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HomeMy WebLinkAboutTract Map 3552 Lot 49 Soils & Foundation I I I I I I I I I 1 1 I I I I I I I ..1 RECEIVED AUG 311998 CITY OF TEMECULA ENGINEERING DEPARTMENT SOIL AND FOUNDATION INVESTIGATION REPORT LOT TI< PARCEt 4t OF PM 3552 A.P.N. 922-160-018 CORONADO DRIVE TEMECULA. CA gl FOR - .J h f'v -< -I- { CALIFORNIA MR. & MRS. SADEGHI ZADEH ~ , X PROJECT NO. 98-074.PI DATED JUNE 20. 1998 Lakeshore Engineering \ I I I I I I I I I I I I I I I I I I I I LAKESHORE Engineering Consulting Civil Engineering and Geologists June 20, 1998 Project No: 98-074.PI Client: Subject: INTRODUCTION Mr. and Mrs. Sadeghi zadeh 24059 Five Tribes Trail Murrieta, CA 92562 (909) 699-9429 or 677-4629 Soil and Foundation Report Proposed Single Family Residence Parcel 49 of Parcel Map 3552 Temecu1a, CA. A.P.N. 922-160-018 This report presents the findings and conclusions of a soil and foundation investigation for the proposed development of a single family residence to be located at the subject site. The purpose of this investigation was to 1) evaluate the foundation and subsurface soil conditions at the site, and 2) provide pertinent foundation recommendations for proposed development. This investigation included the following scope of work: 1) Performed four exploratory trenches within the proposed building pad area to determine subsurface conditions and recover soil samples for laboratory testing (Appendix A). 2) Laboratory testing of a representative soil sample to determine the soil properties (Appendix B). 3) Engineering analyses for foundation and necessary earthwork preparation. 4) The preparation of this report. PROPOSED DEVELOPMENT The proposed development will consist of a one story, custom built, single family residence of about 3300 square of living space, founded on a level graded pad. Construction is expected to be of woodframed and stucco supported on conventional spread footings. The lot is relatively level and proposed site grading will consist of reworking any substandard existing foundation soils. Import fills will be used to raise the building pad to desired grade. 31606 Railroad Canyon Road, #201 . Canyon Lake, CA 92587 . (909) 244-2913 . FAX: (909) 244-2987 ~ I I I IN:0980017.01 - I z C m >< I s > 1J I I I I I I I I 1 I o , scole 2000 4000 . feet I I INDEX MAP OF ZAHARA PROPERTY CORCNAJ;lO DR. RAN:HO CALIFORNIA 'TEMECULA RIVERSIDE COONIY CALIFORNIA 'I I Base Map: USGS 7.5' Terrecu1a Quad. State of Ca. Earthquake Studies Map - 1990 FIGURE 1 :, I I i I I I I I I I I I I I I I I I I I June 20, 19985 Project No: 97-074.PI Page Two SITE DESCRIPTION The subject site, approximately 2.73 acres is relatively level, with a slight (5%) downward pitch from north to south. It is located at the end of Coronado Drive, a paved cul-de-sac. The cul-de-sac is elevated about 15 feet above the existing pad contours. The property is at present unimproved, and supports annual grass. A stockpile mound of import fills (estimated at 2,000 yards) was observed on the central-west portion of the lot. The mound of dirt is placed rectangular in shape about 6 feet high. The surface contours is smooth and uniform. A drainage course, crosses the property at the southwesterly low corner. The general drainage appears to be by sheetflow from north to south and exits the property at the southerly property line. No boulder masses are evident. The surface cover of annual grass has recently been disced. REGIONAL GEOLOGY SETTING For regional geologic conditions, groundwater, faulting and seismicity and secondary effects, please refer to geology report prepared by Mr. Jonathan L. Rossi, report dated May 15, 1998 (P.N. 0980017.01) attached as part of report in appendix. CONCLUSION AND RECOMMENDATIONS GENERAL From a soil and foundation engineering standpoint, the site will be suitable for the proposed single family residential construction, provided all conclusions and recommendations presented in this report are incorporated in the design considerations, project plans and specifications. Lakeshore Engineering 4. F.'"- '-~~ , ~ ~ g~ /:lirl /"..A ~ :U';: #~.. i'" OO~"/ g'! Z / ~ ~ S ~) ~~~-r ,/ ~ I I ?- ---- --j'----. - - s. I I I I I I I I I I I I I I I I I ",0 ~" .... ~::! :::= 11(- . {}I.'J/i rJ' , :. 0 \ ~Vi' ,! / 'f,' . ~ . if.' i ~ ~~ ~ ~ ~l .1!,l)\ I/;f i ...j.." ,. ),,1 ,J . )' i ;... Ii :" ( ( I ~ ! If( "'{!.;"f~ ,. L,: ,/ , II I!i!;--l' 1/' 1m I 1" 1,) C. I,' , 1'{ i.1 (k.i-J,- t;,. \ '\ ~ . .. .. , I.,:!'..,'" . ,: , ,,' " ..".\,.",,~ _ '.':": ('; ~ J i'/~' ;; )' ~..' ... \ " i'l -' . .,.r ., : " ' \'" .. " .. \ ... < .' g. 