BRES2020-0329 Geotechnical Report*Sladden Engineering
45090 Golf Center Parkway, Suite 1{, Indio, CA 92201 (760) 863-0713
6782 Stanton Avenue, Suite C, Buena Park, CA 90621 (714) 523-0952
450 Egan Avenue, Beaumont, CA 92223 (951) 845-7743
www.Sladdenengineering.com
October 22, 2020
Discovery Builders California, Inc.
53965 Humboldt Boulevard
La Quinta, California 92253
Subject: Geotechnical Update
Project No. 544-20342
20-10-536
BRES2020-0329
CITY OF LA QUINTA
BUILDING DIVISION
REVIEWED FOR
CODE
COMPLIANCE
DATE03/30/2021 ev JF
Project: Proposed Custom Residence
53804 Ross Avenue 15,847SF S.F.D.
The Madison Club
La Quinta, California
Ref: Geotechnical Investigation report prepared by Sladden Engineering dated January
28,2005; Project No. 544-4810, Report No. 05-01-101
Report of Testing and Observation During Rough Grading prepared by Sladden
Engineering dated March 2, 2006; Project No. 522-4810; Report No. 06-02-120
In accordance with your request, we have reviewed the above referenced geotechnical reports as
they relate to the design and construction of the proposed custom residence to be constructed on
the subject site located at 53804 Ross Avenue within the Madison Club development in the City
of La Quinta, California. It is our understanding that the proposed residential structure will be of
relatively lightweight wood -frame construction and will be supported by conventional shallow
spread footings and concrete slabs on grade.
The referenced reports include recommendations pertaining to the design and construction of
residential structure foundations. The previous reports also address the potential for
liquefaction, subsidence and differential settlement. Based upon our review of the referenced
reports, it is our opinion that the structural values included in these reports remain applicable for
the design and construction of the proposed residential structure foundations.
The allowable bearing pressures recommended in the referenced Geotechnical Investigation
report remain applicable. Conventional shallow spread footings should be bottomed into
properly compacted fill material a minimum of 12 inches below lowest adjacent grade.
Continuous footings should be at least 12 inches wide and isolated pad footings should be at least
2 feet wide. Continuous footings and isolated pad footings should be designed utilizing
allowable bearing pressures of 1500 psf and 2000 psf, respectively. Allowable increases of 300 psf
for each additional 1 foot of width and 300 psf for each additional 6 inches of depth may be
utilized, if desired. The maximum allowable bearing pressure should be 3000 psf. The
recommended allowable bearing pressures may be increased by one-third for wind and seismic
loading.
Sladden Engineering
October 22, 2020 -2- Project No. 544-20342
20-10-536
Lateral forces may be resisted by friction along the base of the foundations and passive resistance
along the sides of the footings. A friction coefficient of 0.48 times the normal dead load forces is
recommended fox use in design. Passive resistance may be estimated using an equivalent fluid
weight of 300 pcf. If used in combination with the passive resistance, the frictional resistance
should be reduced by one third to 0.33 times the normal dead load forces.
The bearing soil is generally non -expansive and falls within the "very low' expansion category in
accordance with the 2019 (CBC) classification criteria. Slab thickness and reinforcement should
be determined by the Project Structural Engineer. We recommend a minimum floor slab
thickness of 4.0 inches and minimum reinforcement of M3 bars at 24 inches on center in both
directions. All slab reinforcement should be supported on concrete chairs to ensure that
reinforcement is placed at slab mid -height.
Slabs with moisture sensitive surfaces should be underlain with a moisture vapor retarder
consisting of a polyvinyl chloride membrane such as 10 -mil visqueen, or equivalent. All laps
within the membrane should be sealed and at least 2 inches of clean sand should be placed over
the membrane to promote uniform curing of the concrete. To reduce the potential for punctures,
the membrane should be placed on a pad surface that has been graded smooth without any sharp
protrusions. If a smooth surface cannot be achieved by grading, consideration should be given to
placing a 1 -inch thick leveling course of sand across the pad surface prior to placement of the
membrane.
The seismic design category for a structure may be determined in accordance with Section 1613
of the 2019 CBC or ASCE?-16. According to the 2019 CBC, Site Class D measured may be used to
estimate design seismic loading for the proposed structures with sufficient understanding of the
subsurface conditions. The 2019 CBC Site Specific Seismic Hazard Analyses are attached.
The subject lot was previously graded during the rough grading of the Madison Club project site.
The rough grading included over -excavation and re -compaction of the native surface soil along
with the placement of engineered fill material to construct the building pads. The site grading is
summarized in the referenced report of Testing and Observation During Rough Grading along
with the compaction test results.
Because the lot has been previously rough graded, the remedial grading required at this time
should be minimal provided that the building area falls within the previously assumed building
envelope. The building areas should be cleared of surface vegetation, scarified and moisture
conditioned prior to precise grading. The exposed surface should be compacted to a minimum of
90 percent relative compaction prior to fill placement. The previously removed soil and any fill
material should be placed in thin lifts at near optimum moisture content and compacted to at
least 90 percent relative compaction.
