HomeMy WebLinkAboutPD 2020-0042; 4100 SUNNYHILL DRIVE; GEOTECHNICAL INVESTIGATION 4100 SUNNYHILL DRIVE; 2020-11-25HETHERINGTON ENGINEERING, INC.
SOIL & FOUNDATION ENGINEER ING • ENGINEERING GEOLOGY• HYDROGEOLOGY
Ron Severino
3295 Pio Pico Dri ve
Ca rlsbad, California 92008
Subject: GEOTECHNJCAL INVESTlGATTON
Proposed Retain ing Wall
4 100 Sunny Hill Drive
Carl sbad, California
References: Attached
Dea r Mr. Severino:
November 25, 2020
Project No. 9235.1
Log No. 2 1222
ln accordance with your request, we have performed a geotechni ca l investigation for a
proposed retaining wa ll at the subject site. Our work was performed in October and
November 2020. The purpose of our investigation was to evaluate the geologic and soil
conditions within the area of the proposed retaining wall and Lo provide grading and
foundation recommendations. Our scope of work included the following:
• Research and review of available plans and geologic literature pertinent lo the site
(see References).
• Su bsurface exploration cons isting of one test pit and one hand -auger borin g for
soil/bedrock observation and sampling to a maxim um depth of 6-feet.
• Laboratory testing of samples obtained from the subsurface exp loration.
• Engineering and geologic analysis.
• Preparation of this report providing the results of our field and laboratory work,
analyses, and our conclusions and recommendations.
SITE DESCRJPTlON
The subject property is located at 4100 Sunny Hill Drive, Carlsbad, Ca lifornia (see
Location Map, Figure l ). The relatively level building pad suppo1ts an existing sin gle-
fam ily residence with attached garage. Topographically, the site gently slopes down from
east to west. An approximately 3±-feet high retaining wall exists along the north and west
si des of the property. The west side retaining wal l ex ists outside of the property line. The
5365 Avenida Encinas, Suite A • Carlsbad, CA 92008-4369 • (760) 931 -1 917 • Fax (760) 931-0545
333 Third Stree • Laguna Beach, CA 9265 • (949) 715-5440 • Fax (949) 715-5442
www.hetheringtonengineering.com
GEOTECHN ICAL INVESTIGATJON
Project No. 9235.1
Log No. 2 1222
November 25, 2020
Page 2
property is bounded by Sunny f-1 i II Drive lo the wcsl, Tamarack /\ venue to the north and
ex isting single-fam ily residential properties to the south and east.
PROPOSE D CONSTRUCTION
Proposed construction consists of dem olishing th e west sid e retaining wa ll and
constructing a new, 30-inch high retain ing wall approximately 4-feet east o f the existing
wa ll. Th e retaining ,-vall wil l be supported on conventi onal continu ous rootings.
SUBSURFACE EXPLORATION
Subsurface conditions were explored by manually excavating on e hand-au ger boring and
one test pit to depths of 5 and 6-feet, respectively, in the area of the proposed retaining
wa ll. The locations of the proposed retaining wall, hand-auger boring and test pit are
shown on the attached Plot Plan, Figure 2.
The subsurface exploration was supervised by a engineer from thi s office, who visually
classified the soil, and obtained bulk and relatively undisturbed samples for laboratory
testing. The so ils were visually classified accordiJ1g to the Unified Soil Cla ssification
System. Classi ftcations are shown on the attached Boring Log and Log of Test Pits,
Figures 3 and 4.
LABORATORY TESTING
Laboratory testing was performed on samples obtained during the subsurface exploration.
Tests performed consisted of the following:
• Dry Density/Moisture Content (ASTM: D 22 16)
• Maximum Dry Density/Optimum Moisture Content (ASTM: D 1557)
• Direct Shea r (ASTM: D 3080)
• Solu ble Sulfate (Cal Test 417)
The results of the dry density and moisture content determinations are presented on the
Boring Log and Log of Test Pits, Figures 3 and 4. The rema ining laboratory test results
are presented on the attached Laboratory Test Results, Figure 5.
