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•
t PETRA
COSTA MESA • SAN DIEGO • TEMECULA • LOS ANGELES
I
February 15, 2002
Revised MaJ 02
N 208 00
EXCEL LEGACY CORPORATION
17140 Bernardo Center Drive
Suite 300
San Diego, California 92128
Attention: Mr. Geoffrey Sherman
Subject: Summary of Geotechnical Investigations,
Proposed Redhawk
Towne Center,South of Route 79 Between Redhawk a.Parkway
dhawkarkway and
Apis Road,Temecula, County of Riverside,
Californi
Gentlemen:
As requested, we are summarizing
recent geotechnical investigations conducted by
three different firms at the proposed Redhawk Towne Center. Two additional
late
ded in
geotechnical investigations were conductedt in
The pertOnent reports ar's and are e part of
Appendix Volume
2 C of Volumeequ of the nt BR andsa e herein referred to,but are not duplicated in
Volume 2 of the Subsequent endix A.
this summary. A list of references is attached as App
There are three main purposes of this summary:
1.
To review and resolve apparent discrepancies in the geotechnical reports about
the distance of the site from active faults and how they relate to the calculated
peak site acceleration;
2. To discuss the likely elevation of future ground water levels; and,
and associated mitigation
3 To summarize the technical background
recrecommendations for four geotechnical areas of concern for this project:
a. the expected peak, seismically induced ground acceleration;
PETRA GEOTECHNICAL, INC. etrasd ip m.net
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b. the extent and amount of site static and dynamic total and differential
I
settlement;
c. the potential for site-specific ground failure due to lateral spread; and,
d. the potential for site liquefaction. geotechnical
The above three purposes are interrelated to each other and
c four geotechnical (b, c,
issues are also interrelated to ontfrom andthree
expected magnitude of an earthquake
and d)basically depend upon distance
originating on the Wildomar Fault, a branch of the active Elsinore Fault Zone.
eak ground acceleration of applicable faults are discussed on
Distances from and p
ground water elevations are discussed on page
i page 6, under"Peak Acceleration", gr eotechnical area of concern,
4 under "Ground Water Elevations", and the four g inning
which includes the discussion on peak ground accelerations, are discussed beg
on page 5.
Background of Geotechnical Investigations
ro osed Redhawk Towne Center area has been subject to several previous
Thep P preliminary (Inland,reference
geotechnical investigations. Earlier studies were mainly p to substantialf
no. 11; Highland, reference no. 10), and are now "outdated" owing
professional standards-of-practice, and to new information on nearby aconcerningt h e
e
changesinin p uakes orig
location,length and expected magnitude of earthq
faults.
ertinent to the site are those by Geocon(reference no. 8),
More recent investigations p to
and related responses to
EnGEN (reference no. 7), and Petra(references 1, 4, and 6) responses
l
the County of Riverside(see attached references). All three firms calculated p
te.
ver,
seismic accelerations,liquefaction and settlement at thesi tedHowe num crpariti e and
es are
) calcu
evident. For example, Geocon (reference
8tg ssite-specific peak accelerations of
probable earthquakes of Mw 6.8 and 6.3,yseld
002
2
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Redhawk Towne Center 1.
In contrast,EnGEN (reference no.7) concluded that the
0.46 and 0.39 g,respectively. stemming from a Mw 6.5
site could be subject to a peak ground acceleration of 0.62 g, •
event on the nearby Wildomar fault. Petra, in references 3, 4 and 6,used a Mw 6.5
°round acceleration of 0.55g for preliminary
design earthquake with a peak a tete
liquefaction analysis. In some cases, the consultants did not provide the comp
rationale used for calculating peak ground accelerations at the site. In references 1 and
2, a value of 0.48g was used for a new analysis based on the acceleration Accordingly,mo iificatin
ort.
from a Mw 7.5 event as discussed in a following section of this rep
the"peak acceleration" section of this report now provides the specific procedures and
•
assumptions for the analysis, and therefore should alleviate reasonable concerns about
apparent inconsistencies in the various reports.
Ground water elevations, either existingspreading or anticipated,
differential settlement. Th any
is
analysis of site liquefaction, lateral sp g
1-:. of particular concern in the Temecula area because it has been well do
e t mectesd that
pumping and related groundwater declines can aseismically
therebyhe
causing deleterious ground fissures, subsidence
nearby Elsinore fault system, Additionally,rising
and differential settlement(Shlemon and Davi�,rted urban wat eference no. r)similarly can initiate
groundwater levels, caused by runoff of imp
• fissures, settlement and differential subsidence, as expressed in the nearby California
Oaks area of Murrieta (Shlemon and Hakakian, reference no. 24), although, as next
discussed, the conditions at the Red Hawk Towne Center site are not conducive to
similar problems.
