HomeMy WebLinkAboutTract Map 9833 Lot 1 Fault Investigation
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SURPLI:MENTAL GEOLOGIC/FAULT INVESTIGATION'
" . :!\ND,HQl!~F~~TION EVALUATION
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"RIVERSIDECOUNTY, CALIFORNIA
FOR
MR. ROBERT TUCCINARDI
45310CALLESITO BURGOS
TEMECULA,CALlFORNIA 92592
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Geotechnical. Coastal. Geologic. Environmental
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SUPPLEMENTAL GEOLOGIC/FAULT INVESTIGATION
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/1i@T:'1fe1"TRAGt M~P'9833CI:rv OF TEMECULA
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RIVERSIDE COUNTY, CALIFORNIA
FOR
MR. ROBERT TUCCINARDI
4531 0 CALLESITO BURGOS
TEMECULA, CALIFORNIA 92592
vV.O.4553-A-SC
JANUARY 14, 2005
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Geotechnical. Coastal. Geologic. Environmental
26590 Madison Avenue . Murrieta, California 92562 . (909) 677-9651 . FAX (909) 677-9301
January 14, 2005
W.O,4553-A-SC
I Mr. Robert Tuccinardi
,45310 Callesito Burgos
Temecula, California 92592
: Subject:
Supplemental Geologic Fault Investigation and Liquefaction Evaluation,
Lot 1 of Tract Map 9833, City of Temecula, Riverside County, California
: Dear Mr. Tuccinardi:
In accordance with the request of the controlling authorities and your authorization,
: GeoSoils, Inc. (GSI) is pleased to present the results of our supplemental geologic fault
investigation and liquefaction evaluation of Lot 1 of Tract Map 9833, City of Temecula,
: Riverside County, California. Based on our review, a portion of the site is located within
,an Alquist-Priolo Earthquake Fault Zone established by the State of California. This
'supplemental investigation is generally intended to meet requirements ofthe Alquist-Priolo
; Zoning Act for the State of California, and the requirements of the local controlling
: authorities. In addition, this supplemental investigation is intended to evaluate the potential
'for onsite liquefaction, as a "liquefaction potential area," established by the County, has
'also been mapped as transecting the northern portion of the site. This report is not
intended to be:a soils investigation of the site, and does not address overall site or slope
,stability. These conditions should be evaluated by the soils engineer of record.
SUMMARY
: Based on our literature review (see the Appendix), onsite field investigations, and geologic
,analyses, it is GSI's opinion that development of the site is feasible from a geologic
,viewpoint, provided the recommendations contained herein are implemented.
'This supplemental investigation indicates that likely active faulting (i.e., movement within
: the Holocene epoch, or last :t 11 ,000 years [Hart and Bryant, 1997]) crosses the southern
: portion of the property. Accordingly, a fault setback zone has been established for the
: property based on subsurface conditions encountered during this investigation
I (see Plate 1). This subsurface exploration, after approval by the controlling authorities,
'should meet the requirements of the Alquist-Priolo Zoning Act concerning onsite faulting.
Iln addition, based on our subsurface investigation, geologic evaluation, and the extremely
: dense nature of the underlying sedimentary bedrock materials within the direct influence
3
of the building pad areas, it is our opinion that the potential for liquefaction, surface
manifestations of liquefaction, and liquefaction related lateral spreading, within the building
pad areas, is considered low.
SCOPE OF SERVICES
The scope of our services included the following:
1. Review of available soils and geologic data for the site area, including previous
geologic reports for the site and site area (see the Appendix).
2. Geologic/geomorphic site reconnaissance and field mapping.
3. Review of stereoscopic infrared aerial photography (see the Appendix), and
performance of a lineament analysis for the site,
4. Emplacement of one trench (totaling approximately :t360 feet), across the
Alquist~Priolo Fault Zone onsite (see Plate 1), and related formal geologic
documentation of subsurface conditions exposed (see Plates 2 and 3).
5. Performance of an onsite liquefaction evaluation, as required by the controlling
authorities.
6. Analysis of the data collected and preparation of this report and accompaniments,
SITE DESCRIPTION
The subject site is an irregular parcel consisting of approximately :t4.8 acres. In general,
the property is located southeast of Jedediah Smith Road, and is bounded on the north
and south by existing residential properties, and on the west by an EMWD easement, in
the City of Temecula, Riverside County, California (see the Site Location Map, Figure 1).
