HomeMy WebLinkAboutSDP 15-26; LEGOLAND HOTEL CALIFORNIA II; GEOTECHNICAL UPDATE REPORT PROPOSED CASTLE HOTEL EXPANSION; 2015-11-23GEOTECHNICAL UPDATE REPORT
PROPOSED CASTLE HOTEL EXPANSION
LEGOLAND THEME PARK
CARLSBAD, CALIFORNIA
LEGOLAND HOTEL CALIFORNIA II
SDP 15-26 / CDP 15-50
DWG 498-2A
Prepared for:
MERLIN ENTERTAINMENT GROUP!
US HOLDING, INC.
One Lego Drive
Carlsbad,, California 92008
Project No. 10075.011
November 23, 2015
RECEVED
40
:NOV 2 5 2016
LAND DEvEOPMENT
ENGINEERING
Leighton and Associ ates, Inc
A LEIGH:TO.pl GROUP COMPANY
Leighton and Associates, Inc.
A LEIGHTON GROUP COMPANY
November 23, 2015
Project No. 10075.011
To: Merlin Entertainment Group/US Holding, Inc.
do LEGOLAND California, LLC
One Lego Drive
Carlsbad, California 92008
Attention: Mr. Keith Carr
Subject: Geotechnical Update Report, Proposed Castle Hotel Expansion,
LEGOLAND Theme Park, Carlsbad, California
In accordance with your request and authorization, Leighton and Associates, Inc.
(Leighton) has conducted a geotechnical update for the proposed Castle Hotel
Expansion that is planned for the LEGOLAND Theme Park in Carlsbad, California (see
Figure 1). This report presents the results of our review of pertinent geotechnical
documents, subsurface exploration, laboratory testing, geotechnical analyses, and
provides our conclusions and recommendations for the proposed development.
Based on the result of our current geotechnical study,
considered feasible from a geotechnical standpoint provided
implemented in the design and construction of the project.
regarding our report, please do not hesitate to contact this
opportunity to be of service.
Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC.
the proposed project is
our recommendations are
If you have any questions
office. We appreciate this
-No. 45283
William D. Olson, RCE 45289 \\t Exp.______
Associate Engineer CIV'-4
Distribution: (4) Addressee
Mike D. Jensen, CEG 2457
Senior Project Geologist
3934 Murphy Canyon Road, Suite B205 • San Diego, CA 92123-4425
858. 292.8030 a Fax 858.292.0771 .www.Ieightongeo.com
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TABLE OF-CONTENTS
Section Page
1.0 INTRODUCTION ...................................................................................................... I
1.1 PURPOSEANDSCOPE.............................................................................................1
1.2 SITE LOCATION AND DESCRIPTION............................................................................1
1.3 PROPOSED DEVELOPMENT......................................................................................2
2.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING..........................3
2.1 SITE INVESTIGATION................................................................................................3
2.2 LABORATORY TESTING ............................................................................................3
3.0 SUMMARY OF GEOTECHNICAL CONDITIONS ..................................................... 4
3.1 GEOLOGIC SETTING .................................................................................................4
3.2 SITE SPECIFIC GEOLOGY.........................................................................................4
3.2.1 Artificial Fill Undocumented (Not Mapped)....................................................4
3.2.2 Artificial Fill Documented (Map Symbol - Afd) ..............................................5
3.2.3 Quaternary-Aged Old Paralic Deposits (Map Symbol - Qop) ........................5
3.2.4 Santiago Formation (Map Symbol - Tsa)......................................................5
3.4 ENGINEERING CHARACTERISTICS OF ON-SITE SOIL...................................................6
3.4.1 Soil Compressibility and Collapse Potential ..................................................6
3.4.2 Expansive Soils.............................................................................................6
3.4.3 Soil Corrosivity ..............................................................................................7
3.4.4 Excavation Characteristics ............................................................................7
3.4.5 Infiltration Characteristics..............................................................................7
4.0 FAULTING AND SEISMICITY.................................................................................8
4.1 FAULTING...............................................................................................................8
4.2 LOCAL FAULTING ....................................................................................................'8
4.3 SEISMICITY.............................................................................................................8
4.4 SEISMIC HAZARDS ..................................................................................................8
4.4.1 ShallowGround Rupture ...............................................................................9
4.4.2 Mapped Fault Zones .....................................................................................9
4.4.3 Site Class ......................................................................................................9
4.4.4 Building Code Mapped Spectral Acceleration Parameters............................9
4.5 SECONDARY SEISMIC HAZARDS .............................................................................10
4.5.1 Liquefaction and Dynamic Settlement.........................................................10
4.5.2 Lateral Spread ............................................................................................. 11
4.5.3 Tsunamis and Seiches................................................................................11
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TABLE OF CONTENTS (Continued)
Section Pane
4.6 LANDSLIDES .........................................................................................................11
4.7 SLOPES................................................................................................................12
4.8 FLOOD HAZARD ....................................................................................................12
5.0 CONCLUSIONS.....................................................................................................13
6.0 RECOMMENDATIONS ........................................................................................... 15
6.1 EARTHWORK ........................................................................................................15
6.1.1 Site Preparation ............................................................................................ 15
6.1.2 Excavations and Oversize Material .............................................................15
6.1.3 Removal of Compressible Soils...................................................................16
6.1.4 Pad Overexcavation....................................................................................16
6.1.5 Engineered Fill .............................................................................................17
6.1.6 Earthwork Shrinkage/Bulking ......................................................................17
6.1.7 Trench Backfill.............................................................................................17
6.1.8 Expansive Soils and Selective Grading.......................................................18
6.1.9 Import Soils .................................................................................................18
6.2 TEMPORARY EXCAVATIONS .................................................................................... 18
6.3 FOUNDATION DESIGN CONSIDERATIONS .................................................................19
6.3.1 Conventional Foundations...........................................................................19
6.3.2 Preliminary Slab Design..............................................................................20
6.3.3 Foundation Setback ....................................................................................20
6.3.4 Settlement...................................................................................................21
6.3.5 Moisture Conditioning..................................................................................22
6.4 LATERAL EARTH PRESSURES AND RETAINING WALL DESIGN ....................................23
6.5 GEOCHEMICAL CONSIDERATIONS ...........................................................................25
6.6 CONCRETE FLATWORK..........................................................................................25
6.7 SURFACE DRAINAGE AND EROSION ........................................................................26
6.8 PLAN REVIEW.......................................................................................................26
6.9 CONSTRUCTION OBSERVATION ..............................................................................26
7.0 LIMITATIONS .................................................................................................27
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TABLE OF CONTENTS
TABLES
TABLE 1 -2013 MAPPED SPECTRAL ACCELERATIONS PARAMETERS - PAGE 10
TABLE 2- MAXIMUM SLOPE RATIOS - PAGE 19
TABLE 3- MINIMUM FOUNDATION SETBACK FROM SLOPE FACES - PAGE 21
TABLE 4- PRESOAKING RECOMMENDATIONS BASED ON FINISH GRADE SOIL EXPANSION
POTENTIAL - PAGE 23
TABLE 5 - STATIC EQUIVALENT FLUID WEIGHT - PAGE 23
TABLE 6- RETAINING WALL SOIL PARAMETERS - PAGE 25
FIGURES
FIGURE 1 - SITE LOCATION MAP - REAR OF TEXT
FIGURE 2 - GEOTECHNICAL MAP - REAR OF TEXT
FIGURE 3 - GEOLOGICAL CROSS SECTION A-A' - REAR OF TEXT
FIGURE 4 - GEOLOGICAL CROSS SECTION B-B' - REAR OF TEXT
APPENDICES
APPENDIX A - REFERENCES
APPENDIX B - BORING LOGS
APPENDIX C - LABORATORY TESTING PROCEDURES AND TEST RESULTS -
APPENDIX D - GENERAL EARTHWORK AND, GRADING SPECIFICATIONS FOR ROUGH GRADING
APPENDIX E - GBC INSERT
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1.0 INTRODUCTION
We recommend that all individuals utilizing this report read the preceding information
sheet prepared by GBC (the Geotechnical Business Council of the Geoprofessional
Business Council) and the Limitations, Section 7.0, located at the end of this report.
1.1 Purpose and Scope
This report presents the results of our updated geotechnical study for the
proposed Castle Hotel Expansion Project located at the LEGOLAND Theme Park
in Carlsbad, California (see Figure 1). The purpose of our update report was to
identify and evaluate the existing geotechnical conditions present at the site and
to provide conclusions and recommendations relative to the proposed
development.
1.2 Site Location and Description
The LEGOLAND Theme Park is located north of Palomar Airport Road and west
of College Boulevard in Carlsbad, California (see Figure 1). The proposed Castle
Hotel Expansion will be located just south of the existing Sea Life Aquarium and
directly west of the existing Castle Hotel within the LEGOLAND Theme Park (see
Figure 2). Currently, the site is occupied by an asphaltic surfaced parking lot
which has direct access from LEGOLAND Drive. In addition, vegetation at the
site consists of typical lawns, shrubs and trees.
Topographically, the site is nearly level with elevations gently sloping from the
north to the south, ranging from approximately 150 to 146 feet above mean sea
level (msl).
As background, Leighton performed the initial geotechnical investigation for the
LEGOLAND Theme Park in 1995. Subsequently, the site was mass graded
between 1996 and 1998 under the direct observation and testing of Leighton. As
a result of the. mass grading operations for the development of the LEGOLAND
Theme Park, a cut to fill transition was created at the site, which perpendicularly
transects the center of the site in a north to south orientation (see Figure 2).
Site Latitude and Longitude
33.1254° N
117.31230 W
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1.3 Proposed Development
It is our understanding that the proposed Castle Hotel Expansion Project will.
consist of a new two to three story hotel building and pool. Additionally,
improvements at the site will consist of associated driveways, utilities, landscape
and hardscape. We anticipate the site earthwork will consist of an overexcavation
of cut areas, remedial grading to account for weathered fill and general grading
(i.e., cut to fill mitigation) to reach the proposed site finish grades. In addition, we
anticipate the foundation system for the proposed building and site structures will
be constructed using conventional foundations. Preliminary grading and
foundation plans or structural loads were not available prior to the preparation of
this report.
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2.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING
2.1 Site Investigation
Our exploration consisted of excavating five (5) 8-inch small diameter
geotechnical borings (B-I through B-5) to approximately 16 to 26.5 feet below
the existing ground surface (bgs). All. borings were drilled using a heavy duty
truck mounted hollow-stem auger drill rig. During the exploration operations, a
geologist from our firm prepared geologic logs and collected bulk and relatively
undisturbed samples for laboratory testing and evaluation.
