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Parcel Map 33923 Parcel 11 Geotechnical Site Faulting
&N w"Iftfimm-1 Leighton and Associates A GTG Company GEOTECHNICAL CONSULTANTS UPDATED GEOTECHNICAL SITE FAULTING EVALUATION REPORT PARCEL 11 OF PARCEL MAP 19580 BUSINESS PARK DRIVE TEMECULA, CALIFORNIA August 30, 2002 Project No. 110768-002 Prepared For: EDGE DEVELOPMENT INC. 42430 Winchester Road Temecula, California 92590-2504 41715 Enterprise Circle N. Suite 103, Temecula, CA 92590-5661 (909) 296-0530 • FAX (909) 296-0534 • www.leightongeo.com J Leighton and Associates A GTG Company GEOTECHNICAL CONSULTANTS August 30, 2002 Project No. 110768-002 To: Edge Development, Inc. 42430 Winchester Road Temecula, California 92590-2504 Attention: Mr. Steve Prophet Subject: Updated Geotechnical Site Faulting Evaluation Report, Parcel 11 of Parcel Map 19580, Business Park Drive, Temecula, California In accordance with your request, Leighton and Associates, Inc. has completed a geotechnical review of site faulting for Parcel 11 of Parcel Map 19580, located on Business Park Drive in the City of Temecula. This report summarizes our findings, conclusions, and recommendations regarding the on-site faulting and revised structural setback to the proposed commercial d6V616pment. Respectfully submitted, LEIGHTON AND ASSOCIATES, INC. Robert R Riha, CEG 19: Vice President/Principal RFR/KAB/mm/dhn/final 110768-002 Update Geotechtucal and Fault Distribution: (6) Kevin A. Bryan, Senior Project G 41715 Enterprise Circle N. Suite 103, Temecula, CA 92590-5661 (909) 296-0530 a FAX (909) 296-0534 • www.leightongeo.com 0 0 TABLE OF CONTENTS Section 110768-002 Page 1.0 INTRODUCTION.........................................................................................1 1.1 Scope of Work ............................................ 1.2 Site Description and Background .............. 1.3 Field Investigation ...................................... ................................................................1 .............:..................................................1 ................................................................2 2.0 SUMMARY OF GEOTECHNICAL FINDINGS.....................................................3 2.1 Regional Geology...................................................................................................................3 2.2 Site Geologic Units.................................................................................................................3 2.2.1 Artificial Fill by Others(Afo).....................................................................................3 2.2.2 Quaternary Alluvium(Qal).........................................................................................4 2.3 Faulting and Seismicity 2.3.1 On -Site Fault Activity ...................................................................................................4 2.3.2 Seismicity......................................................................................................................5 2.4 Secondary Seismic Hazards....................................................................................................5 2.4.1 Ground Rupture.............................................................................................................6 2.4.2 Liquefaction...................................................................................................................6 2.4.3 Seiches/Tsunamis..........................................................................................................6 2.4.4 Flooding Due to Dam or Levee Failures......................................................................6 2.4.5 Lansliding(Rocck Eall.....................................................................................................6 ,_2�regeismicallY-Induced Settlement....................................................................................6 3.0 CONCLUSIONS AND RECOMMENDATIONS...................................................7 4.0 GEOTECHNICAL REVIEW............................................................................8 4.1 Plans and Specifications 4.2 Construction Review..... ..................................... 8 ..................................... 8 5.0 LIMJ`rATIONS...........................................................................................9 • • 110768-002 TABLE OF CONTENTS (continued) Accompanying Figures, Tables, Plates and Appendices Figures Figure 1 Site Location Map End of Text Figure 2 Alquist-Priolo Earthquake Fault Zone Map End of Text Figure 3 Fault Location Map End of Text Figure 4 Photos of Fault Exposed in FT -1 and FT -2 End of Text Plates Plate 1 Fault Trench Log, FT -1 and FT -2 In Pocket AAvnendices Appendix — References AIN • • 110768-002 1.0 INTRODUCTION The purpose of our geotechnical evaluation was to summarize pertinent geologic and geotechnical data, and evaluate this site's potential for active faulting based on site specific subsurface fault trenching and provide updated fault zone setbacks. The scope of services conducted during our study is provided below: 1.1 Scope of Work Our scope of work for this investigation included the following items: • Review of available information, including aerial photographs of the property, and reports presented in Appendix A. • Geologic site reconnaissance of the subject property. • Excavation of 2 exploratory fault trenches (240 feet in total length) within the subject property to verify the existence and location of faulting and/or evidence of previous earth movement. • Preparation of this report, presenting our findings, conclusions and preliminary recommendations regarding site faulting and revised structural fault zone setback. 