HomeMy WebLinkAboutCT 08-07; LA COSTA TOWN SQ OFFICE; GEOTECHNICAL INVESTIGATION; 2012-07-01SOUTHERN CALIFORNIA
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GEOTECHNICAL INVESTIGATION
LA COSTA TOWN SQUARE
OFFICE DEVELOPMENT
CARLSBAD, CALIFORNIA
PREPARED FOR:
MR. JIM REUTER
PROPERTY DEVELOPMENT CENTERS
5918 STONERIDGE MALL ROAD
PLEASANTON, CALIFORNIA 94588
PREPARED BY:
SOUTHERN CALIFORNIA SOIL & TESTING, INC.
6280 RIVERDALE STREET
SAN DIEGO, CALIFORNIA 92120
Providing Professional Engineering Sen/ices Since 1959
SOUTHERN CALIFORNIA
SOIL&TESTINGJNC.
A California Certified Small Business Enterprise (SBE:
San Diego 6280 Riverdale Street
619.280.4321 San Diego. CA 92120
Indio 83-740 Citrus Avenue
760.775.5983 Suite G
Indio. CA 92201-3438
Riverside 1130 Palmyrita Avenue
951.965.8711 Suite 330-A
Riverside. CA 92507
Toll Free
877.215.4321 www.scst.com
January'I, 2012 SCS&T No. 1111198
Revised July 31, 2012 Report No. IR
Mr. Jim Reuter
Property Development Centers
5918 Stoneridge Mall Road
Pleasanton, California 94588
Subject: GEOTECHNICAL INVESTIGATION
LA COSTA TOWN SQUARE
OFFICE DEVELOPMENT
CARLSBAD, CALIFORNIA
Dear Mr. Reuter:
This letter transmits Southern California Soil & Testing Inc.'s (SCS&T) report describing the
geotechnical investigation performed for the planned east office development. The proposed
development will be located on the north side of La Costa Avenue at the intersection of Calle
Timiteo and La Costa Avenue in the City of Carlsbad, California.
This investigation was conducted in general conformance with the scope of work presented in
SCS&T's proposal dated November 16, 2011. If you have any questions concerning this report,
or need additional information, please call us at (619) 280-4321.
Respectfully Submitted,
SOUTHERN CALIFORNIA S( TESTING, INC.
2) -7
GaffeffB. Fountain, GE 275^
Vice President/ Principal Engineer
GBF:AKN:aw
(8) Addressee
(1) Addressee via e-mail at jim.reuter(gpdcenters.com
Douglas A. Skinner, CEG 2472
Senior Engineering Geologist
TABLE OF CONTENTS (Continued)
SECTION PAGE
EXECUTIVE SUMMARY I
1. INTRODUCTION 1
Ll GENERAL 1
L2 SCOPE OF WORK 1
1.2.1 Field Exploration 1
1.2.2 Laboratory Testing 1
1.2.3 Analysis and Report /
2. SITE AND SUBSURFACE CONDITIONS 2
2.1 SITE DESCRIPTION 2
2.2 SUBSURFACE CONDITIONS 2
2.3 GROUNDWATER 3
2.4 POTENTIAL GEOLOGIC HAZARDS 3
2.5 SEISMIC DESIGN PARAMETERS 3
3. CONCLUSIONS 3
4. RECOMMENDATIONS 4
4.1 SITE PREPARATION AND GRADING 4
4.1.1 Site Preparation 4
4.1.2 Compressible Soil Removal 4
4.1.3 Excavation Characteristics 4
4.1.4 Expansive Soil 4
4.1.5 Building Pad Over-Excavation Requirements 5
4.1.6 Earthwork 5
4.1.7 Keyway 5
4.1.8 Subdrains 6
4.1.9 Fill Slopes 6
4.1.10 Permanent Cut Slopes 6
4.1.11 Temporary Excavation Slopes 6
4.1.12 Shrinkage and Bulkage Estimates 7
4.1.13 Imported Soil 7
4.1.14 Surface Drainage 7
4.1.15 Grading Plan Review 7
4.2 FOUNDATIONS 7
4.2.1 Conventional Footings 7
4.2.2 Foundation Excavation Observations 8
4.2.3 Static Settlement Characteristics 8
4.2.4 Resistance to Lateral Loads 8
4.2.5 Foundation Plan Review 8
4.3 SLABS-ON-GRADE 8
4.3.1 Interior Concrete Slabs-on-Grade 8
4.3.2 Exterior Concrete Slabs-on- Grade 9
4.4 EARTH RETAINING WALLS 10
4.4.1 Foundations 10
4.4.2 Passive Pressure 10
4.4.3 Active Pressure 10
4.4.4 At-Rest Pressure 10
TABLE OF CONTENTS (Continued)
SECTION PAGE
4.4.5 Seismic Earth Pressure 10
4.4.6 Waterproofing and Backdrain Observation 11
4.4.7 Backfill 11
4.4.8 Factor of Safety 11
4.5 MSE WALL DESIGN PARAMETERS 11
TABLE 3 11
4.6 PAVEMENT SECTION RECOMMENDATIONS 11
TABLE 4 12
4.7 INFILTRATION RATES 13
5. GEOTECHNICAL ENGINEERING DURING CONSTRUCTION 13
6. CLOSURE 13
TABLES
Table 1 Expansion Index Requirements
Table 2 Estimated Shrinkage and Bulkage Estimates
Table 3 Mechanically Stabilized Earth Wall Design Parameters
Table 4 Flexible Pavement Recommendations
Table 5 Rigid Pavement Recommendations
ATTACHMENTS
FIGURES
Figure 1 Site Vicinity Map
Figure 2 Subsurface Investigation Map
Figure 3 Grading Considerations Map
Figure 4 Subdrain Detail
Figure 5 Wall Backdrain Details
APPENDICES
Appendix I Logs of Exploratory Test Trenches
Appendix II Laboratory Testing
EXECUTIVE SUMMARY
This report presents the results of the geotechnical investigation Southern California Soil and
Testing, Inc. (SCS&T), performed for the planned office development to be located on the north
side of La Costa Avenue at the intersection of Calle Timiteo and La Costa Avenue in the City of
Carlsbad, California. The purpose of our work is to provide conclusions and recommendations
regarding the geotechnical aspects of the project.