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J -< , ~ ,~ / ~ , , I I I I I I I I I I I I I I I I I I I June 20, 19985 Project No: 97-074.PI Page Four EXCAVATING AND RIPPABILITY Rework of the on-site soils should not be difficult to accomplish with standard earthmoving equipment such as a D-5 or larger. The walls of temporary construction excavations should stand nearly vertical, provided the total depth does not exceed 5 feet and surficial stability is verified. Shoring of excavation walls or flattening may be required if greater excavation depths are necessary. For deeper cuts, slopes should not be made steeper than 1:1 (H:V). All work associated with trench shoring must conform to the State of California Safety Codes. Native organic free soils may be permitted provided both the backfill and the native materials have a minimum sand equivalent of 30 and the required relative compaction can be achieved. GRADING CONTROL All grading and earthwork including trench backfill should be performed under the observation and testing of the soils consultant or their representative. Sufficient notification prior to stripping and earthwork construction is essential in order that the work be adequately observed and tested. In order for us to provide a written opinion as to the adequacy of the soil compaction and trench backfill, the entire operation, most importantly at the time of trench backfill, should be performed under our observation and testing. FOUNDATION DESIGN FOOTING The proposed single family residential development may be supported on conventional spread footings established in engineered (compacted) fills. These spread footings may be designed for an allowable bearing value of 1500 pounds per square foot. This design value may be increase by one third, if the Structural Engineer takes into consideration short duration structural loading conditions, such as induced by wind and/or seismic forces. Footings should be founded at least 12 inches below the lowest adjacent ground surface, for one story structure. All continuous foundations should be reinforced with at least two no. 4 rebars at top and two rebars at bottom and consistent with the recommendations of the Structural Engineer or Architect and the guidelines in the U.B.C. Reinforcement should also be placed across garage grade beam at door opening. Lakeshore Engineering C::. I I I I I I I I I I I I I I I I I I I June 20, 19985 Project No: 97-074.PI Page Five SETTLEMENT Total settlement due to structural loads should not be a design factor as they should be less than 3/4 inch. Differential settlement should be within tolerable limits. LATERAL CAPACITY For design, resistance to lateral loads can be assumed to be provided by friction acting at the based of the foundations and by passive earth pressure and may be combine without reduction. If passive earth pressure is used, it is important that backfill should be placed under engineering observation and testing. A coefficient of friction of 0.30 may be used with the dead load forces. An allowable lateral passive earth pressure of 200 pounds per square foot per foot of depth may be used for the sides of footings poured against undisturbed and/or recompacted soils. The lateral bearing values indicated above are for the total of dead and frequently applied live loads. If the normal code requirements are used for seismic design, the values may be increased by 1/3 for short durations of the loading which include the effect of wind or seismic forces. RETAINING WALLS No retaining walls are proposed at this time. SLOPE STABILITY Proposed slopes are less than 5 feet in height and sloped at less than 3:1 (H:V). Slopes to be constructed as proposed considered stable for its intended use. CONCRETE SLAB - ON - GRADE The onsite native and stockpile soils are granular in nature and considered to be low in expansion potential. If on site soils are used as pad fills then the concrete floor slabs may be supported directly on properly prepared subgrade. Presaturation of subgrade is not required. If a floor covering that could be critically affected by moisture, such as vinyl tile, slabs should be protected by a plastic vapor barrier of six-mil thickness. The sheet should be covered by at least two-inches of sand to prevent punctures and aid in concrete cure. The concrete floor slabs should be reinforced with at least 6" x 6"-#10 /#10 welded wire mesh or equivalent bar reinforcing ( no. 4 rebars at 24 inches on center) and installed at mid-height (using chair support). Concrete floor slabs should be at least 4 inches thick nominal. Lakeshore Engineering 1 I I I I I I I I I I I I I I I I I I I June 20, 19985 Project No: 97-074.PI Page Six SITE DRAINAGE Positive drainage should be provided around the perimeter of all structures to minimize water infiltrating into the underlying soils. Finish subgrade adjacent to exterior footings should be sloped down and away to facilitate surface drainage. All drainage should be directed off-site via non-erosive devices (swales and ditches). The homeowner should be made aware of the potential problems which may develop when drainage is altered through construction of retaining walls, patios and pools. Ponding water, leaking irrigation systems, overwatering or other conditions which could lead to ground saturation must be avoided. FOOTING TRENCH EXCAVATION INSPECTION All footing excavations should be inspected and approved by the Soils Consultant prior to placement of footing forms, reinforcement, or