1992-2984 I/PE/PM
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Category
If /Yl q (" 0 if '--'
Name
Plan ck. #
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Street Address
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2.-8? </3
Serial #
Description
Year
SCANNED
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LEIGHTON AND ASSOCIATES, INC.
Geotechnical and Environmental Engineering Consultants
GEOTECHNICAL FEASIBILITY EVALUATION,
PROPOSED TWO-LOT RESIDENTIAL SUBDIVISION,
2920 LONE JACK ROAD (A.P.N 264-160-31),
ENCINITAS, CALIFORNIA
December 9, 1988
Project No. 8881554-01
Prepared for:
MR. KENNETH D. SMITH
C/O RANCHO SANTA FE ENGINEERING COMPANY
535 Encinitas Blvd., Suite 120
Encinitas, California 92024
Attention: Mr. C. L. Newton
5421 AVENIDA ENCINAS, SUITE C, CARLSBAD, CALIFORNIA 9200B
(619) 931-9953
FAX (619) 931-9326
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LEIGHTON AND ASSOCIATES, INC
Geotechnical and Environmental Engineering Consultants
December 9, 1988
Project No. 8881554-01
TO: Mr. Kenneth D. Smith
c/o Rancho Santa Fe Engineering Company
535 Encinitas Blvd., Suite 120
Encinitas, California 92024
ATTENTION: Mr. C. L. Newton
SUBJECT:
Geotechnical
Subdivision,
Ca 1 Horni a
Feasibility Evaluation, Proposed Two-Lot Residential
2920 Lone Jack Road (A.P.N. 264-160-31), Encinitas,
Introduction
In accordance with your written authorization dated November 11, 1988, we have
performed a geotechnical feasibility study for the subject site. The purpose of
this report is to provide a general feasibility evaluation of the existing
geotechnical conditions pertinent to the proposed residential subdivision.
Please note that this report is based solely on surface observations, with
limited knowledge of the underlying soil and bedrock conditions. A comprehensive
geotechnical investigation, including subsurface exploration, laboratory testing,
and analysis, is necessary in order to more accurately evaluate the geotechnical
site conditions prior to construction of the proposed development.
The scope of our work included a review of readily available, pertinent published
and unpublished literature and maps, analysis of sequential pairs of aerial
photographs, a field reconnaissance of the existing onsite geotechnical condi-
tions, analysis of the acquired data, and preparation of this report.
Accomoanvina Maos. Tables. and Aooendices
Figure 1 - Site Location Map - Page 2
Figure 2 - Regional Seismicity Index Map - Rear of Text
Figure 3 - Prominent Earthquakes in California - Rear of Text
Table 1 - Seismic Parameters for Active and Potentially Active Faults - Rear of
Text
Table 2 - Minimum Foundation and Slab Recommendations for Expansive Soils - Rear
of Text
Appendix A - References
Appendix B - General Earthwork and Grading Specifications
5421 AVENIDA ENCINAS, SUITE C, CARlSBAD, CALIFORNIA 9200B
(6191931-9953
fAX (619) 931-9326
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Base Map. U.S.G.S. Rancho Santa Fe, California Quadrangle
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Project No.
8881554-01
IEIGHTOH AHO ASSOCIATES
2000
4000
,
feet
SITE LOCATION MAP
SMITH I LONE JACK ROAD
ENCINIT AS, CALIFORNIA
Fi ure 1
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8881554-01
Site Location and Descriotion
The irregularly shaped site encompasses approximately 3.2 acres and is located at
2920 Lone Jack Road, Encinitas, California (Figure I). An existing 10-foot-wide
asphaltic driveway provides access along the western and northern property
boundaries to an existing 2-story, single-family residence located in the
northeastern portion of the property. With the exception of the above improve-
ments and buried underground utilities, the site is essentially in a natural
condition.
The site is located southerly of a northeast-trending ridge and is situated on a
moderate to steep, southerly facing, undulating slope. A review of the project
tentative parcel map (Appendix A, Map 2) indicates slope inclinations range from
approximately 6:1 (horizontal to vertical) in the vicinity of the proposed
westerly lot to approximately 2:1 (horizontal to vertical) near the head of a
tributary drainage course which has been incised in the southeastern portion of
the site. Surface drainage appears to follow present slope gradients.
The project tentative parcel map indicates the maximum relief on the site,
excluding the proposed 30-foot easement, is approximately 85 feet. Site eleva-
tions range from approximately 275 feet in the northeast portion of the
subdivision to approximately 190 feet in the southeast area of the site.
Prooosed Develooment
Based on our review of the project tentative parcel map (Appendix A, Map 2), we
understand the property is intended to be subdivided into two separate parcels.
Based on our conversation with Mr. C. L. Newton of Rancho Santa Fe Engineering
Co., we understand the easterly lot will incorporate the existing single-family
residence, while the westerly lot will be developed with a single-family
residence. A 30-foot-wide easement is proposed from the southern portion of the
subdivision and extends southerly and easterly to Lone Jack Road. Detailed
project and/or grading plans were not available at the time of the preparation of
this report.
Summarv of Geotechnical Conditions
1. GeoloQic SettinQ
The subject site is situated in the coastal section of the Peninsular Range
Province, a geomorphic province with a long and active geologic history
throughout southern California. Through the last 54 million years, the area
known as the "San Diego Embayment" has undergone several episodes of marine
inundation and subsequent marine regression, resulting in the deposition of a
thick sequence of marine and nonmarine sedimentary rocks on the basement rock
of the southern California batholith.
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lEIGHTON AND ASSOCIATES, INe
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8881554-01
Gradual emergence of the region from the sea occurred in Pleistocene time,
and numerous wave-cut platforms, most of which were covered by relatively
thin marine and nonmarine terrace deposits, formed as the sea receded from
the land. Accelerated fluvial erosion during periods of heavy rainfall,
coupled with the lowering of the base sea level during Quaternary times,
resulted in the rolling hills, mesas, and deeply incised canyons which
characterize the landforms of the area.
2. Site-Soecific Geoloqy
Based on our review of pertinent geotechnical literature and maps, aerial
photographic analysis, and our site reconnaissance, the bedrock unit underly-
ing the site consists of the Tertiary-aged Delmar Formation. The Delmar
Formation is mantled by a topsoil horizon. A brief description of these
units (oldest to youngest) encountered on the site is presented below.
. Delmar Formation {MaD Svmbol - Tdl
Based on our experience with the Delmar Formation on nearby sites, this
sedimentary formation primarily consists of well consolidated, stiff to
very stiff, sandy siltstone to sandy claystone and dense to very dense,
silty sandstone. Occasional cemented interbeds may be encountered in this
formation. Due to its generally fine-grained nature, the Delmar Formation
has been associated with landslide activity and near surface expansion.
. Toosoil {Unmaooed Unitl
A topsoil horizon has been developed over much of the site through
weathering of the onsite bedrock. These potentially expansive and
compressible soils consist of sandy, silty clay. Numerous desiccation
cracks were noted in this unit.
3. Faultinq
Our review of available geologic literature (Appendix A), indicates that
there are no known major or active faults on or in the immediate vicinity of
the site. The nearest active regional faults are the Coronado Banks fault
zone, located offshore approximately 23 miles southwest of the site and the
Elsinore fault zone, located approximately 25 miles northeast of the site.
Figure 2 (rear of text) indicates the location of the site in relationship to
known major faults in the southern California region. Figure 3 (rear of
text) summarizes the approximate epicentral area and magnitude of prominent
earthquakes in California during the period of 1769 to 1988.
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LEIGHTON AND ASSOCIATES, INC.
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8881554-01
4. Seismicitv
The subject site can be considered to lie within a seismically active region,
as can all of southern California. Table 1 (rear of text) indicates poten-
tial seismic events that could be produced by maximum probable earthquakes.
A maximum probable earthquake is the maximum exoectable earthquake produced
from a causative fault during a IOO-year interval. Site-specific seismic
parameters included in Table 1 are the distances to the causative faults,
Richter earthquake magnitudes, expected peak/repeatable high ground accelera-
tions (RHGA), and estimated period and duration of ground shaking.
As indicated in Table 1, the Elsinore fault is considered to have the most
significant effect at the site from a design standpoint. A maximum probable
earthquake of Richter Magnitude of 7.3 on the fault could produce a peak
horizontal bedrock acceleration of approximately 0.22g. The effect of
seismic shaking may be mitigated by adhering to the Uniform Building Code or
state-of-the-art seismic design parameters of the Structural Engineers
Association of California.
Secondary effects associated with severe ground shaking following a rela-
tively large earthquake which may affect the site include ground lurching and
shallow ground rupture, soil liquefaction and dynamic settlement, seiches and
tsunamis. These secondary effects of seismic shaking are discussed below.
. Lurchino and Shallow Ground Ruoture
Soil lurching refers to the rolling motion on the surface by the passage
of seismic surface waves. Effects of this nature are likely to be
significant where the thickness of soft sediments vary appreciably under
structure. Damage to the proposed development should not be significant
if the potentially compressible soils present on the site are properly
densified in accordance with the attached General Earthwork and Grading
Specifications (Appendix B).
Breaking of the ground because of active faulting is not likely to occur
on site due to the absence of active faults. Cracking due to shaking from
distant seismic events is not considered a significant hazard, although it
is a possibility at any site.
. Liauefaction and Dvnamic Settlement
Liquefaction and dynamic settlement of soils can be caused by strong
vibratory motion due to earthquakes. Both research and historical data
indicate that loose, saturated, granular soils are susceptible to li-
quefaction and dynamic settlement while the stability of silty clays and
clays is not adversely affected by vibratory motion. Liquefaction is
typified by a total loss of shear strength in the affected soil layer,
thereby causing the soil to flow as a liquid. This effect may be
manifested by excessive settlements and sand boils at the ground surface.
The onsite Delmar Formation and topsoil are not considered liquefiable due
to their physical characteristics and unsaturated condition. .
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LEIGHTON AND ASSOCIATES, INC
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8881554-01
. Tsunamis and Seiches
Tsunamis and seiches are seismically induced waves created in oceans and
closed bodies of water, respectively. Based on the relatively far
distance between the site and large, open bodies of water, and the
elevation of the site with respect to sea level, the possibility of
seiches and/or tsunamis is considered nil.
5. Ancient landslides
During our review of aerial photographs and site reconnaissance, several
geomorphic features similar to landslide topography were noted on the site.
In order to evaluate whether or not these features are actually ancient
landslides, several exploratory borings should be drilled at the site.
Alternatively, these suspected features also may be attributable to the
erosion characteristics of the underlying bedrock materials. In any event,
these features should be evaluated subsequent to, and considered during, the
development of the site project plans.
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LEIGHTON AND ASSOCIATES, 1Me.
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8881554-01
CONCLUSIONS AND RECOMMENDATIONS
The results of our study indicate that the proposed development of the subject
property is feasible from a geologic standpoint. With the exception of the
possible presence of ancient landslide(s), there does not appear to be sig-
nificant geologic constraints on the site that cannot be mitigated by proper
planning, design, and sound construction practices.
Please note that the purpose of this preliminary study was to provide a geotech-
nical feasibility evaluation with respect to the proposed site development.
Accordingly, geotechnical studies that include detailed subsurface exploration
and laboratory testing should be performed to provide specific design recommenda-
tions for earthwork, foundations, and other geotechnical and construction
considerations. We recommend the following geotechnical concerns and appropriate
mitigative measures be considered during planning and development.
