HomeMy WebLinkAboutCT 00-16; Poinsettia Properties; Update Geotechnical Investigation; 2000-07-20*•>
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UPDATE
GEOTECHNICAL INVESTIGATION
POINSETTIA PROPERTY
CARLSBAD, CALIFORNIA
PREPARED FOR
JOHN LAING HOMES
IRVINE, CALIFORNIA
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m JULY 2000
to:
GEOCON
INCORPORATED
GEOTECHNICAL CONSULTANTS
Project No. 06514-12-01
July 20, 2000
John Laing Homes
19600 Fairchild, Suite 150
Irvine, California 92612
Attention:
Subject:
Gentlemen:
Mr. Timothy W. McSunas
POINSETTIA PROPERTIES
CARLSBAD, CALIFORNIA
UPDATE GEOTECHNICAL INVESTIGATION
In accordance with your authorization and our proposal dated March 23, 1999, we have reviewed
and updated our original study for the subject project entitled Geotechnical Investigation for
Poinsettia Promenade, Carlsbad, California, dated January 26, 1988 (Project No. D-4052-J01). In
addition, a site reconnaissance was performed on May 17, 2000, at which time it was observed that
the site remains essentially unchanged since the submittal of the original report with the exception of
import soils that are currently being stockpiled on the property.
The accompanying report presents the results of our study and site specific conclusions and
recommendations pertaining to developing the property as presently proposed. Provided the
recommendations of this report are followed, the site is considered suitable for development as
currently planned.
Should you have any questions regarding this report, or if we may be of further service, please
contact the undersigned at your convenience.
Very truly yours,
GEOCON INCO
RCE 22527
AS:DFL:lek
(6) Addressee
(2/del) Hunsaker & Associates San Diego
Attention: Mr. Ron Grunow
6960 Flanders Drive • San Diego, California 92121-2974 • Telephone (858) 558-6900 • Fax (858) 558-6159
TABLE OF CONTENTS
1 . PURPOSE AND SCOPE 1
2 . SITE AND PROJECT DESCRIPTIONS 2
3 . SOIL AND GEOLOGIC CONDITIONS 2
3.1 Artificial Fill (Qaf-Unmapped) 2
3.2 Topsoils (Unmapped) 3
3.3 Alluvium (Qal) 3
3.4 Terrace Deposits (Qt) 3
3.5 Santiago Formation (Ts) 3
4. GROUNDWATER 3
5. GEOLOGIC HAZARDS 4
5.1 Faulting and Seismicity 4
5.2 Seismic Design Criteria 5
5.3 Liquefaction 5
5.4 Landslides 5
6. CONCLUSIONS AND RECOMMENDATIONS 6
6.1 General 6
6.2 Soil and Excavation Characteristics 6
6.3 Grading 6
6.4 Subdrains 8
6.5 Slope Stability 8
6.6 Temporary Excavations 9
6.7 Earthwork and Grading Factors 9
6.8 Foundation Recommendations 10
6.9 Retaining Walls and Lateral Loads 14
6.10 Slope Maintenance 15
6.11 Drainage 15
6.12 Plan Review 16
LIMITATIONS AND UNIFORMITY OF CONDITIONS
*» MAPS AND ILLUSTRATIONS
Figure 1, Vicinity Map
Figure 2, Geologic Map
HI
APPENDIX A
** FIELD INVESTIGATION
to Figures A-1, A-2, A-5, A-7 - A-9, Logs of Borings
Figures A-10 - A-15, A-18, A-19, Logs of Trenches
TABLE OF CONTENTS (continued)
APPENDIX B
LABORATORY TESTING
Table B-I, Summary of Laboratory Maximum Dry Density and Optimum Moisture
Content Test Results
Table B-H, Summary of Direct Shear Test Results
Table B-DI, Summary of Laboratory Expansion Index Test Results
Figures B-l and B-3, Consolidation Curves
Figures B-5 and B-6, Gradation Curves
APPENDIX C
RECOMMENDED GRADING SPECIFICATIONS
w
m
m
UPDATE GEOTECHNICAL INVESTIGATION
1. PURPOSE AND SCOPE
This report presents the results of a previous geotechnical investigation but oriented to the proposed
Poinsettia Property site located within the eastern two-thirds portion of the original 59-acre property
situated at the northwest corner of Poinsettia Lane and Avenida Encinas in Carlsbad, California (see
Vicinity Map, Figure 1). The purpose of the original investigation was to evaluate the surface and
subsurface soil and geologic conditions encountered. The purpose of this update report is to provide
project specific recommendations pertaining to the geotechnical aspects of future development.
The scope of the services to update the geotechnical investigation included a site reconnaissance and
review of the following:
1. Geotechnical Investigation for Poinsettia Promenade, Carlsbad, California, prepared by
Geocon Incorporated, dated January 26, 1988 (Project No. D-4052-J01).
2. Poinsettia Property, Carlsbad, California (Site Plan), prepared by Hunsaker & Associates
San Diego, undated.
3. Stockpile and Erosion Control Plans For: Poinsettia Properties Areas 2, 3, and 4
C.T. 07-10, prepared by O'Day Consultants, undated.
4. Unpublished reports, aerial photographs and maps on file with Geocon Incorporated.
The scope of the field investigation associated with the subject site consisted of a geologic
reconnaissance and the excavation of 5 small-diameter borings and excavation of 9 trenches. Logs of
the exploration excavations are presented in Appendix A. The approximate locations of the
exploratory excavations are depicted on the Geologic Map, Figure 2. It should be noted that the
number designation, of the excavations is from the original investigation, covering the entire project
site, and are therefore not in numerical sequence.
Laboratory tests were performed on selected soil samples to evaluate pertinent properties. Details of
the field investigation and laboratory tests are presented in Appendices A and B.
The recommendations presented herein are based upon analysis of the data in the referenced report,
observations during the investigation, and our experience with similar soil and geologic conditions.
Project No. 06514-12-01 - 1 - July 20, 2000
2. SITE AND PROJECT DESCRIPTIONS
The site consists of approximately 41 acres of undeveloped land fronting on the south side of
Avenida Encinas, to the north of Poinsettia Lane in the city of Carlsbad, California (see Vicinity
Map, Figure 1).
Topographically, the site is characterized as relatively flat but gently sloping to the west. The site is
roughly rectangular and is bounded by Avenida Encinas on the east, Poinsettia Lane on the south,
Poinsettia Station (multifamily residential) and The Poinsettia Lane Transit Center on the north, and
the San Diego Northern Railroad alignment on the west. Elevations vary from a high of
approximately 65 feet Mean Sea Level (MSL) at the east property line to a low of 48 feet MSL at the
southwest corner. Site vegetation is limited to weeds and grasses.
It is understood that the property will be developed to receive 246 single-family residential units
with associated streets and infrastructure. Off-site improvements will include widening of Avenida
Encinas along the eastern frontage. Grading will require import soils to achieve planned finish
elevations. Plans indicate fill slopes with maximum heights of 10 feet inclined at 2:1
(horizontal: vertical).
3. SOIL AND GEOLOGIC CONDITIONS
Three surficial soil types and two geologic formations exist at the property. The surficial units
include topsoil and alluvium plus the import soils currently being stockpiled. Geologic units
encountered include Pleistocene-aged Terrace Deposits and the Eocene-aged Santiago Formation.
Each of the soil types and geologic formations is discussed below in order of increasing age. With
the exception of the import soils, their estimated areal extent is shown on the Geologic Map,
Figure 2. It should be noted that the referenced investigation did not explore subsurface conditions
within the area planned for widening Avenida Encinas. Therefore, while the data from the on-site
excavations may be extrapolated, the vertical extent of the soil types may vary and fill soils may be
present from previous roadway construction.
3.1 Artificial Fill (Oaf-Unmapped)
In accordance with the previously referenced stockpile plans, soils from various locations in San
Diego County are currently being imported to the site to provide the necessary material to balance
the earthwork and achieve proposed finish grades. It is anticipated that approximately 100,000 cubic
yards of soils will be imported. The soils will not be placed as structural fill and no remediation of
Project No. 06514-12-01 - 2 - July 20, 2000
the on-site topsoils and alluvium is being performed prior to stockpiling. Therefore, the import soils
will require removal and compaction during final site development earthwork operations.
3.2 Topsoils (Unmapped)
Topsoils consisting of loose, dry to moist fine silty sands and sandy silts cover the entire site. The
topsoils average 2 to 3 feet in thickness and generally exhibited low expansive characteristics.
Removal of the topsoils will be required in areas to receive settlement sensitive structures or
structural fills as the materials are generally loose and compressible.
3.3 Alluvium (Qal)
Alluvial soils underlie the topsoils within the central portion of the site and consist of loose to
medium dense moist silty sands and soft sandy clays. In the test trenches and borings, the depth of
alluvial materials varied from approximately 2 to 6 feet. The alluvial soils possess highly expansive
characteristics and are compressible in their present state. Remedial grading recommendations for
the alluvial soils are presented in the Conclusions and Recommendations Section of this report.
3.4 Terrace Deposits (Qt)
Underlying the topsoils and alluvial soils are dense to very dense Quaternary-aged Terrace Deposits.
Typically these soils consist of fine to medium sands with traces of clay and clayey sands with a low
expansion potential. The Terrace Deposits in their present condition are suitable for support of
structural fills and posses good foundation engineering characteristics.
3.5 Santiago Formation (Ts)
The Tertiary-aged Santiago Formation is the underlying formational unit encountered at the site.
