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UPDATE
GEOTECHNICAL REPORT
VILLAGES OF LA COSTA-
THE GREENS;
NEIGHBORHOOD 1.02,
KINGDOM HALL
CARLSBAD, CALIFORNIA
PREPARED FOR
PALOMAR CONGREGATION
c/o HACKER ENGINEERING, INC.
PALM DESERT, CALIFORNIA
ttECEN!D
st.P l ~ 7.n\n
C\1Y Or CARLS!e0
pLANN\NG OEr •·
OCTOBER 20, 2008
PROJECT NO. 06403-52-33
GEOCON
INCORPORATED
Project No. 06403-52-33
October 20. 2008
Palomar Congregation
"io Hacker Engineering, Inc.
77-530 Enfield Lane, Suite E-1
Palm Desert, California 92221
Attention:
Subject:
Mr. Dave Hacker
VILLAGES OF LA COSTA THE GREENS
NEIGIIBORHOOD 1.02. KINGDOM HALl.
CARLSBAD. CALIFORNIA
UPDATE GEOTECHNICAL REPORT
Dcnr Mr. llacker:
GEOTECHNICAL CONSULTANTS 0
In accordance with your authorization of our Proposal No. LG-08271 dated September 4, 2008, we
have prcpan:d this update geotechnical repon for the subject project. The accompanying rcpon presents
the results of our study and our condusions and recommendations pcr1aining to the geotechnical
aspects of project devdopmcnt.
We understand the proposed project includes line grading the existing sheet-graded site to suppon a
worship hall with associated improvements. We expect the building will consist of wood framed
structure supported by conventional continuous and/or isolated spread footings with slab-on-grade
construction. Based on the results of this study, it is our opinion that the site can be developed as
planned, provided the recommendations of this report are followed.
Should you have any qm:stions regarding this report, or if we may be of further service, please contact
the undersigned at your convenience.
Very truly yours.
GEOCONINCORPORATED
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AS:SW:dmc
( 4) Addressee
(2) Mr. Neillmmcgrt
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Shawn Weedon
GE2714
6960 Flanders Drive • Son Diego, California 92121·2974 • Telephone [8581558-6900 • Fox [8581558-6159
TABLE OF CONTENTS
1. PURPOSE AND SCOPE ................................................................................................................. 1
2. PREVIOUS SITE DEVELOPMENT ............................................................................................... I
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 Lindavista Formation (Qln) ................................................................................................... 3
4.4 Santiago Forn1ation (Ts) ........................................................................................................ 3
5. GROUNDWATER ........................................................................................................................... 3
6. GEOLOGIC HAZARDS .................................................................................................................. 3
6.1 Faulting and Seismicity .......................................................................................................... 3
6.2 Liquefaction ........................................................................................................................... 5
6.3 Seiches and Tsunamis ............................................................................................................ 5
6.4 Landslides .............................................................................................................................. 5
7. CONCLUSIONS AND RECOMMENDATIONS ........................................................................... 6
7.1 General ................................................................................................................................... 6
7.2 Soil and Excavation Characteristics ....................................................................................... ?
7.3 Grading .................................................................................................................................. 8
7.4 Seismic Design .................................................. , .................................................................. 10
7.5 Slopes ................................................................................................................................... ll
7.6 Conventional Shallow Foundations ..................................................................................... 11
7.7 Concrete Slabs-on-Grade and Flatwork Recommendations ................................................ 12
7.8 Retaining Walls and Lateral Loads ...................................................................................... 14
7. 9 Lateral Loading .................................................................................................................... 15
7.10 Preliminary Flexible Pavement Recommendations ............................................................. 15
7.11 Drainage and Maintenance ................................................................................................... 18
7.12 SlopeMaintenance ............................................................................................................... l9
7.13 Plan Review ......................................................................................................................... 19
LIMITATIONS AND UNIFORMITY OF CONDITIONS
MAPS AND ILLUSTRATIONS
Figure l, Vicinity Map
Figure 2, Geologic Map (map pocket)
Figure 3, Wall/Column Footing Dimension Detail
Figure 4, Retaining Wall Drainage Detail
APPENDIX A
LABORATORY RESULTS
Table A-I, Summary of Expansion Index Test Results
Table A-II, Summary of Laboratory Water-Soluble Sulfate Test Results
APPENDIX B
RECOMMENDED GRADING SPECIFICATIONS
UPDATE GEOTECHNICAL REPORT
1. PURPOSE AND SCOPE
This report presents the results of an update geotechnical study for the proposed development of the
southern portion of Neighborhood 1.02 located in the Villages of La Costa-The Greens in Carlsbad.
California (see Vicinity Map, Figure 1). The purpose of this update report is to evaluate the soils and
geologic conditions within the site and provide specific geotechnical recommendations pertaining to
the ultimate development of the property as proposed.
The scope of the study included a site visit to observe whether the lot is essentially the same as it was
upon the completion of mass grading operations, review of the following reports and plan associated
with the site:
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 Geocon Incorporated, dated January 3, 2007 (Project No. 06403-
52-22).
2. 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
Geocon Incorporated, dated April 3, 2006 (Project No. 06403-52-22).
3. Grading and Erosion Control Plans for: Kingdom Hall, Carlsbad, California, prepared by
Hacker Engineering Inc., undated.
The descriptions of the soil and geologic conditions and proposed development described herein are
based on review of the referenced reports and plan, and observations made during mass grading
operations for Neighborhood 1.02 of the Villages of La Costa -The Greens development.
