HomeMy WebLinkAboutCT 07-05; LA COSTA GREENS NEIGHBOROOD 1.3; UPDATE GEOTECHNICAL REPORT; 2008-02-07I
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UPDATE
GEOTECHNICAL REPORT
VILLAGES OF LA ·COSTA -
THE GRE'ENS
NEIGHBORHOOD 1.03
LOTS 1 THROUGH 38
CARLSBAD, CALIFORNIA .-----cr 07~DS
PREPARED FOR
LA COSTA GREENS 1.3 LLC
clO EPPSTEINER & ASSOCIATES
SOLANA BEACH, CALIFORNIA
FEBRUARY 7,2008
PROJECT NO. 0'6403-52-32
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GEDeON
INOORPORATED
Project No. 06403-52-32
February 7, 2008
La Costa Greens 1.3 LLC
Cfo Eppsteiner & Associates
201 Lomas Santa Fe, Suite 460
Solana Beach, California 92075
Attention: Mr. Stuart M. Eppsteiner
Subject: VILLAGES OF LA COSTA -THE GREENS
NEIGHBORHOOD 1.03
LOTS 1 THROUGH 38
CARLSBAD, CALIFORNIA
UPDATE GEOTECHNICAL REPORT
Dear lVIr. Eppsteiller
GEOTECHNICAl CONSULTANTS
In accordance with your authorization of our Proposal No. LG-0J344 dated October 19, 2007, we have
prepared this update geotechnical report for the subject project The accompanying report presents the
results of our study and conclusions and recommendations pertaining to the geotechnical aspects of
proposed development of the site .
The site was sheet graded as part of the Villages of La Costa -The Greens, Neighborhoods 1.01
through 1.03 development and is located southeast of the inte'rsectioll of EI Camino Real and Camino
Vida Roble in Carlsbad, California. The grading operations for Neighborhood 1.03 were completed in
April 2006. Dense formational deposits of the Santiago Formation and compacted fill underlie the site.
Provided the recommendations contained in this update report are followed, the site is considered
suitable for construction and support of the proposed development.
Should you have any questions regarding this report, or if we may be of further service,please contact
the undersigned atyouT convenience.
Very truly yours,
GEOCONINCORPORATED
"n~CCc::;
Michael C. Ertwine
Senior Staff Geoiogist
MCE:AS:SW:dmc
(3/del)
(3/del)
Addressee
Colrich Communities
Attention: Mr. Steve Butler
6960 Flanders Drive • San Diego, California 92121-2974 • Telephone (858)-558-6900 • Fax (8581558-6159
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TABLE OF CONTENTS
1. PURPOSE AND SCOPE ................................................................................................................. 1
2. PREVIOUS SITE DEVELOPMENT ............................................................................................... 1
3. SITE AND PROJECT DESCRIPTION ........................................................................................... 2
4. SOIL AND GEOLOGIC CONDITIONS ...................................................................... : .................. 2
4.1 Compacted Fill (Qcf) ............................................................................................................. 2
4.2 Undocumented Fill (Qudf) ..................................................................................................... 2
4.3 Santiago Fonnation (Ts) ........................................................................................................ 3
5. GROUNDWATER ........................................................................................................................... 3
6. GEOLOGIC HAZARDS ................................................................................................................... 3
6.1 Faulting and Seismicity .......................................................................................................... 3
6.2 Liquefaction ........................................................................................................................... 4
6.3 Landslides .............................................................................................................................. 4
7. CONCLUSIONS AND RECOMMENDATIONS ........................................................................... 5
7.1 General ........................................................................................................................ , .......... 5
7.2 Excavation and Soil Characteristics ....................................................................................... 5
7.3 Seismic Design Criteria ............................................................................................... : ......... 6
7.4 Grading .................................................................................................................................. 8
7.5 Slopes ..................................................................................................................................... 9
7.6 Foundation and Concrete Slabs-On-Grade Recommendations .............................................. 9
7.7 Retaining Walls and Lateral Loads ................................................................................ : ..... 14
7.8 Preliminary Flexible Pavement Recommendations ............................................................. 15
7.9 Slope Maintenance ............................................................................................................... 16
7.10 Site Drainage and Moisture Protection ................................................................................ 16
7.11 Grading and Foundation Plan Review ................................................................................. 17
LIMITATIONS AND UNIFORMITY OF CONDITIONS
MAPS AND ILLUSTRATIONS
Figure 1, Vicinity Map
Figure 2, Geologic Map
. Figure 3, Wall/Column Footing Dimension Detail
Figure 4, Retaining Wall Drainage Detail
APPENDIX A
LABORATORY RESULTS
Table A-I, Summary of Finish Grade Laboratory Expansion Index Test Results
Table A-II, Summary of Laboratory Water-Soluble Sulfate Test Results
APPENDIX B
RECOMMENDED GRADING SPECIFICATIONS
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UPDATE GEOTECHNICAL REPORT
1. PURPOSE AND SCOPE
This report presents the results of an update geotechnical study for the proposed development of
Neighborhood 1.03 located in the Villages of La Costa -The Greens in Carlsbad, California. The site
is located south of intersection of EI Camino Real and Camino Vida Roble in the City of Carlsbad,
California (see Vicinity Map, Figure 1). The purpose of this update report is to provide information
regarding the geologic conditions underlying the site and provide specific geotechnical
recommendations pertaining to the ultimate development of the property as proposed.
The scope of this study included a review of:
1. Addendum to Final Report of Testing and Observation Services Performed During Site
Grading, Villages of La Costa -The Greens, Neighborhoods 1.02 and 1.03, Carlsbad,
California, prepared by Geoeon Incorporated, dated January 3, 2007 (Project No. 06403-
52-22).
2.
3.
Final Report of Testing and Observation Services Performed During Site Grading, Villages of
La Costa -The Greens, Neighborhoods 1.02 and 1.03, Carlsbad, California, prepared by
Geoeon Incorporated, dated April 3, 2006 (Project No. 06403-52-22).
Update Soil and Geological Investigation, Volume I and IL Villages of La Costa -The Greens,
Carlsbad, California, prepared by Geocon Incorporated, dated June 25, 2001 (Project
No. 06403-12-03).
4. Tentative Map: La Costa Greens -NEI 1.03, City of Carlsbad, California, prepared by
Hunsaker and Associates, dated October 2,2007.
The descriptions of the soil and geologic conditions and proposed development described herein is
based on review of the referenced reports and plan, and observations made during mass grading
operations for Neighborhood 1.03 of the Villages of La Costa -The Greens development.
2. PREVIOUS SITE DEVELOPMENT
The site was previously sheet-graded to the current configuration during mass grading operations for
the Villages of La Costa -The Greens, Neighborhoods 1.01 through 1.03. The mass grading operations
were performed in conjunction with the observation and testing services of Geocop Incorporated. A
summary of the observations, compaction test results and professional opinions .pertaining to the
grading are presented in the referenced reports dated April 3, 2006 and January 3,2007. Mass gradipg
for the site has been completed and consists of sheet-graded pads with drainage generally flowing to
the southwest toward a desilting basin. The As-Graded Geologic Map (Figure 2 map pocket) has been
Project No. 06403-52-32 -1-. February 7, 2008
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modified .showing the sheet-graded pad, proposed development, and the as-graded geologic
information presented in the referenced final reports dated April 3, 2006 and January 3, 2007. This
exhibit was the basis for our evaluation and recommendations pertaining t? project development.