HETHERINGTON ENGINEERING, INC.
GEOTECHN1CAL INVEST IGATION
Project No. 9235.1
Log No. 2 1222
Novem ber 25, 2020
Page 3
SOIL AN D Gl~OLOGlC CONDIT IONS
I. Geologic Setting
The subject site lies within a relatively level marine terrace that is conta ined within
the coastal plain region of nort hern San Diego County, Ca lifornia. The coastal plai n
region is characterized by numerous regressive marine terraces of Pleistocene age that
have been establi shed above wave-cut platforms of underlying Eocene bedrock and
vvere fo rm ed during glacio-eustatic changes in sea level. The terraces extend from
areas of higher elevations east of the site and descend generally west -southv.iest in a
"sta irstep" fashion down to the present clay coastline. These marine terraces increase
in age eastward. The site area is contained within the central portion of the USGS
San Luis Rey 7.5-minute quadrangle.
As observed in the subsurface exploration, the site is mantled by granular fill
underlain by Quaternary paralic deposits. Structurally, bedding within the para lic
deposits is considered to be essentially massive. The paralic deposits are granular and
have a very low expansion potential.
2. Geologic Uni ts
a. fill -Fill mantles the site to depths of 2.5 to 3-feet. The fill consists of light
orange brown sil ty sand that is dry, loose, and contains scattered construction
debris and rounded cobble.
b. Paralic Deposits -Paralic deposits underlie the fi ll to the maximum depth
explored. The paralic deposits co nsist of orange brown, coarse, silty sand with
lenses of sandy clay and are medi um dense to stiff.
3. Groundwater
Groundwater was not encountered in the excavations. It should be noted, however,
that fluctuations in the amount and level of groundwater might occur due to variations
in rainfall, irrigation and other factors that may not have been evident at the time of
our field in vestigation.
SEISMlClTY
The fo llowing table li sts the lmown active fau lts that would have the most significant
impact on the site:
HETHERINGTON ENGINEERING, INC.
GEOTECHNJ CA L INVESTIGATlON
Proj ect No. 9235 .1
Log No. 21222
November 25, 2020
Page 4
Fault
Rose Canyon
(9.2-kilomelers/ 5.7-m iles southwest)
Coronado Bank
(35-kil omelers/ 22-mil es southwest)
Elsinore (Julian Segment)
(3 5-kil ometers/ 22-mi les northeast)
SEJSMlC EFFECTS
I. Ground Accelerations
Maximum Probable
Earthquake Slip Rate
(Moment Magnitude) (mm/yea!')
7.5 1.5
7.4 3
7.5 .... .)
The most significant probable earthquake to effect the property would be a 7.5
magnitude ea rthquake on the Newport Inglewood/Rose Canyon fault. Based on
Section 1803.5.12 of the 20 19 Califo rnia Bu ilding Code and Section 11 .8.3 of ASCE
7-16, peak ground accelerations (PGAM) of 0.517g are possible for the design
earthquake.
2. Lands lidin g
Review of the referenced geologic literature ind icates that the subject property has no
previously mapped ancient landslide deposits. The risk of seismically induced
landslidin g effecting the site is considered low due to th e gently sloping site
topography.
3. Ground Cracks
The risk of surface fault rupture due to active fau lting is considered low due to the
absence of a known active fau lt on site. Ground cracks due to shaking from seism ic
events in the region are possible, as with all of southern California.
4. Liquefaction
The risk of seismically induced liquefaction within the site is considered very lovv due
to the dense nature of the paralic deposits and lack of shal low groundwater.
HETHERINGTON ENGINEERING, INC.
GEOT ECHNICAL fNVESTTGAT rON
Project No. 9235.1
Log No. 2 1222
November 25, 2020
Page 5
5. Tsunam is
The risk ror seismica lly generated ocean waves to effect the site is considered low
clue to the elevation of the site above sea level.