The site is generally characterized by gently rolling hills covered with native weeds,
grasses, and low chaparral. Site drainage is variable based on location, however; is
generally by sheet flow and by incised drainage corridors which drain to T emecula Creek
offsite. General relief of the property is approximately :t 115 feet, ranging from a high of
:t 1,190 feet (Mean Sea Level [MSL]) in the central portion of the property to a low of
:t 1,075 feet (MSL) in the northern portion of the property.
Mr. Robert Tuccinardi
Lot 1 of Parcel Map 9833, City of T emecula
File: e:\wp9\murr\rc4500\4553a.sgf
GeoSoils, Ine.
W,Q, 4553-A-SC
January 14, 2005 A.
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,Base,Map: Alquist-Priolo Earthquake Fault Zones, 7.5 minute, Temecula and Pechanga
Quadrangles, topographic base USGS 1968, photorevised 1988.
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SITE LOCATION MAP -5
Figure 1
PROPOSED DEVELOPMENT
Based on conversations with the Client, and our review of the rough grading plan by
Gunvant Thakkar P.E. (2004), typical cut and fill grading techniques would be utilized to
prepare the site for construction of a single family residence, associated utility and roadway
improvements, It is our understanding that the buildings would be one- and/or two-story
structures, using typical wood-frame construction with slabs on grade and continuous
footings. Building loads are assumed to be typical for this type of relatively light
construction. Sewage disposal is to be accommodated by a septic tank and leach field
system designed by others. The need for export soils is anticipated.
BACKGROUND AND PREVIOUS INVESTIGATIONS
The subject site was previously investigated by Gunvant Thakkar, P,E. (2004). This
investigation included recommendations for development of the property, however; did not
include a fault finding/liquefaction investigation/evaluation as required by the controlling
authorities. In addition, GSI has performed a fault finding investigation on the adjoining
property (GSI, 2001). Active faulting was also encountered on the adjoining property, as
such, a building setback zone across the central portion of that property was established.
These previous studies examined the site and adjacent property on a preliminary basis,
and concluded that development of the properties was feasible from a soils engineering
viewpoint, provided the conclusions and recommendations provided were properly
incorporated into planning and development considerations.
FIELD STUDIES
Field studies conducted during our evaluation of the property consisted of the follOWing:
1. Initial geologic and geomorphic site reconnaissance and field mapping.
: 2. Emplacement of one (1) trench (totaling approximately :t360 feet), across the entire
width of the buildable area of Lot 1 (see Plate 1). This subsurface investigation
included formal geologic documentation of subsurface conditions exposed. The
fault finding trench was logged by staff from our firm, followed by subsequent field
reviews by a registered and/or engineering geologist from our firm. The location of
GSl's trench from this investigation is shown on Plate 1. Field logs of the trench
from this investigation are presented on Plates 2 and 3,
'3, Appropriate geologic analyses of data collected and preparation of this report and
accompaniments.
'Mr. Robert Tuccinardi
,Lot 1 of Parcel Map 9833, City of Temecula
File: e:\wp9\murr\rc4500\4553a.sgf
GeoSoils, lne.
W,Q, 4553-A-SC
January 14, 2005
Page 4
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Lineament Analvsis
In order to identify possible unmapped faults and to evaluate topographic expressions of
the published'fault trace, a lineament analysis was performed, As listed in the Appendix,
the imagery utilized were stereoscopic "false-color" infrared aerial photographs
(scale 1 "=3333').
Photographic lineaments are generally classified as strong, moderate, or weak. A strong
lineament is a well defined feature that can be continuously traced several hundred feet
to a few thousand feet. A moderate lineament is less well defined, somewhat
discontinuous, and can be traced for only a few hundred feet. A weak lineament is
discontinuous, poorly defined, and can be traced for a few hundred feet or less, A
moderate to strong lineament, generally corresponding with the break-in-slope and actual
fault location, was noted transecting the southern portion of the site during our analysis.