As stated in each of the geotechnical investigation reports, no known active faults
T
occur within the proposed Redhawk Towne Center development.
wherefore, fault
on.
reactivation cannot occur within the site regardless of local ground ) show that
Additionally, investigations of the California Oaksarea
be present resent befone ono. set of ground
a combination of the following four conditionsnamethe presence of: (1) sediments (soils)
fissures, settlement and subsidence; Y
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Redhawk Towne
h dro-consolidation); (2) a steep
walled (steeper than
2:1 •
(11:V) slopepe
drocollapse ( Y (3) substantial loading by fill and
susceptible to buried channel sidewalkratio), rnent rise in groundwater levels.
structures; and (4) a potential for post-development
geology at the proposed Redhawk Towne Center
A summary of the subsurface
indicates that hydrocollapse soils do not exist and no major Pleistocene channels
in contrast to that in the Californiaa O�sread'",
reference nos.3 and 6) be ` Oaks
underie the site (
Accordingly,any future rise in regional water levels will most likely
u re
unsaturated, narrow channel sediments.
previously unsatur from asphalt
rather than confined top by engineered positive drainage
ground water rise is inherently mitigated development.
impermeable surfaces constructed for the
proposed oh and south sides.
and other-Highway
79 p commercial corridor both directhes.
;. hway 79 has a comm complexes will generally
State rtig commercial or office comp them
Properties developed as
engineeredthe
drainage systems rather than allowing
majority provide a substantial
of surface waters into
'�'> to infiltrate into the subsurface. Proposed structures will not
ral loading to the site and minor cuts and fills of
ll loads less than three feet from
structural
existing grade will not dramatically increase existing
Ground Water Levelsground water
articular geotechnical interest because bothgr
Ground water levelscoare of p onbaent for the
contributed to subsidence and differentials masettlement
urban areas
rise and declineinand are
elsewhere in Riverside County (reference no. 20),
evaluation of the liquefaction potential for the site.
As discussed in reference no. 6,
ground water levels were approximately 16
historical gr ground
feet below the existing ground surface (see reference no. 17). The early high h
prior to channelization of Temecula Creek, and thus may
water level was recorded gnGLN
agricultural irrigation in the area. More recent water
have reflected the influence, approximately 30 feet. In April
Geocon, April 1999, were at
levels, depth. Petra identified water levels of 26to .
recorded water levels at the 26 to 34 foot
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Redhawk Towne Center
29 feet below the surface. An on-going site-specific investigation in the southwest k
corner of the site shows that static water levels tae e now ow about 33 to 35 feet deep,
ge rainfall in
possibly due to recent below-avera
path of least resistance. Since open channel
flow provides resistance only
Water flow within soils always seeks the ground wille
with the wetted surface of the channel, of 5 to water feet
With an approximate channel depth of30 least
seek the open channel or body. provides this path
ound water elevations could rise to no more than
below the adjacent surface, the Temecula Creek channel
resistance,and it is anticipated that gr
a few feet above the channel bottom.
Compacted Fill Mat
(reference no. 8) stated that no remedial grading is necessary for this
Geocon,
reference no. 7) postulated that a 15-foot thick
EnGEN ( anchor structures.
rem val andIcontrast, for proposed
' action effort should be undertakenrecommendation.
removal recomp did not provide a rationale for their recomm16 feet
Unfortunately, EnGEN
based on site boring-log data indicates that the upper
Liquefaction analysis, will not liquify due to in-place densities and other
(above historic ground water)
reference no. 6)recommended that a 5-foot thick mat
favorable dit properties. Petra( a minimum of 95 percent
be requiredthe footings. However,the lessee does not
based on the fact that the lessee also requires
relative compaction for material underlying action. Accordingly, conservatively,
provide a specific depth for the increased comported on a ordingly,five-foot thick, uniformly
we recommended that the foundations be supported
compacted mat of 95 percent relative comp
KEY GEOTECHNICAL ISSUES
the potential for
near-proximity of the active Wildomar
Because no active faults are Ne°Wi-nat the the Nevertheless,h a near phawk Towne Center,
low, dynamic
ground rupture is very ground accelerations, 2)
• fault requires appropriate mitigation for 1) peak4
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• liquefaction. Pertinent these
lateral spreading, and 4) q to these
•
bedrock", as stated by
issues is tl eettlemhat, 3) G some
issues is the fact that the site is not underlain by Holocene alluvium or,
(reference, by el 8),
but rather is underlain either by formation
e
areas, by relatively unconsolidated units of onion o f hestocene site bordersbhe north side
(Kennedy,reference no. 19). Additionally, P
possibly subject to lateral spreading
and is therefore p geotechnical
of Temecula Creek channelAccordingly, the above four, intertwined
during high seismic shaking ecific mitigation. These are
issues have been singled out for analysis and for site-sp
summarized in the sections following.