After logging, the borings were backfilled per County of San Diego Department of
Environmental Health (DEH) requirements. The boring logs are provided in
Appendix B. Geotechnical boring locations are depicted on the Geotechnical Map
(see Figure 2).
2.2 Laboratory Testing
Laboratory testing performed, on soil samples representative of on-site soils
obtained during the recent subsurface exploration included, moisture content,
density determination, shear strength, consolidation, expansion index, and a
screening geochemical analysis for corrosion. A discussion of the laboratory
tests performed and a summary of the laboratory test results are presented in
Appendix C.
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3.0 SUMMARY OF GEOTECHNICAL CONDITIONS
3.1 Geologic Setting
The site is located in the coastal section of the Peninsular Range Province, a
geomorphic province with a long and active geologic history throughout Southern
California. Throughout the last 54 million years, the area known as "San Diego
Embayment" has undergone several episodes of marine inundation and
subsequent marine regression, resulting in the deposition of a thick sequence of
marine and nonmarine sedimentary rocks on the basement rock of the Southern
California batholith.
Gradual emergence of the region from the sea occurred in Pleistocene time, and
numerous wave-cut platforms, most of which were covered by relatively thin
marine and nonmarine terrace deposits,, formed as the sea receded from the
land. Accelerated fluvial erosion during periods of heavy rainfall, coupled with the
lowering of the base sea level during Quaternary times, resulted in the rolling
hills, mesas, and deeply incised canyons which characterize the landforms we
see in the general site area today.
3.2 Site SDecific Geology
Based on our subsurface exploration, geologic mapping during previous grading
operations (Leighton, 1998), and review of pertinent geologic literature and
maps, the geologic units underlying the site consist of documented artificial fill
soils, Quaternary-aged Old Paralic Deposits, and the Tertiary-aged Santiago
Formation. Brief descriptions of the geologic units present at the site are
presented in the following sections. The approximate areal distribution of the
geologic units is depicted on the Geotechnical Map (see Figure 2) and the
geotechnical boring logs with detailed soils descriptions are presented in
Appendix B.
3.2.1 Artificial Fill Undocumented (Not Mapped)
Areas of undocumented fill up to approximately 5 feet in thickness may be
encountered in planters and landscape areas. The fill was derived from on-
site excavations that were placed following the rough grading operations
which occurred in the late 1990's.
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3.2.2 Artificial Fill Documented (Map Symbol
The site is generally overlain by documented artificial fill that was placed
and compacted during previous grading operations (Leighton, 1998). The
depth of the fill soils at the site is expected to vary between 3 and 22 feet
bgs. The fill soils consists of moist, reddish brown medium dense to very
dense, silty sand and moist reddish brown, stiff to very stiff, sandy lean
clay. In addition, the fill soils were compacted to at least 90 percent relative
compaction based on ASTM Test Method D1557 (Leighton, 1998). The
upper 2 feet of previously placed documented fill is weathered or disturbed
by existing improvements and should be remo('ed and reprocessed prior
to the placement of additional fills or construction of new improvements.
3.2.3 Quaternary-Aped Old Paralic Deposits (Mar) Symbol - Qop)
Quaternary-aged Old Paralic Deposits are present beneath the site. To
the east of the cut to fill transition, a thin veneer of documented artificial fill
overlies the Old Paralic Deposits. These Old Paralic Deposits consist of
yellowish brown to reddish brown, moist, medium dense to very dense, silty
sand. Sand lenses within the Old Paralic Deposits are known to contain
layers that transmit water seepage. In addition, we anticipate that portions
of the Old Paralic Deposits may need tobe excavated and/or undercut
and replaced as compacted fill during the mitigation of the differential fill
thickness caused by cut to fill transition at the site.
3.2.4 Santiago Formation (Mar) Symbol - Tsa)
The Santiago Formation underlies the entire the site at depth. The
Santiago Formation consists of a very pale brown, moist, very dense, silty
fine to medium grained sandstone. We anticipate that portions of the
Santiago Formation in the southeast corner of the site may need to be
excavated and/or undercut and replaced as compacted fill during the
mitigation of the differential fill thickness cut to fill transition at the site.
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3.3 Surface Water and Ground Water
No indication of surface water or evidence of surface ponding was encountered
during our geotechnicál investigation at the site. However, surface water may
drain as sheet flow across the site during rainy periods.
Based on our experience and given the approximate elevation of the site, we
anticipate the ground water to be at a depth of 75 feet or more. However, it
should be noted that previous nearby investigations have encountered perched
ground water accumulated on the geologic contact between the Santiago
Formation and the Old Paralic Deposits observed at the site. These conditions
will need to be evaluated on a case-by-case basis during site grading and within
sandy layers in the Old Paralic Deposits. Therefore, based on the above
information, we do not anticipate ground water will be a constraint to the
construction of the project.
3.4 Engineering Characteristics of On-Site Soil
Based on our subsurface exploration, geologic mapping during previous grading
operations (Leighton, 1998), review of pertinent geologic literature and maps,
and our professional experience on adjacent sites with similar soils, the
engineering characteristics of the on-site soils are discussed below.
3.4.1 Soil Compressibility and Collapse Potential
Based on the dense nature of the on-site documented fill, Old Paralic
Deposits and the Santiago Formation, it is our opinion that the potential for
settlement and collapse at the site is low. However, the upper 2 feet of
previously placed documented fill that is weathered or disturbed by
existing improvements are expected to be removed by planned grading
and/or remedial grading.
3.4.2 Expansive Soils
The majority of the onsite material is expected to have a low to medium
expansion potential. In addition, soils generated from excavations in the
Old Paralic Deposits and the Santiago Formation are also expected to
possess a very low to low expansion potential. Laboratory testing upon
completion of remedial and fine grading operations for the proposed
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building pad is recommended to determine actual expansion potential of
finish grade soil at the site.
3.4.3 Soil Corrosivitv
During our investigation, a preliminary screening of one representative on-
site soil sample was performed to evaluate its potential corrosive effect on
concrete and ferrous metals. In summary, laboratory testing on the
representative soil sample obtained during our subsurface exploration
evaluated pH minimum electrical resistivity, and chloride and soluble
sulfate content. The sample tested had a measured Ph of 7.52 and a
measured minimum electrical resistivity of 1,080 ohm-cm. The test result
also indicated that the sample had a chloride content of 307 parts per
million (ppm) and a soluble sulfate content range of less than 130 ppm.
3.4.4 Excavation Characteristics
It is anticipated the on-site soils can be excavated with conventional
heavy-duty construction equipment. Localized cemented zones located
within the Old Paralic Deposits and the Santiago Formation, if
encountered, may require heavy ripping or breaking. In addition, localized
loose soil zones and friable sands, if encountered, may require special
excavation techniques to prevent collapsing of the excavation.
3.4.5 Infiltration Characteristics
Based on our experience, we anticipate that the underlying documented
fill consisting of a mixture of soils and the underlying formation will have
permeable and impermeable layers can transmit and perched ground
water in unpredictable ways. Therefore, Low Impact Development (LID)
measures may impact down gradient improvements and the use of some
unlined LID measures may not be appropriate for this project. All
Infiltration and Bioretention Stormwater Systems design should be
reviewed by geotechnical consultant.
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4.0 FAULTING AND SEISMICITY
4.1 Faulting
Our discussion of faults on the site is prefaced with a discussion of California
legislation and policies concerning the classification and land-use criteria
associated with faults. By definition of the California Geological Survey, an active
fault is a fault which has had surface displacement within Holocene time (about the
last 11,000 years). The state geologist has defined a potentially active fault as any
fault considered to have been active during Quaternary time (last 1,600,000
years). This definition is used in delineating Earthquake Fault Zones as mandated
by the Aiquist-Priolo Geologic Hazards Zones Act of 1972 and most recently
revised in 2007 (Bryant and Hart, 2007). The intent of this act is to assure that
unwise urban development and certain habitable structures do not occur across
the traces of active faults. The subject site is not included within any Earthquake
Fault Zones as created by the Alquist-Priolo Act.
4.2 Local Faulting
Our review of available geologic literature (Appendix A) and geologic mapping
during previous grading indicates that there are no known major or active faults
on or in the immediate vicinity of the site. The nearest active regional fault is the
offshore segment of the Rose Canyon Fault Zone located approximately 4.7
miles west of the site (USGS, 2008).
4.3 Seismicity
The site is considered to lie within a seismically active region, as is all of
Southern California. As previously mentioned above, the Rose Canyon fault zone
located approximately 4.7 miles west of the site is considered the 'active' fault
having the most significant effect at the site from a design standpoint.
4.4 Seismic Hazards
Severe ground shaking is most likely to occur during an earthquake on one of the
regional active faults in Southern California. The effect of seismic shaking may
be mitigated by adhering to the California Building Code or state-of-the-art
seismic design parameters of the Structural Engineers Association of California.
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4.4.1 Shallow Ground Rupture
As previously discussed, no active faults are mapped transecting or
projecting toward the site. Therefore, surface rupture hazard due to
faulting is'considered very low. Ground cracking due to shaking from a
seismic event is not considered a significant hazard either, since the site is
not located near slopes.
4.4.2 Mapped Fault Zones
The site is not located within a State mapped Earthquake Fault Zone
(EFZ). As previously discussed, the subject site is not underlain by. known
active or potentially active faults.
4.4.3 Site Class
Utilizing 2013 California Building Code (CBC) procedures, we have
characterized the site soil profile to be Site Class D based on our
experience with similar sites in the project area and the results of our
subsurface evaluation.
4.4.4 Building Code Marrned Spectral Acceleration Parameters
The effect of seismic shaking may be mitigated by adhering to the
California Building Code and state-of-the-art seismic design practices of
the Structural Engineers Association of California. Provided below in
Table I are the spectral acceleration parameters for the project
determined in accordance with the 2013 CBC (CBSC, 2013) and the
USGS Worldwide Seismic Design Values tool (Version 3.1.0).
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Table I
2013 CBC Mapped Spectral Acceleration Parameters
Site Class - D
• Site Coefficients Fa = 1.048
FV 1.566
Mapped MCE Spectral Accelerations Ss = 1.129g
S1 = 0.434g
Site Modified MCE Spectral Accelerations SMS = 1.184g
SM1 = 0.680g
Design Spectral Accelerations SDS = 0.789g
SD1 = 0.453g
Utilizing ASCE Standard 7-10, in accordance with Section 11.8.3, the
following additional parameters for the peak horizontal ground acceleration
are associated with the Geometric Mean Maximum Considered
Earthquake (MCEG). The mapped MCEG peak ground acceleration (PGA)
is 0.448g for the site. For a Site Class D, the FPGA is 1.052 and the
mapped peak ground acceleration adjusted for Site Class effects (PGAM)
is 0.471g for the site.