This formation consisted of dense to very dense, moist, white fine to medium sand with traces of silt
and clay. The sandy portions of this formation are generally low in expansion potential and possess
excellent foundation engineering characteristics.
4. GROUNDWATER
Groundwater was encountered in several of the borings and trenches during the field investigation.
Groundwater depths varied from 10 feet (Boring No. 9) to 19 feet (Boring No. 2) as measured below
existing grade. The groundwater generally appeared to be perched on the underlying Santiago
Formation. It is not anticipated that groundwater will significantly impact mass grading operations
Project No. 06514-12-01 ~- July 20, 2000
during the remedial earthwork. However, overly wet to saturated soils should be anticipated within
the lower depths of the alluvial soil cleanouts. We understand that during the site improvement, a
deep sewer line will be constructed to outfall at the southwest corner of the site. Groundwater should
be anticipated and the contractor should be prepared to implement an appropriate dewatering system.
5. GEOLOGIC HAZARDS
5.1 Faulting and Seismicity
A review of geologic literature, experience with the soil and geologic conditions in the general area,
and observations during the field investigation indicate that no active faults are located at the site.
The nearest known active fault is the Rose Canyon Fault Zone located approximately 4 miles west of
the site. Maximum Credible and Maximum Probable seismic events of Magnitude 6.9 and
Magnitude 5.70, respectively, are postulated for the Rose Canyon Fault Zone.
The estimated Maximum Credible and Maximum Probable peak site accelerations are 0.40 g and
0.21 g, respectively. Seismic parameters for other regional faults capable of generating ground
acceleration at the site are summarized below.
TABLE 5.1
DETERMINISTIC SITE PARAMETERS FOR SELECTED FAULTS*
Fault Name
Rose Canyon
Newport-Inglewood-Offshore
Coronado Bank
Elsinore- Julian
Elsinore-Temecula
Palos Verdes
Distance
From Site
(miles)
4
7
20
25
25
38
Maximum Credible Event
Maximum
Credible
(Mag.)
6.90
6.90
7.40
7.10
6.80
7.10
Peak Site
Acceleration
(g)
0.40
0.27
0.14
0.09
0.08
0.05
Maximum Probable Event
Maximum
Probable
(Mag.)
5.70
5.80
6.30
6.40
6.30
6.20
Peak Site
Acceleration
(g)
0.21
0.15
0.08
0.06
0.06
0.03
* EQFault Computer Program, Blake 1997 (CDMG data file)
m
m
Project No. 06514-12-01 -4-July 20, 2000
It is our opinion that the site could be subjected to moderate to severe ground shaking in the event of
a major earthquake along any of the above mentioned faults, however, the seismic risk at the site is
not considered to be significantly different than that of the surrounding developments of similar
geologic settings in the Carlsbad area.
5.2 Seismic Design Criteria
The following table summarizes site specific seismic design criteria obtained from the 1997 Uniform
Building Code (UBC). The values listed in Table 5.2 are for the Rose Canyon Fault (located
approximately 4 miles west of the site) which is identified as a Type B fault and is more dominant
than the nearest Type A fault (Elsinore) due to its close proximity to the site.
TABLE 5.2
SEISMIC DESIGN PARAMETERS
Parameter
Seismic Zone Factor, Z
Soil Profile Type
Seismic Coefficient, Ca
Seismic Coefficient, Cv
Near-Source Factor, Na
Near-Source Factor, Nv
Seismic Source
Value
0.40
sc
0.40
0.65
1.0
1.2
B
UBC Reference
Table 16-1
Table 16-J
Table 16-Q
Table 16-R
Table 16-S
Table 16-T
Table 16-U
5.3 Liquefaction
Liquefaction occurs in loose cohesionless soils located below the water table that are subjected to
large accelerations during strong earthquakes. Due to the dense nature of the formational units, the
removal and recompaction of the surficial soils, and the lack of a permanent groundwater table, the
potential for liquefaction of the site subsoils is considered to be very low.
5.4 Landslides
Based on the geologic reconnaissance and the exploration excavations, there are no landslides
present on the site anymore arg/to known to exist in near proximity that would impact the proposed
development.
Project No. 06514-12-01 -5-July 20, 2000
6. CONCLUSIONS AND RECOMMENDATIONS
6.1 General
6.1.1 No soil or geologic conditions were encountered during this geotechnical investigation
performed by Geocon Incorporated that would preclude the development of the property
provided that the recommendations of this report are followed.
6.1.2 The surficial soils such as topsoil and alluvium as well as the stockpiled import soils are
not considered suitable for support of structural fill or structural loads in their present
condition and will require remedial grading in the form of removal and recompaction.
Also, the debris and trash, if present, will need to be removed and disposed of off site.
6.1.3 Groundwater was encountered within several of the exploration excavations and generally
appears to be perched on the underlying Santiago Formation. Within the lower depths of
excavation for remedial grading the alluvial soils, earthwork operation should anticipate
overly wet to saturated soils. These soils will require drying or mixing with drier soils
prior to placement as fill. Therefore, groundwater is not expected to significantly impact
grading operations. However, groundwater will require some form of dewatering during
installation of the deeper utilities. Design of the dewatering system is considered the
responsibility of the respective contractor.
6.2 Soil and Excavation Characteristics
6.2.1 The prevailing soil conditions encountered during the field exploration consisted of very
low expansive sands derived from the Terrace Deposits. The majority of the surficial soils
posses medium to very high expansion potential.
6.2.2 It is anticipated that the surficial deposits can be excavated with a light effort using
conventional heavy duty grading equipment. A moderate to heavy effort is anticipated for
excavations within the formational sedimentary units.
6.3 Grading
6.3.1 All grading should be performed in accordance with the Recommended Grading
Specifications in Appendix C and the City of Carlsbad Grading Ordinance. Where the
recommendations of this section conflict with those in Appendix C, the recommendations
Project No. 06514-12-01 -6- July 20, 2000
of this section take precedence. All earthwork should be observed and all fills tested for
proper compaction by Geocon Incorporated.
6.3.2 Prior to commencing grading, a preconstruction conference should be held at the site with
the owner or developer, grading contractor, civil engineer and geotechnical engineer in
attendance. Special soil handling and/or the grading plans can be discussed at that time.
6.3.3 Site preparation should begin with the removal of all deleterious material and vegetation.
The depth of removal should be such that material exposed in cut areas or soils to be used
as fill are relatively free of organic matter. Material generated during stripping and/or site
demolition should be exported from the site.
6.3.4 All compressible surficial soil deposits (topsoil and, alluvium) and stockpiled import soils
within areas of planned grading should be removed to firm natural ground and properly
compacted prior to placing additional fill and/or structural loads. Removals along the edge
of grading should include excavation of unsuitable soils that would adversely affect the
performance of the planned fill; i.e., extend removals within a zone defined by a line
project down and out at a slope of 1:1 from the limit of grading to intersect with firm
natural ground. The actual extent of unsuitable soil removals will be determined in the
field during grading by the soil engineer and/or engineering geologist.
6.3.5 After removal of unsuitable materials as recommended above, the site should then be
brought to final subgrade elevations with structural fill placed and compacted in layers.
Prior to placing fill, the exposed natural ground surface should be scarified to a depth of at
least 12 inches, moisture conditioned and compacted. In general, soils native to the site are
suitable for use as fill if free from vegetation, debris and other deleterious material and
moisture content is acceptable to the geotechnical engineer. Layers of fill should be no
thicker than will allow for adequate bonding and compaction. All fill, including scarified
ground surfaces, should be compacted to at least 90 percent of laboratory maximum dry
density in accordance with ASTM Test Procedure D 1557-91, at or slightly above
optimum moisture content. Fill materials with in-place density test results indicating
moisture contents less than optimum will require additional moisture conditioning before
placing additional fill.
6.3.6 To reduce the potential for differential settlement, it is recommended that, where
applicable, the cut portion of cut/fill transition building pads be undercut at least 4 feet and
replaced with properly compacted low expansive fill soils. The undercut should extend
Project No. 06514-12-01 -7- July 20, 2000
from the back of the pad to the street and be graded at a gradient of at least 1 percent
towards the street.
6.3.7 Grading operations should be scheduled so as to permit the placement of expansive soils in
the deeper fills and to cap the building pads with at least 4 feet of granular materials
having a low expansive potential (Expansion Index less than 50 per UBC Table 18-I-B).
6.3.8 Grading plans indicate that import soils will be required to achieve finish elevations. All
import soils should be sampled, tested and approved by Geocon Incorporated prior to
import. Where practical, the import soils should consist of granular soils having a low
expansion potential. Finish grading the site with soils possessing an Expansion Index
greater than 50 will impact foundation design, concrete flatwork and pavement section
design.
6.4 Subdrains
6.4.1 No subdrains are required for grading the site.
6.5 Slope Stability
6.5.1 The grading plans indicate that all proposed slopes will be comprised of fill with a
maximum height of approximately 10 feet and at an inclination of 2:1 (horizontahvertical)
or less. These slopes will be stable for both gross and surficial stability with a factor of
safety in excess of 1.5.
6.5.2 The outer 15 feet of fill slopes, measured horizontal to the slope face, should be composed
of properly compacted "granular soil" fill to reduce the potential for surface sloughing.