CONCLUSIONS AND RECOMMENDATIONS
I. General
The proposed reta ining wall is considered reasible from a geotechnical standpoint.
foundation plans should take into account the appropriate geotechnical reaturcs of the
site. Assuming that Lhe recommendations presented in this report and good
construction practices are utilized during the design and construction, the proposed
construction is not anticipated to adversely impact the adjacent properties fro m a
geotechn ica I standpoin t.
2. Seismic Parameters for Structural Design
Seismic considerations that may be used for structu ral design at the site include the
fo llowing:
a. Ground Motion -The proposed retain ing wall should be des igned and constructed
to resist the effects of seism ic ground motions as provided in Section 1613 of the
20 19 California Building Code.
Site Address: 4 100 Sunny Hil l Drive, Carlsbad, Californ ia
Latitude:
Longit11cle:
33.1 5406°N
-l1 7.32 122°W
The proposed retaining wall has a fundamental period of vibration less than 0.5s,
consequently, the exception to site response analyses in ASCE 7-16 (Section .
20.3.1. 1) has been used. Using the Stru ctural Engineers Association Seism ic
Design Maps website, the seism ic parameters Fv, S1v11, and Soi are null and not
applicable. The Simplified Alternative Structural De.sign Criteria provided in
Section 12.14 of ASCE 7-16 should be used.
b. Spectral Response Accelerations -Us in g the location of the property and data
obtained from the U.S.G.S. Earthquake Hazard Program, short period Spectral
Response Acce lerations Ss (0.2 second period) and S1 (1.0 second period) are:
HETHERINGTON ENGINEERING, INC.
GEOTECHNJCAL INVESTIGATION
Project No. 9235 .1
Log No. 2 1222
November 25, 2020
Page 6
Ss = 1.023g
S1 = 0.372g
c. Sile Class -Tn accordan ce with Chapter 20 of ASCE 7, and the und erlying
geologic conditions, a Site Class D is considered app ropriate for the subject
property.
cl. Site Coeffi cients Fa and fv -ln accordan ce with Table [61 3.3.3 and considering
the values ofSs and S1, Sile Coefficients fo r a Class D site are:
F.1 = 1.09 1
fv = nu ll
e. Spectral Response Acceleration Parameters Sms and Sm 1 -In accordan ce with
Section 161 3.3.3 and considering the values of Ss and S 1, and Fa and Fv, Spectral
Response Acceleration Parameters for the Maximum Considered Earthquake are:
Sms= 1.116g
S1111 =null
f. Design Spectral Response Acceleration Parameters Sds and Sd1 -In accordance
with Section 16 13.3.4 and considering the va lues of Sms and Sm 1, Design Spectral
Response Acceleration Parameters fo r the Maximum Consi dered Earthquake are:
Sds = 0.744g
Scl1 =null
g. Long Period Transition Period -A Long Period Transition Period of TL = 8
seconds is provided fo r use in San Diego Cou nty.
h. Seismic Design Category -ln accordance with Tables 1604.5, 1613.3 .5(1) and
1613.3.5(2), and ASCE 7, a Risk Category 11 and a Seismic Design Category D
are considered appropriate for the subject properly.
3. Foundation Recommendations
The proposed retaining wall may be supported on conventiona l contin uous footi ngs
fo unded at least 12-inches into approved parali c deposits, at least 12-inches wide, and
reinfo rced with a minimum of four #4 bars, two top and two bottom.
HETHERINGTON ENGINEERING, INC.
GEOTECHNTCAL INVESTTGA TION
Projec t No. 9235 .1
Log No. 2 1222
November 25, 2020
Page 7.
Fo undations bearing as recom mended may be designed ror a dead plus live load
bearing value of 2000-po unds-per-square-fool. This value may be increased by one-
third fo r loads including wind and se ismic forces. A lateral bearing value of 250-
po unds-per-squ are-foo t per foot of depth and a coefficient of fr iction between
fo undation soil and concrete of 0.35 may be assumed. These values assume that
footings vvill be poured neat against the found ation soils. Footing excavations shou ld
be observed by the Geotechn ical Consulta nt prior to the placement of reinforcing
steel in order to veri fy thal they are founded in sui table bearing materials.