concrete. Materials generated from excavations should not be spread on slab-on-grade areas, provided they are compacted and tested. GENERAL INFORMATION AND LIMITATIONS This report presents recommendations pertaining to the subject site based on the assumption that the subsurface conditions do not deviate appreciably from those disclosed by our exploratory trenches. In view of the general conditions of the area, the possibility of different local soil conditions cannot be discounted. It is the responsibility of the owner to bring any deviations or unexpected conditions observed during construction to the attention of the consulting engineer. In this way, any required supplemental recommendations can be made with a minimum of delay to the project. Prior to initiation of grading, a meeting should be arranged by the developer and should be attended by representatives of the governmental agencies, contractors, consultants and the developer. Construction should be inspected at the following stages by the Geotechnical Consultant. Lakeshore Engineering [) o I I I I I I I I I I I 1 I I I I I I I June 20, 19985 Project No: 97-074.PI Page Seven o Upon completion of demolition and clearing. o During all rough grading operations including removal of unstable materials, precompaction and filling operations. o During trench backfilling but prior to paving or other construction over backfill. o When any unusual conditions are encountered. The findings and recommendations of this report were prepared in accordance with generally accepted professional principles and practice in the field of geotechnical engineering. This warranty is in lieu of all other warranties, either express or implied. We sincerely appreciate the opportunity to be of service. If you have any questions concerning this report or require further information and services, please contact this office at your convenience. FY7f'y ENCLOSED: APPENDIX A - EXPLORATORY LOGS APPENDIX B - LAB. RESULTS APPENDIX C - GEOLOGIC REPORT BY JOHN L. ROSSI PLOT/GRADING PLAN IN POCKET Lakeshore Engineering ~ II I I I I I I I I I I I I I PLOT PLAN 1.6r. 4SL ExI~T. IZE:&. . COl1D1\J ADc D1<I0E... €:- -- N APl'b. LbC, ~(j>~~' 0> ". ~7 N.T.S. 6f ':::,l'DCK.?\LE.. T-3 . ) . EXPLANATION T-4 APPROX. LOCATION OF EXPLORATORY TRENCH. LAKESHORE . Engineering ZAHARA PROPERTY CORONADO DRIVE TEMECULA, CA CONSULTING CIVIL ENGINEERS Project No: Date 98-074.PI ' 6/20/98 Agur'l No: A.-~. \0 I I I I I I I I I I I I I I 'I I I I I TRENCH LOG ~ Surface Elevation rrenc~ Oilenta/lon :rencn DimenSions 'Z-L+".>< lS' X la' t Grounawaler Deprn NOiI:l~ Logged By F.'~o~6 I-'O^c- Dare SI'Z:8/9& I',cmco EouipmenlY\.(.ON\lEu;o~E.. ~lc~_ I fll.1OQ 'I ~ ICP'_"UIIO" Of 'lIc.u"'ct. 5oCl. inp Q/"Q~.~Q4o"ICr CQnQ"lllf'll ill/W "tn, illO Plite 01 Uc....11Cn T - taL ....In lne UI4.IQc at tIlT'll or II '1lV Olf'c. OUllOn Il'llr'!T\lv III CO....IOU.""I! c....nQn .n COIl;l~'onl 1-1. kJrz CcQ\)~ b..:6. T - '2... . (t;N,. EvL..- E;./\ ~ l' , :JSi.v. , T01>~lL - 1-CO"'l.' ~rz I R::n2.cu.l:.., Y2Go\ ~1U1.. ~ - "'-- 'i..lcr~ ~O. ~"''T. ~ . ~l L\\l SA1'\)~. L.T. /1.~lJ. Loo-'lsE-. 1'6u U<'Cl ~ ') (M1Ir<-l':l\ 'DtL'r'l ~- nA~,!~'T LA:'-1B:lU Nc;.. Ac.c.u fl.4,(LKO ON ." '1") BlAL~' ~u..U~IAc.... S1l-'Nn... 1'\1.& OCNS;E.. V. Llt:b-l, ~1I2OU)1\l. LD~. ~L. ",,-(:)6.T. ~~'C. loTAL -e.-e.\l)"1l.\ 10'/2'/ No <:(\b.\.~W1\n:~. 1\) 0 CAt I I'J(; . -' "\~ r?:,1'leIcFI11 C't"'\ Logged By: '0 15 I I I' I 'I 'I 20 'I I Surface Elevation Trencn Oilentation: Trencn DimenSIons ,.I Grounowater Deprn ':: . ~ 10 Date T-~ ~ T-4 Qt.ulLAL :':U",~2' EqUipment ~ PlrJi PLhN faL LOc..... 3. ~.4 . ~SltA tOPSOIL - Li. f?.--e,), '2.\oc.fIl..~ To C~ b' FT. _ :% L-- ~t..:t'l Silto.\t'> ~ ~(cr<:" / L.oc&E I ~L.VtZ.(lClW.s tl.ecst ~ A I a.S.. <t>L. \'V..o1 ~ \' . V. Lo~ 5 ~ ~'V-> To 3(;11. 1IA.1'b<L, ~\l..lS. fs:E:.Ovt!::.. N . &~L-ALLUVI~ ~D... L'\. ~l.<J~, . c..o~~ ~l;-ND, O~.( q, p) . t:EN'b.e.. _ Pcoe..C'{ G~-D. L-A~~ (;0 q 1. 6.LCc3 15 ~"I 'Tc1'.QL 12f:.1::sr1-l. l ~ ~ I CAvI~(. WreL ~\cacPIU:: ~/L<;". C^,YIiTlt'.,. To ~~_T-.3 . \\la. H'LO --n~l<,,-lct1 ~~~F1c...l.ECl LAKESHORE Engineering CONSULTING ENGINEERS AND GEOLOGIST SINGLE F MflL Y RESIDENCE , LOT 10 - TRACT 3777 VILLAGE WAY FOR: MR: CIARLETI A F'g, No 4 PROJ ",0 98-064,PI \\ I I I I I I I I I I I I I I I I I I I APPENDIX ~ FIELD EXPLORATION Field exploration was performed using a backhoe (Monteleone Excavating 677-6403). The soils were continuously logged by our field personnel and classified by visual examination in accordance with the Unified Soil Classification System. Our trench logs are attached for review. To evaluate the compaction characteristics of the fill material, field density tests were performed. Also, representative bulk samples were recovered and shipped to the laboratory in polythelene bags for laboratory testing. ZAHARA PROPERTY CORONADO DRIVE P.N. 98-074.PI Lakeshore Engineering \z" I I I I I I I I I I I I I I I I I I I APPENDIX B LABORATORY TESTING MOISTURE DENSITY RELATIONSHIP Moisture- density information usually provides a gross