SloDe Stabil itv
Several landforms were observed on the site which may be suggestive of
landslides. In addition, other areas of planned development may be underlain by
adversely orientated (out-of-slope) bedding and/or weak clay beds within the
Delmar Formation.
. Mitioative Measures: Subsequent to the development of the project tentative
map, an appropriate geotechnical investigation including subsurface explora-
tion, laboratory testing and analysis should be performed to assess the deep-
seated and surficial slope stability of the site. Mitigative measures for
detected landslides and/or other adverse geologic conditions may include the
construction of earth fill buttresses and other remedial grading measures as
designated by the geotechnical engineer.
We recommend the geotechnical consultant document and geologically map all
excavations including cut slopes during construction. The purpose of this
mapping will be to document the integrity of the cut slopes and to check for
potentially adverse geotechnical conditions.
Seismic Ground Shakino
The possibility of severe ground shaking is considered high during the an-
ticipated economic life of the proposed structures (50 to 100 years). The most
severe seismic shaking of the site would originate from an earthquake emanating
from the Elsinore fault. The maximum ground acceleration from a maximum probable
earthquake of Richter Magnitude 6.0 will be approximately 0.22g. The response
and performance of the structures subjected to seismic ground shaking will depend
on the underlying material and the type and design of the structures.
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LElGNTON AND ASSOCIATES, INC.
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8881554-01
· MitiQative Measures: Proposed structures on the site which are not subject to
secondary seismic hazards, as discussed in the following section, are expected
to perform satisfactorily if designed in accordance with Uniform Building Code
or state-of-the-art seismic design parameters of the Structural Engineers
Association of California. Grading of the site in accordance with current
code specifications is expected to provide adequate densification of the
planned fills and removal of surficial soils which otherwise may tend to
amplify certain types of seismic motion.
Secondarv Seismic Phenomena
Geologic conditions conducive to secondary earthquake hazards such as lurching
and shallow ground rupture, liquefaction, and seiches/tsunamis were not
encountered during this investigation and, therefore, are not expected to require
special mitigative measures.
Excavations and Oversize Material
Based on our experience with similar materials on nearby sites, we anticipate
excavations of the onsite materials may generally be accomplished with conven-
tional heavy-duty earthwork equipment. However, local heavy ripping may be
required where cemented and concretionary lenses are encountered. Excavation for
utilities also may be difficult in some areas. We anticipate that scattered
amounts of oversize material may be generated during excavation of the cemented
lenses and concretionary layers.
· MitiQative Measures: Recommendations for treatment of oversize material are
included in the attached General Earthwork and Grading Specifications
(Appendix B). In addition, oversize material may be utilized in approved
surface applications or hauled off site.
Settlement and Exoansive Soil
The surficial soils that occur on site, including any undocumented fill, may be
potentially compressible in their present state and may settle under the sur-
charge of fills or foundation loads. The foundation-bearing capacity of the
underlying bedrock materials is anticipated to be sufficient for the residential
structures planned. Therefore, settlement of the structures built on competent
formational soils or properly placed and compacted fills is expected to be within
tolerable limits.
Based on visual classification and our experience with similar materials, we
anticipate that the expansion potential of the onsite soils will generally range
from medium to high.
· MitiQative Measures: Standard grading techniques (Appendix B) and conformance
with current grading requirements are anticipated to satisfactorily mitigate
constraints caused by settlement or expansive soil. Expansive soils may be
mitigated by appropriate foundation and slab design (Table 2). However,
settlement and expansive soils considerations should be more fully evaluated
during the preliminary investigation of the site.
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LEIGHTON AND ASSOCIATES. INC.
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8881554-01
Soil Constraints
Based on our visual observation and experience with similar materials, the onsite
soils are generally suitable for use as compacted fill, provided they are free of
organic material, debris, and rock fragments larger than 8 inches in maximum
dimension.
· MitiQative Measures: All grading on the site, including placement and
compaction of fill, should be performed in accordance with City of Encinitas
grading ordinances, sound construction practice, and the General Earthwork and
Grading Specifications presented in Appendix B.
If you have any questions regarding this report, please do not hesitate to
contact this office. We appreciate this opportunity to be of service.
Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC.
~~~
Michael R. Stewart, CEG 1349 (Exp. 6/30/90)
Chief Engineering Geologist
2r.-ll~
Stan Helenschmidt, GE 2064 (Exp. 6/30/92)
Chief Engineer/Manager
RLW/MRS/SRH/bje
Distribution: (5) Addressee
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LEIGHTON AND ASSOCIATES. INC.
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LA NACION I
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MAJOR EARTHQUAKES AND RECENTLY ACTIVE FAULTS
IN THE SOUTHERN CALIFORNIA REGION
EXPLANATION"
ACTIVE FAULTS
EARTHOUAKE LOCATIONS
-
Approximate epicenlral area Ii earlhquakes IIIaI
occurred 1769'1933. MaQn.ludes nalrecorded
by inslruments priar Ia 1906 .ere eslimaled
from damaQe reports auiJlfd on Inlen.il, W
I Modified Mereali scale) ar pIe<; Ih~ ~ tOUQh/J
equivalenl to Richler M 6.0. 31 moderale""
earthquakes, 7 major and one QrtaI earthquake
(857) were reparled in ... 164.,... periacf
1769-1933.
TolallenQth of 'aull zone thaI breaks Holacene deposils
or !hot hos hod seismic oCli,il,.
Foull seQmenl .ilh surfoce rupture durinQ an historic
""'hquoke, or .ilh oseismic 'aull creep.
o Holocene ..Iconic acti,if,
I MllloJ, P1sgoh, Ceno Prieto and SoUon IkIIIIn I
..520
1177
EarIhquoke epicenters since 1933, pIoMed ""'"
improoed ilslnrnenls. Z9 '"""""Ie"" and line
major eor1I>quokes ..... rtCllrdtd in ... 4O.JIO"
period 1933 -1973.
. SIt U-, ~""I ..... ...... ...... fit "'111_ ......... rI ..,.
.. c.tt. . I...." .. Strwchlrel b,ill....AUOClet*" CeIl"'iI *,1.. . ...." ........." ... ....
... . Ita.. ..iI... If 7 % fI .....Ier, '''J'f wt~ 7 .. J y.. . .......1. ..".." , " 7.
c..,;1t. .. R_ J. _ _Iy ... ""'iolled .., ..""b1i,h.. _I. 01 "" CIIi_ DMJitIII" ._ .. ~ Q1t..... ~f
,,- ~ ""ltli'fl6'111K4Ii.~ledlO/l' ""'" boilltl,n.""", koIoi"M'" 51.....1 ':ttI S<<II",."AMiraf;.... C.f.R_.
C_.,." Sti.-g ll'~'l; ... IloIlJIditJMI Afftn. p.M. . "
REGIONAL SEISMICITY
INDEX MAP
Project No. 8881554-01 ~m
Project Name Smith/Lone Jack Road WW
Date 12/9/88 Figure NO-L- 2095 788
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DATE
28 07 1769
08 12 1812
21 12
10 06 1836
06 1838
10 or
11 07 1855
09 01 1857
26 11 1857
12 11 1860
03 07 1861
01 10 1865
08 10
21 10 1868
26 03 1872
19 04 1892
21 04
04 04 1893
20 06 1897
14 04 1898
22 07 1899
25 12
27 and
31 07 1902
18 04 1906
18 04
28 10 1909
11 01 1915
22 06
21 04 1918
21 06 1920
10 03 1922
29 06 1925
22 10 1926
20 08 1~27
04 11
25 02 1930
06 06 1932
10 03 1933
07 06 1934
18 05 1940
30 06 1941
15 03 1946
29 07 1950
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REGION
Los Angeles
Southern California
Off Coast of So. CA
San Francisco Bay
San Franciso
Los Angeles County
Near Fort Tejon
San Jose
Humboldt Bay
Near Livermore
Fort Humboldt/Eureka
Santa Cruz Mountains
Hayward
Near Lone Pine
Vacaville
Win ters
NW of Los Angeles
Near Hollister
Mendocino
San Bernardino County
San Jacinto/Hemet
Santa Barbara County
San Francisco
Brawley/Imperial Valley
Humboldt County
Los Alamos
El Centro/Calexico/Mexicali
San Jacinto/Hemet
Inglewood
Cholame Valley
San ta Barbara
Monterey Bay
Humboldt Bay
West of Point Arguello
Westmorland
Humboldt County
Near Long Beach
Parkfield
Imperial Valley
Santa Barbara/Carpinteria
North of Walker Pass
Imperial Valley
RICHTER
MAGNITUDE
.
6.8
7.2
6.8
7.0
6.1
7.9
6.3
5.7
5.6
5.7
6.5
6.8
7.8
6.8
6.5
5.6
6.3
6.7
6.5
6.7
5.5
8.3
6 to 6.9
6+
5.5
6.25
6.8
6.5
6.3
6 to 6.9
7.5
7.0
6.4
6.3
6.0
7.1
5.9
6.25
5.5
DATE
21 07 1952
22 08
21 12
08 04 1968
01 10 1969
09 02 1971
21 02 1973
01 08 1975
04 10 1978
15 03 1979
06 08 1979
16 10 1979
16 10 1979
24 01 1980
27 01 1980
25 02 1980
25 05 1980
25 05 1980
25 05 1980
25 05 1980
25 05 1980
26 05 1980
26 05 1980
27 05 1980
08 11 1980
26 04 1981
04 09 1981
30 09 1981
02 05 1983
22 07 1983
24 04 1984
23 11 1984
26 11 1984
04 08 1985
26 01 1986
31 03 1986
08 07 1986
21 07 1986
31 07 1986
31 07 1987
01 10 1987
04 10 1987
24 11 1987
24 11 1987
REGION
Kern County
Bakersfield
Eureka
NE San Diego County
Santa Rosa
San Fernando
Off Coast of So. CA
Oroville
Bishop
Palm Springs
Coyote Lake
Imperial Valley
Imperial Valley
Livermore
Livermore
Palm Springs
Bishop/Mammoth Lakes
Bishop/Mammoth Lakes
Bishop/Mammoth Lakes
Bishop/Mammoth Lakes
Bishop/Mammoth Lakes
Bishop/Mammoth Lakes
Bishop/Mammoth Lakes
Bishop/Mammoth Lakes
Off Coast Near Eureka
Off Coast of So. CA
Bishop/Mammoth Lakes
Coalinga
Coalinga
Morgan Hill
Bishop/Mammoth Lakes
Bishop/Mammoth Lakes
Coalinga
Coalinga
Livermore
North Palm Springs
Chalfant Valley
Chalfant Valley
Eureka
Whittier
Whittier
Imperial Valley
Imperial Valley
RICHTER
MAGNITUDE
7.7
5.8
6.6
6.5
5.7
6.6
5.9
5.7
5.8
5.7
5.9
5.6
5.5
5.5
5.9
5.6
6.5
5.9
6.7
5.9
5.5
5.6
5.5
6.3
7.0
6.3
5.6
5.8
6.3
5.8
6.2
6.2
5.5
5.8
5.5
5.7
6.0 I
6.0
5.9
5.5
6.1
5.6
6.5
6.7
"The Richter magnitude Beale was not devised until 1931. If values appear in this column for earthquakes which
occurred prior to that date, the magnitudes were determined as tollovs: (1) if given to the nearest tenth, the
record. of older instruments were correlated vith records of instruments now in use; (2) other--oiae, historical
recorda of intensity were used to estimate magnitude.
