HomeMy WebLinkAboutCDP 2019-0005; CARLSBAD CORPORATE PLAZA PARKING STRUCTURE; GEOTECHNICAL INVESTIGATION; 2019-03-13GEOTECHNICAL INVESTIGATION
PASEO DEL NORTE
PARKING STRUCTURE
6183 AND 6185 PASEO DEL NORTE
CARLSBAD, CALIFORNIA
Ci7p.201- 000/sDP.20I -3
GRQo&O -00I3.
PREPARED FOR
NEXT MED III, LLC
CARLSBAD, CALIFORNIA
RECEIVED
AUG 27 2020
LAND DEVELOPMENT
ENGINEERING
MARCH 13, 2019
PROJECT NO. G2369-42-01
adams
CEG 2561
GEOCON INCORPORATED
RCE 8984
'I
ey C. Mikesell
GE 2533
GEOCON
INCORPORATED
GEOTECHNICAL • ENVIRONMENTAL. MATER I A IS <<]O)
Project No. G2369-42-01
March 13, 2019
Next Med III, LLC
6125 Paseo Del Norte, Suite 210
Carlsbad, California 92120
Attention: Mr. Scott Leggett
Subject: GEOTECHNICAL INVESTIGATION
PASEO DEL NORTE PARKING STRUCTURE
6183 AND 6185 PASEO DEL NORTE
CARLSBAD, CALIFORNIA
Dear Mr. Leggett:
In accordance with your request and authorization of our proposal (LG- 18474, dated December 24,
2018), we performed a geotechnical investigation to evaluate the underlying soil and geologic
conditions and potential geologic hazards, and to assist in the design of the proposed parking structure
and associated improvements.
This report presents the findings of our study and conclusions and recommendations pertaining to
geotechnical aspects of the proposed project. Based on the results of our investigation, it is our opinion
that the site can be developed as planned, provided the recommendations of this report are followed.
Should you have questions regarding this report, or if we may be of further service, please contact the
undersigned at your convenience.
Very truly yours,
BRK:RCM:RSA:dmë
(1) Addressee
6960 Flanders Drive 5 Son Diego, California 92121.2974 M Telephone 858.558.6900 E Fax 858.558.6159
TABLE OF CONTENTS
=5T
PURPOSE AND SCOPE.................................................................................................................I
SITE AND PROJECT DESCRIPTION ........................................................................................... 1
PREVIOUS GRADING...................................................................................................................2
SOIL AND GEOLOGIC CONDITIONS ........................................................................................2
4.1 Compacted Fill (Qcf).............................................................................................................2
4.2 Undocumented Fill (Qudf) ....................................................................................................2
4.3 Old Paralic Deposits (Qop)....................................................................................................3
GROUNDWATER..........................................................................................................................3
GEOLOGIC HAZARDS .................................................................................................................3
6.1 Seismic Hazard Analysis .............. . ......................................................................................... 3
6.2 Ground Rupture.....................................................................................................................5
6.3 Liquefaction...........................................................................................................................5
6.4 Landslides..............................................................................................................................5
6.5 Tsunamis and Seiches............................................................................................................6
6.6 Subsidence ............................................................................................................................. 6°
6.7 Flooding .................................................................................................................................. 6
CONCLUSIONS AND RECOMMENDATIONS...........................................................................7
7.1 General...................................................................................................................................7
7.2 Excavation and Soil Characteristics......................................................................................8
7.3 Grading ................................................................................................................................... 8
7.4 Slopes...................................................................................................................................10
7.5 Seismic Design Criteria.......................................................................................................10
7.6 Foundation and Concrete Slabs-On-Grade Recommendations...........................................11
7.7 Conventional Retaining Wall Recommendations................................................................14
7.8 Preliminary Pavement Recommendations...........................................................................16
7.9 Storm Water Management .................................................. . ................................................. 18
7.10 Site Drainage and Moisture Protection................................................................................19
7.11 Grading and Foundation Plan Review.................................................................................19
LIMITATIONS AND UNIFORMITY OF CONDITIONS
MAPS AND ILLUSTRATIONS
Figure 1, Vicinity Map
Figure 2, Geologic Map
Figure 3, Wall/Column Footing Dimension Detail
Figure 4, Typical Retaining Wall Drain Detail
-• APPENDIX A
FIELD INVESTIGATION
Figures A-i - A-6, Logs of Exploratory Borings
TABLE OF CONTENTS (Concluded)
APPENDIX B
LABORATORY TESTING
Table B-I, Summary of Laboratory Maximum Dry Density and optimum Moisture Content Test Results
Table B-Il, Summary of Laboratory Direct Shear Test Results
Table B-ffl, Summary of Laboratory Expansion Index Test Results
Table B-N, Summary of Laboratory Water-Soluble Sulfate Test Results
Figure B-i, Gradation Curve
Figure B-2 - B-3, Consolidation Curves
APPENDIX C
RECOMMENDED GRADING SPECIFICATIONS
LIST OF REFERENCES
GEOTECHNICAL INVESTIGATION
1. PURPOSE AND SCOPE
This report presents the results of our geotechnical investigation for the proposed parking structure
and improvements at 6183 and 6185 Paseo del Norte in Carlsbad, California (see Vicinity Map,
Figure 1). The purpose of this geotechnical investigation is to evaluate the surface and subsurface soil
conditions, general site geology, and to identify geotechnical constraints that may impact construction
of the proposed parking structure and improvements. This report also provides grading and
foundation recommendations, retaining wall design criteria, and storm water management
recommendations.
To aid in preparing this geotechnical investigation, we reviewed the site plan titled Nextmed Parking
Structure, Carlsbad Corporate Plaza, Carlsbad, California, prepared Pasco Laret Suiter &
Associates, dated March 6, 2019.
We drilled six, small-diameter, borings to evaluate geologic conditions in the area of proposed
improvements. The approximate boring and infiltration test locations are shown the Geologic Map,
Figure 2. The base map used for Figure 2 is a CAD file of the site plan prepared by Pasco Laret Suiter
& Associates. Logs of the exploratory borings and a detailed discussion of our field investigation are
presented in Appendix A.
We performed laboratory tests on selected soil samples obtained during the field investigation to
evaluate pertinent physical and chemical properties for engineering analyses, and to assist in
providing recommendations for site grading and foundation design criteria. Details of the laboratory
testing and a summary of test results are presented in Appendix B.
The conclusions and recommendations presented herein are based on analyses of the data obtained
from the field investigation, laboratory tests, and our experience with similar soil and geologic
conditions.
2. SITE AND PROJECT DESCRIPTION
Existing site improvements include two, two-story office buildings, a paved parking lot, and
landscaped areas. The site is bordered by an existing commercial building to the northeast, Paseo Del
Norte roadway to the north, Camino Del Parque roadway to the east and residential structures to the
south. Existing grades within the area of the proposed parking structure are relatively flat with
elevations ranging from approximately 73 to 76 feet Mean Sea Level (MSL).
Project No. G2369-42-01 - 1 - March 13, 2019
We understand the project will consist of constructing a new one-story (two-level) parking structure
within the existing parking lot. The parking structure will likely be supported by spread footings at
columns and shear walls. Two storm water BMP basins are planned on the north side of the parking
structure.
The above locations, site descriptions, and proposed development are based on our site
reconnaissance, review of published geologic literature, field investigations, and discussions with
project personnel. If development plans differ from those described herein, Geocon Incorporated
should be contacted for review of the plans and possible revisions to this report.
3. PREVIOUS GRADING
Grading occurred on the property between July and August 1998. Within the parking lot, grading
consisted of removal of undocumented fill and replacement with compacted fill to a depth of 2 feet
below parking lot subgrade elevation. Undocumented fill below 2 feet from subgrade was left in-
place. A summary of grading and compaction test results is contained in Geocon's report titled Final
Report of Testing and Observation Services During Site Grading, Carlsbad Corporate Plaza,
Carlsbad, California, dated January 12, 1999 (Project No. 06040-22-02).
4. SOIL AND GEOLOGIC CONDITIONS
The property is underlain by compacted fill overlying undocumented fill and Old Paralic Deposits. A
description of the soil and geologic units is provided below.
4.1 Compacted Fill (Qcf)
Compacted fill to a depth of approximately 2 to 3 feet below existing grade was encountered in all of
- the borings. The compacted fill generally consists of moist, brown to dark gray, clayey sand with
some brownish gray to brown, silty clay. Laboratory tests indicate the fills possess a low expansion
potential (El of 21 to 50). The compacted fill is suitable for additional fill and/or planned
- improvements, except where it overlies undocumented fill.
4.2 Undocumented Fill (Qudf)
Approximately 2 to 3 feet of undocumented fill soil was encountered underlying the compacted fill in
borings on the west side of the proposed parking structure. The undocumented fill generally consists
of moist, brown to grayish brown, clayey to silty sand. Laboratory consolidation tests indicate the
undocumented fill is moderately compressible. Undocumented fill should be removed and replaced as
compacted fill for support of the parking structure, or alternatively, footings deepened to extend
through the fill to the underlying Old Paralic Deposits.
Project No. G236942-01 - 2 - March 13, 2019
4.3 Old Paralic Deposits (Qop)
The Quaternary-age Old Paralic Deposits exist below the compacted fill and undocumented fill.
These deposits generally consist of medium dense to dense, light to dark reddish brown and olive
brown, silty to clayey, fine to medium sand and stiff, olive brown, sandy clay. The Old Paralic
Deposits typically possess a "very low" to "medium" expansion potential (expansion index of 90 or
less). The Old Paralic Deposits are considered suitable for support of additional fill and proposed
foundation loads.
5. GROUNDWATER
We did not encounter groundwater or seepage during our site investigation. However, it is not
uncommon for shallow seepage conditions to develop where none previously existed when sites are
irrigated or infiltration is implemented. Seepage is dependent on seasonal precipitation, irrigation,
land use, among other factors, and varies as a result. Proper surface drainage will be important to
future performance of the project. We expect groundwater is deeper than about 40 feet below existing
grade, based on geologic data obtained during other investigations close to the subject site. We do not
expect groundwater to be encountered during construction of the proposed development.
