HomeMy WebLinkAboutCT 2019-0003; CARLSBAD STATION; GEOTECHNICAL DUE DILIGENCE EVALUATION, ANTIQUE BLOCK; 2019-02-12
ADVANCED GEOTECHNICAL SOLUTIONS, INC.
485 Corporate Drive, Suite B
Escondido, California 92029
Telephone: (619) 867-0487
ORANGE AND L.A. COUNTIES INLAND EMPIRE SAN DIEGO AND IMPERIAL COUNTIES
(714) 786-5661 (619) 708-1649 (619) 867-0487
Carlsbad Village 80, LLC February 12, 2019
HomeFed Corporation P/W 1809-04
HF CV80LLC Report No. 1809-04-B-2
1903 Wright Place, Ste. 220
Carlsbad, CA 92008
Attention: Mr. Bob Penner
Subject: Geotechnical Due Diligence Evaluation, Antique Block (Carlsbad Village 80 LLC),
Carlsbad, California
References: See Appendix
Gentlepersons:
Presented herein is Advanced Geotechnical Solutions, Inc.’s, (AGS) limited geotechnical/geologic due
diligence evaluation for the proposed development of the Antique Block (Carlsbad Village 80 LLC) project
located in the City of Carlsbad, California. The purpose of this evaluation is to provide McKellar &
McGowan with geologic and geotechnical information that should be considered in your due diligence
process towards development of the subject property. In preparing this report AGS has observed the existing
site conditions and reviewed the referenced geologic reports and maps.
In this document, we first describe the site and proposed development, then summarize the anticipated soils
and geologic conditions at the site. Secondly, we assess key geologic/geotechnical issues which could
potentially impact site development and outline possible measures which can be employed to mitigate and
or minimize the impact these issues could have on the development as currently proposed. Finally, we
provide conclusions regarding the adequacy of currently available geologic/geotechnical information, the
feasibility of site development and provide recommendations for future study needs. This abbreviated
document is intended to serve as a "first step" for acquiring geotechnical information useful for planning
and design.
1.0 INTRODUCTION
1.1. Existing Site Conditions
The “L” shaped 1.7-acre site (see Figure 1) is bounded by Roosevelt Street to the northeast;
commercial and residential to the north, south and west and extends southwesterly to State Street.
Currently the site supports several one- to two-story commercial buildings constructed in the 1950’s
to 1980’s (?) along with several driveways and at-grade parking. Based upon our review of Google
Earth imagery the elevations onsite range from a high of 52 feet MSL at the western limits, to a
low of 45 feet MSL at the northwest corner of the site.
1.2. Proposed Development
It is our understanding that the existing commercial and residential structure will be demolished
and replaced with a 3- to 4-story high residential structure with one level of underground parking.
We anticipate that the proposed structure will be supported by a concrete podium level on a “slab-
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ADVANCED GEOTECHNICAL SOLUTIONS, INC.
on-grade” foundation system with the podium portion consisting of wood frame construction.
Cut/Fill grading is anticipated to consist of one (1) to three (3) feet along the perimeter with deeper
cuts of up to fifteen (15) feet at the bottom of the subterranean garage portion of the structure.
2.0 SITE INVESTIGATION
2.1. Previous Studies
To the best of AGS’s knowledge no geotechnical studies have been prepared in support of the
current land use. It is likely that geotechnical reports for the various properties within the
development footprint were not required during the original development of the subject lots. Based
upon our historic air photo review the current structures in the study area extend as far back as the
late 1940’s to 1950’s (?).
2.2. Current Investigation
In preparing this Geotechnical Due Diligence Investigation representatives of AGS conducted a
site walkover and reviewed available published geologic/geotechnical information. As part of our
desktop study AGS reviewed geotechnical studies of recent projects we have investigated and
developed within the last 7 years and available geotechnical studies done by others within the last
25 years. The approximate location of the previous geotechnical studies is presented in Figure 1.