4.5 Secondary Seismic Hazards
In general, secondary seismic hazards can include soil liquefaction, seismically-
induced settlement, lateral displacement, surface manifestations of liquefaction,
landsliding, seiches, and tsunamis. The potential for secondary seismic hazards
at the subject site is discussed below.
4.5.1 Liquefaction and Dynamic Settlement
Liquefaction and dynamic settlement of soils can be caused by strong
vibratory motion due to earthquakes. Both research and historical data
indicate that loose, saturated, granular soils are susceptible to liquefaction
and dynamic settlement. Liquefaction is typified by a loss of shear strength
in the affected soil layer, thereby causing the soil to behave as a viscous
liquid. This effect may be manifested by excessive settlements and sand
boils at the ground surface. •
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Based on our evaluation, the on-site soils are not considered liquefiable
due to their dense condition and absence of a shallow ground water
condition. Considering planned grading and foundation design measures,
dynamic settlement potential is also considered negligible.
4.5.2 Lateral Spread
Empirical relationships have been derived (Youd et al., 1999) to estimate
the magnitude of lateral spread due to liquefaction. These relationships
include parameters such as earthquake magnitude, distance of the
earthquake from the site, slope height and angle, the thickness of
liquefiable, soil, and gradation characteristics of the soil. Based on the low
susceptibility to liquefaction and the formational material unit underlying
the site, the possibility of earthquake-induced lateral spread is considered
to be low for the site.
4.5.3 Tsunamis and Seiches
Based on the site elevation and the distances of the site from the Pacific
coastline, there is no potential for flood damage to occur at the site from a
/ tsunami or seiche.
4.6 Landslides
Landslides are deep-seated ground failures (several tens to hundreds of feet
deep) in which a large arcuate shaped section of a slope detaches and slides
downhill. Landslides are not to be confused with minor slope failures (slumps),
which are usually limited to the topsoil zone and can occur on slopes composed
of almost any geologic material. Landslides can cause damage to structures both
above and below the slide mass. Structures above the slide area are typically
damaged by undermining of foundations. Areas below a slide mass can be
damaged by being overridden and crushed by the failed slope material.
Several formations within the San' Diego region are particularly prone to
landsliding. These formations generally have high clay content and mobilize
when they become saturated with water. Other factors, such as steeply dipping
bedding that project out of the face of the slope and/or the presence of fracture
planes, will also increase the potential for landsliding. Based on our geologic
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review and previous geologic mapping, the materials on site are generally
massive with no distinctive structure.
No active landslides or indications of deep-seated landsliding were noted at the
site during previous site grading, or our review of available geologic literature,
topographic maps, and stereoscopic aerial photographs. Furthermore, our field
exploration and the local geologic maps indicate the site is underlain by favorable
oriented geologic structure, and no nearby slopes. Therefore, the potential for
significant landslides or large-scale slope instability at the site is considered low.
4.7 Slopes
If grading of the site includes the construction of new slopes, we recommend that
permanent slopes be inclined no steeper than 2:1 (horizontal to vertical). Fills over
sloping ground should be benched to produce a level area to receive fill. Benches
should be wide enough to provide complete coverage by the compaction
equipment during fill placement. If cut slopes are proposed to reach site grades,
they should be evaluated by the geotechnical consultant during grading plan
review and grading.
All slopes may be susceptible to surficial slope instability and erosion given
substantial wetting of the slope face. Surficial slope stability may be enhanced by
providing proper site drainage. The site should be graded so that water from the
surrounding areas is not able to flow over the top of slopes. Diversion structures
should be provided where necessary.
4.8 Flood Hazard
According to a Federal Emergency Management Agency (FEMA) flood insurance
rate map (FEMA, 2012); the site is not located within a floodplain. In addition, the
site is not located downstream of a dam or within a dam inundation area based
on our review of topographic maps. Therefore, the potential for flooding of the
site is considered very low.
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5.0 CONCLUSIONS
Based on the results of our geotechnical review of the site, it is our opinion that the
proposed development is feasible from a geotechnical viewpoint, provided the following
conclusions and. recommendations are incorporated into the project plans and
specifications. The following is a summary of the significant geotechnical factors that we
expect may affect development of the site.
As the site is located in the seismically active southern California area, all
structures should be designed to tolerate the dynamic loading resulting from
seismic ground motions;
. The site is not transected by Potentially Active or Active faults;
The location of the proposed Castle Hotel Expansion Project is within an area
underlain by existing documented fill placed as part of the original rough grading of
the LEGOLAND Theme Park, Quaternary-aged. Old Paralic Deposits, and the
Tertiary-aged Santiago Formation;
Areas of undocumented fill and disturbed soils, ranging from I to 5 feet in
thickness, may be located in areas of existing improvements and landscape areas.
These materials, if encountered, should be removed prior to the placement of
additional fills or construction of improvements;
The upper 2 feet of previously placed documented fill is weathered and should be
removed and reprocessed prior to the placement of additional fills or construction
of improvements;
As a result of the mass grading operations for the development of the
LEGOLAND Theme Park, a cut to fill transition was created which
perpendicularly transects the center of the site in a north to south orientation.
Over-excavation and/or undercutting should be performed to mitigate the cut to
fill transition to prevent the potential for differential settlement under the proposed
structure;
Existing underground utilities and construction debris should be anticipated during
future grading and construction. The depths and location of these, utilities are
unknown at this time. It should be noted that backfill associated with utility trenches
should be evaluated on a case-by-case basis and may require complete removal
prior to placement of additional fill or construction of foundations;
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We anticipate that the soils present on the site will be generally rippable with
/ conventional heavy-duty earthwork equipment;
The existing onsite soils are suitable material for fill construction provided they
are relatively free of organic material, debris, and cobbles or rock fragments
larger than 8 inches in maximum dimension.
Based on laboratory testing, the soils on the site generally possess a low to
medium expansion potential. Nevertheless, there may be localized areas across
the site and between our exploration locations having a higher expansion
potential;
Ground water was not encountered during the site investigation or pervious
grading operations.-Therefore, ground water is not considered a constraint on the
proposed project development. However, perched ground water and seepage
may develop within sandy layers and along the less permeable clay and silt
layers within the Old Paralic Deposits and along the fill and Old Paralic Deposits
contact during periods of precipitation or increased landscape irrigation;
Although foundation plans have not been finalized and building loads were not
provided at the time this report was drafted, we anticipate that a conventional
foundation system, consisting of continuous and spread footings with slab-on-
grade flooring supported by competent documented fill materials, will be utilized
for the proposed building and site structures;
Although Leighton does not practice corrosion engineering, laboratory test results
indicate the soils present on the site have a negligible potential for sulfate attack
on normal concrete. In addition, the onsite soils are considered to be corrosive to
buried uncoated ferrous metals. We recommend that a corrosion engineer be
retained to design corrosion protection systems and to evaluate the appropriate
concrete properties for the project; and
Low Impact Development (LID) measures may impact down gradient
improvements and the use of unlined LID measures may not be appropriate for
this project.
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6.0 RECOMMENDATIONS
6.1 Earthwork
We anticipate that earthwork at the site will consist of site preparation, building
pad overexcavation of cut areas and remedial grading. We recommend that
earthwork on the site be performed in accordance with the following
recommendations and the General Earthwork and Grading Specifications for
Rough Grading included in Appendix. D. In case of conflict, the following
recommendations supersede those in Appendix D.
6.1.1 Site PreDaration
Prior to grading, all areas to receive structural fill, engineered structures,
and pavements should be cleared of surface and subsurface obstructions,
including any existing debris and undocumented fill, old slabs, loose,
compressible, or unsuitable soils, and stripped of vegetation. Removed
vegetation and debris should be properly disposed off-site. All areas to
receive fill and/or other surface improvements should be scarified to a
minimum depth of 8 inches, brought to optimum or above-optimum
moisture conditions, and recompacted to at least 90 percent relative
compaction based on ASTM Test Method 01557.
6.1.2 Excavations and Oversize Material
Shallow excavations of the onsite materials may generally be
accomplished with conventional heavy-duty earthwork equipment.
Localized heavy ripping may be required if cemented and concretionary
lenses are encountered in deeper excavations.
Due to the high-density characteristics of the Old Paralic Deposits and the
Santiago Formation, temporary shallow excavations less than 5 feet in
depth with vertical sides should remain stable for the period required to
construct utilities, provided the trenches are free of adverse geologic
conditions. Overlying artificial fill soils and beds of friable sands within the
Old Paralic Deposits present at the site may cave during trenching
operations. In accordance with OSHA requirements, excavations deeper
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than 5 feet should be shored or be laid back in accordance with Section
6.2 if workers are to enter such excavations.
6.1.3 Removal of Compressible Soils
The upper 2 feet of the previously placed documented fill at the site is
weathered and is therefore considered to be potentially compressible and
may settle as a result of wetting or settle under the surcharge of
engineered fill.and/or structural loads supported on shallow foundations.
11
The upper two feet of fill materials at the site should be removed and
reprocessed prior to the placement of additional fills or construction of new
improvements. In addition, the lateral limits of the removal excavations
should extend at least 5 feet beyond the foundation limits of the site
sensitive improvements. The bottom of all removals should be evaluated
by a Certified Engineering Geologist to confirm conditions are as
anticipated.
In general, the soil that is removed may be reused and placed as
engineered fill provided the material is free of oversized rock,'organic
materials, and deleterious debris, and moisture conditioned to above
optimum moisture content. Soil with an expansion index greater than 50
should not be used within 5 feet of finish grade in the building pad. The
actual depth and extent of the required removals should be confirmed
during grading operations by the geotechnical consultant.
6.1.4 Pad Overexcavation
In order to mininiize the potential for differential settlement, we
recommend that the proposed building and settlement sensitive structures
be entirely underlain by a layer of properly compacted fill. Therefore, the
cut portion areas located east of the cut to fill transition at the site that is
planned for structures should be over-excavated to a depth of 12 feet bgs
or 10 feet below lowest footing bottom elevation, whichever is less, and
replaced with properly compacted fill. The over-excavated areas should be
graded with a 1 percent gradient sloping toward the deeper fill areas, if
possible. The approximate limit of overexcavation is depicted on the
geotechnical map (Figure 2).
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6.1.5 Engineered Fill
The onsite soils are generally suitable for use as compacted fill provided
they are free of organic material, debris, and rock fragments larger than 6
inches in maximum dimension. All fill soils should be brought to at least
3 percent optimum moisture conditions (i.e., depending on the soil types)
and compacted in uniform lifts to at least 90 percent relative compaction
based on laboratory standard ASTM Test Method 01557, 95 percent for
wall backfill soils or if used for structural purposes (such as to support a
footing, wall, etc). The optimum lift thickness required to produce a
uniformly compacted fill will depend on the type and size of compaction
equipment used. In general, fill should be placed in lifts not exceeding 8
inches in thickness.
