HomeMy WebLinkAboutCT 72-24; SPANISH VILLAGE WEST; PRELIMINARY SOILS; 1973-05-24•
•
PHILIP HENKING BENTON
PRESloi>:NT • CIVIL ENGINEER
l.a Costa Land Company
BENTON ENGINEERING, INC.
APPLIED SOIL MECHANICS -FOUNDATIONS
6717 CONVOY COURT
SAN DIEGO, CALIFORNIA 92.IU
May 24, 1973 1.
£'.'.EEIII. J I C-r7:<-~T
TELEPHONE (714) 565.1955
• Costa Del Mat Road
Carlsbad., California 92008
•
•
•
•
•
Attention:
Subject:
Gentlemen:
Mr. Irv Roston
Project No. 73-3-9BC
Preliminary Soils Investigation
Spanish Village West, 7 Acre Site
Rancho La Costa
Carlsba,d, Cal ifornia
'It is concluded from the field investigation and laboratory test res,ults that:
1. A~ old lan~suvas,i9.ul;ld .~.e,t~~~n the .de~t~s of ~1:~ a!l~ ~PJ_~~gt
Boring 1, where the'5lfde debris consists of a mixture of clayey fine sand, fine sandy clay and
clOy~y 'silt. Abundant gypsum. filling and some brownish iron stains were also encountered'in'
the fractures. Also, extensively slickensided gray clay and silty clay zones were found below
a d~pth of 19.0 feet and to the end of the bori ng at 46.5 feet in Bori ng 2. Some of the cI ay
strata between these depths were highly sheared and fractured f~om previous tectoni(; movements.
Ifexcavations are to be made in these zones, the excavation slopes should be kept no steeper
than 3 horizontal to 1 vertical and to the lowest possible heights., The lateral extent and stabil-,
ity of these zones should be carefully examined during grading operations to check whether buttress
fiUs or stabilized fil'ls will be required. If feasible, it would he preferable to plan grading so as
not to cut into these unstable zones. .
-----~-
, 2. 'In the centrak valley reentrant area where ]Br!ng~aIt~.A_,«eJ:e_~tt.lU,~d, the upper
'4~,5'feet of soils in Boring:;3 arid the upper 8.5 feet of soils in Boring 4 were found to be compress-
'ibl'e' and low in density. The soils in these zones should be properly densified before using for
any structural support or the' pl'acement of compacted fills upon these soils • This may be accom-
plished either by removal and recompaction of the compressfble soils or by a surcharge fill.
Detqiled soi~:_~estJg~tlQlls'should ~e undert<:,ken_l!lfh~. v~H~}' rELeQJ:.r..aDt9r~~~f high rise buJld-
i ngs_or anx..b'§'Q..'(y.JjJ".!:!.f.t~ .. L~~~ !~ __ ~~ ~~-".:!ru~r~~_L'1,_th ~~..9:.~.--, . . ,: ,.'
3." The-in-place' granular type sC?ils such as' slightly c!Qyeysand, clayey sand and silty
sand, are -suitable for structural support, both as natural soils and as compacted fiUed ground. The
,fine-g~ained type of soils such a~ slickensided clay and silty clay, sandy clay dnd clayey silt,
I
I
•
•
•
•
•
•
•
•
•
I.
•
Project No. 73-3-9BC -2-May24, 1973
La Costa -Spanish Village West, 7 Acre Site
should not be used for structural support unless special design precautions are observed, because
of their expansive potentials, 'based on the laboratory :test results and our post experience with
the fine-grained soils in these areas; When used as c9!!',e...~te5LmLm9t_~_riQ.l,_tb~LfLtte::gr..aine:d~type
of soils should be ~lacedgt~qA~pt.b __ of 3-feet or rnoie-~_~lQw. .. prqp.ose(Lfi,nished grad~s of concr~te slabsCindf~9~_ ~nd, be'pTg~e-ctQtJ ~~st.i6. feet' Q-;:~Qre inside compa~te-(ffn i ;GP~;:~"-Irp--;;t~~:
tially expansive types of soils are exposed in the upper 3.0 feet below finished grade after
excavation, these should either be removed and replaced wHh nonexponsive soils uniformly eam-
pacted to at least 90 percent of maximum dry density or, if these soils are permitted to remair~ in
the upper 3 feet below .finished grode, footings and concrete slobs should be specially designed
for expansive soils conditions. Recommended procedures for special design of footings and con-
crete floor slobs are presented in the attached Appendix C. It is recommended that all lots be
inspected at the time of grading in order to determine those lots which contain potentially expan-
sive cloy soils within the upper 3 feet below grade. If necessary, hand-augered holes 3 feet in
depth may be drilled in the lots in order to make this determination.
4. The excavated natural soils, when properly compacted fo at least 90 percent of
,:,aximum dry de~sity in acc~~dance wi~h the A.S. T .M. D 1557-70.method o.f compaction a~
In accordance With the applicable sections of the attached Appendix AA, wd I have an al-loW~'"
able bearing value up to 3930 pounds per square foot for one foof wide continuous footings
placed at a minimum depth of one foot below finished grade. The settlement of a one foot wide
continuous footing placed one foot below finished grade and loaded to as much as 3000 pounds
per square foot is estimated to be less than 1/4 inch. This value applies to all soil types encoun-
tered within th.e subject property. .
, .
5. Undisturbed firm natural soils have on allowable bearing value of 2490 pounds
per square foot, for one foot wide continuous footings located at a depth of one foot in sucb
soils. The estimated total' settlement of a one foot wide continuous footing loaded to 2490
pounds per square foot is le~s than 1/4 inch.
6. When bedding plane failures are not involved, cut slopes may safely be mode to
tb~ following maximum heis~ts witb adequate factors of safety:. .
Predominant Soil Cut Slope Safe Maximum
Type in Cut Slope 'Horizontal to Vertical Heights in Feet
Case A Case B
Fine-grained soils 2.5: 1 29
3.0: 1 19 35
4:0: 1 26 5,1
Granular soi Is 1.5: 1 30
2.0:1 54
The safe maximum heights presented under Case A apply to excavations, made through
old landslide zones and slickensided clay zQnes described under paragraph. 1. The recommended
slope under Case A is 3 horizontal to 1 vertical or flatter. The'safe mqximum heights presentee!
under Case B apply to excavations made through relativeJy frqcture-free fine-grQined soils, based
on the information obtained from this investigation. The recommended slope gradient under Case
B is 2.5 horizontal to 1 verti¢al or flatter. ILoid landsI.Lde~d...z..Qne_s ... ar.e,..£ound .. dur.iRg .. gF~(;Ung
BENTON ENGINEERING. INC.
•
•
•
•
•
••
•
•
•
,.
I
•
Project No. 73-3-9BC -3-Mqy 24, 1973
La Costa -Spanish Village West, 7 Acre Site
bperafi0ns that ~ not foun..d...i.Jr:\der-thi,s-j,nvest.igat-i0nrthe-sl.ope_gLqQl~n~. an~~~ximum sqfe'
heightsshOUId be changed to <;ase A_pt_thQttime~ ~~l!Jyili depend on. the findings pf lnspecti.9ns
at tne -fime of graering.
~ _~_)oOUo'>.O"";;_" __ ' -
'7. If the excavated granular sons are compactedunaer: CQntinuous inspection and in
accordance with the appl icable sections of the pr0cedures descrtb.ed in the attached Appendix
M, then the compacted fill slopes may be safely constructed up to the following maximum
heights with adequate factors·'Of safety.
Slopes
Horizontal to Vertical
1.5: 1
2: T
2.5: 1
Recommended Maximum
Heights in Feet
38
66
154
8. For both excavated slopes and compacted fill slopes, it is assumed that suitable
erosion control devices will be provided at top and toe of the sl.opes in order to minimize erosi'on
of the slopes by surface runoff and to avoid the possibility of loss in lateral resistance due to '.
sC0uri ng of the toe by surfa_<;.~u:vnoff. --_. -.--~--~--......... --~ .. -.-~ ... -
9. For earthwork estimates, a shrinkage factor of 3 perce.nt may be assumed for the
excavated soils, in addition to the settlements of the supporting $oIls due to surcharge fil'ls. If
fill soils greater than 10 feet in thickness are placed in the areas of Borings 3 and 4 and the
supporting existing soHs are later su~iected to water intrusion and become saturated, then settle-
ments up to 3 inches and 1 inch, respectively, may be assumed for: aadhwork estimated in the. areas
of B~rings 3 and 4.
