HomeMy WebLinkAboutPD 2022-0003; KEMPER RESIDENCE; UPDATED GEOTECHNICAL REPORT; 2022-07-01ALL,IED EARTH TECHNC•LOGY
ROBERT CHAN. P.E.
7915 SILVERTON AVENUE, SUITE 317
SAN DIEGO. CALIFORNIA 92126
PH. (858) 586-1665 FAX (858) 586-1650
(6 I 9) 44 7-474 7
UPDATE GEOTECHNICAL REPORT
PROPOSED RESIDENTIAL BUILDING SITE
7133 A VIARA DRIVE
CARLSBAD, CALIFORNIA
FOR
MR. STEVE KEMPER
PROJECT NO. 21-1127C6
JULY 1, 2022
ALLIED EARTI-1 TECHNOLOGY
7915 SIL VER TON A VENUE. SUITE 317
SAN DIEGO. CALIFORNIA 92126
PH. (858) 586-1665 FAX (858) 586-1650
(619)447-4747
ROBERT CHAN. P.E.
July 1, 2022
Mr. Steve Kemper
Clo Marrokal Design Center
9474 Kearny Villa Road, Suite 205
San Diego, CA. 92126
Subject: Project No. 21-l 127C6
Update Geotechnical Report
Proposed Residential Building Site
713 3 A viara Drive
Carlsbad, California
Dear Mr. Kemper :
In accordance with your request, we have performed an update geotechnical report for the
proposed residential building site on subject property, more specifically referred to as being Lot
No. 29 of Tract No. 85-35, according to Map thereof No. 12412 (APN 215-610-28-00), in the
City of Carlsbad, State of California.
It is our understanding that a single-family residence is proposed for the site. The proposed
structure, will be of wood-frame/stucco and slab-on-grade construction.
The approximate location of subject property is shown on Figure No. 1, entitled, "Site Location
Map".
The purpose of this update geotechnical investigation was to inspect and determine the subsurface
soil conditions and certain physical engineering properties of the soils beneath the site, so that
engineering recommendations could be presented for the safe and economical construction of the
residence as proposed.
1. In order to accomplish this purpose, the following were accomplished :
a. Review of"As-Built Grading Plans, Aviara, Carlsbad Tract No. 85-35, Unit D"
dated December 30 1991.
b. Review of "As-Graded Geotechnical Repot, Units A through E, A viara, Carlsbad,
California", dated January 18, 1990.
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7133 Aviara Drive
c. A reconnaissance of the site, and the excavation of 3 exploratory trenches on
July 20, 2021.
d. Preparation of this Update Geotechnical Report to present our finding and
recommendations.
2. From the review of documents and site inspection, it was determined that :
a. Subject property is a rectangular-shaped property of approximately 0.25 acres,
situated on the west side of A viara Drive. Topographically, the site is
approximately 2 feet lower than the lot to the north and approximately 2 feet higher
than the lot to the south. The site is graded as a split level lot, with a 5-foot
descending slope between the eastern and western portions of the site. A
descending slope at the west end of the existing pad building descends onto the
A viara golf course.
Proposed site grading will consist of slight elevation of the existing pads, and the
import of 385 cubic yards of fill soils.
b. The site was graded as part of the A viara development between April and
November, 1989. Currently the site is vacant, and covered with low weeds. There
were no evidence of any seepage, erosion or slope instability.
c. Three exploratory trenches were excavated on the property. The location of these
exploratory trenches ae shown on Figure No. 2, entitled, "Approximate Location of
Exploratory Trenches". The exploratory trenches were excavated to a depth of 8
feet below existing ground surface. The soil type encountered consist of light
brown/light gray, dense to very dense silty fine sand of the Torrey Sandstone
Formation.
Samples of the soils encountered were obtained for laboratory testing and analysis.
The results of the laboratory test are presented on page L-1 hereto.
Laboratory test results indicate that the on-site soils possess low expansion
potential (Expansion Index= 22), and a sulfate content of 0.003%.(negliglble)
d. Regional and local faulting
With regard to local faulting, our review of the Geologic Map of the Encinitas and
Rancho Santa Fe Quadrangles (Tan and Kennedy, 1996) indicates the site is not
underlain by known active or potentially active faults. Tan and Kennedy (1996)
indicate that several steeply dipping northwest trending short fault segments no
Project No. 21-1127C6 Steve Kemper 07 /0 l /22 Page 3
7133 Aviara Drive
more than a few hundred feet in length lie to the north and east of the site.