indication of the soil consistency and can delineate local variations at the time of investigation and provide a correlation between soils found on this site. The dry unite weight and field moisture content were determined for selected samples, and the results are shown on the log sheets. MAXIMUM DENSITY- OPTIMUM MOISTURE TESTS A selected soil sample was tested in the laboratory to determine maximum dry density and optimum moisture content using the A.S.T.M. D1557-78 compaction test method. This test procedure uses a 10 pound hammer falling a height of 18 inches on each of five layers to a 1/30 cubic foot cylinder. The results of the tests are presented below: Trench No. Depth (Ft.) Soil Description Maximum Dry Density (P.C.F) Optimum Moisture (% Dry Wt.) T-1 0-2 Silty SAND (SM) 121. 0 9.5 EXPANSION INDEX TEST A representative soil sample was collected in the field and tested in the laboratory in accordance with the A.S.C.E. Expansion Index Test Method as specified by U.B.C. The degree of expansion potential was evaluated from measured soil volume changes obtained during soil moisture alterations. The results of the test are presented below: Trench Depth Soil No. (Ft. ) Description ------ ----- ----------- T-1 0-2 Sil ty SAND (SM/SP) Expansion Index Expansion Potential 21 LOW ZAHARA PROPERTY CORONADO DRIVE P.N. 98-074.PI Lakeshore Engineering \~ I I I I I I I I I I I I I I I I I I I ) REGIONAL GEOLOGIC CONDITIONS AT THE ZAHARA PROPERTY CORONADO DRIVE TEMECULAIRANCHO CALIFORNIA AREA RIVERSIDE COUNTY CAeIFORNIA PR01ECT NO. 0980017.01 PREPARED FOR: LAKESHORE ENGINEERING 31606 Railroad Canyon Road #101 Canyon Lakes, California 92587 PREPARED BY: JONATHAN L. ROSSI, CONSULTING GEOLOGIST P.O. Box 4018, Big Bear Lake California 92315 May 15. 1998 ~ \~ I ,I I I I I I I I I I I I I I I I I I - IN: 0980017.01 TABLE OF CONTENTS Page 1.0 INTRODUCTION 1.0 2.0 SUMMARY OF FINDINGS 2.1 Geologic Setting 2.2 Earth Materials - 2.2.1 Topsoil 2.2.2 Quaternary Alluvium 2.2.3 Bedrock - Pauba Formation 1.0 3,0 3.0 4,0 4.0 4,0 3.0 GROUNDWATER 4,0 4.0 FAULTING AND SEISMICITY 4.1 Faulting 4.2 Seismicity 4.3 Secondary Seismic Effects 5,0 5,0 7.0 8,0 5.0 CONCLUSIONS & RECOMMENDATIONS 5.1 Conclusions 5.2 Recommendations 8.0 8,0 8,0 6.0 LIMITATI(lNS STATEMENT 9,0 ACCOMPANYING MAPS. TABLES. PLATES AND APPENDICES FiI!UTeS - Figure 1 - Index Map (EQ Fault Map; 2000 sc.) ---------------------------------- 2.0 Figure 2 - Regional Fault & Seismicity Map -------------------------------------------_ 6,0 ~- Table I - Regional Active Faulting ------------------------------------_ 5,0 Table II- Maximum Credible EQ., Maximun Ground Acceleration ---------------------------------__ 7,0 Anoendicies - Appendix - References ii /\"5 I I I I I I I I I I I I I I I I I I I ~ May 15. 1998 IN: 0980017,01 TO: Lakeshore Engineering 31606 Railroad Canyon Rd. #101 Canyon Lakes, Ca. 92587 SUBJECT: REPORT - Geologic Conditions at the Site of Proposed Residential Structure, Zahara Property. Located on the South Side of Coronado Dr.. in Rancho California/Temecula Area, Riverside County, California.(NW1I4, SWl/4, Sec 18, T8S, R2W, SBB&M). ATIENTION: Fen Yong. RCE - Principal, Lakeshore Engineering 1.0 INTRODUCTION- We are pleased to present this letter report of findings for the existing geologic conditions at the proposed residential development located on the south side of south Coronado Drive. East TemeculalRancho California area. Riverside County, California. The proposed site consists of an Cndeveloped naturaIlot facing Coranado Dr., west of Ynez Rnad. Roads are paved with curb and gutter in places. Our scope of work is limited to providing a description of the geologic conditions present at the subject site including general geology, faulting and seismicity, groundwater description. and presentation in this letter report, Seismic conditions were evaluated based on published earthquake and seismic infonnstion. Our scope of work does not address or consider any aspects of a Phase I Site Assessment for Hazardous Materials or Asbestos containing building materials, and is not a soils & foundation investigation, but provides geologic interpretation of site conditions for the soils engineer and the geotechnical report. This letter report presents our findings. conclusions. and recommendations concerning the existing geologic and earthquake/seismic, conditions present at the subject site. Our work is provided to the soils engineer for further geotechnical evalulltion. 