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Home My WebLink AboutTract Map 3929 Lot 236 Limited Geotechnical Study I~ A' I ~"".("'GEN Corporation . Soil Engineering and ConsullingServices- EngineeringGeology. CompaClionTesling -Inspections- ConslruclionMaterialsTesting. LaboraloryTesting. Percolation Testing . Goology.WaterResourceStudies . Phasel& II Environmental 5ileAssessments ENVIRONMENTAL & GEOTECHNICAL ENGINEERING NETWORK I I I I I I I I I I I I I I // , \ \ , ' , , , , , , LIMITED GEOTECHNICAL STUDY Proposed Single Family Residence, Lot 236 of Tract 3929 Del Rey Road, City of Temecula, County of Riverside, Califomia Project Number: T1813-LGS August 9, 1999 Prepared for: Mr. and Mrs. Donald F. Lassig 29996 Via Norte /~ Temecula, California 92591 '-.' - '/,~~-- ~/, " F , ... \ _ _ _ \ ...." ' , ... \ _ _ _ \ __ ~ ' ~~~*~~~~~~1~~:i~~,iJS-~:::7 ,'~ ,:,' ~;~~~*w;iii~"",'~8,*,h',.,*>X-,''''"":f'.'-':"".".:--,.,, "-~"-~" - ~----~..-----1~~1:~~ii~m~tt~~a~ .NET' - ...... .. . h . , ' , . , . .. \ ,;,_2_=/ - ~~~. ,--_:_:~~~I?f{i I I I I I I I I I I I I I I I I I I I I Mr. and Mrs. Donald F. Lassig Project No: T1813-LGS TABLE OF CONTENTS Section Number and Title Paae 1.0 SITE DESCRIPTION ....................................................................................................... 1 1.1 Location ............................................................................................................... 1 1.2 Site Review/Project Description........................................................................... 1 2.0 EARTHWORK RECOMMENDATIONS .......................................................................... 2 2.1 Structure Area......................................................................................................2 2.2 Structural Fill........................................................................................................3 3.0 FOUNDATION DESIGN RECOMMENDATIONS ........................................................... 3 3.1 General ............................................................................................................... 3 4.0 RETAINING WALL RECOMMENDATIONS................................................................... 3 4.1 Earth Pressures .................................................................................................... 3 4.2 Foundation Design............................. ...... .......................................... .................. 4 4.3 Subdrain................................................ ............ .............. .............. ........ ......... ...... 4 4.4 Backfill......................................................................................... ...................... 4 5.0 GENERAL RECOMMENDATIONS................................................................................. 5 5.1 Utility Trench ........................................................................................................5 5.2 Finish Lot Drainage Recommendations............................................................... 5 5.3 Planter Recommendations...................................................................................6 5.4 Supplemental Construction Observations and Testing........................................ 6 5.5 Plan Review .........................................................................................................6 5.6 Pre-Bid Conference ............................................................................................. 6 5.7 Pre-Grading Conference...................................................................................... 7 6.0 CLOSURE.... .................................... ................ ........................................... .................. 7 EnGEN Corporation 2-- I . "~ I :Q;.:, GEN I I I I I I I I I I I I I I Corporation . Soil EngineeringandConsullingServices- EngineeringGeology- Compaction Testing -lnspeclions-ConstruclionMa\erialsTesling-LaboraloryTesting-PercolationTestifl\l -Geology-WalerResourceSludies . Phase 1& II Environmenlal Site Assessments ENVIRONMENTAL & GEOTECHNICAL ENGINEERING NETWORK August 9, 1999 Mr. and Mrs. Donald F. Lassig 29996 Via Norte Temecula, Califomia 92591 (909) 676-7974 LIMITED GEOTECHNICAL STUDY Proposed Single Family Residence, Lot 236 of Tract 3929 Del Hey Road, City of Temecula, County of Riverside, California Project Number: T1813-LGS Regarding: Reference: 1. Manning Engineering, Grading Plan for Mr. and Mrs. Donald F. Lassig, 20 scale plans undated. Dear Mr. and Mrs. Lassig: Per your request and signed authorization, a representative of this firm has visited the subject site on August 5, 1999, to visually observe the surface within the subject lot. Based on this firm's experience with this type of project and on the well known and relatively simplistic underlying geologic conditions of the site and immediate vicinity, subsurface exploration was not considered necessary. However, in lieu of subsurface exploration, additional grading beyond that anticipated in this report may be necessary depending on exposed conditions encountered during grading. 