1.2 Site Description and Background Parcel 1 I of Parcel Map 19580 encompasses approximately 4.7 acres and is located on the west side of Business Park Drive approximately 600 feet north of the intersection with Single Oak Drive. At the time of our investigation the site was partially graded and relatively flat lying, The; site has.been.disced and is relatively free of vegetation. `l Previous studies have been perform on this and adjacent parcels by Aragon Geotechnical Consultants (Aragon, 1987), Schaefer Dixon Associates, Inc. (1988, 1989a, b, c) and ENGEN (1999b). Fault studies relative to the ground fissures of early 1988 were performed within the Business Park Phase 2 development by Schaefer Dixon Associates Inc. (1988 and 1989a). A site specific soils investigation has been performed on Lot 11 by Engen (1999). A fault zone setback had been previously established on Lot 11 of Business Park 2 by Schaefer Dixon (1988) based on ground fissuring and adjacent lot subsurface investigations by trenching, borings and Cone Penetrometer Tests (CPT). 0 1.3 Field Investigation • 110768-002 Two exploratory fault trenches were excavated on August 16 and 17, 2002 utilizing a tracked excavator. The approximate location of the trench excavations are shown on the Fault Location Map, Figure 3. Logs of these trenches are depicted on Plate 1. The trenches were excavated to lengths of approximately 105 lineal feet on FT -1 and 135 lineal feet on FT -2. Each trench was excavated to a minimum width of three feet, and benched symmetrically upwards according to current OHSA guidelines. Each trench was excavated to a consistent depth of approximately 15 to 20 feet. The fault trenches were continuously logged by a certified engineering geologist from our firm. Upon completion of logging, the trenches were backfilled with uncompacted native materials by a rubber tire loader. The detailed trench logs are presented on Plate 1 and were prepared at a 1:1 (horizontal to vertical) scale with 1 -inch equaling 5 feet. A summary of our findings is provided in Section 2.0. -2- "MIS = n U • 110768-002 2.0 SUMMARY OF GEOTECHNICAL FINDINGS 2.1 Regional Geology The subject property is located within a prominent natural geomorphic province in southwestern California known as the Peninsular Ranges. It is characterized by steep, elongated ranges and valleys that generally trend northwestward. The most common rock types found in the Peninsular Ranges consist of 140 to 105 million -year old formations (Silver and Chappel, 1988), including the metasedimentary Bedford Canyon Formation and Santiago Peak Volcanics. These formations were intruded by granodiorite, quartz monzonite and other granitics of the Southern California Batholith during the Cretaceous period (Kennedy, 1977). Tectonic activity along the numerous faults in the region has created the geomorphology present today. More specifically, the property is located in the southern portion of a fault controlled, down dropped graben, known as the Elsinore Trough (Figure 2). This graben is believed to contain as much as 3000 feet of alluvium which has been accumulated since Miocene time. The Elsinore Trough is bounded on the northeast by the Wildomar Fault and on the southwest by the Willard Fault. These faults are part of the Elsinore -Whittier Fault Zone which extends from the San Gabriel River Valley southeasterly beyond the United States -Mexican border. The Wildomar fault is considered active and the Willard fault is considered in -active. The Santa Ana Mountains lie along the western side of the Elsinore-Whitter Fault Zone and Perris Block is located along the eastern side of the fault zone. The mountain ranges are underlain by Pre -Cretaceous metasedimentary and metavolcanic rocks and Cretaceous plutonic rocks of the Southern California batholith. Tertiary sediments, volcanics and Quaternary sediments flank the mountain ranges. The Tertiary and, Quaternary rocks are generally comprised of non -marine sediments consisting of sandstones, mudstones, conglomerates, and occasional volcanic units. 2.2 Site Geologic Units The ia—rd materials encountered on site consist of Artificial Fill by others and Holocene -Aged alluvium. These units are discussed in the following sections in order of increasing age. 2.2.1 Artificial Fill by Others Mfg) Artificial fill soils were exposed during this study up to a maximum depth of approximately 8 feet below existing grades. This fill material appears to have been placed as engineered fill as relatively horizontal "Lifts" or layers 8" to 18" thick can be observed. This material generally consisted of dark gray to brown, damp, relatively dense, silty sand to sandy silt with scattered gravel sized clasts. The upper 1 to 2 feet of this material was highly disturbed and contained abundant organic debris likely due to repeated discing. -3 • 110768-002 2.2.2 Quaternary Alluvium (Oal Alluvial soil was encountered underlying the Artificial Fill by others to the total depth explored in both fault trenches. As encountered, the alluvium generally consisted of interbedded light gray to olive green gray, damp to moist, silt to silty sand and sandy clays. Cross bedded channel sands interbedded with fine sands silt and clay suggest this material was deposited in a active channel margin type of environment. The upper 1 to 3 feet of alluvium appeared to be relatively dry and porous. 2.3 Faulting and Seismicity Temecula, like the rest of Southern California, is located within a seismically active region as a result of being located near the active margin between the North American and Pacific tectonic plates. The principal source of seismic activity is movement along the northwest - trending regional faults such as the San Andreas, San Jacinto and Elsinore fault zones. These fault systems produce approximately 55 millimeters per year of slip between the plates. The Elsinore fault zone comprised of the Willard Fault and the Wildomar Fault, are estimated to accommodate 10 to 15 percent of the plate boundary slip (WGCEP, 1995). The location of the site in relationship to known active faults in the subject area is depicted on the Alquist- Priolo Earthquake Fault Zone Map (Figure 2). By definition of the State Mining and Geology Board, an active fault is one which has had surface displacement within the Holocene Epoch (roughly the last 11,000 years). The State Mining and Geology Board has defined a potentially active fault as any fault which has been active during the Quaternary Period (approximately the last 1,600,000 years). These definitions are used in delineating Earthquake Fault Zones as mandated by the Alquist-Priolo Geologic Hazard Zones Act of 1972 and as subsequently revised in 1994 and 1997 (Hart, 1997) as the Alquist-Priolo Earthquake Fault Zoning Act and Earthquake Fault Zones. The intent of the act is to require fault investigations on sites located within Earthquake Fault Zones to preclude new construction of certain inhabited structures across the trace of active faults. The subject site is located within an Alquist-Priolo Earthquake Fault Zone (Hart, 1997) and evidence of active faulting was.observed_within+our- exploratory fault trenches. 