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Home My WebLink AboutParcel Map 30404 Parcel 2 Prelim Soils Dec. 11, 2006r. -~ • • W. C. HOBBS, CONSULTING ENGINEER 30833 LILAC CIRCLE MURRIETA, CALIFORNIA 92563 (909) 696-7059 Date: December 11, 2006 Project No: 02019-2 Mr. Charles Delgado 30270 Santiago Road Temecula, Califomia 92592 ~~1.1~~ V ~~ A°~ 0 6 2007 CITY GF iE1v1ECULA PUBLIC WORKS DEPARTMENT Reference: Preliminary Soil Engineering Evaluation, Tentative Parcel Map 30404, Portion of Lot 6 of PM 6807, 30270 Santiago Road, City of Temecula, Califomia, dated April 24, 2002 by W. C. Hobbs, Consulting Engineer, Project No: 02019-1 Subject: Evaluation of Slope Stability, Cut Slopes on Proposed Grading and Street Improvement Plans, 30270 Santiago Road, City of Temecula, California Dear Gentlemen, Pursuant to your authorization, this geotechnical evaluation was conducted on the subject lot to determine the distribution and engineering characteristics ofearth materials present and the stability of the cut siopes on the site adjacent to the pads and driveway resulting from Street Improvements and new driveway construction. The results of field exploration, together with the results of the laboratory tests and engineering analysis are summarized in this report and attached appendices. Accompanying Maps and Appendices Plate 1, Geotechnical/Section Location Map Attached Appendix A, Summary of Laboratory and Field Test Results Attached Appendix B, Summary of Slope Stability Analyses Scope of Work The scope of work performed for this study included the following: Onsite observation and recovery of samples from the parcel in areas to be tested; 2. Laboratory testing, and; 3. Preparation of this report including stability of constructed cut slopes. ~ ~ Mi. Charles Delgado, Stability Analysis Report, 30270 Santiago Road @ Ormsby Rd. Page: 2 Project No: 02019-2 Site Description The site is regularshaped and is located northwest ofthe intersection ofOrmsby Road and Santiago Road, specifically, the proposed cutslopes adjacentto the pad resulting from the proposed roadway improvements. Thetopographyofthesiteismoderatetosevere. Developmentconsistsimproving the intersection and portions of the roadway along the subject property, resulting in the creation of cul slopes south and east of the existing pad adjacent to the roadway. Field Work Field work on the site consisted of observation several small excavations made by hand in existing culs 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 ihe nearby area was conducted in order to obtain information pe~inent to the site. Observation and testing ofthe excavations indicated that the existing materials were of moderate to high density in place with no visible pores, and is uniformly dry at the surface. Observation of earth materialsonthesiteindicatethattheyconsistofsiltytoslightlysandswithscatteredgravel. Existing cuts indicate the topsoil is a layer that is relatively thin, on the order of 1 to 2 feet in most areas and may be slightiy thicker in local ravines. Topsoil is generally characterized by a darker color with slightly more fines than the bedrock beneath. Bedrock consists of a sandstone of the Pauba Famation, slightly silty, massive, low bedding angles where found (2 degrees southwest) and containing beds of fine to medium sand with little or no fine grained soils for cohesiveness. Laboratory Testing Direct shear testing was conducted on relatively undisturbed samples recovered from the site representing cut slope strength parameters. Shear testing on in situ sampies was conducted along joint fractures to represent the weakest shear strengths in the bedrock. It is presumed that cross bedding or cross jointing shear strengths may be substantially higher than along joints. 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. 1. The site has been graded with a driveway and building pad with an existing residence. 