HomeMy WebLinkAboutPUD 15-09; Shea Industrial Bressi Ranch; Planned Unit Development - Non-Residential (PUD) (2)GEOTECHNICAL UPDATE INVESTIGATION,
LOTS 19 TO 22 OF CARLSBAD TRACT CT-02-15
BRESSI RANCH,
CARLSBAD, CALIFORNIA
Prepared For
Shea Properties
Management Company, Inc.
130 Vantis, Suite 200
Aliso Viejo, California 92656
ProjectNo. 10570.001
January 21, 2014
4
Leighton and Associates, Inc.
ALEIGHTONGROUPCOiPANY
Leighton and Associates, Inc.
A LEIGHTON GROUP COMPANY
January 21, 2014
ProjectNo. 10570.001
Shea Properties Management Company, Inc.
130 Vantis, Suite 200
Aliso Viejo, CA. 92656
Attention; Mr. Jim Peterson
Subject: Geotechnical Update Investigation
Lots 19 to 22 of Carlsbad Tract CT-02-15
Bressi Ranch, Carlsbad, California
In accordance with your request and authorization, we have conducted a geotechnical
update investigation for the proposed Lots 19 to 22 of Carlsbad Tract CT-02-15 in the
Bressi Ranch area of Carlsbad, California. Based on the results of our study, it is our
professional opinion that the site is suitable for the proposed commercial development
and associated improvements. The accompanying report presents a summary of our
update investigation and provides preliminary geotechnical conclusions and
recommendations relative to the proposed site development.
If you have any questions regarding our report, please do not hesitate to contact this
office. We appreciate this opportunity to be of service. >€0^^'' ^ ^^/^
Respectfully submitted,
LEIGHTON AND ASSOCIATES,
William D. Olson, RCE 45283
Associate Engineer
dolson@leiqhtonqroup.com
Distribution: (4) Addressee
Mike Jensen, CEG 2457
Project Geologist
miensen(S>.leiqhtonqroup.com
I
3934 Murphy Canyon Road, Suite B205 . San Diego, CA 92123-4425
858.292.8030 . Fax 858.292.0771 . vwAW.Ieightongroup.com
Geotechnical Uodate Investigation. Bressi Ranch. Carlsbad. California 10570.001
TABLE OF CONTENTS
Section Paqe
1.0 INTRODUCTION 1
1.2 SITE LOCATION AND DESCRIPTION 2
1.3 PROPOSED DEVELOPMENT 2
2.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING 4
3.0 SUMMARY OF GEOTECHNICAL CONDITIONS 5
3.1 GEOLOGIC SETTING 5
3.2 AS-GRADED GEOLOGIC CONDITIONS 5
3.3 SITE-SPECIFIC GEOLOGY 5
3.3.1 Artificial Documented Fill (Map Symbol-Af) 5
3.3.2 Santiago Formation (Map Symbol-Tsa) 6
3.4 SURFACE AND GROUND WATER 7
3.4.1 Infiltration 7
3.5 GRADED SLOPES 8
3.6 SOIL CORROSIVITY 8
4.0 FAULTING AND SEISMICITY 9
5.0 CONCLUSIONS 11
6.0 RECOMMENDATIONS 13
6.1 EARTHWORK..... 13
6.1.1 Site Preparation 13
6.1.2 Mitigation of Cut/Fill Transition Conditions 14
6.1.3 Mitigation of High to Very High Expansive Soils at Finish Grade 14
6.1.4 Excavations 14
6.1.5 Fill Placement and Compaction 15
6.2 FOUNDATION AND SLAB DESIGN CONSIDERATIONS 15
6.2.1 Moisture Conditioning 17
6.2.2 Foundation Setback 18
6.2.3 Anticipated Settlement 18
6.3 LATERAL EARTH PRESSURES 19
6.4 FENCES AND FREESTANDING WALLS 21
6.5 CONCRETE FLATWORK 22
6.6 GEOCHEMICAL CONSIDERATIONS 23
6.7 PRELIMINARY PAVEMENT DESIGN 23
6.8 CONTROL OF SURFACE WATER AND DRAINAGE 25
6.9 SLOPE MAINTENANCE GUIDELINES 26
6.10 LANDSCAPING AND POST-CONSTRUCTION 27
6.11 CONSTRUCTION OBSERVATION AND TESTING 28
Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
TABLE OF CONTENTS
Section
7.0 LIMITATIONS
Page
...29
Tables
TABLE 1 - CBC MAPPED SPECTRAL ACCELERATION PARAMETERS - PAGE 10
TABLE 2 - PRESATURATION RECOMMENDATIONS BASED ON FINISH GRADE
SOIL EXPANSION POTENTIAL - PAGE 17
TABLE 3 - MINIMUM FOUNDATION SETBACK FROM DESCENDING SLOPE FACES - PAGE 18
TABLE 4 - LATERAL EARTH PRESSURES - PAGE 20
TABLE 5 - PRELIMINARY PAVEMENT SECTION DESIGNS - PAGE 24
FIGURE
FIGURE 1 - SITE LOCATION MAP - AT END OF TEXT
PLATE
PLATE 1 - GEOTECHNICAL MAP - IN POCKET
APPENDICES
APPENDIX A - REFERENCES
APPENDIX B - TEST PIT LOGS AND FIELD PERCOLATION TESTS
APPENDIX C - LABORATORY TESTING PROCEDURES AND TEST RESULTS
APPENDIX D - GENERAL EARTHWORK AND GRADING SPECIFICATIONS
APPENDIX E -ASFE
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Geotechnical Update Report. Bressi Ranch. Carlsbad. California 10570.001
1.0 INTRODUCTION
1.1 Purpose and Scope
This report presents the results of our geotechnical update investigation for Lots
19 to 22 of Carisbad Tract CT-02-15 in the Bressi Ranch area of Carisbad,
California (Figure 1). The purpose of our geotechnical update investigation was
to evaluate existing geotechnical conditions present at the site and to provide
preliminary geotechnical conclusions and recommendations relative to the
proposed commercial development.
AS part of our update investigation ofthe site, we performed the following:
• Review of available pertinent, published and unpublished geotechnical
reports, geologic literature, and maps (Appendix A).
• Field reconnaissance of the existing onsite geotechnical conditions.
» Coordination with Underground Services Alert (USA) to locate potential
underground utilities on or adjacent to the site.
• Subsurface exploration consisting of eight (8) test pits and two field
percolation tests. The approximate boring and field percolation test locations
are shown on the Geotechnical Map (Plate 1). The logs of the borings are
presented in Appendix B.
• Laboratory testing of representative soii samples obtained from the
subsurface exploration. Results of these tests are presented in Appendix C,
with the exception of moisture/density determinations, which are provided on
the boring logs (included in Appendix B)
• Compilation and analysis of the geotechnical data obtained from the field
investigation and laboratory testing.
• Preparation of this report presenting our findings, conclusions, and
geotechnical recommendations (including General Earthwork and Grading
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
Specifications presented as Appendix D) with respect to the proposed design,
site grading, and general construction considerations.
1.2 Site Location and Description
The site consists of a square shaped property bordered on the north by elevated
vacant commercial lots, on the west by a descending slope to existing
commercial property, on the south by Gateway Road, and on the east by
Innovation Way with Slater Place cul-de-sac projecting approximately 300 feet
into the site in a westem direction perpendicular from Innovation Way. The total
area of the proposed project is approximately 8.27 acres (360,000 ft^) and
recently abated vegetation consisting of native grasses and weeds. A total of four
desilting basins exist throughout site that are approximately 6 feet below the
adjacent grades.
As background, the mass grading operations for the overall area. Planning Area
PA-1 to PA-5 and the associated streets was performed between September
2003 and May 2004 (Leighton, 2004a). The rough grading resulted in a generally
southwest sloping sheet-graded pad. The mass graded pad elevation ranges
from approximately 365 feet mean sea level (msl) in the southwest portion of the
site to 375 feet msl in the northeast portion. The grading operations were
performed by Nelson and Belding, while Leighton and Associates perfonned the
geotechnical observation and testing services. Grading of the site included: 1)
the removal of potentially compressible desiccated older fill soils, undocumented
fill soils, topsoil, colluvium, alluvium, and weathered fomnational material; 2) the
excavation of fill slope keys; 3) preparation of areas to receive fill; 4) the
placement of a subidrain in the canyon bottom; 5) excavation of formational
material; and 6) the placement of compacted fill soils.
Site Latitude and Longitude
33.1286° N
-117,2606° W
1.3 Proposed Development
The proposed development is anticipated to consist of two 54,000 ft^
commercial/industrial buildings, tnjck loading docks, patio areas, driveways,
parking areas, minor slopes, and associated landscaped areas (Shea, 2013). We
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Geotechnical Update Report. Bressi Ranch. Carlsbad. California 10570.001
anticipate that the proposed buildings will be concrete tilt-up structures with
concrete slab-on-grade floor and conventional foundations. Currently, precise
grading plans were not available; however, we anticipate that the proposed site
grades will remain close to existing grades (i.e., relatively minor cuts and fills to
achieve site grade(s) and a balanced site).
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
2.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING
On January 7 and January 8, 2014 our subsurface investigation of Lots 19 to 22
included the excavation of eight (8) exploratory test pits to depths ranging from
approximately 5.5 to 9.5 feet below the existing ground surface (bgs) and two (2) field
percolation tests advanced to approximately 4 feet bgs. The test pits were excavated
with a 430 Caterpillar backhoe with a 24-inch wide bucket. The field percolation test
holes were advanced with a 3.25-inch diameter hand auger. The purpose of these
excavations was to evaluate the engineering characteristics of the onsite soils with
regard to the proposed development. Our subsurface investigation allowed evaluation of
the onsite soils, including those likely to be encountered at the proposed foundation
elevations and provided representative samples for laboratory testing. A log of the test
pits CT-1 through T-8) and data from the field percolation tests (P-1 and P-2) are
presented in Appendix B.
The exploratory excavations were logged by a geologist from our firm. Representative
bulk samples were obtained at selected intervals for laboratory testing. The approximate
locations of the test pits and field percolation tests are shown on the Geotechnical Map
(Plate 1). Subsequent to logging and sampling, the test pits were backfilled with native
soils, and a compactive effort was applied to the backfill utilizing a compaction wheel. The
compactive effort was observed and probed by a representative from our firm; however,
compaction testing was not performed.
Laboratory testing for was performed on representative samples to evaluate the
expansion potential, maximum density, shear strength parameters, and geochemical
tests consisting of soluble sulfate and chloride contents, and minimum resistivity and pH
tests. A discussion of the laboratory tests performed and a summary of the laboratory
test results are presented in Appendix C.
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Geotechnical Update Report. Bressi Ranch. Carlsbad. California 10570.001
3.0 SUMMARY OF GEOTECHNICAL CONDITIONS
3.1 Geologic Setting
The subject 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 the "San Diego Embaymenf 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 Quatemary time, resulted in the rolling hills,
mesas, and deeply incised canyons which characterize the landforms we see in
the general site area today.