6. GEOLOGIC HAZARDS
6.1 Seismic Hazard Analysis
-, We performed a deterministic seismic hazard analysis using Risk Engineering (2019). Ten, known
active faults were located within a search radius of 50 miles from the property. We used the USGS
fault database, which provides several models and combinations of fault data, to evaluate the fault
information. Based on this database, the Newport-Inglewood/Rose Canyon Fault Zone, located
approximately 4 miles west of the site, is the nearest known active fault and is the dominant source of
potential ground motion. Earthquakes occurring on the Newport-Inglewood/Rose Canyon Fault Zone
or other faults within the southern California and northern Baja California area are potential
generators of significant ground motion at the site. The estimated maximum earthquake magnitude
and peak ground acceleration for the Newport-Inglewood/Rose Canyon Fault are 7.5 and 0.420g,
respectively. Table 6.1.1 lists the estimated maximum earthquake magnitude and peak ground
acceleration for the most dominant faults in relation to the site location. We calculated peak ground
acceleration (PGA) using Boore-Atkinson (2008) NGA USGS 2008, Campbell-Bozorgnia (2008)
NGA USGS 2008, and Chiou-Youngs (2007) NGA USGS 2008 acceleration-attenuation
relationships.
Project No. G2369-42-01 -3- March 13, 2019
TABLE 6.1.1
DETERMINISTIC SITE PARAMETERS
Fault Name Distance from
Site (miles)
Maximum
Earthquake
Magnitude
(Mw)
Peak Ground Acceleration
Boore-
Atkinson
2008(g)
Campbell-
Bozorgnia
2008(g)
Chiou-
Youngs 2007
(g)
Newport-Inglewood 4 7.5 0.352 0.328 0.420
Rose Canyon 4 6.9 0.315 0.318 0.367
Coronado Bank 20 7.4 0.190 0.133 0.159
Palos Verdes Connected 20 7.7 0.209 0.144 0.185
Elsinore 24 7.85 0.201 0.134 0.176
Palos Verdes 37 7.3 0.125 0.082 0.087
San Joaquin Hills 38 7.1 0.112 0.095 0.087
Earthquake Valley 42 6.8 0.088 0.059 '0.050
San Jacinto 48 7.88 0.124 0.083 0.102
Chino 50 6.8 0.074 0.051 0.042
In the event of a major earthquake on the referenced faults or other significant faults in the southern
California and northern Baja California area, the site could be subjected to moderate to severe ground
shaking. With respect to this hazard, the, site is considered comparable to others in the general
vicinity.
We performed a site-specific probabilistic seismic hazard analysis using Risk Engineering (2019).
Geologic parameters not addressed in the deterministic analysis are included in this analysis. The
program operates under the assumption that the occurrence rate of earthquakes on each mapped
- Quaternary fault is proportional to the fault's slip rate. The program accounts for earthquake
magnitude as a function of fault rupture length, and site acceleration estimates are made using the
-
earthquake magnitude and distance from the site to the rupture zone. The program also accounts for
uncertainty in each of following: (1) earthquake magnitude, (2) rupture length for a given magnitude,
- (3) location of the rupture zone, (4) maximum possible magnitude of a given earthquake, and
(5) acceleration at the site from a given earthquake along each fault. By calculating the expected
accelerations from considered earthquake sources, the program calculates the total average annual
expected number of occurrences of site acceleration greater than a specified value. We utilized
acceleration-attenuation relationships suggested by Boore-Atkinson (2008), Campbell-Bozorgnia
(2008) and Chiou-Youngs (2007) in the analysis. Table 6.1.2 presents the site-specific probabilistic
seismic hazard parameters including acceleration-attenuation relationships and the probability of
exceedence.
Project No. G236942-01 -4 - March 13, 2019
TABLE 6.1.2
PROBABILISTIC SEISMIC HAZARD PARAMETERS
Probability of Exceedence
Peak Ground Acceleration
Boore-Atkinson
2008 (g)
Campbell-Bozorgnia
2008 (g)
Chiou-Youngs
2007 (g)
2% in a 50 Year Period 0.53 0.45 0.53
5% in a 50 Year Period 0.40 0.33 0.38
10% in a 50 Year Period 0.31 0.25 0.28
While listing peak accelerations is useful for comparison of potential effects of fault activity in a
region, other considerations are important in seismic design, including the frequency and duration of
motion and the soil conditions underlying the site. Seismic design of the structures should be
performed in accordance with the 2016 California Building Code (CBC) guidelines currently adopted
by the City of Carlsbad.
6.2 Ground Rupture
No evidence of faulting was observed during our investigation. The USGS (2019) shows that there
are no mapped Quaternary faults crossing or trending toward the property. The site is not located
within a currently established Alquist-Priolo Earthquake Fault Zone. No active faults are known to
exist at the site. The nearest active fault, the Newport Inglewood/Rose Canyon Fault Zone, lies
approximately 4 miles west of the site. The site is not located within a State of California Earthquake
Special Study Zone. The risk associated with ground-rupture hazard due to faulting is low.
6.3 Liquefaction
- Liquefaction typically occurs when a site is subjected to seismic activity, onsite soils are
cohesionless, groundwater is encountered within 50 feet of the surface, and soil relative densities are
less than about 70 percent. If all four previous criteria are met, a seismic event could result in a rapid
pore water pressure increase from the earthquake-generated ground accelerations. The potential for
liquefaction occurring at the site is considered to be "very low" due to the lack of a near surface
permanent groundwater condition and the dense nature of the on-site soils.
6.4 Landslides
Examination of topographic maps, our geologic reconnaissance, and review of available geotechnical
and geologic reports for the site vicinity indicate that landslides are not present at the property or at a
location that could impact the site. The risk associated with landsliding hazard is low.
Project No. G2369-42-01 -5 - March 13, 2019
6.5 Tsunamis and Seiches
The site is approximately 0.5 miles from the Pacific Ocean at an elevation of approximately 73 feet
above MSL. The risk associated with inundation hazard due to tsunamis is low.
The site is located approximately 1.5 miles from Agua Hedionda Lagoon and 1.8 miles from
Batiquitos Lagoon; therefore, the risk associated with inundation hazard associated with a seiche is
low.
6.6 Subsidence
Based on the subsurface soil conditions encountered during our field investigation, the risk associated
with ground subsidence hazard is low.
6.7 Flooding
According to the FEMA (2012), the subject site is located within Zone X, an area of minimal flood
hazard. The risk associated with flood hazard is low.
Project No. G2369-42-01 -6- March 13, 2019
7. CONCLUSIONS AND RECOMMENDATIONS
7.1 General
7.1.1 From a geotechnical engineering standpoint, it is our opinion that the site is suitable for
development of the proposed project provided the recommendations presented herein are
implemented in design and construction of the project.
7.1.2 The results of our field investigation indicate the site is underlain by compacted fill
overlying undocumented fill and Old Paralic Deposits. The undocumented fill is not
considered suitable for the support of structural improvements and should be removed and
recompacted for support of structural footings. The compacted fill and Old Paralic Deposits
are considered suitable for support of additional fill or proposed improvements.
7.1.3 In lieu of remedial grading, footings can be deepened to extend through undocumented and
compacted fill to bear entirely on the underlying Old Paralic Deposits.
7.1.4 The site is located approximately 4 miles from the nearest active fault, the Newport-
Inglewood/Rose Canyon Fault Zone. Based on our research, no active, potentially active,
or activity unknown faults are mapped crossing the site or are trending toward the site.
7.1.5 The risks associated with liquefaction, ground rupture, landslides, tsunamis, seiches,
ground subsidence, and flooding hazards are low.
7.1.6 Groundwater is not expected to be encountered during grading or utility construction for
this project. No subdrains will be required on the project, with the exception of subdrains
for retaining walls.
7.1.7 The proposed structures can be supported on shallow foundations system bearing on
properly compacted fill or Old Paralic Deposits.
7.1.8 Subsurface conditions observed in the exploratory borings may be extrapolated to reflect
general soil/geologic conditions at the site; however, some variations in subsurface
conditions between borings should be expected.
7.1.9 Based on our geotechnical investigation and a review of the proposed improvement, we
opine that the new development will not have an adverse impact on the adjacent properties.
Project No. G2369-42-0 -7- March 13, 2019
7.2 Excavation and Soil Characteristics
7.2.1 Excavations within the undocumented fill and alluvium should be possible with moderate
to heavy effort using conventional, heavy-duty equipment during grading and trenching
operations.
7.2.2 The soil encountered in our field investigation is considered to be "expansive" (Expansion
Index [El] greater than 20) as defined by 2016 California Building Code (CBC)
Section 1803.5.3. Table 7.2 presents soil classifications based on the expansion index.
TABLE 7.2.
EXPANSION CLASSIFICATION BASED ON EXPANSION INDEX
Expansion Index (El) Expansion Classification 2016 CBC
Expansion Classification
0-20 Very Low Non-Expansive
21-50 Low
Expansive
Very High
51-90 Medium
91-130 High
Greater Than 130
7.2.3 We performed laboratory tests on samples of the site materials to evaluate the percentage
of water-soluble sulfate content. Appendix B presents results of the laboratory water-
soluble sulfate content tests. The test results indicate the on-site materials at the locations
tested possess "SO" sulfate exposure to concrete structures as defined by 2016 CBC Section
1904 and ACI 318-14 Chapter 19. The presence of water-soluble sulfates is not a visually
discernible characteristic; therefore, other soil samples from the site could yield different
concentrations. Additionally, over time landscaping activities (i.e., addition of fertilizers
and other soil nutrients) may affect the concentration.
7.2.4 Geocon Incorporated does not practice in the field of corrosion engineering. Therefore, if
improvements that could be susceptible to corrosion are planned, further evaluation by a
corrosion engineer may be needed.