10. Residential buildi.ngs may be constructed partly on cuJ:. and p.artly on compacted, filled
ground provided the load-settlement characteristics of the-natural ,soils and the compacted,fiHed
ground are comparoble.
ff any soil types are encountered during grading operation that were not tested in this investigation,
additional laboratory tests will be conducted in order to determine, the.ir physical characteristics,
and ~uppleniental repor~ and recort:lmendations wi II automatically b,come a part of this report '!
The data presented on the attocheCi pages are a part· of this report.
Respectfully submitted,
BEN10N ENGINEERING, INC.
By :vwe:'~~~ -'w=-
S. H. Shu, Civil Engineer
Reviewed by 'IJ1AI~
M. V • Pothier, Civil Engineer
Chief Engineer
Distr: La Costa Land Company
(3) Attention:' Mr. ltv Roston
(1 )"·.Attention: Mr. Bob Stork
Herman D. Ruth & Associ ates
(1) Attention: Mr. Herman D Ruth
(1) Rick Engineering, Carlsbad
SHS/MVP/ew
BENTON ENGII'IEERING, INC.
•
•
•
•
•
Project No. 73-3-9BC -4-May 24, 1973
La Costa -Spanish Village West, 7 Acre Site
DISCUSSION
A preliminary soils investigation has been completed on the praperty known as Spanish Village
West, 7 Acre Site, of Rancho La Costa, Carlsbadl California. The site is located easterly of
EI Cam ino Real, and the south boundary of the si te is approximately 3300 feet southerl y of the
intersection of La Costa Avenue and EI Camino Real.
The objectives of this preliminary investigation were to determine the general subsurface condi-
tions of the subject area, to identify potentially problematic areas and to present appropriate
soil parameters for preparing gradirig plans and future foundation design. In order to accompl ish
the objectives, four borings were drilled and representative soil $omples were obtained from t.he
borings for laboratory testing. Also, pertinent portions of our report of Project No. 73-3-16BC
Were reviewed.
The general terrain of the site may be described as gently rolling to steep sloping terrain in the
southern and northern portions of the site and a 51 ightly sloping valley reentrant in the central.
portiC!)n of the site.
According to 'the "Soi'! Map II prepared by the U. S. Department of Agriculture, the upper seils in
the area are described as Las Flores loamy fine sand and Botel'la loamy sand. The soils encountered
in the investigation consisted primarily of clayey and slightly clayey sand, silty sand, clayey silt,
day, silty clay and sandy clay.
Field Inv:estigation
The four borings were drilled with a truck-mounted rotary bucket-type dri /I rig at the approximate
locationss"flown on the attached Drawing No. 1, entitled IILocation of Test 'Borings. II The borings
were dril-Ied to depths of 14.0 to 46.5 feet below ~he existing ground surface. A continuous log
of the soils encountered in the horings was recorded at the time of drilling and is shown in detail
• on Drawing Nos. 2 to 10, inclusive, each entitled II Summary Sheet. II
The soils were visually classified by field identi.fication procedures in accordance with the Unified
Soil Classification Chart •. A simplified description of this. classification system is presented in the
attached Appendix A at the end of th is report.
• Undisturbed samples were obtained at frequent intervals, in the soils ahead of the drilling. The
drop weight used for driving the sampling tube into the soils was the "Keny" bar of the drill rig
which weighs 2200 pounds, and the average drop was 12 in.ches. The general procedures used
in field sampling are described under IlSamplingll in AppeRdix B.
• In addition, a geological r.econnaissance investigation was completed for this area and is attached
as Appendix D.
•
Laborat0ry Tests
laboratory tests were performed on all undisturbed samples of the soils in order to determine the
dry density and moisture· content. The resu I ts of these tests are presented on Drawi ng Nos. 2 to
10, inclusive. Consolidat·ion tests were performed on representative samples in order to determine
BENTON ENGINEERING, INC.
•
•
•
•
•
•
•
•
•
•
Project No. 73-3-9BC -5-May 24, 1973
La Costa -Spanish Village West, 7 Acre Site
the load-settlement characteristics of the soils and the results of the tests are presented graphically
on Drawing Nos. 11 and 12, each entitled "Consolidation Curves. II A Summary Sheet and two
Consolidation Curves from Our report of Project No. 73-3-16BC ate also included and are shown. on
Drawing Nos. 11 arid 14. The general procedures used for the above laboratory tests aredesc~ibed
briefly in Appendix B.
In addition to the above laboratory tests, e~pansion _~.~. were performed on some of the clayey soils
and other potentially expansive soils encountered to determine their volumetric .change character-
isti cs with change in moisture content. rhe recorded expansions of the samples are presented as
follows:
Boring
No.
Sample
No.
Depth of,
Sample,
in Feet.
Soil
Description
CI ayey Hne sand.
Percent ExpanSion
Under UnU Load of
500 Pounds per Squqte
Foot from Air Dry
to Saturati on
1
1
2.
'3
1
3
6
2
5.0
15.0
31.0
6.0
Silty fine sand with clay binder'
Clay
1.00 ,-
0.30
7.22., .
0.25 . ~ Cloyey fi ne sand
Compaction tests were perform~d on representative samples of the soils to be excavated to establ ish
cQrnpaction criteria. The soils were tested according to theA.S. T .M. D 1'557-70 method of c;om-
paction whi ch uses 25 blows of a 10 pound rammer dropping 18 inches on each of 5 layers in 'a:4
inch diameter 1/30 cubic foot mold. The results of the tests are presented as follows:
Maximum Optimum Mois-
Boring Bag Depth Soil " Dry Density tureContenf
No. Sample in Fe.et Description Ib/cu ft % dry wt
1 1 2.0~ 3.0 CI ayey fi nesand 111.0 15.0
1 2 12.0-13.0 Silty fi ne sand 114.4 13.5
One. mechanical analysis test was performed on a silty sand soil in accordance with the A.S. T.M.
D 422-6lT method of testing, in order to determine the fraction of fine-grained portion in the
soi-! mass. The result Is presented below:
U. S. Sieve Size
No. 200
Soil Classification
Boring 4-, Bag 1, At 1.0-2.0'
Percent Finer by Weight
32.4
Silty sand
In order better to classify the finer grained soils, Atterberg Limit tests were performed on certain
sampl es in accordance with A. S. T .M. Designations D 423-66 and D 424-59. The results of
these tests and the group syml;>ols for the soil classifi.cationsare presented on the following page.
BENTON ENGINEERING. INC.
• Project No. 73-3-9BC -6-
La Costa -Spanish Village West, 7 Acre Site
May 24, 1973
Bag
Boring Sample Depth
No. No. in Feet Soil Description
Liquid Plastic Plasticity Group
Limit Limit Index Symbol
• 2 1 21.0-22.0 Clay
2 2 33.0-34.0 Sri ty clay
56.8 20.8 36.0 CH
36.5 18.6 17.9 CL
Direct shear tests were performed on selected loose soil samples remolded to 90 percent of maximum • dry density and on selected undisturbed samples that were all saturated and drained prior to testing.
The results of these tests are presented betow:
Maximum Angle of
Normal Shear Internal Apparent
• Load in Load Fri ction CohesiOn
kips/sq ft kips/sq ft Degrees Ib/sq ft
(A) Undisturbed Sample
• Boring 1, Sample 2 0.5 1.54 24.0 820
Depth: 10.0 Feet 1.0 ·1.27
2.0 2.22
Boring 1, Sample 7 0.5 1.63 36.0 * 820
• Depth: 35.0 Feet 1.0 lAO
2.0 4.06
Boring 1, Sampl e 8 0.5 1.30 31.0 970
Depth: 36.5 Feet 1.0 1.58
2.0 2.21 • Boring 2, Sample 8 0.5 0.91 36.0 * 260
Depth: 41.0 Feet 1.0 2.03
2.0 3.31
• -Boring 4, Sample 1 0.5 0.75 32.0 430
Depth: 3.0 Feet 1.0 1.06
2.0 1.72
(B) Loose Soil Sample Remolded to 90 Percent of Maximum Drt Density
• Boring 1, Bag Sample 1 0.5 1.22 35.0 820
Depth: 2.0-3.0 Feet 1.0 1.58
2.0 2AO
Boring 1, Bag Sample 2 0.5 0.95 40.0 540 • Depth: 12.0-13.0 Feet 1.0 1.37
2.0 2.27
* Arbitrarily reduced
• BENTON ENGINEERING, INC.