Placement and compaction of fill should be performed in general
accordance with the current City of Carlsbad grading ordinances, sound
construction practice, and the General Earthwork and Grading
Specifications for Rough Grading presented in Appendix D.
6.1.6 Earthwork Shrinkage/Bulking
The volume change of excavated onsite materials upon recompaction as
fill is expected to vary with material and location. Typically, the fill soils and
formational materials vary significantly in natural and compacted density,
and therefore, accurate earthwork shrinkage/bulking estimates cannot be
determined. However, based on the results of our geotechnical analysis
and our experience, a 5 percent shrinkage factor is considered
appropriate for the artificial fill and a 3 to 5 percent bulking factor is
considered appropriate for the Old Paralic Deposits and the Santiago
Formation.
6:1.7 Trench Backfill
Pipe bedding should consist of sand with a sand equivalent (SE) of not
less than 30. Bedding should be extended the full width of the trench for
the entire pipe zone, which is the zone from the bottom of the trench, to
one foot above the top of the pipe. The sand should be brought up evenly
on each side of the pipe to avoid unbalanced loads. Onsite materials will
probably not meet bedding requirements. Except for predominantly clayey
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soils, the onsite soils may be used as trench backfill above the pipe zone
(i.e. in the trench zone) provided they are free of organic matter and have
a maximum particle size of three inches. Compaction by jetting or flooding
is not recommended.
6.1.8 Expansive Soils and Selective Grading
Based on our laboratory testing and observations, we anticipate the onsite
soil materials possess a low to medium expansion potential (Appendix C).
Although not anticipated, should an abundance of highly expansive
materials be encountered, selective grading may need to be performed. In
addition, to accommodate conventional foundation design, the upper 5
feet of materials within the building pad and 5 feet outside the limits of the
building foundation should have a very low to low expansion potential
(Ek5O).
6.1.9 Import Soils
If import soils are necessary to bring the site up to the proposed grades,
these soils should be granular in nature, and have an expansion index
less than 50 (per ASTM Test Method 04829) and have a low corrosion
impact to the proposed improvements. Beneath pavements, subgrade
materials should possess an R-value of 30, or greater. Import soils and/or
the borrow site location should be evaluated by the geotechnical
consultant prior to import.
6.2 Temporary Excavations
Sloping excavations may be utilized when adequate space allows in accordance
with OSHA requirements. Based on the results of our update evaluation, we
provide the following recommendations for sloped excavations in fill soils or
competent Old Paralic Deposits and the Santiago Formation without seepage
conditions.
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Table 2
Maximum Slope Ratios
Maximum Slope Ratio
Excavation Depth Maximum Slope Ratio In Old Paralic Deposits
(feet) In Fill Soils and/or Santiago
Formation
0 to 5 1:1 (Horizontal to Vertical) Vertical
5 to 15 1:1 (Horizontal to Vertical) 1:1 (Horizontal to Vertical)
The above values are based on the assumption that no surcharge loading or
equipment will be placed within 10 feet of the top of slope. Care should be taken
during excavation adjacent to the existing structures so that undermining does
not occur. A "competent person" should observe the slope on a daily basis for
signs of instability.
6.3 Foundation Design Considerations
At the time of drafting this report, building loads were not known. However, based
on our understanding of the project, the proposed structure and settlement
sensitive improvements may be constructed with conventional foundations.
Foundations and slabs should be designed in accordance with structural
considerations and the following recommendations. These recommendations
assume that the soils encountered within 5 feet of pad grade have a low potential
for expansion (Ek50). If more expansive materials are encountered and
selective grading cannot be accomplished, revised foundation recommendations
may be necessary. The foundation recommendations below assume that the all
building foundations willtbe underlain by properly compacted fill.
6.3.1 Conventional Foundations
The proposed structure and settlement sensitive improvements may be
supported by conventional, continuous or isolated spread footings.
Footings should extend a minimum of 24 inches beneath the lowest
adjacent soil grade. At these depths, footings may be designed for a
maximum allowable bearing pressure of 4,000 pounds per square foot
(psf) if founded in dense compacted fill soils. The allowable bearing
pressures may also be increased by one-third when considering loads of
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short duration such as wind or seismic forces. The minimum
recommended width of footings is 18 inches for continuous footings and
24 inches for square or round footings.
6.3.2 Preliminary Slab Design S 11 C
Slabs on grade should be reinforced with reinforcing bars placed at slab
mid-height. Slabs should have crack joints at spacings designed by the
structural engineer. Columns, if any, should be structurally isolated from
slabs. Slabs should be a minimum of 5 inches thick and reinforced with
No. 3 rebars at 18 inches on center on center (each way). The slab should
be underlain by 2-inch layer of clean sand (S.E. greater than 30). A
moisture barrier (10-mil non-recycled plastic sheeting) should be placed
below the sand layer if reduction of moisture vapor up through the
concrete slab is desired (such as below equipment, living/office areas,
etc.), which is in turn underlain by an additional 2-inches of clean sand. If
applicable, slabs should also be designed for the anticipated traffic loading
using a modulus of subgrade reaction of 140 pounds per cubic inch. All
waterproofing measures should be designed by the project architect.
The slab subgrade soils underlying the foundation systems should be
presoaked in accordance with the recommendations presented in Table 3
prior to placement of the moisture barrier and slab concrete. The subgrade
soil moisture content should be checked by a representative of Leighton
prior to slab construction.
6.3.3 Foundation Setback
We recommend a minimum horizontal setback distance from the face of
slopes for all structural foundations, footings, and other settlement-
sensitive structures as indicated on the Table 3 below. This distance is
measured from the outside bottom edge of the footing, horizontally to the
slope face, and is based on the slope height. However, the foundation
setback distance may be revised by the geotechnical consultant on a case-
by-case basis if the geotechnical conditions are different than anticipated.
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Table 3
Minimum Foundation Setback from Slope Faces
Slope Height Setback
less than 5 feet.• 5 feet
5to15feet 7feet
15 to 30 feet 10 feet
Please note that the soils within the structural setback area possess poor
lateral stability, and improvements (such as retaining walls, sidewalks,
fences, pavements, etc.) constructed within this setback area may be
subject to lateral movement and/or differential settlement. Potential distress
to such imprOvements may be mitigated by providing a deepened footing or
a grade beam foundation system to support the improvement.
In addition, open or backfilled utility trenches .that parallel or nearly parallel
structure footings should not encroach within an imaginary 2:1 (horizontal
to vertical)' downward sloping line starting 9 inches above the bottom edge
of the footing and should also not be located closer than 18 inches from the
face of the footing. Deepened footings should meet the, setbacks as
described above. Also, over-excavation should be accomplished such that
deepening of footings to accomplish the setback will not introduce a cut/fill
transition bearing condition.
Where pipes may cross under footings, the footings should be specially
designed. Pipe sleeves should be provided where pipes cross through
footings or footing walls and sleeve clearances should provide for possible
footing settlement, but not less than 1 inch around the pipe.
6.3.4 Settlement
Fill depths between 12 and 22 feet are anticipated beneath the proposed
building foundations following final grading. For conventional footings, the
recommended allowable-bearing capacity is based on a maximum total
and differential static settlement of 3/4 inch and 1/2 inch, respectively.
Since settlements are a function of footing size and contact bearing
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pressures, some differential settlement can be expected where a large
differential loading condition exists. However for most cases, differential
settlements are considered unlikely to exceed 1/2 inch.
6.3.5 Moisture Conditioning
The slab subgrade soils underlying the foundation) systems should be
presoaked in accordance with the recommendations presented in Table 4
prior to placement of the moisture barrier and slab concrete. The subgrade
soil moisture content should be checked by a representative of Leighton
prior to slab construction.
Presoaking or moisture conditioning may be achieved in a number of ways.
But based on our professional experience, we have found that minimizing
the moisture loss on pads that have been completed (by periodic wetting to
keep the upper portion of the pad from drying out) and/or berming the lot
and flooding for a short period of time (days to a few weeks) are some of
the more efficient ways to meet the presoaking recommendations. If
flooding is performed, a couple of days to let the upper portion of the pad
dry out and form a crust so equipment can be utilized should be
anticipated.
Table 4
Presoaking Recommendations Based on Finish Grade Soil Expansion
Potential
Expansion Potential Presoaking Recommendations
Very Low Near-optimum moisture content to a minimum
depth of 6 inches
Low 120 percent of the optimum moisture content to
a minimum depth of 12 inches below slab
subgrade
Medium 130 percent of the Optimum moisture content to
a minimum depth of 18 inches below slab
subgrade
High 130 percent of the optimum moisture content to
a minimum depth of 24 inches below slab
subgrade
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6.4 Lateral Earth Pressures and Retaining Wall Design
Should retaining walls be added to the project, Table 5 presents the lateral earth
pressure values for level or sloping backfill for walls backfilled with and bearing
against fully drained soils of very low to low expansion potential (less than 50 per
ASTM D4829).
Table 5
Static Equivalent Fluid Weight (pcf)
Conditions Level 2:1 Slope
Active 35 55
At-Rest 55 65
Passive 3 50
(Maximum of 3 ksf)
150 (sloping down)
Walls up to 10 feet in height should be designed for the applicable equivalent
fluid unit weight values provided above. If conditions other than those covered
herein are anticipated, the equivalent fluid unit weight values should be provided
on an individual case-by-case basis by the geotechnical engineer. A surcharge
load for a restrained or unrestrained wall resulting from automobile traffic may be
assumed to be equivalent to a uniform lateral pressure of 75 psf which is in
addition to the equivalent fluid pressure given above. For other uniform
surcharge loads, a uniform pressure equal to 0.35q should be applied to the wall.
The wall pressures assume walls are backfilled with free draining materials and
water is not allowed to accumulate behind walls. A typical drainage design is
contained in Appendix D. Wall backfill should be compacted by mechanical
methods to at least 90 percent relative compaction (based on ASTM D1557). If
foundations are planned over the backfill, the backfill should be compacted to 95
percent. Wall footings should be designed in accordance with the foundation
design recommendations and reinforced in accordance with structural
considerations. For all retaining walls, we recommend a minimum horizontal
distance from the outside base of the footing to daylight as outlined in
Section 6.3.3.
Lateral soil resistance developed against lateral structural movement can be
obtained from the passive pressure value provided above. Further, for sliding
resistance, the friction coefficient of 0.35 may be used at the concrete and soil•
interface. These values may be increased by one-third when considering loads of
q
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short duration including wind or seismic loads. The total resistance may be taken
as the sum of the frictional and passive resistance provided that the passive
portion does not exceed two-thirds of the total resistance.