2.3.1 On -Site Fault Activity Traces of the zoned "active" Murrieta Creek segment of the Elsinore fault zone were encountered within the exploratory trench excavations. A graphical representation of the trench exposures are presented on Plate 1, Fault Trench Logs, included with this report in the map pocket at the rear of text. As exposed within the exploratory fault trenches, the fault can be characterized as a relatively narrow zone of steeply dipping fractures which visibly offset alluvial strata. It has been suggested by others, (Schlemon, R. J., and Davis, P., 1988) that this alluvial material is between approximately 3,000 and 4,000 (soil stratigraphic) and 9,100 (radiocarbon) years old. Several distinctive clayey silt to silty clay beds can be traced across the fault zone in both trenches with down -to -the -east displacement. A minimum of approximately 5 feet of vertical displacent was measured -4 0 • 110768-002 across the fault zone assuming the clayey/silt beds were initially deposited relatively horizontally. Indications of active faulting west of the relatively narrow zone of fracturing and offset bedding was not observed within the trenches. This does not preclude the possibility that additional strands of the fault zone exist to the east (towards the street), beyond the limits of our trenches. 2.3.2 Seismicity Our evaluation of the regional seismicity included a deterministic analysis utilizing EQFAULT, (Blake, 2000b) and a probabilistic analysis utilizing FRISKSP (Blake, 2000c). The nearest known active fault and source of the design earthquake is the Murrieta Creek Fault, (which is a segment of the Elsinore -Temecula Fault as part of the greater Elsinore Fault Zone Complex), which traverses the proposed parking lot area of the subject site (see Figure 3). The maximum credible earthquake was estimated to be magnitude 6.8 using the referenced geologic programs and available geologic documents (Appendix A). The Uniform Building Code (UBC) established Seismic Zones (often accepted as minimum standards) based on maps showing ground motion with a 475 -year return period or a 10% probability of exceedence in 50 years. Our analysis indicates a 10% probability that a peak ground shaking of 0.73g would be exceeded in 50 years. The design earthquake, therefore, is considered a magnitude magnitude 6.8 event that would generate a probabilistic peak ground acceleration of 0.738 (FRISKSP, Blake 2000c). The effect of seismic shaking may be reduced by adhering to the 1997 Uniform Building Code (UBC) and seismic design parameters suggested by the Structural Engineers Association of California. This site is located within seismic zone 4. The UBC seismic design parameters are presented below: Seismic Zone =4 Seismic Source Type =B Near Source Factor, N. = 1.3 Near Source Factor, N. =1.6 Soil ProfileJype...:. =SD Horizontal Peak Ground Acceleration = 0.73g (10% probability in 50 years) 2.4 Secondary Seismic Hazards Secondary hazards generally associated with severe ground shaking during an earthquake are ground rupture, liquefaction, seiches or tsunamis, flooding (dam or levee failure), landsliding, rock falls, and seismically -induced settlement. 0 0 2.4.1 Ground Rupture 110768-002 Ground rupture is generally considered to most likely occur along pre-existing active faults. Since our review has identified on-site recent (Holocene) fault activity, the potential for site ground rupture during a seismic event on the Murrieta Creek Fault is considered high. Ground rupture could potentially affect existing and future facilities (such as gas, electrical, water mains and aqueducts) crossing the onsite or nearby active faults. 2.4.2 LLi uefaction The subject site is located in the County of Riverside identified liquefaction hazard zone. The potential for liquefaction has been addressed under separate cover (Leighton, 2002). 2.4.3 Seiches/Tsunamis As the subject site is not located near the coast or adjacent to any large bodies of water the potential for seiches or tsunamis is considered nil. 2.4.4 Flooding Due to Dam or Levee Failures The subject site is not located directly in a mapped dam or levee failure inundation zone. However, the project civil engineer should address the possible flooding from regional dam failures in the project design documents. 