•
•
•
•
•
•
I
I-
•
•
•
Proi.ect No. 73-3:"9BC :"7-May 24, 1973
l.d Costtl1-Spanish Village West, 7 Acre Site
.·:Using the lower values of internal angle of friction and apparent cohesion~ and the Terzaghl
FormulafQr local shear failure, the safe allowable bearing pressures for the soils are determined
as JciU ows: .
Local' Shear F~rmula Q'd = 2/3 CN' c + y. -Of N' + y BN'y . . q
·Assumptions:
Undisturb~d natural soils
<P ~ 32 Degrees
N' = 21 c
.(1) Continuous footing 1 fOQt wide = 2B
(2), Depth of footing = 1.0 foot = Df
C = 430 Ib/sq ft
N' =11 q
y = 102 Ib/cu ft
.' Q'd = (2/3 x 430 x 21) + (102 x 1 x21) + (102 x 0.5 x 7 )=1476 Ib/sq ft
Q'd Safe = Q'd +3 (Factor of Safety) = 2490 IQ/sq ft
. ~, .
Fill s9Hs compacted to 90 percent of maximum dry density
. <P = 35 Degrees
. N' = 25 'c .
C = 540 .Ib/sq ft
N' = 14 q
y = 117 Ib/cu ft
N'y = lO
Q'd = (2/3 x 540 x 25) + (117 x 1 x 14) + (117 x 0.5 x 10) = 16,577 Ib/sq ft
Q'd Safe = Qld -:-:3 (Factor of Safety) = 3930 Ib/sq ft
BENTON ENGINEERING. INC.
•
•
•
•
•
•
•
•
.'
•
•
.'1; f
." .
·4-PROJ£CT 80VNDAflY-APPROA'IMAT£
(lI -lod.icat.es Approximate ocqtion Of Test Boring Project No. 73 ... 3 ... 9BC
'," S -Indicates Approximate L()cation Of Test Boring Profect No. 73-3-16BC
PROJECT NO.
73-3-9BC
. DRAWN· RW
LOCATION OF reST BORINGS
SPANIS.H VILlAGE WEST - 7 ACR~S
RANCHO LA COSTA
CARLSBAD, CALIFORNIA
BENTON ~NGINEEIING, INC.
SC. LE:l ll=200'
DRAWING NO. 1 .
•
•
•
•
•
•
•
•
•
•
•
w ~ < z
'"," w w .u.. ...... ::t t-Q.
W 0
0 .-, ..... ..
.:. ...... ..
SUMMARY SHEET
BORING NO._--L1 -.-. ....
ELEVATION 125,01 *
-
1 .....
Brown, Moist, Loose : $tJ GHTL Y ..... '{
•. ~. . . CLAYEY tiNE TO FILL ': : : : >\~_~ _______ -4M_jED_I_U_M_S_A_N ...... D.-.IJ}-----1~-'-+---I-~-+-""'l:-'-' -I
, .........
-. . . .. Light Brown To Brown And T
2= n ':': : :: Yellow With Yellow And Orange
W .... .. Staining In Spots And In.
3-': : : :: Frqctures, Slightly Moist, Very
-:: : : :: Fi rm
4-~~:Z::~:~:~~~~~~~~~~ .-{,\ ...... 15 Inch Layer With Clay Filling
'. 5-\.!..J ::::: In. Fractures, Roots, Dips 10 To
;" -;:::: 20 Degrees
6-.. ~ ...... ,-.. ........
' ......... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..........
'e ........
-.......... .......... 9-;;._ .......
~. .. .. .. ..
, -{,:;\
:: 10-\.6J """.-,. -. -, ,-I
............
-
Bedding :Dips 7 Degrees Due
North
White To Light Gray,Slightly
Moist, Very Firm, Clay Binder,
Micaceous, C(oss-bedding
Dips 5 To 10 Degrees '
CLAYEY
FINE
SAND
SILTY FINE
SAND
46.2 9.3 107.1
19.8 ]3.9 96.8
99.0
Cont-inued on Drawing No. 3
8.6h 10.1 .
-
-
-
-
-
-
-' -
-
-
-
D -Indicates Loose Bag Sample
o -Indicates Undisturbed Drive Sqmple
* -Elevations Shown 'Were Obtained By Interpolation Between
Contour Lines On Drawing Fumished By Rick Engineering, Inc.
at -o .,
PROJECT NO.
73-3-9BC
DRAWING NO.
BENTON ENGINEERING, INC. 2
•
•
•
•
•
•
•
•
•
•
•
W ::E < z
SUMMARY SHEET
BORING NO. 1 (Cont)
,I-W wa: W u. .... w -Q.co :x: ~:E I-Q. en~ W Q
, 15 -
, 16-1;~~White ToUght Gray,Slightly ,:.':~ Moist, Very Firm, Clay Binder, ~ Micaceous, Thinly Beddea Bi.oHte ~ : aaods Dip 0 to 5 Degrees
SILTY FIN!:
-SAND
17-:: :: : : 1\\-__ ---, ______ -+ _____ ..,..1/
18=:: ::: Light Yeliow;Light Gl'ay,And
_ ~ :': : : Light Brown.,Slightl')! Moist, Very
~ .... Firm, Bedding Dips 8 Degrees t\t
]9-'.. . .. North 60 D,8grees, East
":' ' ... 1\ . , ',____.
20=@ :,: : : :: Lenses otMicaceous Silty Fine
_ :",' .. , 5qhd, Thinly Bedded
-
26-
-
27-
-
28-
-
29-
-@ '6 sO-
-
31--
32-
-
33-
-
-
-
-
;. ' ... ·0" · .......
.. .. .. .. .. · .......
'. >::. Light Yellow And Light Gray
.. " .e o .•.. ~...... .. .. ., ':" .. -.-0. e.
0": . : .0.:. _: ...
~-:": .. '.
.. -......
· .. :. Dark YeUow To Brown With
: : : : : Yellow And Orange Staining,
: :: : :' Slightly Moist" Very Firm,
: : : :' : Slightly Micaceous, Lenses Of
: ':' : :: i\Silty Fine Sand
: : : :: 1/16 To 1/8 Inch Gypsum Seams
:: : : : Along Bedding .. .. .. .~ ..
: : :' : : : Slightly Moist TQ Moist,
; ... ',' Abundant Gypsum In Fractures .. , .. '"And Bedding
Very Soft Pods Of Orange Clqye}'
Sand On West Side Of Hole Due To
Old Landslide Movement ,Bedding
Dips 2 Degrees At South 15 Degrees
East
CLAYEY F=INE
SAND
SILTY
FINE
SAND'
CLAYEY
F=INE
SAND
> >. W' o· Q~~ 1-1-(JI-a: I-W~ ~': zu. a: < . zen 0-11-> W~ <1-0, w2: Wena:, Q~ Wen~ W~ iLe Q >:g i3ic;;~ 2:..= ::E~ w-a:u. ' l!i .... ~lII::
Q
52.8 ] 1'.4104.0
55.0 6.8 105.1
97.9 17.8 1 07.2
-Continued, on Drawing No. 4:
PROJECT NO.
73-3-9BC BENTON ENGINEERING, INC.
DRAWING NO.
3
•
•
•
•
•
•
•
•
•
•
•
cu ... . -V')
!! ~
........
....
w :E « Z
m ~
z
SUMMARY SHEET
... 0
w wa: i=...1 w ..Jw ..1«0 ~ Q.m -(Jm
:J: . :E.:E 0 iL:E
Ii: ~~ (I)~~ w « c ...I
BORING NO. ] (Cont)
(J
33 , .. , .. Dark Yellow Te Brown With
-.. : : : Yellow And Orange Staining,
34-., ... : : : Slightly Moblt'To Moist, Very
-;.= <Z) ,":':', " ',firm, Slightly Micaceous, Len~es
35 " . :, \of Silty .Fine Sand -.. ,. .. '
" 39--' . ,'--_____ -.,-______ --1
_ r:l " , Blue-Gray, Gray-Brown, Dark
W .,.. :, \Brown And Orange-Brown, Very 40-, _ ," '~, , : lv'Ioist, Very Firm
41-~ ~ ,: '
_ ' , Dark Gray To Blue-Gray, Moist,
42-'iQ) '"'' Very Firm, With Fine Sand,
-
43-
~
44-
-
45-
-
47-
-
-
-'
.. ':
" '
, .
" .
"
.'
,,'
' .