The closest active fault is the Rose Canyon fault that lies offshore several miles to
the west. The Coronado Bank Fault is the nearest regional fault and lies
approximately 24 miles to the west. Other active regional faults, the Elsinore, San
Jacinto, and San Andreas Faults lie approximately 28, 50, and 80 miles,
respectively, to the east.
e. Mapping of the Encinitas Quadrangle by Tan and Griffen for the California
Division of Mines and Geology ( 1995) indicates the site lies in Hazard Category
3-1 defined as generally susceptible to land sliding particularly when adverse dips
are present in graded cut slopes. Review of historic aerial photographs that predate
the development of the property made for this report indicates there is no
geomorphic evidence of past land sliding and it is concluded the presence of an
ancient landslide in this area is unlikely. In addition, the original geotechnical
report prepared by San Diego Soils Engineering for the development of the
subdivision, then known as Pacific Rim Country Club and Resort ( dated January
29, 1986) also indicates that there re no landslides present in the area of Aviary
Drive. Several large landslides were identified in that report that are present on the
west side of the canyon below and to the west of A viara Drive. The presence of
these landslides will not adversely affect the stability of the subject property.
The geologic unit underlying the site as indicated by test pits placed during our
geotechnical investigation of the site is composed of moderately cemented
sandstone that is not prone to seismic induced land sliding or surficial instability.
Manufactured and proposed slopes on the site do not exceed 5 feet in height and
once they are properly landscaped with erosion resistant vegetation they will not be
subject to surficial instability or creep. Since the site is underlain by sandstone
bedrock, total and differential settlements are anticipated to be less than one inch
across the length and width of the floor slab.
The site is located 1.6 miles from the Pacific Ocean at an elevation of approximately
263 feet. Accordingly it is our professional opinion that the proposed residence
will not be subject to tsunami inundation.
The site classification and Spectral response characteristics are included on Page 6
of our geotechnical report.
3. Based on the results of the document review and site inspection, there appear to be no
significant geotechnical hazard constraints on site that preclude the proposed development,
and it is our opinion that the development is feasible from a geotechnical engineering
Project No. 21-1127C6 Steve Kemper 07/01/22 Page 4
7133 A viara Drive
standpoint, provided that the recommendations presented in this report are incorporated
into the design plan(s) and are properly implemented during the construction phase:
Grading
a. There will be no impacts to adjacent property and improvements as a result of
site grading and construction.
b. The grading of subject property has been accomplished as part of mass grading of
Aviara development in 1989, The grading of subject building pad had been done
in accordance with the approved grading plans, and has remained substantially in
the same condition, with no changes. It is our conclusion that the existing building
pad is adequate for it intended purpose as support of the proposed residential
building.
However, the upper soils have been subject to weathering since grading was
completed inl 989, and the upper 12 inches of the on-site soils were found to be dry
and loose.
c. It is recommended that the upper soils within 5 feet outside the foundation line of
the proposed structure(s) be scarified to a depth of 12 inches. The scarified soils
should be properly moistened, and uniformly compacted to at least 90 percent of
maximum dry density in accordance with ASTM Dl557, in order to provide an
uniform base for the slab of the proposed structure(s)
Foundation and Slab Design
d. It is recommended that a safe allowable soil bearing value of 2,000 pounds per
square foot be used for the design and checking of continuous footings that are 12
inches in minimum horizontal dimension, and isolated pier footings that are 15
inches in minimum horizontal dimension, and are embedded at least 12 inches (for
single story) and 18 inches (for two stories) below the surface of the competent
natural or compacted fill soils.
e. It is recommended that the continuous footings for the proposed structure(s) be
reinforced with a minimum of 4 #5 rebars; two rebars located near the top, and the
other two rebars near the bottom of the footings. All isolated pier footings should
be reinforced with a minimum of 2 #5 rebars in both directions, placed near the
bottom of the footings.
f. The concrete slab-on-grade should be 4 ½ inches in thickness, and be reinforced
with #3 rebars @ 18 inches on center in both directions, placed at mid-height of
Project No. 21-l 127C6 Steve Kemper 07/01 /22 Page 5
7133 Aviara Drive
concrete slab. The concrete slab should be underlain by 4 inches of clean sand, a
10-mil moisture barrier and covered by another inch of clean sand.