2.4.5 Lansliding/Rock Fall Due to the flat lying nature of the subject site, the potential for landsliding or rock fall is considered nil. 2.4.6 Seismically -Induced Settlement The bje, ct.site,,is=iecated.in-Riverside• County Designated Hazard Zone for subsidence and is addressed under separate cover (Leighton, 2002). -6- • C� 110768-002 3.0 CONCLUSIONS AND RECOMMENDATIONS Based on our geotechnical evaluation, it is our opinion that the proposed development is feasible from a geotechnical standpoint and may be constructed provided the following recommendations are implemented during grading and incorporated into the design and construction. • Active Holocene -aged faulting has been identified onsite. Specific preliminary structural setback provisions have been prepared so that no habitable structures are placed across the ground surface projections of identified site faulting. The limits of the preliminary recommended structural setback are presented on the accompanying Fault Location Map (Figure 3). The structural setback limits should be surveyed by the project civil engineer based on curb markings made at the site and the recommended 25 -foot horizontal setback from the projected Fault Trace. The setback zone should then be incorporated onto the development plans. • The fault encompassed by the setback zone has a dipping component and cut or fill grading which significantly changes the present site elevations may shift the recommended setback zone. The setback presented on Figure 3 included with this report was simply plotted as a 25 - foot setback from the mapped fault location projected to the ground surface without adjustment for any proposed overlying cuts or fills. Significant ground shaking, possible ground rupture, and/or settlement may occur due to on-site or local earthquake fault activity during the life of the project. • The design ground motion having a 10 percent probability of being exceeded in 50 years is expected to produce a peak horizontal ground surface acceleration at the site of up to 0.73g. • The fault trenches excavated during this investigation were backfilled with loose uncompacted fill soils. These trenches will need to be re -excavated and recompacted during future grading operations in accordance with the recommendations provided in Section 4.0 of this report. _The..existingionsite soils=appear-to be suitable material for reuse as fill during proposed grading provided they are relatively free of organic material and debris. ' _N Z_ IT 7 • 110768-002 4.0 GEOTECHNICAL REVIEW Geotechnical review is of paramount importance in engineering practice. The poor performances of many foundation and earthwork projects have been attributed to inadequate construction review. We recommend that Leighton and Associates be provided the opportunity to review the following items. 4.1 Plans and Specifications The geotechnical engineer should review the project rough grading, foundation plans and specifications prior to release for bidding and construction. Such review is necessary to determine whether the geotechnical recommendations have been effectively implemented. Review findings should be reported in writing by the geotechnical engineer. 4.2 Construction Review Observation and testing should be performed by Leighton and Associates representatives during grading and construction. It should be anticipated that the substrata and fault locations exposed during construction may vary from that encountered in the previously excavated test pits. Reasonably continuous construction observation and review during site grading and foundation installation allows for evaluation of the actual soil and fault conditions and the ability to provide appropriate revisions during construction, if required. Site preparation, removal of unsuitable soils, approval of imported earth materials, fill placement, foundation installation and other site geotechnically-related operations should be observed and tested by representatives of Leighton and Associates. -8- • 5.0 LIMITATIONS CI 110768-002 This report was necessarily based in part upon data obtained from a limited number of observances, site visits, soil samples, tests, analyses, histories of occurrences, spaced subsurface explorations and limited information on historical events and observations. Such information is necessarily incomplete. The nature of many sites is such that differing characteristics can be experienced within small distances and under various climatic conditions. Changes in subsurface conditions can and do occur over time. This report was prepared for Edge Development Inc., based on Edge Development's needs, directions, and requirements. This report is not authorized for use by, and is not to be relied upon by any party except Edge Development Inc. and its successors and assigns as owner of the property, with whom Leighton has contracted for the work. Use of or reliance on this report by any other party is at that parry's risk. Unauthorized use of or reliance on this report constitutes an agreement to defend and indemnify Leighton and Associates from and against any liability which may arise as a result of such use or reliance, regardless of any fault, negligence, or strict liability of Leighton and Associates. -9-C Base Map: Thomas Guide, Digital Edition, 2000, Not To Scale Project No. Edge Development - Parcel SITE LOCATION 1107118-002 fig 11 of Parcel Map 19580 Business Park Drive, MAP Date Temecula, Califomia August 2002 FiigureNo. 1 i proximate ;1 - 10. A % i'Nit Jr. Base Map: Composite: California Division of Mines and Geology, Special Studies Zone Map, Murrieta and Temecula 7.5 Min Quadrangles, 1980, 1:24,000 Edge Development Inc. ALOUIST-PRIOLO Project No. Parcel 11 of EARTHQUAKE FAULTZONE 110768-002 Parcel Map 19580 MAP Date fig Temecula, California August, 2002 Figure No. 2 • s • • FT -1 southeast facing wall looking northwest Figure 4 • • 110768-002 References Aragon Geotechnical Consultants, Inc., Preliminary Soils and Foundation Investigation, Portion of Industrial Park III, Portion of Parcel Map 19580, Temecula, California, Project No. 3350PR, dated September 21, 1987. Blake, T.F., 2000a, EQSEARCH, Version 3.00a, A Computer Program for the Estimation of Peak Horizontal Acceleration from Southern California Historical Earthquake Catalogs, Users Manual, 94pp., with update data, 2000 Version 4.0. Blake, T. F., 2000b, EQFAULT, Version 3.00b, A Computer Program, for the Deterministic Prediction of Peak Horizontal Acceleration from Digitized California Faults, User's Manual, 77pp. Blake, T. F., 2000c, FRISKSP, Version 4.00 Computer Program, for Determining the Probabilistic Horizontal Acceleration, User's Manual, 99pp. Blake, T. F., 2000d, UBCSEIS, Version 1.0, User's Manual for Evaluating the Seismic Parameters in accordance with the 1997 UBC, 53 pp. Boore, David M., Joyner, William