4. Retaining Wa lls
Retaining wa ll foundations should be designed in accordance with the previous
fo undation recommendations. Retaining wa lls free to rotate (cantileve red walls)
should be designed for an acti ve pressure or 40-pouncls-per-cubic-foo l (equi valent
fluid pressure) assuming level backfill consisting of onsite granul ar soils. Walls
restrain ed from movement at the top should be designed for an at-rest earth press ure
of 60-pounds-per-cubi c-foot (equivalent fluid pressure). Any additional surcharge
pressures behind the retaining walls should be added to these va lues.
Retaining wall s should be provided with adequate drainage to prevent buildup of
hyd rostatic pressure and should be adequately waterproofed. The subdrain system
behind retaining walls should consist at a minimum of 4-inch diameter Schedule 40
(or equivalent) perforated (perforations "down") PVC pipe embedded in at least 1-
cubi c-foot of 3/4-inch crushed rock per lineal foot of pipe all wrapped in approved
filter fabri c. Other subdrain systems that may be contemplated fo r use behind
retaining walls due to the ultimate design and construction methodology wi ll be
consid ered on a case-by-case basis. Recommendations for wall waterproofin g should
be provided by the Project Architect and/or Structural Engineer.
The lateral pressure on retaining walls clue to earthquake motions (dynamic lateral
force) may be cal culated as PA= 3/8 y H2k1i where
'Y
H
dynamic lateral force (pounds/foot)
unit weight = 110 (pounds-per-cubic-foot)
height of wall (feet)
seismic coefficient = 0.1 7
HETHERINGTON ENGINEERING, INC.
GEOTECHNICAL lNYESTIGATfON
Project No. 9235.1
Log No. 2 1222
November 25, 2020
Page 8
The dynamic latera l force may also be expressed as 14.0-pounds-per-cubic-rool
(equ ivalent nuid pressure).
The dynam ic latera l force is in add ition to the static force and should be app lied as a
triangular distribution at 1/3H above the base of the wa ll. The dynamic latera l rorce
need not be applied to retain ing wal.l s 6-feet or less in height.
5. Reta ining Wall Backfil l
All retainin g wa ll backfi ll shou ld be compacted lo at least 90-percent relative
compaction (ASTM: D 1557). Backfill should be tested and observed by the
Geo techn ical Co nsu ltanl.
4. Sulfa te Content
A rep resentative sample of the on-site so ils was sub mitted fo r sul fate testing. The
resul t of the sulfate test is summarized on the Laboratory Test Results, Figure 5. The
sulfate content is consistent with a not applicable sul fate exposure classification per
Table 4.2.1 of the American Concrete In st itute Publication 3 18, consequently, no
special provisions for sulfate resistant concrete are considered necessary. Other
corrosivity testi ng has not been perform ed, consequently, on-site so ils should be
assumed to be severely corrosive to buried metals unl ess testing is performed to
indica te otherwise.
6. Recommended Observation and Testing During Co nstruction
The fo llowin g tests and/or observations by the Geotechnical Consultant are
recommended:
a. Foundation excavations pri or to placement of fo rms and reinforcement.
b. Retaining wall backdrains and backfi ll.
7. Foundation Plan Review
Foundation plans should be reviewed by the Geotechnical Consul tant to confirm
conformance with the recommend ations presented here in or to modify the
recommendations as necessary.
HETHERINGTON ENGINEERING, INC.
GEOTECHN ICAL INVESTIGATION
Project No. 9235.1
Log No . 21222
Novem ber 25, 2020
Page 9
LIMITATIONS
The ana lyses, concl usions and recommendations contained in this report are based on site
conditi ons as they existed at the time of our investigation and further assume the
excavations to be representative of the subsurface conditions throughout the site. If
different subsur face cond itions fr om those encountered during our exploration are
observed or appear to be present in excavations, the Geotechnical Co nsultant shou ld be
promptly notifi ed for review and reconsideration of recommendations.