2. PREVIOUS SITE DEVELOPMENT
Mass grading for the site occurred between December 2005 and November 2006. We performed
compaction testing and observation services during the grading operations. Test results and
professional opinions pertaining to the mass grading are summarized in the referenced geotechnical
reports (Reference Nos. 1 and 2). A canyon subdrain was installed along the eastern margins of the
property during the mass grading operations and outlets into open space. We used the referenced
development plan as the base for the Geologic Map, Figure 2 (map pocket) showing the sheet-graded
pad and proposed development. The map has been modified to include the as-graded geologic
information presented in the referenced geotechnical reports dated April 3, 2006 and January 3, 2007.
ProJect No. 06403-52-33 . (. October 20, 2008
3. SITE AND PROJECT DESCRIPTION
The irregular-shaped site consists of a previously graded, vacant lot. The site is bound to the north by
the northern portion of Neighborhood 1.02 which has developed as a daycare center, El Camino Real to
the west, Neighborhood 1.03 to the south, and undeveloped/open space land to the east. Prior to
grading, topography within the subject improvements varied from gently sloping to moderately steep
hillside terrain.
Fill slopes were constructed with a maximum height of 30 feet. Topographically, the sheet-graded pad
slopes south to north with elevations varying from approximately 317 above Mean Sea Level (MSL) to
approximately 304 MSL.
The referenced site plan indicates the site will be developed to support a worship hall and two, 1-story
care-taker residences with accompanied infrastructure, pavement, and landscaping. We expect the
structures will be founded on conventional continuous and isolated spread foundations with slab-on-grade
floors. We understand a majority of driveway traffic will consist of cars and light trucks. We expect
grading will consist of cuts and fills generally less than 5 feet to create relatively flat building pads.
The descriptions contained herein are based upon the site reconnaissance and a review of the
referenced reports and plan. If project details vary significantly from those outlined herein, Geocon
Incorporated should be notified for review and possible revisions to this report prior to final design
4. SOIL AND GEOLOGIC CONDITIONS
Compacted fill, undocumented fill, the Santiago Formation, and Linda vista Formation underlie the site.
The as-graded geology is presented on the Geologic Map, Figure 2 (map pocket). The soil types and
geologic units are discussed below.
4.1 Compacted Fill (Qcf)
Fill materials comprise the southeast half of the site and generally consist of silty sand. The maximum
fill thickness is approximately 27 feet. Fill soil was placed in conjunction with our observation and
testing services and are summarized in the referenced geotechnical reports dated April 3, 2006, and
January 3, 2007. With the exception of the upper I to 2 feet, the compacted fill is considered suitable
for support of the proposed structure and ancillary improvements.
4.2 Undocumented Fill (Qudf)
Undocumented fill associated with an existing (in service) 30-inch high pressure gas line is located
along the western boundary. adjacent to El Camino Real. Previous grading in this vicinity was limited
due to the presence of the gas line. The undocumented fill is approximately 2 to 5 feet thick and is
Project No. 06403-52-33 . 2. October 20. 2008
considered unsuitable for support of settlement sensitive improvements. These soils are located beyond
planned development and we do not expect there will be an impact to the project as presently proposed.
4.3 Lindavista Formation (Qin)
The majority of the Lindavista Formation was removed during the mass grading operations, except
within the vicinity of the existing high pressure gas line, along the western boundary. The Lindavista
Formation generally consists of dense to very dense, silty sandstone and is considered suitable for the
support of the proposed development.
4.4 Santiago Formation (Ts)
The Eocene-age Santiago Formation consists of dense, massive, white to light green, silty, fine to
coarse sandstones with occasional interbeds of hard, greenish gray to brown claystones and siltstones.
The Santiago Formation is exposed at finish grade within the northwestern 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 will be important to future performance of the project.
6. GEOLOGIC HAZARDS
6.1 Faulting and Seismicity
It is our opinion, based on our site reconnaissance 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 northwest 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 EQFAULT to 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. 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). The estimated maximum
ground acceleration expected at the site is calculated to be approximately 0.32 using the Sadigh, et al.
Project No. 06403-52-33 . 3. October 20. 2008
(1997), acceleration-attenuation relationship. Table 6.1.1 presents the earthquake events and site
accelerations for the most significant faults considered most likely to subject the site to ground shaking.
TABLE 6.1.1
DETERMINISTIC SITE PARAMETERS FOR SELECTED FAULTS
Fault Name Distance from Site Maximum Maximum Site
(miles) Earthquake Acceleration (g)
Rose Canyon 7 7.2 0.32
Newport-Inglewood (Offshore) 10 7.1 0.25
Coronado Banks Fault 7.A)ne 22 7.6 0.17
Elsinore-Julian 23 7.1 0.13
Elsinore-Temecula 23 6.8 0.10
Elsinore-Glen Ivy 37 6.8 0.06
Earthquake Valley 40 6.5 0.04
Palos Verdes 41 7.2 0.06
San Jacinto-Anza 46 7.2 0.06
In the event of a major earthquake on any of the referenced faults in Table 6.1.1 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 California Building Code (CBC) guidelines
and/or those currently adopted by the City of Carlsbad.
The California Geologic Survey (COS) has a program that calculates the ground motion for a
lO percent of probability of exceedance in 50 years based on an average of several attenuation
relationships. Table 6.1.2 presents the calculated results from the Probabilistic Seismic Hazards
Mapping Ground Motion Page from the COS website.