REGIONAL GEOLOGY
Reaional Geoloaic Settina
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 trend northwestward. The Santa Ana Mountains lie
along the western side of the Elsinore fault zone, and the 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 and volcanics, and Quaternary sediments flank the
mountain ranges. The Tertiary and Quaternary rocks are generally comprised of
nonmarine sediments consisting of sandstones, mudstones, fanglomerates, and scattered
, volcanic rocks. Uplift on the regional faults, and erosion has resulted in the incision of the
I older rocks, and subsequent deposition of coalescing alluvial fans in the valleys. A
I regional geologic map of the site area is provided as Figure 2.
I Reaional Tectonic Settina
, The Elsinore fault zone is generally a major northwest-striking group of faults associated
I with the San Andreas fault system (Kennedy, 1977). The Elsinore fault zone generally
I extends from the Corona area on the north to beyond the international border with Mexico
: on the south. The Elsinore fault zone is considered a youthful structural boundary between
I the Perris Block and the Santa Ana Mountains (Kennedy, 1977), Seismically the Elsinore
I fault zone is relatively quiet, especially when compared with other nearby fault zones
,associated with the San Andreas system. Fault motion along the Elsinore fault zone is
; generally complex; however, right lateral strike-slip and normal faulting (associated with
I Mr. Roberl Tuccinardi
,Lot 1 of Parcel Map 9833, City ofTemecula
File: e:\wp9\murrlrc450014553a,sgf
GeoSoils, Ine.
W,Q,4553-A-SC
January 14, 2005
Page 5
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Very old alluvial flood plain depo.it> (early Pleisloc.ne) - Mostly w.:lL-indumlcd, poorly sort.d,
scmi.:pcmu:oblo cloy and S4Ild flood plain dcpooits.
Very old .oll."iol deposits (.orly Pleislo....) - Mostly w.:1I-indumtcd, poorly oorlcd, bilbilopc,
.I.y and S4Ild .01Luvial deposit>.
Very old alluvial fan deposits (early Pleistoc.ne) - Mostly ''<I}' ..-clI-induroted, rcddiah-bro..lI,
, s.nd and .obble. .urly Plcistoc.ne oluvial f.n deposits.
,Pouba Fonnalion (.ady PI.isloc...) - Lisht-brown modero..I)' ....lL-indur.ted, ......iwly
crossbcdd.d, channeled and filled SIIIldslone and wlslone that .0Dlai"" "",...ionai intcm:ning
.obblc-ond -bouldcr conglonu:mt. b.ds.
Dripping Spring:; FonnalioD (.orty Pleisto....) - Pebbl., robblc and boulder tansIonu:mt.
in a rcddiah-broWD, poorly consolid....!, poody sorted .andslDoc matriK.
BEDROCK UNITS
TcmccuJa Arkose (pleistocene) . Pale: grccnish--yc:llow, \\'CLl~indur4b:d. medium- and coarse-
sraincd sandstone with thin imcrstratified beds of fme-grained. tuffaceous sandstone. siltstone.,
and claystone. Pebbl. and .obbl. .onglom.rote iDletbcds composed of locally derived
basrntent rock clasts an: Also common and range in thiiClmesa from a KW centimeters to a
meter or mo",.
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Figure 2
IAdapted from: Geologic Map of the Pechanga 7.5'
:Quadrangle, San Diego and Riverside Counties
I California: A Digital Database, v1.0,
I by Kennedy, M.P., 2000,
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REGIONAL
GEOLOGIC MAP
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RIVERSIDE co.
ORANGE co. .
SAN DIEGO CO.
W.O. 4553-A-SC
DATE 1/05 SCALE 1"=2000"
the Elsinore trough) is the most prevalent sense of movement within the study area,
Combined movement along the Elsinore fault zone has resulted in the significant uplift of
the Santa Ana Mountains, the Elsinore trough, and associated fault scarp features that form
the boundary area between them, An estimated maximum magnitude (M=6.8) and an
average slip rate of :t5 millimeters (mm) a year along the Elsinore fault zone has been
determined as appropriate for design purposes (ICBO, 1998),
SITE GEOLOGY
Geologic units identified within the study area were: artificial fill, colluvium/topsoil (younger
and older). relatively younger alluvium, and sedimentary bedrock of the Pauba Formation.
Although current mapping (Kennedy, 2000) indicates a portion of the site lies within the
Pleistocene-age TemeculaArkose, previous mapping (Kennedy, 1977) and our subsurface
investigation indicates the underlying onsite geologic unit to be the Pauba Formation.
