HomeMy WebLinkAboutCT 01-09; LA COSTA TOWN SQUARE COMMERCIAL; REVIEW OF SCALE MASS GRADING PLANS; 1990-12-17.4.'
C-rQI•O'
eotechnical 'Geologic • EnvironentaI
5741 Palmer Way • Carlsbad California 92006
• (760) 438-3155 • FAX (760) 9811-0915
/ -December 17, 1990
W.O. 1047-SD
M.A.G PROPERTIES
7690 El Camjnb Real, Suite 20
9
Carlsbad, California 92009
Attention:. Mr. Fred Morey
Subject: Review of l"=40' Scale Mass G
r
a
d
i
n
g
P
l
a
n
La Costa Town Center
La Costa" Avenue and Rancho S
a
n
t
a
F
e
R
o
a
d
Carlsbad,'California.
Reference: "Prelimirary Geotechnical Stud
y
U
p
d
a
t
e
Parcels S.E. 13, and 25 Acres
E
a
s
t
e
r
l
y
o
f
L
a
C
o
s
t
a
Avenue' and Mission Esjancia,
Là Costa City of', Carlsbad, California", by Ge
o
S
o
i
l
s
,
I
n
c
.
,
d
a
t
e
d
June 6, 1990.
Dear Mr. Morey:
As requested. by Rick Engin
e
e
r
i
n
g
C
o
m
p
a
n
y
,
G
e
o
S
o
i
l
s
,
I
n
c
.
h
a
s
reviewed the 111=401 scale mass grading plans fo
r
t
h
e
L
a
C
o
s
t
a
Town Center.
The purpose of this', review was to evaluate t
h
e
e
f
f
e
c
t
s
o
f
geologic and soil "engineer
i
n
g
c
o
n
d
i
t
i
o
n
s
o
n
t
h
e
p
r
o
p
e
r
t
y
a
n
d
proposed development; hs re
v
i
e
w
i
s
b
a
s
e
d
u
p
o
n
i
n
f
o
r
m
a
t
i
o
n
presented in our referenced
r
e
p
o
r
t
a
n
d
t
h
e
m
a
s
s
g
r
a
d
i
n
g
p
l
a
n
s
f
o
r
La Costa Town Center, prepa
r
e
d
b
y
'
F
i
c
k
E
n
g
i
n
e
e
r
i
n
g
C
o
m
p
a
n
y
.
Pertinent geotechnical data is
p
r
e
s
e
n
t
e
d
i
n
t
h
e
r
e
f
e
r
e
n
c
e
d
r
e
p
o
r
t
and not included herein; t
h
e
r
e
f
o
r
e
,
t
h
a
t
r
e
p
o
r
t
s
h
o
u
l
d
b
e
RECEIVED
.1 . 0CT 02 1097
1.
N.A.G PROPERTIES DECEMBER 17, 1990
W.O. 1047-SD PAGE 2
utilized in conjunction with this review.-' Specific
recommendations provided in this report supersede those presented
in and referenced report. Other' rèco&inendations, not
specifically discussed in this review are considered applicable.
The sheet numbers related to herein are consistent with the
numbering of the 12 sheets of the grading plans
PROPOSED DEVELOPMENT
The subject site, roughly 75(±) acres in area, is proposed to be
sheet graded for future commercial, development. : Mass grading
plans indicate that the proposed development would consist of cut
and fill sheet grading. to construct level building sites for
further commercial development.
All slopes are proposed :;.at .gradients of 2:1 or flatter. The
basic grading concepts are similar to those indicated in our
referenced :report.
In the event that any significant changes in the design (as noted
above) are planned, conclusions and recommendation contained in
this review shall not be considered valid unless changes are
reviewed and the conclusions of this report verified or modified
in writing by this office.
4)S?ilc. Inc.
M.A.G PROPERTIES DECEMBER 17, 1990
W.O. 1047-SD PAGE 3
CONCLUSIONS-AND RECOMMENDATIONS
The, following-.items are significant actors' effeáting site
development. As suggested in the previous report, these items
are further discussed below.
1'. Claystones present in the southern portion of the site (near
La Costa Avenue), •exhibit west and southerly bedding
orientations which' would require stabilization in western
and southern facing slopes.
2. 'The' need for subdrains in canyons, stabilization/buttress
fill slopes and along 'the. clàystone/sandstOne 'bedrock
contacts where buried by fill.
Fill Slopes '
The highest proposed fill slope is approximately 40 (±) foot high
and planned at a gradient of 2:1. This slope shown on Sheet 3 of
the grading plans, as' well as other 'large fill slopes ranging
from 15 to 4,0 (±) feet in height are to be constructed along the
perimeter areas of the property.
Typical keyways for interior slopes less 'than 20.. feet in height,
are anticipated to be on the order of 12(±) feet wide-and 2 feet
when excavated into sandstone or volcanic rock. Typical keyways
for interior slopes less than 20 feet in height, are anticipated
to be roughly 15(±) feet wide and 4 feet when excavated into
GeóSoiis, Inc.
M.'A.G PROPERTIES
' I
DECEMBER 17, 1990
W.O. 1047-SD ' PAGE 4
claystone bedrock. Keys for perimeter gill slopes along 'La Costa
Avenue,, would require larger (deepe'rj and, wider) keys due to
proposed heights and claystones that 'are anticipated to be
encountered in the keys. For example, perimeter fill slopes will
require a key roughly 25 feet wide and 7 feet in depth for slope t
heights over 20 feet. Perimeter slope keys, exposing volcanic
rock a imo3
Perimeter slope keys for fill slopes on
Sheets 6 and 9 are anticipated to expose volcanic rock. Typical
stabilization type backdrains would be recommended for all
perimeter fill slope keys.