3.2 As-graded Geologic Conditions
The geologic or geotechnical conditions encountered during our current update
study of the site were essentially as anticipated. A comprehensive summary of the
geologic conditions (including geologic units, geologic staicture, and faulting) are
presented below.
3.3 Site-Specific Geology
The geologic units encountered during our investigation and site grading
consisted of artificial documented fill soils and the Santiago Fonnation. The
approximate limits of the geologic units encountered are presented on the
Geotechnical Map (Plate 1) and discussed (youngest to oldest) below.
3.3.1 Artificial Documented Fill (Map Symbol-Af)
Documented fill soils placed during the prior grading operations that were
observed and tested by Leighton and Associates are generally located
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
along the western perimeter, a central section and in the southeast corner of
the site (as indicated on Plate 1). In addition to the fill limits, tiie elevations
of tine bottom of the fill are provided on tiie geotechnical map so that
potential fill differentials across tiie site can be identified.
The field density test results presented in the as-graded geotechnical report
for tiie project (Leighton, 2004c) indicated the fill soils were placed and
compacted to at least a 90 percent relative compaction witii moisture
contents at or near the optimum moisture content.
During our update study, the upper portion of tiie fill soils was found to be
desiccated and removals and/or scarification and recompaction will be
necessary prior to the placement of additional fill or structural
improvements. The fill soils typically consisted of silty sands, clayey sands,
and to a lesser extent sandy to silty clays. Based on our review of the as-
graded geotechnical report (Leighton, 2004c), tiie thickness of fill on the site
ranges from zero to approximately 53 feet below existing grades.
3.3.2 Santiago Formation (Map Symbol-Tsa)
The Tertiary-aged Santiago Formation, as encountered during our update
study, consisted primarily of massively bedded siltstones and claystones,
and to a lesser extent sandstone. The sandstone generally consisted of
orange-brown (iron oxide staining) to light brown, damp to moist, dense to
very dense, silty very fine to medium grained sandstone. The siltstones
and claystones were generally olive-green, dry to moist, stiff to hard,
moderately weathered in the upper 5 feet, and occasionally fractured and
moderately sheared.
Several well-cemented fossiliferous sandstone beds and clay seams were
encountered during the mass grading (Leighton, 2004c). Hiqh to verv high
expansive formational claystones and siltstones are present at the existina
finish grade elevation of the sheet-graded pad in the northeastern portions
of the site.
Well-cemented fossiliferous sandstone beds may be present in tiie
Santiago Formation near the surface or at deptii. Deep excavations
should anticipate the well-cemented beds and be prepared to utilized
Geotechnical Update Report. Bressi Ranch. Carlsbad. California 10570.001
larger excavations, breakers, and single-shank ripper to excavate
trenches.
3.4 Surface and Ground Water
No indication of surface water or evidence of surface ponding was observed site
visit. However, surface water may drain as sheet flow across the site during rainy
periods and accumulate in lower elevations and in the on-site desilting basins.
Ground water was not observed in the test pits during our investigation; however,
perched ground water levels may develop and fluctuate during periods of
precipitation and after initial landscaping and in-igation has been installed.
3.4.1 Infiltration
We performed two field percolation tests to evaluate tiie soil for potential
infiltration of storm water. Field percolation test, P-1, is located witiiin
weathered Santiago Formational material; and field percolation test, P-2,
and is located within documented artificial fill. The results of the field
percolation tests indicated that the existing onsite soils generally have a
percolation rates at 62 minutes per inch and 83 minutes per inch in P-1
and P-2, respectively. It should be noted that generally, a percolation rate
less than 120 minutes per inch is considered necessary to consider a site
suitable for onsite surface infiltration of storm water. However, the site
artificial fill consists of mixture of soils ranging from silty sands to clays
witii permeable and impermeable layers, which 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 LID measures may not be appropriate for this project. Infilti-ation and
Bio-retention Stormwater Systems design should be reviewed by
geotechnical consultant.
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Geotechnical Update Report. Bressi Ranch, Carlsbad. Califomia 10570.001
3.5 Graded Slopes
Graded and natural slopes within the developed portion of the tract are considered
grossly and surficially stable from a geotechnical standpoint. Manufactured cut and
fill slopes within the tract were surveyed by tiie civil engineer are understood to
have been constmcted with slope inclinations of 2:1 (horizontal to vertical) or
flatter.
3.6 Soil Corrosivity
A preliminary con-osive soil screening for the on-site materials was completed to
evaluate their potential effect on concrete and fen-ous metals. The corrosion
potential was evaluated using the results of laboratory testing on one
representative soil sample obtained during our subsurface evaluation.
Laboratory testing was performed on two representative samples to evaluate pH,
minimum electrical resistivity, and chloride and soluble sulfate content. The
samples tested had a measured pH ranging from 7.7 to 8.0, and a measured
minimum electrical resistivity ranging from 618 to 697 ohm-cm. Test results also
indicated that the samples had a chloride content ranging from 109 to 214 ppm,
and a soluble sulfate content of less than 450 ppm.
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
4.0 FAULTING AND SEISMICITY
Our discussion of faults on the site is prefaced with a discussion of Califomia legislation
and state policies concerning the classification and land-use criteria associated with faults.
By definition of the California Mining and Geology Board, an active fault is a fault tiiat has
had surface displacement within Holocene time (about tiie last 11,000 years). The State
Geologist has defined a potentiallv active fault as any fault considered to have been active
during Quatemary time (last 1,600,000 years) but that has not been proven to be active or
inactive. This definition is used in delineating Fault-Rupture Hazard Zones as mandated
by tiie Alquist-Priolo Earthquake Fault Zoning Act of 1972 and as most recently revised in
2007. The intent of this act is to assure that unwise urban development does not occur
across the traces of active faults. Based on our review of ttie Fault-Rupture Hazard
Zones, the site is not located within any Fault-Rupture Hazard Zone as created by the
Alquist-Priolo Act (Bryant and Hart, 2007).
San Diego, like the rest of southern California, is seismically active as a result of being
located near the active margin between the North American and Pacific tectonic plates.
The principal source of seismic activity is movement along the northwest-trending
regional fault zones such as the San Andreas, San Jacinto and Elsinore Faults Zones,
as well as along less active faults such as the Rose Canyon Fault Zone. As indicated in
the Supplemental Geotechnical Report for the Bressi Ranch project (Leighton, 2001),
there are no known major or active faults on or in the immediate vicinity of tiie site. The
nearest known active fault is the Rose Canyon Fault Zone, which is located approximately
7.0 miles (11.2 kilometers) west of the site.
As discussed above, evidence of active faulting was not encountered within the site during
the mass grading operations in 2003-2004 (Leighton, 2004b). However, several minor
inactive faults were encountered within tiie limits of the Bressi Ranch development that
are not considered a consti-aint to development of Planning Area 2. Geologic mapping of
the onsite minor faults, where topsoil was encountered over the faults, indicated that the
faults did not extend into or offset the topsoil, suggesting that the faults are not active.
Because of the lack of known active faults on the site, the potential for surface rupture at
the site is considered low. Shallow ground rupture due to shaking from distant seismic
events is not considered a significant hazard, altiiough it is a possibility at any site.
However, due to the presence of slopes on-site, lurching and associated ground
cracking near the tops of slopes is possible.
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
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
act as a viscous liquid. This effect may be manifested by excessive settlements and
sand boils at the ground surface. The fill and fomnational materials underiying the site
are not considered liquefiable due to their fine-grained nature, dense physical
characteristics, and unsaturated condition.
The effect of seismic shaking may be mitigated by adhering to tiie California Building
Code and state-of-the-art seismic design practices of the Structural Engineers
Association of California. Provided below in Table 1 are the risk-targeted spectral
acceleration parameters for the project determined in accordance with the 2013
Califomia Building Code (CBSC, 2013) and the USGS Woridwide Seismic Design
Values tool (Version 3.1.0).
Table 1
1 CBC Mapped Spectral Acceleration Parameters
Site Class D
Site Coefficients Fa = 1.081
Fv = 1.594
Mapped MCER Spectral Accelerations Ss = 1047g
Si = 0.406g
Site Modified MCER Spectral Accelerations SMS = 1.132g
SMI = 0.647g
Design Spectral Accelerations SDS = 0.755g
SDI = 0.431 g
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 Eartiiquake (MCEG). The mapped MCEG
peak ground acceleration (PGA) is 0.401 g for the site. For a Site Class D, the FPGA is
1.099 and the mapped peak ground acceleration adjusted for Site Class effects (PGAM)
is 0.44lg for tiie site.
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
5.0 CONCLUSIONS
Based on the results of our update geotechnical study of the site, it is our professional
opinion that the proposed commercial development is feasible from a geotechnical
standpoint, provided the following conclusions and recommendations are incorporated
into the project plans and specifications. The following is a summary of the geotechnical
factors that may affect development of the site.
• Based on our subsurface exploration, the near-surface fill soils are locally disturbed
(i.e., the upper 2 feet). These soils are not considered suitable fbr support of
additional fill soils, stmctural loads or surface improvements in their present
condition. Remedial grading measures such as scarification, removals and
recompaction will be necessary to mitigate this condition if the disturbed soils are not
removed by the proposed excavation.
• High to verv high expansive formational claystones and siltstones are present at the
existing finish grade elevation of tiie sheet-graded pad in the northeastem portions
of the site. Remedial grading of this area will be required for proposed
improvements.
• A cut/fill transition condition is anticipated beneath proposed northern building, and
will need to be mitigated by the over excavation of the cut portion of the building pad.
Note that once final civil and building structural plans are completed, a geotechnical
review will required to evaluate cut/fill transitions conditions and determine the
recommended over excavation depths for mitigation.
• Laboratory test results indicate the fill soils present on the site have a moderate
potential for sulfate attack on normal concrete, and are moderately to severely
corrosive on buried metal pipes and conduits.
• The existing onsite soils, with exception of the highly expansive soil in the
northeastern portion of the site, appear to be suitable material for reuse as fill
provided they are relatively free of organic material, debris, and rock fragments
larger than 8 inches in maximum dimension.
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Geotechnical Update Report. Bressi Ranch. Carlsbad. California 10570.001
• Near surface ground water or seepage was not encountered during our
investigation; however, perched ground water and seepage may develop during
periods of precipitation and after site imgation.
• Altiiough foundation plans have not been developed nor building loads determined,
we anticipate that conventional foundation system, consisting of continuous and
spread footings with slab-on-grade flooring supported by competent fill or
formational materials, will be used.
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
6.0 RECOMMENDATIONS
6.1 Earthwork
We anticipate that earthwork at the site will consist of site preparation, remedial
and fine grading, utility trench excavation and backfill, and driveway and pari<ing
area pavement section preparation and compaction. We recommend that the
earthwork on site be performed in accordance with the following
recommendations, the General Earthwork and Grading Specifications for Rough
Grading included in Appendix D, and the City of Carisbad grading requirements.