Supplemental descriptions for subunits within the Pauba Formation encountered in the
subsurface explorations are shown on Plates 2 and 3. The major geologic units within the
site are shown on Plate 1, and are generally described, from youngest to oldest below:
Artificial Fill - Undocumented (Map Svmbol - Afu)
Undocumented artificial fill occurs locally within the site and is generally associated with
the EMWD easement and onsite dirt roads. Also present is undocumented (uncompacted)
backfill of the current fault finding/exploratory trench. The fill materials are generally light
to dark brown and light gray silty and clayey sands, derived onsite. These unengineered
fill materials are dry, loose and are potentially compressible and may settle appreciably
under additional fill, foundation, and roadway improvement loadings. These materials are
unsuitable for .support of structures and/or improvements in their existing state, and will
require removal an.d recompaction, if settlement sensitive improvements are proposed
within their influence.
Alluvium - YounQer (Map Svmbol - Qal)
Quaternary alluvial sediments were mapped in the incised drainage area on the northern
portion of the site (see Plate 1), These sediments were generally observed to be
predominantly light to dark brown, silty, fine- to coarse-grained sands and silty sands. The
alluvial sediments varied from dry to damp, and were generally loose. Due to the
potentially compressible, and collapsible nature of these soils, they are considered
unsuitable for 'support of structures and/or improvements in their existing state and will
therefore need to be removed and recompacted, if settlement sensitive improvements are
proposed within their influence.
Mr. Robert Tuccinardi
Lot 1 of Parcel Map 9833, City of Temecula
File: e:\wp9\murr\rc4500\4553a.sgf
W,Q,4553-A-SC
January 14, 2005
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GeoSoils, Inc.
Quaternarv Colluvium/Topsoil (Not Mapped)
Colluvium/topsoil mantles the younger alluvial materials and bedrock deposits onsite, The
colluvium/topsoil ranges in thickness from about :t2 to as much as :t 1 0 feet in the
northern portion of the site, The collUVium/topsoil is generally silty to clayey, fine- to
coarse-grained sands, and sandy clays with some locally abundant gravels. These
materials are dry to damp, loose/soft to medium dense/medium stiff, and locally porous
near the surface. In general, the colluvium is located on an active geomorphic surface,
and is likely Holocene in age (:t 11 ,000 years old or younger). Supplemental soil profiles
are shown on Plates 2 and 3. These soils are generally considered unsuitable for support
of structures and/or improvements in their existing state.
Quaternarv Pauba Formation (Map Svmbol - Qp)
Relatively older sedimentary bedrock materials of the Pauba Formation underlie a majority
of the study area at depth. The Pauba Formation is late Pleistocene in age
(>:t 11,000 years old, Kennedy, 1977), The bedrock is composed of sandstones,
siltstones, and claystones with minor pebble and gravel sized clasts. The bedrock is
generally dark grayish brown to light gray, dry to damp, and medium dense to dense,
Additionally, it is medium to thickly bedded and massive. It is generally moderately to
steeply inclined to the northeast. This sedimentary bedrock may reach several tens of feet
in thickness,
FAULTING AND REGIONAL SEISMICITY
The site is situated in an area of active as well as potentially-active faults. The Elsinore fault
zone is considered active and is included within an Alquist-Priolo Earthquake Fault Zone.
As indicated previously, the site is traversed by a "Earthquake Fault Zone" associated with
the Wildomar fault (considered part of the Elsinore Fault Zone) as designated by the
Alquist-Priolo Earthquake Fault Zoning Act (Hart and Bryant, 1997).
The acceleration-attenuation relations of Bozorgnia, Campbell, and Niazi (1999), and
Campbell and Bozorgnia (1994 and 1997) have been incorporated into EOFAULT
(Blake, 2000a). For this study, peak horizontal ground accelerations anticipated at the site
were determined based on the random mean and random mean plus 1 - sigma attenuation
curves developed by Bozorgnia, Campbell, and Niazi (1999), and Campbell and
Bozorgnia (1994 and 1997). These acceleration-attenuation relations have been
incorporated in EOFAULT, a computer program by Thomas F. Blake (2000a), which
performs deterministic seismic hazard analyses using up to 150 digitized California faults
as earthquake sources, The program estimates the closest distance between each fault
and a user-specified file, If a fault is found to be within a user-selected radius, the program
estimates peak horizontal ground acceleration that may occur at the site from the upper
bound ("maximum credible") earthquake on that fault. Site acceleration (g) is computed
Mr. Robert Tuccinardi
Lot 1 of Parcel Map 9833, City of Temecula
File: e:\wp9\murr\rc4500\4553a.sgf
GeoSoils, Ine.