TABLE 6.1.2
PROBABILISTIC SITE PARAMETERS FOR SELECTED FAULTS CALIFORNIA GEOLOGIC SURVEY
Calculated Acceleration (g) Calculated Acceleration (g) Calculated Acceleration (g)
Firm Rock Soft Rock Alluvium
0.26 0.28 0.32
Project No. 06403-52-33 -4-October 20, 2008
6.2 Liquefaction
Liquefaction typically occurs when a site is located in a zone with seismic activity, on-site soil is
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 formational materials and compacted fill, installation of a canyon subdrain during previous
mass grading operations, and lack of permanent groundwater table, the potential for liquefaction
occurring at the site is considered to be very low.
6.3 Seiches and Tsunamis
Seiches are caused by the movement of an inland body of water due to the movement from seismic
forces and tsunamis are large sea waves caused by submarine earthquakes or volcano eruptions. The
potential of seiches to occur is considered to be very low due to the absence of a nearby inland body of
water. The potential of tsunamis to occur at the site is considered to be very low due to the relatively
large distance from the coastline to the site.
6.4 Landslides
We did not encounter landslides in the subject property during the grading operations. In addition, we
do not expect landslide to affect the subject site.
Project No. 06403-52-33 -5-O<.:tober 20. 2008
7. CONCLUSIONS AND RECOMMENDATIONS
7.1 General
7.1.1 No soil or geologic conditions were encountered during previous geotechnical investigations
or grading operations that, in our opinion, would preclude the continued development of the
property as presently planned, provided that the recommendations of this report are
followed.
7.1.2 The site is underlain by compacted fill and undocumented fill, overlying Lindavista and
Santiago Formations. The undocumented fill is not considered suitable for the support of
settlement-sensitive structures; however, because it is located outside of the planned
development area, it should not impact the planned development. The compacted fill and the
formational materials are considered suitable for the support of compacted fill and
settlement-sensitive structures. The upper 1 to 2 feet of the compacted fill will need to be
processed, moisture conditioned as necessary, and compacted prior to placement of
additional fill or improvements.
7.1.3 The site is approximately 7 miles from the Rose Canyon Fault. It is our opinion that active,
potentially active, and inactive faults are not present at the site based on the results of our
field investigation and our review of the referenced background materials. Risks associated
with seismic activity consist of the potential for strong seismic shaking. It is our opinion that
the potential for surface rupture due to faulting in the area of the proposed development is
considered low and building setbacks will not be required.
7 .1.4 Groundwater or seepage were not observed in the exploratory borings to the total depths
explored and is not expected to be encountered during construction of the proposed
development.
7.1.5 The proposed structures can be supported on conventional shallow footings founded in
compacted fill materials.
7.1.6 Excavation of the on site soil should generally be possible with moderate to heavy effort
using conventional, heavy-duty equipment during grading and trenching operations. Very
heavy effort should be expected with possible refusal in localized areas for excavations into
strongly cemented formational materials. Oversize materials may be generated which would
require special handling or exportation from the site.
7.1.7 Surface settlement monuments will not be required on the project; however, monitoring of
the temporary shoring, as discussed herein, should be performed.
Project No. 06403-52-33 -6-October 20, 2008
7.1.8 The on-site geologic units have permeability characteristics and/or fractu
conducive to water transmission, natural or otherwise (e.g., landscape)
future seepage conditions. It is not uncommon for groundwater or see
develop where none previously existed, particularly after landscape im
The occurrence of induced groundwater seepage from landscaping can be
implementing and monitoring a landscape program that limits irrigation
support the vegetative cover without over watering. Shallow subdrains
the future if seeps occur after rainy periods or after landscaping is installe
re systems that are
, and may result in
page conditions to
gation is initiated.
greatly reduced by
to that sufficient to
may be required in
d.
7.2 Soil and Excavation Characteristics
i ve/non-expansi ve"
California Building
7.2.1 The soil encountered in the field investigation is considered to be "expans
(expansion index [EI] of 20 or less/greater than 20) as defined by 2007
Code (CBC) Section 1802.3.2. Table 7.2.1 presents soil classificat
expansion index. A majority of the soil encountered is planned to poss
"low" expansion potential. The laboratory test results are presented in Ap
ions based on the
es a "very low" to
pendix A.
TABLE 7.2.1
SOIL CLASSIFICATION BASED ON EXPANSION INDE X
Expansion Index (EI) Soil Classifi cation
0-20 Very Lo w
21 -50 Low
51 -90 Medium
91-130 High
Greater Than 130 Very Hig h
e the percentage of 7.2.2 We performed laboratory tests on samples of the site materials to evaluat
water-soluble sulfate content. Results from the laboratory water-soluble s
are presented in Appendix A and indicate that the on-site materials at t
possess a "negligible" to "severe" sulfate exposure to concrete structures
CBC Section 1904.3 and ACI 318-08 Sections 4.2 and 4.3. Table 7.2.2 p
of concrete requirements set forth by 2007 CBC Section 1904.3 and ACI 3
ulfate content tests
he locations tested
as defined by 2007
resents a summary
18.
ProJect No. 06403-52-33 -7-October 20, 2008
TABLE 7.2.2
REQUIREMENTS FOR CONCRETE EXPOSED TO SULFATE-CON T AJNING SOLUTIONS
Water-Soluble Max imum
Sulfate Exposure Sulfate Wa terto Minimum
Exposure Class Percent Cement Type Ce ment Compre~ive
by Weight R atio Strength (psi)
byW eight
Negligible so 0.00-0.10 --2,500
Moderate Sl 0.10-0.20 II 0 .50 4,000
Severe S2 0.20-2.00 v 0 .45 4,500
Very Severe S3 >2.00 V+Pozzolan or Slag 0 .45 4,500
7.2.3 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 (i.e., addition of fertilizers and other soil nutrients) may affect the
concentration.