The above foundation and slab reinforcement requirements are based on soil
characteristics, and should be superseded by the requirements of the project
architect.
g. Foundations placed closer to the existing slope should be deepened such that
the outer edge of the foundation along the bottom is at least 5 feet back from the
face of slope at that level.
h. It is recommended that our firm inspect the foundation trench excavations to ensure
proper embedment into competent natural or compacted fill soils.
1. The soils in the exploratory trenches were loosely backfilled after completion of
the field investigation. It is recommended that these exploratory trenches be located
during the development of the site, and the backfill sols removed and them properly
compacted with a backhoe mounted sheepsfoot roller.
J. It is recommended that surface drainage along the perimeter of the building be
allowed to flow away from the structure at a minimum gradient of 2 percent for a
distance of at least 5 feet. No surface water is permitted to pond adjacent to
the structure.
k. The on-site soils possess negligible sulfate content. The on-site soils also possess
low expansion potential, and no special design of foundation and slab to resist the
detrimental effects of expansive soils are necessary.
I. According to the project civil engineer, no infiltration of on-site storm water is
proposed.
Lateral Loading
m. To resist lateral loads, it is recommended that the pressure exerted by an equivalent
fluid weight of 300 pounds per square foot per foot of depth (maximum of 1,200
pounds per square foot) be used for footings or shear keys poured neat against
competent natural or compacted fill soils. The upper 12 inches of material in areas
not protected by floor slabs or pavements should not be included in the design for
passive resistance. This value assumes that the horizontal distance of the soil mass
extends at least 10 feet or three times the height of the surface generating the passive
pressure, whichever is greater.
Project No. 21-1127C6 Steve Kemper 07/01 /22 Page 6
7133 Aviara Drive
n. A coefficient of sliding friction of 0.35 (total frictional resistance equals
coefficients of friction times the dead load) may be used for cast-in-place concrete
on competent natural or compacted fill soils. Footings can be designed to resist
lateral loads by using a combination of sliding friction and passive resistance. The
coefficient of friction should be applied to dead load forces only.
o. Seismic earth pressures can be taken as an inverted triangular distribution with a
maximum pressure at the top equal to 12H pound per square foot (with H being the
height ofretained earth in feet). This pressure is in addition to the static design wall
load. The allowable passive pressure and bearing capacity can be increased by 1/3
in determining the stability of the wall. A factor-of-safety of 1.2 can be used in
determining the stability of the retaining wall under seismic conditions.
p. The seismic coefficients in accordance with the current California Building Code
were determined and the results are presented below :
Site Coordinates : Latitude = 33.1014
Longitude = -117.0290
Site Class = C
Spectral Response Acceleration
At Short Periods Ss = 0.896 g
Spectral Response Acceleration
At I -second Period SI = 0.326 g
Sms = FaSs = 1.075 g
Sml = FvSl = 0.489 g
Sds = 2/3*Sms = 0.717 g
Sdl = 2/3*Sml = 0.326 g
Seismic Design Category = D
Fa = 1.2
Fv = 1.5
q. In consideration of the competent natural and compacted fill soils underlying the
site, and the lack of a permanent groundwater table near the ground surface, it is
our opinion that soil liquefaction does not present a significant geotechnical hazard
to the proposed site development
r. It is recommended that our firm review the foundation plans to ascertain that the
recommendations presented herein are incorporated.
s. We have reviewed the project grading and foundation plans, and confirmed that the
plans have been prepared in accordance with the geotechnical recommendations.
Project No. 21-1127C6 Steve Kemper 07/01 /22 Page 7
7133 Aviara Drive
t. It is further recommended that the proposed residence be constructed in
accordance with the approved plans and applicable regulations, except where
items 2(a) to sr) above are more stringent.
Page L-1 , and Figure Nos. I to 5, inclusive are parts of this report.
Michael W. Hart CEG 706
Engineering Geologist
Project No. 21-1127C6 Steve Kemper
7133 Aviara Drive
REFERENCE
07/01/22
-Aerial Photographic, vertical -San Diego County, 1978/79, flt 15, frames 33 and 34
California Building Code, 2019, Title 24, Part 2 Volume l & 2
Page 8
California Department of Conservation, Division of Mines and Geology (California Geological Survey),
1997.
-Civil Landwork -Grading Plan for Kemper Residence, dated February 17, 2022
Foundation and Earth Structures, Naval Facilities Engineering Command, DM7.02
"Green Book" Standard Specifications for Public Works Construction, Public Works Standards, 2018
edition.