1.0 1.1 1.2 SITE I PROJECT DESCRIPTION Location I Proiect Description: The subject property is comprised of approximately one (1) acre located on Del Rey Road in the City of Temecula. The proposed development is a one or two story slab-on-grade residential structure. The remainder of the site will consist of a driveway and associated hardscape and landscape improvements. Site Review: Based on the site visit and literature research, it appears that Pauba Formation bedrock and shallow depths of slopewash underlie the site and surrounding area. Based on the density of the underlying earth material type (Pauba Formation) the potential for hazards associated with liquefaction is considered low. No active faults traverse the site. Based on favorable topography:th!:!"potential for hazards associated with rockfalls or landslides is \ considered low. !':lounusual~eOIOgical conditions were noted. I' - ' / " ,,/ _' - ' / "- " I _' _ <' / " ,,/ '- . _~=: ... ~ I/"\ _ _ _ \.... '- , { , \ ~ _ _ \ __ "' ' J , \ _ _ _ \ " " ' , F .r " _ "_ ' '- _ "_ ' , , - \ ' \ / \-, ~ ------<~ ~.-, '.~/_''':::' , ' , I , ~ , '/ .... ~, , I " \ _ _ _ \ F ,,_ '-_ \ / ~ / , -- I \ ',' - ~" , -- I ~~' -- ...._._.~..,~.. - ',.- -,.-,-,' -.-_....~ ---..-..,....-- .. .,_..-.~~-..~~. .,,' ....,-~ _.;.,:~~~;:~~~~:f:;.-,~~~; I I I I I I I I I I I I I I I I I I I I 2.0 2.1 Mr. and Mrs. Donald F. Lassig Project No; T1813-LGS August 1999 Page 2 EARTHWORK RECOMMENDATIONS Structure Area . All vegetation should be removed from areas to be graded and not used in fills. . A cut/fill transition traverses the proposed residential structure. Therefore the cut portion (and shallow fill portion) will need to be overexcavated so that all footings will be embedded into competent engineered fill. The depth of overexcavation is expected to be a minimum of three (3) feet below proposed finish grades and may be deeper depending on exposed conditions encountered during grading. Overexcavation should extend a minimum of five (5) feet beyond the perimeter footings (where possible). . All areas to receive fill will require removals of loose, incompetent slopewash. Depths of removals are expected to be two (2) to three (3) feet below existing grades but may be deeper depending on exposed conditions encountered. . All removal and overexcavation bottoms should be inspected by the Soil Engineer's representative prior to placing fill. After bottom approval, all bottoms should be scarified 12-inches, moisture conditioned to near optimum moisture and then recompacted to a minimum of 90 percent relative compaction. . A keyway excavated into competent native earth materials should be constructed at the toe of all fill slopes that are proposed on natural grades of 5: 1 (horizontal to vertical) or steeper. Keyways should be a minimum of 15 feet wide (equipment width) and tilted a minimum of 2 percent into the hillside. A series of level benches should be constructed into native competent earth materials on natural grades of 5: 1 (horizontal to vertical) or steeper prior to placing fill. . All cut and fill slopes should be constructed at slope ratios no steeper than 2: 1 (horizontal to vertical). . All cut slopes should be inspected during grading (or immediately after) to verify surficial and gross stability. . An expansion test should be performed on a representative soil sample retrieved from the finished pad area subgrade so that foundation recommendations can be verified. EnGEN Corporation A., I I I I I I I I I I I I I I I I I I I Mr. and Mrs. Donald F. Lassig Project No: T1813-LGS Augusl1999 Page 3 2.2 Structural Fill: All fill material, whether on-site material or import, should be approved by the Project Geotechnical Engineer and/or his representative before placement. All fill should be free from vegetation, organic material, and other debris. Import fill should be no more expansive than the existing on-site material. Approved fill material should be placed in horizontal lifts not exceeding 6.0 to 8.0-inches in thickness and watered or aerated to obtain near-optimum moisture content (2.0 percent of optimum). Each lift should be spread evenly and should be thoroughiy mixed to ensure uniformity of soil moisture. Structural fill should meet a minimum relative compaction of 90 percent of maximum dry density based upon ASTM D1557-78 (90) procedures. Moisture content of fill materials should not vary more than 2.0 percent of optimum, unless approved by the Project Geotechnical Engineer. 