To account for potential redistribution of forces during a seismic event, retaining
walls providing lateral support where exterior grades on opposites sides differ by
more than 6 feet fall under, the requirements of 2013 CBC Section 1803.5.12
and/or ASCE 7-10 Section 15.6.1 should also be analyzed for seismic loading.
For that analysis, an additional uniform lateral seismic force of 8H should be
considered for the design of the retaining walls with level backfill, where H is the
height of the wall. This value should be increased by 150% for restrained walls.
Based on the geotechnical conditions of the site, the recommended soil
parameters presented on Table 6 should be utilized in the design of the proposed
MSE retaining walls, if any. Temporary sloping should be performed in
accordance-with current OSHA requirements.
Table 6
Retaining Wall Soil Parameters
Soil Parameter Reinforced
Zone
Retained Zone Foundation
Zone
Internal Friction Angle
(degrees)
30 28 30
Cohesion (psf) 0 0 0
Total Unit Weight (pcf) 128 125 128
Additional details relevant to the design of the MSE wall are presented on Detail
G - Segmental Retaining Walls in Appendix D - General Earthwork and Grading
Specifications. In addition, we recommend that water should be prevented from
infiltrating into the reinforced soil zone. All drains and swales should outlet to
suitable locations as determined by the project civil engineer. In general, the
project civil engineer should verify that the subdrain is connected to the proper
drainage facility.
Note that we also recommend a 7 foot minimum horizontal setback distance from
the face of slopes for all retaining wall footings. This distance is measured from
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the outside bottom edge of the footing, horizontally to the slope face and is based
on the slope height and type of soil. Appropriate surcharge pressures should also
be applied for walls influenced within the retained or reinforced zones by
improvements or vehicular traffic. The wall design engineer should also select
grid design strength based on deflections tolerable to the proposed
improvements. Settlement sensitive structures should not be located within the
reinforced zone or active backfill prism.
6.5 Geochemical Considerations
Concrete in direct contact with soil or water that contains a high concentration of
soluble sulfates can be subject to chemical deterioration commonly known as
"sulfate attack." Soluble sulfate results • (Appendix C) indicated a negligible
soluble sulfate content. We recommend that concrete in contact with earth
materials be designed in accordance with Section 4 of ACI 318-11 (ACI, 2011).
Based on the results of preliminary screening laboratory testing, the site soils
have a generally high corrosion. potential to buried uncoated metal conduits. We
recommend measures to mitigate corrosion be implemented during design and
construction.
6.6 Concrete Flatwork
Concrete sidewalks and other flatwbrk (including construction joints) should be
designed by the project civil engineer and should have a minimum thickness of 4
inches. For all concrete flatwork, the upper 12 inches of subgrade soils should be
moisture conditioned to at least 2 percent above optimum moisture content and
compacted to at least 90 percent relative compaction based on ASTM Test
Method D1557 prior to the concrete placement. These recommendations are
assuming low expansive materials are present within the upper 2 feet below
subgrade. If medium to highly expansive material are present at subgrade, these
areas should be moisture conditioned in accordance with Section 6.3.5.
Control joints should be provided at a distance equal to 24 times the slab
thickness in inches, not exceed 12 feet. Expansion joints should be incorporated
where paving abuts a vertical surface, where paving changes direction and at 30
feet maximum spacing, joints should be laid out so as to create square or nearly
square areas. Sidewalks should be reinforced with 6x6-6/6, or heavier, welded
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wire mesh slip dowels should be provided across control joints along ADA
walkways, curbs, and at doorways.
6.7 Surface Drainage and Erosion
Surface drainage should be controlled at all times. The proposed structures
should have appropriate drainage systems to collect runoff: Positive surface
drainage should be provided to direct surface water away from the structure
toward suitable drainage facilities. In general, ponding of water should be
avoided adjacent to the structure or pavements. Over-watering of the site should
be avoided. Protective measures to mitigate excessive site erosion during
construction should also be implemented in accordance with the latest City of
Carlsbad grading ordinances.
6.8 Plan Review
Final project grading and foundation plans should be reviewed by Leighton as
part of the design development process to ensure that recommendations in this
report are incorporated in project plans.
6.9 Construction Observation
The recommendations provided in this report are based on prelimiary design
information, our experience during rough grading, and subsurface conditions
disclosed by widely spaced excavations. The interpolated subsurface conditions
should be checked in the field during construction. Construction observation of all
onsite excavations and should be performed by a representative of this office so
that construction is in accordance with the recommendations of this report. All
footing excavations should be reviewed by this office prior to steel placement.
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7.0 LIMITATIONS
The conclusions and recommendations in this report are based in part upon field
exploration and our previous geotechnical study with widely spaced subsurface
explorations. Such information is by necessity incomplete. The nature of many sites is
such that differing geotechnical or geological conditions can occur within small
distances and under varying climatic conditions. Changes in subsurface conditions can
and do occur over time. Therefore, the findings, conclusions, and recommendations
presented in this report can be relied upon only if Leighton has the opportunity to
observe the subsurface conditions during grading and construction of the project, in
order to confirm that our preliminary findings are representative for the site.
FA
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References
10075.011
APPENDIX A
References
American Concrete Institute (Ad), 2011, Building Code Requirements for Structural
Concrete (ACI 318-11) and Commentary.
Bryant, W. A. and Hart, E. W., 2007, Fault Rupture Hazard Zones in California, Alquist-
Priolo Special Studies Zones Act of 1972 with Index to Special Study Zone Maps,
Department of Conservation, Division of Mines and Geology, Special Publication
42, dated 1997 with 2007 Interim Revision.
California Building Standards Commission (CBSC), 2013, California Building Code,
Volumes I and 2.
Kennedy, M.P., and Tan, S.S., 2007, 'Geologic Map of the Oceanside 30'x60'
Quadrangle, California, California Geologic Survey, 1:100,000 scale.
Leighton and Associates, Inc., 1995, Preliminary Geotechnical Investigation, Lego
Family Park and Pointe Resorts, Lots 17 and 18 of the Carlsbad Ranch,
Carlsbad, California, Project No. 950294-001, dated October 5, 1995.
1996, Supplemental Geotechnical Investigation, Lego Family Park,
Carlsbad Ranch, Carlsbad, California, Project No. 960151-001, dated July 23.
1998, Final As-Graded Report of Rough-Grading, LEGOLLAND, Carlsbad,
California, Project No. 4960151-003, dated February 10.
Tan, S. S. and Kennedy, M. P., 1996, Geologic Maps of the Northwestern Part of San
Diego County, California, Division of Mines and Geology (0MG) Open-File
Report 96-02, San Luis Rey and San Marcos Quadrangles.
Treirnan, J.A., 1993, The Rose Canyon Fault Zone, Southern California: California
Division of Mines and Geology, Open-File Report 93-02,45 p.
A-I
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APPENDIX A (Continued)
United States Geologic Survey (USGS), 2008, US Seismic Design Map Tool/Calculator,
Version 3.1.0.
F.
A-2
APPENDIX B
Boring Logs
APPENDIX C
Laboratory Testing Procedures and Test Results
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APPENDIX C
Laboratory Testing Procedures and Test Results
Consolidation Tests: Consolidation tests were performed on selected, relatively•
undisturbed ring samples in accordance with Modified ASTM Test Method D2435.
Samples were placed in a consolidometer and loads were applied in geometric
progression. The percent consolidation for each load cycle was recorded as the ratio of
the amount of vertical compression to the original 1-inch height. The consolidation
pressure curves are presented on the attached figures.
Direct Shear Test: A remolded direct shear test was performed on a selected bulk
sample which was soaked for a minimum of 24 hours under a surcharge equal to the
applied normal force during testing. After transfer of the sample to the shear box and
reloading of the sample, the pore pressures set up in the sample (due to the transfer)
were allowed to dissipate for a period of approximately 1 hour prior to application of
shearing force. The sample was tested under various normal loads utilizing a motor-
driven, strain-controlled, direct-shear testing apparatus at a strain rate of 'less 0.05 inches
per minute. The test result is presented on the attached figure.
Expansion Index Tests: The expansion potential of selected material was evaluated by
the Expansion Index Text, ASTM Test Method 4829. The specimen was molded under a
given compactive energy to approximately 50 percent saturation. The prepared 1-inch
thick by 4-inch diameter specimen was loaded to an equivalent 144 psf surcharge and
was inundated with water until volumetric equilibrium was reached. The result of this test
is presented in the table below:
Sample Location Sample Description Expansion
Index
Expansion
Potential
B-5 @ I - 5 feet Sandy Lean CLAY 46 Low
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APPENDIX C (Continued)
Moisture and Density Determination Tests: Moisture content (ASTM Test Method D2937)
and dry density determinations were performed on relatively undisturbed ring samples
obtained from the test borings. The results of these tests are presented in the
geotechnical boring logs (Appendix B).
Soluble Sulfates: The soluble sulfate content of a selected sample was determined by
standard geochemical methods (Caltrans Test Method C1417). The test result is
presented in the table below:
Sample Location Sulfate Potential Degree of Sulfate
Cohtent (%) Attack*
B-5 @ 1 -5 feet 0.013 Negligible
* Based on the 2008 edition of American Concrete Institute (ACl) Committee 318R,
Table No. 4.2.1.
Chloride Content: Chloride content was tested. in accordance with DOT Test Method No.
422. The results are presented below:
Sample Location Chloride Content, ppm
B-5 @ I - 5 feet 307
Minimum Resistivity-and DH Tests: Minimum resistivity and pH tests were performed in
general accordance with California Test Method 643. The results are presented in the
table below:
Sample Location . pH Minimum Resistivity
(ohms-cm)
B-5 @ 1 -5 feet 752 1080
C-2
APPENDIX D
General Earthwork and Grading Specifications for Rough Grading
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
1.0 General
1.1 Intent
These General Earthwork and Grading Specifications are for the grading
and earthwork shown on the approved grading plan(s) and/or indicated in
the geotechnical report(s). These Specifications are a part of the
recommendations contained in the geotechnical report(s). In case of
conflict, the specific recommendations in the geotechnical report shall
supersede these more general Specifications. Observations of the
earthwork by the project Geotechnical Consultant during the course of
grading may result in new or revised recommendations that could
supersede these specifications or the recommendations in the
geotechnical report(s).
1.2 The Geotechnical Consultant of Record
Prior to commencement of work, the owner shall employ the Geotechnical
Consultant of Record (Geotechnical Consultant). The Geotechnical
Consultants shall be responsible for reviewing the approved geotechnical
report(s) and accepting the adequacy of the preliminary geotechnical
findings, conclusions, and recommendations prior to the commencement
of the grading.