3. SITE AND PROJECT DESCRIPTION
Proposed residential development is expected to consist of 38, two-story, single-family structures with
associated on-grade parking, driveways, utilities, and landscaping. We expect site grading to be
relatively minor consisting of cuts and fills less than approximately 5 feet to construct thebuiIding pads
and accommodating site drainage.
The site description and proposed development are based on a site reconnaissance, review Of the
conceptual grading and site plans, and discussions with you. If development plans differ from those
described herein, Geocon Incorporated should be contacted for review of the plans and possible
revisions to this report.
4. SOIL AND GEOLOGIC CONDITIONS
The existing soil and geologic conditions consist of compacted fill, undocumented fill, and the
Santiago Formation. The lateral extent of the geologic units is shown on the Geologic Map, Figure 2
(map pocket), and the geologic units are described below. Cut-fill transitions exist across the
southeastern portion of the site, trending north and south, of the property.
4.1 Compacted Fill (Ocf)
In general, the fill materials consist of light yellowish brown, sandy to silty clay and silty sand. The, "; ". ',.".', ,-d-, :',
maximum fill thickness is approximately 20 feet. Fill soil was placed in conjunction with the .. , i',
observation and testing services of Geocon Incorporated. The results of our testing and observation
services are summarized in the referenced grading reports dated April 3, 2006 and :January 3, 2007.
The compacted fill is considered suitable to provide adequate support for the proposed development. 'd' '
4.2 Undocumented Fill (Qudf)
Undocumented fill associated with an existing (in service) utility access road is located along the
central portion of the site. Previous grading in this vicinity was limited due to the presence of the
existing utility lines. These soils are located within the private roadway and are not expected to impact
the project as presently proposed.
Project No. 06403-52-32 -2-February 7, 2008
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4.3 Santiago Formation (Ts)
The Eocene-age Santiago Formation, consisting of dense, massive, white to light green, silty, fine to
coarse sandstones with occasional interbeds of hard, greenish-gray to brown claystones and_ siltstones,
is exposed at fmish grade within the southeastern portion of the site and underlies the compacted fill.
The Santiago Formation is considered suitable for the support of the proposed development.
5. GROUNDWATER
We did not encounter groundwater during grading operations of the site. It is not uncommon for
groundwater or seepage conditions to develop where none previously existed. Groundwater elevations
are dependent on seasonal precipitation, irrigation, and land use, among other factors, and vary as a
result. Proper surface drainage of irrigation and rainwater wil1 be important to future performance of
the project.
6. GEOLOGIC H,A4ARDS
6.1 Faulting and Seismicity
It is our opinion, based on the previous site grading operations and a review of published geologic
maps and reports that the site is not located on any known active, potentially active, or inactive fault
traces. The nearest known active fault is the Rose Canyon Fault Zone located approximately 7 miles
west of the site.
Earthquakes that might occur on the Rose Canyon Fault Zone or other faults within the southern-
California and northern Baja California area are potential generators of significant ground motion at the
site. We used the computer program EQFAULTto calculate the distance of known faults to the site.
Earthquakes on the Rose Canyon Fault Zone having a maximum magnitude of 7.2 are considered
representative of the potential for seismic ground shaking within the property. We calculated the
maximum magnitude is defined as the maximum earthquake that appears capable of occurring under
the presently known tectonic .framework (California Geological Survey, Number 43). We calculated
the estimated maximum ground acceleration expected at the site to be approximately 0.33g using the
Sadigh, et al. (1997), acceleration-attenuation relationship. Table 6.1 presents the earthquake events
and site accelerations for the most significant faults considered most likely to subject the site to ground
shaking.
Project No. 06403-52-32 -3-February 7, 4008
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TABLE 6.1
DETERMINISTIC SITE PARAMETERS FOR SELECTED FAULTS
Fault Name Distance from Maximum Maximum Site
Site (miles) Earthquake Acceleration (g)
Rose Canyon 7 7.2 0.33
Newport-Inglewood (Offshore) 10 7.1 026
Coronado Banks Fault Zone 22 7.6 0.17
Elsinore-Julian 23 7.1 0.12
Elsinore-Temecula 23 6.8 0.10
Elsinore-Glen Ivy 37 6.8 0.06
40 6.5 Earthquake Valley 0.04 -~ ~--~~~~~~----~r-------------+_------------_r~--~~----_;
Palos Verdes 41 7.2 0.06 ~-------------7--------~-----------_+-~-------~_;
San lacinto-Anza 46 7.2 0.06 L-____________________ ~ ____________ ~ ____________ ~ ____________ ~
In the event of a major earthquake on any of the referenced faults in Table 6.1 or other significant
faults in the southern California/northern Baja California area, the site could be subjected to moderate
to severe ground shaking. With respect to this hazard, the site is considered comparable to others in the.
general vicinity. While listing peak accelerations is useful for comparison of potential effects of fault
activity in a region. other considerations are important in seismic design, including the frequency and
duration of motion and the soil conditions underlying the site. The structures should be built in
accordance with the seismic design criteria presented in the Uniform Building Code (UBC) and/or the
California Building Code (CBC).
6.2 Liquefaction
Liquefaction typically occurs when a site is located in a zone with seismic activity, onsite soils are·
cohesionless, groundwater is encountered within 50 feet of the surface, and soil relative densities are
less than about 70 percent. If the four previous criteria are met, a seismic event could result in a rapid
pore water pressure increase from the earthquake-generated ground accelerations. Due to the dense
nature of the compacted fill and formational materials and the lack of a permanent groundwater table,
the potential for liquefaction occurring at the site is considered to be very low.
6.3 Landslides
Examination of aerial photographs in our files, review of available geologic maps and geotechnical
reports for the site vicinity, and the results our field investigation indicate that landslides are not
present at the property or at a location that could impact the site.
~P-ro71e-ct~N70-.70674~073-~52~-732~----------------------~4~-------------------------~F~eb~ru-ruy--7~,~2~OO~8
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7.1
7.1.1
7.1.2
7.1.3
7.1.4
7.2
7.2.1
7.2.2
7. CONCLUSIONS AND RECOMMENDATIONS
General
No soil or geologic conditions were encountered during previous geotechnical investigations
or grading operations that, in our opinion, would preclude the continued dl;\velopment of the
property as presently planned, provided that the recommendations of this, report are
followed.
The site is underlain by compacted fill composed of silty, fine sand and sandy to silty clay
and materials of the Santiago Formation consisting of interbeds of dense satldstone, siltstone,
and claystone. The fonnational materials and the fiU are considered suitable for support of
additional structural fill andlor loads from the proposed development; however, processing,
moisture conditioning as necessary, and compaction of the near-surface soil will be required.
The site is considered suitable for the use of conventional foundations and slab-on-grade
andlor a post-tensioned foundation system ..
The building pads should be graded such that at least the upper 3 feet of materials below
proposed pad grade are composed of compacted fill. The undercuts should be sloped to drain
away from the building pads and toward adjacent streets or toward the deeper fill.