Sladden Engineering
October 22, 2020 -3- Project No.544-20342
20-10-536
We appreciate the opportunity to provide service to you on this project. If you have any
questions regarding this letter or the referenced reports,. please contact the undersigned.
Respectfully submitted,
SLADDEN ENGINEERING
Brett L. Anderso AND@R90N
Principal Engineer C7 No. 045389
� CNIL
it ENGINEERING
s
SER/ra T'9T,� _ ,,nF
Copies: 4/Discovery Builders California, Tnc.
.. gg`" -
Ja Minor III a JAMES W
S for Geologist MINOR III
No. 9735
N�,
ATF OF CA��F
Sladden Engineering
5 �{I- - Z03 L(2.
Please verify that soils reports contain all of the above Information. in addition, to assure
continuity between the investigation/reporfing stage and the execution stage, please use
the following checklist to verify that the conclusions and recommendations in the report
cover all the required elements. Only then can we be assured that the construction
documents address all of the site soil conditions.
La Qulnta Geotechnical Report Checklist
Does the "Conclusions and Recommendations" section of the report address each of the
following criteria?
"Address" means.
(a) the criterion is considered significant and mitigation measure(s) noted, or;
(b) the criterion is considered insignificant and explicitly so stated.
Yds .No Criterion
C] ❑ Foundation criteria based upon bearing capacity of natural or compacted soil.
[l/ ❑ Foundation criteria to mitigate the effects of expansive sobs.
t� ❑ Foundation criteria based upon bearing capacity, of natural or compacted soil.
l_I ❑ Foundation criteria to mitigate.the effects of liquefaction.
t[I ❑ Foundation criteria to mitigate the effects of seismically induced differential
—/ settlement. - '
Lr ❑ Foundation criteria to mitigate the effects of long-term differential settlement.
CC ❑ Foundation criteria to mitigate the effects of varying soil strength.
❑ Foundation criteria to mitigate expected total and differential setflement.
Any "No" answers to the above checklist should be noted as specific required
corrections.
BRETT L.
ANDERSON
rr0. C45389
CNIL
Project:
Custom Residence
<=0.2,
Project Number:
544-20342
0.907
Client:
Discovery Builders
California, inc
Site Let/Long:
3346582/-116.2479
Controlling Seismic Source:
Southern San Andreas
REFERENCE
NOTATION
VALUE
Site Class
C, D, D default, or E
D measured
Site Class D -Table 11.44
Fa
1.0
Site Class D - 21.3(11)
F„
2.5
0.2*(Sm/SDs)
To
0.137
Sol/Sos
Ts
0.686
Fundamental Period (12.8.2)
T
Period
CRI
Seismic Design Maps or Fig 22-14
Ti
8
Equation 11.4-4-2/3*SMI
SDI
0,6857*
Equation 11.4-2 - Fv*SI
SMI
1.0285*
Cr -
At Perods
<=0.2,
Cr=Cas
Cas
0.907
Cr -At
Periods
>=1,0,
Cr=CRI
CRI
0.89
" Cedo based desigro value. See accompanying data for Site Specific Design values.
Sladden Engineering
REFERENCE
NOTATION
VALUE
Fv (Table 11.4-2)[Used for General Spectrum]
Fv
1.7
Design Maps
S,
1.500
Design Maps
51
0.605
Equation 11.4-1- FA*Ss
SMS
Equation11.4-3 - 2/3*SMs
SOS
--
Design Maps
PGA
0.649
Table 11.8-1
FPGA
1.1
Equation 11.8-1- FPGA*PGA
PGAM
14*
Section 21.5.3
80% of PGAM
0.571
Design Maps
Cas0.907
Design Maps
CRI
0.89
Cr - At Periods between 0.2 and 1.0 Period Cr
use trendline formula to complete 0.200 0.907
0.300 0.905
0.400 0.903
0.500 0.901
0.600 0.899
0.680 0.897
1.000 0.89
Mapped values from httos//seismicmaas.or
PRO BABILISTICSPECr I
2% in 50 year Exceedence
Period
UGHM
RTHM
Max Directional
Scale Factor'
Probabilistic
MCE
0.010
0.802
0.769
1.19
0.915
0.100
1.333
1.305
'1, 1r1
1.553
0.200
1.777
1.747
1.10
2.096
0.300
.2.041
1.939
1.22
2.366
0.500
2.033
1.872
1.23
2.303
0.750
1.686
1.532
1.24
1.900
1.000
1.445
1.286
7..74
1.595
2.000
0.834
0.739
1.24
0.916
3.000
0.573
0.505
1.15
0.631
4.000
0.423
0.371
1..'Z;
0.464
5.000
0.322
0.283
1.7.6
0,357
ProbabiAstic PGA: 0.802
IS ProbabjOsticSalm„151.2Fat_ NO
Project No: 544-20342
'Data Sources:
htt i//e nho k sas eov/hazards/interacive/
htt s://eanhouakeusaseoy/desixnmBRslrtem/
z 5hahi-Baker RotD100/RotD50 Factors (2014)
Sladden Engineering
MCER
DETERMINISTIC SPECTRUM
largest Amplitudes ot6raund Motiqns [onsitl¢dng All spurces Calculated using Weighted Mean of Attenuation Equattorrs'
Canttolling Source: gouthem San Andreas
IS Probabilistic Salm,y<1.2Fa1 NO
Period
Deterministic PSa
Median+S.o for 9%
Damping
Max Directional Scale
Factor!