Prior to commencement of grading, the .Geotechnical Consultant shall
review the "work plan" prepared by the Earthwork Contractor (Contractor)
and schedule sufficient personnel to perform the appropriate level of
observation, mapping, and compaction testing.
During the grading and earthwork operations, the Geotechnical Consultant
shall observe, map, and document the subsurface exposures to verify the
geotechnical design assumptions. If the observed conditions are found to
be significantly different than the interpreted assumptions during the
design phase, the Geotechnical Consultant shall inform the owner,
recommend appropriate changes in design to accommodate the observed
conditions, and notify the review agency where required. Subsurface
areas to be geotechnically observed, mapped, elevations recorded, and/or
tested include natural ground after it has been cleared for receiving fill but
before fill is placed, bottoms of all "remedial removal" areas, all key
bottoms, and benches made on sloping ground to receive fill.
The Geotechnical Consultant shall observe the moisture-conditioning and
processing of the subgrade and fill materials and perform relative
compaction testing of fill to determine the attained level of compaction.
The Geotechnical Consultant shall provide the test results to the owner
and the Contractor on a routine and frequent basis.
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LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
1.3 The Earthwork Contractor
The Earthwork Contractor (Contractor) shall be qualified, experienced,
and knowledgeable in earthwork logistics, preparation and processing of
ground to receive fill, moisture-conditioning and processing of fill, and
compacting fill. The Contractor shall review and accept the plans,
geotechnical report(s), and these Specifications prior to commencement of
grading. The Contractor shall be solely responsible for performing the
grading in accordance with the plans and specifications.
The Contractor shall prepare and submit to the owner and the
Geotechnical Consultant a work plan that indicates the sequence of
earthwork grading, the number of "spreads" of work and the estimated
quantities of daily earthwork contemplated for the site prior to
commencement of grading. The Contractor shall inform the owner and
the Geotechnical Consultant of changes in work schedules and updates to
the work plan at least 24 hours in advance of such changes so that
appropriate observations and tests can be planned and accomplished.
The Contractor shall not assume that the Geotechnical Consultant is
aware of all grading operations.
The Contractor shall have the sole responsibility to provide adequate
equipment and methods to accomplish the earthwork in accordance with
the applicable grading codes and agency ordinances, these
Specifications, and the recommendations in the approved geotechnical
report(s) and grading plan(s). If, in the opinion of the Geotechnical
Consultant, unsatisfactory conditions, such as unsuitable soil, improper
moisture condition, inadequate compaction, insufficient buttress key size,
adverse weather, etc., are resulting in a quality of work less than required
in these specifications, the Geotechnical Consultant shall reject the work
and may recommend to the owner that construction be stopped until the
conditions are rectified.
2.0 Preparation of Areas to be Filled
2.1 Clearing and Grubbing
Vegetati6n, such as brush, grass, roots, and other deleterious material
shall be sufficiently removed and properly disposed of in a method
acceptable to the owner, governing agencies, and the Geotechnical
Consultant.
-2-
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
The Geotechnical Consultant shall evaluate the extent of these removals
depending on specific site conditions. Earth fill material shall not contain
more than 1 percent of organic materials (by volume). No fill lift shall
contain more than 5 percent of organic matter. Nesting of the organic
materials shall not be allowed.
If potentially hazardous materials are encountered, the Contractor shall
stop work in the affected area, and a hazardous material specialist shall
be informed immediately for proper evaluation and handling of these
materials prior to continuing to work in that area.
As presently defined by the State of California, most refined petroleum
products (gasoline, diesel fuel, motor oil, grease, coolant, etc.) have
chemical constituents that are considered to be hazardous waste. As
such, the indiscriminate dumping or spillage of these fluids onto the
ground may constitute a misdemeanor, punishable by fines and/or
imprisonment, and shall not be allowed.
2.2 Processinci
Existing ground that has been declared satisfactory for support of fill by
the Geotechnical Consultant shall be scarified to a minimum depth of
6 inches. Existing ground that is not satisfactory shall be overexcavated
as specified in the following section. Scarification shall continue until soils
are broken down and free of large clay lumps or clods and the working
surface is reasonably uniform, flat, and free of uneven features that would
inhibit uniform compaction.
2.3 Overexcavation
In addition to removals and overexcavations recommended in the
approved geotechnical report(s) and the grading plan, soft, loose, dry,
saturated, spongy, organic-rich, highly fractured or otherwise unsuitable
ground shall be overexcavated to competent ground as evaluated by the
Geotechnical Consultant during grading.
2.4. Benchinci
Where fills are to be placed on ground with slopes steeper than 5:1
(horizontal to vertical units), the ground shall be stepped or benched.
Please see the Standard Details for a graphic illustration. The lowest
bench or key shall be a minimum of 15 feet wide and at least 2 feet deep,
into competent material as evaluated by the Geotechnical Consultant.
Other benches shall be excavated a minimum height of 4 feet into
competent material or as otherwise recommended by the Geotechnical
/
-3-
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
Consultant. Fill placed on ground sloping flatter than 5:1 shall also be
benched or otherwise overexcavated to provide a flat subgrade for the fill.
2.5 Eva luation/AcceDtance of Fill Areas
All areas to receive fill, including removal and processed areas, key
bottoms, and benches, shall be observed, mapped, elevations recorded,
and/or tested prior to being accepted by the Geotechnical Consultant as
suitable to receive fill. The Contractor shall obtain a written acceptance
from the Geotechnical Consultant prior to fill placement. A licensed
surveyor shall provide the survey control for determining elevations of
processed areas, keys, and benches.
3.0 Fill Material
3.1 General
Material to be used as fill shall be essentially free of organic matter and
other deleterious substances evaluated and accepted by the Geotechnical
Consultant prior to placement. Soils of poor quality, such as those with
unacceptable gradation, high expansion potential, or low strength shall be
placed in areas acceptable to the Geotechnical Consultant or mixed with
other soils to achieve satisfactory fill material.
3.2 Oversize -
Oversize material defined as rock, or other irreducible material with a
maximum dimension greater than 8 inches, shall not be buried or placed
in fill unless location, materials, and placement methods are specifically
accepted by the Geotechnical Consultant. Placement operations shall be
such that nesting of oversized material does not occur and such that
oversize material is completely surrounded by compacted or densified fill.
Oversize material shall not be placed within 10 vertical feet of finish-grade
or within 2 feet of future utilities or underground construction.
3.3 lmort
If importing of fill material is required for grading, proposed import material
shall meet the requirements of Section 3.1. The potential import source
shall be given to the Geotechnical Consultant at least 48 hours (2 working
days) before importing begins so that its suitability can be determined and
appropriate tests performed.
-4-
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
4.0 Fill Placement and Compaction
4.1 Fill Layers
Approved fill material shall be placed in areas prepared to receive fill (per
Section 3.0) in near-horizontal layers not exceeding 8 inches in loose
thickness. The Geotechnical Consultant may accept thicker layers if
testing indicates the grading procedures can adequately compact the
thicker layers. Each layer shall be spread evenly and mixed thoroughly to
attain relative uniformity of material and moisture throughout.
4.2 Fill Moisture Conditioning
Fill soils shall be watered, dried back, blended, and/or mixed, as
necessary to attain a relatively uniform moisture content at or slightly over
optimum. Maximum density and optimum soil moisture content tests shall
be performed in accordance with the American Society of Testing and
Materials (ASTM Test Method D1557).
4.3 Compaction of Fill
After each layer has been moisture-conditioned, mixed, and evenly
spread, it shall be uniformly compacted to not less than 90 percent of
maximum dry density (ASTM Test Method D1557). Compaction
equipment shall be adequately sized and be either specifically designed
for soil compaction or of proven reliability to efficiently achieve the
specified level of compaction with uniformity.
4.4 Compaction of Fill Slopes
In addition to normal compaction procedures specified above, compaction
of slopes shall be accomplished by backrolling of slopes with sheepsfoot
rollers at increments of 3 to 4 feet in fill elevation, or by other methods
producing satisfactory results acceptable to the Geotechnical Consultant.
Upon completion of grading, relative compaction of the fill, out to the slope
face, shall be at least 90 percent of maximum density per ASTM Test
Method D1557. -
4.5 Compaction Testing
Field-tests for moisture content and relative compaction of the fill soils
shall be performed by the Geotechnical Consultant. Location and
frequency of tests shall be at the Consultant's discretion based on field
conditions encountered. Compaction test locations' will not necessarily be
selected on a random basis. Test locations shall be selected to verify
adequacy of compaction levels in areas that are judged to be prone to
-5-
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
inadequate compaction (such as close to slope faces and at the
fill/bedrock benches).
4.6 Frequency of Compaction Testing
Tests shall be taken al intervals not exceeding 2 feet in vertical rise and/or
1,000 cubic yards of compacted fill soils embankment. In addition, as a
guideline, at least one test shall be taken on slope faces for each
5,000 square feet of slope face and/or each 10 feet of vertical height of
slope. The Contractor shall assure that fill construction is such that the
testing schedule can be accomplished by the Geotechnical Consultant.
The Contractor shall stop or slow down the earthwork construction if these
minimum standards are not met.
4.7 Compaction Test Locations
The Geotechnical Consultant shall document the approximate elevation
and horizontal coordinates of each test location. The Contractor shall
coordinate with the project surveyor to assure that sufficient grade stakes
are established so that the Geotechnical Consultant can determine the
test locations with sufficient accuracy. At a minimum, two grade stakes
within a horizontal distance of 100 feet and vertically less than 5 feet apart
from potential test locations shall be provided.
5.0 Subdrain Installation
Subdrain systems shall be installed in accordance with the approved
geotechnical report(s), the grading plan, and the Standard Details. The
Geotechnical Consultant may recommend additional subdrains and/or changes in
subdrain extent, location, grade, or material depending on conditions
encountered during grading. All subdrains shall be surveyed by a land
surveyor/civil engineer for line and grade after installation and prior to burial.
Sufficient time should be allowed by the Contractor for these surveys.
6.0 Excavation
Excavations, as well as over-excavation for remedial purposes, shall be
evaluated by the Geotechnical Consultant during grading. Remedial removal
depths shown on geotechnical plans are estimates only. The actual extent of
removal shall be determined by the Geotechnical Consultant based on the field
evaluation of exposed conditions during grading. Where fill-over-cut slopes are
to be graded, the cut portion of the slope shall be made, evaluated, and accepted
by the Geotechnical Consultant prior to placement of materials for construction of
the fill portion of the slope, unless otherwise recommended by the Geotechnical
Consultant.