2.0 SUMMARY of FINDINGS - 2.1 GEOLOGIC SETTING- The subject site is situated at the southwestern margin of an elevated older alluvial plain forming a pediment surface of rolling foothills north and east of the Temecula Valley, and north of the Pauba Valley. The older alluvium in this area consists primarily of a massive. partially cemented, well indurated Pleistocene sandstone (Fabua Formation-Sandstone unit) exposed across most of the region. The Pauba Formation contains a massive to poorly bedded, reddish brown, coarse to graded sandstone unit. in places containing thin (6" to 12") interbeds of gl'l'Y green to grey brown micaceous siltstone, Siltstone can be predominant in a portion of the section with minor sandstone, In the south Temecula Valley and Pauba Valley the older Pleistocene Temecula Arkose underlies the Pauha Sandstone. The Temecula Arkose consists of a thick section of layered very fine sandstone to siltstone, Narrow, thin deposits of younger alluvium are present within the erosional canyons developed within the pediment surface. The older alluvial , pediment surface is bordered on the north and east by intrusive granitic and older marine metasediments of Bachelor Min. and Black Hills. Traces of the Agua Caliente Fault zone are mapped (CDMG Santa Ana Sheet-1965) at the contact of the Pauba sandstone with these hard rock units. The Temecula/Elsinore Graben is bordered by the Wildomar Fault on the northeast, and the Willard Fault on the southwest. Both of these fault segments are considered part of greater WIllttierlElsinore Fault Zone. The Pabua sandstone pediment surface is located within the boundaries of the Perris structural block. ' -1- \0 I I I I I I I I I I I I I I I I I I I ~ IN:0980017.01 - z o m >< S > ,,1J 2000 4000 I feet INDEX MAP OF ZAHARA PROPERTY CORCNAJ;lO DR. RAN:HO CALIFORNIA ''I'EMECULA RIVERSIDE COUNTY CALIFORNIA \1 Base Map: USGS' 7 .5 I Terrecula Quad. State of Ca. Earthquake Studies Map - 1990 FIGURE 1 I , I -3- May IS, 1998 IN: 0980017,01 I I The Perris Block is a northwest-southeast trending structural block bordered on the northeast by the San Jacinto Fault. on the southwest by the WhittierlElsinore Faull System (Wildomar Fault), on the northwest by the Chino Basin. and on the southeast by the Agua Calenti fault Zone and Boreggo Valley. Similarly, the Santa Ana Mountains Block is bordered on the northeast by the WhittierlElsinore Fault Zone, on the southwest by the off-shore NewportlInglewood - Rose Canyon Fault System, on the northwest by the Orange Coastal Basin. and on the southeast by older cross faults in the San Diego - Baja California area, ,I I The closest active or polentially active faults capable of effecting the subject site (if an earthquake event were to occur on one of these faults near the site) are the Wildomar Fault approximately 1/4 mile to the northeast, and the San Jacinto Fault approximately 22.0 miles to the northeast. Both of these faults are considered active, and are Earthquake Faull Zones. The recently zoned Wolf Valley fault located some 1.5 miles to the south, on the southwest side of the Temecula Graben, is considered a portion of the Elsinore Fault Zone, and possibly an extension of the Willard Fault identified further to the northeast on the southwest side of the Temecula Valley. No active or polentially active faults were observed on the subject property, or were present on the site in the literature reviewed. The site is not included within the Wildomar Fault Earthquake Fault Zone. Other fault features or linear fault like features are reported on M.P. Kennedy's Map (CDMG Sp.Rpt. 131, Plate I) within the Pauba Plain to the north and east of the site, These faults are not Earthquake Fault Zones, and are not well defined in the literature. The original and the second MWD San Diego Aqueducts (oriented N-S) are located 1/2 mile to the east. ,I I I I 2.2 ON-SITE GEOLOGY - EARTH MATERIALS- ) I 2.2.1 Tonsoils- I A thin layer of poorly developed topsoil is usually present over native subsoils and bedrock. Topsoils in the area consist of loose, brown to reddish brown, porous, well graded silty sands and clayey sands where shallow bedrock is present (Pauba Fm, sandsione). In the exploratory trenches a thick soil zone of layered, very porous, and burrowed silty sand alluvial soil continue in the soil section to approximately 7 1/2 feet below grade. It appears that the soil section is the result of an alluvial accumulation within a localized topographic depression associated with nearby active faulting along the Wildomar Fault zone.(see Trench Logs). The soil section appears to rest on layered sandy fluvial soils. I I 2.2.2 Alluviwn (Oan - I Exploratory trench T -I encountered the above described thick topsoil section resting over sandy alluvial soils typical of stream deposited alluvium (fluvial deposits). The unconsolidated soils were observed (F. Y ong) to be loose to medium dense, easily excavated thinly layered poorly graded fine to medium sand, sandy silts, and gravelly sands. Pauba Sandstone bedrock was not encountered in the trench, however is expected to exist a few feet below the bottom of the trench. Pauba Sandstone is present at the higher elevations in the local area. Pauba Sandstone is mapped across the local area (CDMG SpRpt. 