W,Q,4553-A-SC
January 14, 2005
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by any of the 19 user-selected acceleration-attenuation relations that are contained in
EQFAULT. Based on the above, peak horizontal ground accelerations from an upper
bound event may be on the order of 0.65g to a.98g.
The fOllowing table lists the major faults and fault zones in southern California that could
have a significant effect on the site should they experience activity,
ABBREVIATED FAULT NAME APPROXIMATE DISTANCE MILES (KMI
Burnt Mountain 53,51 (86,1)
Chino - Central Avenue (Elsinore) 35,5 (57,2)
Cleghorn 55,4 (89.2)
Compton Thrust 54,3 (87,4)
Coronado Bank 45,2 (72,8)
Cucamonga . 53,7 (86,5)
Earthquake Valley 37.2 (59,9)
Elsinore - Coyote Mountain 56,3 (90,6)
Elsinore - Glen Ivy 17,5 (28,1)
Elsinore - Julian 9,6 (15,4)
Elsinore - Temecula" Wildomar Splay 0,0 (0,0)
Elysian Park Thrust 52,9 (85,1)
Eureka Peak 56,3 (90.6)
Helendale - South Lockhardt 63.1 (101,6)
Landers 62,1 (100,0)
Newport - Englewood (LA Basin)) 47,3 (76.1)
Newport - Inglewood (Offshore) 28,1 (45,2)
North Frontal Fault Zone (East) 54.9 (88,3)
North Frontal Fault Zone (West) 52,9 (85.2)
Palos Verdes 49,3 (79,3)
Pinto Mountain 46,0 (74,0)
Rose Canyon 30,1 (48,4)
San Andreas - 1857 Rupture 62.1 (99,9)
San Andreas - Coachella 48,3 (77,7)
San Andreas - Mojave 62,1 (99,9)
San Andreas - San Bernardino 39,1 (62,9)
San Andreas - Southern 39,1 (62,9)
San Jacinto - Anza 21,3 (34,2)
Mr. Robert Tuccinardi
Lot 1 of Parcel Map 9833, City of Temecula
File: e:\wp9\murr\rc4500\4553a,sgf
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ABBREVIATED FAULT NAME APPROXIMATE DISTANCE MILES (KM)
San Jacinto - Borrego 56,7 (91,3)
San Jacinto - Coyote Creek 35,2 (56,7)
San Jacinto - San Bernardino 37,7 (60,7)
San Jacinto - San Jacinto Valley 21 .4 (34,5)
San Jose 55,2 (88,8)
Sierra Madre 58,0 (93.4)
Whittier 39,5 (63,6\
Historical site seismicity was evaluated with the acceleration-attenuation relations of
Bozorgnia, Campbell, and Niazi (1999). and the computer program EQSEARCH
(Blake, 2000b). This program performs a search of historical earthquake records for
liTlagnitude 5.0 to 9.0 seismic events within a 100-mile radius, between the years
1800 to 2004, Based on the selected acceleration-attenuation relationship, a peak
horizontal ground acceleration is estimated, which may have effected the site during the
specific event listed. Based on the available data and the attenuation relationship used,
the estimated maximum peak site acceleration during the period 1800 through June 2004
was 0.15g. In addition, site specific probability of exceeding various peak horizontal
ground accelerations and a seismic recurrence curve are also estimated/generated from
the historical data.
A probabilistic seismic hazards analysis was performed using FRISKSP (Blake, 2000c)
which models earthquake sources as three-dimensional planes and evaluates the site
specific probabilities bf exceedance for given peak acceleration levels or pseudo-relative
velocity levels. Based on a review of these data, and considering the relative seismic
activity of the southern California region, a peak horizontal ground acceleration of 0.87g
was calculated. This value was chosen as it corresponds to a 10 percent probability of
exceedance in 50 years (or a 475-year return period), The possibility of ground shaking
at the site may be considered similar to the southern California region as a whole. The
relationship of the site location to these major mapped faults is indicated on the California
Fault Map (Figure 3).