In case of conflict, the following recommendations shall supersede those in
Appendix D. The contract between tiie developer and earthwork contractor
should be worded such that it is the responsibility of the contractor to place the fill
properly and in accordance with the recommendations of this report and tiie
specifications in Appendix D, notwithstanding tiie testing and observation of the
geotechnical consultant.
6.1.1 Site Preparation
During grading, the areas to receive stmctural fill or engineered stmctures
should be cleared of surface obstmctions, potentially compressible material
(such as desiccated fill soils or weathered formational material), and
stripped of vegetation. Vegetation and debris should be removed and
properiy disposed of offeite. Holes resulting from removal of buried
obsti-uctions that extend below finish site grades should be replaced with
suitable compacted fill material. Areas to receive fill and/or other surface
improvements should be reprocessed to a minimum depth of 24 inches,
brought to 2 percent above optimum moisture condition, and recompacted
to at least 90 percent relative compaction (based on ASTM Test Method
D1557).
If the length of time between the completion of grading and the construction
is longer than six months, we recommend that tiie building pads be
evaluated by the geotechnical consultant and, if needed, the finish grade
soils on the building pads should be scarified a minimum of 12 inches,
moisture-conditioned to 2 percent above optimum moisture-content and
recompacted to a minimum 90 percent relative compaction (based on
ASTM Test Method D1557).
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Geotechnical Update Report. Bressi Ranch. Carlsbad. California 10570.001
6.1.2 Mitigation of Cut/Fill Transition Conditions
In order to reduce tiie potential for differential settlement of the proposed
buildings in areas of cut/fill transitions, we recommend the entire cut portion
ofthe building pad be overexcavated and replaced with properly compacted
fill. Currently, we recommend that tiie overexcavation of the cut portion of
the building pad should be made a minimum of 5 feet below tiie lowest
planned footing elevation or load dock bottom, and it should extend laterally
at least 10 feet beyond the building perimeter or fcxjtprint. Note that once
final civil and building stmctural plans are completed, a geotechnical
review will reguired to evaluate cut/fill ti^ansitions conditions and determine
the recx?mmended over excavation depths for mitigation
6.1.3 Mitigation of High to Very High Expansive Soils at Finish Grade
High to very high expansive soils were encountered in tiie nortiieastern
portion of the site during the original site grading (Leighton, 2014c).
Therefore, we recommend that these soils be removed and replaced with
low to medium expansive soils below tiie planned finish grade of tiie
proposed buildings and other movement sensitive improvements. The
removal deptii should be a minimum of 3 feet below the lowest planned
footing elevation or until lower expansive sandy soils are encountered. We
also recommend tiiat the overexcavation bottom be tilted a minimum of 2-
percent toward the fill side of the building pad or toward the street/driveway
in order to minimize perched ground water conditions. The resulting
excavation should be replaced witii properiy compacted fill possessing a
lower expansion potential. The actual location of the claystones and
siltstones at or near finish grade at the site should be evaluated during the
future fine grading operations. It should also be noted that the reuse of the
highly expansive soils is guestionable and/or limited, and offsite disposal
mav be reguired.
6.1.4 Excavations
Excavations of the on-site materials may generally be accomplished with
conventional heavy-duty eartiiwork equipment. It is not anticipated that
blasting will be required or that significant quantities of oversized rock (i.e.
rock with maximum dimensions greater than 8 inches) will be generated
during futojre grading. However, localized cemented zones within the cut
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Geotechnical Update Report. Bressi Ranch. Carlsbad. California 10570.001
areas and oversized rock placed within the compacted fill may be
encountered on the site that may require heavy ripping and/or removal. If
oversized rock is encountered, it should be placed in accordance with tiie
recommendations presented in Appendix D, hauled offsite, or placed in non-
structural or landscape areas. Deep excavations should anticipate well-
cemented sandstone beds across the site. Larger excavations, breakers,
and single-shank ripping may be required in deep utility and in-grading
excavations.
Due to the relatively dense characteristics of the on-site soils, temporary
excavations such as utility trenches in the on-site soils should remain stable
for the period required to consti-uct tiie utility, provided they are constructed
and monitored in accordance with OSHA requirements.
6.1.5 Fill Placement and Compaction
The on-site soils are generally suitable for use as compacted fill provided
they are free or organic material, debris, and rock fragments larger than
8 inches in maximum dimension. We do not recommend that high or very
high expansive soils be utilized as fill for the building pads or as retaining
wall backfill.
All fill soils should be brought to 2-percent over tiie optimum moisture
content and compacted in uniform lifts to at least 90 percent relative
compaction based on the laboratory maximum dry density (ASTM Test
Method D1557). 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
compacted thickness. Placement and compaction of fill should be
perfomied in general accordance witii Appendix D, the current City of
Carisbad grading ordinances, sound consti-uction practices, and tiie
geoteciinicai recommendations presented herein.
6.2 Foundation and Slab Design Considerations
The foundations and slabs for the proposed buildings should be designed in
accordance with stmctural considerations and the following preliminary
recommendations. These preliminary recommendations assume that the soils
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Geotechnical Update Report. Bressi Ranch. Carlsbad. California 10570.001
encountered within 5 feet of finish pad grade will have a very low to medium
potential for expansion. If highly expansive soils are encountered within 5 feet of
the proposed finish grade elevations during site grading, these expansive soils
should be removed and replaced with lower expansive soils. If replacement of
the expansive soils is not feasible, additional foundation design will be necessary.
The proposed buildings 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 2,500 pounds per square
foot (psf) if founded in properiy compacted fill soils or formational material. An
allowable capacity increase of 500 psf for every 6 inches of additional
embedment may be used to a maximum of 3,500 psf. The allowable pressures
may be increased by one-third when considering loads of short duration such as
wind or seismic forces. The minimum recommended widtii of footings is 18
inches for continuous footings and 24 inches for square or round footings.
Footings should be designed in accordance with the stmctural engineer's
requirements and have a minimum reinforcement of four No. 5 reinforcing bars
(two top and two bottom).
The slab-on-grade finish floors should be at least 5 inches thick and be
reinforced with No. 4 rebars 18 inches on center or No. 5 rebars at 24 inches on
center, each way. All reinforcing should be placed at mid-height in the slab. Slabs
should be underiain by a 2-inch layer of clean sand (sand equivalent greater than
30), which is in-turn underiain by a minimum 10-mil plastic sheeting (moisture
ban-ier) and an additional 2 inches of clean sand. We recommend that control
joints be provided across the slab at appropriate intervals as designed by tiie
project architect. Some moisture sensitive flooring may require additional
measures to mitigate moisture migration through tiie slab as designed by the
project architect.
For heavy equipment loading, greater slab-on-grade thicknesses and increased
reinforcing may be required, as determined by the structural engineer. Based on
the anticipated subgrade soil, we recommend using a modulus of subgrade
reaction of 100 psi per inch for the design of the interior slab-on-grade floor
subject to equipment loading.
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Geotechnical Update Report. Bressi Ranch. Carlsbad. California 10570.001
The potential for slab cracking may be reduced by carefiji control of
water/cement ratios. The contractor should take appropriate curing precautions
during the pouring of concrete in hot weather to minimize cracking of slabs. We
recommend that a slipsheet (or equivalent) be utilized if grouted tile, marble tile,
or other crack-sensitive floor covering is planned directiy on concrete slabs. All
slabs should be designed in accordance with structural considerations.
6.2.1 Moisture Conditioning
The slab subgrade soils underlying the foundation systems of the
proposed structures should be presoaked in accordance with the
recommendations presented in Table 2 prior to placement of the moisture
barrier and slab concrete. The subgrade soil moisture content should be
checked by a representative of Leighton and Associates prior to slab
construction.
Table 2
Presaturation Recommendations Based on Finish Grade Soil Expansion
Potential
Expansion Potential
Presaturation Very Low Low Medium
Criteria (0-20) (21-50) (51-90) 1
Minimum
Presoaking Depth 6 12 18
(in inches)
Minimum
Recommended
Moisture Content
2% above
optimum
moisture
1.3 times
optimum
moisture
1.4 times optimum
moisture
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 of 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 if for a short period of time (days to a
few weeks) are some of the more efficient ways to meet the presoaking
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
requirements. If fiooding 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.
6.2.2 Foundation Setback
We recommend a minimum horizontal setback distance fl-om the face of
slopes or adjacent retaining walls for all stmctural foundations, footings, and
otiier settlement-sensitive structures as indicated on Table 3. This distance
is measured from the outside bottom edge ofthe footing, horizontally to the
slope face and is based on the slope height and type of soil. 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.
Table 3
Minimum Foundation Setback from Descending Slope Faces
1 Slope Height Minimum Recommended Foundation
Setback
1 Less than 5 feet 5 feet
1 5 to 15 feet 7 feet
Please note that the soils within the stmctural 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 pier and grade beam foundation system to support the improvement. The
deepened footing should meet the setback as described above.
6.2.3 Anticipated Settlement
Settlement is anticipated to occur at varying times over the life of the
project. Short-term settlement typically occurs upon application of the
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Geotechnical Update Report. Bressi Ranch. Carlsbad. California 10570.001
foundation loads and is essentially completed within the construction
period. Long-term (hydroconsolidation) settlement typically occurs in deep
fills upon additional water infiltration into the fill soils (even in properly
compacted fill soils and even with subdrains provided). This settlement
typically occurs over many years. Long-term settlement values and the
effects on the foundations should be evaluated after the site is graded and
the actual fill thicknesses beneath the proposed foundations known.
However, for preliminary planning purposes, total future settlement is
expected to be order of 1 inch and differential settlement is estimated to
be on the order of 1/2 inch in 50 feet.
6.3 Lateral Earth Pressures
The recommended lateral pressures for the onsite very low to low expansive soil
(expansion index less than 50) and level or sloping backfill are presented on Table
4. High to very high expansive soils (having an expansion potential greater than
91) should not be used as backfill soils on tiie site.
Embedded structural walls should be designed for lateral earth pressures exerted
on them. The magnitude of these pressures depends on tiie amount of defonnation
that the wall can yield under load. If the wall can yield enough to mobilize the full
shear strength ofthe soil, it can be designed for "active" pressure. If the wall cannot
yield under the applied load, the shear strength of the soil cannot be mobilized and
the earth pressure will be higher. Such walls should be designed for "at rest"
conditions. If a stmcture moves toward the soils, the resulting resistance developed
by the soil is the "passive" resistance. The above noted passive resistance
assumes an appropriate setback per Section 6.2.2.
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Geotechnical Update Report. Bressi Ranch. Carlsbad. California 10570.001
Table 4
Lateral Earth Pressures
Equivalent Fluid Weight (pcf)
Very Low to Low Expansive Soils
Conditions Expansion Index less than 50
Level 2:1 Slope
Active 35 55
At-Rest 55 65
Passive 350 150
For design purposes, the recommended equivalent fluid pressure for each case for
walls founded above the static ground water and backfilled with soils of very low to
low expansion potential or medium expansion potential is provided on Table 4. The
equivalent fluid pressure values assume free-draining conditions. If conditions other
than those assumed above are anticipated, the equivalent fluid pressures values
should be provided on an individual-case basis by the geotechnical engineer. The
geotechnical and stmctural engineer should evaluate surcharge-loading effects
from the adjacent stmctures. All retaining wall stmctures should be provided with
appropriate drainage and appropriately waterproofed. The outiet pipe should be
sloped to drain to a suitable outlet. Typical wall drainage design is illustrated in
Appendix D.