An SCS&T geologist observed the excavation of 3 exploratory test trenches to depths of
between 6 feet and 15 feet below the existing grade with a rubber tire backhoe equipped with an
18-inch bucket. SCS&T tested selected samples from the trenches to evaluate pertinent
classification and engineering properties and assist in the development of geotechnical
conclusions and recommendations.
Materials encountered in the test trenches and exposed near the surface consist of fill, alluvium,
Delmar Formation and Metavolcanic rock. The fill and alluvium are comprised of loose, clayey
sand and soft, sandy clay. The Delmar Formation is comprised of very stiff to hard, sandy
claystone, clayey sandstone and silty sandstone. The metavolcanic rock is comprised of
metamorphosed and un-metamorphosed volcanic and sedimentary rock commonly identified as
the Santiago Peak Volcanics.
The main geotechnical considerations affecting the planned development are:
• The presence of compressible alluvial materials;
• Expansive soils;
• Cut/fill transitions below the building pads.
Mass grading operations are expected to consist of cuts and fills ranging from between about 5
feet and 20 feet. The on-site clayey materials are expected to have medium to high expansion
potentials. To reduce the potential for differential settlement and/or heaving select grading and
over-excavation of the building pads will need to be performed. We expect that sandy soil will
need to be processed with the expansive soil to produce a suitable fill material. Other
alternatives to produce a suitable fill material can also be considered. Shallow spread footings
with bottom levels in compacted fill can be used forthe support ofthe planned structures.
1. INTRODUCTION
1.1 GENERAL
This report presents the results of the geotechnical investigation Southern California Soil and
Testing, Inc. (SCS&T), performed for the planned office development to be located on the north
side of La Costa Avenue at the intersection of Calle Timiteo and La Costa Avenue in the City of
Carlsbad, California. The purpose of our work is to provide conclusions and recommendations
regarding the geotechnical aspects ofthe project. Figure 1 presents a site vicinity map.
1.2 SCOPE OF WORK
1.2.1 Field Exploration
Subsurface conditions were explored by excavating a total of 3 exploratory test trenches to
depths of between 6 feet and 15 feet below the existing grade with a rubber tire backhoe
equipped with an 18-inch bucket. Figure 2 shows the locations of the test trenches. An
SCS&T geologist logged the test trenches and obtained samples for examination and
laboratory testing. The logs of the test trenches are in Appendix I. Soils are classified
according to the Unified Soil Classification System illustrated on Figure 1-1.
1.2.2 Laboratory Testing
The laboratory program consisted of tests for:
• Grain size distribution;
• Atterberg limits;
• Shear strength.
The results of the laboratory tests, and brief explanations of test procedures, are in
Appendix II.
1.2.3 Analysis and Report
SCS&T evaluated the results of the field and laboratory tests to develop conclusions and
recommendations regarding:
1. Subsurface conditions beneath the site;
2. Site preparation;
3. Excavation characteristics;
4. Potential geologic hazards that may affect the site;
5. Criteria for seismic design in accordance with California Building Code procedures;
6. Appropriate alternatives for foundation support along with geotechnical engineering
criteria for design ofthe foundations;
7. Resistance to lateral loads;
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8. Estimated foundation settlements;
9. Support for concrete slabs-on-grade floors;
10. Lateral pressures for the design of retaining walls;
11. Pavement sections.
2. SITE AND SUBSURFACE CONDITIONS
2.1 SITE DESCRIPTION
The subject site is an irregular shaped lot located on the north side of La Costa Avenue at the
intersection of La Costa Avenue and Calle Timiteo in the City of Carlsbad, California. The site is
bounded by vacant land on the north and east, and La Costa Avenue and a residential
subdivision on the south and west sides. The site is located along a south-facing slope that with
a north-south trending, natural drainage swale that flows to the south and sloping terrain.
Vegetation consists of native grasses and shrubs.
2.2 SUBSURFACE CONDITIONS
Fill, Alluvium, Delmar Formation, and metavolcanic rock underlie the subject site. Figure 2
shows the approximate limits of the geologic materials.
Fill: SCS&T's geologist observed fill comprised of loose clayey sand and sift sandy clay
and boulders along the western border of the site. Figure 2 shows the approximate limits of
this material.
Alluvium: SCS&T's geologist observed alluvium comprised of soft sandy clay in test trench
T-2. In general, this material is located within the drainage swales at the site. This alluvium
encountered in our test trench extended to a depth of about 7 feet below the ground surface
and overlies the Delmar Formation.
Delmar Formation: SCS&T's geologist observed the Delmar Formation comprised of very
stiff to hard, sandy claystone at the surface in test trenches T-1 and T-3. This material
extended beyond the maximum depth explored of 15 feet in test trench T-3.
Metavolcanic Rock: SCS&T's geologist observed Metavolcanic rock on the surface
exposed along the eastern portion of the site. The metavolcanic rock is typically comprised
of metamorphosed and un-metamorphosed volcanic and sedimentary rock commonly
identified as the Santiago Peak Volcanics.
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2.3 GROUNDWATER
SCS&T's geologist did not observe groundwater in the excavations performed at the site.
However, water and wet soil should be expected at the bottoms of the existing alluvial channels.
Groundwater levels can fluctuate seasonally, and can rise significantly following periods of
precipitation. In addition, groundwater can be perched on impermeable layers of the claystone
and/or rock as a result of rainfall and irrigation.