Cut Slopes
Cut slopes are designed at gradients of 2:1 or flatter. The
highest cut slope is approximately 30 (±) •foot high (see Sheet 7
of' the grading plans). Cut slopes • from '15 to 30 (±)' feet' in
are proposed in the north and east portion of the
development.. •
Generally, the sedimentary' bedrock' units exhibit gentle (2 to' 5
(±) degree) dips to the west, and southwest. Stabilization of
westerly and southwesterly facing cut slopes exposing sedimentary
rock is anticipated. Specifically, the slopes on Sheets 3 and 4
of the grading plans are anticipated to require stabilization due
to adverse bedding planes and exposure of a sandstone/claystone
contact. •
ffDn.cn;1
M.A.G PROPERTIES ' ' DECEMBER17, 1990.
W.O. 1047-SD ' '' PAGE,' 5'
Cut slopes 'exposing the contact between sedimentary." and volcanic
bedrock may also require stabilization. The slope descending from
the, proposed alignment of Rancho Santa Fe Road "(Sheets 7 and 8)'
is anticipated to require stabilization.. The cut portion of. the
slope on' Sheet 6 is anticipated to, require stabilization as
dlaystone bedrock may be exposed. from' Stations 151±. to .155±.
Typically, 'stabilization fills should'$e a consistent width of at
least 15 feet from tap to,bottoin. Stabilization fills' should. be
provided with backdrainage as presented in the referenced report.
Cut slopes exposing volcanic bedrock are not anticipated to
require' buttressing 'r stabilization unless continuous .fractures
or shears are 'encountered'.' 'Also, overb]iasting can weaken the rock
material, necessitating stabilization.
All cut slopes should be mapped by a geologist from this office
during grading to 'allow for amendments to recommendations, should
exposed conditions warrant alteration of the 'design on
stabilization.
Subdrainage
Placement of subdrá.i'nsshou1d ,be evaluated during grading;
however subdrains should.,-.be anticipated in all canyon cleanouts
and stabilization/buttress' fills slpes exceeding 8 feet' in
height prior 'to placing fill. Drains are also anticipated in all
perimeter fill'slope keyways. All drains should be observed by a
GeoSoils, Inc.
M.A..G PROPERTIES ( DECEMBER 17, 1990
W.O. 1047-SD PAGE 6
geologist from this office during grading to allow for amendments
to recommendations, should exposed çonditions warrant alteration
of the design •on stabilization. /
Due to the potential for groundwater accumulation and migration
along sandstone/claystone contacts, drains are also anticipated
along this.contact to drain the impermeable claystone. Subdrains
should be constructed in accordance with designs presented in
Appendix II of the referenced report.
Detentiàn/Desilting Basins
Review of the mass grading plans indicate that the basins will be
constructed in close proximity •to fill slopes. It is our
• understanding that these basins are permanent structures. We
recommend therefore, that the detentiorjdesi1ting basins be lined
with either concrete or other impermeable material to hinder the
migration of water in the subsurface. •
CeóSoIls, inc.
M.A.G PROPERTIES DECEMBER 17, 1990 W.O. 1047-SD PAGE.7
If you should have, any questions regarding this review or if we
may' be of further service, please do not hesitate to contact this
office.
Sincerely,
'
GeoSoils, Inc.
NA
104
p ' /' Vit'hya SJ4-ighane, .GE 782 st. ' Geothchnial Eng'ineer'
V/i=J 1142
Princiál Geoiogi '
EPL/ VS/TEN/inc /
cc: (2) Addressee ' (l) Rick Engineering, Mr. Ray Martin
(1) Rick Engineering, Mr. Norm Arandt
'(1) Rick Engineering,,.Mr. Dennis Bawling
GeoSoils, Inc.
GeoSoils, Inc.
TABLE. OF CONTESTS
SITE DESCRIPTION
PROPOSED DEVELOP4ENT.. .......................
FIELD EXPLORATION
0
EARTH MATERIALS
Dump Fill ...........................
Artificial Pill .........................
Topsoil .. .......................
- Alluvium •. .......................
Bedrock - Delmar Formation..................
Bedrock - Lusardi. Formation ...........
Bedrock -. Santiago Peak Volcanics ..............
GEOLOGIC STRUCTURE ..........................
GROUNDWATER
FAULTING AND REGIONAL .SEISI4ICITY
LABORATORY TESTING .. .
Field Moisture and Density
Laboratory Standard
Expansion Tests .. .
Shear Test .......-
Sulfates
CONCLUSIONS
EARTHWORK RECOMMENDATIONS.......... . .........
Rock Hardness •. ...
Claystones . . .. . . ................
Fill Suitability :.• ..................
Natural Slopes
Cut Slopes
Fill Slopes ........................
Existing Fills
Perimeter Fill Slope Keys ................
Removals
Shrinkage - Bulking .........................
Su.bdrainage ........................
Fill Placement . .................
Piping Potential and Filter Blankets . .......
LotCapping ..........................
Foundation Recommendations
PlanReview ......................
LIMITATIONS . . . . . ...................
GeoSoils, Inc.
1
2
3
4
5
5
6
7
7
8
8
9
10
11
12
13
13.
13
14
15
15
16
16
17
18
19
20
20
21
22
22
23
23
25
26
27
27
28