For sliding resistance, tiie friction coefficient of 0.35 may be used at the concrete
and soil interface. In combining the total lateral resistance, the passive pressure or
the fi-ictional resistance should be reduced by 50 percent. Wall footings should be
designed in accordance witii structural considerations. The passive resistance
value may be inaeased by one-third when considering loads of short duration
including wind or seismic loads. The horizontal distance between foundation
elements providing passive resistance should be minimum of three times the depth
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
of the elements to allow full development of these passive pressures. The total
depth of retained earth for the design of cantilever walls should be the vertical
distance below the ground surface measured at the wall face for stem design or
measured at the heel of the footing for overturning and sliding. All wall backcute
should be made in accx>rdance with the current OSHA requirements.
The granular and native backfill soils should be compacted to at least 90 percent
relative compaction (based on ASTM Test Method D1557). The granular fill should
extend horizontally to a minimum distance equal to one-half tiie wall height behind
the walls. The walls should be constmcrted and backfilled as soon as possible after
backcut excavations. Prolonged exposure of backcut slopes may result in some
Icxalized slope instability.
Foundations for retaining walls in competent formational soils or properly
compacted fill should be embedded at least 24 inches below lowest adjacent
grade. At tiiis depth, an allowable bearing capacity of 2,000 psf may be assumed.
6.4 Fences and Freestanding Walls
Footings for freestanding walls should t>e founded a minimum of 24 inches below
lowest adjacent grade. To reduce tiie potential for unsightiy cracks in fi-eestanding
walls, we recommend inclusion of consti-uction joints at a maximum of 15-foot
intervals. This spacing may be altered in accordance with the recommendations of
the stmctural engineer, based on wall reinforcement details.
Our experience on similar sites in older developments indicates that many walls
on shallow foundations near the top-of-slopes tend to tilt excessively over time as
a result of slope creep. If the effects of slope creep on top-of-slope walls are not
deemed acceptable, one or a combination of the options provided in the following
paragraphs should be utilized in the design of such structures, based on the
desired level of mitigation of creep-related effects on them.
A relatively inexpensive option to address creep related problems in top-of-slope
walls and fences is to allow some degree of creep damage and design the
structures so tiiat tilting or cracking will be less visually obvious, or such that they
may be economically repaired or replaced. If, however, a better degree of creep
mitigation is desired, the walls and fences may be provided with tiie deepened
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
footings to meet the foundation setback criteria, or these structures may be
constmcted to accommodate potential movement.
Under certain circumstances, an effective solution to minimize the effects of creep
on top-of-slope walls and fences is to support these sti-ucttjres on a pier-and-
grade-beam system. The piers normally consist of minimum 12-inch diameter cast-
in-place caissons spaced at a maximum of 8 feet on center, and connected
together by a minimum 12-inch-thick grade beam at a shallow depth. The piers are
typically at least 10 feet deep for medium or high expansive soil. The steel
reinforcement for the system should be designed with consideration of wall/fence
type and loading. Walls or fences aligned essentially perpendicular to the top of tiie
slope are normally supported on the pier-and-grade-beam system for at least that
part of the wall that is witiiin 15 feet from the top-of-slope. Caisson support is
recommended for all top-of-slope walls where slopes are greater than 10 feet in
height and/or the soil on and adjacent to the slope consists of high to very high
expansive soils.
6.5 Concrete Flatwork
Some of the on-site soils possess a high expansion potential. If possible,
selected grading should be performed to reduce the amount of expansive soil
placed at subgrade elevations in the areas of concrete flatwork. Based on the
anticipated conditions and experience the adjacent commercial development, we
recommend tiiat the upper 24 inches of subgrade soils be pre-saturated to at
least 5 percent above optimum moisture content prior to placement of concrete
flatwork. For areas previously graded that require reprocessing, we recommend
that the upper 18 inches of subgrade soils be scarified and moisture conditioned
and lightiy re-compacted prior to placement of the concrete flatwork. The
reprocessed subgrade soils should be moisture-conditioned to at least 5 percent
above optimum moisture content and compacted to around 90 percent relative
ciompaction based on American Standard of Testing and Materials (ASTM) Test
Method D1557. Note that these recommendations are for sidewalks and other
concrete flatwork only and are not applicable to concrete pavement areas subject
to traffic loading.
We also recommend that the sidewalk and/or concrete flatwork be at least 4
inches thick and be reinforced with No. 3 rebars at a minimum spacing of at least
18 inches, each way. In addition, the sidewalk sections should be doweled into
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
the adjacent curbs at a spacing of 36 inches on center and doweled into adjacent
existing sidewalk sections and slabs (at doorways) at a minimum spacing of 18
inches on center. Note that our representative should also observe and test the
compaction of the reprocess subgrade soil prior to placement of the
reinforcement for new sidewalk sections.
6.6 Geochemical Considerations
Geochemical screening of the representative onsite soils was perfonned as part
of our original study and the results presented in Appendix C. As indicated in
Appendix C, the results of our limited testing and our professional knowledge of
similar soils in other portions ofthe Bressi Ranch project, indicates that concrete
in contact with the on-site soils should be designed in accordance with the
"severe" category. In addition, the onsite soils are anticipated to have a corrosive
environment for buried metal pipes or uncoated metal conduits. Laboratory
testing should be perfomned on the soils placed at or near finish grade after
completion of site grading to ascertain tiie actual corrosivity characteristics.
6.7 Preliminary Pavement Design
Based on our past experience on adjacent development to the northeast and east
a preliminary R-Value of 5 is factored into our pavement analysis. The appropriate
pavement sections will depend on tiie type of subgrade soil, shear strength, traffic
load, and planned pavement life. Since an evaluation of the actual subgrade soils
cannot be made at this time, we have assumed an R-value of 5 and Traffic Indexes
(Tl) of 4.0, 5.0, and 6.0. The Asphalt Concrete (AC) and Class 2 aggregate base
(AB) pavement sections presented on Table 4 should be used for preliminary
planning purposes only.
The pavement sections for the onsite tmck and vehicle driveways should be based
on an assumed Tl of 6.0 and 5.0, respectively. The pavement sections for vehicle
parking stalls should t>e based on a Tl of 4.0. Final pavement designs should be
completed in accordance with the City of Carisbad design criteria after R-value
tests have been performed on the actual subgrade materials.
•<^BSSr
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
Table 5
Preliminary Pavement Section Designs
Traffic
Index
Assumed
R-Value
Preliminary Pavement Sections Traffic
Index
Assumed
R-Value AC and Base Section Full Deptii AC Section
4.0 5 4 inches AC over 5 inches
Class 2 Aggregate Base
6.5 inches AC over native
subgrade soils
5.0 5 4 inches AC over 8 inches
Class 2 Aggregate Base
8.0 inches AC over native
subgrade soils
6.0 5 4 inches AC over 12 inches
Class 2 Aggregate Base
10 inches AC over native
subgrade soils
Asphalt Concrete (AC) and Class 2 aggregate base materials should conform to
and be placed in accordance witii tiie latest revision of California Department of
Transportation Standard Specifications. Prior to placing the pavement section,
the subgrade soils should have a relative compaction of at least 95 percent to a
minimum depth of 12 inches (based on ASTM Test Method D1557). Aggregate
Base should be compacted to a minimum of 95 percent relative compaction
(based on ASTM Test Method D1557) prior to placement of the AC.
For pavement areas subject to heavy tmck loading (i.e., delivery trucks, fori< lifts
etc.), we recommend a full depth of Portland Cement Concrete (PCC) section of
8 inches with steel reinforcement (number 4 bars at 18-inch centers, each way)
and crack-control joints at a minimum spacing of 10 feet. We recommend that
sections be as neariy square as possible. A 3,500-psi mix that produces a 600-
psi modulus of rupture should be utilized. The actual pavement design should
also be in accordance with City of Carisbad and ACI design criteria.
If pavement areas are adjacent to heavily watered landscaping areas, we
recommend some measures of moisture conti-ol be taken to prevent the subgrade
soils from becoming saturated. It is recommended that the concrete curbing,
separating the landscaping area ft-om tiie pavement, extend below tiie aggregate
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
base to help seal the ends of the sections where heavy landscape watering may
have access to the aggregate base. Concrete swales should be designed if asphalt
pavement is used for drainage of surface waters.
6.8 Control of Surface Water and Drainage
Regarding Low Impact Development (LID) measures, we are of the opinion that
infiltration basins, and other onsite storm water retention and infiltration systems
can potentially create adverse perched ground water conditions. In addition, the
existing onsite soils are anticipated to provide relatively low or minimal infiltration
rates for the surface water. Therefore, given the site location and underlying
geologic conditions, infiltration type LID measures are not considered to be
appropriate for this site and proiect.
Surface drainage should t»e carefljily taken into consideration during precise
grading, landscaping, and building constiuction. Positive drainage (e.g., roof
gutters, downspouts, area drain, etc.) should be provided to direct surface water
away fl-om stmctures and towards the street or suitable drainage devices. Ponding
of water adjacent to structures should be avoided; roof gutters, downspouts, and
area drains should be aligned so as to transport surface water to a minimum
distance of 5 feet away fi-om stmctures. The performance of stmctural foundations
is dependent upon maintaining adequate surface drainage away from stmctures.
Water should be transported off the site in approved drainage devices or
unobstructed swales. We recommend that tiie minimum flow gradient for tiie
drainage be 1-percent for area drains and paved drainage swales; and 2-percent
for unpaved drainage swales. We recommend that where structures will be
located within 5 feet of a proposed drainage swale, the surface drainage adjacent
to the structures be accomplished with a gradient of at least 3-1/2 percent away
from the structure for a minimum horizontal distance of 3 feet. Drainage should
be further maintained by a swale or drainage path at a gradient of at least 1-
percent for area drains and paved drainage swales and 2-percent for unpaved
drainage swales to a suitable collection device (i.e. area drain, street gutter, etc.).
We also recommend that structural footings within 4 feet of the drainage swale
flowline be deepened so that the bottom of the footing is at least 12 inches below
the flow-line of the drainage swale. In places where tiie prospect of maintaining
the minimum recommended gradient for the drainage swales and tiie consti-uction
^^^^
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Geotechnical Update Report. Bressi Ranch. Carlsbad. California 10570.001
of additional area drains is not feasible, provisions for specific recommendations
may be necessary, outlining the importance of maintaining positive drainage.
The impact of heavy irrigation or inadequate runoff gradient can create perched
water conditions, resulting in seepage or shallow groundwater conditions where
previously none existed. Maintaining adequate surface drainage and controlled
irrigation will significantly reduce the potential for nuisance-type moisture problems.