B., and Fumal, Thomas E., 1997, Empirical Near -Source Attenuation Relationships for Horizontal and Vertical Components of Peak Ground Acceleration, Peak Ground Velocity, and Peudo-Absolute Acceleration Response Spectra, in Seismological Research Letter Vol. 68, No. 1, January/February 1997. California, State of, Department of Conservation, Division of Mines and Geology, 1997, SP 117, GuidelinesJor®Evaluatiorr•-and-MitigatingSeismic Hazards in California, adopted March 13, 1997. California, State of, Department of Transportation, 1987, Peak Acceleration from Maximum Credible Earthquakes in California, Modified from Maulchin and Jones, CDMG Map Sheet 45. California, State of, Department of Special Studies Zone Map, Murrieta Quadrangle, Preliminary Review Map, dated January 01, 1990 Scale 1:24,000. Campbell, Kenneth, W., 1996, Strong Motion Attenuation Relationships, in Seismic Hazards Analysis, AEG Short Course, Thomas F. Blake Program Coordinator, January 20, 1996. A-1 • References (cont'd) • 110768-002 EnGEN Corporation, 1999, Geotechnical/Geological Engineering Study, Proposed Structure, Parcel 13 of Parcel Map 19580-1, City of Temecula, County of Riverside, California, Project No. T1653 -GS, dated March 19,1999. EnGEN Corporation, 1999, Geotechnical/Geological Engineering Study, Proposed Structures, Parcel 11 of Parcel Map 19580, Business Park Drive, City of Temecula, County of Riveride, California, Project No. T1894 -GS, dated December 7, 1999. Hart, E.W., 1997, Fault -Rupture Hazard Zones in California, Alquist-Priolo Earthquake Fault Zoning with Index to Special Study Zones Maps: Department of Conservation, Division of Mines and Geology, Special Publication 42. International Conference of Building Officials, 1997 Uniform Building Code, Volumes 1-3. International Conference of Building Officials, 1988, Maps of Known Active Fault -Near Source Zones in California and Adjacent Portions of Nevada. Ishihara, K., 1985, "Stability of Natural Deposits During Earthquakes", Proceedings of the Eleventh International Conference on Soil Mechanics and Foundation Engineering, A.A. Belkema Publishers, Rotterdam, Netherlands. Ishihara, K., 1996, "Soil Behavior in Earthquake Geotechnics", Oxford Science Publications. Jennings, C.W., 1994, Fault Activity Map of California and Adjacent Areas, California Division of Mines and Geology, Geologic Data Map Series, No. 6, Scale 1:750,000. Kennedy, Michael, P., 1977, Recency and Character of Faulting Along the Elsinore Fault Zone LJin SrzouthernRiverside,County 'California, California Division of Mines and Geology, Special Report 131. Kramer, Steven, L., 1996, Geotechnical Earthquake Engineering, Prentice Hall, 1996. Krinitsky, E.L., Gould, J. P., Edinger, P.H., 1993, Fundamentals of Earthquake -Resistant Construction John Wiley & Sons, Inc., 1993. National Center for Earthquake Engineering Research, (NCEER), 1997, Proceedings of the NCEER Workshop of Liquefaction Resistance of Soils, Technical Report NCEER-97-0022, dated December 31, 1997. Schaefer Dixon Associates, Inc., 1988, Geotechnical Investigation, A Portion of Business Park III, Phase 2, Parcels 1, 7, 8, 9, 10 and 11, Rancho California, dated September. 2, 1988. A-2 _` � • References (cont'd) 0 110768-002 Schaefer Dixon Associates, Inc., 1989a, Assessment of Ground Fissuring/Subsidence Report Zone, The "Airport Parcels", Business Park III, Phase 2, Parcels 1 through 11, and Tentative Parcel Map 23043, Airport Parcel 2, Rancho California, Job No. 9R -1208N, dated August 23, 1989. Schaefer Dixon Associates, Inc., 1989b,Geotechnical Investigation and Grading Plan Review, Business Park III, Phase 2, Parcel Map 19580 (Parcels 1-11), Tentative Parcel Map 23043 (Airport Parcel) Rancho California, California, Job No. 9R- 12080, dated July 7, 1989. Schaefer Dixon Associates, Inc., 1989c, Hazardous Materials Assessment Report, Rancho California Business Park -Phase 2, Parcel Map 19580 and Tentative Parcel Map 23043, Rancho California, California, Job No. 90-858, dated May 5, 1989. Schlemon, R.J., and Davis, P., 1988, "Ground fissures in the Ranch California Area, Riverside County, California", in Abstracts with Programs 1988 Centennial Celebration. Annual Meeting, Geological Society of America, Denver, Colorado, October 31 to November 3, 1988; Abstract. Tokimatsu, K., and Seed, H.B., 1987, Evaluation of Settlements in Sands Due to Earthquake Shaking, ASCE Journal of Geotechnical Engineering, Vol. 113, No. 8, dated August 1987. WGCEP - Working Group on California Earthquake Probabilities, 1995, Seismic Hazards in Southern Califomia: Probable Earthquake Probabilities, Bull. Seismol. Soc. Amer., Vol. 85, No. 2, pp 379-439. J mmizz A3 �ANN RESPONSE TO RIVERSIDE COUNTY PLANNING DEPARTMENT 2ND REQUEST FOR ADDITIONAL INFORMATION COUNTY GEOLOGIC REPORT NO. 1375 PARCEL 11, PARCEL MAP 19580, PA 03-0728 TEMECULA, CALIFORNIA Prepared For: County of Riverside Department of Building and Safety 4080 Lemon Street, 9 Floor Riverside, California 92502-1409 Project No. 110768-004 February 17, 2005 4 ' Leighton and Associates, Inc. A LEIGHTON GROUP COMPANY Leighton and Associates, Inc. A LEIGHTON GROUP COMPANY February 17, 2005 Project No. 110768-004 To: County of Riverside Building and Safety Department 4080 Lemon Street, 12 Floor P.O. Box 1409 Riverside, California 92502-1409 Attention: Mr. Brad Fagrell, Engineering Division Manager Subject: Response to Riverside County Planning Department 2nd Request for Additional Information, County Geologic Report No. 1375, Parcel 11 of Parcel Map 19580, PA 03-0728, Temecula, California. In accordance with your request, Leighton and Associates, Inc., (Leighton) has prepared this letter in response to the 2nd request from the County of Riverside Planning Department for additional information on the findings of our evaluation of site faulting (Leighton, 2002b). For ease of reference, we have addressed each item in the order in which it was requested and a copy of the review comment sheet, dated January 13, 2005 is contained in