7.3 Grading
7.3.1 We expect grading will be minor with planned new grades closely matching existing
grades. Grading should be performed in accordance with the Recommended Grading
Specifications contained in Appendix C. Where the recommendations of Appendix C
Project No. G2369-42-01 -8- March 13, 2019
conflict with this section of the report, the recommendations of this section take
precedence.
7.3.2 Prior to commencing grading, a preconstruction conference should be held at the site with
the owner or developer, grading contractor, civil engineer, and geotechnical engineer, in
attendance. Special soil handling and/or the grading plans can be discussed at that time.
7.3.3 Geocon Incorporated should provide observation and compaction testing services during
grading. Fill soil should be observed on a full-time basis during placement and tested to
check in-place dry density and moisture content.
7.3.4 Grading should commence with the removal of vegetation, asphalt, and concrete from the
area to be graded. Deleterious debris such as wood, asphalt, brick, plastic, and concrete
should be exported from the site and not be mixed with fill soils. Underground
improvements that will be abandoned should be removed and the resulting depressions
properly backfilled in accordance with the procedures described herein.
7.3.5 To support new structural footings, we recommend the upper 3 feet of soil below pad
grade, or to a depth of 1-foot below the bottom of the deepest footing, whichever deeper,
be removed and replaced as compacted fill. Removals should be observed during grading
by the geotechnical engineer and/or engineering geologist. If unsuitable soils are
encountered at the bottom of the excavation, deeper removals may be required. Removals
should extend out a horizontal distance of at least 5 feet outside of the building pad limits
and limits of structural footings.
7.3.6 As an alternative to remedial grading, footings supporting the new parking structure can be
deepened to extend through the compacted and undocumented fill to bear entirely on the
underlying Old Paralic Deposits. Based on borings, we expect footing depths between
approximately 2 to 6 feet may be required to extend through the fill.
7.3.7 If remedial grading is performed, prior to placing fill, the bottom of the removal and other
areas to receive fill should be scarified to a depth of at least 1-foot, moisture conditioned as
necessary, and recompacted. Soils derived from onsite excavations can then be placed and
compacted in the overexcavated area. Fill lifts should be no thicker than will allow for
adequate bonding and compaction. Fill soils, including scarified removal bottoms, should
be compacted to a dry density of at least 90 percent of maximum dry density at or slightly
above optimum moisture content, as determined in accordance with ASTM D 1557.
Grading should be performed so that the upper 3 feet of soil below finish pad subgrade
consist of soil with a low expansive potential (El of 50 or less).
Project No. G2369-42-01 - 9 - March 13, 2019
7.3.8. Oversize rock (generally greater than 12 inches), if encountered will need to be exported.
Rock greater than 6 inches should not be placed in the upper 3 feet below building pad grade.
7.3.9 Imported fill, if needed, should consist of granular soil with a low expansion potential (El
of 50 or less), and be free of deleterious material or stones larger than 3 inches. Geocon
Incorporated should be notified of the import soil source and should perform laboratory
testing prior to its arrival at the site to evaluate its suitability as fill material.
7.4 Slopes
7.4.1 No new slopes are planned.
7.5 Seismic Design Criteria
7.5.1 We used SEAOC (2019) to summarize site-specific design criteria obtained (Table 7.5.1)
from the 2016 California Building Code (CBC; Based on the 2012 International Building
Code [IBC] and ASCE 7-10), Chapter 16 Structural Design, Section 1613 Earthquake
Loads. The short spectral response uses a period of 0.2 seconds. Based on existing geologic
conditions and planned development, the structures may be designed using a Site Class D.
We evaluated the Site Class based on the discussion in Section 1613.3.2 of the 2016 CBC
and Table 20.3-1 of ASCE 7-10. The values presented in Table 7.5.1 are for the risk-
targeted maximum considered earthquake (MCER).
TABLE 7.5.1
2016 CBC SEISMIC DESIGN PARAMETERS
Parameter Value 2016 CBC Reference
Site Class D Table 1613.3 .2
MCER Ground Motion Spectral 1.151g Figure 1613..3.1(1) Response Acceleration - Class B (short), Ss
MCER Ground Motion Spectral O.443g Figure 16 13.3.1(2) Response Acceleration - Class B (1 sec), Si
Site Coefficient, FA 1.040 Table 1613.3.3(1)
Site Coefficient, Fv 1.557 Table 1613.3.3(2)
Site Class Modified MCER Spectral 1.196g Section 1613.3.3 (Eqn 16-37) Response Acceleration (short), SMs
Site Class Modified MCER Spectral O.690g Section 1613.3.3 (Eqn 16-38) Response Acceleration - (1 sec), SMI
5% Damped Design Spectral
Response Acceleration (short), SDS 0.798g Section 16 13.3.4 (Eqn 16-39)
5% Damped Design Spectral
Response Acceleration (1 sec), Si 0.460g Section 1613.3.4 (Eqn 16-40)
Project No. G2369-42-01 -10- March 13, 2019
7.5.2 Table 7.5.2 presents additional seismic design parameters for projects located in Seismic
Design Categories of D through F in accordance with ASCE 7-10 for the mapped
maximum considered geometric mean (MCEG).
TABLE 7.5.2
2016 CBC SITE ACCELERATION DESIGN PARAMETERS
Parameter Value ASCE 7-10 Reference
Mapped MCEo Peak Ground Acceleration, PGA 0.462g Figure 22-7
Site Coefficient, FPGA 1.038 Table 11.8-1
Site Class Modified MCE
Peak Ground Acceleration, PGAM 0.479g Section 11.8.3 (Eqn 11.8-1)
7.5.3 Conformance to the criteria in Tables 7.5.1 and 7.5.2 for seismic design does not constitute
any kind of guarantee or assurance that significant structural damage or ground failure will
not occur if a maximum level earthquake occurs. The primary goal of seismic design is to
protect life and not to avoid all damage, since such design may be economically
prohibitive.
7.6 Foundation and Concrete Slabs-On-Grade Recommendations
7.6.1 The following foundation recommendations assume the proposed structure will bear
entirely on either properly compacted fill or native Old Paralic Deposits. Footings should
not be supported on both compacted fill and native Old Paralic Deposits. The
recommendations also assume that the prevailing soil within 3 feet of pad grade will have
an Expansion Index (El) 50 or less.
7.6.2 Foundations for the new structure should consist of continuous strip footings and/or
isolated spread footings. Continuous footings should be at least 12 inches wide and extend
at least 24 inches below lowest adjacent pad grade. Isolated spread footings should have a
minimum width of 24 inches and should extend at least 24 inches below lowest adjacent
pad grade. Concrete reinforcement for continuous footings should consist of at least four,
No. 5 steel, reinforcing bars placed horizontally in the footings, two near the top and two
near the bottom. The project structural engineer should design the concrete reinforcement
for the spread footings. A typical footing dimension detail depicting lowest adjacent grade
is provided on Figure 3.
7.6.3 Foundations may be designed for an allowable soil bearing pressure of 3,000 pounds per
square foot (psf) (dead plus live load). The bearing pressure may be increased by 300 psf
and 500 psf for each additional foot of foundation width and depth, respectively, up to a
Project No. G2369-42-0I - I - March 13, 2019
maximum allowable bearing pressure of 4,000 psf. The allowable bearing pressure may
also be increased by up to one-third for transient loads such as those due to wind or seismic
forces.
7.6.4 Total and differential settlements as a result of static loading under the imposed allowable
loads are estimated to be 1- inch total and 3/4-inch differential over a span of 40 feet.
7.6.5 The minimum foundation dimensions and concrete reinforcement recommendations
presented above are based on soil characteristics only and are not intended to replace
reinforcement required for structural considerations.
7.6.6 The proximity of the foundation to the top of a slope steeper than 3:1 could impact the
allowable soil bearing pressure. Therefore, Geocon Incorporated should be consulted where
such a condition is anticipated. As a minimum, wall footings should be deepened such that
the bottom outside edge of the footing is at least seven feet from the face of slope.
7.6.7 Interior concrete slabs-on-grade should be at least 5 inches thick and reinforced with No. 3,
steel, bars placed 18 inches on center in both directions placed at the slab midpoint. The
concrete slab-on-grade recommendations are based on soil support characteristics only.
The project structural engineer should evaluate the structural requirements of the concrete
slabs for supporting planned loading. Thicker concrete slabs may be required for heavier
loads.
7.6.8 The use of isolated footings, which are located beyond the perimeter of the building and
support structural elements connected to the building, are not recommended. Where this
condition cannot be avoided, the isolated footings should be connected to the building
foundation system with grade beams.
7.6.9 A vapor barrier should underlie slabs that may receive moisture-sensitive floor coverings or
may be used to store moisture-sensitive materials. The design of the vapor retarder should be
consistent with the guidelines presented in the American Concrete Institute's (ACI) Guide for
Concrete Slabs that Receive Moisture-Sensitive Flooring Materials (ACI 302.2R-06). The
project architect or developer should specify the vapor retarder based on the type of floor
covering that will be installed and if the structure will possess a humidity controlled
environment.
7.6.10 The project foundation engineer, architect, and/or developer should determine the thickness
of bedding sand below the slab. Sand bedding thicknesses of 3 to 4 inches are typical in the
Project No. G2369-42-01 -12- March 13, 2019
Southern California area. Geocon should be contacted to provide recommendations if the
bedding sand is thicker than 6 inches.
7.6.11 The foundation design engineer should provide appropriate concrete mix design criteria
and curing measures to assure proper curing of the slab by reducing the potential for rapid
moisture loss and subsequent cracking and/or slab curl. We suggest that the foundation
design engineer present the concrete mix design and proper curing methods on the
foundation plans. It is critical that the foundation contractor understands and follows the
recommendations presented on the foundation plans.
7.6.12 Special subgrade presaturation is not deemed necessary prior to placing concrete; however,
the exposed foundation and slab subgrade soil should be moisture conditioned, as
necessary, to maintain a moist condition as would be expected in any such concrete
placement.
7.6.13 Exterior slabs not subjected to vehicular traffic should be a minimum of four inches thick,
and when panels are in excess of 8 feet wide, reinforced with 6 x 6-6/6 welded wire mesh.
