACKFILL 8,1 Supervision: Trench excavatia-s for the utility pipes shall be backfilled, under engineering supervision. 8.2 I?ipe Zone: After the utility pi;:" has been laid, the space under and around the pipe shall be backfilled with clean sand or approved granular solita a depth c' at least one foot over the top of the pipe. The sand backfill shall be uniformly jetted into place before the controlled backfill is pla:ed over the sand. 8,3 Rill Placement The onsite ma:~rials, or other soils approved by the engineer, shall be watered and mixed as necessary prior to placement in lifts over the sane JackfilL 8.4 Compaction: The controlled ba:xfill shall be compacted to at least 90 percent of the maximum laboratory density as determined by the ASTM compaction methoc jescribed above. 8.5 Observation and Testing: Fiee jensity tests and inspection of the backfill procedures shall be made by the soil engineer during backfilling too see that the proper rcoisture content and uniform compaction is being maintained, The contractor shall provide test holes and exploratory pits as requ'3d by the soli engineer to enable sampling and testing, W, C, HOBBS, CONSULTING ENGINEER t~