HomeMy WebLinkAboutAttachment 8Q - Addendum to Geotechnical InvestigationADDENDUM TO GEOTECHNICAL
INVESTIGATION
NIRVANA INDUSTRIAL BUILDINGS
AND SELF STORAGE COMPLEX
821 MAIN STREET
CHULA VISTA, CALIFORNIA
PREPARED FOR
VWP-OP NIRVANA OWNER, LLC
PHOENIX, ARIZONA
FEBRUARY 18, 2022
PROJECT NO. G2755-42-01
GROCON
INCORPORATED
GEOTECHNICAL • ENVIRONMENTAL MATERIALSO
6960 Flanders Drive • San Diego, California 92121-2974 • Telephone 858.558.6900 • Fax 858.558.6159
Project No. G2755-42-01
February 18, 2022
VWP-OP Nirvana Owner, LLC
2390 East Camelback Road, Suite 305
Phoenix, Arizona 85016
Attention: Mr. Steven Schwarz
Subject: ADDENDUM TO GEOTECHNICAL INVESTIGATION
NIRVANA INDUSTRIAL BUILDINGS
AND SELF STORAGE COMPLEX
821 MAIN STREET
CHULA VISTA, CALIFORNIA
References: 1. Preliminary Geotechnical Investigation, Nirvana Industrial Buildings and Self
Storage Complex, 821 Main Street, Chula Vista, California, prepared by Geocon
Incorporated, dated September 14, 2021 (Project No. G2755-42-01).
2. Limits of Grading at Easterly Property Line, Nirvana Business Park, 821 Main
Street, Chula Vista, California, prepared by Pasco Laret Suiter & Associates, dated
February 1, 2022.
Dear Mr. Schwarz:
In accordance with the request of Mr. Andrew Gracey, we prepared this addendum to the geotechnical
investigation for the subject project. Recommendations provided in Reference 1 were to construct
buttress fills along the eastern property line to mitigate for claystone beds that are expected to be
present within and near the toe of the slope. Buttress cuts are shown in Reference 1 extending into the
jurisdictional area. We understand that you desire to eliminate grading within the jurisdictional area
and requested we provide revised grading recommendations.
To provide revised recommendations, we generated two additional cross sections (Cross Sections H
and I) and performed slope stability analyses. The locations of the cross sections are shown on the
Geologic Map, Figure 1. The cross sections are provided on Figure 2. For our analyses, we assumed
grading can extend to within 10 feet of the jurisdictional limits shown in Reference 2.
The slope stability analysis was performed utilizing the computer program GeoStudio 2018
(SLOPE/W) distributed by Geo-Slope International. This program uses conventional slope stability
Project No. G2755-42-01 - 2 - February 18, 2022
equations and a two-dimensional limit-equilibrium method to calculate the factor of safety against
deep-seated failure. For our analysis, Spencer’s Method with a block failure mode was used for failure
in the claystone bed. We also analyzed a circular failure mode to check stability within the compacted
fill buttress. Spencer’s Method satisfies both moment and force equilibrium.
The computer program searches for the critical failure surface based on parameters inputted, including
the location of the “left” and “right” sliding blocks. The critical failure surface for each analysis is
shown on computer-generated output. The factor of safety is shown on each figure directly above the
failure surface.
The results of the stability analysis are provided on Figures 3 through 6. Based on our analysis,
remedial grading can be performed to construct the stability buttresses outside of the jurisdictional
limits. To construct the revised buttresses, the forecut on the buttress will need to start at a distance of
10 feet from the jurisdictional limits and down at a 1:1 plane to a vertical distance of approximately 5
feet below the clay bed. At this elevation, a minimum 15-foot-wide buttress key needs to be
constructed. We estimate the bottom of the clay bed to around elevation 145 feet MSL. We estimate
the buttress key bottom elevation to be near 140 feet MSL, as shown on Figure 2.
Within a portion of the eastern buttress, geotextile reinforcing grid will be required to provide a factor
of safety against slope instability of at least 1.5. The geotextile reinforcing grid should consist of
Miragrid 20XT that has a length of at least 20 feet extending from the face of the buttress forecut. The
grid should be placed every 3 feet vertical height as shown on Figure 2 and on the stability figures
(Figures 3 and 4). The locations where geotextile reinforcing grid will be needed to installed is shown
on Figure 1.