. ' Micaceous,l.enses of Silty Clay,
Slight Petroleum Odor i ," ,
, Thinly. Bedded, Slide Piane Dips
31 Degrees At North 65 Degrees
" West,Gypsum FJ lied 'to 1/4
l\
Cal iche 6 Inch~ayer, Gypsum
fill~d Fractures An~ Along
Bedding To 1/4 In,ch
-
CLAYEY FINE
SAND
CLAYEY FINE
SAND AND
FINE SANDY
CLAY MIXED
WITH CLAYEY
SILT
CLAYEY
SILT
/
I
Hiahlv Cemented .' .. ' I -
-
-
-
-
---
-
-'
-
-
-
PROJECT NO.
73-3 ... 98C BENTON ENGINEERING;' INC.
> CI~ w~ a:u. Q~ . wen zQ. U:t;~ w_
w~ >. iLeQ _ ... ~~ a:u. c
~49.6 17.9
-1-6.3
146.3 15.2
133.1 15.3
>. ...... (if': z.::l w(J Q~
>'lB ~..J
102,.1
82.5
112.2
110.2
,
.... .. "
w.,: (Ju. a:z , ««d wt;S!!
iiUif w-a:~
DRAWING NO.
4
. ,
I
•
•
•
•
•
•
· (;;
••
•
•
•
o --.... > ..s:: lit '2 o
en
I-w W
II. .... :J: Ii: w ,Q
0
1
2'
4
5
6
7
8
9
10
11
12
:1
14
SUMMARY SHEET
BORING NO. 2
ELEVATION ] 05.,01
~ f
: : : : : : ~igh~ Brown To Light Orange-
: : : : : : Brown With Pods And Streaks Of
: : :: : : Yellow And Orange, Slightly
: : : ; : : Moist, Very Firm, Slightly
: : : : : Micaceous, Brown Clay Filling
..... , Fractures, Occasional Rootlets
· ....
Ci): .... . · ... . · ... . · ' .. -' .
,<:':: <':: Light Brown To Light Orange-
:<' .... >: Brown With Pods And Streaks Of
:--,:-:.,'.:: ': Yellow And· Orange,Slightly
. Moist, Very Firm,Lenses Of
Clayey Fine Sand ,
.' ... ,
® .~«.': 2 ,', ..... . ',' .. . :. ~"::,
9 Inch Layer Of Brown ,Dry ,
Highly Cemented Clam Shells
:/.>:::: ::: Light Gray To White With
:',: " :' .. ' Yellow Streaks,Micaceous
~~ .. ~::: ':,:',:: AI ternating Layers Of Brown And·
.,>: :: ::':', Light Gray Lenses of Clayey
',',;':: ~:-Fine Sand, Bedding Dips 2
.,','. Degrees At South 20 Degrees
East
CLAYEY I=INE
SAND
SILTY FINE
SAND
15 ®
. 16 Bedding Dips 2 Degrees At South
::>:'::;':.:; 60 Degrees, East
. > ..... :: " Very Soft Pockets And Hard Lime
Cemented Nodules-Slide Zone
With Gypsum Veins
PROJECT NO.
73-3-9BC
Continued on Drawing No.6
BENTON ENGINEERING, INC.
> >. W' CI' w..: 1-1-(JI-0:1--II. w~ QO:~ ~. zu. a:< • zll) .J1:> w::l < " w2: WII).a: Q~ wI-II)
~ :J:II)-W iLi5 Q >:g 1I)0~ >. ::E~ w--I-a:.J a:.lII: a: II. . Q Q
15.4 9.8 102.0
26.4 7.7 06.3
24.2 10.0 112.4
DRAWING NO.
S
• ~ w W,
II. -. ~
Q;.. w Q
~ ~..1 ..1(.)0 0-111 ,~u. :iE v.-> ~en c( ..I
SUMMARY SHEET
.. 2{Cont) BORING NO •
> >. W' ClI' w..: ~~ (.)~ a:~ w!!:: Q~~ ~': zu.
zen a: c( •
w!!:: ..I~.> w::l c(~O Wena: Q~ wenS!! w:.:: U::oQ >~ l:C;;!f >. :iE~
.en w_
-~ a:-I a::':: a: II. Q
• 19''1' t--C=(.):::::I-::--=---:-:--=--:-:-:-:--.,-------r----r-~t--1~4-"I -t::=::t Gray-Green' T~ Greeh;Moist,
Q
•
•
•
•
.... s · ~
•
2"-E§" §~ Firm, S.I ickensided,Gyp$um. ;v ' ... ' . VeIns, 'Fractured, LandsJide Zone -'4' . . Slip PI.(;me Dip's 6 Degrees Due
21-V .; West, Root !,e t:s In Fr.actu~s . -[1] :... '
22-c.. 1\ ----.,..---~
. L, I yery Firm, Slip Plane. Dips 290
.., :;:' ....... ~ At South 20,0 West ~ '23-. -" ----.,.. : ';,: . '. Firm, 1 Foot shear Zone . -
.'24'-
,'-i::~:"~' ~jV~ery~F~ir~m~:§:J~~;;;-A~ ,,:25-.,
"26= t,:'\5 ::,':,:,: .. :::,': .... Slip Plane'Dips 28 Degrees At ,_ \V . South 60 Degrees West
.' -
27-
-.
,28-
-.
29-
'-
32-
-
Yellow-Green, Moist, Very Firm,
' ... , .. Micaceous,.
'Dark-Green To Gray-Green,
t;i:E: ~3lv\oist, Very Firm, Some e' , Slickensides And Fracturing
..
'"'' , , .' , Yellow-Green, Moist, Very Firm, ,"
Micaceous, Some SI ickensides
'0 And Fractuting
34-" _ .,' Dark-Green To ~ray-Green,
~·';=Sf.Aoistl Very Firm, Highly Sheared
·35"" . r::' , And Slickensided, Movement In
·.36.:=®.E!:::::S' Many Directons,Most Shear 1:6::::3 Planes Dipping 60 Degrees '-
CLAY
,.
./
.sILTY CLAY
CLAY
SILTY CLAY
CLAY
Vl '~377""
•
•
w :iE c( Z
III o ..,
-
, 38-.
-
39--
-
40-Continued on Drawing No.7
BENTON ENGINEERING, INC. PROJECT NO.
73-3-9BC
33.0 22.2~·04.9'
36.2 17.4 106.8
61.6 16.8 112.6
62.2 14.3 117.9
l
(
DRAWING NO. 6
•
•
•
•
•
•
•
•
•
I.
I
•
J! .-V'l
2! ~
I'-..
.... ti 3
ci)
..Eo .-> ..s:: CIt . -c 0
V'l
W ::e <t z
III o ..,
z
I-0 i= .... w we:: w ""w .... <to II. -0. III -(Jill X ::e::e Oii:::e
Ii: <t:;, CI)_> Cl)z ~CI) w 0 <t ....
40 .U
-Q' 41-
-
42-
.. -
43-
'. '"'" .~. ;.'
44-
".;, -~,~ -
" 45-"'. .. -
46 ... .(0 ..
. -l,!"
':--47-
-. , -
-:
-.
--
-
---.
--.-..
-
--.
-'
..."
-
-:
-
.,.-.
---
---..
~
PROJECT NO.
73-3-9BC
> >. C!. w' 1-1-W' a: I-(JI-
SUMMARY SHEET wI:!:. a:~ in II. zu. 0:;, z· a: <t • zCl)
BORING NO. 2 (Cont) w!!: ""I-> W:;, ~I-g.
wlW:: WCl)a: o~ xCl)-U::oo >CI) Cl)in~ >. -I-::e~ a:1XI w-a: II. 0"" a:lW::
0
Dark Green To Gray-Green i
. Moist, Very Firm, Highly Sheared 34.1 18.4 119.3
And Slickensided,Novement In
, Mony Directions, Most Shear
Planes D.ip 60 be~rees
\
1 Inch Very Soft Remolded Clay CLAY
Seams Dips 6 Degrees At North
60 Degrees West
Dark Blue-Gray,Moist,
51 ickel1$ided R26.5 .14.1. h 17..4·
,
DRAWING NO.
BENTON ENGINEERING, INC. 7
•
•
•
•
•
•
•
I. ! 0-
•
•
•
II) ....
V')
~ u «
" .... ;
3=
II) g>, -
> ...c 0 .-c:
V>
w :::E < Z
III o ..,
I-w' W II. .... :t'
t: ,w o
SlJMMARY SHEET
BORING NO. 3 '
ELEVATION 73.,Oi
_ : .: : : ; Gray-Brown,Moist,loose,Vety
1 ' • ... : Porous., Roots, ~ome /v1edium
-: Grains, Topsod To 2 1/4 Feet -OJ :::::
2-
-f.\ :::: :. Dry To Slightly Moist,Medium
3-\.lJ ::::: Fi rm · .......