The mesh should be placed in the middle of the slab. Proper mesh positioning is critical to
future performance of the slabs. The contractor should take extra measures to provide
proper mesh placement.
7.6.14 Prior to construction of slabs, the upper 12 inches of subgrade soils should be moisture
conditioned to optimum moisture content or slightly above and compacted to at least 90
percent of the laboratory maximum dry density per ASTM 1557.
7.6.15 The recommendations of this report are intended to reduce the potential for cracking of
slabs and foundations due to expansive soil (if present), differential settlement of fill soil
with varying thicknesses. However, even with the incorporation of the recommendations
presented herein, foundations, stucco walls, and slabs-on-grade placed on such conditions
may still exhibit some cracking due to soil movement and/or shrinkage. The occurrence of
concrete shrinkage cracks is independent of the supporting soil characteristics. Their
occurrence may be reduced by limiting the slump of the concrete, proper concrete
placement and curing, and by the placement of crack control joints at periodic intervals, in
particular, where re-entrant slab corners occur.
7.6.16 Concrete slabs should be provided with adequate crack-control joints, construction joints
and/or expansion joints to reduce unsightly shrinkage cracking. The design ofjoints should
consider criteria of the American Concrete Institute (ACI) when establishing crack-control
It
Project No. G236942-01 - 13 - March 13,2019
spacing. Additional steel reinforcing, concrete admixtures and/or closer crack control joint
spacing should be considered where concrete-exposed finished floors are planned.
7.6.17 Geocon Incorporated should be consulted to provide additional design parameters as
required by the structural engineer.
7.7 Conventional Retaining Wall Recommendations
7.7.1 Retaining walls that are allowed to rotate more than 0.00111 (where H equals the height of
the retaining portion of the wall) at the top of the wall and having a level backfill surface
should be designed for an active soil pressure equivalent to the pressure exerted by a fluid
density of 35 pcf. Where the backfill will be inclined at 2:1 (horizontal:vertical), an active
soil pressure of 50 pcf is recommended. Expansive soils should not be used as backfill
material behind retaining walls. All soil placed for retaining wall backfill should have an
Expansion Index less than 50.
7.7.2 Soil contemplated for use as retaining wall backfill, including import materials, should be
identified in the field prior to backfill. At that time Geocon Incorporated should obtain
samples for laboratory testing to evaluate its suitability. Modified lateral earth pressures
may be necessary if the backfill soil does not meet the required expansion index or shear
strength. City or regional standard wall designs, if used, are based on a specific active
lateral earth pressure and/or soil friction angle. In this regard, on-site soil to be used as
backfill may or may not meet the values for standard wall designs. Geocon Incorporated
should be consulted to assess the suitability of the on-site soil for use as wall backfill if
standard wall designs will be used.
7.7.3 Where walls are restrained from movement at the top, an additional uniform pressure of 8H
psf should be added to the active soil pressure where the wall possesses a height of 8 feet or
less and 12H where the wall is greater than 8 feet. For retaining walls subject to vehicular
loads within a horizontal distance equal to two-thirds the wall height, a surcharge
equivalent to 2 feet of fill soil should be added (unit weight 130 pcf).
7.7.4 Retaining walls should be provided with a drainage system adequate to prevent the buildup
of hydrostatic forces and should be waterproofed as required by the project architect. The
use of drainage openings through the base of the wall (weep holes) is not recommended
where the seepage could be a nuisance or otherwise adversely affect the property adjacent
to the base of the wall. The above recommendations assume a properly compacted granular
(El of less than 50) free-draining backfill material with no hydrostatic forces or imposed
surcharge load. Figure 4 presents a typical retaining wall drainage detail. If conditions
Project No. G2369-42-01 -14- . March 13, 2019
different than those described are expected, or if specific drainage details are desired,
Geocon Incorporated should be contacted for additional recommendations.
7.7.5 The structural engineer should determine the seismic design category for the project in
accordance with Section 1613 of the CBC. If the project possesses a seismic design category
of D, E, or F, retaining walls that support more than 6 feet of backfill should be designed with
seismic lateral pressure in accordance with Section 18.3.5.12 of the 2016 CBC. The seismic
load is dependent on the retained height where H is the height of the wall, in feet, and the
calculated loads result in pounds per square foot (psf) exerted at the base of the wall and zero
at the top of the wall. A seismic load of 17H should be used for design. We used the peak
ground acceleration adjusted for Site Class effects, PGAM, of 0.479 g calculated from
ASCE 7-10 Section 11.8.3 and applied a pseudo-static coefficient of 0.33.
7.7.6 In general, wall foundations having a minimum depth and width of 1 foot may be designed
for an allowable soil bearing pressure of 3,000 psf, provided the soil within 3 feet below
the base of the wall has an Expansion Index of less than 90. The recommended allowable
soil bearing pressures may be increased by 300 psf and 500 psf for each additional foot of
foundation width and depth, respectively, up to a maximum allowable soil bearing pressure
of 4,000 psf. The proximity of the foundation to the top of a slope steeper than 3:1 could
impact the allowable soil bearing pressure. Therefore, Geocon Incorporated should be
consulted where such a condition is expected.
7.7.7 For resistance to lateral loads, an allowable passive earth pressure equivalent to a fluid
density of 300 pcf is recommended for footings or shear keys poured neat against properly
compacted granular fill soils or undisturbed formation materials. The allowable passive
pressure assumes a horizontal surface extending away from the base of the wall at least
5 feet or three times the surface generating the passive pressure, whichever is greater. The
upper 12 inches of soil not protected by floor slabs or pavement should not be included in
the design for lateral resistance. Where walls are planned adjacent to and/or on descending
slopes, a passive pressure of 150 pcf should be used in design.
7.7.8 An allowable friction coefficient of 0.35 may be used for resistance to sliding between soil
and concrete. This friction coefficient may be combined with the allowable passive earth
pressure when determining resistance to lateral loads.
7.7.9 The recommendations presented above are generally applicable to the design of rigid
concrete or masonry retaining walls having a maximum height of eight feet. In the event
that walls higher than eight feet or other types of walls (i.e., soil nail, MSE walls) are
planned, Geocon Incorporated should be consulted for additional recommendations.
Project No. G2369-42-01 - 15- March 13, 2019
7.8 Preliminary Pavement Recommendations
7.8.1 Preliminary pavement recommendations are provided below. The final pavement sections
should be based on the R-Value of the subgrade soil encountered at final subgrade
elevation. For preliminary design, we used a laboratory R-Value of 15. We calculated the
preliminary flexible pavement sections for asphalt concrete using varying traffic indices
(TIs) in general conformance with the Caltrans Method of Flexible Pavement Design
(Highway Design Manual, Section 608.4). The project civil engineer or traffic engineer
should determine the appropriate Traffic Index (TI) or traffic loading expected on the
project for the various pavement areas that will be constructed. Recommended preliminary
asphalt concrete pavement sections are provided on Table 7.8.1
TABLE 7.8.1
PRELIMINARY ASPHALT CONCRETE PAVEMENT SECTIONS
Traffic Index
Pavement Design Section
Asphalt Concrete (inches) Class 2 Base(inches)
5 3 8
5.5 3 10
6 3 12
6.5 3.5 12.5
7 4 13
7.5 4 1 15
7.8.2 Asphalt concrete should conform to Section 203-6 of the Standard Specifications for
Public Works Construction (Green Book). Class 2 aggregate base materials should conform
to Section 26-1.02B of the Standard Specifications of the State of California, Department
of Transportation (Caltrans).
7.8.3 Prior to placing base material or concrete pavement, the subgrade should be scarified,
moisture conditioned and recompacted to a minimum of 95 percent relative compaction.
The depth of compaction should be at least 12 inches. The base material should be
compacted to at least 95 percent relative compaction. Asphalt concrete should be
compacted to a density of at least 95 percent of the laboratory Hveem density in
accordance with ASTM D 2726.
7.8.4 We calculated the rigid pavement section in general conformance with the procedure
recommended by the American Concrete Institute report AC! 330R-08 Guide for Design
and Construction of Concrete Parking Lots using the parameters presented in Table 7.8.2.
Project No. G236942-01 -16- March 13, 2019
TABLE 7.8.2
PRELIMINARY RIGID PAVEMENT DESIGN PARAMETERS
Design Parameter Design Value
Modulus of subgrade reaction, k 100 pci
Modulus of rupture for concrete, MR 500 psi
Traffic Category, TC A and C
Average daily truck traffic, ADTF 1 and 100
7.8.5 Based on the criteria presented herein, the PCC pavement sections should have a minimum
thickness as presented in Table 7.8.3.
TABLE 7.8.3
PRELIMINARY RIGID PAVEMENT RECOMMENDATIONS
Location Portland Cement Concrete (inches)
Automobile Areas (TCA, ADDT = 1) 5
Heavy Truck and Fire Lane Areas (TCC, ADDT = 100) 7
7.8.6 The PCC pavement should be placed over subgrade soil that is compacted to a dry density
of at least 95 percent of the laboratory maximum dry density near to slightly above
optimum moisture content. This pavement section is based on a minimum concrete
compressive strength of approximately 3,200 psi (pounds per square inch).
7.8.7 A thickened edge or integral curb should be constructed on the outside of concrete slabs
subjected to wheel loads. The thickened edge should be 1.2 times the slab thickness or a
minimum thickness of 2 inches, whichever results in a thicker edge, at the slab edge and
taper back to the recommended slab thickness 3 feet behind the face of the slab (e.g., a
7-inch-thick slab would have a 9-inch-thick edge). Reinforcing steel will riot be necessary
within the concrete for geotechnical purposes with the exception of loading docks, trash bin
enclosures, and dowels at construction joints as discussed below.
7.8.8 Loading aprons, such as those used for trash bin enclosures, should be constructed using
Portland cement concrete as recommended above for heavy truck traffic areas. The
pavement should be reinforced with a minimum of No. 3 steel reinforcing bars spaced 24
inches on center in both directions placed at the slab midpoint. The concrete should extend
out from the loading dock or trash bin such that both the front and rear wheels of the truck
will be located on reinforced concrete pavement when loading.