From a geotechnical perspective, the key elements that should be considered given the proposed
subterranean portions of the garage structure are: 1) Potential groundwater/“seepage“ within the
upper 15 feet which may necessitate dewatering as part of the basement construction; 2) Site
geologic conditions which may affect the construction methodology for the proposed basement
partitions of the structure and the effects on existing adjacent structures once the subterranean
portion is excavated; 3) Type of foundation system recommendations based upon subsurface soil
conditions (i.e. piers/piles, “mat” or conventional shallow spread and continuous footings);
4) Establish a suitable bearing strata for the anticipated foundation loads from the podium structure
without causing excessive settlement of the proposed structure or adjacent improvements; and,
5) Effects of loads from the proposed structure on the adjacent existing improvements and structures.
3.0 SITE GEOLOGY
The subject site is situated within the Peninsular Ranges Geomorphic Province. The Peninsular Ranges
province occupies the southwestern portion of California and extends southward to the southern tip of Baja
California. In general, the province consists of young, steeply sloped, northwest trending mountain ranges
underlain by metamorphosed Late Jurassic to Early Cretaceous-aged extrusive volcanic rock and
Cretaceous-aged igneous plutonic rock of the Peninsular Ranges Batholith. The westernmost portion of the
province is predominantly underlain by younger marine and non-marine sedimentary rocks. The Peninsular
Ranges’ dominant structural feature is northwest-southeast trending crustal blocks bounded by active faults
of the San Andreas transform system.
3.1. Subsurface Conditions
Based upon our previous experience in the general area, observations of the surroundings and
review of available geotechnical reports and geologic maps, the following geologic units are
anticipated onsite. The regional geology of the site vicinity is presented in Figure 2. Subsurface
exploration is recommended to verify geologic conditions and groundwater levels at the site.
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3.1.1. Artificial Fill
Undifferentiated topsoil/undocumented fill soils are anticipated onsite. These soils likely
consist of grayish brown to brown and light brown, dry, silty sand to sand in a loose to
moderately dense condition. The undifferentiated topsoil/undocumented fill soils are
estimated to range from approximately 1.0 to 3.0 feet with potential localized deeper areas.
3.1.2. Quaternary Old Paralic Deposits (Map Symbol Qop)
Quaternary-aged Old Paralic Deposits are anticipated at shallow depths onsite. These soils
generally consist of orange-brown, damp to slightly moist, medium dense to very dense,
clean to silty, fine- to medium-grained sands. We anticipate “very low” to “low” expansion
potential for these materials. This unit is massive with portions of it prone to caving. These
deposits are considered suitable for support of fills and anticipated structural loads.
3.1.3. Tertiary-aged Santiago Formation (Map Symbol Tsa)
It is anticipated that Tertiary-aged Santiago Formation materials underlie the entire site at
depth. The Santiago Formation generally consists of light brown to light gray silty
sandstones. These materials are generally very dense although localized friable zones may
be present. These materials will likely be encountered in the basement excavation.
3.2. Groundwater
Based on our review of previous geotechnical reports, the surface elevations and groundwater
levels observed at various locations in the vicinity of the site are summarized in Table 1.
Table 1
Summary of Subsurface Explorations and Groundwater Elevations
Site
Location
(Reference)
Boring
No.
Surface
Elevation
(ft, MSL)
Groundwater
Level
(depth in ft)
Groundwater
Elevation
(ft, MSL)
800 Grand
(AGS, 2017)
HS-1
HS-2
HS-3
HS-4
TB-1
TB-2
Grading (2018)
62
64
60
61
66
61
60
N/A to 20
N/A to 21.5
N/A to 6
N/A to 20
Saturated at 14 (TD=16)
N/A to 11
N/A to 8.5
Saturated at El. 52
No GW at El. 51.5
2600 Carlsbad Blvd.
NCTD
(Kleinfelder, 2003)
B-1
B-2
B-3
B-4
B-5
35
35
35
35
35
50
9, 50
9.5
50
50
-15
26, -15
25.5
-15
-15
880 Carlsbad Village Dr.
(URS, 2009)
MW-1 to MW-5 63 15 48
3136 Carlsbad Blvd.
(Leighton, 2004)
B-1 to B-3 52, 50 38, 33 14, 17
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Table 1 (continued)
Summary of Subsurface Explorations and Groundwater Elevations
Site
Location
(Reference)
Boring
No.