2. The soil is observed to be dense in place. W. C. HOBBS, CONSULTING ENGINEER Z • C~ Mr, Charles Delgado, Stability Analysis Report, 30270 Santiago Road @ Ormsby Rd. Page: 3 Pmject No: 02019-2 Conclusions cont'd. 3. Observed slopes onsite and adjacent to the site indicates that natural and cut slopes to very steep ratios (1.5:1) to heights of 30 feet or more are grossly stable for long periods of time. However, surf'icial stabiliiy appears to be dependent on slope maintenance with erosion being the primary concem. Siopestabilityanalysisagreesfavorablywiththeseconditionswithsafetyfactorsinexcess ofi.5forcutsupto30feetatratiosof1.5:1. Resultsindicatethatadequatesafetyfactorsexceeding 1.5 and 1.25 for static and dynamic stability analyses are achieved for slopes on this site. Attached herewith in Appendix B are the results of calculations together with section drawing indicating failure planes analyced. Analyses were also conducted using a random surface generatoras circularfailure surfaces in homogeneous materials tend to be idealistic. Random surface generation in this case did not yield lower safety factors than did circular surfaces. Slope Maintenance Wrth regard to steep slopes constructed into native sandstones of the Pauba Formation earth materials, erosion is the primary concem. Planting and irrigation to protect slopes from erosion and subsequentpotentialinstabilityshouldbeimplementedassoonasslopesareconstructed. Although the sandy nature of the slopes precludes no erosion, proper planting may minimize adverse effects indudingsedimenttransport. TemporaryerosioncontrolthroughBestManagementPracticesmay also assist in minimizing sediment transport off the site while landscape measures mature. Additionally, no drainage over the slopes should be permitted by surface waters originating on the pad. Surfacedrainageshouidbeaggressivelycollectedandconductedawayfromthetopsofsiopes to appropriate devices for disposal. Construction Observations It is strongly recommended that cutslopes be evaluated by an engineering geologistduring and post construction to confirm that the assumptions made regarding the engineering characteristics and homogenous nature of the sandstone are consistent with the analysis conducted in this report. Should conditions deviate from those assumed in this report, the undersigned should be notified immediately so that additional analysis can be conducted to determi~e if modifications are necessary to the above conclusions. W. C. HOBBS, CONSULTING ENGINEER 3 ~ ~ CLOSURE This evaluation was performed in accordance with generally accepted engineering practices. The wnclusions and recommendations contained in this reportwere based on the data available and the interpretation of such data as dictated by our experience and background. Hence, our conclusions and recommendations are professional opinions; therefore, no otherwarranty is offered or implied. The opportunity to be of service is appreciated. Should questions or comments arise pertaining to this document, or if we may be of further service, please do not hesitate to cali our office. Respectfully Submitted, W. C. HOBBS, CONSULTING ENGINEER WlLLItU1~! \ HOSBS ko.4?265~p(q F.~.3,91-2T .~ Bill Hobbs, RCE 42265 Civil Engineer Distribution: Addressee (4) Attachments: Plate 1, Geotechnical/Section Location Maps Attached Appendix A, Summary of Laboratory Test Results Attached Appendix B, Summary of Slope Stability Analyses W. C. HOBBS, CONSULTING ENGINEER \ ~ APPENDIX A SiJMMAItY OF TEST RESULTS ~ W. C. HOBBS, CONSULTING ENGINEER ~ ~ ~ Mr. Charles Delgado, Stability Analysis Report, 30270 Santiago Road @ Ormsby Rd. Page: 6 Project No: 02019-2 APPENDIX A DIRECT SHEAR TESTING Undisturbed bedrock (Pauba Sandstone) Phi = 34° cohesion = 180 psf W. C. HOBBS, CONSULTING ENGINEER ~ ~ ~ APPENDIX B SUMMARY OF SLOPE STABILITY ANALYSES W. C. HOBBS, CONSULTING ENGINEER ~ ^ r 0 ~ LL ~ N N h 8 ~ ^ ~ ~ 02019-2 5 ° ^ PCSTABL6 ~"~ by Purdue University modified by Peter 7. Bosscher university of wisconsin-Madison --Slope Stability analysis-- Simplified 7anbu, Simplified aishop or Spencer~s Method of Slices PROBLEM DESCRIPTION SECTION 1 STATIC BOUNDARY COORDINATES 5 Top Boundaries 5 TOtdl BOUnddfie5 aoundary x-~eft Y-Left x-aight Y-Right Soil Type No. (ft) (ft) (ft) (ft) Below Bnd 1 0.00 26.50 18.00 26.00 1 2 18.00 26.00 18.10 26.50 1 3 18.10 26.50 32.00 26.80 1 4 32.00 