2.4 POTENTIAL GEOLOGIC HAZARDS
No known geologic hazards are mapped across the site. A geologic hazard likely to affect the
project is groundshaking as a result of movement along an active fault zone in the vicinity of the
subject site.
2.5 SEISMIC DESIGN PARAMETERS
The site coefficients and adjusted maximum considered earthquake spectral response
acceleration parameters in accordance with the 2010 California Building Code based on the
2009 International Building Code are presented below:
Site Coordinates: Latitude 33.083°
Longitude-117.229°
Site Class: D
Site Coefficient Fa = 1.056
Site Coefficient Fv = 1.583
Spectral Response Acceleration at Short Periods Ss = 1.1
Spectral Response Acceleration at 1-Second Period Si = 0.4
SMS^FSSS
SMI^FVSI
SDS=2/3* SMS
SDI=2/3* SMI
3. CONCLUSIONS
The main geotechnical considerations affecting the planned development are:
• The presence of compressible alluvial materials;
• Expansive soils;
• Cut/fill transitions below the building pads.
Mass grading operations are expected to consist of cuts and fills ranging from between about 5
feet and 20 feet. The on-site clayey materials are expected to have medium to high expansion
potentials. To reduce the potential for differential settlement and/or heaving select grading and
over-excavation of the building pads will need to be performed. We expect that sandy soil will
Property Development Centers July 31, 2012
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Carlsbad, California Page 4
need to be processed with the expansive soil to produce a suitable fill material. Other
alternatives to produce a suitable fill material can also be considered. Shallow spread footings
with bottom levels in compacted fill can be used for the support of the planned structures.
4. RECOMMENDATIONS
4.1 SITE PREPARATION AND GRADING
4.1.1 Site Preparation
Site preparation should begin with the removal of the existing vegetation and debris. It is
expected that the upper 6 inches of the exposed surface will need to be brushed and
exported from the site.
4.1.2 Compressible Soil Removal
It is recommended that existing compressible soils (fill, alluvium and highly weathered
formational deposits) underiying areas ofthe site to be graded be excavated in their entirety.
SCS&T expects the compressible soil excavation to be about 7 feet within the alluvial
drainage channels. No excavation for remedial grading is expected where rock is exposed
on the surface. Figure 3 presents the approximate limits of the compressible soil removal.
An SCS&T representative should observe conditions exposed in the bottom of the
excavations to determine if additional excavation is required.
4.1.3 Excavation Characteristics
Conventional heavy equipment in good working order is expected to be able to excavate the
alluvial materials and Del Mar Formation on-site. However, non-rippable rock exists on-site,
and these areas will require rock-breaking equipmenL In addition, oversized, buried hard
rock requiring special handling should be anticipated. Contract documents should specify
that the contractor mobilize equipment capable of excavating and breaking the bedrock.
4.1.4 Expansive Soil
The existing materials on-site that were tested have a high expansion potential in
accordance with ASTM D 4829. Expansive soil with an expansion index (El) greater than
90 should be placed at least 10 feet below the planned final pad grade elevation and at least
10 feet from the face of all fill slopes and retaining walls. Expansive soil with an El less than
90 can be placed at within 10 feet of the planned final pad grade elevation. Table 1
presents updated expansion index recommendations for the placement ofthe soil.
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Table 1
Depth Below Planned Final Grade
Elevation
Expansion Index of Material to be Placed
Oto 10 feet Expansion Index Less Than 90
Greater than 10 feet Expansion Index Greater Than 90 Allowed
4.1.5 Building Pad Over-Excavation Requirements
The planned building pads will span a cut/fill transition with a fill differential ranging between
about 5 and 20 feet. Figure 3 presents the expected over-excavation requirements for each
building pad. The over-excavation depths shown may have to be increased depending on
the final grading. The bottoms of the excavation and subgrades beneath fill areas should be
sloped toward the street or fill portion ofthe lot, and away from its center. Subdrains may be
needed at the bottom of the excavated areas.
4.1.6 Earthwork
The material exposed in the bottom of the excavation should be scarified to a depth of 12
inches, moisture conditioned and compacted to at least 90% relative compaction. Excavated
materials, except for soil containing roots and organic debris, can be used as compacted fill.
Fill should be placed in 6- to 8-inch thick loose lifts, moisture conditioned to near optimum
moisture content, and compacted to at least 90% relative compaction. The maximum dry
density and optimum moisture content for the evaluation of relative compaction should be
determined in accordance with ASTM D 1557.
Utility trench backfill within 3 feet of the structure and beneath pavements and hardscape
should be compacted to a minimum of 90% relative compaction. The upper 12 inches of
subgrade beneath slabs and paved areas should be compacted to at least 95% relative
compaction.
4.1.7 Keyway
A keyway should be established at the base of sloped areas. The keyway should be at least
15 feet wide at the bottom, extend at least 3 feet into competent material and be sloped
back at an inclination of about 2%. The keyway may need to be wider to accommodate
compaction equipment. Final keyway recommendations will depend on the final grading
plans.
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4.1.8 Subdrains
Canyon subdrains shall be installed at the bottom of canyon removals wherever fill depths
exceed 10 feet. Canyon subdrains should consist of a perforated pipe (SDR 35 or
equivalent), surrounded by at least 6 cubic feet per lineal foot of crushed rock wrapped in
filter fabric (Mirafi MON or equivalent). A canyon subdrain is provided as Figure 4. As-
graded canyon subdrain locations should be surveyed.
Subdrains may be required at the heel of keyways for buttress slopes and/or fill-over-cut
slopes. Figure 4. Subdrains may also be required for some transition undercut areas if
warranted by soil conditions or the presence of groundwater. Figure 3 shows the
approximate locations ofthe planned subdrains.