Source: National Earthquake Information Center
PROMINENT EARTHQUAKES IN
CALIFORNIA
(1769 TO KAY 1988)
(Richter Magnitude 5.5 and Above)
Project No.
Proj ect Name
Date 12/9/88
8881554-01
2920 LONE JACK
Figure No. 3
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I 8881554-01
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l~Story Footings
(S.. Not. I)
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2~Story Footings
(See Note 1)
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Kintmum Footing
Width
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Garage Door
Grade Beam
(S.. Not. 2)
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L tying Area
Floor Slabs
(See Notes 3,
4 and 5)
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Garage Floor
Slabs
(See Notes 4
and 6)
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Presoak tng of
L 1v1ng Area and
Garage Slabs
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NOTES:
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Post-Tensioned Slabs
TABLE 2
MINIMUM FOUNDATION AND SLAB RECOMMENDATIONS FOR EXPANSIVE SOILS
(ONE- AND TWO-STORY RESIDENTIAL BUILDINGS)
U.B.C. EXPANSION INDEX
0-20
VERY LOW EXPANSION
All footings 12. deep.
Reinforcement for continuous
footings: one No.4 bar
top and bottom.
Exterior footings IS" deep.
Interior footings 12" deep.
Reinforcement for continuous
footings: one No.4 bar
top and bottom.
Continuous: 12" for I-story
Continuous: IS. for 2-5tory
Isolated column: 24"
A grade beam 12. wide x 12"
deep (IS. deep for 2-storyJ
should be provided across
the garage entrance.
Nominal 4" thick slab.
6x6-10/10 WWF reinforcement
at mid-height. 6-mil
Visqueen moisture barrier
on pad grade with
I" sand above VisQueen.
Nominal 4. thick slab on pad
grade. Garage slabs should
be quarter-sawn.
Hear-optimum to a
depth of 6M.
U.B.C EXPANSION INDEX
21-50
LOW EXPANSION
All footings 12. deep.
Reinforcement for continuous
footings: one No. . bar
top and bottom.
Exterior footings IS. deep.
Interior footings 12" deep.
Reinforcement for continuous
footings: one No.4 bar
top and bottom.
Continuous: 12. for I-story
Continuous: IS" for 2-story
Isolated column: 24.
A grade beam 12" wide x 12"
deep (IS" deep for 2-story)
should be provided across
the garage entrance.
Nominal.. thick slab.
6x6-10/10 WWF reinforcement
at mid-height. 6-mil
Visqueen moisture barrier
above 2" sand base with
1. sand above Visqueen.
Nominal." thick slab on
2" sand base. Garage slabs
should be quarter-sawn.
(1.2) x optimum to a
depth of 12".
U.B.C. EXPANSION INDEX
51-90
MEDIUM EXPANSION
Exterior footings IS" deep.
Interior footings 12" deep.
Reinforcement for continuous
footings: one No.4 bar
top and bottom.
Exterior footings IS" deep.
Interior footings 12" deep.
Reinforcement for continuous
footings: one No.4 bar
top and bottom.
Continuous: 12" for I-story
Continuous: 15. for 2-story
Isolated column: 24"
A grade beam 12. wide x IS.
deep should be provided
across the garage entrance.
Nominal 4M thick slab.
6x6-6/6 WWF reinforcement
at mid-height. 6-mil
Visqueen moisture barrier
above 3" sand base with
I" sand above Visqueen.
Nominal 4" thick slab on
3" sand base. Garage
should be quarter-
sawn or reinforced with
6x6-10/10 WWF at mid-
h.ight.
(1.3) x optimum to a
depth of IS..
U.B.C. EXPANSION INDEX
91-130
HIGH EXPANSION
Exterior footings 24" deep.
Interior footings IS. deep.
Reinforcement for continuous
footings: one No.5 bar
top and bottom; alternately.
two No. 4 bars top.
two No. 4 bars bottom.
Exterior footings 24" deep.
Interior footings IS" deep.
Reinforcement for continuous
footings: one No.5 bar
top and bottom; alternately.
two No.4 bars top,
two No.4 bars bottom.
Continuous: 12" for I-story
Continuous: IS" for 2-story
Isolated column: 24.
A grade beam 12" wide x 24"
deep should be provided
across the garage entrance.
Full 4" thick slab.
6x6-6/6 WWF reinforcement
at mid-height. 6-mil
Visqueen moisture barrier
above 4" sand base with
1. sand above Visqueen.
Nominal 4" thick slab on
4" sand base. Garage slabs
should be quarter-sawn and
reinforced with 6x6-6/6 WWF
at mid-height.
(1.4) x optimum to a
depth of 24".
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As an alternate to conventional foundations, bul1dings may be supported on post-tensioned slabs to be designed by I structural engineer in
consultation with the geotechnical consultant. In addition, a post-tensioned slab is also recommended for VERY HIGH expansion potential
(Expansion Index greater than 130). if encountered. Post-tensioned slabs should have perimeter footings embedded a minimum of 12 inches
below the adjacent grade. The slabs should be designed such that they can be deforllled approximately 1 inch vert tcally over a 'tidth of
30 feet IIftthout distress in the event of shrinkage or swelling of the supporting so11s. Living area slabs should be underlain by a 6-/1111
Yisqueen moisture barrier covered by a I-inch layer of sand. Presoaking as recommended for conventional footings 11.2) x optimum to a depth
of 12, (1.3) x optimulI to a depth of 18. and (1.4) x optilllum to a depth of 24 inches for MEDIUM, HIGH. and VERY HIGH expansion potential
soils, respectively, are also sUCJoested for post-tensioned slab systems.
1. Depth of interior or exterior footings to be measured from lowest adjacent finish grade.
2. The base of the grade beam should be at the same elevation as that of the adjoining footings.
3. Living area slabs may be tied to the footings as directed by the structural engineer. For HIGH EXPANSION: Dowels consisting of No.3
bars should be placed at 36 inches on centers in the footings and bent 3 feet into the slab.
4. It has been observed that lIfelded wire fabric reinforcement seldom stays at the design height within concrete slabs. We recommend the
use of No.3 bars at 24 inches D.C. instead of 6x6-10/10 WWF and No.3 bars at IS inches D.C. instead of 6x6-6/6 WWF.
5. 6-mil VisQueen sheeting has proved successful. Equivalents are acceptable.
6. Garage slabs should be isolated from stem wall footings with a minimum 3/S. felt expansion joint.
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8881554-01
APPENDIX A
REFERENCES
1. Albee,
A.L., and Smith, J.L., October 1966, Earthquake characteristics and
fault activity in southern California in Lung, R. and Proctor, R.,
editors, Engineering Geologist in Southern California, Association
of Engineering Geologists, Special Publication.
2. Allen, C.R., Amand, P., Richter, C.F., and Nordquist, J.M., 1965,
Relationship between seismicity and geologic structure in southern
California, Seismological Society of America Bulletin, Vol. 55,
No.4, p. 753-797.
3. Bolt, B.A., 1973, Duration of strong ground motion, Proc. Fiftieth World
Conference on Earthquake Engineering, Rome, Paper No. 292,
pp. 1304-1313, June.
4.
Bonilla, M.J., 1970,
(editor) ,
pp. 47-74.
Surface faulting and related effects in Wiegel, R.
Earthquake Engineering, Prentice-Hall, Inc., New Jersey,
5. Eisenberg, L.I., 1985, Pleistocene faults and marine terraces, Northern San
Diego County, California in Abbott, P.L., editor, 1983, On the
manner of deposition of the Eocene Strata in northern San Diego
County, San Diego Association of Geologists Fieldtrip Guide,
pp. 87-91.
6. Eisenberg, L.I., and Abbott, P.L, 1985, Eocene lithofacies and geologic
history, northern San Diego County, in Abbott, P.L., editor, 1983,
On the manner of deposition of the Eocene Strata in northern San
Diego County, San Diego Association of Geologists Fieldtrip Guide,
pp. 87-91.
7. Greensfelder, R.W., 1974, Maximum credible rock acceleration from earthquakes
in California, California Division of Mines and Geology, Map
Sheet 23.
8. Hannan, D.L., 1975, Faulting in the Oceanside, Carlsbad, and Vista areas,
northern San Diego County, California in Ross, A. and Dowlen, R.J.,
editors, Studies on the geology of Camp Pendleton and western San
Diego County, California, San Diego Association of Geologists
Fieldtrip Guidebook, pp. 57-60.
C.W., 1985, An explanatory test to accompany the 1:750,000 scale
fault and geologic maps of California, California Division of Mines
and Geology, Bulletin 201.
9. Jennings,
10. Lamar, D.L, Merifield, P.M., and Proctor, R.J., 1973, Earthquake recurrence
intervals on major faults in southern California in Moran, D.E.,
Slosson, J.E., Stone, R.O., Yelverton, California, editors, 1973,
Geology, seismicity, and environmental impact: Association of
Engineering Geologists, Special publication.
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8881554-01
REFERENCES (continued)
11. Leighton
and Associates, Inc., 1988, Preliminary geotechnical investigation,
Stratford Estates, proposed 10-Acre residential subdivision,
assessor's Parcel No. 264-152-07, Encinitas, California, Project
No. 8880772-01, dated July 25.
12. , Published and unpublished in-house data.
13. Ploessel, M.R., and Slosson, J.E., September 1974, Repeatable high ground
accelerations from earthquakes - important design criteria,
California Geology, Vol. 27, No.9.
14. Schnabel, B. and Seed, H.G., 1973, Accelerations in rock for earthquakes in
the western United States, Bulletin of the Seismological Society of
America, Vol 63, No.2, pp. 501-516.
15. Seed, H.B., Idriss, I.M., and Kiefer, F.W., 1969, Characteristics of rock
motions during earthquakes, Journal of Soil Mechanics and
Foundations Divisions, ASCE, Vol. 95, No. SM5, Proc. Paper 6783,
pp. 1199-1218, September.
16. Weber, F.H., Jr., 1982, Recent slope failures, ancient landslides and related
geology of the north-central coastal area, San Diego County,
California, California Division of Mines and Geology, Open-File
Report, 82-12LA.
17. Wilson, Kenneth Lee, 1972, Eocene and related geology of a portion of the San
Luis Rey and Encinitas Quadrangle, San Diego County, California,
Masters Thesis, University of California, Riverside, dated
December.
MAPS
I. California Division of Mines and Geology, 1975, Fault map of California,
Scale 1"=750,000'.
2. Rancho Santa Fe Engineering Co., 1988, Tentative parcel map, W.O. 87-8612,
Scale 1"=100', dated August 10.
3. United States Department of the Interior Geologic Survey,
topographic map, 1968, photo revised 1983,
California Quadrangle.
7.5-minute series
Rancho Santa Fe,
AERIAL PHOTOGRAPHS
Date
Source
Scale
Fl iaht
AXN-8M
Photo No.
15 and 16
4/11/53
USDA
1"=1,667'
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8881554-01
GENERAL EARTHWORK AND GRADING SPECIFICATIONS
1.0 General Intent
These specifications are presented as general procedures and recommendations
for grading and earthwork to be utilized in conjunction with the approved
grading plans. These general earthwork and grading specifications are a
part of the recommendations contained in the geotechnical report and shall
be superseded by the recommendations in the geotechnical report in the case
of conflict. Evaluations performed by the consultant during the course of
grading may result in new recommendations which could supersede these
specifications or the recommendations of the geotechnical report. It shall
be the responsibility of the contractor to read and understand these
specifications, as well as the geotechnical report and approved grading
plans.