Excavation and Soil Characteristics
The soil encountered during mass grading is considered to be "expansive" (expansion index
[EI] greater than 20) as defined by 2007 California Building Code (CBC) Section 1802.3.2.
Table 7.2.1 presents soil classifications based on the expansion index.
TABLE 7.2.1
SOIL CLASSIFICATION BASED ON EXPANSION INDEX
Expansion Index (EI) Soil Classifij!ation
0-20 VeryL6w
21-50 Low
51 -90 Medium
91-130 Hih g
Greater Than 130 Very High.
We tested samples of the site materials during mass grading operations to evaluate the
percentage of water-soluble sulfate content. Results fr9m the laboratory water-sbluble sulfate
Project No. 06403-52-32 -5-February 7, 200S
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7.2.3
content tests are presented in Appendix B and indicate that the on-site materials at the
locations tested possess "severe" sulfate exposure to concrete structures as defined by 2007
CBC Section 1904.3 and ACI 318. Table 7.2.2 presents a summary of concrete requirements
set forth by 2007 CBC Section 1904.3 and ACI 318. The presence of water-soluble sulfates
is not a visually discernible characteristic; therefore, other soil samples from the site could
yield different concentrations. Additionally, over time landscaping activities (Le., addition of
fertilizers and other soil nutrients) may affect the concentration.
Sulfate
Exposure
Negligible
Moderate
Severe
Very Severe
TABLE 7.2.2
REQUIREMENTS FOR CONCRETE EXPOSED
TO SULFATE-CONTAINING SOLUTIONS
Water-SolubIe Cement Maximum Water
Sulfate Percent Type to Cement Ratio
by Weight by Weight
0.00-0.10 ---
0.10-0.20 II 0.50
0.20-2.00 V 0.45
>2.00 V 0.45
Minimum
Compressive
Strength (psi)
--
4000
4500
4500·
Geocon Incorporated does not practice in the field of corrosion engineering. Therefore, if
improvements that could be susceptible to corrosion are planned, further evaluation by a
corrosion engineer should be performed.
7.3 Seismic Design Criteria
7.3.1 Table 7.3.1 summarizes site-specific seismic design criteria obtained from the 1997 Uniform
Building Code (UBC) Table 16-J for soil profile types Scand Sn which are prevalent on this
project. The values listed on Table 7.3.1 are for the Julian segment of the Elsinore Fault
(located approximately 23 miles northeast of the site), which is identified as a Type A fault
and the Rose Canyon Fault (located approximately 7 miles west/southwest of the site), which
is identified as a Type B fault due to its proximity to the site according to the .computer
program UBCSEIS.
Project No. 06403-52-32 -6-February 7, 2008
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7.3.2
7.3.3
TABLE 7.3.1
1997 UBC SEISMIC DESIGN PARAMETERS
Parameter Value UBC Reference
Fill Thickness, T (feet) T<20 T>20 --
Soil Profile Sc SD Table 16-1
Seismic Zone Factor 0.40 0040 Table 16-1
Seismic Coefficient, Ca 0.40 0.44 Table 16-Q
Seismic Coefficient, Cv 0.56 0.64 Table 16-R
Near-Source Factor, Na 1.0 1.0 Table16-S
Near-Source Factor, Nv 1.0 1.0 Table 16-T
Seismic Source AlB AlB Table 16-U
We used the computer program Seismic Hazard Curves and Uniform Hazard Response
Spectra, provided by the USGS to calculate the seismic design criteria. Table 7.3.2
summarizes site-specific design criteria obtained from the 2007 CBC, Chapter 16 Structl,fral
Design, Section 1613 Earthquake Loads. The short spectral response has a period of' 0.2
second.
TABLE 7.3.2
2007 CBC SEISMIC DESIGN PARAMETERS
Parameter Value mC-06 Reference
Site Class C D Table 161:3.5.2
Spectral Response -Class B (short), Ss 1.147g 1.147g Figure 1613.5(3)
Spectral Response -Class B (1 sec), SI 0.434g 0.434g Figure 1613.5(4)
Site Coefficient, F. 1.000 1.041 Table 1613.53(1)
Site Coefficient, Fv 1.366 1.566 Table 1613.5.3(2)
Maximum Considered Earthquake 1.147g l.194g Section 1613.5.3 (Eqn 16-37) Spectral Response Acceleration (short), SMS
Maximum Considered Earthquake 0.592g 0.679g Section 1613.5.3 (Eqn 16-38) Spectral Response Acceleration -(1 sec), SMI
5% Damped Design 0.765g 0.796g Section 1613.5.4 (Eqn 16-39) Spectral Response Acceleration (short), SDS
5% Damped Design O.395g O.453g Section 1613.5.4 (Eqn 16-40) Spectral Response Acceleration (1 sec), SOl
Confonnance to the criteria for seismic design in Tables 7.3.1 and 7.3.2 does not constitute
any kind of guarantee or assurance that significant structural damage or ground failure will
not occur if a maximum level earthquake occurs. The primary goal of seismic design is to
protect life and not to avoid damage, since such design may be economically prohibitive.
Project No. 06403-52-32 -7-February 7, 2008
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7.4
7.4.1
7.4.2
7.4.3
7.4.4
7.4.5
7.4.6
7.4.7
Grading
Grading should be performed in accordance with the Recommended Grading Specifications
contained in Appendix A. Where the recommendations of this section conflict with tho&e of
Appendix A, the recommendations of this section take precedence. Earthwork should be
observed and fill tested by Geocon Incorporated.
Prior to commencing grading operations, a preconstruction meeting 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.
Site preparation should begin with the removal of deleterious matter and vegetation. The
depth of removal should be such that materials to be used in fills ate generally free of
organic matter. Material generated during stripping operations andlor site demolition should
be exported from the site.
In general, the upper 1 to 2 feet of existing fill should be processed, moisture conditioned as·
necessary, and compacted prior to placing additional fill. Deeper removals and/or' moisture.
conditioning should be expected within the existing desilting basin. In addition, building
pads with formational cut-fill transitions and cut pads should be undercut a minimum of 3
feet and replaced with properly compacted fill. The upper 3 feet of the building pads should
be composed of compacted fill and undercuts should be sloped· a minimum of 1 percent and
drain toward the adjacent on-site streets or driveways.
A review of the development plan indicates that the existing sewer easement area would be
utilized as a street and access to the proposed residential units. Remedial grading in this area
will be limited due to the presence of the sewer lines. We recommend a maximum of 2 feet
of removal and recompaction to provide sub grade for the street.
After preparation of the ground surface, the site should be brought to design elevations with
fill compacted in layers. The site material is considered suitable for use as fill provided it is
generally free from vegetation, debris and other deleterious matter. Layers of fill should not
be thicker than will allow for adequate bonding and compaction. Fill, induding wall and·
trench backfill and scarified ground surfaces, should be compacted to a dry density of at least
90 percent of laboratory maximum dry density near to slightly above optimum moisture
content as determined by ASTM Test Procedure D 1557-02.
Import fill (if necessary) should consist of granular materials with a "very low" to "low"
expansion potential (El of 50 or less), free of deleterious material or rocks larger than
Project No. 06403-52-32 -8-February 7, 2008
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7.4.8
7.5
7.5.1
7.5.2
7.5.3
7.6
7.6.1
3 inches, and should be compacted as recommended herein. Geocon Incorporated should be
notified of the import soil source and should perform laboratory testing of import soil prior
to its arrival at the site to determine its suitability as fill material.