To reduce differential earth movements (such as heaving and shrinkage due to tiie
change in moisture content of foundation soils, which may cause distress to a
stmcture or improvement), the moisture content of the soils surrounding the
structure should be kept as relatively constant as possible.
All area drain inlets should be maintained and kept cdear of debris in order to
function properly. Rerouting of site drainage pattems and/or installation of area
drains should be performed, if necessary. A qualified civil engineer or a landscape
architect should be consulted prior to rerouting of drainage.
6.9 Slope Maintenance Guidelines
It is the responsibility of the owner to maintain the slopes, including adequate
planting, proper irrigation and maintenance, and repair of faulty irrigation
systems. To reduce the potential for erosion and slumping of graded slopes, all
slopes should be planted with ground cover, shrubs, and plants that develop
dense, deep root stmctures and require minimal irrigation. Slope planting should
be carried out as soon as practical upon completion of grading. Surface-water
runoff and standing water at the top-of-slopes should be avoided.
Oversteepening of slopes should be avoided during constmction activities and
landscaping. Maintenance of proper lot drainage, undertaking of property
improvements in accordance with sound engineering practices, and proper
maintenance of vegetation, including regular slope irrigation, should be
performed. Slope irrigation sprinklers should be adjusted to provide maximum
uniform coverage with minimal of water usage and overiap. Oven/vatering and
consequent runoff and ground saturation should be avoided. If automatic
sprinklers systems are installed, their use must be adjusted to account for rainfall
conditions.
Trenches excavated on a slope face for any purpose should be properiy
backfilled and compacted in order to obtain a minimum of 90 percent relative
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
compaction, in accordance with ASTM Test Method D1557. Observation/testing
and acceptance by the geotechnical consultant during trench backfill are
recommended. A rodent-control program should be established and maintained.
Prior to planting, recentiy graded slopes should be temporarily protected against
erosion resulting from rainfall, by the implementing slope protection measures
such as polymer covering, jute mesh, etc.
6.10 Landscaping and Post-Construction
Landscaping and post-constmction practices carried out by the owner(s) and their
representative bcxiies exert significant influences on the integrity of stmctures
founded on expansive soils. Improper landscaping and post-constiuction practices,
which are beyond the control of the geotechnical engineer, are frequentiy the
primary cause of distress to these sti-uctijres. Recommendations for proper
landscaping and post-construction practices are provided in the following
paragraphs within this section. Adhering to these recommendations will help in
minimizing distress due to expansive soils, and in ensuring tiiat such effects are
limited to cosmetic damages, without compromising tiie overall integrity of
stmctures.
Initial landscaping should be done on all sides adjacent to tiie foundation of a
sti-ucture, and adequate measures should be taken to ensure drainage of water
away from tiie foundation. If larger, shade providing trees are desired, such trees
should be planted away ft-om structures (at a minimum distance equal to half the
mature height of the ti-ee) in order to prevent penetration of tiie to-ee roots beneath
the foundation of the stmcture.
Locating planters adjacent to buildings or stmctures should be avoided as much as
possible. If planters are utilized in these locations, they should be properiy
designed so as to prevent fluctuations in the moisture content of subgrade soils.
Planting areas at grade should be provided with appropriate positive drainage.
Wherever possible, exposed soil areas should be above paved grades. Planters
should not be depressed below adjacent paved grades unless provisions for
drainage, such as catch basins and drains, are made. Adequate drainage
gradients, devices, and curbing should be provided to prevent mnoff from adjacent
pavement or walks into planting areas.
Watering should be done in a uniform, systematic manner as equally as possible
on all sides of the foundation, to keep the soil moist. Imgation methods should
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Geotechnical Update Report. Bressi Ranch. Carlsbad. Califomia 10570.001
promote unifonnity of moisture in planters and beneath adjacent concrete flatwork.
Overwatering and underwatering of landscape areas must be avoided. Areas of
soil that do not have ground cover may require more moisture, as they are more
susceptible to evaporation. Ponding or trapping of water in localized areas adjacent
to the foundations can cause differential moisture levels in subsurface soils and
should, therefore, not be allowed. Trees located witiiin a distance of 20 feet of
foundations would require more water in periods of exti-eme drought, and in some
cases, a root injection system may be required to maintain moisture equilibrium.
During extreme hot and dry periods, close observations should be can-led out
around foundations to ensure that adequate watering is being undertaken to
prevent soil from separating or pulling back fl-om the foundations.
6.11 Construction Observation and Testing
Consti-uction observation and testing should be perfonned by the geotechnical
consultant during the remaining grading operations, future excavations and
foundation or retaining wall constmction on the graded portions of the site.
Additionally, footing excavations should be observed and moisture determination
tests of sufcigrade soils should be perfonned by the geotechnical consultant prior to
the pouring of concrete. Foundation design plans should also be reviewed by tiie
geotechnical consultant prior to excavations.
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Geotechnical Update Report. Bressi Ranch. Carlsbad. California 10570.001
7.0 LIMITATIONS
The conclusions and recommendations presented in this report are based in part upon
data that were obtained from a limited number of observations, site visits, excavations,
samples, and tests. 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.
-29-
FIGURE
Project: 10570.001
Scale: 1 " = 2.000 ' Date; January 2014
Eng/Geol: WDO/MDJ
Base Map; ESRI ArcGIS Online 2014
Thematic Information Leighton
Author Leighton Geomalics (cgiovando)
SITE LOCATION MAP
Lot 19-22 Of Carlsbad Tract No. CT 02-15
Bressi Ranch
Carlsbad, California
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APPENDIX A
REFERENCES
Geotechnical Update Report. Bressi Ranch. Carisbad, California 10^70,001
APPENDIX A
REFERENCES
Califomia Division of Mines and Geology (CDMG), 1995, Landslide Hazards in tiie
Northern Part of the San Diego Metropolitan Area, San Diego County, Califomia,
Open-File Report 95-04.
, 1996, Probabilistic Seismic Hazard Assessment for the State of Califomia,
open-File Report, 96-08.
, 1998, Maps of Known Active Fault Near-Source Zones in Califomia and
Adjacent Portions of Nevada, dated Febmary 1998.
Califomia Building Standards Commission (CBSC), 2013, California Building Code,
Volume I and Volume II.
California Geological Survey, 2003, The Revised Califomia Probabilistic Seismic Hazard
Assessment Maps, June 2003.
Hannan, D., 1975, Faulting in the Oceanside, Carisbad and Vista Areas, Northern San
Diego County, Califomia in Ross, A. and Dowlens, R.J., eds., Studies on tiie
Geology of Camp Pendleton and Westem San Diego County, California: San
Diego Association of Geologists, pp. 56-59.
Hart, E.W. and Bryant W.A., 2007, Fault-Rupture Hazard Zones in California, Alquist-
Priolo Special Studies Zones Act of 1972 with Index to Special Studies Zones
Maps: Department of Conservation, Division of Mines and Geology, Special
Publication 42.
Jennings, C.W., 1994, Fault Activity Map of California and Adjacent Areas, with Locations
and Ages of Recent Volcanic Eruptions: Califomia Division of Mines and Geology,
Califomia Geologic Data Map Series, Map No. 6, Scale 1:750,000.
Kennedy, M.P. and Welday, E.E., 1980, Character and Recency of Faulting Offshore
Metropolitan San Diego, California: California Division of Mines and Geology Map
Sheet 40.
A-l
Geotechnical Update Report. Bressi Ranch. Carisbad. California 10570.001
APPENDIX A (continued)
Leighton and Associates, Inc., 1997, Preliminary Geotechnical Investigation, Bressi
Ranch, Carisbad, California, Project No. 4971009-002, dated July 29, 1997.
, 2001, Supplemental Geotechnical Investigation for Mass Grading, Bressi
Ranch, Carisbad, California, Project No. 971009-0015, dated March 14, 2001.
, 2002, Geotechnical Conclusions Concerning the Mass Grading
Recommendations Relative to Proposed Fine Grading and Review of the 40-
Scale Tentative Maps, Bressi Ranch, Carisbad, Califomia, Project No. 971009-
007, dated September 12, 2002.
, 2003a, Geotechnical Grading Plan Review of the Mass Grading Plans,
Bressi Ranch, Carlsbad, Califomia, Project No. 971009-007, dated January 17,
2003.
, 2003b, Preliminary Residential and Commercial Foundation Design
Recommendations, Bressi Ranch, Carisbad, Califomia, Project No. 971009-007,
dated Febmary 5, 2003.
, 2004a, Summary of the As-Graded Geotechnical Conditions and Partial
Completion of Rough and Fine Grading, Planning Areas PA-1 Through PA-5,
Bressi Ranch, Carisbad, California, Project No. 971009-014, dated January 20,
2004.
, 2004b, Geotechnical Maps, Planning Areas PA-4 and PA-5, Bressi Ranch,
Carisbad, Califomia, Project No. 971009-014, dated April 15, 2004.
, 2004c, As-Graded Report of Mass Grading, Planning Areas PA-1, PA-2,
and PA-3, Metropolitan Street, and a Portion of Town Garden Road, Gateway
Road, and Alicante Road, Carisbad Tract No. 00-06, Bressi Ranch, Carisbad,
California, Project No. 971009-014, dated April 15, 2004.
A-2
Geotechnical Update Report. Bressi Ranch. Carlsbad. California 1057PrO01
APPENDIX A (continued)
, 2004d, Addendum to the As-Graded Reporte of Mass Grading Concerning
the Completion of Settlement Monitoring, Planning Areas PA-1 through PA-5,
Bressi Ranch, Carisbad, Califomia, Project No. 971009-014, dated October 11,
2004.
, 2006, Geotechnical Update Investigation, Lots 24 through 28 of Planning
Area PA-4, Bressi Ranch, Carisbad, California, Project No. 971009-041, dated
February 3, 2006
Leighton and Associates, Inc., 2007, As-Grade Report of Fine Grading, The Towers at
Bressi Ranch, Lots 24 through 28 of Planning Area PA-4, Carisbad Tract No. CT
02-15, Carisbad, California, Project No. 971009-045, dated February 23, 2007.
Leighton Consulting, Inc., 2012, Geotechnical Update Investigation Proposed Bressi
Ranch Hotels Lot 1 of Carisbad Tract No. CT 06-20 (Planning Area PA-4, Bressi
Ranch), Carlsbad, California, Project No. 603446-001, dated May 15, 2012.
Shea Properties Management Company, Inc., 2013, Conceptual Site Plan, Bressi
Ranch Lots 19, 20, 21, & 22, Carisbad, California, dated September 30, 2013,
revised October 4, 2013.
A-3
APPENDIX B
TEST PIT LOGS
LOG OF TRENCH: JLA.