Kennedy, M.P. and Tan S.S., 2005 Geologic Map of the San Diego 30' x 60' Quadrangle, California Geologic
Survey and U.S. Geological Survey digital map series.
Lindavall, S.C., Rockwell, T.K., and Lindvall, C.E., 1990, the seismic hazard of San Diego revised: New
evidence of Magnitude 6+ Holocene earthquakes on the Rose Canyon Fault Zone, in Proceedings of U.S.
Tan. S.S., and Kennedy, M.P., 1996, Geologic Maps of the Encinitas and Rancho Santa Fe 7.5 min.
Quadrangle, Calif., DMG Open File Report 96-92.
Tan, S.S.,and Giffen, 1995, Preliminary Landslide Map of the Encinitas Quadrangle, Calif. Div. of Mines
and Geology, DMG open file report 95-04.
Project No. 21-l 127C6 Steve Kemper 07/01 /22 Page L-1
7133 Aviara Drive
LABORATORY TEST RESULTS
1. The Expansion Index of the most clayey soils was determined in accordance with
A.S.T.M. D4929-08. The results of the test are presented as follows:
Soil
Type
1
Soil Expansion
Description Index
Light brown/light gray silty fine sand (SM) 22*
*Considered to possess LOW expansion potential
LABORATORY R E P O R T
Telephone (619) 425-1993 Fax 425-7917 Established 1928
CLARKSON LABORATORY AND SUPPLY INC.
350 Trousdale Dr. Chula Vista, Ca. 91910 www.clarksonlab .com
A N A L Y T I C A L A N D C O N S U L T I N G C H E M I S T S
Date: May 25, 2022
Purchase Order Number: NONE
Sales Order Number: 55755
Account Number: A.TORC
To: *-------------------------------------------------* Torres Construction
5267 Edge Park Way
San Diego 92124
Attention: Arturo Torres
Laboratory Number: SO8852
Sample Designation:
Customers Phone: 619-756-5665
*-------------------------------------------------* One soil sample received on 05/23/22 at 10:25am,
marked as follows:
ANALYSIS: Water Soluble Sulfate ($04 ) California Test 417
(Turbidity Method)
Sample
#1 7133 Aviara Dr
Rosa Bernal
,RMB/arr
0.003
Ism
NOT TO SCALE
PROJECT NO. 21-1127 C6 FIGURE N0.1
7129 AWAA DRIVE
LOT 290
APN: 215-610-29
MAP NO.: 12412
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SITE PLAN AND GEOLOGIC MAP
7133 AVIARA DRIVE, CARLSBAD, CALIFORNIA
LEGEND
II I
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~ k_ c--:
·-,
·---... _____ t' .,.2
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I NOTTO SCALE,
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APPROXIMATE LOCATION OF
EXPLORATORY TRENCHES
~ Approximate Location of
Exploratory Trench
T t TORREY SANDSTONE
PROJECT NO. 21-1127 C6 FIGURE N0.2
FT.
0
TRENCH LC)G SHEET
TRENCH NO 1
Elev. 262' ms!
DESCRIPTION
Light brown/light gray, loose
(Torrey Sandstone)
1 ______________ _
Damp, medium dense
2
3
4
5
6
7
8
Moist, dense
BOTTOM OF TRENCH (No Refusal)
LEGEND
SOIL TYPE
SILTY FINE SANO (SMi
0 -Indicates representative sample
Project No. 21-1127(6 Figure No. 3
FT.
(J
I
1
TR ENC H LC) G SH E ET
TRENCH NO . 2
Elev. 262 • msl
DESCRIPTION
Light brown/light gray, dry, loose
(Torrey Sandstone)
-~----------------
2
3
4
5
6
7
8
Medium dense
Moist, dense
SOIL TYPE
SILTY FINE SAND (SM )
·------------·-------·-----____ r
BOTTOM OF TRENCH (No Refusal)
Project No. 21-1127C6 Figure No. 4
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FT.
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I
I 3
I ~ I ..
I s I
5
7
8
Project No. 21-1127C6
TRENCH LOG SHEET
TRENCH NO. 3
E/ev. 266* msl
DESCRIPTION
Brown, damp, oose
(Torrey Sandstone)
Medium dense
Moist, dense
TRENCH (No Refusal)
SOIL TYPE
SIL TY FINE SAND (SM
Figure No. 5