4.1.9 Fill Slopes
Fill slopes can be constructed at an inclination of 2:1 (horizontahvertical). Compaction of
slopes should be performed by back-rolling with a sheepsfoot compactor at vertical intervals
of 2 feet or less as the fill is being placed, and by track-walking the face of the slope when
the fill is completed. Alternatively, slopes can be overfilled and cut back to expose dense
material at the design line and grade. Fills should be benched into temporary slopes and
into the rock when the natural slope is steeper than 5:1 (horizontal: vertical).
4.1.10 Permanent Cut Slopes
It is our opinion that cut slopes constructed at an inclination of 2:1 or flatter ratio will possess
an adequate factor of safety. The engineering geologist should observe all cut slopes
during grading to ascertain that no unforeseen adverse conditions requiring revised
recommendations are encountered.
4.1.11 Temporary Excavation Slopes
It is recommended that temporary cut slopes greater than 3 feet in depth be cut at an
inclination no steeper that 1:1. Cuts less than or equal to 3 feet in depth can be made
vertical. Temporary cut slopes should be observed by an SCS&T Engineering Geologist
during grading to ascertain that no unforeseen adverse conditions are observed. The
temporary slopes should be inspected daily by the contractor's Competent Person before
personnel are allowed to enter the excavation. Zones of potential instability, sloughing or
raveling should be brought to the attention of the Engineer and corrective action
implemented before personnel begin working in the trench. No surcharge loads should be
placed within a distance from the top of temporary cut slopes equal to half the slope height.
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4.1.12 Shrinkage and Bulkage Estimates
The estimate shrinkage and bulkage estimates are presented below.
Table 2
Soil Type Shrinkage Bulkage
Topsoil and alluvium 15% to 20%
Del Mar Formation 5% to 10%
Metavolcanic Rock 10% to 20%
Rock Stockpile 15% to 20%
4.1.13 Imported Soil
Imported fill should meet the specifications for Caltrans structure backfill and, if appropriate,
be tested by SCS&T prior to transport to the site.
4.1.14 Surface Drainage
Final surface grades around the buildings should be designed to collect and direct surface
water away from the structure and toward appropriate drainage facilities. The ground around
the structures should be graded so that surface water flows rapidly away from the structure
without ponding. In general, we recommend that the ground adjacent to the structure slope
away at a gradient of at least 2%. Densely vegetated areas where runoff can be impaired
should have a minimum gradient of at least 5% within the first 5 feet from the structure. Roof
gutters with downspouts that discharge directly into a closed drainage system are
recommended on structures.
Drainage patterns established at the time of fine grading should be maintained throughout
the life of the proposed structures. Site irrigation should be limited to the minimum
necessary to sustain landscape growth. Should excessive irrigation, impaired drainage, or
unusually high rainfall occur, saturated zones of perched groundwater can develop.
4.1.15 Grading Plan Review
The grading plans should be submitted to SCS&T for review to ascertain whether the intent
of the recommendations contained in this report have been implemented, and that no
revised recommendations are necessary due to changes in the development scheme.
4.2 FOUNDATIONS
4.2.1 Conventional Footings
Structures and retaining walls can be supported on shallow spread footings with bottom
levels in compacted fill. A minimum width of 12 inches is recommended for continuous
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footings for single story structures and 15 inches for 2 story structures. Isolated footings
should be at least 24 inches wide. All footings should extend a minimum of 24 inches below
lowest adjacent grade. A bearing capacity of 2,500 pounds per square foot (psf) can be
used. These values can be increased by when considering the total of all loads,
including wind or seismic forces. Footings adjacent to slopes should be extended to a depth
such that a minimum distance of 7 feet exists between the bottom ofthe footing and the face
ofthe slope. For conventional retaining walls, a minimum 10-foot distance is recommended.
4.2.2 Foundation Excavation Observations
It is recommended that all foundation excavations be approved by a representative from
SCS&T priorto forming or placing reinforcing steel.
4.2.3 Static Settlement Characteristics
Total footing settlements are estimated to be less than 1 inch. Differential settlements
between adjacent footings are estimated to be less than 'A inch. Settlements should occur
rapidly, and should be completed shortly after structural loads are applied.
4.2.4 Resistance to Lateral Loads
Lateral loads will be resisted by friction between the bottoms of the footings and passive
pressure on the faces of footings and other structural elements below grade. A friction
factor of 0.3 can be used. Passive pressure can be computed using a lateral pressure value
of 300 psf per foot of depth below the ground surface. The upper foot of soil should not be
relied on for passive support unless the ground is covered with pavements or slabs.
4.2.5 Foundation Plan Review
The foundation plans should be submitted to SCS&T for review to ascertain that the intent of
the recommendations in this report has been implemented and that revised
recommendations are not necessary due to the layout.
4.3 SLABS-ON-GRADE
4.3.1 Interior Concrete Slabs-on-Grade
Concrete slabs-on-grade should be designed by the project structural engineer. Slabs-on-
grade should be underiain by a 4-inch thick blanket of clean, pooriy graded, coarse sand
(sand equivalent = 30 or greater) or y2-inch crushed rock. Where moisture sensitive floor
coverings are planned, a vapor retardant should be placed over the sand layer. Typically,
visqueen is used as a vapor retardant. If visqueen is used, a minimum 10-mil is
recommended.
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Moisture emissions can vary widely, depending upon such factors as concrete type and
subgrade moisture conditions. If these moisture emission values are not within the
manufacturer's specifications for the type of flooring to be installed, SCS&T should be
contacted to develop appropriate additional damp-proofing recommendations. It is
recommended that moisture emission tests be performed prior to the placement of floor
coverings. In addition, over-watering should be avoided, and good site drainage should be
established and maintained to reduce the potential for the build-up of excess sub-slab
moisture.