Oversize material (fragments greater than 6 inches in maximum dimension), if generated,
should not be placed within 3 feet of finish grade in pad areas and 12 inches of sub grade in
driveways. Material greater than 6 inches in maximum dimension, if generated, should be
placed in deeper fill areas. Due to the absence of large areas of available fill volume, it is
unlikely that all of the oversize material could be placed as compacted fill during the grading
operation; hence, the oversize material may require exportation.
Slopes
Based on the referenced geotechnical reports for Villages of La Costa -The Greens
development, existing fill slopes at the site (constructed at 2: 1 inclinations) possess a factor
of safety greater than 1.5 against deep-seated and surficial failure.
No significant new slopes are planned during this phase of grading.
Slopes should be landscaped with drought-tolerant vegetation, having variable root depths
and requiring minimal landscape irrigation. In addition, all slopes should be drained and
properly maintained to reduce erosion.
Foundation and Concrete Siabs-On-Grade Recommendations
The foundation recommendations herein are for proposed one-to three-story residential
structures. The foundation recommendations have been separated into three categories based
on either the maximum and differential fill thickness or Expansion Index. The foundation
category criteria are presented in Table 7.6.1.
Foundation
Category
I
II
III
TABLE 7.6.1
FOUNDATION CATEGORY CRITERIA
Maximum Fill Differential Fill
Thickness, T (feet) Thickness, D (feet)
T<20 --
20<T<50 10<D<20
~50 D2:20
Expansion Index
(EI)
EI<50
50<EI<90
90<EI< 13 0
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7.6.2
7.6.3
7.6.4
7.6.5
7.6.6
Final foundation categories for each building or lot will be provided after finish pad grades
have been achieved and laboratory testing of the subgrade soil has been completed.
Table 7.6.2 presents minimum foundation and interior concrete slab design criteria for
conventional foundation systems.
TABLE 7.6.2
CONVENTIONAL FOUNDATION RECOMMENDATIONS BY CATEGORY,
Foundation
Category
I
Minimum Footing
Embedment Depth
(inches)
12
Continuous Footing
Reinforcement
Interior Slab
Reinforcement
Two No.4 bars, 6 x 6 -10110 welded wire
one top and one bottom mesh at slab mid-point r---------~--------------~----~~----------~---------
II 18 Four No.4 bars, No.3 bars at 24 inches'
two top and two bottom on center, both directions ~--------~-------------r----~--------~r-----~-
III 24 Four No.5 bars, No.3 bars at 18 inches
two top and two bottom on center, both directions L-________ ~ ____________ ~ ____ ~ ________ ~~ ____ ~_
The embedment depths presented in Table 7.6.2 should be measured from the lowest
adjacent pad grade for both interior and exterior footings. The conventional foundations
should have a minimum width of.I2 inches and 24 inches for continuous and isolated
footings, respectively. A typical wall/column footing dimension detail is presented in
Figure 3.
The concrete slab-on-grade should be a minimum of 4 inches thick for Foundation
Categories I and II and 5 inches thick for Foundation Category III.
Concrete slabs on grade should be underlain by 2 inches of clean sand to reduce the potential
for differential curing, slab curl, and cracking. Slabs that may receive moisture-sensitive floor
coverings or may be used to store moisture-sensitive materials should be underlain by a vapor
inhibitor covered with at least 2 inches of clean sand or crushed rock. The vapor inhibitor
should meet or exceed the requirements of ASTM, E 1745-97 (Class A), and exhibit
permeance not greater than 0.012 perm (measured in accordance with ASTM E 96-95. This
vapor inhibitor may be placed directly on finish pad grade. The vapor inhibitor should be
installed in general conformance with ASTM E 1643-98 and the manufacturer's
recommendations. Floor coverings should be installed in accordance with the manufacturer's
recommendations.
Project No. 06403-52-32 -10-February 7, 2008
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7.6.7
7.6.8
7.6.9
As an alternative to the conventional foundation recommendations, 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 Po:;;t-Tensioning Institute
(PT!), Third Edition, as required by the 2007 California Building Code (CBC
Section 1805.8). Although this procedure was developed for expansive soil conditions, we
understand 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 Table 7.6.3 for the particular Foundation Category designated. The
parameters presented in Table 7.6.3 are based on the guidelines presented in the PTI, Third
Edition design manual.
TABLE 7.6.3
POST-TENSIONED FOUNDATION SYSTEM DESIGN PARAMETERS
Post-Tensioning Institute (pTI), Foundation Category
Third Edition Design Parameters I n III
Thomthwaite Index -20 -20 :'20
Equilibrium Suction 3.9 3.9 3.9
Edge Lift Moisture Variation Distance, eM (feet) 5.3 5.1 4.9
Edge Lift, YM (inches) 0.61 1.10 1.58
Center Lift Moisture Variation Distance, eM (feet) 9.0 9.0 9.0
Center Lift, YM (Inches) 0.30 0.47 0.66
The foundations for the post-tensioned slabs should be embedded in accordance with the
recommendations of the structural engineer. If a post-tensioned mat foundation system is
planned, the slab should possess a thickened edge with a minimum width of 12 inches and
extend below the clean sand or crushed rock layer.
If the structural engineer proposes a post-tensioned foundation design method other than
PTI, Third Edition:
•
•
•
•
The deflection criteria presented in Table 7.6.3 are still applicable.
Interior stiffener beams should be used for Foundation Categories II and III.
The width of the perimeter foundations should be at least 12 inches.
The perimeter footing embedment depths should be at least 12 inches, 18 inches and
24 inches for foundation categories I, II, and III, respectively. The embedment
depths should be measured from the lowest adjacent pad grade.
Project No. 06403-52-32 -11 -February 7, 2008
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7.6.10 Our experience indicates post-tensioned slabs are susceptible to excessive edge lift,
regardless of the underlying soil conditions. Placing reinforcing steel at the bottom of the
perimeter footings and the interior stiffener beams may mitigate this potential. Current PTI
design procedures primarily address the potential center lift of slabs but, because of the
placement of the reinforcing tendons in the top of the slab, the reSUlting eccentricity after
tensioning reduces the ability of the system to mitigate edge lift. The structural engineer
should design the foundation system to reduce the potential of edge lift occurring for the
proposed structures.
7.6.1 I During the construction of the post-tension foundation system, the concrete should be placed
monolithically. Under no circumstances should cold joints form between the footings/grade
beams and the slab during the construction of the post-tension foundation system.
7.6.12 Category I, II, or ill foundations may be designed for an allowable soil bearing, pressure of
2,000 pounds per square foot (pst) (dead plus live load). This bearing pressure may be
increased by one-third for transient loads due to wind or seismic forces. The estimated
maximum total and differential settlement for the planned structures due to founda~io~ loads
is 1 inch and Yz inch, respectively.
7.6.13 Isolated footings, if present, should have the minimum embedment depth and width
recommended for conventional foundations for a particular foundation category. The use of
isolated footings, which are located beyond the perimeter of the building and ~upport
structural elements connected to the building, are not recommended for Category III. Where
this condition cannot be avoided, the isolated footings should be connected to the building
foundation system with grade beams.