131). and is mapped at the site. I I I \~ I I ~ I -4- May 15, 1998 IN: 0980017,01 I I I 2.2.3 Bedrock (Ooss) - I Bedrock was Dot exposed on the site, but is seen on the adjacent property to the east, and is mapped (CDMG 131) underlying the property. Bedrock consists of the Quaternary Pauba Formation Sandstone, a regionally distributed poorly cemented (CaCO' & salts), friable well graded sandstone with limited poorly defined bedding, and containing interbeds of grey to brown siltstone. The Pauba is a young continental deposit containing a large number of sedimentary depositional structures : coarse channel fills, cross-bedding and graded bedding, and alluvial fan structures. Pauba sandstone at the subject site co.nsists of reddish brown to brown well graded sandstone with a moderately high silt and clay content. In addition to salt cementation clay acts to bind the sand grains of the arkosic sediment into a poorly consolidated \ continental sandstone. Excavation is relatively easy with standard backhoe, and the Pauba slands up well in cut slopes up to 30 feet. However, the Pauba is easily eroded, and can be cut with water where run-off is not controlled. Erosional gullying and animal burrowing in the slope face is considered a problem with existing slopes in the area. Bedrock is not exposed at the surface at the subject site, however is present some 3 to 5 feet below the existing grade. The Pauba sandstone is thought to be underlain by Temecula Arkose, however the Temecula Arkose is not exposed at the local site area. I I I I 3.0 GROUNDWATER- I Groundwater is present throughout the region' as an unconfmed alluvial aquifer within the Younger and Older Alluvium underlying the site, and in the underlying Pauba sandstone. The bedrock is considered as moderatelY good water bearing aquifer, and can yield limited amounts of groundwater to domestic water wells from primary and secondary porosity. Regional groundwater within the graben basin occurs over a thick section of several hundred feet, and is utilized by numerous domestic, municipal, and irrigation water wells. Localized perched groundwater may be present at the site and typically occurs at the base, of the bedrock weathered zone. Perched groundwater is the result of local winter season percolating surface waters collecting over low permeability silt layers within the upper weathered Pauba sandstone. No springs or seeps were reported on the subject site. 'Additional information concerning the on-site hydrogeologic conditions may be obtained, if required, through the review of available water well drillers logs, and by additional on-site hydrogeologic investigation under separate study. I I I I I I I I \~ I I I I I I I I I I I I I I I I I ,I I I , -5- May IS, 1998 IN: 0980017.01 4.0 FAULTING & SEISMICITY - 4,1 Faultilll!- No surficial or other evidence of active or potentially active faulting was observed at the subject site during our field investigation. The subject site is not included in any Earthquake Study Zone for fauIt hazard, The Wildomar Fault Zone located approximately 1/4 miles to the northeast, the Wolf Valley Fault 1.2 miles to the southwest, and the San Jacinto Fault Zone located approximately 22.0 miles to the northeast are the closest Special Study Zone faults to the site. The Wildomar Fault Zone is considered to be a high angle . and strike slip fault, strongly developed and clearly visible from aerial photographs. The Wolf Valley Fault ' is described as a high angle fault possibly induced due to groundwater withdrawal in the Wolf Valley (lower Temecula Valley). The San Jacinto Fault Zone extends along the foothills of the San Timoteo Badlands, and at the base of the south San Jacmto Mountains. The fault zone is considered to be a complex zone of high angle normal and strike slip faults with multiple and discontinuous fault strands as wide as 2 to 3 miles (San Jacinto & Casa Loma Faults San Jacinto Graben Valley). There are several other faults within the greater Southern California area which could effect the site in terms of ground shaking in the event of an earthquake. The following list includes some of these faults and their maximum probable earthquake magnitude (Richter): , ) TABLE I REGIONAL ACTIVE OR POTENTIALLY ACTIVE CAUSATIVE FAULTS I FAULT I DISfANCE FROM SITE J\.lAXIMUM CREDIBLE APPROXIMATE EARTHQUAKE (RICHTER MAGNITUDE) San Andreas Fault 39.0 mi. NNE 8.0M San Jacinto Fault 22.0 mi. NE 7.5M Elsinore (Wildomar) Fault 1/4 mi, SW 7.5M Banning Fault 36.0 mi. ENE 7.5 M Whittier 50.0 mi. NNW 7.5M Sierra Madre/Cucamonga 53.0 mi. NW 7.5 M 1rL> -~~ /~~~ ~ 1 / ;"~ ,H Alo '" ....... oo~^'/',;' ,< g", 2 ,,:I z';; .!'t ~ ;; s 1D .. ,~.......-.~ ~..-" .~ ./ ,,/"J ,. I I r'- r--- ,\'"2 I I I I I I I I I I I I I I I I I ----. o , i ~! : \~ ; .1!,\ 'I I/;f ~ -y I' .(.:/ / ''V 1/ ! .- ~ r ( i1 :'~i;'7 If I: J' ;' / 1 "~ r .,~ ", ! ' -\ 1.1 ,'" I ~' ~' ,/ ! 