6.5.3 All fill slopes should be overbuilt at least 3 feet horizontally, and cut to the design finish
grade. As an alternative, fill slopes may be compacted by back-rolling at vertical intervals
not to exceed 4 feet and then track-walking with a D-8 dozer, or equivalent, upon
completion such that the fill soils are uniformly compacted to at least 90 percent relative
compaction to the face of the finished slope.
6.5.4. All slopes should be planted, drained and properly maintained to reduce erosion.
Project No. 06514-12-01 - 8 - July 20, 2000m
m
6.6 Temporary Excavations
6.6.1 The following table presents recommendations relative to temporary construction
excavations. The slopes should be relatively stable against deep-seated slope failures, but
may experience localized sloughing.
TABLE 6.6
Slope Ratio
(horizontal to vertical)
Vertical
0.75:1
1:1
Maximum Height of Temporary
Construction Excavations (feet)
5
10
15
6.6.2 The above unbraced slope recommendations assume surcharge loading will not encroach
within a horizontal distance from the top of the excavation equal to the depth of the
excavation.
6.6.3 If it is desired to construct vertical temporary excavations, including trenching, or if it is
necessary to brace or shore the excavation, it is our recommendation that a contractor
familiar in the design and construction of such shoring facilities be retained. The
contractor should be responsible for the design of the shoring system utilizing his
experience and the information provided in this report.
6.7 Earthwork and Grading Factors
6.7.1 Estimates of embankment shrink-swell factors are based on comparing laboratory
compaction tests with the density of the material in its natural state and experience with
similar soil types. It should be emphasized that variations in natural soil density, as well as
in compacted fill, render shrinkage value estimates very approximate. As an example, the
contractor can compact fills to any relative compaction of 90 percent or higher of the
laboratory maximum dry density. Thus, the contractor has at least a 10 percent range of
control over the fill volume. Based on our experience and laboratory testing in similar
geologic materials, the following earthwork factors may be used as a basis for estimating
how much the on-site soils may shrink or swell when removed from their natural state and
placed in compacted fills. It is recommended that the grading be monitored during
earthwork operations and that a balance area be designated to provide adjustments to the
cut/fill as necessary.
Project No. 06514-12-01 -9-July 20, 2000
TABLE 6.7
Soils Unit
Topsoils and Alluvium
Terrace Deposits and Santiago Formation
Import Soils
Shrink-Swell Factors
5% to 10% Shrinkage
2% to 10% Bulk
Unknown
6.8 Foundation Recommendations
6.8.1 The following foundation recommendations are for one-and/or two-story structures and
are based upon the assumption that the soil conditions within 4 feet of finish pad subgrade
consist of granular "low" expansive soil (Expansion Index less than 50). The recommen-
dations are separated into categories dependent upon the depth and geometry of fill
underlying a particular building pad and/or lot and where alluvium left-in-place may
influence the performance of improvements. Final foundation design recommendations for
each building will be presented in the final compaction report after the grading for the
individual building pads has been completed.
6.8.2 Foundations for either Category I, II, or III may be designed for an allowable soil bearing
pressure of 2,000 pounds per square foot (psf) (dead plus live load). This bearing pressure
may be increased by one-third for transient loads such as wind or seismic forces.
6.8.3 The use of isolated footings, which are located beyond the perimeter of the building and
support structural elements connected to the building is not recommended for Category HI.
Where this condition cannot be avoided, the isolated footings should be connected to the
building foundation system with grade beams.
6.8.4 For Foundation Category III, the structural slab design should consider using-interior
stiffening beams and connecting isolated footings and/or increasing the slab thickness. In
addition, consideration should be given to connecting patio slabs, which exceed 5 feet in
width, to the building foundation to reduce the potential for future separation to occur.
6.8.5 No special subgrade preparation is deemed necessary prior to placing concrete, however,
the exposed foundation and slab subgrade soils should be sprinkled, as necessary, to
maintain a moist soil condition as would be expected in any such concrete placement.
Project No. 06514-12-01 -10-July 20, 2000
TABLE 6.8.1.
FOUNDATION RECOMMENDATIONS BY CATEGORY
Foundation
Category
I
n
m
Minimum
Footing Depth
(inches)
12
18
24
Continuous Footing
Reinforcement
One No. 4 bar top and
bottom
Two No. 4 bars top and
bottom
Two No. 5 bars top and
bottom
Interior Slab
Reinforcement
6x6- 10/10 welded wire mesh at
slab mid-point
No. 3 bars at 24 inches on center,
both directions
No. 3 bars at 18 inches on center,,
both directions
CATEGORY CRITERIA
Category I:
Category II:
Category HI:
Notes:
Maximum fill thickness is less than 20 feet and Expansion Index is less than or
equal to 50.
Maximum fill thickness is less than 50 feet and Expansion Index is less than or
equal to 90, or variation in fill thickness is between 10 feet and 20 feet.
Fill thickness exceeds 50 feet, or variation in fill thickness exceeds 20 feet, or
Expansion Index exceeds 90, but is less than 130, or underlain by alluvium left-in-
place (zone of influence).
1. All footings should have a minimum width of 12 inches.
2. Footing depth is measured from lowest adjacent subgrade (including topsoil, if planned). These
depths apply to both exterior and interior footings..
3. All interior living area concrete slabs should be at least 4 inches thick for Categories I and n and 5
inches thick for Category HI. This applies to both building and garage slabs-on-grade.
4. All interior concrete slabs should be underlain by at least 4 inches (3 inches for Category HI) of
clean sand or crushed rock.
5. All slabs expected to receive moisture sensitive floor coverings or used to store moisture sensitive
materials should be underlain by a vapor barrier covered with at least 2 inches of the clean sand
recommended in No. 4 above.
6.8.6 Where buildings or other improvements are planned near the top of a slope steeper
than 3:1 (horizontalrvertical), special foundations and/or design considerations are
recommended due to the tendency for lateral soil movement to occur.
For fill slopes less than 20 feet high, building footings should be deepened such
that the bottom outside edge of the footing is at least 7 feet horizontally from the
face of the slope.
m
m
Project No. 06514-12-01 -11-July 20, 2000
Where the height of the fill slope exceeds 20 feet, the minimum horizontal
distance should be increased to H/3 (where H equals the vertical distance from the
top of the slope to the toe) but need not exceed 40 feet. For composite (fill over
cut) slopes, H equals the vertical distance from the top of the slope to the bottom
of the fill portion of the slope. An acceptable alternative to deepening the footings
would be the use of a post-tensioned slab and foundation system or increased
footing and slab reinforcement. Specific design parameters or recommendations
for either of these alternatives can be provided once the building location and fill
slope geometry have been determined.
For cut slopes in dense formational materials, or fill slopes inclined at 3:1
(horizontahvertical) or flatter, the bottom outside edge of building footings should
be at least 7 feet horizontally from the face of the slope, regardless of slope height.
Swimming pools located within 7 feet of the top of cut or fill slopes are not
recommended. Where such a condition cannot be avoided, it is recommended that
the portion of the swimming pool wall within 7 feet of the slope face be designed
assuming that the adjacent soil provides no lateral support. This recommendation
applies to fill slopes up to 30 feet in height, and cut slopes regardless of height.
For swimming pools located near the top of fill slopes greater than 30 feet in
height, additional recommendations may be required and Geocon Incorporated
should be contacted for a review of specific site conditions.
Although other improvements which are relatively rigid or brittle, such as concrete
flatwork or masonry walls may experience some distress if located near the top of
a slope, it is generally not economical to mitigate this potential. It may be
possible, however, to incorporate design measures which would permit some
lateral soil movement without causing extensive distress. Geocon Incorporated
should be consulted for specific recommendations.
6.8.7 As an alternative to the foundation recommendations for each category, consideration
should be given to the use of post-tensioned concrete slab and foundation systems for the
support of the proposed structures. The post-tensioned systems should be designed by a
structural, engineer experienced in post-tensioned slab design and design criteria of the
Post-Tensioning Institute (UBC Section 1816). Although this procedure was developed for
expansive soils, it is understood that it can also be used to reduce the potential for
foundation distress due to differential fill settlement. The post-tensioned design should
incorporate the geotechnical parameters presented on the following table entitled Post-
Tensioned Foundation System Design Parameters for the particular Foundation Category
designated.
Project No. 06514-12-01 -12- July 20, 2000
TABLE 6.8.2.
POST-TEN SI ON ED FOUNDATION SYSTEM DESIGN PARAMETERS
Post-Tensioning Institute (PTI)
Design Parameters
1. Thornthwaite Index
2. Clay Type - Montmorillonite
3. Clay Portion (Maximum)
4. Depth to Constant Soil Suction
5. Soil Suction
6. Moisture Velocity
7. Edge Lift Moisture Variation Distance
8. Edge Lift
9. Center Lift Moisture Variation Distance
10. Center Lift
Foundation Category
I
-20
Yes
30%
7.0ft.
3.6 ft.
0.7 in./mo.
2.6ft.
0.41 in.
5.3 ft.
2.12 in.
II
-20
Yes
50%
7.0ft.
3.6ft.
0.7 in./mo.
2.6ft.
0.78 in.
5.3 ft.
3.21 in.
m
-20
Yes
70%
7.0ft.
3.6 ft.
0.7 in./mo.
2.6ft.
1.15 in.
5.3ft.
4.74 in.