7.6.14 For Foundation Category III, consideration should be given to 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.
7.6.15 Special sub grade presaturation is not deemed necessary prior to placing concrete; however,
the exposed foundation and slab sub grade soil should be moisture conditioned, as necessary,
to maintain a moist condition as would be expected in any such concrete placement.
Project No. 06403-52-32 -12-February 7, 2008
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7.6.16 Where buildings or other improvements are planned near the top of a slope steeper than 3:1
(horizontal:vertical), 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 or cut slopes regardless of height, 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.
When located next to a descending 3: 1 (horizontal:vertical) fill slope or steeper, the
foundations should be extended to a depth where the minimum horizontal distance is
equal to Hl3 (where H equals the vertical distance from the top of the fill slope to the
base of the fill soil) with a minimum of 7 feet but need not exceed 40 feet. The
horizontal distance is measured from the outer, deepest edge of the footing to the
face 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.
If swimming pools are planned, Geocon Incorporated should be contacted for a
review of specific site conditions.
Swimming pools located within 7 feet of the top of cut or fill slopes are not
recommended. Where such a condition cannot be avoided, 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 fin
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 recom-
mendations 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 wans, 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.
7.6.17 The recommendations of this report are intended to reduce the potential for cracking of slabs
due to expansive soil (if present), differential settlement of existing soil or soil with varying
thicknesses. However, even with the' incorporation of the recommendations presented herein,
foundations, stucco walls, and slabs-on-grade placed on such conditions may stilI exhibit
some cracking due to soil movement andlor 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-entrant slab comers occur.
Project No. 06403-52-32 -13 -February 7, 2008
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7.6.18 Geocon Incorporated should be consulted to provide additional design parameters as
required by the structural engineer.
7.7 Retaining Walls and Lateral Loads
7.7.1 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
35 pounds per cubic foot (pcf). Where the backfill will be inclined at no steeper than 2 to ~,
backfill materials within an area bounded by the wall and a ]: 1 plane extending llpward from
the base of the wall possess an Expansion Index of 50 or ,less. Where backfill materials do
not confonn to the criteria herein, Geocon, Incorporated should be consulted for additiOlial
recommendations.
7.7.2
7.7.3
7.7.4
7.7.5
Unrestrained walls are those that are allowed to rotate more than O.OOlH (where H equals the
height of the retaining wall portion of the' wall in feet) at the top of the wall. Where walls are
restrained from movement at the top, an 'additional uniform pressure of 7H psf should be
added to the above active soil pressure. For retaining walls subjected to vehicular loads
within a horizontal distance equal to two-thirds ofthe wall height, a surcharge equIva]ent to
2 feet soil should be added.
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. A typical retaining wall drainage system is presented asJ;'igure 4. The
recommendations herein assume a properly compacted gr!l.nular (Expansion Index of 50 or
less) backfill material with no hydrostatic forces or imposed surcharge load. If conditions
different than those described are expected, or if specific drainage details are desired,
Geocon Incorporated should be contacted for additional recommendations.
In general, wall foundations having a minimum depth and width of orie foot may be designed
for an allowable soil bearing pressure of 2,000 psf, provided the soil within 3 feet below $e
base of the wall has an Expansion Index of 90 or less. The proximity of the foundation to the
top of a slope steeper than 3: 1 could impact the allowable soil bearing pressure. Therefore,
Geocon Incorporated should be consulted where such a condition is expected.
For resistance to lateral loads, an allowable passive earth pressure equivalent to a fluid
density of300 pcf is recommended for footings or shear keys poured neat against properly
compacted granular fill soil or undisturbed natural soil. The allowable passive pressllre
assumes a horizontal surface extending at least 5 feet or three times the surfact! -generating
Project No. 06403-52-32 -14-February 7, 2008
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7.7.6
7.8·
7.8.1
7.8.2
7.8.3
7.8.4
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 re'sistance to sliding between soil and
concrete. This friction coefficient may be combined with the allowable passive earth
pressure when determining resistance to lateral loads.
The recommendations presented herein 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 (such as crib-type walls) are planned, Geoeon
Incorporated should be c?nsulted for additional recommendations.
Preliminary Flexible Pavement Recommendations
Preliminary pavement recommendations provided are based on our experience with similar
soil conditions. For driveways and parking areas, design and construction criteria should
conform to City of Carlsbad standards. We assume the pavement surface will have
automobile and light-duty truck traffic. We have also assumed an R-value of 15 for the
proposed subgrade soil. Table 7.8 presents preliminary pavement recommendation' is for
planning and estimating purposes only, and not for construction.
Location
Driveways
TABLE 7.8
PRELIMINARY PAVEMENT SECTION
Assumed Assumed Asphalt Concrete
Traffic Index R-Value (inches)
5.0 15 . 4
Aggregate Base
Material (inches)
6
The upper 12 inches of the sub grade supporting the structural section should be scarified,
moisture conditioned as necessary, and compacted to a dry density of at least 95 percent of
the laboratory maximum dry density near to slightly over optimum moisture as determined
by ASTM Test Method D 1557-02.
Aggregate base materials should be compacted to a dry density at least 95 percent of the
laboratory maximum dry density at near to slightly above optimum moisture content.
Asphalt concrete should be compacted to a density of at least 95 percent of the Hveem
density as determined by ASTM D 2726-05A.
Project No. 06403-52-32 • 15 -February 7, 2008
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7.8.5
7.9
7.9.1
7.10
7.10:1
Asphalt concrete should conform to Section 203-6 of the Standard Specifications for Public
Works Construction (Greenbook). Aggregate base (Class II) materials should conform ·to·
Section 26-1.02A of the Standard Specifications of the State of California, Department of
Transportation (Caltrans) or approved equivalent. Additionally, all materials should conform
to City of Carlsbad specifications.
Slope Maintenance
Slopes that are steeper than 3:1 (horizontal:vertical) may, under conditions that are both
difficult to prevent and predict, be susceptible to near-surface (surficial) slope instability.
The instability is typically limited to the outer 3 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 genenilly preceded
by a period of heavy rainfall, excessive irrigation, or the migration of subsurface seepage.
The disturbance andlor loosening of the surficial soil, as might result from root groWth, soil
expansion, or excavation for irrigation lines and siope planting, may also be a significant
contributing factor to surficial instability. It is therefore recommended that, to the maximum
extent practical: (a) disturbedlloosened surficial soil 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 11.ecessary to' rebuild
or repair a portion of the project's slopes in the future.
Site Drainage and Moisture Protection ...... ':!, I'·, .. ; l"~;":.~ . -: .... ~.
Adequate site drainage is critical to reduce the potential for differential soil movement,'.
erosion and subsurface seepage. Under no circumstances should water be allowed to pond
adjacent to footings. The site should be graded and maintained such that surface drainage is
directed away from structures in accordance with 2007 CBC 1803.3 or other applicable
standards. In addition, surface drainage should be directed away from the top of slopes into
swales or other controlled drainage devices. Roof and pavement drainage should be directed
into conduits that carry runoff away from the proposed structure.