26.80 75.00 54.50 1 5 75.00 54.50 150.00 54.50 1 ISOTROPIC SOIL PARAMETERS 1 Type(s) of 5oil Soil rotal 5aturated Cohesion Friction Pore Pressure Piez. Type Unit Wt. Unit wt. Intercept angle Pressure Constant Surface No. (pcf) (pcf) (psf) (deg) Param. (psf) No. 1 125.0 135.0 180.0 34.0 0.00 0.0 0 a Critical Failure Surface 5earching Method, Using a Random Technique For ~enerating circular surfaces, Has eeen 5pecified. Page 1 ~ ~ ~ ~ 02019-2 5 50 Trial Surfaces Have Been Generated. SO Surfaces Initiate From Each Of 1 Points Equally Spaced along The Ground 5urface setween X= 32.00 ft. and x = 32.00 ft. Each Surface Terminates eetween X= 75.00 ft. and x = 150.00 ft. Unless Further Limitations Were Imposed, The Minimum Elevation At which A Surface Extends Is Y= 0.00 ft. 3.00 ft. Line 5egments oefine Each Trial Failure 5urface. Following are oisplayed The Ten Most Critical of The Trial Failure 5urfaces examined. rhey are ordered - Most Critical First. •• ~ Safety Factors are Calculated sy The Modified ~anbu Method ~•• Failure Surface Specified By 21 Coordinate Points Point X-SUrf Y-SUrf No. (ft) (ft) 1 32.00 26.80 2 35.00 26.62 3 37.99 26.64 4 40.99 26.86 5 43.96 27.29 6 46.89 27.91 7 49.78 28.73 8 52.60 29.75 9 55.35 30.95 10 58.01 32.33 11 60.57 33.89 12 63.03 35.62 13 65.36 37.51 14 67.55 39.55 15 69.61 41.74 16 71.51 44.05 17 73.25 46.50 18 74.83 49.05 19 76.22 51.71 20 77.44 54.45 21 77.46 54.50 .. .. .. 1. 676 .. ,, .. Page 2 ~~ . ~ 0 ~ ~ LL ~ ~ ~ Z 0 ~ U w ~ \\ ~ ~ ~ 02019-2 D °~` PCSTABL6 ~`° by Purdue University modified by Peter 7. Bosscher university of wisconsin-Madison --Slope Stability analysis-- Simplified 7anbu, Simplified Bishop or spencer~s Method of 5lices PROBLEM DESCRIPTION SECTION 1 PSEUDOSTATIC BOUNDARY COORDINATES 5 Top Boundaries S Total Boundaries eoundary x-~eft v-~eft x-aight v-aight Soil Type No. (ft) (ft) <ft) (ft) Below and 1 0.00 26.50 18.00 26.00 1 2 18.00 26.00 18.10 26.50 1 3 18.10 26.50 32.00 26.80 1 4 32.00 26.80 75.00 54.50 1 5 75.00 54.50 150.00 54.50 1 ISOTROPI~ SOIL PARAMETERS 1 Type(s) of Soil Soil Total Saturated Cohesion Friction Pore Pressure Piez. Type Unit Wt. Unit Wt. Intercept Angle Pressure Constant Surface No. (pcf) <pcf) (psf) (deg) Param. (psf) No. 1 125.0 135.0 180.0 34.0 0.00 0.0 0 a Horizontal Earthquake ~oading coefficient Of0.150 Has Been Assigned Page 1 \~ ~ ~ ~ 02019-2 0 a vertical Earthquake ~oading Coefficient Of0.100 Has Been Assigned Cavitation Pressure = 0.0 psf a Critical Failure Surface Searching Method, Using A Random Technique For Generating Circular 5urfaces, Has eeen Specified. SO Trial Surfaces Have Been Generated. 50 Surfaces znitiate From Each of 1 Points Equally Spaced along The Ground Surface eetween x= 32.00 ft. and x = 32.00 ft. Each 5urface Terminates eetween x= 75.00 ft. and x = 150.00 ft. unless Further ~imitations were zmposed, The Minimum Elevation at Which A Surface Extends Is v= 0.00 ft. 3.00 ft. ~ine Segments ~efine Each rrial Failure 5urface. Following nre oisplayed rhe Ten Most Critical of The rrial Failure Surfaces exam~ned. They nre ordered - Most Critical First. °~° Safety Pactors Are Calculated sy The Modified 7anbu Method *"' Failure Surface Specified ay 21 Coordinate Points Point x-SUrf Y-SUrf No. (ft) (ft) 1 32.00 26.80 2 35.00 26.62 3 37.99 26.64 4 40.99 26.86 5 43.96 27.29 6 46.89 27.91 7 49.78 28.73 8 52.60 29.75 9 55.35 30.95 10 58.01 32.33 il 60.57 33.89 12 63.03 35.62 13 65.36 37.51 14 67.55 39.55 15 69.61 41.74 16 71.51 44.05 17 73.25 46.50 Page Z ~~ ., . . ~ ~ 02019-2 D 18 74.83 49.05 19 76.22 51.71 20 77.44 54.45 21 77.46 54.50 ...... 1.276 ..... Page 3 ~\ C~ / ~ ~. ~.?Q~ij~~vy% ~: °, ' . . ~, ~ d,~~1~ d ~ ~ l~ o~~ ~- / ~ j ~l a, 0 o~L . L~n. ' ~ '~~ . ~ 00~~1, v~~ - w- : ,. .aot?Li£oooti~l a ~~ d~obo~ ~-G ~ ae. t a0~ _~ d~~'~~~~3~-' -1-. 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I ~~ ~ / ~o 'O I I~~ D~,~ / VIA EL DELORA ~ ' 1, I ~2+so / CLINTERSECTION I' STABILITY SECTION 1 o I ~ ' II ~ ~-- II ~-~A TE 1 ~ ~ o I GEOTECHNICAL MAP I I pROJECT N0: 02019-2 ~I . 12, DATE, DECEMBER 11, 2006 $~ I SCALE: 1" - 40' 30' ~ ~' ~ I I ~ :j II ~ ~ ~~T ~ I~ 1I = : .{ ~ m n lO IIII II ~~ i t~