2.0 Earthwork Observation and Testing
Prior to the commencement of grading, a qual ified geotechnical consultant
should be employed for the purpose of observing earthwork procedures and
testing the fills for conformance with the recommendations of the geotechni-
cal report and these specifications. It shall be the responsibility of the
contractor to assist the consultant and keep him apprised of work schedules
and changes, at least 24 hours in advance, so that he may schedule his
personnel accordingly. No grading operations should be performed without
the knowledge of the geotechnical consultant. The contractor shall not
assume that the geotechnical consultant is aware of all grading operations.
It shall be the sole responsibility of the contractor to provide adequate
equipment and methods to accomplish the work in accordance with applicable
grading codes and agency ordinances, recommendations in the geotechnical
report, and the approved grading plans not withstanding the testing and
observation of the geotechnical consultant. If, in the opinion of the
consultant, unsatisfactory conditions, such as unsuitable soil, poor
moisture condition, inadequate compaction, adverse weather, etc., are
resulting in a quality of work less than recommended in the geotechnical
r.eport and the specifications, the consultant will be empowered to reject
the work and recommend that construction be stopped until the conditions are
rectified.
Maximum dry density tests used to eva1u'ate the degree of compaction should
be performed in general accordance with the latest version of the American
Society for Testing and Materials test method ASTM 01557.
3.0 Preparation of Areas to be Filled
3.1 Clearing and Grubbing: Sufficient brush, vegetation, roots, and all
other deleterious material should be removed or properly disposed of in
a method acceptable to the owner, design engineer, governing agencies
and the geotechnical consultant.
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8881554-01
The geotechnical consultant should evaluate the extent of these
removals depending on specific site conditions. In general, no more
than 1 percent (by volume) of the fill material should consist of these
materials and nesting of these materials should not be allowed.
3.2 Processing: The existing ground which has been evaluated by the
geotechnical consultant to be satisfactory for support of fill, should
be scarified to a minimum depth of 6 inches. Existing ground which is
not satisfactory should be overexcavated as specified in the following
section. Scarification should continue until the soils are broken down
and free of large clay lumps or clods and until the working surface is
reasonably uniform, flat, and free of uneven features which would
inhibit uniform compaction.
3.3 Overexcavation: Soft, dry, organic-rich, spongy, highly fractured, or
otherwise unsuitable ground, extending to such a depth that surface
processing cannot adequately improve the condition, should be overex-
cavated down to competent ground, as evaluated by the geotechnical
consultant. For purposes of determining quantities of materials
overexcavated, a licensed land surveyor/civil engineer should be
utilized.
3.4 Moisture Conditioning: Overexcavated and processed soils should be
watered, dried-back, blended, and/or mixed, as necessary to attain a
uniform moisture content near optimum.
3.5 Recompaction: Overexcavated and processed soils which have been
properly mixed, screened of deleterious material, and moisture-
conditioned should be recompacted to a minimum relative compaction of
90 percent or as otherwise recommended by the geotechnical consultant.
3.6 Benching: Where fills are to be placed on ground with slopes steeper
than 5:1 (horizontal to vertical), the ground should be stepped or
benched. The lowest bench should be a minimum of 15 feet wide, at
least 2 feet into competent material as evaluated by the geotechnical
consultant. Other benches should be excavated into competent material
as evaluated by the geotechnical consultant. Ground sloping flatter
than 5:1 should be benched or otherwise overexcavated when recommended
by the geotechnical consultant.
3.7 Evaluation of Fill Areas: All areas to receive fill, including
processed areas, removal areas, and toe-of-fill benches, should be
evaluated by the geotechnical consultant prior to fill placement.
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4.0 Fill Material
4.1 General: Material to be placed as fill should be sufficiently free of
organic matter and other deleterious substances, and should be
evaluated by the geotechnical consultant prior to placement. Soils of
poor gradation, expansion, or strength characteristics should be placed
as recommended by the geotechnical consultant or mixed with other soils
to achieve satisfactory fill material.
4.2 Oversize: Oversize material, defined as rock or other irreducible
material with a maximum dimension greater than 6 inches, should not be
buried or placed in fills, unless the location, materials, and disposal
methods are specifically recommended by the geotechnical consultant.
Oversize disposal operations should be such that nesting of oversize
material does not occur, and such that the oversize material is
completely surrounded by compacted or densified fill. Oversize
material should not be placed within 10 feet vertically of finish
grade, within 2 feet of future utilities or underground construction,
or within 15 feet horizontally of slope faces, in accordance with the
attached detail.
4.3 Import: If importing of fill material is required for grading, the
import material should meet the requirements of Section 4.1.
Sufficient time should be given to allow the geotechnical consultant to
observe (and test, if necessary) the proposed import materials.
5.0 Fill Placement and Compaction
5.1 Fill Lifts: Fill material should be placed in areas prepared and
previously evaluated to receive fill, in near-horizontal layers
approximately 6 inches in compacted thickness. Each layer should be
spread evenly and thoroughly mixed to attain uniformity of material and
moisture throughout.
~2
Fill soils should be watered, dried-back,
as necessary to attain a uniform moisture
Moisture Conditioning:
blended, and/or mixed,
content near optimum.
5.3 Compaction of Fill: After each layer has been evenly spread, moisture-
conditioned, and mixed, it should be uniformly compacted to not less
than 90 percent of maximum dry density (unless otherwise speCified).
Compaction equipment should be adequately sized and be either specifi-
cally designed for soil compaction or of proven reliability, to
efficiently achieve the specified degree and uniformity of compaction.
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5.4 Fill Slopes: Compacting of slopes should be accomplished, in addition to
normal compacting procedures, by backrolling of slopes with sheepsfoot
rollers at increments of 3 to 4 feet in fill elevation gain, or by other
methods producing satisfactory results. At the completion of grading, the
relative compaction of the fill out to the slope face should be at least
90 percent.
5.5 Compaction Testing: Field tests of the moisture content and degree of
compaction of the fill soils should be performed by the geotechnical
consultant. The location and frequency of tests should be at the consult-
ant's discretion based on field conditions encountered. In general, the
tests should be taken at approximate intervals of 2 feet in vertical rise
and/or 1,000 cubic yards of compacted fill soils. In addition, on slope
faces, as a guideline approximately one test should be taken for each 5,000
square feet of slope face and/or each 10 feet of vertical height of slope.
6.0 Subdrain Installation
Subdrain systems, if recommended, should be installed in areas previously
evaluated for suitability by the geotechnical consultant, to conform to the
approximate alignment and details shown on the plans or herein. The
subdrain location or materials should not be changed or modified unless
recommended by the geotechnical consultant. The consultant, however, may
recommend changes in subdrain line or grade depending on conditions
encountered. All subdrains should be surveyed by a licensed land
surveyor/civil engineer for line and grade after installation. Sufficient
time shall be allowed for the surveys, prior to commencement of filling over
the subdrains.
7.0 Excavation
Excavations and cut slopes should be evaluated by a representative of the
geotechnical consultant (as necessary) during grading. If directed by the
geotechnical consultant, further excavation, overexcavation, and refilling
of cut areas and/or remedial grading of cut slopes (i.e., stability fills or
sJope buttresses) may be recommended.
8.0 Quantity Determination
For purposes of determining quantities of materials excavated during grading
and/or determining the limits of overexcavation, a licensed land
surveyor/civil engineer should be utilized.
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TRANSITION LOT DETAILS
CUT-FILL LOT
EXISTING
GROUND SURFACE
J-
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- -'
...__-- 5'
- ___ MIN.
'':~g}i~1~1!~~~~~~1~~~\j:~0;:3:=-=:3:~~~~~~~~~~~~~~~- 38- MIN. *-,
:~~~~~~:E~::~~-~:;::~:;e\.~,-t~.;:~~ Itll:=-II - 1/ 111::1 I t
~-:-:-~~~~:.;:~-::lis\)'-,--.:-:::~~~~~~~~
:~:f~:-i::t:;-:O~-E. \},-:.:i&;-:- I 71111- OVEREXCAVATE
~~~~~_-=-:::::t:-=~:;::==: - AND RECOMPACT
~::::::j.=-~::_-- -----.:_------:~-:
Vlill COMPETENT BEDROCK I
"...--OR MATERIAL EVALUATED ~
I' BY THE GEOTECHNICAL
CONSULTANT
CUT LOT
EXISTING
GROUND SURFACE
J--
---
-
---
---
-
--
_~-REMOVE ___--
_ _ "--UNSUITABLE --.. _ ____ 5"
_ -- MATERIAL ~ MIN.
:~:;:::f=61J~:~~f fi5~~~~==~~~3=:-::~;::-;:;::;:3:3=i:: ::;:~3:~ ~i::~:f3:~.;:~:;::;:~:f~~~:f:f 38' MIN.*
':::;:::j.:-:::::FILL:-::--"'--:~~:-~:: \/I;~~II--/1 - _n _n____ fllb/7ii _n__ T
::f~!Ii_~m?:-~~;~~:3:: - AONVDE~~~~~~t15T
- 71 ..... \
\....//::::.
COMPETENT BEDROCK /
/OR MATERIAL EVALUATED_________
BY THE GEOTECHNICAL
CONSULTANT
*NOTE:
Deeper or laterally more extensive overexcavatfon and
recompactlon may be recommended by the geotechnical
consultant based on actual field conditions encountered'
and locations of proposed improvements
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STABILITY FILL I BUTTRESS DETAIL
1- 1
OUTLET PIPES
4" " NONPERFORATED PIPE,
100' MAX. O.C. HORIZONTALLY,
30' MAX. O.C. VERTICALLY
SACK CUT
1:1 OR FLATTER
BENCH
SEE SUBDRAIN TRENCH
DETAIL
LOWEST SUBDRAIN SHOULD
BE SITUATED AS LOW AS
POSSIBLE TO ALLOW
SUITABLE OUTLET
KEY
~10'MIN.
PERFORATED l...L-J EACH SIDE
PIPE~
CAP
NON-PERFORA TED
OUTLET PIPE
T-CONNECTION DETAIL
4" ,,_
NON-PERFORATED ,
PIPE - " .
~--
- -
-
SEE T-CONNECTlON
DETAIL
* IF CALTRANS CLASS 2 PERMEABLE
MATERIAL IS USED IN PLACE OF
3/4"-1-112" GRAVEL, FILTER FABRIC
MA Y BE DELETED
SPECIFICATIONS FOR CALTRANS
CLASS 2 PERMEABLE MATERIAL
8" MIN.
COVER
4" gj
PERFORATED
PIPE
U.S. Standard
Sieve Size
% Passinq
FILTER FABRIC
ENVELOPE (MIRAFI
140N OR APPROVED
EQUIVALENT)*
s"-AiiNT
4" MIN.
BEDDING
1" 100
3/4" 90-100
3/8" 40-100
No. 4 25-40
No. 8 18-33
No. 30 5-15
No. 50 0-7
No. 200 0-3
Sand Equivalent>75
SUB DRAIN TRENCH DETAIL
NOTES:
For bullr..a dlmenalona, aee geotechnical report/plana. Actual dlmenalona 01 bullre.. and aubdraln
may be changed by the geotechnical conaullant beaed on lIeld condlllona.
SUB DRAIN INSTALLATION-Sub drain pipe ahould be Inatalled with perlorallona down.. depleted.
At locallona recommended by the geotechnical, conaullant, nonperlorated pipe ahould be Inatalled
SUBDRAIN TYPE-Subdraln type ahould be Acrylonitrile Butadiene Styrene (A.B.S.l, Polyvinyl Chloride
(PVCl or approved equivalent. CI..a 12S,SDR 32.S ahould b. uaed lor maximum 1111 deptha 01 3S leet.