•
•
peak Ground Accelerations
computer analysis by the various consultants for the determination of
reports for the For
Printoutspeak rf the he site. the
the peak ground accelerations were not included in the recTrier first comp
keycomponents are required.
computer analysis, two
; and the second is the attenuation relationship used for analysis.
I actual site location,
reports did not indicate specific site locations used in their
EnGEN shows the site approximately 7/8 of
•
The analyses.Geocand EnGEN P files and 1
As indicated in their reports, Geocon and Petra 2 m entitled
•
the Wildomar Fault, where as indicate program
a mile from Petra used a computer
For site location, which
mile, respectively. (reference no. 27),
"TOPO!", Version 1.2.1, by Wildflower Productions no27),es which
provides both latitude and longitude values for a specific site. These
ed
uadrangle maps
on the United States Geological Survey q
Three different values for site ground accelerations have been assigned for the Redhawk Towne Center (reference nos. 1, 3,
4, 6 and 7). We have examined the
le
documentation for each, and in this section document the basis for our
availablab
i
conclusion.
is
A
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Redhawk Towne Center i
b Blake (see their I
(reference no. 7) used "EQSEARCH" Y
The EnGEN report
for the peak ground
references),but did not provide any reason for their use of 0.62g
ground acceleration of 0.39g
acceleration. Geocon(reference no. 8) discussed a peak
from a maximum probable earthquake obtained from"EQFAULT" (see Geocon List
of References).
Petra used a peak acceleration of 0.55g for the liquefaction
As discussed earlier, higher than the
analysis provided in references 3, 4, and 6. This value was slightly g
0.51g from the maximum credible event from a"EQFAULT" deterministic analysis
in reference no. 6. The location of the site was determined by the computer program
entitled"TOPG . program Petra probabilistic analysis (reference no. 6) used the computer
"FRISKSP" (Blake, 1989-2000)
and adopted the same attenuation relationship as in
ro am. Two approaches to this analysis were evaluated. The first
the"EQFAULT p specific site
used the computer program with the standard settings and with the
This analysis generates a probabilistic peak
location and soil attenuation relationship. magnitude. The results of this
ground acceleration for the program-determined mage robabitis
of
analysis indicated a 0.64g peak ground acceleration(PGA) with a 10%p
being exceeded within a 50 year period. This value is similar to EnGEN's 0.62g.
the standard setting to a specific magnitude
The second method consists of modifying
and using magnitude-weighting factors. As discussed with Thomas P. Blake,
the accepted practical method is
of the programs and as he presents in his seminars,
to assignto determine the PGA.
This appp
ecific magnitude of 7.5 and allow the program
ro ams to apply corrections to magnitudes
a specific
is enables liquefaction p �
At 7.5, the correction factors in the liquefaction program
above or below 7.5. SKSP" programan earthquake mage
itude
"LIQUEFY2" equals 1.0. Within the"FRI
higher or lower than 7.5 is adjusted to the value of 7.5 during input to determine the
PGA. The program then utilizes past historical data and probabilistic values and
4
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Redhawk Towne Center
specified 7.5 mawimde. As an example, a M 5.0 '
event. If the magnitude of the
adjusts the ground acceleration for a sp
quake will produce a given acceleration from a specificbe reduced to result in
•
then the acceleration would necessarily nude .
an5.0 is increased 7.5, equalt the
equivalent seismic event. The reverse of this condition the acceleration to
of
8.0 adjustsground
adjusted •
to 7.5. Here the program eak gr
8.0 is usingthis accepted method, a p
8.0 level. Therefore, Towne Center
seismic avont for a M and is applicable to the Redhawk To
was attained, of Exceedance"
project.
t.acceleration Thisopeak0.4accelerationg the "Probability
project.
value is shown on
graphs attached to this report and used in Petra's liquefaction analysis (reference no.
1).
Differential Settlement potential static and dynamic settlement at the
ation for p interpretation.
The amount and the mitig to differing
1 Redhawk Towne Center has likewise been subject Geocon (see page 7 in reference
data discussed by 0.5 inch with the
Settlement-monument monitoring of approximately•
number 8), indicate a maximum static settlement
Therefore,static settlement of the
last few readings indicating little or no movement.
addition of anticipated structural loads should
tothe so d
in alluvial sediments due is necessary. EnGEN (see page underlying
in
not have a detrimental effect and no mitigation
reference number 6) calculated minor static settlement on the order of 0.75 to 1 inch,
and similarly, no mitigation was recommended.