Project No. G2369-42-01 -17- March 13, 2019
7.8.9 To control the location and spread of concrete shrinkage cracks, crack-control joints
(weakened plane joints) should be included in the design of the concrete pavement slab.
Crack-control joints should not exceed 30 times the slab thickness with a maximum
spacing of 15 feet (e.g., a 7-inch-thick slab would have a 15-foot spacing pattern) and
should be sealed with an appropriate sealant to prevent the migration of water through the
control joint to the subgrade materials. The depth of the crack-control joints should be
determined by the referenced AC! report.
7.8.10 To provide load transfer between adjacent pavement slab sections, a trapezoidal-keyed
construction joint should be installed. As an alternative to the keyed joint, dowelling is
recommended between construction joints. As discussed in the referenced AC! guide,
dowels should consist of smooth, 7/8-inch-diameter reinforcing steel 14 inches long
embedded a minimum of 6 inches into the slab on either side of the construction joint.
Dowels should be located at the midpoint of the slab, spaced at 12 inches on center and
lubricated to allow joint movement while still transferring loads. The project structural
engineer may provide alternative recommendations for load transfer.
7.8.11 The performance of pavement is highly dependent on providing positive surface drainage
away from the edge of the pavement. Ponding of water on or adjacent to the pavement will
likely result in pavement distress and subgrade failure. Drainage from landscaped areas
should be directed to controlled drainage structures. Landscape areas adjacent to the edge
of asphalt pavements are not recommended due to the potential for surface or irrigation
water to infiltrate the underlying permeable aggregate base and cause distress. Where such
a condition cannot be avoided, consideration should be given to incorporating measures
that will significantly reduce the potential for subsurface water migration into the aggregate
base. If planter islands are planned, the perimeter curb should extend at least 6 inches
below the level of the base materials.
7.9 Storm Water Management
7.9.1 If storm water management devices are not properly designed and constructed, there is a
risk for distress to improvements and properties located hydrologically down gradient or
adjacent to these devices. Factors such as the amount of water being detained, its residence
time, and soil permeability have an important effect on seepage transmission and the
potential adverse impacts that may occur if the storm water management features are not
properly designed and constructed. We have not performed a hydrogeological study at the
site. If infiltration of storm water runoff into the subsurface occurs, downstream
improvements may be subjected to seeps, springs, slope instability, raised groundwater,
movement of foundations and slabs, or other undesirable impacts as a result of water
infiltration.
Project No. G2369-42-01 -18- March 13, 2019
7.10 Site Drainage and Moisture Protection
7.10.1 Adequate site drainage is critical to reduce the potential for differential soil movement,
erosion and subsurface seepage. Under no circumstances should water be allowed to pond
adjacent to footings. The site should be graded and maintained such that surface drainage is
directed away from structures in accordance with 2016 CBC 1804.4 or other applicable
standards. In addition, surface drainage should be directed away from the top of slopes into
swales or other controlled drainage devices. Roof and pavement drainage should be
directed into conduits that carry runoff away from the proposed or existing structures.
7.10.2 In the case of basement walls or building walls retaining landscaping areas, a water-
proofing system should be used on the wall and joints, and a Miradrain drainage panel (or
similar) should be placed over the waterproofing. The project architect or civil engineer
should provide detailed specifications on the plans for all waterproofing and drainage.
7.10.3 Underground utilities should be leak free. Utility and irrigation lines should be checked
periodically for leaks, and detected leaks should be repaired promptly. Detrimental soil
movement could occur if water is allowed to infiltrate the soil for prolonged periods of
time.
7.10.4 Landscaping planters adjacent to paved areas are not recommended due to the potential for
surface or irrigation water to infiltrate the pavement's subgrade and base course. Area
drains to collect excess irrigation water and transmit it to drainage structures or impervious
above-grade planter boxes can be used. In addition, where landscaping is planned adjacent
to the pavement, construction of a cutoff wall along the edge of the pavement that extends
at least 6 inches below the bottom of the base material should be considered.
7.11 Grading and Foundation Plan Review
7.11.1 Geocon Incorporated should review the grading and foundation plans for the project prior
to final design submittal to determine if additional analysis and/or recommendations are
required.
Project No. G236942-01 _19- March 13, 2019
LIMITATIONS AND UNIFORMITY OF CONDITIONS
The firm that performed the geotechnical investigation for the project should be retained to
provide testing and observation services during construction to provide continuity of
geotechnical interpretation and to check that the recommendations presented for geotechnical
aspects of site development are incorporated during site grading, construction of
improvements, and excavation of foundations. If another geotechnical firm is selected to
perform the testing and observation services during construction operations, that firm should
prepare a letter indicating their intent to assume the responsibilities of project geotechnical
engineer of record. A copy of the letter should be provided to the regulatory agency for their
records. In addition, that firm should provide revised recommendations concerning the
geotechnical aspects of the proposed development, or a written acknowledgement of their
concurrence with the recommendations presented in our report. They should also perform
additional analyses deemed necessary to assume the role of Geotechnical Engineer of Record.
The recommendations of this report pertain only to the site investigated and are based upon
the assumption that the soil conditions do not deviate from those disclosed in the
investigation. If any variations or undesirable conditions are encountered during construction,
or if the proposed construction will differ from that anticipated herein, Geocon Incorporated
should be notified so that supplemental recommendations can be given. The evaluation or
identification of the potential presence of hazardous or corrosive materials was not part of the
scope of services provided by Geocon Incorporated.
This report is issued with the understanding that it is the responsibility of the owner or his
representative to ensure that the information and recommendations contained herein are
brought to the attention of the architect and engineer for the project and incorporated into the
plans, and the necessary steps are taken to see that the contractor and subcontractors carry out
such recommendations in the field.
The findings of this report are valid as of the present date. However, changes in the
conditions of a property can occur with the passage of time, whether they be due to natural
processes or the works of man on this or adjacent properties. In addition, changes in
applicable or appropriate standards may occur, whether they result from legislation or the
broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly
or partially by changes outside our control. Therefore, this report is subject to review and
should not be relied upon after a period of three years.
Project No. G2369-42-01 March 13, 2019
r
0.
4
N
NO SCALE
THE GEOGRAPHICAL INFORMATION MADE AVAILABLE FOR DISPLAY WAS PROVIDED BY GOOGLE EARTH.
SUBJECT TO A LICENSING AGREEMENT THE INFORMATION IS FOR ILLUSTRATIVE PURPOSES ONLY, IT IS
NOT INTENDED FOR CLIENTS USE OR RELIANCE AND SHALL NOT BE REPRODUCED BY CLIENT. CLIENT
SHALL INDEMNIFY DEFEND AND HOLD HARMLESS GEOCON FROM ANY LIABILITY INCURRED AS A RESULT
OF SUCH USE OR RELIANCE BY CLIENT.
VICINITY MAP
GEOCON
<<R) INCORPORATED
GEOTECHNICAL• ENVIRONMENTAL • MATERIALS
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
RM/AML I DSK/GTYPD
PASEO DEL NORTE PARKING STRUCTURE
CARLSBAD, CALIFORNIA
DATE 03-13-2019 1 PROJECT NO. G2369 -42-01 1 FIG. 1
Plotted 03/12/2019 231PM I By ALVIN LADRILLONO I File Lo,9oe V/I GEOTECI'4/02000/02369 4201/201903 13/DETAILS'G2369.42.01 Vic Mop dwg
APPENDIX
APPENDIX A
FIELD INVESTIGATION
We performed our field investigation on February 12, 2019. The investigation consisted of drilling
six, small-diameter, geotechnical borings. The approximate locations of the geotechnical borings are
shown on Figure 2.
- The geotechnical. borings were drilled to depths ranging from approximately 19 to 19.5 feet below
existing grade using a CME 95 drill rig equipped with hollow-stem augers.
We obtained relatively undisturbed samples from the geotechnical borings by driving a 3-inch-
diameter sampler 12 inches into the undisturbed soil mass with blows from a 140 pound hammer
weighing falling 30 inches. The sampler was lined with 1-inch by 2.5-inch-diameter brass rings to
facilitate sampling. Bulk samples were also collected.
The soil conditions encountered in the borings were visually examined, classified, and logged in
general accordance with American Society for Testing and Materials (ASTM) practice for
Description and Identification of Soils (Visual-Manual Procedure D 2488). Logs of the exploratory
borings are presented on Figures A-i through A-6. The logs depict the soil and geologic conditions
encountered and the depth at which samples were obtained.
Project No. G2369-42-0I March 13, 2019
APPENDIX
APPENDIX B
LABORATORY TESTING
We performed laboratory tests in accordance with generally accepted test methods of the American
Society for Testing and Materials (ASTM) or other suggested procedures. We tested selected samples for
their in-place dry density and moisture content, maximum density and optimum moisture content, direct
shear strength, expansion index, water soluble sulfate, consolidation, and gradation characteristics. The
results of our laboratory tests are presented on the following tables and graphs. The in-place dry density
and moisture content test results are presented on the exploratory boring logs in Appendix A.
TABLE B-I
SUMMARY OF LABORATORY MAXIMUM DRY DENSITY
AND OPTIMUM MOISTURE CONTENT TEST RESULTS
(ASTM D 1557)
Maximum Dry Optimum Sample No. Description Density (pci) Moisture Content
(% dry wt.)
B2-1 Grayish brown, Clayey, fine to medium SAND 128.4 8.7
TABLE B-Il
- SUMMARY OF LABORATORY DIRECT SHEAR TEST RESULTS
ASTM D 3080
Sample
No.
Dry Density
(pci)
Moisture Content (°"°) Unit Cohesion
(psi)
Angle of Shear
Resistance (degrees) Initial I Final
B2-2 108.0 12.9 20.6 380 29
TABLE B-Ill
SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS
ASTM D 4829
Sample No.