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I Ii \ '. ~ I I I I I I I I I I I I I I I I I I I - -7- May 15, 1998 IN: 0980017,01 4.2 Seismicitv- Based on information provided by CDMG Map Sheet 23 - Greensfelder; CDMG OF 92-1, 'Peak Accelerations from Maximum Credible Earthquakes in California - Caltrans 1992'; and Seed & Idriss ' Ground Motion and Soil Liquefaction During Earthquakes'(Earthquake Engineering Research Institute) the following conditions were determined for ground accelerations at the site for specific earthquake events at or near the subject site. Maximum credible earthquake magnitudes listed in CDMG OF-92-1 and associated bedrock accelerations are presented in TABLE II below. The subject site should perform essentially as a bedrock or stiff soil site because of the very close proximity of bedrock, and the limited volume of alluvial fill overlying the bedrock at the site, Repeatable ground accelerations and ground surface deformation will occur to a greater extent in the alluvium than at a bedrock site. The Pauba sandstone can be considered stiff alluvial soil or soft bedrock. Review of CDMG Map Sheet 54, which is presented in CDMG OF-92-1 as a peak ground acceleration contour map includes the area of the subject site within the .6 g acceleration contour, one of the highest ground accelerations for southern California, TABLE n MAXlMUMCREDffiLE EARTHQUAKE PEAK GROUND ACCELERATION c REPEATABLE GROUND ACCELERATIONS , CAUSATIVE FAULTS ~ I FAULT II DISl'ANCE II MAGNITUDE I PEAK REPEATABLE ACCELERATION ACCELERATION WILDOMAR 1/4 :t mi. 7.5M .73 g .475 g SAN JACINTO 22.0 :t mi. 7.5M .250 g .165 g SAN ANDREAS 39,0 :t mi. 8.0M .175 g .113 g BANNING 36.0 :t mi. 7.5M .155 g .101 g WHITI1ER 50.0 :t mi. , 705M .100 g .065 g CUCAMONGA 53.0 :t mi. 705M .080 g .052 g * !<.epeataole ground acceleratIOn .b~ ot maxunum 'g . , These ground acceleration values are for bedrock accelerations, and can be applied for any seismic condition stability evaluation of the subject site. Earthquake design criteria presented in the current Uniform Building Code, or in the County of Riverside Building Code Seismic Design Section, or design provided by the structural engineer and soils engineer in accordance with these requirements, whichever takes precedence, should be applied to the proposed development. Other active or pote!'tially active faults in the region will probably produce less sever effects on the site as a result of an earthquake event, and considering fault to site distances will probably have a less sever to negligible effect on the site. (see Table II above), ~ I I I I I I I I I 1 I I I I I I I I I - -8- May 15, 1998 IN: 0980017,01 4.3 ~ndarv Seismic Hazards - The potential for secondary seismic effects such as liquefaction due to the presence of granular sediments, sballow groundwater, and nearby active faulting capable of generating large earthquake events should be evaluated by the soils engineer. Based on our geologic observations at the site, and knowledge of the geology of the area, we do not consider the subject site to be a high risk for liquefaction due to the presence of the underlying cemented/clay bearing Pauba sandstone. Other secondary seismic effects such as differential settlement/compaction, ground surface rupture due to fault movement, or ground surface rupture due to lurching is not considered likely, but cannot be ruled out due to the faulted nature of the region, and the close proximity of active faulting which has produced ground surface rupture in the past. Seismically induced landsliding is not common in the Pauba sandstone, and is considered unlikely to effect the subject site. Other potential secondary seismic hazards: tsunami, and seiches flooding due to reservoir failure are considered nil due to the site location, and nature of the bedrock deposits. 5.0 CONCLUSIONS & RECOMMENDATIONS- 5.1 Conclusions . The subjdct site is suitable, in terms of the on site geologic conditions, for the proposed residential construction. Topsoils and Pauba Fm. sandstone bedrock should not present any significant geologic, impediment to the excavation of the residential building pad and foundation footings. Footings cannot be " founded in porous, unsuitable soils materials as per the soils engineer. o o The subject site is close to (1/4:t mile) the Wildomar Fault Zone. There are no reported or mapped traces of the fault close to or on the subject site. Strong groundshaking (secondary seismic hazard) is considered a possibility should a medium to large earthquake event occur on the Wildomar Fault adjacent or close to the subject site. 5,2 Recommendations- o The footing excavation should be inspected for competency by the soils engineer or the engineering geologist prior to the setting of reinforcing steel bar, or any imported sand or gravel base. o , Groundshakin2 - Due to close proximity of the active Wildomar Fault, the structural engineer should consider seismic peak accelerations and groundshaking criteria in the steel reinforcing design for the residential foundation. o Draina2e Control - Ally proposed cut slope should have a drainage 'V' brow ditch (24" wide, 12" deep) cut across the top of the proposed cut slope, set back 3 feet from the top of slope. The' brow ditch should be lined with concrete grout. Drainage from all sources should not be allowed to flow over any proposed cut or fill slope faces, z,~ I I 'I I I I I I I I I I I I I I I I I I , -9- May 15, 1998 IN: 0980017,01 5.2 Recommendations - (continued) - o LandscaDe VeeetatiDn - Any proposed cut slopes should be planted with standard grasses and indigenous plants (hydroseed) possibly using a landscape stability growth net on the slope face. Deep rooted vegetation should be planted in order to increase slope surficial stability over time. All landscaping design and plant type should conform to Riverside County landscaping guidelines. o At this time we have not reviewed the proposed grading plan for the subject site, Any proposed cut slopes (2 horz,: I vert.), vertical cut slope for retaining wall, cut pads, !ill slope keys, foundation footing excavations, or other graded exposures of bedrock should be inspected by the engineering geologist upon excavation. 