Seismic Shakino Parameters
Based on the site conditions, Chapter 16 of the UBC (ICBO, 1997), and ICBO (1998), the
following seismic parameters are provided.
Mr. Robert Tuccinardi
Lot 1 of Parcel Map 9833, City of Temecula
File: e:\wp9\murr\rc4500\4553a,sgf
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January 14, 2005
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GeoSoils, Ine.
1100
1000
900
800
700
600
500
400
300
200
100
CALIFORNIA FAULT MAP
Robert Tuccanardi
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-100
-400 -300 -200 -100 0 100 200 300 400 500 600
Figure 3
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GeoSoils, Ine.
Seismic zone (per Figure 16-2*) 4
Seismic zone factor Z (per Table 16-1*) 0.40
Soil Profile Types (per Table 16-J*) SD
Seismic Coefficient C, (per Table 16-Q*) 0.44 N,
Seismic Coefficient C" (per Table 16-R*) 0,64 N"
Near Source factor Na (per Table 16-S*) 1.3
Near Source factor N" (per Table 16-T*) 1.6
Distance to Seismic Source (Wildomar - Elsinore) 0,0 mL (0,0 km)
Seismic Source Type (per Table 16-U*) B**
Upper Bound Earthquake (Wildomar - Elsinore) Mw 6,8**
* Figure and table references from Chapter 16 of the UBC (ICBO, 1997),
** ICBO (1998),
GROUNDWATER
: Seeps, springs, or other indications of a high groundwater level were not noted on the
: subject property during the time of our field investigation. Based on our review,
I groundwater levels in other nearby wells (CDWR, 2004), are documented to range
I between :t 13 and :t 166 feet below the ground surface. Although indications of a shallow,
lor "perched" groundwater conditions (I.e., where relatively impermeable sediments underlie
I relatively permeable sediments filled with water) were not noted, due to the contrasting
I Aature and permeability of the onsite earth materials, the possibility of future, localized
I perched water.conditions cannot be precluded. Should such conditions become apparent
I in within the site area in the future, additional recommendations for mitigation may be
. provided upon request.
LIQUEFACTION POTENTIAL
Seismically-induced liquefaction is a phenomenon in which cyclic stresses, produced by
, earthquake-induced ground motion, create excess pore pressures in soils. The soils may
, thereby acquire a high degree of mobility, and lead to lateral movement, sliding, sand
boils, consolidation and settlement of loose sediments, and other damaging deformations.
This phenomenon occurs only below the watertable; but after liquefaction has developed,
it can propagate upward into overlying, non-saturated soil as excess pore water dissipates.
, Typically, liquefaction has a relatively low potential at depths greater than 45 feet and is
virtually unknown below a depth of 60 feet. Liquefaction susceptibility is related to
numerous factors and the following conditions should be concurrently present for
liquefaction to occur: 1) sediments must be relatively young in age and not have
developed a large amount of cementation: 2) sediments generally consist of medium to
Mr. Robert Tuccinardi
Lot 1 of Parcel Map 9833, City of Temecula
File: e:\wp9\murr\rc4500\4553a.sgf
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January 14, 2005
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fine grained relatively cohesion less sands; 3) the sediments must have low relative density;
4) free groundwater must be present in the sediment; and 5) the site must experience a
seismic event of a sufficient duration and magnitude, to induce straining of soil particles,
The condition of liquefaction has two principal effects. One is the consolidation of loose
sediments with resultant settlement of the ground surface. The other effect is lateral
sliding. Significant permanent lateral movement generally occurs only when there is
significant differential loading, such as fill or natural ground slopes. Few such loading
conditions exist on the site.
Based on our review the northern portion of the site is located with a "liquefaction potential
area," established by the County, and we found there is a potential for seismic activity
onsite; however, the "liquefaction potential area," is out of the areas proposed for
structures, and the site bedrock materials were silty, fine- to coarse-grained, massively
bedded and become dense to very dense with depth,
Inasmuch as three or four of these five required concurrent conditions discussed above
do not have the potential to affect the building pad areas, our evaluation indicates that the
potential for liquefaction and associated adverse effects within the building pad areas is
low, even with a future rise in groundwater levels. Therefore, it is our opinion that the
liquefaction potential does not constitute a significant risk to the currently proposed
building pad areas.