Cia.. 20O,SDR 21 ahould be uaed lor maximum 1111 deptha 01 100 leet.
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ROCK DISPOSAL DETAIL
fiNISH GRADE
oco" '''' A~~~I~I!!'i'I~N!~~i~!f!!!fi!!irf'f'I!'"
-TM-----.:~ --------:~--- ------~---
_.;:~~~~:f:f~~=-:;j:~:~~~~~~~M~~~~~~~
--::~~~~~~~:ft]fj:~~~~~~~~-!~~~1~~~-t~~~}j:t
-------~ ----~--------- Ej:~1t~-.
OVERSIZE WINDROW
GRANULAR SOIL (S.E.2: 30) TO BE
DEN81FIED IN PLACE BY FLOODING
DET AIL
or )(~1fYl-J
TYPICAL PROFILE ALONG WINDROW
1) Rock with maximum dimensions greater than 6 inches should not be used within 10 feet
vertically of finish grade (or 2 feet below depth of lowest utility whichever Is greater),
and 15 feet horizontally of slope faces.
2) Rocks with maximum dimensions greater than 4 feet should not be utilized In fills.
3) Rock placement, flooding ,of granular soil, and fill placement should be observed by the
geotechnical consultant.
4) Maximum size and spacing of windrows should be in accordance with the above details
Width of windrow should not exceed 4 feet. Windrows should be staggered
vertically (as depleted).
5) Rock should be placed In excavated trenches. Granular soil (S.E. greater than or equal
to 30) should be flooded In the windrow to completely fill voids around and beneath
rocks.
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CANYON SUBDRAIN DETAILS
EXI8TING
GROUND SURFACE
~ :~'~~flitf~!l~!~~~E!~IIlfffii~~~~~~=-'
BENCHING \ -~-----*-----------:::::::_-::_~_~ -- _~-
~t,; -~~~.Il;;p~r: ~
SUBDRAIN
TRENCH
SEE BELOW
SUBDRAIN TRENCH DETAILS
4" MIN. BEDDING
3/4"-1;112" CLEAN
GRAVEL (lift. 31ft. MIN.)
8" 9i MIN.
PERFORATED
PIPE
DETAIL OF CANYON SUB DRAIN TERMINAL
DESIGN FINISH
GRADE
SUBDRAIN
TRENCH
SEE ABOVE
" .
" "
PERFORATED
8" ~ MIN. PIPE
3/4"-1-1/2" CLEAN
GRAVEL
3.
(lift. 1ft. MIN.)
* IF CAL TRANS CLASS 2 PERMEABLE
MATERIAL IS USED IN PLACE. OF
3/4"-1-1/2" GRAVEL, FILTER FABRIC
MA Y BE DELETED
SPECIFICATIONS FOR CALTRANS
CLASS 2 PERMEABLE MATERIAL
U.S. Standard
Sieve Size
% Passinq
"
1" 100
3/4" 90-100
3/8" 40-100
No. 4 25-40
No. 8 18-33
No. 30 5-15
No. 50 0-7
No. 200 0-3
Sand Equivalent>75
Subdraln Ihould be conltructed only on competent material II evaluated by the geotechnical
con.urtant.
SUBDRAIN INSTALLATION Subdraln pipe Ihould be Inltalled with perforatlonl down.. depleted.
At locetlonl recommended by the geotechnical conlultant, nonperforated pipe Ihould be Inltalled.
SUBDRAIN TYPE-Subdraln type Ihould be Acrylonitrile Butadiene Styrene (A.B.S.), Polyvinyl
Chloride (PVC) or approved equivalent. Cia.. 125, SDR 32.5 Ihould be uoed tor maximum
fill depth I 01 35 leet. Cia.. 200,SDR 21 Ihould be Uled lor maximum 1111 depthl 01 100 feet.
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SIDE HILL STABILITY FILL DETAIL
FINISHED SLOPE FACE
PROJECT 1 TO 1 LINE
FROM TOP OF SLOPE TO
OUTSIDE EDGE OF KEY
EXISTIKG GROUND ___
SURFACE~........ ____---- ,.../
................ "..-""-
........ "..-
./" "..-
"..- ,/
,... /'
,... ,...
./ ,...
FINISHED CUT PAD
OVERBURDEN OR
UNSUITABLE
MATERIAL
2' I
MIN.
KEY
DEPTH
rQI: I
15' MIN.'
LOWEST
BENCH
(KEY)
(COMPETENT BEDROCK OR
MATERIAL AS EVALU~TED
BY THE GEOTECHNICAL
CONSUL TANT
NOTE: Subdrain details and key width recommendations to be provided based
on exposed subsurface conditions
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KEY AND BENCHING DETAILS
EXISTING
GROUND SURFACE
PROJECT' TO , LINE
FROM TOE OF SLOPE
FILL SLOPE
REMOVE
UNSUITABLE
MATERIAL
:; -::
2' MIN.L,S' MINrl
KEY ILOWEST
DEPTH BENCH
(KEY)
FILL-OVER-CUT SLOPE
---
REMOVE
UNSUITABLE
MATERIAL
PROJECT , TO ,
LINE FROM TOE
OF SLOPE TO
COMPETENT
MATERIAL
/,,/
EXISTING / /
GROUND / /
SURFACE~/ / 1':
// :::;tltY
/ \\\~
/
'::111
-:::'
CUT-OVER-FILL SLOPE
CUT SLOPE
(TO BE EXCAVATED
PRIOR TO FILL
PLACEMENT)
REMOVE
UNSUITABLE
'MATERIAL
NOTE: Back drain may be recommended by the geotechnical consultant based on
actual field conditions encountered. Bench dimension recommendations may
also be altered based on field conditions encountered.
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RETAINING WALL DRAINAGE DETAIL
t~=~~~~~~~~~=ci=~1=~i~~~~~!~~~~~~
.------------------------
----------------------
--------------
-------- --
RETAINING WALL
WALL. WATERPROOFING
PER ARCHITECT'S
SPECIFICA TlONS
FINISH GRADE
W ALL FOOTING m
=11.:311'::'
SPECIFICATIONS FOR CALTRANS
CLASS 2 PERMEABLE MATERIAL
u.S. Standard
Sieve Size
% PassinQ
I" 100
3/4" 90-100
3/B" 40-100
No. 4 25-40
No. 8 18-33
No. 30 5-15
No. 50 0-7
No. 200 0-3
Sand Equivalent>75
SOIL BACKFILL, COMPACTED TO
10 PERCENT RELATIVE COMPACTION.
- ----
-- ---
-- --------- -------------
--- -------- ------------
--- -------- -----------
~~~:t~~~~~~~~ ~~~~~~:!::-
-:..-:..-:..==--:..-:..-:..-:..-:..-:..-:..::- -::::-:-==-==-:.
O I--=- 001 =~=~~:?=~~-
.... r' I ~-::-::.:::-:::~-
10 e' MIN.. :!::!:~~~~ FILTER FABRIC ENVELOPE
OVERLA~ ~~"'. (MIRAFI 140N OR APPROVED
o 0 0 -:..-:.-:.-:
. :, ~~~ EQUIVALENT)-
o
l'MIN. 3/4'-1-1/2' CLEAN GRAVEL....
. .
4' (MIN.) DIAMETER PERFORATED
PVC PIPE (SCHEDULE 40 OR
EQUIVALENT) WITH PERFORATIONS
ORIENTED DOWN AS DEPICTED
MINIMUM 1 PERCENT GRADIENT
TO SUITABLE OUTLET
COMPETENT BEDROCK OR MATERIAL
AS EVALUATED BY THE GEOTECHNICAL
CONSULTANT
.BASED ON ASTM 01551
· .IF CAL TRANS CLASS 2 PERMEABLE MATERIAL
(SEE GRADATION TO LEFT) IS USED IN PLACE OF
3/4'-1-1/2' GRAVEL, FILTER FABRIC MAY BE
DELETED. CAL TRANS CLASS 2 PERMEABLE
MATERIAL SHOULD BE COMPACTED TO 10
PERCENT RELATIVE COMPACTION.
NOT TO SCALE
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LEIGHTON AND ASSOCIATES, INC.
Geotechnical and Environmental Engineering Consultants
SUPPLEMENTAL GEOTECHNICAL EVALUATIO~,
PROPOSED TWO-LOT RESIDENTIAL SUBDIVISION,
2920 LONE JACK ROAD
(A.P.N. 264-160-31),
ENCINITAS, CALIFORNIA
June 25, 1990
Project No. 8881554-02
Prepared For:
MR. KENNETH D. SMITH
2920 Lone Jack Road
Encinitas, California 92024
5421 AVENIDA ENCINAS, SUITE C, CARLSBAD, CALIFORNIA 9200B
(619) 931-9953
FAX (619) 931-9326
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LEIGHTON AND ASSOCIATES, INC
Geotechnical and Environmental Engineering Consultants
June 25, 1990
Project No. 8881554-02
To: Mr. Kenneth D. Smith
2920 Lone Jack Road
Encinitas, California 92024
Subject: Supplemental Geotechnical Evaluation, Proposed Two-Lot Residential
Subdivision, 2920 Lone Jack Road (A.P.N. 264-160-31), Encinitas,
California
Reference: Leighton and Associates, Inc., 1988, Geotechnical Feasibility
Evaluation, Proposed Two-Lot Residential Subdivision, 2920 Lone Jack
Road (A.P.N. 264-160-31), Encinitas, California, Project
No. 8881554-02, dated December 9, 1988
Pasco Engineering, City of Encinitas Tentative Parcel Map (A.P.N.
264-160-31), Undated, Received May 14, 1990
Introduction
In accordance with your request and authorization, we have performed a
supplemental geotechnical evaluation of the subject site. The purpose of this
investigation was to obtain subsurface geotechnical data within the property
and evaluate the site in respect to the proposed two-lot subdivision. We
understand although future grading or development plans have not yet been
developed, new site improvements will be limited to the western lot. The
existing residence on the east lot will remain as is, with no additional
development on this lot.
The scope of our work included a review of pertinent reports, analysis of aerial
photographs, field mapping of geotechnical conditions, excavation, sampling and
downhole logging of three large-diameter bucket-auger borings, analysis of the
acquired data, and preparation of this report.
Geotechnical FindinQs
8ased on our field and downhole logging observations, the subject property is
underlain by ancient landslide material with a recent landslide in the steep
southern portion of the proposed eastern lot. The recent failure appears to have
occurred ten to fifteen years ago based on graben infilling and revegetation of
the disturbed surfaces. It appears this failure probably occurred during a
period of continued heavy rainfall. It appears that the failures are relatively
shallow (19 to 26 feet deep). Our interpretation of the subsurface conditions
5421 AVENIDA ENCINAS, SUITE C, CARLSBAD, CALIfORNIA 92008
(619) 931-9953
fAX (619) 931-9326
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8881554-01
are depicted on Geologic Cross-Section A-A', Plate 2. The Eocene Del Mar/Friars
Formation observed below the basal slide plane consists of very dense, well-
indurated, fi ne- to medi um-gra i ned sandstone. The most recent fa il ure has
occurred on the oversteepened natural canyon slope and is almost ent ire ly
confined within the proposed eastern lot (see Plate 1). In order to evaluate
this recent failure, Boring B-1 was drilled to a depth of 75 feet immediately
upslope of the landslide backscarp. The purpose of this boring was to evaluate
the possible presence of a deeper slide plane. This boring was advanced below
the toe of the recent failure and also below the canyon bottom with no evidence
of a deeper slide plane or potential instability being observed. As a result,
based on our review of aerial photographs, site mapping and subsurface
investigation, it is our opinion that the recent failure observed is the
reactivation of the toe area of the mapped landslide. This ancient landslide
probably included a mud/debris flow that extended over the natural canyon slope
and well down into the canyon area. The recent failure is likely a reactivation
of the debris that flowed into the canyon and not related to a deeper or larger
landslide.