6.8.8 UBC Section 1816 uses interior stiffener beams in its structural design procedures. If the
structural engineer proposes a post-tensioned foundation design method other than UBC
Section 1816, it is recommended that interior stiffener beams be used for Foundation
Categories II and III. The depth of the perimeter foundation should be at least 12 inches
for Foundation Category I. Where the Expansion Index for a particular building pad
exceeds 50 but is less than 91, the perimeter footing depth should be at least 18 inches; and
where it exceeds 90 but is less than 130, the perimeter footing depth should be at least 24
inches. Geocon Incorporated should be consulted to provide additional design parameters
as required by the structural engineer.
6.8.9 The recommendations of this report are intended to reduce the potential for cracking of
slabs due to expansive soils (if present), differential settlement of deep fills or fills of
varying thicknesses. However, even with the incorporation of the recommendations
presented herein, foundations, stucco walls, and slabs-on-grade placed on such conditions
may still exhibit some cracking due to soil movement and/or shrinkage. The occurrence of
concrete shrinkage cracks is independent of the supporting soil characteristics. Their
occurrence may be reduced and/or controlled by limiting the slump of the concrete, proper
concrete placement and curing, and by the placement of crack control joints at periodic
intervals, in particular, where re-entry slab corners occur.
Project No. 06514-12-01 -13-July 20, 2000
6.9 Retaining Walls and Lateral Loads
6.9.1 Retaining walls not restrained at the top and having a level backfill surface should be
designed for an active soil pressure equivalent to the pressure exerted by a fluid density
of 30 pounds per cubic foot (pcf). Where the backfill will be inclined at no steeper than
2:1, an active soil pressure of 40 pcf is recommended. These soil pressures assume that the
backfill materials within an area bounded by the wall and a 1:1 plane extending upward
from the base of the wall possess an Expansion Index of less than 50. For those lots with
finish grade soils having an Expansion Index greater than 50 and/or where backfill
materials do not conform to the above criteria, Geocon Incorporated should be consulted
for additional recommendations.
6.9.2 Unrestrained walls are those that are allowed to rotate more than 0.001H at the top of the
wall. Where walls are restrained from movement at the top, an additional uniform pressure
of 7H psf (where H equals the height of the retaining wall portion of the wall in feet)
should be added to the above active soil pressure.
6.9.3 All retaining walls should be provided with a drainage system adequate to prevent the
buildup of hydrostatic forces and should be waterproofed as required by the project
architect. The use of drainage openings through the base of the wall (weep holes, etc.) is
not recommended where the seepage could be a nuisance or otherwise adversely impact
the property adjacent to the base of the wall. The above recommendations assume a
properly compacted granular (Expansion Index less than 50) backfill material with no
hydrostatic forces or imposed surcharge load. If conditions different than those described
are anticipated, or if specific drainage details are desired, Geocon Incorporated should be
contacted for additional recommendations.
6.9.4 In general, wall foundations having a minimum depth and width of one foot may be
designed for an allowable soil bearing pressure of 2,000 psf, provided the soil within 3 feet
below the base of the wall has an Expansion Index of less than 90. The proximity of the
foundation to the top of a slope steeper than 3:1 could impact the allowable soil bearing
pressure. Therefore, Geocon Incorporated should be consulted where such a condition is
anticipated.
6.9.5 For resistance to lateral loads, an allowable passive earth pressure equivalent to a fluid
density of 300 pcf is recommended for footings or shear keys poured neat against properly
compacted granular fill soils or undisturbed natural soils. The allowable passive pressure
assumes a horizontal surface extending at least 5 feet or three times the surface generating
Project No. 06514-12-01 - 14 - July 20, 2000
the passive pressure, whichever is greater. The upper 12 inches of material not protected
by floor slabs or pavement should not be included in the design for lateral resistance. An
allowable friction coefficient of 0.4 may be used for resistance to sliding between soil and
concrete. This friction coefficient may be combined with the allowable passive earth
pressure when determining resistance to lateral loads.
6.9.6 The recommendations presented above are generally applicable to the design of rigid
concrete or masonry retaining walls having a maximum height of 8 feet. In the event that
walls higher than 8 feet or other types of walls are planned, such as crib-type walls,
Geocon Incorporated should be consulted for additional recommendations.
6.10 Slope Maintenance
6.10.1 Slopes that are steeper than 3:1 (horizontal:vertical) may, under conditions which are both
difficult to prevent and predict, be susceptible to near surface (surficial) slope instability.
The instability is typically limited to the outer three feet of a portion of the slope and
usually does not directly impact the improvements on the pad areas above or below the
slope. The occurrence of surficial instability is more prevalent on fill slopes and is
generally preceded by a period of heavy rainfall, excessive irrigation, or the migration of
subsurface seepage. The disturbance and/or loosening of the surficial soils, as might result
from root growth, soil expansion, or excavation for irrigation lines and slope planting, may
also be a significant contributing factor to surficial instability. It is, therefore, recom-
mended that, to the maximum extent practical: (a) disturbed/loosened surficial soils be
either removed or properly recompacted, (b) irrigation systems be periodically inspected
and maintained to eliminate leaks and excessive irrigation, and (c) surface drains on and
adjacent to slopes be periodically maintained to preclude ponding or erosion. It should be
noted that although the incorporation of the above recommendations should reduce the
potential for surficial slope instability, it will not eliminate the possibility, and, therefore,
it may be necessary to rebuild or repair a portion of the project's slopes in the future.
6.11 Drainage
6.11.1 Establishing proper drainage is imperative to reduce the potential for differential soil
movement, erosion and subsurface seepage. Positive measures should be taken to properly
finish grade the building pads after structures and other improvements are in place, so that
drainage water from the building pads and adjacent properties is directed to streets away
from foundations and tops of slopes. Experience has shown that even with these
provisions, a shallow groundwater or subsurface condition can and may develop in areas
Project No. 06514-12-01 - 15 - July 20, 2000
where no such condition existed prior to site development. This is particularly true where a
substantial increase in surface water infiltration results from an increase in landscape
irrigation.
6.12 Plan Review
6.12.1 The geotechnical engineer and engineering geologist should review the grading plans prior
to finalization to verify their compliance with the recommendations of this report and
determine the necessity for additional comments, recommendations and/or analysis.
6.12.2 The geotechnical engineer should also review the structural foundation plans to verify
general conformance with the recommendations of this report.
Project No. 06514-12-01 - 16 - July 20, 2000
LIMITATIONS AND UNIFORMITY OF CONDITIONS
The recommendations of this report pertain only to the site investigated and are based upon the
assumption that the soil conditions do not deviate from those disclosed in the investigation. If any
variations or undesirable conditions are encountered during construction, or if the proposed
construction will differ from that anticipated herein, Geocon Incorporated should be notified so that
supplemental recommendations can be given. The evaluation or identification of the potential
presence of hazardous or corrosive materials was not part of the scope of services provided by
Geocon Incorporated.
This report is issued with the understanding that it is the responsibility of the owner, or of his
representative, to ensure that the information and recommendations contained herein are brought to
the attention of the architect and engineer for the project and incorporated into the plans, and the
necessary steps are taken to see that the contractor and subcontractors carry out such
recommendations in the field.
The findings of this report are valid as of the present date. However, changes in the conditions of a
property can occur with the passage of time, whether they be due to natural processes or the works of
man on this or adjacent properties. In addition, changes in applicable or appropriate standards may
occur, whether they result from legislation or the broadening of knowledge. Accordingly, the
findings of this report may be invalidated wholly or partially by changes outside our control.
Therefore, this report is subject to review and should not be relied upon after a period of three years.
Project No. 06514-12-01 July 20, 2000
SOURCE : 2000 THOMAS BROTHERS MAP
SAN DIEGO COUNTY, CALIFORNIA
REPRODUCED WITH PERMISSION GRANTED BY THOMAS BROTHERS MAPS.
THIS MAP IS COPYRIGHTED BY THOMAS BROS. MAPS. IT IS UNLAWFUL TO COPY
OR REPRODUCE ALL OR ANY PART THEREOF. WHETHER FOR PERSONAL USE OR
RESALE, WITHOUT PERMISSION
NO SCALE
GEOCON
INCORPORATED
GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
VICINITY MAP
POINSETTIA PROPERTY
CARLSBAD, CALIFORNIA
DFL/TA DSK/EOOOD DATE 07-20-2000 [PROJECT NO. 06514- 12 - 01 FIG. 1
1VICMAP
APPENDIX
APPENDIX A
FIELD INVESTIGATION
That portion of the field investigation associated with the Poinsettia Property site was performed on
January 11 and 23, 1988, and consisted of a visual site reconnaissance and the excavation of 6
exploratory borings and 9 backhoe trenches. The approximately location of the excavations are
shown on Figure 2 (Geologic Map).
The borings were advanced to depths ranging from 12 to 26 feet below existing grade using a truck-
mounted drill rig equipped with 8-inch hollow core augers. Relatively undisturbed samples were
obtained from the borings by driving a 3-inch O.D. split-tube sampler 12 inches into the undisturbed
soil mass with blows from a 140 pound hammer falling 30 inches. The sampler was equipped with
1-inch by 2Vs-inch brass sampler rings to facilitate removal and testing.
The trenches were advanced to depths of 5 to 17 feet using a Case 580-K Backhoe equipped with a
24-inch-wide bucket.
The soils encountered in the borings and backhoe trenches were visually examined and logged. Logs
of the borings and backhoe trenches are presented on Figures A-l, A-2, A-5, A-7 through A-15,
A-18, and A-19 (note: logs extracted from original report; hence, not in numerical sequence). The
logs depict the soil and geologic conditions encountered and the depth at which samples were
obtained.