SUMMARY OF FAULT FINDING TRENCH
As shown on Plate 1, ,Trench T-1 extends across the property from the north to the south,
covering the entire width of the buildable area of lot 1. Exploratory trenching of the site
was conducted in December of 2004, The controlling authorities were given advanced
notice of the .geologic investigation, and invited to review the onsite exploratory fault
trenching in the field. The trenches were excavated :t 1 0 to :t 16 feet deep, extending into
native sedimentary bedrock deposits onsite. Trench T-1 was approximately :t360 feet in
length. The trench was logged by staff from our firm at a scale of 1 "=5' (see Plates 2
and 3), Positive evidence precluding Holocene (active) faulting was not encountered
during our subsurface investigation, thus for conservatism, an appropriate building setback
zone was established based on this subsurface investigation of the property, and available
data (see Plate 1).
CONCLUSIONS AND RECOMMENDATIONS
Based on our review, field investigation, and geologic analyses, it is GSI's opinion that
development of the site is feasible from a geologic viewpoint, provided the
recommendations contained herein are implemented, Recommendations for mitigation
Mr. Roberl Tuccinardi
Lot 1 of Parcel Map 9833, City ofTemecula
File: e:\wp9\murrlrc450014553a,sgf
GeoSoils, 'nc.
W,Q, 4553-A-SC
January 14, 2005
Page 13
\~
of the fault trench backfill, compressible soils, slope stability, etc., should be provided by
the soils engineer of record. In addition, recommendations for proper erosion control of
any undocumented fill materials should be provided by the civil/design engineer.
This supplemental investigation indicates that the Wildomar fault zone that crosses the
southern portion of the site (Figure 1 and Plate 1), cannot be demonstrated to be
pre-Holocene, and is thus considered active, according to the State of California criteria
(i.e., movement within the Holocene epoch, or last :t 11 ,000 years [Hart and Bryant, 1997]),
Habitable structures should not be located within the established setback zone adjacent
to this active fault, as depicted on Plate 1.
PLAN REVIEW
Final grading and improvement plans should be submitted to this office for our review and
comment, as they become available, to minimize any misunderstandings between the
plans and recommendations presented herein. In addition, any earthwork construction
performed on the site should be observed and tested by the geotechnical consultant of
record.
LIMITATIONS
The materials encountered on the project site and utilized for our analysis are believed
representative of the area; however, soil and bedrock materials vary in character between
excavations and natural outcrops or conditions exposed during mass grading, Site
conditions may vary due to seasonal changes or other factors.
Inasmuch as our 'study is based upon our review and engineering analyses, the
conclusions and recommendations are professional opinions. These opinions have been
derived in accordance with current standards of practice, and no warranty, either express
or implied, is given. Standards of practice are subject to change with time. GSI assumes
no responsibility or liability for work or testing performed by others, or their inaction; or
work performed when GSI is not requested to be onsite, to evaluate if our
recommendations have been properly implemented. Use of this report constitutes an
agreement and consent by the user to all the limitations outlined above, notwithstanding
any other agreements that may be in place. In addition, this report may be subject to
review by the controlling authorities. Thus, this report brings to completion our scope of
services for this portion of the project. All samples will be disposed of after 30 days, unless
specifically requested by the client, in writing.
Mr. Robert Tuccinardi
Lot 1 of Parcel Map 9833, City ofTemecula
File: e:\wp9\murr\rc4500\4553a.sgf
W,Q, 4553-A-SC
January 14, 2005
Page 14
\~
GeoSoils, Inc.
The opportunity to be of service is sincerely appreciated, If you should have any
questions, please do not hesitate to contact our office,
Respectfully submitted,
GeoSoils, Inc. 'D
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Enclosures: Appendix A - References
Appendix B - EQFAULT Data
Plate 1 - Geologic Map
Plates 2 and 3 - Trench Log T-1
Distribution: (6) Addressee
JOhne!#
Engineering Geologist, CE
Mr. Robert Tuccinardi
Lot 1 of Parcel Map 9833, City ofTemecula
File: e:\wp9\murr\rc4500\4553a.sgf
GeoSoils, Inc.