7.2.4 Geocon Incorporated does not practice in the field of corrosion engineering. Therefore,
further evaluation by a corrosion engineer should be performed if improvements are planned
that are susceptible to corrosion.
7.2.5 The existing compacted fill soil should generally require light to moderate effort to excavate
using conventional heavy-duty grading equipment. Excavations into Santiago Formation
(exposed at grade and underlying the compacted fill soils) will likely require moderate to
heavy ripping. In addition, concretionary lenses or layers may exist within the Santiago
Formation that may cause difficult excavation and potentially may generate oversize material
(fragments greater than 6 inches in maximum dimension).
7.3 Grading
7.3.1 Grading should be performed in accordance with the Recommended Grading Specifications
in Appendix B and the City of Carlsbad Grading Ordinance. Where the recommendations of
this report conflict with Appendix B. the recommendations of this section take preceden'ce.
7.3.2 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 the fine grading plans can be discussed at that time.
Project No. 06403-52-33 -8-October 20, 2008
7.3.3 Site preparation should begin with the removal of all deleterious material and vegetation, if
present. The depth of removal should be such that material exposed in cut areas or soil to be
used as fill is relatively free of organic matter. Material generated during stripping and/or site
demolition should be exported from the site.
7.3.4 The upper 1 to 2 feet in areas to receive fill or from finish pad grade, whichever results in a
deeper removal, should be removed, moisture conditioned as necessary, and properly
compacted. The actual extent of remedial grading should be evaluated in the field by the
geotechnical engineer or engineering geologist. Overly wet surficial materials will require
drying and/or mixing with drier soils to facilitate proper compaction.
7.3.5 The site should then be brought to final subgrade elevations with structural fill compacted in
layers. In general, the on-site soils are suitable for re-use as fill if free from vegetation, debris
and other deleterious material. Layers of fill should be no thicker than will allow for
adequate bonding and compaction. Fill, including wall and trench backfill, should be
compacted to dry density of at least 90 percent of the laboratory dry density near to slightly
above optimum moisture content in accordance with ASTM Test Procedure D 1557.
7.3.6 To reduce the magnitude of potential differential settlement of the compacted fill, building
pads with a cut-fill transition should be undercut a minimum of three feet and replaced with
compacted fill .. The undercut should extend at least 5 feet horizontally outside the limits of
the building footprint area.
7.3.7 Excavations during the grading operations should be observed by a representative of Geocon
Incorporated to check that soil and geologic conditions do not differ significantly from those
expected.
7.3.8 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 subgrade 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.
7.3.9 It is the responsibility of the contractor to ensure that all excavations and trenches are
properly shored and maintained in accordance with applicable OSHA rules and regulations
in order to maintain safety and maintain the stability of adjacent existing improvements.
Project No. 06403-52-33 -9-October 20, 2008
7.3.10 Import fill soil, if necessary, should consist of 6 inch minus granular materials with a "very
low" to "low" expansion potential (EI of 50 or less) and be generally free of deleterious
material and debris. 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. In addition, the imported soil should be certified as being free of
hazardous contaminants as well as chemical properties that could adversely impact proposed
construction material.
7.4 Seismic Design
7.4.1 We used the computer program Seismic Hazard Curves and Uniform Hazard Response
Spectra, provided by the USGS to calculate the seismic design criteria. Table 7.4
summarizes site-specific design criteria obtained from the 2007 CBC. Chapter 16 Structural
Design, Section 1613 Earthquake Loads. The short spectral response has a period of
0.2 second.
TABLE 7.4
2007 CBC SEISMIC DESIGN PARAMETERS
Parameter IBC-06 Reference
Site Class c Table 1613.5.2
Spectral Response-Class B (short), S5 1.142 g Figure 1613.5(3)
Spectral Response-Class B (I sec), S1 0.432g Figure 1613.5(4)
Site Coefficient, Fa 1.00 Table 1613.5.3(1)
Site Coefficient, F. 1.368 Table 1613.5.3(2)
Maximum Considered Earthquake l.l42.g Section 1613.5.3 (Eqn 16-37) Spectral Response Acceleration (short), SMs
Maximum Considered Earthquake 0.591g Section 1613.5.3 (Eqn 16-38) Spectral Response Acceleration-(I sec), SM1
5% Damped Design 0.76lg Section 1613.5.4 (Eqn 16-39) Spectral Response Acceleration (short), S0s
5% Damped Design 0.394g Section 1613.5.4 (Eqn 16-40) Spectral Response Acceleration (I sec), S01
7.4.2 Conformance to the criteria for seismic design in Table 7.4 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. 06403-52-33 -10-October 20. 2008
7.5 Slopes
7.5.1 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.
7.5.2 Slopes should be landscaped with drought-tolerant vegetation, having variable root depths
and requiring minimal landscape irrigation. In addition, slopes should be drained and
properly maintained to reduce erosion.
7.6 Conventional Shallow Foundations
7 .6.1 The proposed structures can be supported on a conventional shallow foundation system
bearing on compacted fill or formational materials. Foundations for the structure should
consist of continuous strip footings and/or isolated spread footings. Continuous footings
should be at least 12 inches wide and extend at least 18 inches below lowest adjacent pad
grade. Isolated spread footings should have a minimum width and depth of 2 feet. Steel
reinforcement for continuous footings should consist of at least four No. 5 steel reinforcing
bars placed horizontally in the footings; two near the top and two near the bottom. The
project structural engineer should design the steel reinforcement for the footings. A typical
wa!Vcolumn footing dimension detail is presented on Figure 3.