Project No. 06514-12-01 July 20, 2000
File No. D-4052-J01
January 26, 1988
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ELEVATION 49 MSL OATF DRILLED 1/1 1/88
POUIPMPNT Mobile B-61
MATERIAL DESCRIPTION
TOPSOIL
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\
TERRACE DEPOSIT
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ELEVATION 51 MSL DATE DRILLED 1 A 1/88
EQUIPMENT B61
MATERIAL DESCRIPTION
TOPSOIL
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TERRACE DEPOSIT
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brown, fine Silty SAND
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silt
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ELEVATION 53 MSL OATP DBILLED 1/11/88
EQUIPMENT Mobile B-61
MATERIAL DESCRIPTION
TOPSOIL
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TERRACE DEPOSIT
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SANTIAGO FORMATION
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gray, very fine to fine Sandy SILT/Silty
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Mobile B~61
MATERIAL DESCRIPTION
TOPSOIL
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TOPSOIL
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ELEVATION 54 MSL nATP DRILLED 1/11/88
EQUIPMENT Mobile B-61
MATERIAL DESCRIPTION
TOPSOIL
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TERRACE DEPOSITS
1 Moderately dense, moist, light gray,
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TRENCH 2
ELEVATION 49MSL OATF DRILLEO 1/11/88
POUIPMFNT Case 580K
MATERIAL DESCRIPTION
ALLUVIUM
\ Loose, moist, brown, Silty, fine to medium
\ SAND
T Soft, wet, dark gray. CLAY with some
1 fine sandIiI
11 — becomes moderately firm and gray
-
TERRACE DEPOSITS
Moderately dense to dense, moist, light
! grayish orange, Silty fine SAND, micaceous
11Ii1
1i began to cave-in
TRENCH TERMINATED AT 14.0 FEET
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AMPLE
III
(Figure A-ll, Log of Test Trench 2
SAMPLE SYMBOLS D SAMPLING UNSUCCESSFUL
3 _ DISTURBED OR BAG SAMPLE
D — .3TANOASO PENETRATION TEST
B_ CHUNK SAMPLE
_ DRIVE SAMPLE (UNDISTURBED)
•_ WATER TABLE OR SEEPAGE
NOTE THELOG OF SUBSURFACE CONDITIONS SHOWN HEREONAPPLIESONLYATTHESPECtncaORINQORTRENCH LOCATION ANO
ATTHE DATE INDICATED. IT 13 NOT WARRANTED TO BE REPRESENTATIVEOFSUBSURFACECONOITIONSATOTHERLOCATIONSANO TIMES
(File No. D-4052-J01
January 26, 1988
**
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TRENCH 3
47MSL 1/11/88
eouiPMENT Case 580K
MATERIAL DESCRIPTION
TOPSOIL
Loose, moist, brown, Silty, fine SAND
TERRACE DEPOSITS
Moderately dense, moist, light orange-
yellow, Silty, fine to medium SAND
""
becomes wet and micaceous
'
TRENCH TERMINATED AT 17.0 FEET
%pi
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Figure A-l2,Log of Test Trench 3
SAMPLE SYMBOLS O — SAMPLING UNSUCCESSFUL
3 _ DISTURBED OR BAG SAMPLE
B—STANOARO PENETBATION TEST
B_CHUNK SAMPLE
• _ DRIVE SAMPLE (UNDISTURBED)
?• — WATER TABLE OR SEEPAGE
NOTE THELOG OF SUBSURFACE CONOmONSSHOWNHEHEON APPLIES ONLY ATTHESPECIF1C BORING OH TRENCH LOCATION AND
ATTHE DATE INDICATED. IT IS NOT WARRANTED TO BE REPRESENTATIVE OF SU8SURFACECONOITIONS AT OTHER LOCATIONS AND TIMES
File No. D-4052-J01
'January 26, 1988
*•*
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TRENCH 4
50MSL 1/11/88
EQUIPMENT 580K
MATERIAL DESCRIPTION
TOPSOIL
Loose, moist, brown, Silty, fine SAND
TERRACE DEPOSITS
Dense, moist, dark orange-brown, Silty
fine to coarse SAND
TRENCH TERMINATED AT 8.0 FEET
TRENCH 5 Elev. 49MSL
ALLUVIUM
Loose, moist, brown, Silty, fine SAND
\
Moderately firm, dark gray CLAY with
T some fine sand
\
\\
TERRACE DEPOSITS
Dense, moist, light yellow, Silty fine
TRENCH TERMINATED AT 9.0 FEET
illpi
-
»-
m-
-
-
•
-
-
Sg §'
.Figure A-13, Log of Test Trenches 4 and 5
m
m
SAMPLE SYMBOLS LJ SAMPLING UNSUCCESSFUL
S __ DISTURBED OR BAG SAMPLE
D_ STANDARD PENETRATION TEST
B_CHUNK SAMPLE
• — DRIVE SAMPLE IUNOISTURBEOI
?• — WATER TABLE OR SEEPAGE
Wile No. D-4052-J01
January 26, 1988
3
TRENCH b
54MSLP, PVAT,nN .DATE DRILLED 1/11/88
POIilPMFNT 580K
0
MATERIAL DESCRIPTION
2 -
. C6-1
i- " 4 ^
- 6 -
SM TOPSOIL
Loose, moist, brown, Silty fine SAND
SM
TERRACE DEPOSITS
Dense, slightly moist, light yellow, Silty
fine to medium SAND
1ULK S WPLE
7.-.
TRENCH TERMINATED AT 5.0 FEET
TRENCH 7 Elev. 53MSL
- 2
6 •
8 "
TOP SOIL
opse, moist, brown, Silty fine
"
SM TERRACE
Dense, moist
becomes light orange yellow
TRENCH TERMINATED AT 7.0 FEET
_L
Figure A-14, Log of Test Trenches 6 and 7
CAuni e OVIJQ/-II cSAMPLE oYMOvJLo — SAMPUNO UNSUCCESSFUU
— DISTURBED OB SAG SAMPLE
C_3TANOAPO PENETRATION TEST
H_CHUNK SAMPLE
I _ ORIVS SAMPLE (UNDISTURBED)
?"— WATER TABLE OR SEEPAGE
NOTE THE LOG OF SUBSURFACE CONDITIONS SHOWN HEBEON APPLIES ONLY ATTHE SPECIFIC BORING OH TRENCH LOCATIONANO
ATTHE DATE INDICATED. IT IS NOTWARPANTED TO BE REPRESENTATIVE OF SUBSUBFACECONOmONSATOTHEH LOCATIONS AND TIMES
'File No. D-4052-J01
January 26, 1988
«m
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w
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. 0 -
. 2 -
. 4 -
- 6 -
- 8 -
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- 8 -SAMPLE NO.1
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TRENCH 8
ELEVAT.ON ^OMSL „„*„«,,,„, l/"/88
EQUIPMENT 580K Case
MATERIAL DESCRIPTION
ALLUVIUM
Loose, moist, brown, Silty fine SAND
Soft, wet, dark gray, fine Sandy CLAYx^^^
1 .^with scattered calcium carbonate s«ams
TERRACE DEPOSITS ^^
Dense, moist^SogbtTgray yellow, Silty fine
to medium SQ$B^^^^^
TRENCH TERMINATED AT 13.0 FEET
TRENCH 9 Elev. 50MLS
TOP SOIL
Loose, moist, brown, Silty fine SAND
TERRACE DEPOSITS
Dense, moist, dark orange, Silty fine to
medium SAND
TRENCH TERMINATED AT 6.0 FEET
1
•
» ^^^
-
•
•
m
|
^
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^
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Figure A-15, Log of Test Trenches 8 and 9
SAM PL E SYM BO LS LI — SAMPLING UNSUCCESSFUL D «. STANDARD PENETRATION TEST • _ DRIVE SAMPLE (UNDISTURBED)
H~- DISTURBED OR BAG SAMPLE E _ CHUNK SAMPLE ¥>_ WATER TABLE OR SEEPAGE
NOTE THELOG OF SUBSURFACE CONDITIONS SHOWNHEREONAPPLIESONLYATTHESPECIFIC BORING OH TRENCH LOCATION AND
ATTHE DATE INDICATED. IT IS NOTWARRANTEDTO BE REPRESENTATIVE OFSUBSUflFACECONDITIONSATOTHER LOCATIONS AND TIMES
File No. D-4052-J01
January 26, 1988
x ^
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-
TRENCH 14
ELEVATION 53MSL DATP nBILLED 1/11/88
Case 580KEQUIPMENT
MATERIAL DESCRIPTION
TOP SOIL
Loose, moist, brown, Silty, fine SAND •1 -.^ ^f^"^
Dense, motsTs^ark oraagE*7*Silty , fine to
coarse SAND ^^><^7
^^ "^^^.