Project Name: .^tiea/Lots 19-22
Project Number:
Equipment:
1Q5Z0.QQ1
Logged by:
Elevation:_
-Chris Livfisey
373'
Baci<hoe Location/Grid: PBB nantprhninal Map
GEOLOGIC
ATTITUDES DATE: January 7,2014 DESCRIPTION: GEOLOGIC
UNIT
ENGINEERING PROPERTIES
USCS Sample
No.
Moisture
(%)
Density
(pcf)
G.B. N50W,
6N
Tertiary Santiago Fonnation (Tsa)
@ 0-1.7': SILTSTONE, light gray, dry, weathered, severely fractured,
manganeese oxidation, laminated folds of light reddish brown fine silty sandstone,
rootiets fragments.
@ 1.7'-2.3': Fossiliferous silty SANDSTONE, orange brown, slightly moist, fine
sand, abundant shell fragments and bivalve shells.
@ 2.3'-2.6': CLAYSTONE, gray brown, moist, general bedding attitude
@ 2.6'-3.1': White, moist, calcium carbonate
@ 3.1'-3.5': SILTSTONE, medium gray brown, .moist, mottled with oxidized pea
gravel fine sandstone.
@ 3.5'-4.2': SANDSTONE, light gray, slightly moist.flne sand.
@ 4.2'-6':Silty SANDSTONE, orange brown, oist, fine sabd, calcium carbonate
large gravel, gradational contact fi-om above strata.
@ 6-7': SILTSTONE, light gray, moist, oxidized.
@ 7'-9': Sandy SILTSTONE, light gray, moist, fine sand.
Tsa
BB-1
@0'-
1.5'
GB-1
@ 2.3'-
2.6'
GRAPHICAL REPRESENTATION: East Wail SCALE: 1°=5" SURFACE SLOPE: Flat TREND: N5W
f
Ilk
i
1
/
/
Total Oepth = 9 Feet
No Ground Water Encountered
Backfilled: January 7, 2014
LOG OF TRENCH: J:=2_
Project Name:
Project Number: 1057Q.0Q1.
Logged by:.
Elevation:_
Chris Livesey
-•^7fi'
Equipment: Bankhofi Location/Grid: .<SBP> npntanhnlr^al Map
GEOLOGIC
ATTITUDES DATE: January 7,2014 DESCRIPTION: GEOLOGIC
UNIT
ENGINEERING PROPERTIES
USCS Sample
No.
Moisture
(%)
Density
(pcf)
b:N20W,7S
b:N25E,10W
b;N5W,7W
Tertiary Santiago Formation (Tsa)
@ 0'-5.5': CLAYSTONE, medium gray, moist (upper 2' is dry), claystone bedding
varies from laminated to thinly bedded, bedding is distinguished by interiseds of
oxidized orange brown laminated silty sandstone and siltstone, very thin to thin
beds of calcium carbonate, jointing and fractures well healed with calcium
carbonate.
@2': General bedding attitude
@2.3': General bedding attitude
@2.5': General bedding attitude
Tsa BB-1
@0'-
5.5'
GB-1
@
various
location
GRAPHICAL REPRESENTATION: East Wall SCALE: r=5' SURFACE SLOPE: Flat TREND: NS
Total Depth = 5.5 Feet
No Ground Water Encountered
Backfilled: January 7, 2014
LOG OF TRENCH: J:=3_
Project Name:. Shea/Lots 19-22
Project Number:
Equipment:
10570.001
Logged by:.
Elevation:_
Chris livesey
369'
JBackhoe. Location/Grid: .QPP fipntpnhnirial Map
GEOLOGIC
ATTITUDES DATE: January 7, 2014 DESCRIPTION: GEOLOGIC
UNIT
ENGINEERING PROPERTIES
USCS Sample
No.
Moisture
(%)
Density
(pcf)
Artificial fill (Af)
@ 0'-6': Silty SAND, light brown, slightly moist (upper foot Is dry), fine sand, small
angular orange brown siltstone and light gray/black claystone, small 1'-1.5'
diameter concretions
Tertiary Santiago Formation (Tsa)
@ 6'-8.5': Silty SANDSTONE light brown to light gray, moist, fine sand, laminated
orange brown oxide bedding.
Af
SIVI
Tsa
BB-1
@ 0'-4'
GB-1
@4'
GRAPHICAL REPRESENTATION: West Wall SCALE: r=5' SURFACE SLOPE: Flat TREND: NS
LOG OF TRENCH:
Project Name: Shea/Lots 19-22
Project Number:
Equipment:
10570 QQ1
Logged by:
Elevation:-.
Chris Livesey
367'
Backhoe Location/Grid: Reft npr^tiarhnlnal Map
GEOLOGIC
ATTITUDES DATE: January 7,2014 DESCRIPTION: GEOLOGIC
UNIT
ENGINEERING PROPERTIES
USCS Sample
No.
Moisture
(%)
Density
(pcf)
Artificial fill (Af)
@ 0'-7': Sandy SILT with various day content, mottied light brown witti light gray,
dry to moist with depth, small angular siltstone and claystone fragment,
dessication cracks within the upper foot.
Tertiary Santiago Formation (Tsa)
@ 7"-9': Sandy SILTSTONE, light brown to light gray, slightly moist, fine sand,
laminated, oxidized orange bedding differentiates thin bedding.
Af
ML
GB-1
@5'
Tsa
GRAPHICAL REPRESENTATION: West Wall SCALE: r=5' SURFACE SLOPE: Flat TREND: NSE
LOG OF TRENCH: T-5
Project Name:. Shea/Lots 19-22
Project Number: ... 10570001.
Logged by;.
Elevation:—
Chris Livesey
Equipment: -BackhofiL.
GEOLOGIC
ATTITUDES
Location/Grid: fifv^fpnhnir-al Map
DATE: January?, 2014 DESCRIPTION: GEOLOGIC
UNIT
ENGINEERING PROPERTIES
USCS Sample
No.
Moisture
(%)
Density
(pcf)
Artificial fill (Af)
@ 0'-9.5': Sandy SILT with various clay content, light brown mottled with medium
gray and light brown, slightiy moist (upper 2 feet Is dry), small angular dark gray
and ornage brown siltstone gravel, upper 2 feet exhibits dessication cracks.
@ 2'-3': Moist lense
Af
ML
GB-1
GRAPHICAL REPRESENTATION: East Wall SCALE: 1"=5' SURFACE SLOPE: Flat TREND: N10E
Total Depth = 9.5 Feet
No Ground Water Encountered
Backfilied: January 7.2014
LOG OF TRENCH:
Project Name:. Shea/Lots 19-22
Project Number:
Equipment: .
10570.001.
Logged by:.
Elevation:—
Chris Livesey
366'
...Backhoe-Location/Grid: SRB fifiotechninal Map
GEOLOGIC
ATTITUDES DATE: January 7.2014 DESCRIPTION: GEOLOGIC
UNIT
ENGINEERING PROPERTIES
USCS Sample
No.
Moisture
(%)
Density
(pcf)
Artificial fill (Af)
@ O'-T: Sandy SILT, light brown, dry to slightly moist, fine sand, small angular
gray siltstone and orange sandstone fragments, upper 1.5 feet is dry and exhibits
dessication cracks.
Af
ML
BB-1
@ 2'-3'
GB-1
@4'
GRAPHICAL REPRESENTATION: East Wall SCALE: r=5' SURFACE SLOPE: Flat TREND: NS
LOG OF TRENCH:
Project Name:. Shea/Lots 19-22
Project Number:
Equipment:
10570.001
Logged by:
Elevation;-.
Chris Livesey
371'
Backhoe.. Location/Grid: Sp.ft Gftntefshnical Map..
GEOLOGIC
ATTITUDES DATE: January 7,2014 DESCRIPTION: GEOLOGIC
UNIT
ENGINEERING PROPERTIES
USCS Sample
No.
Moisture
(%)
Density
(pcf)
Artificial Fill (Af)
@ 0'-7.5': Sandy SILT, light brown mottled with light gray and orange brown,
slightiy moist, fine sand, cobble size concretions, upper 2 feet is dry and exhibits
desication cracks
Af
ML BB-1
@ 0'-4'
GB-1
@3'
GB-2
@7'
GRAPHICAL REPRESENTATION: East Wall SCALE; 1"=5' SURFACE SLOPE: Flat TREND; NS
LOG OF TRENCH: T-R
Project Name;. Shea/Lots 19-2?
Project Number:
Equipment:
JJQ5Z0,Q01
Logged by:.
Elevation:_
Chris LivesejL
372'
-BacktJCffiL.
GEOLOGIC
ATTITUDES
Location/Grid: Ses Gfintfinhnical Map...
DATE: January?, 2014 DESCRIPTION: GEOLOGIC
UNIT
ENGINEERING PROPERTIES
USCS Sample
No.
Moisture
(%)
Density
(pcf)
Artificial fill (Af)
@ O'-l.5': CLAY (CH), medium gray, dry grades to moist grades to very moist.
1.5'-2.5': Silty SAND (SM), mottled tan brown and light gray, slightly moist, fine
sand.