determined that a static settlement of lss than
during
pelta, as discussed in reference no. 6' roximately 30 feet, would take place an of app
lied. Therefore, no specific mitigation for static
about one-half inch over a sp
construction as footing loads are app
settlement was recommended. dynamic (seismically
N calculated such dynamic settlement as ranging
specific discussion concerning Y
Geocon did not include a r,EnGE
induced)settlement. However,
from 7.4 to 12.4 inches under the existing conditions,but reduced settlement to 5.5 to
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construction of a 15-foot thick recompacted fill mat. These
calculations8.0
inches were assuming
a logs. It should
was utilized in this analysis,was outside the limits
b
were based on the blow counts obtained from the boring under the
B-17, whichmass-grading operations
of noted that boring during past
removal and recomPaction
of Geocon. EnGEN's settlement calculations for dthe other two
nches,
boringobservation, and and
18 indicate dynamic settlements of 6.5 d settlement
borings, ely. and B
respectively. However,EnGEN
did not provide calculations fordynamicBut,
ro osewould not
to show how the p they
d 15-foot compacted mat would behave.P action, dynamic loading
upper 15 feet. EnGEN stated that dynamic differential
apparently assumed that after removal and recom
result in any settlement for the upp
ttlement within a single building would be less than one-half the total settlemen .
se the same
boring B-16 was analyzed using
dynamic-settlement calculations,output from the computer analysis program
In Petra's dy EN, and the level
information utilized by ground
gh
ound
i, �. "LIQUEFY2" based on a a gr water depth of 16 feet, the historic hi will not occur
(Referencevhewater 1). This computer analysis showed that liquefaction soils requires
o.
dynamic settlement of the upper
loads. Because the site will be essentially
above increased the moss Accordingly,taAnticipated
both moisture content and heavy
structures and parking, increased soil moisture is unlikely.
sealed by the strucompared to the fill loads.
loading
from structures and improvements are negligible as deduced
Both Petra and EnGEN calculated a total settlement of about 6.6 inches,
of boring B-16. But it is worth while i o note p that
these
approximately 9 feetacalculated
soil
from analysis
ading. The calculated 6.6 inches is considered
d
settlement values did not take into account that the
be removed and recompacted during gr
a conservative value. 7
ing
As noted previously, in EnGEN's analysis, they utilized the results for bona and B _-11 s
which is within an area not previously mass graded. Both EnGEN
tions indicate that differential settlements for the soils below the historical .
calcula 4
March 5, 2002
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Redhawk Towne Center
differential settlement range of
water table are similar and indicate thatQa would be anticipated. In regards
2.5 to 3 inches across a building padcompacted mat below
approximately ended 5 feet
neither approach affects the
to the usage of 15 feet removal or the recommended
foundations (approximately 7 to 9 feet of removal), from affectssettlemhe
water level. It should be noted that the anticipated future water
anticipated differential settlement values, for these values stemmed
below the historic high
owingto the existence
Temecula Creek channel. Thus, the calculated
en
levels should not be more than about 22 feet below the surface,
presence of the now g
potential dynamic settlement values are inherently conservative.
Seismically
(presently
induced settlement across the site of the originally proposed theater
rod)osed) was calculated by Petra to range from
a department store is p P The range of values reflects
number 1).
4 to 6 inches (referenceliquefiable zones
j approximately potentially
inherent uncertainties, for the boring-log data show that p
are discontinuous under the originally proposed theater site (reference number 2).
r..
According to the present standard-of-practice, if little or no data are available for
then two
of the total settlement is useddata to
differential settlement evaluation, then
field and laboratory
re
estimate differential settlement. However,
•
available, as is the case for the Redhawk Towne Center, then calculated differential
settlement values are used.
provided in reference no. 1, anticipate
dynamic settlements d
ical
Based on the total dY approximately 2.5 to 3.0 inches. Mitigation is nP
differential settlement is•
provided by adjustment of footing dimensions and footing and slab reinforcement
ns
cture(s). We also recommend that flexible connections are
duringdesign ll of the struass through the native/comp
act' appproropriate where any main-line utilities p
boundary.
0
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Lateral Spreadinge
"Lateral spreading" is basically the lateral movement of an inclined sloethe
liquefaction of a underlying soil layer. in due to effect,
The liquefaction of the soil layer,
floats. The seismic shaking
results in a lubricated layer on which the overlying mass will cause movement of the
of this mass causes lateral forces, which if not resisted,
soil mass. Because slope faces are exposed to air,the only passive resistance is at the
in soil. If an inadequate amount of soil exists over
toe of the slope and the underlying
the liquified soil layer or the friction resistance is too low, then the lateral movement
awaywith the slope face is
spread. The California Division of Mines and Geology Special
is not resisted. The distance or amount of soil that breaks
provides guidelines to evaluate lateral spreading.
the amount of lateralp
tion
T e South 117
(reference no. 18) providesn
The Southern California Earthquake Center document (reference no. 20 ,
' approaches to evaluate lateral spreading. EnGEN
at the site,
Although Geocon did not discuss the potential for laterllospreading ed partially
on their
considered the potential for lateral spread to be
see section 8.2.5, page 10 of reference no. 7), and
recommended remedial grading ( (graded and constructed in
Temecula Creek Channel slope specific u design
h) fact that
tithe entire
aengineered slope with materials(within very
1995) that would mitigate the potential
at that time,w
parameters(see section 7.6,page 8 of reference no.7) o thtigs of the channel
slope upstream form the adjacent Redhawk par
Presently,the approximately western two-thirds which
for lateral spreading. bridge, is concrete lined,
kway
inherently further mitigate lateral spreading in this zone. 3 Calculations
Petra discussed the issue of lateral spreading in reference no.
presented therein indicate that an approximately 12-foot wide zone adjacent to
Temecula Creek channel may
be subject to movement. This zone is measured laterally
from the slope face. Movement within or of this zone does not mean that the entire
zone will move laterally 12 feet but rather ie zone or portion thereof may be subject
to some movement. The movement may range from less than an inch to over one foot.