6.0 LIMITATIONS- This Engineering Geologic report section has been completed by Jonathan L. Rossi, Consulting Geologist, Lakeshore Engineering, and licensed or certi!ied subcontractors to Lakeshore Engineering. It should be noted that J.L. Rossi, Consulting Geologist haS been retained for the purposes of providing geologic interpretation of existing and gathered data, to provide the geology portion of the Preliminary Geotechnical Investigation. Our conclusions and recommelidations are hased solely on the data made available to us from one site visit, and information made available by Lakeshore Engineering, Our work has been performed, in accordance with the professional practices currently accepted in the Geotechnical Consulting Industry (oday. No warranty is either expressed or implied. Should you have any questions concerning this Letter Report of Existing Geologic Conditions please do not hesitate to contact me at (909) 584-2084., SINCERELY YOURS; nathan L. Rossi, Consulting Geologist CEG 1460 2A II I I I I I I I I I I I I I I I I I I ~ APPENDIX ) IN: 0980017,01 ~~ I I I I I I I I I I I I I I I I I I I , IN: 0980017.01 Page 1 of2 REFERENCES Association of Engineering Geologist, 1973 - Earthquake Recurrence Intervals on Major Faults in Southern California, ABG Special Publication October 1973; D.L. Lamar, P.M. Merifield, R,J. Proctor. California Division of Mines & Geology - 1974; Map Sheet 23, Maximum Credible Rock Accelerations; R. Greensfelder. - 1992; Peak Acceleration from Maximum Credible Earthquakes in Ca.; DMG Open-File Report 92-1; L. Muaichin, & A,L. Jones. - 1990; CDMG Map Sheet 54; unpublished for CalTrans. - 1954; CDMG SR 43; Geology of a Portion of the Elsinore fault Zone, California; John F. Mann, Jr. - 1977; CDMG SR 131; Recency & Character offaulting Along the Elsinore Fault Zone in Sountern California; M.P, Kennedy - 1988 - Summary Report: Fault Evaluation Program: 1986-1987, Mojave Desert and Other Areas - Open File Report 88-1 LA; E.W. Hart, W.A. Bryant, J.E. Kahle, M.W. Manson, & E.J. Bortugno, - 1967 - Geologic Map of California, Map No. I, Santa Ana Sheet; Jennings, C.W. 1983 - Th~ 1983 Coalinga, California Earthquakes, CDMG Special Publication 66, J,H,Bennett & R. W.Sherburne, Editors, Dudley, Paul H., 1935 - Geology of a Portion of the Perris Block, Southern California; California Division of Mines, California Journal of Mines & Geology Vol. 31, No, 4, October 1935. Earthquake Engineering Research Institute, 1982 - Ground Motion and Soil Liquefaction During Earthquakes; H.Bolton Seed & I.M, Idriss. Pub: EERI Berkley, California.; ISBN 0943198240 Earthquake Engineering, 1970 - Robert Wiegel, Coordinating Editor; Pub: Prentice-Hall, N.J., ISBN 132226464. Earthquake Engineering, Damage Assessment and Structural Design, 1983 - S.F. Borg; Pub:Wiely Heyden, Lid,; ISBN 0471262617. Geologica! Society of America, 1982 - Neotectonics in Southern California, Guidebook Field Trip No.3, 4, 14, 1986 - Neotectonics and Faulting in Southern California, Guidebook Field Trips la, 12, 18. 1987 - Paleoseismicity and Active Tectonics, The Structural Geology and Tectonics Division, GSA, Grey, Cliffton H.,Jr, 1961 - Geology of the Corona South Quadrangle and the Santa Ana Narrows Area, Riverside, Orange & San Bernardino Counties, California., and Mines and Mineral Deposits of the Corona South Quadrangle, Riverside and Orange Counties, California; California Division of Mines and Geology Bulletin 178. 2k I I II I I I II I I I I I ,I I I I I I I I , IN: 0980017,01 Page 2 of2 REFERENCES Instution of Mining & Metallurgy, 1981 - Rock Slope Engineering, 3rd Edition; E. Hoek & J. W. Bray; Pub: Ins!. Mining & Metallurgy, London ISBN 0900488573 . South Coast Geological Society, 1983 - Geology of the Northern Elsinore Trough, Annual Field Trip - 1983. United States Geologic Survey - 1985; PP 1306; 'Earthquake Hazards in the Los Angeles Region'; J.I. Ziony, Webber, Harold F,,1977 - Seismic Hazards Related to Geologic Factors, Elsinore and Chino Fault Zones, " Northwestern Riverside County, California. MAPS UTILIZED USGS 7112' Temecula Quadrangle Topographic Map 1973 rev. USGS 7112' Pauba Quadrangle Topographic Map 1972 CDMG Special Study Zone Map (Earthquake Fault Zone Map), Temecula Quadrangle 7112' Revised Official Map January I, 1990/ - 1967 - Geologic Map of California, Map No. I, Santa Ana Sheet; Jennings, C.W. 201-