Surface
Elevation
(ft, MSL)
Groundwater
Level
(depth in ft)
Groundwater
Elevation
(ft, MSL)
735 Laguna Drive
(V&M, 2007)
Grading
(AGS, 2017)
B-1
B-2
B-3
B-4
B-5
B-6
46
46
47
47
48
47
14, 25
N/A to 30.5
14
10
8
10
32, 21
34
37
40
37
2501 State St.
(AGS, 2016)
BA-1
BA-2
BA-3
36
35
35
N/A to 19.9
N/A to 16.5
N/A to 15.8
2303 Ocean St.
(Geocon, 2004)
(AGS, 2012)
B-1
B-2
B-3
B-4
B-5
B-6
B-7
B-8
B-9
B-10
CPT-1 to 3
38
35
32
38
15
15
14
10
12
13
N/A to 20
N/A to 20
N/A to 20
N/A to 20
11
11.5
11.5
8
N/A to 6
7
4
3.5
2.5
2
6
2
2995 State St.
(DEH, 2000)
Closure
Document
45 15
17
30
28
2855 Carlsbad Blvd.
(DEH, 1997)
Closure
Document
59 29.5 29.5
920 Carlsbad Village Dr.
(DEH, 1998)
Closure
Document
65 10.4 54.6
According to our review of the regional geotechnical studies and the data presented in Table 1,
groundwater levels in the site vicinity are variable. Based upon the recent data and the onsite
elevations we anticipate the approximate seepage/groundwater level at the project site will be at a
depth of 15 feet which corresponds to Elevation 35 ft. (MSL). The seepage/groundwater level is
dependent upon seasonal rainfall, ground elevation and site geology.
3.3. Flooding
According to available FEMA maps, the site is not in a FEMA identified flood hazard area.
3.4. Subsidence/Ground Fissuring
Due to the presence of the dense underlying Old Paralic Deposits and the Santiago Formation the
potential for subsidence/settlement and ground fissuring is unlikely.
3.5. Landsliding/Slope Instability
Given the relatively flat gradients across the site and the surrounding area, landsliding, mass
wasting, and/or surficial instability onsite is considered to be remote.
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4.0 SEISMIC HAZARDS
The site is located in the tectonically active Southern California area, and will therefore likely experience
shaking effects from earthquakes. The type and severity of seismic hazards affecting the site are to a large
degree dependent upon the distance to the causative fault, the intensity of the seismic event, and the
underlying soil characteristics. The seismic hazard may be primary, such as surface rupture and/or ground
shaking, or secondary, such as liquefaction or dynamic settlement.
4.1. Surface Fault Rupture
No known active faults have been mapped at or near the subject site. The nearest known active
surface fault is the Newport-Inglewood - Rose Canyon fault zone which is approximately 4.4 miles
west of the subject site. Accordingly, the potential for fault surface rupture on the subject site is
“very low”. This conclusion is based on literature review and aerial photographic analysis.
4.2. Seismicity
As noted, the site is within the tectonically active southern California area, and is approximately
4.4 miles from an active fault, the Newport-Inglewood-Rose Canyon fault zone. The potential
exists for strong ground motion that may affect future improvements.
At this point in time, non-critical structures (commercial, residential, and industrial) are usually
designed according to the California Building Code (2016) and guidelines of the controlling local
agency.
4.3. Liquefaction
Dependent upon the thickness of undocumented fill and the existing water table, the liquefaction
potential will be evaluated for the site. In order to have liquefaction, onsite loose materials (if
present) would have to extend to depths greater than the existing groundwater level. Due to the
dense nature of the underlying old paralic deposits the potential for seismically induced liquefaction
is anticipated to be “very low”.
4.4. Dynamic Settlement
Dynamic settlement occurs in response to an earthquake event affecting loose sandy earth
materials. The potential of dynamic settlement at the subject site is anticipated to be “very low”
due to the presence of the shallow old paralic deposits.
4.5. Seismically Induced Landsliding
Given the flat topography onsite the potential for landsliding is negligible.
4.6. Tsunami
Our review of the 2009 Tsunami Inundation Map for Emergency Planning prepared by CalEMA,
indicates that the site is not within the tsunami inundation limits.
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5.0 ENGINEERING ANALYSIS
Presented herein is a general discussion of the geotechnical properties of the various soil types and earth
materials summarized from our review of previous work conducted by AGS and available geotechnical
reports by others in the general area. It should be anticipated that detailed site-specific geotechnical analyses
of the project should be conducted during the design and entitlement phase. Dependent upon these future
studies these recommendations could change. The following is a summary of our opinions based upon the
available data.