1
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The amount of movement, soil separation or spreading is controlled by the magnitude,
acceleration,and duration of a seismic event. The nearest presently proposed structure
is about 80 feet away from the top of the channel slope, and therefore, is well outside
of this zone. Given the specific design parameters used for slope construction, and
with the structures set back 80 feet from the slope, the risk of damage from lateral
spreading is considered low.
However, if the placement of a structure within about 12 feet from the top of the
channel, we recommend use of traditional methods form tig mitigation suchuctioas n e
ge
of
containment structures, berm, dike, and compacted soil
roadways, parking, trash enclosures, etc. do not warrant the need for this type of
mitigation. The adequacy of the design for the Temecula Creek channel is beyond the
scope of site specific investigations for the Redhawk Towne Center.
.wever,y Corps f
we
note that the design was most likely reviewed and accepted by
theEngineers and the County
of Riverside.
Nevertheless, we note that all presently proposed structures are sufficiently setback
from the Temecula Creek Channel;
therefore, no special mitigation is required.
act only driveway pavement which can be
Further, any distress would likely imp
readily repaired.
Liquefaction Potential
Liquefaction is a phenomenon that occurs during an earthquake when a loss of shear
re water pressure.
loss
strength in cohesionless soil results from f a fracture, loss of bearing capacityesand
of shear strength can cause settlement
boils, surface cracking, and lateral spreading. For liquefaction to occur at least four
factors must be present. The first two factors involve the earthquake. The earthquake
accelerati
n
has to have a large enough 1ePeatable theror�roaselof pore water pressure e iohave a
i the soil.
sufficient number of cycles to produceiThe third factor is the presence of a high water table. In the current geotechnical
v
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March 5, 2002
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Redhawk Towne Center
s those within
standard-of-practice,
tapdad of practice, high ground water levels are defined s the presence of
approximately 50 feet from the ground surface. The fourth factor
the er 50 feet. These factors were addressed by
tloose, cohesionless soils withiotentiapfor site-specific liquefaction has been discussed
Petra in reference no. 1. The p
and agreed by the various consultants to be low based on the acted filll mcts and
consistencies of the alluvial deposits above the historic ground water elevation.
Liquefaction mitigation norm
all involves changing at least one characteristic soil
Y
property or its response to increased pore water pressure. These mitigation measure
based on the configuration of the site, on
s
and on site elevations, it was
were provided in reference no. 1. In brief,
construction methods for the proposed structures,
placement of a compacted soil mat, combined with a reinforced
determined that p ade beams,would be the most practical mitigation
perimeter footing and connected gr
measure.
(reference no. 8) concluded that liquefaction could occur between about 31
� Geocon approximate 6- to 10-foot
and 35 feet below the existing ground surface,based on an relation about
ir interp
thickness of compacted fill. Their conclusion depended on
heat the Pauba Formation
the thickness and extent of potentially liquefiable zones, an
that the
is a "bedrock" or dense formational material.
a isfacto nyrm re ligate the poe nnaltfor
existing compacted fill across the site would s
liquefaction.
page 8) stated in their report that"the potential for hazards
EnGEN (reference no. 7, Paa
and
undation
associated with liquefaction should be low if the earthwork Their f ourthwork
recommendations presented in the report are adhered to".action of the upper 15 feet of existing
recommendations called for removal andTthe reasons for their recommendation.
appendix indicate that the existing fill soils and
soils. Unfortunately,EnGEN did not provide
factor-of-safety above 1.2. Their
The settlement calculations in their
upper portions of the alluvial soils have a
I
March 5, 2002
Corporation J.N.ch2002
Corp Page 14
Excel Legacy
Redhawk Towne Center1
i.
calculations also indicate that the existing upper
u
fill and alluvial soils within the
approximately 15 feet will settle about 0.7 inches to 4.5 inches prior to anyt removal
pper
and recompaction with a total dynamic settlement ranging from about 7.4 to 12.4
wing a differential settlement of approximately 5 inches. With removal and
inches, givingrange from approximately
recompaction,the total settlement after a seismishoWntwillthe EnGEN tables indicates
8-17. However, EnGEN
5.5 inches to 8.0 inches. The factor-of-safety
a layer of loose alluvium exists at the surface a boring on this zone would be densified
• pointed out that by normal removal and recomp
and thus reduce their susceptibility to liquefaction.