Appendix C. Item 1. "The log of Leighton's fault trench FT -2 indicated a strike and dip of the fault of N70W 75NE, whereas the log ofLeighton's fault trench FT -1 did not indicate the measured strike and dip of the fault encountered in that trench. The trend of the fault in FT -1 should be indicated. If this trend is different than the trend encountered in FT -2, the geologic consultant should consider widening the setback zone to accommodate potential variations in trend. The geologic consultant should also consider variations in trend of the faulting in nearby trenches excavated by others. " Response: The Log of fault trench FT -1 (Plate 2 herein) has been amended to include the strike and dip of the fault observed. The strike and dip of the fault identified within FT -I was apparently omitted during the original report preparation. The strike and dip as recorded on the field log is N45 -48W 80NE and N50W 50NE. 41715 Enterprise Circle N., Suite 103 ■ Temecula, CA 92590-5661 909.296.0530 • Fax 909.296.0534 . www.leightongeo.com • • 110768-004 + February 17, 2005 In the fault trench, Trench 4 recorded by Schaefer Dixon Associates (SDA, 1998, Figure 6), located approximately 400 feet southeast of Lot 11 (in the adjacent Parcel 13), the fault trend was recorded as N50 -55W 90. This fault orientation is similar to the trend observed in the Leighton trench FT -1. This trend and the trend observed in F1'-2 are also similar to the variation in surface expression of the ground fissures identified and mapped within Lot 11 in 1988 (SDA 1988). The mapped ground fissure has been presented on the accompanying Geotechnical Map, Plate 1. It is apparent from our investigation that the surface manifestation of ground fissure closely parallels the orientation of subsurface faulting that occurred in October 1987 and was exposed in Leighton Trenches FT -1 and FT - 2. Additionally, the trend of the fault observed in FT -2 (N70W) parallels the surface fissure expression at that location (See Plate 1). If the fault were to continue at this trend from FT - 2, the excavation of FT -3 would intercept a projection of this fault trend, however no indications of faulting were encountered (see Figure 1, Log of FT -3). Item 2. Alquist-Priolo Earthquake Fault Zoning Act policies indicate that the area within 50 feet of an active fault is presumed to be underlain by branches of that active fault unless proven otherwise by an appropriate geologic investigation, and that no human occupancy structures should be permitted within the 50 foot zone. As indicated on Leighton's trench logs (FT -1 and FT -2), the active faulting has ruptured relatively unconsolidated Holocene materials. A 50 foot setback should be considered due to unconsolidated nature of these Holocene materials, since it cannot be conclusively proven that no branches of the active fault exists within this zone. Alternatively, the consultant desires to retain a 25 foot setback consideration should be given to performing additional trenching between FT -1 and FT -2 so as to provide at least three or four points of observation of the nature and trend of the active fault and any fault branches within the Holocene materials on the project site. " Response: As suggested in the later part of the above. Item 2, Leighton was authorized to excavate, examine and log an additional trench (FT -3) located approximately midway between FT -1 and FT -2 (See Plate 1). This provides a lateral spacing of approximately 200 feet between the centerline of each trench. This trench was excavated, logged and reviewed between February 7 and February 10, 2005. Riverside County Geologist representative Mr. David Jones reviewed the trench excavation and we discussed our findings and conclusions on Thursday, February 10, 2005. Backfilling of this trench commenced on February 16, 2005 and should be completed by February 17, 2005. The trench was loosely backfilled with spoils from the excavation. This fault trench was excavated by a Caterpillar 245 track excavator using a 4 foot wide bucket, to a maximum depth of approximately 21 feet. The trench was benched symmetrically upwards in general accordance with OSHA guidelines. The northwest wall was scraped of smeared materials caused during the excavation to expose a fresh surface. 2 Leighton 0 110768-004 February 17, 2005 IThe trench wall was examined and logged by a certified engineering geologist from this firm at a scale of one -inch equals five feet. The approximate location of Fault Trench FT -3 is presented on Plate 1, Geotechnical Map. The log of FT -3 is included as Figure 1 herein. As encountered and depicted on Figure 1, FT -3 encountered previously placed fill soils overlying generally unbroken strata of alluvium. A non -fault related paleo-liquefaction feature was observed at approximately Station 0+93. Some down warping of the sediments. immediately to the east was observed. It is our opinion that Unit F and overlying dark gray. sandy clay (Unit D) observed in fault Trenches FT -1, FT -2 and FT -3 correlate with Unit 6 in SDA's 1988 Trench T4. A carbon sample within Unit 6 was sampled and a radio carbon date of 9,170 f 80 years before present was determined (SDA, 1988, and Shlemon, 1992). This sample was collected at a depth of approximately 13 feet in SDA's Trench T-4. It is our opinion that the materials exposed at the base of our trenches (20 feet deep t) are corresponding to very early to pre-holocene materials, based on the depth to age relationship: established by previous age dating. Based on the lack of faulting, fractures or fissures in FT -3, the active fault trace is interpreted to be located east of the easternmost extent of the FT -3. This interpreted . expression is consistent with the mapped trace of ground fissure that occurred in early 1987 (SDA, 1988). The previously mapped fissure location has been presented on the accompanying Geotechnical Map, Plate 1. As mapped, the actual fissure varies slightly across the subject lot and generally coincides with