(g 2.5'-5': Sandy Clayey SILT (ML), mottled gray clay with light brown silt with
orange brown fine sand, slightiy moist
Tertian/ Santiago Formation (Tsa)
@ 5'-6.5': SILTSTONE, medium gray, moist, thinly bedded with orange brown
sandy siltstone
Af
CH
SM
ML
Tsa
GRAPHICAL REPRESENTATION: East Wall SCALE: 1"=5' SURFACE SLOPE: Flat TREND: NSE
Total Deptti = 6.S Feet
No Ground Water Encountered
Backfilled: January 7. 2014
Leighton
FIELD PERCOLATI TEST DATA SHEET
Projert Name: Shea/Lots 19 to 22 Project No.: 10570.001
Proj. Address: Gateway & Innovation Way. Carlsbad, GA
SOIL TYPE / TEST LOCATION / BOREHOLE
Soil Type: Af
Location: See Geotechnical Map
Hole Dia: 4"
Depth 3.70'
Tested by: CDL Pre-Saturation Date: 1-7-2014 Test Date: 1-8-2014
Notes: Measurements in lOOths of foot
Time of Day Inten/al / Notes Water Level Time of Day Intenral / Notes Water Level
10:31 added water 2,9
11:01 30" 2.94
11:31 30" 2.97
12:01 30" 3.02
12:31 30" 3,05
12:33 30" 3,07
1:03 added water 2.85
1:33 30" 2.91
2:03 30" 2.96
2:33 30" 3.03
3:03 30" 3.07
3:33 30" 3.1
FOR OFFICE USE ONLY DATE RECEIVED: -5E
Notes: 0.012 inch per minute or 83.3 minutes per inch
Leighton
FIELD PERCOLATION TEST DATASHEET
Project Nanne; Shea/Lots 19 to 22 Project No.: 10570.001
Proj. Address: Gateway & Innovation Way, Carlsbad, CA
SOIL TYPE / TEST LOCATION / BOREHOLE
Soil Type: Tsa
Location: See Geotechnical Map
Hole Dia: 4"
Depth 3.60'
Tested by: CDL Pre-Saturation Date: 1-7-2014 Test Date: 1-8-2014
Notes: Measurements in lOOths of foot
Time of Day Interval / Notes Water Level Time of Day Interval / Notes Water Level
10:12 added water 2.9
10:42 30" 3.05
10:46 added water 2.77
11:16 30' 2.84
11:45 30" 2.87
12:16 30" 2.94
12:18 added water 2.86
12:48 30" 2.96
12:49 added water 2.73
1:19 30" 2.75
1:49 30" 2.8
2:19 30" 2.83
2:49 30" 2.87
3:19 30" 2,91
FOR OFFICE USE ONLY DATE RECEIVED: By:
Notes: 0.016 inch per minute or 62.5 minutes per inch
APPENDIX C
LABORATORY TESTING PROCEDURES AND TEST RESULTS
Geotechnical Update Reoort. Bressi Ranch. Carisbad. California 10570.001
APPENDIX C
Laboraton/ Testing Procedures and Test Results
Expansion Index Tests: The expansion potential of selected materials was evaluated by
the Expansion Index Test, ASTM Standard D4829. Specimens are molded under a given
compacrtive energy to approximately the optimum moisture content and approximately 50
percent saturation. The prepared 1-inch thick by 4-inch diameter specimens are loaded to
an equivalent 144 psf surcharge and are inundated with water until volumetric equilibrium
is reached. The resulte of these tests are presented in the table below:
Sample Location Sample Description Expansion
Index
Expansion
Potential
T-1 (g 0 to 1 foot Light Brown CLAY 140 Very High
T-6 (g 2 to 3 feet Brown lean sandy SILT 79 Medium
E-6* Olive-brown CLAY 163 Very High
*Leighton, 2004c
Minimum Resistivity and pH Tests: Minimum resistivity and pH tests were perfomied in
general accordance with Caltrans Test Method CT643 for Steel or CT532 for concrete
and standard geochemical methods. The resulte are presented in tiie table below:
1 Sample Location Sample Description pH
Minimum Resistivity
(ohms-c^)
T-3 Brown Silty SAND 7.7 618
T-7 Brown Sandy SILT 8.0 697
C-1
Geotechnical Update Report. Bressi Ranch. Carisbad. California 10570.001
APPENDIX C (Continued)
Chloride Content: Chloride cx>ntent was tested in accordance witii Caltrans Test Method
CT422. The resulte are presented below:
1 Sample Location Chloride Content, ppm Chloride Attack 1
Potential 1
T-3 214 Threshold |
T-7 109 Threshold 1
Soluble Sulfates: The soluble sulfate contents of selected samples were determined by
standard geochemical methods (Calti-ans Test Method CT417). The test results are
presented in the table below:
Sample Location Sulfate Content
(ppm)
Potential Degree
of Sulfate Attack
T-3 450 Moderate
T-7 270 Moderate
C-2
APPENDIX D
GENERAL EARTHWORK AND GRADING SPECIFICATIONS
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 tiie
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
ofthe 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 significantiy 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.
-1-
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 Conti-actor 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 tiie 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 wori< schedules and updates to
the wori< 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 earthwori^ 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
Vegetation, such as bmsh, grass, roots, and other deleterious material
shall be sufficientiy removed and properiy disposed of in a method
acceptable to the owner, governing agencies, and the Geotechnical
Consultant.
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 presentiy 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 Processing
Existing ground that has been declared satisfactory for support of fill by
the Geotechnical Consultant shall be scarified to a minimum deptii 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 fl-ee of large clay lumps or clods and the woricing
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 othenvise unsuitable
ground shall be overexcavated to competent ground as evaluated by the
Geotechnical Consultant during grading.
2.4 Benching
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 illusfi-ation. 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 tiie Geotechnical Consultant.
Other benches shall be excavated a minimum height of 4 feet into
competent material or as otherwise recommended by the Geotechnical
I
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
Consultant. Fill placed on ground sloping flatter than 5:1 shall also be
benched or othenvise overexcavated to provide a flat subgrade forthe fill.
2.5 Evaluation/Acceptance 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 witii 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 Import
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 woricing
days) before importing begins so that its suitability can be determined and
appropriate tests performed.
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 slightiy over
optimum. Maximum density and optimum soil moisture content tests shall
be perfomied 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 efficientiy achieve the
specified level of compaction with unifonnity.
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 t>e 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 necjessarily 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 Freguencv of Compaction Testing
Tests shall be taken at 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 c^onstruction is such that the
testing schedule can be accomplished by the Geotechnical Consultant.
The Contractor shall stop or slow down the earthwork constmction 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
witiiin 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
deptiis 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 tiie Geotechnical
Consultant.
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
7.0 Trench Backfills
7.1 Safetv
The Conti-actor 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 Worics Constmction 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 Geotechnical Consultant.
-7-
RLL SLOPE
PROJECTED PLANE 1:1
(HORIZONTAL: WRTICAL)
MAXIMUM FROM TOE
OF SLOK TO
APPROVEO GROUND
EXISTING-
GROUND SURFACE
2 FEET
KEY DEPTH
BENCH HEIGHT
(4 FEET Pd^lCAL)
REMOVE
UNSUITABLE
MATERIAL
15 FEET MIN-
LOWEST
BENCH (KEY)
RLL-OVB1-CUT SLOPE
EXISTING
GROUND SURFACE
:gsjj« , BENCH I L-BENCH HEIGHT
LOWEST
2 FEET-J BENCH (KEY)
MIN. KEY
DEPTH
(4 FEET TYPICAL)
REMOVE
UNSUITABLE
MATERIAL
CUT-OVEFl-FILL SLOPE
"CUT FACE
SHALL BE CONSTRUCTED PRIOR TO
FILL PLACEMENT TO ALLOW VIEWING
OF GEOLOGIC CONDITIONS
EXISTING-
GROUND
SURFACE
PROJECTED PLANE
1 TO 1 MAXIMUM
FROM TOE OF SLOPE
TO APPROVED GROUND
2 FEET
KEY DEPTH
UT FACE SHALL BE
CONSTRUCTED PRIOR
TO FILL PLACEMENT
OVERBUILD AND
TRIM BACK REMOVE
UNSUITABLE
MATERIAL
15 FEET MIN.
LOWCST
BENCH (KEY)
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.
KEYING AND BENCHING
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL A
-FINISH GRADE
SLOPE FACE
5" MIN. -i!?<'-:-:-:-:-:-:-:-:-:-:->fe-:-:-:-:-^^
fK-10 MtN.-:-:-»:-»:-;4 MlNr:-f*«:
OVCRSIZE WINDROW
• OVtRSZE ROCK IS LARGER THAN
8 INCHES IN LARGEST DIMENSION.
• EXCAVATE A TRENCH IN THE CC»«PACTEO
FILL DEEP ENOUGH TO BURY ALL THE
ROCK.
• BACKFILL WITH GRANULAR SOIL JETTED
OR FLOODED IN PLACE TO FILL ALL THE
VOIDS.
• 00 NOT BURY ROCK WITHIN 10 FEET OF
FINISH GRADE.
• WINDROW OF BURIED ROCK SHALL BE
PARALLEL TO THE FINISHED SLOPE.
GRANULAR MATERIAL TO BE
DENSIFIED IN PLACE BY
FLOODING OR JETTING,
DETAIL
— - ^ ^JETTED OR FLOODED
GRANULAR MATERIAL
TYPICAL PROFILE ALONG WINDROW
OVERSIZE ROCK
DISPOSAL
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL B
BENCHING
REMOVE
UNSUITABLE
MATERIAL
SUBDRAIN
TRENCH
SEE DETAIL BELOW
CALTRANS aASS 2 PERMEABLE
OR #2 ROCK (9FT''3/FT) WRAPPED
IN FILTER FABRIC fl
FILTER FABRIC
{\mm 14!»i OR APPROWD
ECJUIVALENl)'
BEDDING
CCX.LECTOR PIPE SHALL
BE MINIMUM 6" DIAMETER
SCHEDULE 40 PVC PERFORATED
PIPE. SEE STANDARD DETAIL 0
FOR PIPE SPECIFIC ATIC^IS
SV6PRAIN PETAIL
DESIGN FINISH
GRADE
NONPERFORATED 6 0 MIN 6" 0MIN, PIPE
FILTER FABRIC
(MIRAFI 140N OR APPROVED
EQUIVALENT)
CALTRANS CLASS 2 PERMEABLE
OR |2 ROCK (SFT^J/FT) ViS?APPED
IN FILIER FABRIC
P£TAIL OF CANYON SMgPRAiN OUTLET
CANYON SUBDRAINS GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL C
15' MIN.
OUTLET PIPES
4" 0 NONPERFORATED PIPE.
100" MAX. O.C. HORIZONTALLY.
30* MAX O.C. VERTICALLY
SACK CUT
1:1 OR FLATTER
SEE SUBDRAIN TRENCH
OETAIL
LOWEST SUBDRAIN SHOULD
BE SITUATED AS LOW AS
POSSIBLE TO ALLOW
SUITABLE OUTLET
-KEY DEPTH
(2' MIN.)
KEY WIDTH
AS NOTED ON GRADING PLANS
(15' MIN.) 12" MIN, OVERLAP —
FROM THE TOP HOG
RING TIED EVERY
6 FEET
CALTRANS CLASS II
PERMEABLE OR #2
ROCK (3 FT~3/FT)
VSRAPPED IN FILTER
FABRIC
-4" 0
NON-PERFORATED
OUTLET PfPE
PROWDE POSITIVE
SCAL AT THE
jaNT
T-CON,NECTION
FOR COLLECTCW?
PIPE TO OUTLET PIPE
4"0
PERFORATED
PIPE
-FILTER FABRIC
ENVELOPE (MIRAFI
140 m APPROVEO
EQUIVALENT)
4 MIN.
BEDDING
SUBDRAIN TRENCH DETAIL
SUBDRAIN INSTALLATION - subdroir? c<^lector pipe sholl be instoiied with perforotion down or,
unless otherwise designoted by the geotechnicol cor^sultont. Outlet pipes shoM be f>on-perforoted
pipe. The subdroin p'^e sholl hove ot leost 8 perforotions uniformiy spoced per fool. Pwforotion
sholl be l/-*" to 1/2" it drill hoJes ore used. All subdroin pipes shoil hove o grodieht of ot
ieost 2% towords the outlet.
SUBDRAIN PIPE - Subdroin pipe sholl be ASTM 02751. SDR 23,5 or ASTM 01527. Schedule 40. or
ASTM 03034. SDR 23.5. Schedule 40 Polyvinyl CWoricie Plostic (PVC) pipe.
All outlet pipe sholl be ploced in o trench no wider thon twice the subdrain pipe.