Petra also concluded that liquefaction could occur at the site (see reference nos. 1, 2,
•
both
3 4, and 6). We also concluded that becauseliquefiable and non-liquefiable
zones are thin and disco potential for liquefaction is low.
te, the
We therefore recommended that areasross h1r P
or P °Sd structures underlain by only
alluvial soils be removed and recom acted to a minimum of 5 feet below the deepest
. , .
foundation. However, for additional mitigation, we also recommend anyloose
d
soils encountered below the 5-foot depth below the lowest footing during site grading
operations,be replaced by suitably engineered fill.
provide anon-liquefiable surface layer that would
A proposed engineered soil mat will henomena, i.e., sand boils, etc.
prevent the surface manifestation of liquefaction p
Each structure would have such a mat below its footings. The anchor or major retail
f
95%of
e
ive maximum -
stores that this mat be installed at a minimuma °e effort i creasest
dthe protection
ns req
density of the fill material. This increased comp
of the overlying structure.
with a compacted fill mat beneath all
of
discussed by
Petra in reference no. 3, thelmjority the
structures and asphaltic and Portland cement concrete covering
remainder of the site, the potential for the surface manifestation of liquefaction
phenomenon beneath the site is therefore low.
4
•
Excel Legacy Corporation March 5, 2002 Page 15
Redhawk Towne Center J.N. 208-00
Site Floodingeaz event",
l for site flooding based on the"100-y
tia
We have also considered the potential
induced failure of the Vail Lake dam approximately 8 mi es
or on possible seismically- ro ect design engineer
upstream on Temecula Creek. In this regard,we note that
to accommodate the 100-
has the responsibility to determine site grade requirements
year flood and hypothetical failure of the dam and that the Temecula Creek channel
slopes were also designed for such occurrences.
SUMMARY AND CONCLUSIONS
The following summarizes the key
technical conclusions and recommended mitigation
1 appropriate to the proposed Redhawk Towne Center:
•
The nearest active fault is the Wildomar, a component of the Elsinore system
�'�. 1 published and widely
located approximately 1 mile from the site. Using ro nay
ground acceleration of 0.48 is appropriate
'I .. accepted attenuation curves, a peak� at the site.
for analysis of ground shaking and liquefaction potential
The site lies outside any State or County subsidence or active fault zone. The
potential for seismic ground rupture ture is therefore inherently very low.
3. The
level is approximately 16 feet below existing
The historic high groundwater otential is thus present.
ground surface. Aseismically-induced liquefaction
failure is mitigated by
The potential for liquefaction-caused ed mat below the deepest foundation
construction of a five-foot thick compfootprint, appropriate
of a given structure. For those areas outside a building mat
mitigation is accomplished by construction of a two-foot thick compacted
lowproposed subgrades of concrete or asphaltic surfaces and related
be P
infrastructure.
.
March 5, 2002
Legacy Corporation rch 208-00
Page 16
•
Excel Leg Y
Redhawk Towne Center t
post-construction groundwater levels is
q The potential for significant rise in p the site to
very low. There are no known subsurface channels underlying
rigngd eaxcegsive hydro
potentially concentrate urban derived runoff and sface drainage is
•
•
consolidation and differential settlement; and positive
•
accomplished by engineering design.
dynamic settlement ranges from about 2.5 to 3.0 inches across
5 Potential potential
building pads; total settlement is about 4.0 to 6.5 inches. The el by
dynamic settlement is inherently mitigated to an insignificant
construction of the above-specified compacted fill mat.
6.
Possible adverse static settlement is dependent on specific building design and,
•
accordingly, is traditionally mitigated to code standards by the project
Structural Engineer.
ground failure caused by liquefaction-induced lateral spreading is
7.
Potential gr adjacent Temecula Creek.
limited to a
12-feet wide zone parallel to the
Mitigation is readily accomplished by the proposed siting of structures some
80 feet from the Creek,well outside the influence of possible lateral spreading.
However, should the project ultimately envision building within 12 feet from
lateral spreading is
the Creek, traditional mitigation for potential
readily
accomplished by construction of edge containment structures such asproperly
designed berms, dikes and compacted soil zones.
• "100-yr flood" or by hypothetical
g The potential for site flooding caused by the
failure of the Vail Lake dam has been evaluated by the project design engineer.
Mitigation is both regional and local in extent, mainly by engineering design
of the Temecula Creek channel, and by raising site elevations above any
•
reasonably anticipated flood levels.
4,
i
I
2002
�
J.N. 08-00 {`"
Excel Legacy Corporation March 5,
Redhawk Towne Center
Page 17
Leasure to be of service to you on this project. Should you have any
It has been a p or should you require additional
questions regarding the contents of this report,
information, please do not hesitate to contact us.