Moisture Content (%) Dry
Density (pci)
Expansion
Index
Expansion
Classification Before Test I After Test
B2-1 8.9 17.8 112.4 27 Low
B5-1 9.0 I 16.8 114.6 23 Low
Project No. G2369-42-01 -B-i - March 13, 2019
TABLE B-IV
SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS
CALIFORNIA TEST NO. 417
Sample No. Water-Soluble Sulfate (%) Classification
132-1 0.026 SO
135-1 0.037 SO
Project No. 02369-42-01 - B-2 - March 13, 2019
PROJECT NO. G2369-42-01
1tfskIiliV 'Ni II II
I..'
0 S
iiiii. 1iiiii:!u!iiIuHuiIIII 11111111 • .111111_11111111_IIIIi11_11011111_11111111 111111 11111111 IIIIIII 111111111 11111111 111111 1111111 IIIIIII1NIIIIIIIII 11111111 111111_11111111_iiiiiiiiiiuiiiii 11111111 .111111_11111111_11111111_b!iIIIII--IIIIIIII___ .111111_1111111_11111111_111111111_11111111 11111111 11111111 11011111 11111111 .111111 .111111_11111111_11111111_111111111_11111111
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I.
GRADATI ON CURVE
PASEO DEL [']lI1PARKINGIII1UM STRUCTURE
.] 1Ii :] 'XCALI FORNIAIi
36942O1.GPJ Figure B-I
GE000N
SAMPLE DEPTH (ft) CLASSIFICATION NAT WC LL PL P1
B5-1 1.0 Sc - Clayey SAND
PROJECT NO. G2369-42-01
SAMPLE NO. BI-1
-6
-4
-2
10
12 " 10 100
APPLIED PRESSURE (ksf)
ASTM D2435
Initial Saturation (%) 98.5
Sample Saturated at (ksf) .5
CONSOLIDATION CURVE
PASEO DEL NORTE PARKING STRUCTURE
CARLSBAD, CALIFORNIA
G2389-42-01.GPJ Figure B-2
GE000N
Initial Dry Density (pcf) 102.2
Initial Water Content (%) 23.1
PROJECT NO. G2369-42-01
SAMPLE NO. B3-2
-6
2
10
12 0.1 1 10 lu0
APPLIED PRESSURE (ksf)
ASTM D2435
Initial Dry Density (pcf) 112.2 Initial Saturation (%) 56.0
Initial Water Content (%) 9.0 Sample Saturated at (ksf) .5
CONSOLIDATION CURVE
PASEO DEL NORTE PARKING STRUCTURE
CARLSBAD, CALIFORNIA
G23894201.GPJ
- Figure B-3
GE000N
APPENDIX
I
APPENDIX C
RECOMMENDED GRADING SPECIFICATIONS
FOR
PASEO DEL NORTE PARKING STRUCTURE
6183 AND 6185 PASEO DEL NORTE
CARLSBAD, CALIFORNIA
PROJECT NO. G2369-42-01
RECOMMENDED GRADING SPECIFICATIONS
1. GENERAL
1.1 These Recommended Grading Specifications shall be used in conjunction with the
Geotechnical Report for the project prepared by Geocon. The recommendations contained
in the text of the Geotechnical Repoit are a part of the earthwork and grading specifications
and shall supersede the provisions contained hereinafter in the case of conflict.
1.2 Prior to the commencement of grading, a geotechnical consultant (Consultant) shall be
employed for the purpose of observing earthwork procedures and testing the fills for
substantial conformance with the recommendations of the Geotechnical Report and these
specifications. The Consultant should provide adequate testing and observation services so
that they may assess whether, in their opinion, the work was performed in substantial
conformance with these specifications. It shall be the responsibility of the Contractor to
assist the Consultant and keep them apprised of work schedules and changes so that
personnel may be scheduled accordingly.
1.3 It shall be the sole responsibility of the Contractor to provide adequate equipment and
methods to accomplish the work in accordance with applicable grading codes or agency
ordinances, these specifications and the approved grading plans. If, in the opinion of the
Consultant, unsatisfactory conditions such as questionable soil materials, poor moisture
condition, inadequate compaction, and/or adverse weather result in a quality of work not in
conformance with these specifications, the Consultant will be empowered to reject the
work and recommend to the Owner that grading be stopped until the unacceptable
conditions are corrected.
2. DEFINITIONS
2.1 Owner shall refer to the owner of the property or the entity on whose behalf the grading
work is being performed and who has contracted with the Contractor to have grading
performed.
2.2 Contractor shall refer to the Contractor performing the site grading work.
2.3 Civil Engineer or Engineer of Work shall refer to the California licensed Civil Engineer
or consulting firm responsible for preparation of the grading plans, surveying and verifying
as-graded topography.
2.4 Consultant shall refer to the soil engineering and engineering geology consulting firm
retained to provide geotechnical services for the project.
GI rev. 07/2015
2.5 Soil Engineer shall refer to a California licensed Civil Engineer retained by the Owner,
who is experienced in the practice of geotechnical engineering. The Soil Engineer shall be
responsible for having qualified representatives on-site to observe and test the Contractor's
work for conformance with these specifications.
2.6 Engineering Geologist shall refer to a California licensed Engineering Geologist retained
by the Owner to provide geologic observations and recommendations during the site
grading.
2.7 Geotechnical Report shall refer to a soil report (including all addenda) which may include
a geologic reconnaissance or geologic investigation that was prepared specifically for the
development of the project for which these Recommended Grading Specifications are
intended to apply.
3. MATERIALS
3.1 Materials for compacted fill shall consist of any soil excavated from the cut areas or
imported to the site that, in the opinion of the Consultant, is suitable for use in construction
of fills. In general, fill materials can be classified as soil fills, soil-rock fills or rock fills, as
defined below.
3.1.1 Soil fills are defined as fills containing no rocks or hard lumps greater than
12 inches in maximum dimension and containing at least 40 percent by weight of
material smaller than 3% inch in size.
3.1.2 Soil-rock fills are defined as fills containing no rocks or hard lumps larger than
4 feet in maximum dimension and containing a sufficient matrix of soil fill to allow
for proper compaction of soil fill around the rock fragments or hard lumps as
specified in Paragraph 6.2. Oversize rock is defined as material greater than
12 inches.
3.1.3 Rock fills are defined as fills containing no rocks or hard lumps larger than 3 feet
in maximum dimension and containing little or no fines. Fines are defined as
material smaller than 3% inch in maximum dimension. The quantity of fines shall be
less than approximately 20 percent of the rock fill quantity.
3.2 Material of a perishable, spongy, or otherwise unsuitable nature as determined by the
Consultant shall not be used in fills.
3.3 Materials used for fill, either imported or on-site, shall not contain hazardous materials as
defined by the California Code of Regulations, Title 22, Division 4, Chapter 30, Articles 9
GI rev. 07/2015
and 10; 40CFR; and any other applicable local, state or federal laws. The Consultant shall
not be responsible for the identification or analysis of the potential presence of hazardous
materials. However, if observations, odors or soil discoloration cause Consultant to suspect
the presence of hazardous materials, the Consultant may request from the Owner the
termination of grading operations within the affected area. Prior to resuming grading
operations, the Owner shall provide a written report to the Consultant indicating that the
suspected materials are not hazardous as defined by applicable laws and regulations.
3.4 The outer 15 feet of soil-rock fill slopes, measured horizontally, should be composed of
properly compacted soil fill materials approved by the Consultant. Rock fill may extend to
the slope face, provided that the slope is not steeper than 2:1 (horizontal:vertical) and a soil
layer no thicker than 12 inches is track-walked onto the face for landscaping purposes. This
procedure may be utilized provided it is acceptable to the governing agency, Owner and
Consultant.
3.5 Samples of soil materials to be used for fill should be tested in the laboratory by the
Consultant to determine the maximum density, optimum moisture content, and, where
appropriate, shear strength, expansion, and gradation characteristics of the soil.
3.6 During grading, soil or groundwater conditions other than those identified in the
Geotechnical Report may be encountered by the Contractor. The Consultant shall be
notified immediately to evaluate the significance of the unanticipated condition
4. CLEARING AND PREPARING AREAS TO BE FILLED
4.1 Areas to be excavated and filled shall be cleared and grubbed. Clearing shall consist of
complete removal above the ground surface of trees, stumps, brush, vegetation, man-made
structures, and similar debris. Grubbing shall consist of removal of stumps, roots, buried
logs and other unsuitable material and shall be performed in areas to be graded. Roots and
other projections exceeding 11/2 inches in diameter shall be removed to a depth of 3 feet
below the surface of the ground. Borrow areas shall be grubbed to the extent necessary to
provide suitable fill materials.
4.2 Asphalt pavement material removed during clearing operations should be properly
disposed at an approved off-site facility or in an acceptable area of the project evaluated by
Geocon and the property owner. Concrete fragments that are free of reinforcing steel may
be placed in fills, provided they are placed in accordance with Section 6.2 or 6.3 of this
document.
Cl rev. 07/2015
5. COMPACTION EQUIPMENT
5.1 Compaction of soil or soil-rock fill shall be accomplished by sheepsfoot or segmented-steel
wheeled rollers, vibratory rollers, multiple-wheel pneumatic-tired rollers, or other types of
acceptable compaction equipment. Equipment shall be of such a design that it will be
capable of compacting the soil or soil-rock fill to the specified relative compaction at the
specified moisture content.
5.2 Compaction of rock fills shall be performed in accordance with Section 6.3.
6. PLACING, SPREADING AND COMPACTION OF FILL MATERIAL
6.1 Soil fill, as defined in Paragraph 3.1.1, shall be placed by the Contractor in accordance with
the following recommendations:
6.1.1 Soil fill shall be placed by the Contractor in layers that, when compacted, should
generally not exceed 8 inches. Each layer shall be spread evenly and shall be
thoroughly mixed during spreading to obtain uniformity of material and moisture
in each layer. The entire fill shall be constructed as a unit in nearly level lifts. Rock
materials greater than 12 inches in maximum dimension shall be placed in
accordance with Section 6.2 or 6.3 of these specifications.
6.1.2 In general, the soil fill shall be compacted at a moisture content at or above the
optimum moisture content as determined by ASTM D 1557.