') .. of" • .. .... .. .. . ' ........
':~:::.Firm ..........
," ..... ..
. o· .. .-.. ..
of" ...... .. .. .. .. ..
.. .. .. .. .. -..... · ........ 7-.......... .. .. .. .. ..
Of" i ....
I
CLAYEY
FINE
SAND
> >. C!I' a:1-O~~ 1-1-
w!:!:. 011.
zen ..I~> Z· w~ w2: Wena: O~ wX ii:5° >. >en
-I-:::E~ a:CQ a: II. 0..1
0
~
13.2 4,7 87.2
22.0 6.5 92;4
w .,
Ul-a:zlI. «d wti en ' :I:-~ en en w-a:x
-8~ ~.~~:~~~~~:~--~--~--------------~~' (UM~e~ro~.es~~ __ ~-i __ ~~ __ ~ __ ~ __ -i __ ~
'" Gray-Brown To ~ight Brown, Dry
-;. ~~ To Slightly Moist, Firm, Very
9""" ><.. '" • ... " Porous, Some Medium Groins -t:::\ '.",', ...... ,:
10--~ .~ .~ ." ...... -
1l~
..., ." ....
12--· .. ......
MIXED CLAYEY
FINE SAND
.' -[i] "~~ . . AND SILTY
13.".. ~~~. ~;~~:.~: -SI-i9-h-tl-y-Mo---j.,-st---------'---i FINE SAND
--:
14~
~
',15-
-
.16"'-
..,.
17...;
-
18-,---
19-
...;.
20-
-
21-
@
@
.", .
'" .'<'<
., ",<
",< '(
',", .'" x.," ."
," ..... ., ....
''-.... • ~ •• ,>.,. I"'''' .. ",. Nv' ". ,"'''' ,,~. ,'" "'''', ".
,'t '" '" "'''' ,"""'" .,.
.,< '< '" '" '" '<'<""''''
'o.'o.Y·" "" '.:",' ,,~,' .'\ ., ." " .... "-...... · .....
PROJECT NO.
73-3-9BC
Continued on Drawing No.9
BENTON ENGINEERING, INC.
26.4. 7.5 97.2
24.27.2.99.0
15.4· 4.8 90.4
DRAWING NO. S .
•
•
•
•
.! .-en • 4)' I;. ~ .......
I .... a • 3: .,
0 ....,. ._.
> ...c en -C •• 0
I
Vl
•
•
... w wo: W
11. .Jw ...... Q.m :E: ~~ Ii: et:;>
w enz Q
'2.1
....
22-
-
23-
-
24-
SUMMARY SHEET
BORING NO. 3 (Cont)
ELEVAl'ION_ ........... __
!~'.,' ..... : Gray-Brown To Light "Brown,
Slightly Moist, Firm, V~ry ~~"d ~. ,~~ Porous, Some Medium Grains
, . ",
f '-.
MIXEDCLA YEY
FINE SAND
> > . WI4 CJ' w,,: ...... a:'" -11. a:~~ w!!:: Q'~'~ en· zen Z::i eteto w!!: .J .... > wo wt;~ w'~ wen'a: Q~
>. U:o'Q' >en ~u;f ...... '~~ a:m w-a: 11. Q.J a:~ Q
AND SILTY 24.2 11.2 95.8,
-
27-
-, .....
" .. '.,'.-.-. ' .. .. .. .. .,' . .. ' ... ' .. "
t .......
-..
FINE SAND
Moist
/~~~'~' '; r' Yej.jy Moist
\ li'l~.,:" ~" , .
; ;.':.23 .. 09,:~ '-'7 \.'~':"I:·~"'i'-~~··i"-·f-'~G:ra~y~-~B~ro~W~' n~An~d!jGGr;ra~y;:-:Cc;;;;r;ee;;;n;;:. '~~~:~~~-G~I~l~J=~':" [J . ,~ \U E -, -Saturated, Firm I ,CLAY WITH 30.8 19.6105.4 ,
'cLAYEY FINE TO -
MEDIUMSAND I
AND SILTY FINE -, ..
-TO MEDIUM
SAND J -\ -
,-. ' ,': '. '--
~ '-~---
,-
--
-
-
-
-
-
---
-
-
-
-
-
-
PROJECT NO. DRAWING NO.
73-3-9BC BENTON ENGINEERING, INC.' 9~'
•
•
'.
•
•
•
•
•
•
•
•
... w W II. ..... SUMMARY SH~ET
x
Ii: w Q
BORING NO. 4
ELEVATION 59.5i
v_ ~~ Light arown To Brown,Moist, .
1-. ~ Loose~ Rootsl Very Porous, _ IjJI ~. ~ Topsod To. ~ 1/~ Fe'et, Lenses of
2-~ Slightly Srlty Fine Sand,
_ . 'I'~' .':-.:,-. \Occasional Green Clay Chunks 0···:· \ 3-\.V :.,: ,':.
_. ~:.... Very Moist
~~. 4= : ~ : :: Dark Gr~y-Brown, Very Moist, ® ..... Loose
5--.:.~:::::': _ ...... ' Dark Gray-Brown, Very Moist,
6-
-
7-
-
-
10-
-
.......... ' .... ' .. :.... Very Soft, Very Porous
.', ...... . . ", ....
' .... , ... ...
, . Brown, Very Moist, Very Soft, .
Chunks And Pods Of Brown And
Green Clay, Very Porous'
Soft To Medium Firm
SILTY FINE
SAND
~LAYEY FINE TO
MEDIUM SAND
FINE SANDY
CLAY
MIXED CLAYEY
FINE TO MEDIUM
SAND AND SILTY
rlNE TO MEDIUM
SAND
.. ,-.... 11,... .......... Black-Brown, Very Moist, CLAYEY FINE TO
-
12-
-
13-
......... .......... .. .. .. .. .. .......... .. .. .. .. ..
.. ',"
e' ..... " ..... -... .......... .. .. .. .. ..
Medium Firm, Lenses Of Clay, MEDIUM SAND
Very' Porous
0.6 14.0 89.8
0.6 18.6 ~02.3
5.5 20.7 100.2
14=GV~:~::~:~:~ __ ~ ________ ~ __ i-________ -L5~,~5J~ll9~,A~9~8~L-~ __ ~
-
-
-
.,..,
-
-
-
-
-
-
-
-
-
!XI -o -.
PROJECT NO.
73-3-9BC BENTON ENGINEERING, INC.
DRAWING NO., '10 .. ,. .
'.
•
•
•
•
0
•
.e 8 u
• oS
•
•
l-•• SUMMARY SHEET III III ... III '" . ..... t. '" ... ",IG z 2::2:: -c2:: BORING NO. 6
l-0 ... )0 ,ll( :) .. . ., z "'u'" 54' III, ELEVATION Q'
1
2
,3
4
5
6.
7
8
9
H)
·11
12
Light Brown, Dry , Loose SILTY VERY FINE
TO FINE SAND
Medium Firm
Light Brown, Dry, Firm, Few
Small Chunks of Ou.ve-gray
Claystone and Pockets of Fine SLIGHTbYSILTY
to Medium Sand; Some Zones VERY Fl Nt:' TO Slightly Cemented, Slightly FINE SAND Porous
Light Brown and Gray-brown,
Moist, Medium Loose
..
Gray-brown,' ,Moist, Medium
Loose
SLIGHTLY
SILTY FINE TO
MEDIUM SAND
: ::~, , -_ ..
Gray-brown With Light Brown, " ' .. '. , .. Saturated ' ..
,PROJECT NO,
73 ... 3-16Be 3-3-9BC
BENTON ENGINEERING, INC.
>-~ ri c . . IU"': rJri III Ii: o~. ~ . IU", Z ::) IIIZ " ! JC ... )0 IU U iCII(~
IU 52 . IU"'III a", 1Ut; ...... ii:C5o ')0 vi :Z:'_~ > . "'''' -I-2::;at III • IU_ III ~ a ... 111:l1li: o .
6.5 4.1 87.
11;4
:E'
,::J :;:
::J o.a 12~6 106.8 ..J
<l
0.8
0.8
DRAWING· NO. :j -rr-n :-1 '.