ANG\NEERIyC
Respectfully submitted, /=:.• ()A
s RUSy�F�!
C. ' r�� 2 a
PETRO GEOTECHNICO ESsrp�.ti �' .N
F / 7a
qd o m Roy J.Rushing s �Q
rL u0, 042204 m
2
Ronald S. Hal, g�-oy Senior Associate C4' 'r�n�k0
Senior Associa = �giver C.E.G. 1080
R.C.E. 42204 sr . of C:V\� 4,,-Distribution: (6) Ate
(4) Tom Dodson & Associates
•
i
\/,
I
r-,
VUi3d
V X1U143ddV
Excel Legacy Corporation March 5, 2002
Redhawk Towne Center J.N. 208-00
Page 18
APPENDIX A
REFERENCES
1. "Supplemental Information for the Liquefaction Hazard Analysis, Redhawk
Towne Center, Historical Commercial Area A, Vail Ranch at Rancho
California, County of Riverside, Final Environmental Report Number 240",
prepared by Petra Geotechnical, Inc., dated August 27, 2001 (Appendix D,
Volume 2 of Subsequent EIR).
2. "Response to Riverside County Second Review of Liquefaction Report for
Redhawk Towne Center, County Geologic Report No. 1013", prepared by
Petra Geotechnical, Inc., dated July 18, 2000 (Appendix G, Volume 2 of
Subsequent E[R).
•
3. "Response to Riverside County Review of Redhawk Towne Center Review
Report dated April 25, 2000,Plot Plan No. 16535, county Geologic Report no.
1013", prepared by Petra Geotechnical, Inc.,.dated June 29, 2000 (Revised)
July 17, 2000 (Appendix F, Volume 2 of Subsequent EIR).
4. "Geotechnical Investigation Proposed Walmart,Redhawk Towne Center Route
79 South, between Redhawk Parkway and Apis Road, Temecula, County of
Riverside,California"prepared by Petra Geotechnical Inc. dated May 25,2000
(Appendix E,Volume 2 of Subsequent EIR).
5. "Revised Seismic Design Parameter Table for the Geotechnical Investigation
and Geotechnical/Geological Engineering Study, Proposed Redhawk Towne
Center, Route 79 South Between Redhawk Parkway and Apis Road,
Temecula, County of Riverside, California", prepared by Petra Geotechnical
, Inc., dated May 8, 2000.
6. "Review of Geotechnical Investigation and Geotechnical/Geological
Engineering Study Proposed Redhawk Towne Center, Route 79 South,
between Redhawk Parkway and Apis Road, Temecula, County of Riverside,
California" prepared by Petra Geotechnical Inc. dated April 25, 2000
(Appendix H, Volume 2 of Subsequent EIR).
7. "Geotechnical/Geological Engineering Study, Proposed Redhawk Towne
Center, South Side of Route 79 South, Between Redhawk Parkway and Apis
Road, City of Temecula, County of Riverside, California", prepared by
EnGEN Corporation, dated April 7, 2000 (Part of Appendix F, Volume 2 of
Subsequent E1R).
t
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8. "Geotechnical Investigation, WalMart at Temecula, Temecula, California",
prepared by Geocon Incorporated, dated May 18, 1999 (Appendix E, Volume
2 of Subsequent EIR).
9. "Report of Testing and Observation Services During Remedial Grading for
Vail Ranch Commercial Site Tentative Tract 23172, Temecula, California",
prepared by Geocon Incorporated, dated September 1994 (Part of Appendix
F, Volume 2 of Subsequent EIR).
•
10. "Preliminary Geotechnical Investigation, 700+ Acre Vail Ranch, Southeast
Corner of Intersection of Margarita Road and State Highway 79, Rancho
California, Riverside County, California", prepared by Highland Soils
Engineering, Inc., dated March 11, 1988 (Part of Appendix C, Volume 2 of
Subsequent EIR).
11. "Geotechnical Investigation,Rancho Villages Assessment District, Temecula
Creek Bridge. Butterfield Stage Road, Rancho California area, Riverside,
California",prepared by Inland Foundation Engineering, Inc.,dated September
4, 1987 (Part of Appendix C, Volume 2 of Subsequent EIR).
12. "Geotechnical Investigation,Rancho Villages Assessment District,Temecula
Creek Bridge - Margarita Road, Rancho California area, Riverside,
California", prepared by Inland Foundation Engineering, Inc., dated August
31, 1987 (Part of Appendix C, Volume 2 of Subsequent EIR).
13. Bartlett, S. F., and Youd, T. L., 1995, Empirical Prediction of Liquefaction-
Induced Lateral Spread, Journal of Geotechnical Engineering, Vol. 121, No.
4, Paper 7247.
14. Blake,T. F., 1998, "UBCSEIS" - A Computer Program for Determining, 1997
Uniform Building Code Design Parameters, Version 1.03.