7.6.2 The recommendations presented herein are based on soil characteristics only (EI of 50 or
less) and is not intended to replace reinforcement required for structural considerations.
7.6.3 The recommended allowable bearing capacity for foundations designed as recommended
above is 2,000 pounds per square foot (psf) for foundations in properly compacted fill
material or Santiago Formation. The allowable soil bearing pressure may be increased by an
additional 500 psf and 300 psf for each additional foot of depth and width, respectively, to a
maximum allowable bearing capacity of 3,500 psf. The values presented above are for dead
plus live loads and may be increased by one-third when considering transient loads due to
wind or seismic forces.
7.6.4 The use of isolated footings, which are located beyond the perimeter of the building and
support structural elements connected to the building, are not recommended. Where this
condition cannot be avoided, the isolated footings should be connected to the building
foundation system with grade beams.
7.6.5 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
Project No. 06403-52-33 -II-October 20, 2008
connecting exterior slabs, which exceed 5 feet in width, to the building foundation to reduce
the potential for future separation to occur.
7.6.6 Total and differential settlements under the imposed allowable loads are estimated to be %
inch and 1/2 inch, respectively.
7.6.7 No special subgrade presaturation is deemed necessary prior to placing concrete, however,
the exposed foundation and slab subgrade soils should be moistened as necessary to maintain
a moist soil condition as would be expected in any such concrete placement.
7.6.8 Foundation excavations should be observed by the Geotechnical Engineer (a representative
of Geocon Incorporated) prior to the placement of reinforcing steel and concrete to check
that the exposed soil conditions are consistent with those expected and have been extended
to appropriate bearing strata. If unexpected soil conditions are encountered, foundation
modifications may be required.
7.7 Concrete Slabs-on-Grade and Flatwork Recommendations
7.7.1 Interior concrete slabs-on-grade should be at least 5 inches thick. As a minimum, slab
reinforcement should consist of No. 3 steel reinforcing bars spaced 18 inches on center in
both horizontal directions placed mid-height in the slab.
7.7.2 Concrete slabs on grade should be underlain by 3 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 retarder placed near the middle of the sand bedding. The vapor retarder used should be
specified by the project architect or developer based on the type of floor covering that will be
installed. The vapor retarder design should be consistent with the guidelines presented in
Section 9.3 of the American Concrete Institute's (ACI) Guide for Concrete Slabs that
Receive Moisture-Sensitive Flooring Materials (ACI 302.2R-06).
7.7.3 The foundation and slab-on-grade dimensions and minimum reinforcement recom-
mendations are based upon soil conditions only and are not intended to be used in lieu of
those required for structural purposes.
7.7.4 Exterior concrete slabs should be provided with adequate construction JOmts and/or
expansion joints to control unsightly shrinkage cracking. The spacing should be determined
by the project structural engineer based upon the intended slab usage, type and extent of
brittle floor-covering materials, thickness, and reinforcement. The structural engineer should
Project No. 06403-52-33 -12-October 20, 2008
----------------------~ --~-----------
take into consideration criteria of the American Concrete Institute (ACI) when establishing
crack-control spacing patterns.
7.7.5 Exterior concrete flatwork not subject to vehicular traffic should be constructed in
accordance with the recommendations herein. Slab panels should be a minimum of 4 inches
thick and, when in excess of 8 feet square, should be reinforced with 6 x 6-W2.9/W2.9
(6 x 6-6/6) welded wire mesh to reduce the potential for cracking. In addition, concrete
flatwork should be provided with crack control joints to reduce and/or control shrinkage
cracking. Crack control spacing should be determined by the project structural engineer
based upon the slab thickness and intended usage. Criteria of the American Concrete
Institute (ACI) should be taken into consideration when establishing crack control spacing.
Subgrade soil for exterior slabs not subjected to vehicle loads should be compacted in
accordance with criteria presented in the grading section prior to concrete placement.
Subgrade soil should be properly compacted and the moisture content of subgrade soil
should be checked prior to placing concrete.
7.7.6 Where exterior flatwork abuts the structure at entrant or exit points, the exterior slab should
be dowelled into the structure's foundation stemwall. This recommendation is intended to
reduce the potential for differential elevations that could result from differential settlement or
minor heave of the flatwork. Dowelling details should be designed by the project structural
engineer.
7.7.7 Where buildings or other improvements are planned near the top of a slope steeper than 3: I
(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.
• Although other improvements, which are relatively rigid or brittle, such as concrete
flat work 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.
7.7.8 The recommendations of this report are intended to reduce the potential for cracking of slabs
due to expansive soils (if present) and differential settlement of fill soil. However, even with
the incorporation of the recommendations presented herein, foundations and slabs-on-grade
placed on such conditions may still exhibit cracking. The occurrence of concrete shrinkage
Project No. 06403-52-33 -13 • October 20, 2008
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 the placement of crack-control joints at proper locations, particularly where re-
entrant slab comers occur.
7.8 Retaining Walls and Lateral Loads
7.8.1 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: 1
(horizontal:vertical), 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 50 or less. Where
backfill materials do not conform to the criteria herein, Geocon Incorporated should be
consulted for additional recommendations.
7.8.2 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 of the wall height, a surcharge equivalent to
2 feet soil should be added.
7.8.3 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 Figure 4 presents a typical retaining wall drainage detaiL The above
recommendations assume a properly compacted granular (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.