7.10.2 If detention basins, bioswales, or retention basins are planned, distress may be caused 'to
planned improvements and properties located hydrologically downstream. The distress
depends on the amount of water to be detained, its residence time, soil permeability, and
other factors. We have not performed a hydrogeology study at the site. Downstream
properties may be subjected to seeps, springs, slope instability, raised-groun~water,
Project No. 06403-52-32 -16-F~bruary 7; 2008
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movement of foundations and slabs, or other impacts as a result of water infiltration through
the detention basins, bioswales, or retention basins.
7.11 Grading and Foundation Plan Review
7.11.1 Grading and foundation plans should be reviewed by Geocon Incorporated to check that the
plans have been prepared in substantial conformance with the recommendations of this
report.
Project No. 06403-52-32 -17 -February 7, 2008
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1.
2.
3.
4.
LIMITATIONS AND UNIFORMITY OF CONDITIONS
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 that the necessary steps are taken to see that the contractor and subcontractors carry
out such recommendations in the field.
The fmdings 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 are 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.
The firm that performed the geotechnical investigation for the project should be retained to
provide testing and observation services during construction to provide continl,1ity of
geotecImical interpretation and to check that the recommendations presented for geotechnical
aspects of site development are incorporated during site grading, construction of
improvements, and excavation of foundations. If another geotechnical firm is selected to
perform the testing and observation services during construction operations, that firm should
prepare a letter indicating their intent to assume the responsibilities of project geotechnical
engineer of record. A copy of the letter should be provided to the regulatory agency for their
records. In addition, that firm should provide revised recommendations concerning the
geotechnical aspects of the proposed development, or a written acknowledgement of their
concurrence with the recommendations presented in our report. They should also perform
additional analyses deemed necessary to assume the role of Geotechnical Engineer of Record.
Project No. 06403-52-32 February 7, 2008
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SOURCE: 2006 THOMAS BROTHERS MAP
SAN DIEGO COUNTY. CALIFORNIA
REPRODUCED WITH PERMISSION GRANTED BY THOMAS BROTHERS MAPS.
t
1'J
NO SCALE THIS MAP IS COPYRIGHT BY THOMAS BROS. MAPS. IT IS UNLAWFUl. TO COPY
OR REPROOUCEALI. OR ANY PART THEREOF. WHETHER FOR PERSONAL USE OR
RESAI.E. WITHOUT PERMISSION: L-______________________________ ---....... "''' .. ~ ..... , ....
GEOCON
INCORPORATED
GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121-2974. '
PHONE 858 558-6900 • FAX 858 558·6159
AS/RA I 1 DSKlGTYPD
Vicinllyl'llop
VICINITY MAP
VILLAGES AT LA COSTA -THE .. G~EJ:NS ........ "
NEIGHBORHOOD 1.03, LOTS 1 THROUGH 38
CARLSBAD, CALIFORNIA
DATE 02 -07 -2008 1 PROJECT NO. 06403 -52', 321 FIG. 1
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WALL FOOTING
CONCRETE SLAB
PAD GRADE
VISQUEEN
COLUMN FOOTING
CONCRETE SLAB
• • :1\ 4
~4 • .. .
4 ~ •
f------FOOTING WIDTH' ------I
* .... SEE REPORT FOR FOUNDATION WITDH AND DEPTH RECOMMENDATION
1---------------------------------------1. "" .....
WALL / COLUMN FOOTING DIMENSION DETAIL . 1-0 _____________________________________ ....... " ", ..
G'EOCON
INCORPORATED • GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121-2974-
PHONE 858 558-6900 -FAX 858 558-6159
AS/RA DSKlGTYPD
VILLAGES AT LA COSTA -THE GREENS
NEIGHBORHOOD 1.03, LOTS 1 THROUGH 38
CARLSBAD, CALIFORNIA
DATE 02 -07 -2008 PROJECT NO. 06403 -52 -32 FIG. 3
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GROUND SURFACE
213H ____ """""-MIRAFI140 FILTER FABRIC
(OR EQUIVALENT)
GROUND SURFACE \
NOTE:
RETAINING
WALL
PROPOSED
GRADE~
12"
CONCRETE
OPEN GRADED
1" MAX. AGGREGATE
4" DIA. PERFORATED SCHEDULE
40 PVC PIPE EXTENDED TO
APPROVep OUTLET
GROUND SURFACE
BROWDITCH J ,--_-'--=====.,.-___ _
WATER PROOFING
PER ARCHITECT
DRAINAGE PANEL (MlRADRAIN 6000
OR EQUIVALENT)
12~ 3/4" CRUSHED ROCK
(1 CU.FT.lFT.)
__ . FILTER FABRIC ENVELOPE
'.:;:.', .~:.~ MlRAFI140N OR EQUIVALENT ' ... ~ 4" DIA. SCHEDULE 40 PERFORATED y,:~ -PVCPIPEORAPPROVEDTOTALDRAIN
-~ EXTENDED TO APPROVED OUTLET
FOOTING .
DRAIN SHOULD BE UNIFORMLY SLOPED TO GRAVITY OUTLET
OR TO A SUMP WHERE WATER CAN BE REMOVED BY PUMPING
1----------------------------------1 .............. .
TYPICAL RETAINING WALL DRAIN DETAIL'
GEDeON
INCORPORATED o
GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121-2974
PHONE 858 558-6900 -FAX 858 558-6159
AS/RA DSKlGTYPD
Y:IR141EMP/1..,AUTOCAD PlATE TEMPlATEII_DETAlUREI'AINlNG WALL DRAiNAGOIRET WALL DIWN DETAlLS_:1.DWG
VILLAGES AT LA COSTA -THE GR~ENS
NEIGHBORHOOD 1.03, LOTS 1 THROUGH 38
CARLSBAD, CALIFORNIA
DATE 02 -07 -2008 PROJECT NO; 06403 -52 -32' FIG. 4
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APPENDIX A
LABORATORY RESULTS
FOR
VILLAGES OF LA COSTA -THE GREENS
NEIGHBORHOOD 1.03; LOTS 1 THROUGH ~8
CARLSBAD, CALIFORNIA
PROJECT NO. 06403-52-32
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TABLE A-I
SUMMARY OF FINISH GRADE LABORATORY EXPANSION INDEX TEST RESULTS
ASTM D 4829-03
Moisture Content (%) Dry Density Expansion Sample No. (pet) Index Before Test After Test
EI-E 11.2 24.1 103.9 59
El-F 11.4 24.2 103.6 63
TABLE A-II
SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS . !., 'f}:;;;;, ~ W\!~.J\ :'F':',,::'i-':'';;,:
CALIFORNIA TEST 417 .,,',
"
Sample No. Water-Soluble Sulfate (%) Sulfate Exposur.e '1,-
"
EI-E 0.306 Severe
EI-F 0,281 Severe
Project No. 06403-52-03 February 7; 2008
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APPENDIX B
RECOMMENDED GRADING SPECIFICATIONS
FOR
VILLAGES OF LA COSTA -THE GREENS
NEIGHBORHOOD 1.03; LOTS 1 THROUGH 38
CARLSBAD, CALIFORNIA
PROJECT NO. 06403-52-32
.'1,:' ",.. ~, .:'" -'"
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1.1
1.2
1.3
2.1
2.2
2.3
RECOMMENDED GRADING SPECIFICATIONS
1. GENERAL
These Recommended Grading Specifications shall be used in conjun~tion with the
Geotechnical Report for the project prepared by Geocon Incorporated. The
'recommendations cQntained 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.