the subsurface expression encountered in our fault trenches FT -1 and FT -2. This relationship is consistent with the findings of Schaefer Dixon Associates (SDA, 1988 and Shlemon, 1992) As presented in Schaefer Dixon's report (SDA 1988, pg. 16), 'Many of the modem cracks clearly follow pre-existing sand -filled fractures and faults" The previously established Leighton setback zone within Parcel 11 was extrapolated from the most southern fault or fracture feature exposed in fault trenches FT -1 and FT -2. The lack of faulting in FT -3 confirms that recent faulting follows closely the ground fissures of 1987. In the vicinity of FT -3, the fault is likely located east of the easterly terminus of FT -3. However, an existing potential weak plane exists at approximately Station 0+93, (See Figure 1). This feature is located approximately 40 feet north easterly from our recommended 25 foot structural setback. This feature appears to be a paleo-liquefaction vent infrlled with sediments similar to the surrounding materials. This feature clearly does not offset the encompassing adjacent materials. Offset or shearing indicative of faulting was not observed in FT -3. The faults observed in our trenches and as reported by SDA have exhibited apparent repeated displacements and we believe the potential for future displacement along the existing fault trace exists. Based on past fault activity, it is expected that future displacements will occur along the established existing Holocene faults, as it did in 1987. It is not expected that the future displacements will occur away from (into Lot 11) from the Holocene faults. 49 3 Leighton 110768.004 February 17, 2005 It is our opinion that the remainder of Parcel 11 (outside and southwest of the Leighton and Associates Structural Setback Zone, Plate 1) is free of active faults and ground rupture hazards and is safe for the placement of structures for human occupancy. It is our opinion that the fault setback of 25. feet is appropriate as depicted on Plate 1. This setback is established by projecting between the most southern fault or fissure observed. In summary, it our opinion that the restricted use, structural setback zone depicted on Plate 1 is appropriate for Parcel 11. The conceptual Grading Plan prepared by RDS & Associates has placed structures for human occupancy outside of the setback zone as recommended. If you have any questions regarding this letter -report please contact this office at your convenience. We appreciate the opportunity to be of continued service. Respectfully submitted, LEIGHTON /ASSOCIATES, INC. 1 Robert R R1ha, CEG 1921 (Exp. 02/28/06) Vice PresidenuPrincipal Geologist RFR/rum 110768-004/Final/Pa l 11 2nd Resp to County Corm is Figure nepzr Na. 1 % y cEflTIF!EG ENGINEERING �} GEOLOGIST Accompanying Figures Plates and Appendices Figure 1 Log of Fault Trench FT -3 Rear of Text Plate Plate I Geotechnical Map (Amended) In Pocket Plate 2 Logs of Fault Trenches FT -1 and FT -2 (Revised) In Pocket Appendices i Appendix A - References Appendix B - County of Riverside Planning Dept. Review Sheet, dated January 13, 2005 Distribution: (3) Addressee (1) EDGE Development; Attention: Mr. Scott Barone -4- Leighton Legend to Figure 1 Fault Trench FT -3 Artificial Fill ® Medium to dark brown to red brown, damp to moist, clayey silty SAND (SC/SM) to coarse SAND (SP); few gravels Quaternary Alluvium ® Olive. gray, damp to moist, dense, fine to medium grained silty SAND (SM) to sandy SILT (ML); abundant calcium carbonate (CaCO3) nodules in upper 2 feet © Olive gray to light gray, damp to moist, dense, silty fine SAND (SM) to fine SAND (ML); locally iron stained (mottled), manganese (MnO) staining in equally spaced sets, generally vertical, locally very porous ® very dark gray to olive gray to dark brown, moist, soft to firm, sandy very porous CLAY to locally micaceous CLAY (CL), locally ORGANIC rich (OH); finely laminated, very sharp contact with sand unit above and below 0 Light gray to olive gray, damp to moist, medium dense, fine to medium SAND (SM); locally iron stained, locally manganese deposits QF very light gray, damp, loose to medium dense, fine to coarse SAND (SM/SP); poorly sorted, local cross -cutting channel beds, cross bedding, locally iron stained laminae I in 9 0 0+00 0+10 0+20 1 1 1 1 FAULT TRENCH LOG FT -3 Lot 11 Temecula, California North 0+60 1 A) 0+70 0+80 0+90 1 1 P.inch4s out :D Sa Norl FAULT TRENCH LOG FT -3 Lot 11 Temecula, California 110768-004 February 17, 2005 Appendix A Leighton and Associates, Inc., 2002a, Geotechnical Update, Lot 11, PM 19780, Business Park Drive, Temecula, California, Project No. 110768-001, dated August 30, 2002. Leighton and Associates, Inc., 2002b, Updated Geotechnical Site Faulting. Evaluation Report, Parcel 11 of Parcel Map 19580, Business Park Drive, Temecula, California. Project No. 110768-002, dated August 30, 2002. Leighton and Associates, Inc., 2004, Response to County Planning Department Request for Clarification/And Or Additional Information, County Geologic Report No. 1375, Parcel 11, Parcel Map 19580, business Park Drive, Temecula, Califomia: Project No. 110768-003, dated December 22, 2004. Riverside County, 1989a, Department of Transportation and Land Management, Building and Safety Department, Planning Department, Transportation Department, Letter, County Geologic Report No. 601, Steven A. Kupferman, May 19, 1989. Riverside County, 1989b, Department of Transportation and Land Management, Building and Safety Department, Planning Department, Transportation Department, Letter, County Geologic Report No. 601. Steven A. Kupfetman, dated July 3, 1989. Riverside County, 2003, General Plan Safety Element and Appendix H - Geotechincal Report (Technical Background Docmnent), Adopted October 7, 2003. r Riverside County, 2004, Riverside County, Department of Transportation and Land Management, Building and Safety Department, Planning Department, Transportation Department, Letter, County Geologic Report No 1375, Brad Fagrell, dated November 12, 