BUTTRESS OR
REPLACEMENT
FILL SUBDRAINS
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL D
CUT-FILL TRANSITION LOT OVEREXCAVATION
REMOVE
UNSUITABLE
GROUND•
5" MIN, ^
OVEREXCAVATE
AND RECOMPACT
UNWEATHERED BEDROCK DR MATERIAL AP^ROWD
BY THE GEOTECHNICAL CONSULTANT-
TRANSITION LOT FILLS
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL E
RETAINING WALL
WAU WATERPROOFING
PER ARCHITECT'S
SPECIFICATIONS
SOIL BACKFILL. COMPACTED TO
90 PERCENT RELATIVE COMPACTION
BASED ON ASTM 01557
WALL FOOTING
FILTER FABRIC ENVELOPE
'(MIRAFI HON OR APPROVED
EOUIVALENT)"
-3/4" TO 1-1/2" CLEAN GRAVEL
-4" (MIN.) DIAMETER PERFORATED
PVC PIPE (SCHEDULE 40 OR
EQUIVALENT) WITH PERFORATIONS
ORIENTED DOWN AS DEPICTED
MINIMUM 1 PERCENT GRADIENT
TO SUITABLE OUTLET
-3" MIN.
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 ^9
GRAVEL
DRAINAGE FILL
MIN GT BELOW WALL
mn 12" BEHIND UNITS
FOUNDATION SOILS
REAR SUBDRAIN:
4" (MIN) DIAMETER PERFORATED PVC PIPE
(SCHEDULE 40 OR EQUIVALENT) WITH
PEra^ORATIONS DOWN. SURROUNDED BY
1 CU. FT/FT OF 3/4- GRAVEL WRAPPED IN
FILTER FABRIC (MIRAFI 140N OR EQUIVALENT)
OUTLET SUBDRAINS EVERY 100 FEET, OR CLOSER,
BY TIGHTLINE TO SUrrABLE PROTECTED OUTLET
GRAVEL DRAINAGF FILL-
SIEVE Sl^ % PASSING
11NCH
3/4 INCH
NO.4
NO. 40
NO. 20)
100
75-100
0-60
0-50
0-5
NOTES:
1) MATERIAL GRADATION AND PLASTICITY
REINFnRr.FD ZONE:
SIEVE SIZE % PASSING
1 INCH 100
NO. 4 20-100
NO. 40 0-60
NO. 200 0-35
FOR WALL HEIGHT < 10 FEET, PLASTICITY INDEX < ^
FOR WALL HEIGHT 10 TO 20 FEET, PLASTICITY INDEX < 10
FOR TIERED WALLS. USE COMBINED WALL HEIGHTS
WALL DESIGNER TO RECR/EST SITE-SPECIFIC CRITERIA FOR WALL HEIGHT > 20 FEET
2) CONTRACTS? TO USE SOILS WITHIN THE RETAINED AND REINFORCED ZONES THAT MEET THE STRENGTH REQUIREMENTS OF WALL DESIGN.
3) GEOGRID REINFORCEMENT TO BE DESIGNED BY WALL DESIGNER CONSIDERING INTERNAL, EXTERNAL, AND COMPOUND STABILITY.
3) GEOGRID TO BE PRETENSIONED DURING INSTALLATION.
4) IMPROVEMENTS WITHIN THE ACTIVE ZONE ARE SUSCEPTIBLE TO POST-CONSTRUCTION SETTLEMENT. ANGLE a 45+0/2, WHERE * IS THE
FRICTION ANGLE OF THE MATERIAL IN THE RETAINED ZONE.
5) 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
RETAINING WALLS
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL G
APPENDIX E
ASFE
mportant Information about Your
Geoteclmical Engineeping Report
Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes.
While you cannot eliminate all such risks, you can manage them. The foltowing information is provided to help.
Geoteclmical Services Are Pepformed (OP Specific Purposes, Persons, ami Projects
Geotechnica! engineers strudure their services to meet the specific needs ot
their clients, A geotechnical engineering study conducted for a civil engi-
neer may not fulfill the needs of a construction contractor or even another
civil engineer. Because each geotechnica! engineering study is unique, each
geotechnical engineering report is unique, preparpn so/e/yfor the client. No
one except you shouid reiy on your geotechnical engineering report without
first conferring with the geotechnical engineer who prepared it. And no one
—not em you—should apply the report for any purpose or project
except the one originally contemplated.
Serious problems have occurred because those relying on a geotechnica^
engineering repo.l did not read it all. Do not reiy on an executive summary.
Do not read selected elements oniy.
A fieotecMcal Qiglneering ^wrt Is Based on A Unique Set of Prjogect-Spoim Factors
Geotechnical engineers consider a number of unique, project-specific fac-
tors when establishing the scope of a study, Typical factors include; the
client's goals, objectives, and risk management preferences; the general
nature of the structure involved, its size, and configuration; the location of
tne structure on the site; and other planned or existing site improvements,
such as access roads, parking lots, and underground utilities. Unless the
geotechnical engirieer who conducted the study specifically indicates
otherwise, do not rely on a geoiechnicai engineering .report that was:
• not prepared for you,
• not prepared for your project,
• no! prepared for the specific site expiored, or
• completed before important project changes were made.
Typical changes that can erode the reliability of an exisling geotechnica
engineering report inciude those that affect:
• the function of the proposed structure, as when it's changed from a
parl<ing garage to an office buiiding, or from a light industrial plant
to a refrioerated w3rehou.se.
elevation, configuration, location, orientation, or weight of the
proposed structure,
composition of the design team, or
project owner:
As a general rule, a/wsys inform your geotechnical engineer of project
changes—even minor ones—and r^uest an assessment of their impact.
Geotechnica! engineers cannot accept responsibHify or liability for problems
ttiat occur because ttieir reports do not consider developments of which
they were not informed.
A geotechnical engineering report is based on conditions fhat existed at the
time the sUJdy MS performed. Do not rely on a geotechnical engineering
reportwhDse adequacy may have been affected by: the passage of time; by
man-mads events, such as construction on or adjacent to the site; or by
natural events, such as floods, earthquakes, or gmnimte fluctuations.
Aimys contact the geotechnical engineer before applying the report to
determine if il is still reliable, A minor amounl of additional testing or
analysis could prevent major problems.
Most fieotechnical Findings Are Professional
Site exploration identifies subsurface conditions only at those points 'lAfhere
subsurface tests are conducted or samples are taken. Geotechnical engi-
n^rs review field and laboratory date and then apply their professional
judgment to render an opinion about subsurface conditions throughout the
site. Actual subsurface conditions may differ—sometimes signilicantiy—
from those indicated in your report. Retaining the geotechnical engineer
who developed your report to provide construction observation is the
most effective method of managing the risks associated with unanticipated
conditions.
A Report's Recommendations Are Atof Rnal
Do not overrely on the construction recommendations included in your
report. Those recommendations are not final because geotechnical engi-
neers 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 responsibiiity or
liability for the report's recommendations If that engineer does not perform
construction obsenration
Report is Suiiject to
Other design team members' misinterpretation of geotechnical engineering
reports has resulted in costly problems. Lower that risk by having your geo-
tffihnical engineer confer mlh appropriate members of ttie design team after
submitting the report. Also retain your geotectinical engineer to review perti-
nent elements of the design team's plans and specifications. Contractors can
also misinterpret a geotechnical engineering report. Reduce fhat risk by
having your geotectinical engineer participate in prebid and preconstruction
conferences, and by providing construction observation,
Do IMot Redraw Um Engineer's Logs
Geotechnica! 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 \m redrawn for inclusion in architectural or other design drawings.
Only photographic or electronic reproduction is acceptable, but wcognim
that separating logs from the report can elevate risk.
Give Contractors a Compiete Report and
Some owners and design professionals mistakenly believe they can make
contractors liable for unanticipated subsurface conditions by limiting what
they provide for bid preparation. To help prevent costly problems, give con-
traclors the compiete geotechnical engineering report. Wpreface it with a
clearly written letter of transmittal, in that letter, advise contractors 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 ttiey
need or prefer A prebid conference can also be valuable. Be sure contrac-
tors have sufficient lime lo perform additional study. Only then might you
be in a position to give contractors the best information available to you,
while requiring them to at least share some of the financial responsibilities
stemming from unanticipated conditions.
Read ResponsiUlrty Provisions Cioseiy
Some clients, design professionals, and contractors do not recognise thaf
geotechnical engineering is far less exact than other engineering disci-
plines. This lack of understanding has created unrealistic expectations that
have led to disappointments, claims, and disputes. To help reduce ths 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' responsi-
bilities begin and end, to help others recognize their oftTi responsibilities
and risks, ftead these provisions closely Ask questions. Your geotechnical
engineer shouid respond fully and frankly.
Geoenvironmentai Concerns Are IVot Covered
The equipment, techniques, and personnel used to perform a geoenviron-
mentai sM'i' differ significantly from those used to perform a geotectinical
study. For that reason^ a geotechnical engineering report does not usually
relate any geoenvironmentai findings, conclusions, or recommendations;
e.g., about the likelihood of encountering underground storage tanks or
regulated contaminants. Unanticipated environmental problems have led to
numerous project failures. If you have not yet obtained your own geoenvi-
ronmentai information, ask your geotechnical consultant for risk manage-
ment guidance. Do not rely on an environmental report prepared for
someone else.
Obtain Professionai Assistance To Deal with lUold
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 etfective, ali such strategies should be
devised tor the express purpose of mold prevention, integrated into a com-
prehensive plan, and executed with diligent oversight by a professional
mold prevention consultant Because just a small amount of water or
moisture can lead to ttie development of severe mold infestations, a num-
ber of mold prevention strategies focus on keeping buiiding surtacss 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; nmw of the sermxs per-
tonned in connection mth the geotedmlcal aigmeer's ^tudy
were designed or conducted for the purpose of nrnld foevmi-
tion. Proper imptonmitation of the reamnmSi^ons cmveyed
in this report win not of itself be sufBc^ to premd mold frm
grovmg in orm the structure iimrived.
Rely on Your ASFi-Member Geoteclmical Bigineer for Additional Assistance
Membership in ASFE/The Geoprofessional Business Association exposes
geotechnical engineers to a wide array of risk management techniaues that
can be of genuine benefit for everyone involved with a construction projel
Confer with your ASFE-member geotechnica! engineer for more information.
THE GEOPROFESSIONAL
BUSINESS ASSOCIATION
8811 Colesville Road/Siiit3G106, Silver Spring. MD 20910
Tcitjphoiix 301/565 2733 Facsimile: 301/589-2017
e-maii: irifo@asfe,Drg '»Wi'.3sfe,org
Copyright 2004 iy ASf£, inc. Owlication, reprodvctm, or copying of this document. In whole or in pan, 6y any means whatsoever, is strictly prohibited, except mith ASFFs
specilic written permission. Excerpting, quoting, or otherxisB axtracting wonling from this document is permitted only with tne ei^ress rnlten pemUsskm otASFE, ani only tor
purposes ot scholarly research or book review. Only memtiers otASFE may use tNs document as a complement to or as an element of a geotechnical engineenng report. Any othei
firm, Individual, or other entity that so uses this document witnout being an ASFE member could he committing negligent or intentional (fraudulent) miswpressntstion.
liGEROI115,OM;!P