•
•
•
•
•
•
•
•
•
•
lit ~ u
III
JI c z
•• o "a
OQ~ 0.4
1
2
3
'4 ., .,
1&1
Z 5 ~
2 :z: ~
1&1 6
..J Go 2 c ., 7
&&. 0
~ 8 z 1&1 Co) g:
1&1 9 Go
Z o 10 i .'
0 :::;
~11 5 u
12
•
13 .
14
0
• ..
PROJECT NO.
73-3-9BC
CONSOLIDATION CURVES
LOAD IN KIPS PEl SQUAIE FOOT
_ 0.6 0.8 1.0 2 4 6 8 10 IE
Borin~ 3
t--Somp e 1 -,p . Deoth· 31
-\
\
\ --_ ..
\
-\ -
\
\
4~
1\
\ -f\ --. " .... "
..
INDICATES PERCENT CONSOl.lDATION AT FIELD MOISTURE
INDICATES PERCENT CONSOLIDATION AFTER SATURATION
DRAWING N().
BENTON ENGINEERING, INC. 12
•
•
•
•
•
•
•
•
•
• III •
•
= .. o .,
OQ2 0.4
.(~
1
2
3· r"-_
4 ., ., .... z ~ 5 2 :I: t-
.... ...
0.. • • .,
I&. 0
, t-z I .... u a: .... 0..
Z 0
-ij i
f· a I ~ 0 .,
! u
;
i
0
•
PROJECT NO.
73-3-9BC
---
CONSOLIDATION CURVES
LOAD IN I(IPS PER SQUARE FOOT
0.6 0.8 1.0 2 4 6 8 10 If
Borin~ 4
--.'SamH e 2
t:--Dep h: 51 r""'1
~ ~
......... ~ ~
" -~ ~ I-_
~. -1-_
1-_ -'-. .l4~
--
,
--
INDICATES PERCENT CONSOLID~TION AT FlELD MOISTURE
IND!CATES PERCENT CONSOLIDATION AFTER SATURATION !
DRAWING NO.
BENTON ENGINEERING, INC. 13
•
•
•
•
•
C -S u • c ..oJ
C a:I ~
•
•
•
• III ::I c z
• ,0 '"'it '.
1
2
3
4 .,
CI)
III Z 5 ~
~ :z: ...
6
III ... Q. :I C CI)
....
0
0 ... Z III (,) g: 1 III Q.
z 2 0 ij
Q
:;j 3 0 CI)
I (,)
4
PROJECT NO.
.;z:eu l'-tatr
73-3 ... 9~C .
,
CONSOLIDATION CURVES
LOAD IN ,KIPi PER SQUARE FOOT
1.0
o INDICATES PERCENT CONSOl.lDATION AT FIELD MOISTURE
• INDICATES PERCENT CONSOLIDATION AFTER SATURATION
DRAWING NO.
BENTON ENGINEERING. INC. -sa-
•
•
•
•
•
•
•
•
•
•
•
BENTON ENGINEERING. INC.
APPLIED SOIL MECHANICS ---FOUNDATIONS
6717 CONVOY COURT
SAN DIEGO. CALIFORNIA 92111
PHILIP HENKING BENTON
,.RESIDENT. CIVIL ENGINI!:ER
APPENDIX A
TELEPHONE (714) 1S61S·191S1S'
Unified Soil Classification Chart*
SOIL DESCRIPTION
I. COARSE GRAI NED, More than half of
material is larger than No. 200 sieve
size. **
GRAVELS
More than half of
coarse fraction is
larger than No. 4
CLEAN GRAVE LS
sieve size but smaller GRAVELS WITH FINES
than 3 inches (Appreciable amount
of fines)
SANDS CLEAN SANDS
More than half ot
coarse fraction is
smaller than No.4
sieve size SANDS WITH FINES
(Appreciable amount
of fines)
II. FINE GRAINED, More than half of
material is smaller than No. 200
sieve size.** SILTS AND CLAYS
Liquid limit
Less than 50
SILTS AND CLAYS
liquid Limit
Greater than 50
I'll. HIGHLY ORGANIC SOILS
GROUP
SYMBOL
GW
GP
GM
GC
SW
SP
SM
SC
Ml
CL
OL
MH
CH
OH
PT
TYPICAL
NAMES
Well graded gravels, gravel-sand mixtures,
little or no fines. '
Poorly graded gravels, gravel-sand
mixtures, little or no fines.
Silty gravels, poorly graded gravel-
sand-silt. mix'tures.
Clayey gravels, poorly graded gravel-
sand -c lay m ixtu res.
Well graded sand, gravelly sands, little
or no fines.
Poorly graded sands, grav'elly sands,
little or no fines.
Silty sands, poorly graded sand-silt
mixtures.
:Clayey 'sands, poorly graded sand-clay
mixtures.
Inorganic silts and very fine sands, rock
flo\Jr; sandy silt or clayey-silt-sand
mixtures with sl ight plasticity.
Inorganic clays of low to medium pJas-
ticity, gravel·ly clays, sandy clays,
silty clays, lean clays.
Organic silts and organic silty-clays of
low plasticity.
Inorganic silts, micaceous or diatomaceous
fine sandy or silty soils, elastic silts.
Inorganic clays of high plasticity, fat
clays.
Organic clays of medium to high '.'
plasticity
Peat and other highly organic soils~ ,
* Adopted by the Corps of Engineers arid Bureau of Reclamation in January, 1952.
** All sieve sizes on this chart are U. S. Standard. :.
.... --------------------------------~-~.----.. -
•
•
•
•
•
•
•
•
•
•
PHILIP HENKING BENTON
PftIE8'DIENT· CIVIL ENGINEER
Sampling
BENTON ENGINEERING. INC.
APPLIED SOIL MECHANICS -FOUNDATIONS
6717 CONVOY COURT
SAN DIEGO, CALIFORNIA 92111
TELEPHONE (714) 5615.191511
APPENDIX B
The undisturbed soil samples are obtained by forcing a special sampling tube into the
undisturbed soi Is at the bottom of the boring, at frequent intervals below the ground surface.
'The sampling tube consists of a steel barrel 3.0 inches outside diameter, with a special cutting'
tip on one end and a double ball valve on the other, and with a lining of twelve thin brass
rings, each one inch long by 2.42 inches inside diameter. The sampler, connected to a twelve
inch long waste barrel, is either pushed or driven approximately 18 inches into the soil and a
six inch section of the center portion of the sample is taken for laboratory tests, the soil being,
still confined in the brass rings, after extraction from the sampler tube. The sqmplesare taken
to the laboratory in close fitting waterproof containers in order to retain the fie'ld'moisture until
completion of the tests. The driving energy is calculated as the average energy in foot-kips
required to force the sampling tube through one foot of soil at the depth at which the sample is
obtained.
Shear Tests
The shear tests are run using a direct shear machine of the strain control type in which'
the rate of deformation is approximately 0.05 inch per minute. The machine 'is so designed tha~
t.he tests are mad~ without removing the samples from the brass liner ring$ in which they are
secured. Each sample is sheared under a normal load equivalent to the weight of the soil above
the point of sampling. In some instances, samples are sheared under various normal loads in
order to obtain the internal angle of friction and cohesion., Where considered necessary, samples
are saturated and drained before shearing in order to simulate extreme field moist~re conditions.
Consolidation Tests
The apparatus used for the consolidation tests is designed to receive one of the one inch
high rings of soil as it comes from the field. Loads are applied in'several increments to the upper
, surface of the test specimen and the resulting deformations are recorded at selected time intervals
'for each increment. Generally, each increment of load is maintained on the s<:Jmple unti I the rate
of deformation is equal to or less than 1/10000 inch per hour. Porous stones are placed in contact
wrth the top and bottom of each specimen to permit the ready addition or release of water.
Expansion Tests
One inch high samples confined In the brass rings are permitted to 'air dry at 105° F for
at least 48 hours prior to placing into the expansion apparatus. A unit 'load of 500 pounds per
.square foot is then applied to the upper porous stone in contact with the top of each 'sample'~ Water
,is permitted to contact both the top and bottom of each sample through porous stones~ Continuous,'
observations are made unti I downward movement stops. The dial reading is recorded ,and expansion
Is recorded until the rate of 'upward movement is less tha~ :1/10000 inch per ho~r. ' .
•
•
•
•
• APPENDIX C
•
•
•
• BENTON ENGINEERING. INC.
•
Case I:
•
i.
•
••
t c:a ~ ,.!.
I ~ •
•
Case II:
•
••
•
APPENDIX C
For foundation soils with an expansion potential over 6 percent under a unit load
of 144 pounds per square foot from air dried to saturation.