4.3.2 Exterior Concrete Slabs-on-Grade
Exterior slabs should have a minimum thickness of 4 inches and should be reinforced with
at least No. 3 bars at 18 inches on center each way. Additionally, slabs should be underiain
by at least 6 inches of aggregate base. Slabs should be provided with weakened plane
joints. Joints should be placed in accordance with the American Concrete Institute (ACI)
Guidelines Section 3.13. Joints should be placed where cracks are anticipated to develop
naturally. Alternative patterns consistent with ACI guidelines also can be used. The
landscape architect can be consulted in selecting the final joint patterns.
A 1-inch maximum size aggregate mix is recommended for concrete for exterior slabs. A
water/cement ratio of less than 0.6 is recommended, in order to decrease the potential for
shrinkage cracks. It is strongly suggested that the driveway concrete mix have a minimum
compressive strength of 3,000 pounds per square inch (psi). Coarse and fine aggregate in
concrete should conform to the "Greenbook" Standard Specifications for Public Works
Construction.
Special attention should be paid to the method of curing the concrete to reduce the potential
for excessive shrinkage and resultant random cracking. Minor cracks occur normally in
concrete slabs and foundations due to shrinkage during curing and redistribution of
stresses. Some shrinkage cracks can be expected. These cracks are not necessarily an
indication of vertical movements or structural distress.
Factors that contribute to the amount of shrinkage that takes place in a slab-on-grade
include joint spacing, depth, and design; concrete mix components; water/cement ratio and
surface finishing techniques. According to the undated 'Technical Bulletin" published by the
Southern California Rock Products Association and Southern California Ready Mixed
Concrete Association, flatwork formed of high-slump concrete (high water/cement ratio)
utilizing 3/8-inch maximum size aggregate ("Pea Gravel Grout" mix) is likely to exhibit
extensive shrinkage and cracking. Cracks most often occur in random patterns between
construction joints.
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4.4 EARTH RETAINING WALLS
4.4.1 Foundations
The recommendations provided in the foundation section of this report are also applicable to
earth retaining structures.
4.4.2 Passive Pressure
The passive pressure for the retaining walls can be considered to be 300 psf per foot of
depth up to a maximum of 1,500 psf. This pressure may be increased by 14 for seismic
loading. The coefficient of friction for concrete to soil may be taken as 0.3 for resistance to
lateral movement. When combining friction and passive resistance, the friction should be
reduced by The upper 12 inches of soil in front of retaining wall footings should not be
included in passive pressure calculations unless pavement extends adjacent to the footing.
4.4.3 Active Pressure
The active soil pressure for the design of unrestrained earth retaining structures with level
backfills can be taken as equivalent to the pressure of a fluid weighing 40 pounds per cubic
foot (pcf). An additional 20 pcf should be added for walls with sloping backfills of
2:1 (horizontahvertical) or flatter. A granular and drained backfill condition has been
assumed. Surcharge loads from vehicles can be taken into account by assuming an
additional 2 feet of soil is supported by the wall. If any other surcharge loads are anticipated,
SCS&T should be contacted for the necessary increase in soil pressure. The project
architect should provide waterproofing specifications and details. A typical wall backdrain
detail is shown on Figure 5.
4.4.4 At-Rest Pressure
The at-rest soil pressure for the design of restrained earth retaining structures with level
backfills can be taken as equivalent to the pressure of a fluid weighing 60 pcf. An additional
20 pcf should be added for walls with sloping backfills of 2:1 (horizontahvertical) or flatter. A
granular and drained backfill condition has been assumed. If any surcharge loads are
anticipated, SCS&T should be contacted for the necessary increase in soil pressure.
4.4.5 Seismic Earth Pressure
The seismic earth pressures can be taken as an inverted triangular distribution with a
maximum pressure at the top equal to 16H pounds per square foot (with H being the height
of the retained earth in feet). This pressure is in addition to the un-factored static design
wall load. The allowable passive pressure and bearing capacity can be increased by Vs in
determining the stability of the wall.
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4.4.6 Waterproofing and Backdrain Observation
The geotechnical engineer should be requested to verify that waterproofing has been
applied and that the backdrain has been properiy installed. However, unless specifically
asked to do so, we will not verify proper application of the waterproofing. SCS&T does have
a waterproofing division that can provide this service if requested.
4.4.7 Backfill
All backfill soils should be compacted to at least 90 percent relative compaction. Expansive
or clayey soils should not be used for backfill material. The wall should not be backfilled
until the grout has reached an adequate strength.
4.4.8 Factor of Safety
The above values, with the exception ofthe allowable soil bearing pressure, do not include a
factor of safety. Appropriate factors of safety should be incorporated into the design.
4.5 MSE WALL DESIGN PARAMETERS
The following soil parameters can be used for the design of Mechanically Stabilized Earth
(MSE) walls.
Table 3
Reinforced Soil Retained Soil Foundation Soil
Internal Friction Angle
(degrees) 30° 30° 30°
Cohesion
(pounds per sguare foot) 0 0 0
Moist Unit Weight (pounds
per cubic foot) 130 130 130
4.6 PAVEMENT SECTION RECOMMENDATIONS
The pavement support characteristics of the soils encountered during our investigation range
from poor to good. It is anticipated that these deposits will be mixed and the resulting blend will
have moderately good pavement support characteristics. An "R" value of 25 was assumed for
this blend. The actual "R" value of the subgrade soils will be determined after grading. Based
on an "R" value of 25, the following structural sections are recommended for the assumed
Traffic Indices.
Property Development Centers
La Costa Town Square Office Development
Carlsbad, California
July 31, 2012
SCS&T Proposal No. 1111198-01R
Page 12
Table 4
Traffic Index Asphalt Concrete
(inches)
Aggregate Base^
(inches)
6.0 4 9
7.5 5 12
v.«ww .-.gg.wgw... 111 W.^.«I.IVII , .MM. VI fcllC .^lOMUaiU .9 pCUl I lUdllUllS UI IHC
state of California Department of Transportation or Crushed IMiscellaneous Base In accordance with the
standard Specifications for Public Works and City of Carlsbad Standards.