W,Q, 4553-A-SC
January 14, 2005
Page 15
\1
APPENDIXA
REFERENCES
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APPENDIX A
REFERENCES
Blake, T.F., 2000a, EOFAULT, A computer program for the estimation of peak horizontal
acceleration from 3-D fault sources; Windows 95/98 version.
_, 2000b, EOSEARCH, A computer program for the estimation of peak horizontal
acceleration from California historical earthquake catalogs; updated to June 2003,
Windows 95/98 version.
_, 2000c, FRISKSP, A computer program for the probabilistic estimation of peak
acceleration and uniform hazard spectra using 3-D faults as earthquake sources;
Windows 95/98 version.
Bozorgnia, Y., Campbell, KW., and Niazi, M., 1999, Vertical ground motion:
Characteristics, relationship with horizontal component, and building-code
implications; Proceedings of the SMIP99 seminar on utilization of strong-motion
data, September 15, Oakland, pp. 23-49.
Campbell, KW. and Bozorgnia, Y., 1997, Attenuation relations for soft rock conditions; in
EOFAUL T, A computer program for the estimation of peak horizontal acceleration
from 3-D fault sources; Windows 95/98 version, Blake, 2000a.
_, 1994, Near-source attenuation of peak horizontal acceleration from worldwide
accelerograms recorded from 1957 to 1993; proceedings, Fifth U.S. National
Conference on Earthquake Engineering, Vol. III, Earthquake Engineering Research
Institute, pp. 283-292,
County of Riverside, 2000, Technical guidelines for review of geotechnical and geologic
reports.
California Department of Water Resources, 2004, Water Data Library
(www.well.water.ca.gov/) .
Envicom Corporation, 1976, Seismic safety and safety elements technical report for the
county of Riverside and the cities of Beaumont, Blythe, Coach ella, Corona, Desert
Hot Springs, Hemet, Indian Wells, Indio, Norco, Perris, Riverside, and San Jacinto.
GeoSoils, Inc., 2001, Supplemental geologic/fault investigation, Lots 19 and 20,
Tract 9833-3, City of Temecula, Riverside County, California, W.O, 2963-A-SC,
dated January 31.
Hart, E.W. and Bryant, W.A., 1997, Fault-Rupture Hazard Zones in California, Alquist-Priolo
Earthquake Fault Zoning Act with Index to Earthquake Fault Zones Maps; California
Division of Mines and Geology Special Publication 42, with Supplements 1 and 2,
1999.
\'\
GeoSoils, Inc.
International Conference of Building Officials, 2001, California building code, California
code of regulations title 24, part 2, volume 1 and 2.
_, 1998, Maps of known active fault near-source zones in California and adjacent
portions of Nevada.
_, 1997, Uniform building code: Whittier, California, vol. 1, 2, and 3.
Joyner, W.B, and Boore, D.M" 1982a, Estimation of response-spectral values as functions
of magnitude, distance and site conditions, in eds., Johnson, J.A., Campbell, KW.,
and Blake, TF.: AEG short course, seismic hazard analysis, June 18, 1994,
Kennedy, M.P" 2000, Geologic map of the Pechanga 7,5' quadrangle, San Diego
and Riverside Counties, California: adigital database, version 1.0, California Division
of Mines and Geology, and U.S, Geological Survey.
, 1977, Recency and character of faulting along the Elsinore fault zone in southern
Riverside County, California: California Division of Mines and Geology, Special
Report 131, 12p.
Mann, J.F., 1955, Geology of a portion of the Elsinore fault zone, California: California
Division of Mines and Geology, Special Report 43, 22p.
Southern California Earthquake Center, 1999, Recommended procedures for
implementation of DMG Special Publication 117, guidelines for analyzing and
mitigating liquefaction in California, pp. 28-32, dated March,
Thakkar, Gunvant, P.E" 2004, Preliminary soil investigation for Lot 1; TR 9833,
APN: 945-160-012, Temecula, California, dated February 24.
United States:Department of Agriculture, 1980, Aerial photographs, project no, 615020,
flight date August 10th and 20th, flight line 180 and 580, photo nos. 29-32 and 184
and 185 respectively, scale :t 1 "=3333',
Mr. Robert Tuccinardi
File: e:\wp9\murr\rc4500\4553a.sgf
Appendix A
Page 2
'l,;O
GeoSoils, Ine.
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APPENDIX B
EQFAUL T DATA
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