3.0 FOUNDATION DESIGN RECOMMENDATIONS 3.1 General: Foundations for the proposed structure may consist of conventional column footings and continuous wall footings founded in competent engineered fill. Minimum footing depth should be 12-inches below lowest adjacent grade. Recommendations for foundation design and construction should be provided by the Structural Engineer in accordance with the latest edition of the UBC and, for preliminary design purposes, should be based on geotechnical characteristics for a silty sand (SM) and a low expansion potential for the supporting soils and should not preclude more restrictive structural requirements. The expansive characteristics should be checked at the completion of grading, and appropriate design changed made if necessary. 4.0 RETAINING WALL RECOMMENDATIONS 4.1 Earth Pressures: Retaining walls backfilled with non-expansive granular soil (EI=O) or very low expansive potential materials (Expansion Index of 20 or less) within a zone extending upward and away from the heel of the footing at a slope of 0.5:1 (horizontal to vertical) or flatter can be designed to resist the following static lateral soil pressures: Condition Level Backfill 2:1 Slope Active 30 pet 45 pet At Rest 60 pet Walls that are free to deflect 0.001 radian at the top should be designed for the above- EnGEN Corporation I I I I I I I I I I I I I I I I I I I Mr. and Mrs. Donald F. Lassig Project No: T1813-LGS Augusl1999 Page 4 recommended active condition. Walls that are not capable of this movement should be assumed rigid and designed for the at-rest condition. The above values assume well drained backfill and no buildup of hydrostatic pressure. Surcharge loads, dead and/or live, acting on the backfill within a horizontal distance behind the wall should also be should considered in the design. Uniform surcharge pressures should be applied as an additional uniform (rectangular) pressure distribution. The lateral earth pressure coefficient for a uniform vertical surcharge load behind the wall is 0.50. 4.2 Foundation Oesian: Retaining wall footings should be founded to the same depths into properly compacted fill, or firm, competent, undisturbed, natural soil as standard foundations and may be designed for the same average allowable bearing value across the footing (as long as the resultant force is located in the middle one-third of the footing),and with the same allowable static lateral bearing pressure and allowable sliding resistance as determined per section 3.1. 4.3 Subdrain: A subdrain system should be constructed behind and at the base of all retaining walls to allow drainage and to prevent the buildup of excessive hydrostatic pressures. Typical subdrains may include weep holes with a continuous gravel gallery, perforated pipe surrounded by filter rock, or some other approved system. Gravel galleries and/or filter rock, if not properly designed and graded for the on-site and/or import materials, should be enclosed in a geotextile fabric such as Mirafi 140N, Supac 4NP,. or a suitable substitute in order to prevent infiltration of fines and clogging of the system. The perforated pipes should be at least 4.0 inches in diameter. Pipe perforations should be placed downward. Gravel filters should have volume of at least 1.0 cubic foot per lineal foot of pipe. Subdrains should maintain a positive flow gradient and have outlets that drain in a non-erosive manner. In the case of subdrains for basement walls, they need to empty into a sump provided with a submersible pump activated by a change in the water level. 