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
7.0 Trench Backfills
7.1 Safety
The Contractor shall follow all OSHA and Cal/OSHA requirements for
safety of trench excavations.
7.2 Bedding and Backfill
All bedding and backfill of utility trenches shall be performed in
accordance with the applicable provisions of Standard Specifications of
Public Works Construction. Bedding material shall have a Sand
Equivalent greater than 30 (SE>30). The bedding shall be placed to 1 foot
over the top of the conduit and densified. Backfill shall be placed and
densified to a minimum of 90 percent of relative compaction from 1 foot
above the top of the conduit to the surface.
The Geotechnical Consultant shall test the trench backfill for relative
compaction. At least one test should be made for every 300 feet of trench
and 2 feet of fill.
7.3 Lift Thickness
Lift thickness of trench backfill shall not exceed those allowed in the
Standard Specifications of Public Works Construction unless the
Contractor can demonstrate to the Geotechnical Consultant that the fill lift
can be compacted to the minimum relative compaction by his alternative
equipment and method.
7.4 Observation and Testing
The densification of the bedding around the conduits shall be observed by
the Geotéchnical Consultant.
-7-
PROJECTED PLANE 1:1-
(HORIZONTAL: VERTICAL)
MAXIMUM FROM TOE
OF SLOPE TO
APPROVED GROUND
EXISTING
GROUND SURFACE
'REMOVE
UNSUITABLE
c BENCH HEIGHT I MATERIAL
(4 FEET TYPICAL)
2 FEET MIN
KEY DEPTH BENCH (KEY)
FILL-OVER-CUT SLOPE
EXISTING
GROUND SURFACE --x-x:-Y-_
J -
LBENCH HEIGHT .i- - I ' (4 FEET TYPICAL)
-
CUT FACE
SHALL BE CONSTRUCTED PRIOR TO
FILL PLACEMENT TO ALLOW VIEWiNG // OF GEOLOGIC CONDITIONS
EXISTING
GROUND CUT-OVER-FILL SLOPE SURFACE -
-
k15
L
7 FEET
FEET MIN.-
LOWEST
BENCH (KEY)
MIN. KEY
DEPTH
CUT FACE SHALL BE
CONSTRUCTED PRIOR
TO FILL PLACEMENT
REMOVE
UNSUITABLE
MATERIAL
OVERBUILD A
TRIM BACK
DESIGN SLOPE
PROJECTED PLANE
1 TO 1 MAXIMUM
FROM TOE OF SLOPE
TO APPROVED GROUND -
-, I 15 FEET MIN.
2 FEET MIN:- LOWEST
KEY DEPTH BENCH (KEY)
UNSUITABLE
MATERIAL
BENCH HEIGHT
(4 FEET TYPICAL)
BENCHING SHALL BE DONE WHEN SLOPE'S
ANGLE IS EQUAL TO OR GREATER THAN 5:1.
MINIMUM BENCH HEIGHT SHALL BE 4 FEET
AND MINIMUM FILL WIDTH SHALL BE 9 FEET.
GENERAL EARTHWORK AND
KEYING AND BENCHING GRADING SPECIFICATIONS
STANDARD DETAIL A ki
GRADE
SLOPE FACE
OVERSIZE WINDROW
OVERSIZE ROCK IS LARGER THAN
8 INCHES IN LARGEST DIMENSION.
EXCAVATE A TRENCH IN THE COMPACTED
FILL DEEP ENOUGH TO BURY ALL THE
ROCK.
BACKFILL WITH GRANULAR SOIL JETTED
OR FLOODED IN PLACE TO FILL ALL THE
VOIDS.
DO NOT BURY ROCK WITHIN 10 FEET OF
FINISH GRADE.
W1NDROW OF BURIED ROCK SHALL BE
PARALLEL TO THE FINISHED SLOPE.
-.---------.,
y -
GRANULAR MATERIAL TO BE"DETAIL DENSIFIED IN PLACE BY
FLOODING OR JETTING.
-----j- -m1
GRANULAR MATERIAL
TYPICAL PROFILE ALONG WINDROW
OVERSIZE ROCK
DISPOSAL
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL B
i4ft
EXISTING
GROUND
GROUND SURFACE
: EJE' -------------------
-----------------------------------
REMOVE
UNSUITABLE
MATERIAL BE NCHING
SUBDRAIN
TRENCH
SEE DETAIL BELOW
FILTER FABRIC
/ (MIRAFI 140N OR APPROVED 6 MIN. EQUIVALENT)' OVERLAP
CALTRANS CLASS 2 PERMEABLE :..:-..i ]" MIN.
OR fl2 ROCK (9Fr3/FT) WRAPPED ::'.--.
1COVER
IN FILTER FABRIC •• •• ..s I t:,
4 J 4 MIN. BEDDING
t
COLLEC FOR PIPE SHALL
BE MINIMUM 6 DIAMETER
SCHEDULE 40 pvc PERFORATED
PIPE. SEE STANDARD DETAIL D
FOR PIPE SPECIFICATIONS
SUBDRAIN DETAIL
DESIGN FINISH
GRADE 4iT
/ io MIN. ,..FILTER FABRIC
:- tBACKFIL1 ' (MIRAFI 140N OR APPROVED
/ EQUIVALENT)
-CALTRANS CLASS 2 PERMEABLE
IN FILTER FABRIC
20' MIN. ' 5' MIN. PERFORATED
NONPERFORATED 6" 0 MIN.
6" 0 MIN. PIPE
DETAIL OF CANYON SUBDRAIN OUTLET
CANYON SUBDRAINS GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL
15' MIN. -
OUTLET PIPES
4" 0 NONPERF'ORATED PIPE.
100' WAX. O.C. HORIZONTALLY,
30' MAX O.C. VERTICALLY
-BACK CUT
1: 1 OR FLATTER
-BENCH
SEE SUBDRAIN TRENCH
DETAIL
LOWEST SUBDRAIN SHOULD
BE SITUATED AS LOW AS
POSSIBLE TO ALLOW
SUITABLE OUTLET
KEY WIDTH
' AS NOTED ON GRADING PLANS
i
12" MIN. OVERLAP -KEY DEPTH (15' MIN.) FROM THE TOP H01 (2' MIN.) RIND TIED EVERY I
6 FEET I T-CONNECTION
FOR COLLECTOR
PERMEABLE OR 12 / PIPE TO OUTLET PIPE CALTRANS CLASS II
ROCK (3 FT-3/FT)
WRAPPED IN FILTER WIN. FABRIC COVER
PERFORATED
4"ø 4" 0
NON-PERFORATED PIPE OUTLET PIPE
4" MIN.
- -
PROVIDE POSITIVE FILTER FABRIC BEDDING
SEAL AT THE ENVELOPE (MIRAFI
JOINT 140 OR APPROVED
EQUIVALENT)
SUBDRAIN TRENCH DETAIL
SUBDRAIN INSTALLATION - subdroin collector pipe shall be installed with perforation down or,
unless otherwise designated by the geotechnicol consultant. Outlet pipes shall be non-perforoted
pipe. The subdroin pipe shall have at least 8 perforations uniformly spaced per foot. Perforation
sholl be 1/4" to 1/2" if drill holes ore used. All subdroin pipes sholl hove o gradient of at
least 2% towards the outlet.
SUBDRAIN PIPE - Subdroin pipe shall be ASTM D2751, SOR 23.5 or ASTM D1527, Schedule 40, or
ASTM D3034, SDR 23.5. Schedule 40 Polyvinyl Chloride Plastic (PVC) pjpe.
All outlet pipe sholl be placed in a trench no wider than twice the subdroin pipe.
BUTTRESS OR GENERAL EARTHWORK AND
REPLACEMENT GRADING SPECIFICATIONS
FILL SUBDRAINS STANDARD DETAIL D
vi
CUT-FILL TRANSITION LOT OVEREXCAVATION
REMOVE -
H.
UNSUITABLE
GROUND
- -r - - -
-r5 - IMIN. I pr
MIN "
- -COMPACTED FII±
------------
- -
'. OVEREXCAVATE
AND RECOMPACT
- - - - - - -...TYPICAL BENCHING -p.--
- - UNWEATI-ERED BEDROCK OR MATERIAL APROVED
BY THE GEOTECHNICAL CONSULTANT
TRANSITION LOT FILLS
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL E 4
SOIL BACKFILL COMPACTED TO
90 PERCENT RELATIVE COMPACTION
BASED ON ASTM D1557
RETAINING WALL-..
WALL WATERPROOFING --— OVERLAP 'FILTER FABRIC ENVELOPE
PER ARCHITECTS • o• --(MIRAFI 140N OR APPROVED
SPECIFICATIONS ..
o .01 :-i.:: EQUIVALENT)"
0
V MIN. __3/4" TO 1-1/2" CLEAN GRAVEL
FINISH GRADE
• 4 (MIN.) DIAMETER PERFORATED
'o -:--: PVC PIPE (SCHEDULE 40 OR
/ • .-..-:- EQUIVALENT) WITH PERFORATIONS
0
:-:-:-:-. ORIENTED DOWN AS DEPICTED
FIL TO SUITABLE OUTLET l I :11 MU.JIMUM1PERCENT GRADIENT
..:-E----_3 - MIN.
WALL FOOliNG I
COMPETENT BEDROCK OR MATERIAL
AS EVALUATED BY THE GEOTECHNICAL
CONSULTANT
NOTE: UPON REVIEW BY THE GEOTECHNICAL CONSULTANT,
COMPOSITE DRAINAGE PRODUCTS SUCH AS MIRADRAIN OR
J-DRAIN MAY BE USED AS AN ALTERNATIVE TO GRAVEL OR
CLASS 2 PERMEABLE MATERIAL. INSTALLATION SHOULD BE
PERFORMED IN ACCORDANCE WITH MANUFACTURER'S
SPECIFICATIONS.
RETAINING WALL
DRAINAGE
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL F 4
OUTLET SUBDRAINS EVERY 100 FEET, OR CLOSER,
BY TIGHTLINE TO SUITABLE PROTECTED OUTLET
GRAVEL DRAINAGE FILL
SIEVE SIZE % PASSING
1 INCH 100
3/4 INCH 75-100
NO.4 0-60
NO. 40 0-50
FOR WALL HEIGHT < 10 FEET, PLASTICITY INDEX <20 NO. 200 0-5
FOR WALL HEIGHT 10 TO 20 FEET, PLASTICITY INDEX < 10
FOR TIERED WALLS, USE COMBINED WALL HEIGHTS
WALL DESIGNER TO REQUEST SITE-SPECIFIC CRITERIA FOR WALL HEIGHT >20 FEET
NOTES:
1) MATERIAL GRADATION AND PLASTICITY
SIEVE SIZE % PASSING
1 INCH 100
NO.4 20-100
NO. 40 0-60
NO. 200 0-35
ACTIVE
ZONE
- FILTER FABRIC
REINFORCED 1.