15. Blake; T. F., 1998, "LIQUEFY2" - A Computer Program for Empirical
Prediction of Earthquake - Induced Liquefaction Potential, Version 1.50.
16. Blake, T. F., 1996, "EQFAULT"-A Computer Program for the Deterministic
Prediction of Peak Horizontal Acceleration from Digitalize California Faults,
Version 2.20.
17. California Department of Water Resources, 1971, Water Wells and Springs in
the Western Portion of the Upper Santa Margarita Watershed, Bulletin No. 91-
20.
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18. "Guidelines for Evaluating and Mitigating Seismic Hazards in California",
California Division of Mines and Geology Special Publication 117, March 13,
1997.
19. Kennedy, M. P., 1977, Recency and Character of Faulting Along the Elsinore
Fault Zone in Southern Riverside County, California, Division of Mines and
Geology, Special Report 131.
20. Martin, G.R. and Lew, M., 1999, Recommended Procedures for
Implementation of DMG Special Publication 117, Southern California
Earthquake Center, University of Southern California.
21. Shlemon, R. J., 2000, "Ground Fissures, Subsidence Zones and Litigation at
Temecula and Murrieta, Southwest Riverside County, California"in Birnbaum
and Cato (eds..), 2000. Geology and Enology of the Temecula Valley,
Riverside County, California: Field Trip Guidebook, San Diego Association
of Geologists, p.119-133.
22. Shlemon, R. J., 1998, Ground fissures and subsidence in the southwestern
United States: an increasing challenge for the engineering geologist: in Moore,
i.•
D., and Hungr, 0. (e's.), Proceedings, Eighth International Congress,
International Association for Engineering Geology and the Environment
(Vancouver, BC, Canada), A.A. Balkema (Rotterdam, The Netherlands), p.
( 2167-2172.
• 23. Shlemon, R. J., 1995, Groundwater rise and hydrocollapse: technical and
political implications of "Special Geologic Report Zones" in Riverside
County, California, USA: in Barends, F.B.J., Brouwer, F.J.J., and Schroder,
F.H. (eds.), Land subsidence, Proceedings of the Fifth International
Symposium on Land Subsidence (The Hague,The Netherlands),International
Association of Hydrological Sciences Publication No. 234, p. 481-486.
• 24. Shlemon, R. J., and Hakakian, M., 1997, Impact of the 1992-1993 winter
storms on hydroconsolidation, differential settlement, and ground fissures,
Murrieta area,southwestern Riverside County, California: in Larson,R.A.,and
Slosson, J. E. (eds.), Storm-induced geologic hazards: case histories from the
1992-1993 winter in Southern California and Arizona: Geological Society of
America Reviews in Engineering Geology, v. XI, p. 49-59.
25. Shlemon, R. J., and Hakakian, M., 1992, Fissures produced by groundwater
rise and by groundwater fall: a geological paradox in the Temecula-Murrieta
area, southwestern Riverside County, California: in Stout, M.L. (ed.),
Proceedings, Association of Engineering Geologists 35' Annual Meeting
• (Long Beach, CA), p. 165-169.
•
Excel Legacy Corporation March 5, 2002
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26. Shlemon, R. J., and Davis, P., 1992, Ground fissures in the Temecula area,
Southwestern Riverside County, California: in Pipkin, B. W., and Proctor, R.
J. (eds), Engineering geology practice in Southern California, Association of
Engineering Geologists Southern California Section Special Publication No.
4, Star Publishing Company (Belmont, CA), p. 275-288.
27. Wildflower Productions, 1997, "TOPO!", Version 1.2.1.
28. Tokimatsu, K, and Seed, H. B., 1998, Evaluation of Settlements in Sands Due
to Earthquake Shaking, Journal of Geotechnical engineering, Vol. 113, No. 8,
Paper No. 21706.
•
PROBABILITY OF EXCEEDANCE 208-00
CAMP. & BOZ. (1994/1997) Standard
• A ■ •
100 25 yrs 50 yrs 75 yrs 100 yrs
90 ki1/4
80 -
70
0
60 - \
ii
c9
° 50
a
a)
o
c
-a0 40
a)
a)
0
X
W 30
20
10
0 1111 1111 1111 1
0.00 0.25 0.50 0.75 1.00 1 .25 1 .50
Acceleration (g)
I
PROBABILITY OF EXCEEDANCE 208-00
CAMP. & BOZ. (1994/1997) 7.5 Mw Modification
• A ■ 1 •
100 ��, 25 yrs 50 yrs 75 yrs 100 yrs
1
1
gi
90
80
70
0
1 60
s
ri as
2 50
a
L..
m
m 40
FT -C3
a>
a)
U
X
w 30
20
10
K...• 0 �� =_ i_ 1 11 sm . !
0.00 0.25 0.50 0.75 1 .00 1 .25 1 .50
Acceleration (g)
,.
is
O