Our investigation was performed using the deg ree of ca re and skill ordinaril y exercised,
under similar circumstances, by reputable Geotcchnical Consultants practicing in this or
similar local ities. No other warranty, ex press or implied, is made as to the conclusions
and professional adv ice included in this report.
This opportunity to be of service is sincerely ap preciated. If you have any questions,
please call this office.
Respectfully submitted,
HETHERLNGTON ENGINEER ING, fNC.
Jaemin G. Blackwelder
Engineer in Traini ng J 7-505-14 Civil Engineer
Geotechnical Engin
Attachments: Location Map
Plot Plan
Boring Log
Log of Test Pits
Laboratory Test Results
Distribution: 4-Addressee
Figure I
Figu re 2
Figu re 3
Figu re 4
Figu re 5
( expires 3/3 1 /22)
1-via e-mail (ronseverino44@gmai l.com@grnail.com)
HETHERINGTON ENGINEERING, INC.
REFERENCES
I. ASCE 7-16, "Minimum Design Loads for Buildings and Other Structures", Am erican
Society of Civil Engineers/Structural Engineers lnstilule.
2. Calirorni a Emergency Management Agency, "Tsunami Inundati on l\lfap for
Em ergency Planning, Oceanside Quadrangle/San Lui s Rey Quadrangle," dated Ju ne
I, 2009.
3. California Build ing Standards Commission, California Bu ilding Code, 20 19 Edition.
4. lCBO, ·'Maps of Known Active Fault Near-Source Zon es in California and Adjacent
Portions or Nevada," Cali forn ia Division of Mines and Geology, 1998.
5. Peterson, Mark P., et al, "Docum entati on for the 2008 Update of the United States
National Seismi c Hazards Maps," USGS Open Fi le Report 2008-1 128, dated 2008.
6. Raymond Sharpe, "Site Plan and Demolition P lan, Glesrnann Residence, 4100 Sunny
Hill Drive, Carlsbad, Cal iforn ia," elated September 24, 2020.
7. Structural Engineers Association, Seismic Design Maps Website.
8. Tan, Siang S. and Kennedy, Michael P., "Geologic Ma ps of the Northwestern Part of
San Diego County, California," California Division of Mines and Geo logy, Open-File
Report 96-02, dated 1996.
9. U.S. Geological Su rvey, "2008 National Seismic Hazards Maps-Source Parameters",
Earthquake Hazards Program.
10. Weber, F.H. Sr., "Recent Slope Failures, Ancient Landslides, and Related Geology of
th e North-Central Coastal Area, San Diego County, California," California Division of
Mines and Geology, Open-File Report 89-l 2LA, dated 1982.
11 . 2007 Working Group and California Earthquake Probability, "The Uniform Californ ia
Earthquake Rupture Forecast, Version 2 (UCERF-2)," USGS Open File Report 2007-
1437 and California Geological Survey Special Report 203, dated 2008.
HETHERINGTON ENGINEERING, INC.
Project No. 9235.1
Log No. 21222
ADAPTED FROM: The Thomas Guide, San Diego County, 57th Edition, Page 1106
LOCATION MAP
HETHERINGTON ENGINEERING, INC.
SCALE: 1" -2000'
(1 Grid Equals: 0.5 x 0.5 miles)
4100 Sunny Hill Drive
Carlsbad California
GEOTECHNICAL CONSULTANTS PROJECT NO. 9235.1 I FIGURE NO. 1
2
PROPOSED RETAINING WALLS
APPROXIMATE LOCATION OF TEST PIT
APPROXIMATE LOCATION OF HAND AUGER BORING
LEGEND
TP-1
HA-1
TP-1HA-1
PLOT PLAN
GEOTECHNICAL CONSULTANTS
HETHERINGTON ENGINEERING,INC.
PROJECT NO. FIGURE NO.