7.8.4 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 90 or less. The proximity of the foundation to the
top of a slope steeper than 3: I could impact the allowable soil bearing pressure. Therefore,
Geocon Incorporated should be consulted where such a condition is expected.
ProJeCt No. 06403-52-33 -14-October 20. 2008
7 .8.5 The structural engineer should determine the seismic design category for the project. If the
project possesses a seismic design category of D, E, or F, the proposed retaining walls
should be designed with seismic latenil pressure. A seismic load of 24H should be used for
design. The seismic load is dependent on the retained height where H is the height of the
wall, in feet, and the calculated loads result in pounds per square foot (psf) exerted at the top
of the wall and zero at the base of the wall. We used a peak site acceleration of 0.30g
calculated form the 2007 California Building Code (S0s/2.5) and applying a pseudo-static
coefficient of 0.5.
7.8.6 Although this seismic loading on the wall was evaluated for an active pressure case and the
walls will be in an at-rest condition, some researchers have reported that this analysis
produces reasonable design earth pressures. Because seismic loads will be analyzed using
lower factors of safety than static earth pressures, we expect the design can be controlled by
static loads.
7.8.7 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, Geocon
Incorporated should be consulted for additional recommendations.
7.9 Lateral Loading
7.9.1 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 till soil or undisturbed natural soil. The allowable passive pressure
assumes a horizontal surface extending at least 5 feet or three times the surface generating
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.
7.9.2 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.
7.10
7.10.1
Preliminary Flexible Pavement Recommendations
We understand the planned driveways will be paved with asphalt concrete pavement. The
final pavement sections for the roadways should be based on the R-Value of the subgrade
soil encountered at final subgrade elevation. We have assumed an R-Value of 15 for the
subgrade soil for the purposes of this preliminary analysis. Preliminary flexible pavement
sections are presented in Table 7 .10.1.
ProJect No. 06403-52-33 -15-October 20, 2008
7.10.2
7.10.3
7.10.4
7.10.5
TABLE 7.10.1
PRELIMINARY FLEXIBLE PAVEMENT SECTION
Assumed Assumed Asphalt Class 2
Location Subgrade Concrete Aggregate Traffic Index R-Value (inches) Base (inches)
Parking stalls for automobiles 5.0 15 4 6 and light-duty vehicles
Driveways for automobiles 5.5 15 4 8 and light-duty vehicles
Driveways for heavy truck traffic 7.0 15 4 13
Base materials should conform to Section 26-1.028 of the Standard Specifications for The
State of California Department of Transportation ( Caltrans) with a %-inch maximum size
aggregate. Base materials should be compacted to a dry density of at least 95 percent of the
laboratory maximum dry density near to slightly above optimum moisture content. The
asphalt concrete should conform to Section 203-6 of the Standard Specifications for Public
Works Construction (Greenbook). Asphalt concrete should be compacted to a density of at
least 95 percent of the laboratory Hveem density in accordance with ASTM D 2726.
The base thickness can be reduced if a reinforcement geogrid is used during the installation
of the pavement. Geocon should be contact for additional recommendations, if required.
Prior to placing base materials, the subgrade soil should be scarified, moisture conditioned as
necessary, and recompacted to a dry density of at least 95 percent of the laboratory
maximum dry density near to slightly above optimum moisture content as determined by
ASTM D 1557. The depth of compaction should be at least 12 inches. Similarly, the base
materials should be compacted to a dry density of at least 95 percent of the laboratory
maximum dry density near to slightly above optimum moisture content.
A rigid Portland Cement concrete (PCC) pavement section should be placed in driveway
entrance aprons and trash bin loading/storage areas. The concrete pad for trash truck areas
should be large enough such that the truck wheels will be positioned on the concrete during
loading. We calculated the rigid pavement section in general conformance with the
procedure recommended by the American Concrete Institute report ACI 330R-Ol Guide for
Design and Construction of Concrete Parking Lots using the parameters presented in
Table 7.10.2.
Project No. 06403-52-33 -16-October 20, 2008
TABLE 7.10.2
RIGID PAVEMENT DESIGN PARAMETE RS
Design Parameter Design Value
Modulus of subgrade reaction, k 100 pci
Modulus of rupture for concrete, MR 500 psi
Traffic Category, TC A-1 and C
Average daily truck traffic, ADTT lO and 100
7 .10. 6 Based on the criteria presented herein, the PCC pavement sectio ns should have a minimum
thickness as presented in Table 7.10.3.
TABLE 7.1 0.3
RIGID PAVEMENT RECOMMENDATION s
Location Portland Cement Concrete (inches)
Automobile Parking Areas (TC=A-1) 6
Heavy Truck and Fire Lane Areas (TC=C) 7
mpacted to a dry density of 7.1 0. 7 The PCC pavement should be placed over subgrade soil that is co
at least 95 percent of the laboratory maximum dry density near
moisture content. This pavement section is based on a minim
strength of approximately 3,000 psi (pounds per square inch).
to slightly above optimum
urn concrete compressive
outside of concrete slabs 7.10.8 A thickened edge or integral curb should be constructed on the
subjected to wheel loads. The thickened edge should be 1.2 tim
minimum thickness of 2 inches, whichever results in a thicker ed
taper back to the recommended slab thickness 3 feet behind th
7-inch-thick slab would have a 9-inch-thick edge). Reinforcing s
within the concrete for geotechnical purposes with the possibl
es the slab thickness or a
ge, at the slab edge and
e face of the slab (e.g., a
teel will not be necessary
e exception of dowels at
construction joints as discussed below.
acks, crack-control joints 7 .10. 9 To control the location and spread of concrete shrinkage cr
(weakened plane joints) should be included in the design of th
Crack-control joints should not exceed 30 times the slab thickness
of 15 feet (e.g., a 7-inch-thick slab would have a 15-foot spaci
sealed with an appropriate sealant to prevent the migration of wate
to the subgrade materials. The depth of the crack-control joints sh
e concrete pavement slab.
with a maximum spacing
ng pattern) and should be
r through the control joint
ould be determined by the
referenced ACI report.