Modifications to the buttress dimensions, location, and grid reinforced area may be needed based on
actual conditions encountered during grading. A representative of Geocon will observe buttress
construction during grading and can provide additional and/or modified recommendations, if they are
needed.
All other recommendations contained in Reference 1 outside of Cross Sections I and H area remain
applicable. Additionally, all buttresses should incorporated drainage as recommended in Reference 1.
Project No. G2755-42-01 - 3 - February 18, 2022
If you have any questions regarding this letter, or if we may be of further service, please contact the
undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
Rodney C. Mikesell
GE 2533
RCM:arm
(e-mail) Addressee
137.9
138.1
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LOT 23
MAP 8147
HELD RECORD ANGLE
LOT 22
MAP 8147 LOT 21
MAP 8147 LOT 20
MAP 8147
LOT 19
MAP 8147
LOT 3
MAP 8147
LOT 2 SEC 20
T18S R1E SBM
ROS 16999
PARCEL 1
PM 21587
PARCEL 2
PM 21587
64'64'2
2
3
3
4
4
4
4
4
4
4
5
N 87°34'46" W 1356.85'
(
N
8
7
°
3
4
'
0
8
"
W
1
3
5
6
.
6
6
'
R
2
)
N 02°26'11" E 0.15'
N 02°25'25" E 0.13'N 02°26'11" E 276.91' (N 02°25'152 E 276.79' R2)749.13'
607.72'N 00°14'32" E 287.73' (N 00°12'10" E 287.52' R2)N 00°27'05" E 424.23' (N 00°27'28" E 424.24' R2)L =2 9 9 .2 0 ' R =2 0 6 4 .0 0 ' D =8 °1 8 '2 0 " M &R 2
N 82°38'33" E
3
7
3
.
1
3
'
(
N
8
2
°
3
8
'
3
6
"
E
3
7
3
.
1
5
'
R
2
)
D =2 °0 9 '1 1 " M &R 2L=7 7 .5 5 ' L =5 9 7 .1 7 ' D =1 6 °3 4 '3 8 " M &R 2L=6 7 4 .7 0 ' R =2 0 6 4 .0 0 ' D =1 8 °4 3 '4 6 " M &R 2
N 78°37'
4
1
"
W
2
3
.
9
7
'
(N 78°3
7
'
3
8
"
W
2
3
.
9
8
'
R
2
)
NW COR
SW 1/4 NW 1/4 SEC 20
2'1
25'2
NE COR
SW 1/4 NW 1/4 SEC 20
3
27'
15'
28'
20'
28'5
5
5
5
5128'7720'1424'13
20'
13
24'121
2
'
1
24'1
24'2
64'64'3433'
34'
12'4
5
4
4
4
6
7
(137.94 FG)
(131.82 FG)
183.0 TW
141.5 FG
H=41.5'
184.0
TW
145.0 FG
H=39'
183.1
TW 162.5
FG
H=20.6'
189.75 TW
183.5 BW
H=6.25'
185.25
TW 146.2
FG
H=39.1'MAIN STREET 2:12:12:12:1202.5 TW
184.5 FG
H=18'205.75
TW
185.75 FG
H=20'
184.00 TW
184.00 FG
H=0'
212.25 TW
186.75 FG
H=25.5'
180.9
TW 155.6
FG
H=25.3'
180.9 TW
139.4 FG
H=41.5'
(139.7 FG)
(186.00 FG)
(186.00 FG)
INDUSTRIAL
BLDG 4
187.5 FF
186.0
TW
186.0
BW
H=0'
189.5 TW
184.5 FG
H=5'
186.0 TW
186.0 FS
H=0'
186.25
TW 146.9
FG
H=39.4'
187.0 TW
183.3 FS
H=3.7'
186.25
TW 159.1
FG
H=27.2'
TYPE A-6 CO
188.8 RIM
172.60 IE OUT
MOD. TYPE A-6
CO
135.32 TOP
129.38 FL
MOD. TYPE A-8 CO
WITH TYPE F
OPENING
175.0 TOP
154.35 IE OUT