6.1.3 When the moisture content of soil fill is below that specified by the Consultant,
water shall be added by the Contractor until the moisture content is in the range
specified.
6.1.4 When the moisture content of the soil fill is above the range specified by the
Consultant or too wet to achieve proper compaction, the soil fill shall be aerated by
the Contractor by blading/mixing, or other satisfactory methods until the moisture
content is within the range specified.
6.1.5 After each layer has been placed, mixed, and spread evenly, it shall be thoroughly
compacted by the Contractor to a relative compaction of at least 90 percent.
Relative compaction is defined as the ratio (expressed in percent) of the in-place
dry density of the compacted fill to the maximum laboratory dry density as
determined in accordance with ASTM D 1557. Compaction shall be continuous
over the entire area, and compaction equipment shall make sufficient passes so that
the specified minimum relative compaction has been achieved throughout the
entire fill.
GI rev. 07/2015
6.1.6 Where practical, soils having an Expansion Index greater than 50 should be placed
at least 3 feet below finish pad grade and should be compacted at a moisture
content generally 2 to 4 percent greater than the optimum moisture content for the
material.
6.1.7 Properly compacted soil fill shall extend to the design surface of fill slopes. To
achieve proper compaction, it is recommended that fill slopes be over-built by at
least 3 feet and than cut to the design grade. This procedure is considered
preferable to track-walking of slopes, as described in the following paragraph.
6.1.8 As an alternative to over-building of slopes, slope faces may be back-rolled with a
heavy-duty loaded sheepsfoot or vibratory roller at maximum 4-foot fill height
intervals. Upon completion, slopes should then be track-walked with a D-8 dozer
or similar equipment, such that a dozer track covers all slope surfaces at least
twice.
6.2 Soil-rock fill, as defined in Paragraph 3.1.2, shall be placed by the Contractor in accordance
with the following recommendations:
6.2.1 Rocks larger than 12 inches but less than 4 feet in maximum dimension may be
incorporated into the compacted soil fill, but shall be limited to the area measured
15 feet minimum horizontally from the slope face and 5 feet below finish grade or
3 feet below the deepest utility, whichever is deeper.
6.2.2 Rocks or rock fragments up to 4 feet in maximum dimension may either be
individually placed or placed in windrows. Under certain conditions, rocks or rock
fragments up to 10 feet in maximum dimension may be placed using similar
methods. The acceptability of placing rock materials greater than 4 feet in
maximum dimension shall be evaluated during grading as specific cases arise and
shall be approved by the Consultant prior to placement.
6.2.3 For individual placement, sufficient space shall be provided between rocks to allow
for passage of compaction equipment.
6.2.4 For windrow placement, the rocks should be placed in trenches excavated in
properly compacted soil fill. Trenches should be approximately 5 feet wide and
4 feet deep in maximum dimension. The voids around and beneath rocks should be
filled with approved granular soil having a Sand Equivalent of 30 or greater and
should be compacted by flooding. Windrows may also be placed utilizing an
"open-face" method in lieu of the trench procedure, however, this method should
first be approved by the Consultant.
GI rev. 07/205
6.2.5 Windrows should generally be parallel to each other and may be placed either
parallel to or perpendicular to the face of the slope depending on the site geometry.
The minimum horizontal spacing for windrows shall be 12 feet center-to-center
with a 5-foot stagger or offset from lower courses to next overlying course. The
minimum vertical spacing between windrow courses shall be 2 feet from the top of
a lower windrow to the bottom of the next higher windrow.
6.2.6 Rock placement, fill placement and flooding of approved granular soil in the
windrows should be continuously observed by the Consultant.
6.3 Rock fills, as defined in Section 3.1.3, shall be placed by the Contractor in accordance with
the following recommendations:
6.3.1 The base of the rock fill shall be placed on a sloping surface (minimum slope of 2
percent). The surface shall slope toward suitable subdrainage outlet facilities. The
rock fills shall be provided with subdrains during construction so that a hydrostatic
pressure buildup does not develop. The subdrains shall be permanently connected
to controlled drainage facilities to control post-construction infiltration of water.
6.3.2 Rock fills shall be placed in lifts not exceeding 3 feet. Placement shall be by rock
trucks traversing previously placed lifts and dumping at the edge of the currently
placed lift. Spreading of the rock fill shall be by dozer to facilitate seating of the
rock. The rock fill shall be watered heavily during placement. Watering shall
consist of water trucks traversing in front of the current rock lift face and spraying
water continuously during rock placement. Compaction equipment with
compactive energy comparable to or greater than that of a 20-ton steel vibratory
roller or other compaction equipment providing suitable energy to achieve the
required compaction or deflection as recommended in Paragraph 6.3.3 shall be
utilized. The number of passes to be made should be determined as described in
Paragraph 6.3.3. Once a rock fill lift has been covered with soil fill, no additional
rock fill lifts will be permitted over the soil fill.
6.3.3 Plate bearing tests, in accordance with ASTM D 1196, may be performed in both
the compacted soil fill and in the rock fill to aid in determining the required
minimum number of passes of the compaction equipment. If performed, a
minimum of three plate bearing tests should be performed in the properly
compacted soil fill (minimum relative compaction of 90 percent). Plate bearing
tests shall then be performed on areas of rock fill having two passes, four passes
and six passes of the compaction equipment, respectively. The number of passes
required for the rock fill shall be determined by comparing the results of the plate
bearing tests for the soil fill and the rock fill and by evaluating the deflection
GI rev. 07/2015
variation with number of passes. The required number of passes of the compaction
equipment will be performed as necessary until the plate bearing deflections are
equal to or less than that determined for the properly compacted soil fill. In no case
will the required number of passes be less than two.
6.3.4 A representative of the Consultant should be present during rock fill operations to
observe that the minimum number of "passes" have been obtained, that water is
being properly applied and that specified procedures are being followed. The actual
number of plate bearing tests will be determined by the Consultant during grading.
6.3.5 Test pits shall be excavated by the Contractor so that the Consultant can state that,
in their opinion, sufficient water is present and that voids between large rocks are
properly filled with smaller rock material. In-place density testing will not be
required in the rock fills.
6.3.6 To reduce the potential for "piping" of fines into the rock fill from overlying soil
fill material, a 2-foot layer of graded filter material shall be placed above the
uppermost lift of rock fill. The need to place graded filter material below the rock
should be determined by the Consultant prior to commencing grading. The
gradation of the graded filter material will be determined at the time the rock fill is
being excavated. Materials typical of the rock fill should be submitted to the
Consultant in a timely manner, to allow design of the graded filter prior to the
commencement of rock fill placement.
6.3.7 Rock fill placement should be continuously observed during placement by the
Consultant.
7. SUBDRAINS
7.1 The geologic units on the site may have permeability characteristics and/or fracture
systems that could be susceptible under certain conditions to seepage. The use of canyon
subdrains may be necessary to mitigate the potential for adverse impacts associated with
seepage conditions. Canyon subdrains with lengths in excess of 500 feet or extensions of
existing offsite subdrains should use 8-inch-diameter pipes. Canyon subdrains less than 500
feet in length should use 6-inch-diameter pipes.
GI rev. 07/2015
8. OBSERVATION AND TESTING
8.1 The Consultant shall be the Owner's representative to observe and perform tests during
clearing, grubbing, filling, and compaction operations. In general, no more than 2 feet in
vertical elevation of soil or soil-rock fill should be placed without at least one field density
test being performed within that interval. In addition, a minimum of one field density test
should be, performed for every 2,000 cubic yards of soil or soil-rock fill placed and
compacted.
8.2 The Consultant should perform a sufficient distribution of field density tests of the
compacted soil or soil-rock fill to provide a basis for expressing an opinion whether the fill
material is compacted as specified. Density tests shall be performed in the compacted
materials below any disturbed surface. When these tests indicate that the density of any
layer of fill or portion thereof is below that specified, the particular layer or areas
represented by the test shall be reworked until the specified density has been achieved.
8.3 During placement of rock fill, the Consultant should observe that the minimum number of
passes have been obtained per the criteria discussed in Section 6.3.3. The Consultant
should request the excavation of observation pits and may perform plate bearing tests on
the placed rock fills. The observation pits will be excavated to provide a basis for
expressing an opinion as to whether the rock fill is properly seated and sufficient moisture
has been applied to the material. When observations indicate that a layer of rock fill or any
portion thereof is below that specified, the affected layer or area shall be reworked until the
rock fill has been adequately seated and sufficient moisture applied.
8.4 A settlement monitoring program designed by the Consultant may be conducted in areas of
rock fill placement. The specific design of the monitoring program shall be as
recommended in the Conclusions and Recommendations section of the project
Geotechnical Report or in the final report of testing and observation services performed
during grading.
8.5 We should observe the placement of subdrains, to check that the drainage devices have
been placed and constructed in substantial conformance with project specifications.
8.6 Testing procedures shall conform to the following Standards as appropriate:
8.6.1 Soil and Soil-Rock Fills:
8.6.1.1 Field Density Test, ASTM D 1556, Density of Soil In-Place By the
Sand-Cone Method.
GI rev. 07/2015
8.6.1.2 Field Density Test, Nuclear Method, ASTM D 6938, Density of Soil and
Soil-Aggregate In-Place by Nuclear Methods (Shallow Depth).
8.6.1.3 Laboratory Compaction Test, ASTM D 1557, Moisture-Density
Relations of Soils and Soil-Aggregate Mixtures Using 10-Pound
Hammer and 18-Inch Drop.
8.6.1.4. Expansion Index Test,* ASTM D 4829, Expansion Index Test.
9. PROTECTION OF WORK
9.1 During construction, the Contractor shall properly grade all excavated surfaces to provide
positive drainage and prevent ponding of water. Drainage of surface water shall be
controlled to avoid damage to adjoining properties or to finished work on the site. The
Contractor shall take remedial measures to prevent erosion of freshly graded areas until
such time as permanent drainage and erosion control features have been installed. Areas
subjected to erosion or sedimentation shall be properly prepared in accordance with the
Specifications prior to placing additional fill or structures.