Prior to the commencement of grading, a geotechnical consultant (Consultant) shall be
employed for the purpose of observing earthwork procedures and testing the fills for'
substantial conformance with the recommendations of the Geotechnical Report and these
specifications. The Consultant should provide adequate testing and observation s~rvices so
that they may assess whether, in their opinion, the work waS performed in substantial
conformance with these specifications. It shall be the responsibility of the Contractor to
assist the Consultant and keep them apprised of work schedules and changes so that
personnel may be scheduled accordingly.
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, result in a quality of work not in
conformance with these specifications, the Consultant will be empowered tel reject the
work and recommend to the Owner that grading be stopped until the unacceptabie
conditions are corrected.
2. DEFINITIONS
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. '
Contractor shall refer to the Contractor performing the site grading work.
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.
ei rev. 10/06
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2.4
2.5
2.6
2.7
3.1
Consultant shall refer to the soil engineering and engineering geology consulting firm
retained to provide geotechnical services for the project.
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 confonnance with these specifications.
Engineering Geologist shall refer to a California licensed Engineering Geologist retainet;l
by the Owner to provide geologic observations and recommendations during the site
grading.
Geotechnical Report shall refer to a soil report (including all addenda) which inay 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
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 % 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 arotmd the rock fragments or hard lumps as
specified in Paragraph 6.2. Oversize rock is defined as material grea,ter t~an 12
inches.
3.1.3 Rock fills are dermed 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 % inch in maximum dimension. The quantity of fmes shall be
less than approximately 20 percent ofthe rock fill quantity.
GI rev. 10/06
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3.2
3.3
3.4
3.5
3.6
4.1
Material of a perishable, spongy, or otherwise unsuitable nature as determined by the
Consultant shall not be used in fills.
Materials used for fill, either imported or on-site, shall not contain hazardous mliterials 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
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.
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 ] 2 inches is track-walked onto the face for landscaping purposes. This
procedure may be utilized provided it is acceptable to the governing agency, 0YVller and
Consultant.
Samples of soil materials to be used for fill should be tested in the laboratory by the
Consultant to determine the maximum density, optimum moisture content, and, where
appropriate, shear strength, expansion, and gradation characteristics of the soil.
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 unariticipated condition
4. CLEARING AND PREPARING AREAS TO BE FILLED
Areas to be excavated and filled shall be cleared and grubbed. Clearing shall consist of
complete removal above the ground surface of trees, stumps, brush, vegetation, man-made
structures, and similar debris. Grubbing shall consist of removal of stumps, roots, buried
logs and other unsuitable material and shaH be performed in areas to be graded. Roots and
other projections exceeding Ilh 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.
Gl rev. 10/06
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4.2
4.3
Any asphalt pavement material removed during clearing operations should be properly
disposed at an approved off-site facility. Concrete fragments that are free of reinforcing
steel may be placed in fills, provided they are placed in accordance with Section 6.2 or 6.3
ofthis document.
After clearing and grubbing of organic matter and other unsuitable material, loose or
porous soils shall be removed to the depth recommended in the Geotechnical Report. The.
depth of removal and compaction should 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 5:1 (horizontai:vertical), or
where recommended by the Consultant, the original ground should be benched in
accordance with the following illustration.
TYPICAL BENCHING DETAIL
Finish Grade
Remove All
Unsuitable Material
As Recommended By
Consultant Slope To Be Such That
Sloughing Or Sliding
Does Not Occur
Original Ground
/ Finish Slope SUrfa~e
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See Note 1
No Scale
DETAil., NOTES: (1) Key width "B" should be a minimum of 10 feet, or sufficiently wide to permit
complete coverage with the compaction equipment used. The base oHhe key should
be graded horizontal, or inclined slightly into the natural' slope.
(2) The outside of the 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. 10/06
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4.5
5.1
5.2
6.1
After areas to receive fill have been cleared and scarified, the surface should be moisture
conditioned to achieve the proper moisture content, and compacted as recommended in
Section 6 of these specifications.
5. COMPACTION EQUIPMENT
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.
Compaction of rock fills shall be performed in accordance with Section 6.3.
6. PLACING, SPREADING AND COMPACTION OF FILL MATERIAL '''';''9.:-',
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 shaH 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 Iifts; Rock
materials greater' than 12 inches in maximum dimension shall be placed in
accordance with Section 6.2 or 6.3 ofthese specifications.
6.1.2 In general, the soil fill shall be compacted at a moisture content at or .abovethe
optimum moisture content as determined by ASTM D 1557-02.
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. 10106
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6.2
6.1.5 After each layer has been placed, mixed, and spread evenly, it shall be thoroughly
compacted by the Contractor to a relative compaction of at least 90 percent.
Relative compaction is defmed as the ratio (expressed in percent) of the in-place
dry density of the compacted fill to the maximum laboratory dry. density as
determined in accordance with ASTM D 1557-02. 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.
6.1.6 Where practical, soils having an Expansion Index greater than 50 should be placed
at least 3 feet below finish pad grade and should be compacted at a moisture
content generally 2 to 4 percent greater than the optimum moisture content for the
material.
6.1.7 Properly compacted soil fill shall extend to the design surface of fill slopes. To
achieve proper compaction, it is recommended that fill slopes be over-built by at
least 3 feet and then cut to the design grade. This procedure is considered
preferable to track-walking of slopes, as described in the following paragraph.
6.1.8 As an alternative to over-building of slopes, slope faces may be back-rolled with a
heavy-duty loaded sheepsfoot or vibratory roller at maximum 4-foot fit,1 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.
Soil-rock fill, as defined in Paragraph 3.1.2, shall be placed by the Contractor in accordance" , .. .': :,"
with the following recommendations:
6.2.1 Rocks larger than 12 inches but less than 4 feet in maximum dimension may be
incorporated into the compacted soil fill, but shall be limited to the area measured
15 feet minimum horizontally from the slope face and 5 feet below finish grade or
3 feet below the deepest utility, whichever is deeper.
6.2.2 Rocks or rock fragments up 'to 4 feet in maximum dimension may either be
individually placed or placed in windrows. Under certain conditions, rocks' or rock
fragments up to ] 0 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.
Gl rev. 10/06
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6.3
6.2.3 For individual placement, sufficient space shall be provided between rocks to allow
for passage of compaction equipment.
6.2.4 For windrow placement, the rocks should be placed in trenches excavated in
properly compacted soil fill. Trenches should be approximately 5 feet wide and
4 feet deep in maximum dimension. The voids around and beneath rocks should be
filled with approved granular soil having a Sand Equivalent of 30 or greater and
should be compacted by flooding. Windrows may also be placed utilizing an.
"open-face" method in lieu of the trench procedure, however, this method should
first be approved by the Consultant.
6.2.5 Windrows should generally be parallel to each other and may be placed either
parallel to or perpendicular to the face of the slope depending on .the site geometry.
The minimum horizontal spacing for windrows shall be 12 feet center-to-center
with a 5-foot stagger or offset from lower courses to next .overlying course. The
minimum vertical spacing between windrow courses shall be 2 feet from the top of
a lower windrow to the bottom of the next higher windrow.