5.1. Remedial Grading
If undocumented fill, colluvium, alluvium, and weathered Old Paralic Deposits are present at the
new commercial/residential structure proposed location, these materials will be considered
compressible. Where compressible soils are encountered they should be removed to competent
materials. It is anticipated that the onsite soils can likely be re-used for compacted fill. Engineered
fill should be compacted to a relative compaction of 95% of the dry density obtained per ASTM
D1557 and will be suitable for support of the proposed three- to four-story structure. In general, it
is anticipated that the extent of unsuitable soils could range from a few feet to as deep as 10 feet.
Dependent upon the depth to Old Paralic Deposits deeper removals could be required. However,
given that the proposed structure will have one subterranean floor it is likely that the majority of
the compressible soils will be removed as part of the basement excavation. Based upon our research
of the groundwater elevations encountered in other projects in the general area it is anticipated that
the approximate groundwater level at the project site will likely be at a depth of approximately 15
feet from existing grades which roughly corresponds to an elevation of 35 ft. (MSL).
5.2. Soil Expansion Potential
It is anticipated that the expansion potential of the onsite soils will vary from "very low to low".
Testing should be conducted to define the as-graded expansive soil characteristics prior to
construction. The results of these tests and the final as-graded conditions will govern design of
foundations and street pavement sections.
5.3. Preliminary Foundation Design
Generally, once grading is conducted, the onsite soils are expected to exhibit favorable bearing
characteristics. Estimated bearing capacity is anticipated to range from 2,000 to 2,500 psf for
shallow near surface soils. For deeper basement continuous footings and isolated spread footings
founded in Old Paralic Deposits, increased bearing values of 3,000 psf to 5,000 psf may be
achievable dependent upon footing size and embedment.
5.4. Corrosivity and Sulfates
It is anticipated that the onsite soils will generally be classified as having “negligible” soluble
sulfate concentration when classified in accordance with ACI 318-11 Table 4.2.1 (per 2016 CBC).
However, the onsite soils will likely be moderately corrosive to buried ferrous metals. Final
determination should be based upon post-graded testing of near-surface soils.
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6.0 CONCLUSIONS
The above geotechnical issues have been identified during our due diligence for the project. These issues
will need to be explored further and addressed as part of a preliminary geotechnical investigation and
grading plan review for the project.
Based upon AGS's observations, the proposed residential/commercial development at the subject site is
considered feasible. As project entitlements move forward, a preliminary geotechnical investigation and
associated infiltration feasibility report will be required to assess the suitability of the soils with regard to
the proposed development and for geotechnical review by the governing municipality. As part of this scope
of work, three to four borings should be excavated, logged and sampled to more accurately assess the actual
subsurface conditions onsite. The proposed boring locations are shown in Figure 3.
Advanced Geotechnical Solutions, Inc. appreciates the opportunity to be of service to you. Please do not
hesitate to contact the undersigned should you have any questions regarding this report.
Respectfully Submitted,
Advanced Geotechnical Solutions, Inc.
_____________________________
JEFFREY A. CHANEY, President
CE 46544/GE 2314, Reg. Exp. 6-30-19
Distribution: (3) Addressee
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REFERENCES
Advanced Geotechnical Solutions (AGS), 2017, Geotechnical Investigation and Foundation Design
Recommendations for Proposed Residential Multi-Family Podium Structure (Grand Ave.) and
Single Family (Home Ave.), 800 Grand Project, Carlsbad, California, Report No. 1607-03-B-2R,
dated November 21, 2017.
---. 2016. Preliminary Geotechnical Investigation, State Street Condominium Project, 2501 State Street,
Carlsbad, California. Report 1602-03-B-2, dated March 30, 2016.
California Division of Mines and Geology (CDMG 2008). Guidelines for Evaluating and Mitigating
Seismic Hazards in California, 2008, Special Publication 117A.
California Building Standards Commission, 2016, California Building Code, Title 24, Part 2, Volumes 1
and 2.
County of San Diego Department of Environmental Health (DEH), 1997, Case Closure Summary, Carlsbad
by the Sea, 2855 Carlsbad Blvd., Carlsbad, California. 92008. Case # H36613-00l (Geotracker No.