012
5 1015200
4100 Sunny Hill Drive
Carlsbad, California
9235.1NSCALE: 1" = 10'
DRILLING COMPANY: HEI RIG: Hand Auger DATE: 10/30/20
BORING DIAMETER: 4" DRIVE WEIGHT: 40Ib DROP: 30" ELEVATION: I +
-w E--< w ,_:i >--< -w ,_:i p., E--< E--< o\O if) -w p., ~ 0 H -if) BORING NO. HA-1 i:,.. ~ 0 if) w st! (/) -if) i:,.. z 0:: E--< ,_:i
::r: if)
-----
w p z u u w if) 0 -E--< w E--< :,,:; :> 8: 4--l if) E--< ,_:i ifl p., ,_:i H 0 >--< {) H z H i,.l . p 0:: ,_:i 0:: p, 0 0 0 p 0 ill 0 ill 0 -:,:: u if) -SOIL DESCRIPTION -0.0 SM FILL: Light orange brown silty sand, dry, loose, scattered
construction debris and rounded cobble, caving in top 2.5-feet
-'--
--~
11 2 6.6
PARALIC DEPOSITS: Orange brown silty sand and sandy clay, --moist, dense/stiff .__
->-~
11 2 17.5
5.0
Total depth 5-feet
No seepage
-Caving from O to 2.5-feet '--
-.._
--
--
10.0--
--
--
--
-'--
15.G
BORING LOG
HETHERINGTON ENGINEERING,
4100 Sunny Hill Drive
INC. Carlsbad, California
GEOTECHNICAL CONSULTANTS PROJECT NO. 9235.1 I FIGURE NO. 3
I
BACKHOE COMPANY: HEI
w ->-< >-< i:,: E--< w E--< E--< :=i z ::r: E--< ....:l H H -E--< w E--< w :,,; 0.. (/) E--< (/) 4-l (/) E--< 0.. w 5~ z (/) :>-< Z 0 HZ-w ti, l'.il w i:,: w °' Q Q o\O o-O'.l (/) 0 E--< oo-:8 u -~o.o
-x
115 7.0
--
5.o-x~
11 5 7.8
-
10.0-
-
-
-
15.0
(/) -(/) <C (/)
>---1 u u
>---1 (fJ H
0 :=i
(/) -
SM
BUCKET SIZE: Hand Pit DATE: 10/30/20
SOIL DESCRIPTION
TEST PIT NO. TP-1 ELEVATION: ' +
FILL: Light orange brown silty sand, dry, loose, scattered
construction debris and rounded cobble, caving in top 2.5-feet
@1': sampler refusal, soil too loose
PARALIC DEPOSITS: Orange brown silty sand, moist, medium
dense, coarse grained
@4': start hand auger
@5': orange brown and gray silty sand with sandy clay lenses,
moist, medium dense/stiff
Total depth 6-feet
No seepage
Caving from Oto 2.5-feet
LOG OF TEST PITS
HETHERINGTON ENGINEERING, INC.
4100 Sunny Hill Drive
Carlsbad, California
GEOTECHNICAL CONSULTANTS PROJECT NO. 9235.1 I FIGURE NO. 4
.._
-
-
-
-
LABORATORY TEST RESULTS
DIRECT SHEAR
(ASTM: D 3080)
Angle of Internal Cohesion
Sample Location Friction (psi) Remarks
(0)
HA-1 @4' 38 250 Undisturbed, soaked, consolidated,
drained
TP-1 @ 0-2' 30 200 Remolded to 90% at optimum,
soaked, consolidated, drained
MAXIMUM DRY DENSITY/OPTIMUM MOISTURE CONTENT
Sample Location
TP-1 (a), 0-2'
Sample Location
TP-1 (a), 0-2'
TP-1 (a), 4-6'
(ASTM: D 1557 A)
Description Maximum D11' Optimum Moisture
Density foci) Content (%)
Brown silty sand 124.5 10.0
SULFATE TEST RESULTS
(Cal Test 417)
Soluble Sulfate in Soil (%)
0.0020
0.0330
Fig ure 5
Project No. 9235.1
Log No. 21222