Conclusions and Recommendations
Based on the results of this supplemental investigation, it is our opinion that
the subject property is underlain by ancient landslide material with a recent
failure within the central portion of the site. It is our opinion, however, that
the proposed lot split and development of the eastern subject lot is feasible
provided mitigation of the existing landslide materials is provided. Mitigation
may include earth fill buttressing or complete removal and recompaction of the
landslide material, dependent upon proposed lot grading and structure locations.
Recommendat ions for mit igat ion shoul d be provided by Leighton and Associ ates
after preliminary development plans become available and prior to any site
grading or construction. Based on our conversations, we understand that similar
remedial earthwork was also required for the recently constructed residence to
the west of the proposed western lot. We assume this was recommended to mitigate
the probable extension of this ancient landslide material within the adjacent
lot.
Existino Residence
The exi st i ng two-story wood-frame res idence is located near the northern property
boundary of the proposed eastern lot. It is presently located approximately
100 feet behind the backscarp of the most recent landslide failure in the canyon
area below. Based on conversat ions with Mr. Smi th, we understand that the
residence is approximately 15 years old, and although there is some minor
cracking of the foundation slabs, no ongoing distress has been noted. Detailed
evaluation of the stability of the existing residence was not a part of this
scope of work. However, based on our observations and discussions with you, the
distress may be due to minor settlement or expansion of fill soils underlying
the foundation or indications of gradual downslope creep of the lot. In any
event, care should be taken to direct water runoff away from the downslope rear
yard and to restrict irrigation in this area. In addition, existing cracks
should be monitored for signs of future movement. In the event significant
- 2 -
LElGHTOH AND ASSOCIATES, INe.
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8881554-01
addit i ona 1 di stress is noted, we recommend that Leighton and Associates be
contacted in order that additional recommendations can be provided.
If you have any questions regarding this report, please do not hesitate to
contact this office. We appreciate this opportunity to be of service.
Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC.
c4::~'0/
Robert F. Riha
Senior Staff Geologist
~~
Michael R. Stewart, CEG 1349 (Exp. 6/30/90)
Chief Geologist
RFR/MRS/bje
Attachments: Figure 1 - Site Location Map
Figure 2 - Geologic Cross-Section A-A'
Appendix A - Boring Logs
Plate 1 - Geotechnical Map
Distribution: (3) Addressee
(3) Pasco Engineering
Attention: Ms. Patricia Geary
- 3 -
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t> ';:}: p 7 ~?\~Il\ ~ "- ~- ' - ..~ ~ '~ '''<.,-- '---t-'
.... . r ;-(; ..'":: ~ 0, m \ fiIt ~. :: CJ ~.I:\ >
rt-J~\\.# ~'---" ~)/ i'f ~,^ -~~ ~k I ~~
~. ~ ~&@ ~,J ~ ,( 0 ~~-~'WG ,,~ 7~ ~ vii:
~i ~ ,Ya?\i.,no. ,1). ",,-~ ,i ,,- ~ OJ/I!}') '~ rS?-0~f(o--.~
I'---V>?'~\\~~ \r;~~~ /'~~'l-- ?'j~.~\ H~~
",' <--r..~':; ~~7!S' ~ ~ ~C) --" :1" ' j[("S: 9"",
~~;~ i~ ::, 0_ .. \~ (' ~ 'to'0J '
, .'" , ~ -",.'" , '" ~ @):
~ ~...r.::: ,<<.-- '\.. ^- .:
r--' . . . ~ !:~'. ).~,: : l~ ,,", . Qiso A 7. ~.~~,..~~ ' ~
"'"'- \ ~~""'.. , . ~~1 '/ 1\
.' >.)'y\... = ~ =~~-: ~(' ,. ~
: .' L ~~~}it ~.;~. ~ .~ r' !. ITE1./ @ ~ ~~ ' ..hfj
,<'.::. ~ ",') ,f' , "~:~/~@~
0- \C; ,I j I ~/( (I ;//1^,
V~l V q jf l- \:: II ';/
I) , " , : ': , '1 -.
q q '/. Q " "I. ',pO '4'
If" ... .. ~"" '
,\~. ole:'. _ IS.
-" ,\, ()
N~~" .
!
<
}~:~~j:: .
0":
/
'8
"
" ~~""
'.
.<:::l
.
04.>:
.. ~
~..
"
.
o '".
, . "^' .v . ~-" ,," ...... .
\\ :::---.! ' ......... >'5~. :::--- .
::::: ,..... "'''~? '. ---..'
':;:'; ~ )~; lZ:-fQ\5 ,
C) '-AIIL~.' ~ ~
0' :~ . 1-., :') ",:.Jf/
'j'\ . ~ ,~ p, 0
~Af, . ~ ~ ~I(<
4ff ~( .Y=: [@~ 0J"<;," ~'--...tJ "
,~ ~'''''.\ ,~'\, i
/~CCz('\l ~~~~'7;.0T~ ,~\:\.\))/ ~rr
/' r;}- ;/ \ ~~~~!iJ1I.ffi. '. , './.1I.I/?'" j / ,-'.
Base Map: U,S.G.S. Rancho Santa Fe, California Quadrangle
....
,
-;.
~
~
2
'J /1 I' 0
r r I I ~ D
&1'ti~~~:W
11~i.
~.
Project No.
8881554-02
LEIGHTON AHO ASSOCIATES
o
,
scole
SITE LOCATION MAP
SMITH / LONE JACK ROAD
ENCINIT AS, CALIFORNIA
FI ure 1
2000
4000
,
feet
-2-
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DATE June IS, 1990
PROJECT Smith/Lone J~ck Road
DRILLING Co San Diego Drflllng
HOLE DIAMETER 30 In. DRIVE WEIGHT 0-30': 3841#: 31-57':
ELEVATION Top OF HOLE~ REF, OR DATUM See Geotechnical Map
GEOTECHNICAL BORING LOG
DRILL HOLE No,
B-]
SHEET 1 OF 3
PROJECT No, 8881554-02
TYPE OF RJ G Bucket Auger
2446#: 58-85': ]3]3# DROP ]2
IN.
~ -
u> . ".. ."....
'" 0 .... - '" u> . GEOTECHNICAL DESCRIPTION
u Cl :z: u>o u> '" . :5"!
:r.... - ::> '" :<:0 zu. ::>....
....'" :rc:> .... ltl'" '3-'- "'u ....z uu
0-", 0-0 - ::>.J <=> 0- u>'"
~l..L. ......J 1-0- IX> '" -.... -'V>
.... ~ '" ~~ - . LOGGED BY RFR/MRS
'" .... ... <>- ~ o=>
U> ex:
V) <=> u V)~ SAMPLED BY RFR
0 COLLUVIUM:
- r- Medium brown, moist, silty sand: trace of clay, caliche
pods and Infilled jOints: few pores; few roots; open
- - fractures (1/8 inCh) -
- I-
- l-
S- I- LANDSLIDE MATERIAL:
- r- @ 6' Light red to olive-tan, moist, loose to medium
dense, silty sand: mottled
-
- @ 8' Red-brown to tan, damp, loose to medium dense.
- fine sand: mottled: few carbonized organics
10- @ 10' Light red-brown to gray, damp. medium dense.
1 2 99.3 11.7 fine sand: mottled
.
.
. GC:N35E/
- @ 13' North wa 11 : sharp, irregular contact to olive-
30NN gray, mo~st, firm, silty clay: iron oxide stained
- @ 13.5' Light gray, friable sand
SH:N30N/
15 - 35NE
-
- @ 17' 1/2-inch thick, soft, wet, gray clay on contact:
- randomly sheared by east-west, 6-inch offset: I-
below is olive-gray, clayey, silty sand: mottled:
- iron stained; minor rootlets; discontinuous
claystone: discontinuous fractures and joints:
20 - appears disturbed
2 3 102.7 21.4 @ 19.5' Grades'to olive-gray, very stiff, sheared clay-
- stone: vertical jOints infilled with brown sand:
8:N60E- appears very jumbled
- E-N/5S r- @ 20' Medium gray, damp, highly sheared, silty clay-
stone: iron oxide stained: punky
. I- @ 21. 5' 1/4 to 3/8-lnch thick, olive-brown, soft,
slightly sheared, continuous clay seam: above is
- .... 1/2 to 3/4 Inch 'thick, light gray, silty clay
DELMAR/FRIARS FORMATION:
25 - I- Gray to maroon, mott~ed. well indurated. fine to medium
sandstone: drilling becomes very difficult
-
.
.
. I l-
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SOSA(Il/77)
LEIGHTON & ASSOCIATES
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GEOTECHNICAL BORING LOG
DATE June 15. 1990 DRILL HOLE No, B-1 SHEET 2 OF 3
PROJECT Smith/Lone J"k Road PROJECT No, 8881554-02
DRILLING Co San Diego Ori1l1no TYPE OF RIG Bucket Auger
HOLE DIAMETER 30 in. DRIVE WEIGHT 0-30': 3841#: 31-57': 2446#: 58-85': 1313# DROP 12
ELEVATION Top OF HOLE~ REF. OR DATUM See Geotechnical Map
IN,
~ .
u> . N u>~
UJ 0 f- - UJ u> . GEOTECHNICAL DESCRIPTION
u Cl z: u>o u> e>: . :5~
"'f- - => UJ xo zu. ~!z
f-UJ "'''' f- <,\UJ ou... UJu L.>W
"-UJ "-0 =>..J ..J U>UJ
~LL. <-' - ...."- o<le>: ~"- -f- ...lVl
f- LOGGED BY RFR/MRS
e>: .l;: ~ UJ ~ .$2z. - .
l.<) Q.. "-8 0::::> 0
(I) ~ (I)~ SAMPLED BY RFR
3v DELMAR/FRIARS FORMATION:
- t-
- t-
- t-
o t-
35_ t-
o t-
-
0 - @ 38' Near refusal; use ripper bar; olive-brown, very
- well indurated
:HORIlOHTA . @ 39' Grades to olive-brown, dry, dense, mottled sand-
40- stone w1th gray sandstone clasts
@ 39.5' Sharp contact to gray, maroon, well indurated
0 sandstone with red-tan, sandstone clasts; very ro
difficult drilling
- t-
-
0
45 -
0
-
-
-
50- @ 50' Light gray to maroon, dense, s 11 ty sand with
3 15/10' ll7.9 12.6
- calcium carbonate pods
- t-
o @ 53' t-
Continues well indurated, maroon and medium gray
- sandstone; few rounded granite cobbles
55_
-
-
-
-
.
60
".
SOSA(1Ij77)
LEIGHTON & ASSOCIATES
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I 505"'(11/77)
DATE June 15, 1990
PROJECT Smith/Lone Jock Rood
DR I LL I NG CO Son Di ego Drill i nq
HOLE DIAMETER 30 in. DRIVE WEIGHT 0-30': 3841#: 31-57': 2446#:
ELEVATION Top OF HOLE~ REF. OR DATUM See Geotechnicol Map
GEOTECHNICAL BORING LOG
DRILL HOLE No, B-1
SHEET 3 OF 3
PROJECT No, B8B1554-02
TYPE OF RIG Bucket Auger
58-B5': 1313# DROP 12
IN.