Deterministic MCE
Section 21.2.2
Scaling Factor
Applied
0.010
0.626
1.39
0.749
- -
0.020
0.628
1.19
0.748
.-�.
0.030
0.639
119
0.761
U.iul
0.050
0.683
1.19
0.813
U..;15
0.073
0.823
1.19
0.979
U:'%J
0.100
0.978
1.19
1.164
1.1 �,4
0.150
1.207
1.20
1.448
'�..•`1'
O.ZOD
1.351
1.20
1.621
!���'�-
0.250
1.444
1.21
1.747
;. x.1'1
0300
1.490
L22
1.818
l.�'x5
0.400
1.490
L23
1.833
......
0.900
1.434
1.23
1.764
.. �..
0.760
1.194
1.24
1.430
-� .
-1.!700
--096fi___.._
_.__.1.24_..___.
_.. 1.197__
__ ��"_"_-__.
1500
O.fi94
1.24
0.861
�.,.o..
2.000
0.529
1.24
0.657
U.i:S!'
3.000
0.363
1.29
0.454
,�...�
4.D00
0.256
1.29
0.322
U.3:7
9A00
0.192
LZ6
0.242
ii2�l:
1.50
� � S.pO
I¢
050
0.00
0.000
Project No: 944-20342
Is Detennlnstic 9al�l<1.5"Fa7 NO
Section 2LZ.25wling Factor. N/A
Deterministic PGA: 0.626
Is Deterministic PGA>=Frw,"0.57 YE5
r NGAWest2GMPEworksheetand
- - Ungorm Cal'rfarnta Earthquake Rupture
Fomcas4 Version 3ftICERF31-Time
pependemmpdel
s Shahi-Baker Rotpi0o/RIND50 Factors
(2019)
Sladden Engineering
L000
z.oa0
3.a0o
a.000
s.00o
Pertgd Isemnds)
__ ___--.--
_
__
--�-D¢cermmiade
MCER
circ cocririr CPFCTRA
Period
Probabilistic
MCE
Deterministic
MCE
Site -Specific
MCE
Design Response
Spectrum (Sa)
0.010
0.915
,.-
0.745
-
0.100
1.553
0.030
1.164
-
0.200
2.096
0.908
1.621
1.636
0.300
2.366
I.;.1.<.
1.818
..-.. -.
0.500
2.303
;..:Ez,
1.764
....-....
0.750
1.900
0.705
1.430
-- -
1.000
1.595
_....-:
1.197
---
2.000
0.916
b.5".7
0.657
_
3.000
0.631
.:. _
0.454
-
4.000
0.464
6.�-'___
0.322
0.250
5.000
1 0.357
1 u.._'.'.
0.242
0.800
SDS:
SDI:
SMS:
SM1:
Site Specific PGAm:
Site Class:
ASCE 7-16: Section
21.4
Site
Specific
0.422
Calculated
0.010
Design
Value
0.020
Value
1.091
0.030
1.091
0. -5
0.908
0.619
0.908
0.060
1.636
0-`•�"-'
1.636
0.728
1.362
0.090
1.362
0.635
0.626
0.838
0.626
0.110
D measured
0.705
0.120
Seismic Design Category -Short* D
SeismicDes ignCategory
* Risk Categories I, II, or III
Sladden Engineering
Period
ASCE 7 SECTION 11.4.6
General Spectrum
80% General
Response Spectrum
0.005
0.422
0.010
0.444
0.020
0.488
0..'••:;u
0.030
0.531
0. -5
0.050
0.619
0.060
0.663
0-`•�"-'
0.075
0.728
0.090
0.794
0.635
0.100
0.838
0.670
0.110
0.881
0.705
0.120
0.925
0.740
0.136
0.995
0.79u
- 50
- - - 1.000
0.800
0.160
1.000
0.800
0.170
1.000
0.800
0.180
1.000
4800
0.200
1.000
0.250
1.000
0. %'-6
0.300
1.000
0.800
0.400
1.000
0.800
0.500
1.000
0.800
0.600
1.000
0,800
0.640
1.000
0.800
0.680
1.000
0.800
0.850
0.807
0.645
0.900
0.762
0.609
0.950
0.722
0.577
1.000
0.686
0.549
1.500
0.457
0.366
2.000
0.343
0.27 �
3.000
0.229
0.183
4.000
0.171
0.137
5.000
0.137
X01%10
Project No: 544-20342
Slada9ana Engineering
=Probabilistic MCE
Deterministic MCE
ma® Site -Specific MCE
Design Response Spectrum
—Df —ASCE 7 Section 11.4.6 General Spectrum
•–..==g0%General Response Spectrum
Project No: 54420342