ZONE
: : : : . : - : . : . : . : : - : :
-fILTER FABRIC -:- •:• .
-;_-• --;•1—— :-;-;-;-;
(C
RETAINED
ZONE
TO 70% OF
WALL HEIGHT
GRAVEL—
DRAINAGE FILL
MIN 6" BELOW WALL
MIN 12' BEHIND UNITS
I FOUNDATION SOILSI
SUBDRAIN
REAR SUBDRAIN:
4" (MIN) DIAMETER PERFORATED PVC PIPE
(SCHEDULE 40 OR EQUIVALENT) WITH
PERFORATIONS DOWN. SURROUNDED BY
I CU. FT/FT OF 3/4" GRAVEL WRAPPED IN
FILTER FABRIC (MIRAFI 140N OR EQUIVALENT)
CONTRACTOR TO USE SOILS WITHIN THE RETAINED AND REINFORCED ZONES THAT MEET THE STRENGTH REQUIREMENTS OF WALL DESIGN.
GEOGRID REINFORCEMENT TO BE DESIGNED BY WALL DESIGNER CONSIDERING INTERNAL, EXTERNAL, AND COMPOUND STABILITY.
3) GEOGRID TO BE PRETENSIONED DURING INSTALLATION.
IMPROVEMENTS WITHIN THE ACTIVE ZONE ARE SUSCEPTIBLE TO POST-CONSTRUCTION SETTLEMENT. ANGLE cx=45+cb/2, WHERE 4 IS THE
FRICTION ANGLE OF THE MATERIAL IN THE RETAINED ZONE.
BACKDRAIN SHOULD CONSIST OF J-DRAIN 302 (OR EQUIVALENT) OR 6-INCH THICK DRAINAGE FILL WRAPPED IN FILTER FABRIC. PERCENT
COVERAGE OF BACKDRAIN TO BE PER GEOTECHNICAL REVIEW.
SEGMENTAL I GENERAL EARTHWORK AND I GRADING SPECIFICATIONS RETAINING WALLS I STANDARD DETAIL
APPENDIX E
GBC Insert
Geol ochnical-Engineering Report
Geotechnical Services Are Performed for
Specific Purposes, Persons, and Projects
Geotechnical engineers structure their services to meet the
specific needs of their clients. A geotechnical-engineering
study conducted for a civil engineer may not fulfill the needs of
a constructor - a construction contractor - or even another
civil engineer. Because each geotechnical- engineering study
is unique, each geotechnical-engineering report is unique,
prepared solely for the client. No one except you should rely on
this geotechnical-engineering report without first conferring
with the geotechnical engineer who prepared it. And no one
- not even you - should apply this report for any purpose or
project except the one originally contemplated.
Read the Full Report
Serious problems have occurred because those relying on
a geotechnical-engineering report did not read it all. Do
not rely on an executive summary. Do not read selected
elements only.
Geotechnical Engineers Base Each Report on
a Unique Set of Project-Specific Factors
Geotechnical engineers consider many unique, project-specific
factors when establishing the scope of a study. Typical factors
include: the client's goals, objectives, and risk-management
pieferences; the general nature of the structure involved, its
size, and configuration; the location of the structure on the
site; and other planned or existing site improvements, such as
access roads, parking lots, and underground utilities. Unless
the geotechnical engineer who conducted the study specifically
indicates otherwise, do not rely on a geotechnical-engineering
report that was:
not prepared for you;
not prepared for your project;
not prepared for the specific site explored; or
completed before important project changes were made.
Typical changes that can erode the reliability of an existing
geotechnical-engineering report include those that affect:
the function of the proposed structure, as when it's changed
from a parking garage to an office building, or from alight-
industrial plant to a refrigerated warehouse;
the elevation, configuration, location, orientation, or weight
of the proposed structure;
the composition of the design team; or
project ownership.
As a general rule, always inform your geotechnical engineer
of project changes—even minor ones—and request an
assessment of their impact. Geotechnical engineers cannot
accept responsibility or liabilityforproblenms that occur because
their reports do not consider developments of which they were
not informed.
Subsurface Conditions Can Change
A geotechnical-engineering report is based on conditions that
existed at the time the geotechnical engineer performed the
study. Do not rely on a geotechnical-engineering report whose
adequacy may have been affected by. the passage of time;
than-made events, such as construction on or adjacent to the
site; or natural events, such as floods, droughts, earthquakes,
or groundwater fluctuations. Contact the geotechnical 'engineer
before applying this report to determine if it is still reliable. A
minor amount of additional testing or analysis could prevent
'major problems.
Most Geotechnical Findings Are Professional
Opinions
Site exploration identifies subsurface conditions only at those
points where subsurface tests are conducted or samples are
taken. Geotechnical engineers review field and laboratory
data and then apply their professional judgment to render
an opinion about subsurface conditions throughout the
site. Actual subsurface conditions may differ - sometimes
significantly - from those indicated in your report. Retaining
the geotechnical engineer who developed your report to
provide geotechnical-construction observation is the most
effective method of managing the risks associated with
unanticipated conditions.
A Report's Recommendations Are Not Final
Do not overrely on the confirmation-dependent
recommendations included in your report. Confirmation-
dependent recommendations arc notfinal, because
geotechnical engineers develop them principally from
judgment and opinion. Geotechnical engineers can finalize
their recommendations only by observing actual subsurface
conditions revealed during construction. The geotechnical
engineer who developed your report cannot assume
responsibility or liability for the report's confirmation-dependent
recommendations if that engineer does not perform the
geotechnical-construction observation required to confirm the
recommendations' applicability.
A Geotechnical-Engineering Report Is Subject
to Misinterpretation
Other design-team members' misinterpretation of
geotechnical-engineering reports has resulted in costly
problems. Confront that risk by having your geotechnical
engineer confer with appropriate members of the design team
after submitting the report. Also retain your geotechnical
engineer to review pertinent elements of the design team's
plans and specifications. Constructors can also misinterpret
a geotechnical-engineering report. Confront that risk by
having your geotechnical engineer participate in prebid and
preconstruction conferences, and by providing geotechnical
construction observation.
Do Not Redraw the Engineer's Logs
Geotechnical engineers prepare final boring and testing logs
based upon their interpretation of field logs and laboratory
data. To prevent errors or omissions, the logs included in a
geotechnical-engineering report should never be redrawn
for inclusion in architectural or other design drawings. Only
photographic or electronic reproduction is acceptable, but
recognize that separating logs from the report can elevate risk
Give Constructors a Complete Report and
Guidance
Some owners and design professionals mistakenly believe they
can make constructors liable for unanticipated subsurface
conditions by limiting what they provide for bid preparation.
To help prevent costly problems, give constructors the
complete geotechnical-engineering report, but preface it with
a clearly written letter of transmittal. In that letter, advise
constructors that the report was not prepared for purposes
of bid development and that the report's accuracy is limited;
encourage them to confer with the geotechnical engineer
who prepared the report (a modest fee may be required) and/
or to conduct additional study to obtain the specific types of
information they need or prefer. A prebid conference can also
be valuable. Be sure constructors have sufficient time to perform
additional study. Only then might you be in a position to
give constructors the best information available to you,
while requiring them to at least share some of the financial
responsibilities stemming from unanticipated conditions.
Read Responsibility Provisions Closely
Some clients, design professionals, and constructors fail to
recognize that geotechnical engineering is far less exact than
other engineering disciplines. This lack of understanding
has created unrealistic expectations that have led to
disappointments, claims, and disputes. To help reduce the risk
of such outcomes, geotechnical engineers commonly include
a variety of explanatory provisions in their reports. Sometimes
labeled "limitations," many of these provisions indicate where
geotechnical engineers' responsibilities begin and end, to help
others recognize their own responsibilities and risks. Read
these provisions closely. Ask questions. Your geotechnical
engineer should respond fully and frankly.
Environmental Concerns Are Not Covered
The equipment, techniques, and personnel used to perform
an environmental study differ significantly from those used to
perform a geotechnical study. For that reason, a geotechnical-
engineering report does not usually relate any environmental
findings, conclusions, or recommendations; e.g., about
the likelihood of encountering underground storage tanks
or regulated contaminants. Unanticipated environmental
problems have led to nunierousprojectfailures. If you have not
yet obtained your own environmental information,
ask your geotechnical consultant for risk-management
guidance. Do not rely on an environmental report preparedfor
someone else.
Obtain Professional Assistance To Deal
with Mold
Diverse strategies can be applied during building design,
construction, operation, and maintenance to prevent
significant amounts of mold from growing on indoor surfaces.
To be effective, all such strategies should be devised for
the express purpose of mold prevention, integrated into a
comprehensive plan, and executed with diligent oversight by a
professional mold-prevention consultant. Because just a small
amount of water or moisture can lead to the development of
severe mold infestations, many mold- prevention strategies
focus on keeping building surfaces dry. While groundwater,
water infiltration, and similar issues may have been addressed
as part of the geotechnical- engineering study whose findings
are conveyed in this report, the geotechnical engineer in
charge of this project is not a mold prevention consultant;
none of the services performed in connection with the
geotechnical engineer's study were designed or conducted for
the purpose of mold preve ntion. Proper implementation of the
recommendations conveyed in this report will not of itself be
sufficient to prevent nzoldfroin growing in or on the structure
involved.
Rely, on Your GBC-Member Geotechnical Engineer
for Additional Assistance
Membership in the Geotechnical Business Council of the
Geoprofessional Business Association exposes geotechnical
engineers to a wide array of risk-confrontation techniques
that can be of genuine benefit for everyone involved with
a construction project. Confer with you GBC-Member
geotechnical engineer for more information.
E GEOTECHNICAL
___
BUSINESS COUNCIL
GUN eftheGmp*ixwJBusMsMsodaflon
8811 Colesville Road/Suite G106, Silver Spring, MD 20910
Telephone: 301/565-2733 Facsimile: 301/589-2017
e-mail: info@geoprofessional.org www.geoprofessional.org
Copyright 1015 by Geoprofessional Business Association (GBA). Duplication, reproduction, or copying of this document, or its contents, in whole or in part,
by any means whatsoever, is strictly prohibited, except with GBA's specific written permission. Excerpting, quoting, or otherwise extracting wording from this document
is permitted only with the express written permission of GBA, and only for purposes of scholarly research or book miew. Only members of GBA may use
this document as a complement to or as an element ole geotechnical -engineering report. Any other firm, individual, or other entity that so uses this document without
being a GBA member could be commiting negligent or intentional (fraudulent) misrepresentation.