~ -
'" .... CIl~
UJ 0 I- - UJ CIl . GEOTECHNICAL DESCRIPTION
u Cl z: CIlO CIl '" , :5V?
'" I- - UJ xo =>1-
I-UJ "'''' => lQUJ 'J'"- zu. I-Z uu
I- UJu
I>.UJ 1>.0 - =>..J <=l I>. CIlUJ
~u... <-' I- ..... I>. ""'" -I- ...JU)
'" .l;: x: UJ >- ~i!5. - . LOGGED BY RFR/MRS
<D < 0- '" 0:::>
(I) <=l u (I)~ SAMPLED BY RFR
60 DELMAR/FRIARS FORMATION:
- 41 @ 61' Olive to li9ht gray, very dense. mottled, silty,
25/10" 112.1 12.3
- fi ne sond
- f-
- f-
65- ..
- -
- f-
-
-
70 - .
5 25/8" @ 70' Oork olive-brown to gray, mottled, well indurated,
- fine sondstone: sample disturbed
-
.
-
-
75 -
- Total Depth = 75 Feet
No Ground Water Encountered
- No Caving
Geologically Logged to 73 Feet
- Backfilled 6/15/90
-
BO- I-
- I-
- ....
- -
-
85-
-
-
.
.
90
LEIGHTON & ASSOCIATES
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DATE June IS, Ig90
PROJECT Smith/Lone J~ck Ro~d
DRILLING Co San Dieoo Orilling
HOLE DIAMETER 30 in. DRIVE WEIGHT
ELEVATION Top OF HOLE~ REF. OR DATUM
GEOTECHNICAL BORING LOG
DRILL HOLE No,
SHEET I OF I
PROJECT No, 8881554-02
TYPE OF RIG Bucket Auger
0-30': 3841#: 31-57': 24461; 58-85'; 13131 DROP 12
See Geotechnical Map
IN.
B-2
>- .
U) I- .... U)~
W 0 I- - W U) . GEOTECHNICAL DESCRIPTION
u <=l :z: u)o U) '" . <(I')
"I- - ::l W 3:0 zu. ::ll- ..J .
I-w :,,,,, I- lQW '.:f'- wu I-Z UL.l
I>. W 1>.0 ::l..J U)W
~u. <-' - 1-1>. ""'" r:::l I>. -I- ..JV>
I- LOGGED BY RFR
'" .:;: ~ W ~ :E~ - .
<!> a.. 0:::>
en r:::l u tho-' SAMPLED BY RFR
0 COLLUV IUM:
- Medium brown, moist, medium dense, slightly clayey,
silty sand; few roots
- I-
0
0 l-
S-
.
-
. LANDSLIDE MATERIAL:
0 @ 7' Grades to light gray-olive, moist, soft, silty
sand; mottled
0 I-
10- @ 10' Light gray, silty sand and olive-gray, clayey
0 I- silty: soft/friable; very jumbled, disturbed
- l-
. 0 @ 13' Chunks of topsoil in very sheared, jumbled,
- t- olive-gray clay
@ 14' Irregular contact to light gray, soft, silty sand
IS - I-
- t-
o I- @ 17' Grades to olive-gray, disturbed,
si lty clay with
0 I- iron stained sand pOds
- @ 19.5' North wall and 22.5 feet south wall; sharp c--
20- C:E-W 40 contact to olive-gray, dense, jumbled silty sand;
iron stained joint surfaces; above is light
0 gray, soft, friable, silty sand
0
.
.
- I-
25 - I- @ 25' Random shears in medium gray, clayey silty; iron
- ~S:N20-50 I- stained
E/ @ 26.1' Olive-brown, soft, moist, sheared clay with dis-
- 4SE continuous gypsum bed; above clay is very sheared
DELMAR~FRIARS FORMATION:
0 '26.2 Medium gray to maroon, well indurated sandstone;
mottled No Caving
- Total Depth = 32 Feet Geologically Logged to 30 Feet
I No Ground Water Encountered Backfilled 6/15/90
30
SOSA(lI/77)
LEIGHTON & ASSOCIATES
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GEOTECHNICAL BORING LOG
DRILL HOLE No.
DATE June IS, 1990
PROJECT Smith/Lone J~ck Road
DRILLING Co San OieQo Or111ino
HOLE DIAMETER 30 in. DRIVE WEIGHT 0-30': 3841#: 31-57':
ELEVATION Top OF HOLE~ REF. OR DATUM See Geotechnic~l Map
SHEET 1 OF 1
PROJECT No. 8881554-02
TYPE OF RIG 8ucket Auger
2446#: 58-85': 1313# DROP 12
8-3
IN,
>- .
. .... """
<I> 0 l- I- LU <I> . GEOTECHNICAL DESCRIPTION
LU -
U '" :z <1>0 <I> '" . <en
:J: I- - ::> LU xo zu.. ::>1- ...I .
I-LU :J:'" I- "'LU ou.. LUU I-Z uu
0.. LU 0..0 - ::>...1 ...I <=> 0.. <l>LU
~u... <-' I- 1-0.. ,",'" -I- ...IV) LOGGED BY RFR
'" I- :E LU >- ~15. - .
'-'> <C < c- '" 0:::>
en <=> u en~ SAMPLED BY RFR
0 COLLUVIUM:
- Medium brown, dry to moist, medium dense. fi ne sand; few
fractures in upper 2 feet
- I-
-
- l-
S-
1 2 100.5 9.1 LANDSLIDE MATERIAL:
- @ 5' Dark to medium brown, damp. dense, fine- to medium
@ 6' sand: caliche pods: chunky
- Common chunks of light brown to tan to dark brown,
fine sandi porous
-
-
10-
- . @ 11' Grades to light olive-gray, slightly clayey sand
- and olive-gray, silty clay: disturbed: chunky
- @ 13' Few pods of medium brown, fine sand (topsoil?)
-
15 - 2 4/6" @ IS' Grades to light gray, medium dense, friable, silty
112.2 9.7
- sand: sample driven into sandstone cobble -
-
- @ 18' On north wall and 17 feet west wall: well indur-
- ated sandstone: fractured into 6-inch blocks: -
6-inch offset in olive-gray, silty clay
20 - @ 18.5' Discontinuous, 2 to 3 inch thick, sheared, silty
clay lone: disturbed: below is light gray, friable,
- s 11 ty sand
@ 20' Sharp contact to dark gray, stiff, very sheared,
- silty clay: discontinuous gypsum bed 1/4 inch thick
- OELMAR~RIARS FORMATION:
~ ZI' narp contact to light gray, very dense, well
- indurated, silty sand: fractured gypsum bed at
contact ..
25 - I- @ 25' L1 ght red, very dense I fine sand: very difficult
- I- drilling
l-
.
- I- Total Depth = 25 Feet I-
No Ground Water Encountered
- I- No Caving
- Geologically Logged to 23 Feet
Backfilled 6/15/90
30
SOSA(1l/77)
LEIGHTON 81 ASSOCIATES
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L~GHrON AND AssoclralNC
Geotechnical and Environmental Engineering Consultants
December 20, 1990
Project No. 8881554-02
To: Mr. Kenneth D. Smith
2920 Lone Jack Road
Encinitas, California 92024
Subject: Soils Report for Proposed Three-Lot Residential Subdivision,
2920 Lone Jack Road, (A.P.N. 264-160-31) ,Encinitas, Cal ifornia
Reference: Leighton and Associates, 1990, Supplemental Geotechnical
Evaluation, Proposed Two-Lot Residential Subdivision, 2920 Lone
Jack Road (A.P.N. 264-160-31), Encinitas, California, Project
No. 8881554-02, dated June 25, 1990
In accordance with your request, we have prepared this letter regarding the
referenced soils report on the subject site. We understand that plans for a
three-lot subdivision are being proposed for the site. The geologic conditions
underlying all three lots are discussed in the referenced report and shown on the .
geologic map included as part of that report.
The recommendat ions of the referenced report are, in our opi ni on, st ill
considered appropriate for preliminary design purposes.
Upon completion of site development grading plans, Leighton and Associates should
perform a grading plan review so that recommendations for mitigation of existing
landslide materials identified in our referenced report and any other
supplemental recommendations can be prepared.' .
Pleasedo not hesitate to contact this office if you have any questions regarding
our- report. We appreciate this opportunity to be of service.
Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC.
~~~. . Jb
Michael R. Stewart, CEG 1349 (Exp. 6/30/92)
Chief Geologist
RLW/MRS/SRH/bje
Distribution: (3) Addressee
(3) Pasco Engineering
Attention: Mr. Dale Greenhalgh
~
Stan Helenschmidt, GE 2064 (Exp. 6/30/92)
Chief Engineer/Manager
5421 AVENIDA ENCINAS, SUITE C, CARLSBAD, CALIFORNIA 92008
(619) 931-9953
FAX (619) 931-9326
HYDROLOGY/HYDRAULICS
REPORT
FOR
TM 91-042
MAY 18, 1992
PREPARED BY:
PASCO ENGINEERING, INC.
531 NORTH HIGHWAY 101
SOLANA BEACH, CA 92075
(619) 259-8212
L~~ / o/kAJ
WAYNE P SCO, RCE 29577
EXPIRATION DATE: 3/31/95
DATE: <;;/2k!9~
/
,
wrn@rn~~/~p~
MAY 2 6 1992 ..
CITY OF ENCINii 'oS
DEPT. OF PUBLIC WORKS
. .
TABLE OF CONTENTS
MAY 18, 1992
SECTION
PAGE
I INTRODUCTION
II DISCUSSION
III CONCLUSION
IV CALCULATIONS (HYDROLOGY & HYDRAULIC).
V REFERENCES
VI EXHIBIT
1
1
1
2 - 6
7 - 11
FOLDED
~
~
Page 1 of 11
.
I. INTRODUCTION
The subject property known as APN 264-160-31 is geographically at
N 33 03'26" Latitude and W 117 14'04" Longitude. The property
address is 2920 Lone Jack Road.
The purpose of this report is to calculate the amount of storm
run-off produced during a 100 year frequency storm of the areas
that are directly tributary to each of the two proposed AC
spillways shown on Improvement Plan Drawing Number 2984-1. Then
use that data to determine the appropriate size and type of rip-
rap energy dissipater at the point of discharge.
II. DISCUSSION
As shown on Exhibit "A", the drainage area (Node 1 - 3) tributary
to the first AC down drain (node 3) consists approximately 1.64
acres. Run-off flows overland in a southerly direction until it
is intercepted by the proposed road. Once on the road, the water
flows in the flowline of the AC berm until it reaches Node 3. In
the 100 year event, approximately 3.61 cfs (as calculated in this
report) reach Node 3. However, only approximately 1.4 cfs are
actually intercepted, and 2.21 cfs continue beyond the downdrain.
.
The second downdrain (Node 30) is designed to intercept the sum
of the runoff produced by the drainage area between Node 10 and
30 and the water flowing by Node 3, totaling approximately 3.5
cfs in the 100 year storm.
III. CONCLUSION
According to the calculations contained herein, 3.5 cfs flow down
the proposed AC downdrain at Node 30 at approximately 9.84 cfs.