Project No. 06403-52-33 -17-October 20, 2008
7.10.10 To provide load transfer between adjacent pavement slab sections, a trapezoidal-keyed
construction joint should be installed. As an alternative to the keyed joint, dowelling is
recommended between construction joints. As discussed in the referenced ACI guide, dowels
should consist of smooth, Ys-inch-diameter reinforcing steel 14 inches long embedded a
minimum of 6 inches into the slab on either side of the construction joint. Dowels should be
located at the midpoint of the slab, spaced at 12 inches on center and lubricated to allow joint
movement while still transferring loads. Other alternative recommendations for load transfer
should be provided by the project structural engineer.
7.10.11 The performance of pavement is highly dependent on providing positive surface drainage
away from the edge of the pavement. Ponding of water on or adjacent to the pavement will
likely result in pavement distress and subgrade failure. Drainage from landscaped areas
should be directed to controlled drainage structures. Landscape areas adjacent to the edge of
asphalt pavements are not recommended due to the potential for surface or irrigation water to
infiltrate the underlying permeable aggregate base and cause distress. Where such a
condition cannot be avoided, consideration should be given to incorporating measures that
will significantly reduce the potential for subsurface water migration into the aggregate base.
If planter islands are planned, the perimeter curb should extend at least 6 inches below the
level of the base materials.
7.11
7.11.1
7.11.2
7.11.3
Drainage and Maintenance
Establishing proper drainage is critical to reduce the potential for differential soil movement,
erosion and subsurface seepage. Positive measures should be taken to properly finish-grade
the pads after the structures and other improvements are in place so that the drainage water
from the lots and adjacent properties are directed off the lots and to the street away from
foundations and the top of the slopes. Experience has shown that even with these provisions,
a shallow groundwater or subsurface water condition can and may develop in areas where no
such water conditions existed prior to the site development; this is particularly true where a
substantial increase in surface water infiltration results from an increase in landscape
irrigation.
Underground utilities should be leak free. Utility and irrigation lines should be checked
periodically for leaks for early detection of water infiltration and detected leaks should be
repaired promptly. Detrimental soil movement could occur if water is allowed to infiltrate
the soil for a prolonged period.
Landscaping planters adjacent to paved areas are not recommended due to the potential for
surface or irrigation water to infiltrate the pavement's subgrade and base course. Surface
drains to collect excess irrigation water and transmit it to drainage structures, or impervious
Project No. 06403-52-33 -18-October 20, 2008
7.11.4
7.12
7.12.1
7.13
7.13.1
above-grade planter boxes should be used. In addition, where landscaping is planned
adjacent to the pavement, a cutoff wall should be provided along the edge of the pavement
and should extend at least 6 inches below the bottom of the base material.
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 groundwater,
movement of foundations and slabs, or other impacts as a result of water infiltration through
the detention basins, bios wales, or retention basins.
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 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, recommended 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. 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.
Plan Review
A review of the grading and foundation plans should be performed prior to finalization to
verify their compliance with the recommendations of this report and determine the need for
additional comments, recommendations and/or analysis.
Project No. 06403-52-33 -19 -October 20, 2008
LIMITATIONS AND UNIFORMITY OF CONDITIONS
L 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.
2. 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.
3. 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 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.
4. The firm that performed the geotechnical investigation for the project should be retained to
provide testing and observation services during construction to provide continuity of
geotechnical 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. 06403-52-33 October 20, 2008
i. ,'l"_ ·~·
'
~-' ··~~ %t .. ··
\ ~i~i 'L .. --L~~.
cnRT£ o.: \ tA PIV. • \ cos~ I • .. -·iil CT
SOURCE: 2007 THOMAS BROTHERS MAP
SAN DIEGO COUNTY, CALIFORNIA
"Map C Rand McNally, R.L.08-S·100, reproduced with permission. It Ia unlawfUl to copy
or reproduce, whether lor peraonal use or reeale, without permission"
GEOCON • INCORPORATED
GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE· SAN DIEGO, CALIFORNIA 92121· 297 4
PHOI'-E 858 558·6900-FAX 858 558-6159
AS/AML I I DSKIGTYPD
NO SCALE
VICINITY MAP
VILLAGES OF LA COSTA -THE GREENS
NEIGHBORHOOD 1.02 KINGDOM HAll
CARLSBAD, CALIFORNIA
DATE 10. 20. 2008 I PROJECT NO. 06403.52.33 I FIG. 1
Qcf .C~TEOFIU
Qudf UOOle\.Uf.HTf.oFu
Qln o..M».-t"f<R¥ol10M~-..._,
Ts SNfTioi.GOfORMO.TI()Nc~-........
"""""* U£VATOIOI'~1Jri
-~ ~El.£'.1AToCIJriAl ..... 0F'tU
GEOLOGIC MI>J'
VIJ.AGfS OF lA COSTA • THE GIEENS
NfkiHBOIHOOO I 02 ~HAll
CAI:ts&AO. CA1JFOIN&A.
~HE9~9!': $ b,;;..:::...........,...,--r.o;j
:z~:.::a~~-..........