1. Avoid the use of isolated interior piers where possIble. Use continuous
footings throughout, andplace these at a minimum depth of two feet
below the lowest adJacent exterior final ground surface~
2. Reinforce and interconnect continuously with steel' bars all interior
and exterior footings with one IS bor at 3 inches above the bottom
of all footings and one #5 bar placed 1 1/2 inches below the top of
the stems of the footings. If possible, use raised wooden floors that
span between the continuous footings.
3. Reinforce all concrete slabs with 6x, 6 -10/10 welded wire fabric.
4. Provide a'minimum of 4 inches of crushed rock 3/4 to 1 inch in size
beneath all concrete slabs. A moisture barrier should also be provided
over the crushed rock and this should be covered with 2 inches of s~nd
beneath concrete sl abs •
5. Separate garage .slabs frQrn perimeter footings by 1/2 inch thickness of
construction fl;llt or equivalent, to allow independent moveml;lnt of
garage slabs relative to perimeter footings. Assure complete separation
by extending the' construction felt over the full depth of the front
thickened edge of the gqrage slab. Cut off garage door stops at I east
1/2 inch above the garage slab.
6. Provide positive drainage away from all perimeter footings with a
verti cal fall of Qt least 6 inches in a horizontal distance of 5 feet,
outside the house walls.
7. Exercise every effort to assure that the soil under the foundations and
slabs has a uniform moisture content at leaSt 1 to 3 percent greater
than optimum throughout the top 1"5 feet below finished grade at the
time of placing the foundations and sl.abs.
For foundation soils with an expansion potenticd over.2 percent but less than 6
percent und~r a unit load of 144 pounds per squar~ foot from air dried to saturation.
, Same as above, except: (A) Continuous footings may be placed at a minimum depth
of 18 inches in Ii ell of 2 feet as i'tem 1 under Case (I). ( B) No. 4 bars may be used
in lieu of No.5 bars as item 2 under Case (I). (C) items 3 to 6, inclusive, of .
Case (I) are also applicable to Case (II) •
BENTON ENGINEERING. INC.
~~'
•
•
•
•
•
•
•
•
•
•
APPENDIX D
Reconnaissance Geologic Investigation
Spanish Village West, 7 Acre Site
Rancho La Costa
Carlsbad, California
Project No. 73-3-9BC
. May 17, 1973
BENTON ENGINEERING. INC.
'.
•
•
•
•
•
•
•
•
•
•
•
Project No. 73-3-9BC -1-May 17, 1973.
APPENDIX D
As a part of the subject prel iminary soils investigation, we have also completed a reconnaissance
. geologic investigati.oILand_tr.ansm.i1-herewlt.h-our_f.i.ndings. The intent of this appendix is to
summarize our observatiQns concerning the geology and potential geologic hazards on the subject
site. The scope of this investigation consisted of a visual site examination, literature research,
and a review of the boring logs from this investigation.
In general, the site is underlain by the Delmar FQ.n:n't!ic;m., Tor@y~qt,-d~Jo.rL~·, a.JI!Lvj!!!!h.£olluvllllll,-.
lans1sl·ideA~!?ili.l eans.. t()8$oil.§~ Principal geologic hazards inclode: old landslide zones, the clayey
De I ma r FormaHpJl_wbJ-;hJ ~~ds I i d~,,:p-!..2!l~_9DSLC:PJ\taJns, .expans iye cJ 2Y~;'-~E~'I~ C~kde'pc?Srts:--ar
soft compressible alluvium in the valley bottom. . . -"~"'" ..
. It is our understanding that one and or two story wood frame dwellings are planned for this proposed
residential development. '. .
During the period from April 4 fo April 12, 1973, the four borings (see Summary Sheets, Drawing
Nos. 2 to 10, inclusive) were logged and inspected by the writer and a visual site examination
was made. Surrounding areas were also inspected to provide relevant information for comparison.
Available pertinent literature (including our previous soils ~ep6rts in the vicinity) was searched
. for data on geology and geologic hazards in the vicinity.
Tb1Lt9J!9~1 Y ~~~ylf1r.-s~.qp"~d% ear!:;-el consis.ts~[oximate IX 7 acr~e.sJ>_oJ.J.tld.eA.b.y_EI.;hQm i no
R~Qn..t.he_w~est, a lSOJe.e.twld.~LS.an_D_Le.g.Q.....Q.q~_~_~! e.~tri.~~ome.gnY-c.~Q~.~n.UmJb~ .~~~t and
undeveloped hillsides on the north and south. If.' lies in a portion of the SE 1/4 of Section 35,
T 12S, R 4W, S. B. B.M. and the N 1/2 of Section 2, T 135, R4W, S. B. B.M. City of Carlsbad,
San Diego County, California.
Gently sloping topography is predominant 6n this site which lies moStly in a broad valley bottom .•
Along the northern and southern boundaries the valley sides rise abrlJptly to form moderately to
steeply sloping hillsides. Drainage is in a westerly direction. Annual grasses and .scrub brush
cover most of this area which has been partly cultivated in the recent past. Elevations vary from
49.3 feet in the valley bottom adjacent to EI Camino Real along the western boundary to approx-
imately 110 feet along the southern boundary. Total rel'ief is 60.7 feet.
The soils, and geology were observed in natural surface exposures and in nearby and adjacent cut
slopes. In addition, the four borings from the subject report were logged and inspected by the
writer and boring logs were reviewed from our previous soils report, Project No. 70-11-18B,
entitled "Pre-Prel iminary Soils Investigation, MBD Property, Rancho La Costa, San Diego.
County, Cal ifornia," dated December 11, 1970.
The entire area is lmderlaLr:d~y_tb~J}1J~~l§..,t.oc.ene .. ;ag~=(~RP!'Qximately 45 million years before
present) Delmo.r.l"£rmatio~ w~icb,..g:QP.s_Q.I,I)-Pl~lJ.g_tbJ~.l2~LY.~ __ ~l~.,gs,.. It is overlain by the
Middle Eocene age Torrey Sandstone which crops out on the hi'gher elevation ridges on each side
of the valley. Quaternary alluvium and colluvium ar¥e_~_elJ.Li.IJ ... the valley bottom and lower
valley sides. Landslide and slump debris i~-p'resent along the sides o.f the valley. Topsoils are
variable in thick;)ess and-nave been deeply~ c~ltivafecfor1fne~nearlyfrarvciiT;Y bottom.
BENTON ENGINEERING. INC.
•
•
•
•
•
•
•
•
•
•
•
.Project No. 73-3-9BC -2-May 17, 1973
The ~e~~~rm,a,tion is the oldest and lowest elevation unit, underlying QII of the other forma-
ti<;ms which are xounge~.ln age. Du~ to a slight regional dip of approximately 1.50 downward
in a w~st-southwest direcfion, the top of the Delmar FormQtion is at different eleva.tions across
the area. On the ridge along the northern bovndary the top is at about 86 feet elevation and
on the ridge along the southern boundary the top is at about 87.5 feet elevation. The base of
this formation is not E;lxposed in this area,·but it is at least as low as SO feet elevation where
the formation is exposed in road cuts along EI Camino Real.
The D~mar Format!.:>n is composed primarily of~reen and..9ra.y--gr..e_eD-~lqy-"'qn.<LcJ.9.X.~y~h
iJite~eds of light gray and light brown, clayey and silty sand:.. CI(:IYs in this formation are
e~pe~!~lly w~EJ5~~~I_~~~~~'::~J:S?.ne·: ~'$p~clarattenti()~~;h;,uld be' given' to· fhem 'When they are
encountered duriE~~adi!1QJ~,.2L~,~!.?_n_d!2!Jl! L ~t<?e.~~_ ~t:..~ __ r:'0t _?V~!~~!~~p~~~d. In
(]ddition to their landslide danger, they are (]Iso critically expans·ive and special foundation
designs wirLt)~~i:e~uired iCthe:Y~J;lr~IJ.QY...ecLto.-':.~qin wttE!njne:19~t!~9:~Cjri.~·~o(p;,~~_Cis~~ struc-
tures. In generaL, we recommend laying cut slope$made entirely or in part within this clayey
formation back to at least 3:1 (horizontal to vertical) or flatter.Of~~rticular noteL.m.!n.is
regard, is the grade planned for the LeV-ante Street extension at EI Camino Real on the south
side ~Qll.eY,. where s~verqLQy.D~r~dJ~~I 9i7<iadyfay;;n r-en.qountC!l~tfie~Q~LM~E ~oTmation
day (see Tentative Map and Specific Plan, Carls~d Tl:.aJ:.t..Z2..=-2A.,_Sf;1,ar.li.sJ1YJJlqge~qt La Costa,
Units 1 and 2, prepared by Rick Engineering Company, 509 Elm Avenue, Carlsbad, California,
dated July 20, 1972, Job·No. 3937, map not included in this report).