MOD. TYPE A
CO
137.63 TOP
130.64 FL
183.75 FS 5%NIRVANA AVEINDUSTRIAL
BLDG 3
186.5 FF
INDUSTRIAL
BLDG 2
185.25 FF
INDUSTRIAL
BLDG 1
184.25 FF
182.9 TW
141.4 FG
H=41.5'
184.0 TW
143.5 FG
H=40.5'
184.0 TW
144.3 FG
H=39.7'
185.25
TW 146.5
FG
H=38.8'
186.25
TW 145.9
FG
H=40.4'
187.0
TW
183.6 FS
H=3.4'
187.0
TW
183.4 FS
H=3.6'2:12:12:12.0%198.5
TW
183.5
BW
H=15'
202.0
TW
183.5
BW
H=18.5'
202.5
TW
183.5
BW
H=19'
200.5 TW
184.5 FG
H=16'
184.5 TW
184.5 FG
H=0'
203.0 TW
184.5 FG
H=18.5'
206.25 TW
185.75 FG
H=20.5'
209.25 TW
185.75 FG
H=23.5'
211.0 TW
185.75 FG
H=25.25'211.25 TW
186.75 FG
H=24.5'
210.0 TW
186.75 FG
H=23.25'
208.25 TW
186.75 FG
H=21.5'
191.75 TW
186.75 FG
H=5'
184.5 TW
184.5 FG
H=0'
189.5
TW
184.5 FG
H=5'
212.25 TW
186.25 FG
H=26'
212.0 TW
185.75 FG
H=26.25'2.0%2.0%2.0%2.0%AA'BB'Qal
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APPROX. FRONT
LIMIT OF CLAYBED
REMOVAL
APPROX. FRONT
LIMIT OF CLAYBED
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10' OFFSET FROM
JURISDICTIONAL
LIMITS
APPROX. AREA
OF GEOGRID
STABILIZATION
JURISDICTIONAL
DELINEATION
LIMITS
PROJECT NO.
SCALE DATE
FIGURE
SHEET OF
Plotted:02/18/2022 9:39AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\G2755-42-01 (Nirvana Self Storage)\SHEETS\G2755-42-01 Geo Map.20.dwg
GEOLOGIC MAP
NIRVANA INDUSTRIAL BUILDINGS AND SELF STORAGE COMPLEX
821 MAIN STREET
CHULA VISTA, CALIFORNIA
50'02 - 18 - 2022
G2755 - 42 - 01
1 1 1 *LA2(E67 (6I:E 7A2 (IEGO CALI*O62IA
P,O2E *A<
GEOTECHNICAL ENVIRONMENTAL MATERIALS
1" =
T-6
TP-7
B-2
........UNDOCUMENTED FILL
........ALLUVIUM
........TERRACE DEPOSITS
........OTAY FORMATION
........APPROX. LOCATION OF GEOLOGIC CONTACT
........APPROX. LOCATION OF EXPLORATORY LARGE DIAMETER
BORING (Current)
........APPROX. LOCATION OF EXPLORATORY BORING
........APPROX. LOCATION OF EXPLORATORY TEST PIT (Current)
........APPROX. LOCATION OF EXPLORATORY TEST PIT (AGS, 2014)
........APPROX. LOCATION OF EXPLORATORY TEST PIT (AET, 2008)
........APPROX. LOCATION OF GEOLOGIC CROSS SECTION
........APPROX. LOCATION OF PROPOSED SUBDRAIN
........APPROX. SURFACE EXPOSURE OF BENTONITIC CLAYSTONE
GEOCON LEGEND
Qudf
I I'
Qal
Qt
To
LB-5
TP-8
0 10050 150 200 0 10050 150 200 250E L E V A T I O N (M S L)100
150
200
250
H
E L E V A T I O N (M S L)100
150
200
250
IH'E L E V A T I O N (M S L)100
150
200
250
I'E L E V A T I O N (M S L)100
150
200
250
D I S T A N C E
SCALE: 1" = 50' (Vert. = Horiz.)
GEOLOGIC CROSS-SECTION H-H'
D I S T A N C E
SCALE: 1" = 50' (Vert. = Horiz.)