TRENCH TERMINATED AT 8.0 FEET
TRENCH 15 Elev. 49MSL
ALLUVIUM
Loose, moist, brown, Silty, fine SAND
Soft, wet, dark gray CLAY with some .
fine sand
TERRACE DEPOSITS
Dense, moist, light yellow gray, Silty
fine to coarse SAND
\
TRENCH TERMINATED AT 8.0 FEET
|«t
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AMPLE
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Figure A-18, Log of Test Trenches 14 and 15
« . i . m r- ev» « D/-M e>SAM PL t SYMUC/Lo D — SAMPLING UNSUCCESSFUL
El — DISTURBED OR SAG SAMPLE
E_STANDARO PENETRATION TEST
H_ CHUNK SAMPLE
__ DRIVE SAMPLE IUNOISTURBEOI
?•_ WATER TABLE OR SEEPAGE
NOTE THELOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY ATTHESP6C1FIC BORING OR TRENCH LOCATION AND
ATTHE DATE INDICATED. ITISNOTWARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONOITIONSATOTHER LOCATIONS AND TIMES
File No. D-4052-J01
January 26, 1988
5*a
• •
2 "
» m
- 4-
- 6 '
- 8'
" 10"
- -
1
i
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TRENCH 16
ELEVATION ^EloJj rvATJ? ORILLPD
Case 380K
MATERIAL DESCRIPTION
ALLUVIUM
Loose, moist, brown, Silty, fine SAND
Soft, wet, dark gray CLAY with some
fine sand
~
ZliKKAUJi U Jibuti ITS
Dense, moist, light yellow gray, Silty,
fine to coarse SAND
\
TRENCH TERMINATED AT 9.0 FEET
•
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IP
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-
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Figure A-19, Log of Test Trench 16
Pto
a
hi
SAMPLE SYMBOLS D _ SAMPLING UNSUCCESSFUL
H — DISTURBED OH BAG SAMPLE
Ij—STANOARO PENETRATION TEST
B_CHUNK SAMPLE
_ DRIVE SAMPLE (UNDISTURBED)
-—WATER TABLE OR SEEPAGE
ATTHE DATE INDICATED. IT IS NOTWARRANTED TO BE REPRESENTATIVEOFSUBSURFACECONOITIONS ATOTHER LOCATIONS AND TIMES
APPENDIX
m
m
APPENDIX B
LABORATORY TESTING
Laboratory tests were performed in accordance with the generally accepted test methods of the
American Society for Testing and Materials (ASTM) or other suggested procedures. Selected
relatively undisturbed drive samples and chunk samples were tested for their in-place dry density
and moisture content, shear strength and consolidation characteristics.
The maximum dry density and optimum moisture content of selected bulk samples were determined
in accordance with ASTM Test Procedure D 1557-78. Portions of the bulk samples were also tested
for their expansion potential.
The results of our laboratory tests are presented in tabular and graphical forms hereinafter. The in-
place density and moisture characteristics are also presented on the logs of the test trenches and
borings in Appendix A. Only select laboratory data has been extracted from the original
investigation; therefore, the figures included are not in numerical order.
TABLE B-l
SUMMARY OF LABORATORY MAXIMUM DRY DENSITY
AND OPTIMUM MOISTURE CONTENT TEST RESULTS
ASTM D 1557
Sample
No.
Tl-1
T2-2
T14-1*
Description
Green to rust, fine to medium SAND with
little silt (Topsoils)
Dark gray CLAY with little silt and a trace
of sand (Alluvial Soils)
Dark yellow-brown, Silty, fine to medium
SAND (Terrace Deposits)
Maximum
Dry Density
(pcf)
130.3
109.0
132.6
Optimum Moisture
(% dry wt.)
9.3
16.9
9.0
1 Representative of soil type from exploratory excavation outside of the Poinsettia Property site.
pi
M
Project No. 06514-12-01 -B-l -July 20, 2000
m
m
TABLE B-ll
SUMMARY OF DIRECT SHEAR TEST RESULTS
Sample
No.
Bl-2
B4-2*
Dry Density
(pcf)
120.1
119.6
Moisture Content
11.4
9.9
Unit Cohesion
(psf)
1180
860
Angle of Shear
Resistance
(degrees)
32
26
* Representative of soil type from exploratory excavation outside of the Poinsettia Property site.
TABLE B-lll
SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS
Sample No.
Tl-1
T2-1*
T14-1
Moisture Content
Before Test (%)
8.1
16.1
8.1
After Test (%)
16.7
45.6
15.8
Dry Density
(pcf)
117.0
89.6
118.5
Expansion
Index
0
167
0
' Representative of alluvial soils from exploratory excavation outside of the Poinsettia Property site.
pi
tt
Project No. 06514-12-01 -B-2-July 20, 2000
File No. D-4052-J01
January 26, 1988
O
oCOzoo
HioorUJQ-
SAMPLE NO. B2-3
0.1
WATER ADDED
\
0.5 1.0 5.0 1O.O
APPLIED PRESSURE (ksf)
50.0 100.0
INITIAL DRY DENSITY
INITIAL WATER CONTENT
IOS.6 (pet)
8-5 (%)
INITIAL SATURATION
SAMPLE SATURATED AT
39.2 (%)
0.5 (ksf)
CONSOLIDATION CURVE
POINSETTIA PROMENADE
CARLSBAD, CALIFORNIA
Figure B-l
File No. D-4052-J01
January 26, 1988
PERCENT CONSOLIDATIONO 0> 01 -|k W fO — OSAMPLE NO. 85- 1
••^=•• 1-"** —-****•^^
^p—
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•«
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M
-WATER t
\
— - —
kDOED
\
\s s
i~
1
1
1 0.5 1.0 5.0 10.0 .50.0 100.0
APPLIED PRESSURE (ksf)
INITIAL DRY DENSITY
INITIAL WATER CONTENT
106.2 (pcO
3^ <%)
INITIAL SATURATION
SAMPLE SATURATED AT
15.6 (%)
0.5 (ksf)
CONSOLIDATION CURVE
POINSETTIA PROMENADE
CARLSBAD, CALIFORNIA
Figure B-3
• I II f 1 ff I • I • 1 I ) I ! I 1 I 1 t 1 I I i 1 f 1 f 1 I 1 f I I 1 • I
u.s. STANDARD SIEVE SIZE
654 3 IN. I.5IN. 3/4 IN. 3/8 IN. 4 10 2O 40 60 100 200
00
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00
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1000 100 K> 1.0 O.I
GRAIN SIZE IN MILLIMETERS
COBBLES
SAMPLE NO.
T2-1
DEPTH
2-4'
GRAVEL
COARSE | FINE
SAND
COARSE | MEDIUM | FINE
CLASSIFICATION
Silty SAND with some
sand i
NAT. WC LL PL PI
0.01 0001
SILT OR CLAY
GRADATION CURVE
(11
3
N)
ON O
» I-P-i- O10 t-n00 N300 I
R-108
• i ii r i vi vi r i 11 r i r i ri v i • i • i t i • i t i i i i t f i
U.S. STANDARD SIEVE SIZE
6543IN. 1.5 IN. 3/4 IN. 3/8 IN. 4 10 20 40 60 100 200
9O
T
O
UJ 70
00
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1000 100 K> i.o o.i o-oi oooi
GRAIN SIZE IN MILLIMETERS
COBBLES
SAMPLE NO
T6-1
DEPTH
2-4'
GRAVEL 1
COARSE | FINE JCOARSE
SAND I
CLASSIFICATION
Silty SAND
NAT. WC LL PL
SILT OR CLAV
PI
GRADATION CURVE
& o» I*>
t- O
VO Ul
CO K>
CO I
I""
In*
APPENDIX
APPENDIX C
RECOMMENDED GRADING SPECIFICATIONS
FOR
POINSETTIA PROPERTY
CARLSBAD, CALIFORNIA
PROJECT NO. 06514-12-01
m RECOMMENDED GRADING SPECIFICATIONS
***
m 1. GENERAL
m 1.1. These Recommended Grading Specifications shall be used in conjunction with the
Geotechnical Report for the project prepared by Geocon Incorporated. The recom-
mendations contained in the text of the Geotechnical Report are a part of the earthwork and
*"* grading specifications and shall supersede the provisions contained hereinafter in the case
«* of conflict.
— 1.2. Prior to the commencement of grading, a geotechnical consultant (Consultant) shall be
employed for the purpose of observing earthwork procedures and testing the fills for
** substantial conformance with the recommendations of the Geotechnical Report and these
** specifications. It will be necessary that the Consultant provide adequate testing and
^ observation services so that he may determine that, in his opinion, the work was performed
^ in substantial conformance with these specifications. It shall be the responsibility of the
Contractor to assist the Consultant and keep him apprised of work schedules and changes
*** so that personnel may be scheduled accordingly.
m
*•* 1.3. It shall be the sole responsibility of the Contractor to provide adequate equipment and
^ methods to accomplish the work in accordance with applicable grading codes or agency
ordinances, these specifications and the approved grading plans. If, in the opinion of the
Consultant, unsatisfactory conditions such as questionable soil materials, poor moisture
"*"' condition, inadequate compaction, adverse weather, and so forth, result in a quality of work
not in conformance with these specifications, the Consultant will be empowered to reject
the work and recommend to the Owner that construction be stopped until the unacceptable
conditions are corrected.
2. DEFINITIONS
2.1. Owner shall refer to the owner of the property or the entity on whose behalf the grading
work is being performed and who has contracted with the Contractor to have grading
performed.
2.2. Contractor shall refer to the Contractor performing the site grading work.
2.3. Civil Engineer or Engineer of Work shall refer to the California licensed Civil Engineer
or consulting firm responsible for preparation of the grading plans, surveying and verifying
as-graded topography.
GI rev. 8/98
2.4. Consultant shall refer to the soil engineering and engineering geology consulting firm
retained to provide geotechnical services for the project.
2.5. Soil Engineer shall refer to a California licensed Civil Engineer retained by the Owner,
who is experienced in the practice of geotechnical engineering. The Soil Engineer shall be
responsible for having qualified representatives on-site to observe and test the Contractor's
work for conformance with these specifications.