Based on an "R"-Value of 25 the following rigid pavement sections are recommended for the
Traffic Index presented below.
Table 5
Traffic Type Traffic Index JPCP*/Aggregate Base^
(inches)
Parking Stalls 6.0 6/6
Drive Lanes 7.5 6/6
Note 1: AB shall conform to Class 2 Aggregate Base in Section 26-1.02 ofthe Standard Specifications of The
State of California Department of Transportation or Crushed Miscellaneous Base In accordance with the
Standard Specifications for Public Works and City of Carlsbad Standards.
Bus turnouts should be constructed in accordance with the San Diego Regional Standard
Drawings SDG-109, 9 inches of concrete underiain by at least 12 inches of aggregate base.
The concrete should have a compressive strength of at least 3250 pounds per square inch.
SDG&E concrete maintenance areas should have a concrete thickness of at least T'A inches
underiain by at least 12 inches of aggregate base.
Trash enclosures should have a thickness of at least T'A and be underiain by at least 12 inches
of aggregate base.
The upper 12 inches of subgrade should be scarified, moisture conditioned to above optimum
moisture requirements, and compacted to at least 95% of the maximum dry density. All soft or
spongy areas should be excavated and replaced with compacted fill. The base material should
be compacted to at least 95% of its maximum dry density. All materials and methods of
construction should conform to good engineering practices and the minimum standards set forth
by the City of Carisbad.
Property Development Centers July 31, 2012
La Costa Town Square Office Development SCS&T Proposal No. Ill 1198-01R
Carlsbad, California Page 13
4.7 INFILTRATION RATES
The underiying earthen materials are comprised of impermeable clay and rock. Infiltration rates
will be dependent on the materials placed during mass grading operations. The project civil
engineer should design permeable surfaces to collect surface water and direct it toward
appropriate drainage facilities.
5. GEOTECHNICAL ENGINEERING DURING CONSTRUCTION
The geotechnical engineer should review project plans and specifications prior to bidding and
construction to check that the intent of the recommendations in this report has been
incorporated. Observations and tests should be performed during construction. If the
conditions encountered during construction differ from those anticipated based on the
subsurface exploration program, the presence of the geotechnical engineer during construction
will enable an evaluation of the exposed conditions and modifications of the recommendations
in this report or development of additional recommendations in a timely manner.
6. CLOSURE
SCS&T should be advised of any changes in the project scope so that the recommendations
contained in this report can be evaluated with respect to the revised plans. Changes in
recommendations will be verified in writing. The findings in this report are valid as ofthe date of
this report. Changes in the condition of the site can, however, occur with the passage of time,
whether they are due to natural processes or work on this or adjacent areas. In addition,
changes in the standards of practice and government regulations can occur. Thus, the findings
in this report may be invalidated wholly or in part by changes beyond our control. This report
should not be relied upon after a period of two years without a review by us verifying the
suitability of the conclusions and recommendations to site conditions at that time.
In the performance of our professional services, we comply with that level of care and skill
ordinarily exercised by members of our profession currently practicing under similar conditions
and in the same locality. The client recognizes that subsurface conditions may vary from those
encountered at the boring locations, and that our data, interpretations, and recommendations
are based solely on the information obtained by us. We will be responsible for those data,
interpretations, and recommendations, but shall not be responsible for interpretations by others
of the information developed. Our services consist of professional consultation and observation
only, and no warranty of any kind whatsoever, express or implied, is made or intended in
connection with the work performed or to be performed by us, or by our proposal for consulting
or other services, or by our furnishing of oral or written reports or findings.
SOUTHERN CALIFORNIA
SOIL & TESTING, INC.
SITE VICINITY MAP
lA COSTA TOWN SQUARE
OFFICE
Date:
By:
Job No.
Scale:
12/23/2011
AKN
1111198-1
Not To Scale
Figure:
1
\
Natural
Ground
Benching
CANYON SUBDRAIN DETAIL
Subgrain Trench:
See Details A and B
Remove
Unsuitable
Material
DETAIL A Perforated Pipe Surrounded with Filter Material
Filter Material 6 cubic feet/foot
-Cover
Perforated Pipe
Filter Material Shall be Class 2
permeable material per Section 68 of
CALTRANS standard specifications, or
approved alternate.
DETAIL B 4 inch open-graded gravel
wrapped in filter fabric (Mirafi
140N or equivalent)
6" minimum overlap
Detail
B-1
Filter Material (Mirafi UON or approved equivalent)
Perforated Pipe
f inch open graded gravel or equivalent 6 cubic feet/foot
Detail
B-2
(for fills
over 35'
deep)
DETAIL of Canyon
Subdrain Outlet
Design Finish Grade
SUBDRAIN INSTALLATION
Subdrain pipe shall be installed with perforation down.
SUBDRAIN PIPE
Subdrain pipe shall be PVC or ABS, type SDR35 for fills up
to 35 feet deep, or type SDR21 for fills up to 100 feet deep.
* MINIMUM DIAMETER
4" min - 0 - 500' Drain.
6" nnin = 500- 1,000' Drain
8" min = 1,000+ Drain
SOUTHERN CALIFORNIA
SOIL & TESTING, INC.
SUBDRAIN DETAILS
UK COSTA TOWN SQUARE
OFFICE
Date:
By:
Job No.
Scale:
1/1/2012
EL
1111198-1
Not To Scale
Figure:
4
Miradrain 6000 or Equivalent
1 - Filter fabric between rock and soil.
2 - Backcut as recommended in accordance with CALOSHA
3 - Waterproof back of wall.