9.2 After completion of grading as observed and tested by the Consultant, no further
excavation or filling shall be conducted except in conjunction with the services of the
Consultant.
10. CERTIFICATIONS AND FINAL REPORTS
10.1 Upon completion of the work, Contractor shall furnish Owner a certification by the Civil
Engineer stating that the lots and/or building pads are graded to within 0.1 foot vertically of
elevations shown on the grading plan and that all tops and toes of slopes are within 0.5 foot
horizontally of the positions shown on the grading plans. After installation of a section of
subdrain, the project Civil Engineer should survey its location and prepare an as-built plan
of the subdrain location. The project Civil Engineer should verify the proper outlet for the
subdrains and the Contractor should ensure that the drain system is free of obstructions.
10.2 The Owner is responsible for furnishing a final as-graded soil and geologic report
satisfactory to the appropriate governing or accepting agencies. The as-graded report
should be prepared and signed by a California licensed Civil Engineer experienced in
geotechnical engineering and by a California Certified Engineering Geologist, indicating
that the geotechnical aspects of the grading were performed in substantial conformance
with the Specifications *or approved changes to the Specifications.
GI rev. 07/2015
LIST OF REFERENCES
FEMA (2012), Flood Map Service Center, FEMA website, https://msc.fema.gov/portallhome, flood
map number 06073C1358G, effective May 16, 2012, accessed February 13, 2019;
Kennedy, M.P. and Tan, S. S., (2007), Geologic Map of the Oceanside 30'x 60' Quadrangle, California,
California Geological Survey, 1:100,000 Scale;
Risk Engineering (2019), EZ-FRISK (version 7.65), software package used to perform site-specific
earthquake hazard analyses, accessed February 13, 2019;
SEAOC (2019), OSHPD Seismic Design Maps: Structural Engineers Association of California website,
http://seismicmaps.org/, accessed February 13, 2019;
USGS (2018), Quaternary Fault and Fold Database of the United States: U.S. Geological Survey
website, http://earthquakes.usgs.gov/hazards/qfaults, accessed February 13, 2019.
Project No. G2369-42-0I March 13, 2019
GEOCON
INCORPORATED
GEOTECHNICAL U ENVIRONMENTAL MATERIALS
(07)
Project No. G2369-42-01
June 5, 2020
Next Med Ill, LLC
6125 Paseo Del Norte, Suite 210
Carlsbad, California 92120
Attention: Mr. Scott Leggett
Subject: RESPONSE TO THIRD-PARTY REVIEW COMMENTS
CARLSBAD CORPORATE PLAZA PARKING STRUCTURE
6183 AND 6185 PASEO DEL NORTE
CARLSBAD, CALIFORNIA
- 1Za00 —)OI
Reference: 1. Geotechnical Investigation, Paseo Del Norte, Parking Structure, 6183 and 6185
Paseo Del Norte, Carlsbad, California, prepared by Geocon Incorporated, dated
March 13, 2019 (Project No. G2369-42-01).
Update to Geotechnical Investigation: 2019 CBC Seismic Design Parameters, Paseo
Del Norte Parking Structure, 6183 and 6185 Paseo Del Norte, Carlsbad, California,
prepared by Geocon Incorporated, dated January 13, 2020 (Project No. G2369-42-01).
Precise Grading Plans for Carlsbad Corporate Plaza Parking Structure, 6183 -
6185 Paseo Del Norte, 6183 - 6185 Paseo Del Norte, Carlsbad, California,
prepared by Pasco Laret Suiter & Associates, issue date January 30, 2020.
Third Party Geotechnical Review (First), Proposed Parking Structure, 6183 and 6185
Paseo del Norte, Carlsbad, California, prepared by Hetherington Engineering, Inc.,
dated May 5, 2020 (Project ID: GR2020-0013).
Dear Mr. Leggett:
We prepared this letter to respond to third-party review comments provided in Reference 4 for the
subject project. Each review comment followed by our response is presented below.
Comment 1: Due to the age of the "Geotechnical Investigation..." (Reference 1), the Consultant
should provide an updated geotechnical report addressing the plans, and provide
updated grading and foundation recommendations consistent with the 2019
California Building Code, as necessary.
Response: Based on our review of the referenced plans, the grading and foundation
recommendations provided in References I and 2 remain applicable to the project.
6960 Flanders Drive • San Diego, California 92121.2974 U Telephone 858.558.6900 0 Fox 858.558.6159
Updated seismic design parameters for the 2019 California Building Code are
provided in Reference 2. No additional updated recommendations are necessary at
this time.
Comment 2: The Consultant should review the project grading and foundation plans, provide any
additional geotechnical recommendations considered necessary, and confirm that
the plans have been prepared in accordance with the geotechnical recommendations
provided in the referenced reports.
Response: We have reviewed the project grading and foundation plans. Based on our review,
the plans have been prepared in accordance with the geotechnical recommendations
contained in References 1 and 2. No additional geotechnical recommendations are
necessary.
Comment 3: The Consultant should provide an updated geotechnical map/plot plan utilizing the latest
grading plan for the project to clearly show (at a minimum) a) existing site topography,
b) proposed structures/improvements, c) proposed finish grades, d) locations of the
subsurface exploration, e) geologic contacts, andf) remedial grading limits, etc.
Response: The requested geologic map is appended. We used a CAD file of Reference 3 as the
base map. With respect to proposed finish grades, the majority of the existing
parking lot will remain, therefore, finish grade matches existing grade. In pavement
areas that are replaced, the new pavement surface will match the existing surface.
With respect to remedial grading limits, remedial grading will only be performed
within footing excavations.
Comment 4: The Consultant should provide a statement with respect to the stability of the existing
slopes.
Response: The proposed parking structure is planned within an existing parking lot that only has
about 3 feet of topographic relief across the building pad. The closest slopes to the
parking structure (greater than 40 feet away) are along the northeast and east sides of
the property and have heights of approximately 3 feet to 9 feet. These slopes also
have an inclination 2:1 (horizontal to vertical) and flatter. The slopes are well
vegetated and appear to be stable. The proposed project is not encroaching into or
near these slopes. The project will not impact the stability of existing slopes.
Comment 5: The Consultant should provide recommendations for temporary excavations
(backcuts/ slopes, etc.).
Project No. G236942-01 - 2 - June 5, 2020
Response: As previously indicated, the proposed project is located in an existing parking lot that
only has about 3 feet of topographic relief. The only excavations planned for the site
are what are required to install footings and utility trenches. However, to satisfy the
review comment, recommendations for temporary excavations are provided below.
In general, special shoring requirements may not be necessary if temporary excavations
will be less than 4 feet in height. It is the responsibility of the contractor and their
competent person to ensure all excavations, temporary slopes and trenches are properly
constructed and maintained in accordance with applicable OSHA guidelines, in order to
maintain safety and the stability of the excavations and adjacent improvements. These
excavations should not be allowed to become saturated or to dry out. Surcharge loads
should not be permitted to a distance equal to the height of the excavation from the top of
the excavation. The top of the excavation should be a minimum of 15 feet from the edge
of existing improvements. Excavations steeper than those recommended or closer than
15 feet from an existing surface improvement should be shored in accordance with
applicable OSHA codes and regulations.
Comment 6: The Consultant should provide a statement confirming that the foundation and slab
recommendations are consistent with the requirements of Section 1808.6 (expansive
soils) of the 2019 California Building Code or revise the recommendations accordingly.
Response: The foundation and slab recommendations are consistent with the requirements of
Section 1808.6 of the 2019 CBC. Recommendations provided in Reference 1 are
based on the on-site soil conditions. Revised recommendations are not necessary.
Comment 7: The Consultant should provide a list of recommended geotechnical observations and
testing during grading and construction.
Response Recommended geotechnical observations and testing during grading and construction
are the following:
Observation and compaction testing during grading;
Observation and compaction testing during utility trench backfill and wall
backfill;
Observation of foundation excavations;
Compaction testing of concrete hardscape and curb subgrade;
Compaction testing of pavement subgrade, base, and asphalt concrete.
Project No. G23694201 -3 - June 5, 2020
If there are any questions regarding this correspondence, or if we may be of further service, please
contact the undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
Ro y C. Mikesell
GE 2533
RCM:arm
(e-mail) Addressee
Project No. G2369-42-01 1 -4- June 5, 2020
GEOCON
INCORPORATED
(10m)
GEOTECHNICAL • ENVIRONMENTAL • MATERIALS
Project No. G2369-42-01
July 27, 2020
Next Med III, LLC
6125 Paseo Del Norte, Suite 210
Carlsbad, California 92120
Attention: Mr. Scott Leggett
Subject: LANDSCAPE AREAS ADJACENT TO FOOTINGS
CARLSBAD CORPORATE PLAZA PARKING STRUCTURE
6183 AND 6185 PASEO DEL NORTE
CARLSBAD, CALIFORNIA
copc9ol-q -060Y 160-0004-0011
References: Precise Grading Plans for Carlsbad Corporate Plaza Parking Structure, 6183 - 6185
Paseo Del Norte, 6183 - 6185 Paseo Del Norte, Carlsbad, California, prepared by Pasco
Laret Suiter & Associates.
Dear Mr. Leggett:
In accordance with the request of Pasco Laret Suiter & Associates, we have prepared this letter to
respond to a review comment by the City of Carlsbad. The comment is with respect to landscape areas
adjacent to footings. There are several landscape areas adjacent to the parking structure footing where
runoff water from the paved driveway will be directed. Based on the referenced grading plans, the
landscape areas will have drains to intercept runoff and transmit it to the storm drain system. It is our
opinion that the landscape areas are acceptable provided water is not allowed to pond adjacent to the
footings.
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
Zhey C. Mikesell
GE 2533
RCM:arm
(e-mail) Addressee
(e-mail) PLSA
AttiitionT Mr. Ryan Taylor
6960 Flanders Drive 0 San Diego, California 92121 0 Telephone (858) 558-6900 U Fax (858) 558.6159