2.6. Engineering Geologist shall refer to a California licensed Engineering Geologist retained
by the Owner to provide geologic observations and recommendations during the site
grading.
2.7. Geotechnical Report shall refer to a soil report (including all addenda) which may include
a geologic reconnaissance or geologic investigation that was prepared specifically for the
development of the project for which these Recommended Grading Specifications are
intended to apply.
3. MATERIALS
3.1. Materials for compacted fill shall consist of any soil excavated from the cut areas or
imported to the site that, in the opinion of the Consultant, is suitable for use in construction
of fills. In general, fill materials can be classified as soil fills, soil-rock fills or rock fills, as
defined below.
3.1.1. Soil fills are defined as fills containing no rocks or hard lumps greater than 12
inches in maximum dimension and containing at least 40 percent by weight of
material smaller than 3/4 inch in size.
3.1.2. Soil-rock fills are defined as fills containing no rocks or hard lumps larger than 4
feet in maximum dimension and containing a sufficient matrix of soil fill to allow
for proper compaction of soil fill around the rock fragments or hard lumps as
specified in Paragraph 6.2. Oversize rock is defined as material greater than 12
inches.
3.1.3. Rock fills are defined as fills containing no rocks or hard lumps larger than 3 feet
in maximum dimension and containing little or no fines. Fines are defined as
material smaller than 3/4 inch in maximum dimension. The quantity of fines shall
be less than approximately 20 percent of the rock fill quantity.
GI rev. 8/98
** 3.2. Material of a perishable, spongy, or otherwise unsuitable nature as determined by the
*** Consultant shall not be used in fills.
-*»
— 3.3. Materials used for fill, either imported or on-site, shall not contain hazardous materials as
defined by the California Code of Regulations, Title 22, Division 4, Chapter 30, Articles 9
** and 10; 40CFR; and any other applicable local, state or federal laws. The Consultant shall
m not be responsible for the identification or analysis of the potential presence of hazardous
.„» materials. However, if observations, odors or soil discoloration cause Consultant to
— suspect the presence of hazardous materials, the Consultant may request from the Owner
the termination of grading operations within the affected area. Prior to resuming grading
*** operations, the Owner shall provide a written report to the Consultant indicating that the
— suspected materials are not hazardous as defined by applicable laws and regulations.
^m
w 3.4. The outer 15 feet of soil-rock fill slopes, measured horizontally, should be composed of
properly compacted soil fill materials approved by the Consultant. Rock fill may extend to
the slope face, provided that the slope is not steeper than 2:1 (horizontal:vertical) and a soil
** layer no thicker than 12 inches is track-walked onto the face for landscaping purposes.
<•» This procedure may be utilized, provided it is acceptable to the governing agency, Owner
m and Consultant.
*M
3.5. Representative samples of soil materials to be used for fill shall be tested in the laboratory
"** by the Consultant to determine the maximum density, Optimum moisture content, and,
where appropriate, shear strength, expansion, and gradation characteristics of the soil.
««*«
3.6. During grading, soil or groundwater conditions other than those identified in the
Geotechnical Report may be encountered by the Contractor. The Consultant shall be
notified immediately to evaluate the significance of the unanticipated condition
4. CLEARING AND PREPARING AREAS TO BE FILLED
ww
4.1. Areas to be excavated and filled shall be cleared and grubbed. Clearing shall consist of
complete removal above the ground surface of trees, stumps, brush, vegetation, man-made
>"» structures and similar debris. Grubbing shall consist of removal of stumps, roots, buried
m logs and other unsuitable material and shall be performed in areas to be graded. Roots and
other projections exceeding 1-1/2 inches in diameter shall be removed to a depth of 3 feet?**below the surface of the ground. Borrow areas shall be grubbed to the extent necessary to
provide suitable fill materials.
GI rev. 8/98
4.2. Any asphalt pavement material removed during clearing operations should be properly
disposed at an approved off-site facility. Concrete fragments which are free of reinforcing
steel may be placed in fills, provided they are placed in accordance with Section 6.2 or 6.3
of this document.
4.3. After clearing and grubbing of organic matter or other unsuitable material, loose or porous
soils shall be removed to the depth recommended in the Geotechnical Report. The depth of
removal and compaction shall be observed and approved by a representative of the
Consultant. The exposed surface shall then be plowed or scarified to a minimum depth of
6 inches and until the surface is free from uneven features that would tend to prevent
uniform compaction by the equipment to be used.
4.4. Where the slope ratio of the original ground is steeper than 6:1 (horizontal:vertical), or
where recommended by the Consultant, the original ground should be benched in
accordance with the following illustration.
TYPICAL BENCHING DETAIL
Finish Grade Original Ground
Finish Slope Surface
Remove All
Unsuitable Material
As Recommended By
Soil Engineer Slope To Be Such That
Sloughing Or Sliding
Does Not Occur
"B"
See Note 1 See Note 2-
No Scale
DETAIL NOTES:(1) Key width "B" should be a minimum of 10 feet wide, or sufficiently wide to
permit complete coverage with the compaction equipment used. The base of the
key should be graded horizontal, or inclined slightly into the natural slope.
(2) The outside of the bottom key should be below the topsoil or unsuitable surficial
material and at least 2 feet into dense formational material. Where hard rock is
exposed in the bottom of the key, the depth and configuration of the key may be
modified as approved by the Consultant.
GI rev. 8/98
4.5. After areas to receive fill have been cleared, plowed or scarified, the surface should be
disced or bladed by the Contractor until it is uniform and free from large clods. The area
should then be moisture conditioned to achieve the proper moisture content, and compacted
as recommended in Section 6.0 of these specifications.
5. COMPACTION EQUIPMENT
5.1. Compaction of soil or soil-rock fill shall be accomplished by sheepsfoot or segmented-steel
wheeled rollers, vibratory rollers, multiple-wheel pneumatic-tired rollers, or other types of
acceptable compaction equipment. Equipment shall be of such a design that it will be
capable of compacting the soil or soil-rock fill to the specified relative compaction at the
specified moisture content.
5.2. Compaction of rock fills shall be performed in accordance with Section 6.3.
6. PLACING, SPREADING AND COMPACTION OF FILL MATERIAL
6.1. Soil fill, as defined in Paragraph 3.1.1, shall be placed by the Contractor in accordance with
the following recommendations:
6.1.1. Soil fill shall be placed by the Contractor in layers that, when compacted, should
generally not exceed 8 inches. Each layer shall be spread evenly and shall be
thoroughly mixed during spreading to obtain uniformity of material and moisture
in each layer. The entire fill shall be constructed as a unit in nearly level lifts.
Rock materials greater than 12 inches in maximum dimension shall be placed in
accordance with Section 6.2 or 6.3 of these specifications.
6.1.2. In general, the soil fill shall be compacted at a moisture content at or above the
optimum moisture content as determined by ASTM D1557-91.
6.1.3. When the moisture content of soil fill is below that specified by the Consultant,
water shall be added by the Contractor until the moisture content is in the range
specified.
6.1.4. When the moisture content of the soil fill is above the range specified by the
Consultant or too wet to achieve proper compaction, the soil fill shall be aerated by
the Contractor by blading/mixing, or other satisfactory methods until the moisture
content is within the range specified.
GI rev. 8/98
•m 6.1.5. After each layer has been placed, mixed, and spread evenly, it shall be thoroughly
m compacted by the Contractor to a relative compaction of at least 90 percent.
Relative compaction is defined as the ratio (expressed in percent) of the in-place
dry density of the compacted fill to the maximum laboratory dry density as
** determined in accordance with ASTM D1557-91. Compaction shall be continuous
«• over the entire area, and compaction equipment shall make sufficient passes so that
— the specified minimum relative compaction has been achieved throughout the
entire fill.
•xm
gMM 6.1.6. Soils having an Expansion Index of greater than 50 may be used in fills if placed at
«•* least 3 feet below finish pad grade and should be compacted at a moisture content
iw generally 2 to 4 percent greater than the optimum moisture content for the material.
•urn
6.1.7. Properly compacted soil fill shall extend to the design surface of fill slopes. To
&t
achieve proper compaction, it is recommended that fill slopes be over-built by at
•" least 3 feet and then cut to the design grade. This procedure is considered
m preferable to track-walking of slopes, as described in the following paragraph.
6.1.8. As an alternative to over-building of slopes, slope faces may be back-rolled with a
heavy-duty loaded sheepsfoot or vibratory roller at maximum 4-foot fill height
** intervals. Upon completion, slopes should then be track-walked with a D-8 dozer
*• or similar equipment, such that a dozer track covers all slope surfaces at least
twice.
"*' 6.2. Soil-rock fill, as defined in Paragraph 3.1.2, shall be placed by the Contractor in accordance
with the following recommendations:
MH
6.2.1. Rocks larger than 12 inches but less than 4 feet in maximum dimension may be
^ incorporated into the compacted soil fill, but shall be limited to the area measured
15 feet minimum horizontally from the slope face and 5 feet below finish grade or
3 feet below the deepest utility, whichever is deeper.
<••
•« 6.2.2. Rocks or rock fragments up to 4 feet in maximum dimension may either be
^ individually placed or placed in windrows. Under certain conditions, rocks or rock
fragments up to 10 feet in maximum dimension may be placed using similar
methods. The acceptability of placing rock materials greater than 4 feet in
"*** maximum dimension shall be evaluated during grading as specific cases arise and
«• shall be approved by the Consultant prior to placement.