4-A 4-inch minmum diameter perforated pipe, SDR35 or equivalent, holes c
1% fall to outlet, encased in 3/4" crushed rock. Provide 3 cubic feet per
lineal foot of crushed rock minimum. Crushed rock to be surrounded
by filter fabric (Mirafi 140N or equivalent), with a 6-inch minumum
overiap. Provide solid outlet pipe at suitable location.
5 - 3/4-inch crushed rock
SOUTHERN CALIFORNIA
SOIL & TESTING, INC.
WALL.BACKDRAIN
LA.COSTA.TOWN. SQUARE.-.COMM ERCIAL
Date:
By:
Job No.
Scale:
4/16/2011
GBF
1111199-01
NOTTOSCALE
Figure:
7
APPENDIX I
APPENDIX I
FIELD INVESTIGATION
Three exploratory test trenches were excavated at the locations shown on Figure 2. The
fieldwork was performed under the observation of our geology personnel, who also logged the
trenches and obtained samples of the materials encountered.
The logs are presented on Figures 1-2 through 1-4. Soils are classified in accordance with the
Unified Soil Classification System illustrated on Figure 1-1.
SUBSURFACE EXPLORATION LEGEND
UNIFIED SOIL CLASSIFICATION CHART
SOIL DESCRIPTION GROUP
SYMBOL TYPICAL NAMES
COARSE GRAINED, more than 50% of material is larger than No. 200 sieve size.
CLEAN GRAVELS GW Well graded gravels, gravel-sand mixtures, little or no fines
GP Poorly graded gravels, gravel sand mixtures, little or no fines.
GRAVELS
More than half of
coarse fraction is
larger than No. 4
sieve size but
smaller than 3".
SANDS
More than half of
coarse fraction is
smaller than No.
4 sieve size.
GRAVELS WITH FINES GM Silty gravels, poorly graded gravel-sand-silt mixtures.
(Appreciable amount of
fines) GC Clayey gravels, poorly graded gravel-sand-clay mixtures.
CLEAN SANDS SW Well graded sand, gravelly sands, little or no fines.
SP Poorly graded sands, gravelly sands, little or no fines.
SANDS WITH FINES SM Silty sands, poorly graded sand and silty mixtures.
(Appreciable amount of
fines) SC Clayey sands, poorly graded sand and clay mixtures.
II. FINE GRAINED, more than 50% of material is smaller than No. 200 sieve size.
SILTS AND CLAYS
(Liquid Limit less
than 50)
SILTS AND CLAYS
(Liquid Limit
greater than 50)
Inorganic silts and very fine sands, rock flour, sandy silt or clayey-silt-
sand mixtures with slight plasticity.
Q|_ Inorganic clays of low to medium plasticity, gravelly clays, sandy clays,
silty clays, lean clays.
OL Organic silts and organic silty clays of low plasticity.
|^|-| Inorganic silts, micaceous or diatomaceous fine sandy or silty soils,
elastic silts.
CH Inorganic clays of high plasticity, fat clays.
OH Organic clays of medium to high plasticity.
HIGHLY ORGANIC SOILS PT Peat and other highly organic soils.
FIELD SAMPLE SYMBOLS
- Bulk Sample
CAL - Modified California penetration test sampler
CK - Undisturbed chunk sample
MS - Maximum Size of Particle
- Water seepage at time of excavation or as indicated
SPT - Standard penetration test sampler
ST -ShelbyTube
\/ - Water level at time of excavation or as indicated
LABORATORY TEST SYMBOLS
AL - Atterberg Limits
CON - Consolidation
COR - Corrosivity Test
- Sulfate
- Chloride
- pH and Resistivity
OS - Direct Shear
El - Expansion Index
MAX - Maximum Density
RV - Rvalue
SA - Sieve Analysis
UC - Unconfined Compression
SOUTHERN CALIFORNIA
SOIL & TESTING, INC.
LA COSTA TOWN SQUARE OFFICE
By: DAS
Job Number: 1111198-1
Date: 1/5/2012
Figure: 1-1
LOG OF TEST TRENCH NUMBER T-1
Date Excavated: 12/8/2011 Logged by: AKN
Equipment: Case 580L with 18-inch bucket Project Manager: GBF
Surface Elevation (ft): 294 Depth to Water (ft): not observed
X
I-
CL
UJ
Q
CO
O
CO
3 SUMMARY OF SUBSURFACE CONDITIONS
SAMPLES
UJ
a:
H
CO
o
o
Q.
3
>-
Q
- 2
- 4
- 6
- 8
- 10
- 12
- 14
- 16
- 18
L 20
DELMAR FORMATION (Td) - Light gray, moist, very dense.
fine- to medium-grained, SILTY SANDSTONE.
BOTTOM OF TEST TRENCH AT 6 FEET. NO
GROUNDWATER OR SEEPAGE ENCOUNTERED.
AL,
SA,
MAX,
DS
SOUTHERN CALIFORNIA
SOIL & TESTING, INC.
LA COSTA TOWN SQUARE OFFICE SOUTHERN CALIFORNIA
SOIL & TESTING, INC. By: AKN Date: 1/5/2012
SOUTHERN CALIFORNIA
SOIL & TESTING, INC.
Job Number: 1111198-1 Figure: 1-2
Date Excavated:
Equipment:
Surface Elevation (ft):
LOG OF TEST TRENCH NUMBER T-2
12/8/2011 Logged by: AKN
Case SSOL with 18-inch bucket Project Manager: GBF
275 Depth to Water (ft): not observed
X
\-Q. UJ Q
CO O CO 3 SUMMARY OF SUBSURFACE CONDITIONS
SAMPLES
111
CH
3
1-
co o
Q.