WALL FOOTING
SAND
VISQUEEN
COLUMN FOOTING
LFOOTING· j
WIDTH
'1-·-----FOOTING WIDTH' ------1
NO SCALE
* .... SEE REPORT FOR FOUNDATION WITDH AND DEPTH RECOMMENDATION
WALL I COLUMN FOOTING DIMENSION DETAIL
GEOCON
INCORPORATED
GEOTEOINICAL CONSULTANTS
6960 FLANDERS DRIVE· SAN DIEGO, CALIFORNIA 92121· 297 4
PHONE 858 558·6900 ·FAX 858 558·6159
NA/AML DSKIEOOOO
VILLAGES OF LA COSTA -THE GREENS
NEIGHBORHOOD 1 .02 KINGDOM HALL
CARLSBAD, CALIFORNIA
DATE 10 • 20-2008 PROJECT NO. 06403 ·52 • 33 FIG. 3
t
! I ~
I ! I u
GROUND SURFACE
NOTE:
PROPOSED
GRADE
CONCRETE
BROWOITCH
DRAIN SHOULD BE SLOPED TO GRAVITY OUTLET OR TO A SUMP
WHERE WATER CAN BE REMOVED BY PUMPING.
GROUND SURFACE
4" DIA. PERFORATED SCHEDULE
40 PVC PIPE EXTENDED TO
APPROVED OUTLET
GROUND SURFACE
DRAINAGE PANEL (MIRADRAIN 6000
OR EQUIVALENT)
TYPICAL RETAINING WAll DRAIN DET All
GEOCON • VILLAGES OF LA COSTA -THE GREENS INCORPORATED NEIGHBORHOOD 1 .02 KINGDOM HALL GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE· SAN DIEGO, CALIFORNIA 92121· 297 4 CARLSBAD, CALIFORNIA
PHONE 858 558·6900 ·FAX 858 558·6159
NA/AML I I DSK/GTYPD DATE 10-20-2008 I PROJECT NO. 06403 -52 -33 I FIG. 4
ALVN
APPENDIX A
LABORATORY RESULTS
FOR
VILLAGES OF LA COSTA-THE GREENS
NEIGHBORHOOD 1.02, KINGDOM HALL
CARLSBAD, CALIFORNIA
TABLE A-1
SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS
ASTM D 4829-03
Moisture Content (%) Dry Density Expansion Expansion Sample No. Before Test After Test (pcO Index Classification
EI-B
EI-D
11.2 20.0 105.8 13 Very Low
11.5 20.3 103.5 15 Very Low
TABLE A-ll
SUMMARY OF WATER-SOLUBLE SULFATE LABORATORY TEST RESULTS
CALIFORNIA TEST 417
Sample No. Water-Soluble Sulfate (%) Sulfate Exposure
--~~--------~----_, EI-B 0.044 Negligible
EI-D 0.219 Severe
Project No. 06403-52-33 October 20. 2008
APPENDIX B
RECOMMENDED GRADING SPECIFICATIONS
FOR
VILLAGES OF LA COSTA-THE GREENS
NEIGHBORHOOD 1.02, KINGDOM HALL
CARLSBAD, CALIFORNIA
RECOMMENDED GRADING SPECIFICATIONS
1. GENERAL
1.1 These Recommended Grading Specifications shall be used in conjunction with the
Geotechnical Report for the project prepared by Geocon Incorporated. The
recommendations 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. The Consultant should provide adequate testing and observation services 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.
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, 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 grading 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.
Gl rev. I 0/06
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 o/.1 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 mattix 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 % inch in maximum dimension. The quantity of fines shall be
less than approximately 20 percent of the rock fill quantity.
Gl rev. 10/06
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 till, 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
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.
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 and
Consultant.
3.5 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.
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
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
logs and other unsuitable material and shall be performed in areas to be graded. Roots and
other projections exceeding 1 Yz 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
4.2 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
of this document.
4.3 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: I (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
Remove All
Unsuitable Material
As Recommended By
Consultant Slope To Be Such That
Sloughing Or Sliding
Does Not Occur
Ground
Finish Slope Surface
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 of the 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.
Glrev. 10/06
4.5 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
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 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.
Gl rev. !0/06
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 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 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 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:
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.
Gl rev. I 0/06
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 m the
windrows should be continuously observed by the Consultant.
6.3 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 of 2
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 subdrains shall be permanently connected
to controlled 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
Gl rev. I 0/06
required compaction or deflection as recommended in Paragraph 6.3.3 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 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 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 bearing tests will be determined by the Consultant during grading.
6.3.5 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 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.
6.3.7 Rock fill placement should be continuously observed during placement by the
Consultant.
Gl rev 10/06
7. OBSERVATION AND TESTING
7.1 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.
7.2 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 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 should observe that the minimum number of
passes have been obtained per the criteria discussed in Section 6.3.3. The Consultant
should 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. 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.
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.
7.5 The Consultant should observe the placement of subdrains, to verify that the drainage
devices have been placed and constructed in substantial conformance with project
specifications.
7.6 Testing procedures shall conform to the following Standards as appropriate:
Gl rev. 10/06
7.6.1 Soil and 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 10-Pound
Hammer and IS-Inch Drop.
7.6.1.4. Expansion Index Test, ASTM D 4829-03, Expansion Index Test.
7.6.2 Rock Fills
7.6.2.1 Field Plate Bearing Test, ASTM D 1196-93 (Reapproved 1997)
Standard Method for Nonreparative Static Plate Load Tests of Soils and
Flexible Pavement Components, For Use in Evaluation and Design of
Airport and 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
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
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.
Gl rev. 10/06