GI rev. 8/98
6.2.3. For individual placement, sufficient space shall be provided between rocks to allow
for passage of compaction equipment.
*"" 6.2.4. For windrow placement, the rocks should be placed in trenches excavated in
• properly compacted soil fill. Trenches should be approximately 5 feet wide and 4
feet deep in maximum dimension. The voids around and beneath rocks should be
"TWl *
filled with approved granular soil having a Sand Equivalent of 30 or greater and
should be compacted by flooding. Windrows may also be placed utilizing an
*" "open-face" method in lieu of the trench procedure, however, this method should
» first be approved by the Consultant.
m 6.2.5. Windrows should generally be parallel to each other and may be placed either
parallel to or perpendicular to the face of the slope depending on the site
*"* geometry. The minimum horizontal spacing for windrows shall be 12 feet
m center-to-center with a 5-foot stagger or offset from lower courses to next
,,„ overlying course. The minimum vertical spacing between windrow courses shall
— be 2 feet from the top of a lower windrow to the bottom of the next higher
windrow.
6.2.6. All rock placement, fill placement and flooding of approved granular soil in the
<*. windrows must be continuously observed by the Consultant or his representative.
M 6.3. Rock fills, as defined in Section 3.1.3., shall be placed by the Contractor in accordance with
**" the following recommendations:
mm
6.3.1. The base of the rock fill shall be placed on a sloping surface (minimum slope of 2
«., percent, maximum slope of 5 percent). The surface shall slope toward suitable
subdrainage outlet facilities. The rock fills shall be provided with subdrains during
construction so that a hydrostatic pressure buildup does not develop. The
IdHA subdrains shall be permanently connected to controlled drainage facilities to
"" control post-construction infiltration of water.
MM
6.3.2. Rock fills shall be placed in lifts not exceeding 3 feet. Placement shall be by rock
trucks traversing previously placed lifts and dumping at the edge of the currently
*K placed lift. Spreading of the rock fill shall be by dozer to facilitate seating of the
"** rock. The rock fill shall be watered heavily during placement. Watering shall
•m consist of water trucks traversing in front of the current rock lift face and spraying
water continuously during rock placement. Compaction equipment with
compactive energy comparable to or greater than that of a 20-ton steel vibratory
M»roller or other compaction equipment providing suitable energy to achieve the
&m
** GI rev. 8/98
required compaction or deflection as recommended in Paragraph 6.3.3 shall be
utilized. The number of passes to be made will be determined as described in
Paragraph 6.3.3. Once a rock fill lift has been covered with soil fill, no additional
rock fill lifts will be permitted over the soil fill.
6.3.3. Plate bearing tests, in accordance with ASTM Dl 196-64, may be performed in
both the compacted soil fill and in the rock fill to aid in determining the number of
passes of the compaction equipment to be performed. If performed, a minimum of
three plate bearing tests shall be performed in the properly compacted soil fill
(minimum relative compaction of 90 percent). Plate bearing tests shall then be
performed on areas of rock fill having two passes, four passes and six passes of the
compaction equipment, respectively. The number of passes required for the rock
fill shall be determined by comparing the results of the plate bearing tests for the
soil fill and the rock fill and by evaluating the deflection variation with number of
passes. The required number of passes of the compaction equipment will be
performed as necessary until the plate bearing deflections are equal to or less than
that determined for the properly compacted soil fill. In no case will the required
number of passes be less than two.
6.3.4. A representative of the Consultant shall be present during rock fill operations to
verify that the minimum number of "passes" have been obtained, that water is
being properly applied and that specified procedures are being followed. The
actual number of plate bearing tests will be determined by the Consultant during
grading. In general, at least one test should be performed for each approximately
5,000 to 10,000 cubic yards of rock fill placed.
6.3.5. Test pits shall be excavated by the Contractor so that the Consultant can state that,
in his opinion, sufficient water is present and that voids between large rocks are
properly filled with smaller rock material. In-place density testing will not be
required in the rock fills.
6.3.6. To reduce the potential for "piping" of fines into the rock fill from overlying soil
fill material, a 2-foot layer of graded filter material shall be placed above the
uppermost lift of rock fill. The need to place graded filter material below the rock
should be determined by the Consultant prior to commencing grading. The
gradation of the graded filter material will be determined at the time the rock fill is
being excavated. Materials typical of the rock fill should be submitted to the
Consultant in a timely manner, to allow design of the graded filter prior to the
commencement of rock fill placement.
GI rev. 8/98
6.3.7. All rock fill placement shall be continuously observed during placement by
representatives of the Consultant.
7. OBSERVATION AND TESTING
7.1. The Consultant shall be the Owners representative to observe and perform tests during
clearing, grubbing, filling and compaction operations. In general, no more than 2 feet in
vertical elevation of soil or soil-rock fill shall be placed without at least one field density
test being performed within that interval. In addition, a minimum of one field density test
shall be performed for every 2,000 cubic yards of soil or soil-rock fill placed and
compacted.
7.2. The Consultant shall perform random field density tests of the compacted soil or soil-rock
fill to provide a basis for expressing an opinion as to whether the fill material is compacted
as specified. Density tests shall be performed in the compacted materials below any
disturbed surface. When these tests indicate that the density of any layer of fill or portion
thereof is below that specified, the particular layer or areas represented by the test shall be
reworked until the specified density has been achieved.
7.3. During placement of rock fill, the Consultant shall verify that the minimum number of
passes have been obtained per the criteria discussed in Section 6.3.3. The Consultant shall
request the excavation of observation pits and may perform plate bearing tests on the
placed rock fills. The observation pits will be excavated to provide a basis for expressing
an opinion as to whether the rock fill is properly seated and sufficient moisture has been
applied to the material. If performed, plate bearing tests will be performed randomly on
the surface of the most-recently placed lift. Plate bearing tests will be performed to provide
a basis for expressing an opinion as to whether the rock fill is adequately seated. The
maximum deflection in the rock fill determined in Section 6.3.3 shall be less than the
maximum deflection of the properly compacted soil fill. When any of the above criteria
indicate that a layer of rock fill or any portion thereof is below that specified, the affected
layer or area shall be reworked until the rock fill has been adequately seated and sufficient
moisture applied.
7.4. A settlement monitoring program designed by the Consultant may be conducted in areas of
rock fill placement. The specific design of the monitoring program shall be as
recommended in the Conclusions and Recommendations section of the project
Geotechnical Report or in the final report of testing and observation services performed
during grading.
GI rev. 8/98
m
m
•* 7.5. The Consultant shall observe the placement of subdrains, to verify that the drainage devices
Ml have been placed and constructed in substantial conformance with project specifications.
m
^ 7.6. Testing procedures shall conform to the following Standards as appropriate:
*" 7.6.1. Soil and Soil-Rock Fills:M
pi 7.6.1.1. Field Density Test, ASTM D1556-82, Density of Soil In-Place By the
^ Sand-Cone Method.
7.6.1.2. Field Density Test, Nuclear Method, ASTM D2922-81, Density of Soil and
Soil-Aggregate In-Place by Nuclear Methods (Shallow Depth).
7.6.1.3. Laboratory Compaction Test, ASTM D1557-91, Moisture-Density
** Relations of Soils and Soil-Aggregate Mixtures Using 10-Pound Hammer
H and 18-Inch Drop.
m 7.6.1.4. Expansion Index Test, Uniform Building Code Standard 29-2, Expansion
^ Index Test.
m 7.6.2. Rock Fills
* 7.6.2.1. Field Plate Bearing Test, ASTM Dl 196-64 (Reapproved 1977) Standard
Method for Nonrepresentative Static Plate Load Tests of Soils and Flexible
m Pavement Components, For Use in Evaluation and Design of Airport and
Hi Highway Pavements.
"" 8. PROTECTION OF WORK
!•
8.1. During construction, the Contractor shall properly grade all excavated surfaces to provide
positive drainage and prevent ponding of water. Drainage of surface water shall be
controlled to avoid damage to adjoining properties or to finished work on the site. The
p* Contractor shall take remedial measures to prevent erosion of freshly graded areas until
li such time as permanent drainage and erosion control features have been installed. Areas
subjected to erosion or sedimentation shall be properly prepared in accordance with the
Specifications prior to placing additional fill or structures.
m 8.2. After completion of grading as observed and tested by the Consultant, no further
|| excavation or filling shall be conducted except in conjunction with the services of the
Consultant.
GI rev. 8/98
- 9. CERTIFICATIONS AND FINAL REPORTS
Hi 9.1. Upon completion of the work, Contractor shall furnish Owner a certification by the Civil
•* Engineer stating that the lots and/or building pads are graded to within 0.1 foot vertically of
In elevations shown on the grading plan and that all tops and toes of slopes are within 0.5 foot
horizontally of the positions shown on the grading plans. After installation of a section of
subdrain, die project Civil Engineer should survey its location and prepare an as-built plan
of the subdrain location. The project Civil Engineer should verify the proper outlet for the
m subdrains and the Contractor should ensure that the drain system is free of obstructions.
«.
9.2. The Owner is responsible for furnishing a final as-graded soil and geologic report
satisfactory to the appropriate governing or accepting agencies. The as-graded report
should be prepared and signed by a California licensed Civil Engineer experienced in
** geotechnical engineering and by a California Certified Engineering Geologist, indicating
In that the geotechnical aspects of the grading were performed in substantial conformance
with the Specifications or approved changes to the Specifications.
m
m
m
m
to
GI rev. 8/98