T0607302409), dated March 27, 1997.
---. 1998, Closure Letter, Underground Storage Tank (UST) Case #H20078-001, Desert Petroleum Station
#511, 920 Carlsbad Village Drive, Carlsbad, CA 92008. Case # H20078-001 (Geotracker No.
T0607301478), dated May 8, 1998.
---. 2000, Closure Letter, Underground Storage Tank (UST) Case #H13731-001, Joe's Transmission &
Auto Repair, 2995 State Street, Carlsbad, CA 92008-2337. Case # H13731-001 (Geotracker No.
T0607302017), dated March 15, 2000.
Geocon, Inc., 2004, Geotechnical Investigation, Ocean Street Condominiums, Ocean Street and Mountain
View Drive, Carlsbad, California. Project No. 07353-22-01, dated September 3, 2004.
Jennings, C.W., 1994, Fault Activity Map of California and Adjacent Areas: California Geological Survey,
California Geologic Data Map No. 6, Scale 1:750,000.
Kennedy, M.P., and Tan, S.S., 2005, Geologic Map of the Oceanside 30’ x 60’ Quadrangle, California
Regional Geologic Map Series, Scale 1:100,000.
Kleinfelder, Inc., 2003, Site Assessment Report, State Street Property North of Carlsbad Village Coaster
Station, Carlsbad, California. Project No. 27142, dated September 8, 2003.
Leighton and Associates, Inc., 2004, Preliminary Geotechnical Investigation, Hampton Inn and Suites,
Carlsbad Boulevard and Oak Avenue, Carlsbad, California. Project No. 600670-001, dated
December 16, 2004 (Revised April 27, 2005).
URS, 2009, Report of UST Removal and Soil Sampling, Former 76 Station No. 5723, 880 Carlsbad Village
Drive, Carlsbad, CA. County of San Diego DEH SAM Case No. H12427-003 (Geotracker No.
T10000000288), URS Project No. 29879558, dated March 9, 2009.
Vinje & Middleton Engineering, Inc., 2007, Geotechnical Investigation, Proposed Condominium
Development, 735 Laguna Drive, Carlsbad, California. Job #07-334-P, dated October 25, 2007.
DATE:
2/19
PROJECT NO.:
1809-04
FIGURE :1NOTE: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE.
ANTIQUE BLOCK
STATE STREET AND ROOSEVELT STREET
CARLSBAD, CALIFORNIA
SITE LOCATION MAP
SITE
N
SCALE 1”= 400’
SOURCE: GOOGLE MAPS, 2019.
LEGEND
GEOTECHNICAL SUBSURFACE DATABY AGS (PREVIOUS REPORTS)
800 Grand Ave.
2995 State
St.
GEOTECHNICAL SUBSURFACE DATABY OTHERS
FIGURE
2
DATE
2/19
PROJECT NO.
1809-04
REGIONAL GEOLOGIC MAP
NOTE: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE.
ANTIQUE BLOCK
STATE STREET AND ROOSEVELT STREET
CARLSBAD, CALIFORNIA
LEGEND
ARTIFICIAL FILL
MARINE BEACH DEPOSITS
OLD PARALIC DEPOSITS, UNITS 2-4
OLD PARALIC DEPOSITS, UNITS 6-7
SANTIAGO FORMATION
TONALITE UNDIVIDED
N
Tsa
SOURCE: GEOLOGIC MAP OF THE OCEANSIDE 30’ X 60’ QUADRANGLE, 2005.
SITE
Qa
Qls
Kt
Qvop12
SCALE 1”= 2,000’
Qop2-4
DATE:2/19PROJECT NO.:1809-04FIGURE :3NOTE: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE.ANTIQUE BLOCKSTATE STREET AND ROOSEVELT STREET CARLSBAD, CALIFORNIABORING LOCATION MAPSOURCE: GOOGLE EARTH, 2019.LEGENDAPPROXIMATE BORING LOCATIONAND SURFACE ELEVATIONB-1El. 46 ftB-2El. 45 ftB-3El. 50 ftB-4El. 45 ftB-4El. 45 ftRoosevelt St.State St.SCALE 1”= 125’