(See calculations). Since the amount of water discharging from
the downdrain is so small, it is our opinion that a 6 foot x 10
foot rip-rap energy dissipater constructed with 1.5 feet of No.2
backing on top of one layer of woven filter fabric will be
sufficient to dissipate the waters energy to non-erosive levels.
~
~
IV CALCULATIONS (HYDROLOGY & HYDRAULIC)
J
Page 2 of 11
3
........_.......n.............................._.........................____....................._........................................ .......
*.~**~.****~.*******~.**,~.~***..**..***,~*************************...0*.~*.~**~.,~***~****
.
F~Al"IONAL I~ETHOI) ~iVDROL(JGV (:()11PIJTER PF~(]GRAM f)ACKA(3E
F~e'l:ef-erlce~ SAN DIEGO (:OIJN1'V F'LIJOD CONTROL 1)ISl'-RI(~'r
19E15,1981 HVDROL(]GY ~IANI_JAl,_
(/-) Copyright 1982-'9C) Adv211ced Engillcering SCJf-twa~e ~aps
Ver. 5ulJA I~elease Date: 8/213/90 Seria:! # 13638
.
Allalys;is preparp(j by~
PASCO ENGINEEPING
531 NOR1"1'~ HWY 101.
SIJL..ANA BEACH, (:A 92()75
F' l...! CJ i\J F: :: ( ..:) J 9 ) :~? ~:.) (~~; ,,-. H :',:':'~ J ~:?
F'AX (610) 259'-41~112
*.***.~**********.~****.~**,~*,~ DES(:F~IF)TIOI~ or E;TUDY *****.*.~~..~*****~~l~***~*~.~~*
.~ ~1VI)R[ILOGY ANALYS:rS FOR RII~-'RAP SIZING.
.. :i. ()() \(F:(jt~< U'"j"Clhi'.'!" H(J I!.... C;F:~[JtJF' II D II (::l~::;E:Ul""'11 :.0"
.~ Aueu DOWI~DRAINS (IN PF~IVA1'E ROAD"
S i~'l I 'r I...! F~' F: .il_ ::~':'::5
.J!:.
, ...:\. ().. ,':', :,.',': !"'l~::)
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FILE NAMI~~ 425A"DA1'
'TIl""i)E:/O{.\'T"[: [IF' ':::!'fLJD'-l:: l:l.::
~~:;.... :I. :J../ :!. 9C)~?
U~3E:F< EiF>C:C; J F~ J 1.::0 1'''!\(DF:Cil..CiC:,Y (':)i\I.D I"'!V'I)F;~(';ILII.. I [: !'..-!UDE:!.... J !''.iF'Cii::::i''.I('I'T I [JI\I::
-.--.---..---..--..,.-......-..-..--..-.-..-..........--
..-...... ............... ..... ........ ....... .....-... .............. .............. ......... ..............-....- . ..."...... .................................. ..........
1 (?H~::.:; F;r.jl\! D I E:Ci[1 l""i(11\11....t(..,II.... cr;: I 'fl :F::: I (1
USER SPECIF~IED STORM EVE:NT(YEAR) = te)O.llll
""...i..IUIIF': DUF":PiT I it 1,.1 F'F':FC I P I '1"(',T:I: Ui\1 i I i\ICI.11 :1':,) :;,': ,,/HG
SF'ECIFIED MINIJ1lJI1 PIPE SIZE(II~C~1) 10,,()()
!3F'E:::C J F I E:O F'F:r::C:F:l\j'T CJF' LiF<(:',D:r E:l\I'fE; (DE:I,; I r...!(:il.... j 'f(J LJE,;L: F (JF:: F'r:~ I ':::::'T I (:)I\! ~::)I....(jF'F:
;"-,1""
-,;. J
~3())\! I) I F:bD j...i\'Or:::UI .CJCi\" l'ij(.j!\ltJ(.'i!.... II L: II .....I,/(:~Ii.. L..lE:h L.I~3E:D
1\1 cl'r I : :: C! 1\1 L. '-{ F' E: (~I< c::: U t\; F' t.. U E: /'-..1 C: E: ~) ::::j t.. U F: b C [I 1\1 E; I :U I:: r;~ E: {)
*.~.*.~.M..~.~***-~.~******.~*~.~,.~***.~-~*,K***.~,~.*~.
FI....OW I:'ROCESS F:'ROM j~()DE
:!. ,,00 'f(J l\!CJDL
, i'" I ~::; C:Cl:UC
.....................................................................-................................................................................................................ ...........-.....................................................
.... ";."> >F:<I~\.r I CiI\iPIL l''''11 :'Tl...!(JD J hI I -I I (:;:1.... :3LJE{PII:~F:(:; (11\)('11 .Y~::; I U< <" .:......
F:C) I 1.... c::1....(\~;H J r:' J C:Pl'T I CJh! I h i' D 'I
RURAL DEVEL..OP!1E!\!T I~UN[)FF COEr~F':[CJENT ,,4500
NA1'URAi,.. WA1'~:F<SI~EI) NOi10GRAPH l"IME IJF (:ON(:ENTF~A.1IIJi~
[,IJ I 'r !,"I 1 () .....1'.-'1 J: i\i l.J -r F: ~::; (::~I L) D F: D 1. 0 " 6 :',? ( j'ij I 1\II..J'r i . ;::) )
11\1 I'r I (:'11.... b\...f:C:{(::jF:~E:(:~1 F.i....Uhi.....L..1 :i\jFi'fJ...j (F'!::::E:'T) :i. ',?~.:.:;" O()
I..JF'~::;..rF:::E:(~il"-': FL..r:::\/PI r I C}!\~ ' ( .'" ' II I
DOW!\IB"r'F~EAM El,..E~VA'l.j:[:Ji~ 25(1,,(10
El...I~VAT:[(Ji~ D]:Ff:'ERE~i~Cl~ 22,,50
J () 0 \/ E::: (', F;: F-: (.) T 1\1 F (.j L 1.... i: i\!'r I : 1\1 ::; I T '.y" ( It,.! c:; H .I I...l D U F:: ) .-:l" ~~.:.) 0 ~:,:.',;
SUBAPEA RUNUFFICFS) ,,32
"rO"!"AL AF~I::~A(ACF~ES) ,.16 ..r.O-i'.AI.... RLJN[IFF([~f:E;)
"'.',
~
~~~-,~.,~..~ ~'*-K"~'~~~* ~~..
FL,OW PR(Ji:E"i~~ r:POlV! i~(Jr)E~
:'.?,U() 'TU 1\1(:)))[::
.::' " ()(} J ~::; C;CIf'IF
/--\
4-
"'>COMPUTE STREETFEOW TRAVEETIME THRU SUBAREA<<<<
UPSTREAM E~L_EVA'T'ION 244.00 [)(]WNSTREAM ELEVATI[I!~ 19'7.20
STREET LEMUTHeFEET) - 410.00 CURB HEIUTH(INCHES) _ 6.
E:;'rF~~E:E:::'r I'''!(\L..F'V-J I U"TH .; F"E:!::::'r) :!. ~:?" 00 H'rr:;;E:::E:-r CF:UH~3F' (11....1.... (.OI::::C: J 1'i1(~fL.. ) . O/I.()()
· SPECIF'IED i~UMBER OF HALFS1'REETS CARRYING RU!~OFF -- 1
1:;~LJr:<{.1L. DE:1')E:L..(Jr:'I'/IEI\IT" F:<l.JI\JCJF'F~ CCJEF'r:" I C I E:l\I"r ,,~::5:'::;:"l() OUpa517l?
**TRAVELTINE COMPUTED USIMG MEAN FLOWeCFS) - 1.97
STREET FLOWDEPTHeFEET) .23
I~A!_i:-S"r'RI~E'l- FL..C)ClDWID"T'H(FEE"T") = ~~u3()
AVERAGE r:'L..I:)W VEl_OCI'rY(f~EET/SE(~.) 6.~~U
F'r:::DDUCT UF ocr::"111::'V[::I...,OC IIY 1.4.::;
U'IF(EI :'IF'L.(J~J!'I::;:(:,VEL.I I I"'IF. e 1'/ I 1\1) 1.. 09 'IC I !"I I 1\1) 11.7:1
lOCI YEAR RAINFAl_L II~l'ENSITY(INCHjHOUR) 4u230
*USER UPCCIFIEOISU8AREA),
RURAL DEVELOPMENT RUNOFF COEFFICIENT = .5240
SUBAREA AREA(ACRES) 1.48 SLIBAREA I~UNOFI:(CFS)
SUM11ED AREA(AC:RES) = 1.64 TO.T.AL. RUNOFF(CFS)
I"':nu DF' UL.lb(iF:::[:':::, bT'F(F:F'TF'I...DL,J 1...lfDn(,LJL. I C:!::;::
DEPTHeFFETl .27 HALFUTnCET FLODOWIDTHIFEFT)
FLOW VELC)CI-I'.V(FEE-rISE:C.) 1./t! DEPT~!.~VEL[ICI-rY
'_., i.'.,
..:'" .Le;
:::::" 6:1.
,<1- " ~;:.;~ (?
:.;?" 0::3
****.~.~******.**.~.~.~~.***.~***************.~**************.~.~*.~******************~.*
FL.OW PROCESU FROM nODE
:L ()" O() .ffJ I\!(JDE:
~;:.:.:o. O() I H [:(::)01::::
'_.,
..;.'>.>.>>r~(.).rIO)\I(',l.... )"IF-fl..-IUI) 11\11 T'I(:il.... HUDPIF::I :(.) Pil\I(:JI.\!F:lb<<.,....
. :~)OIL CL.(:IE.~F:IF.IC().rJ[I!\! lb 11011
· RUnAL. OFVELDPMENT RUNDFF COEFFICIENT ..4500
NATunAL WATFnUHED NOMDGRAPH TI~~ DF CW~CEnTnATION
l,lJ J .fH 10.....1../1 I 1..,.lu.rE:~:::: (:l:UOr::::D J 0" ~;?7 (IV! I !\IU.Ti :8)
INI"j-IAl_ SI.JBAREA 1=I_OW-L.E~N(3TH(FEE.'r).- lel.OO
LJF)S.fREAM El_EVATION 220"OCl
DOWNS.fREAi1 I~LEVA1'10N = 219u90
ElEVA-l'.IO~i DIFFERENCE = .10
100 YEAR RAINFAL.L. INTCNSITYIINCH7HDUR) 4.604
SUBAREA RIJNOFF(CF.S) - .00
TOTAL. AREA(ACI~ES) ,,00 TOTAL I~LJNOFf~(CF'S)
(j()
*.~**.~****,~.~.~.~***.~*.~*.~,~.~~,************.~****~..N-.N'.~'~**.~.~.~*******.~,*,~.*****.~**.~***,~*,~,
FLOW PROCEUS FRDM NODE
:;:.:.:()" ()O 'TU !\IUDF:
::::;0" 00 1 b e[I.DE:
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PRODUC:T OF DEF).r'H&VEL..OCII-Y
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SUBAREA AREA(ACRES) .52 BlJBAREA RUNOFF (Cr:
SUMMED AREA(A(~RES) - .52 'TOTAL_ RIJNOFF(CFS)
END OF SUBAREA STREETFLOW HYDRAULICS:
DEPTHlFEETl = .18 HALFSTRO:T FLOODWIDTHCFEETl
FL..DW VELOC]:l-Y(FEET/SI~C") 7.50 DEPTH*VEL.OCI1-Y
-------------------
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PEAK FLOW RATElCFSl -
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END UF RATIONAL METHOD ANALYSIS
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Page 7 of 11
V REFERENCES
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