2004. i l Riverside County, 2005, Riverside County, Department of Transportation and Land Management, Building and Safety Department, Planning Department, Transportation Department, Letter, Fault Hazard Report Review, County Geologic Report No 1375, PA 03- 0728, Steve Kupferman, dated January 13, 2005, Schaefer Dixon Associates, Inc., 1988, Geotechnical Investigation, A portion of Business Park III, Phase 2, Parcels 1, 7, 8, 9, 10 and 11, Rancho California. Volume I Report of f Investigation Including Appendices A and B. Project No. 80-182, dated September i 2, 1988. A-1 Leighton 110768-004 February 17, 2005 References (ConYd) Schaefer Dixon Associates, Inc., 1989, Response to County Review. Letter, Geotechnical Investigation, A Portion of Business Park II, Phase 2, Parcels 1,7,8,9,10 and 11. Rancho California, California (Building and Safety Log #232505), dated Junel2, 1989. Shlemon, Roy J., and Davis, Paul, 1992, Ground Fissures in the Temecula Area, Riverside County, California in Association of Engineering Geologist Special Publication No.4, Engineering Geology Practice in Southern California. A-2 Leighton V I, LU/LVVJ Io. YV rMA 0VU0U0bVIJ NUeAYS UNLIMINIEU INC 12002/004 0 TY AIV BLDG & SF TY :9519552023 Jan 25 2008:06 P.01 COUNTY OF .RIVERSIDE TRANSPORTATION AND LAND MANAGEMENT AGENCY Building and Safety Department Director City of Temecula Planting Department January 21, 2005 Phone: (909) 694-6400, FAX: (909) 694-6477 Attention: Matt Petals 3 pa1les (including this cover sheet) RE: REVIEW COMMENTS Y12 GEO NO, I375 CITY OF T1i;1VIECrn.A CASE NO. PA03•0729 County Geologic Report (GEO) No. 1375 wee prepared for this project (City of Temecula PA03-0728) by Leighton and Associates and is entitled: "Geotechnical Update) Lot 11, PM19580, Business Park Drive, Temecula, Callforola", dated August 30, 2002. In addition, L"ight" prepared "Updated Geotechnical Site Faulting Evaluation Report, Parcel I I of Parcel Map 19580,Business Park Dl'ivs, Temecula California", dated August 30, 2002, and "R>rsponsc to Riverside County Planning Dopartment, Request for Clarification and/or Additional Information, County Geologic Report No. 1375 dated December 22, 2004. These rtports are heroin incorporated as a part of GBO No, 1375. Frior to scheduling this project for public hearing, clarification and/or additional information, relative to the ii sues enumerated by Mr. Stow KUpferman in his January 13, 2005 Fault Hazard Report Review comments memo, shall be submitted to the County Geologist for review and approval. Please call me at (951) 955-2006, or David L. Jones at (951) 955-6863, if you have any questions, Sincably, RIVERSIDE COUNTY BUILDING AND SAFETY DEPARTMENT James J. Miller, Building and Safety Director Arad'well, P.E. 8nglnlxeing Division grsion Man er Building and Safety Dcpartment cct 0e0. Consultant: Robert Rlha; Leighton and Associates, Fax: (951) 296-0534 Eng- Rep.; Scott Barone, Edge Development, Fax: (951) 296-0775 Applicant Rep,: Robin Arenz, Nu Ways Unlimited, Fax: (951) 698-6013 Teruecula Review File Yddrol,eaevmh4e.kwrlPAN 0113 w i,a Ibr4aeom5ex t County Admial trluve Center 4080 Lamar Smoot, 121h ptaar Riveroidc, CA 92502 Vl/LO/2VUD 16:41 FAX CNTY AIV BLD Jen 20 06 09r09p Amoary 13, 2005 `,JMJBJtltlU 1J NU'YAYJ UNLIMINTED INC C R SFTY W9519552023 Jan 25 200, 0:06 9097899786 TO; David Jones - En&oering Geologist, Dopartment of Building and S.dety FROM: Stove Kupferman - Consulting Engineering Goologlst, CEG 1205 RE: Fault Hazard Report Review County C%ologic Report No, )375 FA 03.0728 CNty of Temecula P. 02 2nd Review - At your request, I have reviewed the following reports and response with respect to fault hazard issues at the subject project site: 1. "Updated Geotechnical Site Faulting 13valuation Report, Parcel 11 of Parcel Map 19580, Business Park Drive, Temccula, CA," by Leighton and Associates, dated August 30, 2002_ 2, "Geotechnical Update, Lot 11., PM 19580, Business Park Drive, Temecula, CA," by Leighton and Associates, dated August 30, 2002. 3. "Response to Rivcrside County Planning Departrnent, Request for Clarification and/or Additional Information, County Geologic Report No. 1375," by Leighton and Associates, dated December 22, 2004. The following additional infonnation and/or clarification should he provided: 1. The log of Leighton's fault trench FT -2 indicated a strike and dip of the fault of N70W 75NE, whereas the log ofW$hton's ituit trencb FI' -1 did not indicate the measured strike and dip of the fruit encountered it Shat trencb: The trend of the fault in FT -I should be indicated. If this trend is different than the trend enoountered in FC -2, the geologic consultant should consider widening the setback zone to accommodate potential variations in trend. The geologic oonsiltant should also consider variations in trend of the faulting in nearby trenches excavated by others. 2. Alquist-Frlolo Earthquake Fault Zoning Act policies indicate that tba area within 50 feet of an active fault is presumed to be underlain by branches of that active fault unless proven otherwise by an appropriate goologio investigation_ and that no human occupancy structums should be pertn.ined within the 50 foot zone. As indicated on Leighton's trench logs (rT.1 and FT -2), the active faulting has ruptured relatively unconsolidated Rotoeeste materials. A 56 foot setback shou.d be considered due w the unconsolidated nattue of these Holocene materials, since it IA 0031004 P,I u cVi cvVV 10.rI rAn JV0000i NuwAYS UnL1MINIGU LNG CNiY RIV BLDG & SFTY ax:9519552023 Jan 25 2005 8:06 Jan 20 05 08108P 8097989788 IJ004/004 P. 03 P.2 omm be conclusively proven that no braaobes of the active fault exist within this zone. Alternatively, the consultant desires to retain a 25 foot setback. consideration should be given to perfuming additional trenching between MI. and FT -2 so as to provide at least three or four points of observation of tho nature and trend of the active fault and any fhult branches within the Hollmae materials on the project site,