Torrey Sandstone overlies the Delmar Formation and forms the high-relief topography on the hill-
stdes both north and south of the property. It underlies the highest hills and ridges which st~nd
out in bord relief in contrast to the Delmar Formafion which is found in subdued gentle relief only
in the lower elevations along the valley bottom. Torrey Sandstone is composed primarily of light
gray and light brown slightly silty to silty and clayey fine. to medium sand. LocaUy, these soils
can be expansive and should be tested prior to use for select borrow mat~rial. The Torrey Sand-
stone is not normally subject to landsliding by itself. However, since it overlies the landslide-
prone Delmar FormatiOll,.J.t is often directly involved with landslicfin.9.".i.n~.9_ "pi~q9k!! ... sty..l.e_v-d.ih...t~j!)g_ t<?iIfD.9,.Nj:mii-'clays:' ._I~ this regard, whenev7~.!:!~~:.r Sands.tol'le~and"'Del'mar~Formahon~.g~~.c!qys g,re ~nco~~~?~"'I.~ !~:_sa~~:~l1t s'-~P:.L tile enflre ~ut slope should be treated as thougl1 It were all clay ana snoulC/ oe Icud back to a slope on the
ordE;lr of 3: 1 (horizontal to vertical) or flatter to mitigate the possibHity of landsliding.
Quaternary alluvium and colluvium are present in the valley bottom and lower valley side·s.
Colluvium in this area is essentially slope wash that has not yet been transported downward into the
creek bottoms and it may be treated like alluvium for grading proposes. Alluvium in the broad
valley bottom is at least 20+ feet thick. It consists of loose and soft, porous deposits of sand, silt,
ancl clay in varying mixtures. In all cases, alluvial and colluvial soils should be removed ane;)
recompacted, or in the case of deep valley fill partially removed and recompacted prior to placing
qdditional fill or footings. The water table in the valley is at about 44 to 45 feet elevation.
Looseo<!!l,!p-_()r~us t~J~its .. should be removed and recompacted prior to P-'-~sJ!:!.QJlIL9.Lf~otings on th -*_.... ~~~ ~.,.-...-.-::,. ~..... --._--.... ~ ........ ~--.. ~ ... ~"';. ............... -::""-~-.---...... -. "'-'W..~_.r-...'_ .. ~_~ ~-" ~
At I east t!!<?,,, '!'c:i.:>!: 1.~.'ldsJ. i ~~ ,gre.9s.",~er.e.~9Itse..!Y~Ji...d_u.dng-ou r-r.ecor.ma issan~e~oLtb~Mte .• _ In addi ti on,
shallow slumping and creep was noted in the topsoils and in the clayey Delmar Formation. The
principal landslide areas are located in the valley sides along the northern and southern property
BENTON ENGINEERING, INC.
•
•
•
•
•
e
,e
•
•
Project No. 73-3-9BC -3-May 17, 1973
boundaries. One maiM slide_~ne-w.OLencountered in each of two boring~ (~odngs3?1-Ql'.ld~2, ____ u O;~ ......... ~~. __ ~,.,....c~~ _~
see Summary Sheets, Drawi ng Nos.' 2 to .l, .... .Incll!.s iyel~!loJ.:tog~l,-1~J!~~r:t .. try,tt ridge .
overLQQ~lng,.,tbe,~s,o_utb.e.m..e.grL.Q£j.b.e_Z acres, ~ maiorlan~slid~ne W?$_~gpwJ§.t4?~(Lqt ... ~~e.!:h.s
of 34.5 to 39.0 feet. This crushed and mixed zori'e lies on the top of the Delmar Fonnation
clays wifuthe ~ri;;;tation of the slide plane dipping 300 ,N 650 W~ adYerSely out of slope into
the valley below. In Boring 2, located on the ridge overlooking the northern part of the 7 acres,
a lTiaj or landslide zone was encountered at depths of 19 to 21 feet. As above ,th is crushed zone,
lies on top of the Delmar cloys. It too is dipping adversely out of slOpe 290 S 200 W into the
valley below. Grading operations around these two ridges (especially along the aforementioned
Levante Avenue ~xtension) should be done with cqution. Buttressing or laying the slopes back
ma'y be necessary, depending upon each individual situation.
Based upon our observations to date, it is our opinion that cut slop'es..§.nti,r.gJx~!bin the Terrer'
San~~t..9lle""ro(l¥-.be. pJQ.!J,~...,eAJ()LLQJiQS .... ol. • .L.5:,l",,{hQrizontal to vertical) or flatter and~'sloP;s-'
within the Delmar Formation or combined D~J1Jlar_Eor.mat,ion",.rol'rey SQndstcme shQ,uld-be~planned
for ratios of 3.:.L{b,oriz.onta! to""v .. e.~-'Il)"or flatter, unless special recommendations are made to
the contrary (see Concluslon No.6 on page 20f the main body of'this report).
Locally, small faults_a[e_p.l:e.s~ar..ea.,_b.u.Lnone~are known_to_be active 'at this time. The
closest potentially ac.tive fault is the 'north-northwest trending Rose Canyon fault located approx--
imately 6.2 miles southwesterly under the Pacific Ocean'. No mdjor earthquakes have been
recorded __ :.of __ ar.:~J~noWh to have occurred along this fault in..!'..~.c:,ent history. A'~_rl'!!~~J()YUnqg,
nitude eart~!:,.a_~E}.~ bqve .!:>foen_l:ep,9r!~_cnE!!i!:_a~Ial-qr.ea.l~~~~.~' but have caused little, if
any, aam'ciSe,.' . ~----"-..-~"-",.'-"~'~-'
The closest large aCtive faults are the E!!i.!'or~ and San ~.tQ.,J(lults located 25.5 and 42.0 miles
northeasterly!: respectively. The closest major earthquakes have 'occurred to the northeast-along .,
the San Jacinto fault and 56 miles to the northwest on the Newport-Inglewood fault. Thes~ lftod-
erate-si;z:ed earthquakes had Richter scale mQgnitudes ranging from 6,0 to 6.8 and produced
Modified Mercalli scale intensities on the order of V to VI in the La Costa area. These intenshies
are, approximately equivalent to ground acc;:elerations-;;ro.-015 g to 0.032 g, respectively. In. our
opinion, similar earthqua~esin the future will generate similaQ3reund accelerations in the La
Cesta area.
An area subjected to Modified Mercalli scale intensity VI ground' acc~lerations wO\.ild experience
the following maximum effects: Felt by all; many frightenedclncrrun-·outdoors. Some heayy furni-
ture moved; a few instances of fQllen plaster or damaged chimneys. Pendulum clocks stop. 'Damage
slight. No damage is antic.ipated to buildings of good design and construction.
Southern California has been placed in Seismic Risk Probabilit"y Zone No.3 (Uniform Building
Code, 1970, Page 122). In this zone, Modified Mercalli scale intensities of VIH (approximately
equal to a ground acceleration of 0.149 g) or gredter may be expected. An drea subjected to
earthquake induced Modified Mercalliscale VIII ground accelerations would experience the
following effects: Damage slight in specially designed structures; considerable in ordinary sub-
stantial buildings, and great in pOQrly built structures. Panel walls thrown ouf of frame structures •
Fall of chimneys, columns, and walls. Heavy furniture overturned. Well-water levels change •.
Persons driving motor cars disturbed.
BENTON ENGINEERING, INC.
•
•
•
•
•
•
•
•
•
•
•
Project No. 73-3-9BC -4-May 17, 1973
However, based on 0ur experience in the area and the known seismi c record, it is our opinion
that Int.ensity VIII or greater seismic ground accelerations are unlikely to occur in the La Costa
area. Therefore, a normal seismic factor for this area of Southern California should be adequate
for most structural design.
If you have any questions after reviewing this appendix, please do not hesitate to contact this
office.
This opportunity to be of service is sincerely appreciated.
Respectfully submitted,
BENTON ENGINEERING, INC.
By tJ~.~ ./. z:::a;~V/-
William J. Elliott, Registered Geologist #1101
WJE/PHB/~w
BENTON ENGINEERING. INC.