4.4 Backfill: Backfill directly behind retaining walls (if backfill width is less than 3 feet) may consist of 0.5 - to 0.75-inch diameter, rounded to subrounded gravel enclosed in a geotextile fabric such as Mirafi 140N, Supac 4NP, or a suitable substitute or a clean sand (Sand Equivalent Value greater than 50) water jetted into place to obtain proper compaction. If water jetting is used, the subdrain system should be in place. Even if water jetting is used, the sand should be densified to a minimum of 90 percent relative compaction. If the specified EnGEN Corporation I I I I I I I I I I I I I I I I I I I 5.0 5.1 5.2 Mr. and Mrs. Donald F. Lassig Project No: T1813-LGS Augusl1999 Page 5 density is not obtained by water jetting, mechanical methods will be required. If other types of soil or gravel are used for backfill, mechanical compaction methods will be required to obtain a relative compaction of at least 90 percent of maximum dry density. Backfill directly behind retaining walls should not be compacted by wheel, track or other rolling by heavy construction equipment unless the wall is designed for the surcharge loading. If gravel, clean sand or other imported backfill is used behind retaining walls, the upper 18-inches of backfill in unpaved areas should consist of typical on-site material compacted to a minimum of 90 percent relative compaction in order to prevent the influx of surface runoff into the granular backfill and into the subdrain system. Maximum dry density and optimum moisture content for backfill materials should be determined in accordance with ASTM D1557-78 (90) procedures. GENERAL RECOMMENDATIONS Utility Trench Recommendations: Utility trenches within the zone of influence of foundations or under building floor slabs, hardscape, and/or pavement areas should be backfilled with properly compacted soil. It is recommended that all utility trenches excavated to depths of 5.0 feet or deeper be cut back to an inclination not steeper than 1: 1 (horizontal to vertical) or be adequately shored during construction. Where interior or exterior utility trenches are proposed parallel and/or perpendiculartci any building footing, the bottom of the trench should not be located below a 1:1 plane projected downward from the outside bottom edge of the adjacent footing unless the utility lines are designed for the footing surcharge loads. Backfill material should be placed in a lift thickness appropriate for the type of backfill material and compaction equipment used. Backfill material should be compacted to a minimum of 90 percent relative compaction by mechanical means. Jetting of the backfill material will not be considered a satisfactory method for compaction. Maximum dry density and optimum moisture content for backfill material should be determined according to ASTM D1557-78(90) procedures. Finish Lot Orainaqe Recommendations: Finish lot surface gradients in unpaved areas should be provided next to tops of slopes and buildings to direct surface water away from foundations and slabs and from flowing over the tops of slopes. The surface water should be directed toward suitable drainage facilities. Ponding of surface water should not be allowed next to structures or on pavements. In unpaved areas, a minimum positive gradient of 2.0 percent away from the structures and tops of slopes for a minimum distance of 5.0 feet and a ~ EnGEN Corporation __ I I I I I I I I I I I I I I I I I I I 5.3 5.4 5.5 5.6 Mr. and Mrs. Donald F. Lassig Project No: T1813-LGS August 1999 Page 6 minimum of 1.0 percent pad drainage off the property in a non-erosive manner should be provided. Planter Recommendations: Planters around the perimeter of the structure should be designed with proper surface slope to ensure that adequate drainage is maintained and minimal irrigation water is allowed to percolate into the soils underlying the building. Supplemental Construction Observations and Testina: Any subsequent grading for development of the subject property should be performed under engineering observation and testing performed by EnGEN Corporation. Subsequent grading includes, but is not limited to, any additional overexcavation of cut and/or cut/fill transitions, fill placement, and excavation of temporary and permanent cut and fill slopes. In addition, EnGEN Corporation, should observe all foundation excavations. Observations should be made prior to installation of concrete forms and/or reinforcing steel so as to verify and/or modify, if necessary, the conclusions and recommendations in this report. Observations of overexcavation cuts, fill placement, finish grading, utility or other trench backfill, pavement subgrade and base course, retaining wall backfill, slab presaturation, or other earthwork completed for the development of subject property should be performed by EnGEN Corporation If any of the observations and testing to verify site geotechnical conditions are not performed by EnGEN Corporation, liability for the safety and performance of the development is limited to the actual portions of the project observed and/or tested by EnGEN Corporation. Plan Review: Subsequent to formulation of final plans and