6.2.6 Rock placement, fill placement and flooding of approved granular soil in the.
windrows should be continuously observed by the Consultant.
Rock fills, as defined in Section 3.1.3, shall be placed by the Contractor in accordance with
the following recommendations:
6.3.1 The base of the rock fill shall be placed on a sloping surface (minimum ·slope of2
percent). The surface shall slope toward suitable subdrainage outlet facilities. The
rock fills shall be provided with sub drains during construction so that a hydrostatic
pressure buildup does not develop. The subdrains shall be permanently connected
to Qontrolled drainage facilities to control post-construction infiltration of water.
6.3.2 Rock fills shall be placed in lifts not exceeding 3 feet. Placement shall be by rock
trucks traversing previously placed lifts and dumping at the edge of the currently
placed lift. Spreading of the rock fill shall be by dozer to facilitate seating of the
rock. The rock fill shall be watered heavily during placement. Watering shall
consist of water trucks traversing in front of the current rock lift face and spraying
water continuously during rock placement. Compaction equipment with
compactive energy comparable to or greater than that of a 20-ton steel vibratory
roller or other compaction equipment providing suitable energy to achieve the
GI rev. 1()/06
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required compaction or deflection as recommended in Paragraph 6.3.J shall be
utilized. The number of passes to be made should be determined as described in
Paragraph 6.3.3. Once a rock fill lift has been covered with soil fill; no additional
rock fill lifts will be permitted over the soil fill.
6.3.3 Plate bearing tests, in accordance with ASTM D 1196-93, may be performed in
both the compacted soil fill and in the rock fill to aid in determining the required
minimum number of passes of the compaction equipment. If performed, a
minimum of three plate bearing tests should be performed jn 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
6.3.5
A representative of the Consultant should be present during rock fill operations to
observe that the minimum number of "passes" have been obtained, that water is
being properly applied and that specified procedures are being followed. The actual
number of plate bearipg tests will be detennined by the Consultant during grading.
Test pits shall be excavated by the Contractor so that the Consultant can state that,
in their opinion, sufficient water is present and that voids between large rocks are
properly filled with smaller rock material. In-place density testing will not be
required in the rock fills.
6.3.6 To reduce the potential for "piping" of fines .into the rock fill from overlying soil
fill material, a 2-foot layer of graded filter material shall be placed· above the
uppermost lift of rock fill. The need to place graded filter mat~ri;~l below the rock •
should be determined by the Consultant prior to commencing grading. The
gradation of the graded filter material will be detennined at the time th~rock fill is
being excavated. Materials typical of the rock fill should be submitted to the
Consultant in a timely maImer, to allow design of the graded filter prior to. the .
commencement of rock fill placement.
6.3.7 Rock fill placement should be continuously observed during placement by the
Consultant.
GI rev. i 0/96
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7.1
7.2
7.3
7.4
7.5
7.6
7. OBSERVATION AND TESTING
The Consultant shall be the Owner's representative to observe and perform tests during
clearing, grubbing, filling, and compaction operations. In general, no more than 2 feet in
vertical elevation of soil or soil-rock fill should be placed without at least one field density
test being performed within that interval. In addition, a minimum of one field density test
should be performed for every 2,000 cubic yards of soil or soil-rock fill placed and
compacted.
The Consultant should perform a sufficient distribution of field density tests of the
compacted soil or soil-rock fill to provide a basis for expressing an opinion whether the fill
material is compacted as specified. Density tests shall be performed in the compacted
materials below any disturbed surface. When these tests indicate that the density 9fany
layer of fiU or portion thereof is below that specified, the particular layer or areas
represented by the test shall be reworked until the specified density has bee.n achieved.
During placement of rock fill, the Consultant should observe that the minimum~ number of .' ..
passes have been obtained per the criteria discussed in Section 6.3.3. The C.on~uJtant ',0
should request the excavation of observation pits and may ,perform plate bearing tests 011, '.",'" .. ,,: , ..
the placed rock fills. The observation pits will be excavated to provide a basis for
expressing an opinion as to whether the rock fill is properly seated and sufficient moistUre
has been applied to the material. When observations indicate that a layer of rock fill or any .
portion thereof is below that specified, the affected layer or area shall be reworked until the
rock fill has been adequately seated and sufficient moisture applied.
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.
The Consultant should observe the placement of sub drains, to verify that the drainage
devices have been placed and constructed in substantial conformance with project
specifications.
Testing procedures shall conform to the following Standards as appropriate:
GI rev, 10/06
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8.1
7.6.1 Soil arid Soil-Rock Fills:
7.6.1.1 Field Density Test, ASTM D 1556-02, Density of Soil In-Place By the
Sand-Cone Method
7.6.1.2 Field Density Test, Nuclear Method, ASTM D 2922-01, Density of Soil
and Soil-Aggregate In-Place by Nuclear Methods (Shallow Depth).
7.6.1.3 Laboratory Compaction Test, ASTM D 1557-02, Moisture-Density
Relations of Soils and Soil-Aggregate Mixtures. Using IO-Pound
Hammer and I8-Inch D1·op.
7.6.1.4. Expansion Index Test, ASTM D 4829-0~, Expansion Index Test.
7.6.2 Rock Fills
7.6.2.1 Field Plate Bearing Test, ASTM D 1196-93 (Reapproved 1997)
Standard Methodfor Nonreparative Static Plate Load Te,y(s of Soils and
Flexible Pavement Components, For Use in evaluation and Design of
Airport and Highway Pavements.
8. PROTECTION OF WORK
During construction, the Contractor shall properly grade all excavated surfaces to provide
positive drainage and prevent ponding of water. Drainage of surface water shall be
controlled to avoid damage to adjoining properties or to finished work on the site. The
Contractor shall take remedial measures to prevent erosion of freshly graded areas until
such time as permanent drainage and erosion control features have been installed. Areas
subjected to erosion or sedimentation shall be properly prepared in accordance with the.·"", ........ ·r( [il •• ' •• '~
Specifications prior to placing additional fill or structures.
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. 10/06
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9.1
9.2
9. CERTIFICATIONS AND FINAL REPORTS
Upon completion of the work, Contractor shall furnish Owner a certification by the Civil
Engineer stating that the lots andlor building pads are graded to within 0.1 foot vertically of
elevations shown on the grading plan and that all tops and toes of slopes are withi'n 0.5 foot
horizontally of the positions shown on the grading .plans. After installation' of a section of
subdrain, the project Civil Engineer should survey its location and prepare an as-built plan
of the subdrain location. The project Civil Engineer should verify the proper outlet for the
subdrains and the Contractor should ensure that the drain system is free of obstructions.
The Owner is responsible for furnishing a final as-graded soil and geologic report
satisfactory to the appropriate governing or accepting agencies. The as-gl'?ded report
should be prepared and signed by a California licensed Civil Engineer experienced in
geotechnical engineering and by a California Certified Engineering Geologist, indicating
that the geotechnical aspects of the grading were performed' in substantial conformance
with the Specifications or approved changes to the Specifications.
GI rev. 10/06
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RECEIVED
~IH~ 06 2008
ENGiNEERING
DEPARTMENT
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