GEOLOGIC CROSS-SECTION I-I'
15' WIDE
BUTTRESS KEY
10'
EXISTING
GRADE
EXISTING
GRADE
PROPOSED
GRADE
PROPOSED
GRADE
STABILITY BUTTRESSSTABILITY BUTTRESS
MIRAGRID 20XT AT
3' VERTICAL SPACING,
20 FEET LONG
Qt Qt
To
To
To
15' WIDE
BUTTRESS KEY To
JURISDICTIAL
LIMITS
10'JURISDICTIAL
LIMITS
2
NIRVANA INDUSTRIAL BUILDINGS AND SELF STORAGE COMPLEX
821 MAIN STREET
CHULA VISTA, CALIFORNIA
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159PROJECT NO. G2755 - 42 - 01
DATE 02 - 18 - 2022
FIGURE
GEOTECHNICAL ENVIRONMENTAL MATERIALS
Plotted:02/18/2022 2:09PM | By:ALVIN LADRILLONO | File Location:W:\1_GEOTECH\G2000\G2755-42-01\2022-02-18\G2755-42-01 XSections.20.dwg
........TERRACE DEPOSITS
........OTAY FORMATION
........APPROX. LOCATION OF GEOLOGIC CONTACT
GEOCON LEGEND
Qt
To
1.5Distance (Feet)0 25 50 75 100 125 150 175 200 225 250Elevation (Feet)100125150175200Elevation (Feet)100125150175200Color Name Unit Weight(pcf)Cohesion'(psf)Phi' (°)PiezometricLineClaystoneBed (CL/CH)130 50 18 1Qcf 130 250 28 1Qt 130 350 35 1To 130 300 34 1To (2) 1NIRVANAProject No. G2755-42-01File Name: I-I' - Case3 Geogrid (15 ft Key).gszDate: 02/18/2022Directory: S:\Engineering and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE2018\G2755-42-01 (Nirvana)\CROSS SECTION I-I'QcfToToToTo - CH/CLTo - CH/CLQtGeogrid Reinforcement20 ft long, Miragrid 20 XT @ 3 ft spacing10 ft20 ftFIGURE 3
1.5Distance (Feet)0 25 50 75 100 125 150 175 200 225 250Elevation (Feet)100125150175200Elevation (Feet)100125150175200Color Name Unit Weight(pcf)Cohesion'(psf)Phi' (°)PiezometricLineClaystoneBed (CL/CH)130 50 18 1Qcf 130 250 28 1Qt 130 350 35 1To 130 300 34 1To (2) 1NIRVANAProject No. G2755-42-01File Name: I-I' - Case3 Geogrid (15 ft Key) Circular.gszDate: 02/18/2022Directory: S:\Engineering and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE2018\G2755-42-01 (Nirvana)\CROSS SECTION I-I'QcfToToToTo - CH/CLTo - CH/CLQtGeogrid Reinforcement20 ft long, Miragrid 20 XT @ 3 ft spacing10 ft20 ftFIGURE 4
1.6Distance (Feet)0 25 50 75 100 125 150 175 200 225 250Elevation (Feet)100125150175200Elevation (Feet)100125150175200Color Name Unit Weight (pcf)Cohesion'(psf)Phi' (°)PiezometricLineClaystoneBed (CL/CH)130 50 18 1Qcf 130 250 28 1Qt 130 350 35 1To 130 300 34 1NIRVANAProject No. G2755-42-01File Name: H-H' - Case1 (15 ft Key).gszDate: 02/18/2022Directory: S:\Engineering and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE2018\G2755-42-01 (Nirvana)\CROSS SECTION H-H'QcfToToToTo - CH/CLTo - CH/CLQt10 ft15 ft Wide Buttress Shear KeyJurisdictional LimitsFIGURE 5
1.6Distance (Feet)0 25 50 75 100 125 150 175 200 225 250Elevation (Feet)100125150175200Elevation (Feet)100125150175200Color Name Unit Weight (pcf)Cohesion'(psf)Phi' (°)PiezometricLineClaystoneBed (CL/CH)130 50 18 1Qcf 130 250 28 1Qt 130 350 35 1To 130 300 34 1NIRVANAProject No. G2755-42-01File Name: H-H' - Case1 (15 ft Key) Circular.gszDate: 02/18/2022Directory: S:\Engineering and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE2018\G2755-42-01 (Nirvana)\CROSS SECTION H-H'QcfToToToTo - CH/CLTo - CH/CLQt10 ft15 ft Wide Buttress Shear KeyJurisdictional LimitsFIGURE 6