3
>-
Q
- 2
- 4
- 6
- 8
- 10
- 12
- 14
- 16
- 18
L 20
CL ALLUVIUM (Qal) - Dark brown, very moist, soft, SANDY
CLAY.
DELMAR FORMATION (Td) - Light grayish brown, moist.
very stiff to hard, SANDY CLAYSTONE.
BOTTOM OF TEST TRENCH AT 10 FEET. NO
GROUNDWATER OR SEEPAGE ENCOUNTERED.
SOUTHERN CALIFORNIA
1 SC^ SOIL & TESTING, INC.
LA COSTA TOWN SQUARE OFFICE SOUTHERN CALIFORNIA
1 SC^ SOIL & TESTING, INC. By: AKN Date: 1/5/2012
SOUTHERN CALIFORNIA
1 SC^ SOIL & TESTING, INC.
Job Number: 1111198-1 Figure: 1-3
LOG OF TEST TRENCH NUMBER T-3
Date Excavated: 12/8/2011 Logged by: AKN
Equipment: Case 580L with 18-inch bucket Project Manager: GBF
Surface Elevation (ft): 311 Depth to Water (ft): not observed
SAMPLES
X CO O RBED ISTURE (%) VT. (pcf) >-CC
2 v> DEP1 CO
3 SUMMARY OF SUBSURFACE CONDITIONS DISTU BUL ISTURE (%) 1-z
—\ LABORA TESl z
3
O DRYL LABORA TESl DEL MAR FORMATION (Td) - Liaht aravish brown, moist.
-dense, SILTY SANDSTONE
- 2
\\
AL,
SA,
A \\ MAX,
— 4
\
DS
- 6
- 8
—
- 10
- 12
- 14
PRACTICAL REFUSAL AT 15 FEET. NO GROUNDWATER
- 16 OR SEEPAGE ENCOUNTERED.
- 18
- 20
4)- SOUTHERN CALIFORNIA
SOIL & TESTING, INC.
LA COSTA TOWN SQUARE OFFICE 4)- SOUTHERN CALIFORNIA
SOIL & TESTING, INC. By: AKN Date: 1/5/2012
4)- SOUTHERN CALIFORNIA
SOIL & TESTING, INC.
Job Number: 1111198-1 Figure: 1-4
APPENDIX II
APPENDIX II
LABORATORY TESTING
SUMMARY
Laboratory tests were performed to provide geotechnical parameters for engineering analyses.
The following tests were conducted:
• CLASSIFICATION: Field classifications were verified in the laboratory by visual
examination. The final soil classifications are in accordance with the Unified Soil
Classification System.
• GRAIN SIZE DISTRIBUTION: The grain size distribution for 2 samples was performed
in accordance with ASTM D 422. The results of these tests are presented on Figure 11-1
and Figure 11-2.
• ATTERBERG LIMITS: The Atterberg Limits for 2 samples were performed in
accordance with ASTM D 4318. The result of these tests are presented on Figure 11-1
and Figure 11-2.
• DIRECT SHEAR: Direct shear tests were performed in accordance with ASTM D 3080.
The shear stress was applied at a constant rate of strain of approximately 0.003 inch per
minute. The results of these tests are presented on Figure 11-3 and 11-4.
Soil samples not tested are now stored in our laboratory for future reference and analysis, if
needed. Unless notified to the contrary, all samples will be disposed of 30 days from the date of
this report.
O
O
w
CO CO
OT
o a
Ul
m
UI
HI Q
O
I-
3
a.
z
o feet feet < CO
u o
o -1 o o UJ _l a. ro
s CM
< 0)
is
o fc o
CO
cr W
c
o
o O
0) •(5 Q
CO O)
0}
E
3
CQ
o -st o
UJ H
oS
3 O O (0
o
CO
O
t v « I
i
»
N
V)
c "(5 k.
O
o o
o o o
JO
O
o
o o o o CO o o
CO
o o o CO o o
CM T-
z
o feet H feet < r.-
u o
o _l LE a. ro S Tf
< CO
0)
a
O
CO 3 CT
V)
C
o I-co
.4-. in o O
CD
0} .Q
E
oe. o
z
H (0 UJ
I-
00
3 O O (0
(O
cn
SJ
S 20
(0
Direct Shear Test Results
• Shear Strength at 0.2 inches ol
Deformation
• Shear Strength at 0.2 inches ol
Deformation
^«
-
4 >
•
f
Confining Pressure (ksf)
INTERNAL
FRICTION
SAMPLE DESCRIPTION
0.0 0.5 1.0 1.5 2.0 2.5 3,0 3.5 4.0 4.5 5,0
COHESION
INTERCEPT
T2@1-6 Silty Sand
Remolded to 90% Relative Compaction
Shear Strenath at
0.2 inches of Deformation
38 103
^feO- SOUTHERN CALIFORNIA LA COSTA TOWN SQUARE OFFICE
1^^^^^ SOIL & TESTING BY: CA DATE: 1/5/2012 1^^^^^ SOIL & TESTING
JOB NUMBER: 1111198 Figure II: 3
(~ 3,0
III
IB in a ^ 2.5
in
(0
Direct Shear Test Results
• Shear Strength at 0.2 inches of
Deformation
t
•
>
•
•
•
0.0 0.5 1,0 1,5 2,0 2,5 3.0 3.£
Confining Pressure (ksf)
INTERNAL
FRICTION
SAMPLE DESCRIPTION
4.0 4,5 5.0
COHESION
INTERCEPT
T4@2-7 Clayey Sand
Remolded to 90% Relative Compaction
Shear Strenpth at 38 154
0.2 inches of Deformation
Jt SOUTHERN CALIFORNIA La Costa Town Square - Office
^^^^^ SOIL & TESTING BY: GBF DATE: 1/5/2012 ^^^^^ SOIL & TESTING
JOB NUMBER: 1111198-1 Figure II: 4