specifications for the project but before bids for construction are requested, grading and foundation plans for the proposed development should be reviewed by EnGEN Corporation to verify compatibility with site geotechnical conditions and conformance with the recommendations contained in this report. If EnGEN Corporation is not accorded the opportunity to make the recommended review, we will assume no responsibility for misinterpretation of the recommendations presented in this report. Pre-Bid Conference: It is recommended that a pre-bid conference be held with the owner or an authorized representative, the Project Architect, the Project Civil Engineer, the Project Geotechnical Engineer and the proposed contractors present. This conference will provide continuity in the bidding process and clarify questions relative to the supplemental grading and construction requirements of the project. EnGEN Corporation I I I I I I I I I I I I I I I I I I I 5.7 6.0 Mr. and Mrs. Donald F. Lassig Project No: T1813-LGS August 1999 Page 7 Pre-GradinCl Conference: Before the start of any grading, a conference should be held with the owner or an authorized representative, the contractor, the Project Architect, the Project Civil Engineer, and the Project Geotechnical Engineer present. The purpose of this meeting should be to clarify questions relating to the intent of the supplemental grading recommendations and to verify that the project specifications comply with the recommendations of this geotechnical engineering report. Any special grading procedures and/or difficulties proposed by the contractor can also be discussed at that time. CLOSURE: This report has been prepared for use by the parties or project named or described in this document. It mayor may not contain sufficient information for other parties or purposes. In the event that changes in the assumed nature, design, or location of the proposed structure and/or project as described in this report, are planned, the conclusions and recommendations contained in this report will not be considered valid unless the changes are reviewed and the conclusions and recommendations of this report modified or verified in writing. This study was conducted in general accordance with the applicable standards of our profession and the accepted soil and foundation engineering principles and practices at the time this report was prepared. No other warranty, implied or expressed beyond the representations of this report, is made. Although every effort has been made to obtain information regarding the geotechnical and subsurface conditions of the site, limitations exist with respect to the knowledge of unknown regional or localized off-site conditions that may have an impact at the site. The recommendations presented in this report are valid as of the date of the report. However, changes in the conditions of a property can occur with the passage of time, whether they are due to natural processes or to the works of man on this and/or adjacent properties. If conditions are observed or information becomes available during the design and construction process that are not reflected in this report, EnGEN Corporation should be notified so that supplemental evaluations can be performed and the conclusions and recommendations presented in this report can be modified or verified in writing. Changes in applicable or appropriate standards of care or practice occur, whether they result from legislation or the broadening of knowledge and experience. Accordingly, the conclusions and recommendations presented in this report may be invalidated, wholly or in part, by changes outside of the control of EnGEN Corporation which occur in the future. EnGEN Corporation <p I I I I I I .r1LOh iJ(?IauL '-/jason D. Gar;;;r" I Field Operations Manager I I I I I I I I I I I I Mr. and Mrs. Donald F. Lassig Project No: T1813-LGS August 1999 Page 8 Thank you for the opportunity to provide our services. Often, because of design and construction details which occur on a project, questions arise concerning the geotechnical conditions on the site. If we can be of further service or you should have questions regarding this report, please do not hesitate to contact this office at your convenience. Because of our involvement in the project to date, we would be pleased to discuss engineering testing and observation services that may be applicable on the project. Respectfully submitted, EnGEN Corporation TD/OB:ch Distribution: (4) Addressee FilE: EnGENlReportingIGSIT1813LGS Donald lassig, limited Geotechnical Study ~ EnGEN Corporation " , 1 /